JP2021129472A - Magnetoelectric conversion device - Google Patents

Abstract

To provide a magnetoelectric conversion device having excellent durability.SOLUTION: A magnetoelectric conversion device includes a laminate supported by a substrate. The laminate includes a fixed part fixed to the substrate and a movable part capable of performing expansion/contraction vibration. The movable part includes a first electrode thin film, a piezoelectric thin film, and a ferromagnetic thin film positioned at an opposite side to the first electrode thin film while sandwiching the piezoelectric thin film. In a magnetoelectric conversion element having the above configuration, an outer periphery edge of the ferromagnetic thin film is arranged at an inner side in an in-plane direction than an outer periphery edge of the piezoelectric thin film.SELECTED DRAWING: Figure 3

Description

The present invention relates to a magnetic-electric conversion element in which a piezoelectric thin film and a ferromagnetic thin film are laminated.

As shown in Patent Documents 1 and 2, as an element used for an antenna, a magnetic sensor, an energy conversion device, or the like, a magnetic-electric conversion element in which a piezoelectric layer and a magnetostrictive layer are laminated is known. This magnetic-electric conversion element can convert energy (input signal) such as a magnetic field, an electromagnetic wave, and an ultrasonic wave into an electric output. In the above element, the electric output is generated when the strain generated in the magnetostrictive layer is transmitted to the piezoelectric layer and the piezoelectric layer itself bends.

In such a magnetic-electric conversion element, the piezoelectric layer is made of a ceramic material having lower toughness (that is, brittle fracture easily) than metal. Therefore, cracks may occur in the piezoelectric layer, which poses a problem in the durability of the device. In particular, the magnetic-electric conversion element is required to be thin, but if the piezoelectric layer is made thin, the durability of the element is further lowered.

Jitsuzensho 58-40853 U.S. Patent Application Publication No. 2018/0115070 (US, A1)

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a magnetic-electric conversion element having excellent durability.

In order to achieve the above object, the magnetic-electric conversion element according to the first aspect of the present invention is
A magnetic-electric conversion element having a laminated body supported by a substrate.
The laminated body has a fixed portion fixed to the substrate and a movable portion capable of expansion and contraction vibration.
The movable portion has a first electrode thin film, a piezoelectric thin film, and a ferromagnetic thin film located on the opposite side of the first electrode thin film with the piezoelectric thin film interposed therebetween.
The outer peripheral edge of the ferromagnetic thin film is located inside the outer peripheral edge of the piezoelectric thin film in the in-plane direction.

The magnetic-electric conversion element according to the first aspect of the present invention has a structure in which the movable portion can expand and contract and vibrate, and the piezoelectric thin film is distorted by the expansion and contraction vibration of the movable portion. As a result of diligent studies, the present inventors have made the device durable by laminating the ferromagnetic thin film so as to be located inside the outer peripheral edge of the piezoelectric thin film in the in-plane direction in this magnetic-electric conversion element. It was found that the sex was improved. From the first aspect of the present invention, since distortion is unlikely to occur in the vicinity of the outer peripheral edge of the piezoelectric thin film, it is possible to prevent cracks from occurring in the piezoelectric thin film.

Further, from the first aspect of the present invention, the distance from the outer peripheral edge of the piezoelectric thin film to the outer peripheral edge of the ferromagnetic thin film in the in-plane direction of the movable portion is defined as the offset length. The offset length is preferably 5 μm or more and less than 20 μm, and more preferably 5 μm or more and 10 μm or less. When the offset length is within the above range, the durability of the device can be improved while sufficiently securing the piezoelectric active region of the piezoelectric thin film.

Further, from the first aspect of the present invention, the outer peripheral edge of the ferromagnetic thin film can be formed by removing a part of the ferromagnetic thin film after lamination by etching or lift-off.

The magnetic-electric conversion element according to the second aspect of the present invention is
A magnetic-electric conversion element having a laminated body supported by a substrate.
The laminated body has a fixed portion fixed to the substrate and a movable portion capable of expansion and contraction vibration.
The movable portion has a first electrode thin film, a piezoelectric thin film, and a ferromagnetic thin film located on the opposite side of the first electrode thin film with the piezoelectric thin film interposed therebetween.
The portion where the piezoelectric thin film and the ferromagnetic thin film effectively overlap in the stacking direction of the movable portion is defined as an effective region.
The outer peripheral edge of the effective region is located inside the outer peripheral edge of the piezoelectric thin film in the in-plane direction.

In the above, the "effectively overlapping portion (effective region)" is a portion where the ferromagnetic thin film and the piezoelectric thin film are in direct contact with each other, or a portion where the ferromagnetic thin film and the piezoelectric thin film overlap with each other via another electrode film or the like. In other words, the "effective domain" means a region in which the electric charge generated in the piezoelectric thin film due to the magnetostrictive effect of the ferromagnetic thin film can be taken out.

The above-mentioned first aspect of the present invention is characterized by the relationship between the outer peripheral edge of the ferromagnetic thin film and the outer peripheral edge of the piezoelectric thin film, but the second aspect of the present invention is the outer peripheral edge of the effective region. It is characterized by its relationship with the outer peripheral edge of the piezoelectric thin film. From the first viewpoint, the planar dimension of the piezoelectric thin film is larger than the planar dimension of the ferromagnetic thin film in a plan view. On the other hand, from the second viewpoint, in the plan view, the planar dimension of the ferromagnetic thin film may be larger than the planar dimension of the ferromagnetic thin film, but conversely, the planar dimension of the ferromagnetic thin film may be larger. Is also possible. This is the difference between the first viewpoint and the second viewpoint.

In the magnetic-electric conversion element according to the second aspect of the present invention, the durability of the element is improved by locating the outer peripheral edge of the effective region inside the outer peripheral edge of the piezoelectric thin film in the in-plane direction. That is, even in the case of the second viewpoint, the same effect as that of the first viewpoint can be obtained.

Further, from the second aspect of the present invention, the distance from the outer peripheral edge of the piezoelectric thin film to the outer peripheral edge of the effective region in the in-plane direction of the movable portion is defined as the offset length. The offset length is preferably 5 μm or more and less than 20 μm, and more preferably 5 μm or more and 10 μm or less. When the offset length is within the above range, the durability of the element can be improved while sufficiently securing the effective region.

Further, from the second aspect of the present invention, the second electrode thin film may be laminated between the piezoelectric thin film and the ferromagnetic thin film in the stacking direction of the movable portion. Further, from the second aspect of the present invention, an insulating layer may be interposed between the second electrode thin film and the ferromagnetic thin film in the stacking direction of the movable portion.

From the first aspect and the second aspect of the present invention, the movable portion has an unconstrained surface that does not come into contact with the substrate, and in-plane expansion / contraction vibration is possible.

FIG. 1 is a perspective view showing a magnetic-electric conversion element according to the first embodiment of the present invention. FIG. 2A is a cross-sectional view taken along the line IIA-IIA of FIG. FIG. 2B is a cross-sectional view taken along the line IIB-IIB of FIG. FIG. 2C is a cross-sectional view taken along the line IIC-IIC of FIG. FIG. 3 is a plan view showing the internal structure of the magnetic-electric conversion element shown in FIG. FIG. 4A is a plan view showing a magnetic-electric conversion element according to a second embodiment of the present invention. FIG. 4B is a cross-sectional view taken along the line IVB-IVB shown in FIG. 4A. FIG. 5A is a plan view showing a magnetic-electric conversion element according to a third embodiment of the present invention. FIG. 5B is a cross-sectional view taken along the line VB-VB shown in FIG. 5A. FIG. 6A is a plan view showing a magnetic-electric conversion element according to a fourth embodiment of the present invention. FIG. 6B is a cross-sectional view taken along the line VIB-VIB shown in FIG. 6A. FIG. 7 is a graph showing the evaluation results of the durability test. FIG. 8 is a perspective view showing a modified example of the present invention. FIG. 9 is a plan view showing a modified example of the present invention.

Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

First Embodiment As shown in FIG. 1, the magnetic-electric conversion element 2a according to the embodiment of the present invention includes a substrate 6 and a laminate 4 supported by the substrate 6. In the present embodiment, the laminated body 4 has a rectangular parallelepiped shape, and the longitudinal direction of the laminated body 4 is the X-axis, the width direction is the Y-axis, and the height (thickness) direction is the Z-axis. In FIGS. 1 to 3, the X-axis, the Y-axis, and the Z-axis are substantially perpendicular to each other.

In the magnetic-electric conversion element 2a, one end of the laminate 4 in the X-axis direction is fixed to the surface of the substrate 6, and the other end of the laminate 4 in the X-axis direction is a free end. That is, the magnetic-electric conversion element 2a has a cantilever-type structure, and a part of the laminated body 4 can expand and contract and vibrate. In the present embodiment, in the laminated body 4, the portion in contact with the surface of the substrate 6 is referred to as a fixed portion 41, and the portion that expands and contracts and vibrates is referred to as a movable portion 42.

The movable portion 42 of the laminated body 4 extends from the fixed portion 41 in the X-axis direction, and the front surface and the back surface of the movable portion 42 are non-constraining surfaces that are not in contact with the substrate. The movable portion 42 can expand and contract, especially in the in-plane direction. Here, in-plane expansion and contraction means that the movable portion 42 expands and contracts in the XY plane, and out-of-plane expansion and contraction means that the movable portion 42 expands and contracts in the Z-axis direction. When in-plane expansion and contraction is possible as in the present embodiment, the movable portion 42 can also expand and contract and vibrate in the out-of-plane direction.

On the other hand, the back surface of the fixing portion 41 is connected to the front surface of the substrate 6, and the first external electrode 8a and the second external electrode 8b are formed on the front surface of the fixing portion 41 so as to be separated from each other. .. In the magnetic-electric conversion element 2a, an external circuit (not shown) or the like is connected to the external electrodes 8a and 8b.

Next, the internal structure of the laminated body 4 will be described with reference to FIGS. 2A to 2C. As shown in FIGS. 2A to 2C, the base electrode film 12, the piezoelectric thin film 14, and the ferromagnetic thin film 16 are laminated inside the laminated body 4. The base electrode film 12 is located in the lowermost layer in the Z-axis direction, and the piezoelectric thin film 14 is formed on the base electrode film 12. Further, the ferromagnetic thin film 16 is formed on the piezoelectric thin film 14, and is located on the opposite side of the base electrode film 12 with the piezoelectric thin film 14 interposed therebetween.

Further, on the side surface side and the surface side of the laminated body 4, an insulating layer 20 is formed so as to cover the portion where the films 12, 14 and 16 are laminated. The insulating layer 20 has a role of protecting the films 12, 14 and 16 as the exterior of the laminated body 4. Further, the insulating layer 20 prevents the base electrode film 12 and the ferromagnetic thin film 16 from being short-circuited.

As shown in FIG. 2A, the extraction electrode 18 is electrically connected to the ferromagnetic thin film 16. A via hole electrode 19a is formed above the extraction electrode 18 in the Z-axis direction so as to penetrate the insulating layer 20. In the present embodiment, the ferromagnetic thin film 16 is electrically connected to the first external electrode 8a via the extraction electrode 18 and the via hole electrode 19a.

On the other hand, in the cross section shown in FIG. 2B, the via hole electrode 19b is formed so as to penetrate the insulating layer 20 and the piezoelectric thin film 14. The base electrode film 12 is electrically connected to the second external electrode 8b via the via hole electrode 19b.

As described above, in the magnetic-electric conversion element 2a of the present embodiment, the piezoelectric thin film 14 is laminated in the movable portion 42 in a state of being sandwiched between the base electrode film 12 and the ferromagnetic thin film 16. Therefore, a voltage can be applied to the piezoelectric thin film 14 via the base electrode film 12 and the ferromagnetic thin film 16. Alternatively, the electric charge generated on the surface of the piezoelectric thin film 14 can be taken out via the base electrode film 12 and the ferromagnetic thin film 16.

Next, with reference to FIG. 3, the laminated structure of each of the films 12, 14 and 16 will be described in more detail. FIG. 3 is a plan view of the magnetic-electrical conversion element 2a, and the insulating layer 20 as an exterior is represented by a virtual line (dashed line) in order to show a laminated structure.

As shown in FIG. 3, in the present embodiment, each of the laminated films 12, 14 and 16 has a substantially rectangular plan view shape. However, the planar dimension of the ferromagnetic thin film 16 is smaller than the planar dimension of the piezoelectric thin film 14, and the outer peripheral edge of the ferromagnetic thin film 16 is in the in-plane direction with respect to the outer peripheral edge of the piezoelectric thin film 14. It is located inside. As described above, the durability of the magnetic-electric conversion element 2a can be improved by laminating the ferromagnetic thin film 16 so that the plane size is smaller than that of the piezoelectric thin film 14.

In particular, in the present embodiment, it is preferable that the distance from the outer peripheral edge of the piezoelectric thin film 14 to the outer peripheral edge of the ferromagnetic thin film 16 is within a predetermined range in the in-plane direction of the movable portion 42. Specifically, in the present embodiment, the distance from the outer peripheral edge of the piezoelectric thin film 14 to the outer peripheral edge of the ferromagnetic thin film 16 is set as the offset length, and this offset length is set to at least 3 μm or more. The offset length is preferably 5 μm or more and less than 20 μm, and more preferably 5 μm or more and 10 μm or less.

In the above, the offset length is measured at a position where the outer peripheral edge of the piezoelectric thin film 14 and the outer peripheral edge of the ferromagnetic thin film 16 are close to each other. For example, in the case of FIG. 3, on the tip side of the movable portion 42 (opposite side of the fixed portion 41), the offset length is the distance in the X-axis direction from the outer peripheral edge of the piezoelectric thin film 14 to the outer peripheral edge of the ferromagnetic thin film 16. Let it be La1. Further, at both ends of the movable portion 42 in the Y-axis direction, the distance in the Y-axis direction from the outer peripheral edge of the piezoelectric thin film 14 to the outer peripheral edge of the ferromagnetic thin film 16 is defined as the offset length La2. La1 and La2 may have the same width or may be different.

The offset lengths La1 and La2 are measured by observing the surface shown in FIG. 3 (the surface with the insulating layer 20 of the outermost layer removed) using a scanning electron microscope (SEM) or an optical microscope having a length measuring function. Is required by. Alternatively, it can also be obtained by observing the cross section shown in FIGS. 2A to 2C with a scanning transmission electron microscope (STEM) or the like and performing image analysis of the cross section photograph obtained at that time. At this time, it is preferable that the measurement is performed at at least three points and the average value is calculated.

Further, the planar dimension of the base electrode film 12 can be about the same as the planar dimension of the piezoelectric thin film 14. However, the planar dimension of the base electrode film 12 may be larger than the planar dimension of the piezoelectric thin film 14. In other words, the outer peripheral edge of the base electrode film 12 may overlap with the outer peripheral edge of the piezoelectric thin film 14 in the Z-axis direction, or is located outside the outer peripheral edge of the piezoelectric thin film 14 in the in-plane direction. May be.

Subsequently, the features of each element constituting the magnetic-electric conversion element 2a will be described in detail.

(Board 6)
In the present embodiment, the substrate 6 may be an insulator capable of supporting at least the laminate 4, but is preferably a single crystal substrate. Examples of the single crystal substrate include Si, MgO, strontium titanate (SrTIO ₃ ), lithium niobate (LiNbO ₃ ) and the like. In this embodiment, it is more preferable to use a silicon substrate whose surface is a single crystal of Si (100) plane. The single crystal of the Si (100) plane means that the (100) plane of the cubic crystal is oriented so as to be substantially parallel to the thickness direction on the silicon substrate.

(Piezoelectric thin film 14)
The piezoelectric thin film 14 is made of a piezoelectric material and exhibits a piezoelectric effect or an inverse piezoelectric effect. The piezoelectric effect means the effect of generating an electric charge by applying an external force (stress), and the inverse piezoelectric effect means the effect of generating distortion by applying a voltage. Piezoelectric materials that exhibit such effects include crystals, lithium niobate, aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT: Pb (Zr, Ti) O ₃ ), and potassium niobate. Examples thereof include sodium (KNN: (K, Na) NbO ₃ ), barium calcium titanate titanate (BCZT: (Ba, Ca) (Zr, Ti) O ₃ ), and the like.

In the present embodiment, among the above-mentioned piezoelectric materials, it is particularly preferable to use a piezoelectric material having a perovskite structure such as PZT, KNN, and BCZT. Since the piezoelectric material having a perovskite structure has excellent piezoelectric characteristics, the performance of the magnetic-electric conversion element 2a is improved by forming the piezoelectric thin film 14 with these materials. In addition, other elements or compounds may be appropriately added to the above-mentioned piezoelectric material constituting the piezoelectric thin film 14 in order to further improve the piezoelectric characteristics.

Further, when a piezoelectric material having a perovskite structure is used, it is more preferable that the piezoelectric thin film 14 is an epitaxially grown film. Here, epitaxial growth means that during film formation, the crystals of the film match the crystal lattice of the underlying material in the film thickness direction (Z-axis direction) and in-plane direction (X-axis and Y-axis directions). It means to grow while being aligned. Therefore, in a more preferable mode, the piezoelectric thin film 14 is in a state in which crystals are aligned in all three directions of the X-axis direction, the Y-axis direction, and the Z-axis direction in a high temperature state during film formation ( Triaxial orientation).

Whether or not the epitaxial growth is carried out so as to be triaxially oriented can be confirmed by performing a reflection high-speed electron diffraction evaluation (RHEED evaluation) in the thin film forming process. When the crystal orientation is disturbed on the film surface during film formation, the RHEED image shows a ring-shaped elongated pattern. On the other hand, when epitaxially grown as described above, the RHEED image shows a sharp spot-like or streak-like pattern. The RHEED image as described above is observed in a high temperature state during film formation.

When epitaxially grown, the piezoelectric thin film 14 has a crystal structure close to a single crystal (not a perfect single crystal) with almost no crystal grain boundaries formed at room temperature after film formation. More specifically, the crystal structure of the piezoelectric thin film 14 after film formation preferably has a plurality of crystal phases after being triaxially oriented, and has a domain structure containing at least three types of domains (regions). It is preferable to have. When the piezoelectric thin film 14 has a domain structure, the piezoelectric characteristics are further improved and the piezoelectric response to external stress is enhanced.

When the piezoelectric thin film 14 has a domain structure, the specific configuration of the domain structure differs depending on the piezoelectric material used. For example, when the piezoelectric thin film 14 is a PZT epitaxial growth film, it can have at least two types of crystal phases, a tetragonal crystal and a rhombohedral crystal. In this case, the tetragonal crystal has a domain in which the c-axis (the longitudinal axis of the rectangular parallelepiped (crystal lattice)) faces the film thickness direction and a domain in which the c-axis faces the in-plane direction. Further, the crystal phase of the rhombohedral crystal is oriented so that the (100) plane is parallel to the film thickness direction. That is, when the piezoelectric thin film 14 is a PZT epitaxial growth film, it preferably contains a total of three domains, that is, two domains of square crystals and a domain of rhombohedral crystals.

On the other hand, when the piezoelectric thin film 14 is a KNN epitaxial growth film, it preferably has two domains of orthorhombic crystals and one domain of monoclinic crystals (three domains in total). In the above case, the two types of orthorhombic domains are the domain (a domain) in which the (001) plane of the orthorhombic crystal is oriented so as to be substantially parallel to the film thickness direction, and the domain (a domain) of the orthorhombic crystal. 010) There may be a domain (c domain) oriented so that the plane is substantially parallel to the film thickness direction. Further, in the monoclinic domain, it is preferable that the (100) plane or the (010) plane is substantially parallel to the film thickness direction.

When the piezoelectric thin film 14 is a BCZT epitaxial growth film, it preferably has two tetragonal domains and two orthorhombic domains (a total of four domains).

Since a plurality of domains as described above are in contact with each other with a common domain boundary in between, the direction of the crystal axis of each domain is about several degrees at the maximum from the film thickness direction and the in-plane direction (specifically, ± 3). It may be off (about degree). Further, the plurality of domains as described above are equivalent domains oriented in the same orientation of the same crystal system, at least in a high temperature state at the time of film formation, and in the process of being cooled to room temperature or operating temperature after film formation, It is formed by transitioning to a more stable crystal phase or domain. The state in which a plurality of domains coexist can be confirmed by analyzing the piezoelectric thin film 14 by electron diffraction or X-ray diffraction (XRD) of a transmission electron microscope (TEM).

The thickness of the piezoelectric thin film 14 is preferably in the range of 0.5 to 10 μm. The thickness of the piezoelectric thin film 14 is determined by observing the XZ cross section or the YZ cross section by, for example, SEM or STEM, and performing image analysis of the cross-sectional photograph obtained at that time. In this case, it is preferable that the thickness of the piezoelectric thin film 14 is measured at three or more points in the in-plane direction and calculated as an average value thereof. The variation in thickness is as small as ± 5% or less.

(Base electrode film 12)
The base electrode film 12 is made of a conductive material such as a metal or an oxide conductor. In particular, when the piezoelectric thin film 14 is an epitaxially grown film, it is preferable that the base electrode film 12 is also an epitaxially grown film. In this case, the material of the base electrode film 12 is, for example, a metal thin film having a face-centered cubic structure such as platinum (Pt), iridium (Ir), or gold (Au), or strontium ruthenate (SrRuO ₃ : hereinafter abbreviated as SRO). It is preferable to use an oxide conductor thin film such as lithium nickelate (LiNiO _3). Such a metal thin film and an oxide conductor thin film can be epitaxially grown on a single crystal substrate, and become a film in which the (100) plane is oriented with respect to the film thickness direction.

The base electrode film 12 may be formed by laminating the above metal thin film and the above oxide conductor thin film. In that case, the stacking order of the metal thin film and the oxide conductor thin film is not particularly limited, but it is preferable that the oxide conductor thin film is located on the upper side of the Z axis, that is, on the piezoelectric thin film 14 side. The average thickness of the base electrode film 12 is preferably 3 nm to 200 nm as a whole.

(Ferromagnetic thin film 16)
The ferromagnet thin film 16 of the present embodiment contains a ferromagnet having magnetostrictive properties. Examples of the ferromagnetic material include pure metals such as iron (Fe), cobalt (Co), and nickel (Ni), or alloys containing at least one of the above metal elements (for example, Fe-Co-based and Fe-Ni-based). , Fe-Si type, Fe-Dy-Tb type, Fe-Ga type, Fe-Si-Al type alloy, etc.), or an oxide magnetic material containing an oxide of the above metal element can be used. Further, the ferromagnet thin film 16 may be a single film containing the above-mentioned ferromagnet, a multilayer film composed of a plurality of layers, or a laminated film of a ferromagnet and an antiferromagnet. Is also good.

In the present embodiment, the ferromagnetic thin film 16 is preferably a soft magnetic high magnetostrictive film among the above materials. Examples of the soft magnetic high magnetic strain film include Fe-Si-B alloy, Fe-Cr-Si-B alloy, Fe-Ni-Mo-B alloy, Fe-Co-B alloy, and Fe-Ni-B. Examples thereof include an alloy film containing a system alloy, a Fe-Al-Si-B system alloy, a Fe-Co-Si-B system alloy, or the like as a main component. Most ferromagnets exhibit a magnetostrictive effect, but the above-mentioned soft magnetic high-magnetostrictive film can generate a large amount of distortion even with a weak magnetic field (input signal), and the performance of the magnetic-electric conversion element 2a. Contribute to improvement.

The crystal structure of the ferromagnetic thin film 16 may be amorphous or polycrystalline, but when the ferromagnetic thin film 16 is a soft magnetostrictive film, it is said to be an amorphous phase. It is preferable to have a crystalline phase in a mixed manner. Since the ferromagnetic thin film 16 contains an amorphous phase, the responsiveness to an input signal can be improved. That is, the threshold magnetic field H _TH and the holding force H _c required to generate magnetostriction can be reduced. Further, since the ferromagnetic thin film 16 contains a crystal phase, the amount of change in magnetostriction (dλ / dH) per unit magnetic field in a low magnetic field can be increased.

The crystal structure of the ferromagnetic thin film 16 can be confirmed by analysis by electron diffraction of TEM, XRD, or the like, similarly to the piezoelectric thin film 14. For example, when the ferromagnetic thin film 16 is composed of only an amorphous phase, when θ-2θ measurement with Cu—Kα rays is performed using XRD, only a broad and wide halo pattern is detected. On the other hand, when the ferromagnetic thin film 16 is composed of only the crystal phase, only an extremely sharp reflection peak having a narrow half width is detected. Further, when the ferromagnetic thin film 16 has a mixture of an amorphous phase and a crystalline phase, a broad swelling (halo) portion indicating the presence of the amorphous phase and a sharp peak portion indicating the presence of the crystalline phase are present. A reflection peak having both of and is detected.

The average thickness of the ferromagnetic thin film 16 is preferably in the range of 0.1 to 5 μm. The average thickness of the ferromagnetic thin film 16 can also be measured in the same manner as the piezoelectric thin film 14. In addition, the thickness of the ferromagnetic thin film 16 has a small variation in the in-plane direction and is about the same as that of the piezoelectric thin film 14.

(Other electrodes)
The external electrodes 8a and 8b, the extraction electrodes 18, and the via hole electrodes 19a and 19b may all have conductivity, and the materials and dimensions thereof are not particularly limited. For example, the electrode may contain a conductive metal such as Pt, Ag, Cu, Au, Al, or may contain other glass components or the like.

(Insulation layer 20)
The insulating layer 20 may have electrical insulating properties, and its material and thickness are not particularly limited. _{For example, SiO 2} , Al ₂ O ₃ , polyimide, or the like can be applied as the insulating layer 20.

Subsequently, an example of a method for manufacturing the magnetic-electric conversion element 2a shown in FIGS. 1 to 3 will be described.

In the production of the magnetic-electric conversion element 2a, first, a base electrode film 12, a piezoelectric thin film 14, and a ferromagnetic thin film 16 are formed on a film-forming substrate by various thin film manufacturing methods. As the thin film forming method, a thin film deposition method, a sputtering method, a sol-gel method, a CDV method, a PLD method and the like can be applied, and a sputtering method is particularly preferable. By forming the magnetic film by the sputtering method, the adhesion between the piezoelectric thin film 14 and the ferromagnetic thin film 16 is enhanced, the occurrence of defects such as film peeling is suppressed, and the distortion of the ferromagnetic thin film is suppressed. It can be effectively transmitted to the piezoelectric thin film (and vice versa). As a result, the magnetic-electric conversion efficiency is improved.

As the film forming conditions of the films 12, 14 and 16, known conditions can be adopted and are not particularly limited. However, when the piezoelectric thin film 14 is used as an epitaxial growth film, the composition of the sputtering target, the temperature of the film-forming substrate, the film-forming rate, the gas composition, the degree of vacuum, the distance between the substrate targets, and the like are appropriately controlled. Further, in order for the piezoelectric thin film 14 to have a domain structure, in particular, the composition of the sputtering target, the temperature of the film-forming substrate, the stress of the ferromagnetic thin film 16 laminated on the piezoelectric thin film 14, and the like. You just have to control it.

For example, the composition of the sputtering target selects a composition in which a plurality of domains and crystal phases are likely to be formed depending on the material of the piezoelectric material, and increases the element having a high vapor pressure by 20 to 120% of the stoichiometric composition. Is preferable. 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 1-1. It is preferable to control the ratio to 5. Further, it is preferable to control the temperature of the film-forming substrate so that it is 550 to 650 ° C. Further, the stress of the ferromagnetic thin film 16 is preferably a compressive stress. In addition, after epitaxially growing the piezoelectric thin film 14, it is also effective to perform annealing treatment at a temperature of 300 ° C. to 500 ° C. in an oxidizing atmosphere in order to obtain the above-mentioned domain structure.

When the piezoelectric thin film 14 is epitaxially grown, it is preferable to use a single crystal silicon substrate (wafer) as the film-forming substrate as described above. Further, it is preferable that the base electrode film 12 is also formed by epitaxially growing on a silicon substrate. As a method for epitaxially growing the base electrode film 12, a known method may be adopted.

Regarding the ferromagnetic thin film 16, when the amorphous phase and the crystalline phase are mixed, the degree of vacuum, the temperature of the film-forming substrate, the gas composition, the gas pressure, the power, the target and the film-forming substrate are used during sputtering. Appropriately control the film formation conditions such as the distance between the two. For example, the gas pressure is preferably 0.01 to 0.1 Pa. The temperature of the film-forming substrate is preferably 20 to 200 ° C., and the distance between the target and the film-forming substrate is preferably 100 mm or more so that the substrate temperature does not rise during film formation.

The film-forming substrate on which the laminated film is formed as described above is subjected to patterning processing by various etching methods such as photo etching and laser dry etching. In this patterning process, the laminated pattern shown in FIG. 3 is formed on the film-forming substrate.

For example, in the case of patterning by photoetching, first, a photoresist agent is applied onto the ferromagnetic thin film 16 by various coating methods such as a spin coating method. Then, a mask having a desired pattern shape is applied onto the coated photoresist agent, and ultraviolet rays are irradiated to expose only the portion to which the ferromagnetic thin film 16 is to be removed (that is, the ferromagnetic thin film 16 remains. Mask the part). After that, the photoresist film is developed and the ferromagnetic thin film 16 is etched, and the photoresist film and the ferromagnetic thin film 16 corresponding to the exposed portion are removed to form the outer peripheral edge of the ferromagnetic thin film 16. Will be done. The photoresist remaining on the ferromagnetic thin film 16 can be removed by surface treatment with oxygen plasma or a predetermined chemical. Further, the photoresist remaining on the ferromagnetic thin film 16 may be used as a protective layer without being removed.

After forming the pattern of the ferromagnetic thin film 16 by the above procedure, the piezoelectric thin film 14 and the base electrode film 12 are also patterned by the same method as described above. When patterning the piezoelectric thin film 14, the dimensions of the mask are adjusted so that the offset lengths La1 and La2 are at desired intervals. That is, the mask used for patterning the piezoelectric thin film 14 is adjusted so that the size per pattern is larger than the mask used for patterning the ferromagnetic thin film 16.

Further, when the piezoelectric thin film 14 is epitaxially grown, it is preferable to control the extending surface direction (patterning shape) of the laminated body 4 in accordance with a predetermined crystal orientation of the piezoelectric thin film 14. Specifically, in the above patterning process, the longitudinal direction (X-axis direction) or the lateral direction (Y-axis direction) of the laminate 4 is the <110> direction of the piezoelectric thin film 16 and the <110> direction of the single crystal silicon substrate. The position of the mask is adjusted so that it is substantially parallel to the 110> direction.

In addition, in the above, substantially parallel means that it is within a range of ± 3 degrees with respect to a direction that is completely parallel. Further, the <110> direction means a direction that comprehensively indicates equivalent directions such as [110] and [101]. For example, when the piezoelectric thin film 14 is PZT, the [110] and [101] directions of the square crystal, the [110] direction of the rhombic crystal, and the directions equivalent thereto are the respective directions of the element 30. Adjust the position of the mask so that it is approximately parallel to the longitudinal or lateral direction.

By controlling the extending surface direction (patterning shape) of the laminated body 4 as described above, the durability of the magnetic-electric conversion element 2a tends to be further improved. Further, the polarization direction of the piezoelectric body tends to be oriented in the film thickness direction, and the piezoelectric characteristics of the piezoelectric thin film 14 are improved. The mask position is adjusted with reference to the orientation flat (orientation flat) or notch formed on the single crystal silicon substrate. That is, an orientation flat or a notch is formed in advance on the single crystal silicon substrate before film formation so that the crystal orientation of the substrate can be known. Further, in the present embodiment, the parentheses represent the Miller index (plane), and the triangular brackets and the square brackets represent the crystal orientation (direction).

After the patterning process is performed in the above procedure, the extraction electrode 18 is formed, and the insulating layer 20 is further formed so as to cover the films 12, 14 and 16. Further, as shown in FIGS. 2A and 2B, the via hole electrodes 19a and 19b are formed by a known method, and the external electrodes 8a and 8b are formed so as to be connected to the via hole electrodes 19a and 19b.

Then, as shown in FIG. 1, a part of the film-forming substrate is removed by etching so that the substrate 6 remains only below the fixing portion 41. For the etching of the film-forming substrate, dry etching such as the Deep-RIE method, anisotropic wet etching, or the like can be applied. The film-forming substrate may be completely removed by the above etching. In this case, after removing the film-forming substrate, the laminated body 4 is attached and fixed to the substrate 6 of another member.

The magnetic-electric conversion element 2a according to the present embodiment can be obtained by the above manufacturing process. Generally, in the manufacture of the magnetic-electric conversion element 2a, a plurality of laminated patterns are patterned on the above-mentioned film-forming substrate, and a plurality of magnetic-electric conversion elements 2a are formed from one film-forming substrate. obtain. Therefore, after etching the film-forming substrate, the remaining members are cut into element units and divided.

Further, in the above manufacturing process, the method of patterning by the etching method has been described, but the patterning process of the ferromagnetic thin film 16 may be carried out by the lift-off method. In the case of the lift-off method, before forming the ferromagnetic thin film 16, a resist film is formed on the piezoelectric thin film 14 so as to cover a region other than the planned formation region of the ferromagnetic thin film 16. The ferromagnetic thin film 16 is formed by sputtering a ferromagnetic component on a piezoelectric thin film 14 on which a resist film is formed, and then peeling (lifting off) the resist film. That is, in the case of the lift-off method, the outer peripheral edge of the ferromagnetic thin film 16 is formed by removing the ferromagnetic thin film 16 formed on the resist film by lift-off.

(Summary of the first embodiment)
In the conventional magnetic-electric conversion element, in order to widen the piezoelectric active region, it is common that the planar dimension of the piezoelectric layer and the planar dimension of the ferromagnetic layer are about the same in the moving portion.

In the magnetic-electric conversion element 2a of the present embodiment, unlike the conventional case, the outer peripheral edge of the ferromagnetic thin film 16 is located inside the outer peripheral edge of the piezoelectric thin film 14 in the in-plane direction. By laminating the ferromagnetic thin film 16 in this way, the strain generated by the ferromagnetic thin film 16 is less likely to be affected in the vicinity of the outer peripheral edge of the piezoelectric thin film 14. As a result, in the magnetic-electric conversion element 2a of the present embodiment, cracks are less likely to occur in the piezoelectric thin film 14, and durability is improved. In particular, in the magnetic-electric conversion element 2a of the present embodiment, the durability of the element can be improved even when the piezoelectric thin film 14 is thinned or when the piezoelectric thin film 14 is used as an epitaxial growth film.

In the present embodiment, "the outer peripheral edge of the ferromagnetic thin film 16 is located inside the outer peripheral edge of the piezoelectric thin film 14 in the in-plane direction" means that the offset lengths b1 and Lb2 are at least 3 μm or more. It means that. The offset lengths Lb1 and Lb2 are preferably 5 μm or more and less than 20 μm, and more preferably 5 μm or more and 10 μm or less. When the offset lengths Lb1 and Lb2 are within the above ranges, the durability of the magnetic-electric conversion element 2a can be improved while sufficiently securing the piezoelectric active region of the piezoelectric thin film 14. When the offset lengths Lb1 and Lb2 are set to 20 μm or more, the durability of the device is improved, but the piezoelectric active region tends to decrease.

The magnetic and electrical transformation element 2a can be used as an electronic device by being connected to a power source or an electric / electronic circuit and mounted on a circuit board or packaged. For example, if an amplifier and a rectifier circuit are connected and packaged, various sensors such as a magnetic sensor can be obtained. Similarly, if the power storage element and the rectifying power management circuit are connected to the magnetic-electric conversion element 2a, it becomes an energy conversion device (energy harvester) that generates electric power by receiving a magnetic field or vibration from the outside.

Second Embodiment Hereinafter, the second embodiment of the present invention will be described with reference to FIGS. 4A and 4B. Regarding the configuration common to the first embodiment in the second embodiment, the description thereof will be omitted and the same reference numerals will be used.

As shown in FIGS. 4A and 4B, the magnetic-electric conversion element 2b of the second embodiment also has a cantilever-type structure like the first embodiment. However, in the magnetic-electric conversion element 2b, the laminated state of the ferromagnetic thin film 161 is different from that of the first embodiment.

As shown in FIG. 4A, in the second embodiment, the ferromagnetic thin film 161 is laminated on the uppermost layer of the laminated body 4 in the Z-axis direction. The ferromagnetic thin film 161 integrally has a central portion 161a, an outer peripheral portion 161b, and a drawer portion 161c. The central portion 161a is an inner portion surrounded by the alternate long and short dash line in FIG. 4A, and is in direct contact with the piezoelectric thin film 14 as shown in FIG. 4B. On the other hand, the outer peripheral portion 161b is a portion located outside the alternate long and short dash line, and is in direct contact with the insulating layer 20 as shown in FIG. 4B. Further, the drawer portion 161c is a portion that is pulled out from the movable portion 42 toward the fixed portion 41 and is electrically connected to the first external electrode 8a.

In the magnetic-electric conversion element 2b, the strain generated by the magnetostrictive effect of the ferromagnetic thin film 161 is transmitted to the piezoelectric thin film 14, and the piezoelectric thin film 14 bends to generate an electric charge on the surface of the piezoelectric thin film 14. .. The electric charge generated here can be taken out through the ferromagnetic thin film 161 and the base electrode film 12. That is, in the case of the second embodiment, since the ferromagnetic thin film 161 has the above-described form, the electric charge generated in the piezoelectric thin film 14 is such that the piezoelectric thin film 14 and the ferromagnetic thin film 161 are in direct contact with each other. It can be taken out only in the portion corresponding to the central portion 161a. In the second embodiment, the portion where the electric charge can be taken out, that is, the region shown by the alternate long and short dash line in FIG. 4A is referred to as an effective region 10b.

In the magnetic-electric conversion element 2b of the second embodiment, the outer peripheral edge of the effective region 10b is located inside the outer peripheral edge of the piezoelectric thin film 14 in the in-plane direction. With such a configuration, the vicinity of the outer peripheral edge of the piezoelectric thin film 14 is less susceptible to the strain generated by the ferromagnetic thin film 161. That is, even in the magnetic-electric conversion element 2b of the second embodiment, the same effect as that of the first embodiment can be obtained, cracks are less likely to occur in the piezoelectric thin film 14, and the durability is improved.

In the second embodiment, the offset length is the distance from the outer peripheral edge of the piezoelectric thin film 14 to the outer peripheral edge of the effective region 10b in the in-plane direction of the movable portion 42. Specifically, the offset length is measured at a position where the outer peripheral edge of the piezoelectric thin film 14 and the outer peripheral edge of the effective region 10b are close to each other. For example, in the case of FIG. 4A, the distance in the X-axis direction from the outer peripheral edge of the piezoelectric thin film 14 to the outer peripheral edge of the effective region 10b on the tip end side of the movable portion 42 is set to the offset length Lb1. Further, at both ends of the movable portion 42 in the Y-axis direction, the distance in the Y-axis direction from the outer peripheral edge of the piezoelectric thin film 14 to the outer peripheral edge of the effective region 10b is defined as the offset length Lb2.

The offset lengths Lb1 and Lb2 are both at least 3 μm or more, preferably 5 μm or more and less than 20 μm, and more preferably 5 μm or more and 10 μm or less. By setting the offset lengths Lb1 and Lb2 to the above range, it is possible to improve the durability of the magnetic-electric conversion element 2b while sufficiently securing the effective region 10b. In addition, Lb1 and Lb2 may have the same width or may be different. Further, the offset lengths Lb1 and Lb2 can also be measured by an SEM, an optical microscope, or the like having a length measuring function as in the first embodiment.

In the second embodiment, in the fixed portion 41, the piezoelectric thin film 14 and the base electrode film 12 are only partially laminated, and the thickness of the fixed portion 41 is smaller than the thickness of the movable portion 42. ing. Further, the base electrode film 12 has a pull-out portion 12a partially pulled out from the movable portion 42 toward the fixed portion 41, and the pull-out portion 12a passes through a via hole electrode (not shown) to the second outside. It is electrically connected to the electrode 8b.

Next, a method of manufacturing the magnetic-electric conversion element 2b according to the second embodiment will be described. The magnetic-electric conversion element 2b can also be manufactured by the same method as in the first embodiment, but the film formation order is slightly different.

In the production of the magnetic-electric conversion element 2b, first, the base electrode film 12 and the piezoelectric thin film 14 are formed, and then the films 12 and 14 are patterned. After that, the insulating layer 20 is formed so as to cover the patterned piezoelectric thin film 14 and the base electrode film 12. Then, the formed insulating layer 20 is etched to remove the insulating layer 20 in the region shown by the alternate long and short dash line in FIG. 4A. After partially removing the insulating layer 20 in this way, the ferromagnetic thin film 161 is formed by mask vapor deposition, a photoetching method, a lift-off method, or the like. The above is the difference in the manufacturing method between the first embodiment and the second embodiment.

Third Embodiment Hereinafter, the third embodiment of the present invention will be described with reference to FIGS. 5A and 5B. Regarding the configuration common to the first and second embodiments in the third embodiment, the description thereof will be omitted and the same reference numerals will be used.

As shown in FIGS. 5A and 5B, the magnetic-electric conversion element 2c of the third embodiment has a structure fixed at both ends, unlike the first and second embodiments. More specifically, the laminated body 4 of the magnetic-electric conversion element 2c has fixed portions 41 at both ends in the X-axis direction, and the movable portion 42 exists so as to bridge the two fixed portions 41. .. Even with such a structure fixed at both ends, since the movable portion 42 has an unconstrained surface that is not in contact with the substrate, expansion and contraction vibration is possible in the in-plane direction.

Further, as shown in FIG. 5A, in the magnetic-electric conversion element 2c, the first external electrode 8a is formed on the surface of one of the fixing portions 41 and is electrically connected to the ferromagnetic thin film 162. The second external electrode 8b is formed on the surface of the other fixing portion 41, and is electrically connected to the base electrode film 12 via the via hole electrode 19.

Further, in the magnetic-electric conversion element 2c, similarly to the second embodiment, the ferromagnetic thin film 162 is formed on the uppermost layer of the laminated body 4, and the ferromagnetic thin film 162 is formed on the central portion 162a and the outer peripheral portion. It has 162b and a drawer 162c. However, in the magnetic-electric conversion element 2c, as shown in FIG. 5B, the upper electrode film 13 is laminated between the piezoelectric thin film 14 and the ferromagnetic thin film 162. Therefore, the central portion 162a of the ferromagnetic thin film 162 is in direct contact with the upper electrode film 13. The upper electrode film 13 may be made of a conductive material, and may have the same structure as the base electrode film 12.

With the above configuration, the electric charge generated in the piezoelectric thin film 14 can be taken out at the central portion 162a. That is, in the magnetic-electric conversion element 2c of the third embodiment, the effective region 10c is a portion where the piezoelectric thin film 14 and the ferromagnetic thin film 162 overlap each other via the upper electrode film 13 in the Z-axis direction. In FIG. 5A, the effective region 10c is indicated by a chain double-dashed line.

Also in the magnetic-electric conversion element 2c of the third embodiment, the outer peripheral edge of the effective region 10c is located inside the outer peripheral edge of the piezoelectric thin film 14 in the in-plane direction, and has the same operation as that of the second embodiment. The effect is obtained. In the case of the magnetic-electric conversion element 2b, as shown in FIG. 5A, the distance in the X-axis direction from the outer peripheral edge of the piezoelectric thin film 14 to the outer peripheral edge of the effective region 10c is set at both ends of the movable portion 42 in the X-axis direction. , The offset length is Lc1. Further, at both ends of the movable portion 42 in the Y-axis direction, the distance in the Y-axis direction from the outer peripheral edge of the piezoelectric thin film 14 to the outer peripheral edge of the effective region 10c is defined as the offset length Lc2. The offset lengths Lc1 and Lc2 are at least 3 μm or more, preferably 5 μm or more and less than 20 μm, and more preferably 5 μm or more and 10 μm or less, as in the second embodiment.

In the above-described first embodiment, since the piezoelectric active region depends on the planar dimension of the ferromagnetic thin film 16, the planar dimension of the ferromagnetic thin film 16 is made smaller than that of the piezoelectric thin film 14. On the other hand, in the magnetic-electric conversion element 2c of the third embodiment, as shown in FIG. 5A, the planar dimension of the ferromagnetic thin film 162 is made larger than the planar dimension of the piezoelectric thin film 14. As shown in the third embodiment, when the planar dimension of the effective region 10c, which is the piezoelectric active region, is smaller than that of the piezoelectric thin film 14, the planar dimension of the ferromagnetic thin film 16 is not particularly limited. That is, the planar dimension of the ferromagnetic thin film 162 may be larger than that of the piezoelectric thin film 16, may be about the same, or may be smaller.

The magnetic-electric conversion element 2c of the third embodiment can be manufactured by the same method as that of the second embodiment. However, in the third embodiment, the upper electrode film 13 is formed after the piezoelectric thin film 14 is formed.

Fourth Embodiment Hereinafter, the fourth embodiment of the present invention will be described with reference to FIGS. 6A and 6B.
Regarding the configuration common to the first to third embodiments in the fourth embodiment, the description thereof will be omitted and the same reference numerals will be used.

As shown in FIGS. 6A and 6B, the magnetic-electric conversion element 2d of the fourth embodiment has a structure in which both ends are fixed, as in the third embodiment. In this magnetic-electric conversion element 2d, as shown in FIG. 6B, an insulating layer 20 is interposed between the upper electrode film 13 and the ferromagnetic thin film 16. That is, in the manufacture of the magnetic-electric conversion element 2d, the ferromagnetic thin film 16 is directly formed on the insulating layer 20 without removing the insulating layer 20 at the center of the movable portion 42. The average thickness of the insulating layer 20 located between the upper electrode film 13 and the ferromagnetic thin film 16 is preferably 0.01 μm to 10 μm.

When the ferromagnetic thin film 16 is formed on the insulating layer 20 as described above, the ferromagnetic thin film 16 does not function as an electrode. Therefore, in the magnetic-electric conversion element 2d, the first external electrode 8a is electrically connected to the upper electrode film 13 via the via hole electrode 19. With this configuration, the electric charge generated in the piezoelectric thin film 14 can be taken out via the base electrode film 12 and the upper electrode film 13. As shown in the fourth embodiment, even when the insulating layer is interposed between the ferromagnetic thin film 16 and the piezoelectric thin film 14, the movable portion 42 is due to the magnetostrictive effect of the ferromagnetic thin film 16. Expansion and contraction vibration in the in-plane direction is possible.

Further, even in the case of the magnetic-electric conversion element 2d, the portion where the piezoelectric thin film 14 and the ferromagnetic thin film 16 overlap with each other via the upper electrode film 13 in the Z-axis direction is the effective region 10d. Specifically, in FIG. 6A, the effective region 10d is shown by hatching.

Further, in the fourth embodiment as well, as in the second and third embodiments, the outer peripheral edge of the effective region 10d is located inside the outer peripheral edge of the piezoelectric thin film 14 in the in-plane direction. Therefore, even in the magnetic-electric conversion element 2d of the fourth embodiment, cracks are less likely to occur in the piezoelectric thin film 14, and the durability of the element is improved. The offset lengths Ld1 and Ld2 shown in FIG. 6A are at least 3 μm or more, preferably 5 μm or more and less than 20 μm, and more preferably 5 μm or more and 10 μm or less.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be variously modified within the scope of the present invention.

For example, in the above-described embodiment, the movable portion 42 has a substantially rectangular plan-view shape, but the form of the movable portion 42 is not limited to this, and the movable portion 42 has an elliptical shape, a circular shape, a meander shape, or a spiral shape. It may have a shape in a plan view. Further, in each of the above-described embodiments, the fixed portion 41 and the movable portion 42 are integrally and continuously formed, and the width in the Y-axis direction is about the same, but the present invention is not limited to this. For example, the fixed portion 41 and the movable portion 42 may be connected via a connecting portion, or may have different widths in the Y-axis direction.

Further, in the above-described embodiment, the magnetic-electric conversion element has a cantilever type or both ends fixed type structure, but may have a form as shown in FIG. In the magnetic-electric conversion element 2e shown in FIG. 8, the substrate 6 has an opening 61, and the movable portion 42 is located above the opening 61 in the Z-axis direction. More specifically, the movable portion 42 is fixed to the substrate 6 via the support portions 43 located at both ends in the X-axis direction, and can be expanded and contracted and vibrated in the in-plane direction above the opening 61. ing.

Further, the laminated body 4 of the magnetic-electric conversion element may include other functional films (not shown in FIGS. 1 to 6B). For example, a buffer layer may be formed as a crystallinity control film below the base electrode film 12 in the Z-axis direction. The buffer layer preferably contains zirconium oxide (ZrO2) or zirconium oxide (stabilized zirconia) stabilized by rare earth elements (including Sc and Y) as a main component.

This buffer layer functions as an etching stopper layer when a part of the film-forming substrate is removed by etching. Further, when the piezoelectric thin film 14 is used as an epitaxial growth film, the buffer layer is formed, so that the epitaxial growth of the film located above the buffer layer in the stacking direction is promoted (high quality). When forming the buffer layer, the average thickness thereof is preferably 5 nm to 100 nm.

In any of the above-described embodiments, when the piezoelectric thin film 14 is used as an epitaxial growth film, it is preferable that both the base electrode film and the buffer layer are epitaxial growth films. In the film thickness direction, the buffer layer, the base electrode film, and the piezoelectric thin film are all preferably (001) oriented films, and in the in-plane direction, the respective (100) planes are substantially parallel. It is preferably an epitaxial film formed. Specifically, when the buffer layer is ZrO2, the base electrode film is Pt, and the piezoelectric thin film is PZT, the preferable orientation relationship of each layer is ZrO2 (001) // Pt (001) // PZT ( 001), which is ZrO2 (100) // Pt (100) // PZT (100) in the in-plane direction.

Further, in each of the above-described embodiments, the magnetic-electric conversion element has one movable portion 42 capable of expanding and contracting vibration, but may be an array element having a plurality of movable portions 42. Examples of the array element include a 1D array element, a 2D array element, and a 3D array element.

The 1D array element has a structure in which a plurality of movable portions 42 are arranged and connected in a uniaxial direction from a common fixed portion. As shown in FIG. 9, the 2D array element has a structure in which a plurality of movable portions 42 are arranged on the XY plane of a single substrate 60. In the 2D array type magnetic-electric conversion element 2f shown in FIG. 9, a plurality of openings 61 are formed in the substrate 60, and a plurality of movable portions 42 are formed corresponding to the openings 61. be. Electric power can be delivered to the plurality of movable portions 42 via the wirings 80a and 80b. Further, the 3D array element is configured by laminating a plurality of 2D array type substrates 60 as shown in FIG. 9 in the thickness direction (Z-axis direction).

By using the magnetic-electric conversion element as the array element as described above, the input energy can be effectively absorbed and a high output can be obtained. Further, by setting the natural frequencies of the plurality of movable parts constituting the array element to be different from each other, a magnetic-electric conversion element having high sensitivity to a wide range of frequencies and a plurality of frequencies can be obtained. The natural frequency of each movable part can be adjusted by changing the dimensions and thickness of the movable part.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following examples.

In this embodiment, a plurality of magnetic-electric conversion elements 2a shown in FIG. 1 were manufactured by varying the level of offset length, and the durability of the obtained magnetic-electric conversion elements 2a was evaluated.

Specifically, in this embodiment, the films 12, 14 and 16 were formed on a silicon wafer (silicon substrate) whose surface is a single crystal on the Si (100) plane. At this time, the base electrode film 12 is a laminated film of a Pt electrode film having an average thickness of 100 nm and a conductive oxide thin film composed of SrRuO3 (hereinafter referred to as SRO) having an average thickness of 100 nm, and these films are epitaxially grown. And formed. The piezoelectric thin film 14 was a PZT epitaxial growth film having an average thickness of 1 μm. Further, the ferromagnetic thin film 16 was made into a FeCoSiB alloy film having an average thickness of 1 μm.

When the patterning process of each of the films 12, 14 and 16 was carried out by the photoetching method, the conditions of the patterning process were set so that the offset lengths La1 and La2 were 3 μm, 4 μm, 5 μm, 6 μm, 9 μm, 10 μm and 12 μm. A plurality of magnetic-electric conversion elements 2a were manufactured. Then, the durability test shown below was carried out for the magnetic-electric conversion element 2a having each offset length.

Durability test (accelerated test)
In the durability test, an AC magnetic field of 1 kHz and 6366 A / m (80 Oe) was continuously applied to the obtained magnetic-electric conversion element 2a for 100 hours. Then, the magnetic-electric conversion element 2a after the test was carried out was observed with an optical microscope to confirm whether or not the element (particularly the piezoelectric thin film 14) had cracks. The durability test was performed on 100 elements at each level of offset length, and the rate of crack occurrence was calculated as the defect occurrence rate.

(Comparison example)
In the comparative example, the magnetic-electric conversion element was manufactured with offset lengths of 1 μm and 2 μm, and the same durability test as in the above-mentioned example was performed. In the production of the magnetic-electric conversion element according to the comparative example, the manufacturing conditions other than the offset length were the same as those in the example.

Evaluation Results The results of durability tests of Examples and Comparative Examples are shown in FIG. As shown in FIG. 7, it was confirmed that the defect occurrence rate was reduced to 10% or less by setting the offset length to 3 μm or more. When the offset length was 5 μm or more, the defect occurrence rate was reduced to 2% or less, and when the offset length was 9 μm or more, the defect occurrence rate was 0% and no cracks occurred in the device.

From the above results, it was proved that the durability of the device is improved by increasing the offset length. As described in the embodiment, when the offset length is 20 μm or more, the durability is good, but the piezoelectric active region is reduced. Therefore, in view of the experimental results of FIG. 7, the offset length is preferably 5 μm or more and less than 20 μm, and preferably 5 μm or more and 10 μm or less.

Further, the durability test as described above was also carried out for the magnetic-electric conversion elements 2b to 2d shown in FIGS. 4A, 5A and 6A. As a result, it was confirmed that the same results as those in the above-mentioned examples can be obtained in all the elements.

2a to 2e ... Magnetic-electric conversion element 4 ... Laminated body 41 ... Fixed part 42 ... Moving part 6 ... Substrate 8a ... First external electrode 8b ... Second external electrode 10 ... Effective area 12 ... Base electrode film 13 ... Upper electrode film 14 … Piezoelectric thin film 16… ferromagnetic thin film 18… extraction electrode 19… via hole electrode 20… insulating layer

Claims (8)

A magnetic-electric conversion element having a laminated body supported by a substrate.
The laminated body has a fixed portion fixed to the substrate and a movable portion capable of expansion and contraction vibration.
The movable portion has a first electrode thin film, a piezoelectric thin film, and a ferromagnetic thin film located on the opposite side of the first electrode thin film with the piezoelectric thin film interposed therebetween.
The outer peripheral edge of the ferromagnetic thin film is a magnetic-electric conversion element located inside the outer peripheral edge of the piezoelectric thin film in the in-plane direction. In the in-plane direction of the movable part,
The distance from the outer peripheral edge of the piezoelectric thin film to the outer peripheral edge of the ferromagnetic thin film is defined as the offset length.
The magnetic-electric conversion element according to claim 1, wherein the offset length is 5 μm or more and less than 20 μm. The magnetic-electric conversion element according to claim 1 or 2, wherein the outer peripheral edge of the ferromagnetic thin film is formed by removing a part of the ferromagnetic thin film after lamination by etching or lift-off. A magnetic-electric conversion element having a laminated body supported by a substrate.
The laminated body has a fixed portion fixed to the substrate and a movable portion capable of expansion and contraction vibration.
The movable portion has a first electrode thin film, a piezoelectric thin film, and a ferromagnetic thin film located on the opposite side of the first electrode thin film with the piezoelectric thin film interposed therebetween.
The portion where the piezoelectric thin film and the ferromagnetic thin film effectively overlap in the stacking direction of the movable portion is defined as an effective region.
The outer peripheral edge of the effective region is a magnetic-electric conversion element located inside the outer peripheral edge of the piezoelectric thin film in the in-plane direction. In the in-plane direction of the movable part,
The distance from the outer peripheral edge of the piezoelectric thin film to the outer peripheral edge of the effective region is defined as the offset length.
The magnetic-electric conversion element according to claim 4, wherein the offset length is 5 μm or more and less than 20 μm. The magnetic-electric conversion element according to claim 4 or 5, wherein a second electrode thin film is laminated between the piezoelectric thin film and the ferromagnetic thin film in the stacking direction of the movable portion. The magnetic-electric conversion element according to claim 6, wherein an insulating layer is interposed between the second electrode thin film and the ferromagnetic thin film in the stacking direction of the movable portion. The magnetic-electric conversion element according to any one of claims 1 to 7, wherein the movable portion has an unconstrained surface that does not come into contact with the substrate, and in-plane expansion / contraction vibration is possible.

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