WO2021141081A1 - 圧電振動基板および圧電振動素子 - Google Patents
圧電振動基板および圧電振動素子 Download PDFInfo
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- WO2021141081A1 WO2021141081A1 PCT/JP2021/000351 JP2021000351W WO2021141081A1 WO 2021141081 A1 WO2021141081 A1 WO 2021141081A1 JP 2021000351 W JP2021000351 W JP 2021000351W WO 2021141081 A1 WO2021141081 A1 WO 2021141081A1
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- piezoelectric
- intermediate layer
- layer
- support substrate
- lower electrode
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Images
Classifications
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/88—Mounts; Supports; Enclosures; Casings
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
- H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
- H03H9/172—Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
- G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
- G02B26/0858—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD the reflecting means being moved or deformed by piezoelectric means
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
- H10N30/072—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by laminating or bonding of piezoelectric or electrostrictive bodies
- H10N30/073—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by laminating or bonding of piezoelectric or electrostrictive bodies by fusion of metals or by adhesives
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/704—Piezoelectric or electrostrictive devices based on piezoelectric or electrostrictive films or coatings
- H10N30/706—Piezoelectric or electrostrictive devices based on piezoelectric or electrostrictive films or coatings characterised by the underlying bases, e.g. substrates
- H10N30/708—Intermediate layers, e.g. barrier, adhesion or growth control buffer layers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/87—Electrodes or interconnections, e.g. leads or terminals
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/87—Electrodes or interconnections, e.g. leads or terminals
- H10N30/871—Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes
Definitions
- the present invention relates to a piezoelectric vibrating substrate and an element that can be suitably used for a MEMS mirror or the like.
- a head-up display is a "device that overlaps and displays necessary information in the field of view while keeping the line of sight forward.”
- the information can be visually recognized while keeping the line of sight forward, which is effective in preventing sideways driving and also reduces the focus movement of the eyes. This can reduce driver fatigue and improve safety.
- HUD The principle of HUD is to project images from fluorescent tubes, CRTs and LCDs on the windshield of a car or a transparent screen (combiner).
- the image is recognized on the screen (combiner) like a normal projector, but in the Virtual Imaging method, the image is recognized in the space several meters away from the driver's line of sight.
- the movement of the driver's front view and the line of sight between the instrument panel and console panel is significantly smaller than when the HUD is not used.
- the Virtual Imaging method the focus shift from the field of view during normal operation is also possible. Since less is required, more attention can be paid to driving and less fatigue.
- the Virtual Imaging method the development of a new method for scanning and drawing a laser beam has been progressing in recent years.
- a laser beam of three RGB colors is combined by an optical element called a combiner, and this one beam is reflected by a minute mirror and scanned in two dimensions to perform drawing.
- This method is similar to the electron beam scanning of a CRT, but instead of exciting the phosphor, it controls the pulse width and output of each laser at the position corresponding to the pixel on the horizontal scanning line to change the color and brightness of the pixel. Is point-drawn at high speed. The achievable resolution depends on the vibration frequency of the mirror and the modulation frequency of the laser.
- the main advantages of this method are as follows. (1) Since the number of parts is small, miniaturization, cost reduction, and reliability improvement can be realized. (2) Since the laser is turned on with the brightness required for each pixel, low power consumption can be realized. (3) Since collimated (parallel light) laser light is used, focus adjustment is not required.
- the micro mirror which is the core component of the laser scanning display, processes Si with MEMS (Micro Electro Mechanical System) technology and deposits metal.
- Methods for driving the MEMS mirror include an electrostatic method driven by an electrostatic attraction, an electromagnetic method driven by an electromagnetic force, and a piezoelectric method driven by a piezoelectric element.
- the advantages of the piezoelectric method are high-speed drive, low power consumption, large driving force, and the disadvantage is that it is difficult to form a piezoelectric element.
- a piezoelectric film such as PZT is formed on a silicon substrate by a sputtering method or the like (Patent Document 1).
- the HUD will be required to have a larger screen and a wider angle of view, and there is also a request to increase the angle of view up to 20 degrees from the current angle of view of 7 to 8 degrees.
- it is necessary to improve the frequency, amplitude and reliability of the piezoelectric vibrating element of the MEMS mirror.
- a piezoelectric vibrating element in which a piezoelectric layer is formed on a conventional silicon substrate by a film forming method cannot realize a piezoelectric vibrating element having such a high frequency, amplitude, and reliability. It has become clear.
- An object of the present invention is to make it possible to suppress cracks and chipping due to heating, ultrasonic vibration, and weight applied when mounting a piezoelectric vibration element.
- the invention according to the first aspect is A piezoelectric layer made of a bulk piezoelectric material and having a first surface and a second surface opposite to the first surface.
- the present invention relates to a piezoelectric vibration substrate, which comprises a lower electrode on the first surface of the piezoelectric layer and a support substrate bonded to the lower electrode.
- the present invention also relates to a piezoelectric vibrating element, which comprises the piezoelectric vibrating substrate and an upper electrode on the piezoelectric layer.
- the invention according to the second aspect is A piezoelectric layer made of a bulk piezoelectric material and having a first surface and a second surface opposite to the first surface.
- the lower electrode on the first surface of the piezoelectric layer The present invention relates to a piezoelectric vibration substrate, which comprises a high-rigidity ceramic plate bonded to the lower electrode and a support substrate bonded to the high-rigidity ceramic plate.
- the present invention also relates to a piezoelectric vibrating element, which comprises the piezoelectric vibrating substrate and an upper electrode on the second surface of the piezoelectric layer.
- the present inventor investigated the reason why the piezoelectric vibration element cracks or chips due to heating, ultrasonic vibration, and weighting when the piezoelectric vibration element is mounted on a package or a substrate and electrically connected. As a result, it was found that when a piezoelectric film such as PZT was formed by various film forming methods such as sputtering, the crystal quality of the piezoelectric film was poor, which caused cracks and chipping.
- the present inventor has also considered manufacturing a piezoelectric diaphragm by thinning a bulk piezoelectric material substrate.
- the thickness of the piezoelectric material substrate of Parc is reduced to, for example, 50 ⁇ m or less by processing, it tends to crack due to insufficient strength, so that it is difficult to use it as a piezoelectric vibrating element.
- the present inventor directly bonded the bulk piezoelectric material substrate to a separate support substrate via the lower electrode and the intermediate layer, and made this piezoelectric material substrate suitable for vibration at high frequencies.
- polishing thinly to a desired thickness we succeeded in forming a piezoelectric vibrating layer with thin thickness and good crystallinity, which can suppress cracks and chipping of the piezoelectric vibrating element due to heating, ultrasonic vibration and weighting. I found it.
- the present inventor heats and superimposes by providing a separate high-rigidity ceramic plate between the lower electrode provided on the first surface of the piezoelectric layer and the support substrate. It was found that cracks and chipping of the piezoelectric vibrating element due to ultrasonic vibration and weight can be further reduced. As a result, the present invention makes it possible to realize a piezoelectric actuator device having excellent piezoelectric characteristics and durability.
- (A) shows a laminate of the piezoelectric body 2, the lower electrode 3 and the intermediate layer 4, (b) shows the support substrate 5, and (c) directly joins the intermediate layer 4 and the support substrate 5.
- (A) shows the bonded body obtained by processing the piezoelectric body in the bonded body of FIG. 1 (c), and (b) shows the piezoelectric layer 2A, the upper electrode 1, the lower electrode 3, the intermediate layer 4, The piezoelectric vibrating element 11 having an amorphous layer 6 and a support substrate 5 is shown.
- (A) shows a state in which the intermediate layer 8 is provided on the first surface of the high-rigidity ceramic body 7, (b) shows the support substrate 5, and (c) shows the high-rigidity ceramic plate on the support substrate 5.
- a state in which 7A is joined is shown, and (d) shows a state in which the lower electrode 3 and the intermediate layer 4 are provided on the piezoelectric body 2.
- (A) shows the joint of the support substrate 5, the lower electrode 3, the high-rigidity ceramic plate 7A and the piezoelectric body 2, and (b) shows the piezoelectric body 2 processed in the joint of FIG. 4 (a) to make piezoelectric.
- a state in which the layer 2A is formed is shown, and (c) shows the piezoelectric vibrating element 12.
- TEM transmission electron microscope
- TEM transmission electron microscope
- TEM transmission electron microscope
- TEM cross-section transmission electron microscope
- TEM cross-section transmission electron microscope
- TEM cross-section transmission electron microscope
- the piezoelectric body 2 has a first surface 2a and a second surface 2b.
- the lower electrode 3 and the intermediate layer 4 are provided on the first surface 2a of the piezoelectric body 2.
- the intermediate layer 4a is activated by irradiating the junction surface 4a of the intermediate layer 4 with a neutralized atomic beam as shown by an arrow A.
- the bonding surface 5a is activated by irradiating the bonding surface 5a of the support substrate 5 with a neutralized atomic beam as shown by an arrow B.
- the joint surface 4a of the intermediate layer 4 and the joint surface 5a of the support substrate 5 are brought into contact with each other and directly bonded to obtain a bonded body.
- the amorphous layer 6 is formed along the boundary between the support substrate 5 and the intermediate layer 4.
- the piezoelectric layer 2A having a desired thickness is formed by processing and thinning the piezoelectric body of the bonded body.
- the thickness of the piezoelectric layer 2A is appropriately changed according to the target vibration frequency.
- Reference numeral 2c is a processed surface (second surface) of the piezoelectric layer 2A.
- the piezoelectric vibrating element 11 is obtained by forming the upper electrode 1 on the second surface 2c of the piezoelectric layer 2A.
- the high-rigidity ceramic body 7 has a first surface 7a and a second surface 7b.
- the intermediate layer 8 is provided on the first surface 7a of the high-rigidity ceramic body 7.
- the bonding surface 8a of the intermediate layer 8 is activated by irradiating the bonding surface 8a with a neutralized atomic beam as shown by an arrow C.
- the bonding surface 5a is activated by irradiating the bonding surface 5a of the support substrate 5 with a neutralized atomic beam as shown by an arrow B.
- the bonding surface 8a of the intermediate layer 8 and the bonding surface 5a of the support substrate 5 are brought into contact with each other and directly bonded to obtain a bonded body.
- the amorphous layer 10 is formed along the interface between the joint surface 8a and the joint surface 5a.
- the high-rigidity ceramic body 7 is processed to be thinned to form a high-rigidity ceramic plate 7A having a desired thickness.
- the intermediate layer 16 is provided on the second surface 7c of the high-rigidity ceramic plate 7A, and the bonding surface 16a of the intermediate layer is irradiated with a neutralized atomic beam as shown by arrow D to activate the surface.
- the lower electrode 3 and the intermediate layer 4 are sequentially provided on the first surface 2a of the piezoelectric body 2, and the bonding surface 4a of the intermediate layer 4 is activated by the neutralized atomic beam E.
- the bonding surface 4a of the intermediate layer 4 is activated by the neutralized atomic beam E.
- the joint surface 4a of the intermediate layer 4 and the intermediate layer 16 on the second surface 7c of the high-rigidity ceramic plate 7A are brought into contact with each other and directly bonded to obtain a bonded body. ..
- an amorphous layer is formed along the interface between the directly joined intermediate layer 4 and the intermediate layer 16.
- the piezoelectric layer 2 of the bonded body is processed to be thinned to form the piezoelectric layer 2A having a desired thickness.
- the thickness of the piezoelectric layer 2A is appropriately changed according to the target vibration frequency.
- Reference numeral 2c is a processed surface (second surface) of the piezoelectric layer 2A.
- the piezoelectric vibrating element 12 is obtained by forming the upper electrode 1 on the second surface 2c of the piezoelectric layer 2A.
- the device of the present invention is made of a bulk piezoelectric material and has a piezoelectric layer having a first surface and a second surface.
- the bulk piezoelectric material means not a piezoelectric material formed on a substrate but a piezoelectric material formed in a bulk by a crystal growth method or a sintering method. Such piezoelectric materials usually have good crystallinity and high strength.
- d 31 expansion and contraction in the direction warped from the electrode surface
- d 31 is one of the piezoelectric characteristics required for the device
- the film-formed product is 150 or less, and is 100 on average. Often around.
- the piezoelectric material is not particularly limited, and examples thereof include lead-based perovskite oxides (for example, lead zirconate titanate (PZT) and lead magnesium niobate-lead titanate (PMN-PT)), and lead-based perovskite oxidation.
- PZT lead zirconate titanate
- PMN-PT lead magnesium niobate-lead titanate
- La (lantern), Nb (niobium), and / or Sr (strontium) can be added to the substance (for example, PZT), and Pb (Mg, Nb) O 3 and Pb (Ni, Nb) O 3 can be added.
- PbTiO 3 and the like oxides or combinations thereof can be used.
- the thickness of the piezoelectric body before processing is preferably 200 ⁇ m or more from the viewpoint of mechanical strength during handling.
- the thickness of the processed piezoelectric layer (vibrating body) is determined by throwing it at a target vibration frequency, and can be, for example, 0.5 ⁇ m to 50 ⁇ m.
- the materials of the upper electrode and the lower electrode are not particularly limited, and there is no problem as long as a voltage for controlling the vibration of the piezoelectric layer can be applied.
- a voltage for controlling the vibration of the piezoelectric layer can be applied.
- platinum, gold, Au-Cu, Al, and Al-Cu alloys are exemplified. it can.
- a buffer layer such as Cr or Ti for improving the adhesion of each electrode can be provided between the piezoelectric layer and the upper electrode and between the high-rigidity ceramic plate and the lower electrode.
- a seed layer for growing the piezoelectric material on the support substrate is indispensable.
- Pt is generally used as the material of the seed layer, and there is virtually no choice of lower electrode other than Pt in the film formation method.
- the lower electrode is attached to the piezoelectric body without being affected by the material and film thickness of the lower electrode. Can be joined. Therefore, the optimum electrode material for the device or process can be selected.
- Au can be easily etched as compared with Pt, so that the lower electrode can be miniaturized.
- the wiring resistance increases and the deterioration of device characteristics and reliability due to heat generation become problems.
- Au has a lower resistivity than Pt, so even if it is miniaturized, the wiring resistance The problem caused by the rise in the number can be avoided. Therefore, it is possible to achieve both miniaturization and high performance of the device.
- Au is particularly preferable as the material of the lower electrode, but Ag, Cu, Al, W, and Mo can also be preferably used, and alloys of Au, Ag, Cu, Al, W, and Mo can also be preferably used. .. Further, it is preferable to provide the above-mentioned buffer layer between the lower electrode and the piezoelectric body to improve the adhesion.
- the intermediate layer can be provided on the lower electrode, and the intermediate layer can be provided on the support substrate.
- the direct joining has the following embodiments. (1) The intermediate layer on the lower electrode and the support substrate are directly joined. (2) The intermediate layer on the support substrate and the lower electrode are directly joined. (3) The intermediate layer on the lower electrode and the intermediate layer on the support substrate are directly joined.
- the intermediate layer can be provided on the joint surface of the lower electrode, and the intermediate layer can be provided on the first surface of the high-rigidity ceramic plate.
- the direct joining has the following embodiments. (1) The intermediate layer on the joint surface of the lower electrode and the second surface of the high-rigidity ceramic plate are directly joined. (2) The intermediate layer on the second surface of the high-rigidity ceramic plate and the joint surface of the lower electrode are directly bonded. (3) The intermediate layer on the joint surface of the lower electrode and the intermediate layer on the second surface of the high-rigidity ceramic plate are directly bonded.
- the intermediate layer can be provided on the joint surface of the support substrate, and the intermediate layer can be provided on the first surface of the high-rigidity ceramic body.
- the direct joining has the following embodiments. (1) The intermediate layer on the joint surface of the support substrate and the first surface of the high-rigidity ceramic body are directly bonded. (2) The intermediate layer on the first surface of the high-rigidity ceramic plate and the joint surface of the support substrate are directly joined. (3) The intermediate layer on the first surface of the high-rigidity ceramic plate and the intermediate layer on the joint surface of the support substrate are directly bonded. In either form, an amorphous layer may form along the interface of the direct junction.
- Such an intermediate layer is preferable for increasing the bonding strength between the lower electrode and the high-rigidity ceramic plate, and between the high-rigidity ceramic plate and the support substrate.
- the material of the intermediate layer is not limited, and examples thereof include silicon oxide, tantalum pentoxide, titanium oxide, zirconium oxide, hafnium oxide, niobium oxide, bismuth oxide, alumina, magnesium oxide, aluminum nitride, silicon nitride, and silicon.
- the thickness of the intermediate layer is not particularly limited, but is preferably 0.01 to 1 ⁇ m, more preferably 0.01 to 0.5 ⁇ m from the viewpoint of manufacturing cost.
- the method for forming the intermediate layer is not limited, and examples thereof include a sputtering method, a chemical vapor deposition method (CVD), and a vapor deposition method.
- the material of the support substrate is not particularly limited, but it is preferably metal oxide, aluminum nitride, silicon carbide, silicon, glass, metal, and SOI (Silicon on Insulator).
- This metal oxide may be an oxide of a single metal, or may be a composite oxide of a plurality of kinds of metals.
- This metal oxide is preferably selected from the group consisting of sialone, sapphire, cordierite, mullite and alumina.
- Alumina is preferably translucent alumina. Examples of the metal include SUS, copper, and aluminum.
- the relative density of the support substrate is preferably 95.5% or more, and may be 100%. Relative density is measured by the Archimedes method.
- the method for producing the support substrate is not particularly limited, but a sintered body and crystal growth are preferable.
- the high-rigidity ceramics constituting the high-rigidity ceramic plate are materials having Young's modulus (JIS R1602): 200 GPa or more, bending strength (JIS R1601): 310 MPa or more, and fracture toughness (JIS R1607): 1.5 MPa ⁇ m or more.
- Examples of the types of high-rigidity ceramics include sialon, translucent alumina, and sapphire.
- Sialon is a ceramic obtained by sintering a mixture of silicon nitride and alumina, and has the following composition.
- the z is more preferably 0.5 or more. Further, z is more preferably 4.0 or less.
- Sapphire is a single crystal having a composition of Al 2 O 3
- alumina is a polycrystal having a composition of Al 2 O 3.
- the following methods are preferable.
- the joint surface of each intermediate layer, the joint surface of the support substrate, the joint surface of the high-rigidity ceramic body, and the joint surface of the lower electrode are flattened to obtain each flat surface.
- methods for flattening each joint surface include lap polishing and chemical mechanical polishing (CMP).
- the arithmetic average roughness Ra of the flat surface is preferably 1 nm or less, more preferably 0.3 nm or less.
- each joint surface is cleaned to remove the residue of the abrasive and the work-altered layer.
- Methods for cleaning each joint surface include wet cleaning, dry cleaning, scrub cleaning, and the like, but scrub cleaning is preferable in order to obtain a clean surface easily and efficiently.
- each joint surface is activated by irradiating each joint surface with a neutralized atomic beam.
- a neutralized atomic beam When the surface is activated by the neutralized beam, it is preferable to generate and irradiate the neutralized beam by using an apparatus as described in Patent Document 2. That is, a saddle field type high-speed atomic beam source is used as the beam source. Then, an inert gas is introduced into the chamber, and a high voltage is applied to the electrodes from a DC power source. As a result, the saddle field type electric field generated between the electrode (positive electrode) and the housing (negative electrode) causes the electrons e to move, and a beam of atoms and ions due to the inert gas is generated.
- the ion beam is neutralized by the grid, so that the beam of neutral atoms is emitted from the high-speed atomic beam source.
- the atomic species constituting the beam is preferably an inert gas (argon, nitrogen, etc.).
- the voltage at the time of activation by beam irradiation is preferably 0.5 to 2.0 kV, and the current is preferably 50 to 200 mA.
- the temperature at this time is room temperature, but specifically, it is preferably 40 ° C. or lower, and more preferably 30 ° C. or lower. Further, the temperature at the time of joining is particularly preferably 20 ° C. or higher and 25 ° C. or lower.
- the pressure at the time of joining is preferably 100 to 20000 N.
- An amorphous layer may be formed between the support substrate and the intermediate layer.
- the composition of such an amorphous layer contains metal atoms constituting the intermediate layer, metal atoms constituting the support substrate, oxygen atoms or nitrogen atoms constituting the support substrate, and optionally argon.
- an amorphous layer may be formed between the lower electrode and the intermediate layer.
- the composition of such an amorphous layer contains metal atoms constituting the intermediate layer, metal atoms constituting the lower electrode, and optionally argon.
- an amorphous layer may be formed between the high-rigidity ceramic plate and the intermediate layer.
- the composition of such an amorphous layer contains a metal atom constituting an intermediate layer, a metal atom constituting a high-rigidity ceramic plate, an oxygen atom or a nitrogen atom constituting a high-rigidity ceramic plate, and optionally argon.
- an amorphous layer may be formed between the piezoelectric material and the intermediate layer.
- the composition of such an amorphous layer contains metal atoms constituting the intermediate layer, metal atoms constituting the piezoelectric body, and optionally argon.
- a lower electrode and an intermediate layer are provided on the piezoelectric body, and then the bonding surface of the intermediate layer and the bonding surface of the support substrate are directly bonded. To obtain a joint.
- an amorphous layer is typically formed along the boundary between the support substrate and the intermediate layer.
- the piezoelectric body of the bonded body is processed to be thinned to form a piezoelectric layer having a desired thickness, and a piezoelectric vibrating substrate is obtained.
- a piezoelectric vibrating element is obtained by forming an upper electrode on the second surface of the piezoelectric layer.
- an intermediate layer is provided on the first surface of the high-rigidity ceramic body.
- the intermediate layer and the bonding surface of the support substrate are directly bonded to obtain a bonded body.
- an amorphous layer is formed along the interface between the intermediate layer and the joint surface of the support substrate.
- the high-rigidity ceramic body is processed to be thinned to form a high-rigidity ceramic plate having a desired thickness.
- a lower electrode is provided on the first surface of the piezoelectric body, and an intermediate layer is provided on the joint surface of the lower electrode.
- an intermediate layer is provided on the second surface of the high-rigidity ceramic plate, and this intermediate layer is directly bonded to the intermediate layer on the joint surface of the lower electrode.
- the piezoelectric layer is obtained by processing the piezoelectric body.
- the piezoelectric vibrating element of the present invention can be suitably used as an actuator for a MEMS element or the like.
- Example A1 The piezoelectric vibrating element 11 shown in FIG. 2B was prototyped according to the method described with reference to FIGS. 1 and 2. .. However, the piezoelectric body 2 was a bulk body of PZT having a thickness of 250 ⁇ m, and the materials of the upper electrode 1 and the lower electrode 3 were Pt. An intermediate layer 4 made of amorphous silicon was provided on the lower electrode 3 by a sputtering method. Moreover, the support substrate 5 made of silicon was prepared. Next, the joint surface 5a of the support substrate 5 and the joint surface 4a of the intermediate layer 4 were finished by chemical mechanical polishing (CMP), and each arithmetic average roughness Ra was set to 0.2 nm.
- CMP chemical mechanical polishing
- each junction surface 4a and 5a was irradiated with a high-speed atomic beam (acceleration voltage 1 kV, Ar flow rate 27 sccm) for 120 seconds. Then, after the joining surface 5a of the support substrate 5 and the joining surface 4a of the intermediate layer 4 were brought into contact with each other, they were joined by pressurizing at 10000 N for 2 minutes. Next, one main surface 2b of the piezoelectric body 2 was ground and polished to form a piezoelectric layer 2A having a thickness of 1 ⁇ m. Next, the upper electrode 1 was formed on the second surface 2c of the piezoelectric layer 2A by a sputtering method to obtain a piezoelectric vibrating element 11.
- the piezoelectric vibrating element 11 was mounted on the package and wire bonded. In the bonding step, heating (150 ° C.), ultrasonic vibration (80 kHz) and load (500 gf) were applied to the piezoelectric vibrating element 11. As a result, the incidence of defective products in which cracks and chipping occurred in the piezoelectric vibrating element 11 was 5%.
- FIG. 5 is a cross-sectional transmission electron microscope (TEM) photograph showing the bonding interface between the intermediate layer of the piezoelectric vibrating element 11 and the supporting substrate and its surroundings (magnification: 2 million times).
- the bright region on the upper side is an intermediate layer (amorphous silicon)
- the lower side is a support substrate (silicon)
- the strip-shaped region in the central portion is an amorphous layer generated at the time of joining.
- the ratio of each atom in the support substrate, the amorphous layer, and the intermediate layer is as follows.
- Example A1 A piezoelectric layer was formed by the vapor phase film formation method, and a piezoelectric vibrating element was prototyped. That is, a lower electrode 3 made of Pt, a piezoelectric layer made of PZT having a thickness of 1 ⁇ m, and an upper electrode made of Pt were formed on a support substrate made of silicon by a sputtering method to obtain a piezoelectric vibrating element. Next, the piezoelectric vibrating element was mounted on the package, and heat, ultrasonic vibration, and load were applied in the same manner as in Example A1. As a result, the incidence of defective products in which cracks and chipping occurred in the piezoelectric vibrating element was 20%.
- Example B1 The piezoelectric vibrating element 11 was prototyped in the same manner as in Example A1. However, unlike Example A1, the material of the piezoelectric body 2 and the piezoelectric layer 2A was PMN-PT. Others were the same as in Example A1. The obtained piezoelectric vibration element 11 was mounted on a package, and heat, ultrasonic vibration and load were applied in the same manner as in Example A1. As a result, the incidence of defective products in which cracks and chipping occurred in the piezoelectric vibrating element was 6%.
- Example B1 The piezoelectric vibrating element 11 was prototyped in the same manner as in Comparative Example A1. However, unlike Comparative Example A1, the material of the piezoelectric layer was PMN-PT. Others were the same as in Comparative Example A1. The obtained piezoelectric vibrating element was mounted on a package, and heat, ultrasonic vibration and load were applied in the same manner as in Example A1. As a result, the incidence of defective products in which cracks and chipping occurred in the piezoelectric vibrating element was 22%.
- Example C1 The piezoelectric vibrating element 12 shown in FIG. 4C was prototyped according to the method described with reference to FIGS. 3 and 4. However, as shown in FIG. 3A, an intermediate layer 8 made of amorphous silicon was provided on the first surface 7a of the high-rigidity ceramic body 7 made of Sialon having a thickness of 250 ⁇ m. Further, as shown in FIG. 3B, an intermediate layer made of amorphous silicon was prepared on the surface of the support substrate 5 having a thickness of 500 ⁇ m made of silicon. Next, the intermediate layer joint surface 5a of the support substrate 5 and the joint surface 8a of the intermediate layer 8 were finished by chemical mechanical polishing (CMP), and each arithmetic average roughness Ra was set to 0.2 nm.
- CMP chemical mechanical polishing
- the intermediate layer joint surface 5a of the support substrate 5 and the joint surface 8a of the intermediate layer 8 were washed to remove stains, and then introduced into a vacuum chamber. After evacuating to 10-6 Pa, the joint surfaces 5a and 8a were irradiated with a high-speed atomic beam (acceleration voltage 1 kV, Ar flow rate 27 sccm) for 120 seconds. Then, the intermediate layer bonding surface 5a of the support substrate 5 and the bonding surface 8a of the intermediate layer 8 were brought into contact with each other, and then pressurized at 10000 N for 2 minutes for bonding. The resulting conjugate was then heated at 100 ° C. for 20 hours.
- a high-speed atomic beam acceleration voltage 1 kV, Ar flow rate 27 sccm
- the second surface 7b of the high-rigidity ceramic body 7 was ground and polished to form a high-rigidity ceramic plate 7A having a thickness of 50 ⁇ m as shown in FIG. 3C.
- the intermediate layer 16 is not provided on the second surface 7c of the high-rigidity ceramic plate 7A.
- the piezoelectric body 2 is a bulk body of PZT having a thickness of 250 ⁇ m, and Ti (15 nm) / Pt (200 nm) is used as the lower electrode 3 on the first surface 2a of the piezoelectric body 2.
- an intermediate layer 4 made of amorphous silicon was further provided by a sputtering method.
- the second surface 7c of the high-rigidity ceramic plate 7A and the joint surface 4a of the intermediate layer 4 are finished by chemical mechanical polishing (CMP), and each arithmetic average roughness Ra is set to 0. It was set to .2 nm.
- CMP chemical mechanical polishing
- the second surface 7c of the high-rigidity ceramic plate 7A and the joint surface 4a of the intermediate layer 4 were washed to remove dirt, and then introduced into a vacuum chamber. After vacuuming to 10-6 Pa, the second surface 7c and the junction surface 4a were irradiated with a high-speed atomic beam (acceleration voltage 1 kV, Ar flow rate 27 sccm) for 120 seconds. Then, the second surface 7c of the high-rigidity ceramic plate 7A and the joint surface 4a of the intermediate layer 4 were brought into contact with each other, and then pressurized at 10000 N for 2 minutes for joining. The resulting conjugate was then heated at 100 ° C. for 20 hours.
- a high-speed atomic beam acceleration voltage 1 kV, Ar flow rate 27 sccm
- the second surface 2b of the piezoelectric body 2 was ground and polished to form a piezoelectric layer 2A having a thickness of 1 ⁇ m as shown in FIG. 4 (b).
- the upper electrode 1 Ti (15 nm) / Pt (200 nm) was formed into a film by a sputtering method to obtain a piezoelectric vibrating element 12.
- the piezoelectric vibrating element 12 was mounted on the package and wire bonded. In the bonding step, heating (150 ° C.), ultrasonic vibration (80 kHz) and load (500 gf) were applied to the piezoelectric vibrating element 12. As a result, the incidence of defective products in which cracks and chipping occurred in the piezoelectric vibrating element 11 was 5%.
- FIG. 6 is a cross-sectional transmission electron microscope (TEM) photograph showing the bonding interface between the intermediate layer on the bonding surface of the lower electrode 3 and the high-rigidity ceramic plate and its surroundings (magnification: 2 million times).
- the bright region on the upper side is an intermediate layer (amorphous silicon)
- the lower side is a high-rigidity ceramic plate (Sialon)
- the strip-shaped region in the central portion is an amorphous layer formed at the time of joining.
- the ratio of each atom in the high-rigidity ceramic plate, amorphous layer, and intermediate layer is as follows.
- FIG. 7 is a cross-section transmission electron microscope (TEM) photograph showing the bonding interface between the intermediate layer on the bonding surface 5a of the support substrate 5 and the intermediate layer on the first surface of the high-rigidity ceramic plate and its periphery (magnification). 2 million times).
- the upper bright region is the intermediate layer (amorphous silicon)
- the lower dark region is the support substrate (silicon).
- the band-shaped region between the two intermediate layers is an amorphous layer formed at the time of joining.
- the ratio of each atom in the intermediate layer on the high-rigidity ceramic plate, the amorphous layer on the first surface, the intermediate layer on the support substrate, and the support substrate is as follows.
- Example D1 A piezoelectric vibrating element was produced in the same manner as in Example A1.
- the material of the buffer layer on the piezoelectric body was Cr, and the material of the lower electrode and the upper electrode was Au.
- no intermediate layer was provided on the lower electrode, no intermediate layer was provided on the support substrate, and the lower electrode and the support substrate were directly bonded.
- the piezoelectric body 2 was a bulk body of PZT having a thickness of 250 ⁇ m, and a buffer layer and a lower electrode were formed on the piezoelectric body 2 by a sputtering method.
- the material of the buffer layer was Cr
- the material of the lower electrode was Au.
- the support substrate 5 made of silicon was prepared.
- the joint surface 5a of the support substrate 5 and the joint surface of the lower electrode were finished by chemical mechanical polishing (CMP), and each arithmetic average roughness Ra was set to 0.2 nm.
- each junction surface was irradiated with a high-speed atomic beam (acceleration voltage 1 kV, Ar flow rate 27 sccm) for 120 seconds. Then, after the joint surface 5a of the support substrate 5 and the joint surface of the lower electrode were brought into contact with each other, the bonding was performed by pressurizing at 10000 N for 2 minutes.
- one main surface 2b of the piezoelectric body 2 was ground and polished to form a piezoelectric layer 2A having a thickness of 1 ⁇ m.
- a buffer layer made of Cr and an upper electrode made of Au were formed on the second surface 2c of the piezoelectric layer 2A by a sputtering method to obtain a piezoelectric vibrating element.
- FIG. 8 is a cross-section transmission electron microscope (TEM) photograph of the piezoelectric vibrating element (magnification: 2 million times).
- TEM transmission electron microscope
- the bright region on the upper side is the piezoelectric layer, and the Cr layer and the Au layer are displayed as bands on the first surface of the piezoelectric layer, respectively.
- the lower side is a support substrate (silicon), and the band-shaped region between the support substrate and the Au layer is an amorphous layer formed at the time of joining.
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Abstract
Description
(1) フロントガラスなどをスクリーンとして直接画像を投影するDirect Projection方式
(2) フロントガラスなどを反射ミラーとして作用させドライバーの網膜上に結像させるVirtual Imaging方式
この方式による主な利点は以下のとおりである。
(1) 部品点数が少ないため小型化、低コスト化、信頼性向上を実現できる。
(2) 各画素に必要な明るさでレーザーを点灯するため、低消費電力を実現できる。
(3) コリメート(平行光)されたレーザー光を用いるため、フォーカス調整が不要である。
バルク状の圧電性材料からなり、第一面および前記第一面と反対側の第二面を有する圧電層、
前記圧電層の第一面上の下部電極、および
前記下部電極に対して接合されている支持基板
を備えていることを特徴とする、圧電振動基板
に係るものである。
前記圧電層上の上部電極
を備えることを特徴とする、圧電振動素子に係るものである。
バルク状の圧電性材料からなり、第一面および前記第一面と反対側の第二面を有する圧電層、
前記圧電層の第一面上の下部電極、
前記下部電極に対して接合されている高剛性セラミック板、および
前記高剛性セラミック板に対して接合されている支持基板
を備えていることを特徴とする、圧電振動基板に係るものである。
前記圧電層の第二面上の上部電極
を備えることを特徴とする、圧電振動素子に係るものである。
この結果、本発明によって、圧電特性および耐久性に優れた圧電アクチュエーターデバイスを実現可能となる。
図1および図2は、第一の態様の発明に係るものである。
好適な実施形態においては、図1(a)に示すように、圧電体2は第一面2aと第二面2bとを有する。圧電体2の第一面2a上に下部電極3、中間層4を設ける。次いで、中間層4の接合面4aに対して矢印Aのように中性化原子ビームを照射することによって,中間層4aを活性化する。
図3(a)に示すように、高剛性セラミック体7は第一面7aおよび第二面7bを有する。高剛性セラミック体7の第一面7a上に中間層8を設ける。次いで、中間層8の接合面8aに対して矢印Cのように中性化原子ビームを照射することによって、接合面8aを活性化する。一方、図3(b)に示すように、支持基板5の接合面5aに対して矢印Bのように中性化原子ビームを照射することによって、接合面5aを活性化する。
バルク状の圧電性材料とは、基板上に成膜された状態の圧電性材料ではなく、結晶成長法や焼結法によってバルク状に形成された圧電性材料を意味する。こうした圧電性材料は通常結晶性がよく、強度が高い。
(1) 下部電極上の中間層と支持基板とを直接接合する。
(2) 支持基板の上の中間層と下部電極とを直接接合する。
(3) 下部電極上の中間層と支持基板上の中間層とを直接接合する。
(1) 下部電極の接合面上の中間層と高剛性セラミックス板の第二面とを直接接合する。
(2) 高剛性セラミックス板の第二面上の中間層と下部電極の接合面とを直接接合する。
(3) 下部電極の接合面上の中間層と高剛性セラミックス板の第二面上の中間層とを直接接合する。
(1) 支持基板の接合面上の中間層と高剛性セラミックス体の第一面とを直接接合する。
(2) 高剛性セラミックス板の第一面上の中間層と支持基板の接合面とを直接接合する。
(3) 高剛性セラミックス板の第一面上の中間層と支持基板の接合面上の中間層とを直接接合する。
いずれの形態においても、直接接合の界面に沿って非晶質層が生成することがある。
中間層の材質は限定されないが、酸化珪素、五酸化タンタル、酸化チタン、酸化ジルコニウム、酸化ハフニウム、酸化ニオブ、酸化ビスマス、アルミナ、酸化マグネシウム、窒化アルミニウム、窒化珪素、珪素を例示できる。
中間層の成膜方法は限定されないが、スパッタリング(sputtering)法、化学的気相成長法(CVD)、蒸着を例示できる。
高剛性セラミックスの種類としては、サイアロン、透光性アルミナ、サファイアなどを例示できる。
サイアロンは、窒化珪素とアルミナとの混合物を焼結して得られるセラミックスであり、以下のような組成を有する。
Si6-zAlzOzN8-z
すなわち、サイアロンは、窒化珪素中にアルミナが混合された組成を有しており、zがアルミナの混合比率を示している。zは、0.5以上が更に好ましい。また、zは、4.0以下が更に好ましい。
まず、各中間層の接合面、支持基板の接合面、高剛性セラミック体の接合面、下部電極の接合面を平坦化して各平坦面を得る。ここで、各接合面を平坦化する方法は、ラップ(lap)研磨、化学機械研磨加工(CMP)などがある。また、平坦面の算術平均粗さRaは、1nm以下が好ましく、0.3nm以下が更に好ましい。
中性化ビームによる表面活性化を行う際には、特許文献2に記載のような装置を使用して中性化ビームを発生させ、照射することが好ましい。すなわち、ビーム源として、サドルフィールド型の高速原子ビーム源を使用する。そして、チャンバーに不活性ガスを導入し、電極へ直流電源から高電圧を印加する。これにより、電極(正極)と筺体(負極)との間に生じるサドルフィールド型の電界により、電子eが運動して、不活性ガスによる原子とイオンのビームが生成される。グリッドに達したビームのうち、イオンビームはグリッドで中和されるので、中性原子のビームが高速原子ビーム源から出射される。ビームを構成する原子種は、不活性ガス(アルゴン、窒素等)が好ましい。
ビーム照射による活性化時の電圧は0.5~2.0kVとすることが好ましく、電流は50~200mAとすることが好ましい。
また、下部電極と中間層との間には非晶質層が生成することがある。こうした非晶質層の組成は、中間層を構成する金属原子、下部電極を構成する金属原子、および場合によってはアルゴンを含有する。
次いで、接合体の圧電体を加工して薄くすることによって、所望の厚さを有する圧電層を形成し、圧電振動基板を得る。次いで、図2(b)に示すように、圧電層の第二面上に上部電極を形成することによって、圧電振動素子を得る。
一方、圧電体の第一面に下部電極を設け、下部電極の接合面上に中間層を設ける。
、そして、高剛性セラミックス板の第二面上に中間層を設け、この中間層を下部電極の接合面上の中間層に直接接合する。次いで、圧電体を加工することで圧電層を得る。
図1および図2を参照しつつ説明した方法にしたがって、図2(b)に示す圧電振動素子11を試作した。.
ただし、圧電体2は厚さ250μmのPZTのバルク体とし、上部電極1、下部電極3の材質をPtとした。下部電極3上にスパッタリング法によってアモルファスシリコンからなる中間層4を設けた。また、シリコンからなる支持基板5を準備した。次いで、支持基板5の接合面5aおよび中間層4の接合面4aを、化学機械研磨加工(CMP)によって仕上げ加工し、各算術平均粗さRaを0.2nmとした。
次いで、圧電体2の一方の主面2bを研削および研磨加工することによって、厚み1μmの圧電層2Aを形成した。次いで、圧電層2Aの第二面2c上に上部電極1をスパッタリング法で成膜し、圧電振動素子11を得た。
気相成膜法によって圧電層を成膜し、圧電振動素子を試作した。
すなわち、シリコンからなる支持基板上に、Ptからなる下部電極3、厚さ1μmのPZTからなる圧電層およびPtからなる上部電極をスパッタリング法で成膜し、圧電振動素子を得た。
次いで、圧電振動素子をパッケージに実装し、実施例A1と同様にして熱、超音波振動および荷重を加えた。この結果、圧電振動素子にクラックやチッピングが発生した不良品の発生率は20%であった。
実施例A1と同様にして圧電振動素子11を試作した。ただし、実施例A1とは異なり、圧電体2および圧電層2Aの材質をPMN-PTとした。その他は実施例A1と同様とした。得られた圧電振動素子11をパッケージに実装し、実施例A1と同様にして熱、超音波振動および荷重を加えた。この結果、圧電振動素子にクラックやチッピングが発生した不良品の発生率は6%であった。
比較例A1と同様にして圧電振動素子11を試作した。ただし、比較例A1とは異なり、圧電層の材質をPMN-PTとした。その他は比較例A1と同様とした。得られた圧電振動素子をパッケージに実装し、実施例A1と同様にして熱、超音波振動および荷重を加えた。この結果、圧電振動素子にクラックやチッピングが発生した不良品の発生率は22%であった。
図3および図4を参照しつつ説明した方法にしたがって、図4(c)に示す圧電振動素子12を試作した。
ただし、図3(a)に示すように、厚さ250μmのサイアロンからなる高剛性セラミック体7の第一面7aに、アモルファスシリコンからなる中間層8を設けた。また、図3(b)に示すように、シリコンからなる厚さ500μmの支持基板5の表面にアモルファスシリコンからなる中間層を準備した。次いで、支持基板5の中間層接合面5aおよび中間層8の接合面8aを、化学機械研磨加工(CMP)によって仕上げ加工し、各算術平均粗さRaを0.2nmとした。
次いで、支持基板5の中間層接合面5aおよび中間層8の接合面8aを洗浄し、汚れを取った後、真空チャンバーに導入した。10-6Pa台まで真空引きした後、各接合面5a、8aに高速原子ビーム(加速電圧1kV、Ar流量27sccm)を120sec間照射した。ついで、支持基板5の中間層接合面5aと中間層8の接合面8aとを接触させた後、10000Nで2分間加圧して接合した。次いで、得られた接合体を100℃で20時間加熱した。
一方、図3(d)に示すように、圧電体2は厚さ250μmのPZTのバルク体とし、圧電体2の第一面2a上に、下部電極3としてTi(15nm)/Pt(200nm)を成膜し、更にスパッタリング法によってアモルファスシリコンからなる中間層4を設けた。
次いで、高剛性セラミック板7Aの第二面7cおよび中間層4(図1(a)参照)の接合面4aを、化学機械研磨加工(CMP)によって仕上げ加工し、各算術平均粗さRaを0.2nmとした。
次いで、圧電体2の第二面2bを研削および研磨加工することによって、図4(b)に示すように、厚さ1μmの圧電層2Aを形成した。次いで、上部電極1(Ti(15nm)/Pt(200nm))をスパッタリング法で成膜し、圧電振動素子12を得た。
実施例A1と同様にして圧電振動素子を作製した。
ただし、実施例A1と異なり、圧電体上のバッファ層の材質をCrとし、下部電極および上部電極の材質をAuとした。また下部電極上には中間層を設けず、支持基板上にも中間層を設けず、下部電極と支持基板とを直接接合した。
図8は、圧電振動素子の断面透過型電子顕微鏡(TEM)写真である(倍率200万倍)。図8において、上側の明るい領域は圧電層であり、圧電層の第一面にCr層およびAu層がそれぞれ帯として表示されている。そして、下側は支持基板(シリコン)であり、支持基板とAu層との間の帯状領域は、接合時に生じた非晶質層である。
Claims (10)
- バルク状の圧電性材料からなり、第一面および前記第一面と反対側の第二面を有する圧電層、
前記圧電層の第一面上の下部電極、および
前記下部電極に対して接合されている支持基板
を備えていることを特徴とする、圧電振動基板。 - 前記下部電極と前記支持基板との界面に沿って非晶質層が存在することを特徴とする、請求項1記載の圧電振動基板。
- 前記下部電極と前記支持基板との間に中間層を有することを特徴とする、請求項1または2記載の圧電振動基板。
- 請求項1~3のいずれか一つの請求項に記載の圧電振動基板、および
前記圧電層の前記第二面上の上部電極
を備えることを特徴とする、圧電振動素子。 - バルク状の圧電性材料からなり、第一面および前記第一面と反対側の第二面を有する圧電層、
前記圧電層の前記第一面上の下部電極、
前記下部電極に対して接合されている高剛性セラミック板、および
前記高剛性セラミック板に対して接合されている支持基板
を備えていることを特徴とする、圧電振動基板。 - 前記下部電極と前記高剛性セラミック板との界面に沿って非晶質層が存在することを特徴とする、請求項5記載の圧電振動基板。
- 前記高剛性セラミック板と前記支持基板の界面に沿って非晶質層が存在することを特徴とする、請求項5または6記載の圧電振動基板。
- 前記下部電極と前記高剛性セラミックの間に中間層を有することを特徴とする、請求項5~7のいずれか一つの請求項に記載の圧電振動基板。
- 前記高剛性セラミックと前記支持基板の間に中間層を有することを特徴とする、請求項5~8のいずれか一つの請求項に記載の圧電振動基板。
- 前記圧電層の前記第二面上に上部電極を備えることを特徴とする、請求項5~9のいずれか一つの請求項に記載の圧電振動素子。
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