WO2017149675A1 - Piezoelectric film, method for producing same, and piezoelectric component using piezoelectric film - Google Patents

Piezoelectric film, method for producing same, and piezoelectric component using piezoelectric film Download PDF

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Publication number
WO2017149675A1
WO2017149675A1 PCT/JP2016/056303 JP2016056303W WO2017149675A1 WO 2017149675 A1 WO2017149675 A1 WO 2017149675A1 JP 2016056303 W JP2016056303 W JP 2016056303W WO 2017149675 A1 WO2017149675 A1 WO 2017149675A1
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piezoelectric
atoms
thin film
film
piezoelectric film
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PCT/JP2016/056303
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French (fr)
Japanese (ja)
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圭一 梅田
孝昭 水野
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株式会社村田製作所
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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
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/38—Nitrides
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator

Definitions

  • the present invention relates to a piezoelectric film, a manufacturing method thereof, and a piezoelectric component using the piezoelectric film.
  • a piezoelectric film made of aluminum nitride (hereinafter also referred to as “AlN piezoelectric film”) has a high Young's modulus and good Q value and frequency temperature coefficient characteristics.
  • the AlN piezoelectric film has a low piezoelectric constant. Therefore, when an AlN piezoelectric film is used as a piezoelectric material for a MEMS device or the like, a higher operating voltage is required than when other piezoelectric materials such as zinc oxide are used.
  • Patent Document 1 discloses a technique for improving the piezoelectric constant of an AlN piezoelectric film.
  • the piezoelectric constant of the AlN piezoelectric film is improved by adding an appropriate amount of scandium to the AlN piezoelectric film and changing the crystal structure of AlN.
  • the present invention has been made in view of such circumstances, and an object of the present invention is to improve the piezoelectric constant while suppressing the generation of film stress in an AlN piezoelectric film.
  • a piezoelectric film according to one aspect of the present invention is a piezoelectric film made of an aluminum nitride crystal having a wurtzite structure, and the aluminum nitride crystal contains scandium atoms and boron atoms, and a part of the aluminum atoms in the aluminum nitride crystal Has a structure substituted with a scandium atom or a boron atom.
  • the piezoelectric constant in the AlN piezoelectric film, the piezoelectric constant can be improved while suppressing the generation of film stress.
  • FIG. 1 is a plan view schematically showing an example of a piezoelectric device 10 (an example of a piezoelectric component) formed using the piezoelectric film according to the first embodiment of the present invention.
  • the piezoelectric device 10 is a device for use in a MEMS vibrator manufactured using the MEMS technology, and vibrates in the plane in the XY plane in the orthogonal coordinate system of FIG.
  • the piezoelectric film according to the present invention is not limited to a MEMS vibrator that vibrates in a plane, and may be used for a thickness longitudinal vibrator or the like.
  • the piezoelectric device 10 includes a vibrating part 120, a holding part 140, and a holding arm 110.
  • the vibrating unit 120 has a plate-like contour that extends in a plane along the XY plane.
  • the vibrating unit 120 is provided inside the holding unit 140, and a space is formed between the vibrating unit 120 and the holding unit 140 at a predetermined interval.
  • the holding unit 140 is formed in a rectangular frame shape so as to surround the outside of the vibrating unit 120 along the XY plane.
  • the holding part 140 is integrally formed from a prismatic frame.
  • maintenance part 140 should just be provided in at least one part of the circumference
  • the holding arm 110 is provided inside the holding unit 140 and connects the vibrating unit 120 and the holding unit 140.
  • FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG.
  • the vibration unit 120 is formed by laminating the lower electrode E1 on the substrate F1.
  • a piezoelectric thin film F2 (which is an example of a piezoelectric film) is laminated on the lower electrode E1 so as to cover the lower electrode E1, and an upper electrode E2 is laminated on the piezoelectric thin film F2. Yes.
  • the substrate F1 includes an oxidized Si (silicon) layer F11 and an Si layer F12.
  • the oxidized Si layer F11 is a SiO 2 layer having a thickness of about 40 nm, for example.
  • the Si layer F12 is formed of, for example, a degenerated n-type Si semiconductor having a thickness of about 10 ⁇ m and a resistivity of about 1 m ⁇ ⁇ cm (concentration 7 ⁇ 10 19 / cm 3 ).
  • the Si layer F12 can contain P (phosphorus), As (arsenic), Sb (antimony), or the like as an n-type dopant.
  • the lower electrode E1 and the upper electrode E2 are formed using, for example, Mo (molybdenum), Al (aluminum), Ag (gold), or the like.
  • the thicknesses of the lower electrode E1 and the upper electrode E2 are, for example, about 100 nm.
  • the piezoelectric thin film F2 is a piezoelectric thin film that converts an applied voltage into vibration.
  • the thickness of the piezoelectric thin film F2 is, for example, about 1000 nm.
  • the piezoelectric thin film F2 expands and contracts in the in-plane direction of the XY plane according to the electric field applied to the piezoelectric thin film F2 by the lower electrode E1 and the upper electrode E2. Due to the expansion and contraction of the piezoelectric thin film F2, the vibration unit 120 undergoes contour vibration in the Y-axis direction.
  • the piezoelectric thin film F2 is made of AlN (aluminum nitride) crystal having a wurtzite structure.
  • the AlN crystal in the piezoelectric thin film F2 includes Sc (scandium) atoms and B (boron) atoms, and has a structure in which some Al atoms in the AlN crystal are replaced with Sc atoms or B atoms. More specifically, in the AlN crystal constituting the piezoelectric thin film F2, Sc atoms or B atoms exist at the positions of Al atoms.
  • the ratio of the number of B atoms to the total amount of Al atoms and B atoms in the piezoelectric thin film F2 (hereinafter also referred to as “the composition ratio of B with respect to Al”) is 0 at%. It is largely 13 at% or less. More preferably, the composition ratio of B to Al is greater than 0 at% and less than or equal to 12 at%, and more preferably greater than 0 at% and less than or equal to 8 at%. In this case, the piezoelectric thin film F2 can reduce the film stress generated by replacing Al with Sc.
  • the ratio of the number of Sc atoms to the total amount of Al atoms and Sc atoms in the piezoelectric thin film F2 (hereinafter also referred to as “the composition ratio of Sc to Al”) is 0 at. % And not more than 58 at%, more preferably not less than 44 at% and not more than 52.5 at% In this case, the piezoelectric thin film F2 can improve the piezoelectric constant.
  • the composition ratio of the piezoelectric thin film F2 is B according to the X Sc Y Al 1-X- Y N (0 ⁇ X ⁇ 14,0 ⁇ Y ⁇ 52) can suppress the generation of film stress In addition, the piezoelectric constant can be improved.
  • a preferable X value range is 0 ⁇ X ⁇ 14, and more preferably 0 ⁇ X ⁇ 5.5, more preferably 0 ⁇ X ⁇ 5.2, and even more preferably 0 ⁇ X ⁇ 4.
  • the preferable range of the Y value at this time is 0 ⁇ Y ⁇ 52, more preferably 38 ⁇ Y ⁇ 50.
  • the preferred combination of the X value and the Y value in the composition ratio B X Sc Y Al 1-XY N of the piezoelectric thin film F2 according to this embodiment is 0 ⁇ X ⁇ 14 and 0 ⁇ Y ⁇ 52. More preferably 0 ⁇ X ⁇ 5.5 and 0 ⁇ Y ⁇ 52, more preferably 0 ⁇ X ⁇ 5.2 and 0 ⁇ Y ⁇ 52, and still more preferably 0 ⁇ X ⁇ 4, 38 ⁇ Y ⁇ 50.
  • the piezoelectric thin film F2 is formed on the substrate F1 by sputtering.
  • sputtering method for example, two types of sputtering, that is, ternary sputtering using each of Al, Sc, and B as a target and single sputtering using a BScAl alloy as a target can be used.
  • the piezoelectric thin film F2 is formed by ternary sputtering, an Al simple metal, an Sc simple metal, and a sintered body of BN (boron nitride) are used as targets.
  • the pressure in the vacuum chamber of the sputtering apparatus is preferably from 0.1 Pa to 0.5 Pa, and the temperature is preferably from room temperature to 300 ° C.
  • a gas mixture of Ar (argon) gas and nitrogen gas is introduced into the vacuum chamber.
  • the nitrogen concentration in the mixed gas is preferably 30% or more and 70% or less.
  • the composition ratio of B to Al and the composition ratio of Sc to Al in the piezoelectric thin film F2 formed by sputtering can be adjusted by adjusting the power supplied to the target.
  • the power supplied to the Al target is, for example, 100 W or more and 300 W or less.
  • the power supplied to the BN target is 0 W or more and 200 W or less when the B composition ratio to Al is greater than 0 at% and 13 at% or less, and the B composition ratio to Al is greater than 0 at% and less than 12 at%. Is 0 W or more and 180 W or less, and when the composition ratio of B to Al is more than 0 at% and 8 at% or less, it is 0 W or more and 100 W or less.
  • the power supplied to the Sc target is 0 W or more and 300 W or less when the composition ratio of Sc to Al is greater than 0 at% and 58 at% or less, and the composition ratio of Sc to Al is 44 at% or more and 52.5 at%. In the case of the following, it is 200 W or more and 300 W or less.
  • the piezoelectric thin film F2 according to this embodiment is formed on the substrate F1.
  • the pressure in the vacuum chamber of the sputtering apparatus is preferably 0.1 Pa or more and 0.5 Pa or less, and the temperature is preferably room temperature or more and 300 ° C. or less.
  • the nitrogen concentration in Ar (argon) gas introduced into the vacuum chamber is preferably 30% or more and 70% or less.
  • the power supplied to the target is preferably 500 W or more and 1200 W or less.
  • composition ratio of B to Al and the composition ratio of Sc to Al in the formed piezoelectric thin film F2 can be adjusted by adjusting the composition ratio in the target alloy.
  • the composition ratio B: Sc: Al of the BScAl alloy is preferably 45: 50: 5.
  • the piezoelectric thin film F2 according to this embodiment is formed on the substrate F1.
  • FIG. 3 is a graph showing the results of Experiment 1.
  • the horizontal axis of the graph of FIG. 3 indicates the number of the BN member used as a target, and the vertical axis indicates the content (at%) of Al, Sc, B in the formed piezoelectric thin film F2.
  • a piezoelectric thin film was formed by ternary sputtering using the following parameters. ⁇ Pressure 0.2Pa ⁇ Temperature 200 °C ⁇ Time 2 hours ⁇ Nitrogen concentration 50%
  • the composition ratio of B to Al was adjusted by setting the power applied to the BN target to 100W.
  • the composition ratio of Sc with respect to Al was adjusted by setting the electric power given to a BN target to 300W.
  • the power applied to the Al target is 300 W in this experimental example.
  • the Al, Sc, and B contents in the piezoelectric thin film F2 were measured using X-ray photoelectron spectroscopy. As apparent from FIG. 3, the Al content decreases as the B content increases. On the other hand, the Sc content is constant regardless of the B content. From this result, it is understood that the B atom is replaced with the Al atom.
  • the ionic radius of B is about 11 pm, the ionic radius of Al is 39 pm, and the ionic radius of Sc is about 75 pm. That is, the ionic radius of B is closer to the ionic radius of Al than Sc. Therefore, from the viewpoint of energy stability, it is considered that B and Al having a close ionic radius are replaced.
  • FIG. 4 is a graph showing the relationship between the doping amount of B and the Young's modulus of the piezoelectric thin film F2.
  • the horizontal axis represents the ratio of the atomic weight of Sc to the sum of the atomic weight of Al and the atomic weight of Sc in the piezoelectric thin film F2, and the vertical axis represents the Young's modulus of the piezoelectric thin film F2.
  • the graph showing the measurement points with diamonds shows the case where the composition ratio of B to Al is 0 at%
  • the graph showing the measurement points with squares shows the case where the composition ratio of B to Al is 12.5 at%
  • the graph showing the measurement points with triangles shows the case where the composition ratio of B to Al is 25 at%.
  • X-ray photoelectron spectroscopy was used to identify the composition ratio of B and Sc to Al in the formed piezoelectric thin film F2.
  • the Young's modulus of the piezoelectric thin film F2 was calculated from the resonance frequency of the piezoelectric resonator or measured by the nanoindentation method.
  • a piezoelectric thin film was formed by ternary sputtering using the following parameters. ⁇ Pressure 0.2Pa ⁇ Temperature 300 °C ⁇ Time 2 hours ⁇ Nitrogen concentration 50% The composition ratio of B to Al was adjusted by setting the power applied to the BN target to 100W. Moreover, the composition ratio of Sc with respect to Al was adjusted by setting the electric power given to a BN target to 300W. Furthermore, the power applied to the Al target is 300 W in this experimental example.
  • Experiment 3 Measurement of piezoelectric constant and film stress
  • Experiment 3 the effect of the doping amount of B on the piezoelectric constant and film stress in the piezoelectric thin film F2 was verified.
  • Experiment 3 (FIGS. 5 and 6), measurements were performed using three types of piezoelectric thin film samples 1 to 3 formed at the composition ratios shown in Table 1 below. In the graphs of FIGS. 5 and 6, the points indicated by diamonds or squares are the measurement results of samples 1 to 3.
  • the piezoelectric constant of the piezoelectric thin film F2 was measured with a Piezo System Meter PM300.
  • the film stress of the piezoelectric thin film F2 was measured by KLA-Tencor FLX-2320.
  • the method for identifying the composition ratio of B and Sc to Al in the formed piezoelectric thin film F2 is the same as in Experiment 2.
  • the piezoelectric thin film of Sample 1 was formed by performing ternary sputtering with the following parameters. ⁇ Pressure 0.4Pa ⁇ Temperature 200 °C ⁇ Time 2 hours ⁇ Nitrogen concentration 50% ⁇ Power Al 300 [W] BN 50 [W] Sc 250 [W]
  • the piezoelectric thin film of Sample 2 was formed by performing ternary sputtering with the following parameters. ⁇ Pressure 0.2Pa ⁇ Temperature 200 °C ⁇ Time 2 hours ⁇ Nitrogen concentration 50% ⁇ Power Al 300 [W] BN 70 [W] Sc 280 [W]
  • the piezoelectric thin film of Sample 3 was formed by performing ternary sputtering with the following parameters. ⁇ Pressure 0.2Pa ⁇ Temperature 200 °C ⁇ Time 2 hours ⁇ Nitrogen concentration 50% ⁇ Power Al 300 [W] BN 90 [W] Sc 300 [W]
  • FIG. 5 is a graph showing the relationship between the doping amount of B, the piezoelectric constant, and the film stress.
  • the horizontal axis represents the composition ratio of B to Al
  • the vertical axis represents the piezoelectric constant and the film stress.
  • the straight line indicated by the dotted line K is the piezoelectric constant in the Sc Y Al 1-Y N film of the comparative example in which only B is doped without doping B
  • the straight line indicated by the dotted line L is the Sc Y of the comparative example.
  • This is the film stress in the Al 1-Y N film.
  • the piezoelectric constant is about 20 pC / N and the film stress is ⁇ 1400 Mpa or more.
  • Sc is an atom having an ionic radius larger than that of Al. Therefore, when Al in the AlN crystal is replaced with Sc, the crystal lattice in the wurtzite structure of AlN is distorted so as to partially swell. As a result, a strong compressive stress is generated in the Sc Y Al 1-Y N film of the comparative example doped only with Sc.
  • the range of the composition ratio of B to Al that can reduce the film stress and maintain a high piezoelectric constant is greater than 0 at% and less than or equal to 13 at%, more preferably greater than 0 at% and 12 at%. It is below, More preferably, it is larger than 0 at% and below 8 at%.
  • the piezoelectric constant is improved while suppressing the generation of film stress.
  • the range of the value of X in the composition ratio of the piezoelectric thin film F2 according to the present embodiment is more preferably 0 ⁇ X ⁇ 5.2, and more preferably 0 ⁇ X ⁇ 4.
  • FIG. 6 is a graph showing the relationship between the Sc doping amount and the piezoelectric constant.
  • the horizontal axis represents the composition ratio of Sc to Al, and the vertical axis represents the piezoelectric constant.
  • the straight line indicated by the dotted line M is the piezoelectric constant in the AlN film of the comparative example in which neither B nor Sc is doped.
  • the graph indicated by the dotted line shows the piezoelectric constant of the piezoelectric thin film F2 of this embodiment, the graph shown by the solid line in comparative examples doped Sc only without doping B Sc Y Al 1- It shows the piezoelectric constant in the Y N film.
  • the piezoelectric constant of the piezoelectric thin film F2 according to this embodiment exceeds the piezoelectric constant of the AlN film of the comparative example even when the composition ratio of Sc to Al is in the range of 50% or more.
  • the range of the composition ratio of Sc to Al that can maintain a piezoelectric constant higher than the piezoelectric constant of the AlN film is greater than 0 at% and less than or equal to 58 at%, more preferably 44 at% or more and 52.5 at% or less. That is, when 0 ⁇ Y ⁇ 52 in the composition ratio B X Sc Y Al 1-XY N of the piezoelectric thin film F2 according to this embodiment, a piezoelectric constant higher than the piezoelectric constant of the AlN film can be maintained.
  • the range of the value of Y in the composition ratio of the piezoelectric thin film F2 according to this embodiment is more preferably 0 ⁇ Y ⁇ 52, and further preferably 38 ⁇ Y ⁇ 50.
  • FIG. 7 is a diagram showing an appearance of the piezoelectric device 20 formed using the piezoelectric thin film F2 according to the present embodiment.
  • the piezoelectric device 20 is a device for configuring a MEMS microphone that converts sound pressure into an electrical signal, and includes a diaphragm 210, a support portion 211, and a piezoelectric portion 212.
  • the piezoelectric device 20 is divided into two by a minute slit 213 having a size of about 1 ⁇ m or less, for example.
  • the diaphragm 210 is a thin film that vibrates due to sound pressure, and is formed of silicon (Si).
  • the diaphragm 210 has a substantially square shape, and the lower portions of a pair of opposing sides 214 and 215 are supported by the support portion 211. That is, the diaphragm 210 has a double-supported beam structure.
  • Si forming the vibration plate 210 is a degenerated n-type Si semiconductor having a resistivity of 1.5 m ⁇ ⁇ cm or less, and has a function as a lower electrode of the piezoelectric portion 212 as described later.
  • the piezoelectric portion 212 is disposed along a portion of the diaphragm 210 that is supported by the support portion 211. In the configuration shown in FIG. 7, the four piezoelectric portions 212 are disposed on the vibration plate 210, but the number of piezoelectric portions 212 is not limited to this. In the configuration shown in FIG. 7, the end of the piezoelectric portion 212 is disposed on the side 214 or the side 215, but the end may be disposed away from the side 214 or the side 215.
  • FIG. 8 is a cross-sectional view of the piezoelectric device 20 taken along line NN ′ shown in FIG.
  • the support part 211 includes a base body 220 and an insulating layer 221.
  • the base body 220 is made of, for example, silicon (Si).
  • the insulating layer 221 is made of, for example, silicon oxide (SiO 2).
  • the diaphragm 210 is formed on the support portion 211 formed in this way.
  • the piezoelectric portion 212 disposed along the portion of the diaphragm 210 supported by the support portion 211 includes a piezoelectric thin film F2, an upper electrode E2, and wirings 222 and 223.
  • the piezoelectric thin film F2 is disposed on the diaphragm 210 so as to vibrate with the vibration of the diaphragm 210.
  • the ratio of the width (D) of the vibrating portion of the piezoelectric thin film F2 to the width (C) from the center of the diaphragm 210 to the support portion 211 can be, for example, about 40%.
  • the width C can be about 300 ⁇ m and the width D can be about 120 ⁇ m.
  • An upper electrode E2 is disposed on the upper side of the piezoelectric thin film F2.
  • the upper electrode E2 can have a thickness of about 50 nm.
  • the upper electrode E2 can have a structure having a tensile stress. By giving the upper electrode E2 a tensile stress, the stress in the piezoelectric portion 212 is corrected, and deformation of the diaphragm 210 can be suppressed.
  • the wiring 222 is electrically connected to the upper electrode E2.
  • the wiring 223 is electrically connected to the lower electrode (the diaphragm 210).
  • the wirings 222 and 223 are formed using, for example, gold (Au), platinum (Pt), titanium (Ti), aluminum (Al), or the like.
  • the piezoelectric thin film F2 vibrates as the diaphragm 210 vibrates due to sound pressure.
  • a voltage corresponding to the vibration of the piezoelectric thin film F ⁇ b> 2 is output via the wirings 222 and 223 of the piezoelectric portion 212.
  • the piezoelectric thin film F2 is a piezoelectric film made of an AlN crystal having a wurtzite structure, and the AlN crystal contains Sc atoms and B atoms, and some Al atoms in the AlN crystal. Has a structure substituted with Sc atom or B atom. Thereby, a piezoelectric film capable of improving the piezoelectric constant while suppressing the generation of film stress can be obtained.
  • the ratio of the number of B atoms to the total amount of the number of Al atoms and the number of B atoms in the piezoelectric thin film F2 is greater than 0 at% and not more than 13 at%. More preferably, it is more than 0 at% and not more than 12 at%, and more preferably more than 0 at% and not more than 8 at%. In this case, generation of film stress can be suppressed in the piezoelectric thin film F2.
  • the ratio of the number of Sc atoms to the total amount of the number of Al atoms and the number of Sc atoms in the piezoelectric thin film F2 is greater than 0 at% and not more than 58 at%. It is preferable that it is greater than 44 at% and more preferably 52.5 at% or less. In this case, the piezoelectric constant can be improved in the piezoelectric thin film F2.
  • the ratio of the number of B atoms to the total amount of the number of Al atoms, the number of B atoms, and the number of Sc atoms in the piezoelectric thin film F2 is from 0 at%. It is preferably 5.5 at% or less. In this case, generation of film stress can be suppressed in the piezoelectric thin film F2.
  • the ratio of the number of Sc atoms to the total amount of the number of Al atoms, the number of B atoms, and the number of Sc atoms in the piezoelectric thin film F2 is 0 at% or more. It is preferable that it is 50 at% or less. In this case, the piezoelectric constant can be improved in the piezoelectric thin film F2.
  • a piezoelectric device includes the above-described piezoelectric thin film F2. Thereby, in the piezoelectric device, it is possible to improve the piezoelectric constant while suppressing generation of film stress.
  • the piezoelectric film manufacturing method manufactures the above-described piezoelectric thin film F2 on the substrate F1, using an alloy composed of Al, B, and Sc as a target.
  • the above-described piezoelectric thin film F2 is formed on the substrate F1 using a target made of Al, a target made of B, and a target made of scandium.
  • each embodiment described above is for facilitating understanding of the present invention, and is not intended to limit the present invention.
  • the present invention can be changed / improved without departing from the spirit thereof, and the present invention includes equivalents thereof.
  • those obtained by appropriately modifying the design of each embodiment by those skilled in the art are also included in the scope of the present invention as long as they include the features of the present invention.
  • each element included in each embodiment and its arrangement, material, condition, shape, size, and the like are not limited to those illustrated, and can be changed as appropriate.
  • Each embodiment is an exemplification, and it is needless to say that a partial replacement or combination of configurations shown in different embodiments is possible, and these are also included in the scope of the present invention as long as they include the features of the present invention. .

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Abstract

Provided is an AlN piezoelectric film wherein the piezoelectric constant is improved, while suppressing the generation of a film stress. A piezoelectric film which is formed of an aluminum nitride crystal having a wurtzite structure, and wherein the aluminum nitride crystal has a structure in which scandium atoms and boron atoms are contained and some of aluminum atoms in the aluminum nitride crystal are substituted by scandium atoms or boron atoms.

Description

圧電膜、その製造方法、及び圧電膜を用いた圧電部品Piezoelectric film, manufacturing method thereof, and piezoelectric component using the piezoelectric film
　本発明は、圧電膜、その製造方法、及び圧電膜を用いた圧電部品に関する。 The present invention relates to a piezoelectric film, a manufacturing method thereof, and a piezoelectric component using the piezoelectric film.
　窒化アルミニウムから成る圧電膜（以下、「ＡｌＮ圧電膜」とも呼ぶ。）は、高いヤング率を有し、またＱ値や周波数温度係数の特性が良好である。他方で、ＡｌＮ圧電膜は、圧電定数が低い。そのため、ＭＥＭＳデバイス等にＡｌＮ圧電膜を圧電材料として用いる場合、酸化亜鉛等の他の圧電材料を用いる場合よりも高い動作電圧が必要である。 A piezoelectric film made of aluminum nitride (hereinafter also referred to as “AlN piezoelectric film”) has a high Young's modulus and good Q value and frequency temperature coefficient characteristics. On the other hand, the AlN piezoelectric film has a low piezoelectric constant. Therefore, when an AlN piezoelectric film is used as a piezoelectric material for a MEMS device or the like, a higher operating voltage is required than when other piezoelectric materials such as zinc oxide are used.
　特許文献１には、ＡｌＮ圧電膜の圧電定数を向上させるための技術が開示されている。特許文献１には、ＡｌＮ圧電膜にスカンジウムを適量添加して、ＡｌＮの結晶構造を変化させることで、ＡｌＮ圧電膜の圧電定数を向上させている。 Patent Document 1 discloses a technique for improving the piezoelectric constant of an AlN piezoelectric film. In Patent Document 1, the piezoelectric constant of the AlN piezoelectric film is improved by adding an appropriate amount of scandium to the AlN piezoelectric film and changing the crystal structure of AlN.
特開２００９－１０９２６号公報JP 2009-10926 A
　しかしながら、特許文献１に記載の方法では、スカンジウムの添加によってＡｌＮ結晶構造が歪むことにより、ＡｌＮ圧電膜の圧電定数は向上する一方で、強い圧縮応力（膜応力）が発生してしまう。 However, in the method described in Patent Document 1, the AlN crystal structure is distorted by the addition of scandium, whereby the piezoelectric constant of the AlN piezoelectric film is improved, but a strong compressive stress (film stress) is generated.
　本発明はこのような事情に鑑みてなされたものであり、ＡｌＮ圧電膜において、膜応力の発生を抑制しながら、圧電定数の向上させることを目的とする。 The present invention has been made in view of such circumstances, and an object of the present invention is to improve the piezoelectric constant while suppressing the generation of film stress in an AlN piezoelectric film.
　本発明の一側面に係る圧電膜は、ウルツ鉱構造を有する窒化アルミニウム結晶からなる圧電膜であって、窒化アルミニウム結晶は、スカンジウム原子及びホウ素原子を含み、窒化アルミニウム結晶中における一部のアルミニウム原子がスカンジウム原子又はホウ素原子に置換された構造を有する。 A piezoelectric film according to one aspect of the present invention is a piezoelectric film made of an aluminum nitride crystal having a wurtzite structure, and the aluminum nitride crystal contains scandium atoms and boron atoms, and a part of the aluminum atoms in the aluminum nitride crystal Has a structure substituted with a scandium atom or a boron atom.
　本発明によれば、ＡｌＮ圧電膜において、膜応力の発生を抑制しながら、圧電定数を向上させることができる。 According to the present invention, in the AlN piezoelectric film, the piezoelectric constant can be improved while suppressing the generation of film stress.
本発明の第１実施形態に係る圧電薄膜を備える圧電デバイスの構造を概略的に示す平面図である。It is a top view which shows roughly the structure of a piezoelectric device provided with the piezoelectric thin film which concerns on 1st Embodiment of this invention. 図１のＡＡ´線に沿った断面の模式図である。It is a schematic diagram of the cross section along the AA 'line of FIG. スパッタリングによってＡｌＮ結晶中の原子が置換される様態を示すグラフである。It is a graph which shows the aspect by which the atom in an AlN crystal | crystallization is substituted by sputtering. Ｂのドープ量と圧電薄膜Ｆ２のヤング率との関係を示すグラフである。It is a graph which shows the relationship between the doping amount of B, and the Young's modulus of the piezoelectric thin film F2. Ｂのドープ量と、圧電定数及び膜応力との関係を示すグラフである。It is a graph which shows the relationship between the doping amount of B, a piezoelectric constant, and film | membrane stress. Ｓｃのドープ量と、圧電定数との関係を示すグラフである。It is a graph which shows the relationship between the doping amount of Sc, and a piezoelectric constant. 本発明の第２実施形態に係る圧電薄膜を備える圧電デバイスの構造を概略的に示す平面図である。It is a top view which shows roughly the structure of a piezoelectric device provided with the piezoelectric thin film which concerns on 2nd Embodiment of this invention. 図７のＮＮ´線に沿った断面の模式図である。It is a schematic diagram of the cross section along the NN 'line | wire of FIG.
［第１の実施形態］
（１．圧電デバイスの構成）
　以下、添付の図面を参照して本発明の第１実施形態について説明する。図１は、本発明の第１実施形態に係る圧電膜を用いて形成した圧電デバイス１０（圧電部品の一例である。）の一例を概略的に示す平面図である。圧電デバイス１０は、ＭＥＭＳ技術を用いて製造されるＭＥＭＳ振動子に用いられるためのデバイスであり、図１の直交座標系におけるＸＹ平面内で面内振動する。なお、本発明に係る圧電膜が用いられるのは面内振動するＭＥＭＳ振動子に限定されず、厚み縦振動子等に用いられても良い。 [First Embodiment]
(1. Configuration of piezoelectric device)
Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a plan view schematically showing an example of a piezoelectric device 10 (an example of a piezoelectric component) formed using the piezoelectric film according to the first embodiment of the present invention. The piezoelectric device 10 is a device for use in a MEMS vibrator manufactured using the MEMS technology, and vibrates in the plane in the XY plane in the orthogonal coordinate system of FIG. The piezoelectric film according to the present invention is not limited to a MEMS vibrator that vibrates in a plane, and may be used for a thickness longitudinal vibrator or the like.
　図１に示すように、圧電デバイス１０は、振動部１２０と、保持部１４０と、保持腕１１０を備えている。 As shown in FIG. 1, the piezoelectric device 10 includes a vibrating part 120, a holding part 140, and a holding arm 110.
　振動部１２０は、ＸＹ平面に沿って平面状に広がる板状の輪郭を有している。振動部１２０は、保持部１４０の内側に設けられており、振動部１２０と保持部１４０との間には、所定の間隔で空間が形成されている。 The vibrating unit 120 has a plate-like contour that extends in a plane along the XY plane. The vibrating unit 120 is provided inside the holding unit 140, and a space is formed between the vibrating unit 120 and the holding unit 140 at a predetermined interval.
　保持部１４０は、ＸＹ平面に沿って振動部１２０の外側を囲むように、矩形の枠状に形成される。例えば、保持部１４０は、角柱形状の枠体から一体に形成されている。なお、保持部１４０は、振動部１２０の周囲の少なくとも一部に設けられていればよく、枠状の形状に限定されない。 The holding unit 140 is formed in a rectangular frame shape so as to surround the outside of the vibrating unit 120 along the XY plane. For example, the holding part 140 is integrally formed from a prismatic frame. In addition, the holding | maintenance part 140 should just be provided in at least one part of the circumference | surroundings of the vibration part 120, and is not limited to a frame shape.
　保持腕１１０は、保持部１４０の内側に設けられ、振動部１２０と保持部１４０とを接続する。 The holding arm 110 is provided inside the holding unit 140 and connects the vibrating unit 120 and the holding unit 140.
（２．振動部の積層構造）
　次に、図２を用いて本実施形態に係る振動部１２０の積層構造について説明する。図２は、図１のＡＡ´断面図である。 (2. Laminate structure of vibration part)
Next, the laminated structure of the vibration unit 120 according to this embodiment will be described with reference to FIG. FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG.
　本実施形態において、振動部１２０は、基板Ｆ１上に、下部電極Ｅ１が積層されて形成される。そして、下部電極Ｅ１の上には下部電極Ｅ１を覆うように圧電薄膜Ｆ２（圧電膜の一例である。）が積層されており、さらに圧電薄膜Ｆ２の上には、上部電極Ｅ２が積層されている。 In the present embodiment, the vibration unit 120 is formed by laminating the lower electrode E1 on the substrate F1. A piezoelectric thin film F2 (which is an example of a piezoelectric film) is laminated on the lower electrode E1 so as to cover the lower electrode E1, and an upper electrode E2 is laminated on the piezoelectric thin film F2. Yes.
　基板Ｆ１は、酸化Ｓｉ（シリコン）層Ｆ１１と、Ｓｉ層Ｆ１２とから成る。酸化Ｓｉ層Ｆ１１は、例えば厚さ４０ｎｍ程度のＳｉＯ２の層である。また、Ｓｉ層Ｆ１２は、例えば、厚さ１０μｍ程度であり、抵抗率が１ｍΩ・ｃｍ（濃度７×１０１９／ｃｍ３）程度である縮退したｎ型Ｓｉ半導体から形成されている。Ｓｉ層Ｆ１２は、ｎ型ドーパントとしてＰ（リン）やＡｓ（ヒ素）、Ｓｂ（アンチモン）などを含むことができる。 The substrate F1 includes an oxidized Si (silicon) layer F11 and an Si layer F12. The oxidized Si layer F11 is a SiO 2 layer having a thickness of about 40 nm, for example. In addition, the Si layer F12 is formed of, for example, a degenerated n-type Si semiconductor having a thickness of about 10 μm and a resistivity of about 1 mΩ · cm (concentration 7 × 10 19 / cm 3 ). The Si layer F12 can contain P (phosphorus), As (arsenic), Sb (antimony), or the like as an n-type dopant.
　下部電極Ｅ１、及び上部電極Ｅ２は、例えばＭｏ（モリブデン）やＡｌ（アルミニウム）、Ａｇ（金）等を用いて形成される。下部電極Ｅ１、及び上部電極Ｅ２の厚みは例えば１００ｎｍ程度である。 The lower electrode E1 and the upper electrode E2 are formed using, for example, Mo (molybdenum), Al (aluminum), Ag (gold), or the like. The thicknesses of the lower electrode E1 and the upper electrode E2 are, for example, about 100 nm.
　圧電薄膜Ｆ２は、印加された電圧を振動に変換する圧電体の薄膜である。また、圧電薄膜Ｆ２の厚みは例えば１０００ｎｍ程度である。圧電薄膜Ｆ２は、下部電極Ｅ１、上部電極Ｅ２によって圧電薄膜Ｆ２に印加される電界に応じて、ＸＹ平面の面内方向に伸縮する。この圧電薄膜Ｆ２の伸縮によって、振動部１２０は、Ｙ軸方向に輪郭振動する。 The piezoelectric thin film F2 is a piezoelectric thin film that converts an applied voltage into vibration. The thickness of the piezoelectric thin film F2 is, for example, about 1000 nm. The piezoelectric thin film F2 expands and contracts in the in-plane direction of the XY plane according to the electric field applied to the piezoelectric thin film F2 by the lower electrode E1 and the upper electrode E2. Due to the expansion and contraction of the piezoelectric thin film F2, the vibration unit 120 undergoes contour vibration in the Y-axis direction.
　圧電薄膜Ｆ２の成分について説明する。圧電薄膜Ｆ２は、ウルツ鉱構造を有するＡｌＮ（窒化アルミニウム）結晶からなる。圧電薄膜Ｆ２におけるＡｌＮ結晶は、Ｓｃ（スカンジウム）原子及びＢ（ホウ素）原子を含み、ＡｌＮ結晶中における一部のＡｌ原子がＳｃ原子又はＢ原子に置換された構造を有する。より具体的には、圧電薄膜Ｆ２を構成するＡｌＮ結晶において、Ａｌ原子の位置にＳｃ原子又はＢ原子が存在する。
　本実施形態において、圧電薄膜Ｆ２におけるＡｌ原子の数と、Ｂ原子の数との総量に対する、Ｂ原子の数の割合（以下、「Ａｌに対するＢの組成比」とも呼ぶ。）は、０ａｔ％より大きく１３ａｔ％以下である。より好ましくは、Ａｌに対するＢの組成比は、０ａｔ％より大きく１２ａｔ％以下であり、さらに好ましくは、０ａｔ％より大きく８ａｔ％以下である。この場合、圧電薄膜Ｆ２は、ＡｌをＳｃに置換したことによって発生する膜応力を低減することができる。 The components of the piezoelectric thin film F2 will be described. The piezoelectric thin film F2 is made of AlN (aluminum nitride) crystal having a wurtzite structure. The AlN crystal in the piezoelectric thin film F2 includes Sc (scandium) atoms and B (boron) atoms, and has a structure in which some Al atoms in the AlN crystal are replaced with Sc atoms or B atoms. More specifically, in the AlN crystal constituting the piezoelectric thin film F2, Sc atoms or B atoms exist at the positions of Al atoms.
In the present embodiment, the ratio of the number of B atoms to the total amount of Al atoms and B atoms in the piezoelectric thin film F2 (hereinafter also referred to as “the composition ratio of B with respect to Al”) is 0 at%. It is largely 13 at% or less. More preferably, the composition ratio of B to Al is greater than 0 at% and less than or equal to 12 at%, and more preferably greater than 0 at% and less than or equal to 8 at%. In this case, the piezoelectric thin film F2 can reduce the film stress generated by replacing Al with Sc.
　また、本実施形態において、圧電薄膜Ｆ２におけるＡｌ原子の数と、Ｓｃ原子の数との総量に対する、Ｓｃ原子の数の割合（以下、「Ａｌに対するＳｃの組成比）とも呼ぶ。）は、０ａｔ％より大きく５８ａｔ％以下であり、より好ましくは、４４ａｔ％以上５２．５ａｔ％以下である。この場合、圧電薄膜Ｆ２は、圧電定数を向上させることができる。 In this embodiment, the ratio of the number of Sc atoms to the total amount of Al atoms and Sc atoms in the piezoelectric thin film F2 (hereinafter also referred to as “the composition ratio of Sc to Al”) is 0 at. % And not more than 58 at%, more preferably not less than 44 at% and not more than 52.5 at% In this case, the piezoelectric thin film F2 can improve the piezoelectric constant.
　即ち、本実施形態に係る圧電薄膜Ｆ２の組成比がＢＸＳｃＹＡｌ１－Ｘ－ＹＮ（０＜Ｘ≦１４、０＜Ｙ≦５２）である場合には、膜応力の発生を抑制しながら圧電定数を向上させることができる。なお、本実施形態に係る圧電薄膜Ｆ２の組成比ＢＸＳｃＹＡｌ１－Ｘ－ＹＮにおける、好ましいＸの値の範囲は、０＜Ｘ≦１４であり、より好ましくは、０＜Ｘ≦５．５であり、より好ましくは、０＜Ｘ≦５．２であり、さらに好ましくは、０＜Ｘ≦４である。また、このときの好ましいＹの値の範囲は、０＜Ｙ≦５２であり、さらに好ましくは、３８＜Ｙ≦５０である。なお、本実施形態に係る圧電薄膜Ｆ２の組成比ＢＸＳｃＹＡｌ１－Ｘ－ＹＮにおける好ましいＸの値とＹの値との組み合わせは、０＜Ｘ≦１４、０＜Ｙ≦５２であり、より好ましくは、０＜Ｘ≦５．５、０＜Ｙ≦５２であり、より好ましくは、０＜Ｘ≦５．２、０＜Ｙ≦５２であり、さらに好ましくは、０＜Ｘ≦４、３８＜Ｙ≦５０である。 That is, in the case of this embodiment the composition ratio of the piezoelectric thin film F2 is B according to the X Sc Y Al 1-X- Y N (0 <X ≦ 14,0 <Y ≦ 52) can suppress the generation of film stress In addition, the piezoelectric constant can be improved. In the composition ratio B X Sc Y Al 1- XYN of the piezoelectric thin film F2 according to the present embodiment, a preferable X value range is 0 <X ≦ 14, and more preferably 0 <X ≦ 5.5, more preferably 0 <X ≦ 5.2, and even more preferably 0 <X ≦ 4. In addition, the preferable range of the Y value at this time is 0 <Y ≦ 52, more preferably 38 <Y ≦ 50. The preferred combination of the X value and the Y value in the composition ratio B X Sc Y Al 1-XY N of the piezoelectric thin film F2 according to this embodiment is 0 <X ≦ 14 and 0 <Y ≦ 52. More preferably 0 <X ≦ 5.5 and 0 <Y ≦ 52, more preferably 0 <X ≦ 5.2 and 0 <Y ≦ 52, and still more preferably 0 <X ≦ 4, 38 <Y ≦ 50.
（３．成膜方法）
　次に、本実施形態に係る、圧電薄膜Ｆ２の成膜方法について説明する。圧電薄膜Ｆ２はスパッタ法によって基板Ｆ１上に成膜される。スパッタ法は、例えば、Ａｌ，Ｓｃ，Ｂのそれぞれをターゲットに用いる３元スパッタリングと、ＢＳｃＡｌ合金をターゲットとして用いる１元スパッタリングの２種類を用いることができる。 (3. Film formation method)
Next, a method for forming the piezoelectric thin film F2 according to this embodiment will be described. The piezoelectric thin film F2 is formed on the substrate F1 by sputtering. As the sputtering method, for example, two types of sputtering, that is, ternary sputtering using each of Al, Sc, and B as a target and single sputtering using a BScAl alloy as a target can be used.
（３－１．３元スパッタリング）
　３元スパッタリングによって圧電薄膜Ｆ２を成膜する場合、ターゲットにはＡｌの単体金属、Ｓｃの単体金属、及びＢＮ（窒化ホウ素）の焼結体を用いる。スパッタリング装置の真空チャンバー内における圧力は、０．１Ｐａ以上０．５Ｐａ以下が好ましく、温度は、室温以上３００℃以下が好ましい。また、真空チャンバー内には、Ａｒ（アルゴン）ガスと窒素ガスを混合したガスが導入される。当該混合ガスにおける窒素濃度は、３０％以上７０％以下が好ましい。 (3-1.3 yuan sputtering)
When the piezoelectric thin film F2 is formed by ternary sputtering, an Al simple metal, an Sc simple metal, and a sintered body of BN (boron nitride) are used as targets. The pressure in the vacuum chamber of the sputtering apparatus is preferably from 0.1 Pa to 0.5 Pa, and the temperature is preferably from room temperature to 300 ° C. A gas mixture of Ar (argon) gas and nitrogen gas is introduced into the vacuum chamber. The nitrogen concentration in the mixed gas is preferably 30% or more and 70% or less.
　スパッタリングによって形成する圧電薄膜Ｆ２における、Ａｌに対するＢの組成比、及びＡｌに対するＳｃの組成比は、ターゲットに供給する電力を調整することによって、調整することができる。本実施形態において、Ａｌターゲットに供給する電力は、例えば１００Ｗ以上３００Ｗ以下である。また、ＢＮターゲットに供給する電力は、Ａｌに対するＢの組成比を０ａｔ％より大きく１３ａｔ％以下とする場合には０Ｗ以上２００Ｗ以下であり、Ａｌに対するＢの組成比を０ａｔ％より大きく１２ａｔ％以下とする場合には０Ｗ以上１８０Ｗ以下であり、Ａｌに対するＢの組成比を０ａｔ％より大きく８ａｔ％以下とする場合には、０Ｗ以上１００Ｗ以下である。さらに、Ｓｃターゲットに供給する電力は、Ａｌに対するＳｃの組成比を０ａｔ％より大きく５８ａｔ％以下とする場合には０Ｗ以上３００Ｗ以下であり、Ａｌに対するＳｃの組成比を４４ａｔ％以上５２．５ａｔ％以下とする場合には２００Ｗ以上３００Ｗ以下である。 The composition ratio of B to Al and the composition ratio of Sc to Al in the piezoelectric thin film F2 formed by sputtering can be adjusted by adjusting the power supplied to the target. In the present embodiment, the power supplied to the Al target is, for example, 100 W or more and 300 W or less. The power supplied to the BN target is 0 W or more and 200 W or less when the B composition ratio to Al is greater than 0 at% and 13 at% or less, and the B composition ratio to Al is greater than 0 at% and less than 12 at%. Is 0 W or more and 180 W or less, and when the composition ratio of B to Al is more than 0 at% and 8 at% or less, it is 0 W or more and 100 W or less. Furthermore, the power supplied to the Sc target is 0 W or more and 300 W or less when the composition ratio of Sc to Al is greater than 0 at% and 58 at% or less, and the composition ratio of Sc to Al is 44 at% or more and 52.5 at%. In the case of the following, it is 200 W or more and 300 W or less.
　この条件において、スパッタリングを２時間程度行うことによって、本実施形態に係る圧電薄膜Ｆ２が基板Ｆ１上に形成される。 Under this condition, by performing sputtering for about 2 hours, the piezoelectric thin film F2 according to this embodiment is formed on the substrate F1.
（３－２．１元スパッタリング）
　１元スパッタリングによって圧電薄膜Ｆ２を成膜する場合、ターゲットにはＢＳｃＡｌ合金を用いる。この場合、６インチや８インチのような大型ウエハに対しても、均一な膜厚分布と圧電性分布で成膜することができる。 (3-2.1 yuan sputtering)
When the piezoelectric thin film F2 is formed by single sputtering, a BScAl alloy is used as a target. In this case, even a large wafer such as 6 inches or 8 inches can be formed with a uniform film thickness distribution and piezoelectric distribution.
　１元スパッタリングにおいて、スパッタリング装置の真空チャンバー内における圧力は、０．１Ｐａ以上０．５Ｐａ以下が好ましく、温度は、室温以上３００℃以下が好ましい。また、真空チャンバー内に導入されるＡｒ（アルゴン）ガスにおける窒素濃度は、３０％以上７０％以下が好ましい。また、ターゲットに供給する電力は、５００Ｗ以上１２００Ｗ以下が好ましい。 In the one-way sputtering, the pressure in the vacuum chamber of the sputtering apparatus is preferably 0.1 Pa or more and 0.5 Pa or less, and the temperature is preferably room temperature or more and 300 ° C. or less. The nitrogen concentration in Ar (argon) gas introduced into the vacuum chamber is preferably 30% or more and 70% or less. The power supplied to the target is preferably 500 W or more and 1200 W or less.
　形成する圧電薄膜Ｆ２におけるＡｌに対するＢの組成比、及びＡｌに対するＳｃの組成比は、ターゲットとする合金における組成比を調整することによって、調整することができる。本実施形態において、ＢＳｃＡｌ合金の組成比Ｂ：Ｓｃ：Ａｌは、４５:５０:５であることが好ましい。 The composition ratio of B to Al and the composition ratio of Sc to Al in the formed piezoelectric thin film F2 can be adjusted by adjusting the composition ratio in the target alloy. In the present embodiment, the composition ratio B: Sc: Al of the BScAl alloy is preferably 45: 50: 5.
　この条件において、スパッタリングを２時間程度行うことによって、本実施形態に係る圧電薄膜Ｆ２が基板Ｆ１上に形成される。 Under this condition, by performing sputtering for about 2 hours, the piezoelectric thin film F2 according to this embodiment is formed on the substrate F1.
（４．実験例）
　図３～図６を用いて、形成した圧電薄膜Ｆ２の特性に関する実験結果について説明する。 (4. Experimental example)
The experimental results regarding the characteristics of the formed piezoelectric thin film F2 will be described with reference to FIGS.
（４－１．実験１　置換態様の測定）
　実験１では、スパッタリングによってＡｌＮ結晶中の原子が置換される様態を測定した。図３は実験１の結果を示すグラフである。図３のグラフの横軸は、ターゲットとした用いたＢＮ部材の番号を、縦軸は、形成された圧電薄膜Ｆ２中におけるＡｌ，Ｓｃ，Ｂの含有率（ａｔ％）を示している。実験１においては、以下のパラメータを用いて３元スパッタリングをすることによって圧電薄膜を成膜した。
・圧力　０．２Ｐａ
・温度　２００℃
・時間　２時間
・窒素濃度　５０％
　なお、Ａｌに対するＢの組成比は、ＢＮターゲットに与える電力を１００Ｗに設定することで調整した。また、Ａｌに対するＳｃの組成比は、ＢＮターゲットに与える電力を３００Ｗに設定することで調整した。さらに、Ａｌターゲットに与えた電力は、本実験例においては３００Ｗである。 (4-1. Experiment 1 Measurement of substitution mode)
In Experiment 1, the state in which atoms in the AlN crystal were replaced by sputtering was measured. FIG. 3 is a graph showing the results of Experiment 1. The horizontal axis of the graph of FIG. 3 indicates the number of the BN member used as a target, and the vertical axis indicates the content (at%) of Al, Sc, B in the formed piezoelectric thin film F2. In Experiment 1, a piezoelectric thin film was formed by ternary sputtering using the following parameters.
・ Pressure 0.2Pa
・ Temperature 200 ℃
・ Time 2 hours ・ Nitrogen concentration 50%
The composition ratio of B to Al was adjusted by setting the power applied to the BN target to 100W. Moreover, the composition ratio of Sc with respect to Al was adjusted by setting the electric power given to a BN target to 300W. Furthermore, the power applied to the Al target is 300 W in this experimental example.
　圧電薄膜Ｆ２におけるＡｌ，Ｓｃ，Ｂの含有率は、Ｘ線光電子分光法を用いて測定した。図３から明らかなように、Ａｌの含有率は、Ｂの含有率が増加するに伴って低下している。他方で、Ｓｃの含有率はＢの含有率に関わらず一定である。この結果から、Ｂの原子は、Ａｌの原子と置換されることが分かる。 The Al, Sc, and B contents in the piezoelectric thin film F2 were measured using X-ray photoelectron spectroscopy. As apparent from FIG. 3, the Al content decreases as the B content increases. On the other hand, the Sc content is constant regardless of the B content. From this result, it is understood that the B atom is replaced with the Al atom.
　Ｂのイオン半径は１１ｐｍ程度であり、Ａｌのイオン半径は３９ｐｍであり、Ｓｃのイオン半径は、７５ｐｍ程度である。即ち、Ｂのイオン半径は、ＳｃよりもＡｌのイオン半径に近い。そのため、エネルギーの安定性の観点から、イオン半径の近いＢとＡｌとが置換すると考えられる。 The ionic radius of B is about 11 pm, the ionic radius of Al is 39 pm, and the ionic radius of Sc is about 75 pm. That is, the ionic radius of B is closer to the ionic radius of Al than Sc. Therefore, from the viewpoint of energy stability, it is considered that B and Al having a close ionic radius are replaced.
（４－２．実験２　ヤング率の測定）
　次に、図４を参照して実験２について説明する。実験２では、Ｂをドープすることによる効果を検証した。図４は、Ｂのドープ量と圧電薄膜Ｆ２のヤング率との関係を示す図である。横軸は、圧電薄膜Ｆ２中のＡｌの原子量とＳｃの原子量との総和に対するＳｃの原子量の割合を示し、縦軸は圧電薄膜Ｆ２のヤング率を示している。また、図４において、ひし形で測定点を示すグラフはＡｌに対するＢの組成比が０ａｔ％の場合を示し、四角形で測定点を示すグラフはＡｌに対するＢの組成比が１２．５ａｔ％の場合を示し、三角形で測定点を示すグラフはＡｌに対するＢの組成比が２５ａｔ％の場合を示している。なお、形成した圧電薄膜Ｆ２における、Ａｌに対するＢ，Ｓｃの組成比の同定には、Ｘ線光電子分光法を用いた。また、圧電薄膜Ｆ２のヤング率は、圧電共振子の共振周波数から算出またはナノインデンテーション法によって測定した。 (4-2. Experiment 2 Measurement of Young's modulus)
Next, Experiment 2 will be described with reference to FIG. In Experiment 2, the effect of doping B was verified. FIG. 4 is a graph showing the relationship between the doping amount of B and the Young's modulus of the piezoelectric thin film F2. The horizontal axis represents the ratio of the atomic weight of Sc to the sum of the atomic weight of Al and the atomic weight of Sc in the piezoelectric thin film F2, and the vertical axis represents the Young's modulus of the piezoelectric thin film F2. In FIG. 4, the graph showing the measurement points with diamonds shows the case where the composition ratio of B to Al is 0 at%, and the graph showing the measurement points with squares shows the case where the composition ratio of B to Al is 12.5 at%. The graph showing the measurement points with triangles shows the case where the composition ratio of B to Al is 25 at%. X-ray photoelectron spectroscopy was used to identify the composition ratio of B and Sc to Al in the formed piezoelectric thin film F2. The Young's modulus of the piezoelectric thin film F2 was calculated from the resonance frequency of the piezoelectric resonator or measured by the nanoindentation method.
　実験２においては、以下のパラメータを用いて３元スパッタリングをすることによって圧電薄膜を成膜した。
・圧力　０．２Ｐａ
・温度　３００℃
・時間　２時間
・窒素濃度　５０％
　なお、Ａｌに対するＢの組成比は、ＢＮターゲットに与える電力を１００Ｗに設定することで調整した。また、Ａｌに対するＳｃの組成比は、ＢＮターゲットに与える電力を３００Ｗに設定することで調整した。さらに、Ａｌターゲットに与えた電力は、本実験例においては３００Ｗである。 In Experiment 2, a piezoelectric thin film was formed by ternary sputtering using the following parameters.
・ Pressure 0.2Pa
・ Temperature 300 ℃
・ Time 2 hours ・ Nitrogen concentration 50%
The composition ratio of B to Al was adjusted by setting the power applied to the BN target to 100W. Moreover, the composition ratio of Sc with respect to Al was adjusted by setting the electric power given to a BN target to 300W. Furthermore, the power applied to the Al target is 300 W in this experimental example.
　図４から明らかなように、Ｂのドープ量を増加させることで、Ｓｃドープによるヤング率の低下が緩和することが分かる。Ｂと窒素とは強い結合力で結びつくため、圧電薄膜Ｆ２にＢをドープすることで、ヤング率を向上すると考えられる。 As is clear from FIG. 4, it can be seen that the decrease in Young's modulus due to Sc doping is alleviated by increasing the amount of B doped. Since B and nitrogen are bound by a strong bonding force, it is considered that doping the piezoelectric thin film F2 with B improves the Young's modulus.
（４－３．実験３　圧電定数及び膜応力の測定）
　次に、図５及び図６を参照して、実験３について説明する。実験３では、Ｂのドープ量が圧電薄膜Ｆ２における圧電定数及び膜応力に与える効果を検証した。実験３（図５及び図６）においては、下表１に示す組成比で形成した３種類の圧電薄膜のサンプル１～３を用いて測定を行った。図５及び図６のグラフにおいて、ひし形又は四角形で示す点がサンプル１～３における測定結果である。圧電薄膜Ｆ２の圧電定数はＰｉｅｚｏ　Ｓｙｓｔｅｍ Ｍｅｔｅｒ　ＰＭ３００によって測定した。また、圧電薄膜Ｆ２の膜応力はＫＬＡ－Ｔｅｎｃｏｒ　ＦＬＸ－２３２０によって測定した。なお、形成した圧電薄膜Ｆ２における、Ａｌに対するＢ，Ｓｃの組成比の同定方法は、実験２と同様である。 (4-3. Experiment 3 Measurement of piezoelectric constant and film stress)
Next, Experiment 3 will be described with reference to FIGS. In Experiment 3, the effect of the doping amount of B on the piezoelectric constant and film stress in the piezoelectric thin film F2 was verified. In Experiment 3 (FIGS. 5 and 6), measurements were performed using three types of piezoelectric thin film samples 1 to 3 formed at the composition ratios shown in Table 1 below. In the graphs of FIGS. 5 and 6, the points indicated by diamonds or squares are the measurement results of samples 1 to 3. The piezoelectric constant of the piezoelectric thin film F2 was measured with a Piezo System Meter PM300. The film stress of the piezoelectric thin film F2 was measured by KLA-Tencor FLX-2320. The method for identifying the composition ratio of B and Sc to Al in the formed piezoelectric thin film F2 is the same as in Experiment 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　サンプル１の圧電薄膜は、以下のパラメータで３元スパッタリングを行って形成した。
・圧力　０．４Ｐａ
・温度　２００℃
・時間　２時間
・窒素濃度　５０％
・電力
　Ａｌ　３００［Ｗ］
　ＢＮ　５０［Ｗ］
　Ｓｃ　２５０［Ｗ］
　サンプル２の圧電薄膜は、以下のパラメータで３元スパッタリングを行って形成した。
・圧力　０．２Ｐａ
・温度　２００℃
・時間　２時間
・窒素濃度　５０％
・電力　
　Ａｌ　３００［Ｗ］
　ＢＮ　７０［Ｗ］
　Ｓｃ　２８０［Ｗ］
　サンプル３の圧電薄膜は、以下のパラメータで３元スパッタリングを行って形成した。
・圧力　０．２Ｐａ
・温度　２００℃
・時間　２時間
・窒素濃度　５０％
・電力　
　Ａｌ　３００［Ｗ］
　ＢＮ　９０［Ｗ］
　Ｓｃ　３００［Ｗ］ The piezoelectric thin film of Sample 1 was formed by performing ternary sputtering with the following parameters.
・ Pressure 0.4Pa
・ Temperature 200 ℃
・ Time 2 hours ・ Nitrogen concentration 50%
・ Power Al 300 [W]
BN 50 [W]
Sc 250 [W]
The piezoelectric thin film of Sample 2 was formed by performing ternary sputtering with the following parameters.
・ Pressure 0.2Pa
・ Temperature 200 ℃
・ Time 2 hours ・ Nitrogen concentration 50%
・ Power
Al 300 [W]
BN 70 [W]
Sc 280 [W]
The piezoelectric thin film of Sample 3 was formed by performing ternary sputtering with the following parameters.
・ Pressure 0.2Pa
・ Temperature 200 ℃
・ Time 2 hours ・ Nitrogen concentration 50%
・ Power
Al 300 [W]
BN 90 [W]
Sc 300 [W]
　図５は、Ｂのドープ量と、圧電定数及び膜応力との関係を示すグラフである。図５において、横軸はＡｌに対するＢの組成比を示し、縦軸は圧電定数と膜応力とを示している。 FIG. 5 is a graph showing the relationship between the doping amount of B, the piezoelectric constant, and the film stress. In FIG. 5, the horizontal axis represents the composition ratio of B to Al, and the vertical axis represents the piezoelectric constant and the film stress.
　図５において、点線Ｋで示す直線は、ＢをドープせずＳｃのみをドープした比較例のＳｃＹＡｌ１－ＹＮ膜における圧電定数であり、点線Ｌで示す直線は、比較例のＳｃＹＡｌ１－ＹＮ膜における膜応力である。比較例のＳｃＹＡｌ１－ＹＮ膜では、圧電定数は２０ｐＣ／Ｎ程度、膜応力は－１４００Ｍｐａ以上である。Ｓｃは、Ａｌよりもイオン半径の大きい原子である。従ってＡｌＮ結晶におけるＡｌがＳｃに置換されると、ＡｌＮのウルツ鉱構造における結晶格子が部分的に膨らむように歪んでしまう。この結果、Ｓｃのみをドープした比較例のＳｃＹＡｌ１－ＹＮ膜には強い圧縮応力が発生する。 In FIG. 5, the straight line indicated by the dotted line K is the piezoelectric constant in the Sc Y Al 1-Y N film of the comparative example in which only B is doped without doping B, and the straight line indicated by the dotted line L is the Sc Y of the comparative example. This is the film stress in the Al 1-Y N film. In the Sc Y Al 1-Y N film of the comparative example, the piezoelectric constant is about 20 pC / N and the film stress is −1400 Mpa or more. Sc is an atom having an ionic radius larger than that of Al. Therefore, when Al in the AlN crystal is replaced with Sc, the crystal lattice in the wurtzite structure of AlN is distorted so as to partially swell. As a result, a strong compressive stress is generated in the Sc Y Al 1-Y N film of the comparative example doped only with Sc.
　他方で、上述のとおり、ＢはＡｌよりもイオン半径の小さい原子である。従って、ＡｌＮ結晶における一部のＡｌをＢで置換することで、Ｓｃのドープによって発生した膜応力を低減することができる。図５の結果から、膜応力を低減し、かつ高い圧電定数を維持可能なＡｌに対するＢの組成比の範囲は、０ａｔ％より大きく１３ａｔ％以下であり、より好ましくは、０ａｔ％より大きく１２ａｔ％以下であり、さらに好ましくは、０ａｔ％より大きく８ａｔ％以下である。即ち、本実施形態に係る圧電薄膜Ｆ２の組成比ＢＸＳｃＹＡｌ１－Ｘ－ＹＮにおいて０＜Ｘ≦５．５である場合には、膜応力の発生を抑制しながら圧電定数を向上させることができる。なお、本実施形態に係る圧電薄膜Ｆ２の組成比におけるＸの値の範囲はより好ましくは、０＜Ｘ≦５．２であり、さらに好ましくは、０＜Ｘ≦４である。 On the other hand, as described above, B is an atom having an ionic radius smaller than that of Al. Therefore, by replacing a part of Al in the AlN crystal with B, the film stress generated by Sc doping can be reduced. From the results of FIG. 5, the range of the composition ratio of B to Al that can reduce the film stress and maintain a high piezoelectric constant is greater than 0 at% and less than or equal to 13 at%, more preferably greater than 0 at% and 12 at%. It is below, More preferably, it is larger than 0 at% and below 8 at%. That is, when 0 <X ≦ 5.5 in the composition ratio B X Sc Y Al 1-XY N of the piezoelectric thin film F2 according to this embodiment, the piezoelectric constant is improved while suppressing the generation of film stress. Can be made. In addition, the range of the value of X in the composition ratio of the piezoelectric thin film F2 according to the present embodiment is more preferably 0 <X ≦ 5.2, and more preferably 0 <X ≦ 4.
　図６は、Ｓｃのドープ量と、圧電定数との関係を示すグラフである。図６において、横軸はＡｌに対するＳｃの組成比を示し、縦軸は圧電定数を示している。 FIG. 6 is a graph showing the relationship between the Sc doping amount and the piezoelectric constant. In FIG. 6, the horizontal axis represents the composition ratio of Sc to Al, and the vertical axis represents the piezoelectric constant.
　図６において、点線Ｍで示す直線は、ＢもＳｃもドープしていない比較例のＡｌＮ膜における圧電定数である。また、図６において、点線で示すグラフは本実施形態に係る圧電薄膜Ｆ２における圧電定数を示しており、実線で示すグラフはＢをドープせずＳｃのみをドープした比較例のＳｃＹＡｌ１－ＹＮ膜における圧電定数を示している。図６から明らかなように、比較例のＳｃＹＡｌ１－ＹＮ膜では、Ａｌに対するＳｃの組成比が５０％を超えると、圧電定数が比較例のＡｌＮ膜を下回ってしまう。他方で、本実施形態に係る圧電薄膜Ｆ２の圧電定数は、Ａｌに対するＳｃの組成比が５０％以上の範囲でも比較例のＡｌＮ膜の圧電定数を上回っている。 In FIG. 6, the straight line indicated by the dotted line M is the piezoelectric constant in the AlN film of the comparative example in which neither B nor Sc is doped. Further, in FIG. 6, the graph indicated by the dotted line shows the piezoelectric constant of the piezoelectric thin film F2 of this embodiment, the graph shown by the solid line in comparative examples doped Sc only without doping B Sc Y Al 1- It shows the piezoelectric constant in the Y N film. As is apparent from FIG. 6, in the Sc Y Al 1-Y N film of the comparative example, when the composition ratio of Sc to Al exceeds 50%, the piezoelectric constant is lower than that of the AlN film of the comparative example. On the other hand, the piezoelectric constant of the piezoelectric thin film F2 according to this embodiment exceeds the piezoelectric constant of the AlN film of the comparative example even when the composition ratio of Sc to Al is in the range of 50% or more.
　図６の結果から、Ｂをドープした場合には、ＡｌＮ膜の圧電定数よりも高い圧電定数を維持できるＡｌに対するＳｃの組成比の範囲は、０ａｔ％より大きく５８ａｔ％以下であり、より好ましくは、４４ａｔ％以上５２．５ａｔ％以下である。即ち、本実施形態に係る圧電薄膜Ｆ２の組成比ＢＸＳｃＹＡｌ１－Ｘ－ＹＮにおいて０＜Ｙ≦５２である場合には、ＡｌＮ膜の圧電定数よりも高い圧電定数を維持できる。なお、本実施形態に係る圧電薄膜Ｆ２の組成比におけるＹの値の範囲はより好ましくは、０＜Ｙ≦５２であり、さらに好ましくは、３８＜Ｙ≦５０である。 From the result of FIG. 6, when B is doped, the range of the composition ratio of Sc to Al that can maintain a piezoelectric constant higher than the piezoelectric constant of the AlN film is greater than 0 at% and less than or equal to 58 at%, more preferably 44 at% or more and 52.5 at% or less. That is, when 0 <Y ≦ 52 in the composition ratio B X Sc Y Al 1-XY N of the piezoelectric thin film F2 according to this embodiment, a piezoelectric constant higher than the piezoelectric constant of the AlN film can be maintained. In addition, the range of the value of Y in the composition ratio of the piezoelectric thin film F2 according to this embodiment is more preferably 0 <Y ≦ 52, and further preferably 38 <Y ≦ 50.
［第２の実施形態］
　第２の実施形態以降では第１の実施形態と共通の事柄についての記述を省略し、異なる点についてのみ説明する。特に、同様の構成による同様の作用効果については実施形態毎には逐次言及しない。 [Second Embodiment]
In the second and subsequent embodiments, description of matters common to the first embodiment is omitted, and only different points will be described. In particular, the same operation effect by the same configuration will not be sequentially described for each embodiment.
　図７は、本実施形態に係る圧電薄膜Ｆ２を用いて形成された圧電デバイス２０の外観を示す図である。圧電デバイス２０は、音圧を電気信号に変換するＭＥＭＳマイクを構成するためのデバイスであり、振動板２１０、支持部２１１、及び圧電部２１２を含んでいる。また、圧電デバイス２０は、例えば１μｍ以下程度の微小なスリット２１３によって２分割されている。 FIG. 7 is a diagram showing an appearance of the piezoelectric device 20 formed using the piezoelectric thin film F2 according to the present embodiment. The piezoelectric device 20 is a device for configuring a MEMS microphone that converts sound pressure into an electrical signal, and includes a diaphragm 210, a support portion 211, and a piezoelectric portion 212. The piezoelectric device 20 is divided into two by a minute slit 213 having a size of about 1 μm or less, for example.
　振動板２１０は、音圧により振動する薄膜であり、シリコン（Ｓｉ）により形成される。振動板２１０は、略方形の形状を有しており、対向する１組の辺２１４，２１５の下部が、支持部２１１によって支持される。即ち、振動板２１０は、両持ち梁構造となっている。振動板２１０を形成するＳｉは、抵抗率１．５ｍΩ・ｃｍ以下の縮退したｎ型Ｓｉ半導体であり、後述するように、圧電部２１２の下部電極としての機能を有する。 The diaphragm 210 is a thin film that vibrates due to sound pressure, and is formed of silicon (Si). The diaphragm 210 has a substantially square shape, and the lower portions of a pair of opposing sides 214 and 215 are supported by the support portion 211. That is, the diaphragm 210 has a double-supported beam structure. Si forming the vibration plate 210 is a degenerated n-type Si semiconductor having a resistivity of 1.5 mΩ · cm or less, and has a function as a lower electrode of the piezoelectric portion 212 as described later.
　圧電部２１２は、振動板２１０上における、支持部２１１によって支持された部分に沿って配設される。なお、図７に示す構成では、振動板２１０上に４つの圧電部２１２が配設されているが、圧電部２１２の数はこれに限られない。また、図７に示す構成では、圧電部２１２は、端部が辺２１４または辺２１５の上に配設されているが、端部が辺２１４または辺２１５から離れて配設されてもよい。 The piezoelectric portion 212 is disposed along a portion of the diaphragm 210 that is supported by the support portion 211. In the configuration shown in FIG. 7, the four piezoelectric portions 212 are disposed on the vibration plate 210, but the number of piezoelectric portions 212 is not limited to this. In the configuration shown in FIG. 7, the end of the piezoelectric portion 212 is disposed on the side 214 or the side 215, but the end may be disposed away from the side 214 or the side 215.
　図８は、図７に示すＮＮ´線における、圧電デバイス２０の断面図である。支持部２１１は、基体２２０及び絶縁層２２１を含んでいる。 FIG. 8 is a cross-sectional view of the piezoelectric device 20 taken along line NN ′ shown in FIG. The support part 211 includes a base body 220 and an insulating layer 221.
　基体２２０は、例えば、シリコン（Ｓｉ）により形成される。また、絶縁層２２１は、例えば、酸化シリコン（ＳｉＯ２）により形成される。このように形成される支持部２１１の上に、振動板２１０が形成される。 The base body 220 is made of, for example, silicon (Si). The insulating layer 221 is made of, for example, silicon oxide (SiO 2). The diaphragm 210 is formed on the support portion 211 formed in this way.
　振動板２１０上における、支持部２１１によって支持された部分に沿って配設された圧電部２１２は、圧電薄膜Ｆ２、上部電極Ｅ２、配線２２２，２２３を含んでいる。 The piezoelectric portion 212 disposed along the portion of the diaphragm 210 supported by the support portion 211 includes a piezoelectric thin film F2, an upper electrode E2, and wirings 222 and 223.
　本実施形態において圧電薄膜Ｆ２は、振動板２１０の振動に伴って振動するように振動板２１０上に配設される。振動板２１０の中央から支持部２１１までの幅（Ｃ）に対する、圧電薄膜Ｆ２の振動部分の幅（Ｄ）の割合は、例えば４０％程度とすることができる。例えば、幅Ｃを３００μｍ程度、幅Ｄを１２０μｍ程度とすることができる。 In the present embodiment, the piezoelectric thin film F2 is disposed on the diaphragm 210 so as to vibrate with the vibration of the diaphragm 210. The ratio of the width (D) of the vibrating portion of the piezoelectric thin film F2 to the width (C) from the center of the diaphragm 210 to the support portion 211 can be, for example, about 40%. For example, the width C can be about 300 μm and the width D can be about 120 μm.
　圧電薄膜Ｆ２の上側には、上部電極Ｅ２が配設される。上部電極Ｅ２は、本実施形態では、５０ｎｍ程度の厚さとすることができる。また、上部電極Ｅ２は、引張応力を有する構造とすることができる。上部電極Ｅ２に引張応力を持たせることにより、圧電部２１２における応力が補正され、振動板２１０の変形を抑制することができる。 An upper electrode E2 is disposed on the upper side of the piezoelectric thin film F2. In this embodiment, the upper electrode E2 can have a thickness of about 50 nm. Further, the upper electrode E2 can have a structure having a tensile stress. By giving the upper electrode E2 a tensile stress, the stress in the piezoelectric portion 212 is corrected, and deformation of the diaphragm 210 can be suppressed.
　配線２２２は、上部電極Ｅ２と電気的に接続される。また、配線２２３は、下部電極（振動板２１０）と電気的に接続される。配線２２２，２２３は、例えば、金（Ａｕ）や白金（Ｐｔ）、チタン（Ｔｉ）、アルミニウム（Ａｌ）等を用いて形成される。 The wiring 222 is electrically connected to the upper electrode E2. The wiring 223 is electrically connected to the lower electrode (the diaphragm 210). The wirings 222 and 223 are formed using, for example, gold (Au), platinum (Pt), titanium (Ti), aluminum (Al), or the like.
　以上に説明した構成の圧電デバイス１００においては、音圧による振動板２１０の振動に伴って、圧電薄膜Ｆ２が振動する。そして、圧電薄膜Ｆ２の振動に応じた電圧が圧電部２１２の配線２２２，２２３を介して出力される。 In the piezoelectric device 100 having the configuration described above, the piezoelectric thin film F2 vibrates as the diaphragm 210 vibrates due to sound pressure. A voltage corresponding to the vibration of the piezoelectric thin film F <b> 2 is output via the wirings 222 and 223 of the piezoelectric portion 212.
　以上、本発明の例示的な実施形態について説明した。本発明の一実施形態に係る圧電薄膜Ｆ２は、ウルツ鉱構造を有するＡｌＮ結晶からなる圧電膜であって、ＡｌＮ結晶中は、Ｓｃ原子及びＢ原子を含み、ＡｌＮ結晶中における一部のＡｌ原子がＳｃ原子又はＢ原子に置換された構造を有する。これによって、膜応力の発生を抑制しながら、圧電定数を向上させることが可能な圧電膜を得ることができる。 The exemplary embodiments of the present invention have been described above. The piezoelectric thin film F2 according to an embodiment of the present invention is a piezoelectric film made of an AlN crystal having a wurtzite structure, and the AlN crystal contains Sc atoms and B atoms, and some Al atoms in the AlN crystal. Has a structure substituted with Sc atom or B atom. Thereby, a piezoelectric film capable of improving the piezoelectric constant while suppressing the generation of film stress can be obtained.
　また、本発明の一実施形態に係る圧電薄膜Ｆ２は、圧電薄膜Ｆ２におけるＡｌ原子の数と、Ｂ原子の数との総量に対する、Ｂ原子の数の割合は、０ａｔ％より大きく１３ａｔ％以下であることが好ましく、より好適には、０ａｔ％より大きく１２ａｔ％以下であり、さらに好適には０ａｔ％より大きく８ａｔ％以下である。この場合、圧電薄膜Ｆ２において、膜応力の発生を抑制することができる。 In addition, in the piezoelectric thin film F2 according to one embodiment of the present invention, the ratio of the number of B atoms to the total amount of the number of Al atoms and the number of B atoms in the piezoelectric thin film F2 is greater than 0 at% and not more than 13 at%. More preferably, it is more than 0 at% and not more than 12 at%, and more preferably more than 0 at% and not more than 8 at%. In this case, generation of film stress can be suppressed in the piezoelectric thin film F2.
　また、本発明の一実施形態に係る圧電薄膜Ｆ２は、圧電薄膜Ｆ２におけるＡｌ原子の数と、Ｓｃ原子の数との総量に対する、Ｓｃ原子の数の割合は、０ａｔ％より大きく５８ａｔ％以下であることが好ましく、より好適には、４４ａｔ％より大きく５２．５ａｔ％以下である。この場合、圧電薄膜Ｆ２において、圧電定数を向上させることができる。 In the piezoelectric thin film F2 according to an embodiment of the present invention, the ratio of the number of Sc atoms to the total amount of the number of Al atoms and the number of Sc atoms in the piezoelectric thin film F2 is greater than 0 at% and not more than 58 at%. It is preferable that it is greater than 44 at% and more preferably 52.5 at% or less. In this case, the piezoelectric constant can be improved in the piezoelectric thin film F2.
　また、本発明の一実施形態に係る圧電薄膜Ｆ２は圧電薄膜Ｆ２におけるＡｌ原子の数と、Ｂ原子の数と、Ｓｃ原子の数との総量に対する、Ｂ原子の数の割合は、０ａｔ％より大きく５．５ａｔ％以下であることが好ましい。この場合、圧電薄膜Ｆ２において、膜応力の発生を抑制することができる。 In the piezoelectric thin film F2 according to the embodiment of the present invention, the ratio of the number of B atoms to the total amount of the number of Al atoms, the number of B atoms, and the number of Sc atoms in the piezoelectric thin film F2 is from 0 at%. It is preferably 5.5 at% or less. In this case, generation of film stress can be suppressed in the piezoelectric thin film F2.
　また、本発明の一実施形態に係る圧電薄膜Ｆ２は圧電薄膜Ｆ２におけるＡｌ原子の数と、Ｂ原子の数と、Ｓｃ原子の数との総量に対する、Ｓｃ原子の数の割合は、０ａｔ％以上５０ａｔ％以下であることが好ましい。この場合、圧電薄膜Ｆ２において、圧電定数を向上させることができる。 In the piezoelectric thin film F2 according to the embodiment of the present invention, the ratio of the number of Sc atoms to the total amount of the number of Al atoms, the number of B atoms, and the number of Sc atoms in the piezoelectric thin film F2 is 0 at% or more. It is preferable that it is 50 at% or less. In this case, the piezoelectric constant can be improved in the piezoelectric thin film F2.
　また、本発明の一実施形態に係る圧電デバイスは、上述の圧電薄膜Ｆ２を備える。これによって、圧電デバイスにおいて、膜応力の発生を抑制させつつ、圧電定数を向上させることができる。 Further, a piezoelectric device according to an embodiment of the present invention includes the above-described piezoelectric thin film F2. Thereby, in the piezoelectric device, it is possible to improve the piezoelectric constant while suppressing generation of film stress.
　また、本発明の一実施形態に係る圧電膜製造方法は、Ａｌ，Ｂ，及びＳｃから成る合金をターゲットとして、基板Ｆ１上に、上述の圧電薄膜Ｆ２を製造する。また、本発明の一実施形態に係る圧電膜製造方法は、Ａｌから成るターゲット、Ｂから成るターゲット、及びスカンジウムから成るターゲットを用いて、基板Ｆ１上に上述の圧電薄膜Ｆ２を形成する。これによって、膜応力の発生を抑制しながら、圧電定数を向上させることが可能な圧電膜を得ることができる。 Also, the piezoelectric film manufacturing method according to one embodiment of the present invention manufactures the above-described piezoelectric thin film F2 on the substrate F1, using an alloy composed of Al, B, and Sc as a target. In the piezoelectric film manufacturing method according to an embodiment of the present invention, the above-described piezoelectric thin film F2 is formed on the substrate F1 using a target made of Al, a target made of B, and a target made of scandium. Thereby, a piezoelectric film capable of improving the piezoelectric constant while suppressing the generation of film stress can be obtained.
　なお、以上説明した各実施形態は、本発明の理解を容易にするためのものであり、本発明を限定して解釈するためのものではない。本発明は、その趣旨を逸脱することなく、変更／改良され得るととともに、本発明にはその等価物も含まれる。即ち、各実施形態に当業者が適宜設計変更を加えたものも、本発明の特徴を備えている限り、本発明の範囲に包含される。例えば、各実施形態が備える各要素およびその配置、材料、条件、形状、サイズなどは、例示したものに限定されるわけではなく適宜変更することができる。また、各実施形態は例示であり、異なる実施形態で示した構成の部分的な置換または組み合わせが可能であることは言うまでもなく、これらも本発明の特徴を含む限り本発明の範囲に包含される。 Each embodiment described above is for facilitating understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed / improved without departing from the spirit thereof, and the present invention includes equivalents thereof. In other words, those obtained by appropriately modifying the design of each embodiment by those skilled in the art are also included in the scope of the present invention as long as they include the features of the present invention. For example, each element included in each embodiment and its arrangement, material, condition, shape, size, and the like are not limited to those illustrated, and can be changed as appropriate. Each embodiment is an exemplification, and it is needless to say that a partial replacement or combination of configurations shown in different embodiments is possible, and these are also included in the scope of the present invention as long as they include the features of the present invention. .
　１０，２０　　　　　　　圧電デバイス
　Ｆ１　　　　　　　基板
　Ｆ２　　　　　　　圧電薄膜
　Ｅ１　　　　　　　下部電極
　Ｅ２　　　　　　　上部電極
　
 
  10, 20 Piezoelectric device F1 Substrate F2 Piezoelectric thin film E1 Lower electrode E2 Upper electrode

Claims (11)

  1. 　ウルツ鉱構造を有する窒化アルミニウム結晶からなる圧電膜であって、前記窒化アルミニウム結晶は、スカンジウム原子及びホウ素原子を含み、前記窒化アルミニウム結晶中における一部のアルミニウム原子が前記スカンジウム原子又は前記ホウ素原子に置換された構造を有する、圧電膜。 A piezoelectric film made of an aluminum nitride crystal having a wurtzite structure, wherein the aluminum nitride crystal contains scandium atoms and boron atoms, and some of the aluminum atoms in the aluminum nitride crystal are converted to the scandium atoms or the boron atoms. A piezoelectric film having a substituted structure.
  2. 　前記圧電膜におけるアルミニウム原子の数と、前記ホウ素原子の数との総量に対する、前記ホウ素原子の数の割合は、０ａｔ％より大きく１３ａｔ％以下である、請求項１に記載の圧電膜。 The piezoelectric film according to claim 1, wherein a ratio of the number of boron atoms to a total amount of the number of aluminum atoms and the number of boron atoms in the piezoelectric film is greater than 0 at% and equal to or less than 13 at%.
  3. 　前記ホウ素原子の数の割合は、０ａｔ％より大きく１２ａｔ％以下である、請求項２に記載の圧電膜。 3. The piezoelectric film according to claim 2, wherein a ratio of the number of boron atoms is greater than 0 at% and equal to or less than 12 at%.
  4. 　前記ホウ素原子の数の割合は、０ａｔ％より大きく８ａｔ％以下である、請求項３に記載の圧電膜。 4. The piezoelectric film according to claim 3, wherein a ratio of the number of boron atoms is greater than 0 at% and equal to or less than 8 at%.
  5. 　前記圧電膜におけるアルミニウム原子の数と、前記スカンジウム原子の数との総量に対する、前記スカンジウム原子の数の割合は、０ａｔ％より大きく５８ａｔ％以下である、請求項１に記載の圧電膜。 2. The piezoelectric film according to claim 1, wherein a ratio of the number of scandium atoms to a total amount of aluminum atoms and scandium atoms in the piezoelectric film is greater than 0 at% and equal to or less than 58 at%.
  6. 　前記スカンジウム原子の数の割合は、４４ａｔ％以上５２．５ａｔ％以下である、請求項５に記載の圧電膜。 The piezoelectric film according to claim 5, wherein a ratio of the number of scandium atoms is 44 at% or more and 52.5 at% or less.
  7. 　前記圧電膜におけるアルミニウム原子の数と、前記ホウ素原子の数と、前記スカンジウム原子の数との総量に対する、前記ホウ素原子の数の割合は、０ａｔ％より大きく５．５ａｔ％以下である、請求項１に記載の圧電膜。 The ratio of the number of boron atoms to the total amount of the number of aluminum atoms, the number of boron atoms, and the number of scandium atoms in the piezoelectric film is greater than 0 at% and less than or equal to 5.5 at%. 1. The piezoelectric film according to 1.
  8. 　前記圧電膜におけるアルミニウム原子の数と、前記ホウ素原子の数と、前記スカンジウム原子の数との総量に対する、前記スカンジウム原子の数の割合は、０ａｔ％以上５２ａｔ％以下である、請求項１又は７に記載の圧電膜。 8. The ratio of the number of scandium atoms to the total amount of the number of aluminum atoms, the number of boron atoms, and the number of scandium atoms in the piezoelectric film is 0 at% or more and 52 at% or less. 2. The piezoelectric film according to 1.
  9. 　請求項１～８いずれか一項に記載の圧電膜を備える圧電部品。 A piezoelectric component comprising the piezoelectric film according to any one of claims 1 to 8.
  10. 　アルミニウム、ホウ素、及びスカンジウムから成る合金をターゲットとして、基板上に請求項１～８いずれか一項に記載の圧電膜を形成する、圧電膜製造方法。 A method for manufacturing a piezoelectric film, wherein the piezoelectric film according to any one of claims 1 to 8 is formed on a substrate using an alloy composed of aluminum, boron, and scandium as a target.
  11. 　アルミニウムから成るターゲット、ホウ素から成るターゲット、及びスカンジウムから成るターゲットを用いて、基板上に請求項１～８いずれか一項に記載の圧電膜を形成する、圧電膜製造方法。
     
          9. A method for producing a piezoelectric film, comprising: forming a piezoelectric film according to claim 1 on a substrate using a target made of aluminum, a target made of boron, and a target made of scandium.

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