TWI787071B - Membrane structure and manufacturing method thereof - Google Patents

Abstract

The object of the present invention is to provide a film structure that can increase the piezoelectric constant of the piezoelectric film in a film structure having a conductive film formed on a silicon substrate and a piezoelectric film formed on the conductive film. The method of manufacturing a film structure as a solution of the present invention is characterized in that it has the (b) step of forming a zirconium-containing film on a substrate (11) as a silicon substrate, and after the (b) step, on the substrate (11) ) step (c) of forming an epitaxially grown zirconia-containing alignment film (12b). In addition, the manufacturing method of the film structure includes: the (d) step of forming a platinum-containing conductive film (13) grown epitaxially on the alignment film (12b); Step (e) of the grown piezoelectric film (15).

Description

Membrane structure and manufacturing method thereof

The present invention relates to a membranous structure and a manufacturing method thereof.

As a film structure having a substrate, a conductive film formed on the substrate, and a piezoelectric film formed on the conductive film, there are known a substrate, a platinum-containing conductive film formed on the substrate, and a piezoelectric film formed on the substrate. A film structure of a piezoelectric film containing lead zirconate titanate (PZT), that is, Pb(Zr _1-x Ti _x )O ₃ (0<x<1) on a conductive film. Such a film structure is processed to form a piezoelectric element. As a substrate having such a film structure, a silicon substrate can be used.

In Japanese Patent Application Laid-Open No. 2015-154015 (Patent Document 1), it is disclosed that ferroelectric ceramics are provided with a ZrO ₂ film oriented at (200), and platinum formed on the ZrO ₂ film and oriented at (200) film, and a piezoelectric film formed on a platinum film. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-154015

[Problem to be Solved by the Invention]

When a zirconia (ZrO ₂ ) film is directly formed on a silicon substrate, the crystallinity of the formed ZrO ₂ film may be lowered, and the ZrO ₂ film may not be epitaxially grown satisfactorily. In such a case, the conductive film cannot be epitaxially grown satisfactorily on the ZrO ₂ film, and the piezoelectric film cannot be epitaxially grown satisfactorily on the conductive film. When an electric field is applied, for example, in a direction parallel to the polarization direction or in a direction at a certain angle to the polarization direction to a piezoelectric film containing lead zirconate titanate, the piezoelectric constant is large. Therefore, if the piezoelectric film is not epitaxially grown well, the piezoelectric constant of the piezoelectric film cannot be increased because the polarization directions of the entire piezoelectric film are not uniform, and the characteristics of the piezoelectric element are degraded.

The present invention was made to solve the above-mentioned conventional problems, and its object is to provide a film structure having a conductive film formed on a silicon substrate and a piezoelectric film formed on the conductive film, which can A film structure that increases the piezoelectric constant of a piezoelectric film. [Means for solving problems]

Among the creations disclosed in this specification, the summary contents of the representative ones are briefly described as follows.

A method for manufacturing a membrane structure according to an aspect of the present invention is characterized by comprising (a) step of preparing a silicon substrate, (b) step of forming a first zirconium-containing film on the silicon substrate, and (b) step Thereafter, step (c) of forming a second film containing zirconia grown epitaxially on the silicon substrate. In addition, the method of manufacturing the film structure includes the step (d) of forming a first conductive film containing platinum epitaxially grown on the second film, and forming a piezoelectric film grown epitaxially on the first conductive film. (e) step.

In addition, as another aspect, the silicon substrate may also have a main surface constituted by a (100) plane. It is also possible to form a second film of zirconium oxide that is epitaxially grown on the main surface, has a cubic crystal structure, and contains (100) oriented zirconia in the (c) step; and forms a cubic crystal in the (d) step. structure, and includes a (100)-oriented platinum-containing first conductive film.

In addition, as another aspect, in the step (b), the first film may be formed by vapor deposition, and in the step (c), the second film may be formed by vapor deposition.

In addition, as another aspect, in the step (b), the first film having a thickness of 5-10 nm may be formed at a temperature of 650-700°C.

In addition, as another aspect, in the step (c), the second film may be formed at a temperature of 500 to 600°C.

In addition, as another aspect, in the step (c), a second film having a thickness of 8 to 12 nm may be formed.

In addition, as another aspect, in the step (e), a piezoelectric film having a tetragonal crystal structure and including (001)-oriented lead zirconate titanate may also be formed.

In addition, as another aspect, in step (e), a piezoelectric film having a crystal structure of rhombohedral crystals and including (100)-oriented lead zirconate titanate can also be formed.

In addition, as another aspect, the method of manufacturing the film structure may include (f) step of forming the second conductive film on the piezoelectric film.

A film structure according to an aspect of the present invention is characterized by comprising: a silicon substrate, a first film containing zirconium formed on the silicon substrate, a second film containing zirconium oxide epitaxially grown on the first film, A platinum-containing first conductive film epitaxially grown on the second film, and a piezoelectric film epitaxially grown on the first conductive film.

In addition, as another aspect, the silicon substrate may have a main surface composed of a (100) plane, the second film may have a cubic crystal structure and include (100) oriented zirconia, and the first conductive film may be Platinum having a cubic crystal structure and including (100) alignment.

In addition, as another aspect, it is preferable that the first film has a thickness of 5 to 10 nm, and the second film has a thickness of 8 to 12 nm.

In addition, as another aspect, it is preferable that the piezoelectric film has a tetragonal crystal structure and contains (001)-oriented lead zirconate titanate.

In addition, as another aspect, it is preferable that the piezoelectric film has a rhombohedral crystal structure and includes (100)-oriented lead zirconate titanate.

In addition, as another aspect, the film structure may have a second conductive film formed on the piezoelectric film. [Effect of Invention]

By applying one aspect of the present invention, the piezoelectric constant of the piezoelectric film can be increased in a film structure having a conductive film formed on a silicon substrate and a piezoelectric film formed on the conductive film.

Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings.

In addition, the disclosure is only an example after all, and those who are familiar with the art will obviously think of appropriate changes while maintaining the gist of the invention, and of course all are included in the scope of the present invention. In addition, the drawings can make the description clearer, and when the width, thickness, shape, etc. of each part are also schematically shown compared with the embodiment, it is only an illustration after all, and is not intended to limit the scope of the present invention. Explanation.

In addition, in this specification and each drawing, the same code|symbol is attached|subjected to the same element mentioned above about what was already shown in figure, and detailed description is abbreviate|omitted suitably.

In addition, in the drawings used in the embodiments, hatching (hatching lines) provided for distinguishing structural objects may be omitted depending on the drawings.

(implementation form) ＜Membrane structure＞ First, a film structure of an embodiment of an 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 membrane structure in the case where the membrane structure according to the embodiment has a conductive film as an upper electrode.

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 conductive film 14 , and a piezoelectric film 15 . The alignment film 12 is formed on the substrate 11 . The conductive film 13 is formed on the alignment film 12 . The conductive film 14 is formed on the conductive film 13 . The piezoelectric film 15 is formed on the conductive film 14 .

Furthermore, as shown in FIG. 2 , the film structure 10 of this embodiment may have a conductive film 16 . The conductive film 16 is formed on the piezoelectric film 15 . In this case, the conductive films 13 and 14 are conductive films serving as lower electrodes, and the conductive film 16 is a conductive film serving as an upper electrode. Thereby, an electric field can be applied to the piezoelectric film 15 in the thickness direction.

The substrate 11 is, for example, a silicon substrate made of silicon (Si) single crystal. In addition, the substrate 11 has an upper surface 11a as a main surface.

The alignment film 12 includes, for example, zirconia (ZrO ₂ ) epitaxially grown on the upper surface 11 a of the substrate 11 . The conductive film 13 is made of metal, such as platinum (Pt) epitaxially grown on the alignment film 12 . The conductive film 14 is epitaxially grown on the conductive film 13 . The piezoelectric film 15 is epitaxially grown on the conductive film 14 .

Here, when two directions perpendicular to each other in the upper surface 11a of the substrate 11 as the main surface are referred to as the X-axis direction and the Y-axis direction, and when the direction perpendicular to the upper surface 11a is referred to as the Z-axis direction, a certain film epitaxial growth , means that the film is aligned in any one of the X-axis direction, the Y-axis direction and the Z-axis direction.

When the alignment film 12 is not epitaxially grown on the substrate 11 and the conductive film 13 is not epitaxially grown on the alignment film 12, the conductive film 14 cannot be epitaxially grown on the conductive film 13, and the pressure on the conductive film 14 cannot be applied. The electrical film 15 is epitaxially grown. When an electric field is applied to the piezoelectric film 15, for example, in a direction parallel to the polarization direction or in a direction at a certain angle to the polarization direction, the piezoelectric constants d33 and d31 are large. Therefore, when the piezoelectric film 15 is not epitaxially grown, the piezoelectric constants d33 and d31 of the piezoelectric film 15 cannot be increased because the polarization directions of the entire piezoelectric film 15 are not uniform, and the characteristics of the piezoelectric element are degraded. .

On the other hand, in this embodiment, since the alignment film 12 is epitaxially grown on the substrate 11, and the conductive film 13 is epitaxially grown on the alignment film 12, the conductive film 14 can be epitaxially grown on the conductive film 13. The piezoelectric film 15 is epitaxially grown on the conductive film 14 . Therefore, the polarization directions of the entire piezoelectric film 15 can be unified, the piezoelectric constants d33 and d31 of the piezoelectric film 15 can be increased, and the characteristics of the piezoelectric element can be improved.

Preferably, the conductive film 14 includes a metal oxide, including strontium ruthenate (SrRuO ₃ , hereinafter referred to as SRO) epitaxially grown on the alignment film 12 . In addition, the piezoelectric film 15 is composed of lead zirconate titanate (Pb(Zr _1-x Ti _x )O ₃ (0<x<1), the following Also referred to as PZT).

When the piezoelectric film 15 contains PZT, the piezoelectric constant of the piezoelectric film 15 can be increased compared to the case where the piezoelectric film 15 does not contain PZT.

In addition, the SRO contained in the conductive film 14 has the same crystal structure as the perovskite structure of the PZT contained in the piezoelectric film 15 . Therefore, the PZT contained in the piezoelectric film 15 is easily aligned in a certain direction. In addition, since the PZT contained in the piezoelectric film 15 has a tetragonal crystal structure or a rhombohedral crystal structure, the PZT contained in the piezoelectric film 15 is easily aligned in a certain direction, and its polarization directions are easily unified. In a certain direction, the piezoelectric characteristics are improved.

In addition, as shown in FIG. 12 described later, the film structure 10 may not have the conductive film 14, and the piezoelectric film 15 may be directly formed on the conductive film 13. In this case, the piezoelectric film 15 is less likely to be aligned than when it is formed on the conductive film 14 containing SRO, but it can be aligned in a certain direction even on the conductive film 13 containing platinum.

Preferably, the silicon single crystal contained in the substrate 11 has an upper surface 11a consisting of a (100) plane as a main surface in a cubic crystal structure. Zirconia (ZrO ₂ ) contained in the alignment film 12 has a cubic crystal structure and is (100) aligned. Platinum (Pt) contained in the conductive film 13 has a cubic crystal structure and is (100) aligned.

Thereby, when the SRO included in the conductive film 14 has a pseudo-cubic crystal structure, the conductive film 14 can be aligned (100) on the substrate 11 . In addition, when the PZT contained in the piezoelectric film 15 has a tetragonal crystal structure, the piezoelectric film 15 can be aligned (001) on the substrate 11; In the case of a crystal structure, the piezoelectric film 15 can be aligned (100) on the substrate 11.

Here, the alignment film 12 is a (100) alignment, which means that the (100) plane of the alignment film 12 having a cubic crystal structure is formed along the substrate 11 made of silicon single crystal and is composed of a (100) plane. As the upper surface 11a of the main surface. In addition, the alignment film 12 is (100) oriented, preferably the (100) plane of the alignment film 12 is parallel to the upper surface 11a formed by the (100) plane of the substrate 11 made of silicon single crystal. In addition, the (100) plane of the alignment film 12 is parallel to the upper surface 11a formed by the (100) plane of the substrate 11, which means that not only the (100) plane of the alignment film 12 is completely parallel to the upper surface 11a of the substrate 11, but also includes The angle between the plane completely parallel to the upper surface 11a of the substrate 11 and the (100) plane of the alignment film 12 is less than 20°.

In addition, zirconia, which is a bulk material, has a monoclinic crystal structure at room temperature, and when the temperature is raised from room temperature, it undergoes phase transition at about 1170°C to have a tetragonal crystal structure. When it is high, it will phase transition at about 2370°C and become a crystal structure with cubic crystals. However, since the zirconia contained in the alignment film 12 is stressed from the upper and lower films or the substrate, the phase transition behavior of the zirconia contained in the alignment film 12 and the phase transition behavior of the zirconia as the bulk material Not different. In addition, since the thickness of the alignment film 12 is as thin as several tens of nanometers or less, it is difficult to accurately distinguish the crystal structure of zirconia contained in the alignment film 12 from a tetragonal crystal structure to a cubic crystal structure. .

Therefore, in the following, when the zirconia contained in the alignment film 12 has the crystal structure of the tetragonal crystal, it is regarded as the case where the zirconia has the crystal structure of the cubic crystal. That is, in the description of this case, when the zirconia contained in the alignment film 12 has a cubic crystal structure, it includes the case of actually having a cubic crystal structure, and the fact that it has a non-cubic crystal structure. In the case of a tetragonal crystal structure.

In addition, similarly, in the following, the case where the SRO included in the conductive film 14 has an orthorhombic crystal structure, the case where the SRO has a pseudo-cubic crystal structure, and further, the case where the SRO is regarded as When having a cubic crystal structure. That is, in the description of this case, when the SRO contained in the conductive film 14 has a cubic crystal structure, it includes the case where it actually has a cubic crystal structure, and actually has a non-cubic crystal structure. In the case of orthorhombic crystal, that is, the crystal structure of pseudo-cubic crystal.

Preferably, the piezoelectric film 15 has a tetragonal crystal structure and (001) orientation. In Pb(Zr _1-x Ti _x )O ₃ (0<x<1), x is 0. By satisfying 48<x<1, the PZT contained in the piezoelectric film 15 has a tetragonal crystal structure, facilitates epitaxial growth, and facilitates (001) alignment. Therefore, when PZT having a tetragonal crystal structure is (001) aligned, the polarization direction parallel to the [001] direction and the electric field direction parallel to the thickness direction of the piezoelectric film 15 become parallel to each other, thereby improving the piezoelectric properties. promote. That is, when an electric field along the [001] direction is applied to PZT having a tetragonal crystal structure, large piezoelectric constants d33 and d31 can be obtained. Therefore, the piezoelectric constant of the piezoelectric film 15 can be further increased.

Alternatively, preferably, the piezoelectric film 15 has a rhombohedral crystal structure and (100) orientation. By satisfying that x in Pb(Zr _1-x Ti _x )O ₃ (0<x<1) is 0.20<x≦0.48, the PZT contained in the piezoelectric film 15 has a rhombohedral crystal structure, and it is easy to Make epitaxy grow, easy (100) alignment. Therefore, when PZT having a rhombohedral crystal structure has a (100) orientation, the PZT has a so-called Engineered Domain Configuration, which is parallel to the polarization direction of each direction equivalent to the [111] direction, and parallel to the piezoelectric direction. The angle of the electric field direction in the thickness direction of the electric film 15 is equal to each other in any sub-polar domain (domain), so that the piezoelectric characteristics are improved. That is, when an electric field along the [100] direction is applied to PZT having a rhombohedral crystal structure, large piezoelectric constants d33 and d31 can be obtained. Therefore, the piezoelectric characteristics of the piezoelectric film 15 can be further increased.

FIG. 3 is a diagram illustrating a state of epitaxial growth of an alignment film included in the film structure of the embodiment. On the other hand, FIG. 4 is a diagram illustrating a state where the alignment film included in the film structure is not epitaxially grown. 3 schematically shows the layers of the substrate 11, alignment film 12, conductive films 13 and 14, and piezoelectric film 15; and FIG. 4 schematically shows the substrate 11 and alignment film 12.

The lattice constant of silicon contained in the substrate 11, the lattice constant of ZrO contained in the alignment film ₁₂ , the lattice constant of Pt contained in the conductive film 13, the lattice constant of SRO contained in the film 14, and the lattice constant contained in Table 1 shows the lattice constant of PZT of the piezoelectric film 15 .

As shown in Table ₁ , the lattice constant of silicon is 0.543nm, and the lattice constant of ZrO ₂ is _0.514nm . The lattice constant is well integrated with that of silicon. Therefore, as shown in FIG. 3 , the alignment film 12 containing ZrO ₂ can be epitaxially grown on the main surface formed by the (100) plane of the substrate 11 containing silicon single crystal. Therefore, the alignment film ₁₂ containing ZrO2 can be aligned with a cubic crystal structure on the (100) plane of the substrate 11 containing silicon, and the crystallinity of the alignment film 12 can be improved.

In addition, as shown in Table 1, the lattice constant of ZrO ₂ is 0.514nm, and the lattice constant of platinum is 0.392nm, but when platinum is rotated by 45° in the plane, the length of the diagonal is 0.554nm, and the length of the diagonal is 0.554nm. The unconformity of the length of ZrO ₂ to the lattice constant of ZrO 2 is as small as 7.8%, so the integration of the lattice constant of platinum to the lattice constant of ZrO ₂ is good. Therefore, as shown in Figure 3, can make the conductive film 13 containing platinum, on the (100) face of the alignment film ₁₂ that contains ZrO , form (100) alignment with the crystal structure of cubic crystal, can improve the conductive film 13 crystallinity.

In addition, as shown in Table 1, the lattice constant of platinum is 0.392 nm, the lattice constant of SRO is 0.390-0.393 nm, and the unconformity of the lattice constant of SRO to the lattice constant of platinum is as small as 0.51%, so SRO The lattice constant of platinum is well integrated with the lattice constant of platinum. Therefore, the conductive film 14 containing SRO can be aligned in (100) with a cubic crystal structure on the (100) plane of the conductive film 13 containing platinum, and the crystallinity of the conductive film 14 can be improved.

In addition, as shown in Table 1, the lattice constant of SRO is 0.390-0.393nm, the lattice constant of PZT is 0.401nm, and the unconformity of the lattice constant of PZT to the lattice constant of SRO is as small as 2.0-2.8%, so The lattice constant of PZT is well integrated with the lattice constant of SRO. Therefore, the piezoelectric film 15 containing PZT can be made into (001) alignment with a tetragonal crystal structure on the (100) plane of the conductive film 14 containing SRO, or with a rhombohedral crystal structure ( 100) alignment, the crystallinity of the piezoelectric film 15 can be improved.

On the other hand, as shown in FIG. 4 , in the state where the alignment film 12 containing ZrO ₂ is not epitaxially grown on the main surface formed by the (100) plane of the substrate 11 containing silicon single crystal, for example, ZrO ₂ The alignment film 12 is on the (100) plane of the silicon-containing single crystal substrate 11, and has a (111) alignment in a cubic crystal structure, for example. Therefore, the crystallinity of the alignment film 12 cannot be improved.

In addition, as shown in FIG. 4, in the state where the alignment film 12 containing ZrO ₂ is not epitaxially grown on the main surface formed by the (100) plane of the substrate 11 containing silicon single crystal, although the diagram is omitted in FIG. However, the conductive film 13 containing platinum has a crystal structure such as a cubic crystal and is (111) oriented. Therefore, the crystallinity of the conductive film 13 cannot be improved. Then, in the state where the platinum-containing conductive film 13 has, for example, a cubic crystal structure and (111) alignment, it is impossible to make the SRO-containing conductive film 14 have a cubic crystal structure and (100) alignment, and it is impossible to make the PZT-containing The piezoelectric film 15 has a tetragonal crystal structure and a (001) orientation, or a rhombohedral crystal structure and a (100) orientation.

Preferably, the alignment film 12 has a thickness of 13-22 nm. When the thickness of the alignment film 12 is less than 13 nm, since the thickness of the alignment film 12 is too thin, the effect of facilitating the epitaxial growth of the alignment film 12 on the substrate 11 becomes small. Therefore, when the thickness of the alignment film 12 is less than 13 nm, a part of the alignment film 12 is not (100) aligned but (111) aligned.

In addition, when the thickness of the alignment film 12 exceeds 22 nm, the effect of the alignment film 12 on the substrate 11 being easy to grow epitaxially will be reduced because the thickness of the alignment film 12 is too thick. Therefore, when the thickness of the alignment film 12 exceeds 22 nm, a part of the alignment film 12 is not (100) aligned but (111) aligned.

Fig. 5 is a cross-sectional view of the film structure in the case where the alignment film of the film structure according to the embodiment has a two-layer structure.

The alignment film 12 may also include a film 12a and an alignment film 12b. The film 12a, including zirconium, is formed on the substrate 11, but the zirconium included in the film 12a is not oxidized, but is metallic zirconium. That is, the film 12a is a metal film containing zirconium. On the other hand, the alignment film 12b includes zirconia epitaxially grown on the film 12a. Therefore, the alignment film 12 shown in FIGS. 1 and 2 is equivalent to the alignment film 12b shown in FIG. 5 .

When the alignment film 12b is formed on the substrate 11 via the film 12a, epitaxial growth is easier than when the alignment film 12b is formed on the substrate 11 without the film 12a. Therefore, the alignment film 12b containing ZrO ₂ can be further stabilized and epitaxially grown on the upper surface 11a as the main surface constituted by the (100) plane of the silicon-containing single crystal substrate 11 . Therefore, the alignment film 12 containing ZrO ₂ can be stabilized and (100) aligned on the (100) plane of the substrate 11 containing silicon single crystal, and the crystallinity of the alignment film 12 can be further improved.

However, when forming the alignment film 12b containing ZrO ₂ , the zirconium contained in the film 12a may be oxidized, so that the film 12a may be destroyed and become the alignment film 12b. In such a case, as shown in FIG. 1, the alignment film 12b is directly formed on the substrate 11, and the alignment film 12 including only the directly formed alignment film 12b is formed on the substrate 11.

Preferably, the film 12a has a thickness of 5 to 10 nm. When the thickness of the film 12a is less than 5 nm, the effect of facilitating the epitaxial growth of the alignment film 12b on the substrate 11 becomes small because the thickness of the film 12a is too thin. Therefore, when the thickness of the film 12a is less than 5 nm, a part of the alignment film 12b is not (100) aligned but (111) aligned.

In addition, when the thickness of the film 12a exceeds 10 nm, the effect of facilitating the epitaxial growth of the alignment film 12b on the substrate 11 is also reduced because the thickness of the film 12a is too thick. Therefore, when the thickness of the film 12a exceeds 10 nm, a part of the alignment film 12b is not (100) aligned but (111) aligned.

Preferably, the alignment film 12b has a thickness of 8-12nm. When the thickness of the alignment film 12b is less than 8 nm, the effect of facilitating the epitaxial growth of the alignment film 12b on the substrate 11 becomes small because the thickness of the alignment film 12b is too thin. Therefore, when the thickness of the alignment film 12b is less than 8 nm, a part of the alignment film 12b is not (100) aligned but (111) aligned.

In addition, when the thickness of the alignment film 12b exceeds 12nm, the effect of facilitating the epitaxial growth of the alignment film 12b on the substrate 11 is also reduced because the thickness of the alignment film 12b is too thick. Therefore, when the thickness of the alignment film 12b exceeds 12 nm, a part of the alignment film 12b is not (100) aligned but (111) aligned.

In addition, the film structure 10 of this embodiment may include only the substrate 11, the alignment film 12, and the conductive film 13 without the conductive film 14 and the piezoelectric film 15. Even in such a case, by forming the piezoelectric film 15 and the conductive film 16 as an upper electrode on the film structure 10, it is possible to easily form a structure with a structure sandwiched by the conductive film 13 and the conductive film 16 from above and below. The piezoelectric element of the piezoelectric film 15 .

<Manufacturing method of membrane structure> Next, the manufacturing method of the membrane structure of this embodiment is demonstrated. 6 to 11 are cross-sectional views in the manufacturing steps of the film structure according to the embodiment.

First, as shown in FIG. 6 , a substrate 11 as a silicon substrate is prepared (step S1 ).

Preferably, the substrate 11 has a cubic crystal structure and has an upper surface 11a as a main surface composed of a (100) plane. In addition, on the upper surface 11d of the substrate 11, an oxide film such as a SiO ₂ film as a natural oxide film may be formed.

In addition, as the substrate 11, various substrates other than a silicon substrate can be used, for example, substrates composed of various semiconductor single crystals other than silicon can be used.

As shown in FIG. 6, two directions perpendicular to each other in the upper surface 11a formed by the (100) plane of the substrate 11 made of silicon single crystals are defined as the X-axis direction and the Y-axis direction, and the direction perpendicular to the upper surface 11a is defined as the X-axis direction and the Y-axis direction. is the Z-axis direction.

Next, as shown in FIG. 7, the film 12a is formed (step S2). In this step S2, on the substrate 11, a zirconium-containing film 12a is formed.

In step S2, the case where the alignment film 12 is formed by the electron beam evaporation method is exemplified and described, but it may be formed by various methods such as the sputtering method, for example.

In step S2, first, the substrate 11 is placed in the vacuum chamber of the electron beam evaporation apparatus, and the pressure in the vacuum chamber is adjusted to a certain vacuum atmosphere such as 2.1×10 ⁻⁵ Pa, and the substrate 11 is heated to For example, 600-750°C.

In step S2, next, zirconium is evaporated by an electron beam evaporation method using an evaporation material of zirconium (Zr) single crystal. At this time, evaporated zirconium forms a zirconium (Zr) film. Then, on the substrate 11, the zirconium-containing film 12a having a thickness of, for example, 20 nm or less is formed. Also, the zirconium contained in the film 12a is not oxidized but is metallic zirconium. That is, the film 12a is a metal film containing zirconium.

Preferably, in step S2, a film 12a having a thickness of 5 to 10 nm is formed. When the thickness of the film 12a is less than 5 nm, the film 12a is too thin, and the effect of facilitating the epitaxial growth of the alignment film 12b (see FIG. 8 described later) on the substrate 11 becomes small. Therefore, when the thickness of the film 12a is less than 5 nm, a part of the alignment film 12b is not (100) aligned but (111) aligned.

In addition, when the thickness of the film 12a exceeds 10 nm, the effect of facilitating the epitaxial growth of the alignment film 12b on the substrate 11 is also reduced because the thickness of the film 12a is too thick. Therefore, when the thickness of the film 12a exceeds 10 nm, a part of the alignment film 12b is not (100) aligned but (111) aligned.

Preferably, in step S2, the film 12a is formed at a temperature of 650-700°C. When the temperature of the substrate 11 is less than 650° C., the temperature of the substrate 11 is too low, and the effect of facilitating the epitaxial growth of the alignment film 12 b on the substrate 11 becomes small. Therefore, when the temperature of the substrate 11 is less than 650° C., a part of the alignment film 12 b is not (100) aligned but (111) aligned.

In addition, when the temperature of the substrate 11 exceeds 700° C., the temperature of the substrate 11 is too high, and the effect of facilitating the epitaxial growth of the alignment film 12 b on the substrate 11 becomes small. Therefore, when the temperature of the substrate 11 exceeds 700°C, a part of the alignment film 12b is not (100) aligned but (111) aligned.

Next, as shown in FIG. 8, an alignment film 12b is formed (step S3). In this step S3, an alignment film 12b containing zirconia epitaxially grown on the film 12a is formed.

In step S3 , similarly to step S2 , the case where the alignment film 12 is formed by electron beam vapor deposition is described as an example, but it may also be formed by various methods such as sputtering.

In step S3, first, after setting the substrate 11 in the vacuum chamber of the electron beam evaporation apparatus, flow oxygen (O ₂ ) into the vacuum chamber at a flow rate of, for example, 10 sccm, and adjust the pressure in the vacuum chamber to, for example, 7.0×10 ⁻³ In the state of Pa, the substrate 11 is heated to, for example, 500 to 600°C.

In step S3, next, zirconium is evaporated by an electron beam evaporation method using an evaporation material of zirconium (Zr) single crystal. At this time, the vaporized zirconium reacts with oxygen on the film 12a to form a zirconia (ZrO ₂ ) film. Next, an alignment film 12b composed of a ZrO ₂ film is formed as a single layer film. Next, an alignment film 12b containing zirconium oxide epitaxially grown on the film containing zirconium 12a is formed.

The alignment film 12b is epitaxially grown on the upper surface 11a as the main surface formed by the (100) plane of the substrate 11 made of silicon single crystal through the film 12a. The alignment film 12 has a cubic crystal structure and includes (100) oriented zirconia (ZrO ₂ ). That is, on the upper surface 11a of the (100) plane of the substrate 11 made of silicon single crystal, an alignment film 12 containing zirconium oxide (ZrO ₂ ) having a (100) alignment is formed via the film 12a.

As described above with reference to FIG. 6, the two directions perpendicular to each other in the upper surface 11a of the (100) plane of the substrate 11 made of silicon single crystals are defined as the X-axis direction and the Y-axis direction. The direction of the upper face 11a is referred to as the Z-axis direction. At this time, epitaxial growth of a certain film means that the film is aligned in any one of the X-axis direction, the Y-axis direction, and the Z-axis direction.

Preferably, in step S3, an alignment film 12b having a thickness of 8-12 nm is formed. When the thickness of the alignment film 12b is less than 8 nm, the effect of facilitating the epitaxial growth of the alignment film 12b on the substrate 11 becomes small because the thickness of the alignment film 12b is too thin. Therefore, when the thickness of the alignment film 12b is less than 8 nm, a part of the alignment film 12b is not (100) aligned but (111) aligned.

In addition, when the thickness of the alignment film 12b exceeds 12nm, the effect of facilitating the epitaxial growth of the alignment film 12b on the substrate 11 is also reduced because the thickness of the alignment film 12b is too thick. Therefore, when the thickness of the alignment film 12b exceeds 12 nm, a part of the alignment film 12b is not (100) aligned but (111) aligned.

As mentioned above, preferably, in step S3, the alignment film 12b is formed at a temperature of 500-600°C. When the temperature of the substrate 11 is less than 500°C, since the temperature of the substrate 11 is too low, for example, zirconium atoms and oxygen atoms on the film 12a become difficult to be rearranged, etc., resulting in the epitaxial growth of the alignment film 12b on the substrate 11. The effect becomes smaller. Therefore, when the temperature of the substrate 11 is less than 500° C., a part of the alignment film 12 b is not (100) aligned but (111) aligned.

In addition, when the temperature of the substrate 11 exceeds 600° C., the temperature of the substrate 11 is too high, and the effect of facilitating the epitaxial growth of the alignment film 12 b on the substrate 11 becomes small. Therefore, when the temperature of the substrate 11 exceeds 600° C., a part of the alignment film 12 b is not (100) aligned but (111) aligned.

When forming the alignment film 12b containing ZrO ₂ , the zirconium contained in the film 12a may be oxidized, causing the film 12a to disappear and become the alignment film 12b. In such a case, as shown in FIG. 9 , an alignment film 12 b is directly formed on the substrate 11 , and an alignment film 12 including only the directly formed alignment film 12 b is formed on the substrate 11 . Therefore, it is preferable to form the alignment film 12 including the new alignment film 12b having a total thickness of 13-22 nm by using the film 12a having a thickness of 5-10 nm and the original alignment film 12b having a thickness of 8-12 nm. In the following description, as shown in FIG. 9, the case where the alignment film 12b is directly formed on the substrate 11 in step S3 will be described as an example.

Next, as shown in FIG. 10, the conductive film 13 is formed (step S4). In this step S4, the conductive film 13 which is epitaxially grown on the alignment film 12b as a part of the lower electrode is formed. The conductive film 13 is made of metal. As the conductive film 13 made of metal, for example, a conductive film containing platinum (Pt) can be used.

When a conductive film containing platinum is formed as the conductive film 13, the epitaxially grown conductive film 13 is formed on the alignment film 12 at a temperature of 550° C. or lower, preferably at a temperature of 400° C., by sputtering. part of the lower electrode. The conductive film 13 containing platinum is epitaxially grown on the alignment film 12b. In addition, platinum contained in the conductive film 13 has a cubic crystal structure and is (100) oriented.

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

Next, as shown in FIG. 11, the conductive film 14 is formed (step S5). In this step S5, the conductive film 14 epitaxially grown on the conductive film 13 as a part of the lower electrode is formed. The conductive film 14 is made of metal oxide. As the conductive film 14 made of metal oxide, for example, a conductive film containing strontium ruthenate (SrRuO ₃ :SRO) can be used.

When forming a conductive film containing SRO as the conductive film 14, the epitaxially grown conductive film 14 is formed as a part of the lower electrode on the conductive film 13 at a temperature of about 600°C by sputtering. The conductive film 14 containing SRO is epitaxially grown on the conductive film 13 . In addition, the SRO included in the conductive film 14 has a cubic crystal structure and is (100) oriented.

Also, as the conductive film 14 made of metal oxide, instead of the conductive film containing SRO, for example, a film containing strontium titanate ruthenate (Sr(Ti _y Ru _1-y )O ₃ (0≦y≦ 0.4)) Conductive film.

Next, as shown in FIG. 1, the piezoelectric film 15 is formed (step S6). In this step S6, a coating method such as a sol-gel (Sol-Gel) method or a sputtering method is used to form an epitaxially grown lead zirconate titanate (Pb(Zr _1-x Ti _x ) O ₃ (0<x<1): PZT) piezoelectric film 15 .

In addition, when the piezoelectric film 15 is formed by the sol-gel method, in step S6, first, a plurality of times is repeated on the conductive film 14, and a precursor containing PZT is formed by coating a solution containing lead, zirconium, and titanium. The steps of the membrane of the body. Thereby, a film including a plurality of films laminated on each other is formed.

Next, when the piezoelectric film 15 is formed by the sol-gel method, in step S6, the precursor is oxidized and crystallized by heat-treating the film to form the piezoelectric film 15 containing PZT.

Preferably, the piezoelectric film 15 has a tetragonal crystal structure and (001) orientation. By satisfying that x in Pb(Zr _1-x Ti _x )O ₃ (0<x<1) is 0.48<x<1, the PZT contained in the piezoelectric film 15 has a tetragonal crystal structure, which facilitates epitaxy. Growth, easy (001) orientation. Therefore, when PZT having a tetragonal crystal structure is (001) aligned, the polarization direction parallel to the [001] direction and the electric field direction parallel to the thickness direction of the piezoelectric film 15 become parallel to each other, thereby improving the piezoelectric properties. promote. That is, when an electric field along the [001] direction is applied to PZT having a tetragonal crystal structure, large piezoelectric constants d33 and d31 can be obtained. Therefore, the piezoelectric constant of the piezoelectric film 15 can be further increased.

Alternatively, preferably, the piezoelectric film 15 has a rhombohedral crystal structure and (100) orientation. By satisfying that x in Pb(Zr _1-x Ti _x )O ₃ (0<x<1) is 0.20<x≦0.48, the PZT contained in the piezoelectric film 15 has a rhombohedral crystal structure, and it is easy to make Epitaxy growth, easy (100) alignment. Therefore, when PZT having a rhombohedral crystal structure has a (100) orientation, the PZT has a so-called Engineered Domain Configuration, which is parallel to the polarization direction of each direction equivalent to the [111] direction, and parallel to the piezoelectric direction. The angle of the electric field direction in the thickness direction of the electric film 15 is equal to each other in any sub-polar domain (domain), so that the piezoelectric characteristics are improved. That is, when an electric field along the [100] direction is applied to PZT having a rhombohedral crystal structure, large piezoelectric constants d33 and d31 can be obtained. Therefore, the piezoelectric characteristics of the piezoelectric film 15 can be further increased.

In this way, the membrane structure 10 shown in FIG. 1 is formed. Moreover, when the film 12a remains without being eliminated when the alignment film 12b is formed, the film structure 10 shown in FIG. 5 is formed.

When the alignment film 12b containing zirconia (ZrO ₂ ) is directly formed on the substrate 11 which is a silicon substrate, the crystallinity of the formed ZrO ₂ film decreases, and the alignment film 12b may not be epitaxially grown satisfactorily. In such a case, the conductive film 13 cannot be satisfactorily epitaxially grown on the alignment film 12 b, and the piezoelectric film 15 cannot be satisfactorily epitaxially grown on the conductive film 13 . When an electric field is applied to the piezoelectric film 15, for example, in a direction parallel to the polarization direction or in a direction at a certain angle to the polarization direction, the piezoelectric constants d33 and d31 are large. Therefore, when the piezoelectric film 15 is not epitaxially grown well, the piezoelectric constants d33 and d31 of the piezoelectric film 15 cannot be increased because the polarization directions of the piezoelectric film 15 as a whole are not uniform, and the piezoelectric element's Reduced characteristics.

On the other hand, in this embodiment, after the film 12a containing zirconium (Zr) is formed on the substrate 11, the alignment film 12b containing ZrO ₂ is epitaxially grown on the substrate 11. The zirconium contained in the film 12a, which is not oxidized, is metallic zirconium. In such a case, compared with the case where the alignment film 12 b containing ZrO ₂ is directly formed on the substrate 11 , the alignment film 12 can be epitaxially grown favorably in the former. Therefore, it is possible to satisfactorily epitaxially grow the conductive film 13 on the alignment film 12 b and to satisfactorily epitaxially grow the piezoelectric film 15 on the conductive film 13 . Therefore, the polarization directions of the entire piezoelectric film 15 can be unified, the piezoelectric constants d33 and d31 of the piezoelectric film 15 can be increased, and the characteristics of the piezoelectric element can be improved.

In addition, after the piezoelectric film 15 is formed, as step S7, the conductive film 16 as an upper electrode may be formed on the piezoelectric film 15 (see FIG. 2 ). Thereby, an electric field can be applied to the piezoelectric film 15 in the thickness direction.

<Modification of Embodiment> In the embodiment, as shown in FIG. 1 , a piezoelectric film 15 is formed on a conductive film 13 via a conductive film 14 . However, the piezoelectric film 15 may be directly formed on the conductive film 13 without interposing the conductive film 14 . Such an example will be described as a modified example of the embodiment.

Fig. 12 is a cross-sectional view of a membrane structure according to a modified example of the embodiment.

As shown in FIG. 12 , the film structure 10 of this modification has a substrate 11 , an alignment film 12 , a conductive film 13 , and a piezoelectric film 15 . The alignment film 12 is formed on the substrate 11 . The conductive film 13 is formed on the alignment film 12 . The piezoelectric film 15 is formed on the conductive film 13 .

That is, the film structure 10 of this modified example is different from the film structure 10 of the embodiment except that the piezoelectric film 15 is directly formed on the conductive film 13 without intervening the conductive film 14 (see FIG. 1 ). Are the same.

When the PZT-containing piezoelectric film 15 is formed on the platinum-containing conductive film 13 without intervening the SRO-containing conductive film 14 (see FIG. When the conductive film 14 (see FIG. 1 ) of SRO is formed into the piezoelectric film 15 containing PZT, the crystallinity of the piezoelectric film 15 is relatively lowered. However, when the PZT-containing piezoelectric film 15 is formed on the platinum-containing conductive film 13 without intervening the SRO-containing conductive film 14 (see FIG. 1 ), the conductive film 13 is easily aligned or epitaxially formed on the alignment film 12. crystal growth. Therefore, the piezoelectric film 15 formed on the conductive film 13 is also easier to align or epitaxially grow to some extent, and the crystallinity of the piezoelectric film 15 can be improved to some extent.

Moreover, the film structure 10 of this modification may have the electroconductive film 16 similarly to the film structure 10 of Embodiment (refer FIG. 2). [Example]

Hereinafter, this embodiment will be described in more detail based on examples. In addition, this invention is not limited to the following Example.

(Example 1~60) Hereinafter, the membrane structure 10 described in the embodiment with reference to FIG. 1 is formed into the membrane structures of Examples 1 to 60. FIG. In addition, the film structures of Examples 1 to 60 were formed by changing the thickness of the film 12a (see FIG. 7 ), the substrate temperature when the film 12a was formed, and the substrate temperature when the alignment film 12b (see FIG. 8 ) was formed. Membrane structure.

First, as shown in FIG. 6 , as the substrate 11 , a wafer comprising a 6-inch silicon substrate having an upper surface 11 a as a main surface formed of a (100) plane is prepared.

Next, as shown in FIG. 7, a zirconium (Zr) film is formed on the substrate 11 as the film 12a by electron beam evaporation. Conditions at this time are shown below. Equipment: Electron beam evaporation device Pressure: 2.10×10 ^-5 Pa Evaporation source: Zr Acceleration voltage/emission current: 7.5kV/1.50mA Thickness: below 20nm Film formation speed: 0.005nm/s Oxygen flow rate: 0sccm Substrate temperature: 600～750℃

Next, as shown in FIG. 8 , as the alignment film 12 , a zirconia (ZrO ₂ ) film is formed by electron beam vapor deposition. Conditions at this time are shown below. Equipment: Electron beam evaporation device Pressure: 7.00×10 ^-3 Pa Evaporation source: Zr+O ₂ Acceleration voltage/emission current: 7.5kV/1.80mA Thickness: 10nm Film formation speed: 0.005nm/s Oxygen flow rate: 10sccm Substrate Temperature: 500～600℃

Here, the thickness of the zirconium film, the substrate temperature at the time of forming the zirconium film, and the substrate temperature at the time of forming the ZrO ₂ film are shown in Tables 2 to 4 in each of Examples 1 to 60. In Examples 1 to 20 shown in Table 2, the substrate temperature at the time of forming the ZrO ₂ film was 500°C. In Examples 21 to 40 shown in Table 3, the substrate temperature at the time of forming the ZrO ₂ film was 550°C. Next, in Examples 41 to 60 shown in Table 4, the substrate temperature at the time of forming the ZrO ₂ film was 600°C. Also, as mentioned above, the thickness of the ZrO ₂ film in each of Examples 1 to 60 is 10 nm. In addition, in Table 2 to Table 4, the evaluation results of the crystallinity of the ZrO ₂ film are shown using single circle and double circle. In the case of double turns, the crystallinity is higher than in the case of single turns.

Regarding Examples 1 to 60, the θ-2θ spectrum of the film structure formed up to the ZrO ₂ film was measured by the X-ray diffraction (XRD) method. 13 and 14 are diagrams showing examples of θ-2θ spectra of the film structure formed up to the ZrO ₂ film by the XRD method. The abscissas of each of Figs. 13 and 14 show the angle 2θ, and the ordinates of each of Figs. 13 and 14 show the intensity of X-rays.

13 is an example where the thickness of the zirconium film is 7nm, the substrate temperature when forming the zirconium film is 700°C, and the substrate temperature when forming the _ZrO2 film is 550°C. In addition, FIG. 14 is an example where the thickness of the zirconium film is ₇ nm, the substrate temperature when the zirconium film is formed is 750°C, and the substrate temperature when the ZrO2 film is formed is 550°C. In addition, in FIG. 13 and FIG. 14 , T-ZrO ₂ means tetragonal ZrO ₂ , and M-ZrO ₂ means monoclinic ZrO ₂ . Also, as described above, it is assumed that tetragonal ZrO ₂ is contained in cubic ZrO ₂ .

In the example shown in FIG. 13 , in the θ-2θ spectrum, a peak corresponding to (200) of ZrO ₂ having a tetragonal crystal structure was observed. Therefore, it can be known that the alignment film 12b has a tetragonal crystal structure and contains (100) aligned ZrO ₂ .

In addition, in the example shown in FIG. 13 , peaks other than the (200) peak corresponding to ZrO ₂ having a tetragonal crystal structure were not observed in the θ-2θ spectrum. Therefore, it can be seen that the alignment film 12b has a tetragonal crystal structure, and ZrO ₂ aligned on a plane other than the (100) plane, or ZrO ₂ with a monoclinic crystal structure, at least does not contain any content above the detection limit. Compare.

On the other hand, in the example shown in FIG. 14, also in the θ-2θ spectrum, a peak corresponding to (200) of ZrO ₂ having a tetragonal crystal structure was observed. Therefore, it can be known that the alignment film 12b has a tetragonal crystal structure and contains (100) aligned ZrO ₂ .

However, in the example shown in FIG. 14 , in the θ-2θ spectrum, peaks other than the (200) peak corresponding to ZrO ₂ having a tetragonal crystal structure are observed, which correspond to ZrO having a tetragonal crystal structure. ₂ , and the (111) peak corresponding to ZrO ₂ having a monoclinic crystal structure. Therefore, it can be seen that the alignment film 12b contains less ZrO 2 having a tetragonal crystal structure and (111) orientation than ZrO ₂ having a tetragonal crystal structure and (111) orientation to some extent. ZrO ₂ , and ZrO ₂ with monoclinic crystal structure and (111) alignment.

As mentioned above, the film structures of Examples ₁ to 60 are film structures formed by changing the thickness of the zirconium film, the substrate temperature when the zirconium film is formed, and the substrate temperature when the ZrO2 film is formed. For such film structures of Examples 1 to 60, the peak observed in the measured θ _- 2θ spectrum, the thickness of the zirconium film, the substrate temperature when the zirconium film is formed, and the substrate temperature when the ZrO2 film is formed are classified. and tidy up. Figures 15 to 17 are tables showing the peaks observed in the θ-2θ spectra of Examples 1 to 60, classified and organized according to the thickness of the zirconium film and the substrate temperature when the zirconium film was formed. Fig. 15 to Fig. 17 respectively show the cases where the substrate temperature is 500°C, 550°C or 600°C when forming the ZrO ₂ film. In addition, each column in each figure of FIG. 15 to FIG. 17 corresponds to the thickness of the different Zr films; each row of each figure in FIGS. 15 to 17 corresponds to the substrate temperature when forming the different Zr films.

First, as shown in Fig. 15, when the substrate temperature at the time of forming the ZrO2 film is 500°C, the thickness of the zirconium film is ₂₀ nm or less, and when the substrate temperature at the time of forming the zirconium film is 600 to 750°C, it is observed that The peak of (100)-aligned ZrO ₂ (shown as ZrO ₂ (200) in FIG. 15 ). On the other hand, although not shown in FIG. 15, when the substrate temperature at the time of forming the ZrO2 film is 500°C, when the thickness of the zirconium film exceeds ₂₀ nm, the substrate temperature at the time of forming the zirconium film is less than 600°C. In the case where the substrate temperature was higher than 750° C. when the zirconium film was formed, the peak of (100)-oriented ZrO ₂ was not observed.

In addition, as shown in FIG. 16, when the substrate temperature at the time of forming the ZrO2 film is 550°C, the thickness of the zirconium film is ₂₀ nm or less, and when the substrate temperature at the time of forming the zirconium film is 600 to 750°C, it is observed that The peak of (100)-aligned ZrO ₂ (shown as ZrO ₂ (200) in FIG. 16 ). On the other hand, although the illustration is omitted in FIG. 16, when the substrate temperature at the time of forming the ZrO2 film is 550°C, when the thickness of the zirconium film exceeds ₂₀ nm, the substrate temperature at the time of forming the zirconium film is less than 600°C. In the case where the substrate temperature was higher than 750° C. when the zirconium film was formed, the peak of (100)-oriented ZrO ₂ was not observed.

In addition, as shown in FIG. 17, when the substrate temperature at the time of forming the ZrO2 film is 600°C, the thickness of the zirconium film is ₂₀ nm or less, and when the substrate temperature at the time of forming the zirconium film is 600 to 750°C, it is observed that The peak of (100)-aligned ZrO ₂ (shown as ZrO ₂ (200) in FIG. 17 ). On the other hand, although the illustration is omitted in FIG. 17, when the substrate temperature at the time of forming the ZrO2 film is 600°C, when the thickness of the zirconium film exceeds ₂₀ nm, the substrate temperature at the time of forming the zirconium film is less than 600°C. In the case where the substrate temperature was higher than 750° C. when the zirconium film was formed, the peak of (100)-oriented ZrO ₂ was not observed.

15 to 17 are omitted from illustration, but as the examples other than the examples ₁ to 60 shown in FIGS. , also obtained the same result as in the case of forming a ZrO ₂ film having a thickness of 10 nm.

From the above results, it can be seen that at least when the zirconium-containing film 12a having a thickness of 20nm or less is formed at a temperature of 600-750°C, and the alignment film 12b containing a zirconium oxide having a thickness of 5-20nm is formed at a temperature of 500-600°C , the (100) _-aligned ZrO peak was observed. In such cases, the alignment film 12b has a tetragonal crystal structure and contains more (100)-aligned zirconia.

In addition, as shown by hatching in FIG. 15, when the substrate temperature at the time of forming the ZrO2 film is 500°C, the thickness of the zirconium film is ₅ to 10 nm, and the substrate temperature at the time of forming the zirconium film is 650 to 700°C. In the case of ℃, no peaks other than the peak of (100)-oriented ZrO ₂ were observed. On the other hand, when the substrate temperature at the time of forming the ZrO2 film is 500° C., when the thickness of the zirconium film is less than ₅ nm, and when the thickness of the zirconium film exceeds 10 nm, the substrate temperature at the time of forming the zirconium film is less than 5 nm. Peaks other than ZrO ₂ (100) were observed when the substrate temperature was over 650°C or when the zirconium film was formed at a temperature exceeding 700°C. The observed peaks are, for example, the peak of (111)-aligned ZrO ₂ (represented as ZrO ₂ (111) in FIG. 15 ), the peak of (111)-oriented Zr ₃ O (represented as Zr ₃ O(111 )), (101) oriented Zr ₃ O peaks (depicted as Zr ₃ O(101) in FIG. 15 ).

Also, the above results in the case where the substrate temperature at the time of forming the ZrO ₂ film is 500° C. are shown in the column of “Crystallinity of the ZrO ₂ film” in Table 2 as follows. That is, when the thickness of the zirconium film was 5 to 10 nm and the substrate temperature when the zirconium film was formed was 650 to 700° C. (Examples 7 to 9, 12 to 14), the crystallinity evaluation results were higher than that of the single circle. Excellent double circle representation. On the other hand, in the cases other than this (Examples 1 to 6, 10, 11, 15 to 20), the evaluation results of crystallinity are shown by a single circle.

In addition, as shown by hatching in FIG. 16, when the substrate temperature at the time of forming the ZrO2 film is 550°C, the thickness of the zirconium film is ₅ to 10 nm, and the substrate temperature at the time of forming the zirconium film is 650 to 700°C. In the case of ℃, no peaks other than the peak of (100)-oriented ZrO ₂ were observed. On the other hand, when the substrate temperature at the time of forming the ZrO2 film is 550° C., when the thickness of the zirconium film is less than ₅ nm, and when the thickness of the zirconium film exceeds 10 nm, the substrate temperature at the time of forming the zirconium film is less than 5 nm. Peaks other than ZrO ₂ (100) were observed when the substrate temperature was over 650°C or when the zirconium film was formed at a temperature exceeding 700°C. The observed peaks are, for example, the peak of (111)-aligned ZrO ₂ (represented as ZrO ₂ (111) in FIG. 16 ), the peak of (111)-oriented Zr ₃ O (represented as Zr ₃ O(111 )), (101) aligned Zr ₃ O peaks (depicted as Zr ₃ O(101) in FIG. 16 ).

In addition, regarding the above results when the substrate temperature when forming the ZrO ₂ film was 550° C., the column “Crystallinity of the ZrO ₂ film” in Table 3 shows as follows. That is, when the thickness of the zirconium film was 5 to 10 nm and the substrate temperature when the zirconium film was formed was 650 to 700° C. (Examples 27 to 29, 32 to 34), the crystallinity evaluation results were higher than that of the single circle. Excellent double circle representation. On the other hand, in cases other than this (Examples 21 to 26, 30, 31, 35 to 40), the evaluation results of crystallinity are shown by a single circle.

In addition, as shown by hatching in FIG. 17, when the substrate temperature at the time of forming the ZrO2 film is 600°C, the thickness of the zirconium film is ₅ to 10 nm, and the substrate temperature at the time of forming the zirconium film is 650 to 700°C. In the case of ℃, no peaks other than the peak of (100)-oriented ZrO ₂ were observed. On the other hand, when the substrate temperature at the time of forming the ZrO2 film is 600° C., when the thickness of the zirconium film is less than ₅ nm, and when the thickness of the zirconium film exceeds 10 nm, the substrate temperature at the time of forming the zirconium film is less than 5 nm. Peaks other than ZrO ₂ (100) were observed when the substrate temperature was over 650°C or when the zirconium film was formed at a temperature exceeding 700°C. The observed peaks are, for example, the peak of (111)-aligned ZrO ₂ (represented as ZrO ₂ (111) in FIG. 17 ), the peak of (111)-oriented Zr ₃ O (represented as Zr ₃ O(111 )), (101) aligned Zr ₃ O peaks (depicted as Zr ₃ O(101) in FIG. 17 ).

Also, the above results in the case where the substrate temperature at the time of forming the ZrO ₂ film was 600° C. are shown in the column of “Crystallinity of the ZrO ₂ film” in Table 4 as follows. That is, when the thickness of the zirconium film is 5 to 10 nm, and the substrate temperature at the time of forming the zirconium film is 650 to 700° C. (Examples 47 to 49, 52 to 54), the evaluation results of crystallinity are higher than that of the single circle. Excellent double circle representation. On the other hand, in cases other than this (Examples 41 to 46, 50, 51, 55 to 60), the evaluation results of crystallinity are represented by a single circle.

In addition, in Fig. 15 to Fig. 17, the peak intensity described as "ZrO ₂ (200) weak" means less than 5.0×10 ³ cps, and the other peaks described as "ZrO ₂ (200)" 1/2 the strength.

In addition, the illustrations are omitted in FIGS. 15 to 17 , but as examples other than Examples 1 to 60, when a ZrO _{2 film with a thickness of 8 nm or 12 nm is formed, it is also obtained when a ZrO 2 film} with a thickness of 10 nm is formed. Exactly the same result.

From the above results, it can be seen that it is best to form the zirconium-containing film 12a with a thickness of 5-10nm at a temperature of 650-700°C, and to form an alignment film 12b with a thickness of 8-12nm containing zirconium oxide at a temperature of 500-600°C. . Under such conditions, the alignment film 12b may have a tetragonal crystal structure and contain more (100) oriented zirconia.

Zirconium (Zr) is easier to oxidize and ionize than silicon (Si). Therefore, by forming the zirconium-containing film 12a having a thickness of 5-10 nm at a temperature of 650-700° C., and forming the alignment film 12 b containing zirconia having a thickness of 8-12 nm at a temperature of 500-600° C., the silicon The natural oxide film (SiO ₂ ) existing on the upper surface 11a of the substrate 11, which is the substrate, is more completely removed. Therefore, the alignment film 12 b containing zirconia (Zr) can be epitaxially grown directly on the upper surface 11 a of the substrate 11 .

Also, in Examples 1 to 60, when forming the alignment film 12b containing ZrO ₂ , since the zirconium contained in the film 12a is oxidized, the film 12a is destroyed and becomes the alignment film 12b. Therefore, the alignment film 12 b is directly formed on the substrate 11 , and the alignment film 12 including only the directly formed alignment film 12 b is formed on the substrate 11 .

Next, as shown in FIG. 10, a platinum (Pt) film was formed on the alignment film 12 as the conductive film 13 by sputtering. The conditions at this time are shown below. Device: DC sputtering device Pressure: 3.20×10 ^-2 Pa Evaporation source: Pt Power: 100W Thickness: 100nm Film formation speed: 0.14nm/s Ar flow rate: 16sccm Substrate temperature: 400℃

In the θ-2θ spectrum of the ZrO ₂ film, when the peaks of ZrO ₂ (111), Zr ₃ O (111) and Zr ₃ O (101) are observed in addition to the peak of ZrO ₂ (200), the platinum film In the θ-2θ spectrum, the peak of platinum (111) was observed in addition to the peak of platinum (200). On the other hand, in the θ-2θ spectrum of the ZrO ₂ film, the peaks of ZrO ₂ (111), Zr ₃ O (111), and Zr ₃ O (101) are not observed other than the peak of ZrO ₂ (200). , in the θ-2θ spectrum of the platinum film, the peak of platinum (111) is not observed except the peak of platinum (200), and the crystallinity of the conductive film 13 can be improved.

Next, as shown in FIG. 11, an SRO film is formed on the conductive film 13 as the film 14 by sputtering. The conditions at this time are shown below. Device: RF magnetron sputtering device Power: 300W Gas: Ar Pressure: 1.8Pa Substrate temperature: 600°C Film forming speed: 0.11nm/s Thickness: 20nm

Regarding Examples 1 to 60, the θ-2θ spectrum by the XRD method of the film structure formed up to the SRO film was measured. FIG. 18 is a diagram showing an example of the θ-2θ spectrum by the XRD method of the film structure formed up to the SRO film. The horizontal axis of the graph in FIG. 18 shows the angle 2θ, and the vertical axis of the graph in FIG. 18 shows the intensity of X-rays.

18 is an example where the thickness of the zirconium film is 7nm, the substrate temperature when forming the zirconium film is 700°C, and the substrate temperature when forming the _ZrO2 film is 550°C.

In the example shown in FIG. 18 , in the θ-2θ spectrum, a peak corresponding to (200) of Pt having a cubic crystal structure was observed. Therefore, it can be seen that the conductive film 13 has a cubic crystal structure and contains (100)-oriented Pt.

In addition, in the example shown in FIG. 18 , in the θ-2θ spectrum, a peak corresponding to (100) of SRO having a cubic crystal structure was observed. Therefore, it can be seen that the conductive film 13 has a cubic crystal structure and contains SROs of (100) orientation.

Next, as shown in FIG _. 1 , a laminated film of a Pb(Zr _{0 .52} Ti _{0 .48} )O ₃ film (PZT film) is formed by coating on the conductive film 14 as the piezoelectric film 15 _. The conditions at this time are shown below.

The organometallic compounds of lead, zirconium and titanium are mixed in such a way that the composition ratio of Pb:Zr:Ti=100+δ:52:48 is mixed, and the mixed solvent of ethanol and 2-n-butoxy alcohol is used as Pb( The raw material solution for dissolution was adjusted so that the concentration of Zr _{0 . 52} Ti _{0 . 48} )O ₃ became 0.35 mol/l. The δ here refers to the residual Pb amount that is added to the volatilization of the Pb oxide in the subsequent heat treatment process, and in this embodiment, δ=20. Next, 20 g of polyrolidone having a weight of K value of 27-33 was further dissolved in the raw material solution.

Next, drop 3ml of the prepared raw material solution onto the substrate 11 made of a 6-inch wafer and rotate it at 3000rpm for 10 seconds to coat the raw material solution on the substrate 11 to form a body membrane. Next, by placing the substrate 11 on a hot plate at a temperature of 200° C. for 30 seconds, and further placing the substrate 11 on a hot plate at a temperature of 450° C. for 30 seconds, the solvent was evaporated and the film was dried. After that, the precursor was oxidized and crystallized by heat treatment at 600-700° C. for 60 seconds in an oxygen (O ₂ ) atmosphere of 0.2 MPa to form a piezoelectric film with a film thickness of 100 nm. A PZT film having a film thickness of, for example, 500 nm is formed by repeating, for example, five times the steps from application of the raw material solution to crystallization.

Regarding Examples 1 to 60, the θ-2θ spectrum by the XRD method of the film structure formed up to the PZT film was measured. FIG. 19 is a diagram 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 the graph in FIG. 19 shows the angle 2θ, and the vertical axis of the graph in FIG. 19 shows the intensity of X-rays.

19 is an example where the thickness of the zirconium film is 7nm, the substrate temperature when forming the zirconium film is 700°C, and the substrate temperature when forming the _ZrO2 film is 550°C.

In addition, in the example shown in FIG. 19 , peaks corresponding to (001) and (002) corresponding to PZT having a tetragonal crystal structure were observed in the θ-2θ spectrum. Therefore, it can be seen that the piezoelectric film 15 has a tetragonal crystal structure and includes (001)-oriented PZT.

In addition, when the PZT film is formed by the coating method, when the substrate temperature is formed at a temperature range of 600 to 700°C, which is wider than before, it can be seen that the piezoelectric film 15 has It has a tetragonal crystal structure and contains (001)-oriented PZT.

Also, unlike Examples 1 to 60, even if a PZT film was formed as the piezoelectric film 15 by the sputtering method instead of the coating method, exactly the same results were obtained. The conditions for forming the PZT film by the sputtering method as the piezoelectric film 15 are shown below. Device: RF magnetron sputtering device Power: 2500W Gas: Ar/O ₂ Pressure: 0.14Pa Substrate temperature: 425～525℃ Film forming speed: 0.63nm/s

When the PZT film is formed by the sputtering method instead of the coating method, when the substrate temperature is also formed at a temperature range of 425 to 525°C, which is wider than before, it can be seen that, similarly to the example shown in FIG. 19 , The piezoelectric film 15 has a tetragonal crystal structure and includes (001)-oriented PZT.

As mentioned above, the invention made by the inventor of this application was concretely demonstrated based on the embodiment, However, this invention is not limited to the said embodiment, Of course, various changes are possible in the range which does not deviate from the gist.

Within the scope of the idea of the present invention, as long as those skilled in the art (professionals) can think of various modifications and amendments, it should also be understood that these alterations and amendments belong to the scope of the present invention.

For example, those skilled in the art make appropriate additions, deletions, or design changes to components, or additions, omissions, or changes in conditions to the above-mentioned embodiments, as long as they have the gist of the present invention, all include within the scope of the present invention.

10:Membrane structure 11: Substrate 11a: above 12,12b: Alignment film 12a: Membrane 13,14,16: Conductive film 15: Piezoelectric film

[ Fig. 1 ] is a cross-sectional view of a membrane structure according to an embodiment. [ Fig. 2] Fig. 2 is a cross-sectional view of a membrane structure in the case where the membrane structure according to the embodiment has a conductive film as an upper electrode. [ Fig. 3 ] is a diagram illustrating a state of epitaxial growth of an alignment film included in the film structure of the embodiment. [ Fig. 4] Fig. 4 is a diagram illustrating a state in which an alignment film included in a film structure is not epitaxially grown. [ Fig. 5] Fig. 5 is a cross-sectional view of the film structure in the case where the alignment film of the film structure according to the embodiment has a two-layer structure. [ Fig. 6] Fig. 6 is a cross-sectional view in the manufacturing steps of the membrane structure of the embodiment. [ Fig. 7] Fig. 7 is a cross-sectional view in the manufacturing steps of the membrane structure of the embodiment. [ Fig. 8] Fig. 8 is a cross-sectional view in the manufacturing steps of the membrane structure of the embodiment. [ Fig. 9] Fig. 9 is a cross-sectional view in the manufacturing steps of the membrane structure of the embodiment. [ Fig. 10 ] is a sectional view in the manufacturing steps of the membrane structure of the embodiment. [ Fig. 11] Fig. 11 is a cross-sectional view in the manufacturing steps of the membrane structure of the embodiment. [ Fig. 12 ] is a cross-sectional view of a membrane structure according to a modified example of the embodiment. [ Fig. 13 ] is a diagram showing an example of the θ-2θ spectrum by the XRD method of the film structure formed up to the ZrO ₂ film. [ Fig. 14 ] is a diagram showing an example of the θ-2θ spectrum by the XRD method of the film structure formed up to the ZrO ₂ film. [ Fig. 15 ] is a table showing the peaks observed in the θ-2θ spectra of Examples 1 to 20, classified and organized according to the thickness of the zirconium film and the substrate temperature when the zirconium film was formed. [ Fig. 16 ] is a table showing the peaks observed in the θ-2θ spectra of Examples 21 to 40, classified and organized according to the thickness of the zirconium film and the substrate temperature when the zirconium film was formed. [ Fig. 17 ] is a table showing the peaks observed in the θ-2θ spectra of Examples 41 to 60, classified and organized according to the thickness of the zirconium film and the substrate temperature when the zirconium film was formed. [ Fig. 18 ] is a diagram showing an example of the θ-2θ spectrum by the XRD method of the film structure formed up to the SRO film. [ Fig. 19 ] is a diagram showing an example of the θ-2θ spectrum by the XRD method of the film structure formed up to the PZT film.

10:Membrane structure

11: Substrate

11a: above

12,12b: Alignment film

13,14: Conductive film

15: Piezoelectric film

Claims (5)

A film forming apparatus comprising: a first forming part for forming a first film containing zirconium on a silicon substrate; a second forming part for forming a second film containing zirconium oxide on the first film by vapor deposition; and A control unit that controls the operations of the first forming unit and the second forming unit; the control unit forms the first film having a thickness of 5 to 10 nm at a temperature of 650 to 700° C. on the first forming unit Take control. In the film forming apparatus according to claim 1, the control unit controls the second forming unit so as to form the second film at a temperature of 500 to 600°C. A film forming apparatus comprising: a first forming part for forming a first film containing zirconium on a silicon substrate; a second forming part for forming a second film containing zirconium oxide on the first film by vapor deposition; and A control unit that controls the operations of the first forming unit and the second forming unit; the control unit forms the first film having a thickness of 5 to 10 nm at a temperature of 650 to 700° C. on the first forming unit performing control; the control unit controls the second forming unit so as to form the second film at a temperature of 500 to 600°C. A film structure comprising: a silicon substrate, and a first film containing zirconia epitaxially grown on the silicon substrate; the first film including a second film containing zirconium formed on the silicon substrate; The second film has a thickness of 5 to 10 nm. A film forming apparatus for forming a metal film on the film structure of claim 4, and forming the metal film grown epitaxially on the first film.

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