WO2012105139A1 - Switching element, semiconductor device, and methods for manufacturing switching element and semiconductor device - Google Patents

Switching element, semiconductor device, and methods for manufacturing switching element and semiconductor device Download PDF

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Publication number
WO2012105139A1
WO2012105139A1 PCT/JP2011/079577 JP2011079577W WO2012105139A1 WO 2012105139 A1 WO2012105139 A1 WO 2012105139A1 JP 2011079577 W JP2011079577 W JP 2011079577W WO 2012105139 A1 WO2012105139 A1 WO 2012105139A1
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WIPO (PCT)
Prior art keywords
ion conductive
conductive layer
electrode
metal
switching element
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PCT/JP2011/079577
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French (fr)
Japanese (ja)
Inventor
直樹 伴野
阪本　利司
山口　周
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日本電気株式会社
国立大学法人東京大学
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Priority to JP2012555704A priority Critical patent/JP5807789B2/en
Publication of WO2012105139A1 publication Critical patent/WO2012105139A1/en

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/20—Multistable switching devices, e.g. memristors
    • H10N70/24—Multistable switching devices, e.g. memristors based on migration or redistribution of ionic species, e.g. anions, vacancies
    • H10N70/245—Multistable switching devices, e.g. memristors based on migration or redistribution of ionic species, e.g. anions, vacancies the species being metal cations, e.g. programmable metallization cells
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/801—Constructional details of multistable switching devices
    • H10N70/821—Device geometry
    • H10N70/826—Device geometry adapted for essentially vertical current flow, e.g. sandwich or pillar type devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/801—Constructional details of multistable switching devices
    • H10N70/841—Electrodes
    • H10N70/8416—Electrodes adapted for supplying ionic species
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/801—Constructional details of multistable switching devices
    • H10N70/881—Switching materials
    • H10N70/883—Oxides or nitrides
    • H10N70/8833—Binary metal oxides, e.g. TaOx

Definitions

  • the present invention relates to a switching element used in an electronic device such as a programmable logic and a memory, and more particularly to a switching element using an electrochemical reaction between two electrodes.
  • switching elements or resistance change elements that connect logic cells to each other or change the resistance value between logic cells. Therefore, it is necessary to reduce the size of the device and to reduce its on-resistance.
  • switching element an element utilizing an electrochemical reaction between two electrodes, that is, an element utilizing deposition of metal between two electrodes, is smaller in size and smaller in on-resistance than a semiconductor switching element such as an FET.
  • the metal deposition switching element includes a two-terminal switching element disclosed in Patent Documents 1 and 2, and a three-terminal switch disclosed in Patent Document 2 and Non-Patent Document 1, for example.
  • a two-terminal switching device includes a first electrode 621 and a second electrode 622 that are arranged to face each other at a distance, and an ion conductive layer 611 provided between both electrodes.
  • the first electrode 621 is an electrode that supplies metal ions.
  • the second electrode 622 is an electrode that does not supply metal ions.
  • the two electrodes are switched by the formation / disappearance of metal bridges by the deposited metal in the ion conductive layer 611. Since the two-terminal switching element has a simple structure, the manufacturing process is simple, and the element size can be reduced to the nanometer order.
  • the thickness of the metal bridge can be controlled, and the current required for writing and erasing the switch can be greatly reduced.
  • this type of switching element As switching means or resistance changing means for switching wiring of programmable logic, it is necessary to have a switching voltage higher than the logic operating voltage (1V) and heat resistance to withstand the manufacturing process of the semiconductor integrated circuit. It becomes. Since the switching voltage greatly depends on the diffusion rate of metal ions in the ion conductor, selection and optimization of the ion conductor material is important.
  • Patent Documents 3 and 4 disclose switching elements that increase the switching voltage and obtain high heat resistance by using an oxide as an ion conductive layer.
  • Non-Patent Document 2 discloses a technology for integrating switching elements using an electrochemical reaction between two electrodes in a semiconductor device such as a programmable logic. Specifically, Non-Patent Document 2 discloses a structure in which the copper wiring on the semiconductor substrate and the first electrode of the switching element are combined. If this structure is used, the process for newly forming the first electrode can be reduced.
  • the number of photomasks (PR: Photo Reticles) to be added for manufacturing the switching element can be reduced to two.
  • PR Photo Reticles
  • this type of switching element is applied as a switching means or resistance changing means of a programmable logic, a logic operating voltage is applied even in an off state.
  • the disturb characteristic that is, the reliability when applying a constant voltage in the off state (voltage resistance in the off state) needs to be sufficiently ensured.
  • a specific disturb characteristic for example, when the logic operating voltage is 1V, it is necessary to keep the OFF state for 10 years when 1V is applied.
  • the present invention has an ion conductive layer containing oxygen and allowing conduction of metal ions, and a first electrode and a second electrode formed on each of the front and back surfaces of the ion conductive layer, the first electrode being The second electrode is made of a metal that does not supply metal ions to the ion conductive layer, and is supplied from the first electrode into the ion conductive layer.
  • the ion conductive layer includes: An ion conductive layer interface including an interface with the first electrode and an ion conductive layer main part which is the remaining part, and the ion conductive layer main part is a compound containing a metal oxide or oxygen.
  • the ion conducting layer interface unit is composed of a compound containing a metal oxide or oxygen, the oxygen composition ratio switching element is obtained which is a substoichiometric amount.
  • FIG. 1 is a schematic cross-sectional view showing the configuration of a switching element according to the related art of the present invention.
  • FIG. 2 is a schematic cross-sectional view showing the configuration of the switching element according to the first embodiment of the present invention.
  • FIG. 3 is a schematic cross-sectional view for explaining the operation of the switching element shown in FIG. 4A to 4C are schematic cross-sectional views for explaining a method of manufacturing the switching element shown in FIG.
  • FIG. 5 is a graph showing a disturb characteristic as a characteristic verification result of the switching element shown in FIG. 6 (a) to 6 (d) are schematic cross-sectional views for explaining a method for manufacturing a switching element according to the second embodiment of the present invention.
  • FIG. 1 is a schematic cross-sectional view showing the configuration of a switching element according to the related art of the present invention.
  • FIG. 2 is a schematic cross-sectional view showing the configuration of the switching element according to the first embodiment of the present invention.
  • FIG. 3 is a schematic cross-sectional
  • FIG. 7 is a schematic cross-sectional view showing the configuration of the switching element according to the third embodiment of the present invention.
  • FIG. 8 is a schematic cross-sectional view for explaining the operation of the switching element shown in FIG. 9A to 9D are schematic cross-sectional views for explaining a method of manufacturing the switching element shown in FIG.
  • FIG. 10 is a graph showing a disturb characteristic as a characteristic verification result of the switching element shown in FIG.
  • FIGS. 11A and 11B are graphs showing the photoelectron spectroscopy measurement results of the switching element shown in FIG.
  • FIG. 12 is a schematic cross-sectional view showing a configuration of a semiconductor device according to Example 4 of the present invention.
  • 13A to 13F are schematic cross-sectional views for explaining a method of manufacturing the semiconductor device shown in FIG. 14A to 14F are schematic cross-sectional views for explaining a method for manufacturing the semiconductor device shown in FIG.
  • the switching element includes an ion conductive layer containing oxygen and allowing conduction of metal ions, and a first electrode and a second electrode formed on the front and back surfaces of the ion conductive layer.
  • the first electrode is made of a metal capable of supplying metal ions to the ion conductive layer.
  • the second electrode is made of a metal that does not supply metal ions to the ion conductive layer.
  • the metal ions supplied from the first electrode into the ion conductive layer receive electrons from the second electrode and precipitate as metal, and the deposited metal grows to change the resistance value between the first electrode and the second electrode. Switching element.
  • the entire ion conduction layer or the ion conduction layer interface including the interface with the first electrode of the ion conduction layer is made of a metal oxide or a compound containing oxygen and has a thickness.
  • a metal oxide whose material is 5 nm or less or whose standard Gibbs energy at 300 K is larger than ⁇ 600 kJ / mol
  • the entire ion conductive layer or the interface with the first electrode is included.
  • the composition ratio of oxygen at the interface portion of the ion conductive layer is less than the stoichiometric amount.
  • metal ions should not be supplied into the ion conductive layer as much as possible from the first electrode that supplies metal ions when a low voltage is applied.
  • Supply of metal ions into the ion conductive layer proceeds by an ionization reaction of the metal, but the presence of an anion serving as an oxidizing agent is necessary for the ionization of the metal forming the cation.
  • oxygen ions in the ion conductive layer function as an oxidizing agent, and promote ionization of the metal.
  • TDDB dielectric breakdown life
  • the rate at which the metal of the first electrode is injected into the ion conductive layer varies depending on the concentration of oxygen contained in the ion conductive layer. Therefore, in this switching element, the oxygen contained in the interface portion of the ion conductive layer facing the first electrode in the ion conductive layer is less than the stoichiometric amount, so that the supply amount of oxygen ions to the first electrode is small. The ionization of the metal from the first electrode and the supply of the metal ion into the ion conductive layer are suppressed. When a low voltage is applied, since the amount of oxygen ions reaching the first electrode is small, the transition time from off to on becomes long, and the disturb characteristic is excellent.
  • the switching element according to the present invention is excellent in the voltage dependency of the transition time from OFF to ON.
  • the switching device includes an ion conductive layer 11 containing oxygen and allowing conduction of metal ions, a first electrode 21 formed on each of the front and back surfaces of the ion conductive layer 11, and And a second electrode 22.
  • the first electrode 21 is made of a metal that can supply metal ions to the ion conductive layer 11.
  • the second electrode 22 is made of a metal that does not supply metal ions to the ion conductive layer.
  • the metal ions supplied from the first electrode 21 into the ion conductive layer 11 receive electrons from the second electrode 22 and are deposited as metal, and the deposited metal grows, whereby the first electrode 21 and the second electrode 22 are grown.
  • the ion conductive layer 11 has a total thickness, or the layer thickness of the ion conductive layer interface 112 including the interface with the first electrode 21 is 5 nm or less, and the oxygen composition ratio is chemical. Less than stoichiometric amount.
  • reference numeral 112 denotes an ion conductive layer interface 112 that is a part of the ion conductive layer 11 including the interface with the first electrode 21.
  • the ion conductive layer interface 112 in the ion conductive layer 11 and the remainder of the ion conductive layer interface 112 in the ion conductive layer 11 have the same composition, and for convenience of explanation. They are only drawn separately.
  • the first electrode 21 is made of copper for supplying metal ions into the ion conductive layer 11 when a voltage is applied, and is formed by sputtering, chemical vapor deposition (CVD), or electroplating.
  • the second electrode 22 is made of a material that does not supply metal ions into the ion conductive layer 11 when a voltage is applied.
  • the material of the second electrode 22 is preferably ruthenium, platinum, or nickel, and particularly preferably ruthenium.
  • the ion conductive layer 11 is a layer serving as a medium for conducting metal ions, and is made of a metal oxide or a compound containing oxygen.
  • the ion conductive layer 11 is made of a metal oxide, for example, tantalum oxide, zirconium oxide, aluminum oxide, titanium oxide, or a mixture of these oxides is used as the metal oxide.
  • the ion conductive layer 11 made of a metal oxide is formed using a sputtering method, a laser ablation method, or a plasma CVD method.
  • the ion conductive layer 11 is formed by sputtering using a sintered target.
  • the ion conductive layer 11 is formed without flowing oxygen into the sputtering chamber so that the oxygen content in the metal oxide is less than the stoichiometric amount.
  • the ion conductive layer 11 is made of a compound containing oxygen, for example, a SiOCH compound containing silicon, oxygen, carbon, and hydrogen is used as the compound containing oxygen.
  • the ion conductive layer 11 made of an oxygen-containing compound such as SiOCH is formed by plasma CVD. The cyclic organosiloxane raw material and the carrier gas helium flow into the reaction chamber, the supply of both is stabilized, and the application of RF power is started when the pressure in the reaction chamber becomes constant.
  • the ion conductive layer 11 is formed by flowing about 10 sccm of hydrogen into the chamber so that the composition ratio of oxygen in a compound containing oxygen such as SiOCH is less than the stoichiometric amount.
  • the supply amount of the raw material is 10 to 200 sccm
  • the supply of helium is 500 sccm via the raw material vaporizer
  • 500 sccm is directly supplied to the reaction chamber through a separate line.
  • the metal of the first electrode 21 becomes metal ions MI through the ion conductive layer interface 112 and dissolves in the ion conductive layer 11. Then, the metal ions MI in the ion conductive layer 11 including the ion conductive layer interface 112 are deposited on the surface of the second electrode 22 as metal bridge B, and the first electrode 21 and the second electrode are extended as the metal bridge B extends. The electrical resistance between the two is reduced. Furthermore, when the deposited metal bridge B sufficiently reaches the first electrode 21, the first electrode 21 and the second electrode 22 are electrically connected. When the first electrode 21 and the second electrode 22 are electrically connected by the metal bridge B, the switch is turned on.
  • the metal bridge B dissolves in the ion conductive layer 11 including the ion conductive layer interface 112 as metal ions MI.
  • the electrical resistance between the first electrode 21 and the second electrode 22 increases as part of the metal bridge B is cut and the metal bridge B is lost.
  • the metal ions MI are collected by the metal dispersed in the ion conductive layer 11 including the ion conductive layer interface 112 and the first electrode 21.
  • the metal bridge B is sufficiently lost, the electrical connection between the first electrode 21 and the second electrode 22 is cut, and the switch is turned off.
  • a positive voltage may be applied to the second electrode 22 again.
  • the first electrode 21 is grounded and a negative voltage is applied to the second electrode 22 to turn on the switch, or the first electrode 21 is grounded and a positive voltage is applied to the second electrode 22 to turn off the switch. Or may be in a state.
  • the switch is turned off, the electrical characteristics such as the resistance between the first electrode 21 and the second electrode 22 increases and the capacitance between the electrodes changes from the stage before the electrical connection is completely cut off. There is a change and eventually the electrical connection is broken.
  • This manufacturing method is a case where the ion conductive layer 11 is made of a metal oxide.
  • a second electrode 22 is formed by depositing 5 nm thick titanium nitride on the surface of the low resistance silicon substrate S and 40 nm ruthenium thereon by sputtering. To do.
  • a tantalum oxide thin film having a thickness of 5 nm is formed by sputtering as the ion conductive layer 11 made of a metal oxide.
  • the composition of oxygen in the formed tantalum oxide is set to be less than the stoichiometric amount. Specifically, when performing sputtering, oxygen that is normally supplied is not supplied.
  • the inventors of the present invention formed a tantalum oxide film under the film formation conditions with an argon flow rate of 40 sccm without an oxygen flow rate, and obtained tantalum oxide having an oxygen ratio to tantalum of 96% of the stoichiometry.
  • Step 3 copper having a thickness of 80 nm is deposited on the ion conductive layer 11 made of tantalum oxide by a vacuum evaporation method or a sputtering method. At this time, copper is deposited through a shadow mask made of stainless steel or silicon to form a square first electrode 21 having a planar shape of 30 ⁇ m to 150 ⁇ m on a side.
  • FIG. 5 is a diagram showing the time from off to on with respect to the applied voltage for two types of switching elements having an ion conductive layer made of tantalum oxide as a characteristic verification of the switching element according to the first embodiment.
  • the measurement for verification was performed by applying a constant voltage in the positive direction to Cu of the first electrode 21 and measuring the time from off to on. At this time, titanium nitride and ruthenium of the second electrode 22 were grounded through the low resistance silicon substrate S.
  • One of the two types is manufactured by introducing oxygen at a flow rate of 10 sccm when forming a tantalum oxide film, and the composition ratio of tantalum and oxygen constituting the tantalum oxide is equal to or higher than the stoichiometric amount ( Comparative example).
  • the other is manufactured without introducing oxygen at the time of tantalum oxide film formation, and the oxygen content in tantalum oxide is low, and the composition ratio of oxygen is less than stoichiometric (Example 1). As apparent from FIG.
  • the switching element has a long transition time from off to on when the same voltage is applied. That is, it can be seen that when the oxygen composition ratio at the interface portion of the ion conductive layer is less than the stoichiometric amount, it is difficult to make the transition from off to on and the disturbance characteristics are excellent.
  • the oxygen composition ratio is less than the stoichiometric amount only in the interface portion of the ion conductive layer, which is a part including at least the interface with the first electrode. Is different from the first embodiment. For this reason, detailed description of the same or similar parts as those in the first embodiment is omitted.
  • the composition ratio of oxygen at the interface portion of the ion conductive layer, which is a part including at least the interface with the first electrode of the ion conductive layer, rather than the entire ion conductive layer may be less than the stoichiometric amount. .
  • the ion conductive layer is made of metal oxide
  • about 10 sccm of oxygen is flowed to form the main part of the ion conductive layer so that the composition of oxygen satisfies the stoichiometry, and then oxygen is put into the chamber.
  • the interface portion of the ion conductive layer of the ion conductive layer is formed without introducing.
  • it is desirable that the ion conductive layer interface has a film thickness of one third or less of the ion conductive layer.
  • the ion conductive layer when the ion conductive layer is made of a compound containing oxygen, the ion conductive layer interface which is a part including at least the interface with the first electrode 21 in the ion conductive layer, similarly to the ion conductive layer made of metal oxide.
  • the composition ratio of oxygen in the part may be less than the stoichiometric amount.
  • the main part of the ion conductive layer is formed so that the oxygen composition of the film satisfies the stoichiometry without hydrogen flowing in immediately after the start of film formation, and then hydrogen is flowed into the chamber. Then, an ion conductive layer interface portion of the ion conductive layer is formed.
  • the interface portion of the ion conductive layer is preferably 1/3 or less of the thickness of the ion conductive layer, but it is preferably 0.5 nm or more that can be stably formed by sputtering, laser ablation, or CVD.
  • the switching element according to the second embodiment of the present invention is in the form of a two-terminal switching element.
  • the switching element includes a first electrode 21, an ion conductive layer 11 in contact with the first electrode 21, and a second electrode 22 provided via the first electrode 21 and the ion conductive layer 11.
  • reference numeral 112 denotes an ion conductive layer interface 112 that is a part of the ion conductive layer 11 including the interface with the first electrode 21.
  • the composition ratio of oxygen is such that the ion conduction layer interface portion 112 (the oxygen composition ratio is less than the stoichiometric amount) in the ion conduction layer 11 and the remainder of the ion conduction layer 11 (the composition ratio of oxygen). Is more than the stoichiometric amount).
  • the ion conductive layer 11 is made of a metal oxide.
  • the second electrode 22 is formed by depositing 5 nm of titanium nitride on the surface of the low-resistance silicon substrate S and 40 nm of ruthenium on the surface by sputtering. To do.
  • a tantalum oxide thin film having a thickness of 8 nm is formed by sputtering as the ion conductive layer main part 111 made of a metal oxide.
  • the composition of oxygen in the formed tantalum oxide is set to a stoichiometric amount or more. Specifically, oxygen is supplied into the chamber when performing sputtering.
  • the inventors of the present invention formed tantalum oxide under film formation conditions with an oxygen flow rate of 10 sccm and an argon flow rate of 40 sccm, and obtained tantalum oxide in which the oxygen ratio to tantalum was a stoichiometric amount or more.
  • a tantalum oxide thin film having a thickness of 2 nm is formed by sputtering as the ion conductive layer interface 112.
  • the composition of oxygen in the formed tantalum oxide is set to be less than the stoichiometric amount. Specifically, oxygen that is normally supplied is not supplied when sputtering is performed.
  • the inventors of the present invention formed a tantalum oxide film under the film formation conditions with an argon flow rate of 40 sccm without an oxygen flow rate, and obtained tantalum oxide having an oxygen ratio to tantalum of 96% of the stoichiometry.
  • Step 4 As shown in FIG. 6 (d), copper having a film thickness of 80 nm is deposited on the ion conductive layer interface 112 by vacuum evaporation or sputtering. At this time, copper is deposited through a shadow mask made of stainless steel or silicon to form a square first electrode 21 having a planar shape of 30 ⁇ m to 150 ⁇ m on a side.
  • the switching element according to Example 3 of the present invention includes a main ion conductive layer and an interface ion conductive layer in which the ion conductive layers are stacked on each other, and the oxygen composition ratio of the interface ion conductive layer including the interface with the first electrode is chemical.
  • the difference from Example 2 is that the amount is less than the stoichiometric amount. For this reason, detailed description of the same or similar parts as in the second embodiment will be omitted.
  • the switching element according to the third embodiment of the present invention is in the form of a two-terminal switching element.
  • the switching element includes a first electrode 21 and a second electrode 22 which are arranged to face each other at a distance, and an interfacial ion conductive layer 52 and a main ion conductive layer 51 sandwiched between both electrodes.
  • the interfacial ion conductive layer 52 is in contact with the first electrode 21 (including the interface with the first electrode).
  • the first electrode 21 is made of copper for supplying metal ions into the interface ion conductive layer 52 and the main ion conductive layer 51 when a voltage is applied.
  • the first electrode 21 is formed by sputtering, chemical vapor deposition (CVD), electroplating. Formed by law.
  • the material of the second electrode 22 is preferably a material that does not supply metal ions into the main ion conduction layer 51 and the interface ion conduction layer 52 when a voltage is applied. More specifically, the second electrode 22 is preferably made of ruthenium, platinum, or nickel. In particular, it is preferably made of ruthenium.
  • the main ion conduction layer 51 and the interface ion conduction layer 52 serve as a medium for conducting metal ions.
  • Interfacial ion conductive layer 52 is formed of a metal oxide. First, a metal constituting an oxide is formed on the first electrode 21, and is oxidized by oxygen existing in the chamber during the formation of the main ion conductive layer 51 containing oxygen as described later.
  • the interfacial ion conductive layer 52 made of a metal oxide is obtained.
  • the metal material of the interfacial ion conductive layer 52 made of a metal oxide is preferably a metal that is difficult to oxidize, that is, a metal having a small standard Gibbs energy absolute value. This is because a standard Gibbs energy having a small absolute value and a metal that is difficult to oxidize is not sufficiently oxidized even by oxygen present in the chamber during the formation of the main ion conductive layer 51, and therefore, an interface ion made of a metal oxide. This is because the oxygen composition ratio of the conductive layer 52 is less than the stoichiometric amount.
  • a metal having a standard Gibbs energy greater than ⁇ 600 kJ / mol at 300 K has obtained good results as a metal material for an interfacial ion conductive layer made of a metal oxide.
  • the composition ratio of oxygen could be made less than the stoichiometric amount even when the thickness of the interface ion conductive layer was greater than 5 nm.
  • the metal material of the interfacial ion conductive layer that satisfies this condition include nickel, cobalt, iron, ruthenium, iridium, or a mixture of these metals. Therefore, the interfacial ion conductive layer 52 is made of nickel oxide, cobalt oxide, iron oxide, ruthenium oxide, iridium oxide, or a mixture of these metals.
  • the interfacial ion conductive layer made of a metal oxide is formed by sputtering, laser ablation, or plasma CVD.
  • the interfacial ion conduction layer 52 is desirably 50% or less of the film thickness of the main ion conduction layer 51, but is desirably 0.5 nm or more that can be stably formed by sputtering, laser ablation, or CVD. .
  • the main ion conductive layer 51 is made of a metal oxide or a compound containing oxygen.
  • the main ion conductive layer 51 made of a metal oxide is formed using a sputtering method, a laser ablation method, or a plasma CVD method. In order to form the main ion conductive layer 51 made of metal oxide, sputtering is performed using a sintered target.
  • the main ion conductive layer 51 made of a metal oxide is preferably tantalum oxide, zirconium oxide, aluminum oxide, titanium oxide, or a mixture of these oxides.
  • the main ion conductive layer 51 made of a compound containing oxygen is, for example, a SiOCH system containing silicon, oxygen, carbon, and hydrogen, and is formed by plasma CVD.
  • the cyclic organosiloxane raw material and the carrier gas helium flow into the reaction chamber, the supply of both is stabilized, and the application of RF power is started when the pressure in the reaction chamber becomes constant.
  • the supply amount of the raw material is 10 to 200 sccm
  • the supply of helium is 500 sccm via the raw material vaporizer
  • 500 sccm is directly supplied to the reaction chamber through a separate line.
  • the metal of the first electrode 21 becomes metal ions MI via the interface ion conductive layer 52 and dissolves in the main ion conductive layer 51. Then, the metal ions MI in the interface ion conductive layer 52 and the main ion conductive layer 51 are deposited on the surface of the second electrode 22 as metal bridges B, and the first electrode 21 and the second electrode 22 are extended as the metal bridge B extends. The electrical resistance between the two becomes smaller. Furthermore, when the deposited metal bridge B sufficiently reaches the first electrode 21, the first electrode 21 and the second electrode 22 are electrically connected. When the first electrode 21 and the second electrode 22 are electrically connected by the metal bridge B, the switch is turned on.
  • the metal bridge B dissolves in the interface ion conductive layer 52 and the main ion conductive layer 51 as metal ions MI.
  • the electrical resistance between the first electrode 21 and the second electrode 22 increases as a part of the metal bridge B is cut and the metal bridge B is lost.
  • the metal ions MI are collected by the metal dispersed in the interfacial ion conductive layer 52 and the main ion conductive layer 51 and the first electrode 21.
  • the metal bridge B is sufficiently lost, the electrical connection between the first electrode 21 and the second electrode 22 is cut, and the switch is turned off.
  • a positive voltage may be applied to the second electrode 22 again.
  • the first electrode 21 is grounded and a negative voltage is applied to the second electrode 22 to turn on the switch, or the first electrode 21 is grounded and a positive voltage is applied to the second electrode 22 to turn off the switch. Or may be in a state.
  • the switch is turned off, the electrical characteristics such as the resistance between the first electrode 21 and the second electrode 22 increases and the capacitance between the electrodes changes from the stage before the electrical connection is completely cut off. There is a change and eventually the electrical connection is broken.
  • a 20-nm-thick tantalum film is formed on the surface of a low-resistance silicon substrate S, and a 100-nm copper film is formed thereon by sputtering to form a first electrode 21.
  • a metal layer 50 is formed by sputtering nickel or iron with a layer thickness of 2 nm.
  • a mixed thin film of tantalum oxide and silicon oxide having a thickness of 8 nm is formed as the main ion conductive layer 51 made of a compound containing oxygen.
  • a sintered target containing 74% tantalum oxide and 24% silicon oxide was used.
  • the main ion conductive layer 51 is deposited by sputtering.
  • the composition of the formed mixture of tantalum oxide and silicon oxide is set to a stoichiometric amount or more.
  • the amount of oxygen to be supplied is optimized when performing sputtering.
  • the inventors of the present invention formed a film under conditions of flowing a mixed gas having an oxygen flow rate of 10 sccm and an argon flow rate of 40 sccm to obtain tantalum oxide having a stoichiometric amount or more.
  • the metal layer 50 is oxidized by being exposed to oxygen at the time of forming the main ion conductive layer 51 to become an interface ion conductive layer 52 made of nickel oxide or iron oxide.
  • the composition of oxygen in the interfacial ion conductive layer 52 is less than the stoichiometric amount.
  • Step 4 As shown in FIG. 9D, ruthenium having a film thickness of 30 nm is deposited on the main ion conductive layer 51 by vacuum vapor deposition or sputtering. At this time, ruthenium is deposited through a shadow mask made of stainless steel or silicon to form a square second electrode 22 having a planar shape with sides of 30 ⁇ m to 150 ⁇ m.
  • Example 10 is a graph showing characteristics of the switching element according to Example 3, in which four types of switching elements having an interface ion conductive layer having different compositions and one type of switching element having no interface ion conductive layer are turned off from an applied electric field. It is the figure which showed the time until ON.
  • the breakdown of the former four types includes two types of switching elements (Example 3) having an interface ion conductive layer 52 made of iron oxide and nickel oxide, and two types having an interface ion conductive layer made of titanium oxide and tungsten oxide, respectively.
  • Switching element (comparative example).
  • a switching element having only the main ion conductive layer without the one type of interfacial ion conductive layer is also a comparative example.
  • the switching element using nickel oxide and iron oxide according to the present invention for the interfacial ion conductive layer 52 has only the main ion conductive layer and does not have the interfacial ion conductive layer. Thus, the transition time from OFF to ON when the same electric field is applied is long. That is, it has excellent disturb characteristics.
  • the switching element of the comparative example using titanium oxide and tungsten oxide for the interfacial ion conductive layer is more in comparison with the switching element of the present invention, and compared with the switching element of the comparative example having only the main ion conductive layer, The transition time from OFF to ON when the same electric field is applied is short. That is, the disturb characteristic is inferior.
  • the photoelectron spectroscopy (XPS) measurement result of the interface ion conductive layer in two types of switching elements is shown in FIGS. Referring to FIGS. 11 (a) and 11 (b), as shown in FIG.
  • the titanium oxide used in the switching element (comparative example) having a short transition time from OFF to ON (inferior to disturb characteristics) (FIG. 11 ( In b)), a peak derived from an oxide is observed, and it can be seen that it has been sufficiently oxidized.
  • the nickel oxide (FIG. 11 (a)) used for the switching element (Example 3) having a long transition time from off to on (excellent in disturb characteristics) is a peak derived from nickel in a metal state instead of an oxide. was mainly confirmed.
  • the oxygen composition ratio becomes less than the stoichiometric amount, and the metallic part remains. I can say that. This is because the absolute value of the standard Gibbs energy of nickel and iron is small.
  • the interface ion conductive layer 52 has an oxygen composition ratio less than the stoichiometric amount, oxygen ions are not sufficiently supplied to the copper of the first electrode 21, and copper ionization is difficult to proceed.
  • the switching element of the present invention takes a long time from off to on. That is, it has excellent disturb characteristics.
  • a semiconductor device according to Example 4 of the present invention is a semiconductor device having a switching element corresponding to the two-terminal switching element of Example 3 in a multilayer wiring layer.
  • the semiconductor device according to the fourth embodiment of the present invention has a switching element 140 inside a multilayer wiring layer on a semiconductor substrate 161.
  • the multilayer wiring layer is formed on the semiconductor substrate 161 by an interlayer insulating film 162, a barrier insulating film 163, an interlayer insulating film 164, a barrier insulating 166, a protective insulating film 167, an interlayer insulating film 168, an etching stopper film ES, and an interlayer insulating film 170.
  • the barrier insulating film 173 in this order.
  • a first wiring 121 is embedded in a wiring groove formed in the interlayer insulating film 164 and the barrier insulating film 163 via a barrier metal 165.
  • a second wiring 172 is embedded in the wiring trench formed in the interlayer insulating film 170 and the etching stopper film ES.
  • plugs 171 are embedded in pilot holes formed in the interlayer insulating film 168, the protective insulating film 167, and the hard mask film HM2. Further, the second wiring 172 and the plug 171 are integrated, and the integrated second wiring 172 and the plug 171 are covered with a barrier metal 169 from the side surface to the bottom surface.
  • the antioxidant film 152, the ion conductive film 151, the second electrode A layer 122a and a second electrode second layer 122b are formed on the first wiring 121 facing the opening formed in the barrier insulating film 166 and the inner wall surface of the opening of the barrier insulating film 166 or on the barrier insulating film 166.
  • a hard mask film HM2 is formed on the second electrode second layer 122b. Further, the top surface or the side surface of the stacked body of the antioxidant film 152, the ion conductive film 151, the second electrode first layer 122a, the second electrode second layer 122b, and the hard mask film HM2 is covered with the protective insulating film 167. Yes.
  • the switching element 140 includes a first wiring 121 as a first electrode, an antioxidant film 152 as an interface ion conductive layer, an ion conductive film 151 as a main ion conductive layer, and a second electrode.
  • the two-electrode first layer 122a and the second electrode second layer 122b are configured.
  • the stacked antioxidant film 152 and ion conductive film 151 are referred to as a resistance change layer 150.
  • the antioxidant film 152 and the first wiring 121 are in direct contact with each other in the region of the opening formed in the barrier insulating film 166, and the ion conductive film 151 and the second electrode first layer 122a are in direct contact.
  • the plug 171 and the second electrode second layer 122b are electrically connected via the barrier metal 169 on the second electrode second layer 122b.
  • the switching element 140 performs on / off control by applying a voltage or passing a current, and uses, for example, electric field diffusion of a metal related to the first wiring 121 into the antioxidant film 152 and the ion conductive film 151.
  • the semiconductor substrate 161 is a substrate on which a semiconductor element is formed.
  • a substrate such as a silicon substrate, a single crystal substrate, an SOI (Silicon on Insulator) substrate, a TFT (Thin Film Transistor) substrate, a liquid crystal manufacturing substrate, or the like can be used.
  • the interlayer insulating film 162 is an insulating film formed on the semiconductor substrate 161.
  • the interlayer insulating film 162 for example, a silicon oxide film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of the silicon oxide film, or the like can be used.
  • the interlayer insulating film 162 may be a stack of a plurality of insulating films.
  • the barrier insulating film 163 is an insulating film having a barrier property interposed between the interlayer insulating films 162 and 164.
  • the barrier insulating film 163 serves as an etching stop layer when processing the wiring groove for the first wiring 121.
  • a silicon nitride film, a SiC film, a SiCN film, or the like can be used for example.
  • a wiring trench for embedding the first wiring 121 is formed in the barrier insulating film 163, and the first wiring 121 is buried in the wiring trench via the barrier metal 165.
  • the barrier insulating film 163 can be removed depending on the selection of the etching conditions for the wiring trench.
  • the interlayer insulating film 164 is an insulating film formed on the barrier insulating film 163.
  • a silicon oxide film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of the silicon oxide film, or the like can be used.
  • the interlayer insulating film 164 may be a stack of a plurality of insulating films.
  • a wiring trench for embedding the first wiring 121 is formed in the interlayer insulating film 164, and the first wiring 121 is buried in the wiring trench via a barrier metal 165.
  • the first wiring 121 as the first electrode of the switching element 140 is a wiring buried in a wiring groove formed in the interlayer insulating film 164 and the barrier insulating film 163 via the barrier metal 165.
  • a metal that can be diffused and ion-conducted in the resistance change layer 150 is used for the first wiring 121.
  • copper or the like can be used.
  • the first wiring 121 may be alloyed with aluminum.
  • the barrier metal 165 is a conductive film having a barrier property that covers the side surface or the bottom surface of the first wiring 121 in order to prevent the metal related to the first wiring 121 from diffusing into the interlayer insulating film 164 and the lower layer.
  • a refractory metal such as tantalum, tantalum nitride, titanium nitride, tungsten carbonitride, a nitride thereof, or the like, Alternatively, a stacked film of them can be used.
  • the barrier insulating film 166 is formed on the interlayer insulating film 164 including the first wiring 121, prevents oxidation of a metal (for example, copper) related to the first wiring 121, and the first wiring 121 into the interlayer insulating film 168. This prevents the metal from diffusing and serves as an etching stop layer when the second electrodes 121 and 120 and the resistance change layer 150 are processed.
  • a metal for example, copper
  • the barrier insulating film 166 for example, a SiC film, a SiCN film, a silicon nitride film, a stacked structure thereof, or the like can be used.
  • the barrier insulating film 166 is preferably made of the same material as the protective insulating film 167 and the hard mask film HM2.
  • the resistance change layer 150 constituted by the stacked antioxidant film 152 and ion conductive film 151 is a film in which the resistance in the switching element 140 changes. Therefore, a material whose resistance is changed by the action (diffusion, ion conduction, etc.) of the metal related to the first wiring 121 (first electrode) is used.
  • a film capable of ion conduction is used.
  • the ion conductive film 151 as the main ion conductive layer in the switching element 140 is formed using a sputtering method, a laser ablation method, or a plasma CVD method.
  • the ion conductive film 151 is formed of a metal oxide
  • sputtering is performed using a sintered target. At this time, 10 sccm of oxygen is introduced into the sputtering chamber so that the stoichiometry of the deposited metal oxide is not impaired.
  • the ion conductive film 151 made of a metal oxide, tantalum oxide, zirconium oxide, aluminum oxide, titanium oxide, and a mixture thereof are preferable.
  • the ion conductive film 151 is formed of a SiOCH compound, it is formed by plasma CVD.
  • the cyclic organosiloxane raw material and the carrier gas helium flow into the reaction chamber, the supply of both is stabilized, and the application of RF power is started when the pressure in the reaction chamber becomes constant.
  • the supply amount of the raw material is 10 to 200 sccm
  • the supply of helium is 500 sccm via the raw material vaporizer
  • 500 sccm is directly supplied to the reaction chamber through a separate line.
  • the anti-oxidation film 152 as the interface ion conductive layer in the switching element 140 is such that the metal related to the first wiring 121 diffuses into the ion conductive film 151 by heating or plasma while the ion conductive film 151 is being deposited.
  • the role of preventing and the ionization of the metal related to the first wiring 121 from the first wiring 121 as the antioxidant film and the injection of metal ions into the antioxidant film 152 and the ion conductive film 151 are controlled.
  • the metal of the antioxidant film 152 such as nickel, cobalt, iron, ruthenium, and iridium, becomes nickel oxide, cobalt oxide, iron oxide, ruthenium oxide, and iridium during the formation of the ion conductive film 151.
  • the resistance change layer 150 is formed on the first wiring 121, the tapered surface of the opening of the barrier insulating film 166, or the barrier insulating film 166.
  • the outer peripheral portion of the connection portion between the first wiring 121 and the resistance change layer 150 is disposed along at least the tapered surface of the opening of the barrier insulating film 166.
  • the second electrode first layer 122 a as a part of the second electrode in the switching element 140 is an electrode on the lower layer side of the second electrode of the switching element 140, and is in direct contact with the ion conductive film 151.
  • a metal that is less ionized than the metal related to the first wiring 121 and is difficult to diffuse or ion-conduct in the ion conductive film 151 is used.
  • platinum, ruthenium, nickel, or the like is used. Can do.
  • the second electrode second layer 122b as a part of the second electrode in the switching element 140 is an upper layer side electrode in the second electrode of the switching element 140, and is formed on the second electrode first layer 122a. Yes.
  • the second electrode second layer 122b has a role of protecting the second electrode first layer 122a. That is, the second electrode second layer 122b protects the second electrode first layer 122a, thereby suppressing damage to the second electrode first layer 122a during the process and maintaining the switching characteristics of the switching element 140. Can do.
  • tantalum, titanium, tungsten, or a nitride thereof can be used for the second electrode second layer 122b.
  • the hard mask film HM2 is a film that serves as a hard mask film and a passivation film when the second electrode second layer 122b, the second electrode first layer 122a, the ion conductive film 151, and the antioxidant film 152 are etched.
  • a SiN film or the like can be used for the hard mask film HM2.
  • the hard mask film HM2 is preferably made of the same material as the protective insulating film 167 and the barrier insulating film 166. That is, by surrounding the entire periphery of the switching element 140 with the same material, the interface portion of the material is integrated, so that it is possible to prevent moisture and the like from entering from the outside and to prevent detachment from the switching element 140 itself. .
  • the protective insulating film 167 is an insulating film having a function of preventing the detachment of oxygen from the ion conductive film 151 without damaging the switching element 140.
  • As the protective insulating film 167 for example, a silicon nitride film, a SiCN film, or the like can be used.
  • the protective insulating film 167 is preferably made of the same material as the hard mask film HM2 and the barrier insulating film 166. In the case of the same material, the protective insulating film 167, the barrier insulating film 166, and the hard mask film HM2 are integrated to improve the adhesion at the interface, and the switching element 140 can be further protected. .
  • the interlayer insulating film 168 is an insulating film formed on the protective insulating film 167.
  • the interlayer insulating film 168 for example, a silicon oxide film, a SiOC film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of the silicon oxide film can be used.
  • the interlayer insulating film 168 may be a stack of a plurality of insulating films.
  • the interlayer insulating film 168 may be made of the same material as the interlayer insulating film 170.
  • a pilot hole for embedding the plug 171 is formed in the interlayer insulating film 168, and the plug 171 is embedded in the pilot hole via a barrier metal 169.
  • the etching stopper film ES is an insulating film interposed between the interlayer insulating films 168 and 170.
  • the etching stopper film ES serves as an etching stop layer when the wiring groove for the second wiring 172 is processed.
  • a SiN film, a SiC film, a SiCN film, or the like can be used for the etching stopper film ES.
  • a wiring trench for embedding the second wiring 172 is formed in the etching stopper film ES, and the second wiring 172 is buried in the wiring trench via a barrier metal 169.
  • the etching stopper film ES can be deleted depending on the selection of the etching conditions for the wiring trench.
  • the interlayer insulating film 170 is an insulating film formed on the etching stopper film ES.
  • the interlayer insulating film 170 for example, a silicon oxide film, a SiOC film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of the silicon oxide film can be used.
  • the interlayer insulating film 170 may be a stack of a plurality of insulating films.
  • the interlayer insulating film 170 may be made of the same material as the interlayer insulating film 15.
  • a wiring groove for embedding the second wiring 172 is formed, and the second wiring 172 is embedded in the wiring groove via a barrier metal 169.
  • the second wiring 172 is a wiring embedded in a wiring groove formed in the interlayer insulating film 170 and the etching stopper film ES via a barrier metal 169.
  • the second wiring 172 is integrated with the plug 171.
  • the plug 171 is buried in a prepared hole formed in the interlayer insulating film 168, the protective insulating film 167, and the hard mask film HM2 via a barrier metal 169.
  • the plug 171 is electrically connected to the second electrode second layer 122b through the barrier metal 169.
  • Cu can be used for the second wiring 172 and the plug 171.
  • the barrier metal 169 covers the side surfaces or bottom surfaces of the second wiring 172 and the plug 171 in order to prevent the metal related to the second wiring 172 (including the plug 171) from diffusing into the interlayer insulating films 168 and 170 and the lower layer. It is a conductive film having a barrier property.
  • the barrier metal 110 includes a refractory metal such as tantalum, tantalum nitride, titanium nitride, tungsten carbonitride, or nitride thereof. A thing etc. or those laminated films can be used.
  • the barrier metal 169 is preferably made of the same material as the second electrode second layer 122b.
  • the barrier metal 169 has a stacked structure of TaN (lower layer) / Ta (upper layer), it is preferable to use TaN as the lower layer material for the second electrode second layer 122b.
  • the barrier metal 110 is Ti (lower layer) / Ru (upper layer)
  • the barrier insulating film 173 is formed on the interlayer insulating film 170 including the second wiring 172, prevents oxidation of the metal (for example, copper) related to the second wiring 172, and prevents the metal related to the second wiring 172 to the upper layer. It is an insulating film having a role of preventing diffusion.
  • the barrier insulating film 173 for example, a SiC film, a SiCN film, a SiN film, and a stacked structure thereof can be used.
  • a semiconductor device manufacturing method according to the fourth embodiment will be described with reference to FIGS. 13 (a) to (f) and FIGS. 14 (a) to (f). [Step 1] As shown in FIG.
  • an interlayer insulating film 162 (for example, a silicon oxide film, a film thickness of 300 nm) is deposited on a semiconductor substrate 161 (for example, a substrate on which a semiconductor element is formed), Thereafter, a barrier insulating film 163 (for example, a silicon nitride film, a film thickness of 50 nm) is deposited on the interlayer insulating film 162, and then an interlayer insulating film 164 (for example, a silicon oxide film, a film thickness of 300 nm) is formed on the barrier insulating film 163.
  • a barrier insulating film 163 for example, a silicon nitride film, a film thickness of 50 nm
  • an interlayer insulating film 164 for example, a silicon oxide film, a film thickness of 300 nm
  • wiring grooves are formed in the interlayer insulating film 164 and the barrier insulating film 163 by using a lithography method (including photoresist formation, dry etching, and photoresist removal). Thereafter, a first wiring 121 (for example, copper) as a first electrode is embedded in the wiring groove via a barrier metal 165 (for example, tantalum nitride / tantalum, film thickness 5 nm / 5 nm).
  • the interlayer insulating films 162 and 164 can be formed by a plasma CVD method.
  • the first wiring 121 is formed, for example, by forming a barrier metal 165 (for example, a tantalum nitride / tantalum laminated film) by the PVD method, and after forming a Cu seed by the PVD method, copper is embedded in the wiring groove by the electrolytic plating method. After the heat treatment at a temperature of 200 ° C. or higher, it can be formed by removing excess copper other than in the wiring trench by CMP. As a method for forming such a series of copper wirings, a general method in this technical field can be used.
  • a barrier metal 165 for example, a tantalum nitride / tantalum laminated film
  • the CMP (Chemical Mechanical Polishing) method is to flatten the unevenness of the wafer surface that occurs during the multilayer wiring formation process by bringing the polishing liquid into contact with a rotating polishing pad while flowing the polishing liquid over the wafer surface and polishing it. Is the method. By polishing excess copper embedded in the trench, a buried wiring (damascene wiring) is formed, or planarization is performed by polishing an interlayer insulating film.
  • a barrier insulating film 166 for example, a silicon nitride film, a film thickness of 50 nm
  • the interlayer insulating film 164 including the first wiring 121.
  • the barrier insulating film 166 can be formed by a plasma CVD method.
  • the thickness of the barrier insulating film 166 is preferably about 10 to 50 nm.
  • a hard mask film HM1 (for example, a silicon oxide film) is formed on the barrier insulating film 166.
  • the hard mask film HM1 is preferably made of a material different from the barrier insulating film 166 from the viewpoint of maintaining a high etching selectivity in the dry etching process, and may be an insulating film or a conductive film.
  • the hard mask film HM1 for example, a silicon oxide film, a silicon nitride film, titanium nitride, titanium, tantalum, tantalum nitride, or the like can be used, and a silicon nitride / silicon oxide film stack can be used.
  • the opening is patterned on the hard mask film HM1 using a photoresist (not shown), and the hard mask film is formed by dry etching using the photoresist as a mask. An opening pattern is formed in HM1, and then the photoresist is peeled off by oxygen plasma ashing or the like.
  • the dry etching is not necessarily stopped on the upper surface of the barrier insulating film 166, and may reach the inside of the barrier insulating film 166.
  • the barrier insulating film 166 exposed from the opening of the hard mask film HM1 is etched back (dry etching), thereby barrier insulation.
  • An opening is formed in the film 166 to expose the first wiring 121 from the opening of the barrier insulating film 166, and then an organic stripping process is performed with an amine-based stripping solution or the like, thereby exposing the exposed surface of the first wiring 121.
  • the etching by-product generated during the etch-back is removed.
  • the inner wall surface of the opening of the barrier insulating film 166 can be tapered by using reactive dry etching.
  • reactive dry etching a gas containing fluorocarbon can be used as an etching gas.
  • the hard mask film HM1 is preferably completely removed during the etch back, but may remain as it is when it is an insulating material.
  • the shape of the opening in the barrier insulating film 166 can be a circle, and the diameter of the circle can be 30 nm to 500 nm.
  • the oxide on the surface of the first wiring 121 is removed by RF (Radio Frequency) using a non-reactive gas.
  • a non-reactive gas helium or argon can be used.
  • iron for example, 1 nm in thickness
  • Iron can be formed using a PVD method or a CVD method.
  • a SiOCH polymer film containing silicon, oxygen, carbon, and hydrogen is formed by plasma CVD.
  • the cyclic organosiloxane raw material and the carrier gas helium flow into the reaction chamber, the supply of both is stabilized, and the application of RF power is started when the pressure in the reaction chamber becomes constant.
  • the supply amount of the raw material is 10 to 200 sccm
  • the supply of helium is 500 sccm via the raw material vaporizer
  • 500 sccm is directly supplied to the reaction chamber through a separate line.
  • Iron is oxidized automatically by being exposed to the raw material of the SiOCH-based polymer film containing oxygen during the formation of the ion conductive film 151, and becomes iron oxide, thereby becoming an antioxidant film 152 as an interface ion conductive layer. It becomes a part of the resistance change layer 150.
  • Step 7 As shown in FIG. 14A, on the resistance change layer 150, the second electrode first layer 122a (for example, ruthenium, film thickness 10 nm) as a part of the second electrode, A second electrode second layer 122b (for example, tantalum, film thickness 50 nm) as a part of the two electrodes is formed in this order.
  • the second electrode first layer 122a for example, ruthenium, film thickness 10 nm
  • a second electrode second layer 122b for example, tantalum, film thickness 50 nm
  • a hard mask film HM2 for example, a SiN film, a film thickness of 30 nm
  • a hard mask film HM3 for example, a SiO2 film, The film thickness is 150 nm.
  • the hard mask film HM2 and the hard mask film HM3 can be formed using a plasma CVD method.
  • the hard mask film HM2 and the hard mask film HM3 are preferably different types of films.
  • the hard mask film HM2 can be a SiN film and the hard mask film HM3 can be a SiO2 film.
  • the hard mask film HM2 is preferably made of the same material as a protective insulating film 167 and a barrier insulating film 166 described later. That is, the entire periphery of the switching element is surrounded by the same material, so that the material interface can be integrated to prevent intrusion of moisture and the like from the outside and to prevent detachment from the switching element itself.
  • the hard mask film HM2 can be formed by a plasma CVD method. For example, it is preferable to use a high-density SiN film or the like by using a high-density plasma with a mixed gas of SiH4 / N2. [Step 9] As shown in FIG.
  • a photoresist (not shown) for patterning the two-terminal switching element portion is formed on the hard mask film HM3, and then the photoresist is used as a mask.
  • the hard mask film HM3 is dry-etched until the hard mask film HM2 appears, and then the photoresist is removed using oxygen plasma ashing and organic peeling.
  • the hard mask film HM2, the second electrode second layer 122b, the second electrode first layer 122a, and the ion conductive film 151 are continuously formed using the hard mask film HM3 as a mask. Dry etching. At this time, the hard mask film HM3 is preferably completely removed during the etch back, but may remain as it is.
  • the second electrode second layer 122b when the second electrode second layer 122b is Ta, it can be processed by Cl2-based RIE, and when the second electrode first layer 122a is Ru, RIE processing is performed with a mixed gas of Cl2 / O2. Can do.
  • RIE processing is performed with a mixed gas of Cl2 / O2.
  • the etching conditions are mixed with a mixed gas such as CF4, CF4 / Cl2, CF4 / Cl2 / Ar, or the like.
  • RIE processing can be performed by adjusting.
  • the switching element part can be processed without exposing the switching element part to oxygen plasma ashing for resist removal. Further, when the oxidation treatment is performed by oxygen plasma after the processing, the oxidation plasma treatment can be irradiated without depending on the resist peeling time.
  • protection is performed on the barrier insulating film 166 including the hard mask film HM2, the second electrode second layer 122b, the second electrode first layer 122a, and the ion conductive film 151.
  • An insulating film 167 (for example, a silicon nitride film, 30 nm) is deposited.
  • the protective insulating film 167 can be formed by a plasma CVD method, it is necessary to maintain a reduced pressure in the reaction chamber before film formation. At this time, oxygen is desorbed from the side surface of the resistance change layer 150 and ion conduction is performed. The problem arises that the leakage current of the layer increases. In order to suppress them, the deposition temperature of the protective insulating film 167 is preferably set to 250 ° C. or lower. Further, it is preferable not to use a reducing gas because the film is exposed to a film forming gas under reduced pressure before film formation.
  • an interlayer insulating film 168 for example, silicon oxide film
  • an etching stopper film ES for example, silicon nitride film
  • an interlayer insulating film 170 are formed on the protective insulating film 167.
  • a silicon oxide film is deposited in this order, and then a wiring groove for the second wiring 172 and a pilot hole for the plug 171 are formed, and the wiring groove and the lower wiring are formed using a copper dual damascene wiring process.
  • a second wiring 172 (for example, copper) and a plug 171 (for example, copper) are simultaneously formed in the hole via a barrier metal 169 (for example, tantalum nitride / tantalum), and then the interlayer insulating film 170 including the second wiring 172 is formed.
  • a barrier insulating film 173 (for example, a silicon nitride film) is deposited thereon.
  • the formation of the second wiring 172 can use the same process as the formation of the lower layer wiring.
  • the barrier metal 169 and the second electrode second layer 122b the same material, the contact resistance between the plug 171 and the second electrode second layer 122b can be reduced, and the device performance can be improved. Become.
  • the interlayer insulating film 168 and the interlayer insulating film 170 can be formed by a plasma CVD method.
  • the interlayer insulating film 168 may be deposited thick, and the interlayer insulating film 168 may be cut and planarized by CMP, so that the interlayer insulating film 168 has a desired thickness.
  • Electrons are received from the second electrode and deposited as a metal, and the deposited metal grows to change a resistance value between the first electrode and the second electrode, and the ion conductive layer is formed by the first electrode.
  • An ion conductive layer interface including the interface between the ion conductive layer and the remaining ion conductive layer main part, wherein the ion conductive layer main part is made of a metal oxide or a compound containing oxygen, and the ion conductive layer interface The part is made of a metal oxide or a compound containing oxygen, and the composition ratio of oxygen is less than the stoichiometric amount.
  • the said ion conductive layer main part consists of a compound containing a metal oxide or oxygen
  • the said ion conductive layer interface part consists of a compound containing a metal oxide or oxygen, and its layer thickness is 5 nm or less.
  • the said ion conductive layer main part consists of a compound containing a metal oxide or oxygen,
  • the said ion conductive layer main part consists of one of the compound containing a metal oxide and oxygen,
  • the main ion conductive layer is made of a compound containing oxygen and functions as the main part of the ion conductive layer.
  • the said ion conductive layer main part consists of a mixture containing 2 or more types of the said metal oxide or the said compound containing oxygen, and the said metal oxide is a tantalum oxide, an aluminum oxide, a zirconium oxide, or 6.
  • the oxygen-containing compound is a polymer containing at least silicon, oxygen, and carbon as main components, and has a relative dielectric constant of 2.1 to 3.0.
  • the said ion conductive layer interface part consists of a mixture containing 2 or more types of the said metal oxide, and the said metal oxide is nickel oxide, cobalt oxide, iron oxide, ruthenium oxide, or iridium oxide.
  • the switching element according to any one of appendices 1 to 7.
  • the said ion conductive layer interface part consists of a mixture containing 2 or more types of the said metal oxide,
  • the said metal oxide is a tantalum oxide, an aluminum oxide, or a titanium oxide.
  • the switching element according to any one of the above.
  • the switching element according to any one of supplementary notes 1 to 9, wherein the first electrode contains copper.
  • interval may be formed in the surface of the said 1st wiring.
  • iridium oxide which functions as the interfacial ion conductive layer of the switching element
  • the ion conductive film is a polycrystal having at least silicon, oxygen, and carbon as main components.
  • the dielectric constant is 2.1 or more and 3.0 or less and functions as the main ion conductive layer of the switching element
  • the plug is made of copper
  • the second electrode and the barrier of the switching element A semiconductor device connected through a metal, wherein the second electrode of the switching element is made of ruthenium.
  • a method for producing a switching element characterized in that it is formed as the interfacial ion conductive layer made of a metal oxide, and the composition of oxygen in the interfacial ion conductive layer is less than the stoichiometric amount.
  • oxygen and an inert gas are allowed to flow into the processing chamber, so that the oxygen composition of the ion conductive film is increased to a stoichiometric amount or more, while oxygen existing in the processing chamber is bathed in the metal layer.
  • the interface ion conductive layer made of the metal oxide of the switching element is formed, and the composition of oxygen in the interface ion conductive layer is made less than the stoichiometric amount.

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Abstract

The present invention has an ion-conducting layer (11), and a first electrode (21) and a second electrode (22) respectively formed on front and reverse surfaces of the ion-conducting layer (11). The first electrode (21) is formed from a metal that is capable of feeding metal ions to the ion-conducting layer (11), while the second electrode (22) is formed from a metal that does not feed metal ions to the ion-conducting layer (11). The ion-conducting layer (11) is formed from a compound containing oxygen or a metal oxide, and has an oxygen composition ratio that is less than a stoichiometric amount.

Description

スイッチング素子、半導体装置およびそれぞれの製造方法Switching element, semiconductor device and manufacturing method thereof
　本発明は、プログラマブルロジックおよびメモリ等の電子デバイスに用いられるスイッチング素子に関し、特に、二電極間における電気化学反応を利用したスイッチング素子に関する。 The present invention relates to a switching element used in an electronic device such as a programmable logic and a memory, and more particularly to a switching element using an electrochemical reaction between two electrodes.
　プログラマブルロジックの機能を多様化し、電子機器などへの実装を推進して行くためには、ロジックセル間を相互に結線もしくはロジックセル間の抵抗値を変化させるスイッチング素子もしくは抵抗変化素子（以後、スイッチング素子と統一して呼ぶ）のサイズを小さくし、そのオン抵抗を小さくすることが必要となる。
　このスイッチング素子として、二電極間における電気化学反応を利用したもの、即ち、二電極間で金属を析出させることを利用したものは、ＦＥＴ等の半導体スイッチング素子よりもサイズが小さく、オン抵抗が小さいことが知られている。金属析出のスイッチング素子は、構造的には、例えば特許文献１、２に開示された２端子スイッチング素子と、特許文献２、非特許文献１に開示された３端子スイッチとがある。
　図１を参照すると、本発明の関連技術による２端子スイッチング素子は、距離を置いて対向配置された第１電極６２１および第２電極６２２と、両電極間に設けられたイオン伝導層６１１とを有している。ここで、第１電極６２１は、金属イオンを供給する電極である。一方、第２電極６２２は、金属イオンを供給しない電極である。両電極間は、イオン伝導層６１１中での析出させた金属による金属架橋の形成・消滅により、スイッチングされる。
　２端子スイッチング素子は、構造が単純であるため、作製プロセスが簡便であり、素子サイズをナノメートルオーダーまで小さくすることが可能である。他方、３端子スイッチング素子は、金属架橋の形成・消滅をコントロールする第３電極を設けることにより、金属架橋の太さを制御可能とし、スイッチの書き込みおよび消去に必要な電流を大幅に低減できる。
　この種のスイッチング素子をプログラマブルロジックの配線切り替えのスイッチ手段もしくは抵抗変化手段として搭載するためには、ロジック動作電圧（１Ｖ）以上のスイッチング電圧と、半導体集積回路の製造工程に耐える熱耐性とが必要となる。スイッチング電圧は、イオン伝導体中の金属イオンの拡散速度に大きく依存するため、イオン伝導体材料の選択・最適化が重要である。特許文献３、４には、イオン伝導層として酸化物を用いることにより、スイッチング電圧を高めると共に、高い熱耐性を得るスイッチング素子が開示されている。
　また、この種のスイッチング素子は、プログラマブルロジック内に形成するに際し、スイッチング素子の小型化によるプログラマブルロジックの高密度化と、作製工程の簡略化が求められる。最先端の半導体装置の配線材料としては主に銅が用いられるため、銅配線内にスイッチング素子を効率的に形成する手法が望まれている。プログラマブルロジック等の半導体装置において、二電極間における電気化学反応を利用したスイッチング素子を集積化する技術については、非特許文献２に開示されている。具体的には、半導体基板上の銅配線と、スイッチング素子の第１電極とを兼用した構造が、非特許文献２には開示されている。この構造を用いれば、第１電極を新たに形成するための工程が削減できる。これに加えて、第１電極を作成するためのマスクが不要であるため、スイッチング素子を作製するために追加すべきフォトマスク（ＰＲ：Ｐｈｏｔｏ　Ｒｅｔｉｃｌｅ）数を２枚に減らすことができる。
　プログラマブルロジックのスイッチ手段もしくは抵抗変化手段としてこの種のスイッチング素子を応用した場合、オフ状態においてもロジック動作電圧が印加されることになる。このため、ディスターブ特性、即ち、オフ状態における定電圧印加時に対する信頼性（オフ状態の電圧耐性）が十分に確保されている必要がある。具体的なディスターブ特性としては、例えば、ロジック動作電圧が１Ｖの場合に、１Ｖ印加時にオフ状態を１０年保持する必要がある。
　ただし、オフからオンへ遷移させるスイッチングの際は、３~６Ｖ付近の印加電圧で１００μｓｅｃ程度の高速で駆動しなくてはならない。即ち、保持時の１Ｖと、スイッチング時の３~６Ｖ付近とで、オフからオンまでの遷移時間が９桁以上変化するような、大きな遷移時間の電圧依存性を有する必要がある。しかし、特許文献３および非特許文献２に開示されている構造のスイッチング素子では、十分な遷移時間の電圧依存性が得られないことが分かった。 In order to diversify the functions of programmable logic and promote its implementation in electronic devices, switching elements or resistance change elements (hereinafter referred to as switching) that connect logic cells to each other or change the resistance value between logic cells. Therefore, it is necessary to reduce the size of the device and to reduce its on-resistance.
As this switching element, an element utilizing an electrochemical reaction between two electrodes, that is, an element utilizing deposition of metal between two electrodes, is smaller in size and smaller in on-resistance than a semiconductor switching element such as an FET. It is known. Structurally, the metal deposition switching element includes a two-terminal switching element disclosed in Patent Documents 1 and 2, and a three-terminal switch disclosed in Patent Document 2 and Non-Patent Document 1, for example.
Referring to FIG. 1, a two-terminal switching device according to the related art of the present invention includes a first electrode 621 and a second electrode 622 that are arranged to face each other at a distance, and an ion conductive layer 611 provided between both electrodes. Have. Here, the first electrode 621 is an electrode that supplies metal ions. On the other hand, the second electrode 622 is an electrode that does not supply metal ions. The two electrodes are switched by the formation / disappearance of metal bridges by the deposited metal in the ion conductive layer 611.
Since the two-terminal switching element has a simple structure, the manufacturing process is simple, and the element size can be reduced to the nanometer order. On the other hand, in the three-terminal switching element, by providing the third electrode for controlling the formation / extinction of the metal bridge, the thickness of the metal bridge can be controlled, and the current required for writing and erasing the switch can be greatly reduced.
In order to mount this type of switching element as switching means or resistance changing means for switching wiring of programmable logic, it is necessary to have a switching voltage higher than the logic operating voltage (1V) and heat resistance to withstand the manufacturing process of the semiconductor integrated circuit. It becomes. Since the switching voltage greatly depends on the diffusion rate of metal ions in the ion conductor, selection and optimization of the ion conductor material is important. Patent Documents 3 and 4 disclose switching elements that increase the switching voltage and obtain high heat resistance by using an oxide as an ion conductive layer.
In addition, when this type of switching element is formed in the programmable logic, it is required to increase the density of the programmable logic by reducing the size of the switching element and to simplify the manufacturing process. Since copper is mainly used as the wiring material of the state-of-the-art semiconductor device, a technique for efficiently forming a switching element in the copper wiring is desired. Non-Patent Document 2 discloses a technology for integrating switching elements using an electrochemical reaction between two electrodes in a semiconductor device such as a programmable logic. Specifically, Non-Patent Document 2 discloses a structure in which the copper wiring on the semiconductor substrate and the first electrode of the switching element are combined. If this structure is used, the process for newly forming the first electrode can be reduced. In addition, since a mask for forming the first electrode is not necessary, the number of photomasks (PR: Photo Reticles) to be added for manufacturing the switching element can be reduced to two.
When this type of switching element is applied as a switching means or resistance changing means of a programmable logic, a logic operating voltage is applied even in an off state. For this reason, the disturb characteristic, that is, the reliability when applying a constant voltage in the off state (voltage resistance in the off state) needs to be sufficiently ensured. As a specific disturb characteristic, for example, when the logic operating voltage is 1V, it is necessary to keep the OFF state for 10 years when 1V is applied.
However, when switching from OFF to ON, it must be driven at a high speed of about 100 μsec with an applied voltage in the vicinity of 3 to 6V. In other words, it is necessary to have a large voltage dependence of the transition time such that the transition time from OFF to ON changes by 9 digits or more between 1 V during holding and around 3 to 6 V during switching. However, it has been found that the switching elements having the structures disclosed in Patent Document 3 and Non-Patent Document 2 cannot obtain sufficient voltage dependency of transition time.
特表２００２−５３６８４０号公報Special Table 2002-536840 Publication 特開２００６−３０３３４３号公報JP 2006-303343 A 特開２００６−３１９０２８号公報JP 2006-319028 A 特開２００８−２４４０９０号公報JP 2008-244090 A
　それ故、本発明の課題は、ディスターブ特性に優れたスイッチング素子を提供することである。
　他の本発明の課題は、ディスターブ特性に加えて遷移時間の電圧依存性にも優れたスイッチング素子を提供することである。
　本発明のさらに他の課題は、上記のようなスイッチング素子を内蔵したプログラマブルロジック等の半導体装置を提供することである。
　本発明のさらに他の課題は、上記のような半導体装置の製造方法を提供することである。
　本発明によれば、酸素を含むと共に金属イオンの伝導を許すイオン伝導層と、前記イオン伝導層の表裏面それぞれに形成された第１電極および第２電極とを有し、前記第１電極は前記イオン伝導層に金属イオンを供給可能な金属から成る一方、前記第２電極は前記イオン伝導層に金属イオンを供給しない金属から成り、前記第１電極から前記イオン伝導層中に供給された金属イオンが第２電極から電子を受け取って金属として析出し、析出した前記金属が成長することにより、前記第１電極および前記第２電極間の抵抗値が変化するスイッチング素子において、前記イオン伝導層は、前記第１電極との界面を含むイオン伝導層界面部と、当該残部であるイオン伝導層主部とを含み、前記イオン伝導層主部は、金属酸化物または酸素を含む化合物から成り、前記イオン伝導層界面部は、金属酸化物または酸素を含む化合物から成り、酸素の組成比が化学量論量未満であることを特徴とするスイッチング素子が得られる。 Therefore, an object of the present invention is to provide a switching element having excellent disturb characteristics.
Another object of the present invention is to provide a switching element that is excellent in voltage dependency of transition time in addition to disturb characteristics.
Still another object of the present invention is to provide a semiconductor device such as a programmable logic that incorporates the switching element as described above.
Still another object of the present invention is to provide a method for manufacturing the semiconductor device as described above.
According to the present invention, it has an ion conductive layer containing oxygen and allowing conduction of metal ions, and a first electrode and a second electrode formed on each of the front and back surfaces of the ion conductive layer, the first electrode being The second electrode is made of a metal that does not supply metal ions to the ion conductive layer, and is supplied from the first electrode into the ion conductive layer. In the switching element in which ions receive electrons from the second electrode and precipitate as a metal, and the deposited metal grows, and the resistance value between the first electrode and the second electrode changes, the ion conductive layer includes: An ion conductive layer interface including an interface with the first electrode and an ion conductive layer main part which is the remaining part, and the ion conductive layer main part is a compound containing a metal oxide or oxygen. Made, the ion conducting layer interface unit is composed of a compound containing a metal oxide or oxygen, the oxygen composition ratio switching element is obtained which is a substoichiometric amount.
　図１は、本発明の関連技術によるスイッチング素子の構成を示す模式的な断面図である。
　図２は、本発明の実施例１によるスイッチング素子の構成を示す模式的な断面図である。
　図３は、図２に示されたスイッチング素子の動作を説明するための模式的な断面図である。
　図４の（ａ）~（ｃ）は、図２に示されたスイッチング素子の製造方法を説明するための模式的な断面図である。
　図５は、図２に示されたスイッチング素子の特性検証結果としてのディスターブ特性を示すグラフ図である。
　図６の（ａ）~（ｄ）は、本発明の実施例２によるスイッチング素子の製造方法を説明するための模式的な断面図である。
　図７は、本発明の実施例３によるスイッチング素子の構成を示す模式的な断面図である。
　図８は、図７に示されたスイッチング素子の動作を説明するための模式的な断面図である。
　図９の（ａ）~（ｄ）は、図７に示されたスイッチング素子の製造方法を説明するための模式的な断面図である。
　図１０は、図７に示されたスイッチング素子の特性検証結果としてのディスターブ特性を示すグラフ図である。
　図１１の（ａ）および（ｂ）は、図７に示されたスイッチング素子の光電子分光法測定結果を示すグラフ図である。
　図１２は、本発明の実施例４による半導体装置の構成を示す模式的な断面図である。
　図１３の（ａ）~（ｆ）は、図７に示された半導体装置の製造方法を説明するための模式的な断面図である。
　図１４の（ａ）~（ｆ）は、図７に示された半導体装置の製造方法を説明するための模式的な断面図である。 FIG. 1 is a schematic cross-sectional view showing the configuration of a switching element according to the related art of the present invention.
FIG. 2 is a schematic cross-sectional view showing the configuration of the switching element according to the first embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view for explaining the operation of the switching element shown in FIG.
4A to 4C are schematic cross-sectional views for explaining a method of manufacturing the switching element shown in FIG.
FIG. 5 is a graph showing a disturb characteristic as a characteristic verification result of the switching element shown in FIG.
6 (a) to 6 (d) are schematic cross-sectional views for explaining a method for manufacturing a switching element according to the second embodiment of the present invention.
FIG. 7 is a schematic cross-sectional view showing the configuration of the switching element according to the third embodiment of the present invention.
FIG. 8 is a schematic cross-sectional view for explaining the operation of the switching element shown in FIG.
9A to 9D are schematic cross-sectional views for explaining a method of manufacturing the switching element shown in FIG.
FIG. 10 is a graph showing a disturb characteristic as a characteristic verification result of the switching element shown in FIG.
FIGS. 11A and 11B are graphs showing the photoelectron spectroscopy measurement results of the switching element shown in FIG.
FIG. 12 is a schematic cross-sectional view showing a configuration of a semiconductor device according to Example 4 of the present invention.
13A to 13F are schematic cross-sectional views for explaining a method of manufacturing the semiconductor device shown in FIG.
14A to 14F are schematic cross-sectional views for explaining a method for manufacturing the semiconductor device shown in FIG.
　［構成］
　本発明によるスイッチング素子は、酸素を含むと共に金属イオンの伝導を許すイオン伝導層と、イオン伝導層の表裏面それぞれに形成された第１電極および第２電極とを有している。第１電極は、イオン伝導層に金属イオンを供給可能な金属から成っている。一方、第２電極は、イオン伝導層に金属イオンを供給しない金属から成っている。第１電極からイオン伝導層中に供給された金属イオンが第２電極から電子を受け取って金属として析出し、析出した金属が成長することにより、第１電極および第２電極間の抵抗値が変化するスイッチング素子である。
　特に、本スイッチング素子において、イオン伝導層の全部、もしくは、イオン伝導層のうちの第１電極との界面を含むイオン伝導層界面部が、金属酸化物または酸素を含む化合物から成ると共に厚さが５ｎｍ以下であるか、あるいは、３００Ｋにおける標準ギブスエネルギーが−６００ｋＪ／ｍｏｌよりも大きい金属を材料とする金属酸化物から成ることにより、イオン伝導層の全部、もしくは、第１電極との界面を含むイオン伝導層界面部における酸素の組成比が化学量論量未満である。
　［作用］
　ディスターブ特性を向上させるには、低電圧印加時に、金属イオンを供給する第１電極からできるだけイオン伝導層中に金属イオンが供給されないようにすればよいことを、本発明者等は見出した。金属イオンのイオン伝導層中への供給は、金属のイオン化反応によって進行しているが、陽イオンを形成する金属のイオン化には酸化剤となる陰イオンの存在が必要である。例えば、イオン伝導層が酸素を含んでいる場合、イオン伝導層中の酸素イオンが酸化剤として機能し、金属のイオン化を促進することになる。
　この作用の参考として、例えば、ＬＳＩの銅配線では、銅配線から層間絶縁膜中への銅イオンの注入による銅配線間のショートが問題となっている（絶縁破壊寿命：ＴＤＤＢ）。特に、銅配線工程中の化学機械研磨工程（ＣＭＰ）などによって生じる酸化銅層が生じた場合、ＴＤＤＢが短くなる傾向が報告されている（非特許文献３）。即ち、銅配線からの銅イオンの層間絶縁膜中への注入が促進されることになる。本スイッチング素子においても、イオン伝導層に含まれる酸素の濃度によって、第１電極の金属がイオン伝導層中に注入される速度が変化することが理解できる。
　そこで、本スイッチング素子においては、イオン伝導層のうちの第１電極を臨むイオン伝導層界面部に含有される酸素が化学量論量未満であるため、第１電極への酸素イオンの供給量が低減され、第１電極からの金属のイオン化および金属イオンのイオン伝導層中への供給が抑制される。
　低電圧印加時には、第１電極に到達する酸素イオン量が少ないため、オフからオンへの遷移時間は長くなり、ディスターブ特性に優れている。一方、スイッチング時に印加電圧が増加すると、イオン伝導層内で分極が進行し、供給量が少ないながらも酸素イオンが第１電極付近に集まることにより、オフからオンへの遷移時間が大幅に短縮される。即ち、本発明によるスイッチング素子は、オフからオンへの遷移時間の電圧依存性にも優れている。
　以下、図面を参照して、本発明によるスイッチング素子、半導体装置、および半導体装置の製造方法のより具体的な実施例を説明する。 [Constitution]
The switching element according to the present invention includes an ion conductive layer containing oxygen and allowing conduction of metal ions, and a first electrode and a second electrode formed on the front and back surfaces of the ion conductive layer. The first electrode is made of a metal capable of supplying metal ions to the ion conductive layer. On the other hand, the second electrode is made of a metal that does not supply metal ions to the ion conductive layer. The metal ions supplied from the first electrode into the ion conductive layer receive electrons from the second electrode and precipitate as metal, and the deposited metal grows to change the resistance value between the first electrode and the second electrode. Switching element.
In particular, in the present switching element, the entire ion conduction layer or the ion conduction layer interface including the interface with the first electrode of the ion conduction layer is made of a metal oxide or a compound containing oxygen and has a thickness. By including a metal oxide whose material is 5 nm or less or whose standard Gibbs energy at 300 K is larger than −600 kJ / mol, the entire ion conductive layer or the interface with the first electrode is included. The composition ratio of oxygen at the interface portion of the ion conductive layer is less than the stoichiometric amount.
[Action]
In order to improve the disturb characteristics, the present inventors have found that metal ions should not be supplied into the ion conductive layer as much as possible from the first electrode that supplies metal ions when a low voltage is applied. Supply of metal ions into the ion conductive layer proceeds by an ionization reaction of the metal, but the presence of an anion serving as an oxidizing agent is necessary for the ionization of the metal forming the cation. For example, when the ion conductive layer contains oxygen, oxygen ions in the ion conductive layer function as an oxidizing agent, and promote ionization of the metal.
As a reference for this action, for example, in an LSI copper wiring, there is a problem of short-circuiting between copper wirings due to the implantation of copper ions from the copper wiring into the interlayer insulating film (dielectric breakdown life: TDDB). In particular, when a copper oxide layer generated by a chemical mechanical polishing process (CMP) or the like in a copper wiring process occurs, a tendency that TDDB is shortened has been reported (Non-patent Document 3). That is, the implantation of copper ions from the copper wiring into the interlayer insulating film is promoted. Also in this switching element, it can be understood that the rate at which the metal of the first electrode is injected into the ion conductive layer varies depending on the concentration of oxygen contained in the ion conductive layer.
Therefore, in this switching element, the oxygen contained in the interface portion of the ion conductive layer facing the first electrode in the ion conductive layer is less than the stoichiometric amount, so that the supply amount of oxygen ions to the first electrode is small. The ionization of the metal from the first electrode and the supply of the metal ion into the ion conductive layer are suppressed.
When a low voltage is applied, since the amount of oxygen ions reaching the first electrode is small, the transition time from off to on becomes long, and the disturb characteristic is excellent. On the other hand, when the applied voltage increases at the time of switching, polarization progresses in the ion conduction layer, and oxygen ions gather near the first electrode even though the supply amount is small, thereby greatly reducing the transition time from off to on. The That is, the switching element according to the present invention is excellent in the voltage dependency of the transition time from OFF to ON.
Hereinafter, with reference to the drawings, a specific example of a switching element, a semiconductor device, and a method of manufacturing a semiconductor device according to the present invention will be described.
　［構成と製造方法の概要］
　図２を参照すると、本発明の実施例１によるスイッチング素子は、酸素を含むと共に金属イオンの伝導を許すイオン伝導層１１と、イオン伝導層１１の表裏面それぞれに形成された第１電極２１および第２電極２２とを有している。第１電極２１は、イオン伝導層１１に金属イオンを供給可能な金属から成っている。一方、第２電極２２は、イオン伝導層に金属イオンを供給しない金属から成っている。第１電極２１からイオン伝導層１１中に供給された金属イオンが第２電極２２から電子を受け取って金属として析出し、析出した金属が成長することにより、第１電極２１および第２電極２２間の抵抗値が変化するスイッチング素子である。
　特に、本スイッチング素子において、イオン伝導層１１は、その全部、もしくは、第１電極２１との界面を含むイオン伝導層界面部１１２の層厚が５ｎｍ以下であり、かつ、酸素の組成比が化学量論量未満である。
　図２中、符号１１２は、イオン伝導層１１のうちの、第１電極２１との界面を含む一部分であるイオン伝導層界面部１１２である。ただし、実施例１において、イオン伝導層１１におけるイオン伝導層界面部１１２と、イオン伝導層１１におけるイオン伝導層界面部１１２の残部（イオン伝導層主部）とは同じ組成であり、説明の便宜上、両者を区別して描いているに過ぎない。
　第１電極２１は、電圧を印加した際に、イオン伝導層１１中に金属イオンを供給する銅から成り、スパッタ法、化学気相成長法（ＣＶＤ法）、電気めっき法で形成される。
　一方、第２電極２２は、電圧を印加した際に、イオン伝導層１１中に金属イオンを供給しない材料から成っている。より具体的には、第２電極２２の材料としては、ルテニウム、プラチナ、ニッケルが好ましく、特に、ルテニウムが好ましい。
　イオン伝導層１１は、金属イオンが伝導するための媒体となる層であり、金属酸化物または酸素を含む化合物から成っている。
　イオン伝導層１１が金属酸化物から成る場合、金属酸化物としては例えば、酸化タンタル、酸化ジルコニウム、酸化アルミニウム、酸化チタン、あるいは、これら酸化物の混合物が用いられる。金属酸化物から成るイオン伝導層１１は、スパッタ法、レーザーアブレーション法、プラズマＣＶＤ法を用いて形成される。イオン伝導層１１を形成するには、焼結したターゲットを用いてスパッタ成膜する。
　特に、イオン伝導層１１は、その金属酸化物における酸素含有量が化学量論量未満となるように、スパッタチャンバー内には酸素の流入を行わないで形成される。
　一方、イオン伝導層１１が酸素を含む化合物から成る場合、酸素を含む化合物としては例えば、シリコン、酸素、炭素、水素を含むＳｉＯＣＨ系化合物が用いられる。ＳｉＯＣＨ系等の酸素を含む化合物から成るイオン伝導層１１は、プラズマＣＶＤによって形成される。環状有機シロキサンの原料とキャリアガスであるヘリウムを反応室内に流入し、両者の供給が安定化し、反応室の圧力が一定になったところでＲＦ電力の印加を開始する。
　特に、イオン伝導層１１は、ＳｉＯＣＨ系等の酸素を含む化合物における酸素の組成比が化学量論量未満となるように、チャンバー内に水素を１０ｓｃｃｍ程度流入して形成される。水素によってチャンバー内を僅かに還元雰囲気に傾けることにより、成膜されたＳｉＯＣＨ系イオン伝導層１１は、酸素含有量が減らされる。原料の供給量は１０~２００ｓｃｃｍ、ヘリウムの供給は原料気化器経由で５００ｓｃｃｍ、別ラインで反応室に直接５００ｓｃｃｍ供給される。
　［動作］
　次に、実施例１による２端子スイッチング素子の動作について、図３を参照して説明する。
　第２電極２２を接地すると共に第１電極２１に正電圧を印加すると、第１電極２１の金属がイオン伝導層界面部１１２を介して金属イオンＭＩになって、イオン伝導層１１に溶解する。そして、イオン伝導層界面部１１２を含むイオン伝導層１１中の金属イオンＭＩが第２電極２２の表面に金属架橋Ｂになって析出し、金属架橋Ｂが延びるほど第１電極２１と第２電極２２との間の電気抵抗が小さくなる。さらに、析出した金属架橋Ｂが第１電極２１にまで十分に達すると、第１電極２１と第２電極２２が電気的に接続される。金属架橋Ｂで第１電極２１と第２電極２２が電気的に接続することで、スイッチがオン状態になる。
　さらに、上記オン状態で、第２電極２２を接地すると共に第１電極２１に負電圧を印加すると、金属架橋Ｂがイオン伝導層界面部１１２を含むイオン伝導層１１に金属イオンＭＩとなって溶解し、金属架橋Ｂの一部が切れ、金属架橋Ｂが欠損するほど第１電極２１と第２電極２２との間の電気抵抗が大きくなる。この際、金属イオンＭＩは、イオン伝導層界面部１１２を含むイオン伝導層１１内に分散した金属と第１電極２１に回収される。さらに、金属架橋Ｂが十分に欠損すると、第１電極２１と第２電極２２との電気的接続が切れ、スイッチがオフ状態になる。
　上記オフ状態からオン状態にするには、再び第２電極２２に正電圧を印加すればよい。また、第１電極２１を接地し、第２電極２２に負電圧を印加してスイッチをオン状態にしたり、第１電極２１を接地し、第２電極２２に正電圧を印加してスイッチをオフ状態にしたりしてもよい。
　尚、スイッチがオフ状態になるとき、電気的接続が完全に切れる前の段階から第１電極２１および第２電極２２間の抵抗が大きくなったり、電極間容量が変化したりするなど電気特性の変化があって、最終的に電気的接続が切れる。
　［製造方法］
　次に、実施例１によるスイッチング素子の製造方法について、図４（ａ）~（ｃ）を参照して説明する。尚、この製造方法は、イオン伝導層１１が金属酸化物から成る場合である。
　［工程１］　図４（ａ）に示されるように、低抵抗シリコン基板Ｓの表面に膜厚５ｎｍの窒化チタン、その上に４０ｎｍのルテニウムをスパッタ法で成膜し、第２電極２２を形成する。
　［工程２］　図４（ｂ）に示されるように、金属酸化物から成るイオン伝導層１１として、膜厚５ｎｍの酸化タンタル薄膜をスパッタ法により形成する。ここで、成膜された酸化タンタルの酸素の組成は化学量論量未満となるようにする。具体的には、スパッタを行う際に、通常は供給する酸素を供給しない。本発明者等は、酸素流量無しでアルゴン流量４０ｓｃｃｍを流した成膜条件で酸化タンタルを成膜し、タンタルに対する酸素比が化学量論の９６％となる酸化タンタルを得た。
　［工程３］　図４（ｃ）に示されるように、酸化タンタルから成るイオン伝導層１１上に、真空蒸着法もしくはスパッタ法により膜厚８０ｎｍの銅を堆積させる。この際、ステンレスもしくはシリコンで作製されたシャドーマスクを介して銅を堆積し、平面形状が一辺３０μｍ~１５０μｍの正方形の第１電極２１を形成する。
　［特性検証］
　次に、実施例１によるスイッチング素子の特性検証について、さらに図５を参照して説明する。
　図５は、実施例１によるスイッチング素子の特性検証として、酸化タンタルから成るイオン伝導層を有する２種類のスイッチング素子について、印加電圧に対するオフからオンまでの時間を示した図である。
　検証のための測定は、第１電極２１のＣｕに正方向の定電圧を印加し、オフからオンまでの時間を測定する方法とした。この際、第２電極２２の窒化チタンおよびルテニウムは低抵抗シリコン基板Ｓを介して接地した。２種類のうちの一方は、酸化タンタルの成膜時に１０ｓｃｃｍの流量で酸素を導入して製造したものであり、酸化タンタルを構成するタンタルと酸素の組成比は、化学量論量以上である（比較例）。他方は、酸化タンタルの成膜時に酸素を導入しないで製造したものであり、酸化タンタルにおける酸素含有量が低く、酸素の組成比は、化学量論未満である（実施例１）。
　図５から明らかなように、少なくとも図示された印加電圧域においては、酸化タンタルを構成する酸素が化学量論量以上である比較例に比べ、酸素が化学量論量未満である実施例１のスイッチング素子は、同じ電圧を印加した場合のオフからオンへの遷移時間が長い。即ち、少なくともイオン伝導層界面部の酸素組成比が化学量論量未満であると、オフからオンに遷移し難く、ディスターブ特性に優れていることが分かる。 [Outline of configuration and manufacturing method]
Referring to FIG. 2, the switching device according to the first embodiment of the present invention includes an ion conductive layer 11 containing oxygen and allowing conduction of metal ions, a first electrode 21 formed on each of the front and back surfaces of the ion conductive layer 11, and And a second electrode 22. The first electrode 21 is made of a metal that can supply metal ions to the ion conductive layer 11. On the other hand, the second electrode 22 is made of a metal that does not supply metal ions to the ion conductive layer. The metal ions supplied from the first electrode 21 into the ion conductive layer 11 receive electrons from the second electrode 22 and are deposited as metal, and the deposited metal grows, whereby the first electrode 21 and the second electrode 22 are grown. This is a switching element in which the resistance value changes.
In particular, in the present switching element, the ion conductive layer 11 has a total thickness, or the layer thickness of the ion conductive layer interface 112 including the interface with the first electrode 21 is 5 nm or less, and the oxygen composition ratio is chemical. Less than stoichiometric amount.
In FIG. 2, reference numeral 112 denotes an ion conductive layer interface 112 that is a part of the ion conductive layer 11 including the interface with the first electrode 21. However, in Example 1, the ion conductive layer interface 112 in the ion conductive layer 11 and the remainder of the ion conductive layer interface 112 in the ion conductive layer 11 (the main part of the ion conductive layer) have the same composition, and for convenience of explanation. They are only drawn separately.
The first electrode 21 is made of copper for supplying metal ions into the ion conductive layer 11 when a voltage is applied, and is formed by sputtering, chemical vapor deposition (CVD), or electroplating.
On the other hand, the second electrode 22 is made of a material that does not supply metal ions into the ion conductive layer 11 when a voltage is applied. More specifically, the material of the second electrode 22 is preferably ruthenium, platinum, or nickel, and particularly preferably ruthenium.
The ion conductive layer 11 is a layer serving as a medium for conducting metal ions, and is made of a metal oxide or a compound containing oxygen.
When the ion conductive layer 11 is made of a metal oxide, for example, tantalum oxide, zirconium oxide, aluminum oxide, titanium oxide, or a mixture of these oxides is used as the metal oxide. The ion conductive layer 11 made of a metal oxide is formed using a sputtering method, a laser ablation method, or a plasma CVD method. The ion conductive layer 11 is formed by sputtering using a sintered target.
In particular, the ion conductive layer 11 is formed without flowing oxygen into the sputtering chamber so that the oxygen content in the metal oxide is less than the stoichiometric amount.
On the other hand, when the ion conductive layer 11 is made of a compound containing oxygen, for example, a SiOCH compound containing silicon, oxygen, carbon, and hydrogen is used as the compound containing oxygen. The ion conductive layer 11 made of an oxygen-containing compound such as SiOCH is formed by plasma CVD. The cyclic organosiloxane raw material and the carrier gas helium flow into the reaction chamber, the supply of both is stabilized, and the application of RF power is started when the pressure in the reaction chamber becomes constant.
In particular, the ion conductive layer 11 is formed by flowing about 10 sccm of hydrogen into the chamber so that the composition ratio of oxygen in a compound containing oxygen such as SiOCH is less than the stoichiometric amount. By tilting the inside of the chamber slightly to a reducing atmosphere with hydrogen, the oxygen content of the formed SiOCH-based ion conductive layer 11 is reduced. The supply amount of the raw material is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is directly supplied to the reaction chamber through a separate line.
[Operation]
Next, the operation of the two-terminal switching element according to the first embodiment will be described with reference to FIG.
When the second electrode 22 is grounded and a positive voltage is applied to the first electrode 21, the metal of the first electrode 21 becomes metal ions MI through the ion conductive layer interface 112 and dissolves in the ion conductive layer 11. Then, the metal ions MI in the ion conductive layer 11 including the ion conductive layer interface 112 are deposited on the surface of the second electrode 22 as metal bridge B, and the first electrode 21 and the second electrode are extended as the metal bridge B extends. The electrical resistance between the two is reduced. Furthermore, when the deposited metal bridge B sufficiently reaches the first electrode 21, the first electrode 21 and the second electrode 22 are electrically connected. When the first electrode 21 and the second electrode 22 are electrically connected by the metal bridge B, the switch is turned on.
Further, when the second electrode 22 is grounded and a negative voltage is applied to the first electrode 21 in the ON state, the metal bridge B dissolves in the ion conductive layer 11 including the ion conductive layer interface 112 as metal ions MI. However, the electrical resistance between the first electrode 21 and the second electrode 22 increases as part of the metal bridge B is cut and the metal bridge B is lost. At this time, the metal ions MI are collected by the metal dispersed in the ion conductive layer 11 including the ion conductive layer interface 112 and the first electrode 21. Furthermore, if the metal bridge B is sufficiently lost, the electrical connection between the first electrode 21 and the second electrode 22 is cut, and the switch is turned off.
In order to change from the off state to the on state, a positive voltage may be applied to the second electrode 22 again. Also, the first electrode 21 is grounded and a negative voltage is applied to the second electrode 22 to turn on the switch, or the first electrode 21 is grounded and a positive voltage is applied to the second electrode 22 to turn off the switch. Or may be in a state.
When the switch is turned off, the electrical characteristics such as the resistance between the first electrode 21 and the second electrode 22 increases and the capacitance between the electrodes changes from the stage before the electrical connection is completely cut off. There is a change and eventually the electrical connection is broken.
[Production method]
Next, a method for manufacturing the switching element according to the first embodiment will be described with reference to FIGS. This manufacturing method is a case where the ion conductive layer 11 is made of a metal oxide.
[Step 1] As shown in FIG. 4A, a second electrode 22 is formed by depositing 5 nm thick titanium nitride on the surface of the low resistance silicon substrate S and 40 nm ruthenium thereon by sputtering. To do.
[Step 2] As shown in FIG. 4B, a tantalum oxide thin film having a thickness of 5 nm is formed by sputtering as the ion conductive layer 11 made of a metal oxide. Here, the composition of oxygen in the formed tantalum oxide is set to be less than the stoichiometric amount. Specifically, when performing sputtering, oxygen that is normally supplied is not supplied. The inventors of the present invention formed a tantalum oxide film under the film formation conditions with an argon flow rate of 40 sccm without an oxygen flow rate, and obtained tantalum oxide having an oxygen ratio to tantalum of 96% of the stoichiometry.
[Step 3] As shown in FIG. 4C, copper having a thickness of 80 nm is deposited on the ion conductive layer 11 made of tantalum oxide by a vacuum evaporation method or a sputtering method. At this time, copper is deposited through a shadow mask made of stainless steel or silicon to form a square first electrode 21 having a planar shape of 30 μm to 150 μm on a side.
[Characteristic verification]
Next, verification of the characteristics of the switching element according to the first embodiment will be further described with reference to FIG.
FIG. 5 is a diagram showing the time from off to on with respect to the applied voltage for two types of switching elements having an ion conductive layer made of tantalum oxide as a characteristic verification of the switching element according to the first embodiment.
The measurement for verification was performed by applying a constant voltage in the positive direction to Cu of the first electrode 21 and measuring the time from off to on. At this time, titanium nitride and ruthenium of the second electrode 22 were grounded through the low resistance silicon substrate S. One of the two types is manufactured by introducing oxygen at a flow rate of 10 sccm when forming a tantalum oxide film, and the composition ratio of tantalum and oxygen constituting the tantalum oxide is equal to or higher than the stoichiometric amount ( Comparative example). The other is manufactured without introducing oxygen at the time of tantalum oxide film formation, and the oxygen content in tantalum oxide is low, and the composition ratio of oxygen is less than stoichiometric (Example 1).
As apparent from FIG. 5, at least in the illustrated applied voltage range, the oxygen in the example 1 in which oxygen is less than the stoichiometric amount compared to the comparative example in which the oxygen constituting the tantalum oxide is greater than or equal to the stoichiometric amount. The switching element has a long transition time from off to on when the same voltage is applied. That is, it can be seen that when the oxygen composition ratio at the interface portion of the ion conductive layer is less than the stoichiometric amount, it is difficult to make the transition from off to on and the disturbance characteristics are excellent.
　本発明の実施例２によるスイッチング素子は、イオン伝導層のうちの少なくとも第１電極との界面を含む一部分であるイオン伝導層界面部のみ、酸素の組成比が化学量論量未満とである点が実施例１とは異なる。このため、実施例１と同一または同様の部分については、詳細な説明を省略する。
　［構成と製造方法の概要］
　本発明においては、イオン伝導層全体ではなく、イオン伝導層のうちの少なくとも第１電極との界面を含む一部分であるイオン伝導層界面部の酸素の組成比が化学量論量未満であればよい。イオン伝導層が酸化金属から成る場合、成膜開始直後は酸素を１０ｓｃｃｍ程度流入して酸素の組成が化学量論を満たすようにイオン伝導層主部の成膜を行い、その後、チャンバー内に酸素を導入せずにイオン伝導層のうちのイオン伝導層界面部を成膜する。尚、イオン伝導層界面部は、イオン伝導層の３分の１以下の膜厚であることが望ましい。
　また、イオン伝導層が酸素を含む化合物から成る場合も、金属酸化物から成るイオン伝導層と同様に、イオン伝導層のうちの少なくとも第１電極２１との界面を含む一部分であるイオン伝導層界面部の酸素の組成比が化学量論量未満であればよい。その場合は、成膜開始直後のみ、水素の流入をせずに、膜の酸素の組成が化学量論を満たすようにイオン伝導層主部の成膜を行い、その後、チャンバー内に水素を流入してイオン伝導層のうちのイオン伝導層界面部を成膜する。イオン伝導層界面部は、イオン伝導層の３分の１以下の膜厚であることが望ましいが、スパッタ法、レーザーアブレーション法、ＣＶＤ法で安定に形成可能な０．５ｎｍ以上であることが望ましい。
　ここで、実施例１を示す図２を流用的に参照すると、本発明の実施例２によるスイッチング素子は、２端子スイッチング素子の形態を呈している。本スイッチング素子は、第１電極２１と、第１電極２１に接したイオン伝導層１１と、第１電極２１とイオン伝導層１１を介して設けられた第２電極２２とを有している。
　図２中、符号１１２は、イオン伝導層１１のうちの第１電極２１との界面を含む一部分であるイオン伝導層界面部１１２である。実施例２においては、酸素の組成比が、イオン伝導層１１のうちのイオン伝導層界面部１１２（酸素の組成比が化学量論量未満）と、イオン伝導層１１の残部（酸素の組成比が化学量論量以上）とで異なっている。
　［製造方法］
　以下、実施例２のスイッチング素子の製造方法について、図６（ａ）~（ｄ）を参照して説明する。尚、この製造方法は、イオン伝導層１１が金属酸化物から成る場合である。
　［工程１］　図６（ａ）に示されるように、低抵抗シリコン基板Ｓの表面に膜厚５ｎｍの窒化チタン、その上に４０ｎｍのルテニウムをスパッタ法で成膜し、第２電極２２を形成する。
　［工程２］　図６（ｂ）に示されるように、金属酸化物から成るイオン伝導層主部１１１として、膜厚８ｎｍの酸化タンタル薄膜をスパッタ法により形成する。この際、成膜された酸化タンタルの酸素の組成は化学量論量以上となるようにする。具体的にはスパッタを行う際に、酸素をチャンバー内に供給する。本発明者等は、酸素流量１０ｓｃｃｍ、アルゴン流量４０ｓｃｃｍを流した成膜条件で酸化タンタルを成膜し、タンタルに対する酸素比が化学量論量以上となる酸化タンタルを得た。
　［工程３］　図６（ｃ）に示されるように、イオン伝導層界面部１１２として、膜厚２ｎｍの酸化タンタル薄膜をスパッタ法によって形成する。この際に、成膜された酸化タンタルの酸素の組成が化学量論量未満となるようにする。具体的には、スパッタを行う際に、通常供給する酸素を供給しない。本発明者等は、酸素流量無しでアルゴン流量４０ｓｃｃｍを流した成膜条件で酸化タンタルを成膜し、タンタルに対する酸素比が化学量論の９６％となる酸化タンタルを得た。
　［工程４］　図６（ｄ）に示されるように、イオン伝導層界面部１１２の上に真空蒸着法もしくはスパッタ法によって膜厚８０ｎｍの銅を堆積させる。この際、ステンレスもしくはシリコンで作製されたシャドーマスクを介して銅を堆積し平面形状が、一辺３０μｍ~１５０μｍの正方形の第１電極２１を形成する。 In the switching element according to Example 2 of the present invention, the oxygen composition ratio is less than the stoichiometric amount only in the interface portion of the ion conductive layer, which is a part including at least the interface with the first electrode. Is different from the first embodiment. For this reason, detailed description of the same or similar parts as those in the first embodiment is omitted.
[Outline of configuration and manufacturing method]
In the present invention, the composition ratio of oxygen at the interface portion of the ion conductive layer, which is a part including at least the interface with the first electrode of the ion conductive layer, rather than the entire ion conductive layer may be less than the stoichiometric amount. . When the ion conductive layer is made of metal oxide, immediately after the start of film formation, about 10 sccm of oxygen is flowed to form the main part of the ion conductive layer so that the composition of oxygen satisfies the stoichiometry, and then oxygen is put into the chamber. The interface portion of the ion conductive layer of the ion conductive layer is formed without introducing. In addition, it is desirable that the ion conductive layer interface has a film thickness of one third or less of the ion conductive layer.
Further, when the ion conductive layer is made of a compound containing oxygen, the ion conductive layer interface which is a part including at least the interface with the first electrode 21 in the ion conductive layer, similarly to the ion conductive layer made of metal oxide. The composition ratio of oxygen in the part may be less than the stoichiometric amount. In that case, the main part of the ion conductive layer is formed so that the oxygen composition of the film satisfies the stoichiometry without hydrogen flowing in immediately after the start of film formation, and then hydrogen is flowed into the chamber. Then, an ion conductive layer interface portion of the ion conductive layer is formed. The interface portion of the ion conductive layer is preferably 1/3 or less of the thickness of the ion conductive layer, but it is preferably 0.5 nm or more that can be stably formed by sputtering, laser ablation, or CVD. .
Here, referring to FIG. 2 showing the first embodiment, the switching element according to the second embodiment of the present invention is in the form of a two-terminal switching element. The switching element includes a first electrode 21, an ion conductive layer 11 in contact with the first electrode 21, and a second electrode 22 provided via the first electrode 21 and the ion conductive layer 11.
In FIG. 2, reference numeral 112 denotes an ion conductive layer interface 112 that is a part of the ion conductive layer 11 including the interface with the first electrode 21. In Example 2, the composition ratio of oxygen is such that the ion conduction layer interface portion 112 (the oxygen composition ratio is less than the stoichiometric amount) in the ion conduction layer 11 and the remainder of the ion conduction layer 11 (the composition ratio of oxygen). Is more than the stoichiometric amount).
[Production method]
Hereinafter, a method for manufacturing the switching element of Example 2 will be described with reference to FIGS. This manufacturing method is a case where the ion conductive layer 11 is made of a metal oxide.
[Step 1] As shown in FIG. 6A, the second electrode 22 is formed by depositing 5 nm of titanium nitride on the surface of the low-resistance silicon substrate S and 40 nm of ruthenium on the surface by sputtering. To do.
[Step 2] As shown in FIG. 6B, a tantalum oxide thin film having a thickness of 8 nm is formed by sputtering as the ion conductive layer main part 111 made of a metal oxide. At this time, the composition of oxygen in the formed tantalum oxide is set to a stoichiometric amount or more. Specifically, oxygen is supplied into the chamber when performing sputtering. The inventors of the present invention formed tantalum oxide under film formation conditions with an oxygen flow rate of 10 sccm and an argon flow rate of 40 sccm, and obtained tantalum oxide in which the oxygen ratio to tantalum was a stoichiometric amount or more.
[Step 3] As shown in FIG. 6C, a tantalum oxide thin film having a thickness of 2 nm is formed by sputtering as the ion conductive layer interface 112. At this time, the composition of oxygen in the formed tantalum oxide is set to be less than the stoichiometric amount. Specifically, oxygen that is normally supplied is not supplied when sputtering is performed. The inventors of the present invention formed a tantalum oxide film under the film formation conditions with an argon flow rate of 40 sccm without an oxygen flow rate, and obtained tantalum oxide having an oxygen ratio to tantalum of 96% of the stoichiometry.
[Step 4] As shown in FIG. 6 (d), copper having a film thickness of 80 nm is deposited on the ion conductive layer interface 112 by vacuum evaporation or sputtering. At this time, copper is deposited through a shadow mask made of stainless steel or silicon to form a square first electrode 21 having a planar shape of 30 μm to 150 μm on a side.
　本発明の実施例３によるスイッチング素子は、イオン伝導層が互いに積層する主イオン伝導層および界面イオン伝導層によって構成され、第１電極との界面を含む界面イオン伝導層の酸素の組成比が化学量論量未満である点が、実施例２とは異なる。このため、実施例２と同一または同様の部分については、詳細な説明を省略する。
　［構成と製造方法の概要］
　図７を参照すると、本発明の実施例３によるスイッチング素子は、２端子スイッチング素子の形態を呈している。本スイッチング素子は、距離を置いて対向配置された第１電極２１および第２電極２２と、両電極間に挟まれた界面イオン伝導層５２および主イオン伝導層５１とを有している。界面イオン伝導層５２は、第１電極２１に接している（第１電極との界面を含んでいる）。
　第１電極２１は、電圧を印加した際に、界面イオン伝導層５２および主イオン伝導層５１中に金属イオンを供給する銅から成り、スパッタ法、化学気相成長法（ＣＶＤ法）、電気めっき法で形成される。
　第２電極２２の材料は、電圧を印加した際に、主イオン伝導層５１および界面イオン伝導層５２中に金属イオンを供給しないものであることが望ましい。より具体的には、第２電極２２は、ルテニウム、プラチナ、またはニッケルから成ることが好ましい。特に、ルテニウムから成ることが好ましい。
　主イオン伝導層５１と界面イオン伝導層５２は、金属イオンが伝導するための媒体となる。
　界面イオン伝導層５２は、金属酸化物で形成される。まず酸化物を構成する金属を第１電極２１上に成膜し、その上に堆積する、後述のごとく酸素を含む主イオン伝導層５１の成膜中にチャンバー内に存在する酸素によって酸化することにより、金属酸化物から成る界面イオン伝導層５２を得る。
　ここで、金属酸化物から成る界面イオン伝導層５２の金属材料としては、酸化し難い金属、即ち、標準ギブズエネルギーの絶対値が小さい金属が好ましい。これは、標準ギブズエネルギーの絶対値が小さく、酸化し難い金属は、主イオン伝導層５１の成膜中にチャンバー内に存在する酸素によっても十分には酸化されないため、金属酸化物から成る界面イオン伝導層５２の酸素の組成比が化学量論量未満となるからである。これにより、銅がイオン化し難くなり、定電圧印加下のオフからオンへの遷移時間を長くすることができる。
　具体的には、発明者等の実験によれば、３００Ｋにおける標準ギブスエネルギーが−６００ｋＪ／ｍｏｌよりも大きい金属が、金属酸化物から成る界面イオン伝導層の金属材料として良好な結果が得られた。特に、標準ギブスエネルギーが−６００ｋＪ／ｍｏｌよりも大きい金属によれば、界面イオン伝導層の層厚が５ｎｍよりも厚くても、酸素の組成比を化学量論量未満にすることができた。
　この条件を満たす界面イオン伝導層の金属材料としては、例えば、ニッケル、コバルト、鉄、ルテニウム、または、イリジウム、あるいは、これら金属の混合物が挙げられる。よって、界面イオン伝導層５２は、酸化ニッケル、酸化コバルト、酸化鉄、酸化ルテニウム、または酸化イリジウム、あるいは、これら金属の混合物から成る。金属酸化物から成る界面イオン伝導層は、スパッタ法、レーザーアブレーション法、プラズマＣＶＤ法を用いて形成する。界面イオン伝導層５２は、主イオン伝導層５１の５０％以下の膜厚であることが望ましいが、スパッタ法、レーザーアブレーション法、ＣＶＤ法で安定に形成可能な０．５ｎｍ以上であることが望ましい。
　一方、主イオン伝導層５１は、金属酸化物または酸素を含む化合物から成る。
　金属酸化物から成る主イオン伝導層５１は、スパッタ法、レーザーアブレーション法、プラズマＣＶＤ法を用いて形成される。金属酸化物から成る主イオン伝導層５１を形成するには、焼結したターゲットを用いてスパッタ成膜する。この時、主イオン伝導層５１の金属酸化物の酸素含有量が化学量論量以上となるよう、スパッタチャンバー内には酸素を１０ｓｃｃｍ程度流入する。金属酸化物から成る主イオン伝導層５１としては、酸化タンタル、酸化ジルコニウム、酸化アルミニウム、酸化チタン、もしくは、これら酸化物の混合物が好ましい。
　他方、酸素を含む化合物から成る主イオン伝導層５１は、例えば、シリコン、酸素、炭素、水素を含むＳｉＯＣＨ系であり、プラズマＣＶＤによって形成される。環状有機シロキサンの原料とキャリアガスであるヘリウムを反応室内に流入し、両者の供給が安定化し、反応室の圧力が一定になったところでＲＦ電力の印加を開始する。原料の供給量は１０~２００ｓｃｃｍ、ヘリウムの供給は原料気化器経由で５００ｓｃｃｍ、別ラインで反応室に直接５００ｓｃｃｍ供給する。
　［動作］
　次に、実施例３による２端子スイッチング素子の動作について、図８を参照して説明する。
　第２電極２２を接地すると共に第１電極２１に正電圧を印加すると、第１電極２１の金属が界面イオン伝導層５２を介して金属イオンＭＩになって、主イオン伝導層５１に溶解する。そして、界面イオン伝導層５２および主イオン伝導層５１中の金属イオンＭＩが第２電極２２の表面に金属架橋Ｂになって析出し、金属架橋Ｂが延びるほど第１電極２１と第２電極２２との間の電気抵抗が小さくなる。さらに、析出した金属架橋Ｂが第１電極２１にまで十分に達すると、第１電極２１と第２電極２２が電気的に接続される。金属架橋Ｂで第１電極２１と第２電極２２が電気的に接続することで、スイッチがオン状態になる。
　さらに、上記オン状態で、第２電極２２を接地すると共に第１電極２１に負電圧を印加すると、金属架橋Ｂが界面イオン伝導層５２および主イオン伝導層５１に金属イオンＭＩとなって溶解し、金属架橋Ｂの一部が切れ、金属架橋Ｂが欠損するほど第１電極２１と第２電極２２との間の電気抵抗が大きくなる。この際、金属イオンＭＩは界面イオン伝導層５２および主イオン伝導層５１内に分散した金属と第１電極２１に回収される。さらに、金属架橋Ｂが十分に欠損すると、第１電極２１と第２電極２２との電気的接続が切れ、スイッチがオフ状態になる。
　上記オフ状態からオン状態にするには、再び第２電極２２に正電圧を印加すればよい。また、第１電極２１を接地し、第２電極２２に負電圧を印加してスイッチをオン状態にしたり、第１電極２１を接地し、第２電極２２に正電圧を印加してスイッチをオフ状態にしたりしてもよい。
　尚、スイッチがオフ状態になるとき、電気的接続が完全に切れる前の段階から第１電極２１および第２電極２２間の抵抗が大きくなったり、電極間容量が変化したりするなど電気特性の変化があって、最終的に電気的接続が切れる。
　［製造方法］
　次に、実施例３によるスイッチング素子の製造方法について、図９（ａ）~（ｄ）を参照して説明する。
　［工程１］　図９（ａ）に示されるように、低抵抗シリコン基板Ｓの表面に膜厚２０ｎｍのタンタル、その上に１００ｎｍの銅をスパッタ法で成膜し、第１電極２１を形成する。
　［工程２］　図９（ｂ）に示されるように、ニッケルもしくは鉄を２ｎｍの層厚でスパッタ成膜し金属層５０を形成する。
　［工程３］　図９（ｃ）に示されるように、酸素を含む化合物から成る主イオン伝導層５１として、膜厚８ｎｍの酸化タンタルと酸化シリコンの混合物薄膜を形成する。スパッタには、酸化タンタルが７４％、酸化シリコンが２４％含まれた焼結ターゲットを用いた。主イオン伝導層５１はスパッタ法により堆積する。ここで、成膜された酸化タンタルと酸化シリコンの混合物の組成は化学量論量以上になるようにする。具体的には、スパッタを行う際に、供給する酸素量を最適化する。本発明者等は、酸素流量１０ｓｃｃｍとアルゴン流量４０ｓｃｃｍの混合ガスを流した成膜条件で成膜し、化学量論量以上の酸化タンタルを得た。
　この際、主イオン伝導層５１成膜時の酸素を浴びることにより、金属層５０は酸化され、酸化ニッケルもしくは酸化鉄から成る界面イオン伝導層５２となる。界面イオン伝導層５２の酸素の組成は化学量論量未満である。
　［工程４］　図９（ｄ）に示されるように、主イオン伝導層５１の上に真空蒸着法もしくはスパッタ法により膜厚３０ｎｍのルテニウムを堆積させる。この際、ステンレスもしくはシリコンで作製されたシャドーマスクを介してルテニウムを堆積し、平面形状が一辺３０μｍ~１５０μｍの正方形の第２電極２２を形成する。
　［特性検証］
　次に、実施例３によるスイッチング素子の特性検証について、さらに図１０ならびに図１１（ａ）および（ｂ）を参照して説明する。
　図１０は、実施例３によるスイッチング素子の特性検証として、組成が異なる界面イオン伝導層を有する４種類のスイッチング素子と、界面イオン伝導層を持たない１種類のスイッチング素子について、印加電界に対するオフからオンまでの時間を示した図である。前者４種類の内訳は、酸化鉄、酸化ニッケルそれぞれから成る界面イオン伝導層５２を有する２種類のスイッチング素子（実施例３）と、酸化チタン、酸化タングステンそれぞれから成る界面イオン伝導層を有する２種類のスイッチング素子（比較例）とである。後者１種類の界面イオン伝導層が無く主イオン伝導層のみのスイッチング素子も比較例である。
　検証のための測定は、第１電極２１のＣｕに低抵抗シリコン基板Ｓを介して正方向の定電圧を印加し、オフからオンまでの時間を測定する方法とした。この際、第２電極２２のルテニウムは接地した。
　図１０から明らかなように、本発明による酸化ニッケル、酸化鉄を界面イオン伝導層５２に用いたスイッチング素子は、主イオン伝導層のみを持ち界面イオン伝導層を持たない比較例のスイッチング素子に比べて、同じ電界を印加した場合のオフからオンへの遷移時間が長い。即ち、ディスターブ特性に優れている。一方、酸化チタン、酸化タングステンを界面イオン伝導層に用いた比較例のスイッチング素子は、本発明のスイッチング素子に比べて、また、主イオン伝導層のみを持つ比較例のスイッチング素子に比べても、同じ電界を印加した場合のオフからオンへの遷移時間が短い。即ち、ディスターブ特性に劣っている。
　ここで、２種類のスイッチング素子における界面イオン伝導層の光電子分光法（ＸＰＳ）測定結果を、図１１（ａ）および（ｂ）に示す。
　図１１（ａ）および（ｂ）を参照すると、図１０に示されるようにオフからオンへの遷移時間が短い（ディスターブ特性に劣る）スイッチング素子（比較例）に用いた酸化チタン（図１１（ｂ））は、酸化物に由来するピークが観測されており、十分に酸化してしまっていることが分かる。
　一方、オフからオンへの遷移時間が長い（ディスターブ特性に優れる）スイッチング素子（実施例３）に用いた酸化ニッケル（図１１（ａ））は、酸化物ではなく金属状態のニッケルに由来するピークが主に確認された。即ち、界面イオン伝導層５２の金属材料としてのニッケルは、主イオン伝導層５１の成膜時に十分には酸化されず、酸素の組成比が化学量論量未満となり、金属的な部分が残ったと言える。これは、ニッケルおよび鉄の標準ギブズエネルギーの絶対値が小さいことに由来している。このように界面イオン伝導層５２は酸素の組成比が化学量論量未満であるため、酸素イオンが第１電極２１の銅に対して十分には供給されず、銅のイオン化が進行し難いため、本発明のスイッチング素子は、オフからオンへの時間が長い。即ち、ディスターブ特性に優れている。 The switching element according to Example 3 of the present invention includes a main ion conductive layer and an interface ion conductive layer in which the ion conductive layers are stacked on each other, and the oxygen composition ratio of the interface ion conductive layer including the interface with the first electrode is chemical. The difference from Example 2 is that the amount is less than the stoichiometric amount. For this reason, detailed description of the same or similar parts as in the second embodiment will be omitted.
[Outline of configuration and manufacturing method]
Referring to FIG. 7, the switching element according to the third embodiment of the present invention is in the form of a two-terminal switching element. The switching element includes a first electrode 21 and a second electrode 22 which are arranged to face each other at a distance, and an interfacial ion conductive layer 52 and a main ion conductive layer 51 sandwiched between both electrodes. The interfacial ion conductive layer 52 is in contact with the first electrode 21 (including the interface with the first electrode).
The first electrode 21 is made of copper for supplying metal ions into the interface ion conductive layer 52 and the main ion conductive layer 51 when a voltage is applied. The first electrode 21 is formed by sputtering, chemical vapor deposition (CVD), electroplating. Formed by law.
The material of the second electrode 22 is preferably a material that does not supply metal ions into the main ion conduction layer 51 and the interface ion conduction layer 52 when a voltage is applied. More specifically, the second electrode 22 is preferably made of ruthenium, platinum, or nickel. In particular, it is preferably made of ruthenium.
The main ion conduction layer 51 and the interface ion conduction layer 52 serve as a medium for conducting metal ions.
Interfacial ion conductive layer 52 is formed of a metal oxide. First, a metal constituting an oxide is formed on the first electrode 21, and is oxidized by oxygen existing in the chamber during the formation of the main ion conductive layer 51 containing oxygen as described later. Thus, the interfacial ion conductive layer 52 made of a metal oxide is obtained.
Here, the metal material of the interfacial ion conductive layer 52 made of a metal oxide is preferably a metal that is difficult to oxidize, that is, a metal having a small standard Gibbs energy absolute value. This is because a standard Gibbs energy having a small absolute value and a metal that is difficult to oxidize is not sufficiently oxidized even by oxygen present in the chamber during the formation of the main ion conductive layer 51, and therefore, an interface ion made of a metal oxide. This is because the oxygen composition ratio of the conductive layer 52 is less than the stoichiometric amount. Thereby, it becomes difficult to ionize copper, and the transition time from OFF to ON under constant voltage application can be lengthened.
Specifically, according to experiments conducted by the inventors, a metal having a standard Gibbs energy greater than −600 kJ / mol at 300 K has obtained good results as a metal material for an interfacial ion conductive layer made of a metal oxide. . In particular, with a metal having a standard Gibbs energy greater than −600 kJ / mol, the composition ratio of oxygen could be made less than the stoichiometric amount even when the thickness of the interface ion conductive layer was greater than 5 nm.
Examples of the metal material of the interfacial ion conductive layer that satisfies this condition include nickel, cobalt, iron, ruthenium, iridium, or a mixture of these metals. Therefore, the interfacial ion conductive layer 52 is made of nickel oxide, cobalt oxide, iron oxide, ruthenium oxide, iridium oxide, or a mixture of these metals. The interfacial ion conductive layer made of a metal oxide is formed by sputtering, laser ablation, or plasma CVD. The interfacial ion conduction layer 52 is desirably 50% or less of the film thickness of the main ion conduction layer 51, but is desirably 0.5 nm or more that can be stably formed by sputtering, laser ablation, or CVD. .
On the other hand, the main ion conductive layer 51 is made of a metal oxide or a compound containing oxygen.
The main ion conductive layer 51 made of a metal oxide is formed using a sputtering method, a laser ablation method, or a plasma CVD method. In order to form the main ion conductive layer 51 made of metal oxide, sputtering is performed using a sintered target. At this time, about 10 sccm of oxygen is allowed to flow into the sputtering chamber so that the oxygen content of the metal oxide of the main ion conductive layer 51 is not less than the stoichiometric amount. The main ion conductive layer 51 made of a metal oxide is preferably tantalum oxide, zirconium oxide, aluminum oxide, titanium oxide, or a mixture of these oxides.
On the other hand, the main ion conductive layer 51 made of a compound containing oxygen is, for example, a SiOCH system containing silicon, oxygen, carbon, and hydrogen, and is formed by plasma CVD. The cyclic organosiloxane raw material and the carrier gas helium flow into the reaction chamber, the supply of both is stabilized, and the application of RF power is started when the pressure in the reaction chamber becomes constant. The supply amount of the raw material is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is directly supplied to the reaction chamber through a separate line.
[Operation]
Next, the operation of the two-terminal switching element according to Example 3 will be described with reference to FIG.
When the second electrode 22 is grounded and a positive voltage is applied to the first electrode 21, the metal of the first electrode 21 becomes metal ions MI via the interface ion conductive layer 52 and dissolves in the main ion conductive layer 51. Then, the metal ions MI in the interface ion conductive layer 52 and the main ion conductive layer 51 are deposited on the surface of the second electrode 22 as metal bridges B, and the first electrode 21 and the second electrode 22 are extended as the metal bridge B extends. The electrical resistance between the two becomes smaller. Furthermore, when the deposited metal bridge B sufficiently reaches the first electrode 21, the first electrode 21 and the second electrode 22 are electrically connected. When the first electrode 21 and the second electrode 22 are electrically connected by the metal bridge B, the switch is turned on.
Further, when the second electrode 22 is grounded and a negative voltage is applied to the first electrode 21 in the ON state, the metal bridge B dissolves in the interface ion conductive layer 52 and the main ion conductive layer 51 as metal ions MI. The electrical resistance between the first electrode 21 and the second electrode 22 increases as a part of the metal bridge B is cut and the metal bridge B is lost. At this time, the metal ions MI are collected by the metal dispersed in the interfacial ion conductive layer 52 and the main ion conductive layer 51 and the first electrode 21. Furthermore, if the metal bridge B is sufficiently lost, the electrical connection between the first electrode 21 and the second electrode 22 is cut, and the switch is turned off.
In order to change from the off state to the on state, a positive voltage may be applied to the second electrode 22 again. Also, the first electrode 21 is grounded and a negative voltage is applied to the second electrode 22 to turn on the switch, or the first electrode 21 is grounded and a positive voltage is applied to the second electrode 22 to turn off the switch. Or may be in a state.
When the switch is turned off, the electrical characteristics such as the resistance between the first electrode 21 and the second electrode 22 increases and the capacitance between the electrodes changes from the stage before the electrical connection is completely cut off. There is a change and eventually the electrical connection is broken.
[Production method]
Next, a method for manufacturing a switching element according to Example 3 will be described with reference to FIGS.
[Step 1] As shown in FIG. 9A, a 20-nm-thick tantalum film is formed on the surface of a low-resistance silicon substrate S, and a 100-nm copper film is formed thereon by sputtering to form a first electrode 21. .
[Step 2] As shown in FIG. 9B, a metal layer 50 is formed by sputtering nickel or iron with a layer thickness of 2 nm.
[Step 3] As shown in FIG. 9C, a mixed thin film of tantalum oxide and silicon oxide having a thickness of 8 nm is formed as the main ion conductive layer 51 made of a compound containing oxygen. For sputtering, a sintered target containing 74% tantalum oxide and 24% silicon oxide was used. The main ion conductive layer 51 is deposited by sputtering. Here, the composition of the formed mixture of tantalum oxide and silicon oxide is set to a stoichiometric amount or more. Specifically, the amount of oxygen to be supplied is optimized when performing sputtering. The inventors of the present invention formed a film under conditions of flowing a mixed gas having an oxygen flow rate of 10 sccm and an argon flow rate of 40 sccm to obtain tantalum oxide having a stoichiometric amount or more.
At this time, the metal layer 50 is oxidized by being exposed to oxygen at the time of forming the main ion conductive layer 51 to become an interface ion conductive layer 52 made of nickel oxide or iron oxide. The composition of oxygen in the interfacial ion conductive layer 52 is less than the stoichiometric amount.
[Step 4] As shown in FIG. 9D, ruthenium having a film thickness of 30 nm is deposited on the main ion conductive layer 51 by vacuum vapor deposition or sputtering. At this time, ruthenium is deposited through a shadow mask made of stainless steel or silicon to form a square second electrode 22 having a planar shape with sides of 30 μm to 150 μm.
[Characteristic verification]
Next, characteristic verification of the switching element according to the third embodiment will be described with reference to FIG. 10 and FIGS. 11 (a) and 11 (b).
FIG. 10 is a graph showing characteristics of the switching element according to Example 3, in which four types of switching elements having an interface ion conductive layer having different compositions and one type of switching element having no interface ion conductive layer are turned off from an applied electric field. It is the figure which showed the time until ON. The breakdown of the former four types includes two types of switching elements (Example 3) having an interface ion conductive layer 52 made of iron oxide and nickel oxide, and two types having an interface ion conductive layer made of titanium oxide and tungsten oxide, respectively. Switching element (comparative example). A switching element having only the main ion conductive layer without the one type of interfacial ion conductive layer is also a comparative example.
For the measurement for verification, a constant voltage in the positive direction was applied to Cu of the first electrode 21 via the low-resistance silicon substrate S, and the time from off to on was measured. At this time, the ruthenium of the second electrode 22 was grounded.
As is clear from FIG. 10, the switching element using nickel oxide and iron oxide according to the present invention for the interfacial ion conductive layer 52 has only the main ion conductive layer and does not have the interfacial ion conductive layer. Thus, the transition time from OFF to ON when the same electric field is applied is long. That is, it has excellent disturb characteristics. On the other hand, the switching element of the comparative example using titanium oxide and tungsten oxide for the interfacial ion conductive layer is more in comparison with the switching element of the present invention, and compared with the switching element of the comparative example having only the main ion conductive layer, The transition time from OFF to ON when the same electric field is applied is short. That is, the disturb characteristic is inferior.
Here, the photoelectron spectroscopy (XPS) measurement result of the interface ion conductive layer in two types of switching elements is shown in FIGS.
Referring to FIGS. 11 (a) and 11 (b), as shown in FIG. 10, the titanium oxide used in the switching element (comparative example) having a short transition time from OFF to ON (inferior to disturb characteristics) (FIG. 11 ( In b)), a peak derived from an oxide is observed, and it can be seen that it has been sufficiently oxidized.
On the other hand, the nickel oxide (FIG. 11 (a)) used for the switching element (Example 3) having a long transition time from off to on (excellent in disturb characteristics) is a peak derived from nickel in a metal state instead of an oxide. Was mainly confirmed. That is, nickel as the metal material of the interfacial ion conductive layer 52 is not sufficiently oxidized when the main ion conductive layer 51 is formed, the oxygen composition ratio becomes less than the stoichiometric amount, and the metallic part remains. I can say that. This is because the absolute value of the standard Gibbs energy of nickel and iron is small. Thus, since the interface ion conductive layer 52 has an oxygen composition ratio less than the stoichiometric amount, oxygen ions are not sufficiently supplied to the copper of the first electrode 21, and copper ionization is difficult to proceed. The switching element of the present invention takes a long time from off to on. That is, it has excellent disturb characteristics.
　本発明の実施例４による半導体装置は、実施例３の２端子スイッチング素子に相当するスイッチング素子を多層配線層内に有する半導体装置である。
　［構成］
　図１２を参照すると、本発明の実施例４による半導体装置は、半導体基板１６１上の多層配線層の内部にスイッチング素子１４０を有している。
　多層配線層は、半導体基板１６１上にて、層間絶縁膜１６２、バリア絶縁膜１６３、層間絶縁膜１６４、バリア絶縁１６６、保護絶縁膜１６７、層間絶縁膜１６８、エッチングストッパ膜ＥＳ、層間絶縁膜１７０、およびバリア絶縁膜１７３の順に積層した絶縁積層体を有している。
　層間絶縁膜１６４およびバリア絶縁膜１６３に形成された配線溝には、バリアメタル１６５を介して第１配線１２１が埋め込まれている。層間絶縁膜１７０およびエッチングストッパ膜ＥＳに形成された配線溝には、第２配線１７２が埋め込まれている。また、層間絶縁膜１６８、保護絶縁膜１６７、およびハードマスク膜ＨＭ２に形成された下穴には、プラグ１７１が埋め込まれている。さらに、第２配線１７２とプラグ１７１とは一体となっており、一体の第２配線１７２およびプラグ１７１は側面から底面に亘ってバリアメタル１６９によって覆われている。
　バリア絶縁膜１６６に形成された開口部を臨む第１配線１２１ならびにバリア絶縁膜１６６の開口部の内壁面乃至バリア絶縁膜１６６上には、酸化防止膜１５２、イオン伝導膜１５１、第２電極第一層１２２ａ、および第２電極第二層１２２ｂが形成されている。第２電極第二層１２２ｂ上には、ハードマスク膜ＨＭ２が形成されている。さらに、酸化防止膜１５２、イオン伝導膜１５１、第２電極第一層１２２ａ、第２電極第二層１２２ｂ、およびハードマスク膜ＨＭ２の積層体の上面乃至側面は、保護絶縁膜１６７で覆われている。
　本半導体装置において、スイッチング素子１４０は、第１電極としての第１配線１２１と、界面イオン伝導層としての酸化防止膜１５２と、主イオン伝導層としてのイオン伝導膜１５１と、第２電極としての２電極第一層１２２ａおよび第２電極第二層１２２ｂとによって構成されている。積層された酸化防止膜１５２およびイオン伝導膜１５１を、抵抗変化層１５０と呼ぶ。
　第１配線１２１がスイッチング素子１４０の第１電極として機能させることにより、工程数を簡略化しながら、電極抵抗を下げることができる。通常の銅ダマシン配線プロセスに追加工程として、少なくとも２ＰＲのマスクセットを作成するだけで、２端子スイッチング素子を搭載することができ、素子の低抵抗化と低コスト化を同時に達成することができるようになる。
　スイッチング素子１４０は、バリア絶縁膜１６６に形成された開口部の領域にて酸化防止膜１５２と第１配線１２１が直接接しており、イオン伝導膜１５１と第２電極第一層１２２ａが直接接しており、第２電極第二層１２２ｂ上にてプラグ１７１と第２電極第二層１２２ｂとがバリアメタル１６９を介して電気的に接続されている。
　スイッチング素子１４０は、電圧の印加、あるいは電流を流すことでオン／オフの制御を行い、例えば、酸化防止膜１５２およびイオン伝導膜１５１中への第１配線１２１に係る金属の電界拡散を利用してオン／オフの制御を行う。
　半導体基板１６１は、半導体素子が形成された基板である。半導体基板１６１には、例えば、シリコン基板、単結晶基板、ＳＯＩ（Ｓｉｌｉｃｏｎ　ｏｎ　Ｉｎｓｕｌａｔｏｒ）基板、ＴＦＴ（Ｔｈｉｎ　Ｆｉｌｍ　Ｔｒａｎｓｉｓｔｏｒ）基板、液晶製造用基板等の基板を用いることができる。
　層間絶縁膜１６２は、半導体基板１６１上に形成された絶縁膜である。層間絶縁膜１６２には、例えば、シリコン酸化膜、シリコン酸化膜よりも比誘電率の低い低誘電率膜（例えば、ＳｉＯＣＨ膜）等を用いることができる。層間絶縁膜１６２は、複数の絶縁膜を積層したものであってもよい。
　バリア絶縁膜１６３は、層間絶縁膜１６２、１６４間に介在したバリア性を有する絶縁膜である。バリア絶縁膜１６３は、第１配線１２１用の配線溝の加工時にエッチングストップ層としての役割を有する。バリア絶縁膜１６３には、例えば、窒化シリコン膜、ＳｉＣ膜、ＳｉＣＮ膜等を用いることができる。バリア絶縁膜１６３には、第１配線１２１を埋め込むための配線溝が形成されており、当該配線溝にバリアメタル１６５を介して第１配線１２１が埋め込まれている。バリア絶縁膜１６３は、配線溝のエッチング条件の選択によっては削除することもできる。
　層間絶縁膜１６４は、バリア絶縁膜１６３上に形成された絶縁膜である。層間絶縁膜１６４には、例えば、シリコン酸化膜、シリコン酸化膜よりも比誘電率の低い低誘電率膜（例えば、ＳｉＯＣＨ膜）等を用いることができる。層間絶縁膜１６４は、複数の絶縁膜を積層したものであってもよい。層間絶縁膜１６４には、第１配線１２１を埋め込むための配線溝が形成されており、当該配線溝にバリアメタル１６５を介して第１配線１２１が埋め込まれている。
　スイッチング素子１４０の第１電極としての第１配線１２１は、層間絶縁膜１６４およびバリア絶縁膜１６３に形成された配線溝にバリアメタル１６５を介して埋め込まれた配線である。第１配線１２１には、抵抗変化層１５０において拡散、イオン電導可能な金属が用いられる。例えば、銅等を用いることができる。第１配線１２１は、アルミニウムと合金化されていてもよい。バリアメタル１６５は、第１配線１２１に係る金属が層間絶縁膜１６４や下層へ拡散することを防止するために、第１配線１２１の側面乃至底面を被覆する、バリア性を有する導電性膜である。バリアメタル１６５には、例えば、第１配線１２１が銅を主成分とする金属元素からなる場合には、タンタル、窒化タンタル、窒化チタン、炭窒化タングステンのような高融点金属やその窒化物等、またはそれらの積層膜を用いることができる。
　バリア絶縁膜１６６は、第１配線１２１を含む層間絶縁膜１６４上に形成され、第１配線１２１に係る金属（例えば、銅）の酸化を防いだり、層間絶縁膜１６８中への第１配線１２１に係る金属の拡散を防いだり、第２電極１２１、１２０、および抵抗変化層１５０の加工時にエッチングストップ層としての役割を有する。バリア絶縁膜１６６には、例えば、ＳｉＣ膜、ＳｉＣＮ膜、窒化シリコン膜、およびそれらの積層構造等を用いることができる。バリア絶縁膜１６６は、保護絶縁膜１６７およびハードマスク膜ＨＭ２と同一材料であることが好ましい。
　積層された酸化防止膜１５２およびイオン伝導膜１５１によって構成された抵抗変化層１５０は、スイッチング素子１４０における抵抗が変化する膜である。よって、第１配線１２１（第１電極）に係る金属の作用（拡散、イオン伝導など）によって抵抗が変化する材料を用いる。スイッチング素子１４０の抵抗変化を金属イオンの析出によって行う場合には、イオン伝導可能な膜が用いられる。
　スイッチング素子１４０における主イオン伝導層としてのイオン伝導膜１５１は、スパッタ法、レーザーアブレーション法、プラズマＣＶＤ法を用いて形成する。イオン伝導膜１５１を金属酸化物によって形成する場合には、焼結したターゲットを用いてスパッタ成膜する。この時、成膜された金属酸化物の化学量論が損なわれないよう、スパッタチャンバー内に１０ｓｃｃｍの酸素を流入する。金属酸化物から成るイオン伝導膜１５１には、酸化タンタル、酸化ジルコニウム、酸化アルミニウム、酸化チタンおよび、それらの混合物が好ましい。他方、イオン伝導膜１５１をＳｉＯＣＨ系化合物によって形成する場合には、プラズマＣＶＤによって形成する。環状有機シロキサンの原料とキャリアガスであるヘリウムを反応室内に流入し、両者の供給が安定化し、反応室の圧力が一定になったところでＲＦ電力の印加を開始する。原料の供給量は１０~２００ｓｃｃｍ、ヘリウムの供給は原料気化器経由で５００ｓｃｃｍ、別ラインで反応室に直接５００ｓｃｃｍ供給する。
　スイッチング素子１４０における界面イオン伝導層としての酸化防止膜１５２は、第１配線１２１に係る金属が、イオン伝導膜１５１を堆積している間の加熱やプラズマでイオン伝導膜１５１中に拡散することを防止する役割と、酸化防止膜として第１配線１２１からの第１配線１２１に関わる金属のイオン化、および金属イオンの酸化防止膜１５２、およびイオン伝導膜１５１への注入を制御する。酸化防止膜１５２の金属、例えばニッケル、コバルト、鉄、ルテニウム、イリジウムは、イオン伝導膜１５１の成膜中に酸化ニッケル、酸化コバルト、酸化鉄、酸化ルテニウム、酸化イリジウムとなり、抵抗変化層１５０の一部となる。抵抗変化層１５０は、第１配線１２１、バリア絶縁膜１６６の開口部のテーパ面、乃至バリア絶縁膜１６６上に形成されている。抵抗変化層１５０は、第１配線１２１と抵抗変化層１５０の接続部の外周部分が少なくともバリア絶縁膜１６６の開口部のテーパ面上に沿って配設されている。
　スイッチング素子１４０における第２電極の一部としての第２電極第一層１２２ａは、スイッチング素子１４０の第２電極における下層側の電極であり、イオン伝導膜１５１と直接接している。第２電極第一層１２２ａには、第１配線１２１に係る金属よりもイオン化し難く、イオン伝導膜１５１において拡散やイオン伝導し難い金属が用いられ、例えば、白金、ルテニウム、ニッケル等を用いることができる。
　また、スイッチング素子１４０における第２電極の一部としての第２電極第二層１２２ｂは、スイッチング素子１４０の第２電極における上層側の電極であり、第２電極第一層１２２ａ上に形成されている。第２電極第二層１２２ｂは、第２電極第一層１２２ａを保護する役割を有する。即ち、第２電極第二層１２２ｂが第２電極第一層１２２ａを保護することで、プロセス中の第２電極第一層１２２ａへのダメージを抑制し、スイッチング素子１４０のスイッチング特性を維持することができる。第２電極第二層１２２ｂには、例えば、タンタル、チタン、タングステンあるいはそれらの窒化物等を用いることができる。
　ハードマスク膜ＨＭ２は、第２電極第二層１２２ｂ、第２電極第一層１２２ａ、およびイオン伝導膜１５１、酸化防止膜１５２をエッチングする際のハードマスク膜兼パッシベーション膜となる膜である。ハードマスク膜ＨＭ２には、例えば、ＳｉＮ膜等を用いることができる。ハードマスク膜ＨＭ２は、保護絶縁膜１６７、およびバリア絶縁膜１６６と同一材料であることが好ましい。即ち、スイッチング素子１４０の周囲を全て同一材料で囲むことで材料界面部が一体化され、外部からの水分などの浸入を防ぐと共に、スイッチング素子１４０自身からの脱離を防ぐことができるようになる。
　保護絶縁膜１６７は、スイッチング素子１４０にダメージを与えることなく、さらにイオン伝導膜１５１からの酸素の脱離を防ぐ機能を有する絶縁膜である。保護絶縁膜１６７には、例えば、窒化シリコン膜、ＳｉＣＮ膜等を用いることができる。保護絶縁膜１６７は、ハードマスク膜ＨＭ２およびバリア絶縁膜１６６と同一材料であることが好ましい。同一材料である場合には、保護絶縁膜１６７とバリア絶縁膜１６６およびハードマスク膜ＨＭ２とが一体化して、界面部の密着性が向上し、スイッチング素子１４０をより保護することができるようになる。
層間絶縁膜１６８は、保護絶縁膜１６７上に形成された絶縁膜である。層間絶縁膜１６８には、例えば、シリコン酸化膜、ＳｉＯＣ膜、シリコン酸化膜よりも比誘電率の低い低誘電率膜（例えば、ＳｉＯＣＨ膜）などを用いることができる。層間絶縁膜１６８は、複数の絶縁膜を積層したものであってもよい。層間絶縁膜１６８は、層間絶縁膜１７０と同一材料としてもよい。層間絶縁膜１６８には、プラグ１７１を埋め込むための下穴が形成されており、当該下穴にバリアメタル１６９を介してプラグ１７１が埋め込まれている。
　エッチングストッパ膜ＥＳは、層間絶縁膜１６８、１７０間に介在した絶縁膜である。エッチングストッパ膜ＥＳは、第２配線１７２用の配線溝の加工時にエッチングストップ層としての役割を有する。エッチングストッパ膜ＥＳには、例えば、ＳｉＮ膜、ＳｉＣ膜、ＳｉＣＮ膜等を用いることができる。エッチングストッパ膜ＥＳには、第２配線１７２を埋め込むための配線溝が形成されており、当該配線溝にバリアメタル１６９を介して第２配線１７２が埋め込まれている。エッチングストッパ膜ＥＳは、配線溝のエッチング条件の選択によっては削除することもできる。
　層間絶縁膜１７０は、エッチングストッパ膜ＥＳ上に形成された絶縁膜である。層間絶縁膜１７０には、例えば、シリコン酸化膜、ＳｉＯＣ膜、シリコン酸化膜よりも比誘電率の低い低誘電率膜（例えば、ＳｉＯＣＨ膜）などを用いることができる。層間絶縁膜１７０は、複数の絶縁膜を積層したものであってもよい。層間絶縁膜１７０は、層間絶縁膜１５と同一材料としてもよい。層間絶縁膜１７０には、第２配線１７２を埋め込むための配線溝が形成されており、当該配線溝にバリアメタル１６９を介して第２配線１７２が埋め込まれている。
　第２配線１７２は、層間絶縁膜１７０およびエッチングストッパ膜ＥＳに形成された配線溝にバリアメタル１６９を介して埋め込まれた配線である。第２配線１７２は、プラグ１７１と一体になっている。プラグ１７１は、層間絶縁膜１６８、保護絶縁膜１６７、およびハードマスク膜ＨＭ２に形成された下穴にバリアメタル１６９を介して埋め込まれている。プラグ１７１は、バリアメタル１６９を介して第２電極第二層１２２ｂと電気的に接続されている。第２配線１７２およびプラグ１７１には、例えば、Ｃｕを用いることができる。
　バリアメタル１６９は、第２配線１７２（プラグ１７１を含む）に係る金属が層間絶縁膜１６８、１７０や下層へ拡散することを防止するために、第２配線１７２およびプラグ１７１の側面乃至底面を被覆する、バリア性を有する導電性膜である。バリアメタル１１０には、例えば、第２配線１０８およびプラグ１７１がＣｕを主成分とする金属元素からなる場合には、タンタル、窒化タンタル、窒化チタン、炭窒化タングステンのような高融点金属やその窒化物等、またはそれらの積層膜を用いることができる。バリアメタル１６９は、第２電極第二層１２２ｂと同一材料であることが好ましい。例えば、バリアメタル１６９がＴａＮ（下層）／Ｔａ（上層）の積層構造である場合には、下層材料であるＴａＮを第２電極第二層１２２ｂに用いることが好ましい。あるいは、バリアメタル１１０がＴｉ（下層）／Ｒｕ（上層）である場合は、下層材料であるＴｉを第２電極第二層１２２ｂに用いることが好ましい。
　バリア絶縁膜１７３は、第２配線１７２を含む層間絶縁膜１７０上に形成され、第２配線１７２に係る金属（例えば、銅）の酸化を防いだり、上層への第２配線１７２に係る金属の拡散を防ぐ役割を有する絶縁膜である。バリア絶縁膜１７３には、例えば、ＳｉＣ膜、ＳｉＣＮ膜、ＳｉＮ膜、およびそれらの積層構造等を用いることができる。
　［製造方法］
　次に、実施例４による半導体装置の製造方法について、図１３（ａ）~（ｆ）ならびに図１４（ａ）~（ｆ）を参照して説明する。
　［工程１］　図１３（ａ）に示されるように、半導体基板１６１（例えば、半導体素子が形成された基板）上に層間絶縁膜１６２（例えば、シリコン酸化膜、膜厚３００ｎｍ）を堆積し、その後、層間絶縁膜１６２にバリア絶縁膜１６３（例えば、窒化シリコン膜、膜厚５０ｎｍ）を堆積し、その後、バリア絶縁膜１６３上に層間絶縁膜１６４（例えば、シリコン酸化膜、膜厚３００ｎｍ）を堆積し、その後、リソグラフィ法（フォトレジスト形成、ドライエッチング、フォトレジスト除去を含む）を用いて、層間絶縁膜１６４およびバリア絶縁膜１６３に配線溝を形成する。
　その後、当該配線溝にバリアメタル１６５（例えば、窒化タンタル／タンタル、膜厚５ｎｍ／５ｎｍ）を介して、第１電極としての第１配線１２１（例えば、銅）を埋め込む。
　層間絶縁膜１６２、１６４は、プラズマＣＶＤ法によって形成することができる。第１配線１２１は、例えば、ＰＶＤ法によってバリアメタル１６５（例えば、窒化タンタル／タンタルの積層膜）を形成し、ＰＶＤ法によるＣｕシードの形成後、電解めっき法によって銅を配線溝内に埋設し、２００℃以上の温度で熱処理処理後、ＣＭＰ法によって配線溝内以外の余剰の銅を除去することで形成することができる。このような一連の銅配線の形成方法は、当該技術分野における一般的な手法を用いることができる。ここで、ＣＭＰ（Ｃｈｅｍｉｃａｌ　Ｍｅｃｈａｎｉｃａｌ　Ｐｏｌｉｓｈｉｎｇ）法とは、多層配線形成プロセス中に生じるウェハ表面の凹凸を、研磨液をウェハ表面に流しながら回転させた研磨パッドに接触させて研磨することによって平坦化する方法である。溝に埋め込まれた余剰の銅を研磨することによって埋め込み配線（ダマシン配線）を形成したり、層間絶縁膜を研磨することで平坦化を行う。
　［工程２］　図１３（ｂ）に示されるように、第１配線１２１を含む層間絶縁膜１６４上にバリア絶縁膜１６６（例えば、窒化シリコン膜、膜厚５０ｎｍ）を形成する。ここで、バリア絶縁膜１６６は、プラズマＣＶＤ法によって形成することができる。バリア絶縁膜１６６の膜厚は、１０~５０ｎｍ程度であることが好ましい。
　［工程３］　図１３（ｃ）に示されるように、バリア絶縁膜１６６上にハードマスク膜ＨＭ１（例えば、シリコン酸化膜）を形成する。このとき、ハードマスク膜ＨＭ１は、ドライエッチング加工におけるエッチング選択比を大きく保つ観点から、バリア絶縁膜１６６とは異なる材料であることが好ましく、絶縁膜であっても導電膜であってもよい。ハードマスク膜ＨＭ１には、例えば、シリコン酸化膜、シリコン窒化膜、窒化チタン、チタン、タンタル、窒化タンタル等を用いることができ、窒化シリコン／シリコン酸化膜の積層体を用いることができる。
　［工程４］　図１３（ｄ）に示されるように、ハードマスク膜ＨＭ１上にフォトレジスト（図示せず）を用いて開口部をパターニングし、フォトレジストをマスクとしてドライエッチングすることによりハードマスク膜ＨＭ１に開口部パターンを形成し、その後、酸素プラズマアッシング等によってフォトレジストを剥離する。このとき、ドライエッチングは必ずしもバリア絶縁膜１６６の上面で停止している必要はなく、バリア絶縁膜１６６の内部にまで到達していてもよい。
　［工程５］　図１３（ｅ）に示されるように、ハードマスク膜ＨＭ１をマスクとして、ハードマスク膜ＨＭ１の開口部から露出するバリア絶縁膜１６６をエッチバック（ドライエッチング）することにより、バリア絶縁膜１６６に開口部を形成して、バリア絶縁膜１６６の開口部から第１配線１２１を露出させ、その後、アミン系の剥離液などで有機剥離処理を行うことで、第１配線１２１の露出面に形成された酸化銅を除去すると共に、エッチバック時に発生したエッチング複生成物などを除去する。バリア絶縁膜１６６をエッチバックでは、反応性ドライエッチングを用いることで、バリア絶縁膜１６６の開口部の内壁面をテーパ面とすることができる。反応性ドライエッチングでは、エッチングガスとしてフルオロカーボンを含むガスを用いることができる。ハードマスク膜ＨＭ１は、エッチバック中に完全に除去されることが好ましいが、絶縁材料である場にはそのまま残存してもよい。また、バリア絶縁膜１６６の開口部の形状は円形とし、円の直径は３０ｎｍから５００ｎｍとすることができる。非反応性ガスを用いたＲＦ（Ｒａｄｉｏ　Ｆｒｅｑｕｅｎｃｙ；高周波）エッチングによって、第１配線１２１の表面の酸化物を除去する。非反応性ガスとしては、ヘリウムやアルゴンを用いることができる。
　［工程６］　図１３（ｆ）に示されるように、第１配線１２１を含むバリア絶縁膜１６６上に４ｎｍ以下の鉄（例えば、膜厚１ｎｍ）を堆積する。鉄はＰＶＤ法やＣＶＤ法を用いて形成することができる。
　さらに、主イオン伝導層としてのイオン伝導膜１５１を、シリコン、酸素、炭素、水素を含むＳｉＯＣＨ系ポリマー膜をプラズマＣＶＤによって形成する。環状有機シロキサンの原料とキャリアガスであるヘリウムを反応室内に流入し、両者の供給が安定化し、反応室の圧力が一定になったところでＲＦ電力の印加を開始する。原料の供給量は１０~２００ｓｃｃｍ、ヘリウムの供給は原料気化器経由で５００ｓｃｃｍ、別ラインで反応室に直接５００ｓｃｃｍ供給する。鉄はイオン伝導膜１５１の形成中に酸素を含むＳｉＯＣＨ系ポリマー膜の原料に曝されることで自動的に酸化し、酸化鉄となることにより、界面イオン伝導層としての酸化防止膜１５２となり、抵抗変化層１５０の一部となる。バリア絶縁膜１６６の開口部は有機剥離処理によって水分などが付着しているため、抵抗変化層１５０の堆積前に２５０℃から３５０℃程度の温度にて、減圧下で熱処理を加えて脱ガスしておくことが好ましい。
　［工程７］　図１４（ａ）に示されるように、抵抗変化層１５０上に、第２電極の一部としての第２電極第一層１２２ａ（例えば、ルテニウム、膜厚１０ｎｍ）と、同じく第２電極の一部としての第２電極第二層１２２ｂ（例えば、タンタル、膜厚５０ｎｍ）とを、この順に形成する。
　［工程８］　図１４（ｂ）に示されるように、第２電極第二層１２２ｂ上にハードマスク膜ＨＭ２（例えば、ＳｉＮ膜、膜厚３０ｎｍ）、およびハードマスク膜ＨＭ３（例えば、ＳｉＯ２膜、膜厚１５０ｎｍ）をこの順に積層する。ハードマスク膜ＨＭ２およびハードマスク膜ＨＭ３は、プラズマＣＶＤ法を用いて成膜することができる。また、ハードマスク膜ＨＭ２とハードマスク膜ＨＭ３とは、異なる種類の膜であることが好ましく、例えば、ハードマスク膜ＨＭ２をＳｉＮ膜とし、ハードマスク膜ＨＭ３をＳｉＯ２膜とすることができる。このとき、ハードマスク膜ＨＭ２は、後述する保護絶縁膜１６７、およびバリア絶縁膜１６６と同一材料であることが好ましい。即ち、スイッチング素子の周囲を全て同一材料で囲むこと材料界面部を一体化し、外部からの水分などの浸入を防ぐと共に、スイッチング素子自身からの脱離防ぐことができるようになる。また、ハードマスク膜ＨＭ２は、プラズマＣＶＤ法によって形成することができるが、例えば、ＳｉＨ４／Ｎ２の混合ガスを高密度プラズマによって、高密度なＳｉＮ膜などを用いることが好ましい。
　［工程９］　図１４（ｃ）に示されるように、ハードマスク膜ＨＭ３上に２端子スイッチング素子部をパターニングするためのフォトレジスト（図示せず）を形成し、その後、当該フォトレジストをマスクとして、ハードマスク膜ＨＭ２が表れるまでハードマスク膜ＨＭ３をドライエッチングし、その後、酸素プラズマアッシングと有機剥離を用いてフォトレジストを除去する。
　［工程１０］　図１４（ｄ）に示されるように、ハードマスク膜ＨＭ３をマスクとして、ハードマスク膜ＨＭ２、第２電極第二層１２２ｂ、第２電極第一層１２２ａ、イオン伝導膜１５１を連続的にドライエッチングする。このとき、ハードマスク膜ＨＭ３は、エッチバック中に完全に除去されることが好ましいが、そのまま残存してもよい。例えば、第２電極第二層１２２ｂがＴａの場合にはＣｌ２系のＲＩＥで加工することができ、第２電極第一層１２２ａがＲｕの場合にはＣｌ２／Ｏ２の混合ガスでＲＩＥ加工することができる。また、イオン伝導膜１５１のエッチングでは、下面のバリア絶縁膜１６６上でドライエッチングを停止させる必要がある。イオン伝導膜１５１がＴａを含む酸化物であり、バリア絶縁膜１６６がＳｉＮ膜やＳｉＣＮ膜である場合には、ＣＦ４系、ＣＦ４／Ｃｌ２系、ＣＦ４／Ｃｌ２／Ａｒ系などの混合ガスでエッチング条件を調節することでＲＩＥ加工することができる。このようなハードマスクＲＩＥ法を用いることで、スイッチング素子部をレジスト除去のための酸素プラズマアッシングに曝すことなく、スイッチング素子部を加工することができる。また、加工後に酸素プラズマによって酸化処理する場合には、レジストの剥離時間に依存することなく酸化プラズマ処理を照射することができるようになる。
　［工程１１］　図１４（ｅ）に示されるように、ハードマスク膜ＨＭ２、第２電極第二層１２２ｂ、第２電極第一層１２２ａ、およびイオン伝導膜１５１を含むバリア絶縁膜１６６上に保護絶縁膜１６７（例えば、窒化シリコン膜、３０ｎｍ）を堆積する。保護絶縁膜１６７は、プラズマＣＶＤ法によって形成することができるが、成膜前には反応室内で減圧化に維持する必要があり、このとき抵抗変化層１５０の側面から酸素が脱離し、イオン伝導層のリーク電流が増加するという問題が生じる。それらを抑制するためには、保護絶縁膜１６７の成膜温度を２５０℃以下とすることが好ましい。さらに、成膜前に減圧化で成膜ガスに曝されるため、還元性のガスを用いないことが好ましい。例えば、ＳｉＨ４／Ｎ２の混合ガスを高密度プラズマによって、基板温度２００℃で形成したＳｉＮ膜などを用いることが好ましい。
　［工程１２］　図１４（ｆ）に示されるように、保護絶縁膜１６７上に、層間絶縁膜１６８（例えば、シリコン酸化膜）、エッチングストッパ膜ＥＳ（例えば、窒化シリコン膜）、層間絶縁膜１７０（例えば、シリコン酸化膜）をこの順に堆積し、その後、第２配線１７２用の配線溝、およびプラグ１７１用の下穴を形成し、銅デュアルダマシン配線プロセスを用いて、当該配線溝および当該下穴内にバリアメタル１６９（例えば、窒化タンタル／タンタル）を介して第２配線１７２（例えば、銅）およびプラグ１７１（例えば、銅）を同時に形成し、その後、第２配線１７２を含む層間絶縁膜１７０上にバリア絶縁膜１７３（例えば、窒化シリコン膜）を堆積する。第２配線１７２の形成は、下層配線形成と同様のプロセスを用いることができる。このとき、バリアメタル１６９と第２電極第二層１２２ｂを同一材料とすることでプラグ１７１と第２電極第二層１２２ｂの間の接触抵抗を低減し、素子性能を向上させることができるようになる。層間絶縁膜１６８および層間絶縁膜１７０はプラズマＣＶＤ法で形成することができる。スイッチング素子１４０によって形成される段差を解消するため、層間絶縁膜１６８を厚く堆積し、ＣＭＰによって層間絶縁膜１６８を削り込んで平坦化し、層間絶縁膜１６８を所望の膜厚としてもよい。
　尚、以上説明した実施例の一部又は全部は、以下のようにも記載され得る。ただし、以下の付記は、本発明を何等限定するものではない。
　（付記１）　酸素を含むと共に金属イオンの伝導を許すイオン伝導層と、前記イオン伝導層の表裏面それぞれに形成された第１電極および第２電極とを有し、前記第１電極は前記イオン伝導層に金属イオンを供給可能な金属から成る一方、前記第２電極は前記イオン伝導層に金属イオンを供給しない金属から成り、前記第１電極から前記イオン伝導層中に供給された金属イオンが第２電極から電子を受け取って金属として析出し、析出した前記金属が成長することにより、前記第１電極および前記第２電極間の抵抗値が変化し、前記イオン伝導層は、前記第１電極との界面を含むイオン伝導層界面部と、当該残部であるイオン伝導層主部とを含み、前記イオン伝導層主部は、金属酸化物または酸素を含む化合物から成り、前記イオン伝導層界面部は、金属酸化物または酸素を含む化合物から成り、酸素の組成比が化学量論量未満であることを特徴とするスイッチング素子。
　（付記２）　前記イオン伝導層主部は、金属酸化物または酸素を含む化合物から成り、前記イオン伝導層界面部は、金属酸化物または酸素を含む化合物から成り、層厚が５ｎｍ以下である付記１に記載のスイッチング素子。スイッチング素子。
　（付記３）　前記イオン伝導層主部は、金属酸化物または酸素を含む化合物から成り、
　前記イオン伝導層界面部は、３００Ｋにおける標準ギブスエネルギーが−６００ｋＪ／ｍｏｌよりも大きい金属を材料とする金属酸化物から成る付記１に記載のスイッチング素子。
　（付記４）　前記イオン伝導層主部は、金属酸化物および酸素を含む化合物の一方から成り、
　前記イオン伝導層界面部は、３００Ｋにおける標準ギブスエネルギーが−６００ｋＪ／ｍｏｌよりも大きい金属を材料とする金属酸化物から成り、層厚が５ｎｍ以下である付記１に記載のスイッチング素子。
　（付記５）　前記主イオン伝導層は、酸素を含む化合物から成り、前記イオン伝導層主部として機能し、
　前記界面イオン伝導層は、金属酸化物から成り、前記イオン伝導層界面部として機能する付記１~４のいずれかに記載のスイッチング素子。
　（付記６）　前記イオン伝導層主部は、前記金属酸化物または前記酸素を含む化合物のうちの二種以上を含む混合物から成り、前記金属酸化物は、酸化タンタル、酸化アルミニウム、酸化ジルコニウム、または酸化チタン、あるいは、酸化シリコンである付記１~５のいずれかに記載のスイッチング素子。
　（付記７）　前記酸素を含む化合物は、少なくともシリコン、酸素、および炭素を主成分としたポリマーであり、比誘電率が２．１以上３．０以下である付記１~５のいずれかに記載のスイッチング素子。
　（付記８）　前記イオン伝導層界面部は、前記金属酸化物のうちの二種以上を含む混合物から成り、前記金属酸化物は、酸化ニッケル、酸化コバルト、酸化鉄、酸化ルテニウム、または酸化イリジウムである付記１~７のいずれかに記載のスイッチング素子。
　（付記９）　前記イオン伝導層界面部は、前記金属酸化物のうちの二種以上を含む混合物から成り、前記金属酸化物は、酸化タンタル、酸化アルミニウム、または酸化チタンである付記１~７のいずれかに記載のスイッチング素子。
　（付記１０）　前記第１電極は、銅を含むことを特徴とする付記１~９のいずれかに記載のスイッチング素子。
　（付記１１）　付記５に記載のスイッチング素子を内蔵した半導体装置であって、半導体基板に互いに間隔を置いて対向するように形成された第１配線およびプラグと、前記第１配線の表面に形成され酸化防止膜と、前記酸化防止膜と前記プラグとの間に形成されたイオン伝導膜と、前記プラグに接続された第２配線とを有し、前記第１配線は、銅から成り、前記スイッチング素子の前記第１電極として機能し、前記酸化防止膜は、前記金属酸化物のうちの二種以上を含む混合物から成り、前記金属酸化物は、酸化ニッケル、酸化コバルト、酸化鉄、酸化ルテニウム、または酸化イリジウムであり、前記スイッチング素子の前記界面イオン伝導層として機能し、前記イオン伝導膜は、少なくともシリコン、酸素、および炭素を主成分としたポリマーから成り、比誘電率が２．１以上３．０以下であり、前記スイッチング素子の前記主イオン伝導層として機能し、前記プラグは、銅から成り、前記スイッチング素子の前記第２電極とバリアメタルを介して接続され、前記スイッチング素子の前記第２電極は、ルテニウムから成ることを特徴とする半導体装置。
　（付記１２）　付記５に記載のスイッチング素子を製造するスイッチング素子の製造方法であって、銅から成る前記第１電極上に、スパッタ法によって、ニッケルまたは鉄から成る金属層を形成する工程と、前記金属層上に、スパッタ法、レーザーアブレーション法、プラズマＣＶＤ法によって酸素を含む化合物を前記主イオン伝導層として形成する工程と、前記主イオン伝導層上に、真空蒸着法もしくはスパッタ法によってルテニウム、プラチナ、またはニッケルを前記第２電極として形成する工程とを有し、前記主イオン伝導層形成工程において、処理室内に酸素および不活性ガスを流入させることにより、前記主イオン伝導層の酸素の組成を化学量論量以上にする一方、処理室内に存在する酸素を前記金属層に浴びさせることにより、金属酸化物から成る前記界面イオン伝導層として形成し、当該界面イオン伝導層の酸素の組成を化学量論量未満にすることを特徴とするスイッチング素子の製造方法。
　（付記１３）　付記１１に記載の半導体装置を製造する半導体装置の製造方法であって、前記半導体基板上に、銅から成り、前記スイッチング素子の前記第１電極として機能する前記第１配線を形成する工程と、前記第１配線上に、開口部を備えたバリア絶縁膜を形成する工程と、前記バリア絶縁膜の開口部を介して、前記第１配線上に、スパッタ法によって、ニッケルまたは鉄から成る金属層を形成する工程と、前記金属層上に、スパッタ法、レーザーアブレーション法、プラズマＣＶＤ法によって酸素を含む化合物を前記スイッチング素子の前記主イオン伝導層として機能する前記イオン伝導膜を形成する工程と、前記イオン伝導膜上に、真空蒸着法もしくはスパッタ法によってルテニウム、プラチナ、またはニッケルから成る前記第２電極を形成する工程と、前記スイッチング素子の前記第２電極上に、バリアメタルを介して、それぞれ銅から成る前記プラグおよび前記第２配線を一体に形成する工程とを有し、前記イオン伝導膜形成工程において、処理室内に酸素および不活性ガスを流入させることにより、前記イオン伝導膜の酸素の組成を化学量論量以上にする一方、処理室内に存在する酸素を前記金属層に浴びさせることにより、前記スイッチング素子の金属酸化物から成る前記界面イオン伝導層として形成し、当該界面イオン伝導層の酸素の組成を化学量論量未満にすることを特徴とする半導体装置の製造方法。
　本出願は、２０１１年２月２日に出願された日本国特許出願第２０１１−０２０３２９号を基礎とする優先権を主張し、その開示のすべてをここに取り込む。 A semiconductor device according to Example 4 of the present invention is a semiconductor device having a switching element corresponding to the two-terminal switching element of Example 3 in a multilayer wiring layer.
[Constitution]
Referring to FIG. 12, the semiconductor device according to the fourth embodiment of the present invention has a switching element 140 inside a multilayer wiring layer on a semiconductor substrate 161.
The multilayer wiring layer is formed on the semiconductor substrate 161 by an interlayer insulating film 162, a barrier insulating film 163, an interlayer insulating film 164, a barrier insulating 166, a protective insulating film 167, an interlayer insulating film 168, an etching stopper film ES, and an interlayer insulating film 170. , And the barrier insulating film 173 in this order.
A first wiring 121 is embedded in a wiring groove formed in the interlayer insulating film 164 and the barrier insulating film 163 via a barrier metal 165. A second wiring 172 is embedded in the wiring trench formed in the interlayer insulating film 170 and the etching stopper film ES. Further, plugs 171 are embedded in pilot holes formed in the interlayer insulating film 168, the protective insulating film 167, and the hard mask film HM2. Further, the second wiring 172 and the plug 171 are integrated, and the integrated second wiring 172 and the plug 171 are covered with a barrier metal 169 from the side surface to the bottom surface.
On the first wiring 121 facing the opening formed in the barrier insulating film 166 and the inner wall surface of the opening of the barrier insulating film 166 or on the barrier insulating film 166, the antioxidant film 152, the ion conductive film 151, the second electrode A layer 122a and a second electrode second layer 122b are formed. A hard mask film HM2 is formed on the second electrode second layer 122b. Further, the top surface or the side surface of the stacked body of the antioxidant film 152, the ion conductive film 151, the second electrode first layer 122a, the second electrode second layer 122b, and the hard mask film HM2 is covered with the protective insulating film 167. Yes.
In this semiconductor device, the switching element 140 includes a first wiring 121 as a first electrode, an antioxidant film 152 as an interface ion conductive layer, an ion conductive film 151 as a main ion conductive layer, and a second electrode. The two-electrode first layer 122a and the second electrode second layer 122b are configured. The stacked antioxidant film 152 and ion conductive film 151 are referred to as a resistance change layer 150.
By causing the first wiring 121 to function as the first electrode of the switching element 140, it is possible to reduce the electrode resistance while simplifying the number of steps. As an additional step to the normal copper damascene wiring process, it is possible to mount a two-terminal switching element simply by creating a mask set of at least 2PR, so that both low resistance and low cost of the element can be achieved simultaneously. become.
In the switching element 140, the antioxidant film 152 and the first wiring 121 are in direct contact with each other in the region of the opening formed in the barrier insulating film 166, and the ion conductive film 151 and the second electrode first layer 122a are in direct contact. The plug 171 and the second electrode second layer 122b are electrically connected via the barrier metal 169 on the second electrode second layer 122b.
The switching element 140 performs on / off control by applying a voltage or passing a current, and uses, for example, electric field diffusion of a metal related to the first wiring 121 into the antioxidant film 152 and the ion conductive film 151. On / off control.
The semiconductor substrate 161 is a substrate on which a semiconductor element is formed. As the semiconductor substrate 161, for example, a substrate such as a silicon substrate, a single crystal substrate, an SOI (Silicon on Insulator) substrate, a TFT (Thin Film Transistor) substrate, a liquid crystal manufacturing substrate, or the like can be used.
The interlayer insulating film 162 is an insulating film formed on the semiconductor substrate 161. As the interlayer insulating film 162, for example, a silicon oxide film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of the silicon oxide film, or the like can be used. The interlayer insulating film 162 may be a stack of a plurality of insulating films.
The barrier insulating film 163 is an insulating film having a barrier property interposed between the interlayer insulating films 162 and 164. The barrier insulating film 163 serves as an etching stop layer when processing the wiring groove for the first wiring 121. For the barrier insulating film 163, for example, a silicon nitride film, a SiC film, a SiCN film, or the like can be used. A wiring trench for embedding the first wiring 121 is formed in the barrier insulating film 163, and the first wiring 121 is buried in the wiring trench via the barrier metal 165. The barrier insulating film 163 can be removed depending on the selection of the etching conditions for the wiring trench.
The interlayer insulating film 164 is an insulating film formed on the barrier insulating film 163. As the interlayer insulating film 164, for example, a silicon oxide film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of the silicon oxide film, or the like can be used. The interlayer insulating film 164 may be a stack of a plurality of insulating films. A wiring trench for embedding the first wiring 121 is formed in the interlayer insulating film 164, and the first wiring 121 is buried in the wiring trench via a barrier metal 165.
The first wiring 121 as the first electrode of the switching element 140 is a wiring buried in a wiring groove formed in the interlayer insulating film 164 and the barrier insulating film 163 via the barrier metal 165. A metal that can be diffused and ion-conducted in the resistance change layer 150 is used for the first wiring 121. For example, copper or the like can be used. The first wiring 121 may be alloyed with aluminum. The barrier metal 165 is a conductive film having a barrier property that covers the side surface or the bottom surface of the first wiring 121 in order to prevent the metal related to the first wiring 121 from diffusing into the interlayer insulating film 164 and the lower layer. . In the barrier metal 165, for example, when the first wiring 121 is made of a metal element whose main component is copper, a refractory metal such as tantalum, tantalum nitride, titanium nitride, tungsten carbonitride, a nitride thereof, or the like, Alternatively, a stacked film of them can be used.
The barrier insulating film 166 is formed on the interlayer insulating film 164 including the first wiring 121, prevents oxidation of a metal (for example, copper) related to the first wiring 121, and the first wiring 121 into the interlayer insulating film 168. This prevents the metal from diffusing and serves as an etching stop layer when the second electrodes 121 and 120 and the resistance change layer 150 are processed. As the barrier insulating film 166, for example, a SiC film, a SiCN film, a silicon nitride film, a stacked structure thereof, or the like can be used. The barrier insulating film 166 is preferably made of the same material as the protective insulating film 167 and the hard mask film HM2.
The resistance change layer 150 constituted by the stacked antioxidant film 152 and ion conductive film 151 is a film in which the resistance in the switching element 140 changes. Therefore, a material whose resistance is changed by the action (diffusion, ion conduction, etc.) of the metal related to the first wiring 121 (first electrode) is used. When the resistance change of the switching element 140 is performed by deposition of metal ions, a film capable of ion conduction is used.
The ion conductive film 151 as the main ion conductive layer in the switching element 140 is formed using a sputtering method, a laser ablation method, or a plasma CVD method. When the ion conductive film 151 is formed of a metal oxide, sputtering is performed using a sintered target. At this time, 10 sccm of oxygen is introduced into the sputtering chamber so that the stoichiometry of the deposited metal oxide is not impaired. For the ion conductive film 151 made of a metal oxide, tantalum oxide, zirconium oxide, aluminum oxide, titanium oxide, and a mixture thereof are preferable. On the other hand, when the ion conductive film 151 is formed of a SiOCH compound, it is formed by plasma CVD. The cyclic organosiloxane raw material and the carrier gas helium flow into the reaction chamber, the supply of both is stabilized, and the application of RF power is started when the pressure in the reaction chamber becomes constant. The supply amount of the raw material is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is directly supplied to the reaction chamber through a separate line.
The anti-oxidation film 152 as the interface ion conductive layer in the switching element 140 is such that the metal related to the first wiring 121 diffuses into the ion conductive film 151 by heating or plasma while the ion conductive film 151 is being deposited. The role of preventing and the ionization of the metal related to the first wiring 121 from the first wiring 121 as the antioxidant film and the injection of metal ions into the antioxidant film 152 and the ion conductive film 151 are controlled. The metal of the antioxidant film 152, such as nickel, cobalt, iron, ruthenium, and iridium, becomes nickel oxide, cobalt oxide, iron oxide, ruthenium oxide, and iridium during the formation of the ion conductive film 151. Part. The resistance change layer 150 is formed on the first wiring 121, the tapered surface of the opening of the barrier insulating film 166, or the barrier insulating film 166. In the resistance change layer 150, the outer peripheral portion of the connection portion between the first wiring 121 and the resistance change layer 150 is disposed along at least the tapered surface of the opening of the barrier insulating film 166.
The second electrode first layer 122 a as a part of the second electrode in the switching element 140 is an electrode on the lower layer side of the second electrode of the switching element 140, and is in direct contact with the ion conductive film 151. For the second electrode first layer 122a, a metal that is less ionized than the metal related to the first wiring 121 and is difficult to diffuse or ion-conduct in the ion conductive film 151 is used. For example, platinum, ruthenium, nickel, or the like is used. Can do.
The second electrode second layer 122b as a part of the second electrode in the switching element 140 is an upper layer side electrode in the second electrode of the switching element 140, and is formed on the second electrode first layer 122a. Yes. The second electrode second layer 122b has a role of protecting the second electrode first layer 122a. That is, the second electrode second layer 122b protects the second electrode first layer 122a, thereby suppressing damage to the second electrode first layer 122a during the process and maintaining the switching characteristics of the switching element 140. Can do. For the second electrode second layer 122b, for example, tantalum, titanium, tungsten, or a nitride thereof can be used.
The hard mask film HM2 is a film that serves as a hard mask film and a passivation film when the second electrode second layer 122b, the second electrode first layer 122a, the ion conductive film 151, and the antioxidant film 152 are etched. For example, a SiN film or the like can be used for the hard mask film HM2. The hard mask film HM2 is preferably made of the same material as the protective insulating film 167 and the barrier insulating film 166. That is, by surrounding the entire periphery of the switching element 140 with the same material, the interface portion of the material is integrated, so that it is possible to prevent moisture and the like from entering from the outside and to prevent detachment from the switching element 140 itself. .
The protective insulating film 167 is an insulating film having a function of preventing the detachment of oxygen from the ion conductive film 151 without damaging the switching element 140. As the protective insulating film 167, for example, a silicon nitride film, a SiCN film, or the like can be used. The protective insulating film 167 is preferably made of the same material as the hard mask film HM2 and the barrier insulating film 166. In the case of the same material, the protective insulating film 167, the barrier insulating film 166, and the hard mask film HM2 are integrated to improve the adhesion at the interface, and the switching element 140 can be further protected. .
The interlayer insulating film 168 is an insulating film formed on the protective insulating film 167. As the interlayer insulating film 168, for example, a silicon oxide film, a SiOC film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of the silicon oxide film can be used. The interlayer insulating film 168 may be a stack of a plurality of insulating films. The interlayer insulating film 168 may be made of the same material as the interlayer insulating film 170. A pilot hole for embedding the plug 171 is formed in the interlayer insulating film 168, and the plug 171 is embedded in the pilot hole via a barrier metal 169.
The etching stopper film ES is an insulating film interposed between the interlayer insulating films 168 and 170. The etching stopper film ES serves as an etching stop layer when the wiring groove for the second wiring 172 is processed. For the etching stopper film ES, for example, a SiN film, a SiC film, a SiCN film, or the like can be used. A wiring trench for embedding the second wiring 172 is formed in the etching stopper film ES, and the second wiring 172 is buried in the wiring trench via a barrier metal 169. The etching stopper film ES can be deleted depending on the selection of the etching conditions for the wiring trench.
The interlayer insulating film 170 is an insulating film formed on the etching stopper film ES. As the interlayer insulating film 170, for example, a silicon oxide film, a SiOC film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of the silicon oxide film can be used. The interlayer insulating film 170 may be a stack of a plurality of insulating films. The interlayer insulating film 170 may be made of the same material as the interlayer insulating film 15. In the interlayer insulating film 170, a wiring groove for embedding the second wiring 172 is formed, and the second wiring 172 is embedded in the wiring groove via a barrier metal 169.
The second wiring 172 is a wiring embedded in a wiring groove formed in the interlayer insulating film 170 and the etching stopper film ES via a barrier metal 169. The second wiring 172 is integrated with the plug 171. The plug 171 is buried in a prepared hole formed in the interlayer insulating film 168, the protective insulating film 167, and the hard mask film HM2 via a barrier metal 169. The plug 171 is electrically connected to the second electrode second layer 122b through the barrier metal 169. For example, Cu can be used for the second wiring 172 and the plug 171.
The barrier metal 169 covers the side surfaces or bottom surfaces of the second wiring 172 and the plug 171 in order to prevent the metal related to the second wiring 172 (including the plug 171) from diffusing into the interlayer insulating films 168 and 170 and the lower layer. It is a conductive film having a barrier property. For example, when the second wiring 108 and the plug 171 are made of a metal element whose main component is Cu, the barrier metal 110 includes a refractory metal such as tantalum, tantalum nitride, titanium nitride, tungsten carbonitride, or nitride thereof. A thing etc. or those laminated films can be used. The barrier metal 169 is preferably made of the same material as the second electrode second layer 122b. For example, when the barrier metal 169 has a stacked structure of TaN (lower layer) / Ta (upper layer), it is preferable to use TaN as the lower layer material for the second electrode second layer 122b. Alternatively, when the barrier metal 110 is Ti (lower layer) / Ru (upper layer), it is preferable to use Ti as the lower layer material for the second electrode second layer 122b.
The barrier insulating film 173 is formed on the interlayer insulating film 170 including the second wiring 172, prevents oxidation of the metal (for example, copper) related to the second wiring 172, and prevents the metal related to the second wiring 172 to the upper layer. It is an insulating film having a role of preventing diffusion. For the barrier insulating film 173, for example, a SiC film, a SiCN film, a SiN film, and a stacked structure thereof can be used.
[Production method]
Next, a semiconductor device manufacturing method according to the fourth embodiment will be described with reference to FIGS. 13 (a) to (f) and FIGS. 14 (a) to (f).
[Step 1] As shown in FIG. 13A, an interlayer insulating film 162 (for example, a silicon oxide film, a film thickness of 300 nm) is deposited on a semiconductor substrate 161 (for example, a substrate on which a semiconductor element is formed), Thereafter, a barrier insulating film 163 (for example, a silicon nitride film, a film thickness of 50 nm) is deposited on the interlayer insulating film 162, and then an interlayer insulating film 164 (for example, a silicon oxide film, a film thickness of 300 nm) is formed on the barrier insulating film 163. After that, wiring grooves are formed in the interlayer insulating film 164 and the barrier insulating film 163 by using a lithography method (including photoresist formation, dry etching, and photoresist removal).
Thereafter, a first wiring 121 (for example, copper) as a first electrode is embedded in the wiring groove via a barrier metal 165 (for example, tantalum nitride / tantalum, film thickness 5 nm / 5 nm).
The interlayer insulating films 162 and 164 can be formed by a plasma CVD method. The first wiring 121 is formed, for example, by forming a barrier metal 165 (for example, a tantalum nitride / tantalum laminated film) by the PVD method, and after forming a Cu seed by the PVD method, copper is embedded in the wiring groove by the electrolytic plating method. After the heat treatment at a temperature of 200 ° C. or higher, it can be formed by removing excess copper other than in the wiring trench by CMP. As a method for forming such a series of copper wirings, a general method in this technical field can be used. Here, the CMP (Chemical Mechanical Polishing) method is to flatten the unevenness of the wafer surface that occurs during the multilayer wiring formation process by bringing the polishing liquid into contact with a rotating polishing pad while flowing the polishing liquid over the wafer surface and polishing it. Is the method. By polishing excess copper embedded in the trench, a buried wiring (damascene wiring) is formed, or planarization is performed by polishing an interlayer insulating film.
[Step 2] As shown in FIG. 13B, a barrier insulating film 166 (for example, a silicon nitride film, a film thickness of 50 nm) is formed on the interlayer insulating film 164 including the first wiring 121. Here, the barrier insulating film 166 can be formed by a plasma CVD method. The thickness of the barrier insulating film 166 is preferably about 10 to 50 nm.
[Step 3] As shown in FIG. 13C, a hard mask film HM1 (for example, a silicon oxide film) is formed on the barrier insulating film 166. At this time, the hard mask film HM1 is preferably made of a material different from the barrier insulating film 166 from the viewpoint of maintaining a high etching selectivity in the dry etching process, and may be an insulating film or a conductive film. For the hard mask film HM1, for example, a silicon oxide film, a silicon nitride film, titanium nitride, titanium, tantalum, tantalum nitride, or the like can be used, and a silicon nitride / silicon oxide film stack can be used.
[Step 4] As shown in FIG. 13 (d), the opening is patterned on the hard mask film HM1 using a photoresist (not shown), and the hard mask film is formed by dry etching using the photoresist as a mask. An opening pattern is formed in HM1, and then the photoresist is peeled off by oxygen plasma ashing or the like. At this time, the dry etching is not necessarily stopped on the upper surface of the barrier insulating film 166, and may reach the inside of the barrier insulating film 166.
[Step 5] As shown in FIG. 13E, by using the hard mask film HM1 as a mask, the barrier insulating film 166 exposed from the opening of the hard mask film HM1 is etched back (dry etching), thereby barrier insulation. An opening is formed in the film 166 to expose the first wiring 121 from the opening of the barrier insulating film 166, and then an organic stripping process is performed with an amine-based stripping solution or the like, thereby exposing the exposed surface of the first wiring 121. In addition to removing the copper oxide formed in step (2), the etching by-product generated during the etch-back is removed. In etching back the barrier insulating film 166, the inner wall surface of the opening of the barrier insulating film 166 can be tapered by using reactive dry etching. In reactive dry etching, a gas containing fluorocarbon can be used as an etching gas. The hard mask film HM1 is preferably completely removed during the etch back, but may remain as it is when it is an insulating material. The shape of the opening in the barrier insulating film 166 can be a circle, and the diameter of the circle can be 30 nm to 500 nm. The oxide on the surface of the first wiring 121 is removed by RF (Radio Frequency) using a non-reactive gas. As the non-reactive gas, helium or argon can be used.
[Step 6] As shown in FIG. 13F, iron (for example, 1 nm in thickness) of 4 nm or less is deposited on the barrier insulating film 166 including the first wiring 121. Iron can be formed using a PVD method or a CVD method.
Further, as the ion conductive film 151 as the main ion conductive layer, a SiOCH polymer film containing silicon, oxygen, carbon, and hydrogen is formed by plasma CVD. The cyclic organosiloxane raw material and the carrier gas helium flow into the reaction chamber, the supply of both is stabilized, and the application of RF power is started when the pressure in the reaction chamber becomes constant. The supply amount of the raw material is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is directly supplied to the reaction chamber through a separate line. Iron is oxidized automatically by being exposed to the raw material of the SiOCH-based polymer film containing oxygen during the formation of the ion conductive film 151, and becomes iron oxide, thereby becoming an antioxidant film 152 as an interface ion conductive layer. It becomes a part of the resistance change layer 150. Since moisture or the like is attached to the opening of the barrier insulating film 166 by organic peeling treatment, degassing is performed by applying a heat treatment under reduced pressure at a temperature of about 250 ° C. to 350 ° C. before the resistance change layer 150 is deposited. It is preferable to keep it.
[Step 7] As shown in FIG. 14A, on the resistance change layer 150, the second electrode first layer 122a (for example, ruthenium, film thickness 10 nm) as a part of the second electrode, A second electrode second layer 122b (for example, tantalum, film thickness 50 nm) as a part of the two electrodes is formed in this order.
[Step 8] As shown in FIG. 14B, on the second electrode second layer 122b, a hard mask film HM2 (for example, a SiN film, a film thickness of 30 nm) and a hard mask film HM3 (for example, a SiO2 film, The film thickness is 150 nm). The hard mask film HM2 and the hard mask film HM3 can be formed using a plasma CVD method. The hard mask film HM2 and the hard mask film HM3 are preferably different types of films. For example, the hard mask film HM2 can be a SiN film and the hard mask film HM3 can be a SiO2 film. At this time, the hard mask film HM2 is preferably made of the same material as a protective insulating film 167 and a barrier insulating film 166 described later. That is, the entire periphery of the switching element is surrounded by the same material, so that the material interface can be integrated to prevent intrusion of moisture and the like from the outside and to prevent detachment from the switching element itself. The hard mask film HM2 can be formed by a plasma CVD method. For example, it is preferable to use a high-density SiN film or the like by using a high-density plasma with a mixed gas of SiH4 / N2.
[Step 9] As shown in FIG. 14C, a photoresist (not shown) for patterning the two-terminal switching element portion is formed on the hard mask film HM3, and then the photoresist is used as a mask. The hard mask film HM3 is dry-etched until the hard mask film HM2 appears, and then the photoresist is removed using oxygen plasma ashing and organic peeling.
[Step 10] As shown in FIG. 14D, the hard mask film HM2, the second electrode second layer 122b, the second electrode first layer 122a, and the ion conductive film 151 are continuously formed using the hard mask film HM3 as a mask. Dry etching. At this time, the hard mask film HM3 is preferably completely removed during the etch back, but may remain as it is. For example, when the second electrode second layer 122b is Ta, it can be processed by Cl2-based RIE, and when the second electrode first layer 122a is Ru, RIE processing is performed with a mixed gas of Cl2 / O2. Can do. In the etching of the ion conductive film 151, it is necessary to stop dry etching on the barrier insulating film 166 on the lower surface. In the case where the ion conductive film 151 is an oxide containing Ta and the barrier insulating film 166 is a SiN film or a SiCN film, the etching conditions are mixed with a mixed gas such as CF4, CF4 / Cl2, CF4 / Cl2 / Ar, or the like. RIE processing can be performed by adjusting. By using such a hard mask RIE method, the switching element part can be processed without exposing the switching element part to oxygen plasma ashing for resist removal. Further, when the oxidation treatment is performed by oxygen plasma after the processing, the oxidation plasma treatment can be irradiated without depending on the resist peeling time.
[Step 11] As shown in FIG. 14 (e), protection is performed on the barrier insulating film 166 including the hard mask film HM2, the second electrode second layer 122b, the second electrode first layer 122a, and the ion conductive film 151. An insulating film 167 (for example, a silicon nitride film, 30 nm) is deposited. Although the protective insulating film 167 can be formed by a plasma CVD method, it is necessary to maintain a reduced pressure in the reaction chamber before film formation. At this time, oxygen is desorbed from the side surface of the resistance change layer 150 and ion conduction is performed. The problem arises that the leakage current of the layer increases. In order to suppress them, the deposition temperature of the protective insulating film 167 is preferably set to 250 ° C. or lower. Further, it is preferable not to use a reducing gas because the film is exposed to a film forming gas under reduced pressure before film formation. For example, it is preferable to use a SiN film or the like formed by using a mixed gas of SiH 4 / N 2 with high-density plasma at a substrate temperature of 200 ° C.
[Step 12] As shown in FIG. 14F, on the protective insulating film 167, an interlayer insulating film 168 (for example, silicon oxide film), an etching stopper film ES (for example, silicon nitride film), and an interlayer insulating film 170 are formed. (For example, a silicon oxide film) is deposited in this order, and then a wiring groove for the second wiring 172 and a pilot hole for the plug 171 are formed, and the wiring groove and the lower wiring are formed using a copper dual damascene wiring process. A second wiring 172 (for example, copper) and a plug 171 (for example, copper) are simultaneously formed in the hole via a barrier metal 169 (for example, tantalum nitride / tantalum), and then the interlayer insulating film 170 including the second wiring 172 is formed. A barrier insulating film 173 (for example, a silicon nitride film) is deposited thereon. The formation of the second wiring 172 can use the same process as the formation of the lower layer wiring. At this time, by making the barrier metal 169 and the second electrode second layer 122b the same material, the contact resistance between the plug 171 and the second electrode second layer 122b can be reduced, and the device performance can be improved. Become. The interlayer insulating film 168 and the interlayer insulating film 170 can be formed by a plasma CVD method. In order to eliminate the step formed by the switching element 140, the interlayer insulating film 168 may be deposited thick, and the interlayer insulating film 168 may be cut and planarized by CMP, so that the interlayer insulating film 168 has a desired thickness.
Part or all of the embodiments described above can be described as follows. However, the following supplementary notes do not limit the present invention in any way.
(Additional remark 1) It has an ion conductive layer containing oxygen and allowing conduction of metal ions, and a first electrode and a second electrode formed on each of the front and back surfaces of the ion conductive layer, the first electrode being the ion The second electrode is made of a metal that does not supply metal ions to the ion conductive layer, and the metal ions supplied from the first electrode into the ion conductive layer are made of metal capable of supplying metal ions to the conductive layer. Electrons are received from the second electrode and deposited as a metal, and the deposited metal grows to change a resistance value between the first electrode and the second electrode, and the ion conductive layer is formed by the first electrode. An ion conductive layer interface including the interface between the ion conductive layer and the remaining ion conductive layer main part, wherein the ion conductive layer main part is made of a metal oxide or a compound containing oxygen, and the ion conductive layer interface The part is made of a metal oxide or a compound containing oxygen, and the composition ratio of oxygen is less than the stoichiometric amount.
(Additional remark 2) The said ion conductive layer main part consists of a compound containing a metal oxide or oxygen, and the said ion conductive layer interface part consists of a compound containing a metal oxide or oxygen, and its layer thickness is 5 nm or less. 2. The switching element according to 1. Switching element.
(Additional remark 3) The said ion conductive layer main part consists of a compound containing a metal oxide or oxygen,
The switching element according to appendix 1, wherein the interface portion of the ion conductive layer is made of a metal oxide made of a metal whose standard Gibbs energy at 300 K is larger than -600 kJ / mol.
(Additional remark 4) The said ion conductive layer main part consists of one of the compound containing a metal oxide and oxygen,
The switching element according to supplementary note 1, wherein the interface portion of the ion conductive layer is made of a metal oxide made of a metal having a standard Gibbs energy greater than −600 kJ / mol at 300 K, and the layer thickness is 5 nm or less.
(Supplementary Note 5) The main ion conductive layer is made of a compound containing oxygen and functions as the main part of the ion conductive layer.
The switching element according to any one of appendices 1 to 4, wherein the interface ion conductive layer is made of a metal oxide and functions as an interface portion of the ion conductive layer.
(Additional remark 6) The said ion conductive layer main part consists of a mixture containing 2 or more types of the said metal oxide or the said compound containing oxygen, and the said metal oxide is a tantalum oxide, an aluminum oxide, a zirconium oxide, or 6. The switching element according to any one of appendices 1 to 5, which is titanium oxide or silicon oxide.
(Supplementary note 7) The oxygen-containing compound is a polymer containing at least silicon, oxygen, and carbon as main components, and has a relative dielectric constant of 2.1 to 3.0. Switching element.
(Additional remark 8) The said ion conductive layer interface part consists of a mixture containing 2 or more types of the said metal oxide, and the said metal oxide is nickel oxide, cobalt oxide, iron oxide, ruthenium oxide, or iridium oxide. The switching element according to any one of appendices 1 to 7.
(Additional remark 9) The said ion conductive layer interface part consists of a mixture containing 2 or more types of the said metal oxide, The said metal oxide is a tantalum oxide, an aluminum oxide, or a titanium oxide. The switching element according to any one of the above.
(Supplementary note 10) The switching element according to any one of supplementary notes 1 to 9, wherein the first electrode contains copper.
(Additional remark 11) It is a semiconductor device which incorporated the switching element of Additional remark 5, Comprising: The 1st wiring and plug formed so that it might mutually oppose with a space | interval may be formed in the surface of the said 1st wiring. And an anti-oxidation film, an ion conductive film formed between the anti-oxidation film and the plug, and a second wiring connected to the plug, wherein the first wiring is made of copper, Acting as the first electrode of the switching element, the antioxidant film is made of a mixture containing two or more of the metal oxides, and the metal oxides are nickel oxide, cobalt oxide, iron oxide, ruthenium oxide. Or iridium oxide, which functions as the interfacial ion conductive layer of the switching element, and the ion conductive film is a polycrystal having at least silicon, oxygen, and carbon as main components. The dielectric constant is 2.1 or more and 3.0 or less and functions as the main ion conductive layer of the switching element, the plug is made of copper, and the second electrode and the barrier of the switching element A semiconductor device connected through a metal, wherein the second electrode of the switching element is made of ruthenium.
(Additional remark 12) It is a manufacturing method of the switching element which manufactures the switching element of Additional remark 5, Comprising: The process of forming the metal layer which consists of nickel or iron by the sputtering method on the 1st electrode which consists of copper, A step of forming a compound containing oxygen as the main ion conductive layer on the metal layer by sputtering, laser ablation, or plasma CVD, and ruthenium on the main ion conductive layer by vacuum deposition or sputtering. Forming platinum or nickel as the second electrode, and in the main ion conductive layer forming step, oxygen and an inert gas are allowed to flow into the processing chamber, whereby the oxygen composition of the main ion conductive layer is formed. Is increased to a stoichiometric amount or more, while oxygen present in the processing chamber is bathed in the metal layer, A method for producing a switching element, characterized in that it is formed as the interfacial ion conductive layer made of a metal oxide, and the composition of oxygen in the interfacial ion conductive layer is less than the stoichiometric amount.
(Additional remark 13) It is a manufacturing method of the semiconductor device which manufactures the semiconductor device of Additional remark 11, Comprising: Forming the said 1st wiring which consists of copper and functions as said 1st electrode of the said switching element on the said semiconductor substrate. A step of forming a barrier insulating film having an opening on the first wiring, and a step of forming nickel or iron on the first wiring by a sputtering method through the opening of the barrier insulating film. And forming the ion conductive film functioning as a main ion conductive layer of the switching element by a sputtering method, a laser ablation method, and a plasma CVD method on the metal layer. And the second electrode made of ruthenium, platinum, or nickel on the ion conductive film by vacuum deposition or sputtering. A step of forming a pole, and a step of integrally forming the plug and the second wiring each made of copper on the second electrode of the switching element through a barrier metal, and the ion conductive film In the forming step, oxygen and an inert gas are allowed to flow into the processing chamber, so that the oxygen composition of the ion conductive film is increased to a stoichiometric amount or more, while oxygen existing in the processing chamber is bathed in the metal layer. Thus, the interface ion conductive layer made of the metal oxide of the switching element is formed, and the composition of oxygen in the interface ion conductive layer is made less than the stoichiometric amount.
This application claims the priority on the basis of the Japan patent application 2011-020329 for which it applied on February 2, 2011, and takes in those the indications of all here.

Claims (13)

  1. 　酸素を含むと共に金属イオンの伝導を許すイオン伝導層と、前記イオン伝導層の表裏面それぞれに形成された第１電極および第２電極とを有し、
    　前記第１電極は前記イオン伝導層に金属イオンを供給可能な金属から成る一方、前記第２電極は前記イオン伝導層に金属イオンを供給しない金属から成り、
    　前記第１電極から前記イオン伝導層中に供給された金属イオンが第２電極から電子を受け取って金属として析出し、析出した前記金属が成長することにより、前記第１電極および前記第２電極間の抵抗値が変化し、
    　前記イオン伝導層は、前記第１電極との界面を含むイオン伝導層界面部と、当該残部であるイオン伝導層主部とを含み、
    　前記イオン伝導層主部は、金属酸化物または酸素を含む化合物から成り、
    　前記イオン伝導層界面部は、金属酸化物または酸素を含む化合物から成り、酸素の組成比が化学量論量未満であることを特徴とするスイッチング素子。     An ion conductive layer containing oxygen and allowing conduction of metal ions, and a first electrode and a second electrode formed on each of the front and back surfaces of the ion conductive layer,
    The first electrode is made of a metal capable of supplying metal ions to the ion conductive layer, while the second electrode is made of a metal that does not supply metal ions to the ion conductive layer,
    The metal ions supplied from the first electrode into the ion conductive layer receive electrons from the second electrode and are deposited as metal, and the deposited metal grows so that the first electrode and the second electrode are grown. The resistance value of
    The ion conductive layer includes an ion conductive layer interface including an interface with the first electrode, and an ion conductive layer main part which is the remaining part,
    The main portion of the ion conductive layer is made of a metal oxide or a compound containing oxygen,
    The ion conduction layer interface is made of a metal oxide or a compound containing oxygen, and the composition ratio of oxygen is less than the stoichiometric amount.
  2. 　前記イオン伝導層主部は、金属酸化物または酸素を含む化合物から成り、
    　前記イオン伝導層界面部は、金属酸化物または酸素を含む化合物から成り、層厚が５ｎｍ以下である請求項１に記載のスイッチング素子。スイッチング素子。     The main portion of the ion conductive layer is made of a metal oxide or a compound containing oxygen,
    The switching element according to claim 1, wherein the interface portion of the ion conductive layer is made of a metal oxide or a compound containing oxygen and has a layer thickness of 5 nm or less. Switching element.
  3. 　前記イオン伝導層主部は、金属酸化物または酸素を含む化合物から成り、
    　前記イオン伝導層界面部は、３００Ｋにおける標準ギブスエネルギーが−６００ｋＪ／ｍｏｌよりも大きい金属を材料とする金属酸化物から成る請求項１に記載のスイッチング素子。     The main portion of the ion conductive layer is made of a metal oxide or a compound containing oxygen,
    2. The switching element according to claim 1, wherein the ion conductive layer interface portion is made of a metal oxide made of a metal having a standard Gibbs energy at −300 K larger than −600 kJ / mol.
  4. 　前記イオン伝導層主部は、金属酸化物および酸素を含む化合物の一方から成り、
    　前記イオン伝導層界面部は、３００Ｋにおける標準ギブスエネルギーが−６００ｋＪ／ｍｏｌよりも大きい金属を材料とする金属酸化物から成り、層厚が５ｎｍ以下である請求項１に記載のスイッチング素子。     The main part of the ion conductive layer is composed of one of a metal oxide and a compound containing oxygen,
    2. The switching element according to claim 1, wherein the interface portion of the ion conductive layer is made of a metal oxide made of a metal having a standard Gibbs energy greater than −600 kJ / mol at 300 K, and has a layer thickness of 5 nm or less.
  5. 　前記イオン伝導層は、主イオン伝導層と、前記主イオン伝導層に積層された界面イオン伝導層とによって構成され、
    　前記主イオン伝導層は、酸素を含む化合物から成り、前記イオン伝導層主部として機能し、
    　前記界面イオン伝導層は、金属酸化物から成り、前記イオン伝導層界面部として機能する請求項１乃至４のいずれか一項に記載のスイッチング素子。     The ion conductive layer includes a main ion conductive layer and an interface ion conductive layer laminated on the main ion conductive layer.
    The main ion conductive layer is made of a compound containing oxygen and functions as the main part of the ion conductive layer.
    The switching element according to any one of claims 1 to 4, wherein the interface ion conductive layer is made of a metal oxide and functions as an interface portion of the ion conductive layer.
  6. 　前記イオン伝導層主部は、前記金属酸化物または前記酸素を含む化合物のうちの二種以上を含む混合物から成り、前記金属酸化物は、酸化タンタル、酸化アルミニウム、酸化ジルコニウム、または酸化チタン、あるいは、酸化シリコンである請求項１乃至５のいずれか一項に記載のスイッチング素子。 The main portion of the ion conductive layer is composed of a mixture containing two or more of the metal oxide or the oxygen-containing compound, and the metal oxide includes tantalum oxide, aluminum oxide, zirconium oxide, or titanium oxide, or The switching element according to claim 1, wherein the switching element is silicon oxide.
  7. 　前記酸素を含む化合物は、少なくともシリコン、酸素、および炭素を主成分としたポリマーであり、比誘電率が２．１以上３．０以下である請求項１乃至５のいずれか一項に記載のスイッチング素子。 6. The compound according to claim 1, wherein the oxygen-containing compound is a polymer containing at least silicon, oxygen, and carbon as main components, and has a relative dielectric constant of 2.1 or more and 3.0 or less. Switching element.
  8. 　前記イオン伝導層界面部は、前記金属酸化物のうちの二種以上を含む混合物から成り、前記金属酸化物は、酸化ニッケル、酸化コバルト、酸化鉄、酸化ルテニウム、または酸化イリジウムである請求項１乃至７のいずれか一項に記載のスイッチング素子。 The interface portion of the ion conductive layer is made of a mixture containing two or more of the metal oxides, and the metal oxide is nickel oxide, cobalt oxide, iron oxide, ruthenium oxide, or iridium oxide. The switching element as described in any one of thru | or 7.
  9. 　前記イオン伝導層界面部は、前記金属酸化物のうちの二種以上を含む混合物から成り、前記金属酸化物は、酸化タンタル、酸化アルミニウム、または酸化チタンである請求項１乃至７のいずれか一項に記載のスイッチング素子。 The interface portion of the ion conductive layer is made of a mixture containing two or more of the metal oxides, and the metal oxide is tantalum oxide, aluminum oxide, or titanium oxide. The switching element according to item.
  10. 　前記第１電極は、銅を含むことを特徴とする請求項１乃至９のいずれか一項に記載のスイッチング素子。 The switching element according to any one of claims 1 to 9, wherein the first electrode contains copper.
  11. 　請求項５に記載のスイッチング素子を内蔵した半導体装置であって、
    　半導体基板に互いに間隔を置いて対向するように形成された第１配線およびプラグと、前記第１配線の表面に形成され酸化防止膜と、前記酸化防止膜と前記プラグとの間に形成されたイオン伝導膜と、前記プラグに接続された第２配線とを有し、
    　前記第１配線は、銅から成り、前記スイッチング素子の前記第１電極として機能し、
    　前記酸化防止膜は、前記金属酸化物のうちの二種以上を含む混合物から成り、前記金属酸化物は、酸化ニッケル、酸化コバルト、酸化鉄、酸化ルテニウム、または酸化イリジウムであり、前記スイッチング素子の前記界面イオン伝導層として機能し、
    　前記イオン伝導膜は、少なくともシリコン、酸素、および炭素を主成分としたポリマーから成り、比誘電率が２．１以上３．０以下であり、前記スイッチング素子の前記主イオン伝導層として機能し、
    　前記プラグは、銅から成り、前記スイッチング素子の前記第２電極とバリアメタルを介して接続され、
    　前記スイッチング素子の前記第２電極は、ルテニウムから成ることを特徴とする半導体装置。     A semiconductor device incorporating the switching element according to claim 5,
    A first wiring and a plug formed on the semiconductor substrate so as to be opposed to each other at an interval; an antioxidant film formed on a surface of the first wiring; and formed between the antioxidant film and the plug An ion conductive film and a second wiring connected to the plug;
    The first wiring is made of copper and functions as the first electrode of the switching element;
    The antioxidant film is made of a mixture containing two or more of the metal oxides, and the metal oxide is nickel oxide, cobalt oxide, iron oxide, ruthenium oxide, or iridium oxide, Functions as the interfacial ion conductive layer,
    The ion conductive film is made of a polymer mainly composed of at least silicon, oxygen, and carbon, and has a relative dielectric constant of 2.1 or more and 3.0 or less, and functions as the main ion conductive layer of the switching element,
    The plug is made of copper, and is connected to the second electrode of the switching element via a barrier metal,
    The semiconductor device, wherein the second electrode of the switching element is made of ruthenium.
  12. 　請求項５に記載のスイッチング素子を製造するスイッチング素子の製造方法であって、
    　銅から成る前記第１電極上に、スパッタ法によって、ニッケルまたは鉄から成る金属層を形成する工程と、
    　前記金属層上に、スパッタ法、レーザーアブレーション法、プラズマＣＶＤ法によって酸素を含む化合物を前記主イオン伝導層として形成する工程と、
    　前記主イオン伝導層上に、真空蒸着法もしくはスパッタ法によってルテニウム、プラチナ、またはニッケルを前記第２電極として形成する工程とを有し、
    　前記主イオン伝導層形成工程において、処理室内に酸素および不活性ガスを流入させることにより、前記主イオン伝導層の酸素の組成を化学量論量以上にする一方、処理室内に存在する酸素を前記金属層に浴びさせることにより、金属酸化物から成る前記界面イオン伝導層として形成し、当該界面イオン伝導層の酸素の組成を化学量論量未満にすることを特徴とするスイッチング素子の製造方法。     A manufacturing method of a switching element for manufacturing the switching element according to claim 5,
    Forming a metal layer made of nickel or iron on the first electrode made of copper by sputtering;
    Forming a compound containing oxygen as the main ion conductive layer on the metal layer by sputtering, laser ablation, or plasma CVD;
    Forming ruthenium, platinum, or nickel as the second electrode on the main ion conductive layer by vacuum deposition or sputtering;
    In the main ion conductive layer forming step, oxygen and an inert gas are allowed to flow into the processing chamber, whereby the oxygen composition of the main ion conductive layer is set to a stoichiometric amount or more, while oxygen existing in the processing chamber is A method for producing a switching element, characterized in that the interface ion conductive layer made of a metal oxide is formed by being exposed to a metal layer, and the composition of oxygen in the interface ion conductive layer is less than the stoichiometric amount.
  13. 　請求項１１に記載の半導体装置を製造する半導体装置の製造方法であって、
    　前記半導体基板上に、銅から成り、前記スイッチング素子の前記第１電極として機能する前記第１配線を形成する工程と、
    　前記第１配線上に、開口部を備えたバリア絶縁膜を形成する工程と、
    　前記バリア絶縁膜の開口部を介して、前記第１配線上に、スパッタ法によって、ニッケルまたは鉄から成る金属層を形成する工程と、
    　前記金属層上に、スパッタ法、レーザーアブレーション法、プラズマＣＶＤ法によって酸素を含む化合物を前記スイッチング素子の前記主イオン伝導層として機能する前記イオン伝導膜を形成する工程と、
    　前記イオン伝導膜上に、真空蒸着法もしくはスパッタ法によってルテニウム、プラチナ、またはニッケルから成る前記第２電極を形成する工程と、
    　前記スイッチング素子の前記第２電極上に、バリアメタルを介して、それぞれ銅から成る前記プラグおよび前記第２配線を一体に形成する工程とを有し、
    　前記イオン伝導膜形成工程において、処理室内に酸素および不活性ガスを流入させることにより、前記イオン伝導膜の酸素の組成を化学量論量以上にする一方、処理室内に存在する酸素を前記金属層に浴びさせることにより、前記スイッチング素子の金属酸化物から成る前記界面イオン伝導層として形成し、当該界面イオン伝導層の酸素の組成を化学量論量未満にすることを特徴とする半導体装置の製造方法。     A semiconductor device manufacturing method for manufacturing the semiconductor device according to claim 11, comprising:
    Forming the first wiring made of copper and functioning as the first electrode of the switching element on the semiconductor substrate;
    Forming a barrier insulating film having an opening on the first wiring;
    Forming a metal layer made of nickel or iron by sputtering on the first wiring through the opening of the barrier insulating film;
    Forming the ion conductive film functioning as the main ion conductive layer of the switching element on the metal layer by a sputtering method, a laser ablation method, or a plasma CVD method;
    Forming the second electrode made of ruthenium, platinum, or nickel on the ion conductive film by vacuum deposition or sputtering;
    A step of integrally forming the plug and the second wiring each made of copper on the second electrode of the switching element through a barrier metal;
    In the ion conductive film forming step, oxygen and an inert gas are allowed to flow into the processing chamber, whereby the oxygen composition of the ion conductive film is set to a stoichiometric amount or more, while oxygen existing in the processing chamber is converted to the metal layer. Forming the interface ion conductive layer made of a metal oxide of the switching element by exposing to water, and making the oxygen composition of the interface ion conductive layer less than the stoichiometric amount. Method.
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