US20030134470A1 - Layer structure having contact hole, fin-shaped capacitor using the layer structure, method of producing the fin-shaped capacitor, and dynamic random access memory having the fin-shaped capacitor - Google Patents

Layer structure having contact hole, fin-shaped capacitor using the layer structure, method of producing the fin-shaped capacitor, and dynamic random access memory having the fin-shaped capacitor Download PDF

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US20030134470A1
US20030134470A1 US10/354,088 US35408803A US2003134470A1 US 20030134470 A1 US20030134470 A1 US 20030134470A1 US 35408803 A US35408803 A US 35408803A US 2003134470 A1 US2003134470 A1 US 2003134470A1
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layer
insulating layer
conductive
conductive layer
contact hole
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US10/354,088
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Taiji Ema
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Fujitsu Ltd
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Fujitsu Ltd
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Priority claimed from JP2054883A external-priority patent/JPH0824170B2/en
Priority claimed from JP2234585A external-priority patent/JP2906350B2/en
Priority claimed from JP2283370A external-priority patent/JPH04158515A/en
Priority claimed from JP2283371A external-priority patent/JPH04158569A/en
Application filed by Fujitsu Ltd filed Critical Fujitsu Ltd
Priority to US10/354,088 priority Critical patent/US20030134470A1/en
Publication of US20030134470A1 publication Critical patent/US20030134470A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
    • H01L21/76802—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
    • H01L21/033—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers
    • H01L21/0332—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers characterised by their composition, e.g. multilayer masks, materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
    • H01L21/033—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers
    • H01L21/0334—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers characterised by their size, orientation, disposition, behaviour, shape, in horizontal or vertical plane
    • H01L21/0337—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers characterised by their size, orientation, disposition, behaviour, shape, in horizontal or vertical plane characterised by the process involved to create the mask, e.g. lift-off masks, sidewalls, or to modify the mask, e.g. pre-treatment, post-treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
    • H01L21/76841—Barrier, adhesion or liner layers
    • H01L21/76843—Barrier, adhesion or liner layers formed in openings in a dielectric
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
    • H01L21/76841—Barrier, adhesion or liner layers
    • H01L21/7687—Thin films associated with contacts of capacitors
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B12/00—Dynamic random access memory [DRAM] devices
    • H10B12/01—Manufacture or treatment
    • H10B12/02—Manufacture or treatment for one transistor one-capacitor [1T-1C] memory cells
    • H10B12/03—Making the capacitor or connections thereto
    • H10B12/033—Making the capacitor or connections thereto the capacitor extending over the transistor
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B12/00—Dynamic random access memory [DRAM] devices
    • H10B12/30—DRAM devices comprising one-transistor - one-capacitor [1T-1C] memory cells
    • H10B12/31—DRAM devices comprising one-transistor - one-capacitor [1T-1C] memory cells having a storage electrode stacked over the transistor
    • H10B12/318—DRAM devices comprising one-transistor - one-capacitor [1T-1C] memory cells having a storage electrode stacked over the transistor the storage electrode having multiple segments
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B12/00—Dynamic random access memory [DRAM] devices
    • H10B12/30—DRAM devices comprising one-transistor - one-capacitor [1T-1C] memory cells
    • H10B12/48—Data lines or contacts therefor
    • H10B12/488—Word lines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02107—Forming insulating materials on a substrate
    • H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
    • H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
    • H01L21/02123—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon
    • H01L21/02126—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC
    • H01L21/02129—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC the material being boron or phosphorus doped silicon oxides, e.g. BPSG, BSG or PSG
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
    • H01L21/314—Inorganic layers
    • H01L21/316—Inorganic layers composed of oxides or glassy oxides or oxide based glass
    • H01L21/31604—Deposition from a gas or vapour
    • H01L21/31625—Deposition of boron or phosphorus doped silicon oxide, e.g. BSG, PSG, BPSG
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S148/00—Metal treatment
    • Y10S148/014—Capacitor

Definitions

  • a window provided for connecting a word line formed of, for example, polysilicon, and a low-resistance wiring line (word-line shunt layer) formed of Al or Al alloy, directed to preventing the occurrence of a delay in signal transmission in the word line.
  • the above-mentioned Patent Application discloses an arrangement in which the mask is formed of SiO 2 and a member to be processed is formed of Si. Thus, the removal of the mask material can be easily made.
  • a multilayer structure such as DRAMS
  • the above-mentioned Japanese Application does not suggest the above matters.
  • Japanese Laid-Open Patent Application No. 63-116430 (which corresponds to U.S. patent application Ser. No. 924,223 filed on Oct. 28, 1986) teaches the use of a sidewall for forming a hole smaller than the scale limit of the conventional photolithgraphy technique.
  • the just above application shows a lift-off process for removing the mask material.
  • the lift-off process has a problem in that some of the mask material separated from the substrate is re-adhered hereto. This frequently causes a pattern fault in a subsequent process.
  • the Japanese application of concern does not disclose an effective step to process the mask material.
  • the Japanese application shows a sidewall formed on the side surface of a photosensitive material. It is necessary to form the sidewall at a low temperature due to the thermal stability of the photosensitive material.
  • the structure shown in the Japanese application of concern is limited to a special application.
  • the second conductive layer comprises polysilicon
  • Another object of the present invention is to provide a layer structure having a contact hole as formed by the above-mentioned methods.
  • an insulating layer formed on the first conductive layer and having a contact hole, the first conductive layer being exposed through the contact hole;
  • a second conductive layer formed on the insulating layer and having an opening having a width larger than that of the contact hole;
  • a conductive sidewall formed on the insulating layer exposed through the opening and formed around an inner wall of the second conductive layer defining the opening, the conductive sidewall having a width substantially equal to that of the contact hole;
  • a barrier layer formed on the second conductive layer, the conductive sidewall and the first conductive layer exposed through the contact hole;
  • a third conductive layer formed on the barrier layer, the barrier layer preventing the third conductive layer from reacting with the second conductive layer and the conductive sidewall.
  • an insulating layer formed on the first conductive layer and having a contact hole, the first conductive layer being exposed through the contact hole;
  • a second conductive layer formed on the insulating layer and having a first opening having a width larger than that of the contact hole;
  • a fourth conductive layer formed on the barrier layer, the barrier layer preventing the fourth conductive layer from reacting with the third conductive layer and the conductive sidewall.
  • an insulating layer formed on the first conductive layer and having a contact hole, the first conductive layer being exposed through the contact hole;
  • a second conductive layer formed on the insulating layer and having an opening having a width larger than that of the contact hole;
  • the third conductive layer comprises a material which causes no reaction with the second conductive layer and the conductive sidewall.
  • FIG. 2 is a cross-sectional view showing a second preferred embodiment of the present invention.
  • FIG. 5 is a cross-sectional view showing a fifth preferred embodiment of the present invention.
  • FIGS. 6A through 6N are cross-sectional views showing steps of a DRAM production method according to a sixth preferred embodiment of the present invention.
  • FIG. 7 is a plan view of a DRAM produced by the sixth preferred embodiment of the present invention.
  • FIGS. 8A through 8E are cross-sectional views showing a seventh preferred embodiment of the present invention.
  • FIG. 10 is a cross-sectional view showing a second variation of the sixth preferred embodiment of the present invention.
  • FIGS. 11A through 11J are cross-sectional views showing an eighth preferred embodiment of the present invention.
  • FIGS. 12A through 12G are cross-sectional views showing a ninth preferred embodiment of the present invention.
  • FIGS. 14A through 14G are cross-sectional views showing a modification of the variation shown in FIGS. 13A through 13F.
  • FIGS. 15A through 15J are cross-sectional views showing a tenth preferred embodiment of the present invention.
  • a photoresist film 11 is formed on the entire surface including the contact hole 10 .
  • the entire surface of the photoresist film 11 is exposed and developed. During this process, a small amount of light enters a bottom portion of the contact hole 10 . Thus, a part of the photoresist film 11 is left in the contact hole 10 .
  • the polysilicon layer 4 and the sidewall 18 are dry-etched in a CF 4 /O 2 plasma atmosphere in a state where the polysilicon layer 2 is protected against dry etching due to the existence of the photoresist film 11 in the contact hole 10 .
  • the polysilicon layer 4 and the sidewall 8 are isotropically etched. After that, the photoresist film 11 is removed in an O 2 plasma.
  • an Al alloy (or Al) 12 is deposited on the upper surface including the contact hole 10 by a sputtering process. Then, the Al alloy layer 12 is etched, so that a desired Al (or Al alloy) pattern is formed. Thereby, the polysilicon word line 2 is connected to the Al alloy layer 12 via the contact hole 10 .
  • the contact hole 10 has a width smaller than the feature scale limit of the conventional photolithographic technique. It will also be noted that the above-mentioned production method is suitable for forming a contact hole for connecting the word line and the word-line shunt layer which is provided for preventing the occurrence of a delay in transmitting a signal via the word line.
  • the BPSG layer 3 can be substituted for a stacked member in which a PSG layer and an SiO 2 layer are alternately stacked. It is also possible to employ an alternative step instead of the step shown in FIG. 1H. In the alternative step, after the polysilicon layer 4 and the sidewall 8 are removed, the BPSG layer 3 is reflowed by heating the device in an N 2 atmosphere at 850° C. for 20 minutes, so that an upper edge of the contact hole 10 is smoothly curved. The existence of such a smoothly curved upper edge of the contact hole 10 improves the coverage of the Al alloy layer 12 .
  • FIG. 2 A layer structure shown in FIG. 2 is the same as that shown in FIG. 1B except that an SiO 2 layer 13 is formed on the polysilicon layer 4 . More specifically, the SiO 2 film 13 is grown to, for example, about 200 angstroms on the polysilicon layer 4 by CVD. Then, the photoresist film 5 shown in FIG. 1A is formed on the entire surface. After that, the first opening 6 is formed in the SiO 2 layer 13 and the polysilicon layer 4 . Then, the polysilicon layer 7 is formed on the photoresist film 5 and in the first opening 6 in the same way as shown in FIG. 1B.
  • the polysilicon layer 7 is anisotropically etched in the vertical direction.
  • the SiO 2 layer 13 functions as an etching stopper during the step shown in FIG. 1C, so that it is possible to prevent a decrease in the thickness of the polysilicon layer 4 . Further, it becomes easy to detect the end of etching since the SiO 2 layer 13 is exposed. It will be noted that the SiO 2 layer 13 is removed together with the BPSG layer 3 during the step shown in FIG. 1E. Thus, it is not necessary to provide a special step to remove the SiO 2 layer 13 .
  • FIGS. 3A through 3C A description will now be given of a third preferred embodiment of the present invention with reference to FIGS. 3A through 3C, in which those parts which are the same as those shown in the previous figures are given the same reference numerals.
  • the BPSG layer 3 is grown to, for example, 0.5 ⁇ m on the entire surface including the polysilicon layer (word line) 2 by CVD.
  • the polysilicon layer 4 is grown to, for example, 1000 angstroms by CVD.
  • the photoresist film 5 is coated, and patterned by the conventional photolithography technique, so that a hole pattern having a width approximately equal to 0.5 ⁇ m is formed in the photoresist film 5 .
  • the polysilicon layer 4 is selectively removed by an RIE process using a CCl 4 /O 2 gas in which the photoresist film 5 serves as a mask, so that the first opening 6 is formed in the polysilicon layer 4 .
  • a polysilicon layer 14 is selectively grown on the upper surface of the polysilicon layer 4 and a side surface thereof by a CVD process in which the device is maintained at 650° C. and an SiH 4 +HCl+H 2 gas is used.
  • the polysilicon layer 14 defines a second opening 15 having a width smaller than that of the first opening 6 . It is easy to control the thickness of the polysilicon layer 14 , that is, easy to control the width of the second opening 15 .
  • the BPSG layer 3 is removed via the second opening 15 by an RIE process using a CHF 3 /He gas, so that the contact hole 10 is formed and the polysilicon layer 2 is partially exposed through the contact hole 10 .
  • a stakced layer 16 fomed of a Ti/TiN layer 16 is formed on the polysilicon layer 14 , and an Al alloy (or Al) layer 17 is formed on the stacked layer 16 , as shown in FIG. 3D.
  • the stacked laye 16 will be described in detail later.
  • FIG. 1G the polysilicon layer 4 and the sidewall 8 are removed, on the other hand, according to the fourth embodiment of the present invention, as shown in FIG. 4, the polysilicon layer 4 and the sidewall 8 are not removed, but left on the BPSG layer 3 .
  • the stacked layer 16 is formed on the entire surface including the polysilicon layer 4 , the sidewall 8 and the exposed surface of the polysilicon layer 2 by CVD, for example.
  • the stacked layer 16 consists of a Ti layer having a thickness of 200 angstroms and a TiN layer having a thickness of 1000 angstroms.
  • the stacked layer 16 is referred to as a Ti/TiN layer 16 .
  • the Al alloy (or pure Al) 17 is deposited on the Ti/TiN layer 16 by sputtering.
  • the polysilicon layer 4 , the Ti/TiN layer 16 and the Al alloy layer 17 are patterned by etching.
  • the Al alloy layer (or pure Al layer) 17 is deposited directly on the polysilicon layer 4 and the polysilicon sidewall 8 , it will easily react to silicon in the layer 4 and the sidewall 8 during a subsequent annealing process in which a protection cover is formed, for example.
  • the above reaction increases the resistance of the Al alloy layer 17 .
  • the Ti/TiN layer 16 functions as a barrier layer which prevents the above-mentioned reaction.
  • the barrier layer 16 is not limited to the Ti/TiN layer.
  • FIG. 5 A description will now be given of a fifth preferred embodiment of the present invention with reference to FIG. 5, in which those parts which are the same as those shown in the previous figures are given the same reference numerals.
  • the fifth embodiment shown in FIG. 5 has the left polysilicon layer 4 and the polysilicon sidewall 8 , and uses a W (tungsten) layer functioning as a wiring line instead of the Al alloy (or pure Al) layer 17 shown in FIG. 4.
  • the use of the W layer 18 does not need the deposition of the Ti/TiN layer 16 .
  • the W layer 18 is grown to, for example, 5000 angstroms on the entire surface including the polysilicon layer 4 , the polysilicon sidewall 8 and the exposed surface of the polysilicon layer 2 by CVD.
  • the contact hole 10 is filled with tungsten, so that the coverage of the W layer 18 can be improved. It will be noted that it is easy to fill the contact hole 10 with tungsten by CVD. It will be noted that tungsten has a poor adhession to BPSG or SiO 2 .
  • the W layer 18 is formed on the polysilicon layer 4 and the polysilicon sidewall 18 . Thus, the adhession problem can be solved.
  • the sixth preferred embodiment of the present invention provides a DRAM having a contact hole defined by a sidewall.
  • an interlayer isolation insulating layer 22 is grown to, for example, 4000 angstroms on a p-type silicon substrate 21 by a selective thermal oxidation process (a local-oxidation-of-silicon process: LOCOS), in which a silicon nitride layer is used as an oxidation-resistant mask.
  • LOCOS local-oxidation-of-silicon process
  • a silicon nitride layer serving as the oxidation-resistant mask is removed, so that active areas in the p-type silicon substrate 21 are exposed.
  • a gate insulating layer 23 having a thickness equal to, for example, 100 angstroms is formed on the exposed surfaces of the p-type silicon substrate 21 by a thermal oxidation process.
  • a polysilicon layer is grown to, for example, 1000 angstroms by CVD. Then, the polysilicon layer is patterned by a resist process and RIE process in the photolithography technique in which a CCl 4 /O 2 gas is used. Thereby, word lines WL are formed. After that, As ions are introduced into the p-type silicon substrate 21 by an ion implantation process in which the word lines WL and the interlayer isolation insulating layer 2 function as masks. Thereby, an n + -type source region 24 and an N + -type drain region 25 of a transfer transistor of a memory cell are formed in the p-type silicon substrate 21 .
  • the dose of As ions is equal to, for example, 1 ⁇ 10 15 atoms/cm 2 .
  • the source and drain regions 24 and 25 are heated.
  • an insulating layer 26 formed of SiO 2 is grown to, for example, 1000 angstroms by CVD.
  • the SiO 2 insulating film 26 is selectively etched in an RIE process in which a CHF 3 /H 2 gas is used, so that a bit line contact hole 24 A is formed in the SiO 2 insulating film 26 .
  • RIE reactive ion etching
  • an SiO 2 insulating layer 41 is grown to, for example, 1000 angstroms on the entire surface by CVD.
  • the SiO 2 insulating layer 41 is selectively etched by an anisotropic etching process, such as, an RIE process using a CHF 3 /H 2 gas.
  • an anisotropic etching process such as, an RIE process using a CHF 3 /H 2 gas.
  • RIE process a sidewall SW 1 having an about 0.1 ⁇ m thickness is formed so that it surrounds a vertical inner wall of the bit line contact window 24 A and a curved part of the SiO 2 insulating layer 26 .
  • the sidewall SW 1 defines the width of the bit line contact hole 24 A, which is approximately equal to 0.3 ⁇ m. It will be noted that this dimension, 0.3 ⁇ m, is considerably smaller than the scale limit by the conventional photolithography technique (approximately 0.5 ⁇ m).
  • the formation of the sidewall SW 1 contributes to reducing the alignment margin. Even if the word line WL is partially exposed due to the positional error of the bit line contact window 24 A, the sidewall 24 will completely cover
  • the above-mentioned contact hole forming process is distinguished from a known self-alignment contact formation method.
  • the self-alignment contact formation method an insulating layer corresponding to the SiO 2 insulating layer 26 and a polysilicon layer provided for the word lines WL are patterned into an identical shape. Then, sidewalls are formed around windows. Thus, the windows are automatically defined by the sidewalls, so that there is no need for any alignment margin.
  • the insulating film corresponding to the SiO 2 insulating layer 26 is 2000 angstroms thick
  • the underlying polysilicon layer provided for forming the word lines WL is 1000 angstron's thick.
  • the sidewall is about 3000 angstrom high, and is a large step portion formed on the surface of the substrate.
  • the process which has been described with reference to FIG. 6D does not form such a great step surface portion.
  • the sidewall SW 1 is also formed on a step portion on the surface of the SiO insulating film, so that the slope of the curved surface portion of the SiO 2 insulating layer 26 can be reduced.
  • a polysilicon layer is grown to, for example, 500 angstroms on the entire surface by CVD.
  • As ions are introduced into the polysilicon layer by an ion implantation process in which the dose of As ions is equal to 1 ⁇ 10 15 atoms/cm 2 .
  • a WSi 2 film is formed to, for example, 500 angstroms on the impurity doped polysilicon layer by CVD.
  • the WSi 2 layer and the impurity doped polysilicon layer are patterned by an RIE process using a CCl 4 /O 2 gas, so that a bit line BL having a two-layer structure is formed.
  • an insulating layer 27 formed of Si 3 N 4 , a spacer layer 28 formed of SiO 2 and a polysilicon layer 29 ′ which forms a part of a storage electrode (fin electrode) of a stacked capacitor are grown in this order by CVD.
  • the Si 3 N 4 insulating layer 27 , the SiO 2 spacer layer 28 and the polysilicon layer 29 ′ are, for example, 1000, 500 and 1000 angstroms, respectively. It will be noted that the polysilicon layer 29 ′ plays the important role, as will be described later.
  • the polysilicon layer 29 ′ is selectively etched by the resist process and RIE process using a CCl 4 /O 2 gas in the conventional photolithography technique, so that an opening 29 A having the same pattern as the storage electrode contact window is formed in the polysilicon layer 29 ′.
  • the opening 29 A has a width approximately equal to 0.5 ⁇ m, which is the scale limit attained by the conventional photolithography technique.
  • a polysilicon layer 32 a is grown to, for example, 1000 angstroms by CVD. Then, as shown in FIG. 6I, the polysilicon layer is anisotropically etched by an RIE process using a CCl 4 /O 2 gas. Thereby, a sidewall 32 formed of polysilicon around the inner surface of the opening 29 A in the polysilicon layer is left on the SiO 2 spacer layer 28 .
  • the sidewall 32 is approximately 0.1 ⁇ m thick.
  • the opening 29 A is reshaped into an opening 32 A having a width of about 0.3 ⁇ m. This dimension of the reshaped opening 29 A is smaller than the scale limit by the conventional photolithography technique.
  • the polysilicon layer 29 ′ and the polysilicon sidewall 32 function as masks when the underlying insulating layers are etched to form the storage electrode contact window. It should be noted that there is no special limitation on the formation of the polysilicon layer 29 ′ and the polysilicon sidewall 32 , since they are formed of polysilicon. It should also be noted that the polysilicon layer 29 ′ and the polysilicon sidewall 32 are not removed during a subsequent process, and are utilized as parts of the storage electrode of the stacked capacitor, as will be described in detail later.
  • the SiO 2 aaaspacer layer 28 , the Si 3 N 4 insulating layer 27 , the SiO 2 insulating layer 26 and the SiO 2 gate insulating layer 23 are selectively etched by an RIE process in which a CHF 3 /H 2 is used and the polysilicon layer 29 ′ and the polysilicon sidewall 32 function as the etching masks.
  • RIE process a storage electrode contact hole 25 A is formed in the above-mentioned layers, so that the n + -type drain region 25 is partially exposed.
  • a polysilicon layer 29 ′′ is grown to, for example, 500 angstroms by CVD.
  • a part of the polysilicon layer 29 ′′ completely covers the inner wall of the storage electrode contact window 25 A and the exposed surface of the n + -type drain region 25 . It is important to form the polysilicon layer 29 ′′ in total contact with the Si 3 N 4 insulating layer 27 .
  • As ions are introduced into the polysilicon layers 29 ′′ and 29 ′ by an ion implantation process in which the dose of the As ions is equal to, for example, 8 ⁇ 10 15 atoms/cm 2 .
  • each of the polysilicon layers 29 ′′ and 29 ′ has a reduced resistance. It will be noted toat the layers consisting of the polysilicon layers 29 ′ and 29 ′′ and the sidewall 32 is thicker than the vertically extending portion of the polysilicon layer 29 ′′.
  • a spacer layer 33 formed of SiO 2 is grown to, for example, 500 angstroms on the entire surface by CVD.
  • the SiO 2 spacer layer 33 is selectively etched by the resist process and RIE process using a CHF 3 /H 2 gas in the conventional photolithography technique.
  • the RIE process an opening 33 A having a belt shape is formed in the SiO 2 spacer layer 33 . It is sufficient to form the opening 33 A so that it is wider than the storage electrode contact window 25 A, because the opening 33 A is used for stacking a polysilicon layer (fin) on the integrated polysilicon layer consisting of the layers 29 ′′ and 29 ′ and the polisilicon sidewall 32 .
  • a polysilicon layer is grown to, for example, 1000 angstroms by CVD.
  • As ions are introduced into the polysilicon layer by an ion implantation process in which the dose of As ions is equal to, for example, 1 ⁇ 10 15 atoms/cm 2 .
  • the resistance of the polysilicon layer is reduced.
  • the above polysilicon layer, the SiO 2 spacer layer 33 , and the polysilicon layers 29 ′′ and 29 ′ are patterned into an electrode shape by the photoresist process and RIE process using a gas of CCl 4 +O 2 or CHF 3 +H 2 .
  • the SiO spacer layer 33 and the SiO 2 spacer layer 28 are completely removed by an etching process in which the device is placed in an HF etchant.
  • polysilicon fins 292 and 291 forming a storage electrode 25 of the stacked capacitor are formed.
  • the fin 292 has a bottom contact area wider than the contact hole 25 A shown in FIG. 6J.
  • the wall of the Si 3 N 4 insulating layer 27 which is a part of the storage electrode contact window 25 A completely makes contact with the polysilicon layer 29 ′, so that there is no possibility that the SiO 2 insulating layer 26 and the SiO 2 interlayer isolation insulating layer 22 are damaged.
  • FIG. 6N a dielectric film 36 around an exposed surface of the storage electrode 29 is formed, and a cell plate 37 (opposed electrode) is formed so that it covers the entire surface.
  • the dielectric film 36 is formed of, for example, Si 3 N 4 .
  • the stacked capacitor is made up of the storage electrode 29 , the dielectric film 36 and the cell plate 37 .
  • a PSG layer 38 is formed on the entire surface, and word-line shunt layers 39 formed of, for example, an Al alloy, are formed on the PSG layer 38 .
  • FIG. 7 is a plan view of the DRAM fabricated by the above-mentioned production process. In FIG. 7, WL 1 and WL 2 indicate word lines, and BL 1 and BL 2 indicate bit lines.
  • the word-line shunt layers 39 are connected to the corresponding word lines WL via contact holes (not shown for the sake of simplicity). It is preferable to form such contact holes by the aforementioned first through fifth embodiments of the present invention.
  • the lowermost polysilicon fin 29 1 has the sidewall 32 , and the polysilicon layers 29 ′ and 29 ′′.
  • the polysilicon layer 29 ′′ is thicker than the polysilicon layer 29 ′, and the largest thickness of the sidewall 32 is approximately equal to the thickness of the polysilicon layer 29 ′.
  • FIGS. 8A through 8E A description will now be given of an eighth embodiment of the present invention with reference to FIGS. 8A through 8E, in which those parts which are the same as those shown in the previous figures are given the same reference numerals.
  • the eighth embodiment of the present invention utilizes the steps which have been described with reference to FIGS. 6A through 6L. After the step related to FIG. 6L, a step shown in FIG. 8A is carried out. A polysilicon layer is grown to, for example, 1000 angstroms on the entire surface.
  • an insulating layer 34 formed of SiO 2 is grown to, for example, 2000 angstroms by CVD. Then, the SiO 2 insulating film 34 is patterned into the shape of the storage electrode by the resist process and RIE process using a CHF 3 /H 2 gas in the photolithography technique, so that openings are formed in the SiO 2 insulating film 34 . Each of the openings is approximately 0.5 ⁇ m wide, which corresponds to the scale limit of the conventional photolithography technique.
  • an insulating layer 35 formed of SiO 2 is grown to, for example, 1000 angstroms on the entire surface by CVD. Thereafter, the SiO 2 insulating layer 35 is anisotropically etched by an RIE process using a CHF 3 and H 2 gas. Thereby, sidewalls 35 are formed around inner walls of the openings in the SiO 2 layer 34 , and the rest thereof is removed. Each sidewall 35 defines an opening 35 A having a width approximately equal to 0.3 ⁇ m, which is smaller than the scale limit of the conventional photolithography technique.
  • the polysilicon layer 42 , the SiO 2 spacer layer 33 , and the polysilicon layers 29 ′′ and 29 ′ are patterned into the shape of the storage electrode by an RIE process in which a CHF 3 /H 2 gas is used and the SiO 2 insulating layer 34 and the SiO 2 sidewalls 15 function as etching masks.
  • the distance between opposite portions of the polysilicon layer 42 is approximately 0.3 ⁇ m.
  • the distance between opposite portions of the polysilicon layer consisting of the polysilicon layer 29 ′′ and 29 ′ is also approximately 0.3 ⁇ m. This means that the adjacent storage electrodes are very close to each other, and thus the surface area of each storage electrode is increased, so that each stacked capacitor can have an increased capacitance.
  • the SiO 2 insulating layer 34 and the SiO 2 sidewalls 35 serving as etching masks are also etched. From this point of view, it is necessary for the layer 34 and the sidewalls 35 to have a sufficient thickness. Further, a special step to remove the SiO 2 insulating layer 34 and the SiO 2 sidewalls 35 is not needed because the SiO 2 insulating layer 34 and the sidewalls 35 are removed during a subsequent step in which the device is placed in an HF etchant, as shown in FIG. 8D.
  • FIG. 8E shows a DRAM fabricated according to the seventh preferred embodiment of the present invention.
  • a storage electrode 40 has two stacked polysilicon fins 40 1 and 40 2 .
  • the polysilicon fin 401 corresponds to the patterned polysilicon layers 29 ′′ and 29 ′ and the polysilicon sidewall 32
  • the polysilicon fin 402 corresponds to the patterned polysilicon layer 42 . It can be seen from FIG. 6N and FIG. 8E that the adjacent stacked capacitors shown in FIG. 8E are closer to each other than those shown in FIG. 6N.
  • the first variation has a storage electrode having only the polysilicon fin 29 1 which consists of the polysilicon layers 29 ′′ and 29 ′ and the polysilicon sidewall 32 .
  • the polysilicon layer consisting of the polysilicon layers 29 ′′ and 29 ′ and the polysilicon sidewall 32 is patterned into the shape of the storage electrode.
  • the device is placed in an HF etchant, so that the insulating layer 28 is completely removed, as shown in FIG. 9A. Then, the process which has been described previously with reference to FIG. 6N is carried out, so that a DRAM shown in FIG. 9B can be obtained.
  • the insulating layer 27 can be formed of SiO 2 or Si 3 N 4 .
  • the fin 29 1 is thicker than a vertically extending portion of the storage electrode.
  • FIG. 10 illustrates a second variation of the aforementioned sixth preferred embodiment of the present invention.
  • the polysilicon fin 29 1 consisting of the polysilicon layers 29 ′′ and 29 ′ and the polysilicon sidewall 32 is formed directly on the insulating layer 27 formed of SiO 2 or Si 3 N 4 .
  • the polysilicon layer 29 ′ shown in FIG. 6F is grown on the insulating layer 27 without forming the insulating layer 28 .
  • the same steps as has been described with reference to FIGS. 6G through 6K and FIG. 6N are carried out. It is also possible to form the polysilicon fin 29 2 on the polysilicon fin 29 1 in the same way as has been described with reference to FIGS. 6L and 6M.
  • FIGS. 11A through 11J A description will now be given of an eighth preferred embodiment of the present invention with reference to FIGS. 11A through 11J, in which those parts which are the same as shown shown in the previous figures are given the same reference numerals.
  • a structure shown in FIG. 11B is the same as that shown in FIG. 6E. Steps to obtain the structure shown in FIG. 11B are the same as those which have been described with reference to FIGS. 6A through 6E.
  • the Si 3 N 4 insulating layer 27 , the SiO 2 spacer layer 28 , the impurity-doped polysilicon layer 29 ′, a spacer layer 45 formed of SiO 2 and an impurity-doped polysilicon layer 46 ′ are formed in this order by CVD. For example, each of these layers is 500 angstorms thick. Then, the polysilicon layer 46 ′, the SiO 2 spacer layer 45 and the polysilicon layer 29 ′ are selectively etched by the resist process and the RIE process, so that an opening 29 A having a thickness equal to, for example, 0.6 ⁇ m is formed therein.
  • a CCl 4 /O 2 gas is used for the polysilicon layers 46 ′ and 29 ′, and a CHF 3 /He gas is used for the SiO 2 spacer layer 45 .
  • a polysilicon layer 47 ′ is grown to, for example, 2000 angstorms on the entire surface by CVD.
  • the polysilicon layer 47 ′ is anisotropically etched by an RIE process in which a CCl 4 /O 2 gas or an HBr/He gas is used.
  • a polysilicon sidewall 47 is formed around an inner surface of the opening 29 A, and the remaining portion of the polysilicon layer 47 ′ is removed.
  • the sidewall 47 defines a new opening 46 A having a width approximately equal to 0.2-0.3 ⁇ m, which is smaller than the width of the opening 29 A shown in FIG. 11C.
  • the SiO 2 spacer layer 28 , the Si 3 N 4 insulating layer 27 , the SiO 2 insulating layer 26 and the SiO 2 gate insulating layer 23 are partially removed by an RIE process in which a CHF 3 /He gas is used and the polysilicon layer 46 ′ and the polysilicon sidewall 47 function as etching masks.
  • RIE process the surface of the n + -type drain region 25 is partially exposed through a contact hole 28 A.
  • the width of the opening 46 A is very small and equal to about 0.2-0.3 ⁇ m, and that the polysilicon layer 46 ′ and the polysilicon layer 47 functioning as the etching masks form a part of the storage electrode without being removed. Thus, it is not necessary to provide a special step to remove the polysilicon layer 46 ′ and the polysilicon sidewall 47 functioning the etching masks.
  • a polysilicon layer 46 ′′ is grown to, for example, 500 angstroms by CVD. During this step, the polysilicon layers 46 ′′ and 46 ′ as well as the polysilicon sidewall 47 are integrated.
  • the polysilicon layers 46 ′′ and 46 ′, the SiO 2 spacer layer 45 , and the polysilicon layer 29 ′ are patterned into the shape of the storage electrode in this order by the resist process using a single mask and the RIE process in the conventional photolithography process.
  • the device shown in FIG. 11H is placed in an HF etchant, so that the exposed SiO 2 insulating layers are isotropically etched, so that a storage electrode 50 having two polysilicon fins 50 1 and 50 2 is formed.
  • the fin 50 1 is formed of the patterned polysilicon layer 29 ′
  • the fin 502 is formed of the patterned polysilicon layers 46 ′′ and 46 ′.
  • the fins 50 1 and 50 2 are connected by the polysilicon sidewall 47 .
  • the polysilicon layer 46 ′′ which is a part of the fin 50 2 vertically extends from its portion on the polysilicon layer 46 ′ and makes contact with the n + -type drain region 25 .
  • a vertical portion 50 3 of the storage electrode 50 consists of the polysilicon sidewall 47 and the polysilicon layer 46 ′′.
  • the vertical portion 50 3 , the polysilicon layer 46 ′′, and the fin 50 2 have mutually different thicknesses t 1 , t 2 and t 3 , respectively.
  • the vertical portion 503 is thicker than the polysilicon layer 46 ′′ and the fin 50 2 .
  • the dielectric film 36 , the cell plate 37 , the PSG passivation layer 38 and the word-line shut layers 39 are formed in the same way as has been described with reference to FIG. 6N.
  • FIGS. 12A and 12B Production steps shown in FIGS. 12A and 12B are carried out in the same way as those shown in FIGS. 11A and 11 B. After that, as shown in FIG. 12C, the Si 3 N 4 insulating layer 27 , the SiO 2 spacer layer 28 , the impurity-doped polysilicon layer 29 ′, the SiO 2 spacer layer 45 and the impurity-doped polysilicon layer 46 ′ are formed in this order by CVD. Each of these layers is 500 angstroms thick, for example.
  • the polysilicon layer 46 ′, the SiO 2 spacer layer 45 , the polysilicon layer 29 ′ and the SiO 2 spacer layer 28 are selectively etched by the resist process and RIE process, so that an opening 28 A is formed therein. It will be noted that the SiO 2 layer 28 is etched as shown in FIG. 12C, while the SiO 2 layer 28 shown in FIG. 11C is not etched.
  • a polysilicon layer 47 ′ is grown to, for example, 2000 angstorms by CVD.
  • the polysilicon layer 47 ′ is selectively etched by an RIE process using a CCl 4 /O 2 gas, so that a polysilicon sidewall 47 a is formed so that it surrounds the inner wall of the opening 28 A.
  • the remaining portion of the polysilicon layer 47 ′ is completely removed.
  • the polysilicon sidewall 47 a defines a new opening 46 A narrower than the opening 28 A.
  • the Si 3 N 4 insulating layer 27 , the SiO 2 insulating layer 26 and the SiO 2 gate insulating layer 23 are selectively etched by an RIE process in which a CHF 3 /He gas is used and the polysilicon layer 46 ′ and the sidewall 47 a function as etching masks.
  • RIE process a CHF 3 /He gas is used and the polysilicon layer 46 ′ and the sidewall 47 a function as etching masks.
  • the surface of the n + -type drain region 25 is partially exposed through a through hole 27 A having the same width as the opening 46 A.
  • the length of the sidewall 37 a used in the ninth embodiment of the present invention is greater than that of the sidewall 37 used in the eighth embodiment of the present invention.
  • the sidewall 47 a functions as the mask more stably than the sidewall 47 .
  • the distance between the sidewall 37 a and the word line WL is closer than the corresponding distance obtained in the eighth embodiment of the present invention.
  • the breakdown voltage of the DRAM shown in FIG. 12G is slightly smaller than that of the DRAM shown in FIG. 11J.
  • FIGS. 13A through 13F are the same as FIGS. 11A and 11B.
  • the Si 3 N 4 insulating layer 27 , the SiO 2 layer 28 , the impurity-doped polysilicon layer 29 ′, the SiO 2 spacer layer 45 and the impurity-doped polysilicon layer 46 ′ are formed in this order by the aforementioned process.
  • an SiO 2 insulating layer 48 is grown to, for example, 200 angstroms by CVD.
  • the SiO 2 layer 48 , the polysilicon layer 46 ′, the SiO 2 spacer layer 45 , the polysilicon layer 29 ′ and the SiO 2 spacer layer 28 are selectively removed, so that the surface of the Si 3 N 4 layer 27 is partially exposed through the opening 28 A.
  • the polysilicon layer 47 ′ is grown to, for example, 2000 angstorms by CVD.
  • the polysilicon layer 47 ′ is selectively etched by RIE, so that a widewall 42 b is formed around an inner wall of the opening 28 A.
  • the Si 3 N 4 layer 27 , the SiO 2 layer 26 and the SiO 2 gate insulating layer 23 are selectively etched via the opening defined by the sidewall 47 b .
  • the SiO 2 layer 48 is removed at the same time as the SiO 2 insulating layer 26 is removed.
  • the SiO 2 layer 48 functions to protect the polysilicon layer 46 ′ against the RIE process of forming the sidewall 47 b . Further, the SiO 2 layer 48 functions as the mask more stably during the time when the Si 3 N 4 insulating layer 27 is being etched.
  • FIGS. 14A and 14B are the same as FIGS. 11A and 11B, respectively.
  • an SOG (spin on glass) layer 49 is formed on the entire surface so that the surface of the SOG layer 49 is substantially flat enough to prevent the growth of residuum during a subsequent process.
  • residuum may be formed on a rough surface after the selective etching process.
  • the SiO 2 layer 48 may be partially left on a rough surface portion of the polysilicon layer 46 ′.
  • FIG. 14C shows that the SOG layer 49 is completely flat. It can be seen from FIG.
  • the SOG layer 49 absorbs a roughness of the surface shown in FIG. 14B. It is also possible to form a PSG reflow layer instead of the SOG layer 49 . After that, the layers 28 , 29 ′ 45 , 46 ′ and 48 are formed in the same way as has been described previously. Then, these layers are selectively etched, so that the opening 28 A is formed, as shown in FIG. 14C.
  • the polysilicon layer 47 ′ is grown to, for example, 2000 angstroms by CVD, and selectively etched by the RIE process, so that a sidewall 47 b is formed, as shown in FIG. 14E.
  • the Si 3 N 4 insulating layer 27 , the SOG layer 49 , the sio 2 layer 26 and the SiO 2 layer 23 are selectively etched, so that the n + -type drain region 25 is partially exposed through the opening 27 A.
  • a DRAM shown in FIG. 14G is fabricated by the aforementioned process which has been described with reference to FIG. 6N.
  • FIGS. 15A through 15J A description will now be given of a tenth preferred embodiment of the present invention with reference to FIGS. 15A through 15J, in which those parts which are the same as those shown in the previous figures are given the same reference numerals.
  • FIGS. 15A and 15B are the same as FIGS. 11A and 11B, respectively.
  • the first bilayer structure consists of an SiO 2 insulating layer 63 and a polysilicon layer 64 .
  • the second bilayer structure consists of an SiO 2 insulating layer 65 and a polysilicon layer 66 .
  • the third bilayer structure consists of an SiO 2 insulating layer 67 and a polysilicon layer 68 .
  • an SiO 2 insulating layer 69 having a thickness of 100 angstroms, a polysilicon layer 70 having a thickness of 2000 angstorms and an SiO 2 insulating layer 71 having a thickness of 100 angstroms are successively grown in this order by CVD.
  • a photoresist film 72 having a window pattern is placed on the SiO 2 insulating layer 71 , and the SiO 2 insulating layer 71 and the polysilicon layer 70 are etched, so that an opening 70 A is formed.
  • the size of the opening 70 A is approximately 0.5 ⁇ m, which is the scale limit in the conventional photolithography technique.
  • the photoresist film 72 is removed, and a polysilicon layer is grown to, for example, 1500 angstroms on the entire surface. Then, the polysilicon layer is anisotropically etched by an RIE process using an HBr/He gas, so that a polysilicon sidewall 74 is formed around an inner wall of the opening 70 A.
  • the polysilicon sidewall 74 defines a new opening 70 B having a size approximately equal to 0.2 ⁇ m.
  • the SiO 2 insulating layer 69 and the polysilicon layer 68 are anisotropically etched by an RIE process in which the polysilicon layer 70 and the sidewall 74 function as etching masks.
  • the SiO 2 insulating layer 71 is removed.
  • the polysilicon layer 70 decreases by approximately 700 angstroms, so that a portion thereof having a thickness of about 1300 angstroms is left.
  • the SiO 2 insulating layer 67 is removed in an RIE process using a CHF 3 /H 2 gas in which the polysilicon layer 70 and the sidewall 74 function as etching masks.
  • a CHF 3 /H 2 gas in which the polysilicon layer 70 and the sidewall 74 function as etching masks.
  • the CHF 3 /H 2 gas acts to SiO 2 greatly.
  • the polysilicon layer 66 and the SiO 2 insulating layer 65 are removed in the same way as has been described above.
  • each of the polysilicon layer 70 and the sidewall 74 decreases by about 700 angstroms, so that they are approximately 600 angstroms thick.
  • the polysilicon layer 64 is removed by RIE. During this RIE process, the polysilicon layer 70 and the sidewall 74 are also removed. It will be noted that the SiO 2 insulating layer 69 prevents the underlying polysilicon layer 68 from being etched even if over-etching is carried out. It is preferable to carry out over-etching so that the polysilicon layer 70 and the sidewall 74 are completely removed.
  • the SiO 2 insulating layer 63 is removed in an etching process in which the polysilicon layer 68 functions as a mask. During this etching, the SiO insulating layer 69 is 2 also removed. Subsequently, the Si 3 N 4 insulating layer 62 is etched, and the SiO 2 insulating layer 26 and SiO 2 gate insulating layer 23 are etched. Thereby, a window formed in the layers 68 through 23 is formed, as shown in FIG. 15G.
  • a polysilicon layer 75 is grown to, for example, 500 angstroms on the entire surface including the window shown in FIG. 15G.
  • the polysilicon layers 75 and 68 , the SiO 2 insulating layer 67 , the polysilicon layer 66 , the SiO 2 insulating layer 65 , and the polysilicon layer 64 are patterned into the shape of the storage electrode. Thereby, a device shown in FIG. 15H is formed.
  • the storage electrode 90 has a first polysilicon fin 90 1 formed of the patterned polysilicon layer 64 , a second polysilicon fin 90 2 formed of the patterned polysilicon layer 66 , and a third polysilicon fin 90 3 having the patterned polysilicon layers 68 and 75 , and a vertical connecting portion formed of the polysilicon layer 75 .
  • the third polysilicon fin 90 3 is thicker than the first and second polysilicon fins 90 1 and 90 2 .
  • the aforementioned processes are carried out for the device shown in FIG. 15I, so that a DRAM shown in FIG. 15J can be formed. It is possible to apply the teachings shown in FIGS. 13A through 13F to the tenth embodiment of the present invention. It is also possible to form the lowermost fin9- 1 directly on the insulating layer 62 . In this case, the insulating layer 62 can be formed of SiO 2 .

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Abstract

A method of forming a structure having a contact hole includes the steps of (a) forming an insulating layer on a first conductive layer, (b) forming a second conductive layer on the insulating layer, (c) forming an opening in the second conductive layer, (d) forming a conductive sidewall around an inner wall of the first conductive layer defining the opening, (e) selectively etching the insulating layer in a state where the second conductive layer and the conductive sidewall function as etching masks, so that the contact hole having a width smaller than that of the opening and defined by the conductive sidewall is formed, and the first conductive layer is exposed through the contact hole, and (f) removing the second conductive layer and the conductive sidewall.

Description

    BACKGROUND OF THE INVENTION
  • The present invention generally relates to a layer structure having a contact hole suitable for dynamic random access memories having fine contact holes, and a method of producing such a layer structure. More particularly, the present invention is concerned with a fin-shaped capacitor having such a layer structure, and a method of forming such a fin-shaped capacitor. Furthermore, the present invention is concerned with a dynamic random access memory having such a fin-shaped capacitor. [0001]
  • Recently, there has been considerable activity as regards the development of 64 Mbit dynamic random access memories (DRAM). There are known DRAMs having three-dimensional stacked capacitor cells capable of providing a storage capacity equal to or higher than 64 Mbits (see Japanese Laid-Open Patent Application Nos. 1-137666, 1-147857 and 1-154549, U.S. Pat. No. 4,974,040 and T. Ema et al., “3-DIMENSIONAL STACKED CAPACITOR CELL FOR 16M AND 64M DRAMS”, International Electron Devices Meetings, 592-IEDM 88, Dec. 11-14, 1988). In order to increase the integration density, it is necessary to reduce the two-dimensional size of each memory cell without reducing the capacitance of each stacked capacitor. [0002]
  • In order to fabricate 64 Mbit DRAMs, a feature scale approximately equal to 0.3 [μm] is required. However, the conventional photolithography technique can realize a feature scale approximately equal to a maximum of 0.5 [μm]. 64 Mbit DRAMs can be realized by reducing the size of each storage (stacked) capacitor. For this purpose, it is necessary to reduce the size of a contact window (opening) for a storage electrode which is a part of the stacked capacitor. As described above, since the feature scale realized by the conventional photolithography technique is approximately 0.5 [μm], it is impossible to form the contact window having a size approximately equal to 0.3 [μm]. It is also necessary to reduce the size of a window (contact hole) provided for connecting a word line formed of, for example, polysilicon, and a low-resistance wiring line (word-line shunt layer) formed of Al or Al alloy, directed to preventing the occurrence of a delay in signal transmission in the word line. [0003]
  • Japanese Laid-Open Patent Application No. 63-119239 discloses a method for forming a fine pattern narrower than a feature scale limit of the conventional photolithography technique. The application teaches a process in which polysilicon, PSG or SiO[0004] 2 is grown on an SiO2 mask having a window through which a substrate is partially exposed, and a grown film on the mask and the exposed substrate surface is anisotropically etched, so that a sidewall is formed on the substrate so that it is formed around the entire inner wall of the window in the mask. The distance between opposite surfaces of the sidewall in the window is less than the feature scale limit. Thus, a surface area of the substrate less than the feature scale limit is exposed through the sidewall in the window. Then, the substrate is etched in such a way that the combination of the sidewall and the mask function as an etching mask, so that a hole is formed in the substrate.
  • The above-mentioned Patent Application discloses an arrangement in which the mask is formed of SiO[0005] 2 and a member to be processed is formed of Si. Thus, the removal of the mask material can be easily made. However, when a multilayer structure, such as DRAMS, is produced, it is necessary to consider three layers of a mask material, a material to be processed and a underlying material which is located under the processed material and which is exposed through a hole formed in the processed material. In this case, it is necessary to prevent the exposed portion of the underlaying material from be damaged during a process in which the mask material is removed. Further, if the mask material is left in the finalized products, it is necessary to have no problem arising from the existence of the left mask material. The above-mentioned Japanese Application does not suggest the above matters.
  • Japanese Laid-Open Patent Application No. 60-224218 discloses the use of a sidewall directed to providing a window (contact hole) smaller than the feature scale limit of the conventional photolithography technique. The sidewall is formed of Al and formed on an SiO[0006] 2 layer and around an inner wall of a window formed in a silicon nitride (Si3N4) layer also formed on the SiO2 layer. The SiO2 layer is selectively etched in such a way that the Al sidewall and the Si3N4 layer function as mask layers. However, it is very difficult to form the Al sidewall in contact with the inner wall of the window in the Si3N4 layer, since Al has a poor coverage characteristic. Further, it is necessary to form the Si3N4 layer which is sufficiently thick, because the selective etching ratio of Si3N4 to SiO2 is small.
  • Japanese Laid-Open Patent Application No. 63-116430 (which corresponds to U.S. patent application Ser. No. 924,223 filed on Oct. 28, 1986) teaches the use of a sidewall for forming a hole smaller than the scale limit of the conventional photolithgraphy technique. The just above application shows a lift-off process for removing the mask material. However, the lift-off process has a problem in that some of the mask material separated from the substrate is re-adhered hereto. This frequently causes a pattern fault in a subsequent process. The Japanese application of concern does not disclose an effective step to process the mask material. Further, the Japanese application shows a sidewall formed on the side surface of a photosensitive material. It is necessary to form the sidewall at a low temperature due to the thermal stability of the photosensitive material. Thus, there is a great limitation regarding the selection of mask materials. In addition, the structure shown in the Japanese application of concern is limited to a special application. [0007]
    • SUMMARY OF THE INVENTION
  • It is a general object of the present invention to provide an improved layer structure having a contact hole, in which the above-mentioned disadvantages are eliminated. [0008]
  • A more specific object of the present invention is to provide a layer structure having a contact hole suitable for DRAMs. [0009]
  • The above-mentioned objects of the present invention are achieved by a method of forming a structure having a contact hole comprising the steps of: [0010]
  • (a) forming an insulating layer on a first conductive layer; [0011]
  • (b) forming a second conductive layer on the insulating layer; [0012]
  • (c) forming an opening in the second conductive layer; [0013]
  • (d) forming a conductive sidewall around an inner wall of the first conductive layer defining the opening; [0014]
  • (e) selectively etching the insulating layer in a state where the second conductive layer and the conductive sidewall function as etching masks, so that the contact hole having a width smaller than that of the opening and defined by the conductive sidewall is formed, and the first conductive layer is exposed through the contact hole; and [0015]
  • (f) removing the second conductive layer and the conductive sidewall. [0016]
  • The above-mentioned objects of the present invention are also achieved by a method of forming a structure having a contact hole comprising the steps of: [0017]
  • (a) forming an insulating layer on a first conductive layer; [0018]
  • (b) forming a second conductive layer on the insulating layer; [0019]
  • (c) forming an opening in the second conductive layer; [0020]
  • (d) forming a conductive sidewall around an inner wall of the first conductive layer defining the opening; [0021]
  • (e) selectively etching the insulating layer in a state where the second conductive layer and the conductive sidewall function as etching masks, so that the contact hole having a width smaller than that of the opening and defined by the conductive sidewall is formed on the insulating layer and the first conductive layer is exposed through the contact hole; [0022]
  • (f) forming a barrier layer on the second conductive layer, the conductive sidewall and the first conductive layer exposed through the contact hole; and [0023]
  • (g) forming a third conductive layer on the barrier layer, the barrier layer preventing the third conductive layer from reacting with the second conductive layer and the conductive sidewall. [0024]
  • The above-mentioned objects of the present invention are also achieved by a method of forming a structure having a contact hole comprising the steps of: [0025]
  • (a) forming an insulating layer on a first conductive layer; [0026]
  • (b) forming a second conductive layer on the insulating layer; [0027]
  • (c) forming an opening in the second conductive layer; [0028]
  • (d) forming a conductive sidewall around an inner wall of the first conductive layer defining the opening; [0029]
  • (e) selectively etching the insulating layer in a state where the second conductive layer and the conductive sidewall function as etching masks, so that the contact hole having a width smaller than that of the opening and defined by the conductive sidewall is formed, and the first conductive layer is exposed through the contact hole; and [0030]
  • (f) forming a third conductive layer on the second conductive layer, the conductive sidewall and the member exposed through the contact hole, [0031]
  • wherein: [0032]
  • the second conductive layer comprises polysilicon; [0033]
  • the conductive sidewall comprises polysilicon; and [0034]
  • the third conductive layer comprises tungsten. [0035]
  • The aforementioned objects of the present inventoin are achieved by a method of forming a structure having a contact hole comprising the steps of: [0036]
  • (a) forming an insulating layer on a first conductive layer; [0037]
  • (b) forming a second conductive layer on the insulating layer; [0038]
  • (c) forming a first opening in the second conductive layer; [0039]
  • (d) selectively growing a third conductive layer on the second conductive layer and an inner wall of the second conductive layer defining the first opening, so that a second opening defined by the third conductive layer and having a width smaller than that of the first opening is formed; and [0040]
  • (e) selectively etching the insulating layer in a state where the third conductive layer functions as an etching mask, so that the contact hole having a width substantially identical to the second opening defined by the third conductive layer is formed, and the first conductive layer is exposed through the contact hole. [0041]
  • Another object of the present invention is to provide a layer structure having a contact hole as formed by the above-mentioned methods. [0042]
  • This object of the present invention is achieved by a layer structure comprising: [0043]
  • a first conductive layer; [0044]
  • an insulating layer formed on the first conductive layer and having a contact hole, the first conductive layer being exposed through the contact hole; [0045]
  • a second conductive layer formed on the insulating layer and having an opening having a width larger than that of the contact hole; [0046]
  • a conductive sidewall formed on the insulating layer exposed through the opening and formed around an inner wall of the second conductive layer defining the opening, the conductive sidewall having a width substantially equal to that of the contact hole; [0047]
  • a barrier layer formed on the second conductive layer, the conductive sidewall and the first conductive layer exposed through the contact hole; and [0048]
  • a third conductive layer formed on the barrier layer, the barrier layer preventing the third conductive layer from reacting with the second conductive layer and the conductive sidewall. [0049]
  • The above-mentioned object of the present invention is achieved by a layer structure comprising: [0050]
  • a first conductive layer; [0051]
  • an insulating layer formed on the first conductive layer and having a contact hole, the first conductive layer being exposed through the contact hole; [0052]
  • a second conductive layer formed on the insulating layer and having a first opening having a width larger than that of the contact hole; [0053]
  • a third conductive layer formed on the insulating layer exposed through the first opening and the second conductive layer and formed around an inner wall of the second conductive layer defining the first opening, the third conductive layer defining a second opening having a width substantially equal to that of the contact hole, the second opening being continuously connected to the contact hole; [0054]
  • a barrier layer formed on the third conductive layer and the first conductive layer exposed through the contact hole; and [0055]
  • a fourth conductive layer formed on the barrier layer, the barrier layer preventing the fourth conductive layer from reacting with the third conductive layer and the conductive sidewall. [0056]
  • The above-mentioned object of the present invention is also achieved by a layer structure comprising: [0057]
  • a first conductive layer; [0058]
  • an insulating layer formed on the first conductive layer and having a contact hole, the first conductive layer being exposed through the contact hole; [0059]
  • a second conductive layer formed on the insulating layer and having an opening having a width larger than that of the contact hole; [0060]
  • a conductive sidewall formed on the insulating layer exposed through the opening and formed around an inner wall of the second conductive layer defining the opening, the conductive sidewall having a width substantially equal to that of the contact hole; and [0061]
  • a third conductive layer formed on the second conductive layer, the conductive sidewall and the first conductive layer exposed through the contact hole, [0062]
  • wherein the third conductive layer comprises a material which causes no reaction with the second conductive layer and the conductive sidewall. [0063]
  • According to the present invention, there is also provided a dynamic random access memory having any of the above-mentioned structures. [0064]
  • According to the present invention, there is also provided a fin-shaped capacitor and a method for producing such a fin-shaped capacitor.[0065]
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which: [0066]
  • FIG. 1A through FIG. 1H are cross-sectional views showing steps of an improved method for producing a layer structure having a contact hole according to a first preferred embodiment of the present invention; [0067]
  • FIG. 2 is a cross-sectional view showing a second preferred embodiment of the present invention; [0068]
  • FIGS. 3A through 3D are cross-sectional views showing a third preferred embodiment of the present invention; [0069]
  • FIG. 4 is a cross-sectional view showing a fourth preferred embodiment of the present invention; [0070]
  • FIG. 5 is a cross-sectional view showing a fifth preferred embodiment of the present invention; [0071]
  • FIGS. 6A through 6N are cross-sectional views showing steps of a DRAM production method according to a sixth preferred embodiment of the present invention; [0072]
  • FIG. 7 is a plan view of a DRAM produced by the sixth preferred embodiment of the present invention; [0073]
  • FIGS. 8A through 8E are cross-sectional views showing a seventh preferred embodiment of the present invention; [0074]
  • FIGS. 9A and 9B are cross-sectional views showing a first variation of the sixth preferred embodiment of the present invention; [0075]
  • FIG. 10 is a cross-sectional view showing a second variation of the sixth preferred embodiment of the present invention; [0076]
  • FIGS. 11A through 11J are cross-sectional views showing an eighth preferred embodiment of the present invention; [0077]
  • FIGS. 12A through 12G are cross-sectional views showing a ninth preferred embodiment of the present invention; [0078]
  • FIGS. 13A through 13F are cross-sectional views showing a variation of the ninth preferred embodiment of the present invention; [0079]
  • FIGS. 14A through 14G are cross-sectional views showing a modification of the variation shown in FIGS. 13A through 13F; and [0080]
  • FIGS. 15A through 15J are cross-sectional views showing a tenth preferred embodiment of the present invention.[0081]
    • DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • A description will now be given of a first preferred embodiment of the present invention with reference to FIG. 1A through FIG. 1H. [0082]
  • Referring to FIG. 1A, a [0083] conductive layer 2 formed of, for example, polysilicon, is formed on a base 1 formed of an insulator, such as SiO2. The polysilicon layer 2 is a word line of a DRAM, for example. An insulating layer 3 formed of, for example, BPSG (boron-phosphosilicate glass), is grown to, for example, 0.5 μm on the entire surface by a CVD process. The BPSG layer 3 is heated in a wet atmosphere at 850° C. for 10 minutes, and reflown, so that a substantially flat surface of the BPSG layer 3 can be formed. Then, a polysilicon layer 4 is grown to, for example, 1000 angstrom by the CVD process. After that, a photoresist film 5 is coated, and etched by the conventional photolithography technique, so that the photoresist film 5 functions as an etching resist having a hole pattern can be formed. Subsequently, the polysilicon layer 4 is selectively etched by an RIE (reactive ion etching) process in which a CCl4/O2 gas is used and the photoresist film 5 functions as an etching mask. Thereby, a first opening 6 having a width (diameter) approximately equal to 0.5 μm is formed in the polysilicon layer 4.
  • As shown in FIG. 1B, a [0084] polysilicon layer 7 is grown to, for example, 1500 angstroms on the entire surface including the first opening 6 by CVD. Then, as shown in FIG. 1C, the polysilicon layer 7 is selectively etched by the RIE process using a CCl4/O2 gas, so that a sidewall 8 is formed on an inner wall (sidewall) of the first opening 6 formed in the polysilicon layer 4. The sidewall 8 defines a second opening 9 having a width approximately equal to 0.2 μm.
  • As shown in FIG. 1D, the [0085] BPSG layer 3 is selectively etched in an RIE process using a CHF3/He gas in which the polysilicon layer 4 and the sidewall 8 function as masks. Thereby, a contact hole 10 through which the polysilicon layer 2 is partially exposed is formed in the BPSG layer 3.
  • As shown in FIG. 1E, a [0086] photoresist film 11 is formed on the entire surface including the contact hole 10. Then, as shown in FIG. 1F, the entire surface of the photoresist film 11 is exposed and developed. During this process, a small amount of light enters a bottom portion of the contact hole 10. Thus, a part of the photoresist film 11 is left in the contact hole 10. The polysilicon layer 4 and the sidewall 18 are dry-etched in a CF4/O2 plasma atmosphere in a state where the polysilicon layer 2 is protected against dry etching due to the existence of the photoresist film 11 in the contact hole 10. During the dry etching process, the polysilicon layer 4 and the sidewall 8 are isotropically etched. After that, the photoresist film 11 is removed in an O2 plasma.
  • After that, an Al alloy (or Al) [0087] 12 is deposited on the upper surface including the contact hole 10 by a sputtering process. Then, the Al alloy layer 12 is etched, so that a desired Al (or Al alloy) pattern is formed. Thereby, the polysilicon word line 2 is connected to the Al alloy layer 12 via the contact hole 10. It will be noted that the contact hole 10 has a width smaller than the feature scale limit of the conventional photolithographic technique. It will also be noted that the above-mentioned production method is suitable for forming a contact hole for connecting the word line and the word-line shunt layer which is provided for preventing the occurrence of a delay in transmitting a signal via the word line.
  • The [0088] BPSG layer 3 can be substituted for a stacked member in which a PSG layer and an SiO2 layer are alternately stacked. It is also possible to employ an alternative step instead of the step shown in FIG. 1H. In the alternative step, after the polysilicon layer 4 and the sidewall 8 are removed, the BPSG layer 3 is reflowed by heating the device in an N2 atmosphere at 850° C. for 20 minutes, so that an upper edge of the contact hole 10 is smoothly curved. The existence of such a smoothly curved upper edge of the contact hole 10 improves the coverage of the Al alloy layer 12.
  • A description will now be given of a second preferred embodiment of the present invention with reference to FIG. 2. A layer structure shown in FIG. 2 is the same as that shown in FIG. 1B except that an SiO[0089] 2 layer 13 is formed on the polysilicon layer 4. More specifically, the SiO2 film 13 is grown to, for example, about 200 angstroms on the polysilicon layer 4 by CVD. Then, the photoresist film 5 shown in FIG. 1A is formed on the entire surface. After that, the first opening 6 is formed in the SiO2 layer 13 and the polysilicon layer 4. Then, the polysilicon layer 7 is formed on the photoresist film 5 and in the first opening 6 in the same way as shown in FIG. 1B. Then, the polysilicon layer 7 is anisotropically etched in the vertical direction. The SiO2 layer 13 functions as an etching stopper during the step shown in FIG. 1C, so that it is possible to prevent a decrease in the thickness of the polysilicon layer 4. Further, it becomes easy to detect the end of etching since the SiO2 layer 13 is exposed. It will be noted that the SiO2 layer 13 is removed together with the BPSG layer 3 during the step shown in FIG. 1E. Thus, it is not necessary to provide a special step to remove the SiO2 layer 13.
  • A description will now be given of a third preferred embodiment of the present invention with reference to FIGS. 3A through 3C, in which those parts which are the same as those shown in the previous figures are given the same reference numerals. [0090]
  • Referring to FIG. 3A, the [0091] BPSG layer 3 is grown to, for example, 0.5 μm on the entire surface including the polysilicon layer (word line) 2 by CVD. Next, the polysilicon layer 4 is grown to, for example, 1000 angstroms by CVD. Then, the photoresist film 5 is coated, and patterned by the conventional photolithography technique, so that a hole pattern having a width approximately equal to 0.5 μm is formed in the photoresist film 5. After that, the polysilicon layer 4 is selectively removed by an RIE process using a CCl4/O2 gas in which the photoresist film 5 serves as a mask, so that the first opening 6 is formed in the polysilicon layer 4.
  • As shown in FIG. 3B, a [0092] polysilicon layer 14 is selectively grown on the upper surface of the polysilicon layer 4 and a side surface thereof by a CVD process in which the device is maintained at 650° C. and an SiH4+HCl+H2 gas is used. The polysilicon layer 14 defines a second opening 15 having a width smaller than that of the first opening 6. It is easy to control the thickness of the polysilicon layer 14, that is, easy to control the width of the second opening 15.
  • Then, as shown in FIG. 3C, the [0093] BPSG layer 3 is removed via the second opening 15 by an RIE process using a CHF3/He gas, so that the contact hole 10 is formed and the polysilicon layer 2 is partially exposed through the contact hole 10. Finally, a stakced layer 16 fomed of a Ti/TiN layer 16 is formed on the polysilicon layer 14, and an Al alloy (or Al) layer 17 is formed on the stacked layer 16, as shown in FIG. 3D. The stacked laye 16 will be described in detail later.
  • A description will now be given of a fourth preferred embodiment of the present invention with reference to FIG. 4, in which those parts which are the same as those shown in the previous figures are given the same reference numerals. In the step shown in FIG. 1G, the [0094] polysilicon layer 4 and the sidewall 8 are removed, on the other hand, according to the fourth embodiment of the present invention, as shown in FIG. 4, the polysilicon layer 4 and the sidewall 8 are not removed, but left on the BPSG layer 3. After the layer structure shown in FIG. 1D is obtained, the stacked layer 16 is formed on the entire surface including the polysilicon layer 4, the sidewall 8 and the exposed surface of the polysilicon layer 2 by CVD, for example. The stacked layer 16 consists of a Ti layer having a thickness of 200 angstroms and a TiN layer having a thickness of 1000 angstroms. Hereafter, the stacked layer 16 is referred to as a Ti/TiN layer 16. After the Ti/TiN layer 16 is formed, the Al alloy (or pure Al) 17 is deposited on the Ti/TiN layer 16 by sputtering. After that, the polysilicon layer 4, the Ti/TiN layer 16 and the Al alloy layer 17 are patterned by etching.
  • It will be noted that if the Al alloy layer (or pure Al layer) [0095] 17 is deposited directly on the polysilicon layer 4 and the polysilicon sidewall 8, it will easily react to silicon in the layer 4 and the sidewall 8 during a subsequent annealing process in which a protection cover is formed, for example. The above reaction increases the resistance of the Al alloy layer 17. The Ti/TiN layer 16 functions as a barrier layer which prevents the above-mentioned reaction. The barrier layer 16 is not limited to the Ti/TiN layer.
  • A description will now be given of a fifth preferred embodiment of the present invention with reference to FIG. 5, in which those parts which are the same as those shown in the previous figures are given the same reference numerals. The fifth embodiment shown in FIG. 5 has the [0096] left polysilicon layer 4 and the polysilicon sidewall 8, and uses a W (tungsten) layer functioning as a wiring line instead of the Al alloy (or pure Al) layer 17 shown in FIG. 4. The use of the W layer 18 does not need the deposition of the Ti/TiN layer 16.
  • After the layer structure shown in FIG. 1D is obtained, the [0097] W layer 18 is grown to, for example, 5000 angstroms on the entire surface including the polysilicon layer 4, the polysilicon sidewall 8 and the exposed surface of the polysilicon layer 2 by CVD. The contact hole 10 is filled with tungsten, so that the coverage of the W layer 18 can be improved. It will be noted that it is easy to fill the contact hole 10 with tungsten by CVD. It will be noted that tungsten has a poor adhession to BPSG or SiO 2. On the other hand, as shown in FIG. 5, the W layer 18 is formed on the polysilicon layer 4 and the polysilicon sidewall 18. Thus, the adhession problem can be solved.
  • A description will now be given of a sixth preferred embodiment of the present invention with reference to FIG. 6A through FIG. 6N. The sixth preferred embodiment of the present invention provides a DRAM having a contact hole defined by a sidewall. [0098]
  • Referring to FIG. 6A, an interlayer [0099] isolation insulating layer 22 is grown to, for example, 4000 angstroms on a p-type silicon substrate 21 by a selective thermal oxidation process (a local-oxidation-of-silicon process: LOCOS), in which a silicon nitride layer is used as an oxidation-resistant mask. Next, the silicon nitride layer serving as the oxidation-resistant mask is removed, so that active areas in the p-type silicon substrate 21 are exposed. Then, a gate insulating layer 23 having a thickness equal to, for example, 100 angstroms is formed on the exposed surfaces of the p-type silicon substrate 21 by a thermal oxidation process. After that, a polysilicon layer is grown to, for example, 1000 angstroms by CVD. Then, the polysilicon layer is patterned by a resist process and RIE process in the photolithography technique in which a CCl4/O2 gas is used. Thereby, word lines WL are formed. After that, As ions are introduced into the p-type silicon substrate 21 by an ion implantation process in which the word lines WL and the interlayer isolation insulating layer 2 function as masks. Thereby, an n+-type source region 24 and an N+-type drain region 25 of a transfer transistor of a memory cell are formed in the p-type silicon substrate 21. The dose of As ions is equal to, for example, 1×1015 atoms/cm2. During a subsequent thermal process, the source and drain regions 24 and 25 are heated. After that, an insulating layer 26 formed of SiO2 is grown to, for example, 1000 angstroms by CVD.
  • As shown in FIG. 6B, the SiO[0100] 2 insulating film 26 is selectively etched in an RIE process in which a CHF3/H2 gas is used, so that a bit line contact hole 24A is formed in the SiO2 insulating film 26. It will be noted that if a positional error occurs in the bit line contact window 24A and thus the word line WL is partially exposed, an exposed portion of the word line WL can be compensated for, as will be described later. Thus, it is sufficient to provide an alignment margin approximately equal to 0.1 μm when the bit line contact window 24A is approximately 0.5 μm in diameter. As will be indicated later, it is preferable to remove a portion of the SiO2 insulating layer 26 in a scribe area defined in a peripheral portion of a chip at the same time as then the bit line contact hole 24A is formed.
  • As shown in FIG. 6C, an SiO[0101] 2 insulating layer 41 is grown to, for example, 1000 angstroms on the entire surface by CVD.
  • After that, as shown in FIG. 6D, the SiO[0102] 2 insulating layer 41 is selectively etched by an anisotropic etching process, such as, an RIE process using a CHF3/H2 gas. By this RIE process, a sidewall SW1 having an about 0.1 μm thickness is formed so that it surrounds a vertical inner wall of the bit line contact window 24A and a curved part of the SiO2 insulating layer 26. The sidewall SW1 defines the width of the bit line contact hole 24A, which is approximately equal to 0.3 μm. It will be noted that this dimension, 0.3 μm, is considerably smaller than the scale limit by the conventional photolithography technique (approximately 0.5 μm). The formation of the sidewall SW1 contributes to reducing the alignment margin. Even if the word line WL is partially exposed due to the positional error of the bit line contact window 24A, the sidewall 24 will completely cover the exposed surface of the word line WL.
  • The above-mentioned contact hole forming process is distinguished from a known self-alignment contact formation method. In the self-alignment contact formation method, an insulating layer corresponding to the SiO[0103] 2 insulating layer 26 and a polysilicon layer provided for the word lines WL are patterned into an identical shape. Then, sidewalls are formed around windows. Thus, the windows are automatically defined by the sidewalls, so that there is no need for any alignment margin. Normally, the insulating film corresponding to the SiO2 insulating layer 26 is 2000 angstroms thick, and the underlying polysilicon layer provided for forming the word lines WL is 1000 angstron's thick. Thus, the sidewall is about 3000 angstrom high, and is a large step portion formed on the surface of the substrate. On the other hand, the process which has been described with reference to FIG. 6D does not form such a great step surface portion. It should be noted that the sidewall SW1 is also formed on a step portion on the surface of the SiO insulating film, so that the slope of the curved surface portion of the SiO2 insulating layer 26 can be reduced.
  • It is necessary to etch only the SiO[0104] 2 insulating layer 41. As has been described previously, the scribe area on the peripheral portion of the chip is exposed during the process shown in FIG. 6B. Since the SiO2 layer 41 is formed on the scribe area, etching is stopped when the scribe area which is a part of the p-type silicon substrate 21 appears. This judgment of whether or not the scribe area has appeared can be carried out by detecting a change of a plasma emitting state during the RIE process, or by detecting the film thickness of the scribe area by means of a laser interference instrument.
  • Referring to FIG. 6E, a polysilicon layer is grown to, for example, 500 angstroms on the entire surface by CVD. Then, As ions are introduced into the polysilicon layer by an ion implantation process in which the dose of As ions is equal to 1×10[0105] 15 atoms/cm2. After that, a WSi2 film is formed to, for example, 500 angstroms on the impurity doped polysilicon layer by CVD. Then, the WSi2 layer and the impurity doped polysilicon layer are patterned by an RIE process using a CCl4/O2 gas, so that a bit line BL having a two-layer structure is formed.
  • As shown in FIG. 6F, an insulating [0106] layer 27 formed of Si3N4, a spacer layer 28 formed of SiO2 and a polysilicon layer 29′ which forms a part of a storage electrode (fin electrode) of a stacked capacitor are grown in this order by CVD. The Si3N4 insulating layer 27, the SiO2 spacer layer 28 and the polysilicon layer 29′ are, for example, 1000, 500 and 1000 angstroms, respectively. It will be noted that the polysilicon layer 29′ plays the important role, as will be described later.
  • As shown in FIG. 6G, the [0107] polysilicon layer 29′ is selectively etched by the resist process and RIE process using a CCl4/O2 gas in the conventional photolithography technique, so that an opening 29A having the same pattern as the storage electrode contact window is formed in the polysilicon layer 29′. During the selective etching process, it is preferable to remove a part of the polysilicon layer 29′ on the scribe area in the chip peripheral region. The opening 29A has a width approximately equal to 0.5 μm, which is the scale limit attained by the conventional photolithography technique.
  • As shown in FIG. 6H, a [0108] polysilicon layer 32 a is grown to, for example, 1000 angstroms by CVD. Then, as shown in FIG. 6I, the polysilicon layer is anisotropically etched by an RIE process using a CCl4/O2 gas. Thereby, a sidewall 32 formed of polysilicon around the inner surface of the opening 29A in the polysilicon layer is left on the SiO2 spacer layer 28. The sidewall 32 is approximately 0.1 μm thick. As a result, the opening 29A is reshaped into an opening 32A having a width of about 0.3 μm. This dimension of the reshaped opening 29A is smaller than the scale limit by the conventional photolithography technique.
  • The [0109] polysilicon layer 29′ and the polysilicon sidewall 32 function as masks when the underlying insulating layers are etched to form the storage electrode contact window. It should be noted that there is no special limitation on the formation of the polysilicon layer 29′ and the polysilicon sidewall 32, since they are formed of polysilicon. It should also be noted that the polysilicon layer 29′ and the polysilicon sidewall 32 are not removed during a subsequent process, and are utilized as parts of the storage electrode of the stacked capacitor, as will be described in detail later.
  • As shown in FIG. 6J, the SiO[0110] 2 aaaspacer layer 28, the Si3N4 insulating layer 27, the SiO2 insulating layer 26 and the SiO2 gate insulating layer 23 are selectively etched by an RIE process in which a CHF3/H2 is used and the polysilicon layer 29′ and the polysilicon sidewall 32 function as the etching masks. By the RIE process, a storage electrode contact hole 25A is formed in the above-mentioned layers, so that the n+-type drain region 25 is partially exposed.
  • As shown in FIG. 6K, a [0111] polysilicon layer 29″ is grown to, for example, 500 angstroms by CVD. A part of the polysilicon layer 29″ completely covers the inner wall of the storage electrode contact window 25A and the exposed surface of the n+-type drain region 25. It is important to form the polysilicon layer 29″ in total contact with the Si3N4 insulating layer 27. Then, As ions are introduced into the polysilicon layers 29″ and 29′ by an ion implantation process in which the dose of the As ions is equal to, for example, 8×1015 atoms/cm2. By this ion implantation process, each of the polysilicon layers 29″ and 29′ has a reduced resistance. It will be noted toat the layers consisting of the polysilicon layers 29′ and 29″ and the sidewall 32 is thicker than the vertically extending portion of the polysilicon layer 29″.
  • Referring to FIG. 6L, a [0112] spacer layer 33 formed of SiO2 is grown to, for example, 500 angstroms on the entire surface by CVD. After that, the SiO2 spacer layer 33 is selectively etched by the resist process and RIE process using a CHF3/H2 gas in the conventional photolithography technique. By the RIE process, an opening 33A having a belt shape is formed in the SiO2 spacer layer 33. It is sufficient to form the opening 33A so that it is wider than the storage electrode contact window 25A, because the opening 33A is used for stacking a polysilicon layer (fin) on the integrated polysilicon layer consisting of the layers 29″ and 29′ and the polisilicon sidewall 32.
  • Referring to FIG. 6M, a polysilicon layer is grown to, for example, 1000 angstroms by CVD. After that, As ions are introduced into the polysilicon layer by an ion implantation process in which the dose of As ions is equal to, for example, 1×10[0113] 15 atoms/cm2. Thereby, the resistance of the polysilicon layer is reduced. After that, the above polysilicon layer, the SiO2 spacer layer 33, and the polysilicon layers 29″ and 29′ are patterned into an electrode shape by the photoresist process and RIE process using a gas of CCl4+O2 or CHF3+H2. Thereafter, the SiO spacer layer 33 and the SiO2 spacer layer 28 are completely removed by an etching process in which the device is placed in an HF etchant. Thereby, polysilicon fins 292 and 291 forming a storage electrode 25 of the stacked capacitor are formed. The fin 292 has a bottom contact area wider than the contact hole 25A shown in FIG. 6J.
  • As has been described previously, the wall of the Si[0114] 3N4 insulating layer 27 which is a part of the storage electrode contact window 25A completely makes contact with the polysilicon layer 29′, so that there is no possibility that the SiO2 insulating layer 26 and the SiO2 interlayer isolation insulating layer 22 are damaged.
  • After that, as shown in FIG. 6N, a [0115] dielectric film 36 around an exposed surface of the storage electrode 29 is formed, and a cell plate 37 (opposed electrode) is formed so that it covers the entire surface. The dielectric film 36 is formed of, for example, Si3N4. The stacked capacitor is made up of the storage electrode 29, the dielectric film 36 and the cell plate 37. Then, a PSG layer 38 is formed on the entire surface, and word-line shunt layers 39 formed of, for example, an Al alloy, are formed on the PSG layer 38. FIG. 7 is a plan view of the DRAM fabricated by the above-mentioned production process. In FIG. 7, WL1 and WL2 indicate word lines, and BL1 and BL2 indicate bit lines.
  • The word-line shunt layers [0116] 39 are connected to the corresponding word lines WL via contact holes (not shown for the sake of simplicity). It is preferable to form such contact holes by the aforementioned first through fifth embodiments of the present invention.
  • It can be seen from FIG. 6K that the [0117] lowermost polysilicon fin 29 1 has the sidewall 32, and the polysilicon layers 29′ and 29″. The polysilicon layer 29″ is thicker than the polysilicon layer 29′, and the largest thickness of the sidewall 32 is approximately equal to the thickness of the polysilicon layer 29′.
  • A description will now be given of an eighth embodiment of the present invention with reference to FIGS. 8A through 8E, in which those parts which are the same as those shown in the previous figures are given the same reference numerals. The eighth embodiment of the present invention utilizes the steps which have been described with reference to FIGS. 6A through 6L. After the step related to FIG. 6L, a step shown in FIG. 8A is carried out. A polysilicon layer is grown to, for example, 1000 angstroms on the entire surface. [0118]
  • After that, as shown in FIG. 8B, an insulating [0119] layer 34 formed of SiO2 is grown to, for example, 2000 angstroms by CVD. Then, the SiO2 insulating film 34 is patterned into the shape of the storage electrode by the resist process and RIE process using a CHF3/H2 gas in the photolithography technique, so that openings are formed in the SiO2 insulating film 34. Each of the openings is approximately 0.5 μm wide, which corresponds to the scale limit of the conventional photolithography technique.
  • Then, an insulating [0120] layer 35 formed of SiO2 is grown to, for example, 1000 angstroms on the entire surface by CVD. Thereafter, the SiO2 insulating layer 35 is anisotropically etched by an RIE process using a CHF3 and H2 gas. Thereby, sidewalls 35 are formed around inner walls of the openings in the SiO2 layer 34, and the rest thereof is removed. Each sidewall 35 defines an opening 35A having a width approximately equal to 0.3 μm, which is smaller than the scale limit of the conventional photolithography technique.
  • Then, as shown in FIG. 8C, the [0121] polysilicon layer 42, the SiO2 spacer layer 33, and the polysilicon layers 29″ and 29′ are patterned into the shape of the storage electrode by an RIE process in which a CHF3/H2 gas is used and the SiO2 insulating layer 34 and the SiO2 sidewalls 15 function as etching masks. It should be noted that the distance between opposite portions of the polysilicon layer 42 is approximately 0.3 μm. Similarly, the distance between opposite portions of the polysilicon layer consisting of the polysilicon layer 29″ and 29′ is also approximately 0.3 μm. This means that the adjacent storage electrodes are very close to each other, and thus the surface area of each storage electrode is increased, so that each stacked capacitor can have an increased capacitance.
  • It will be noted that during etching of the SiO[0122] 2 spacer layer 33, the SiO2 insulating layer 34 and the SiO2 sidewalls 35 serving as etching masks are also etched. From this point of view, it is necessary for the layer 34 and the sidewalls 35 to have a sufficient thickness. Further, a special step to remove the SiO2 insulating layer 34 and the SiO2 sidewalls 35 is not needed because the SiO2 insulating layer 34 and the sidewalls 35 are removed during a subsequent step in which the device is placed in an HF etchant, as shown in FIG. 8D.
  • After that, a process identical to that which has been described with reference to FIG. 6N is carried out. FIG. 8E shows a DRAM fabricated according to the seventh preferred embodiment of the present invention. A [0123] storage electrode 40 has two stacked polysilicon fins 40 1 and 40 2. The polysilicon fin 401 corresponds to the patterned polysilicon layers 29″ and 29′ and the polysilicon sidewall 32, and the polysilicon fin 402 corresponds to the patterned polysilicon layer 42. It can be seen from FIG. 6N and FIG. 8E that the adjacent stacked capacitors shown in FIG. 8E are closer to each other than those shown in FIG. 6N.
  • A description will now be given of a first variation of the aforementioned sixth preferred embodiment of the present invention, with reference to FIGS. 9A and 9B, in which those parts which are the same as those shown in the previous figures are given the same reference numerals. The first variation has a storage electrode having only the [0124] polysilicon fin 29 1 which consists of the polysilicon layers 29″ and 29′ and the polysilicon sidewall 32. After the step which has been described with reference to FIG. 6K, the polysilicon layer consisting of the polysilicon layers 29″ and 29′ and the polysilicon sidewall 32 is patterned into the shape of the storage electrode. After that, the device is placed in an HF etchant, so that the insulating layer 28 is completely removed, as shown in FIG. 9A. Then, the process which has been described previously with reference to FIG. 6N is carried out, so that a DRAM shown in FIG. 9B can be obtained. It 1 is noted that the insulating layer 27 can be formed of SiO2 or Si3N4. As shown in FIG. 9B, the fin 29 1 is thicker than a vertically extending portion of the storage electrode.
  • FIG. 10 illustrates a second variation of the aforementioned sixth preferred embodiment of the present invention. In FIG. 10, those parts which are the same as those shown in the previous figures are given the same reference numerals. The [0125] polysilicon fin 29 1 consisting of the polysilicon layers 29″ and 29′ and the polysilicon sidewall 32 is formed directly on the insulating layer 27 formed of SiO2 or Si3N4. The polysilicon layer 29′ shown in FIG. 6F is grown on the insulating layer 27 without forming the insulating layer 28. Then, the same steps as has been described with reference to FIGS. 6G through 6K and FIG. 6N are carried out. It is also possible to form the polysilicon fin 29 2 on the polysilicon fin 29 1 in the same way as has been described with reference to FIGS. 6L and 6M.
  • A description will now be given of an eighth preferred embodiment of the present invention with reference to FIGS. 11A through 11J, in which those parts which are the same as shown shown in the previous figures are given the same reference numerals. A structure shown in FIG. 11B is the same as that shown in FIG. 6E. Steps to obtain the structure shown in FIG. 11B are the same as those which have been described with reference to FIGS. 6A through 6E. [0126]
  • As shown in FIG. 11C, the Si[0127] 3N4 insulating layer 27, the SiO2 spacer layer 28, the impurity-doped polysilicon layer 29′, a spacer layer 45 formed of SiO2 and an impurity-doped polysilicon layer 46′ are formed in this order by CVD. For example, each of these layers is 500 angstorms thick. Then, the polysilicon layer 46′, the SiO2 spacer layer 45 and the polysilicon layer 29′ are selectively etched by the resist process and the RIE process, so that an opening 29A having a thickness equal to, for example, 0.6 μm is formed therein. During the above RIE process, a CCl4/O2 gas is used for the polysilicon layers 46′ and 29′, and a CHF3/He gas is used for the SiO2 spacer layer 45.
  • As shown in FIG. 11D, a [0128] polysilicon layer 47′ is grown to, for example, 2000 angstorms on the entire surface by CVD. After that, as shown in FIG. 11E, the polysilicon layer 47′ is anisotropically etched by an RIE process in which a CCl4/O2 gas or an HBr/He gas is used. Thereby, a polysilicon sidewall 47 is formed around an inner surface of the opening 29A, and the remaining portion of the polysilicon layer 47′ is removed. The sidewall 47 defines a new opening 46A having a width approximately equal to 0.2-0.3 μm, which is smaller than the width of the opening 29A shown in FIG. 11C.
  • After that, as shown in FIG. 11F, the SiO[0129] 2 spacer layer 28, the Si3N4 insulating layer 27, the SiO2 insulating layer 26 and the SiO2 gate insulating layer 23 are partially removed by an RIE process in which a CHF3/He gas is used and the polysilicon layer 46′ and the polysilicon sidewall 47 function as etching masks. By this RIE process, the surface of the n+-type drain region 25 is partially exposed through a contact hole 28A.
  • It should be noted that the width of the [0130] opening 46A is very small and equal to about 0.2-0.3 μm, and that the polysilicon layer 46′ and the polysilicon layer 47 functioning as the etching masks form a part of the storage electrode without being removed. Thus, it is not necessary to provide a special step to remove the polysilicon layer 46′ and the polysilicon sidewall 47 functioning the etching masks.
  • As shown in FIG. 11G, a [0131] polysilicon layer 46″ is grown to, for example, 500 angstroms by CVD. During this step, the polysilicon layers 46″ and 46′ as well as the polysilicon sidewall 47 are integrated.
  • Then, as shown in FIG. 11H, the polysilicon layers [0132] 46″ and 46′, the SiO2 spacer layer 45, and the polysilicon layer 29′ are patterned into the shape of the storage electrode in this order by the resist process using a single mask and the RIE process in the conventional photolithography process.
  • After that, as shown in FIG. 11I, the device shown in FIG. 11H is placed in an HF etchant, so that the exposed SiO[0133] 2 insulating layers are isotropically etched, so that a storage electrode 50 having two polysilicon fins 50 1 and 50 2 is formed. The fin 50 1 is formed of the patterned polysilicon layer 29′, and the fin 502 is formed of the patterned polysilicon layers 46″ and 46′. The fins 50 1 and 50 2 are connected by the polysilicon sidewall 47. The polysilicon layer 46″ which is a part of the fin 50 2 vertically extends from its portion on the polysilicon layer 46′ and makes contact with the n+-type drain region 25. A vertical portion 50 3 of the storage electrode 50 consists of the polysilicon sidewall 47 and the polysilicon layer 46″. The vertical portion 50 3, the polysilicon layer 46″, and the fin 50 2 have mutually different thicknesses t1, t2 and t3, respectively. The vertical portion 503 is thicker than the polysilicon layer 46″ and the fin 50 2.
  • Finally, as shown in FIG. 11J, the [0134] dielectric film 36, the cell plate 37, the PSG passivation layer 38 and the word-line shut layers 39 are formed in the same way as has been described with reference to FIG. 6N.
  • A description will now be given of a ninth preferred embodiment of the present invention with reference to FIGS. 12A through 12G, in which those parts which are the same as those shown in the previous figures are given the same reference numerals. [0135]
  • Production steps shown in FIGS. 12A and 12B are carried out in the same way as those shown in FIGS. 11A and [0136] 11B. After that, as shown in FIG. 12C, the Si3N4 insulating layer 27, the SiO2 spacer layer 28, the impurity-doped polysilicon layer 29′, the SiO2 spacer layer 45 and the impurity-doped polysilicon layer 46′ are formed in this order by CVD. Each of these layers is 500 angstroms thick, for example. Then, the polysilicon layer 46′, the SiO2 spacer layer 45, the polysilicon layer 29′ and the SiO2 spacer layer 28 are selectively etched by the resist process and RIE process, so that an opening 28A is formed therein. It will be noted that the SiO2 layer 28 is etched as shown in FIG. 12C, while the SiO2 layer 28 shown in FIG. 11C is not etched.
  • After that, as shown in FIG. 12D, a [0137] polysilicon layer 47′ is grown to, for example, 2000 angstorms by CVD. After that, as shown in FIG. 12E, the polysilicon layer 47′ is selectively etched by an RIE process using a CCl4/O2 gas, so that a polysilicon sidewall 47 a is formed so that it surrounds the inner wall of the opening 28A. The remaining portion of the polysilicon layer 47′ is completely removed. The polysilicon sidewall 47 a defines a new opening 46A narrower than the opening 28A.
  • Subsequently, as shown in FIG. 12F, the Si[0138] 3N4 insulating layer 27, the SiO2 insulating layer 26 and the SiO2 gate insulating layer 23 are selectively etched by an RIE process in which a CHF3/He gas is used and the polysilicon layer 46′ and the sidewall 47 a function as etching masks. By this RIE process, the surface of the n+-type drain region 25 is partially exposed through a through hole 27A having the same width as the opening 46A. After that, the aforementioned production steps are carried out, so that a DRAM shown in FIG. 12G can be obtained.
  • The length of the sidewall [0139] 37 a used in the ninth embodiment of the present invention is greater than that of the sidewall 37 used in the eighth embodiment of the present invention. Thus, the sidewall 47 a functions as the mask more stably than the sidewall 47. On the other hand, the distance between the sidewall 37 a and the word line WL is closer than the corresponding distance obtained in the eighth embodiment of the present invention. Thus, the breakdown voltage of the DRAM shown in FIG. 12G is slightly smaller than that of the DRAM shown in FIG. 11J.
  • A description will now be given of a variation of the ninth preferred embodiment of the present invention with reference to FIGS. 13A through 13F, in which those parts which are the same as those shown in the previous figures are given the same reference numerals. FIGS. 13A and 13B are the same as FIGS. 11A and 11B. Then, as shown in FIG. 13C, the Si [0140] 3 N4 insulating layer 27, the SiO2 layer 28, the impurity-doped polysilicon layer 29′, the SiO2 spacer layer 45 and the impurity-doped polysilicon layer 46′ are formed in this order by the aforementioned process. Then, an SiO2 insulating layer 48 is grown to, for example, 200 angstroms by CVD.
  • Then, by using the resist process and the RIE process in the photolithography process, the SiO[0141] 2 layer 48, the polysilicon layer 46′, the SiO2 spacer layer 45, the polysilicon layer 29′ and the SiO2 spacer layer 28 are selectively removed, so that the surface of the Si3N4 layer 27 is partially exposed through the opening 28A.
  • Then, as shown in FIG. 13D, the [0142] polysilicon layer 47′ is grown to, for example, 2000 angstorms by CVD. After that, as shown in FIG. 13E, the polysilicon layer 47′ is selectively etched by RIE, so that a widewall 42 b is formed around an inner wall of the opening 28A.
  • After that, as shown in FIG. 13F, the Si[0143] 3N4 layer 27, the SiO2 layer 26 and the SiO2 gate insulating layer 23 are selectively etched via the opening defined by the sidewall 47 b. The SiO2 layer 48 is removed at the same time as the SiO2 insulating layer 26 is removed.
  • It will be noted that the SiO[0144] 2 layer 48 functions to protect the polysilicon layer 46′ against the RIE process of forming the sidewall 47 b. Further, the SiO2 layer 48 functions as the mask more stably during the time when the Si3N4 insulating layer 27 is being etched.
  • A description will now be given of a modification of the variation shown in FIGS. 13A through 13F, with reference to FIGS. 14A through 14G, in which those parts which are the same as those shown in the previous figures are given the same reference numerals. FIGS. 14A and 14B are the same as FIGS. 11A and 11B, respectively. [0145]
  • After forming the bit line BL, as shown in FIG. 14C, an SOG (spin on glass) [0146] layer 49 is formed on the entire surface so that the surface of the SOG layer 49 is substantially flat enough to prevent the growth of residuum during a subsequent process. There is a possibility that residuum may be formed on a rough surface after the selective etching process. For example, in the variation which has been described with reference to FIGS. 13A through 13F, the SiO2 layer 48 may be partially left on a rough surface portion of the polysilicon layer 46′. For the sake of simplicity, FIG. 14C shows that the SOG layer 49 is completely flat. It can be seen from FIG. 14C, the SOG layer 49 absorbs a roughness of the surface shown in FIG. 14B. It is also possible to form a PSG reflow layer instead of the SOG layer 49. After that, the layers 28, 29′ 45, 46′ and 48 are formed in the same way as has been described previously. Then, these layers are selectively etched, so that the opening 28A is formed, as shown in FIG. 14C.
  • Then, as shown in FIG. 14D, the [0147] polysilicon layer 47′ is grown to, for example, 2000 angstroms by CVD, and selectively etched by the RIE process, so that a sidewall 47 b is formed, as shown in FIG. 14E. Thereafter, as shown in FIG. 14F, the Si3N4 insulating layer 27, the SOG layer 49, the sio2 layer 26 and the SiO2 layer 23 are selectively etched, so that the n+-type drain region 25 is partially exposed through the opening 27A. Finally, a DRAM shown in FIG. 14G is fabricated by the aforementioned process which has been described with reference to FIG. 6N.
  • A description will now be given of a tenth preferred embodiment of the present invention with reference to FIGS. 15A through 15J, in which those parts which are the same as those shown in the previous figures are given the same reference numerals. FIGS. 15A and 15B are the same as FIGS. 11A and 11B, respectively. [0148]
  • Referring to FIG. 11C, after forming an Si[0149] 3N4 layer 62 by CVD, three bilayer structures, each having an SiO2 insulating layer having a thickness of 500 angstroms and a polysilicon layer having a thickness of 500 angstroms, are successively grown by CVD. The first bilayer structure consists of an SiO2 insulating layer 63 and a polysilicon layer 64. The second bilayer structure consists of an SiO2 insulating layer 65 and a polysilicon layer 66. The third bilayer structure consists of an SiO2 insulating layer 67 and a polysilicon layer 68. After that, an SiO2 insulating layer 69 having a thickness of 100 angstroms, a polysilicon layer 70 having a thickness of 2000 angstorms and an SiO2 insulating layer 71 having a thickness of 100 angstroms are successively grown in this order by CVD. Then, a photoresist film 72 having a window pattern is placed on the SiO2 insulating layer 71, and the SiO2 insulating layer 71 and the polysilicon layer 70 are etched, so that an opening 70A is formed. The size of the opening 70A is approximately 0.5 μm, which is the scale limit in the conventional photolithography technique.
  • Referring to FIG. 15D, the [0150] photoresist film 72 is removed, and a polysilicon layer is grown to, for example, 1500 angstroms on the entire surface. Then, the polysilicon layer is anisotropically etched by an RIE process using an HBr/He gas, so that a polysilicon sidewall 74 is formed around an inner wall of the opening 70A. The polysilicon sidewall 74 defines a new opening 70B having a size approximately equal to 0.2 μm.
  • After that, as shown in FIG. 15E, the SiO[0151] 2 insulating layer 69 and the polysilicon layer 68 are anisotropically etched by an RIE process in which the polysilicon layer 70 and the sidewall 74 function as etching masks. During the time when the SiO2 insulating layer 69 is being etched, the SiO2 insulating layer 71 is removed. Further, during the time when the polysilicon layer 68 is being etched, the polysilicon layer 70 decreases by approximately 700 angstroms, so that a portion thereof having a thickness of about 1300 angstroms is left. After that, the SiO2 insulating layer 67 is removed in an RIE process using a CHF3/H2 gas in which the polysilicon layer 70 and the sidewall 74 function as etching masks. During this etching process, there is little decrease in the thicknesses of the polysilicon layer 70 and the sidewall 74 because the CHF3/H2 gas acts to SiO2 greatly. After that, the polysilicon layer 66 and the SiO2 insulating layer 65 are removed in the same way as has been described above. During this etching process, each of the polysilicon layer 70 and the sidewall 74 decreases by about 700 angstroms, so that they are approximately 600 angstroms thick.
  • As shown in FIG. 15F, the [0152] polysilicon layer 64 is removed by RIE. During this RIE process, the polysilicon layer 70 and the sidewall 74 are also removed. It will be noted that the SiO2 insulating layer 69 prevents the underlying polysilicon layer 68 from being etched even if over-etching is carried out. It is preferable to carry out over-etching so that the polysilicon layer 70 and the sidewall 74 are completely removed.
  • Then, as shown in FIG. 15G, the SiO[0153] 2 insulating layer 63 is removed in an etching process in which the polysilicon layer 68 functions as a mask. During this etching, the SiO insulating layer 69 is 2 also removed. Subsequently, the Si 3 N4 insulating layer 62 is etched, and the SiO2 insulating layer 26 and SiO2 gate insulating layer 23 are etched. Thereby, a window formed in the layers 68 through 23 is formed, as shown in FIG. 15G.
  • Then, referring to FIG. 15H, a [0154] polysilicon layer 75 is grown to, for example, 500 angstroms on the entire surface including the window shown in FIG. 15G. After that, the polysilicon layers 75 and 68, the SiO2 insulating layer 67, the polysilicon layer 66, the SiO2 insulating layer 65, and the polysilicon layer 64 are patterned into the shape of the storage electrode. Thereby, a device shown in FIG. 15H is formed.
  • After that, as shown in FIG. 15I, the device shown in FIG. 15H is placed in an HF etchant, so that the SiO[0155] 2 insulating layers 67, 65 and 63 are isotropically etched and completely removed. By this step, a storage electrode 90 can be obtained. The storage electrode 90 has a first polysilicon fin 90 1 formed of the patterned polysilicon layer 64, a second polysilicon fin 90 2 formed of the patterned polysilicon layer 66, and a third polysilicon fin 90 3 having the patterned polysilicon layers 68 and 75, and a vertical connecting portion formed of the polysilicon layer 75. The third polysilicon fin 90 3 is thicker than the first and second polysilicon fins 90 1 and 90 2.
  • After that, the aforementioned processes are carried out for the device shown in FIG. 15I, so that a DRAM shown in FIG. 15J can be formed. It is possible to apply the teachings shown in FIGS. 13A through 13F to the tenth embodiment of the present invention. It is also possible to form the lowermost fin9-[0156] 1 directly on the insulating layer 62. In this case, the insulating layer 62 can be formed of SiO2.
  • The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention. [0157]

Claims (73)

What is claimed is:
1. A method of forming a structure having a contact hole comprising the steps of:
(a) forming an insulating layer on a first conductive layer;
(b) forming a second conductive layer on said insulating layer;
(c) forming an opening in said second conductive layer;
(d) forming a conductive sidewall around an inner wall of said first conductive layer defining said opening;
(e) selectively etching said insulating layer in a state where said second conductive layer and said conductive sidewall function as etching masks, so that said contact hole having a width smaller than that of said opening and defined by said conductive sidewall is formed, and said first conductive layer is exposed through said contact hole; and
(f) removing said second conductive layer and said conductive sidewall.
2. A method as claimed in claim 1, wherein said methd comprises, between said step (e) and said step (f), the steps of:
(e-1) forming an etching resist on said first conductive layer exposed through said contact hole, said second conductive layer and said conductive sidewall; and
(e-2) removing only a part of said etching resist on said second conductive layer and said conductive sidewall so that said first conductive layer exposed through said contact hole is protected by said etching resist.
3. A method as claimed in claim 2, wherein said step (e-2) comprises:
projecting light onto said etching resist; and
developing said etching resist so that a part of said etching resist is left on said first conductive layer exposed through said contact hole.
4. A method as claimed in claim 1, wherein:
said method further comprises the step of forming an etching stopper layer on said second conductive layer; and
said etching stopper layer protects said second conductive layer during said step (d), so that the thickness of said second conductive layer can be prevented from being reduced during said step (d).
5. A method as claimed in claim 1, wherein said method further comprises the step of forming a third conductive layer on said insulating layer and in contact with said first conductive layer exposed through said contact hole.
6. A method as claimed in claim 1, wherein said first conductive layer comprises polysilicon.
7. A method as claimed in claim 1, wherein:
said second conductive layer comprises polysilicon; and
said conductive sidewall comprises polysilicon.
8. A method as claimed in claim 1, wherein said method further comprises the step of heating said insulating layer so that said insulating layer is reflown and an edge portion of said insulating layer defining an upper portion of said contact hole is gradually curved.
9. A method of forming a structure having a contact hole comprising the steps of:
(a) forming an insulating layer on a first conductive layer;
(b) forming a second conductive layer on said insulating layer;
(c) forming an opening in said second conductive layer;
(d) forming a conductive sidewall around an inner wall of said first conductive layer defining said opening;
(e) selectively etching said insulating layer in a state where said second conductive layer and said conductive sidewall function as etching masks, so that said contact hole having a width smaller than that of said opening and defined by said conductive sidewall is formed on said insulating layer and said first conductive layer is exposed through said contact hole;
(f) forming a barrier layer on said second conductive layer, said conductive sidewall and said first conductive layer exposed through said contact hole; and
(g) forming a third conductive layer on said barrier layer, said barrier layer preventing said third conductive layer from reacting with said second conductive layer and said conductive sidewall.
10. A method as claimed in claim 9, wherein:
said barrier layer comprises a bilayer structure having a titanium layer and a titanium nitride layer; and
said third conductive layer comprises aluminum.
11. A method as claimed in claim 9, wherein:
said second conductive layer comprises polysilicon; and
said conductive sidewall comprises polysilicon.
12. A method of forming a structure having a contact hole comprising the steps of:
(a) forming an insulating layer on a first conductive layer;
(b) forming a second conductive layer on said insulating layer;
(c) forming an opening in said second conductive layer;
(d) forming a conductive sidewall around an inner wall of said first conductive layer defining said opening;
(e) selectively etching said insulating layer in a state where said second conductive layer and said conductive sidewall function as etching masks, so that said contact hole having a width smaller than that of said opening and defined by said conductive sidewall is formed, and said first conductive layer is exposed through said contact hole; and
(f) forming a third conductive layer on said second conductive layer, said conductive sidewall and said member exposed through said contact hole,
wherein:
said second conductive layer comprises polysilicon;
said conductive sidewall comprises polysilicon; and
said third conductive layer comprises tungsten.
13. A method as claimed in claim 12, wherein said contact hole is filled with tungsten of said third conductive layer.
14. A method of forming a structure having a contact hole comprising the steps of:
(a) forming an insulating layer on a first conductive layer;
(b) forming a second conductive layer on said insulating layer;
(c) forming a first opening in said second conductive layer;
(d) selectively growing a third conductive layer on said second conductive layer and an inner wall of said second conductive layer defining said first opening, so that a second opening defined by said third conductive layer and having a width smaller than that of said first opening is formed; and
(e) selectively etching said insulating layer in a state where said third conductive layer functions as an etching mask, so that said contact hole having a width substantially identical to said second opening defined by said third conductive layer is formed, and said first conductive layer is exposed through said contact hole.
15. A method as claimed in claim 14, wherein:
said second conductive layer comprises polysilicon; and
said third conductive layer comprises polysilicon.
16. A method as claimed in claim 14, wherein said method further comprises the steps of:
forming a barrier layer on said third conductive layer and said first conductive layer exposed through said contact hole; and
forming a fourth conductive layer on said barrier layer, said barrier layer preventing said third conductive layer from reacting with said fourth conductive layer.
17. A layer structure comprising:
a first conductive layer;
an insulating layer formed on said first conductive layer and having a contact hole, said first conductive layer being exposed through said contact hole;
a second conductive layer formed on said insulating layer and having an opening having a width larger than that of said contact hole;
a conductive sidewall formed on said insulating layer exposed through said opening and formed around an inner wall of said second conductive layer defining said opening, said conductive sidewall having a width substantially equal to that of said contact hole;
a barrier layer formed on said second conductive layer, said conductive sidewall and said first conductive layer exposed through said contact hole; and
a third conductive layer formed on said barrier layer, said barrier layer preventing said third conductive layer from reacting with said second conductive layer and said conductive sidewall.
18. A layer structure as claimed in claim 17, wherein:
said third conductive layer comprises aluminum;
said first and second conductive layers comprise polysilicon; and
said conductive sidewall comprises polysilicon.
19. A layer structure as claimed in claim 17, wherein said barrier layer comprises a bilayer structure having a titanium layer and a titanium nitride layer.
20. A layer structure comprising:
a first conductive layer;
an insulating layer formed on said first conductive layer and having a contact hole, said first conductive layer being exposed through said contact hole;
a second conductive layer formed on said insulating layer and having a first opening having a width larger than that of said contact hole;
a third conductive layer formed on said insulating layer exposed through said first opening and said second conductive layer and formed around an inner wall of said second conductive layer defining said first opening, said third conductive layer defining a second opening having a width substantially equal to that of said contact hole, said second opening being continuously connected to said contact hole;
a barrier layer formed on said third conductive layer and said first conductive layer exposed through said contact hole; and
a fourth conductive layer formed on said barrier layer, said barrier layer preventing said fourth conductive layer from reacting with said third conductive layer and said conductive sidewall.
21. A layer structure as claimed in claim 20, wherein:
said fourth conductive layer comprises aluminum; and
said first, second and third conductive layers comprise polysilicon.
22. A layer structure as claimed in claim 20, wherein said barrier layer comprises a bilayer structure having a titanium layer and a titanium nitride layer.
23. A layer structure comprising:
a first conductive layer;
an insulating layer formed on said first conductive layer and having a contact hole, said first conductive layer being exposed through said contact hole;
a second conductive layer formed on said insulating layer and having an opening having a width larger than that of said contact hole;
a conductive sidewall formed on said insulating layer exposed through said opening and formed around an inner wall of said second conductive layer defining said opening, said conductive sidewall having a width substantially equal to that of said contact hole; and
a third conductive layer formed on said second conductive layer, said conductive sidewall and said first conductive layer exposed through said contact hole,
wherein said third conductive layer comprises a material which causes no reaction with said second conductive layer and said conductive sidewall.
24. A layer structure as claimed in claim 23, wherein:
said third conductive layer comprises tungsten;
said second conductive layer comprises polysilicon; and
said conductive sidewall comprises polysilicon.
25. A dynamic random access memory comprising:
a semiconductor substrate having a first diffusion region and a second diffusion region of a transfer transistor;
a first insulating layer having a first contact hole exposing said first diffusion region, and a second contact hole exposing said second diffusion region;
a word line covered by said first insulating layer;
a stacked capacitor which is in contact with said first diffusion region through said first contact hole;
a bit line which is in contact with said second diffusion region through said second contact hole; and
a second insulating layer covering said stacked capacitor,
wherein:
said stacked capacitor comprises a storage electrode, a dielectric film and a cell plate;
said storage electrode which is in contact with said first diffusion region through said first contact hole has a first fin having a first portion, a second portion and a third portion;
said first portion has a first opening having a width greater than that of said first contact hole;
said second portion serving as a sidewall is formed around an inner wall of said first portion defining said first opening, so that a second opening has a width substantially identical to that of said first contact hole; and
said third portion extends on said first and second portions, substantially vertically extends in said first contact hole, and is in contact with said first diffusion region.
26. A dynamic random access memory as claimed in claim 25, wherein:
said storage electrode comprises a second fin having a contact area in which said second fin is in contact with said first fin;
said contact area is wider than said first contact hole; and
said first and second fins are spaced apart from each other.
27. A dynamic random access memory as claimed in claim 25, wherein said first fin is spaced apart from said first insulating layer.
28. A dynamic random access memory as claimed in claim 25, wherein said first fin of said storage electrode is formed on said first insulating layer.
29. A dynamic random access memory as claimed in claim 26, wherein said first fin of said storage electrode is thicker than said third portion thereof.
30. A dynamic random access memory as claimed in claim 25, wherein said storage electrode having said first fin having said first, second and third portions comprises polysilicon.
31. A dynamic random access memory comprising:
a semiconductor substrate having a first diffusion region and a second diffusion region of a transfer transistor;
a first insulating layer having a first contact hole exposing said first diffusion region, and a second contact hole exposing said second diffusion region;
a word line covered by said first insulating layer;
a stacked capacitor which is in contact with said first diffusion region through said first contact hole;
a bit line which is in contact with said second diffusion region through said second contact hole; and
a second insulating layer covering said stacked capacitor,
wherein:
said stacked capacitor comprises a storage electrode, a dielectric film and a cell plate; and
said storage electrode which is in contact with said first diffusion region through said first contact hole has a plurality of first fin-shaped portions located outside of said first contact hole, a second portion connecting said first fin-shaped portions to each other, and a third portion extending on an uppermost one of said first fin-shaped portions and said second portion, substantially vertically extending in said first contact hole, and being in contact with said first diffusion region.
32. A dynamic random access memory as claimed in claim 31, wherein:
said second portion of said storage electrode is spaced apart from said first insulating layer; and
a lowermost one of said first fin-shaped portions of said storage electrode is spaced apart from said first insulating layer.
33. A dynamic random access memory as claimed in claim 31, wherein:
said second portion of said storage electrode is in contact with said first insulating layer; and
a lowermost one of said first fin-shaped portions of said storage electrode is spaced apart from said first insulating layer.
34. A dynamic random access memory as claimed in claim 33, wherein said storage electrode has a substantially flat surface which extends above said word line.
35. A dynamic random access memory as claimed in claim 31, wherein said storage electrode comprises polysilicon.
36. A dynamic random access memory comprising:
a semiconductor substrate having a first diffusion region and a second diffusion region of a transfer transistor;
a first insulating layer having a first contact hole exposing said first diffusion region, and a second contact hole exposing said second diffusion region;
a word line covered by said first insulating layer;
a stacked capacitor which is in contact with said first diffusion region through said first contact hole;
a bit line which is in contact with said second diffusion region through said second contact hole; and
a second insulating layer covering said stacked capacitor,
wherein:
said stacked capacitor comprises a storage electrode, a dielectric film and a cell plate; and
said storage electrode which is in contact with said first diffusion region through said first contact hole has a plurality of first fin-shaped portions located outside of said first contact hole, and a second portion connecting said first fin-shaped portions to each other, and extending on an uppermost one of said first fin-shaped portions, said second portion substantially vertically extending in said first contact hole, and being in contact with said first diffusion region.
37. A dynamic random access memory as claimed in claim 36, wherein a lowermost one of said first fin-shaped portions is spaced apart from said first insulating layer.
38. A dynamic random access memory device as claimed in claim 36, wherein a lowermost one of said first fin-shaped portions is in contact with said first insulating layer.
39. A dynamic random access memory as claimed in claim 36, wherein said storage electrode comprises polysilicon.
40. A fin-shaped capacitor comprising: a storage electrode having an exposed surface;
a dielectric film formed around said exposed surface of said storage electrode; and
a cell plate covering said storage electrode surrounded by said dielectric film,
wherein:
said storage electrode is in contact with a diffusion region of a semiconductor substrate through a contact hole formed in an insulating layer formed on said semiconductor substrate;
said storage electrode has a first fin having a first portion, a second portion and a third portion;
said first portion has a first opening having a width greater than that of said contact hole;
said second portion is formed around an inner wall of said first portion defining said first opening, so that a second opening has a width substantially identical to that of said contact hole; and
said third portion extends on said first and second portions, substantially vertically extends in said contact hole, and is in contact with said diffusion region in said semiconductor substrate.
41. A fin-shaped capacitor as claimed in claim 40, wherein:
said storage electrode comprises a second fin having a contact area in which said second fin is in contact with said first fin;
said contact area is wider than said contact hole; and
said first and second fins are spaced apart from each other.
42. A fin-shaped capacitor as claimed in claim 40, wherein said first fin is spaced apart from said insulating layer.
43. A fin-shaped capacitor as claimed in claim 40, wherein said first fin of said storage electrode is formed on said insulating layer.
44. A fin-shaped capacitor as claimed in claim 41, wherein said first fin of said storage electrode is thicker than said third portion thereof.
45. A fin-shaped capacitor as claimed in claim 40, wherein said storage electrode having said first fin having said first, second and third portions comprises polysilicon.
46. A fin-shaped capacitor comprising:
a storage electrode having an exposed surface;
a dielectric film formed around said exposed surface of said storage electrode; and
a cell plate covering said storage electrode surrounded by said storage electrde,
wherein:
said storage electrode is in contact with a diffusion region of a semiconductor substrate through a contact hole formed in an insulating layer formed on said semiconductor substrate;
said storage electrode has a plurality of first fin-shaped portions located outside of said contact hole, a second portion connecting said first fin-shaped portions to each other, and a third portion extending on an uppermost one of said first fin-shaped portions and said second portion, substantially vertically extending in said contact hole, and being in contact with said diffusion region of said semiconductor substrate.
47. A fin-shaped capacitor as claimed in claim 46, wherein:
said second portion of said storage electrode is spaced apart from said insulating layer; and
a lowermost one of said first fin-shaped portions of said storage electrode is spaced apart from said insulating layer.
48. A fin-shaped capacitor as claimed in claim 46, wherein:
said second portion of said storage electrode is in contact with said insulating layer; and
a lowermost one of said first fin-shaped portions of said storage electrode is spaced apart from said insulating layer.
49. A fin-shaped capacitor as claimed in claim 48, wherein said insulating layer has a substantially flat surface on which said second portion of said storage electrode is formed.
50. A fin-shaped capacitor as claimed in claim 46, wherein said storage electrode comprises polysilicon.
51. A fin-shaped capacitor comprising:
a storage electrode having an exposed surface;
a dielectric film formed around said exposed surface of said storage electrode; and
a cell plate covering said storage electrode surrounded by said storage electrode,
wherein:
said storage electrode is in contact with a diffusion region of a semiconductor substrate through a contact hole formed in an insulating layer formed on said semiconductor substrate;
said storage electrode has a plurality of first fin-shaped portions located outside of said contact hole, and a second portion connecting said fin-shaped portions to each other, and extending on an uppermost one of said first fin-shaped portions, said second portion substantially vertically extending in said contact hole, and being in contact with said diffusion region in said semiconductor substrate.
52. A fin-shaped capacitor as claimed in claim 51, wherein a lowermost one of said first fin-shaped portions is spaced apart from said insulating layer.
53. A fin-shaped capacitor device as claimed in claim 51, wherein a lowermost one of said first fin-shaped portions is in contact with said insulating layer.
54. A fin-shaped capacitor as claimed in claim 51, wherein said storage electrode comprises polysilicon.
55. A method of producing a fin-shaped capacitor in a dynamic random access memory comprising the steps of:
(a) forming an insulating layer on a semiconductor substrate having a diffusion region;
(b) forming a first conductive layer having a first opening on said insulating layer;
(c) forming a conductive sidewall around an inner wall of said first conductive layer defining said first opening, said conductive sidewall defining a second opening having a width smaller than that of said first opening;
(d) selectively etching said insulating layer in a state where said first conductive layer and said conductive sidewall function as etching masks, so that said diffusion region is exposed through a contact hole formed in said insulating layer and having a width substantially identical to that of said second opening;
(e) forming a second conductive layer on said first conductive layer, said conductive sidewall and said diffusion region exposed through said contact hole;
(f) patterning said first conductive layer and said second conductive layer into a shape of a storage electrode of said fin-shaped capacitor;
(g) forming a dielectric film around an exposed surface of said storage electrode; and
(h) forming a cell plate around said storage electrode covered by said dielectric film.
56. A method as claimed in claim 55, wherein said step (a) comprises the steps of:
forming a first insulating layer directly on said semiconductor substrate; and
forming a second insulating layer on said semiconductor substrate, said insulating layer having said first and second insulating layers, and
wherein said method further comprises the step of isotropically etching said second insulating layer, so that said storage electrode is spaced apart from said first insulating layer.
57. A method of producing a fin-shaped capacitor in a dynamic random access memory comprising the steps of:
(a) forming a first insulating layer on a semiconductor substrate having a diffusion region;
(b) forming a first conductive layer having a first opening on said first insulating layer;
(c) forming a conductive sidewall around an inner wall of said first conductive layer defining said first opening, said conductive sidewall defining a second opening having a width smaller than that of said first opening;
(d) selectively etching said first insulating layer in a state where said first conductive layer and said conductive sidewall function as etching masks, so that said diffusion region is exposed through a contact hole formed in said first insulating layer and having a width substantially identical to that of said second opening;
(e) forming a second conductive layer on said first conductive layer, said conductive sidewall and said diffusion region exposed through said contact hole;
(f) forming, on said second conductive layer, a second insulating layer having a third opening having a width substantially identical to that of said first opening;
(g) forming a third conductive layer on said second insulating layer and said second conductive layer through said third opening;
(h) patterning said first and second conductive layers and said second insulating layer into a shape of a storage electrode of said fin-shaped capacitor;
(i) isotropically etching said second insulating layer so as to be removed;
(j) forming a dielectric film around an exposed surface of said storage electrode; and
(k) forming a cell plate around said storage electrode covered by said dielectric film.
58. A method as claimed in claim 57, wherein said step (a) comprises the steps of:
forming a third insulating layer directly on said semiconductor substrate; and
forming a fourth insulating layer on said third insulating layer;
forming a fifth insulating layer on said fourth insulating layer, said first insulating layer has said third and fourth insulating layers, and
wherein:
said fifth insulating layer is formed of a material identical to that of said third insulating material; and
said fifth insulating layer is removed during said step (i), so that said storage electrode is spaced apart from said fourth insulating layer.
59. A method as claimed in claim 57, wherein:
said step (h) comprises:
forming a third insulating layer having a fourth opening on said third conductive layer, said fourth opening being located at a position different from that of said first opening;
forming an insulating sidewall around an inner surface of said fourth insulating layer defining said fourth opening, said insulating sidewall defining a fifth opening having a width smaller than that of said fourth opening; and
etching said first, second and third conductive layers and said second and third insulating layers in a state where said fourth insulating layer and said insulating sidewall function as etching masks.
60. A method of producing a fin-shaped capacitor in a dynamic random access memory comprising the steps of:
(a) forming a first insulating layer on a semiconductor substrate having a diffusion region;
(b) forming a plurality of stacked-layer structures, a lowermost one of said stacked-layer structures being formed on said first insulating layer, each of said stacked-layer structures having a spacer layer and a first conductive layer;
(c) forming a first opening in said stacked-layer structures except said spacer layer of said lowermost one of said stacked-layer structures;
(d) forming a conductive sidewall around an inner wall of said stacked-layer structures defining said first opening, said conductive sidewall defining a second opening having a width smaller than that of said first opening;
(e) selectively etching said spacer layer of the lowermost one of said stacked-layer structures and said first insulating layer in a state where said first conductive layer of an uppermost one of said stacked layer structures and said conductive sidewall function as masks, so that said diffusion region is exposed through a contact hole formed in said spacer layer of the lowermost one of said stacked-layer structures and said first insulating layer;
(f) forming a second conductive layer on said first conductive layer of the uppermost one of said stacked-layer structures, said conductive sidewall and said diffusion region exposed through said contact hole;
(g) patterning said second conductive layer and said stacked-layer structures except said spacer layer of the lowermost one of said stacked-layer structures into a shape of a storage electrode of said fin-shaped capacitor;
(h) isotropically etching said spacer layer of each of said stacked-layer structures so that said spacer layer is removed;
(i) forming a dielectric film around said storage electrode; and
(j) forming a cell plate around said storage electrode covered by said dielectric film.
61. A method as claimed in claim 60, wherein:
said method further comprises, between said steps (b) and (c), the step of forming a second insulating layer on said first conductive layer of the uppermost one of said stacked-layer structures; and
said second insulating layer is removed during said step (e).
62. A method as claimed in claim 60, wherein said step (a) comprises the steps of:
forming a second insulating layer on said semiconductor substrate;
forming a third insulating layer on said second insulating layer;
heating said third insulating layer so that said third insulating layer has a substantially flat surface; and
forming a fourth insulating layer on said substantially flat surface of said third insulating layer, and
wherein:
said second, third and fourth insulating layers form said first insulating layer.
63. A method as claimed in claim 60, wherein:
said first conductive layer comprises polysilicon; and
said spacer layer comprises silicon oxide.
64. A method as claimed in claim 62, wherein:
said second and fourth insulating layers comprises silicon oxide; and
said third insulating layer comprises one of a spin-on-glass layer and a phosphosilicate glass layer.
65. A method of producing a fin-shaped capacitor in a dynamic random access memory comprising the steps of:
(a) forming a first insulating layer on a semiconductor substrate having a diffusion region;
(b) forming a plurality of stacked-layer structures, a lowermost one of said stacked-layer structures being formed on said first insulating layer, each of said stacked-layer structures having a spacer layer and a first conductive layer;
(c) forming a first opening in said stacked-layer structures;
(d) forming a conductive sidewall around an inner wall of said stacked-layer structures defining said first opening, said conductive sidewall defining a second opening having a width smaller than that of said first opening;
(e) selectively etching said first insulating layer in a state where said first conductive layer of an uppermost one of said stacked layer structures and said conductive sidewall function as masks, so that said diffusion region is exposed through a contact hole formed in said first insulating layer;
(f) forming a second conductive layer on said first conductive layer of the uppermost one of said stacked-layer structures, said conductive sidewall and said diffusion region exposed through said contact hole;
(g) patterning said second conductive layer and said stacked-layer structures into a shape of a storage electrode of said fin-shaped capacitor;
(h) isotropically etching said spacer layer of each of said stacked-layer structures so that said spacer layer is removed;
(i) forming a dielectric film around said storage electrode; and
(j) forming a cell plate around said storage electrode covered by said dielectric film.
66. A method as claimed in claim 65, wherein:
said method further comprises, between said steps (b) and (c), the step of forming a second insulating layer on said first conductive layer of the uppermost one of said stacked-layer structures; and
said second insulating layer is removed during said step (e).
67. A method as claimed in claim 65, wherein said step (a) comprises the steps of:
forming a second insulating layer on said semiconductor substrate;
forming a third insulating layer on said second insulating layer;
heating said third insulating layer so that said third insulating layer has a substantially flat surface; and
forming a fourth insulating layer on said substantially flat surface of said third insulating layer, and
wherein:
said second, third and fourth insulating layers form said first insulating layer.
68. A method as claimed in claim 65, wherein:
said first conductive layer comprises polysilicon; and
said spacer layer comprises silicon oxide.
69. A method as claimed in claim 67, wherein:
said second and fourth insulating layers comprise silicon oxide; and
said third insulating layer comprises one of a spin-on-glass layer and a phosphosilicate glass layer.
70. A method of producing a fin-shaped capacitor in a dynamic random access memory comprising the steps of:
(a) forming a first insulating layer on a semiconductor substrate having a diffusion region;
(b) forming a plurality of stacked-layer structures, a lowermost one of said stacked-layer structures being formed on said first insulating layer, each of said stacked-layer structures having a spacer layer and a first conductive layer;
(c) forming a contact hole in said stacked-layer structures and said first insulating layer so that said diffusion layer is exposed through said contact hole;
(d) forming a second conductive layer on said first conductive layer of an uppermost one of said stacked-layer structure and said diffusion layer exposed through said contact hole, said second conductive layer substantially vertically extending along an inner wall of said contact hole;
(e) patterning said second conductive layer and said stacked-layer structures into a shape of a storage electrode of said fin-shaped capacitor;
(f) isotropically etching said spacer layer of each of said stacked-layer structures so that said spacer layer is removed;
(i) forming a dielectric film around said storage electrode; and
(j) forming a cell plate around said storage electrode covered by said dielectric film.
71. A method as claimed in claim 70, wherein said step (a) comprises the steps of:
forming a second insulating layer on said semiconductor substrate;
forming a third insulating layer on said second insulating layer;
heating said third insulating layer so that said third insulating layer has a substantially flat surface; and
forming a fourth insulating layer on said substantially flat surface of said third insulating layer, and
wherein:
said fourth insulating layer is removed during said step (f).
72. A method as claimed in claim 71, wherein:
said second and fourth insulating layers comprises silicon oxide;
said third insulating layer comprises silicon nitride; and
said first and second conductive layers comprise polysilicon.
73. A method as claimed in claim 70, wherein:
said step (c) comprises:
forming a third conductive layer on a top of said stacked layer structures;
forming a second insulating layer on said third conductive layer;
forming a photoresist film having a window pattern on said second insulating layer;
etching said second insulating layer and said third conductive layer so that a first window is formed in said third conductive layer and said second insulating layer;
removing said photoresist film; and
forming a conductive sidwall around an inner wall of said third conductor layer defining said window,
wherein said contact hole formed by said step (c) having a size defined by said conductive sidewall.
US10/354,088 1990-03-08 2003-01-30 Layer structure having contact hole, fin-shaped capacitor using the layer structure, method of producing the fin-shaped capacitor, and dynamic random access memory having the fin-shaped capacitor Abandoned US20030134470A1 (en)

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US19057394A 1994-02-02 1994-02-02
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US9085731B2 (en) * 2010-03-12 2015-07-21 Bridgestone Corporation Methods for producing light-emitting body containing silicon fine particles and light-emitting silicon fine particles
US20160322261A1 (en) * 2011-12-02 2016-11-03 Unisantis Electronics Singapore Pte. Ltd. Method for producing semiconductor device and semiconductor device
US9837317B2 (en) * 2011-12-02 2017-12-05 Unisantis Electronics Singapore Pte. Ltd. Method for producing semiconductor device and semiconductor device

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DE69133410T2 (en) 2005-09-08
EP0449000A2 (en) 1991-10-02
US5705420A (en) 1998-01-06
EP0449000B1 (en) 2004-08-18
DE69133534T2 (en) 2006-12-28
EP0764974B1 (en) 2006-06-14
DE69133410D1 (en) 2004-09-23
EP0764974A1 (en) 1997-03-26
EP0449000A3 (en) 1992-11-25
EP1465248A1 (en) 2004-10-06
US6528369B1 (en) 2003-03-04
KR950014854B1 (en) 1995-12-16
DE69133534D1 (en) 2006-07-27
US6144058A (en) 2000-11-07

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