JP7307302B2 - MEMBRANE STRUCTURE AND MANUFACTURING METHOD THEREOF - Google Patents

Description

The present invention relates to a membrane structure and its manufacturing method.

As a film structure having a substrate, a conductive film formed on the substrate, and a piezoelectric film formed on the conductive film, a substrate, a conductive film containing platinum formed on the substrate, and a conductive film on the conductive film and a piezoelectric film comprising lead zirconate titanate (PZT) formed on a film structure is known.

In International Publication No. 2016/009698 (Patent Document 1), in ferroelectric ceramics, a Pb(Zr _1-A Ti _A )O ₃ film and on the Pb(Zr _1-A Ti _A )O ₃ film A formed Pb(Zr _1-x Ti _x )O ₃ film, where A and x satisfy 0≦A≦0.1 and 0.1<x<1.

WO2016/009698

A piezoelectric film containing PZT has a large piezoelectric constant, for example, when an electric field is applied in a direction parallel to the polarization direction or along a direction having a certain angle with the polarization direction. Therefore, even if most of the piezoelectric films are oriented in the same direction, if a part of the piezoelectric film is oriented in a different direction, the polarization direction of the entire piezoelectric film will not be aligned. The piezoelectric constant of the film cannot be increased, and the properties of the piezoelectric element are degraded.

The present invention has been made to solve the problems of the prior art as described above, and is a film structure having a conductive film formed on a substrate and a piezoelectric film formed on the conductive film. An object of the present invention is to provide a film structure that can increase the piezoelectric constant of the piezoelectric film.

A brief outline of typical inventions disclosed in the present application is as follows.

A film structure as one aspect of the present invention includes a silicon substrate including a main surface made of a (100) plane, and a silicon substrate formed on the main surface, having a cubic crystal structure, and having a (100) oriented oxide film structure. It has a first film containing zirconium and a first conductive film formed on the first film and having a cubic crystal structure and containing (100) oriented platinum. Further, the film structure is formed on the first conductive film, and is represented by the following general formula (Chemical Formula 1), and includes a first composite oxide that is (100) oriented in a pseudo-cubic system: and a third film formed on the second film, represented by the following general formula (Chemical Formula 2), and containing a second composite oxide that is (100) oriented in a pseudo-cubic system. The film structure also has a first piezoelectric film comprising lead zirconate titanate formed on the third film.
Pb(Zr _1-x Ti _x )O ₃ (Chemical Formula 1)
Pb(Zr _1-y Ti _y )O ₃ (Chemical Formula 2)
x and y satisfy the following formulas (Formula 1) to Formula (Formula 3).
0<x<1 (equation 1)
0≦y≦0.1 (Equation 2)
y<x (Equation 3)

Moreover, as another aspect, both the thickness of the second film and the third film may be thinner than the thickness of the first piezoelectric film.

In another aspect, the first piezoelectric film may contain lead zirconate titanate having a tetragonal crystal structure and (001) orientation.

Further, as another aspect, in the first diffraction pattern of the first piezoelectric film measured by X-ray diffraction measurement using the θ-2θ method, the intensity of the diffraction peak of the (001) plane of lead zirconate titanate is , the ratio of the diffraction peak intensities of both the (110) plane and the (101) plane of lead zirconate titanate may be 4×10 ⁻⁵ or less, or the (110) plane and the (101) plane No diffraction peaks may be observed.

Further, as another aspect, the full width at half maximum of the rocking curve measured for the diffraction peak of the (001) plane in the first diffraction pattern by X-ray diffraction measurement using the rocking curve method is 0.3 to 0.6. ° may be

In another aspect, the first piezoelectric film includes a second piezoelectric film containing a third composite oxide made of lead zirconate titanate formed on the third film, and a second piezoelectric film formed on the second piezoelectric film. and a third piezoelectric film including a fourth composite oxide made of lead zirconate titanate, wherein the second piezoelectric film may have a compressive stress and the third piezoelectric film may have a tensile stress. .

Further, as another aspect, the second piezoelectric film includes a third composite oxide represented by the following general formula (chemical formula 3), and the third piezoelectric film is represented by the following general formula (chemical formula 4) A fourth composite oxide may be included.
Pb(Zr _1-a Ti _a )O ₃ (Chemical Formula 3)
Pb(Zr _1-b Ti _b )O ₃ (Chem. 4)
a may satisfy 0.1<a≦0.48, and b may satisfy 0.1<b≦0.48.

Further, as another aspect, the film structure has a second conductive film formed on the first piezoelectric film, and an alternating current having a frequency of 1 kHz is generated between the first conductive film and the second conductive film. A dielectric constant measured by applying a voltage may be 300-400.

A method for manufacturing a film structure as one aspect of the present invention comprises a step (a) of preparing a silicon substrate including a main surface made of a (100) plane, having a cubic crystal structure on the main surface, and (b) forming a first film containing (100) oriented zirconium oxide. Further, the method for manufacturing the film structure has a step (c) of forming, on the first film, a first conductive film having a cubic crystal structure and containing (100) oriented platinum. Further, in the method for manufacturing the film structure, a second compound oxide represented by the following general formula (Formula 1) and having a (100) orientation in a pseudo-cubic system is formed on the first conductive film. forming a film (d); and (e) a step of forming. Then, the method for manufacturing the film structure has a step (f) of forming a first piezoelectric film containing lead zirconate titanate on the third film.
Pb(Zr _1-x Ti _x )O ₃ (Chemical Formula 1)
Pb(Zr _1-y Ti _y )O ₃ (Chemical Formula 2)
x and y satisfy the following formulas (Formula 1) to Formula (Formula 3).
0<x<1 (equation 1)
0≦y≦0.1 (Equation 2)
y<x (Equation 3)

Further, as another aspect of the method for manufacturing the film structure, after the step (c) and before the step (d), the first conductive film is heat-treated at a temperature of 450 to 600° C. (g) step. may have

Further, as another aspect, the step (d) includes applying a first solution containing lead, zirconium and titanium onto the first conductive film to obtain a first precursor of the first composite oxide. A step (d1) of forming a fourth film and a step (d2) of forming a second film by heat-treating the fourth film may be included. Then, in the step (e), a second solution containing lead and zirconium or lead, zirconium and titanium is applied onto the second film to form a second precursor containing a second composite oxide. A step (e1) of forming a fifth film and a step (e2) of forming a third film by heat-treating the fifth film may be included.

Moreover, as another aspect, both the thickness of the second film and the third film may be thinner than the thickness of the first piezoelectric film.

As another aspect, in the step (f), a first piezoelectric film having a tetragonal crystal structure and containing (001)-oriented lead zirconate titanate may be formed.

Further, as another aspect, the method for manufacturing the film structure includes the step (h) of measuring the first diffraction pattern of the first piezoelectric film by X-ray diffraction measurement using the θ-2θ method. good too. Then, in the first diffraction pattern measured in the step (h), the intensity of the diffraction peak of the (001) plane of the lead zirconate titanate is compared with that of the (110) plane and the (101) plane of the lead zirconate titanate. The ratio of intensities of any diffraction peaks may be 4×10 ⁻⁵ or less, or no diffraction peaks of (110) plane and (101) plane may be observed.

Further, as another aspect of the method for manufacturing the film structure, the diffraction peak of the (001) plane in the first diffraction pattern measured in the step (h) is determined by X-ray diffraction measurement using the rocking curve method. (i) measuring a rocking curve for The full width at half maximum of the rocking curve measured in step (i) may be 0.3 to 0.6°.

In another aspect, the step (f) includes forming a second piezoelectric film containing a third composite oxide made of lead zirconate titanate on the third film, and forming a second piezoelectric film on the third film. (k) forming, on the film, a third piezoelectric film containing a fourth composite oxide made of lead zirconate titanate. Then, in step (j), a second piezoelectric film having compressive stress may be formed, and in step (k), a third piezoelectric film having tensile stress may be formed.

Further, as another aspect, in step (j), a second piezoelectric film containing a third composite oxide represented by the following general formula (Chemical Formula 3) is formed, and in step (k), the following general formula ( A third piezoelectric film containing a fourth composite oxide represented by Chemical formula 4) may be formed.
Pb(Zr _1-a Ti _a )O ₃ (Chemical Formula 3)
Pb(Zr _1-b Ti _b )O ₃ (Chem. 4)
a may satisfy 0.1<a≦0.48, and b may satisfy 0.1<b≦0.48.

As another aspect, in the step (j), the second piezoelectric film may be formed by a sputtering method. Then, in step (k), a sixth film containing a third precursor of the fourth composite oxide is formed by applying a third solution containing lead, zirconium and titanium onto the second piezoelectric film. A step (k1) and a step (k2) of forming a third piezoelectric film by heat-treating the sixth film may be included.

Further, as another aspect, the method for manufacturing the film structure includes a step (l) of forming a second conductive film on the first piezoelectric film, and a 1 kHz vibration between the first conductive film and the second conductive film. and measuring the dielectric constant by applying an alternating voltage having a frequency of (m), and the dielectric constant measured in the step (m) may be 300 to 400.

By applying one embodiment of the present invention, it is possible to increase the piezoelectric constant of the piezoelectric film in a film structure having a conductive film formed over a substrate and a piezoelectric film formed over the conductive film. .

1 is a cross-sectional view of a membrane structure according to an embodiment; FIG. FIG. 4 is a cross-sectional view of a film structure in the case where the film structure of the embodiment has a conductive film as an upper electrode; FIG. 3 is a cross-sectional view of the film structure shown in FIG. 2 from which the substrate and the alignment film are removed; FIG. 2 is a diagram schematically showing a pseudocubic unit cell and an orthorhombic unit cell when a composite oxide having a perovskite structure has an orthorhombic crystal structure. FIG. 4 is a diagram schematically showing cross-sectional structures of two piezoelectric films included in the film structure of the embodiment; 5 is a graph schematically showing electric field dependence of polarization of a piezoelectric film included in the film structure of the embodiment. FIG. 4 is a diagram for explaining a state in which an orientation film included in the film structure of the embodiment is epitaxially grown; FIG. 4 is a cross-sectional view of the membrane structure of the embodiment during a manufacturing process; FIG. 4 is a cross-sectional view of the membrane structure of the embodiment during a manufacturing process; FIG. 4 is a cross-sectional view of the membrane structure of the embodiment during a manufacturing process; FIG. 4 is a cross-sectional view of the membrane structure of the embodiment during a manufacturing process; FIG. 4 is a cross-sectional view of the membrane structure of the embodiment during a manufacturing process; FIG. 4 is a cross-sectional view of the membrane structure of the embodiment during a manufacturing process; FIG. 10 is a cross-sectional view of a membrane structure of a modified example of the embodiment; 3 is a graph showing an example of θ-2θ spectrum by XRD method of a film structure formed up to a PZO film. 3 is a graph showing an example of θ-2θ spectrum by XRD method of a film structure formed up to a PZO film. FIG. 10 is a graph showing an example of θ-2θ spectrum by XRD method of a film structure including a PZT film. FIG. FIG. 10 is a graph showing an example of θ-2θ spectrum by XRD method of a film structure including a PZT film. FIG. It is the measurement result of the reciprocal lattice map of the film structure formed up to the PZT film. It is the measurement result of the reciprocal lattice map of the film structure formed up to the PZT film. This is the result of simulating the reciprocal lattice map of PZT. 4 is a graph showing voltage dependence of polarization of a membrane structure. 4 is a graph showing voltage dependence of polarization of a membrane structure.

Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following description, and those skilled in the art will readily understand that various changes in form and detail may be made without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the descriptions of the embodiments shown below.

In addition, in order to make the description clearer, the drawings may schematically show the width, thickness, shape, etc. of each part compared to the embodiment, but this is only an example, and the interpretation of the present invention is not limited. It is not limited.

Moreover, in this specification and each figure, the same reference numerals may be given to the same elements as those described above with respect to the previous figures, and detailed description thereof may be omitted as appropriate.

Furthermore, in the drawings used in the embodiments, hatching for distinguishing structures may be omitted depending on the drawing.

(Embodiment)
<Membrane structure>
First, a membrane structure according to an embodiment, which is one embodiment of the present invention, will be described. FIG. 1 is a cross-sectional view of a membrane structure according to an embodiment. FIG. 2 is a cross-sectional view of the film structure of the embodiment when the film structure has a conductive film as an upper electrode. FIG. 3 is a cross-sectional view of the film structure when the substrate and the alignment film are removed from the film structure shown in FIG.

As shown in FIG. 1, the film structure 10 of this embodiment has a substrate 11, an alignment film 12, a conductive film 13, a film 14, a film 15, and a piezoelectric film 16. As shown in FIG. The alignment film 12 is formed on the substrate 11 . A conductive film 13 is formed on the alignment film 12 . A film 14 is formed on the conductive film 13 . Membrane 15 is formed on membrane 14 . A piezoelectric film 16 is formed on the film 15 .

In addition, as shown in FIG. 2, the film structure 10 of the present embodiment may have a conductive film 19 . A conductive film 19 is formed on the piezoelectric film 16 . At this time, the conductive film 13 is a conductive film as a lower electrode, and the conductive film 19 is a conductive film as an upper electrode. Further, as shown in FIG. 3, the film structure 10 of the present embodiment does not have the substrate 11 (see FIG. 2) and the alignment film 12 (see FIG. 2), but the conductive film 13 as the lower electrode, It may have only the film 14, the film 15, the piezoelectric film 16, and the conductive film 19 as the upper electrode.

The substrate 11 is a silicon substrate made of silicon (Si) single crystal. A substrate 11 as a silicon substrate includes an upper surface 11a as a principal surface of (100) plane. The orientation film 12 is formed on the upper surface 11a, has a cubic crystal structure, and contains (100)-oriented zirconium oxide. The conductive film 13 has a cubic crystal structure and contains (100) oriented platinum. This allows the piezoelectric film 16 to be (100) oriented on the substrate 11 when the piezoelectric film 16 contains a composite oxide having a perovskite structure.

Here, that the orientation film 12 is (100) oriented means that the (100) plane of the orientation film 12 having a cubic crystal structure is the main (100) plane of the substrate 11, which is a silicon substrate. It means along the top surface 11a as a plane, preferably parallel to the top surface 11a of the (100) plane of the substrate 11, which is a silicon substrate. The (100) plane of the alignment film 12 being parallel to the upper surface 11a of the substrate 11 consisting of the (100) plane only means that the (100) plane of the alignment film 12 is completely parallel to the upper surface 11a of the substrate 11. However, it also includes the case where the angle formed by the plane completely parallel to the upper surface 11a of the substrate 11 and the (100) plane of the alignment film 12 is 20° or less.

Alternatively, as the alignment film 12 , an alignment film 12 made of a laminated film may be formed on the substrate 11 instead of the alignment film 12 made of a single layer film.

Preferably, the orientation film 12 is epitaxially grown on the substrate 11 and the conductive film 13 is epitaxially grown on the orientation film 12 . Thereby, the piezoelectric film 16 can be epitaxially grown on the conductive film 13 when the piezoelectric film 16 contains a composite oxide having a perovskite structure.

Here, when the two directions orthogonal to each other in the upper surface 11a as the main surface of the substrate 11 are the X-axis direction and the Y-axis direction, and the direction perpendicular to the upper surface 11a is the Z-axis direction, a certain film is epitaxially grown. Being oriented means that the film is oriented in any of the X-axis direction, Y-axis direction, and Z-axis direction.

The film 14 includes a complex oxide represented by the following general formula (Formula 1) and having (100) orientation in pseudo-cubic crystal display.
Pb(Zr _1-x Ti _x )O ₃ (Chemical Formula 1)

The film 15 includes a composite oxide represented by the following general formula (Formula 2) and having (100) orientation in pseudo-cubic crystal display.
Pb(Zr _1-y Ti _y )O ₃ (Chemical Formula 2)
Here, x and y satisfy the following formulas (Formula 1) to Formula (Formula 3).
0<x<1 (equation 1)
0≦y≦0.1 (Equation 2)
y<x (Equation 3)

In such a case, the piezoelectric film 16 formed on the film 15 can have a tetragonal crystal structure. Then, the content of lead zirconate titanate having a tetragonal crystal structure and (110) orientation or (101) orientation in the piezoelectric film 16 is and can be made extremely small compared to the content of (001) oriented lead zirconate titanate. Alternatively, the piezoelectric film 16 may not contain lead zirconate titanate with (110) orientation or (101) orientation. Therefore, since the polarization directions of the plurality of crystal grains included in the piezoelectric film 16 can be aligned, the piezoelectric characteristics of the piezoelectric film 16 can be improved.

Preferably, x may satisfy the following formula (Formula 4) instead of the above formula (Formula 1).
0<x≦0.48 (Equation 4)

In the ceramic powder, when x satisfies the above formula (Formula 4) instead of the above formula (Formula 1), the ceramic powder tends to have a rhombohedral crystal structure. On the other hand, in the film 14, when x satisfies the above formula (Formula 4) instead of the above formula (Formula 1), the film 14 has a tetragonal crystal structure mainly due to the restraining force from the substrate 11. easier to have. This ensures that lead zirconate titanate having a tetragonal crystal structure and (110) orientation or (101) orientation is present in the piezoelectric film 16 formed on the film 14 via the film 15. can be excluded.

That is, when x satisfies the above formula (Formula 4) instead of the above formula (Formula 1), the crystal structure of the film 14, which should originally have a rhombohedral crystal structure, changes to a tetragonal crystal structure. Thereby, the orientation direction of the piezoelectric film 16 formed on the film 14 via the film 15 can be controlled more reliably.

The thickness of membrane 14 may be between 10 and 50 nm. In the case of such a range, the piezoelectric film 16 formed on the film 14 via the film 15 has a tetragonal crystal structure and is (110) oriented or (101) oriented zirconate titanate. It can be further ensured that lead is not included.

In the following, Pb(Zr _1−y Ti _y )O ₃ when y satisfies y=0, that is, PbZrO ₃ is referred to as PZO, and Pb(Zr _{1-yTi y} )O ₃ is sometimes referred to as PZT.

The compound oxide represented by the general formula (Chem. 1) or (Chem. 2) and having a perovskite structure is (100) oriented in a pseudo-cubic system means the following cases.

First, in a crystal lattice having a perovskite structure represented by the general formula _ABO3 , which includes a unit cell arranged three-dimensionally, the unit cell has one atom A, one atom B, and three oxygen atoms. Consider the case of including

In such a case, being (100) oriented in the pseudo-cubic system means that the unit cell has a cubic crystal structure and is (100) oriented. At this time, let the length of one side of the unit cell be the lattice constant a _c , let the angle of one of the unit cells be the lattice constant α _c , and let α _c =90°.

On the other hand, for example, consider a case where a composite oxide having a perovskite structure has a rhombohedral crystal structure. Among the two lattice constants of the rhombohedral crystal, the lattice constant _a , which is the length of one side, is approximately equal to the lattice constant _ac of the pseudocubic crystal, and at one angle of the two lattice constants of the rhombohedral crystal, Consider the case where some lattice constant α _r is approximately equal to the lattice constant α _c of the pseudocubic crystal. In the specification of the present application, "the numerical value V1 and the numerical value V2 are substantially equal" means that the ratio of the difference between the numerical value V1 and the numerical value V2 to the average of the numerical value V1 and the numerical value V2 is about 5% or less. means.

In this case, being (100) oriented in the pseudo-cubic system means being (100) oriented in the rhombohedral system.

Alternatively, for example, consider a case where a composite oxide having a perovskite structure has a tetragonal crystal structure. Among the two lattice constants of the tetragonal crystal, the first lattice constant _at is substantially equal to the lattice constant _ac of the pseudo-cubic crystal, and the second lattice constant of the two lattice constants of the tetragonal crystal _is the pseudo-cubic crystal. Consider the case where the lattice constant a of the crystal is approximately equal to _c .

In this case, (100) orientation in pseudo-cubic system representation means (100) orientation or (001) orientation in tetragonal system representation.

Specifically, consider an example in which the composite oxide composed of lead zirconate or lead zirconate titanate represented by the general formula (Chem. 1) has a rhombohedral crystal structure. Among the two lattice constants of the rhombohedral crystal, the lattice constant _a , which is the length of one side, is approximately equal to the lattice constant _ac of the pseudocubic crystal, and at one angle of the two lattice constants of the rhombohedral crystal, Consider the case where some lattice constant α _r is approximately equal to the lattice constant α _c of the pseudocubic crystal.

In this case, being (100) oriented in the pseudo-cubic system means being (100) oriented in the rhombohedral system.

Alternatively, consider the case where the composite oxide composed of lead zirconate or lead zirconate titanate represented by the general formula (Chem. 1) has a tetragonal crystal structure. Among the two lattice constants of the tetragonal crystal, the first lattice constant _at is substantially equal to the lattice constant _ac of the pseudo-cubic crystal, and the second lattice constant of the two lattice constants of the tetragonal crystal _is the pseudo-cubic crystal. Consider the case where the lattice constant a of the crystal is approximately equal to _c .

In this case, (100) orientation in pseudo-cubic system representation means (100) orientation or (001) orientation in tetragonal system representation.

FIG. 4 is a diagram schematically showing a pseudo-cubic unit cell and an orthorhombic unit cell when a composite oxide having a perovskite structure has an orthorhombic crystal structure.

As shown in FIG. 4, consider an example in which the composite oxide represented by the general formula (Chem. 1) or (Chem. 2) and having a perovskite structure has an orthorhombic crystal structure. Among the three lattice constants of the orthorhombic crystal, the first lattice constant _ao1 is substantially equal to the lattice constant _ac of the pseudocubic crystal, and the second lattice constant _bo1 of the three lattice constants of the orthorhombic crystal is Consider an example in which the lattice constant of the pseudocubic crystal is approximately equal to 2 ^1/2 times the lattice constant of _ac , and the third lattice constant of the orthorhombic crystal, c _o1 , is approximately equal to 2 ^1/2 times the lattice constant of _ac . .

In this case, (100) orientation in pseudo-cubic system representation means (011) orientation or (100) orientation in orthorhombic system representation.

Alternatively, as a different example (not shown) from the example shown in FIG. 4, the composite oxide represented by the above general formula (Chem. 1) or (Chem. Consider an example with a crystal structure of Then, the first lattice constant _ao2 among the three lattice constants of the orthorhombic crystal is approximately equal to 2 ^1/2 times the lattice constant _ac of the pseudocubic crystal, and among the three lattice constants of the orthorhombic crystal The second lattice constant b _o2 is approximately equal to 2 ^3/2 times the lattice constant _ac of the pseudocubic crystal, and the third lattice constant _co2 of the lattice constants of the orthorhombic crystal is the lattice constant a of the pseudocubic crystal. Consider the example of approximately equal to twice _c .

In this case, (100) orientation in the pseudo-cubic system representation means (120) orientation or (002) orientation in the orthorhombic system representation.

A piezoelectric film 16 is formed on the film 15 and has a tetragonal crystal structure and includes (001) oriented lead zirconate titanate. The piezoelectric film 16 does not have to be (001) oriented when it has a tetragonal crystal structure. Alternatively, the piezoelectric film 16 may not have a tetragonal crystal structure.

In the present embodiment, in the diffraction pattern of the piezoelectric film 16 measured by X-ray diffraction measurement using the θ-2θ method, the intensity of the diffraction peak of the (001) plane of lead zirconate titanate is compared with that of zirconate titanate. The ratio of the intensities of the diffraction peaks of the (110) plane and the (101) plane of lead is 4 × 10 ^-5 or less, or the diffraction peaks of both the (110) plane and the (101) plane of lead are observed. not.

As a result, the content of lead zirconate titanate having a tetragonal crystal structure and having (110) orientation or (101) orientation in the piezoelectric film 16 is determined by the tetragonal crystal structure in the piezoelectric film 16. It has a structure and can be made extremely small compared to the content of (001) oriented lead zirconate titanate. Alternatively, the piezoelectric film 16 may be free of lead zirconate titanate having a tetragonal crystal structure and (110) orientation or (101) orientation. Therefore, since the polarization directions of the plurality of crystal grains included in the piezoelectric film 16 can be aligned, the piezoelectric characteristics of the piezoelectric film 16 can be improved.

This is probably because the crystallinity of Pt contained in the conductive film 13 is improved by heat-treating the conductive film 13 after the conductive film 13 is formed, as will be described later with reference to FIG. 10, for example. . Alternatively, as will be described later with reference to FIG. 7, the crystallinity of the film 14 is improved because the lattice constant of the PZT contained in the film 14 matches well with the lattice constant of Pt contained in the conductive film 13. However, it is considered that the crystallinity of the film 15 is improved because the lattice constant of the PZO or the like contained in the film 15 matches well with the lattice constant of PZT contained in the film 14 .

Preferably, when the diffraction peak of the (00n) plane (n is an integer of 1 or more) is observed in the diffraction pattern, the diffraction peak of the (00n) plane (n is an integer of 1 or more) at the angle 2θ is observed. The full width at half maximum of the rocking curve measured at a fixed angle is 0.3 to 0.6°. That is, the full width at half maximum of the rocking curve measured for the diffraction peak of the (001) plane in the diffraction pattern by X-ray diffraction measurement using the rocking curve method is 0.3 to 0.6°.

As a result, variations in the orientation directions of the plurality of crystal grains included in the piezoelectric film 16 can be reduced. Therefore, the directions of the polarization axes of the plurality of crystal grains included in the piezoelectric film 16 can be further aligned, so that the piezoelectric characteristics of the piezoelectric film 16 can be further improved.

Preferably, piezoelectric film 16 includes piezoelectric film 17 and piezoelectric film 18 . Piezoelectric film 17 includes a composite oxide of lead zirconate titanate formed on film 15 . The piezoelectric film 18 contains a composite oxide of lead zirconate titanate formed on the piezoelectric film 17 . The piezoelectric film 17 has a compressive stress and the piezoelectric film 18 has a tensile stress.

Consider the case where the piezoelectric film 17 has a tensile stress and the piezoelectric film 18 has a tensile stress. In such a case, the film structure 10 tends to warp to have a downwardly convex shape when the upper surface 11a of the substrate 11 is taken as a main surface. Therefore, for example, when the film structure 10 is processed using a photolithographic technique, the shape accuracy is degraded, and the characteristics of the piezoelectric element formed by processing the film structure 10 are degraded.

Also, consider a case where the piezoelectric film 17 has a compressive stress and the piezoelectric film 18 has a compressive stress. In such a case, the film structure 10 tends to warp to have an upward convex shape when the upper surface 11a of the substrate 11 is taken as a main surface. Therefore, for example, when the film structure 10 is processed using a photolithographic technique, the shape accuracy is degraded, and the characteristics of the piezoelectric element formed by processing the film structure 10 are degraded.

On the other hand, in this embodiment, the piezoelectric film 17 has compressive stress and the piezoelectric film 18 has tensile stress. As a result, compared to the case where both the piezoelectric films 17 and 18 have tensile stress, the warping amount of the film structure 10 can be reduced. The warp amount of the film structure 10 can be reduced as compared with the case of having . Therefore, for example, when the film structure 10 is processed using a photolithographic technique, the shape accuracy can be improved, and the characteristics of the piezoelectric element formed by processing the film structure 10 can be improved.

It should be noted that the fact that the piezoelectric film 17 has compressive stress and the piezoelectric film 18 has tensile stress means that, for example, when the piezoelectric films 18 and 17 are successively removed from the film structure 10 , before and after the removal of the piezoelectric film 18 . , the substrate 11 is deformed from the downwardly convex side to the upwardly convex side, and the substrate 11 is deformed from the upwardly convex side to the downwardly convex side before and after the piezoelectric film 17 is removed.

Preferably, the piezoelectric film 17 contains a composite oxide represented by the following general formula (chemical formula 3).
Pb(Zr _1-a Ti _a )O ₃ (Chemical Formula 3)
Here, a satisfies 0.1<a≦0.48.

Moreover, the piezoelectric film 18 preferably contains a composite oxide represented by the following general formula (Formula 4).
Pb(Zr _1-b Ti _b )O ₃ (Chem. 4)
Here, b satisfies 0.1<b≦0.48.

When the ceramic powder contains the composite oxide represented by the general formula (3) or (4), it has a rhombohedral crystal structure. On the other hand, when the piezoelectric film 17 contains the composite oxide represented by the general formula (3) or the general formula (4), the tetragonal crystal structure is formed mainly by the restraining force from the substrate 11. easier to have. Therefore, the polarization axis of lead zirconate titanate contained in the piezoelectric film 17 can be oriented substantially perpendicular to the upper surface 11a, so that the piezoelectric characteristics of the piezoelectric film 17 can be improved. In addition, since the polarization axis of lead zirconate titanate contained in the piezoelectric film 18 can be oriented substantially perpendicular to the upper surface 11a, the piezoelectric characteristics of the piezoelectric film 18 can be improved.

That is, when a satisfies 0.1<a≦0.48 or b satisfies 0.1<b≦0.48, the piezoelectric film 17 which should originally have a rhombohedral crystal structure or The crystal structure of 18 changes to a tetragonal crystal structure. It is believed that this improves the piezoelectric response of the lead zirconate titanate contained in the piezoelectric film 17 or 18 .

As will be described later with reference to FIG. 13, the piezoelectric film 17 having compressive stress can be formed by sputtering, for example. Moreover, as described with reference to FIG. 1 when describing the manufacturing process of the film structure, the piezoelectric film 18 having a tensile stress can be formed by a coating method such as a sol-gel method.

FIG. 5 is a diagram schematically showing cross-sectional structures of two piezoelectric films included in the film structure of the embodiment. FIG. 5 shows a cross section formed by cleaving the substrate 11 included in the film structure 10 of the embodiment shown in FIG. Of the observed images, the piezoelectric films 17 and 18 are schematically shown.

FIG. 6 is a graph schematically showing the electric field dependence of the polarization of the piezoelectric film included in the film structure of the embodiment. FIG. 6 shows the polarization of the piezoelectric film 16 when the electric field between the lower electrode (conductive film 13) and the upper electrode (conductive film 19) included in the film structure 10 of the embodiment shown in FIG. 2 is changed. 4 is a graph schematically showing a polarization electric field hysteresis curve showing changes in .

As shown in FIG. 5, when the piezoelectric film 17 is formed by sputtering, the piezoelectric film 17 includes a plurality of crystal grains 17a integrally formed from the lower surface to the upper surface of the piezoelectric film 17. As shown in FIG. In addition, holes or gaps are less likely to remain between two crystal grains 17a adjacent to each other on the main surface of the substrate 11 (upper surface 11a in FIG. 1). Therefore, when a cross section for observation with an SEM is processed by a focused ion beam (FIB) method and formed in the piezoelectric film 17, the cross section is likely to be seen as a single cross section, and the crystal grain 17a becomes difficult to observe.

On the other hand, when the piezoelectric film 18 is formed by a coating method, the piezoelectric film 18 includes a plurality of films 18a as layers laminated in the thickness direction of the piezoelectric film 18 . The film 18a as each of the plurality of layers includes a plurality of crystal grains 18b integrally formed from the bottom surface to the top surface of one layer of the film 18a. In addition, holes or gaps may remain between two films 18a that are adjacent to each other in the thickness direction of the piezoelectric film 18 .

Preferably, each of the plurality of crystal grains has spontaneous polarization, as shown in FIG. This spontaneous polarization includes a polarization component P1 parallel to the thickness direction of the piezoelectric film 17, and the polarization components P1 included in the spontaneous polarization of each of the plurality of crystal grains are oriented in the same direction.

As shown in FIG. 5, in this embodiment, the polarization components P1 included in the spontaneous polarization of each of the plurality of crystal grains 17a included in the piezoelectric film 17 are oriented in the same direction. In such a case, as shown in FIG. 6, the piezoelectric film 17 has a large spontaneous polarization in the initial state. Therefore, when the electric field is increased to the positive side from the starting point SP at which the electric field is 0 and returned to 0 again, the electric field is decreased to the negative side and returned to the end point EP to 0 again. A hysteresis curve indicating electric field dependence is a curve with a starting point SP at a point away from the origin. Therefore, when the film structure 10 of the present embodiment is used as a piezoelectric element, it is not necessary to subject the piezoelectric film 17 to polarization treatment before use.

Note that the thickness of both films 14 and 15 is less than the thickness of piezoelectric film 16 . In such a case, the thickness of the piezoelectric film 16 functioning as a piezoelectric film can be made thicker than any of the thicknesses of the films 14 and 15, so that the characteristics of the film structure 10 as a piezoelectric element can be improved. can be improved.

FIG. 7 is a diagram illustrating a state in which the orientation film included in the film structure of the embodiment is epitaxially grown. 7 schematically shows each layer of the substrate 11, the alignment film 12, the conductive film 13, the films 14 and 15, and the piezoelectric film 16. As shown in FIG. In the following description, the case where the film 15 is PZO will be described as an example.

The lattice constant of Si contained in the substrate 11, the lattice constant of _ZrO2 contained in the alignment film 12, the lattice constant of Pt contained in the conductive film 13, the lattice constant of PZT contained in the film 14, the lattice constant of PZO contained in the film 15, Table 1 shows lattice constants of PZT contained in the piezoelectric film 16 .

As shown in Table 1, the lattice constant of Si is 0.543 nm, the lattice constant of _ZrO2 is 0.511 nm, and the mismatch of the lattice constant of _ZrO2 to that of Si is 5.9%. , the lattice constant of ZrO ₂ is well matched to that of Si. Therefore, as shown in FIG. 7, the orientation film 12 containing ZrO ₂ can be epitaxially grown on the main surface of the (100) plane of the substrate 11 containing silicon single crystal. Therefore, the orientation film 12 containing ZrO ₂ can be (100) oriented in a cubic crystal structure on the (100) plane of the substrate 11 containing silicon single crystal, and the crystallinity of the orientation film 12 is improved. be able to.

Also, as shown in Table 1, the lattice constant of _ZrO2 is 0.511 nm and that of Pt is 0.392 nm, but when Pt is rotated 45° in the plane, the diagonal length is , 0.554 nm, _{and the mismatch of the diagonal length with respect to the lattice constant of ZrO 2 is} as small as 8.4%. Therefore, as shown in FIG. 7, the conductive film 13 containing Pt can be (100) oriented on the (100) plane of the oriented film 12 containing ZrO ₂ in a cubic crystal structure. can improve the crystallinity of

Further, as shown in Table 1, the lattice constant of Pt is 0.392 nm, the lattice constant of PZT is 0.411 nm, and the mismatch of the lattice constant of PZT with respect to the lattice constant of Pt is 4.8%. , the lattice constant of PZT matches well with that of Pt. Therefore, the film 14 containing PZT can be (100) oriented on the (100) plane of the conductive film 13 containing Pt in a pseudo-cubic system, and the crystallinity of the film 14 can be improved.

Further, as shown in Table 1, the lattice constant of PZT is 0.411 nm, the lattice constant of PZO is 0.412 nm, and the mismatch of the lattice constant of PZO with respect to the lattice constant of PZT is 0.2%. , the lattice constant of PZO is well matched to that of PZT. Therefore, the film 15 containing PZO can be (100) oriented on the (100) plane of the film 14 containing PZT in a pseudo-cubic system, and the crystallinity of the film 15 can be improved.

Further, as shown in Table 1, the lattice constant of PZO is 0.412 nm, the lattice constant of PZT is 0.411 nm, and the mismatch of the lattice constant of PZT with respect to the lattice constant of PZO is 0.2%. , the lattice constant of PZT matches well with that of PZO. Therefore, the piezoelectric film 16 containing PZT can be (001) oriented with a tetragonal crystal structure on the (100) plane of the film 15 containing PZO, and the crystallinity of the piezoelectric film 16 can be improved. .

Preferably, when the film structure has a conductive film 19 as shown in FIG. is 300-400.

As a result, the detection sensitivity can be improved when the film structure 10 is used as a sensor using the piezoelectric effect, for example. Alternatively, when the membrane structure 10 is used as, for example, an ultrasonic transducer using the inverse piezoelectric effect, the oscillation circuit can be easily designed.

<Manufacturing Method of Membrane Structure>
Next, a method for manufacturing the membrane structure of this embodiment will be described. 8 to 13 are cross-sectional views during manufacturing steps of the film structure of the embodiment.

First, as shown in FIG. 8, a substrate 11 is prepared (step S1). In step S1, a substrate 11, which is a silicon substrate made of silicon (Si) single crystal, is prepared. Preferably, the substrate 11 made of silicon single crystal has a cubic crystal structure and has an upper surface 11a as a main surface made up of the (100) plane. Moreover, when the substrate 11 is a silicon substrate, an oxide film such as a SiO ₂ film may be formed on the upper surface 11a of the substrate 11 .

Various substrates other than a silicon substrate can be used as the substrate 11. For example, an SOI (Silicon on Insulator) substrate, a substrate made of various semiconductor single crystals other than silicon, and various oxide single crystals such as sapphire. A substrate, or a substrate made of a glass substrate having a polysilicon film formed on the surface thereof, or the like can be used.

As shown in FIG. 8, the two directions perpendicular to each other in the upper surface 11a of the (100) plane of the substrate 11 made of silicon single crystal are the X-axis direction and the Y-axis direction, and the direction perpendicular to the upper surface 11a is the Z direction. Axial direction.

Next, as shown in FIG. 9, an alignment film 12 is formed on the substrate 11 (step S2). In the following, the case where the alignment film 12 is formed using the electron beam evaporation method in step S2 will be described as an example, but it can be formed using various methods such as sputtering.

In step S2, first, the substrate 11 is heated to, for example, 700° C. while being placed in a constant vacuum atmosphere.

In step S2, next, Zr is evaporated by an electron beam evaporation method using a zirconium (Zr) single crystal evaporation material. At this time, the evaporated Zr reacts with oxygen on the substrate 11 heated to 700° C., for example, to form a zirconium oxide (ZrO ₂ ) film. Then, an alignment film 12 made of a ZrO ₂ film as a single layer film is formed.

The orientation film 12 is epitaxially grown on the upper surface 11a of the (100) plane of the substrate 11 made of silicon single crystal. The oriented film 12 has a cubic crystal structure and contains (100) oriented zirconium oxide (ZrO ₂ ). That is, the orientation film 12 made of a single layer film containing (100) oriented zirconium oxide (ZrO ₂ ) is formed on the upper surface 11a of the (100) plane of the substrate 11 made of silicon single crystal.
As described above with reference to FIG. 8, two directions orthogonal to each other in the upper surface 11a of the (100) plane of the substrate 11 made of silicon single crystal are defined as the X-axis direction and the Y-axis direction. Let the vertical direction be the Z-axis direction. At this time, epitaxial growth of a certain film means that the film is oriented in any of the X-axis direction, Y-axis direction and Z-axis direction.

The film thickness of the alignment film 12 is preferably 2 to 100 nm, more preferably 10 to 50 nm. By having such a film thickness, it is possible to epitaxially grow and form the oriented film 12 that is very close to a single crystal.

Next, as shown in FIG. 10, a conductive film 13 is formed (step S3).
In this step S3, first, a conductive film 13 is formed epitaxially on the orientation film 12 as a part of the lower electrode. The conductive film 13 is made of metal. As the conductive film 13 made of metal, for example, a conductive film containing platinum (Pt) is used.

When a conductive film containing Pt is formed as the conductive film 13, the conductive film 13 is epitaxially grown on the orientation film 12 at a temperature of 450 to 600° C. by sputtering to form a portion of the lower electrode. A conductive film 13 containing Pt is epitaxially grown on the orientation film 12 . The Pt contained in the conductive film 13 has a cubic crystal structure and is (100) oriented.

As the conductive film 13 made of metal, a conductive film containing, for example, iridium (Ir) can be used instead of the conductive film containing platinum (Pt).

In this step S3, the conductive film 13 is then heat-treated at a temperature of 450 to 600.degree. Specifically, it is preferable that the conductive film 13 is formed by sputtering at a temperature of 450 to 600° C. and then heat-treated by holding the film at a temperature of 450 to 600° C. for 10 to 30 minutes.

If the temperature for heat-treating the conductive film 13 is less than 450° C., the temperature is too low to improve the crystallinity of the platinum contained in the conductive film 13 . The crystallinity of the formed piezoelectric film 16 cannot be improved. If the temperature for heat-treating the conductive film 13 exceeds 600° C., the temperature is too high, and crystal grains of platinum contained in the conductive film 13 grow, so that the crystallinity of platinum cannot be improved, and the conductive film 13 cannot be improved. The crystallinity of the piezoelectric film 16 formed on the film 13 via the films 14 and 15 cannot be improved. On the other hand, when the conductive film 13 is heat-treated at a temperature of 450 to 600° C., the crystallinity of the platinum contained in the conductive film 13 can be improved, and the piezoelectric film formed on the conductive film 13 via the films 14 and 15 can be obtained. Crystallinity of the film 16 can be improved.

Further, when the conductive film 13 is heat-treated at a temperature of 450 to 600° C., it is preferable to perform the heat treatment while holding it for 10 to 30 minutes. If the time for heat-treating the conductive film 13 is less than 10 minutes, the time is too short to improve the crystallinity of the platinum contained in the conductive film 13, and platinum is formed on the conductive film 13 with the films 14 and 15 interposed therebetween. However, the crystallinity of the piezoelectric film 16 cannot be improved. If the time for heat-treating the conductive film 13 exceeds 30 minutes, the temperature is too high and crystal grains of platinum contained in the conductive film 13 grow. The crystallinity of the piezoelectric film 16 formed on the film 13 via the films 14 and 15 cannot be improved.

Next, as shown in FIG. 11, a film 14 is formed (step S4). In this step S4, the film 14 containing the composite oxide (PZT) represented by the general formula (1) is formed on the conductive film 13 by a coating method such as a sol-gel method. A method of forming the film 14 by a sol-gel method will be described below.

In step S4, first, a solution containing lead, zirconium, and titanium is applied onto the conductive film 13 to form a film containing a precursor of the complex oxide (PZT) represented by the above general formula (Chemical Formula 1). to form Note that the step of applying the solution containing lead, zirconium, and titanium may be repeated a plurality of times, thereby forming a film including a plurality of films stacked on each other.

In step S4, the film is then heat-treated to oxidize and crystallize the precursor, thereby forming the film 14 containing the composite oxide represented by the general formula (Chem. 1).

Next, as shown in FIG. 12, a film 15 is formed (step S5). In this step S5, the film 15 containing the composite oxide (PZO) represented by the general formula (2) is formed on the film 14 by a coating method such as a sol-gel method. A method of forming the film 15 by the sol-gel method will be described below.

In step S5, first, a solution containing lead, zirconium, and titanium is applied onto the film 14 to form a film containing a precursor of the composite oxide (PZT) represented by the general formula (2). Form. Note that the step of applying the solution containing lead, zirconium, and titanium may be repeated a plurality of times, thereby forming a film including a plurality of films stacked together.

In step S5, the film is then heat-treated to oxidize and crystallize the precursor, thereby forming the film 15 containing the composite oxide represented by the general formula (Chem. 2).

Here, x and y satisfy the above formulas (Formula 1) to Formula (Formula 3). At this time, the PZT contained in the film 14 is (100) oriented in the pseudo-cubic system, and the PZO contained in the film 15 is (100) oriented in the pseudo-cubic system. A film 14 containing PZT is then epitaxially grown on the conductive film 13 and a film 15 containing PZO is epitaxially grown on the film 14 .

Preferably, x may satisfy the following formula (Formula 4) instead of the above formula (Formula 1).
In steps S4 and S5, for example, the film 14 and the film 15 are formed by evaporating the solvent in the solution during the heat treatment, or by shrinking the film when the precursor is oxidized and crystallized. , has a tensile stress.

Next, as shown in FIG. 13, the piezoelectric film 17 is formed (step S6). In this step S6, the piezoelectric film 17 containing the composite oxide (PZT) represented by the general formula (Chem. 3) is formed on the film 15 by sputtering. In the general formula (Formula 3), a satisfies 0.1<a≦0.48. In such a case, the PZT contained in the piezoelectric film 17 originally has a rhombohedral crystal structure, but has a tetragonal crystal structure and (001) orientation. A piezoelectric film 17 comprising PZT is then epitaxially grown on film 15 .

For example, when the piezoelectric film 17 is formed by sputtering, each of the plurality of crystal grains 17a (see FIG. 5) included in the piezoelectric film 17 can be polarized by plasma. Therefore, each of the plurality of crystal grains 17a included in the deposited piezoelectric film 17 has spontaneous polarization. Also, the spontaneous polarization of each of the plurality of crystal grains 17 a includes a polarization component parallel to the thickness direction of the piezoelectric film 17 . The polarization components included in the spontaneous polarization of each of the plurality of crystal grains 17a are oriented in the same direction. As a result, the formed piezoelectric film 17 has spontaneous polarization as a whole before the polarization treatment.

That is, in step S6, the piezoelectric film 17 can be polarized by plasma when the piezoelectric film 17 is formed by the sputtering method. As a result, as described with reference to FIG. 6, when the film structure 10 of the present embodiment is used as a piezoelectric element, the piezoelectric film 17 does not need to be polarized before use.

In step S6, when the piezoelectric film 17 is formed by sputtering, for example, sputtered particles and argon (Ar) gas enter the piezoelectric film 17 and the piezoelectric film 17 expands. , has compressive stress.

Next, as shown in FIG. 1, the piezoelectric film 18 is formed (step S7). In this step S7, the piezoelectric film 18 containing the composite oxide (PZT) represented by the general formula (4) is formed on the piezoelectric film 17 by a coating method such as a sol-gel method. A method of forming the film 15 by the sol-gel method will be described below.

In step S7, first, a film containing a PZT precursor is formed on the piezoelectric film 17 by applying a solution containing lead, zirconium and titanium. Note that the step of applying the solution containing lead, zirconium, and titanium may be repeated a plurality of times, thereby forming a film including a plurality of films stacked together.

In step S7, the piezoelectric film 18 containing PZT is then formed by heat-treating the film to oxidize and crystallize the precursor. Here, in the above general formula (Formula 4), b satisfies 0.1<b≦0.48. In such a case, the PZT contained in the piezoelectric film 18 originally has a rhombohedral crystal structure, but has a tetragonal crystal structure and (001) orientation. A piezoelectric film 18 comprising PZT is then epitaxially grown on film 15 .

When PZT having a tetragonal crystal structure is (001) oriented, the polarization direction parallel to the [001] direction and the electric field direction parallel to the thickness direction of the piezoelectric film 16 are parallel to each other. Improves properties. That is, PZT having a tetragonal crystal structure provides large piezoelectric constants d33 and d31 when an electric field along the [001] direction is applied. Therefore, the piezoelectric constant of the piezoelectric film 16 can be further increased.

In step S7, the piezoelectric film 18 has a tensile stress, for example due to evaporation of the solvent in the solution during the heat treatment, or due to contraction of the film when the precursor is oxidized and crystallized. .

Thus, the piezoelectric film 16 including the piezoelectric films 17 and 18 is formed, and the film structure 10 shown in FIG. 1 is formed. That is, steps S6 and S7 are included in the process of forming the piezoelectric film 16 containing lead zirconate titanate on the film 15 . It should be noted that the thickness of both films 14 and 15 is less than the thickness of piezoelectric film 16, as described above.

Next, the diffraction pattern of the piezoelectric film 16 is measured by X-ray diffraction measurement using the θ-2θ method (step S8).

Preferably, in the diffraction pattern measured in step S8, either the (110) plane or the (101) plane of lead zirconate titanate with respect to the intensity of the diffraction peak of the (001) plane of lead zirconate titanate The ratio of the diffraction peak intensities is also 4×10 ⁻⁵ or less, or no diffraction peaks for either the (110) plane or the (101) plane are observed.

In such a case, the content of lead zirconate titanate having a tetragonal crystal structure and (110) orientation or (101) orientation in the piezoelectric film 16 is defined as and has a (001) oriented lead zirconate titanate content. Alternatively, the piezoelectric film 16 may be free of lead zirconate titanate having a tetragonal crystal structure and (110) orientation or (101) orientation. Therefore, since the directions of the polarization axes of the plurality of crystal grains included in the piezoelectric film 16 can be aligned, the piezoelectric characteristics of the piezoelectric film 16 can be improved.

Next, by X-ray diffraction measurement using the rocking curve method, the rocking curve for the diffraction peak of the (00n) plane (n is an integer of 1 or more) in the diffraction pattern measured in step S8 is measured (step S9 ).

Preferably, the full width at half maximum of the rocking curve measured in step S9 is 0.3 to 0.6°.

In such a case, variations in the orientation direction of each of the plurality of crystal grains included in the piezoelectric film 16 can be reduced. Therefore, the directions of the polarization axes of the plurality of crystal grains included in the piezoelectric film 16 can be further aligned, so that the piezoelectric characteristics of the piezoelectric film 16 can be further improved.

After forming the piezoelectric film 18, the conductive film 19 (see FIG. 2) as an upper electrode may be formed on the piezoelectric film 18 (step S10). Thereby, an electric field can be applied to the piezoelectric film 18 in the thickness direction.

Alternatively, after the conductive film 19 is formed, an AC voltage having a frequency of 1 kHz may be applied between the conductive films 13 and 19 to measure the dielectric constant (step S11).

Preferably, the dielectric constant measured in step S11 is 300-400. In such a case, the detection sensitivity can be improved when the film structure 10 is used as a sensor using the piezoelectric effect, for example. Alternatively, when the membrane structure 10 is used as, for example, an ultrasonic transducer using the inverse piezoelectric effect, the oscillation circuit can be easily designed.

<Modified example of the embodiment>
In the embodiment, as shown in FIG. 1, piezoelectric film 16 including piezoelectric films 17 and 18 is formed. However, the piezoelectric film 16 may include only the piezoelectric film 17 . Such an example will be described as a modification of the embodiment.

FIG. 14 is a cross-sectional view of a membrane structure according to a modification of the embodiment.
As shown in FIG. 14 , the film structure 10 of this modified example has a substrate 11 , an alignment film 12 , a conductive film 13 , a film 14 , a film 15 and a piezoelectric film 16 . The alignment film 12 is formed on the substrate 11 . A conductive film 13 is formed on the alignment film 12 . A film 14 is formed on the conductive film 13 . Membrane 15 is formed on membrane 14 . A piezoelectric film 16 is formed on the film 15 . Piezoelectric film 16 includes piezoelectric film 17 .

That is, the film structure 10 of this modified example is the same as the film structure 10 of the embodiment except that the piezoelectric film 16 does not include the piezoelectric film 18 (see FIG. 1), but includes only the piezoelectric film 17. is.

If the piezoelectric film 16 comprises a piezoelectric film 17 with compressive stress but does not comprise a piezoelectric film 18 (see FIG. 1) with tensile stress, then the piezoelectric film 16 has a piezoelectric film 17 with compressive stress and a piezoelectric film 17 with tensile stress. The warp amount of the film structure 10 is increased compared to the case where both the piezoelectric films 18 (see FIG. 1) are included. However, for example, when the thickness of the piezoelectric film 16 is thin, the warping amount of the film structure 10 can be reduced. Therefore, even when the piezoelectric film 16 includes only the piezoelectric film 17, it is possible to improve the shape accuracy when the film structure 10 is processed using a photolithographic technique, for example. It is possible to improve the characteristics of the piezoelectric element.

Note that the film structure 10 of this modified example may also have the conductive film 19 (see FIG. 2), like the film structure 10 of the embodiment.

Examples Hereinafter, the present embodiment will be described in further detail based on examples. In addition, the present invention is not limited to the following examples.

(Examples 1 to 7, Comparative Examples 1 to 5)
In the following, the film structure 10 described in the embodiment with reference to FIG. 1 was formed as the film structures of Examples 1 to 7. FIG. The film structures of Examples 1 to 7 were formed while changing the heat treatment temperature and heat treatment time after forming the platinum (Pt) film as the conductive film 13 . On the other hand, the film structure formed while changing the heat treatment temperature and heat treatment time after forming the Pt film to a heat treatment temperature and heat treatment time different from the heat treatment temperature and heat treatment time after forming the Pt film in Examples 1 to 7 was The film structures of Comparative Examples 1 to 5 were obtained.

First, as shown in FIG. 8, as a substrate 11, a 6-inch silicon single crystal wafer having an upper surface 11a as a main surface of (100) plane was prepared.

Next, as shown in FIG. 9, a zirconium oxide (ZrO ₂ ) film was formed as an alignment film 12 on the substrate 11 by electron beam evaporation. The conditions at this time are shown below.
Apparatus: electron beam vapor deposition apparatus Pressure: 7.00×10 ⁻³ Pa
Evaporation source: Zr+ _O2
Acceleration voltage/emission current: 7.5 kV/1.80 mA
Thickness: 24nm
Film formation rate: 0.005 nm/s
Oxygen flow rate: 7sccm
Substrate temperature: 500°C

Next, as shown in FIG. 10, a platinum (Pt) film was formed as a conductive film 13 on the alignment film 12 by sputtering. The conditions at this time are shown below.
Apparatus: DC sputtering apparatus Pressure: 1.20×10 ⁻¹ Pa
Evaporation source: Pt
Power: 100W
Thickness: 150nm
Film formation rate: 0.14 nm/s
Ar flow rate: 16 sccm
Substrate temperature: 450-600°C
Next, the Pt film was heat-treated. The conditions at this time are shown below.
Equipment: DC sputtering equipment Substrate temperature (heat treatment temperature): 450-600°C
Heat treatment time: 10-30 minutes

Here, Table 2 shows the heat treatment temperature and heat treatment time after forming the Pt film in each of Examples 1 to 7 and Comparative Examples 1 to 5. Comparative Example 1 is a sample in which no heat treatment is performed after forming the Pt film.

Next, as shown in FIG. 11, a Pb(Zr _0.58 Ti _0.42 )O ₃ film (PZT film) was formed as a film 14 on the conductive film 13 by a coating method. The conditions at this time are shown below.

Organometallic compounds of Pb, Zr, and Ti were mixed so as to have a composition ratio of Pb:Zr:Ti=100+δ:58:42 _{. 58} Ti _0.42 )O ₃ was dissolved so as to have a concentration of 0.35 mol/l, and a raw material solution was prepared. Here, δ is the surplus Pb amount in consideration of volatilization of Pb oxide in the subsequent heat treatment process, and δ=20 in this example. Then, 20 g of polypyrrolidone having a K value (viscosity characteristic value) of 27 to 33 was further dissolved in the raw material solution.

Next, 3 ml of the raw material solution out of the prepared raw material solutions is dropped onto a substrate 11 made of a 6-inch wafer and rotated at 3000 rpm for 10 seconds to apply the raw material solution onto the substrate 11, thereby removing the precursor. A film containing Then, the substrate 11 was placed on a hot plate at a temperature of 200° C. for 30 seconds, and further placed on a hot plate at a temperature of 450° C. for 30 seconds to evaporate the solvent and form a film. dried. Thereafter, heat treatment is performed at 600 to 700° C. for 60 seconds in an oxygen (O ₂ ) atmosphere of 0.2 MPa to oxidize and crystallize the precursor, thereby forming a PZT film as film 14 having a thickness of 20 nm. bottom.

Next, as shown in FIG. 12, a laminated film in which a PbZrO ₃ film (PZO film) was laminated as a film 15 was formed on the film 14 by a coating method. The conditions at this time are shown below.

Organometallic compounds of Pb and Zr were mixed so that the composition ratio was Pb:Zr = 100 + δ: 100, and added to a mixed solvent of ethanol and 2-n-butoxyethanol to a concentration of 0.35 mol / l as PbZrO _{3 .} A raw material solution was prepared so that As for δ, δ=20. Then, polypyrrolidone with a K value of 27 to 33 with a weight of 20 g was further dissolved in the raw material solution.

Next, 3 ml of the raw material solution out of the prepared raw material solutions is dropped onto a substrate 11 made of a 6-inch wafer and rotated at 3000 rpm for 10 seconds to apply the raw material solution onto the substrate 11, thereby removing the precursor. A film containing Then, the substrate 11 was placed on a hot plate at a temperature of 200° C. for 30 seconds, and further placed on a hot plate at a temperature of 450° C. for 30 seconds to evaporate the solvent and form a film. dried. After that, heat treatment was performed at 650° C. for 60 seconds in an oxygen (O ₂ ) atmosphere of 0.2 MPa to oxidize and crystallize the precursor, thereby forming a PZO film having a thickness of 30 nm.

For Examples 1 to 7 and Comparative Examples 1 to 5, the θ-2θ spectra of the film structures formed up to the PZO film were measured by the XRD method. That is, Examples 1 to 7 and Comparative Examples 1 to 5 were subjected to X-ray diffraction measurement by the θ-2θ method. The X-ray diffraction measurement was performed using a fully automatic horizontal multi-purpose X-ray diffractometer SmartLab manufactured by Rigaku Corporation.

15 and 16 are graphs showing examples of θ-2θ spectra by the XRD method of the film structure including the PZO film. The horizontal axis of the graphs of FIGS. 15 and 16 indicates the angle 2θ, and the vertical axis of the graphs of FIGS. 15 and 16 indicates the X-ray intensity. 15 shows the results for Example 3, and FIG. 16 shows the results for Comparative Example 1. FIG.

In the example shown in FIG. 15 (Example 3), in the θ-2θ spectrum, the peak corresponding to the (200) plane of ZrO ₂ in the pseudo-cubic representation corresponds to the (200) plane of Pt having a cubic crystal structure. , and peaks corresponding to the (100) plane and the (200) plane in the pseudo-cubic representation of PZO were observed. Therefore, in the example shown in FIG. 15 (Embodiment 3), the orientation film 12 contains ZrO ₂ with (100) orientation in the pseudo-cubic system, and the conductive film 13 contains Pt with (100) orientation in the cubic system. It was found that film 15 contained (100) oriented PZO in a pseudo-cubic crystal display.

In the example shown in FIG. 16 (Comparative Example 1) as well, in the θ-2θ spectrum, the peak corresponding to the (200) plane of ZrO ₂ in the pseudo-cubic representation corresponds to the (200) plane of Pt having a cubic crystal structure. , and peaks corresponding to the (100) plane and the (200) plane in the pseudo-cubic representation of PZO were observed. However, in the example shown in FIG. 16 (Comparative Example 1), unlike the example shown in FIG. 15 (Example 3), a peak corresponding to the (101) plane was observed in the pseudo-cubic representation of PZO. Therefore, in the example shown in FIG. 16 (Comparative Example 1), the orientation film 12 contains ZrO ₂ with (100) orientation in the pseudo-cubic system, and the conductive film 13 contains Pt with (100) orientation in the cubic system. Thus, although film 15 contains (100) oriented PZO in the pseudocubic notation, it was found that film 15 also contains (110) oriented PZO in the pseudocubic notation.

That is, in the example shown in FIG. 15 (Example 3), it was found that the film 15 did not contain PZO with (110) orientation in the pseudo-cubic crystal display. Furthermore, in the example shown in FIG. 15 (Example 3), it was found that the conductive film 13 did not contain Pt oriented (111) in the cubic system display.

Next, as shown in FIG. 13, a Pb(Zr _0.55 Ti _0.45 )O ₃ film (PZT film) having a thickness of 2 μm , for example, is deposited on the film 15 as the piezoelectric film 17 by sputtering. formed by The conditions at this time are shown below.
Equipment: RF magnetron sputtering equipment Power: 2500W
Gas: Ar/ _O2
Pressure: 0.14Pa
Substrate temperature: 475°C
Film formation rate: 0.63 nm/s

Next, as shown in FIG. 1, a Pb(Zr _0.55 Ti _0.45 )O ₃ film (PZT film) was formed as the piezoelectric film 18 on the piezoelectric film 17 by a coating method. The conditions at this time are shown below.

Organometallic compounds of Pb, Zr and Ti were mixed so as to have a composition ratio of Pb:Zr:Ti=100+δ:55:45, and Pb (Zr _0.55 A raw material solution was prepared so that the concentration of Ti _0.45 )O ₃ was 0.35 mol/l. As for δ, δ=20. Then, polypyrrolidone with a K value of 27 to 33 with a weight of 20 g was further dissolved in the raw material solution.

Next, 3 ml of the raw material solution out of the prepared raw material solutions is dropped onto a substrate 11 made of a 6-inch wafer and rotated at 3000 rpm for 10 seconds to apply the raw material solution onto the substrate 11, thereby removing the precursor. A film containing Then, the substrate 11 was placed on a hot plate at a temperature of 200° C. for 30 seconds, and further placed on a hot plate at a temperature of 450° C. for 30 seconds to evaporate the solvent and form a film. dried. Thereafter, the precursor was oxidized and crystallized by heat treatment at 600 to 700° C. for 60 seconds in an oxygen (O ₂ ) atmosphere of 0.2 MPa, thereby forming a piezoelectric film 18 having a thickness of 30 nm.

For each of Examples 1 to 7 and Comparative Examples 1 to 5, the θ-2θ spectrum of the film structure formed up to the PZT film as the piezoelectric film 18 was measured by the XRD method. That is, each of Examples 1 to 7 and Comparative Examples 1 to 5 was subjected to X-ray diffraction measurement by the θ-2θ method.

Each of FIGS. 17 and 18 is a graph showing an example of the θ-2θ spectrum by the XRD method of the film structure formed up to the PZT film. The horizontal axis of each graph of FIGS. 17 and 18 indicates the angle 2θ, and the vertical axis of each graph of FIGS. 17 and 18 indicates the X-ray intensity. 17 shows the results for Example 3, and FIG. 18 shows the results for Comparative Example 1. FIG.

In the example shown in FIG. 17 (Example 3), in the θ-2θ spectrum, the peak corresponding to the (200) plane of Pt having a cubic crystal structure and the (001) plane of PZT having a tetragonal crystal structure Peaks corresponding to the plane and (002) plane were observed. Therefore, in the example shown in FIG. 17 (Example 3), the conductive film 13 has a cubic crystal structure and contains (100) oriented Pt, and the piezoelectric film 16 has a tetragonal crystal structure. and contains (001) oriented PZT.

Also in the example shown in FIG. 18 (Comparative Example 1), in the θ-2θ spectrum, the peak corresponding to the (200) plane of Pt having a cubic crystal structure and the (001) plane of PZT having a tetragonal crystal structure Peaks corresponding to the plane and (002) plane were observed. However, in the example shown in FIG. 18 (Comparative Example 1), unlike the example shown in FIG. Observed. Therefore, in the example shown in FIG. 18 (Comparative Example 1), the conductive film 13 has a cubic crystal structure and contains (100) oriented Pt, and the piezoelectric film 16 has a tetragonal crystal structure. and contains (001) oriented PZT, it was found that the piezoelectric film 16 has a tetragonal crystal structure and also contains (110) or (101) oriented PZT.

That is, in the example shown in FIG. 17 (Example 3), it was found that the piezoelectric film 16 did not contain PZT with (110) orientation in the tetragonal display.

Table 2 shows the results of measuring PZT(110)/PZT(001) in the θ-2θ method. Here, PZT(110)/PZT(001) is the (110) plane or (101) plane of PZT having a tetragonal crystal structure with respect to the peak intensity of the (001) plane of PZT having a tetragonal crystal structure. means the ratio of the stronger peak intensities of When neither the (110) plane nor the (101) plane of PZT is observed, the background level at the angle 2θ (2θ≈31°) at which the (110) plane of PZT is observed is the (110) plane of PZT. It was defined as the peak intensity of the stronger one of the plane or (101) plane.

As shown in Table 2, for example, neither the PZT (110) plane nor the (101) plane was observed, and in Examples 1 to 7 in which the crystallinity was good, PZT (110)/PZT (001) was 4×10 ⁻⁵ or less. On the other hand, for example, in Comparative Examples 1 to 5 where the PZT (110) plane or (101) plane is observed and the crystallinity is not good, PZT (110)/PZT (001) is 1 × 10 ^-4 or more. Met.

Wide-area reciprocal lattice map measurement was performed on each of the film structures of Examples 1 to 5 and Comparative Examples 1 to 5. The measurement of the wide-area reciprocal lattice map was performed by installing a hybrid multi-dimensional pixel detector HyPix-3000 to a fully automatic horizontal multi-purpose X-ray diffractometer SmartLab (manufactured by Rigaku Corporation).

19 and 20 are measurement results of a reciprocal lattice map of a film structure formed up to the PZT film. 19 shows the results for Example 3, and FIG. 20 shows the results for Comparative Example 1. FIG. FIG. 21 shows the result of simulation (calculation) of the reciprocal lattice map of PZT. By comparing FIGS. 19 and 20 with FIG. 21, it can be determined whether the piezoelectric film 16 is epitaxially grown, ie, oriented in any of the X-axis, Y-axis and Z-axis directions (see FIG. 1). can be evaluated.

In the measurement of the reciprocal lattice map, first, a scan (ω-2θ scan) by the ω-2θ method similar to the scan by the θ-2θ method (θ-2θ scan) is performed, and the angle ω, the angle 2θ, and the X-ray intensity A plurality of first numerical value groups consisting of three numerical values of are acquired. In the measurement of the reciprocal lattice map, next, among the three numerical values included in each of the plurality of first numerical value groups, two numerical values of the angle ω and the angle 2θ are substituted into the following formula (equation 4) to obtain the reciprocal lattice space Obtain the coordinate _qx , and substitute the two numerical values of the angle ω and the angle 2θ into the following formula (Equation 5) to obtain the reciprocal lattice space coordinate _qz . Then, each first numerical value group is converted into a second numerical value group consisting of three numerical values of reciprocal lattice space coordinates q _x , reciprocal lattice space coordinates q _z and X-ray intensity. In the measurement of the reciprocal lattice map, next, among the three numerical values included in each of the plurality of second numerical value groups, the intensity of the X-ray is set to the reciprocal lattice space coordinate _qx on the horizontal axis, and the reciprocal lattice space coordinate Contour lines are displayed on a plane with _qz as the coordinate on the vertical axis.

Specifically, the ω-2θ scan was performed by changing the angle 2θ in the range of 10 to 120° and changing the angle ω in the range of 10 to 90°. In the ω-2θ scan, the planes of rotation of the angles 2θ and ω are parallel to the Si (110) plane of the substrate 11 .

In addition, in the measurement of the wide-area reciprocal lattice map using the fully automatic horizontal multipurpose X-ray diffractometer SmartLab manufactured by Rigaku Corporation, the measurement was performed at two angles φ of 0° and 45° with the φ axis as the in-plane rotation axis. are doing. Further, as described above, by substituting the angle ω and the angle 2θ obtained by the ω-2θ scan into the above equations (Equation 4) and (Equation 5), the reciprocal lattice space coordinates q _x and reciprocal lattice space coordinates q _z are obtained as It is also possible to measure different components of the polarization domain by superimposing the reciprocal lattice maps measured at multiple angles χ when the χ axis is the tilt axis. is.

When comparing the reciprocal lattice map measurement results (Example 3) shown in FIG. 19 with the reciprocal lattice map calculation results shown in FIG. 21, the reciprocal lattice map measurement results shown in FIG. It agrees with the calculation result. Therefore, it can be seen that the PZT film of Example 3 is a good single crystal film.

On the other hand, when the measurement result of the reciprocal lattice map shown in FIG. 20 (Comparative Example 1) is compared with the calculation result of the reciprocal lattice map shown in FIG. Although the calculated results of the map are substantially the same, each point is wider than the measured results of the reciprocal lattice map shown in FIG. 19 . Therefore, it can be seen that the PZT film of Comparative Example 1 has lower crystallinity than the PZT film of Example 3.

Further, for each of the film structures of Examples 1 to 7 and Comparative Examples 1 to 5, the diffraction peak of the (001) plane in the diffraction pattern measured by X-ray diffraction measurement using the θ-2θ method. was observed, the rocking curve was measured with the angle 2θ fixed at the angle at which the diffraction peak of the (001) plane was observed. Table 2 shows the full width at half maximum (FWHM) of the rocking curve measured in this rocking curve measurement for each of the membrane structures of Examples 1 to 7 and Comparative Examples 1 to 5. shown in

As shown in Table 2, for example, in Examples 1 to 7 in which neither the PZT (110) plane nor the (101) plane was observed, and the crystallinity was good, the half value of the rocking curve of PZT (100) The full width was 0.3-0.6°. On the other hand, for example, in Comparative Examples 1 to 5 in which the PZT (110) plane or (101) plane was observed and the crystallinity was not good, the full width at half maximum in the rocking curve of PZT (100) was 1.0 to 2. .0°.

The full width at half maximum of the rocking curve for each of the diffraction peaks of the (001) plane, (002) plane, (003) plane and (004) plane in the diffraction pattern measured by X-ray diffraction measurement by the θ-2θ method is , is synonymous with the full width at half maximum of the reciprocal lattice points corresponding to the (001) plane, (002) plane, (003) plane, and (004) plane of the reciprocal lattice map.

In addition, the spread of each spot in the measurement result of the reciprocal lattice map in FIG. 19 (Example 3) is smaller than the spread of each spot in the measurement result of the reciprocal lattice map in FIG. 20 (Comparative Example 1). This is because the full width at half maximum of the rocking curve of PZT (001) in each of the film structures of Examples 1 to 7 is the same as the rocking curve of PZT (001) in each of the film structures of Comparative Examples 1 to 5. is smaller than the full width at half maximum.

That is, the full width at half maximum in the rocking curve of PZT (00n) (n is an integer of 1 or more) in each of the film structures of Examples 1 to 7 is It is smaller than the full width at half maximum in the rocking curve of PZT(00n) (n is an integer equal to or greater than 1).

In the region around the (113) plane of PZT (see FIG. 21) in the reciprocal lattice map of FIG. 19, the spots corresponding to the reciprocal lattice points of the (113) plane of PZT having a tetragonal crystal structure are divided into three spots. However, the reciprocal space coordinates _qx for each of these three spots are different. Therefore, it is considered that the stress is relaxed between the portions of the piezoelectric film 16 represented by each of these three spots. The phenomenon in which the reciprocal lattice points of the (113) plane of PZT are divided into three spots in this way, and the reciprocal lattice space coordinates q _x of each of these three spots are different is explained in Examples 1 to 7. was observed in each membrane structure.

On the other hand, in the θ-2θ spectrum of FIG. 17, a peak that is considered to be the (100) plane of PZT having a tetragonal crystal structure, for example, is observed on the high-angle side of the (001) plane of PZT having a tetragonal crystal structure. It is In addition, a peak that is considered to be the (200) plane of PZT having a tetragonal crystal structure, for example, is observed on the high-angle side of the (002) plane of PZT having a tetragonal crystal structure. Considering this together with the fact that the reciprocal lattice map of FIG. 19 suggests that the stress is relaxed between the portions of the piezoelectric film 16 represented by each of these three spots, For example, it is thought that the (100) oriented portion of PZT having a tetragonal crystal structure exists in a very small amount, and that portion functions as a stress relaxation layer.

Next, as shown in FIG. 2, a platinum (Pt) film was formed as a conductive film 19 on the piezoelectric film 16 by sputtering. After that, a voltage was applied between the conductive films 13 and 19 to measure the voltage dependence of polarization.

Each of FIGS. 22 and 23 is a graph showing the voltage dependence of the polarization of the membrane structure. The horizontal axis of each graph of FIGS. 22 and 23 represents voltage, and the vertical axis of each graph of FIGS. 22 and 23 represents polarization. 22 shows the results for Example 3, and FIG. 23 shows the results for Comparative Example 1. FIG. Since the thicknesses of the piezoelectric films 16 included in the film structures of Example 3 and Comparative Example 1 are equal to each other, when the horizontal axis of each graph in FIGS. can be similarly compared.

According to the voltage dependence of polarization of Example 3 shown in FIG. 22, the dielectric constant εr, residual polarization value Pr and coercive voltage Vc were as follows.
εr = 300
Pr=50 μC/cm ²
Vc = 23.2V @ 2.7µm

Further, according to the voltage dependence of polarization of Comparative Example 1 shown in FIG. 23, the dielectric constant εr, residual polarization value Pr, and coercive voltage Vc were as follows.
εr = 500
Pr=20 μC/cm ²
Vc = 19.5V @ 2.7µm

Similarly, Table 2 shows the dielectric constant εr measured by measuring the voltage dependence of polarization for each of the film structures of Examples 1 to 7 and Comparative Examples 1 to 5. The dielectric constant εr is a dielectric constant measured by applying an AC voltage having a frequency of 1 kHz between the conductive films 13 and 19 .

As shown in Table 2, for example, in Examples 1 to 7 in which neither the PZT (110) plane nor the (101) plane was observed and the crystallinity was good, the dielectric constant εr was 300 to 400. Met. On the other hand, in Comparative Examples 1 to 5 in which the PZT (110) plane or (101) plane was observed and the crystallinity was not good, the dielectric constant εr was 450 to 500.

Thus, in each of the film structures of Examples 1 to 7, the dielectric constant of the piezoelectric film 16 is lower than that of the conventional PZT film. As a result, detection sensitivity can be improved when each of the film structures of Examples 1 to 7 is used as a sensor using the piezoelectric effect, for example. Alternatively, when each of the film structures of Examples 1 to 7 is used as an ultrasonic transducer using the inverse piezoelectric effect, the oscillation circuit can be easily designed.

Note that the film 14 included in each of the film structures of Examples 1 to 7 and Comparative Examples 1 to 5 was Pb(Zr _1-x Ti _x ) Pb(Zr ₁ -x Ti _x )O ₃ film where x satisfies 0<x≦0.48, ie PZT film, instead of the O ₃ film, ie Pb(Zr _0.58 Ti _0.42 )O ₃ film Similar results were obtained when forming Moreover, even when a PZT film is formed when x satisfies 0.48<x<1, there is a difference in the direction of slightly lower characteristics compared to the PZT film when x satisfies 0<x≦0.48. However, substantially the same results were obtained.

Further, for the film 15 included in each of the film structures of Examples 1 to 7 and Comparative Examples 1 to 5, Pb(Zr _1-y Ti _y )O when y satisfies y=0. Similar results were obtained when a Pb(Zr _1-y Ti _y )O ₃ film where y satisfies 0<y≦0.1, ie, a PZT film was formed instead of the 3 film _, ie, the PZO film.

Although the invention made by the present inventor has been specifically described based on the embodiment, the invention is not limited to the above embodiment, and can be variously modified without departing from the gist of the invention. Needless to say.

Within the scope of the idea of the present invention, those skilled in the art can conceive of various modifications and modifications, and it is understood that these modifications and modifications also fall within the scope of the present invention.

For example, a person skilled in the art may appropriately add, delete, or change the design of components, or add, omit, or change the conditions of the above-described embodiments. As long as it has the gist, it is included in the scope of the present invention.

10 Film structure 11 Substrate 11a Upper surface 12 Orientation film 13 Conductive films 14, 15 Films 16, 17 Piezoelectric film 17a Crystal grain 18 Piezoelectric film 18a Film 18b Crystal grain 19 Conductive film EP End point P1 Polarization SP Start point

Claims (3)

(a) a step of preparing a silicon substrate including a main surface consisting of a (100) plane;
(b) forming a first film containing (100)-oriented zirconium oxide on the main surface;
(c) forming a first conductive film containing (100)-oriented platinum on the first film;
(d) after the step (c), heat-treating the first conductive film by holding it at a temperature of 450 to 600° C. for 10 to 30 minutes ;
A method for manufacturing a membrane structure having (a) forming a first film containing (100)-oriented zirconium oxide on a main surface of a silicon substrate including a (100) plane;
(b) forming a first conductive film containing (100)-oriented platinum on the first film;
(c) after the step (b), heat-treating the first conductive film by holding it at a temperature of 450 to 600° C. for 10 to 30 minutes ;
is executed by the control unit to manufacture the film structure. A program for causing a control unit to execute each step according to claim 2.

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