Magnetoelectric conversion element and electronic device

Abstract

To provide a magnetoelectric conversion element capable of enhancing magnetoelectric conversion efficiency and output, and a power supply device using the magnetoelectric conversion element.SOLUTION: A magnetoelectric conversion element 1 includes a substrate 6, and an element body 4 fixed to the substrate 6, the element body 4 includes a vibrating portion 41 including single-layer or multi-layer functional films 12 to 20 having both piezoelectric properties and magnetostrictive properties, and a support portion 43 that connects the vibrating portion 41 and the substrate 6, and the vibrating portion 41 is fixed to the substrate 6 via the support portion 43, and the relationship between the width w of the support portion 43, the displacement V in a thickness direction of a warp of the vibrating portion 41, and a width L of the vibrating portion 41 satisfies 2V / (L-w)<0.7.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to a magnetoelectric transducer that can be used, for example, as an antenna or a power generating element, and to an electronic device including the magnetoelectric transducer. [Background technology]

[0002] As the market size of wearable devices grows, the demand for ME devices is also increasing. The inventors of the present invention have developed an ME device that converts magnetic changes into electricity using a thin film consisting of a magnetostrictive layer and a piezoelectric layer (Patent Document 1).

[0003] In such magnetoelectric transducers, it is desirable to increase the magnetoelectric conversion efficiency and improve the output. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-169881 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a magnetoelectric conversion element that can increase magnetoelectric conversion efficiency and improve output, and a power supply device that uses the magnetoelectric conversion element. The purpose of this project is to provide [Means for solving the problem]

[0006] In order to achieve the above object, a magnetoelectric transducer according to a first aspect of the present invention comprises: A vibration section including a single-layer or multi-layer functional film having both piezoelectric and magnetostrictive properties; A support part that holds the vibration part so that the vibration part can vibrate in-plane (preferably in-plane stretching vibration); A magnetoelectric transducer having a substrate on which the support portion is provided, When the width of the support portion is w, the width of the vibration portion is L, and the displacement of the warp of the vibration portion in the thickness direction is V, It is characterized in that the following formula (1) is satisfied. 2V / (Lw)<0.7 …(1)

[0007] The present inventors have discovered that by satisfying the above relationship, the magnetoelectric conversion efficiency in the magnetoelectric conversion element can be increased, and the output can be improved.

[0008] In other words, when the above relationship is satisfied, the vibration of the vibrating part is well-balanced without unnecessary vibration components. This type of vibration has a high Q value, and it is believed that the conversion efficiency of the magnetoelectric conversion element that converts energy through the vibration is increased, resulting in high output.

[0009] Preferably, the substrate has an opening, The vibration portion is disposed in an opening of the substrate, The front surface (upper surface) and the back surface (lower surface) of the vibration part are exposed to a space in which they can vibrate freely, The peripheral edge of the vibrating part other than the part supported by the support part is also exposed to a space in which it can vibrate freely.

[0010] By configuring the magnetoelectric transducer as described above, it is possible to generate elastic wave vibrations of larger amplitude in the vibration section, and the energy conversion efficiency of the magnetoelectric transducer is further improved.

[0011] A magnetoelectric transducer according to a second aspect of the present invention comprises: A vibration section including a single-layer or multi-layer functional film having both piezoelectric and magnetostrictive properties; A magnetoelectric transducer having a substrate that holds the vibration part so that the vibration part can vibrate in-plane (preferably in-plane stretching vibration), When the width of the vibrating part is L and the displacement of the warp of the vibrating part in the thickness direction is V, It is characterized in that the following formula (2) is satisfied. 2V / L<0.2 …(2)

[0012] The present inventors have discovered that by satisfying the above relationship, the magnetoelectric conversion efficiency in the magnetoelectric conversion element can be increased, and the output can be improved.

[0013] In other words, when the above relationship is satisfied, the vibration of the vibrating part is well-balanced without unnecessary vibration components. This type of vibration has a high Q value, and it is believed that the conversion efficiency of the magnetoelectric conversion element that converts energy through the vibration is increased, resulting in high output.

[0014] The shape of the vibrating part is preferably a square, rectangle, or perfect circle (in the case of a perfect circle, the width L is the diameter) in which the width (L) of the vibrating part is uniquely determined, but is not particularly limited.

[0015] Preferably, the substrate has an opening, The vibration portion is disposed in an opening of the substrate, The front and back surfaces of the vibration unit are exposed to a space in which the vibration unit can freely vibrate, The widthwise edges of the vibrating portion are also exposed to a space in which they can vibrate freely.

[0016] By configuring the magnetoelectric transducer as described above, it is possible to generate elastic wave vibrations of larger amplitude in the vibration section, and the energy conversion efficiency of the magnetoelectric transducer is further improved.

[0017] Preferably, the functional film of the vibration portion has a piezoelectric layer and a magnetostrictive layer, The vibrating section has the piezoelectric layer and the magnetostrictive layer laminated thereon. When the vibrating section has the piezoelectric layer and the magnetostrictive layer as described above, the energy conversion efficiency of the magnetoelectric conversion element is further improved.

[0018] The electronic device according to the present invention is not particularly limited as long as it is a device having any one of the magnetoelectric conversion elements described above.

[0019] A preferred example of the electronic device is a power generating element.

[0020] A preferred power generating element is A non-contact type element body that receives energy supplied from an external device in a non-contact manner and generates electric power; The element body has the vibration part, The vibration unit is a vibrator capable of elastic wave vibration at a natural frequency, The vibrating portion has a Q value of 100 or more.

[0021] The vibration part included in the element body resonates upon receiving external energy such as electromagnetic waves or alternating magnetic fields, and generates elastic wave vibrations, thereby generating electric power. In particular, in a preferred power generating element, the Q value of the vibration part that generates elastic wave vibrations is set to 100 or more. By setting the Q value of the vibration part to a high value, the vibration part can generate elastic wave vibrations of a larger amplitude, enabling highly efficient energy conversion. Furthermore, the vibration part that generates elastic wave vibrations can be made much smaller in size than a receiving coil for electromagnetic induction or a receiving coil for magnetic field resonance, making it easier to miniaturize the device.

[0022] Preferably, the element body is mounted on a substrate having an opening, and further comprises a fixed part facing and connected to the substrate, and at least one support part connecting the fixed part and the vibration part. And, preferably, the vibration part is disposed facing the opening of the substrate, and the surface of the vibration part facing the opening is a non-constrained surface that is not in direct contact with the substrate. By configuring the power generation element as described above, it is possible to generate elastic wave vibrations of a larger amplitude in the vibration part, and the energy conversion efficiency of the power generation element is further improved.

[0023] In addition, it is preferable that the outer peripheral edge of the vibrating part and the inner peripheral edge of the opening in the substrate are not in contact with each other in a plan view from a direction parallel to the thickness direction of the vibrating part. It is also preferable that a gap exists between the outer peripheral edge of the vibrating part and the inner peripheral edge of the opening. By having the above configuration, the power generation element of the present invention further improves the energy conversion efficiency.

[0024] In addition, preferably, a direction in which the support parts are connected is defined as a first axis, a direction perpendicular to the first axis is defined as a second axis, and a width of the support parts on the second axis is smaller than a width of the vibration part on the second axis. With the above configuration, elastic wave vibrations of larger amplitude can be generated in the vibration part, and the energy conversion efficiency of the power generating element is further improved.

[0025] Preferably, the width of the vibration part in a direction perpendicular to the connecting direction of the support part is 1 / 100 or less of the wavelength of the electromagnetic wave at the natural frequency. With the above configuration, it is possible to generate elastic wave vibrations of a larger amplitude in the vibration part, and the energy conversion efficiency of the power generation element is further improved.

[0026] Preferably, the elastic wave vibration is a bulk elastic wave, and the vibration part is a bulk elastic wave vibrator. Also, preferably, the vibration mode of the elastic wave vibration is an in-plane stretching vibration, and the vibration part is a bulk elastic wave vibrator capable of elastic wave vibration in the in-plane stretching vibration. When the elastic wave vibration of the vibration part has the above configuration, the energy conversion efficiency of the power generation element is further improved.

[0027] Preferably, the power generating element has a plurality of the element bodies. By forming the power generating element into an array element having a plurality of element bodies as described above, it is possible to increase the power generated by the resonance of the elastic wave vibration. For example, when a plurality of element bodies are arranged in series, it is possible to increase the output voltage, and when a plurality of element bodies are arranged in parallel, it is possible to increase the output current.

[0028] Furthermore, when the power generating element is an array element as described above, it is preferable that the average value of the natural frequency of the plurality of element bodies is fA, and the variation of the natural frequency is within a range of fA±1.0% or less. With the above configuration, the power generating element can generate larger power, and the energy conversion efficiency is further improved.

[0029] The power generating element can be suitably used, for example, by being incorporated into a power supply device. An electronic device incorporating the power supply device can operate for a long time as an independent device that does not require a wired power supply. The power supply device and the electronic device can be made small enough to be worn inside the human body. Examples of the electronic device include hearable devices such as earphones and hearing aids, smart watches, smart glasses, smart contact lenses, wearable thermometers, wearable pulse wave sensors, and other wearable terminals, as well as artificial cochleas and cardiac pacemakers worn inside the human body, electrical stimulation devices for muscles and the brain, neuro-RFID, and microrobots. [Brief description of the drawings]

[0030] [Figure 1A] FIG. 1A is a plan view showing a magnetoelectric transducer element according to one embodiment of the present invention. [Figure 1B] FIG. 1B is a plan view showing a magnetoelectric transducer according to another embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view taken along the line II-II shown in FIG. [Figure 3A] FIG. 3A is a schematic cross-sectional view taken along line IIIA-IIIA shown in FIG. 1A. [Figure 3B] FIG. 3B is a schematic cross-sectional view taken along line IIIB-IIIB shown in FIG. 1B. [Figure 4A] FIG. 4A is a plan view of a magnetoelectric transducer according to another embodiment of the present invention. [Figure 4B] FIG. 4B is a plan view of a magnetoelectric transducer according to still another embodiment of the present invention. [Figure 4C]FIG. 4C is a plan view of a magnetoelectric transducer according to still another embodiment of the present invention. [Figure 4D] FIG. 4D is a plan view of a magnetoelectric transducer according to still another embodiment of the present invention. [Figure 4E] FIG. 4E is a plan view of a magnetoelectric transducer according to still another embodiment of the present invention. [Figure 4F] FIG. 4F is a plan view of a magnetoelectric transducer according to still another embodiment of the present invention. [Figure 4G] FIG. 4G is a plan view of a magnetoelectric transducer according to still another embodiment of the present invention. [Figure 5A] FIG. 5A is a graph showing an experimental result of the magnetoelectric transducer element according to the embodiment of the present invention. [Figure 5B] FIG. 5B is a graph showing an experimental result of the magnetoelectric transducer element according to another embodiment of the present invention. [Figure 6] FIG. 6 is a graph showing the frequency characteristics of the vibration section. [Figure 7] FIG. 7 is a schematic diagram showing a power supply device and electronic equipment incorporating the magnetoelectric conversion element of this embodiment as a power generating element. [Figure 8] FIG. 8 is a plan view showing a modified example of the power generating element. [Figure 9] FIG. 9 is a plan view showing a modified example of the power generating element. [Figure 10] FIG. 10 is a plan view showing a modified example of the power generating element. [Figure 11] FIG. 11 is a schematic cross-sectional view showing a modified example of the power generating element. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0032] First embodiment As shown in FIG. 1A, a magnetoelectric transducer 1 according to an embodiment of the present invention includes a substrate 6 and an element body 4 formed on the substrate 6. In this embodiment, the element body 4 includes a vibration part 41 located approximately in the center in the X-axis direction, two fixed parts 42a and 42b located at both ends in the X-axis direction, and two support parts 43 connecting the vibration part 41 and the fixed parts 42a and 42b. In this embodiment, the direction in which the support parts 43 extend is the X-axis, the width direction of the element body 4 perpendicular to the X-axis is the Y-axis, and the thickness direction of the element body 4 is the Z-axis. The X-axis, Y-axis, and Z-axis are approximately perpendicular to each other.

[0033] 2, the vibration section 41 of the element body 4 has, as functional films, a piezoelectric layer 14 having piezoelectric properties and a magnetostrictive layer 16 having magnetostrictive properties. The piezoelectric layer 14 and the magnetostrictive layer 16 are substantially parallel to the XY plane including the X-axis and the Y-axis, and are laminated along a direction approximately perpendicular to the XY plane (i.e., the Z-axis direction). Note that "substantially parallel" means that most parts are parallel, but there may be some parts that are not parallel, and the piezoelectric layer 14 and the magnetostrictive layer 16 may have some unevenness or be inclined.

[0034] In the magnetoelectric transducer 1 of this embodiment, the vibration part 41 having the functional film as described above plays an important role in generating electric power. Therefore, in this embodiment, the features of the vibration part 41 will be mainly described.

[0035] The vibration part 41 of the element body 4 is an oscillator having a natural frequency f0. The vibration part 41 of this embodiment is an oscillator capable of elastic wave vibration in response to electromagnetic waves, alternating magnetic fields, etc. The natural frequency f0 of the vibration part 41 is the frequency at which the response is maximized, and is also called the resonance frequency. In the case of the magnetoelectric conversion element 1, the "response" means the output power.

[0036] When external energy such as electromagnetic waves or AC magnetic fields having a frequency close to the natural frequency f0 is radiated to the vibration part 41, the vibration part 41, which is an elastic wave vibrator, is excited by the external energy and vibrates elastically. More specifically, when the vibration part 41 receives the external energy, distortion occurs in the magnetostrictive layer 16 due to the magnetostrictive effect, and elastic wave vibration occurs in response to the distortion. When this elastic wave vibration occurs, electric charges are generated on the surface of the piezoelectric layer 14 in the vibration part 41 due to the piezoelectric effect of the piezoelectric layer 14. In other words, in the magnetoelectric conversion element 1 of this embodiment, external energy such as electromagnetic waves or AC magnetic fields can be converted into electric energy by the elastic wave vibration of the vibration part 41.

[0037] As shown in FIG. 2, the bottom layer of the magnetoelectric conversion element 1 in the Z-axis direction is a substrate 6 having an approximately rectangular outer edge shape in a plan view. The plan view shape of the substrate 6 is not particularly limited. The thickness of the substrate 6 is also not particularly limited, and may be any thickness that ensures sufficient strength. The substrate 6 has an opening 61 in the approximate center of the XY plane, and the vibration part 41 is located above the opening 61 in the Z-axis direction. That is, the vibration part 41 of the element body 4 is disposed in accordance with the opening 61 of the substrate 6. The plan view shape and dimensions of the opening 61 are determined in accordance with the shape and dimensions of the vibration part 41. In this embodiment, the opening 61 has an approximately rectangular plan view shape.

[0038] The element body 4 is a laminated structure in which functional films are laminated, and includes at least a lower electrode layer 12, the above-mentioned piezoelectric layer 14, and a magnetostrictive layer 16. In this embodiment, an upper electrode layer 13 is further included. The lower electrode layer 12 is located below the element body 4 in the Z-axis direction, a piezoelectric layer 14 is laminated on the lower electrode layer 12, an upper electrode layer 13 is laminated on the piezoelectric layer 14, and a magnetostrictive layer 16 is laminated on the upper electrode layer 13. The configuration of each functional film will be described in detail later.

[0039] The element body 4 is located above the substrate 6 in the Z-axis direction, bridging the upper opening surface of the opening 61 in the X-axis direction. One end of the element body 4 in the X-axis direction faces and is connected to the surface of the substrate 6, forming a fixed part 42a. The other end of the element body 4 in the X-axis direction also faces and is connected to the surface of the substrate 6, forming a fixed part 42b.

[0040] In the fixed portion 42a, the extraction electrode 18a is electrically connected to the lower electrode layer 12, and an external circuit (not shown) can be connected through the extraction electrode 18a. On the other hand, in the fixed portion 42b, the extraction electrode 18b is electrically connected to the magnetostrictive layer 16, and an external circuit (not shown) can be connected through the extraction electrode 18b. In the fixed portion 42b, an insulating layer 20 is interposed between the extraction electrode 18b and the lower electrode layer 12, and the extraction electrode 18b and the lower electrode layer 12 are insulated from each other by the insulating layer 20 so as not to short-circuit. In the following paragraphs, the fixed portion 42a and the fixed portion 42b may be collectively referred to as the "fixed portion 42". In addition, the extraction electrodes 18a and 18b may be collectively referred to as the "extraction electrode 18".

[0041] The vibration part 41 of the element body 4 has a generally rectangular shape in plan view that is smaller than the upper opening surface of the opening 61, and has edges parallel to the X-axis and edges parallel to the Y-axis. The vibration part 41 is located above the opening 61, and in the cross section shown in FIG. 3A, the vibration part 41 appears to be floating above the Z-axis of the opening 61 or inside the opening 61. As shown in FIG. 3A, the upper and lower surfaces of the vibration part 41 that are parallel to the XY plane are exposed to a space in which they can vibrate freely, and are preferably unconstrained surfaces that are not in direct contact with the substrate 6.

[0042] The element body 4 has a pair of support parts 43, and the vibration part 41 is integrally connected to each of the fixed parts 42a, 42b via the pair of support parts 43. In other words, the vibration part 41 is connected to the substrate 6 via the support parts 43. In this embodiment, the direction in which the vibration part 41 and the fixed part 42 are connected by the support parts 43 is referred to as the connection direction (X-axis direction).

[0043] 1A, the edge of vibration part 41 parallel to the X-axis and the edge of vibration part 4 parallel to the Y-axis are not in contact with the inner peripheral edge of opening 61. That is, in a plan view from the Z-axis direction, the outer peripheral edge of vibration part 41 and the inner peripheral edge of opening 61 are not in contact with each other, and a gap 46 exists between the outer peripheral edge of vibration part 41 and the inner peripheral edge of opening 61. Here, the above-mentioned "outer peripheral edge of vibration part 41" refers to the outer peripheral edge of lower electrode layer 12 in vibration part 41, and more specifically, refers to the outer peripheral edge of lower electrode layer 12 in vibration part 41 excluding the connection portion with support part 43.

[0044] In this embodiment, it is preferable that the outer peripheral edge of the vibration part 4 other than the part held by the support part 43 is also exposed to a space in which it can vibrate freely, and is an unconstrained surface that is not in direct contact with the substrate 6.

[0045] In this embodiment, the average width Wg of the gap 46 is preferably 1 μm to 500 μm. In this embodiment, the gap 46 is a space where the functional films 12 to 16 and the substrate 6 are not present. The width Wg of the gap 46 means the distance from the outer periphery of the lower electrode layer 12 to the inner periphery of the opening 61 in a plan view.

[0046] Furthermore, in the vibrating part 41, the width L in the direction perpendicular to the coupling direction (the width in the Y-axis direction in FIG. 1A) is preferably 1 / 100 times or less, and more preferably 1 / 200 times or less, of the wavelength of the electromagnetic wave EW having the same frequency as the natural frequency f0. The lower limit of the width L in the direction perpendicular to the coupling direction is not particularly limited, but is preferably 1 / 200,000 times or more of the wavelength of the electromagnetic wave having the same frequency as the natural frequency f0, for example.

[0047] In the above, the "wavelength of the electromagnetic wave EW" refers to the wavelength of the electromagnetic wave in a medium (e.g., air) that serves as a transmission path for external energy. For example, in the magnetoelectric conversion element 1 of this embodiment, if the width L is increased without changing the configuration other than the width L, the natural frequency f0 of the vibration part 41 tends to decrease. Conversely, if the width L is narrowed, the natural frequency f0 of the vibration part 41 tends to increase.

[0048] On the other hand, in the vibrating part 41, the width H in the connection direction (the width in the X-axis direction in FIG. 1A) is not particularly limited and can be narrower than the above-mentioned width L, but it is preferable that the width be wider than the width L.

[0049] 3A depends on the thickness of each functional film and is not particularly limited, but is preferably set to, for example, 0.5 μm to 30 μm. In this embodiment, the ratio t14 / t16 of the thickness t14 of the piezoelectric layer 14 to the thickness t16 of the magnetostrictive layer 16 is preferably 0.1 to 10, more preferably 0.5 to 3. When within this range, the warpage displacement V described below can be controlled to be small within a predetermined range.

[0050] The support part 43 of the element body 4 connects the end part in the X-axis direction of the vibration part 41 and the fixed part 42 along the X-axis direction, and in this embodiment, two support parts 43 are formed according to the number of fixed parts 42. This support part 43 is preferably formed in a manner to have a lower rigidity than the vibration part 41 so as not to interfere with the elastic wave vibration of the vibration part 41.

[0051] For example, the width w of the support part 43 in the direction perpendicular to the connection direction (Y-axis direction) is narrower than the width L of the vibration part 41. More specifically, the ratio (w / L) of the width w of the support part 43 to the width L of the vibration part 41 is more preferably 10% to 90%.

[0052] Next, the features of each element constituting the magnetoelectric transducer 1, such as the substrate 6 and the functional film, will be described in detail.

[0053] (Substrate 6) In this embodiment, the substrate 6 may be an insulating material capable of supporting at least the element body 4, but is preferably a single crystal substrate. Examples of single crystal substrates include Si, MgO, strontium titanate (SrTiO3), and lithium niobate (LiNbO3). In this embodiment, it is particularly preferable to use a silicon substrate whose surface is a single crystal Si(100) surface. Note that the single crystal Si(100) surface means that the cubic (100) surface of the silicon substrate is oriented substantially parallel to the thickness direction.

[0054] (Piezoelectric layer 14) The piezoelectric layer 14 is a single thin film extending from one fixed portion 42a to the other fixed portion 42b. As shown in Fig. 1A, the shape of the piezoelectric layer 14 in a plan view matches the shapes of the portions 41 to 43 of the element body 4. The average thickness of the piezoelectric layer 14 is preferably within a range of 0.4 µm to 10 µm, and more preferably 0.4 µm to 2 µm. The variation in thickness of the piezoelectric layer 14 is preferably within ±5%.

[0055] The average thickness t14 of the piezoelectric layer 14 (see FIG. 3A) can be obtained by observing the XZ cross section or YZ cross section with a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM), and analyzing the cross-sectional photograph obtained at that time. At this time, measurements are taken at at least three or more points in the in-plane direction, and the average value is calculated.

[0056] The piezoelectric layer 14 is made of a piezoelectric material and exhibits a piezoelectric effect or an inverse piezoelectric effect. Examples of the piezoelectric material that constitutes the piezoelectric layer 14 include quartz crystal, lithium niobate, aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT: Pb(Zr,Ti)O3), potassium sodium niobate (KNN: (K,Na)NbO3), barium calcium zirconate titanate (BCZT: (Ba,Ca)(Zr,Ti)O3), and the like.

[0057] In this embodiment, among the above piezoelectric materials, it is particularly preferable to use piezoelectric materials having a perovskite structure, such as PZT, KNN, and BCZT. Since piezoelectric materials having a perovskite structure have excellent piezoelectric properties, the performance of the magnetoelectric conversion element 4 is improved by forming the piezoelectric layer 14 from these materials. Note that other elements or compounds may be appropriately added to the above piezoelectric materials forming the piezoelectric layer 14 in order to further improve the piezoelectric properties.

[0058] Moreover, when a piezoelectric material having a perovskite structure is used, the piezoelectric layer 14 is more preferably an epitaxially grown film. Here, epitaxial growth refers to the crystals of the film growing while being aligned in the thickness direction (Z-axis direction) and the planar direction (X-axis and Y-axis direction) in a form that matches the crystal lattice of the base material during film formation. Therefore, in a more preferable embodiment, the crystals of the piezoelectric layer 14 are aligned in all three directions of the X-axis direction, the Y-axis direction, and the Z-axis direction (triaxial orientation) in a high-temperature state during film formation. The more the crystal axes in the piezoelectric layer 14 are aligned to improve the orientation, the higher the Q value of the vibration part 41 tends to be. Furthermore, by making the piezoelectric layer 14 an epitaxially grown film, the vibration part 41 is more likely to vibrate elastically by in-plane stretching vibration.

[0059] Whether or not epitaxial growth has occurred so as to orient along three axes can be confirmed by performing reflection high-energy electron diffraction evaluation (RHEED evaluation) during the thin film formation process. If there is a disturbance in the crystal orientation on the film surface during film formation, the RHEED image will show an extended ring-shaped pattern. On the other hand, if epitaxial growth has occurred as described above, the RHEED image will show a sharp spot-like or streak-like pattern. The above-mentioned RHEED image is observed only at high temperatures during film formation.

[0060] Furthermore, when epitaxially grown, the piezoelectric layer 14 has a crystal structure close to single crystal (not completely single crystal) with almost no crystal grain boundaries at room temperature after film formation. More specifically, the crystal structure of the piezoelectric layer 14 after film formation preferably has multiple crystal phases with three-axis orientation, and preferably has a domain structure including at least three types of domains. When the piezoelectric layer 14 has a domain structure, the piezoelectric properties are further improved, and the piezoelectric responsiveness to vibration is increased.

[0061] When the piezoelectric layer 14 has a domain structure, the specific configuration of the domain structure varies depending on the piezoelectric material used. For example, when the piezoelectric layer 14 is an epitaxially grown film of PZT, it can have at least two crystal phases, tetragonal and rhombohedral. In this case, the tetragonal crystal has a domain in which the c-axis (the longitudinal axis of the rectangular parallelepiped (crystal lattice)) is oriented in the film thickness direction, and a domain in which the c-axis is oriented in the in-plane direction.

[0062] The rhombohedral crystal phase is oriented such that the (100) plane is parallel to the film thickness direction. In other words, when the piezoelectric layer 14 is an epitaxially grown PZT film, it preferably contains a total of three domains: two tetragonal domains and a rhombohedral domain.

[0063] On the other hand, when the piezoelectric layer 14 is an epitaxially grown film of KNN, it is preferable that it has two types of orthorhombic domains and one type of monoclinic domain (three types of domains in total). In the above case, the two types of orthorhombic domains may be a domain (a domain) in which the (001) plane of the orthorhombic crystal is oriented approximately parallel to the film thickness direction, and a domain (c domain) in which the (010) plane of the orthorhombic crystal is oriented approximately parallel to the film thickness direction. In the monoclinic domain, it is preferable that the (100) plane or the (010) plane is approximately parallel to the film thickness direction.

[0064] Furthermore, when the piezoelectric layer 14 is an epitaxially grown film of BCZT, it preferably has two types of tetragonal domains and two types of orthorhombic domains (four types of domains in total).

[0065] Since the above-mentioned multiple domains are adjacent to each other across a common domain boundary, the direction of the crystal axis of each domain may deviate from the film thickness direction or the in-plane direction by a few degrees (specifically, up to about ±3 degrees). Moreover, the above-mentioned multiple domains are equivalent domains oriented in the same direction of the same crystal system, at least in the high temperature state during film formation, and are formed by transitioning to a more stable crystal phase or domain during the process of cooling to room temperature or the usage temperature after film formation.

[0066] The presence of a plurality of domains in a mixed state can be confirmed by analyzing the piezoelectric layer 14 by electron beam diffraction using a STEM or a transmission electron microscope (TEM), or by X-ray diffraction (XRD), or the like.

[0067] (Lower electrode layer 12) The lower electrode layer 12 is a single-layer thin film extending from one fixed portion 42a to the other fixed portion 42b, similar to the piezoelectric layer 14. The lower electrode layer 12 is an electrode for recovering and extracting the charge generated in the piezoelectric layer 14, and one end of the lower electrode layer 12 in the X-axis direction is electrically connected to the extraction electrode 18a. The average thickness of the lower electrode layer 12 is preferably 3 nm to 200 nm.

[0068] The lower electrode layer 12 is made of a conductive material such as a metal or an oxide conductor. In particular, when the piezoelectric layer 14 is an epitaxially grown film, it is preferable that the lower electrode layer 12 is also an epitaxially grown film. In this case, the lower electrode layer 12 is preferably a metal thin film having a face-centered cubic structure such as platinum (Pt), iridium (Ir), or gold (Au), or a conductive oxide thin film such as strontium ruthenate (SrRuO3: hereinafter abbreviated as SRO) or lithium nickel oxide (LiNiO3). Such metal thin films and oxide conductor thin films can be epitaxially grown on a single crystal substrate. When the epitaxially grown film is used, the lower electrode layer 12 preferably has a (001) plane oriented in the film thickness direction (Z-axis direction). Also, in the in-plane direction (X-axis or Y-axis direction), It is preferable that the (100) plane of the piezoelectric layer 14 and the (100) plane of the lower electrode layer 12 are approximately parallel to each other.

[0069] When the lower electrode layer 12 is also an epitaxially grown film, the lower electrode layer 12 may be formed by laminating the above-mentioned metal thin film and the above-mentioned oxide conductive thin film. In this case, it is preferable to laminate a metal thin film on the lower side (i.e., the substrate 6 side) of the lower electrode layer 12, and laminate an oxide conductive thin film on the metal thin film.

[0070] (Magnetostrictive layer 16) 1A, in this embodiment, the magnetostrictive layer 16 is a single-layer thin film laminated on the vibrating part 41, and the magnetostrictive layer 16 is not formed on the fixed part 42 and the support part 43. In this way, the magnetostrictive layer 16 only needs to be laminated on the vibrating part 41, and does not necessarily have to be laminated on the fixed part 42 or the support part 43. However, the magnetostrictive layer 16 may be present on the support part 43 or part of the fixed part 42.

[0071] 1A, the magnetostrictive layer 16 has a generally rectangular shape in plan view. The width of the magnetostrictive layer 16 along the Y-axis direction is generally the same as the width L of the vibration part 41 of the piezoelectric layer 14, but may be smaller than the width of the vibration part 41 of the piezoelectric layer 14. When the width of the magnetostrictive layer 16 along the Y-axis direction is smaller than the width of the vibration part 41 of the piezoelectric layer 14, the durability of the vibration part 41 can be improved.

[0072] The average thickness of the magnetostrictive layer 16 is preferably in the range of 0.1 μm to 5 μm, and more preferably 0.1 μm to 1 μm. The ratio of the average thickness of the magnetostrictive layer 16 to the average thickness of the piezoelectric layer 14 is preferably in the range of 1 / 10 to 10, and more preferably 1 / 10 or more and less than 1. The variation in thickness of the magnetostrictive layer 16 is preferably ±5% or less, similar to the case of the piezoelectric layer 14. The average thickness of the magnetostrictive layer 16 can be measured in the same manner as the piezoelectric layer 14.

[0073] The magnetostrictive layer 16 is made of a ferromagnetic material having magnetostrictive properties. The ferromagnetic material may be a pure metal such as iron (Fe), cobalt (Co), or nickel (Ni), or an alloy containing at least one of the above metal elements (for example, an Fe-Co-based, Fe-Ni-based, Fe-Si-based, Fe-Dy-Tb-based, Fe-Ga-based, or Fe-Si-Al-based alloy), or an oxide magnetic material containing an oxide of the above metal elements. The magnetostrictive layer 16 may be a single film containing the above ferromagnetic material, or may be a multilayer film made of multiple layers, or a laminated film of a ferromagnetic material and an antiferromagnetic material.

[0074] Among the above-mentioned ferromagnetic thin films, the magnetostrictive layer 16 is preferably a soft magnetic highly magnetostrictive film. In this embodiment, the soft magnetic highly magnetostrictive film means a film made of a soft magnetic material having a low coercive force HC and a low threshold magnetic field HTH (preferably HC less than 2500 A / m and HTH less than 500 A / m) and a saturation magnetostriction λMAX of 5 ppm or more.

[0075] Specifically, examples of the magnetostrictive layer 16 of the soft magnetic highly magnetostrictive film include alloy films mainly composed of Fe-Si-B alloys, Fe-Cr-Si-B alloys, Fe-Ni-Mo-B alloys, Fe-Co-B alloys, Fe-Ni-B alloys, Fe-Al-Si-B alloys, Fe-Co-Si-B alloys, etc. Many ferromagnetic materials exhibit the magnetostrictive effect, but when the magnetostrictive layer 16 is made of the soft magnetic highly magnetostrictive film described above, it is possible to generate elastic wave vibrations with a larger amplitude.

[0076] The crystal structure of the magnetostrictive layer 16 may be amorphous or polycrystalline, but when the magnetostrictive layer 16 is a soft magnetic highly magnetostrictive film, it is preferable that the magnetostrictive layer 16 has a mixture of an amorphous phase and a crystalline phase. When the ferromagnetic thin film 16 has a mixture of an amorphous phase and a crystalline phase, the responsiveness to external energy can be improved and the magnetostriction rate of change (dλ / dH) can be increased.

[0077] In addition, alloys containing Fe are usually crystallized in a body-centered cubic structure. In this embodiment, when the magnetostrictive layer 16 has an amorphous phase and a crystalline phase, it is preferable that most of the crystalline phase contained in the magnetostrictive layer 16 has a face-centered cubic structure. When the magnetostrictive layer 16 has the above-mentioned crystalline structure, the energy conversion efficiency of the magnetoelectric conversion element 1 can be further improved.

[0078] The crystal structure of the magnetostrictive layer 16 can be confirmed by analysis using electron beam diffraction in a TEM, XRD, etc., in the same way as the piezoelectric layer 14. For example, if the magnetostrictive layer 16 is composed only of an amorphous phase, only a broad and wide halo pattern will be detected when θ-2θ measurement is performed using XRD with Cu-Kα radiation.

[0079] On the other hand, when the magnetostrictive layer 16 is composed of only the crystalline phase, only a very sharp reflection peak with a narrow half-width is detected.When the magnetostrictive layer 16 has a mixture of an amorphous phase and a crystalline phase, a reflection peak having both a broad halo portion indicating the presence of the amorphous phase and a sharp peak portion indicating the presence of the crystalline phase is detected.

[0080] The ratio of the amorphous phase to the crystalline phase can be confirmed by performing profile fitting on the reflection peak obtained by electron beam diffraction or XRD and calculating the crystallinity. Specifically, fitting is performed on the crystalline phase portion (peak portion) and the amorphous phase portion (halo portion), and the integrated intensity (area) of each portion is measured. The crystallinity (%) is expressed as the ratio (Ic / (Ic+Ia)×100) of the integrated intensity (Ic) of the crystalline phase portion to the sum (i.e., the total peak area) of the integrated intensity (Ic) of the crystalline phase portion. In this embodiment, when the magnetostrictive layer 16 has a mixture of the amorphous phase and the crystalline phase, the crystallinity is preferably 1% to 50%, and more preferably 5% to 20%.

[0081] As described above, the magnetostrictive layer 16 receives external energy such as electromagnetic waves and AC magnetic fields and contributes to the generation of elastic wave vibrations. In the case of the magnetoelectric transducer 1 shown in Fig. 1A and Fig. 2, the magnetostrictive layer 16 also functions as an electrode for recovering and extracting the electric charge generated in the piezoelectric layer 14.

[0082] (Top electrode layer 13) In addition, an upper electrode layer 13 is formed between the piezoelectric layer 14 and the magnetostrictive layer 16. By forming the upper electrode layer 13, the charge generated in the piezoelectric layer 14 can be extracted more efficiently. The upper electrode layer 13 can have the same configuration (thickness and material) as the lower electrode layer 12. However, the upper electrode layer 13 is not necessarily provided, and the magnetostrictive layer 16 may be formed directly on the piezoelectric layer 14.

[0083] When the piezoelectric layer 14 is an epitaxially grown film, it is preferable that the lower electrode layer 12 is also an epitaxially grown film, but it is not necessary to epitaxially grow the upper electrode layer 13. On the other hand, when an amorphous phase and a crystalline phase are mixed in the magnetostrictive layer 16, it is preferable that the crystal structure of the upper electrode layer is a face-centered cubic polycrystalline structure or a crystal structure in which an amorphous phase and a face-centered cubic crystalline phase are mixed.

[0084] (Takeout electrode 18) The extraction electrode 18 is not particularly limited in material or size as long as it is conductive. For example, the extraction electrode 18 may contain a conductive metal such as Pt, Ag, Cu, Au, or Al, and may contain a glass component in addition to the conductive metal. Although the extraction electrode 18 is a thin-film electrode in Fig. 1A and Fig. 2, it may be a via-hole electrode.

[0085] (Insulating layer 20) There are no particular limitations on the material or thickness of the insulating layer 20 as long as it has electrical insulation properties. For example, the insulating layer 20 can be made of SiO2, Al2O3, polyimide, or the like.

[0086] 2, in this embodiment, the insulating layer 20 covers the upper portions of both ends in the X-axis direction of the magnetostrictive layer 16, the upper portions of the support portions 43, the fixed portions 42a and 42b, and the substrate 6. In addition, in order to connect the extraction electrode 18a and the lower electrode layer 12, the insulating layer 20 does not cover the substrate 6 at the connection portion 44.

[0087] (Other functional membranes) Although not shown in Figures 1A and 2, the element body 4 may include other functional films in addition to the lower electrode layer 12, upper electrode layer 13, piezoelectric layer 14, and magnetostrictive layer 16 described above.

[0088] For example, a buffer layer for controlling the crystallinity of the lower electrode layer 12 and the crystallinity of the piezoelectric layer 14 may be formed in the bottom layer of the element body 4 in the Z-axis direction (i.e., below the lower electrode layer 12). In particular, when the piezoelectric layer 14 is an epitaxially grown film, it is preferable to form a buffer layer. The buffer layer is preferably mainly composed of zirconium oxide (ZrO2) or zirconium oxide stabilized with rare earth elements (including Sc and Y) (stabilized zirconia).

[0089] This buffer layer is also preferably a film that has been epitaxially grown with crystals aligned in the thickness direction (Z-axis direction) and in-plane directions (X-axis and Y-axis directions) in a manner that matches the crystal lattice of the deposition substrate. As with the lower electrode layer 12, the buffer layer is preferably oriented with its (001) plane in the thickness direction. More preferably, in the in-plane direction (X-axis or Y-axis direction), the (100) plane of the piezoelectric layer 14, the (100) plane of the lower electrode layer 12, and the (100) plane of the buffer layer are approximately parallel to each other.

[0090] Specifically, when the buffer layer is ZrO2, the lower electrode layer 12 is Pt, and the piezoelectric layer 14 is PZT, the preferred orientation relationship of each layer is ZrO2(001) / / Pt(001) / / PZT(001) in the film thickness direction and ZrO2(100) / / Pt(100) / / PZT(100) in the in-plane direction.

[0091] The presence of the buffer layer facilitates epitaxial growth of the lower electrode layer 12 and the piezoelectric layer 14, improving the crystallinity of these layers 12, 14. The buffer layer also functions as an etching stopper layer when forming the opening 61 by etching. When the buffer layer is formed, its average thickness is preferably 5 nm to 100 nm.

[0092] In addition, an upper electrode layer may be formed between the piezoelectric layer 14 and the magnetostrictive layer 16. By forming the upper electrode layer, the charge generated in the piezoelectric layer 14 can be extracted more efficiently. The upper electrode layer may have the same configuration (thickness and material) as the lower electrode layer 12.

[0093] When the piezoelectric layer 14 is an epitaxially grown film, it is preferable that the lower electrode layer 12 is also an epitaxially grown film, but the upper electrode layer does not necessarily have to be epitaxially grown. On the other hand, when the magnetostrictive layer 16 has a mixture of an amorphous phase and a crystalline phase, it is preferable that the crystal structure of the upper electrode layer is a face-centered cubic polycrystalline structure or a crystal structure in which an amorphous phase and a face-centered cubic crystalline phase are mixed.

[0094] Furthermore, a protective layer may be formed on the outermost layer of the element body 4 except for the lower surface. Examples of the protective layer include a protective layer containing a metal such as Ti, Ta, or Pt, and an insulating protective layer made of SiO2, Al2O3, polyimide, etc., and both a metallic protective layer and an insulating protective layer may be formed. The average thickness of the protective layer is not particularly limited and can be, for example, 5 nm to 50 nm.

[0095] 1A and 2, the magnetoelectric conversion element 1 has the above-mentioned internal structure (the configuration of each functional film) and the above-mentioned morphological characteristics (shape and dimensions of each part of the element body 4, etc.), so that the vibration part 41 becomes a bulk acoustic wave oscillator with in-plane stretching vibration. In particular, when the internal structure and morphological characteristics satisfy the above-mentioned preferable conditions, the vibration mode of the vibration part 41 tends to be an expansion vibration.

[0096] In this embodiment, the vibration part 41 has a plate-like shape along a plane including the X-axis and the Y-axis, and it is preferable that this plate-like vibration part 41 is as flat as possible. For example, it is preferable that the surface roughness of the upper and lower surfaces of the vibration part 41 is 1 μm or less in terms of arithmetic mean roughness (Ra) or root mean square roughness (Rq: old RMS). Alternatively, it is preferable that the surface roughness (Ra or Rq) of the upper surface and the surface roughness (Ra or Rq) of the lower surface of the vibration part 41 are 1 / 10 or less compared to the wavelength of the elastic wave vibration of the vibration part 41.

[0097] The flatness may be measured by contact or non-contact. For example, the flatness can be measured by a CNC image measuring device or a laser microscope. The surface roughness Ra and Rq may also be measured by contact or non-contact, and may be measured in accordance with JIS-B0601.

[0098] In the element body 4 of this embodiment, warping may occur, for example, as shown in Fig. 3A due to differences in residual stress occurring in each stacked layer. Note that the warping of the element body 4 (vibration part 41) shown in Fig. 3A is merely one example, and the warping of the element body 4 may be wavy, both edges of the element body 4 along the Y axis may be warped upward in the Z axis direction, or the center of the element body 4 in the X axis direction may be warped downward in the Z axis direction.

[0099] Here, the warpage displacement V refers to the difference (maximum displacement difference) between the highest and lowest points of displacement along the Z axis in the vibrating part 43. The warpage displacement V can be found, for example, by using a 3D laser microscope to measure the maximum value of height variation from the surface of the substrate 6 as a reference plane.

[0100] In this embodiment, as shown in FIG. 5A, the relationship between the width W of the support portion 43, the width L of the vibration portion 41, and the warpage displacement V is 2V / (Lw)<0.6, preferably 0.001≦2V / (Lw)≦0.2. In such a case, the magnetoelectric conversion efficiency can be increased and the output can be improved. The width w of the support portion 43 is preferably 5 μm or more and 0.5 times (1 / 2) or less of the width L of the vibration portion 41. In this embodiment, the warpage displacement V is preferably 1 / 1000 or more of the width L of the vibration portion 41. The width L of the vibration portion 41 is preferably 30 μm or more and 10 mm or less, and more preferably 75 μm or more, 200 μm, or 300 μm or more.

[0101] The width W of the support part 43 and the width L of the vibration part 41 can be obtained by measurement using, for example, a length measuring microscope. The width W of the support part 43 and the width L of the vibration part 41 are approximately the same as designed. The warpage displacement V of the vibration part 41 can be controlled by the thickness or film formation conditions of the piezoelectric layer 14 and magnetostrictive layer 16 that constitute the vibration part 41, or the formation of an additional functional film (for example, the thickness of a surface protection film).

[0102] Among these, in order to control the warpage displacement V of the vibrating part 41, it is preferable to adjust the deposition conditions of the piezoelectric layer 14 and the magnetostrictive layer 16 constituting the vibrating part 41. By doing so, it is possible to easily control only the warpage without changing the natural frequency of the vibrating part 41. The deposition conditions to be adjusted at this time include the degree of vacuum during deposition, the gas partial pressure, the gas composition, the substrate temperature, the deposition speed, etc.

[0103] The additional functional film may be an insulating film such as a silicon oxide film, a silicon nitride film, or a polyimide film, or a protective film having electrical conductivity. By forming the additional functional film, the warpage displacement V of the vibrating part 41 can be suppressed. The thickness of the additional functional film is preferably smaller than the thickness t14 of the piezoelectric layer 14 shown in FIG. 3A, and is preferably about 1 / 5 or less of the thickness t14. The thicknesses or film formation conditions of the piezoelectric layer 14 and the magnetostrictive layer 16 are determined so that the warpage displacement V of the vibrating part 41 falls within a predetermined range.

[0104] After forming the functional film, the warpage can be adjusted by trimming the functional film (removing all or part of the film to make it thinner) using reactive dry etching, ion milling, etc. In this case, trimming can be performed all at once on the entire wafer, or trimming conditions can be changed for each individual element or region within the wafer.

[0105] In this embodiment, the configuration of the support part 43 may be modified as shown in Fig. 4A and Fig. 4B. For example, as shown in Fig. 4A, the support part 43 may be provided on one side of the vibration part 41 instead of in the center along the Y axis. Also, as shown in Fig. 4B, the support part 43 may be bent along the Y axis instead of being linear along the X axis. In these modified examples, the width w of the support part 43 refers to the length of the portion where the vibration part 41 and the support part 43 intersect.

[0106] In addition, as shown in Figs. 4C to 4G, in this embodiment, the configuration of the vibration section 41 may be modified. For example, as shown in Fig. 4C, the vibration section 41 may be a parallelogram, and as shown in Fig. 4D, the vibration section 41 may be a circle. As shown in Fig. 4E, the vibration section 41 may be a trapezoid. As shown in Fig. 4F, the vibration section 41 may be an ellipse. As shown in Fig. 4G, the vibration section 41 may be a rectangle or another polygon. The width L of the vibration section 41 refers to the maximum length of the vibration section 41 in the Y-axis direction.

[0107] 4A to 4G, the insulating layer 20, the piezoelectric layer 14, and the extraction electrode 18 are omitted in order to explain the vibration section 41 and the support section 43. The shape of the substrate 6 in a plan view is not particularly limited, and may be a parallelogram as shown in Fig. 4C, a circle as shown in Fig. 4D, a trapezoid as shown in Fig. 4E, an ellipse as shown in Fig. 4F, a rectangle as shown in Fig. 4G, or another polygon.

[0108] (Manufacturing method of magnetoelectric conversion element 1) An example of a method for manufacturing the magnetoelectric transducer 1 shown in FIG. 1A and FIG. 2 will now be described.

[0109] The magnetoelectric conversion element 1 of this embodiment can be manufactured using microfabrication technology such as that used in semiconductor manufacturing processes. First, the lower electrode layer 12, the piezoelectric layer 14, the upper electrode layer 13, and the magnetostrictive layer 16 are formed on a film-forming substrate by various thin film formation methods. As the thin film formation method, a deposition method, a sputtering method, a sol-gel method, a CDV method, a PLD method, etc. can be applied, and the sputtering method is particularly preferable. By forming the films by the sputtering method, the adhesion between each functional film can be increased. As a result, the occurrence of defects such as peeling of the film can be suppressed, and the distortion of the magnetostrictive layer 16 can be efficiently transmitted to the piezoelectric layer 14, improving the energy conversion efficiency.

[0110] The deposition conditions for each of the layers 12, 13, 14, and 16 may be known conditions and are not particularly limited. However, when the piezoelectric layer 14 is an epitaxially grown film, the composition of the sputtering target, the temperature of the deposition substrate, the deposition rate, the gas composition, the degree of vacuum, the distance between the substrate and the target, etc. are appropriately controlled. In order for the piezoelectric layer 14 to have a domain structure, it is necessary to control the composition of the sputtering target, the temperature of the deposition substrate, or the stress of the upper electrode layer 13 and the magnetostrictive layer 16 laminated on the piezoelectric layer 14.

[0111] For example, the composition of the sputtering target is selected according to the quality of the piezoelectric material, so that a plurality of domains or crystal phases are easily formed, and the amount of elements with high vapor pressure is preferably increased by 20 to 120% from the stoichiometric composition. Taking PZT as an example, the atomic ratio represented by Pb / (Zr+Ti) is preferably 1.2 to 2.2, and the atomic ratio represented by Zr / (Zr+Ti) is preferably controlled to be 1 to 1.5. The temperature of the film-forming substrate is preferably controlled to be 550 to 650°C. Furthermore, the stress of the magnetostrictive layer 16 is preferably a compressive stress. In addition, after epitaxial growth of the piezoelectric layer 14, annealing at a temperature of 300°C to 500°C in an oxidizing atmosphere is also effective in obtaining the above-mentioned domain structure.

[0112] When epitaxially growing the piezoelectric layer 14, it is preferable to use a single crystal silicon substrate (wafer) as the film-forming substrate, as described above. It is also preferable to form the lower electrode layer 12 by epitaxial growth on the silicon substrate. A known method may be used to epitaxially grow the lower electrode layer 12.

[0113] In addition, when the magnetostrictive layer 16 is to have a mixture of an amorphous phase and a crystalline phase, the film formation conditions during sputtering, such as the degree of vacuum, the temperature of the film formation substrate, the gas composition, the gas pressure, the power, and the distance between the target and the film formation substrate, are appropriately controlled. For example, the gas pressure is preferably 0.01 to 0.1 Pa. The temperature of the film formation substrate is preferably 20 to 200° C., and the distance between the target and the film formation substrate is preferably 100 mm or more so that the substrate temperature does not rise during film formation.

[0114] The film-formation substrate on which the functional film is formed as described above is patterned by various etching methods such as photoetching, laser dry etching, etc. In this patterning process, a laminated pattern shown in Figures 1A and 2 is formed on the film-formation substrate.

[0115] For example, when patterning by photoetching, a photoresist agent is first applied onto the magnetostrictive layer 16 by various coating methods such as spin coating. Then, a mask having a desired pattern shape is placed on the applied photoresist agent, and ultraviolet light is irradiated to expose only the parts of the magnetostrictive layer 16 that are to be removed (i.e., the parts of the magnetostrictive layer 16 that are to remain are masked).

[0116] Thereafter, the photoresist film is developed and the magnetostrictive layer 16 is etched, and the photoresist film and the magnetostrictive layer 16 corresponding to the exposed portion are removed to form the outer periphery of the magnetostrictive layer 16 shown in Fig. 1A. The photoresist remaining on the magnetostrictive layer 16 can be removed by surface treatment using oxygen plasma or a specific chemical. The photoresist remaining on the magnetostrictive layer 16 may be used as a protective layer without being removed.

[0117] After forming the pattern of the magnetostrictive layer 16 by the above procedure, the upper electrode layer 13, the piezoelectric layer 14, and the lower electrode layer 12 are patterned by the same method as above. Note that the mask used when patterning the piezoelectric layer 14 is preferably adjusted so that the dimensions per pattern are larger than those of the mask used when patterning the magnetostrictive layer 16.

[0118] Furthermore, when the piezoelectric layer 14 is epitaxially grown, it is preferable to control the extending direction (patterning shape) of the element body 4 in accordance with a predetermined crystal orientation of the piezoelectric layer 14. Specifically, in the above patterning process, the longitudinal direction (X-axis direction) or the lateral direction (Y-axis direction) of the element body 4 is aligned with the direction of the piezoelectric layer 16. <110> orientation, and the single crystal silicon substrate <110> The position of the mask is adjusted so as to be approximately parallel to the direction.

[0119] As described above, by controlling the extending direction (patterning shape) of the element body 4, the durability of the magnetoelectric conversion element 1 can be improved. In addition, the polarization direction of the piezoelectric layer 14 is more likely to be oriented in the film thickness direction, improving the piezoelectric characteristics of the piezoelectric layer 14. The mask position may be adjusted based on an orientation flat or notch formed on the single crystal silicon substrate. In other words, an orientation flat or notch is formed in advance on the single crystal silicon substrate before film formation so that the crystal orientation of the substrate can be determined. In addition, in this embodiment, parentheses represent Miller indices (planes), and triangular brackets and square brackets represent crystal orientations (directions).

[0120] After carrying out the patterning process according to the above procedure, the extraction electrode 18 and the insulating layer 20 are formed.

[0121] Then, a part of the film formation substrate is removed by etching to form the opening 61 shown in FIG. 1A and FIG. 2. In this case, the part remaining after etching becomes the substrate 6. The film formation substrate can be etched by dry etching such as Deep-RIE method, anisotropic wet etching, or the like. The film formation substrate may be entirely removed by the above-mentioned etching. In this case, the element body 4 may be attached and fixed to the substrate 6, which is a separate member, after the film formation substrate is removed.

[0122] Through the above steps, the magnetoelectric transducer 1 shown in Fig. 1A and Fig. 2 is obtained. In the above manufacturing steps, the patterning method by etching has been described, but the patterning process of each layer may be performed by lift-off.

[0123] In the case of the lift-off method, for example, before forming the magnetostrictive layer 16, a resist film is formed on the piezoelectric layer 14 so as to cover areas other than the area where the magnetostrictive layer 16 is to be formed. The magnetostrictive layer 16 is formed by sputtering a ferromagnetic component onto the piezoelectric layer 14 on which the resist film has been formed, and then peeling off the resist film (lift-off).

[0124] That is, in the case of the lift-off method, the ferromagnetic material components remaining in the areas where the resist film was not formed after lift-off become the magnetostrictive layer 16. The outer periphery of the magnetostrictive layer 16 is formed by removing the ferromagnetic material components formed on the resist film by lift-off.

[0125] (Use of magnetoelectric conversion element) The magnetoelectric conversion element 1 of this embodiment is a type of MEMS element (Micro Electro Mechanical Systems) fabricated by microfabrication technology, and is much easier to miniaturize than conventional receiving devices (such as electromagnetic induction coils and magnetic field resonance coils). In this embodiment, by adjusting the width L of the vibration part 41 of the element body 4, the width w of the support part 43, and the warpage displacement V of the vibration part 41, the magnetoelectric conversion element 1 can generate power with high conversion efficiency even if it is small.

[0126] Such a small magnetoelectric conversion element 1 with high energy conversion efficiency can be suitably used as a power supply source for electronic devices by being incorporated into a power supply device. (Summary of this embodiment) In the magnetoelectric conversion element 1 according to this embodiment, the substrate 6 has an opening 61, and the element body 4 has a vibration part 41 which is an elastic wave vibrator, a fixed part 42 which faces and is connected to the substrate 6, and a support part which connects the fixed part 42 and the vibration part 41. The vibration part 41 is laminated with a lower electrode layer 12, an upper electrode layer 13, a piezoelectric layer 14, and a magnetostrictive layer 16. Such a configuration of the vibration part 41 further improves the energy conversion efficiency of the magnetoelectric conversion element 1. Moreover, the vibrating part 41 is disposed opposite the opening 61 of the substrate 6. By the magnetoelectric conversion element 1 having the above-mentioned configuration, the vibrating part 41 can generate elastic wave vibrations of larger amplitude, and the energy conversion efficiency of the magnetoelectric conversion element 1 can be further improved.

[0127] In this embodiment, the element body 4 is suspended across the opening 61 along the X-axis direction. By configuring the magnetoelectric conversion element 1 as described above, the vibration part 4 can generate elastic wave vibrations with larger amplitude, and the energy conversion efficiency of the magnetoelectric conversion element 1 is further improved.

[0128] Furthermore, the outer peripheral edge of the element body 4, excluding the portion connected to the substrate 6, is not in contact with the inner peripheral edge in the width direction of the opening 61. A gap 46 exists between the outer peripheral edge of the element body 4, excluding the portion connected to the substrate 6, and the inner peripheral edge in the width direction of the opening 61. With the above-mentioned configuration, the magnetoelectric conversion element of the present invention further improves the energy conversion efficiency.

[0129] In this embodiment, the width w of the support portion 43 in the direction perpendicular to the connection direction (Y-axis direction) is set smaller than the width L of the vibration portion 41. Setting the width w of the support portion 43 in this manner can further reduce the rigidity of the support portion 43. As a result, the vibration portion 41 can generate elastic wave vibrations with larger amplitude, and the energy conversion efficiency of the magneto-electric conversion element 1 can be further improved.

[0130] In this embodiment, the width w of the vibration part 41 in the direction perpendicular to the connection direction is 1 / 100 or less of the wavelength of the electromagnetic wave EW having the same frequency as the natural frequency f0. By setting the size of the vibration part 41 within the above condition range, the vibration part 41 can generate elastic wave vibrations of a larger amplitude, and the energy conversion efficiency of the magneto-electric conversion element 1 can be further improved. In this embodiment, the maximum width of the vibration part 41 is the width H in the connection direction with the substrate 6.

[0131] The magnetoelectric transducer 1 of the present embodiment can be suitably used by being incorporated into a power supply device. For example, if the magnetoelectric transducer 1 is incorporated as an antenna for an electronic device, it can sense weak magnetism and output it as electricity.

[0132] The magnetoelectric conversion element 1 of this embodiment can convert not only magnetism to electricity, but also electricity to magnetism. That is, when a voltage is applied to the piezoelectric layer 14 of the vibration part 41, the piezoelectric effect of the piezoelectric layer 14 causes distortion in the piezoelectric layer 14. Elastic vibration occurs in response to the distortion. When this elastic vibration occurs, the magnetostrictive layer 16 generates magnetism due to the magnetostrictive effect. That is, in the magnetoelectric conversion element 1 of this embodiment, the elastic wave vibration of the vibration part 41 can convert electric energy into electromagnetic waves or an AC magnetic field.

[0133] Second embodiment In this embodiment, a modified example of the magnetoelectric transducer 1 will be described with reference to Fig. 1B. Note that a description of the contents common to the above-mentioned first embodiment will be omitted.

[0134] 1B, the element body 4 of this embodiment has a vibration part 41 located approximately in the center in the X-axis direction, and two fixed parts 42a, 42b located at both ends in the X-axis direction. In this embodiment, unlike the first embodiment, the vibration part 41 of the element body 4 is fixed to the substrate 6 by the fixed parts 42a, 42b without a support part.

[0135] The edges of vibrating part 41 parallel to the X-axis are not in contact with the inner peripheral edge of opening 61. That is, in a plan view from the Z-axis direction, vibrating part 41 is disposed in opening 61 of substrate 6, and the front surface (upper surface) and back surface (lower surface) of vibrating part 41 are exposed to a space in which it can vibrate freely, and the edges of vibrating part 41 in the width direction (direction along the Y-axis) are also exposed to the space within opening 61 in which it can vibrate freely.

[0136] In other words, the edge of the vibration part 41 in the Y-axis direction and the inner peripheral edge of the opening 61 are not in contact with each other, and a gap 46 exists between them. Unlike the first embodiment, in this embodiment, both ends of the vibration part 41 in the X-axis direction are fixed to the substrate 6 without being interposed between supporting parts.

[0137] In the element body 4 of this embodiment, warpage V as shown in Fig. 3B may occur due to differences in residual stress occurring in each laminated layer. In this embodiment, the warpage displacement V also refers to the maximum displacement difference in the Z-axis direction between the highest point and the lowest point in the vibrating part 43, as shown in Fig. 3B. Note that the warpage of the element body 4 shown in Fig. 3B is merely an example, and the warpage of the element body 4 may be wavy, both edges of the element body 4 along the Y-axis may be warped upward in the Z-axis direction, or the center of the element body 4 in the X-axis direction may be warped downward in the Z-axis direction.

[0138] In this embodiment, as shown in Fig. 5B, when the relationship between the width L of the vibrating part 41 and the warpage displacement V satisfies 2V / L<0.2, preferably when 2V / L<0.2 is satisfied, the output can be increased. The width L of the vibrating part 41 is preferably 30 µm or more and 10 mm or less, and more preferably 50 µm or more, 100 µm or more, or 200 µm or more. Also, in this embodiment, the warpage displacement V is preferably 1 / 1000 or more of the width L of the vibrating part 41.

[0139] Third embodiment In this embodiment, a case where the magnetoelectric conversion element 1 according to the above-mentioned embodiment is used as a power generating element will be described in detail. Note that the description of the contents common to the first and second embodiments will be omitted.

[0140] In the magnetoelectric conversion element 1 as a power generating element, the Q value (no unit) of the vibration part 41 is preferably 100 or more, more preferably 500 or more, and more preferably 1000 or more. The Q value is a measure representing the sharpness of a peak in the frequency characteristics.

[0141] Here, the frequency characteristics of the vibrating part 41 will be described with reference to Fig. 6. In the graph shown in Fig. 6, the horizontal axis represents the frequency of the external energy supplied from the outside, and the vertical axis represents the output voltage generated in the vibrating part 41. As described above, at the natural frequency f0, the output voltage is maximum (maximum output V0), and the natural frequency f0 is the peak top. If the frequency at which an output of 1 / √2 times the maximum output V0 (V0 x 1 / √2) is obtained on the high frequency side is f1, and the frequency at which the output is 1 / √2 times the maximum output V0 on the low frequency side is f2, the Q value is expressed by the following formula. Q = f0 / (f1-f2)

[0142] In resonators expected to be applied to wearable terminals, the Q value is generally set low so that a wide signal can be received. In contrast, in the power generating element 1 of this embodiment, the Q value of the vibration part 41 is set high, at 100 or more, making it possible to generate elastic wave vibrations of a larger amplitude, and improving the energy conversion efficiency. The higher the Q value of the vibration part 41, the more preferable it is, and the upper limit of the Q value is not particularly limited, but can be set to, for example, 50,000 or less, and preferably 10,000 or less.

[0143] In addition, in the frequency characteristic of the vibration part 41 shown in FIG. 6, a frequency shifted from the natural frequency f0 by (1 / 100)×f0 to the high frequency side is defined as fa (i.e., fa=f0+(1 / 100)×f0), a frequency shifted from the natural frequency f0 by (1 / 100)×f0 to the low frequency side is defined as fb (i.e., fb=f0-(1 / 100)×f0), and outputs at the frequencies fa and fb are defined as Va and Vb, respectively. In this case, it is preferable to design the vibration part 41 so that the maximum output V0 is at least twice the output Va or the output Vb (i.e., V0>2Va, V0>2Vb). Since the vibration part 41 has a frequency characteristic that satisfies the above conditions, the power generation element of this embodiment can obtain a larger power and the energy conversion efficiency is further improved.

[0144] Furthermore, in this embodiment, it is preferable that the vibration unit 41 is a bulk acoustic wave vibrator that vibrates with bulk acoustic waves (BAW: Bulk Acoustic Wave) rather than surface acoustic waves (SAW: Surface Acoustic Wave) or the like. A surface acoustic wave vibrator utilizes waves (vibrations) that propagate to the surface of an object, whereas a bulk acoustic wave vibrator utilizes the vibration of the object itself, not the surface. In the power generation element of this embodiment, by using a bulk acoustic wave vibrator for the vibration unit 41, a larger charge can be generated, and the energy conversion efficiency is further improved.

[0145] Furthermore, it is preferable that the vibration mode of the elastic wave vibration generated in the vibration part 41 is an in-plane stretching vibration rather than an out-of-plane vibration. Here, out-of-plane vibration means that the vibrator vibrates in a dynamic state that does not involve volume change such as rotation or bending. In the case of a vibrator that vibrates out-of-plane (especially a vibrator that vibrates bending), the natural frequency f0 of the vibrator tends to be a low frequency of 100 kHz or less. On the other hand, in-plane stretching vibration means that the vibrator vibrates by stretching and contracting along the XY plane or a plane including the Z axis.

[0146] In this embodiment, the in-plane stretching vibration that stretches along the XY plane is called the spreading vibration, and the in-plane stretching vibration that stretches along the plane including the Z axis is called the thickness-extension vibration. In a vibrator that performs in-plane stretching vibration, the natural frequency f0 tends to be in a higher frequency band than a vibrator that performs out-of-plane vibration, and between the spreading vibration and the thickness-extension vibration, the natural frequency f0 of the thickness-extension vibration tends to be in a higher frequency band.

[0147] In the power generation element of this embodiment, the vibration section 41 is a bulk acoustic wave oscillator that vibrates with in-plane stretching vibration, so that a larger charge can be generated, and the energy conversion efficiency is further improved.

[0148] The natural frequency f0, Q value, frequency characteristics, and vibration mode of the vibrating part 41 as described above can be measured using an impedance analyzer. The vibration mode of the vibrating part 41 is determined by the material of the functional film (piezoelectric layer 14, magnetostrictive layer 16, etc.), the thickness of the functional film, the crystal orientation of the functional film, the shape of the vibrating part 41, and the dimensions of each part of the element body 4 (particularly the dimensions of the vibrating part 41 and the support part 43). The natural frequency f0, Q value, and frequency characteristics of the vibrating part 41 are determined by the structure of each part of the element body 4, the configuration of the functional film, and the vibration mode of the vibrating part 41, just like the vibration mode.

[0149] Fourth embodiment In the fourth embodiment, a power generating element in which the vibration portion 41 is a bulk acoustic wave vibrator that vibrates with in-plane stretching vibration will be described as an example. Note that in the fourth embodiment, the description of the contents common to the first to third embodiments will be omitted.

[0150] In this embodiment, the element 1 as a power generating element can be incorporated into a power supply device and suitably used as a power supply source for electronic devices. Here, as an application example of the element 1, a contactless power supply system 300 shown in FIG. 7 will be briefly described.

[0151] 7, the contactless power supply system 300 includes a transmitting antenna 250, an electronic device 200, and a power supply device 100 mounted inside the electronic device 200. The transmitting antenna 250 is installed at a location separated from the electronic device 200, and supplies external energy E, such as electromagnetic waves or an AC magnetic field, to the electronic device 200 in a contactless manner. Note that the transmitting antenna 250 may be, for example, a dipole antenna, a monopole antenna, a loop antenna, a coil antenna, a rectenna, or the like, and is not particularly limited.

[0152] On the other hand, the power supply device 100, which is the energy receiving side, is configured by connecting and integrating a power management IC (PMIC) 110 equipped with a rectifier circuit and the like, and a capacitor 120 to an element 1. When the element 1 of the power supply device 100 receives external energy E supplied from a transmitting antenna 250, inside the element 1, an elastic wave vibration is induced in the vibration part 41 by the external energy E, and electric power is generated in response to this elastic wave vibration.

[0153] It is preferable that the frequency F of the external energy E supplied from the transmitting antenna is substantially the same as the natural frequency f0 of the vibration part 41 of the element 1. "Substantially the same" means that the deviation FG between the frequency F and the natural frequency f0, expressed by the following formula, is 1% or less. FG = |F-f0| / f0 × 100(%)

[0154] The power generated by the power generating element 1 is sent to the capacitor 120 via the PMIC 110 and stored in the capacitor 120. When the electronic device 200 consumes power, the power stored in the capacitor 120 is sent to each component 210 of the electronic device 200 via the PMIC 110. Note that, for example, in the case where the electronic device 200 is an outer-ear-mounted canal-type earphone, the components 210 shown in Fig. 7 include a piezoelectric speaker, a piezoelectric microphone, a pressure sensor, an audio IC including an amplifier, a storage device, etc.

[0155] In this way, in the contactless power supply system 300, the electromagnetic waves or AC magnetic fields supplied from the transmitting antenna 250 are received by the power supply device 100 and converted into electric energy. The converted electric energy is then used to drive the electronic device 200. In a conventionally known power supply system using an electromagnetic induction method, although contactless power supply is possible, it is necessary to place the electronic device on the power receiving side close to the power transmitting device and stationary.

[0156] On the other hand, in the case of the contactless power supply system 300 shown in FIG. 7, power can be transmitted and received even when the transmitting antenna 250 and the electronic device 200 are separated by a distance of up to about 10 m, and power can be transmitted and received even when the electronic device 200 is not placed stationary.

[0157] Moreover, the above-mentioned contactless power supply system 300 can be applied to various electronic devices, and the type of electronic device 200 to which the power generating element 1 can be applied is not particularly limited. As described above, the power generating element 1 of the second embodiment is small and highly efficient, and therefore is particularly effective when applied to small electronic devices and electronic devices embedded in the body. Examples of such electronic devices include hearable devices such as earphones and hearing aids, smart watches, smart glasses, smart contact lenses, wearable thermometers, wearable pulse wave sensors, and other wearable terminals, as well as artificial cochleas and cardiac pacemakers attached to the human body, electrical stimulation devices for muscles and the brain, neuro-RFID, and microrobots.

[0158] Fifth embodiment In this embodiment, an element 1 in which the vibrating portion 41 is a bulk acoustic wave vibrator that vibrates in an in-plane stretching vibration is illustrated, and a detailed configuration thereof is described. Note that, in this embodiment, the description of the same contents as those in the first to fourth embodiments described above will be omitted.

[0159] 8, a power generating element 1a, which is a type of magnetoelectric conversion element, is an array element having multiple element bodies 4. A substrate 6a of the power generating element 1a has multiple openings 61 formed on the same plane, and an element body 4 is formed in each of the multiple openings 61.

[0160] The element bodies 4 are arranged in both the X-axis direction and the Y-axis direction in the XY plane of the substrate 6a. More specifically, in the power generating element 1a shown in Fig. 8, the element bodies 4 are arranged in five rows along the X-axis direction and eight rows along the Y-axis direction, so that a total of 40 element bodies 4 are formed.

[0161] However, there are no particular limitations on the number and arrangement of the element bodies 4. The number of element bodies 4 arranged on one substrate can be, for example, 1 to 500. The element bodies 4 may also be arranged in only one axial direction (X-axis direction or Y-axis direction) to form a 1D array type arrangement.

[0162] In Fig. 8, multiple element bodies 4 are connected in parallel via wiring 80a, 80b. In this way, by connecting multiple element bodies 4 in parallel, the output voltage (V) of the power generating element 1a can be increased. Although not shown, multiple element bodies 4 may be connected in series. When connected in series, the output current (A) of the power generating element 1a can be increased.

[0163] Each of the element bodies 4 has a vibrating portion 41 having a natural frequency f0, and it is preferable that the natural frequencies f0 of the vibrating portions 41 are all approximately the same value. Specifically, it is preferable that the natural frequencies f0 of the vibrating portions 41 constituting the array element are all within the range of fA±1.0%.

[0164] In the above, fA means the average value when the natural frequencies f0 of the vibration parts 41 are taken as a population. By aligning the natural frequencies f0 of the vibration parts 41 in this way, the output of the power generating element 1a can be increased and the energy conversion efficiency can be improved. In order to align the natural frequencies f0 of the vibration parts 41, for example, the shapes of the element bodies 4 may be aligned to reduce dimensional errors.

[0165] However, the power generating element 1a (array element) may be configured with a plurality of vibration parts 41 having different natural frequencies f0, without aligning the natural frequencies f0 of the vibration parts 41. In this case, the power generating element 1a can respond to external energy in various frequency bands. For example, in an array element, if the variation range of the natural frequencies f0 is 1 MHz to 3 MHz, the array element can generate power in response to external energy of 1 MHz to 3 MHz. Note that in an array element such as the power generating element 1a, the natural frequencies f0 of the vibration parts 41 can be shifted by, for example, adjusting the width Wvy of each vibration part 41.

[0166] 8, multiple element bodies 4 are arranged on one substrate 6a, but multiple substrates 6a may be combined to form a 3D array type power generating element. In this case, the arrangement direction of the multiple substrates 6a is not particularly limited, and they may be arranged on the XY plane or in the Z axis direction. In the case of a 3D array type power generating element, since multiple element bodies 4 are formed on each substrate 6a, the number of element bodies 4 mounted increases, and the output can be increased.

[0167] Next, the power generating element 1b shown in FIG. 9 will be described. In the power generating element 1b shown in FIG. 9, an opening 61b having a circular shape in a plan view is formed in a substrate 6b. An element body 4b is formed on the substrate 6b, and the element body 4b has a vibration part 41b having a circular shape in a plan view. In this power generating element 1b, the vibration part 41b is also located above the opening 61b, and the upper and lower surfaces of the vibration part 41b are non-constrained surfaces. A gap 46 exists between the outer peripheral edge of the vibration part 41b and the inner peripheral edge of the opening 61b.

[0168] In the case of a disk-shaped vibration section 41b as shown in Fig. 9, bulk acoustic wave vibration in thickness-extensional vibration (in-plane expansion and contraction) can be generated by optimizing the crystallinity of each functional film (particularly the piezoelectric layer 14 and the magnetostrictive layer 16). In other words, the vibration section 41b becomes a bulk acoustic wave vibrator of thickness-extensional vibration. A bulk acoustic wave vibrator of thickness-extensional vibration tends to have a higher natural frequency f0 than a bulk acoustic wave vibrator of expansion vibration.

[0169] 10, the power generating element 1c has a vibration part 41c with a cantilever structure. Specifically, the element body 4c of the power generating element 1c is fixed to the substrate 6c only at one end in the X-axis direction, and the other end in the X-axis direction of the element body 4 (i.e., the tip of the vibration part 41c) is a free end. In addition, in the element body 4c of the power generating element 1c, the width in the Y-axis direction of the support part 43c is approximately the same as the width in the Y-axis direction of the vibration part 41c.

[0170] In the case of such a cantilever-type vibration part 41c, it is easy to generate bulk acoustic wave vibration with bending vibration (out-of-plane vibration). When the vibration part 41c of the power generating element 1c generates bending vibration, it is preferable to fill the container in which the power generating element 1c is mounted with a low-viscosity gas. Alternatively, it is preferable to increase the degree of vacuum in the container (reduce the internal pressure of the container). In this way, by controlling the atmosphere around the element, it is possible to reduce the air resistance on the vibration part 41c and improve the energy conversion efficiency.

[0171] The vibration mode of the elastic wave vibrator is not only determined by the shape of the vibrating part, but is also influenced by the thickness of the element body, the shape of the support part, the configuration of each functional film, etc. Therefore, even if the shape of the vibrating part shown in Fig. 10 is used, it may be possible to generate bulk elastic wave vibration of in-plane stretching vibration. Similarly, even if the shape of the vibrating part shown in Figs. 1 to 3 and the shape of the vibrating part shown in Fig. 9 is used, it may be possible to generate not only in-plane stretching vibration but also out-of-plane vibration such as bending vibration.

[0172] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the present invention. For example, in the above-mentioned embodiment, the piezoelectric layer 14 and the magnetostrictive layer 16 are laminated in the vibration section 41, but the functional film may be made of a material that has both piezoelectric properties and magnetostrictive properties. Examples of such materials that have both piezoelectric properties and magnetostrictive properties include BiFeO3 and (Bi,La)FeO3 in which part of Bi is replaced with other elements such as La.

[0173] In the above embodiment (particularly the second embodiment), a single crystal silicon substrate is exemplified as the substrate 6, but an SOI base material 8 (Silicon on Insulator) as shown in FIG. 11(a) may be used as the substrate 6. The SOI base material 8 is composed of a single crystal Si layer 8α oriented so that the surface is a Si(100) surface, an insulating layer 8β made of SiO2, and a substrate 6d made of Si, and the single crystal Si layer 8α is laminated on the surface of the substrate 6d via the insulating layer 8β. The average thickness of the Si layer 8α and the average thickness of the insulating layer 8β are not particularly limited, but can be, for example, about 1 μm to 10 μm. The average thickness of the substrate 6d in the SOI base material 8 is also not particularly limited, but can be, for example, about 100 μm to 700 μm.

[0174] When this SOI base material 8 is used, the fixing portion 42 of the power generating element 4 is connected to the top of the substrate 6d via the Si layer 8α and the insulating layer 8β. When the power generating element is manufactured using the SOI base material 8, a power generating element 1d having a structure as shown in FIG. 11(b) may be obtained. FIG. 11(b) is a cross-sectional view showing a portion similar to FIG. 3. As described in the second embodiment, the opening 61 is formed by etching the substrate to remove a portion of the substrate. When the SOI base material 8 is used, the Si layer 8α and the insulating layer 8β may remain on the lower surface side of the vibration portion 41 after etching. In this case, the Si layer 8α and the insulating layer 8β may remain on the entire lower surface of the vibration portion 41, or may remain partially on a portion of the lower surface.

[0175] 11(b), it is preferable that the Si layer 8α and the insulating layer 8β are also removed in the gap 46, and the lower and upper surfaces of the vibrating part 41 facing the opening 61 are unconstrained surfaces that are not constrained by the substrate 6d. That is, even when the SOI base material 8 is used, it is preferable that the outer peripheral edge of the vibrating part 41 and the inner peripheral edge of the opening 61 are not in contact with each other in a plan view from the Z-axis direction. Note that even if the Si layer 8α and the insulating layer 8β remain on the lower surface of the vibrating part 41, the outer peripheral edge of the vibrating part 41 is determined based on the outer peripheral edge of the lower electrode layer 12 in a plan view.

[0176] When the SOI base material 8 is used, even if the Si layer 8α and the insulating layer 8β remain, the thickness of these remaining layers is about several μm and does not impede the elastic wave vibration of the vibration part 41. Therefore, in the power generation element 1d shown in Fig. 11(b) as well, the vibration part 41 becomes a bulk elastic wave vibrator that performs elastic wave vibration by in-plane expansion and contraction, and the power generation element 1d can obtain the same effects as those of the above-mentioned embodiment. EXAMPLES

[0177] The present invention will be described below with reference to more detailed examples, but the present invention is not limited to these examples.

[0178] Experiment 1 In experiment 1, samples 1 to 23 of magnetoelectric conversion elements were fabricated having the shape shown in FIG. 1A and different dimensions of element body 4 (width L of vibration part 41 in the Y-axis direction, width w of support part 43 in the Y-axis direction) as shown in Table 1, and their performance was compared.

[0179] (Samples 1-23) First, a single crystal silicon substrate with a Si(100) surface was prepared, and the following layers were formed on the silicon substrate by sputtering. An oxide layer (buffer layer) made of ZrO2 and a lower electrode layer 12 made of Pt were epitaxially grown on the top surface of the silicon substrate. The order of lamination was silicon substrate → oxide layer → lower electrode film 12, with the average thickness of the oxide layer being 50 nm and the average thickness of the lower electrode layer 12 being 100 nm.

[0180] Then, a piezoelectric layer 14 made of PZT was epitaxially grown on the lower electrode layer 12. The composition of the sputtering target used in this process was Pb:Zr:Ti, with an atomic ratio of 1.3:0.55:0.45. The substrate temperature during the formation of the PZT film was 600° C., and the film formation rate was 0.1 nm / sec.

[0181] Other conditions were that the gas introduced during sputtering was a mixed gas of 10 mol % oxygen and 90 mol % argon (Ar), the pressure of the introduced gas was 0.3 Pa, and the distance between the substrate and the target was 200 mm. The average thickness of the formed piezoelectric layer 14 was 1 μm.

[0182] During the deposition of the oxide layer through the piezoelectric layer 14, RHEED evaluation was performed to confirm whether each layer had grown epitaxially. As a result, it was confirmed that each layer from the oxide layer through the piezoelectric layer 14 had grown epitaxially during the deposition process. After the deposition of the piezoelectric layer 14, crystal structure analysis was performed by XRD, and it was confirmed that the piezoelectric layer 14 contained a total of three domains: a rhombohedral domain and two tetragonal domains.

[0183] Next, after the piezoelectric layer 14 was formed, the silicon substrate on which the film had been formed was subjected to an annealing treatment, which was performed under conditions of an oxygen atmosphere at 1 atmosphere and a temperature of 350° C. for 1 hour.

[0184] After the annealing treatment, a polycrystalline upper electrode layer made of Pt was formed on the piezoelectric layer 14 with an average thickness of 100 nm. Then, a magnetostrictive layer 16 made of an Fe-Co-Si-B alloy was formed on the upper electrode layer under the conditions shown below. The magnetostrictive layer 16 was formed using an ultra-high vacuum DC sputtering device (C-7960UHV manufactured by Canon Anelva Corporation), and the degree of vacuum during film formation was set to 3×10 -6 The name was Pa.

[0185] During deposition, the substrate was not heated, and a sufficient distance between the target and the substrate was maintained so that the substrate temperature would not rise. Other deposition conditions included the use of Ar gas as the introduced gas, a pressure of the introduced gas of 0.03 Pa, and an output of 200 W (DC). The average thickness of the deposited magnetostrictive layer 16 was 500 nm.

[0186] The crystal structure of the formed magnetostrictive layer 16 was confirmed by XRD and electron beam diffraction of TEM. As a result, it was confirmed that an amorphous phase and a crystalline phase were mixed in the magnetostrictive layer 16. In addition, a surface protection layer made of Pt was further formed on the magnetostrictive layer 16 with a thickness of 10 to 30 nm.

[0187] Each layer stacked on the silicon substrate was patterned by photoetching to form an element body 4 having a planar shape as shown in FIG. 1A. Then, a part of the silicon substrate was removed by RIE etching to form an opening 61. In this manner, magnetoelectric transducers according to samples 1 to 23 were obtained. In each sample, the width H of the vibration part 41 in the X-axis direction was 200 μm, and the width Wg of the gap 43 was 0.5 μm.

[0188] In addition, the warpage displacement V of the vibrating part was obtained by using a 3D laser microscope to measure the maximum height variation from the surface of the substrate 6 as a reference plane. In experiment 1, the warpage displacement V was controlled by changing the thickness of the surface protection layer. The thicker the surface protection layer was, the smaller the warpage displacement V could be controlled.

[0189] (Measurement of output voltage) To evaluate the performance of the fabricated magnetoelectric transducer sample, a magnetic field was applied from a position 10 cm away and the amount of power generated (output) of the sample was measured. In this measurement, the magnetic field was an alternating magnetic field with a natural frequency of the in-plane transverse longitudinal vibration (in-plane stretching vibration) using a coil.

[0190] The natural frequency of the magnetoelectric transducer of the sample was measured using an impedance analyzer. The natural frequencies of the in-plane stretching vibration of the magnetoelectric transducers with vibrating part widths L=75 μm, 200 μm, and 300 μm in the Y-axis direction were 20 MHz, 7.5 MHz, and 5.0 MHz, respectively. The AC voltage generated in the magnetoelectric transducer was measured using a lock-in amplifier. The voltage generated from the magnetoelectric transducers of each shape was measured, and the measurement data normalized with the maximum value set to 1 is shown in Table 1.

[0191] Fig. 5A is a graph showing the relationship between 2V / (Lw) and the normalized output shown in Table 1. As shown in Fig. 5A, it was confirmed that as the value of 2V / (Lw) decreases beyond 0.7, the normalized output can be increased significantly, preferably within a predetermined range of 0.6 or less, more preferably less than 0.2, and particularly preferably within a range of 0.001 to 0.2. The normalized output is a value with the maximum value of the observed output taken as 1, and has an arbitrary unit.

[0192] Experiment 2 In experiment 2, magnetoelectric transducer samples 24 to 45 having different dimensions of element body 4 (width L of vibrating portion 41 in the Y-axis direction) in the shape shown in FIG. 1B were produced, and their performance was compared.

[0193] (Samples 24-45) Samples 24 to 45 were fabricated in the same manner as samples 1 to 23 in experiment 1, except that the dimensions of element body 4 (width L of vibrating portion 41 in the Y-axis direction) in the shape shown in FIG.

[0194] (Measurement of output voltage) The power generation (output) of Samples 22 to 45 was measured in the same manner as in the measurement of the output voltage in Experiment 1. The natural frequencies of the in-plane stretching vibration of magnetoelectric transducers with vibrating part widths of 50 μm, 100 μm, and 200 μm in the Y-axis direction were 30 MHz, 15 MHz, and 7.5 MHz, respectively. The voltage generated by the magnetoelectric transducers of each shape was measured, and the measurement data normalized with the maximum value set to 1 are shown in Table 2.

[0195] Fig. 5B is a graph showing the relationship between 2V / L and the normalized output shown in Table 2. As shown in Fig. 5B, it was confirmed that the value of 2V / L becomes smaller when it reaches 0.2, and the normalized output increases significantly within a predetermined range, preferably 0.2 or less, and more preferably 0.001 to 0.2.

[0196] [Table 1]

[0197] [Table 2] [Explanation of symbols]

[0198] 1 ... Magnetoelectric conversion element 4 … Element body 41 ... Vibration part 12 … Lower electrode layer 13 … Upper electrode layer 14 ... Piezoelectric layer 16 ... Magnetostrictive layer 18,18a,18b … Extraction electrode 20 … Insulation layer 42,42a~42c … Fixed part 43 … Support part 44 … Connection 6 ... Substrate 61 … Opening 46 … Gap

Claims

1. A vibration section including a single-layer or multi-layer functional film having both piezoelectric and magnetostrictive properties; A support portion that holds the vibration portion so that the vibration portion can vibrate in-plane; A magnetoelectric transducer having a substrate on which the support portion is provided, When the width of the support portion is w, the width of the vibration portion is L, and the displacement of the warp of the vibration portion in the thickness direction is V, A magnetoelectric transducer that satisfies the following formula (1): 2V / (L-w)≦0.573…(1)

2. the substrate has an opening; The vibration portion is disposed in an opening of the substrate, The front and back surfaces of the vibration unit are exposed to a space in which the vibration unit can freely vibrate, 2. A magnetoelectric transducer according to claim 1, wherein the periphery of said vibrating portion other than the portion supported by said supporting portion is also exposed to a space in which said vibrating portion can vibrate freely.

3. A vibration section including a single-layer or multi-layer functional film having both piezoelectric and magnetostrictive properties; A magnetoelectric transducer having a substrate that holds the vibration part so that the vibration part can vibrate in-plane, When the width of the vibration part is L and the displacement of the warp of the vibration part in the thickness direction is V, A magnetoelectric transducer that satisfies the following formula (2): 2V / L≦0.164…(2)

4. the substrate has an opening; The vibration portion is disposed in an opening of the substrate, The front and back surfaces of the vibration unit are exposed to a space in which the vibration unit can freely vibrate, 4. A magnetoelectric transducer according to claim 3, wherein the widthwise edge of said vibrating portion is also exposed to a space in which it can vibrate freely.

5. the functional film of the vibration section has a piezoelectric layer and a magnetostrictive layer, 5. The magnetoelectric transducer according to claim 1, wherein the piezoelectric layer and the magnetostrictive layer are laminated in the vibration section.

6. An electronic device comprising the magnetoelectric transducer element according to any one of claims 1 to 5.

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