JP5897436B2 - Method for manufacturing substrate with piezoelectric thin film and method for manufacturing piezoelectric thin film element - Google Patents

Description

  The present invention relates to a method for manufacturing a substrate with a piezoelectric thin film and a method for manufacturing a piezoelectric thin film element.

Piezoelectric bodies are processed into various piezoelectric elements according to various purposes. In particular, they are widely used as functional electronic components such as actuators that generate deformation by applying voltage and sensors that generate voltage from deformation of elements. Yes. As a piezoelectric material used for actuators and sensors, a lead-based dielectric material having large piezoelectric characteristics, particularly a Pb (Zr _1-x Ti _x ) O ₃ -based perovskite ferroelectric material called PZT is used. Widely used.

  In recent years, with the miniaturization and high performance of various electronic components, methods for forming piezoelectric bodies using thin film technology and the like have been studied. Recently, a PZT thin film formed by an RF sputtering method has been put into practical use as a head actuator for a high-definition high-speed inkjet printer or a small and low-priced gyro sensor (for example, see Patent Document 1). A piezoelectric thin film element using a piezoelectric thin film of potassium sodium niobate (KNN) that does not use lead has also been proposed. (For example, refer to Patent Document 2).

  These piezoelectric thin films are processed into the shape of a beam or a tuning fork by a fine processing process such as reactive dry etching or wet etching, and are used as piezoelectric thin film elements. Conventionally, there is only a report by reactive dry etching regarding a microfabrication process necessary for manufacturing an actuator or a sensor using a piezoelectric thin film (see, for example, Patent Document 3).

  However, since dry etching requires an expensive etching apparatus, a technique for processing a KNN film by wet etching that is simpler and lower in cost has been demanded. However, there are few reports of fine processing by wet etching of the KNN film. In the analysis of a hardly soluble oxide containing Nb, a technique is known in which a sample is made into a solution using a mixed acid of hydrofluoric acid (hereinafter referred to as hydrofluoric acid), nitric acid and perchloric acid (for example, Non-patent document 1). However, in reality, the reactivity is low and it takes time to dissolve. For this reason, in wet etching, when it uses for the process of a KNN film | membrane, time will be required and there existed a problem that process cost could not be reduced.

Since there are few reports on wet etching related to KNN, reference is made here to alkali niobium oxide and niobium oxide wet etching techniques. As an example of wet etching of an alkali niobium oxide material, ridge processing for an optical waveguide of lithium niobate (LiNbO ₃ ) crystal is known (for example, Non-Patent Document 2). In the wet etching of LiNbO ₃ , a metal mask such as Ta or Cr is used, and hydrofluoric acid or a mixed acid of hydrofluoric acid and nitric acid is used. On the other hand, referring to the technology of refining metal Nb from niobium ore (a mixture of niobium oxide (Nb ₂ O ₅ ) and tantalum oxide (Ta ₂ O ₅ )), Nb ₂ O ₅ can only be used in high concentrations of hydrofluoric acid. It is known that it does not dissolve (for example, Patent Document 4). From the above, it is speculated that hydrofluoric acid-based etchants are also promising for KNN.

Japanese Patent Laid-Open No. 10-286953 JP 2007-19302 A JP 2012-33693 A US Pat. No. 3,117,833

Hasegawa et al., “Analysis of Slightly Soluble Inorganic Materials”, Analytical Technology Information Magazine SCAS NEWS 2002-II (Vol.16) p. T-L. Ting et al., `` A Novel Wet-Etching Method Using Joint Proton Source in LiNbO3 '' IEEE Photonics Technology Letters, Vol. 18, p.568 (2006)

  However, when hydrofluoric acid alone is used as an etching solution, sodium fluoride, which is a reaction product of KNN and hydrofluoric acid, is generated during etching. This sodium fluoride (NaF) has a particularly low solubility in water, and a high etching rate cannot be obtained.

  In order to solve the above problems, one of the objects of the present invention is a method for manufacturing a substrate with a piezoelectric thin film capable of finely processing a lead-free piezoelectric thin film in a short time by wet etching, and the piezoelectric thin film The object is to provide a method for manufacturing an element.

(1) According to one embodiment of the present invention, in order to achieve the above object, a step of forming a lower electrode on a substrate, and a composition formula (K _1-x Na _x ) NbO ₃ is formed on the lower electrode. Forming a piezoelectric thin film having an alkali niobium oxide-based perovskite structure and wet etching using an etchant composed of a mixture of hydrofluoric acid and hydrochloric acid or sulfuric acid using an etching mask containing a Cr film. and facilities to the body thin film manufacturing method of the piezoelectric thin-film substrate comprising the steps of transferring the pattern of the etching mask on the piezoelectric thin film is provided.

  (2) In the method for manufacturing a substrate with a piezoelectric thin film, in the wet etching, the etching solution is preferably used by heating.

  (3) In the method for manufacturing a substrate with a piezoelectric thin film, the lower electrode may be made of Pt.

  (4) In the method for manufacturing a substrate with a piezoelectric thin film, the crystal system of the piezoelectric thin film is a pseudo-cubic crystal, and the piezoelectric thin film is formed so that a crystal axis is preferentially oriented in a (001) plane direction. May be.

  (5) In the method for manufacturing a substrate with a piezoelectric thin film, the piezoelectric thin film may be formed by a sputtering method so that x in a composition formula is 0.4 or more and 0.730 or less.

  (6) In the method for manufacturing a substrate with a piezoelectric thin film, the substrate may be a Si substrate having an oxide film on a surface thereof.

  (7) Moreover, according to the other aspect of this invention, the said piezoelectric thin film was wet-etched with the manufacturing method of the board | substrate with a piezoelectric thin film in any one of said (1)-(6). Thereafter, a method of manufacturing a piezoelectric thin film element is provided in which an upper electrode is formed on the piezoelectric thin film.

  According to one aspect of the present invention, there are provided a method for manufacturing a substrate with a piezoelectric thin film and a method for manufacturing a piezoelectric thin film element capable of finely processing a lead-free piezoelectric thin film in a short time by wet etching. Can do.

FIGS. 1A and 1B are vertical sectional views of a substrate with a piezoelectric thin film and a piezoelectric thin film element according to the present embodiment, respectively. 2A to 2D are vertical cross-sectional views showing manufacturing steps of the substrate with the piezoelectric thin film according to the embodiment. FIGS. 3E to 3G are vertical cross-sectional views showing the manufacturing process of the substrate with the piezoelectric thin film according to the embodiment. 4 (h) and 4 (i) are vertical sectional views showing a manufacturing process of the piezoelectric thin film element according to the embodiment.

Embodiment
According to one embodiment of the present invention, a step of forming a lower electrode on a substrate and a composition formula (K _1-x Na _x ) NbO ₃ (hereinafter referred to as KNN) are formed on the lower electrode. Forming a piezoelectric thin film having an alkali niobium oxide-based perovskite structure and wet etching using an etchant composed of a mixture of hydrofluoric acid and hydrochloric acid or sulfuric acid using an etching mask containing a Cr film. And a method for manufacturing a substrate with a piezoelectric thin film, the method including: Here, hydrofluoric acid, hydrochloric acid, and sulfuric acid are, for example, a 49% by weight hydrofluoric acid aqueous solution, a 36% by weight hydrochloric acid aqueous solution, and a 96% by weight sulfuric acid aqueous solution for electronic industry, respectively.

When a mixed solution of hydrofluoric acid and hydrochloric acid or sulfuric acid is used as an etching solution, the etching rate of the KNN piezoelectric thin film is remarkably higher than that when hydrofluoric acid is used alone as an etching solution. This is considered to be due to the difference in solubility of the reaction product of the KNN piezoelectric thin film and the acid in water. That is, sodium chloride produced when mixed with an aqueous solution containing hydrochloric acid, rather than the solubility of sodium fluoride (NaF) produced in the case of using fluoride alone in the produced fluoride. The solubility of sodium sulfate (Na ₂ SO ₄ ) or the like produced when mixed with an aqueous solution containing (NaCl) or sulfuric acid is higher.

  FIGS. 1A and 1B are vertical sectional views of a substrate with a piezoelectric thin film and a piezoelectric thin film element according to the present embodiment, respectively. In this embodiment, a substrate having an etched piezoelectric thin film is called a substrate with a piezoelectric thin film.

  The substrate 1 with a piezoelectric thin film includes a substrate 10, a lower electrode 11 on the substrate 10, and a piezoelectric thin film 12 on the lower electrode 11. The piezoelectric thin film element 2 has a configuration in which an upper electrode 15 is added on the piezoelectric thin film 12 of the substrate 1 with the piezoelectric thin film. The shape of the piezoelectric thin film 12 is not limited to that shown in FIGS.

  The substrate 10 is, for example, a Si substrate. The Si substrate preferably has an oxide film (not shown) on the surface. By having the oxide film on the surface, the adhesion between the substrate 10 and the lower electrode 11 can be improved. Examples of the oxide film on the surface include a thermal oxide film formed by performing a thermal oxidation process on the surface of the Si substrate, an Si oxide film formed by a CVD (Chemical Vapor Deposition) method, and the like. The plane orientation of the main surface of the Si substrate is, for example, (001).

The substrate 10 may be an SOI substrate, a quartz glass substrate, a GaAs substrate, a sapphire substrate, a metal substrate such as stainless steel, an MgO substrate, or an SrTiO ₃ substrate.

  The lower electrode 11 is made of a conductive material such as Pt or an alloy containing Pt as a main component. Since Pt is inactive to the hydrofluoric acid-based etching solution, the lower electrode 11 made of Pt functions as an etching stopper in the etching of the piezoelectric thin film 12 using the hydrofluoric acid-based etching solution of the present embodiment. . In order to make the piezoelectric thin film 12 exhibit sufficient piezoelectric characteristics, the arithmetic average surface roughness Ra of the lower electrode 11 is preferably 0.86 nm or less.

  In order to improve the adhesion between the substrate 10 and the lower electrode 11, an adhesion layer (not shown) made of titanium (Ti), tantalum (Ta), or the like is formed between the substrate 10 and the lower electrode 11. Also good. The adhesion layer is formed by, for example, a vapor deposition method. Further, even when the adhesion layer is not provided between the substrate 10 and the lower electrode 11, the adhesion between the substrate 10 and the lower electrode 11 can be improved by controlling the plane orientation of the lower electrode 11.

The piezoelectric thin film 12 is made of (K _1-x Na _x ) NbO ₃ having an alkali niobium oxide-based perovskite structure and does not contain lead. X of the composition formula _{(K 1-x Na x)} NbO 3 , for example, 0.4 or more and 0.730 or less.

  The crystal system of the KNN piezoelectric material constituting the piezoelectric thin film 12 is a pseudo cubic crystal, a tetragonal crystal, an orthorhombic crystal, a monoclinic crystal, or a rhombohedral crystal. In the piezoelectric thin film 12, the crystal axis of KNN is (001). It is preferable to preferentially align in the plane direction. By controlling in the (001) plane direction, crystal domains can be aligned in the voltage application direction, and a high piezoelectric constant can be obtained. In order to control the orientation of the crystal axis, the piezoelectric thin film 12 is formed by sputtering, for example. The piezoelectric thin film 12 may contain impurities such as Li (lithium), Ta, Sb (antimony), Ca (calcium), Cu (copper), Ba (barium), Ti, or the like having 5 atomic% or less.

  For the upper electrode 15, for example, Pt, an alloy containing Pt as a main component, or the like can be used in the same manner as the lower electrode 11 in addition to Al, Au, and Ni.

  FIGS. 2A to 2D and FIGS. 3E to 3G are vertical sectional views showing a manufacturing process of the substrate with the piezoelectric thin film according to the embodiment. 4 (h) and 4 (i) are vertical sectional views showing a manufacturing process of the piezoelectric thin film element according to the embodiment.

  First, as shown in FIG. 2A, the lower electrode 11 is formed on the substrate 10 by RF magnetron sputtering or the like. Alternatively, an adhesion layer made of Ti or the like may be formed on the substrate 10 by vapor deposition or the like, and the lower electrode 11 may be formed thereon.

  Next, as shown in FIG. 2B, a piezoelectric thin film 12 is formed on the lower electrode 11 by an RF magnetron sputtering method or the like. The piezoelectric thin film 12 may be formed by an ion beam deposition method, an aerosol deposition method, a sol-gel method, a hydrothermal synthesis method, or the like.

  Next, as shown in FIG. 2C, a photoresist pattern 13 is formed on the piezoelectric thin film 12 by photolithography. The photoresist pattern 13 is formed by applying a photoresist such as OFPR-800 on the piezoelectric thin film 12, and performing exposure and development.

  Next, as shown in FIG. 2D, the Cr film 14 is formed on the photoresist pattern 13 and the region of the piezoelectric thin film 12 not covered with the photoresist pattern 13 by RF magnetron sputtering or the like. .

  Next, as shown in FIG. 3E, the photoresist pattern 13 is dissolved by acetone cleaning or the like, the photoresist pattern 13 and the Cr film 14 thereon are removed (lift-off), and the Cr film 14 is patterned. Note that the Cr film 14 may be patterned by means other than lift-off such as etching.

  Next, as shown in FIG. 3F, wet etching is performed on the piezoelectric thin film 12 using the patterned Cr film 14 as an etching mask, and the pattern of the Cr film 14 is transferred to the piezoelectric thin film 12. . Here, an etching solution made of the above-described mixed solution of hydrofluoric acid and hydrochloric acid or sulfuric acid is used. The Cr film 14 made of Cr has sufficient resistance to such an etching solution.

By using an etchant composed of a mixture of hydrofluoric acid and hydrochloric acid or sulfuric acid, the etching rate can be improved (for example, 250 nm / min or more) even with a piezoelectric thin film composed of (K _1-x Na _x ) NbO _3. Therefore, the piezoelectric thin film 12 can be finely processed in a short time. In addition, the etching rate can be further improved by heating the etching solution.

  A multilayer film composed of a Cr film and another film may be used as an etching mask instead of the Cr film 14. For example, a film in which an organic resist film is stacked on a Cr film, a film in which a Cr film is stacked on a Ni film, or a film in which a Ni film is stacked on a Cr film can be used as an etching mask.

  Next, as shown in FIG. 3G, the remaining Cr film 14 is removed by wet etching or the like. For the wet etching of the Cr film 14, an etching solution for Cr film such as second ceric ammonium nitrate or potassium ferricyanide can be used. Thereafter, the patterned piezoelectric thin film 12 is washed with water and dried.

  Next, as shown in FIG. 4H, after the photoresist pattern 16 is formed, the upper electrode layer 17 is formed on the photoresist pattern 16 and the region of the piezoelectric thin film 12 that is not covered with the photoresist pattern 16. Form.

  Next, as shown in FIG. 4I, the upper electrode 15 is formed on the piezoelectric thin film 12 by removing (lifting off) the photoresist pattern 16 and the upper electrode layer 17 thereon. Then, after washing and drying, the piezoelectric thin film element 2 having a desired element shape is obtained by separating into chips by dicing or the like.

  A sensor is obtained by connecting a voltage detecting means to the lower electrode 11 and the upper electrode 15 of the piezoelectric thin film element 2 obtained by the above manufacturing method, and an actuator is obtained by connecting the voltage applying means. The actuator can be used for an inkjet printer head, a scanner, an ultrasonic generator, and the like. As the sensor, it can be used for a gyroscope, an ultrasonic sensor, a pressure sensor, a speed / acceleration sensor, and the like. Furthermore, the piezoelectric thin film element 2 can also be applied to a filter device or a MEMS device. Thus, by using the piezoelectric thin film element 2, the piezoelectric film device provided with the voltage detection means or the application means can be manufactured with the same reliability and low manufacturing cost as the conventional product.

(Effect of embodiment)
According to the above embodiment, the piezoelectric thin film made of the KNN piezoelectric material can be finely processed in a short time by wet etching using an etching solution made of a mixed solution of hydrofluoric acid and hydrochloric acid or sulfuric acid. Thereby, a board | substrate with a piezoelectric material thin film and a piezoelectric material thin film element can be manufactured efficiently.

  Hereinafter, with reference to FIG. 2 and Table 1, a method for manufacturing a substrate with a piezoelectric thin film and a method for manufacturing a piezoelectric thin film element will be described in detail with examples and comparative examples.

  First, the steps shown in FIGS. 2A to 3E until the Cr film 14 is patterned are performed, and the substrate 10, the lower electrode 11, the piezoelectric thin film 12, and the patterned Cr film 14 are formed. , To form a sample having six similar configurations. Next, these six samples were etched under different conditions as Examples 1 to 5 and Comparative Example. Details of each step will be described below.

  First, a step of forming the lower electrode 11 on the substrate 10 as shown in FIG. As the substrate 10, a Si substrate having a main surface with a surface orientation of (100), a thickness of 0.525 mm, a size of 4 inches, and a thermal oxide film with a thickness of 200 nm was used. An adhesion layer made of Ti having a thickness of 2.2 nm was formed on the substrate 10 by vapor deposition, and a Pt electrode having a thickness of 205 nm was formed thereon as the lower electrode 11 by RF magnetron sputtering. Adhesion layer and lower electrode 11 are under conditions of Ar atmosphere, substrate temperature of 250 ° C., discharge power of 200 W, pressure of 2.5 Pa, film formation time of 2 minutes (adhesion layer) and 10 minutes (lower electrode 11) Formed below. When the in-plane surface roughness of the formed lower electrode 11 was measured, the arithmetic average surface roughness Ra was 0.86 nm or less.

Next, a step of forming a piezoelectric thin film 12 on the lower electrode 11 as shown in FIG. A piezoelectric thin film 12 made of KNN having a thickness of 2 μm was formed on the lower electrode 11 by RF magnetron sputtering. The piezoelectric thin film 12 uses a (K _1-x Na _x ) NbO ₃ sintered body of Na / (K + Na) = 0.65 as a target, the substrate temperature is 520 ° C., the discharge power is 700 W, and the O ₂ / Ar mixture. The film was formed under the condition that the ratio was 0.005 and the pressure in the chamber was 1.3 Pa. The sputter deposition time was adjusted so that the film thickness was 2 μm.

  Next, a step of forming a photoresist pattern 13 on the piezoelectric thin film 12 as shown in FIG. The photoresist pattern 13 was formed by applying a photoresist OFPR-800 on the piezoelectric thin film 12 and performing exposure and development.

  Next, as shown in FIG. 2D, a step of forming a Cr film 14 on the photoresist pattern 13 and the region of the piezoelectric thin film 12 not covered with the photoresist pattern 13 was performed. Cr was deposited on the piezoelectric thin film 12 by RF magnetron sputtering to form a Cr film 14 having a thickness of about 200 nm.

  Next, a step of patterning the Cr film 14 by lift-off as shown in FIG. The photoresist pattern 13 was dissolved by washing with acetone, the photoresist pattern 13 and the Cr film 14 thereon were removed, and the Cr film 14 was patterned. By repeating the steps up to here in the same manner, six samples having the same configuration were obtained.

  Next, the process of transferring the pattern of the Cr film 14 to the piezoelectric thin film 12 as shown in FIG. 3F was performed on the six samples under different etching conditions, and the etching rates were obtained. The etching rate was measured by immersing a 5 × 10 mm piece of the sample in the etching solution, measuring the time until the lower electrode 11 was exposed, and measuring the thickness of the piezoelectric thin film 12 (2 μm) and the lower electrode 11 being exposed. Calculated from time.

  The process for each sample is described below as Examples 1 to 5 and a comparative example.

Example 1
As an etching solution, a mixed solution of 100 ml of hydrofluoric acid having a concentration of 49% by mass and 6.5 ml of hydrochloric acid having a concentration of 36% by mass was used at room temperature (25 ° C.). The etching rate was 370 nm / min.

(Example 2)
As an etching solution, a mixed solution of 100 ml of hydrofluoric acid having a concentration of 49% by mass and 34.5 ml of hydrochloric acid having a concentration of 36% by mass was used at room temperature (25 ° C.). The etching rate was 260 nm / min.

(Example 3)
As an etching solution, a mixed solution of 100 ml of hydrofluoric acid having a concentration of 49% by mass and 60 ml of sulfuric acid having a concentration of 96% by mass was used at room temperature (25 ° C.). The etching rate was 1000 nm / min.

Example 4
As an etching solution, a mixed solution of 34 ml of hydrofluoric acid having a concentration of 49% by mass and 47.2 ml of sulfuric acid having a concentration of 96% by mass was used at room temperature (25 ° C.). The etching rate was 320 nm / min.

(Example 5)
As the etchant, the same mixture as in Example 3 was heated to 60 ° C. and used. The etching rate was 2000 nm / min.

(Comparative example)
As an etchant, hydrofluoric acid (single) was used at room temperature (25 ° C.). The etching rate was 240 nm / min.

  Table 1 shows the etching conditions and the obtained etching rates of Examples 1 to 5 and Comparative Example.

  When Examples 1-5 are compared with Comparative Examples, the etching rates of Examples 1-5 are greater than the etching rates of Comparative Examples. That is, when the etching solution contains hydrochloric acid or sulfuric acid, the etching rate increases, and an etching rate higher than the etching rate of 240 nm / min when a single hydrofluoric acid is used as the etching solution can be obtained.

  It can be seen that the etching rate is improved when the etching solution contains hydrochloric acid or sulfuric acid as compared with the case where a single hydrofluoric acid is used as the etching solution.

  When Example 1 and Example 2 are compared, the etching rate of Example 1 is larger than the etching rate of Example 2. That is, if the concentration of hydrochloric acid contained in the etching solution is too high, the etching rate is reduced. Similarly, when Example 3 and Example 4 are compared, the etching rate of Example 3 is larger than the etching rate of Example 4. That is, if the concentration of sulfuric acid contained in the etching solution is too high, the etching rate is reduced. These are considered to be due to the fact that the relative concentration of hydrofluoric acid was lowered and the amount of Na reaction product (NaF) in the etching solution was suppressed.

  Moreover, when Example 3 and Example 5 are compared, the etching rate of Example 5 is larger than the etching rate of Example 3. That is, the etching rate is increased by heating the etching solution. This is thought to be due to the large temperature dependence of the solubility of alkali sulfates.

  In each of Examples 1 to 5 and Comparative Example, Pt constituting the lower electrode 11 is inactive with respect to the hydrofluoric acid-based etching solution, so that the etching can be stopped at the lower electrode 11. did it.

  After etching the piezoelectric thin film 12, a step of removing the remaining Cr film 14 as shown in FIG. For removing the remaining Cr film 14, second ceric ammonium nitrate was used as a Cr etching solution.

  The approximate etching selectivity between the piezoelectric thin film 12 and the Cr film 14 was determined by measuring the level difference between the piezoelectric thin film 12 and the Cr film 14 before and after the wet etching of the piezoelectric thin film 12. Hardly reacted with the hydrofluoric acid-based etching solution. For this reason, it has been found that it is not particularly necessary to define the thickness ratio of the piezoelectric thin film 12 and the Cr film 14 in consideration of the etching selectivity. However, if pin holes are present in the Cr film 14, the piezoelectric thin film 12 covered with the Cr film 14 is damaged during wet etching, so that the Cr film 14 without pin holes may be formed. It is required to appropriately set the film forming conditions of the Cr film 14 to the extent possible. For example, the deposition rate of the Cr film 14 is desirably 4 nm / min or less.

  Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the spirit of the invention.

  For example, a mixed solution of hydrofluoric acid and nitric acid may be used as the etching solution. However, since this etching solution dissolves Si, a substrate other than the Si substrate is used as the substrate 10, or the exposed back surface (surface opposite to the lower electrode 11) of the substrate 10 is protected during wet etching. Is required.

  The embodiments and examples described above do not limit the invention according to the claims. It should be noted that not all combinations of features described in the embodiments and examples are necessarily essential to the means for solving the problems of the invention.

DESCRIPTION OF SYMBOLS 1 Substrate with piezoelectric thin film 2 Piezoelectric thin film element 10 Substrate 11 Lower electrode 12 Piezoelectric thin film 13, 16 Photoresist pattern 14 Cr film 15 Upper electrode

Claims (7)

Forming a lower electrode on the substrate;
Forming a piezoelectric thin film having an alkali niobium oxide-based perovskite structure represented by a composition formula (K _1-x Na _x ) NbO ₃ on the lower electrode;
Using an etching mask containing a Cr film, a wet etching using an etchant comprising a mixed liquid of hydrofluoric acid and hydrochloric acid or sulfuric acid and facilities on the piezoelectric thin film, to transfer the pattern of the etching mask on the piezoelectric thin film Process,
A method for manufacturing a substrate with a piezoelectric thin film comprising: In the wet etching, the etchant is heated and used.
The manufacturing method of the board | substrate with a piezoelectric thin film of Claim 1. The lower electrode is made of Pt;
The manufacturing method of the board | substrate with a piezoelectric thin film in any one of Claim 1 or 2. The crystal system of the piezoelectric thin film is a pseudo-cubic crystal,
The piezoelectric thin film is formed such that the crystal axis is preferentially oriented in the (001) plane direction.
The manufacturing method of the board | substrate with a piezoelectric thin film in any one of Claims 1-3. The piezoelectric thin film is formed by sputtering so that x in the composition formula is 0.4 or more and 0.730 or less.
The manufacturing method of the board | substrate with a piezoelectric thin film in any one of Claims 1-4. The substrate is a Si substrate having an oxide film on the surface,
The manufacturing method of the board | substrate with a piezoelectric thin film in any one of Claims 1-5. After performing the wet etching on the piezoelectric thin film by the method for manufacturing a substrate with a piezoelectric thin film according to any one of claims 1 to 6,
Forming an upper electrode on the piezoelectric thin film;
A method for manufacturing a piezoelectric thin film element.

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