JP7824641B2 - Elements, electronic devices, electronic equipment and systems - Google Patents

Description

The present invention relates to elements, electronic devices, electronic equipment, and systems.

A surface acoustic wave (SAW) element, a type of piezoelectric element, has an interdigital transducer (IDT) on a piezoelectric substrate such as a quartz substrate. The interdigital transducers are paired, with the comb-shaped electrodes facing each other without contacting each other on the piezoelectric substrate. By applying an AC voltage to these interdigital transducers, the piezoelectric effect and inverse piezoelectric effect of the piezoelectric substrate can vibrate the surface or near the surface of the piezoelectric substrate on which the interdigital transducers are formed within a frequency band. Depending on the combination and configuration of interdigital transducers, surface acoustic wave elements are widely used in the electronic circuits that make up a variety of electronic devices, such as oscillators, bandpass filters, and gyros.

Furthermore, in recent years, as mobile terminal devices used in mobile communications have become smaller and lighter, there has been a demand for surface acoustic wave elements with even higher precision to achieve high communication quality. To meet this demand, spherical SAW sensors (ball SAW sensors) and other devices have been considered (Patent Document 1). Ball SAW sensors utilize the phenomenon of SAW's natural collimated beam making multiple round trips, significantly increasing the interaction distance compared to planar sensors, making them useful for achieving high sensitivity. However, there are cost issues, such as a complicated manufacturing process, and SAW devices have many issues with regard to high-frequency characteristics, leaving them far from satisfactory. Furthermore, with the demand for energy conservation to address environmental issues and other factors, a new SAW element that could solve these issues has been eagerly awaited.

Japanese Patent Application Laid-Open No. 2015-154015

The present invention aims to provide elements, electronic devices, electronic equipment, and systems that are environmentally friendly and have excellent precision.

As a result of extensive research into achieving the above-mentioned object, the inventors have succeeded in creating a laminated structure in which a piezoelectric body is laminated on a metal film with the piezoelectric body oriented in the same crystal axis direction. They have discovered that such a laminated structure can easily realize an element in which one or more interdigital electrodes are provided on a piezoelectric body, and the piezoelectric body is in sheet form, and have found that such an element can solve all of the above-mentioned conventional problems at once.
Furthermore, after obtaining the above findings, the present inventors conducted further studies and completed the present invention.

That is, the present invention relates to the following inventions.
[1] An element in which one or more interdigital transducers are provided on a piezoelectric body, the piezoelectric body being in the form of a sheet.
[2] The element according to [1], wherein the piezoelectric body is bonded to a substrate.
[3] The element according to [2], wherein the base is cylindrical, approximately cylindrical, barrel-shaped, or approximately barrel-shaped, the piezoelectric body is wound around the base to form a circle or an approximately circle, and the interdigital electrode is disposed so that a surface acoustic wave can propagate in a circumferential direction or an approximately circumferential direction of the circle or the approximately circle.
[4] The element according to [3], wherein a reflector is provided in a propagation path of the surface acoustic wave.
[5] The element according to [4], wherein two or more reflectors are provided, and the joints between the piezoelectric bodies formed by the winding are provided between the reflectors.
[6] The element according to any one of [3] to [5], wherein the interdigital transducer comprises a SAW generating means for generating the surface acoustic waves and a SAW receiving means for receiving the surface acoustic waves.
[7] The element according to any one of [1] to [6], wherein the piezoelectric body is formed on a metal film.
[8] The element according to [7], wherein the piezoelectric body and the metal film are each oriented in the (100) direction.
[9] The element according to [7] or [8], wherein the metal film is composed of two or more types of metal layers.
[10] The element according to any one of [7] to [9], wherein the metal film contains a metal that undergoes martensitic transformation by heat treatment or processing, and the piezoelectric body and the metal film are oriented in approximately the same crystal axis direction.
[11] The element according to [10], wherein the metal film contains Fe.
[12] The element according to [10] or [11], wherein the metal film contains Cr.
[13] The element according to any one of [1] to [12], wherein the piezoelectric body is made of a single crystal film.
[14] An electronic device, an electronic equipment, or a system including an element, wherein the element is the element according to any one of [1] to [13] above.

The elements, electronic devices, electronic equipment, and systems of the present invention have the advantages of being environmentally friendly and having excellent precision.

1 is a diagram schematically illustrating an example of a preferred embodiment of the element of the present invention. FIG. 2 is a diagram schematically illustrating an example of a reflector that can be suitably used in the element of the present invention. FIG. 2 is a diagram schematically illustrating an example of another preferred embodiment of the element of the present invention. 3A and 3B are diagrams for schematically explaining the propagation direction of surface acoustic waves in the element of the present invention. 1 is a diagram schematically illustrating an example of a preferred embodiment of the laminated structure of the present invention. FIG. 2 is a diagram showing XRD diffraction patterns in examples. FIG. 1 is a diagram illustrating a test piece of an example product in a test example. FIG. 1 is a diagram illustrating a test piece of a comparative example in a test example. FIG. 10 is a diagram showing the results of a bending strength test in a test example. FIG. 2 is a diagram schematically illustrating a film forming apparatus preferably used in the examples.

The element of the present invention is not particularly limited as long as it comprises one or more interdigital transducers mounted on a sheet-like piezoelectric body. In the present invention, the piezoelectric body is preferably bonded to a substrate. This bonding may be achieved by any known bonding method, preferably a metal bonding method or a bonding method. The metal bonding method may be a known metal bonding method, or a metal film may be attached to the piezoelectric body. However, in the present invention, it is preferable to form the piezoelectric body on the metal film and use the resulting laminated structure. In the present invention, the piezoelectric body is preferably formed on a metal film, and more preferably, the piezoelectric body and the metal film are each oriented in the (100) direction. In the present invention, the metal film preferably comprises two or more metal layers, one of which contains a metal that undergoes martensitic transformation upon heat treatment or processing, and more preferably, the piezoelectric body and the metal film are each oriented in approximately the same crystal axis direction. This preferred range improves the precision of the element. The metal film preferably contains Fe, and more preferably contains Cr. Within this preferred range, the piezoelectric element has superior flexibility, making it easier to achieve superior precision in elements that involve bending the piezoelectric element. It is preferable that the piezoelectric element be made of a single crystal film. The attachment means is not particularly limited, but suitable examples include the use of a known adhesive.

In addition, in the present invention, it is preferable that the base be cylindrical, approximately cylindrical, barrel-shaped, or approximately barrel-shaped, the piezoelectric body be wound around the base to form a circle or approximately circle, and the interdigital transducer be disposed so that surface acoustic waves can propagate in the circumferential direction or approximately circumferential direction of the circle or approximately circle. This preferred range can further improve the precision of the element as a SAW device, without requiring, for example, a ball SAW. In addition, in the present invention, it is preferable that a reflector be disposed in the propagation path of the surface acoustic waves, and more preferably, two or more reflectors are disposed, and the piezoelectric bodies are joined by the winding between the reflectors. This preferred range can significantly simplify the manufacturing process of the element and further improve versatility. In addition, in the present invention, it is preferable that the interdigital transducer include a SAW generating means for generating the surface acoustic waves and a SAW receiving means for receiving the surface acoustic waves. This preferred range can more easily improve the precision of the element, regardless of the shape of the base.

The element preferably includes a circular or approximately circular piezoelectric body, with one or more interdigital transducers provided on the piezoelectric body so that surface acoustic waves can propagate in the circumferential or approximately circumferential direction. However, in the present invention, it is more preferable that a reflector be provided on the piezoelectric body within the propagation path of the surface acoustic waves.

The reflector is not particularly limited as long as it is provided on the piezoelectric element within the propagation path of the surface acoustic wave (hereinafter also referred to as "SAW"), and may be a known reflector. However, in the present invention, it is preferable that the reflector be positioned adjacent to an interdigital transducer (hereinafter also referred to as "IDT electrode") in the propagation direction of the SAW, as shown in Figure 1. The reflector may be, for example, an electrode formed in a lattice pattern, and in the present invention, it is preferable that the reflector have a pair of opposing reflection bus bars 11 and a plurality of reflection electrode fingers 13 extending between the pair of reflection bus bars 11, as shown in Figure 2.

The shape and dimensions of the reflective busbar 11 and reflective electrode fingers 13 in FIG. 2 may be basically the same as those of the busbars and electrode fingers of an IDT electrode, except that both ends of each reflective electrode finger 13 are connected to a pair of reflective busbars 11. For example, each reflective electrode finger 13 has an elongated shape that extends linearly with a constant width in a direction (direction D2) perpendicular to the SAW propagation direction and has the same length. These multiple reflective electrode fingers 13 are, for example, arranged side by side in the SAW propagation direction. The number of multiple reflective electrode fingers 13 is usually set so that the reflectivity of the SAW in the intended mode is approximately 100% or more. A theoretically necessary minimum number is, for example, several to 10, and the number of reflective electrode fingers 13 is preferably 20 or more.

The reflector is typically not electrically connected to the IDT electrode and may be in an electrically floating state (a state in which no external potential is applied), or may be supplied with a reference potential or the like. In the present invention, the reflector may be electrically connected to one electrode portion of the IDT electrode, but is preferably in an electrically floating state (a state in which no external potential is applied).

Furthermore, in the present invention, it is preferable that the element has a SAW generating means for generating the surface acoustic waves and a SAW receiving means for receiving the surface acoustic waves, in which the interdigital transducer is arranged. Furthermore, in the present invention, it is more preferable that a total of two or more interdigital transducers are provided, sandwiching the two reflectors and the joint of the piezoelectric body, as shown in FIG. 3, for example. This configuration further improves the accuracy of correction using the signal, making it easier to realize a more sensitive sensor.

Here, a preferred example of a correction mode using the SAW receiving means 19 of FIG. 3 is shown. As shown in FIG. 4, when a voltage is applied to the interdigital transducer 13, the electrode fingers of the interdigital transducer apply the voltage to the piezoelectric element 12, exciting a SAW of a predetermined mode that propagates along the piezoelectric element 12 in the D1 and D2 directions. The excited SAW is mechanically reflected by the electrode fingers of the interdigital transducer 13 and the reflector 20, forming a standing wave with the electrode finger pitch equal to half the wavelength. The standing wave is converted into an electrical signal of the same frequency as the standing wave and extracted by the electrode fingers of the interdigital transducer. A phase difference occurs between the wave propagating in the D1 direction and the wave propagating in the D2 direction of the SAW to which the rotational angular velocity is applied. This allows for correction, for example, using the following equation (1) that represents the phase difference:
(In the formula, Ω represents angular velocity, k represents wave number, N represents number of accumulations, and A represents upper area.)

The element can be easily fabricated using the laminated structure. In the present invention, if the laminated structure includes a crystal substrate, it is preferable to peel off the crystal substrate before use. The laminated structure is preferably a flexible laminated structure having at least a second layer stacked on a first layer, with the first layer preferably being a metal film and the second layer preferably being a piezoelectric film (hereinafter also referred to as a "piezoelectric layer") made of the piezoelectric material. Such a laminated structure can exhibit superior piezoelectric properties at high frequencies, etc.

In the present invention, it is preferable that the piezoelectric film and the metal film are each oriented in the (100) direction. Furthermore, in the present invention, it is preferable that the piezoelectric film is a single-crystal film, as this provides better piezoelectric properties and durability. It is preferable that the piezoelectric film is a PTO film or a PZT film. Furthermore, in the present invention, it is preferable that the metal contains Fe, and more preferably Cr. This preferable range allows for better crystal growth and a higher-quality crystal film. It is also preferable that a conductive oxide film be layered between the metal film and the piezoelectric film, and that the metal film be layered on a conductive nitride film. If a conductive oxide film is layered, it is preferable that the conductive oxide film contain Sr and/or Ru. If a conductive nitride film is layered, it is preferable that the conductive nitride film contain Hf.

The metal film is not particularly limited as long as it contains a metal as its main component. The term "main component" refers to the atomic ratio of the metal in the metal film being 0.5 or greater. In the present invention, the atomic ratio of the metal to all metal elements in the metal film is preferably 0.7 or greater, and more preferably 0.8 or greater. The metal is preferably one that undergoes martensitic transformation upon heat treatment or processing, but is not particularly limited and may be any known metal. Examples of the metals that undergo martensitic transformation include Fe—Cr—Ni, Fe, Fe—Cr—Ni—Cu—Nb, Fe—Ni, Fe—Ni—Co, Fe—Si, Fe—Cr, Fe—Mn, Fe—Mn—C, Fe—Mn—Ni, Fe—Mn—Cr, Fe—C, Fe—N, Fe—Ni—C, Fe—Cr—C, Fe—Cu—C, Fe—Si—C, Fe—Cr—Ni—C, Co, and Co—Ni. , Co-Fe, Mn-Cu, In-Tl, In-Tl-Li, Na, Zr, Tl, Hf, Ti, Ti-Al, Ti-Cu, Ti-Cr, Ti-Fe, Ti-Mn, Ti-Mo, Ti-V, Ti-Zr, Ti-Al-V, Zr-U, Cu-Al-Ni, Cu-Al, Ag-Cd, Au-Cd, Au-Cd-Cu, Li, Li-Mg, Cu-Zn, U, U-Cr, Hg, etc. In the present invention, the metal preferably contains Fe, Cr, or Ni, more preferably contains Fe and Cr, and most preferably is stainless steel. Within these preferred ranges, superior bending strength can be achieved.

The above-mentioned "orientation in the (100) direction" means that the crystal orientation angle detected by X-ray diffraction is oriented in the (100) direction. More specifically, the peak ratio in the (100) direction of the total peaks of the metal film detected by X-ray diffraction is 50% or more, and preferably this peak ratio is 90% or more.

In the present invention, the thickness of the metal film is preferably 100 μm or less, and more preferably 1 μm to 10 μm. This preferred range makes it an even better intermediate film for crystal growth in functional films.

The laminated structure can be easily obtained, for example, by laminating a compound film containing Hf as a first intermediate film on a crystal substrate, followed by a metal film containing a metal that undergoes martensitic transformation upon heat treatment or processing as a second intermediate film, and then laminating a piezoelectric film (hereinafter also referred to as a "piezoelectric layer") by crystal growth, either directly or via another layer, and then peeling off the crystal substrate. Examples of crystal growth methods include known crystal growth methods such as PLD or CVD. The peeling method may be any known method capable of peeling the crystal substrate from the piezoelectric film. The peeling method may also be a method for removing the crystal substrate, and known removal methods such as dry etching and wet etching can also be used for the peeling, as long as they do not impede the objectives of the present invention. In the present invention, the crystal substrate is preferably peeled off by wet etching. Known etching agents, such as strong alkalis, can be suitably used as the wet etching method.

The crystal substrate (hereinafter simply referred to as "substrate") is not particularly limited as long as it does not impede the objectives of the present invention, and may be a known crystal substrate. It may be an organic compound or an inorganic compound. In the present invention, it is preferable that the crystal substrate contains an inorganic compound. In the present invention, it is preferable that the substrate has crystals on part or all of its surface, more preferably a crystal substrate having crystals on all or part of the main surface on the crystal growth side, and most preferably a crystal substrate having crystals on the entire main surface on the crystal growth side. The crystal is not particularly limited as long as it does not impede the objectives of the present invention, and the crystal structure is also not particularly limited. However, it is preferable that it be a cubic, tetragonal, trigonal, hexagonal, orthorhombic, or monoclinic crystal, and more preferably a crystal oriented in the (100) or (200) direction. The crystal substrate may also have an off-angle, and examples of the off-angle include an off-angle of 0.2° to 12.0°. Here, "off-angle" refers to the angle between the substrate surface and the crystal growth plane. The substrate shape is not particularly limited as long as it is plate-like and serves as a support for the epitaxial film. It may be an insulating substrate or a semiconductor substrate. However, in the present invention, the substrate is preferably a Si substrate, more preferably a crystalline Si substrate, and most preferably a (100)-oriented crystalline Si substrate. In addition to Si substrates, examples of substrate materials include one or more metals belonging to Groups 3 to 15 of the periodic table, or oxides of these metals. The shape of the substrate is not particularly limited and may be approximately circular (e.g., circular, elliptical, etc.) or polygonal (e.g., triangular, square, rectangular, pentagonal, hexagonal, heptagonal, octagonal, nonagonal, etc.). Various shapes can be suitably used. Furthermore, in the present invention, large-area substrates can be used, which allows for a larger area for the epitaxial film.

In addition, in the present invention, it is preferable that the crystal substrate has a flat surface. However, it is also preferable that the crystal substrate have an uneven surface on part or all of its surface, as this can improve the quality of the crystal growth of the epitaxial film. The crystal substrate having an uneven surface may have an uneven surface consisting of concave or convex portions formed on part or all of its surface. The uneven surface is not particularly limited as long as it consists of convex or concave portions. It may be an uneven surface consisting of convex portions, an uneven surface consisting of concave portions, or an uneven surface consisting of convex and concave portions. The uneven surface may also be formed of regular convex or concave portions, or irregular convex or concave portions. In the present invention, it is preferable that the uneven surface be formed periodically, and more preferably, a periodic and regular pattern is formed. The shape of the uneven surface is not particularly limited and may include, for example, a striped, dotted, meshed, or random pattern. In the present invention, a dotted or striped pattern is preferred, and a dotted pattern is more preferred. Furthermore, when the concave-convex portions are patterned periodically and regularly, the pattern shape of the concave-convex portions is preferably a triangle, quadrangle (e.g., square, rectangle, or trapezoid), polygonal shape such as a pentagon or hexagon, circle, or ellipse. When the concave-convex portions are formed in a dotted pattern, the lattice shape of the dots is preferably a square lattice, orthorhombic lattice, triangular lattice, or hexagonal lattice, with a triangular lattice shape being more preferable. The cross-sectional shape of the concave or convex portions of the concave-convex portions is not particularly limited, but examples include a square, U-shape, inverted U-shape, wave-like shape, or a polygonal shape such as a triangle, quadrangle (e.g., square, rectangle, or trapezoid), pentagon, or hexagon. The thickness of the crystal substrate is not particularly limited, but is preferably 50 to 2000 μm, and more preferably 100 to 1000 μm.

The piezoelectric layer is not particularly limited as long as it is a piezoelectric layer made of the piezoelectric material. The piezoelectric material may be a known piezoelectric material, but in the present invention, it is preferable that the piezoelectric material contains Pb and Ti. Note that, in this specification, the terms "film" and "layer" may be used interchangeably depending on the case or situation.

In the present invention, it is preferable to laminate a first intermediate film on a crystal substrate, then laminate a second intermediate film, and then laminate the piezoelectric layer directly or via another layer. Examples of the other layer include a metal film, a conductive oxide film, or a conductive nitride film. Examples of the conductive oxide film include a conductive oxide film containing Sr and/or Ru. Examples of the conductive nitride film include a conductive nitride film containing Hf. The metal film in the other layer is preferably made of a metal different from the metal mentioned above, such as gold, silver, platinum, palladium, silver-palladium, copper, nickel, or an alloy thereof.
The above-mentioned lamination means can be used for all of the laminations by known film formation means. In the present invention, the film formation means is preferably vapor deposition (including MBE) or sputtering. The thickness of each layer is not particularly limited, but is preferably 10 nm to 100 μm, and more preferably 50 nm to 30 μm.

The laminated structure obtained as described above can be peeled from the crystal substrate by appropriate wet etching or other methods and used as a piezoelectric body in piezoelectric elements and other devices using known techniques. For example, a new, high-performance piezoelectric element can be easily fabricated by winding the resulting piezoelectric body around a roughly cylindrical substrate and providing a reflector and an interdigital transducer in this order from the joining point. Furthermore, the element can be suitably used in electronic devices using conventional methods. For example, various electronic devices can be constructed by connecting the laminated structure as a piezoelectric element to a power source or an electrical/electronic circuit, mounting it on a circuit board, or packaging it. In the present invention, the electronic device is preferably a piezoelectric device, and can be used as a piezoelectric device in electronic devices such as inkjet printer heads, microactuators, gyroscopes, and motion sensors. Furthermore, by connecting an amplifier and a rectifier circuit and packaging it, it can be used in various sensors such as magnetic sensors. It can also be used in constant-voltage-driven memories, and, for example, by connecting a storage element and a rectifier power management circuit to create an energy conversion device (energy harvester) that generates power from external magnetic fields or vibrations. The energy conversion device is incorporated into power supply systems and wearable devices (earphones/hearable devices, smart watches, smart glasses, smart contact lenses, cochlear implants, cardiac pacemakers, etc.). In the present invention, the laminated structure is preferably used in, for example, smart glasses, AR headsets, MEMS mirrors for LiDAR systems, piezoelectric MEMS ultrasonic transducers (PMUTs) for advanced medical applications, and piezo heads for commercial and industrial 3D printers.

The electronic device is suitable for use in electronic devices in the usual way. The electronic device can be applied to a variety of electronic devices in addition to those mentioned above. Specific examples include liquid ejection heads, liquid ejection devices, vibration wave motors, optical devices, vibration devices, imaging devices, piezoelectric acoustic components, and audio playback devices, audio recording devices, mobile phones, and various information terminals that use such piezoelectric acoustic components.

The electronic devices can also be applied to systems in the usual way, such as sensor systems.

Preferred embodiments of the present invention are described below with reference to the drawings, but the present invention is not limited to these preferred embodiments.

Figure 1 shows an example of a suitable element of the present invention. The element in Figure 1 has a piezoelectric element 12 wound around the side of a cylindrical substrate, and an interdigital transducer 10 and a reflector 20 formed on the piezoelectric element 12 on the side. The interdigital transducer 10 and the reflector 20 may be formed using known methods. When a voltage is applied to the interdigital transducer 10, the piezoelectric effect of the piezoelectric element 12 causes strain on the piezoelectric element between adjacent electrode fingers of the interdigital transducer 10, exciting a surface wave. The interdigital transducer has electrode fingers arranged periodically, and the surface wave is excited most strongly when the wavelength is equal to the electrode finger period. Because the frequency is determined by the electrode spacing formed on the surface, high frequencies can be easily accommodated using photolithography or other processing methods.

The element is suitable for use in electronic devices in the usual way. For example, various electronic devices can be constructed by connecting the element as a piezoelectric element to a power source or an electric/electronic circuit, and mounting it on a circuit board or packaging it. In the present invention, the electronic device is preferably a piezoelectric device, and can be used as a piezoelectric device in electronic devices such as gyroscopes and motion sensors. Furthermore, for example, if an amplifier and a rectifier circuit are connected and packaged, it can be used as a variety of sensors such as a magnetic sensor.

The electronic device is suitable for use in electronic devices in the usual way. The electronic device can be applied to a variety of electronic devices in addition to those mentioned above. Specific examples include liquid ejection heads, liquid ejection devices, vibration wave motors, optical devices, vibration devices, imaging devices, piezoelectric acoustic components, and audio playback devices, audio recording devices, mobile phones, and various information terminals that use such piezoelectric acoustic components.

The electronic devices can also be applied to systems in the usual way, such as sensor systems.

Example 1
The crystal growth surface of the Si substrate (100) was treated by RIE, and the metal vapor deposition source was thermally reacted with nitrogen to form a HfZrN single crystal on the Si substrate. The deposition conditions for this film formation were as follows:
Vapor deposition source: Hf, Zr
Voltage: 3.5 to 4.75 V
Pressure: 3×10 ⁻² to 6×10 ⁻² Pa
Substrate temperature: 450-700℃

The evaporation deposition apparatus used to deposit the HfZrN single crystal is shown in Figure 8. The deposition apparatus in Figure 8 is equipped with at least metal sources 1101a-1101b in a crucible, earths 1102a-1102h, ICP electrodes 1103a-1103b, cut filters 1104a-1104b, DC power supplies 1105a-1105b, RF power supplies 1106a-1106b, lamps 1107a-1107b, Ar source 1108, reactive gas source 1109, power supply 1110, substrate holder 1111, substrate 1112, cut filter 1113, ICP ring 1114, vacuum chamber 1115, and rotation shaft 1116. The ICP electrodes 1103a-1103b in Figure 8 have a generally concave or parabolic shape curved toward the center of the substrate 1112.

As shown in FIG. 8, the substrate 1112 is secured to the substrate holder 1111. Next, the rotary shaft 1116 is rotated using the power supply 1110 and a rotation mechanism (not shown), causing the substrate 1112 to rotate. The substrate 1112 is heated by lamps 1107a-1107b, and the vacuum chamber 1115 is evacuated to a vacuum or reduced pressure using a vacuum pump (not shown). Ar gas is then introduced into the vacuum chamber 1115 from the Ar source 1108, and argon plasma is formed on the substrate 1112 using the DC power supplies 1105a-1105b, RF power supplies 1106a-1106b, ICP electrodes 1103a-1103b, cut filters 1104a-1104b, and earths 1102a-1102h, thereby cleaning the surface of the substrate 1112.

Ar gas is introduced into the vacuum chamber 1115, and a reactive gas is introduced using the reactive gas source 1109. At this time, lamps 7a and 7b are configured to irradiate the substrate 12 with different wavelengths. Lamps 7a and 7b may also be lamp heaters. The wavelength is not particularly limited as long as it does not impede the objectives of the present invention, and may be ultraviolet or infrared. The wavelength may be set appropriately depending on the raw material, type of reaction, etc., making it easy to improve the film quality and film formation rate. Also, by alternately turning lamps 7a to 7b on and off, a better quality crystal growth film can be formed.

Next, a SUS304 single crystal film was formed in the same manner as above, except that Fe, Cr, and Ni were used as the evaporation source metals.

Next, a platinum (Pt) metal film was formed as a conductive film on the single crystal film of the crystalline metal oxide by sputtering under the following conditions.
Equipment: ULVAC sputtering equipment QAM-4
Pressure: 1.20×10 ⁻¹ Pa
Target: Pt
Power: 100W (DC)
Thickness: 100 nm
Substrate temperature: 450-600℃

Next, an SRO film was formed on the conductive film by sputtering under the following conditions.
Equipment: ULVAC sputtering equipment QAM-4
Power: 150W (RF)
Gas: Ar
Pressure: 1.8 Pa
Substrate temperature: 600℃
Thickness: 20 nm

Next, a _PbTiO3 film was formed on the SRO film as a piezoelectric film. The resulting laminated structure had good adhesion and crystallinity. Furthermore, the crystallinity of the crystalline substrate of the laminated structure, the single crystal film of the crystalline metal oxide, and the conductive film was measured using an X-ray diffraction device. Figure 2 shows the results of the XRD measurement. As is clear from Figure 2, a SUS304 single crystal film with good crystallinity was formed, and the crystallinity of the _PbTiO3 film and other films was also good.

After the _PbTiO3 film was formed, the Si substrate was removed by wet etching using sodium hydroxide, and the Si substrate was peeled off from the _PbTiO3 film. The resulting laminated structure was flexible.

(Test example)
As a test example, a cantilever microelement like the one shown in Figures 3 and 4 was fabricated using a Hitachi High-Technologies FIB FB2100. Its fracture strength characteristics were evaluated using a NanoTest Xtreme nanoindenter (Micro Materials), resulting in the results shown in Figure 5. Figure 5 shows that the fracture strength of Si was approximately 1 GPa, a fairly constant value. Considering that the bending strength of bulk Si single crystal material is approximately 300 MPa (according to a paper), this micromaterial exhibits significant strength. Furthermore, the fracture strength of a SUS304 single crystal thin film was approximately 5 GPa, approximately five times that of single crystal Si. This suggests that using a SUS304 single crystal thin film for the beams of MEMS devices (moving parts, equivalent to the active layer of an SOI substrate) can be expected to significantly improve not only the displacement of MEMS devices but also their lifespan.

Examples of applications of the obtained piezoelectric material to elements are explained in more detail below with reference to the figures, but the present invention is not limited to these application examples. In addition, in the present invention, elements, electronic devices, etc. can be manufactured from the piezoelectric material using known means, unless otherwise specified.

Figure 3 shows an example of an element according to a preferred embodiment of the present invention. The element in Figure 3 differs from that in Figure 1 in that it includes a SAW receiver for detecting SAW. The element in Figure 3 has a piezoelectric element 12 wound around the side of a cylindrical substrate. Two interdigital transducers 13 and two reflectors 20 are formed on the piezoelectric element 12 on the side of the substrate using known techniques. When a voltage is applied to the interdigital transducers 13, the piezoelectric effect of the piezoelectric element 12 generates strain on the piezoelectric element between adjacent electrode fingers of the interdigital transducer 13, exciting a surface wave. A SAW receiver 19 is connected to the interdigital transducer 13, enabling detection of surface acoustic waves propagating through the SAW propagation path 14 shown in Figure 1. The reflector 20 propagates the surface acoustic waves on the surface of the piezoelectric element 12 in directions D1 and D2 shown in Figure 4, i.e., in opposing directions. This allows the fabrication of an environmentally friendly, highly accurate, and highly sensitive sensor.

The element of the present invention can be used for a variety of purposes, but is particularly suitable for use as a piezoelectric sensor, for example, in electronic devices for sensor systems.

1. Crystal substrate (Si substrate)
2 HfZrN film 3 SUS film (FeCrNi film)
4 Pt film 5 SRO film 6 Piezoelectric layer (PbTiO film)
10 Interdigital electrode 11 Reflection bus bar 12 Piezoelectric body 13 Reflection electrode finger 14 Propagation path 15 Extraction electrode 19 SAW receiver 20 Reflector 1101a to 101b Metal source 1102a to 102j Earth 1103a to 103b ICP electrode 1104a to 104b Cut filter 1105a to 105b DC power supply 1106a to 106b RF power supply 1107a to 107b Lamp 1108 Ar source 1109 Reactive gas source 1110 Power supply 1111 Substrate holder 1112 Substrate 1113 Cut filter 1114 ICP ring 1115 Vacuum chamber 1116 Rotation axis

Claims (13)

a cylindrical, approximately cylindrical, barrel-shaped, or approximately barrel-shaped base;
a piezoelectric body wound around the base to form a circular or substantially circular shape;
Including,
An element in which one or more interdigital transducers are provided on the piezoelectric body so that surface acoustic waves can propagate in a circumferential direction or a substantially circumferential direction of the circular or substantially circular shape ,
the piezoelectric body is bonded to the base;
Two or more reflectors are provided in a propagation path of the surface acoustic wave,
An element characterized in that the joints between the piezoelectric bodies formed by the winding are provided between the reflectors . a cylindrical, approximately cylindrical, barrel-shaped, or approximately barrel-shaped base;
an annular piezoelectric body wound around and bonded to a side peripheral surface of the base body;
Including,
an element in which one or more interdigital transducers are provided on the outer peripheral surface of the annular piezoelectric body so that surface acoustic waves can propagate in the circumferential direction of the annular piezoelectric body,
two reflectors are provided on the outer peripheral surface of the annular piezoelectric body and within a propagation path of the surface acoustic wave;
the annular piezoelectric element includes a joint portion where one end and the other end of the strip-shaped piezoelectric element are joined together,
The element is characterized in that the joint is provided between the two reflectors . The element according to claim 2 , wherein the two reflectors are adjacent to each other with the joint portion therebetween. 3. The element according to claim 2, wherein the one or more interdigital transducers are provided on the outer peripheral surface of the annular piezoelectric body, on a side opposite to the junction side of one of the two reflectors and on a side opposite to the junction side of the other of the two reflectors. 5. The element according to claim 1, wherein the interdigital transducer comprises a SAW generating means for generating the surface acoustic waves and a SAW receiving means for receiving the surface acoustic waves. 5. The element according to claim 1, wherein the piezoelectric body is formed on a metal film. 7. The element according to claim 6 , wherein the piezoelectric body and the metal film are oriented in the (100) direction. 7. The element according to claim 6 , wherein the metal film comprises two or more metal layers. 7. The element according to claim 6 , wherein the metal film contains a metal that undergoes martensitic transformation upon heat treatment or processing, and the piezoelectric body and the metal film are oriented in substantially the same crystal axis direction. The device of claim 9 , wherein the metal film comprises Fe. The device of claim 9 , wherein the metal film comprises Cr. 5. The element according to claim 1, wherein the piezoelectric body is made of a single crystal film. An electronic device, an electronic equipment or a system including an element, wherein the element is the element according to any one of claims 1 to 4 .