WO2011062050A1 - Method of manufacturing piezoelectric thin film, and piezoelectric thin film and piezoelectric element - Google Patents

Method of manufacturing piezoelectric thin film, and piezoelectric thin film and piezoelectric element Download PDF

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WO2011062050A1
WO2011062050A1 PCT/JP2010/069409 JP2010069409W WO2011062050A1 WO 2011062050 A1 WO2011062050 A1 WO 2011062050A1 JP 2010069409 W JP2010069409 W JP 2010069409W WO 2011062050 A1 WO2011062050 A1 WO 2011062050A1
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thin film
piezoelectric
layer
substrate
piezoelectric thin
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PCT/JP2010/069409
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French (fr)
Japanese (ja)
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松田　伸也
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コニカミノルタホールディングス株式会社
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Publication of WO2011062050A1 publication Critical patent/WO2011062050A1/en

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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/08—Oxides
    • C23C14/088—Oxides of the type ABO3 with A representing alkali, alkaline earth metal or Pb and B representing a refractory or rare earth metal
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/54—Controlling or regulating the coating process
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
    • H10N30/074—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing
    • H10N30/076—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing by vapour phase deposition
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/85—Piezoelectric or electrostrictive active materials
    • H10N30/853—Ceramic compositions
    • H10N30/8548—Lead-based oxides
    • H10N30/8554—Lead-zirconium titanate [PZT] based
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
    • H10N30/204—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators using bending displacement, e.g. unimorph, bimorph or multimorph cantilever or membrane benders
    • H10N30/2047—Membrane type

Definitions

  • the present invention relates to a method for manufacturing a piezoelectric thin film, a piezoelectric thin film, and a piezoelectric element.
  • piezoelectric materials such as PZT have been used as mechanical and electrical conversion elements such as drive elements and sensors.
  • MEMS devices Micro Electro Mechanical Systems
  • Si substrate Si substrate
  • the piezoelectric thin film enables easy manufacture of a large number of piezoelectric elements by batch processing on a large-area wafer, the cost reduction, the improvement of the electromechanical conversion efficiency, the drive element Advantages such as contributing to improvement of characteristics and sensor sensitivity occur.
  • a piezoelectric material such as PZT on a substrate such as Si
  • chemical methods such as CVD
  • physical methods such as sputtering and ion plating
  • liquid phase growth methods such as sol-gel.
  • a piezoelectric material such as PZT generally exhibits a good piezoelectric effect when the crystal has a perovskite structure with an ABO 3 type oxide.
  • This crystal structure can be controlled by the temperature at the time of film formation, and the relationship between the substrate temperature (film formation temperature) and the generated phase (crystal structure) when PZT is formed by sputtering or the like is shown in FIG. 1, p.145 FIG.
  • a represents amorphous
  • Flu represents fluorite phase
  • Py represents pyrochlore phase
  • Per represents perovskite phase.
  • the manufacturing method is a sputtering method (Sputter), a PLD method (Pulsed Laser Deposition), a CSD method (Chemical Solution Deposition), and a MOCVD method (Metal Organic Chemical Deposition) in order from the top.
  • sputtering method Sputter
  • PLD method Pulsed Laser Deposition
  • CSD Chemical Solution Deposition
  • MOCVD method Metal Organic Chemical Deposition
  • FIG. 6 shows the relationship between the substrate temperature of PZT and the lead composition ratio (Non-patent Document 1, p.146, FIG. 4).
  • the horizontal axis represents a substrate temperature (° C.)
  • the vertical axis represents a value normalized with a lead composition ratio of 1 when the substrate temperature for PZT film formation is 550 ° C.
  • the lead composition ratio decreases as the substrate temperature increases.
  • the temperature range in which the perovskite structure shown in FIG. 5 is obtained is very close to the temperature at which the constituent element lead is sublimated. In this temperature range, the lead composition ratio decreases as shown in FIG. For this reason, when PZT is formed at a preferred substrate temperature in order to obtain a good perovskite structure, lead deficiency occurs, leading to a decrease in crystallinity and a decrease in piezoelectric characteristics. On the other hand, when the lead is excessive, lead oxide remains in the thin film, and the insulation properties deteriorate.
  • Patent Document 1 a substrate temperature is set when a ferroelectric thin film (Pb x La 1-x Ti 1-x / 4 O 3 (0 ⁇ x ⁇ 0.25)) is formed by using a high-frequency magnetron sputtering method.
  • a ferroelectric thin film Pb x La 1-x Ti 1-x / 4 O 3 (0 ⁇ x ⁇ 0.25)
  • PbO powder is mixed when forming a target.
  • Patent Document 1 Although the amount of lead deposited on the substrate can be relatively increased by increasing the composition ratio of lead contained in the target, since the substrate temperature is high, it is once deposited on the substrate. A part of the lead will evaporate. For this reason, it is difficult to stably obtain a desired crystal structure by changing the lead composition ratio of the formed ferroelectric thin film, but this is not described in Patent Document 1.
  • the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for manufacturing a piezoelectric thin film having a desired crystal structure and a good element configuration, a piezoelectric thin film, and It is to provide a piezoelectric element.
  • the second substrate temperature is a temperature at which the composition ratio of a plurality of elements forming the piezoelectric material of the latter layer is closer to the stoichiometric composition ratio than the composition ratio of the initial layer.
  • the piezoelectric body is an oxide containing lead, 2.
  • a piezoelectric thin film in which a piezoelectric thin film having a predetermined crystal structure of a plurality of elements is formed on a substrate, The piezoelectric thin film has an initial layer and a late layer, A piezoelectric thin film characterized in that a composition ratio of a plurality of elements forming the piezoelectric layer of the latter layer is closer to a stoichiometric composition ratio than a composition ratio of the initial layer.
  • a substrate A piezoelectric thin film having a predetermined crystal structure formed of a plurality of elements formed on the substrate;
  • the piezoelectric thin film has an initial layer and a late layer,
  • the piezoelectric element wherein a composition ratio of a plurality of elements forming the piezoelectric layer of the latter layer is closer to a stoichiometric composition ratio than a composition ratio of the initial layer.
  • a piezoelectric thin film manufacturing method a piezoelectric thin film, and a piezoelectric element having a desired crystal structure and a good element structure.
  • FIG. 1 shows an example of a piezoelectric element 100 according to the present invention.
  • the piezoelectric element 100 has a thermal oxide film (SiO 2 ) 120, a lower electrode 130, a piezoelectric thin film 140, and an upper electrode 150 formed in order on a Si substrate 110.
  • the piezoelectric thin film 140 has an initial layer 140a formed on the lower electrode 130 and a late layer 140b formed continuously on the initial layer 140a.
  • the piezoelectric element 100 having the above configuration will be described below together with a method for manufacturing the piezoelectric element 100.
  • the piezoelectric thin film 140 is formed on the Si substrate 110 by a high-frequency magnetron sputtering method.
  • the piezoelectric thin film 140 is made of lead zirconate titanate (PZT).
  • FIG. 2 schematically shows a piezoelectric thin film manufacturing apparatus 200 (hereinafter referred to as manufacturing apparatus 200) for forming the piezoelectric thin film 140 and the like by the sputtering method.
  • manufacturing apparatus 200 a target 2 having a PZT raw material and a Si substrate 110 to be formed are disposed in a vacuum chamber 1.
  • the target 2 is held by a target dish 3 that also serves as an electrode, and the Si substrate 110 is held by a substrate holder 10 that also serves as an electrode.
  • the edge of the target dish 3 is covered with a cover 4, and the target dish 3 is disposed on the magnet 5, and the magnet 5 and the high-frequency electrode 6 below it are insulated from the vacuum chamber 1 by an insulator 7.
  • the high frequency electrode 6 is connected to a high frequency power source 8.
  • the substrate holder 10 includes a substrate heater 11 for heating the Si substrate 110 therein, and is connected to a rotating shaft 9 so that a film can be uniformly formed on the Si substrate 110.
  • the shaft 9 is connected to a motor 15, which is a rotation driving unit, provided outside the vacuum chamber 1 through a bearing 16 with a seal.
  • the vacuum chamber 1 is provided with a nozzle 14 for introducing a sputtering gas and an exhaust port A connected to an exhaust device (not shown).
  • the sputtering gas introduced from the nozzle 14 is a mixed gas of Ar gas supplied from the supply port B via the valve 12 and O 2 gas supplied from the supply port C via the valve 13.
  • FIG. 3 is a flowchart showing a process of forming a piezoelectric thin film on a Si substrate using the manufacturing apparatus 200 shown in FIG.
  • the target 2 is produced by mixing, firing, and pulverizing the PZT material powder prepared in a predetermined composition ratio, filling the target dish 3 and pressurizing.
  • the target dish 3 is set on the magnet 5 and the cover 4 is set thereon.
  • the composition ratio of the PZT material of the target 2 may be equivalent to a desired composition ratio (stoichiometric composition ratio) that can form a crystal structure in which the thin film after film formation exhibits good piezoelectric characteristics, and is known in the art.
  • the Si substrate 110 uses a Si single crystal plate oriented in ⁇ 100>, a thermal oxide film 120 is formed on the surface thereof, and platinum is preferentially oriented in ⁇ 100> as a lower electrode 130 on one side in advance. (Pt) is formed to a predetermined thickness by sputtering.
  • the thickness of the Si substrate 110 varies depending on the desired configuration of the piezoelectric element, but is generally about 300 to 500 ⁇ m.
  • the thermal oxide film 120 is formed for the purpose of protection and insulation, and is formed by heating the Si substrate at about 1500 ° C., and its thickness is generally about 0.1 ⁇ m.
  • the thickness of the lower electrode 130 is generally about 0.1 ⁇ m.
  • the Si substrate 110 having the thermal oxide film 120 and the lower electrode 130 is held by the substrate holder 10 with the lower electrode 130 facing downward, the vacuum chamber 1 is evacuated, and the Si substrate 110 is removed by the substrate heater 11.
  • the maintained first substrate temperature T1 is the substrate temperature during film formation, and as can be seen from FIG. 5, when forming the PZT thin film, the perovskite structure in which the thin film exhibits good piezoelectric characteristics. This is a temperature at which a crystal having can be easily formed.
  • the first substrate temperature T1 is the crystal structure of the initial layer when the initial layer is formed at the first substrate temperature T1
  • the second substrate temperature T2 The temperature at which the initial layer is formed so as to be closer to the perovskite structure than the crystal structure of the initial layer.
  • the Si substrate 110 while maintaining the above temperature, open the valve 12 and 13, a mixed gas of Ar gas and O 2 gas are mixed in a predetermined ratio is sputter gas was introduced into the vacuum chamber 1 from the nozzle 14 However, the degree of vacuum in the vacuum chamber 1 is maintained at a predetermined value. With the degree of vacuum maintained at a predetermined value, high frequency power is applied to the target 2 from the high frequency power supply 8 to generate plasma, and an initial layer 140a is formed on the Si substrate 110 (first step).
  • the initial layer 140a has a thickness of 0.01 ⁇ m to 10% or less of the thickness of the piezoelectric thin film 140 including the initial layer 140a, preferably 0.01 ⁇ m. To stop sputtering.
  • the initial layer 140a can form a crystal structure.
  • the crystal structure to be formed can be a substantially complete perovskite structure based on the substrate temperature set at the time of film formation with platinum preferentially oriented to ⁇ 100> as a base.
  • the initial layer 140a has a good perovskite structure, but the substrate temperature at the time of film formation is high. Therefore, a defect occurs in a part of the vapor pressure of lead, which is a constituent element, and the polarization changes due to this defect. Therefore, it does not have sufficient piezoelectric characteristics.
  • the thickness of the initial layer 140a By limiting the thickness of the initial layer 140a to 10% or less of the thickness of the piezoelectric thin film 140 formed on the Si substrate 110, the piezoelectric characteristics of the later layer 140b formed subsequently on the initial layer 140a are not significantly hindered. Thus, sufficient piezoelectric characteristics can be exhibited within a practical range.
  • the initial layer 140a is sufficiently thin as described above and close to the Si substrate 110 that is difficult to be displaced, the influence of insufficient piezoelectric characteristics is negligible.
  • the substrate heater 11 is controlled to set and maintain the temperature of the Si substrate 110 from 540 ° C. to 570 ° C., preferably 550 ° C.
  • the late layer 140b formed at the maintained second substrate temperature T2 has a lead composition as compared with the first substrate temperature T1 on which the initial layer 140a is formed.
  • the ratio can be improved and can be close to a desired composition ratio (stoichiometric composition ratio) that can form a crystal structure exhibiting better piezoelectric characteristics.
  • the Si substrate 110 In a state where the Si substrate 110 is maintained at the above temperature, high frequency power is again applied to the target 2 from the high frequency power source 8, and the late layer 140b is continuously formed on the initial layer 140a until a desired film thickness is obtained. (Second step).
  • the thickness of the latter layer 140b may be determined as appropriate according to the displacement, force, etc. required by the specifications. For example, in the case of an actuator, it is generally about 1 ⁇ m to 10 ⁇ m.
  • the late layer 140b Since the late layer 140b has a lower substrate temperature than that of the initial layer 140a, defects of lead, which is a constituent element, are less likely to occur compared to the initial layer 140a. On the other hand, because the substrate temperature is low, the late layer 140b is unlikely to form a perovskite structure, but actually forms a nearly perfect perovskite structure. This is because the initial layer 140a has an almost perfect perovskite structure, and the late layer 140b continuously formed on the initial layer 140a as a base is also helped by the same composition. It is presumed that the perovskite structure almost completely follows the lattice constant of the base.
  • the late layer 140b has an almost complete perovskite structure equivalent to that of the initial layer 140a, and in the constituent elements, lead deficiency is suppressed as compared with the initial layer 140a, and a more desirable composition is obtained. It has a good composition of elements close to the ratio (stoichiometric composition ratio).
  • the late layer 140b has good piezoelectric characteristics, and can adequately cope with the displacement, force, etc. required by the specifications by appropriately determining its thickness.
  • the late layer 140b exists at a position away from the Si substrate 110 that is difficult to be displaced, it is advantageous in obtaining necessary characteristics as a sensor and an actuator.
  • the piezoelectric element 100 is completed by providing the upper electrode 150 with Pt or Al on the latter layer 140b.
  • FIG. 4 shows an example of a piezoelectric element 300 in which the piezoelectric thin film described in this embodiment is applied to a diaphragm.
  • a part of the Si substrate 210 is removed in a circular shape to form a depression 210a, and a thin plate-like member is left on the upper part, and this member forms a diaphragm 210b.
  • a circular initial layer 140a and a late layer 140b corresponding to the shape of the recess 210a are formed on the surface of the diaphragm 210b opposite to the recess 210a.
  • a Pt film is formed as the upper electrode 150 on the latter layer 140b by sputtering or the like.
  • the piezoelectric thin film 140 expands and contracts in the left-right direction, and the diaphragm 210b can be bent up and down by the bimetal effect.
  • the piezoelectric element 300 can be applied as an actuator such as a pump if the recess 210a can be filled with gas or liquid, for example.
  • the piezoelectric element 300 when the diaphragm 210b is vibrated by sound waves or ultrasonic waves, the piezoelectric element 300 generates a voltage between the upper electrode 150 and the lower electrode 130 due to an effect opposite to the above, and the frequency and magnitude of the voltage are reduced. By being detected, it can be applied as a sound wave sensor.
  • the material of the piezoelectric thin film described so far is not limited to PZT, and may be one obtained by adding Nb (niobium), La (lanthanum), Mn (manganese), or the like to PZT.
  • a material containing lead such as PNT (lead niobate titanate), PMN-PT (lead magnesium niobate titanate), or PZNT (lead zinc niobate titanate) may be used.
  • Piezoelectric thin films formed of the materials listed above have the perovskite structure described by taking PZT as an example, and there is no change in that lead deficiency is suppressed, and all show good piezoelectric characteristics that are not inferior to PZT. .
  • the substrate temperature and the composition ratio of the elements constituting the piezoelectric body when the temperature is high, not only the lead listed in the example of the present embodiment, but part of the constituent elements may be lost.
  • the present invention can be applied to a piezoelectric thin film that does not contain lead.
  • the manufacturing apparatus 200 can perform the PLD method, the CSD method, and the MOCVD method.
  • the piezoelectric element 100 shown in FIG. 1 was manufactured according to the flowchart shown in FIG. 3 using the manufacturing apparatus 200 shown in FIG.
  • a Si single crystal plate (thickness 350 ⁇ m) oriented in ⁇ 100> was used as a Si substrate 110, and a thermal oxide film 120 (thickness 0.1 ⁇ m) and a lower electrode 130 (Pt, thickness 0.1 ⁇ m) were prepared on the Si substrate 110.
  • a target 2 made of a PZT material having a composition of Pb (Zr 0.52 Ti 0.48 ) O 3 was prepared.
  • the prepared Si substrate 110 and target 2 were arranged in the manufacturing apparatus 200 shown in FIG.
  • the Si substrate 110 was heated and set so that the first substrate temperature T1 was 600 ° C. After the temperature of the Si substrate 110 reached 600 ° C., while maintaining this temperature, a mixed gas of Ar and O 2 was introduced into the vacuum chamber 1 to form an initial layer 140 a having a thickness of 0.01 ⁇ m.
  • the temperature of the Si substrate 110 was changed, and the second substrate temperature T2 was set to 550 ° C. After the temperature of the Si substrate 110 reaches 550 ° C., while maintaining this temperature, a mixed gas of Ar and O 2 was introduced into the vacuum chamber 1 to form a late layer 140b having a thickness of 2 [mu] m.
  • the late layer 140b had an almost perfect perovskite structure. Further, as a result of measurement using a fluorescent X-ray composition analyzer, it was confirmed that the composition of the late layer 140b was almost the same as the composition ratio of the target 2 and there was almost no deficiency of lead.
  • a Pt film (thickness: 0.1 ⁇ m) was provided as the upper electrode 150 to obtain the piezoelectric element 100.
  • the piezoelectric constant d31 ⁇ 150 pm / V and the relative permittivity were 700, respectively, and it was confirmed that the piezoelectric element functioned sufficiently.

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Abstract

Disclosed is a method of manufacturing a piezoelectric thin film having the desired crystal structure and a favorable element composition. Specifically disclosed is a piezoelectric thin film manufacturing method for forming, on a substrate, a thin film of a piezoelectric substance having a predetermined crystal structure including a plurality of elements, said piezoelectric thin film manufacturing method comprising a first step for forming an initial layer of the piezoelectric substance on the substrate at a first substrate temperature, and a second step for forming a subsequent layer of the piezoelectric substance contiguous with the initial layer at a second substrate temperature, wherein the first substrate temperature is such that the crystal structure of the initial layer, which is formed at the first substrate temperature, more closely resembles the predetermined crystal structure than would be the case if the initial layer were formed at the second substrate temperature, and wherein the second substrate temperature is such that the composition ratio of the plurality of elements constituting the piezoelectric substance of the subsequent layer is closer to a stoichiometric composition ratio than is the composition ratio of the initial layer.

Description

圧電体薄膜の製造方法、圧電体薄膜及び圧電体素子Method for manufacturing piezoelectric thin film, piezoelectric thin film, and piezoelectric element
　本発明は、圧電体薄膜の製造方法、圧電体薄膜及び圧電体素子に関する。 The present invention relates to a method for manufacturing a piezoelectric thin film, a piezoelectric thin film, and a piezoelectric element.
　従来から、ＰＺＴなどの圧電体は、駆動素子やセンサなどの機械電気変換素子として用いられている。また近年、装置の小型化、高密度化、低コスト化などの要求に応えて、Ｓｉ基板を用いたＭＥＭＳ素子（Ｍｉｃｒｏ　Ｅｌｅｃｔｒｏ　Ｍｅｃｈａｎｉｃａｌ　Ｓｙｓｔｅｍｓ：微小電気機械素子）が増加している。 Conventionally, piezoelectric materials such as PZT have been used as mechanical and electrical conversion elements such as drive elements and sensors. In recent years, MEMS devices (Micro Electro Mechanical Systems) using a Si substrate have been increasing in response to demands for downsizing, high density, and low cost of devices.
　圧電体をＭＥＭＳ素子に応用するには、圧電体の薄膜化が望ましく、薄膜化により、成膜、フォトリソグラフィーなど半導体プロセス技術を用いた高精度な加工を適用することができ、ＭＥＭＳ素子の小型化、高密度化が実現できる。また、圧電体の薄膜化は、大面積のウェハに一括加工することによる圧電素子の多数個の製造を容易に可能とするものであるため、コスト低減、機械電気変換効率の向上、駆動素子の特性やセンサの感度の向上に寄与するなどの利点が生じる。 In order to apply a piezoelectric body to a MEMS element, it is desirable to reduce the thickness of the piezoelectric body. By thinning the film, high-precision processing using semiconductor process technology such as film formation and photolithography can be applied. And higher density can be realized. In addition, since the piezoelectric thin film enables easy manufacture of a large number of piezoelectric elements by batch processing on a large-area wafer, the cost reduction, the improvement of the electromechanical conversion efficiency, the drive element Advantages such as contributing to improvement of characteristics and sensor sensitivity occur.
　ＰＺＴなどの圧電体をＳｉなどの基板上に成膜するには、ＣＶＤ法など化学的な方法、スパッタ法やイオンプレーティング法など物理的な方法、ゾルゲル法など液相での成長法がある。 To form a piezoelectric material such as PZT on a substrate such as Si, there are chemical methods such as CVD, physical methods such as sputtering and ion plating, and liquid phase growth methods such as sol-gel. .
　ＰＺＴなどの圧電体は、一般的にＡＢＯ３型の酸化物で結晶がペロブスカイト型構造を持つときに良好な圧電効果を発現する。この結晶構造は成膜時の温度により制御でき、ＰＺＴをスパッタ法等で成膜する場合の基板温度（成膜温度）と生成相（結晶構造）との関係を図５に示す（非特許文献１、ｐ．１４５　図３）。 A piezoelectric material such as PZT generally exhibits a good piezoelectric effect when the crystal has a perovskite structure with an ABO 3 type oxide. This crystal structure can be controlled by the temperature at the time of film formation, and the relationship between the substrate temperature (film formation temperature) and the generated phase (crystal structure) when PZT is formed by sputtering or the like is shown in FIG. 1, p.145 FIG.
　図５において、ａは非晶質、Ｆｌｕはフルオライト相、Ｐｙはパイロクロア相、Ｐｅｒはペロブスカイト相を表している。また、製造方法は、上段から順にスパッタ法（Ｓｐｕｔｔｅｒ）、ＰＬＤ法（Ｐｕｌｓｅｄ　Ｌａｓｅｒ　Ｄｅｐｏｓｉｔｉｏｎ）、ＣＳＤ法（Ｃｈｅｍｉｃａｌ　Ｓｏｌｕｔｉｏｎ　Ｄｅｐｏｓｉｔｉｏｎ）及びＭＯＣＶＤ法（Ｍｅｔａｌ　Ｏｒｇａｎｉｃ　Ｃｈｅｍｉｃａｌ　Ｖａｐｏｒ　Ｄｅｐｏｓｉｔｉｏｎ）である。図５のスパッタ法の場合を例にすると、基板温度が６００℃前後において、成膜の結晶構造がペロブスカイト型構造となるが、その温度域以外の低温側及び高温側の何れにおいても、ペロブスカイト型とは異なる結晶構造や非晶質の部分が発生し圧電特性が低下する。 In FIG. 5, a represents amorphous, Flu represents fluorite phase, Py represents pyrochlore phase, and Per represents perovskite phase. In addition, the manufacturing method is a sputtering method (Sputter), a PLD method (Pulsed Laser Deposition), a CSD method (Chemical Solution Deposition), and a MOCVD method (Metal Organic Chemical Deposition) in order from the top. Taking the case of the sputtering method of FIG. 5 as an example, when the substrate temperature is around 600 ° C., the crystal structure of the film formation becomes a perovskite type structure. A crystal structure or an amorphous part different from that is generated, and the piezoelectric characteristics are deteriorated.
　ＰＺＴの構成元素であるＰｂの蒸気圧は、他の元素であるＴｉやＺｒと比較して高い（１Ｐａ時の昇華温度はＰｂが７０５℃、Ｔｉが１７０９℃、Ｚｒが２３６６℃）。ＰＺＴの基板温度と鉛組成比との関係を図６に示す（非特許文献１、ｐ．１４６　図４）。図６において、横軸は基板温度（℃）、縦軸はＰＺＴ成膜の基板温度が５５０℃における鉛組成比を１として規格化した値である。図６が示すように、基板温度が高くなるに従い鉛組成比が減少する。 The vapor pressure of Pb, which is a constituent element of PZT, is higher than Ti and Zr, which are other elements (sublimation temperatures at 1 Pa are Pb of 705 ° C., Ti of 1709 ° C., and Zr of 2366 ° C.). FIG. 6 shows the relationship between the substrate temperature of PZT and the lead composition ratio (Non-patent Document 1, p.146, FIG. 4). In FIG. 6, the horizontal axis represents a substrate temperature (° C.), and the vertical axis represents a value normalized with a lead composition ratio of 1 when the substrate temperature for PZT film formation is 550 ° C. As shown in FIG. 6, the lead composition ratio decreases as the substrate temperature increases.
　図５で示すペロブスカイト構造が得られる温度域は、構成元素である鉛の昇華する温度が非常に近く、この温度域においては、図６で示すように鉛組成比は減少する。このため、良好なペロブスカイト構造を得るために好ましい基板温度でＰＺＴを成膜すると鉛の欠損が生じ、結晶性の低下を招き、圧電特性が低下する。一方、鉛の過剰は、薄膜に酸化鉛が残存し、絶縁性が低下する。 The temperature range in which the perovskite structure shown in FIG. 5 is obtained is very close to the temperature at which the constituent element lead is sublimated. In this temperature range, the lead composition ratio decreases as shown in FIG. For this reason, when PZT is formed at a preferred substrate temperature in order to obtain a good perovskite structure, lead deficiency occurs, leading to a decrease in crystallinity and a decrease in piezoelectric characteristics. On the other hand, when the lead is excessive, lead oxide remains in the thin film, and the insulation properties deteriorate.
　特許文献１には、高周波マグネトロンスパッタ法を用いて強誘電体薄膜（ＰｂｘＬａ１－ｘＴｉ１－ｘ／４Ｏ３（０≦ｘ≦０．２５））を形成する際、基板温度を６００℃とし、鉛の不足を防止するため、ターゲットを作成する際に過剰のＰｂＯ粉末を混合することが開示されている。 In Patent Document 1, a substrate temperature is set when a ferroelectric thin film (Pb x La 1-x Ti 1-x / 4 O 3 (0 ≦ x ≦ 0.25)) is formed by using a high-frequency magnetron sputtering method. In order to prevent lead shortage at 600 ° C., it is disclosed that excessive PbO powder is mixed when forming a target.
特開平６－２６００１８号公報JP-A-6-260018
　しかしながら、特許文献１においては、ターゲットに含まれる鉛の組成比を高めにすることで、基板に堆積する鉛の量を比較的多くすることができるものの、基板温度が高いため、一度基板に堆積した鉛の一部が蒸発してしまう。このため、形成された強誘電体薄膜の鉛組成比が変動して所望の結晶構造を安定して得ることが困難であるが、これらに関して、特許文献１には記載されていない。 However, in Patent Document 1, although the amount of lead deposited on the substrate can be relatively increased by increasing the composition ratio of lead contained in the target, since the substrate temperature is high, it is once deposited on the substrate. A part of the lead will evaporate. For this reason, it is difficult to stably obtain a desired crystal structure by changing the lead composition ratio of the formed ferroelectric thin film, but this is not described in Patent Document 1.
　本発明は、上記の課題を鑑みてなされたものであって、その目的とするところは、所望の結晶構造で、且つ、元素の良好な構成を有する圧電体薄膜の製造方法、圧電体薄膜及び圧電体素子を提供することである。 The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for manufacturing a piezoelectric thin film having a desired crystal structure and a good element configuration, a piezoelectric thin film, and It is to provide a piezoelectric element.
　上記の課題は、以下の構成により解決される。 The above problem is solved by the following configuration.
　１．複数の元素による所定の結晶構造を有する圧電体の薄膜を基板の上に形成する圧電体薄膜の製造方法において、
　前記基板の上に、第１の基板温度で前記圧電体の初期層を形成する第１工程と、
　前記初期層に連続して、第２の基板温度で前記圧電体の後期層を形成する第２工程と、を含み、
　前記第１の基板温度は、前記第１の基板温度で前記初期層を形成した場合の初期層の結晶構造が、前記第２の基板温度で前記初期層を形成した場合の初期層の結晶構造よりも、前記所定の結晶構造に近くなるように形成される温度であり、
　前記第２の基板温度は、該後期層の圧電体を形成する複数の元素の組成比が、前記初期層の組成比より、化学量論的組成比に近くなるように形成される温度であることを特徴とする圧電体薄膜の製造方法。 1. In a piezoelectric thin film manufacturing method for forming a piezoelectric thin film having a predetermined crystal structure with a plurality of elements on a substrate,
A first step of forming an initial layer of the piezoelectric body on the substrate at a first substrate temperature;
Forming a second layer of the piezoelectric body at a second substrate temperature in succession to the initial layer, and
As for the first substrate temperature, the crystal structure of the initial layer when the initial layer is formed at the first substrate temperature is the crystal structure of the initial layer when the initial layer is formed at the second substrate temperature. Rather than the predetermined crystal structure.
The second substrate temperature is a temperature at which the composition ratio of a plurality of elements forming the piezoelectric material of the latter layer is closer to the stoichiometric composition ratio than the composition ratio of the initial layer. A method for producing a piezoelectric thin film, comprising:
　２．前記所定の結晶構造は、ペロブスカイト型結晶構造であることを特徴とする前記１に記載の圧電体薄膜の製造方法。 2. 2. The method for manufacturing a piezoelectric thin film according to 1 above, wherein the predetermined crystal structure is a perovskite crystal structure.
　３．前記圧電体は、鉛を含む酸化物であり、
　前記第１の基板温度は、前記第２の基板温度より高いことを特徴とする前記１に記載の圧電体薄膜の製造方法。 3. The piezoelectric body is an oxide containing lead,
2. The method for manufacturing a piezoelectric thin film according to 1 above, wherein the first substrate temperature is higher than the second substrate temperature.
　４．前記後期層の厚みは、前記初期層の厚みより厚いことを特徴とする前記１に記載の圧電体薄膜の製造方法。 4. 2. The method for manufacturing a piezoelectric thin film according to 1 above, wherein the thickness of the latter layer is larger than the thickness of the initial layer.
　５．前記初期層及び前記後期層の前記圧電体は、スパッタリング法を用いて形成されることを特徴とする前記１に記載の圧電体薄膜の製造方法。 5. 2. The method of manufacturing a piezoelectric thin film according to 1 above, wherein the piezoelectric bodies of the initial layer and the late layer are formed using a sputtering method.
　６．複数の元素による所定の結晶構造を有する圧電体の薄膜が基板の上に形成されている圧電体薄膜において、
　前記圧電体薄膜は、初期層と後期層とを有し、
　前記後期層の圧電体を形成する複数の元素の組成比は、前記初期層の組成比より化学量論的組成比に近いことを特徴とする圧電体薄膜。 6). In a piezoelectric thin film in which a piezoelectric thin film having a predetermined crystal structure of a plurality of elements is formed on a substrate,
The piezoelectric thin film has an initial layer and a late layer,
A piezoelectric thin film characterized in that a composition ratio of a plurality of elements forming the piezoelectric layer of the latter layer is closer to a stoichiometric composition ratio than a composition ratio of the initial layer.
　７．前記所定の結晶構造は、ペロブスカイト型結晶構造であることを特徴とする前記６に記載の圧電体薄膜。 7. 7. The piezoelectric thin film as described in 6 above, wherein the predetermined crystal structure is a perovskite crystal structure.
　８．前記圧電体は、鉛を含む酸化物であることを特徴とする前記６に記載の圧電体薄膜。 8. 7. The piezoelectric thin film as described in 6 above, wherein the piezoelectric body is an oxide containing lead.
　９．前記後期層の厚みは、前記初期層の厚みより厚いことを特徴とする前記６に記載の圧電体薄膜。 9. 7. The piezoelectric thin film as described in 6 above, wherein the thickness of the latter layer is larger than the thickness of the initial layer.
　１０．基板と、
　前記基板上に形成された、複数の元素による所定の結晶構造を有する圧電体薄膜とを有し、
　前記圧電体薄膜は、初期層と後期層とを有し、
　前記後期層の圧電体を形成する複数の元素の組成比は、前記初期層の組成比より化学量論的組成比に近いことを特徴とする圧電体素子。 10. A substrate,
A piezoelectric thin film having a predetermined crystal structure formed of a plurality of elements formed on the substrate;
The piezoelectric thin film has an initial layer and a late layer,
The piezoelectric element, wherein a composition ratio of a plurality of elements forming the piezoelectric layer of the latter layer is closer to a stoichiometric composition ratio than a composition ratio of the initial layer.
　本発明によれば、所望の結晶構造で、且つ、元素の良好な構成を有する圧電体薄膜の製造方法、圧電体薄膜及び圧電体素子を提供することができる。 According to the present invention, it is possible to provide a piezoelectric thin film manufacturing method, a piezoelectric thin film, and a piezoelectric element having a desired crystal structure and a good element structure.
本発明の圧電体薄膜を有する圧電体素子の例を示す図である。It is a figure which shows the example of the piezoelectric element which has a piezoelectric material thin film of this invention. 圧電体薄膜をスパッタリング法で成膜する製造装置の例を示す図である。It is a figure which shows the example of the manufacturing apparatus which forms a piezoelectric material thin film by sputtering method. 基板上に圧電体薄膜を形成する工程を示すフロー図である。It is a flowchart which shows the process of forming a piezoelectric material thin film on a board | substrate. 本発明の圧電体薄膜をダイヤフラムに応用した圧電体素子の例を示す図である。It is a figure which shows the example of the piezoelectric element which applied the piezoelectric material thin film of this invention to the diaphragm. ＰＺＴ薄膜を成膜する場合、製造方法と、それぞれの製造方法における基板温度と生成相との関係を示す図である。When forming a PZT thin film, it is a figure which shows the relationship between a manufacturing method and the substrate temperature in each manufacturing method, and a production | generation phase. ＰＺＴ薄膜の基板温度と鉛組成比との関係を示す図である。It is a figure which shows the relationship between the substrate temperature of a PZT thin film, and a lead composition ratio.
　本発明を実施の形態に基づいて説明するが、本発明は該実施の形態に限らない。 Although the present invention will be described based on the embodiment, the present invention is not limited to the embodiment.
　図１は、本発明に係る圧電体素子１００の例を示す。図１において、圧電体素子１００は、Ｓｉ基板１１０の上に、順に、熱酸化膜（ＳｉＯ２）１２０、下部電極１３０、圧電体薄膜１４０及び上部電極１５０が形成されている。圧電体薄膜１４０は、下部電極１３０上に形成されている初期層１４０ａ、初期層１４０ａ上に連続して形成されている後期層１４０ｂを有している。 FIG. 1 shows an example of a piezoelectric element 100 according to the present invention. In FIG. 1, the piezoelectric element 100 has a thermal oxide film (SiO 2 ) 120, a lower electrode 130, a piezoelectric thin film 140, and an upper electrode 150 formed in order on a Si substrate 110. The piezoelectric thin film 140 has an initial layer 140a formed on the lower electrode 130 and a late layer 140b formed continuously on the initial layer 140a.
　上記構成の圧電体素子１００に関して、圧電体素子１００の製造方法と共に以下に説明する。圧電体薄膜１４０は、高周波マグネトロンスパッタリング法によりＳｉ基板１１０の上に成膜され、本実施の形態では、圧電体薄膜１４０は、チタン酸ジルコン酸鉛（ＰＺＴ）とする。 The piezoelectric element 100 having the above configuration will be described below together with a method for manufacturing the piezoelectric element 100. The piezoelectric thin film 140 is formed on the Si substrate 110 by a high-frequency magnetron sputtering method. In this embodiment, the piezoelectric thin film 140 is made of lead zirconate titanate (PZT).
　図２は、圧電体薄膜１４０等を上記のスパッタリング法で成膜する圧電体薄膜の製造装置２００（以下、製造装置２００）を模式的に示す。図２に示す製造装置２００において、真空チャンバー１の中に、ＰＺＴの原料を有するターゲット２及び成膜されるＳｉ基板１１０が配置されている。 FIG. 2 schematically shows a piezoelectric thin film manufacturing apparatus 200 (hereinafter referred to as manufacturing apparatus 200) for forming the piezoelectric thin film 140 and the like by the sputtering method. In the manufacturing apparatus 200 shown in FIG. 2, a target 2 having a PZT raw material and a Si substrate 110 to be formed are disposed in a vacuum chamber 1.
　ターゲット２は電極を兼ねたターゲット皿３により保持され、Ｓｉ基板１１０は電極を兼ねた基板ホルダー１０により保持されている。ターゲット皿３の縁はカバー４で覆われ、ターゲット皿３はマグネット５上に配置され、マグネット５とその下にある高周波電極６は、絶縁体７によって真空チャンバー１から絶縁されている。高周波電極６は、高周波電源８に接続されている。 The target 2 is held by a target dish 3 that also serves as an electrode, and the Si substrate 110 is held by a substrate holder 10 that also serves as an electrode. The edge of the target dish 3 is covered with a cover 4, and the target dish 3 is disposed on the magnet 5, and the magnet 5 and the high-frequency electrode 6 below it are insulated from the vacuum chamber 1 by an insulator 7. The high frequency electrode 6 is connected to a high frequency power source 8.
　基板ホルダー１０は、内部にＳｉ基板１１０を加熱するための基板加熱ヒーター１１を備え、Ｓｉ基板１１０上に均一に成膜できるように回転する軸９に接続されている。軸９は、シール付きベアリング１６を通して真空チャンバー１の外部に設けてある回転駆動部であるモータ１５に接続されている。 The substrate holder 10 includes a substrate heater 11 for heating the Si substrate 110 therein, and is connected to a rotating shaft 9 so that a film can be uniformly formed on the Si substrate 110. The shaft 9 is connected to a motor 15, which is a rotation driving unit, provided outside the vacuum chamber 1 through a bearing 16 with a seal.
　真空チャンバー１には、スパッタガスを導入するノズル１４及び図示しない排気装置に接続されている排気口Ａが設けられている。ノズル１４から導入されるスパッタガスは、バルブ１２を介して供給口Ｂから供給されるＡｒガスとバルブ１３を介して供給口Ｃから供給されるＯ２ガスの混合ガスである。 The vacuum chamber 1 is provided with a nozzle 14 for introducing a sputtering gas and an exhaust port A connected to an exhaust device (not shown). The sputtering gas introduced from the nozzle 14 is a mixed gas of Ar gas supplied from the supply port B via the valve 12 and O 2 gas supplied from the supply port C via the valve 13.
　図３は、図２に示す製造装置２００を用いて圧電体薄膜をＳｉ基板上に形成する工程を示すフローチャートである。 FIG. 3 is a flowchart showing a process of forming a piezoelectric thin film on a Si substrate using the manufacturing apparatus 200 shown in FIG.
　所定の組成比に調合したＰＺＴ材料の粉末を混合、焼成、粉砕し、ターゲット皿３に充填して加圧することによりターゲット２を作製する。ターゲット皿３を、マグネット５上に設置し、その上にカバー４を設置する。ターゲット２のＰＺＴ材料の組成比は、成膜後の薄膜が良好な圧電特性を示す結晶構造をなし得る所望の組成比（化学量論的組成比）と同等で良く、従来知られているような、成膜の際に認められる鉛不足を補うような特別な組成比にする必要はない。 The target 2 is produced by mixing, firing, and pulverizing the PZT material powder prepared in a predetermined composition ratio, filling the target dish 3 and pressurizing. The target dish 3 is set on the magnet 5 and the cover 4 is set thereon. The composition ratio of the PZT material of the target 2 may be equivalent to a desired composition ratio (stoichiometric composition ratio) that can form a crystal structure in which the thin film after film formation exhibits good piezoelectric characteristics, and is known in the art. In addition, it is not necessary to use a special composition ratio that compensates for the lead shortage observed during film formation.
　Ｓｉ基板１１０は、＜１００＞に配向したＳｉ単結晶板を用い、その表面には熱酸化膜１２０が形成されており、更に片面に、予め下部電極１３０として、＜１００＞に優先配向した白金（Ｐｔ）がスパッタリング法により、所定の厚さだけ形成してある。 The Si substrate 110 uses a Si single crystal plate oriented in <100>, a thermal oxide film 120 is formed on the surface thereof, and platinum is preferentially oriented in <100> as a lower electrode 130 on one side in advance. (Pt) is formed to a predetermined thickness by sputtering.
　Ｓｉ基板１１０の厚みは、所望の圧電体素子の構成により異なるが、一般的に３００～５００μｍ程度である。熱酸化膜１２０は保護及び絶縁が目的で形成されており、Ｓｉ基板を１５００℃程度で加熱することにより形成され、その厚みは一般的に０．１μｍ程度である。下部電極１３０の厚みは一般的に０．１μｍ程度である。 The thickness of the Si substrate 110 varies depending on the desired configuration of the piezoelectric element, but is generally about 300 to 500 μm. The thermal oxide film 120 is formed for the purpose of protection and insulation, and is formed by heating the Si substrate at about 1500 ° C., and its thickness is generally about 0.1 μm. The thickness of the lower electrode 130 is generally about 0.1 μm.
　次に、熱酸化膜１２０及び下部電極１３０を備えたＳｉ基板１１０を、下部電極１３０を下向きにして基板ホルダー１０に保持させ、真空チャンバー１内を排気し、基板加熱ヒーター１１によってＳｉ基板１１０を６００℃から６５０℃、好ましくは６００℃前後にまで加熱し、維持する。維持されている上記の第１の基板温度Ｔ１は、成膜時の基板温度であって、図５から分かるように、ＰＺＴ薄膜を形成する際、薄膜が良好な圧電特性を発現するペロブスカイト型構造を有する結晶を容易に形成することができる温度である。 Next, the Si substrate 110 having the thermal oxide film 120 and the lower electrode 130 is held by the substrate holder 10 with the lower electrode 130 facing downward, the vacuum chamber 1 is evacuated, and the Si substrate 110 is removed by the substrate heater 11. Heat and maintain from 600 ° C to 650 ° C, preferably around 600 ° C. The maintained first substrate temperature T1 is the substrate temperature during film formation, and as can be seen from FIG. 5, when forming the PZT thin film, the perovskite structure in which the thin film exhibits good piezoelectric characteristics. This is a temperature at which a crystal having can be easily formed.
　また、後述する第２の基板温度Ｔ２との比較において、第１の基板温度Ｔ１は、第１の基板温度Ｔ１で初期層を形成した場合の初期層の結晶構造が、第２の基板温度Ｔ２で初期層を形成した場合の初期層の結晶構造よりも、ペロブスカイト型構造に近くなるように形成される温度である。 Further, in comparison with the second substrate temperature T2, which will be described later, the first substrate temperature T1 is the crystal structure of the initial layer when the initial layer is formed at the first substrate temperature T1, and the second substrate temperature T2 The temperature at which the initial layer is formed so as to be closer to the perovskite structure than the crystal structure of the initial layer.
　Ｓｉ基板１１０を上記の温度に維持した状態で、バルブ１２及び１３を開け、スパッタガスであるＡｒガスとＯ２ガスを所定の割合に混合した混合ガスをノズル１４より真空チャンバー１内に導入しながら、真空チャンバー１内の真空度を所定値に維持する。真空度を所定値に維持した状態で、ターゲット２に、高周波電源８より高周波電力を投入し、プラズマを発生させ、Ｓｉ基板１１０上に初期層１４０ａを成膜する（第１工程）。 The Si substrate 110 while maintaining the above temperature, open the valve 12 and 13, a mixed gas of Ar gas and O 2 gas are mixed in a predetermined ratio is sputter gas was introduced into the vacuum chamber 1 from the nozzle 14 However, the degree of vacuum in the vacuum chamber 1 is maintained at a predetermined value. With the degree of vacuum maintained at a predetermined value, high frequency power is applied to the target 2 from the high frequency power supply 8 to generate plasma, and an initial layer 140a is formed on the Si substrate 110 (first step).
　初期層１４０ａの厚みは、０．０１μｍから初期層１４０ａを含めた圧電体薄膜１４０の厚みの１０％以下、好ましくは０．０１μｍになるまで成膜を行い、初期層１４０ａの成膜後一旦電力を切り、スパッタリングを停止する。 The initial layer 140a has a thickness of 0.01 μm to 10% or less of the thickness of the piezoelectric thin film 140 including the initial layer 140a, preferably 0.01 μm. To stop sputtering.
　初期層１４０ａの厚みを０．０１μｍ以上とすることにより、初期層１４０ａは結晶構造を形成することができる。形成される結晶構造は、＜１００＞に優先配向した白金を下地とし、成膜する際に設定されている基板温度から、ほぼ完全なペロブスカイト型構造とすることができる。 By setting the thickness of the initial layer 140a to 0.01 μm or more, the initial layer 140a can form a crystal structure. The crystal structure to be formed can be a substantially complete perovskite structure based on the substrate temperature set at the time of film formation with platinum preferentially oriented to <100> as a base.
　初期層１４０ａは、良好なペロブスカイト型構造を有する一方で、成膜時の基板温度が高いため、構成元素である鉛の蒸気圧からその一部に欠損が生じ、この欠損により分極の状態が変化するため、十分な圧電特性を有していない。初期層１４０ａの厚みをＳｉ基板１１０上に形成する圧電体薄膜１４０の厚みの１０％以内に抑えることにより、初期層１４０ａ上に引き続いて形成する後期層１４０ｂが有する圧電特性を大きく妨げることが無く、実用的な範囲で十分な圧電特性を示すことができる。また、初期層１４０ａは、上記の通り十分に薄いことと共に、変位し難いＳｉ基板１１０に近いため、圧電特性が十分でないことの影響は軽微である。 The initial layer 140a has a good perovskite structure, but the substrate temperature at the time of film formation is high. Therefore, a defect occurs in a part of the vapor pressure of lead, which is a constituent element, and the polarization changes due to this defect. Therefore, it does not have sufficient piezoelectric characteristics. By limiting the thickness of the initial layer 140a to 10% or less of the thickness of the piezoelectric thin film 140 formed on the Si substrate 110, the piezoelectric characteristics of the later layer 140b formed subsequently on the initial layer 140a are not significantly hindered. Thus, sufficient piezoelectric characteristics can be exhibited within a practical range. In addition, since the initial layer 140a is sufficiently thin as described above and close to the Si substrate 110 that is difficult to be displaced, the influence of insufficient piezoelectric characteristics is negligible.
　次に、基板加熱ヒーター１１を制御して、Ｓｉ基板１１０の温度を５４０℃から５７０℃、好ましくは５５０℃に設定し維持させる。図６から分かるように、この維持されている上記の第２の基板温度Ｔ２で形成される後期層１４０ｂは、先の初期層１４０ａを形成した第１の基板温度Ｔ１と比較して鉛の組成比が改善され、より良好な圧電特性を示す結晶構造をなし得る所望の組成比（化学量論的組成比）に近いものとなることができる。 Next, the substrate heater 11 is controlled to set and maintain the temperature of the Si substrate 110 from 540 ° C. to 570 ° C., preferably 550 ° C. As can be seen from FIG. 6, the late layer 140b formed at the maintained second substrate temperature T2 has a lead composition as compared with the first substrate temperature T1 on which the initial layer 140a is formed. The ratio can be improved and can be close to a desired composition ratio (stoichiometric composition ratio) that can form a crystal structure exhibiting better piezoelectric characteristics.
　Ｓｉ基板１１０を上記の温度に維持した状態で、ターゲット２に、高周波電源８より高周波電力を再度投入し、初期層１４０ａの上に連続して後期層１４０ｂを所望の膜厚になるまで成膜を行う（第２工程）。後期層１４０ｂの厚みは、仕様により必要とされる変位、力等により適宜定めればよく、例えばアクチュエータとする場合は一般的に１μｍから１０μｍ程度である。 In a state where the Si substrate 110 is maintained at the above temperature, high frequency power is again applied to the target 2 from the high frequency power source 8, and the late layer 140b is continuously formed on the initial layer 140a until a desired film thickness is obtained. (Second step). The thickness of the latter layer 140b may be determined as appropriate according to the displacement, force, etc. required by the specifications. For example, in the case of an actuator, it is generally about 1 μm to 10 μm.
　後期層１４０ｂは、その基板温度を初期層１４０ａの場合より低くしているため、初期層１４０ａと比較して構成元素である鉛の欠損が生じ難い。一方、その基板温度が低いため、後期層１４０ｂが、ペロブスカイト型構造を形成するとは考え難いが、実際には、ほぼ完全なペロブスカイト型構造を形成する。これは、初期層１４０ａがほぼ完全なペロブスカイト構造を有しているため、初期層１４０ａを下地として、この上に連続して形成される後期層１４０ｂは、組成が同様であることにも助けられ、下地の格子定数に一致するように倣って、ほぼ完全にペロブスカイト構造となるものと推定される。 Since the late layer 140b has a lower substrate temperature than that of the initial layer 140a, defects of lead, which is a constituent element, are less likely to occur compared to the initial layer 140a. On the other hand, because the substrate temperature is low, the late layer 140b is unlikely to form a perovskite structure, but actually forms a nearly perfect perovskite structure. This is because the initial layer 140a has an almost perfect perovskite structure, and the late layer 140b continuously formed on the initial layer 140a as a base is also helped by the same composition. It is presumed that the perovskite structure almost completely follows the lattice constant of the base.
　このため、後期層１４０ｂは、初期層１４０ａと同等のほぼ完全なペロブスカイト型構造を有すると伴に、その構成元素においては、初期層１４０ａと比較して鉛の欠損が抑えられ、より所望の組成比（化学量論的組成比）に近い、元素の良好な構成を有するものとなっている。 Therefore, the late layer 140b has an almost complete perovskite structure equivalent to that of the initial layer 140a, and in the constituent elements, lead deficiency is suppressed as compared with the initial layer 140a, and a more desirable composition is obtained. It has a good composition of elements close to the ratio (stoichiometric composition ratio).
　従って、後期層１４０ｂは、良好な圧電特性を有し、その厚みを適宜定めることにより、仕様により必要とされる変位、力等に十分に対応出来るものである。また、後期層１４０ｂは、変位し難いＳｉ基板１１０から離れた位置に存在するため、センサ、アクチュエータとしての必要な特性を得る上で有利である。 Therefore, the late layer 140b has good piezoelectric characteristics, and can adequately cope with the displacement, force, etc. required by the specifications by appropriately determining its thickness. In addition, since the late layer 140b exists at a position away from the Si substrate 110 that is difficult to be displaced, it is advantageous in obtaining necessary characteristics as a sensor and an actuator.
　最後に、後期層１４０ｂ上にＰｔ又はＡｌ等で上部電極１５０を設けることにより圧電体素子１００が完成する。 Finally, the piezoelectric element 100 is completed by providing the upper electrode 150 with Pt or Al on the latter layer 140b.
　図４に本実施の形態で説明した圧電体薄膜をダイヤフラムに応用した圧電体素子３００の例を示す。Ｓｉ基板２１０の一部が円形に除去され窪み２１０ａが形成され、上部に薄い板状の部材が残され、この部材がダイヤフラム２１０ｂを成している。 FIG. 4 shows an example of a piezoelectric element 300 in which the piezoelectric thin film described in this embodiment is applied to a diaphragm. A part of the Si substrate 210 is removed in a circular shape to form a depression 210a, and a thin plate-like member is left on the upper part, and this member forms a diaphragm 210b.
　ダイヤフラム２１０ｂの窪み２１０ａ側と反対側の面上に、窪み２１０ａの形状に対応した円形状の初期層１４０ａ、後期層１４０ｂを形成する。後期層１４０ｂ上に上部電極１５０としてＰｔ膜がスパッタ法などで成膜されている。 A circular initial layer 140a and a late layer 140b corresponding to the shape of the recess 210a are formed on the surface of the diaphragm 210b opposite to the recess 210a. A Pt film is formed as the upper electrode 150 on the latter layer 140b by sputtering or the like.
　上部電極１５０と下部電極１３０と間に所定の電圧を加えると、圧電体薄膜１４０が左右方向に伸縮し、バイメタルの効果によりダイヤフラム２１０ｂを上下に湾曲させることができる。圧電体素子３００は、例えば窪み２１０ａに気体や液体を充填できるようにすると、ポンプなどのアクチュエータとして応用できる。 When a predetermined voltage is applied between the upper electrode 150 and the lower electrode 130, the piezoelectric thin film 140 expands and contracts in the left-right direction, and the diaphragm 210b can be bent up and down by the bimetal effect. The piezoelectric element 300 can be applied as an actuator such as a pump if the recess 210a can be filled with gas or liquid, for example.
　また、圧電体素子３００は、音波や超音波によりダイヤフラム２１０ｂが振動させられると、上記と反対の効果により上部電極１５０と下部電極１３０と間に電圧を発生し、この電圧の周波数や大きさを検出されるようにすることによって音波センサとして応用できる。 In addition, when the diaphragm 210b is vibrated by sound waves or ultrasonic waves, the piezoelectric element 300 generates a voltage between the upper electrode 150 and the lower electrode 130 due to an effect opposite to the above, and the frequency and magnitude of the voltage are reduced. By being detected, it can be applied as a sound wave sensor.
　これまで説明した圧電体薄膜の材料は、ＰＺＴに限定されることはなく、ＰＺＴにＮｂ（ニオブ）、Ｌａ（ランタン）、Ｍｎ（マンガン）などを添加したものでも良い。また、ＰＺＴの代わりに、ＰＮＴ（ニオブ酸チタン酸鉛）、ＰＭＮ－ＰＴ（マグネシウムニオブ酸チタン酸鉛）、ＰＺＮＴ（亜鉛ニオブ酸チタン酸鉛）など、鉛を含む材料でも良い。 The material of the piezoelectric thin film described so far is not limited to PZT, and may be one obtained by adding Nb (niobium), La (lanthanum), Mn (manganese), or the like to PZT. Instead of PZT, a material containing lead such as PNT (lead niobate titanate), PMN-PT (lead magnesium niobate titanate), or PZNT (lead zinc niobate titanate) may be used.
　上記に挙げた材料により形成される圧電体薄膜は、ＰＺＴを例に説明したペロブスカイト構造を取り、鉛の欠損が押さえられることには変わりはなく、何れもＰＺＴに劣らず良好な圧電特性を示す。また、一般的に基板温度と圧電体を構成する元素の組成比との関係において、温度が高くなると、本実施の形態の例に挙げた鉛に限らず構成元素の一部が欠損することが考えられ、本発明は鉛を有しない圧電体薄膜においても適用できる。 Piezoelectric thin films formed of the materials listed above have the perovskite structure described by taking PZT as an example, and there is no change in that lead deficiency is suppressed, and all show good piezoelectric characteristics that are not inferior to PZT. . In general, in the relationship between the substrate temperature and the composition ratio of the elements constituting the piezoelectric body, when the temperature is high, not only the lead listed in the example of the present embodiment, but part of the constituent elements may be lost. The present invention can be applied to a piezoelectric thin film that does not contain lead.
　また、製造装置２００は、スパッタ法を行うものとして説明したが、ＰＬＤ法、ＣＳＤ法及びＭＯＣＶＤ法を行うものとすることができる。 In addition, although the manufacturing apparatus 200 has been described as performing the sputtering method, the manufacturing apparatus 200 can perform the PLD method, the CSD method, and the MOCVD method.
　図１に示す圧電体素子１００を、図２に示す製造装置２００を用い、図３に示すフローチャートに従って製造した。 The piezoelectric element 100 shown in FIG. 1 was manufactured according to the flowchart shown in FIG. 3 using the manufacturing apparatus 200 shown in FIG.
　＜１００＞に配向したＳｉ単結晶板（厚み３５０μｍ）をＳｉ基板１１０とし、このＳｉ基板１１０に熱酸化膜１２０（厚み０．１μｍ）及び下部電極１３０（Ｐｔ、厚み０．１μｍ）を準備した。また、ターゲット２として、組成がＰｂ（Ｚｒ０．５２Ｔｉ０．４８）Ｏ３とするＰＺＴ材料からなるものを準備した。 A Si single crystal plate (thickness 350 μm) oriented in <100> was used as a Si substrate 110, and a thermal oxide film 120 (thickness 0.1 μm) and a lower electrode 130 (Pt, thickness 0.1 μm) were prepared on the Si substrate 110. . In addition, a target 2 made of a PZT material having a composition of Pb (Zr 0.52 Ti 0.48 ) O 3 was prepared.
　準備した上記のＳｉ基板１１０及びターゲット２を図２で示した製造装置２００内に配置した。 The prepared Si substrate 110 and target 2 were arranged in the manufacturing apparatus 200 shown in FIG.
　真空チャンバー１内を真空にした後、Ｓｉ基板１１０を加熱し、第１の基板温度Ｔ１が６００℃となるように設定した。Ｓｉ基板１１０の温度が６００℃に達した後、この温度を維持した状態で、ＡｒとＯ２の混合ガスを真空チャンバー１内に導入し、厚み０．０１μｍの初期層１４０ａを形成した。 After the vacuum chamber 1 was evacuated, the Si substrate 110 was heated and set so that the first substrate temperature T1 was 600 ° C. After the temperature of the Si substrate 110 reached 600 ° C., while maintaining this temperature, a mixed gas of Ar and O 2 was introduced into the vacuum chamber 1 to form an initial layer 140 a having a thickness of 0.01 μm.
　次に、Ｓｉ基板１１０の温度を変更し、第２の基板温度Ｔ２が５５０℃となるように設定した。Ｓｉ基板１１０の温度が５５０℃に達した後、この温度を維持した状態で、ＡｒとＯ２の混合ガスを真空チャンバー１内に導入し、厚み２μｍの後期層１４０ｂを形成した。 Next, the temperature of the Si substrate 110 was changed, and the second substrate temperature T2 was set to 550 ° C. After the temperature of the Si substrate 110 reaches 550 ° C., while maintaining this temperature, a mixed gas of Ar and O 2 was introduced into the vacuum chamber 1 to form a late layer 140b having a thickness of 2 [mu] m.
　製造した圧電体薄膜１４０は、Ｘ線回折装置による結晶構造解析の結果、後期層１４０ｂがほぼ完全なペロブスカイト構造であることが確認できた。また、蛍光Ｘ線組成分析装置による測定の結果、後期層１４０ｂの組成はターゲット２の組成比とほぼ同一であって、鉛の欠損がほとんど無いことが確認できた。 As a result of crystal structure analysis by the X-ray diffractometer, it was confirmed that the late layer 140b had an almost perfect perovskite structure. Further, as a result of measurement using a fluorescent X-ray composition analyzer, it was confirmed that the composition of the late layer 140b was almost the same as the composition ratio of the target 2 and there was almost no deficiency of lead.
　この後、上部電極１５０として、Ｐｔ膜（厚み０．１μｍ）を設け、圧電体素子１００とした。 Thereafter, a Pt film (thickness: 0.1 μm) was provided as the upper electrode 150 to obtain the piezoelectric element 100.
　圧電体素子１００の圧電定数、比誘電率を測定した結果、それぞれ圧電定数ｄ３１＝－１５０ｐｍ／Ｖ、比誘電率が７００であって、圧電素子として十分に機能することが確認できた。 As a result of measuring the piezoelectric constant and relative permittivity of the piezoelectric element 100, the piezoelectric constant d31 = −150 pm / V and the relative permittivity were 700, respectively, and it was confirmed that the piezoelectric element functioned sufficiently.
　１００　圧電体素子
　１１０　Ｓｉ基板
　１２０　熱酸化膜
　１３０　下部電極
　１４０　圧電体薄膜
　１４０ａ　初期層
　１４０ｂ　後期層
　１５０　上部電極 DESCRIPTION OF SYMBOLS 100 Piezoelectric element 110 Si substrate 120 Thermal oxide film 130 Lower electrode 140 Piezoelectric thin film 140a Initial layer 140b Late layer 150 Upper electrode

Claims (10)

  1. 　複数の元素による所定の結晶構造を有する圧電体の薄膜を基板の上に形成する圧電体薄膜の製造方法において、
    　前記基板の上に、第１の基板温度で前記圧電体の初期層を形成する第１工程と、
    　前記初期層に連続して、第２の基板温度で前記圧電体の後期層を形成する第２工程と、を含み、
    　前記第１の基板温度は、前記第１の基板温度で前記初期層を形成した場合の初期層の結晶構造が、前記第２の基板温度で前記初期層を形成した場合の初期層の結晶構造よりも、前記所定の結晶構造に近くなるように形成される温度であり、
    　前記第２の基板温度は、該後期層の圧電体を形成する複数の元素の組成比が、前記初期層の組成比より、化学量論的組成比に近くなるように形成される温度であることを特徴とする圧電体薄膜の製造方法。     In a piezoelectric thin film manufacturing method for forming a piezoelectric thin film having a predetermined crystal structure with a plurality of elements on a substrate,
    A first step of forming an initial layer of the piezoelectric body on the substrate at a first substrate temperature;
    Forming a latter layer of the piezoelectric body at a second substrate temperature in succession to the initial layer, and
    As for the first substrate temperature, the crystal structure of the initial layer when the initial layer is formed at the first substrate temperature is the crystal structure of the initial layer when the initial layer is formed at the second substrate temperature. Rather than the predetermined crystal structure.
    The second substrate temperature is a temperature at which the composition ratio of a plurality of elements forming the piezoelectric material of the latter layer is closer to the stoichiometric composition ratio than the composition ratio of the initial layer. A method for producing a piezoelectric thin film, comprising:
  2. 　前記所定の結晶構造は、ペロブスカイト型結晶構造であることを特徴とする請求項１に記載の圧電体薄膜の製造方法。 2. The method for manufacturing a piezoelectric thin film according to claim 1, wherein the predetermined crystal structure is a perovskite crystal structure.
  3. 　前記圧電体は、鉛を含む酸化物であり、
    　前記第１の基板温度は、前記第２の基板温度より高いことを特徴とする請求項１に記載の圧電体薄膜の製造方法。     The piezoelectric body is an oxide containing lead,
    2. The method for manufacturing a piezoelectric thin film according to claim 1, wherein the first substrate temperature is higher than the second substrate temperature.
  4. 　前記後期層の厚みは、前記初期層の厚みより厚いことを特徴とする請求項１に記載の圧電体薄膜の製造方法。 The method for manufacturing a piezoelectric thin film according to claim 1, wherein the thickness of the latter layer is larger than the thickness of the initial layer.
  5. 　前記初期層及び前記後期層の前記圧電体は、スパッタリング法を用いて形成されることを特徴とする請求項１に記載の圧電体薄膜の製造方法。 2. The method for manufacturing a piezoelectric thin film according to claim 1, wherein the piezoelectric bodies of the initial layer and the late layer are formed by a sputtering method.
  6. 　複数の元素による所定の結晶構造を有する圧電体の薄膜が基板の上に形成されている圧電体薄膜において、
    　前記圧電体薄膜は、初期層と後期層とを有し、
    　前記後期層の圧電体を形成する複数の元素の組成比は、前記初期層の組成比より化学量論的組成比に近いことを特徴とする圧電体薄膜。     In a piezoelectric thin film in which a piezoelectric thin film having a predetermined crystal structure of a plurality of elements is formed on a substrate,
    The piezoelectric thin film has an initial layer and a late layer,
    A piezoelectric thin film characterized in that a composition ratio of a plurality of elements forming the piezoelectric layer of the latter layer is closer to a stoichiometric composition ratio than a composition ratio of the initial layer.
  7. 　前記所定の結晶構造は、ペロブスカイト型結晶構造であることを特徴とする請求項６に記載の圧電体薄膜。 The piezoelectric thin film according to claim 6, wherein the predetermined crystal structure is a perovskite crystal structure.
  8. 　前記圧電体は、鉛を含む酸化物であることを特徴とする請求項６に記載の圧電体薄膜。 The piezoelectric thin film according to claim 6, wherein the piezoelectric body is an oxide containing lead.
  9. 　前記後期層の厚みは、前記初期層の厚みより厚いことを特徴とする請求項６に記載の圧電体薄膜。 The piezoelectric thin film according to claim 6, wherein the thickness of the latter layer is larger than the thickness of the initial layer.
  10. 　基板と、
    　前記基板上に形成された、複数の元素による所定の結晶構造を有する圧電体薄膜とを有し、
    　前記圧電体薄膜は、初期層と後期層とを有し、
    　前記後期層の圧電体を形成する複数の元素の組成比は、前記初期層の組成比より化学量論的組成比に近いことを特徴とする圧電体素子。     A substrate,
    A piezoelectric thin film having a predetermined crystal structure formed of a plurality of elements formed on the substrate;
    The piezoelectric thin film has an initial layer and a late layer,
    The piezoelectric element, wherein a composition ratio of a plurality of elements forming the piezoelectric layer of the latter layer is closer to a stoichiometric composition ratio than a composition ratio of the initial layer.
PCT/JP2010/069409 2009-11-17 2010-11-01 Method of manufacturing piezoelectric thin film, and piezoelectric thin film and piezoelectric element WO2011062050A1 (en)

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JPH09256139A (en) * 1996-03-22 1997-09-30 Fuji Electric Co Ltd Production of zinc oxide film
JP2000169297A (en) * 1998-09-29 2000-06-20 Sharp Corp Production of thin ferroelectric oxide film, thin ferroelectric oxide film and thin ferroelectric oxide film element
JP2004096050A (en) * 2002-09-04 2004-03-25 Seiko Epson Corp Manufacturing method for ferroelectric device, ferroelectric memory using the same, piezoelectric element, ink jet head, and ink jet printer
JP2005333108A (en) * 2004-04-02 2005-12-02 Matsushita Electric Ind Co Ltd Piezoelectric element, ink jet head, angular rate sensor, and ink jet type recording device
JP2005354026A (en) * 2004-05-10 2005-12-22 Matsushita Electric Ind Co Ltd Piezoelectric element, ink jet head, and manufacturing method of these, and ink jet type recorder

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JPH065948A (en) * 1992-06-22 1994-01-14 Rohm Co Ltd Manufacture of ferroelectric thin film
JPH09256139A (en) * 1996-03-22 1997-09-30 Fuji Electric Co Ltd Production of zinc oxide film
JP2000169297A (en) * 1998-09-29 2000-06-20 Sharp Corp Production of thin ferroelectric oxide film, thin ferroelectric oxide film and thin ferroelectric oxide film element
JP2004096050A (en) * 2002-09-04 2004-03-25 Seiko Epson Corp Manufacturing method for ferroelectric device, ferroelectric memory using the same, piezoelectric element, ink jet head, and ink jet printer
JP2005333108A (en) * 2004-04-02 2005-12-02 Matsushita Electric Ind Co Ltd Piezoelectric element, ink jet head, angular rate sensor, and ink jet type recording device
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