JP2012054317A - Substrate provided with piezoelectric thin film and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate provided with a piezoelectric thin film capable of performing non-destructive characteristic evaluation of the piezoelectric thin film, and provide a manufacturing method of the substrate.SOLUTION: In a substrate provided with a piezoelectric thin film, a lower electrode layer 6 is formed on a substrate 5, and a piezoelectric thin film 2 having a perovskite structure is formed on the lower electrode layer 6. A lower electrode exposure part 3 in which a portion of the lower electrode layer 6 is exposed from the piezoelectric thin film 2 is provided on the lower electrode layer 6 without removing the piezoelectric thin film 2 because the piezoelectric thin film 2 formed on the lower electrode layer 6 is formed on a area narrower than that of the lower electrode layer 6.

Description

  The present invention relates to a substrate with a piezoelectric thin film provided with a piezoelectric thin film having a perovskite structure and a method for manufacturing the same.

Piezoelectric materials are processed into various piezoelectric elements according to various purposes, and in particular, functionality such as an actuator that applies a voltage to the piezoelectric element to cause deformation, and conversely, a sensor that detects a voltage generated by the deformation of the piezoelectric element. Widely used as electronic components. As a piezoelectric material used for actuators and sensors, a lead-based material dielectric material having excellent piezoelectric characteristics, particularly a PZT-based material represented by a composition formula: Pb (Zr _1-x Ti _x ) O ₃ is used. Perovskite ferroelectrics have been widely used so far, and are usually formed by sintering oxides composed of individual elements. At present, as various electronic components have been reduced in size and performance, there has been a strong demand for miniaturization and high performance in piezoelectric elements.

  However, a piezoelectric material manufactured by a manufacturing method centering on a sintering method, which is a conventional manufacturing method, is a crystal that forms the material as the thickness decreases, particularly as the thickness approaches 10 μm. Approaching the size of the grain, the effect can not be ignored. For this reason, problems such as significant variations in characteristics and deterioration occur, and in order to avoid such problems, methods for forming piezoelectric thin films that apply thin film technology instead of sintering methods have recently been studied. . Recently, a PZT thin film formed on a silicon substrate by a sputtering method has been put into practical use as a piezoelectric thin film for an actuator for a high-speed, high-definition inkjet printer head.

A piezoelectric thin film made of PZT contains about 60 to 70% by weight of lead, which is not preferable from the viewpoint of ecological viewpoint and pollution prevention. Therefore, development of a piezoelectric thin film that does not contain lead is desired in consideration of the environment. Currently, various lead-free piezoelectric materials have been studied. Among them, potassium sodium niobate represented by the composition formula: (K _1-x Na _x ) NbO ₃ (0 <x <1) (Also referred to as “KNN”) (see, for example, Patent Document 1 and Patent Document 2). The KNN thin film has also been attempted to be deposited on a substrate such as an MgO substrate, a SrTiO ₃ substrate, or a Si substrate by a deposition method such as sputtering or PLD. This KNN is a material having a perovskite structure and exhibits relatively good piezoelectric characteristics as a non-lead material, and thus is expected as a promising candidate for a non-lead piezoelectric material.

  By the way, when a piezoelectric thin film is formed by thin film technology, a large number of sheets can be formed simultaneously on the same substrate or between lots of film formation due to changes in equipment structure, film formation conditions, equipment and raw materials over time. In some cases, the film characteristics may vary among substrates in a lot. In particular, when the substrate diameter is increased, the characteristic distribution in the radial direction from the center of the substrate may be increased. If there is such a characteristic distribution in the plane of the same substrate, the element acquisition rate from one substrate when it is made into an element is lowered, which becomes a big problem in terms of cost. Similarly, when there is a characteristic distribution between the substrates, the yield is lowered, which causes a problem. Therefore, it is important to evaluate the characteristics of the piezoelectric thin film.

  In the characteristic evaluation of the piezoelectric thin film, electrodes are attached to the top and bottom of the piezoelectric thin film, a voltage is applied between the electrodes, and the insulation characteristic, dielectric constant characteristic, and piezoelectric characteristic are measured. However, it is difficult to evaluate a conventional substrate with a piezoelectric thin film as it is because the lower electrode is covered with the piezoelectric thin film. Therefore, a region required for evaluation is cut out from the substrate and a simple element is manufactured and measured (Patent Document 2), or a part of the piezoelectric thin film is removed using photolithography or etching after the piezoelectric thin film is formed, A structure in which the lower electrode is exposed is fabricated and measured.

JP 2007-184513 A JP 2008-159807 A (see paragraph 0038, FIG. 6)

  However, the above-described conventional work for piezoelectric thin film evaluation requires a long process, and requires skill and know-how for each. Therefore, if the substrate diameter increases and the number of measurement points increases, the amount of work increases and the burden is large. Become. Moreover, since the evaluation method of the prior art is a destructive inspection, the evaluated substrate with a piezoelectric thin film cannot be sold as a product as it is. The need for a simple evaluation method that is non-destructive and requires a small amount of work is common to not only PZT thin films but also KNN thin films.

  An object of the present invention is to provide a substrate with a piezoelectric thin film that enables non-destructive characteristics evaluation of the piezoelectric thin film and a method for manufacturing the same.

  According to an embodiment of the present invention, in a substrate with a piezoelectric thin film in which a lower electrode layer is formed on a substrate and a piezoelectric thin film having a perovskite structure is formed on the lower electrode layer, the substrate is formed on the lower electrode layer. There is provided a substrate with a piezoelectric thin film in which the piezoelectric thin film is formed with a smaller area than the lower electrode layer, and a lower electrode exposed portion is provided on the lower electrode layer.

In this case, it is preferable that the lower electrode exposed portion is provided so that the outer peripheral portion of the lower electrode layer is exposed. Furthermore, it is preferable that the width | variety of the said lower electrode exposure part formed in the said outer peripheral part is 0.005 * D or more and 0.05 * D or less with respect to the outer diameter D of the said board | substrate. The piezoelectric thin film having a perovskite structure is preferably potassium sodium niobate represented by the general formula (K _1-x Na _x ) NbO ₃ (0 <x <1).

  According to another aspect of the present invention, there is provided a method for manufacturing a substrate with a piezoelectric thin film as described above, wherein an upper electrode having a width of 0.5 mm or more and 5.0 mm or less is formed on the piezoelectric thin film, and the lower electrode is exposed. A method for manufacturing a substrate with a piezoelectric thin film is provided, which includes a step of inspecting characteristics of the piezoelectric thin film by applying a voltage between a portion and the upper electrode.

  In this case, it is preferable that the upper electrode includes a first upper electrode formed at a central portion of the piezoelectric thin film and a plurality of second upper electrodes formed at equal intervals from the first upper electrode. .

  According to another aspect of the present invention, a part of the lower electrode layer is covered with a shielding jig, and a perovskite structure piezoelectric thin film is formed on the other part of the lower electrode layer not covered with the shielding jig. Forming a lower electrode exposed portion where a piezoelectric thin film is not formed on a part of the lower electrode layer, and removing the shielding jig after forming the piezoelectric thin film, thereby forming a part of the lower electrode layer; A method for manufacturing a substrate with a piezoelectric thin film that exposes the exposed portion of the lower electrode formed on the substrate is provided.

In this case, it is preferable that the width of the exposed portion of the lower electrode formed on the outer peripheral portion is 0.005 × D or more and 0.05 × D or less with respect to the outer diameter D of the substrate. Moreover, it is preferable that the linear expansion coefficient α _w of the shielding jig and the linear expansion coefficient α _{b of the} substrate in the range of the formation temperature of the piezoelectric thin film are 1 ≦ α _w / α _b ≦ 4. Furthermore, the piezoelectric thin film having the perovskite structure may be potassium sodium niobate represented by the general formula (K _1-x Na _x ) NbO ₃ (0 <x <1).

  According to the present invention, characteristics of a piezoelectric thin film can be evaluated nondestructively.

It is explanatory drawing of the board | substrate with a piezoelectric thin film which concerns on one embodiment of this invention, Comprising: (a) is a top view, (b) is AA sectional drawing. It is a process flowchart which shows the outline of the manufacturing process of the board | substrate with a piezoelectric thin film which concerns on one embodiment of this invention. It is a top view of the board | substrate with a piezoelectric material thin film produced in Examples 1-6 of this invention. It is the figure which showed the effective utilization factor of the board | substrate surface with respect to the width | variety exposed part of a lower electrode when the comparative example 4 is applied. It is the figure which showed the effective utilization factor of the substrate surface with respect to the upper electrode width when the comparative example 5 is applied. It is explanatory drawing of the film-forming system of the Example of this invention, Comprising: (a) is explanatory drawing of the face-down system of Examples 1-6, (b) is explanatory drawing of the face-up system by Example 7. FIG. It is a top view of the board | substrate with a piezoelectric thin film produced in Example 8 of this invention.

  An embodiment of the present invention will be described below.

[Embodiment]
In the substrate with a piezoelectric thin film of the present embodiment, a lower electrode layer is formed on the substrate, and a piezoelectric thin film having a perovskite structure is formed on the lower electrode layer. The piezoelectric thin film formed on the lower electrode layer is formed with a smaller area than the lower electrode layer, thereby providing a lower electrode exposed portion on which the piezoelectric thin film is not formed on the lower electrode layer. It has been.

  The piezoelectric thin film having a perovskite structure preferably has a film thickness of 0.3 μm or more and 10 μm or less in order to meet the demand for miniaturization and high performance of various electronic components. The perovskite-structured piezoelectric thin film may be a PZT-based perovskite ferroelectric thin film, but a KNN-based perovskite-type ferroelectric thin film is more preferable from a lead-free viewpoint. In particular, when the piezoelectric thin film having a perovskite structure is made of KNN, it is possible to obtain a substrate with a piezoelectric thin film having a large diameter (for example, 4 inches or more) that does not contain lead.

  According to the above-described embodiment, the substrate with the piezoelectric thin film is already provided with the lower electrode exposed portion on which the piezoelectric thin film is not formed without performing a processing process or the like. Without cutting out the necessary area from the substrate with a thin film and simply manufacturing the element, or removing a portion of the piezoelectric thin film and exposing it, the shape of the substrate with the piezoelectric thin film remains unchanged. The characteristics can be reliably evaluated non-destructively. Further, since the non-destructive inspection is performed, the evaluated substrate with the piezoelectric thin film can be sold as a product as it is.

  Depending on the embodiment, the lower electrode exposed portion may be provided so as to be exposed at the outer peripheral portion of the lower electrode layer. When provided on the outer peripheral portion of the lower electrode layer, the outer peripheral portion may be the entire outer periphery of the lower electrode layer or may be a partial region of the outer periphery. If the lower electrode exposed portion is provided so that the outer peripheral portion of the lower electrode layer is exposed, it becomes possible to more reliably and non-destructively evaluate the characteristics of the substrate with the piezoelectric thin film. In addition, it is possible to suppress a decrease in the effective usage rate of the substrate with the piezoelectric thin film and to prevent the element acquisition area from decreasing.

The width of the exposed portion of the lower electrode formed on the outer peripheral portion is 0 with respect to the outer diameter D of the substrate.
. It is preferable that it is 005 × D or more and 0.05 × D or less. Here, the width of the lower electrode exposed portion means the contour width of the lower electrode exposed portion. When the width of the exposed portion of the lower electrode is 0.005 × D or more, it becomes possible to more reliably perform nondestructive evaluation. Moreover, the fall of the effective usage rate of a board | substrate with a piezoelectric thin film can be suppressed as it is 0.05xD or less, and it can prevent that an element acquisition area reduces more.

[Specific example of embodiment]
Next, a specific example of the embodiment in which the lower electrode exposed portion is provided so as to be exposed in the entire outer peripheral portion of the lower electrode layer will be described with reference to the drawings.

  1A and 1B are explanatory views of a substrate with a piezoelectric thin film according to an embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a cross-sectional view.

  The substrate 1 with a piezoelectric thin film according to the present embodiment includes a substrate 5, a lower electrode layer 6 formed on substantially the entire first surface side of the substrate 5, and the opposite side of the lower electrode layer 6 from the substrate 1 side. The piezoelectric thin film 2 is formed on the first surface side, and the upper electrode 4 is partially formed on the first surface side opposite to the lower electrode layer 6 of the piezoelectric thin film 2.

  As the substrate, for example, a (001) plane Si substrate with a thermal oxide film is used. For example, Pt is used for the lower electrode, and Ti is used for the adhesion layer interposed between the lower electrode layer 6 and the piezoelectric thin film 2, for example. On the first surface side of the lower electrode layer 6, there is provided a lower electrode exposed portion 3 where the entire outer peripheral portion of the lower electrode layer 6 where the piezoelectric thin film 2 is not formed is exposed. In the piezoelectric thin film 2, the minimum width W of the lower electrode exposed portion 3 exposed in the entire outer peripheral portion of the lower electrode layer 6 is 0.005 × Dmm or more and 0.05 × Dmm or less with respect to the outer diameter Dmm of the substrate. The film is formed on the first surface side of the lower electrode layer 6 so as to enter the range, leaving the range. Here, the minimum of the minimum width of the lower electrode exposed portion 3 is a name given because it is advantageous that the width of the lower electrode exposed portion is as small as possible, and does not have a corresponding maximum width.

  The lower electrode exposed portion 3 is advantageously as small as possible in view of the element acquisition area in the subsequent element formation. If the upper limit of the width W is 0.05 × Dmm or less, the area of the lower electrode exposed portion 3 where the element cannot be obtained is 10% or less with respect to the total area of the substrate, and this value is within an allowable range.

  The substrate 1 with a piezoelectric thin film has a structure in which one or more upper electrodes 4 having a predetermined width are formed at arbitrary points on the first surface of the piezoelectric thin film 2 for which insulation characteristics, dielectric constant characteristics, piezoelectric characteristics and the like are to be measured. It has become. The minimum width of the upper electrode is preferably from 0.1 mm to 5.0 mm. Here, the width of the upper electrode 4 means the contour width of the upper electrode 4. Also, the minimum width of the upper electrode 4 has the same meaning as the minimum width of the exposed portion of the lower electrode, and the upper electrode 4 is named because it is advantageous to make the width as small as possible, and there is a corresponding maximum width. is not. The minimum width of the upper electrode 4 means, for example, the length of one side if the shape of the upper electrode 4 is square, and the diameter if the shape is circular. It is advantageous that the minimum width range is as small as possible in view of the element acquisition area in the subsequent elementization. However, when applying a voltage to the electrode, it is necessary to contact a terminal with a sharp tip, etc.If the upper electrode has a minimum width that is too small, special equipment such as a dedicated extra-fine terminal or a high-power microscope is required. Necessary. Furthermore, the upper electrode 4 sometimes measures the displacement (deformation) of the film by irradiating laser light from the upper part and measuring the reflection when measuring the piezoelectric characteristics.

Thus, the upper electrode 4 requires a region to which the laser beam is applied in addition to the region to which the voltage is applied. Therefore, the above-described range in which the minimum width of the upper electrode is 0.5 mm to 5.0 mm satisfies both. It becomes a range. Since the laser beam used here is often a red laser having a wavelength of about 700 nm, the electrode material used is Ag, Al, Au, which is a material having a reflectance of 60% or more at a wavelength of 700 nm. Cu, Ni, Pt, Rh, or a multilayer film containing them, or an alloy containing them.

[Method of manufacturing substrate with piezoelectric thin film]
Next, a method for manufacturing a substrate with a piezoelectric thin film according to the present embodiment will be described.

  In the method for manufacturing a substrate with a piezoelectric thin film, a lower electrode layer is formed on the first surface side of the substrate, and a part of the lower electrode layer on the first surface side is covered with a shielding jig. A piezoelectric thin film having a perovskite structure is formed on the other part of the lower electrode layer that is not covered by the shielding jig, and the lower electrode is exposed while the piezoelectric thin film is not formed on a part of the lower electrode layer during the formation of the piezoelectric thin film. Forming part. After the formation of the piezoelectric thin film, the shielding jig is removed to expose a lower electrode exposed portion formed in a part of the lower electrode layer.

  The lower electrode layer is formed by sputtering or vapor deposition, for example. To form the exposed portion of the lower electrode, when forming the piezoelectric thin film, the entire outer peripheral portion or a part of the lower electrode layer is protected by a shielding jig, and the surface of the lower electrode layer on which the piezoelectric thin film is not formed is protected. A step of forming is included. As a result, it is possible to form the exposed portion of the lower electrode necessary for measuring the insulation characteristic, dielectric constant characteristic, and piezoelectric characteristic without removing the piezoelectric thin film after forming the piezoelectric thin film.

  According to this, since a part of the lower electrode layer is shielded by using a shielding jig during formation of the piezoelectric thin film, the exposed portion of the lower electrode necessary for characteristic evaluation is formed. The process of exposing the lower electrode later is eliminated. Therefore, the characteristics of the substrate with the piezoelectric thin film can be evaluated by a non-destructive and simple process. If the evaluated substrate with a piezoelectric film is a non-defective product, it can be sold.

  Next, a method for manufacturing a substrate with a piezoelectric thin film in the case where a part of the lower electrode layer is the entire outer peripheral portion of the lower electrode layer will be specifically described with reference to the drawings.

  FIG. 2 is a process flow diagram showing an outline of the manufacturing process of the substrate with the piezoelectric thin film according to the present embodiment.

  A substrate 5 in which a lower electrode layer 6 is formed on a (001) Si substrate with a thermal oxide film by vapor deposition or sputtering is produced (FIG. 2A). After the production, the substrate 5 with the lower electrode is held by the ring-shaped shielding jig 7. The ring-shaped shielding jig 7 is formed of a ring-shaped plate having a circular opening 9 at the center. The opening 9 of the ring-shaped plate has a wide opening at the upper end through the step surface 10. The outer peripheral portion of the electrode-attached substrate 5 is held by the stepped surface 10 of the shielding jig 7 with the lower electrode surface facing downward (FIG. 2B). The KNN thin film 2 is formed by the sputtering method at the center of the lower electrode layer 6 exposed through the opening 9, and the lower electrode exposed portion 3 in which no piezoelectric thin film is formed at the periphery of the lower electrode layer 6 covered with the stepped surface 10. Is formed (FIG. 2C). By doing so, it is possible to form the lower electrode exposed portion 3 necessary for measuring piezoelectric characteristics and the like during film formation without removing the piezoelectric thin film after the piezoelectric thin film is formed.

  With the piezoelectric thin film surface facing upward, a metal mask 8 having an opening 8a having the same dimension as the minimum width of a predetermined upper electrode is placed on the surface of the piezoelectric thin film 2 (FIG. 2D). The opening 8a formed in the metal mask 8 is formed at an arbitrary point where the piezoelectric thin film 2 is desired to be evaluated. The minimum width of the predetermined upper electrode 4 formed by the metal mask 8 is preferably 0.5 mm or more and 5.0 mm or less. The upper electrode 4 formed by the metal mask 8 includes a first upper electrode formed at the center of the piezoelectric thin film 2 and a plurality of second upper electrodes formed at equal distances from the first upper electrode. More preferably, it consists of

  After the metal mask 8 is put on the surface of the piezoelectric thin film 2, the upper electrode 4 is formed on the piezoelectric thin film by vapor deposition or sputtering, and the substrate with the piezoelectric thin film of the present embodiment is manufactured (FIG. 2E). By forming the upper electrode 4 in this way, when measuring the piezoelectric characteristics of the piezoelectric thin film, it is possible to measure the displacement of the film by irradiating laser light. Further, the upper electrode 4 can be formed at an arbitrary point to be evaluated using the metal mask 8.

By the way, in the manufacturing process described above, the ring-shaped shielding jig 7 having a predetermined opening used when the piezoelectric thin film is formed has a minimum width of the lower electrode exposed portion of 0.005 × D mm or more as described above. in and 0.05 if × Dmm such that below, and the linear expansion coefficient alpha _w shielding jig in the film forming temperature for forming the piezoelectric thin film (e.g., 20 to 800 ° C.), the linear expansion of the substrate It is necessary to select a material so that the coefficient α _b satisfies 1 ≦ α _w / α _b ≦ 4. This is because when α _w / α _b is 1 or less, the substrate may be stretched more than the jig during high-temperature film formation, and the substrate may be damaged, and when α _w / α _b is 4 or more, This is because the opening diameter (inner diameter) of the jig that shields during high temperature film formation becomes larger than the outer diameter of the substrate, and the exposed portion of the lower electrode cannot be formed.

  According to the manufacturing method of the present embodiment, during the formation of the piezoelectric film, the piezoelectric thin film having a smaller area than the lower electrode layer is formed on the entire outer periphery or a part of the substrate with the piezoelectric thin film. A substrate with a piezoelectric thin film having a lower electrode exposed portion having a minimum width of 0.005 × Dmm or more and 0.05 × Dmm or less with respect to the outer diameter D of the substrate is shielded from the film formation surface on the lower electrode. To do. This makes it possible to omit the piezoelectric thin film removal step such as photolithography and etching necessary for the evaluation of the piezoelectric film after the production of the substrate with the piezoelectric thin film. Thereby, the process steps required for evaluating the piezoelectric film can be greatly simplified. In addition to this, it is possible to avoid a decrease in yield due to defects occurring in these process steps, and large equipment is required for photolithography and etching processing, but these are also unnecessary, so a piezoelectric thin film is attached. The manufacturing cost of the substrate and the piezoelectric element using the substrate can be greatly reduced.

  And the structure which has the structure where the lower electrode was exposed as mentioned above, and has an upper electrode with a minimum width of 0.5 mm or more and 5.0 mm or less at a place where evaluation on the piezoelectric film of the substrate with the piezoelectric thin film is necessary By doing so, the evaluation of the piezoelectric film at an arbitrary location in the substrate can be realized non-destructively.

  Moreover, since the board | substrate with a piezoelectric thin film obtained through the process mentioned above has the lower electrode exposure part and upper electrode which are required for evaluation as it is, without processing after that, the board | substrate with a piezoelectric thin film of this embodiment By applying a voltage between the exposed portion of the lower electrode and the upper electrode, it is possible to include a step of inspecting the characteristics of the piezoelectric thin film. Since a process for inspecting the characteristics of the piezoelectric thin film can be incorporated during the manufacturing process, feedback can be made so that the film forming conditions can suppress the characteristic variation.

  Therefore, depending on the structure of the equipment, film formation conditions, equipment and raw materials over time, film characteristics within the same substrate surface, between lots of film formation, and between substrates in a lot even when multiple sheets are formed simultaneously. Can be made uniform. In particular, when the first upper electrode is formed in the center of the piezoelectric thin film and a plurality of second upper electrodes are formed at equal distances from the first upper electrode, in-plane characteristic evaluation on the piezoelectric thin film of the substrate with the piezoelectric thin film is required. Can cover places. Therefore, even when the substrate is increased in diameter, it is possible to suppress in-plane distribution and variation in characteristics between the substrates, increase the element acquisition rate from one substrate when it is formed into an element, and improve the yield. Cost can be reduced. As a result, it is possible to supply a high-quality substrate with a piezoelectric thin film with little characteristic variation and a piezoelectric element using the substrate.

[Other embodiments]
In the embodiment of the present invention, Pt is used for the lower electrode, but the same effect can be obtained when an alloy containing Pt, a metal oxide electrode such as Au, Ru, Ir, or SuRuO ₃ , LaNiO ₃ is used. Can be expected. Although Ti is used for the adhesion layer, the same effect can be expected even when Ta is used for the adhesion layer or when there is no adhesion layer. As the substrate, a (001) plane Si substrate with a thermal oxide film was used, but the same effect can be obtained with a Si substrate having a different plane orientation, a Si substrate without a thermal oxide film, or an SOI substrate. In addition to the Si substrate, a quartz glass substrate, a GaAs substrate, a sapphire substrate, a metal substrate such as stainless steel, a piezoelectric substrate such as an MgO substrate, an SrTiO ₃ substrate, or a KNN substrate may be used. The KNN film is not particularly added with other elements, but the same effect can be obtained even when Li, Ta, Sb, Ca, Cu, Ba, Ti, etc. having 5% or less atomic number are added to the KNN film.

  In the embodiment, the metal mask is used when forming the upper electrode. However, if it is assumed that the cost is increased, it is possible to make the upper electrode smaller by using a photolithography process.

  Hereinafter, an example will be described in which a 3 μm-thick KNN thin film formed on the Si substrates of Examples 1 to 6 and Comparative Examples 1 to 5 was manufactured and piezoelectric characteristics were evaluated.

[Deposition of KNN thin film]
A substrate with a piezoelectric thin film was produced by the manufacturing method according to the present embodiment described above. As the substrate, a circular double-sided mirror Si substrate with a thermal oxide film ((001) plane orientation, thickness 0.525 mm, thermal oxide film thickness 200 nm, diameter 100 mm) was used. First, a Ti adhesion layer (film thickness 2 nm) and a Pt lower electrode ((111) plane preferred orientation, film thickness 200 nm) were formed on a substrate by RF magnetron sputtering. The Ti adhesion layer and the Pt lower electrode were formed under conditions of a substrate temperature of 100 to 350 ° C., a discharge power of 200 W, an introduced gas Ar atmosphere, a pressure of 2.5 Pa, and a film formation time of 1 to 3 minutes.

[Examples 1 to 6]
A 3 μm thick KNN thin film was formed thereon by RF magnetron sputtering so that the minimum width of the exposed portion of the lower electrode was 1 mm, 0.5 mm, and 5 mm. The KNN piezoelectric thin film uses a KNN sintered body of Na / (K + Na) = 0.50 as a target, and has a film formation surface under conditions of a substrate temperature of 700 ° C., a discharge power of 800 W, an introduced gas Ar atmosphere, and a pressure of 1.3 Pa. The film was formed vertically downward. The sputter deposition time of the KNN thin film was adjusted so that the film thickness was about 3 μm. The shielding jig that shields the exposed portion of the lower electrode used during film formation at this time has a minimum width of the exposed portion of the lower electrode of 0.5 mm. Inconel 625 (α _w / α _b = 3.41) and carbon ( α _w / α _b = 1.14) Inconel 625 was used for 1 mm and 5 mm.

  Thereafter, a metal mask on which a circular upper electrode having a diameter of 0.5 mm, 1 mm, and 5 mm was formed was placed on the formed KNN thin film at a position as shown in FIG. The upper electrode has any five points in the plane, for example, the first upper electrode is at the center of the piezoelectric thin film (coordinates (0, 0)), and the plurality of second upper electrodes are separated from the first upper electrode by a predetermined distance. For example, the metal thin film is formed at equal intervals in the periphery (coordinates (0, 40), (40, 0), (0, −40), coordinates (−40, 0)) of the piezoelectric thin film separated by 40 mm. For example, a Pt upper electrode (thickness 20 nm) was formed by RF magnetron sputtering, a combination of those having different minimum width of the lower electrode exposed portion, different jig materials, and different upper electrode diameters. Thus, substrates with piezoelectric thin films of Examples 1 to 6 were produced.

[Comparative Examples 1-5]
On the other hand, as a comparative example, the lower electrode exposed portion minimum width is 0.5 mm, 1 mm, and 6 mm, and the material of the jig for shielding the lower electrode exposed portion used during film formation is Inconel 625 (α _w / α _b = 3.41). ), The minimum width of the lower electrode exposed portion is 0.5 mm, and the material of the jig for shielding the lower electrode exposed portion used during the film formation is SUS304 (α _w / α _b = 4.56), quartz (Α _w / α _b = 0.11) was used.

  Thereafter, a metal mask with the upper electrode diameters of 1 mm, 0.2 mm, and 6 mm is placed on the formed KNN thin film at the position shown in FIG. It formed by the magnetron sputtering method. Substrates with piezoelectric thin films of Comparative Examples 1 to 5 were prepared by combinations of different lower electrode exposed portion minimum widths, different jig materials, and different upper electrode minimum widths.

[Piezoelectric evaluation]
Thereafter, the produced substrate with a KNN thin film was measured for distortion in the same direction (longitudinal direction) as voltage application using a double laser beam interferometer, and the piezoelectric constant d ₃₃ was determined from the amount of distortion. This double laser beam interferometer usually applies a laser beam only to the substrate surface, and when the distortion is measured, the amount of deflection deformation of the substrate is also measured. This deflection of the substrate can be offset. The calculation method of the piezoelectric constant d ₃₃ using this double beam laser interferometer, the configuration of the apparatus, and the measurement method were performed by the methods described in Document 1 and Document 2 below. The Young's modulus of the KNN thin film used in calculating the piezoelectric constant _{d 33} was used 104GPa.

Reference 1: Koji Kajiiwa, Noboru Ichinose, Applied Physics Vol. 71, No. 10 (2002) 1227-1232.
Reference 2: H.C. Maiwa, J .; A. Christman, SH. Kim, JP. Maria, B.M. Chen, S.M. K. Striffer and A.M. I. Kingon: Jpn. J. et al. Appl. Phys. 38, 5402 (1999)

  In Examples 1 to 6 thus measured, as shown in Table 1, the piezoelectric properties at any five points in the plane of the substrate with the piezoelectric thin film were all good (◯). Therefore, measurement is possible with a simple evaluation method that is non-destructive and does not require large-scale facilities such as photolithography and etching.

On the other hand, as shown in Table 2, Comparative Examples 1 to 5 all had poor evaluation results (x). In Comparative Example 1 using SUS304 in which α _w / α _b is 4 or more, as shown in Table 2, the opening diameter of the jig becomes larger than the substrate diameter due to heating during film formation. In the manufacturing method in which the substrate film-forming surface was down, the substrate dropped and measurement could not be performed.

Further, in Comparative Example 2 using quartz in which α _w / α _b is 1 or less, the substrate holding portion of the jig becomes smaller than the substrate diameter due to heating during film formation, and the substrate is cracked. I could not do it.

  Furthermore, in Comparative Example 3 in which the upper electrode diameter was 0.2 mm, an electrode having a desired size could not be formed by the sputtering method using a metal mask, making measurement impossible.

Further, in Comparative Example 4 in which the exposed portion of the lower electrode is 0.05 × Dmm or more (in this example, the substrate diameter = 100 mm, 6 mm is 0.05 × Dmm or more), the substrate surface is the same as in Examples 1-6. Piezoelectric characteristics can be measured at any point. However, as shown in FIG. 4, when the relationship between the effective usage rate of the substrate surface and the minimum width of the exposed portion of the lower electrode is seen, the minimum width of the exposed portion of the lower electrode is 5 mm or more (0.05 × Dmm or more) when the substrate diameter is 100 mm. Then, the effective usage rate becomes 90% or less. When the effective usage rate is 90% or less, the actual element acquisition efficiency is greatly reduced, so 90% or more is desired. Therefore, although Comparative Example 4 can be measured, it is not applicable.

  Similarly, in Comparative Example 5 in which the diameter of the upper electrode is 6 mm (5 mm or more), the effective usage rate is 90% or more in the case of 5 points in this plane. However, as shown in FIG. 5, the relationship between the effective usage rate of the substrate surface and the minimum width of the exposed portion of the upper electrode is less than 90% when the number of measurement points is 9 or more. Therefore, as in the case of the lower electrode exposed portion, it cannot be applied.

[Example 7]
Further, in Examples 1 to 6, as shown in FIG. 6A, the face-down method is adopted as the film formation method to form the KNN film with the film formation surface facing vertically downward. As shown in FIG. 4B, a manufacturing method may be used in which a film is formed by placing the jig 7 that shields the lower electrode exposed portion 3 on the substrate 5 with the face-up method and with the film formation surface facing vertically upward. Good. The face-down method can support the substrate on the ring-shaped shielding jig, and does not require a substrate holding fixture. In contrast, the face-up method employed in Example 7 cannot support a substrate with a shielding jig, and thus requires a substrate holding bracket (not shown) as a substrate holding member. There is an effect that non-destructive evaluation similar to 6 can be performed.

[Example 8]
Moreover, in Examples 1-6, although there exists a lower electrode exposure part in the board | substrate outer periphery whole region, as shown in FIG. 7 in the shape of the jig | tool which shields the lower electrode exposure part of Example 8, lower electrode exposure part 3a It may be in a part of the outer periphery. According to Example 8, the effective usage rate of the substrate with piezoelectric thin film is further improved as compared with Examples 1-7.
[Modification]
In the said Example, although the board | substrate with a piezoelectric thin film was formed using the circular silicon substrate, it is not limited to a circular-shaped board | substrate, You may use polygonal shape. When a polygonal substrate is used, the longest diagonal line may be D ′ and the width of the lower electrode exposed portion may be determined to be 0.005D ′ or more and 0.05D ′ or less. In the above embodiment, a 4-inch circular substrate has been described. However, the present invention can be applied to a 4-inch or larger substrate, for example, a 6-inch size or a 12-inch size.

DESCRIPTION OF SYMBOLS 1 Substrate with piezoelectric thin film 2 Piezoelectric thin film portion 3 Lower electrode exposed portion 4 Upper electrode 5 Substrate 6 Lower electrode 7 Jig 8 for shielding lower electrode exposed portion Metal mask having opening of predetermined upper electrode width

Claims (10)

In a substrate with a piezoelectric thin film in which a lower electrode layer is formed on a substrate, and a piezoelectric thin film having a perovskite structure is formed on the lower electrode layer,
The piezoelectric thin film formed on the lower electrode layer is formed with a smaller area than the lower electrode layer, so that the lower electrode exposed portion where a part of the lower electrode layer is exposed from the piezoelectric thin film A substrate with a piezoelectric thin film provided on the lower electrode layer.   2. The substrate with a piezoelectric thin film according to claim 1, wherein the lower electrode exposed portion is provided so that an outer peripheral portion of the lower electrode layer is exposed.   3. The substrate with a piezoelectric thin film according to claim 2, wherein a width of the exposed portion of the lower electrode formed on the outer peripheral portion is 0.005 × D or more and 0.05 × D with respect to an outer diameter D of the substrate. A substrate with a piezoelectric thin film as follows. Niobium in the piezoelectric thin film-attached substrate according to any one of claims 1 to 3, the piezoelectric thin film of the perovskite structure, represented by the general formula _{(K 1-x Na x)} NbO 3 (0 <x <1) A substrate with a piezoelectric thin film that is potassium sodium oxide. Forming a lower electrode layer on the substrate;
Covering a part of the lower electrode layer with a shielding jig,
By forming a piezoelectric thin film having a perovskite structure on the other part of the lower electrode layer that is not covered by the shielding jig, a lower electrode exposed portion where no piezoelectric thin film is formed on a part of the lower electrode layer is formed,
A method of manufacturing a substrate with a piezoelectric thin film in which the lower electrode exposed portion formed in a part of the lower electrode layer is exposed by removing the shielding jig after the formation of the piezoelectric thin film.   6. The method for manufacturing a substrate with a piezoelectric thin film according to claim 5, wherein a part of the lower electrode layer is an outer peripheral part of the lower electrode layer, and a width of the lower electrode exposed part formed on the outer peripheral part is The manufacturing method of the board | substrate with a piezoelectric thin film which is 0.005 * D or more and 0.05 * D or less with respect to the outer diameter D of the said board | substrate. In the manufacturing method of the substrate with a piezoelectric thin film according to claim 6,
The manufacturing method of the board | substrate with a piezoelectric thin film whose linear expansion coefficient (alpha) _w of the said shielding jig and the linear expansion coefficient (alpha) _b of the said board | substrate in the range of the formation temperature of the said piezoelectric thin film are 1 <= (alpha) _w / (alpha) _b <= 4. A method for manufacturing the substrate with a piezoelectric thin film according to any one of claims 5 to 7,
Forming an upper electrode having a width of 0.5 mm or more and 5.0 mm or less on the piezoelectric thin film, and applying a voltage between the exposed portion of the lower electrode and the upper electrode, thereby inspecting the characteristics of the piezoelectric thin film A method for manufacturing a substrate with a piezoelectric thin film comprising:   9. The method for manufacturing a substrate with a piezoelectric thin film according to claim 5, wherein the upper electrode is equidistant from a first upper electrode formed at a central portion of the piezoelectric thin film and the first upper electrode. The manufacturing method of the board | substrate with a piezoelectric thin film which consists of several 2nd upper electrodes formed in this distance. Table In the method for manufacturing the piezoelectric thin film-attached substrate according to any one of claims 5 to 9, the piezoelectric thin film of the perovskite structure, with the general formula _{(K 1-x Na x)} NbO 3 (0 <x <1) Of manufacturing a substrate with a piezoelectric thin film, which is potassium sodium niobate.

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