CN113690364A - Composite piezoelectric substrate and preparation method thereof - Google Patents
Composite piezoelectric substrate and preparation method thereof Download PDFInfo
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- CN113690364A CN113690364A CN202110963337.2A CN202110963337A CN113690364A CN 113690364 A CN113690364 A CN 113690364A CN 202110963337 A CN202110963337 A CN 202110963337A CN 113690364 A CN113690364 A CN 113690364A
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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
- H10N30/01—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
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- H10N30/706—
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Abstract
The application provides a compound piezoelectric substrate and preparation method thereof, compound piezoelectric substrate includes glaze material layer (1) and piezoelectric film layer (2), the method chooses the frit that the principal ingredients is silica for use as the base of compound piezoelectric substrate, and is as an organic whole through coating and piezoelectric film layer (2) butt fusion, the highest process temperature of method is no more than 550 ℃, and requires lowly to bonding surface roughness, and, the frit is to piezoelectric film layer (2) not damaged, compound piezoelectric substrate can also include stratum basale (3), the frit then regards as the binder, will stratum basale (3) with piezoelectric film layer (2) bond in an organic whole compound piezoelectric substrate, the frit is right stratum basale (3) also not damaged, and used butt fusion equipment is with low costs, can improve production efficiency, reduces the production material cost, the lattice constants of the quasistance layer and the piezoelectric crystal layer need not be close.
Description
Technical Field
The application belongs to the field of functional semiconductor materials, and particularly relates to a composite piezoelectric substrate and a preparation method thereof.
Background
Piezoelectric crystal materials, such as lithium niobate or lithium tantalate, have excellent electro-optic, acousto-optic, piezoelectric, and photorefractive properties and good mechanical properties, and are widely used in the field of optoelectronic integration, for example, in the field of optical fiber communications for the fabrication of waveguide modulators. The device manufactured based on the piezoelectric crystal material has the advantages of small volume, high performance, low power consumption and the like.
The film waveguide is generally obtained by cutting, etching or polishing a composite piezoelectric substrate, and generally comprises a substrate layer and a piezoelectric film layer, wherein the piezoelectric film layer is prepared from a piezoelectric crystal material, and because the refractive index difference between the substrate layer and the piezoelectric film layer is large, for example, the refractive index difference between a lithium niobate film layer and a silicon dioxide substrate layer can reach about 0.7, the film waveguide is beneficial to binding an optical signal to the piezoelectric film layer in the transmission process to reduce loss, and the size of the film waveguide is small, so that the film waveguide is convenient for photoelectronic chip integration, and therefore, the demand for the film waveguide is increasingly large at present.
The composite piezoelectric substrate is usually prepared by adopting a high-temperature bonding method, the method generally bonds a piezoelectric wafer onto the piezoelectric wafer under the high-temperature vacuum condition, optionally can also perform thinning treatment on the piezoelectric wafer, the method has high requirements on the roughness of the bonding surfaces of the piezoelectric wafer and the piezoelectric wafer, the surface roughness of the bonding surface is generally required to be below 0.1nm, and the vacuum degree is kept to be 10 in the bonding process-7Pa or less, and at the same time, a pressure of at least 1MPa needs to be applied to the piezoelectric wafer.
However, the high-temperature bonding method has high cost of equipment, single equipment can only carry out single-chip operation, and the bonding process has long time and low efficiency, so that the industrial mass production is difficult to realize; in the high-temperature bonding process, the physicochemical properties of two wafers to be bonded are similar, so that the selectable range of the material types of the piezoelectric wafers is limited; in addition, in the high-temperature bonding process, the surface oxide layer needs to be removed through high-energy particle bombardment and other modes, so that the surface activation energy of the piezoelectric wafer and the bonding surface of the piezoelectric wafer is increased to ensure a better bonding effect, but the operation can damage the bonding surface of the piezoelectric wafer, so that the utilization rate of the composite piezoelectric substrate is reduced.
Disclosure of Invention
In order to solve at least one of the problems, the application provides a composite piezoelectric substrate and a preparation method thereof, the composite piezoelectric substrate can comprise a glaze layer (1) and a piezoelectric film layer (2), the method selects the glaze with silicon dioxide as a substrate of the composite piezoelectric substrate, and the glaze and the piezoelectric film layer (2) are welded into a whole through coating, the highest process temperature of the method is not more than 550 ℃, the requirement on the surface roughness of a bonding surface is low, the glaze is not damaged on the piezoelectric film layer (2), further, the composite piezoelectric substrate can also comprise a substrate layer (3), the glaze is used as a binder, the substrate layer (3) and the piezoelectric film layer (2) are bonded into a whole to form the composite piezoelectric substrate, the glaze is not damaged on the substrate layer (3), and therefore, the utilization rate of the composite piezoelectric substrate prepared by the method provided by the application can be improved, moreover, the used welding equipment is low in cost, a single device can be used for welding multiple groups of composite piezoelectric substrates at the same time, the production efficiency can be greatly improved, and furthermore, the glaze can serve as a substrate layer (3). The piezoelectric performance of the composite piezoelectric substrate prepared by the method is equivalent to that of a piezoelectric film prepared by a high-temperature bonding method.
The present application aims to provide the following aspects:
in a first aspect, the present application provides a composite piezoelectric substrate comprising: the piezoelectric ceramic film comprises a glaze layer 1 and a piezoelectric thin film layer 2, wherein the glaze layer 1 is formed by coating glaze on the piezoelectric thin film layer 2.
In an achievable mode, the main component of the glaze layer 1 is silicon dioxide, and the auxiliary materials comprise aluminum oxide, zinc oxide, ethyl cellulose and an organic solvent; and/or the thickness of the glaze layer 1 is 2-500 μm, and the thermal expansion coefficient is 3.0 × 10-7K-1～8.0×10-6K-1A refractive index of 1.4 to 1.7 and a Young's modulus of 5.0X 1010Pa(N/m2)～9.0×1010(N/m2) The melting temperature is 200-550 ℃; and/or the porosity of the glaze layer 1 is less than 0.5%.
In a realizable manner, the surface roughness of the bonding surface of the piezoelectric thin film layer 2 is 0.1nm to 5 nm.
In a realisable manner, the composition in the glaze layer 1 is uniformly distributed from the bonding side to the substrate side.
The thickness of the glaze layer 1 is more than 200nm, and the glaze layer 1 is used as a substrate of the composite piezoelectric substrate.
In an achievable mode, the glaze layer 1 is obtained by solidifying a glaze, the main component of the glaze layer 1 is silicon dioxide, the silicon dioxide is a commonly used semiconductor material, the glaze using the silicon dioxide as the main component has almost no negative influence on the performance of the piezoelectric film, the original electrical performance of the piezoelectric film layer 2 can be maintained, and therefore, the difficulty of the preparation process is reduced on the premise of keeping the performance and the volume of the product unchanged.
In one realizable form, the piezoelectric thin film layer 2 is made of piezoelectric materials including homogenous lithium niobate, homogenous lithium tantalate, near stoichiometric lithium niobate, near stoichiometric lithium tantalate, doped lithium niobate, doped lithium tantalate, and gallium nitride.
Optionally, the thickness of the piezoelectric film layer 2 is 0.1 μm to 100 μm, preferably 1 μm to 80 μm, for example, 5 μm to 10 μm, so as to meet the requirement of the semiconductor device on the thickness of the piezoelectric film layer.
In a second aspect, the present application provides a method of making the composite piezoelectric substrate of the first aspect, the method comprising:
and 2, carrying out planarization treatment and sizing on the glaze to obtain the composite piezoelectric substrate.
In an implementable manner, before step 1, the method may further comprise: and carrying out pretreatment on the surface of the piezoelectric wafer, wherein the pretreatment comprises polishing, cleaning and the like.
In an implementable manner, after the pre-processing of the surface of the piezoelectric wafer, before step 2, the method may further include:
step 1-1, preparing a quasi-junction layer on a bonding surface of the piezoelectric wafer;
and 1-2, carrying out planarization treatment on the alignment layer.
The quasi-junction layer comprises at least one quasi-junction layer, each quasi-junction layer is prepared from at least one of metal, metal compound and inorganic nonmetal, wherein the metal comprises at least one of gold, platinum, copper, aluminum, chromium, nickel and the like, the metal compound comprises at least one of gallium nitride, aluminum oxide, aluminum nitride, gallium arsenide and the like, the inorganic nonmetal comprises at least one of silicon dioxide, silicon carbide, polycrystalline silicon and silicon nitride, and the thickness of the quasi-junction layer is 0.1-10 mu m, preferably 1-3 mu m. The thickness of the quasi-junction layer is set to the above thickness in the present application based on cost.
Optionally, the planarizing the alignment layer includes: a combination of grinding and polishing.
In an achievable mode, the main component of the glaze in the step 2 is silicon dioxide, and the auxiliary materials comprise: alumina, zinc oxide, ethyl cellulose, the solvent comprises: esters and at least two of ethers, alcohols and hydrocarbon compounds, generally being a mixture of the lipids and other compounds, wherein the lipids can enable the slurry to have good lubricating performance, namely being capable of being heated more smoothly, and the other compounds are gasified in the heating process due to low boiling point, so that the pores are less after heating, based on the total volume of the glaze, the content of the silicon dioxide is 50 g/mL-200 g/mL, the viscosity of the glaze is 50 Pa.s-400 Pa.s, the main component is high-purity silicon dioxide, the melting point of the glaze is lower than that of a piezoelectric wafer, preferably, the glaze can be glass slurry, wherein the sintering temperature of the glass slurry is 400-550 ℃, the fineness of the glass slurry is less than 8 mu m, and the viscosity of the glass slurry is 100 Pa.s-200 Pa.s, so that only the glaze is in a molten state in the process of preparing the composite piezoelectric substrate, the piezoelectric wafer is in a solid state, and the lattice structure of the piezoelectric wafer can be kept unchanged so as to ensure the piezoelectric performance of the composite piezoelectric substrate.
In one implementation, the method of applying the glaze on the surface of the piezoelectric wafer includes brushing, spin coating, and spraying.
Optionally, the brushing comprises:
laying a layer of silk screen on the piezoelectric wafer, wherein the thickness of the silk screen is 100-500 μm, the grid of the silk screen can be square, the size of the mesh is 1-20 mm, and the material can be copper or stainless steel;
uniformly brushing a layer of glaze on the surface of the piezoelectric wafer through the silk screen, wherein the thickness of the glaze is less than or equal to that of the silk screen;
and taking down the silk screen.
In the present application, the spin coating may be any spin coating method that can take a wafer as an object in the prior art; the spraying can be any spin coating method which can take a wafer as an object in the prior art.
In one implementation, step 2 comprises:
heating the piezoelectric wafer coated with the glaze to the volatilization temperature of a glaze solvent, and preserving heat;
and continuously heating to the melting point of the glaze, and cooling after heat preservation.
Optionally, the glaze layer may be subjected to surface treatment after cooling and solidifying, the surface treatment including grinding and polishing. In the application, after surface treatment, the roughness of the surface of the glaze layer is less than 10nm, so that the upper surface and the lower surface are parallel after the substrate and the upper film are fused.
In one implementation, the thickness of the glaze layer is 0.1-1000 μm to provide sufficient support for the piezoelectric wafer.
In an achievable mode, after the preparation of the glaze layer is completed, the piezoelectric wafer can be thinned, and the thinning method can adopt any method in the prior art, such as a grinding thinning method, a polishing thinning method, an ion implantation stripping method and the like, for thinning the piezoelectric wafer.
Further, the thickness of the piezoelectric wafer after thinning processing can be specifically set according to the use requirement.
In a third aspect, the present application also provides another composite piezoelectric substrate comprising: the piezoelectric ceramic substrate comprises a substrate layer 3, a glaze layer 1 and a piezoelectric thin film layer 2, wherein the substrate layer 3 and the piezoelectric thin film layer 2 are bonded through the glaze layer 1.
In one implementable manner, the base layer 3 includes a single phase substrate and a composite substrate, wherein the single phase substrate is made of a single semiconductor material comprising single crystal silicon, silica, alumina, lithium tantalate, lithium niobate; the composite substrate comprises a base substrate layer and a quasi-junction layer, wherein the base substrate layer is made of a single semiconductor material, the semiconductor material comprises monocrystalline silicon, silicon dioxide, aluminum oxide, lithium tantalate and lithium niobate, the quasi-junction layer comprises at least one quasi-junction sub-layer, each quasi-junction sub-layer is made of at least one of metal, metal compound and inorganic nonmetal, the metal comprises at least one of gold, platinum, copper, aluminum, chromium, nickel and the like, the metal compound comprises at least one of gallium nitride, aluminum oxide, aluminum nitride, gallium arsenide and the like, and the inorganic nonmetal comprises at least one of silicon dioxide, silicon carbide, polycrystalline silicon and silicon nitride.
Optionally, the thickness of the substrate layer 3 is 1 μm to 1000 μm, preferably 20 to 800 μm, for example, 100 to 500 μm.
In a realizable mode, if the composite piezoelectric substrate comprises the substrate layer 3, the thickness of the glaze layer 1 can be reduced to 300-5000 nm, so that the total thickness of the composite piezoelectric substrate is reduced, and the application range of the composite piezoelectric substrate is increased.
In an implementation manner, specific structures and parameters of the glaze layer 1 and the piezoelectric thin film layer 2 are the same as those of the glaze layer 1 and the piezoelectric thin film layer 2 in the composite piezoelectric substrate according to the first aspect, which may be referred to the first aspect specifically, and are not described herein again.
In a fourth aspect, the present application also provides a method of manufacturing the composite piezoelectric substrate according to the third aspect, the method comprising:
step 1', coating glaze on the surface of a piezoelectric wafer and/or a substrate material;
step 2', carrying out planarization treatment on the glaze to obtain a glaze layer;
and 3 ', attaching a substrate material and/or a piezoelectric wafer to the glaze layer obtained in the step 2' to obtain a piezoelectric wafer-substrate material assembly, heating and applying pressure to the piezoelectric wafer-substrate material assembly, and cooling after heat preservation and pressure maintaining.
In an achievable manner, the melting point of the piezoelectric wafers is higher than that of the glaze, so that only the glaze is in a molten state during the preparation of the composite piezoelectric substrate, and the piezoelectric wafers are in a solid state, and the lattice structure of the piezoelectric wafers can be kept unchanged, so as to ensure the piezoelectric performance of the composite piezoelectric substrate.
In a practical manner, the heating rate in step 3' is (1-20) deg.C/min, the heating rate is determined by the piezoelectric crystal, and the crystal is broken when the heating rate is too high; and heating to the melting point temperature of the glaze.
In an implementable manner, in step 3', the pressure applied to the piezoelectric wafer is in the range of 20-5000g/cm2And keeping the temperature and pressure for 0.5-10h at the temperature and the pressure so as to ensure that the piezoelectric wafer, the glaze and the piezoelectric wafer can be fully combined.
Compared with the prior art, the method for preparing the composite piezoelectric substrate does not need high temperature or vacuum environment in the whole process, and has no special requirements on physicochemical properties such as surface roughness, lattice constant and the like of two wafers to be bonded, so that the used equipment cost is reduced, the process parameters are easy to control, a single device can prepare multiple groups of composite piezoelectric substrates simultaneously, the production efficiency is obviously improved, the thickness of a glaze layer can be flexibly set according to the requirement, and if the thickness of the glaze reaches a specific thickness, the glaze can replace the substrate.
Drawings
FIG. 1 shows a schematic cross-sectional view of a preferred composite piezoelectric substrate of the present example;
FIG. 2 shows a flow chart of a method of making the aforementioned composite piezoelectric substrate;
FIG. 3 illustrates a cross-sectional structural view of another composite piezoelectric substrate provided herein;
fig. 4 shows a flow chart of a method for preparing the aforementioned composite piezoelectric substrate.
Description of the reference numerals
1-glaze layer, 2-piezoelectric film layer, 3-base layer and 4-quasi-junction layer.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of methods consistent with certain aspects of the invention, as detailed in the appended claims.
The piezoelectric composite substrate and the method for manufacturing the same provided by the present application are explained in detail by specific examples below.
Fig. 1 shows a schematic cross-sectional structure of a preferred composite piezoelectric substrate of the present example, which, as shown in fig. 1, includes: the piezoelectric ceramic film comprises a glaze layer 1 and a piezoelectric thin film layer 2, wherein the glaze layer 1 is formed by coating glaze on the piezoelectric thin film layer 2.
In the present example, the piezoelectric thin film layer 2 is made of a piezoelectric material including homoconstituent lithium niobate, homoconstituent lithium tantalate, near-stoichiometric lithium niobate, near-stoichiometric lithium tantalate, doped lithium niobate, doped lithium tantalate, and gallium nitride.
Optionally, the thickness of the piezoelectric film layer 2 is 0.1 μm to 100 μm, preferably 1 μm to 80 μm, for example, 5 μm to 10 μm, so as to meet the requirement of the semiconductor device on the thickness of the piezoelectric film layer. It is understood that the thickness of the piezoelectric thin film layer 2 can be specifically set according to actual needs.
In this example, the surface roughness of the bonding surface of the piezoelectric thin film layer 2 is 1nm to 10nm, for example, 5nm to 10nm, which facilitates the glaze to form a flat glaze layer 1 on the piezoelectric thin film layer 2, and enables the interface between the piezoelectric thin film layer 2 and the glaze layer 1 to be flattened, thereby improving the performance of the resulting composite single crystal piezoelectric substrate.
In the present example, the glaze layer 1 is used as a substrate of the composite piezoelectric substrate, and the main component of the glaze layer 1 is silicon dioxide, in the present example, the silicon dioxide in the glaze layer 1 is silicon dioxide particles, wherein the D50 particle size of the silicon dioxide is 0.5-5 μm, so that the glaze layer 1 can be flat and smooth.
In this example, the glaze layer 1 further includes a small amount of auxiliary materials including alumina, zinc oxide, ethyl cellulose, and the like, so that the glaze used to form the glaze layer 1 has appropriate physical and chemical properties, including viscosity, formability, and the like, so that the glaze layer 1 is laid on the piezoelectric thin film layer 2, and has predetermined properties.
Further, the thickness of the glaze layer 1 is 200nm or more, and may be 2 μm to 500 μm, preferably 10 μm to 300 μm, for example, 50 μm to 100 μm, so that the glaze layer 1 can sufficiently support the piezoelectric thin film layer 2.
In this example, the glaze layer 1 may have a thermal expansion coefficient of 3.0 × 10-7K-1～8.0×10-6K-1For example, 5.0X 10-7K-1So that the deformation amount of the glaze layer 1 is small at the working temperature, thereby being based on the composite single crystal piezoelectric base bodyThe manufactured device has higher operation stability.
In this example, the refractive index of the glaze layer 1 is 1.4-1.7, that is, smaller than the refractive index of the piezoelectric thin film layer 2, so that an optical signal or an acoustic signal transmitted in the piezoelectric thin film layer 2 can be limited in the piezoelectric thin film layer 2 without leaking to the glaze layer 1, thereby ensuring that the signal loss is small.
In the present example, the glaze layer 1 has a Young's modulus of 5.0X 1010Pa(N/m2)～9.0×1010Pa(N/m2) For example, 7.0X 1010Pa(N/m2) Thereby providing sufficient supporting function for the piezoelectric film layer 2 and avoiding the deformation of the composite single crystal piezoelectric substrate in the use process.
In this example, the melting temperature of the glaze layer 1 is 200 to 550 ℃, so that the glaze layer 1 is kept in a solid state at the working temperature, thereby ensuring that the composite single crystal piezoelectric substrate is in a normal use state under the working environment.
In this example, the porosity of the glaze layer 1 is less than 0.5% based on the total volume of the glaze layer 1, so that the glaze layer 1 and the piezoelectric thin film layer 2 have a flat interface, and the physical and chemical properties of the glaze layer 1 satisfy the above requirements.
In the present example, the components in the glaze layer 1 are uniformly distributed from the bonding surface, which refers to the interface between the glaze layer 1 and the piezoelectric thin film layer 2, to the substrate surface, which refers to the free surface of the glaze layer 1 that is not bonded to other layers. The applicant has found that a homogeneous distribution of the components of the glaze layer 1 facilitates, on the one hand, the preparation of the glaze layer 1 and, on the other hand, the achievement of the desired action of the glaze layer 1.
In this example, the glaze layer 1 may be solidified by a glaze, the main component of the glaze is silicon dioxide, which is a solid, specifically, the silicon dioxide and the auxiliary material may be mixed into a plastic solid by using an organic solvent, and since the silicon dioxide is a commonly used semiconductor material, the glaze using silicon dioxide as the main component has almost no negative effect on the performance of the piezoelectric film, and can maintain the original electrical performance of the piezoelectric film layer 2, thereby reducing the difficulty of the preparation process on the premise of maintaining the performance of the product and the volume of the product.
Fig. 2 shows a flow chart of a method for producing the aforementioned composite piezoelectric substrate, which, as shown in fig. 2, includes the following steps 1 and 2:
In this example, before step 1, the method may further include: and carrying out pretreatment on the surface of the piezoelectric wafer, wherein the pretreatment comprises polishing, cleaning and the like.
Specifically, the pretreatment may adopt any method for pretreating the surface of the piezoelectric wafer in the prior art, so that the surface of the piezoelectric wafer meets the requirement of the bonding surface.
In this example, the piezoelectric wafer may be an unprocessed, commercially available piezoelectric wafer; the piezoelectric injection sheet can also be a piezoelectric injection sheet which is injected with an ion injection layer in advance, the piezoelectric injection sheet comprises a thin film layer, an injection layer and a residual material layer, and if the piezoelectric injection sheet is the piezoelectric injection sheet, the surface of one side of the thin film layer is the surface coated with glaze; the piezoelectric wafer may be a piezoelectric wafer that is previously subjected to thickness processing and has a thickness reaching a target thickness.
In this example, the thickness of the piezoelectric wafer may be a target thickness or may be slightly greater than the target thickness so as to leave a margin for removing defects for subsequent processing.
In this example, the glaze may have a melting point lower than that of the piezoelectric wafer, the glaze is in a semi-solid state before coating, so that the glaze can be coated on the surface of the piezoelectric wafer, and the physical and chemical properties of the glaze after curing are similar to those of silicon dioxide, so that the formed glaze layer can sufficiently support the piezoelectric wafer (i.e., the piezoelectric thin film layer in the composite single crystal piezoelectric substrate) and can limit the transmitted signal in the piezoelectric wafer to prevent signal leakage.
In the present example, the surface roughness of the glaze after curing is less than 2 μm, so that the composite single crystal piezoelectric substrate has good morphology and provides a good processing base for planarization processing, and further, the surface roughness of the glaze layer after planarization processing is less than 10 nm.
In this example, the glaze may be a doped glass paste or other binder having a melting point lower than that of the piezoelectric wafer, and the organic material, such as an organic solvent, in the glaze may be removed in a high temperature treatment process, and the inorganic component thereof may be doped into the silica particles to form a glaze layer together with the silica particles.
Specifically, the main component of the glaze is silicon dioxide, and the auxiliary materials comprise: alumina, zinc oxide, ethyl cellulose, the solvent comprises: the applicant has found that the lipid solvent enables the glaze to have good lubricating properties, i.e. the glaze performs smoother after heating, and further, the other solvents generally have lower boiling points, so that the other solvents can carry the lipid solvent to gasify together during the heating process, thereby ensuring that fewer pores are formed in the glaze layer 1.
Further, based on the total volume of the glaze, the content of the silicon dioxide is 50 g/mL-200 g/mL, the viscosity of the glaze is 50 Pa.s-400 Pa.s, the main component is high-purity silicon dioxide, the melting point of the glaze is lower than that of the piezoelectric wafer, preferably, the glaze is glass slurry, wherein the sintering temperature of the glass slurry is 400-550 ℃, the fineness is less than 15 μm, and the viscosity is 100 Pa.s-200 Pa.s, so that only the glaze is in a molten state in the process of preparing the composite piezoelectric substrate, and the piezoelectric wafer is in a solid state, and the lattice structure of the piezoelectric wafer can be kept unchanged so as to ensure the piezoelectric performance of the composite piezoelectric substrate.
In this example, the method of applying the glaze on the surface of the piezoelectric wafer includes brushing, spin coating, and spraying.
In the present application, the spin coating may be any spin coating method that can take a wafer as an object in the prior art; the spraying can be any spin coating method which can take a wafer as an object in the prior art, and parameters selected by spin coating and spraying can be specifically set according to actual requirements.
Optionally, the brushing comprises the following steps S101 to S103:
step S101, a layer of silk screen is laid on the piezoelectric wafer.
In this example, the wire mesh is closely attached to the bonding surface of the piezoelectric wafer to reduce the gap between the wire mesh and the piezoelectric wafer.
It will be appreciated that the screen is laid on the side of the piezoelectric wafer to which it can be bonded, i.e. the working side, optionally one side if the piezoelectric wafer has two working sides.
In this example, the thickness of the screen may be 0.1 to 1000 μm, preferably 100 to 500 μm, and more preferably 200 to 300 μm, so that the glaze layer formed of the glaze can reach a target thickness.
In this example, the coating thickness of the glaze can be 0.1 μm to 1000 μm, and the applicant finds that, if the coating thickness of the glaze is less than 0.1 μm, the glaze is less firmly bonded with the piezoelectric wafer and easily falls off from the piezoelectric wafer, which affects the use of the composite piezoelectric substrate, while too large a thickness increases the difficulty of curing and increases the cost, and there are many large pores inside the obtained glaze layer, which causes the refractive index of the glaze layer to be uneven, so that the obtained composite piezoelectric substrate cannot be used.
Furthermore, the meshes of the silk screen can be square, rhombic, rectangular, circular and the like, and can also be in other shapes which are beneficial to uniformly paving the glaze on the surface of the piezoelectric wafer.
Still further, the tension of the glaze on the surface of the screen is less than 0.1 dyne/cm, so as to facilitate the release of the screen from the glaze, i.e. to enable the formation of a uniform distribution of "glaze particles" on the surface of the piezoelectric wafer after the screen has been removed from the glaze. The applicant has found that the wire mesh made of stainless steel, copper, or the like can exhibit a preferable surface tension, and thus, the material of the wire mesh may be stainless steel, copper, or the like.
In this example, the mesh size of the silk screen may be 1mm to 20mm, preferably 5mm to 15mm, and the applicant finds that the silk screen with the mesh is convenient for coating, can form uniform glaze particles on the surface of the piezoelectric wafer after the silk screen is removed, and can be quickly welded into a whole after being heated, so as to form a glaze layer with uniform thickness, and the distribution of air holes in the formed glaze layer is uniform.
Step S102, a layer of glaze is uniformly coated on the surface of the piezoelectric wafer through the silk screen, and the thickness of the glaze is smaller than or equal to that of the silk screen.
In this example, the glaze may be applied to the surface of the piezoelectric wafer through the mesh of the screen using a brush, a roller, or the like, and a scraper may be used to scrape off a portion of the glaze higher than the screen so that the thickness of the glaze in all the meshes is as the same as possible, so that the glaze forms a glaze layer having a uniform thickness.
And step S103, taking down the silk screen.
In the present example, after the surface of the piezoelectric wafer is pretreated, step 1-1 and step 1-2 may be further included before the glaze is applied:
step 1-1, preparing a quasi-junction layer 4 on the bonding surface of the piezoelectric wafer.
In this example, the quasi-junction layer 4 includes at least one quasi-junction layer, each quasi-junction layer is made of at least one of metal, metal compound and inorganic nonmetal, wherein the metal includes at least one of gold, platinum, copper, aluminum, chromium, nickel, etc., the metal compound includes at least one of gallium nitride, aluminum oxide, aluminum nitride, gallium arsenide, etc., the inorganic nonmetal includes at least one of silicon dioxide, silicon carbide, polysilicon and silicon nitride, the physicochemical properties of each quasi-junction layer are similar to those of the glaze layer, and the thickness of the quasi-junction layer 4 may be 0.1nm to 10 μm, preferably 1 to 3 μm, which facilitates the preparation of the quasi-junction layer 4 and reduces the total thickness and the manufacturing cost of the composite piezoelectric substrate.
The applicant finds that each quasi-junction layer is similar to the materials of the piezoelectric wafer and the glaze, particularly similar to the physical and chemical properties of the glaze, so that the coating of the glaze and the fusion of the glaze on the surface of the piezoelectric wafer are easier to perform, and in addition, the quasi-junction layer and the piezoelectric wafer already form a basic structure of a composite piezoelectric substrate, so that the functional requirements of devices such as an electro-optical modulator, a frequency comb and the like can be met, the bonding requirements between the glaze and the quasi-junction layer are remarkably reduced, only the glaze needs to be fused to the quasi-junction layer, and even if the interface between the glaze layer and the quasi-junction layer has a few defects, the performance of the devices cannot be influenced.
In the present application, a metal is used solely as a quasi-junction layer, which can also be used as an electrode.
And 1-2, carrying out planarization treatment on the alignment layer 4.
In this example, the planarization of the landing layer 4 includes a combination of grinding and polishing, so that the surface of the landing layer 4 meets the requirement of fusion with the glaze, for example, the surface roughness is less than 20nm, etc.
And 2, carrying out planarization treatment and sizing on the glaze to obtain the composite piezoelectric substrate.
In this example, the glaze behaves as a solid film on the piezoelectric wafer surface after the screen is removed, and the form of the glaze changes upon application of pressure thereto, but the glaze does not flow spontaneously.
This example will the glaze forms plastic solid film at first, plastic solid film can not spontaneous motion, right plastic solid film heats, makes the solvent volatilize the initial set, heats again, makes the glaze melt, forms the glaze material film that the texture is homogeneous, will the glaze material layer cools off to the planarization processing. If the glaze layer needs to be fused with the substrate material, the glaze layer needs to be heated in a third step, so that the glaze layer is melted again to bond the substrate material.
Specifically, in this example, the planarization treatment of the glaze layer includes bringing the glaze layer to a prescribed thickness dimension and ensuring a flat surface and a uniform thickness by physical and/or chemical mechanical processing.
In this example, removal of the screen involves at least two heating steps, wherein the first heating step is a low temperature heating step for removing the solvent from the moldable solid film of glaze, and the second heating step is a high temperature heating step for melting the glaze to form a homogeneous solid phase and curing the glaze to form a layer of glaze.
Specifically, step 2 may include the following steps 2-1 and 2-2:
step 2-1, heating the piezoelectric wafer coated with the glaze to the volatilization temperature of a glaze solvent, and preserving heat;
in this example, step 2-1 is the first heating step, which may be performed at a temperature of less than 300 ℃, e.g., 160 ℃, and held at this temperature until the thickness of the glaze is uniform and the solvent in the glaze is completely volatilized, e.g., held for half an hour, etc.
The volatilization rate of solid particles in the glaze layer is moderate, and gaps formed in the glaze layer are fine and uniform, so that the glaze layer has stable refractive index, can be used as a substrate layer of the composite piezoelectric substrate, plays a role in limiting signals in the piezoelectric thin film layer, and prevents the signals from leaking.
And 2-2, continuously heating to the melting point of the glaze, and cooling after heat preservation.
The step of heating is the second step, the heating temperature can be above 400 ℃, for example 500 ℃, and the heat preservation is carried out at the temperature until the glaze is vitrified, for example, 0.1-2 hours.
In this example, the temperature rise rate in this step is 1 to 5 ℃/min, for example, 3 ℃/min, and it is found that, at the above temperature rise rate, the glaze particles in the glaze layer can be sufficiently melted to form a glaze thin film layer with a uniform thickness.
In this example, the glaze may be solidified by cooling to form a glaze layer.
Optionally, the cooling rate of the cooling is 3-5 ℃/min, for example, 4 ℃/min, and the applicant finds that the interior of the glaze layer obtained by cooling at the cooling rate is uniform, compact and free of crack and other defects.
The glaze layer is formed to include a main component of silica and the remaining solid components which are not volatilized at the second-step heating temperature.
Optionally, the glaze may be subjected to surface treatment including grinding and polishing on the formed glaze layer after the glaze is cooled and solidified. In the application, after surface treatment, the roughness of the surface of the glaze layer is less than 10nm, so that the upper surface and the lower surface are parallel after the substrate and the upper film are fused.
In this example, the thickness of the glaze layer is 0.1-1000 μm to provide sufficient support for the piezoelectric wafer.
The applicant finds that the glaze layer is prepared by coating glaze on the silk screen serving as the template and then firing the silk screen serving as the template, so that the difficulty of a coating process can be greatly reduced, the glaze can be coated more uniformly, and the large-scale production is facilitated; furthermore, the method is beneficial to the volatilization of the solvent in the glaze, and further, the thickness of the glaze layer can be controlled by adjusting the thickness of the silk screen, so that the thickness of the glaze layer can be adjusted and controlled.
In this example, after the preparation of the glaze layer is completed, the piezoelectric wafer may be thinned, and the thinning method may be any method of thinning the piezoelectric wafer in the prior art, such as an ion implantation method, a grinding and polishing method, and the like.
Further, the thickness of the piezoelectric wafer after thinning processing can be specifically set according to the use requirement.
The applicant finds that the method provided by the application uses low-melting-point glaze which has semi-fluidity in an initial state, for example, is pasty as a raw material for preparing the substrate layer, the maximum process temperature in the whole process is not more than 550 ℃, and the performance and the structure of film layers such as a piezoelectric wafer, a quasi-junction layer and the like are not damaged basically; moreover, the price of equipment used by the method is lower than that of equipment used by the traditional bonding process, and one piece of equipment can be used for simultaneously preparing a plurality of groups of composite piezoelectric substrates, so that the production efficiency is improved, the preparation cost is greatly reduced, and the method is suitable for industrial batch production; in addition, the method provided by the application has low requirements on the material properties of the piezoelectric wafer, and the range of applicable materials is increased; further, the method provided by the application can conveniently control the thickness of the glaze layer to be the target thickness according to the requirement.
Fig. 3 shows a schematic cross-sectional structure of another composite piezoelectric substrate provided by the present application, as shown in fig. 3, the composite piezoelectric substrate includes: the piezoelectric ceramic substrate comprises a substrate layer 3, a glaze layer 1 and a piezoelectric thin film layer 2, wherein the substrate layer 3 and the piezoelectric thin film layer 2 are bonded through the glaze layer 1.
In the present example, the substrate layer 3 includes a single-phase substrate and a composite substrate, wherein the single-phase substrate is made of a single semiconductor material including single crystal silicon, silicon dioxide, aluminum oxide, lithium tantalate, lithium niobate; the composite substrate comprises a base substrate layer and a quasi-junction layer, wherein the base substrate layer is made of a single semiconductor material, the semiconductor material comprises monocrystalline silicon, silicon dioxide, aluminum oxide, lithium tantalate and lithium niobate, and the quasi-junction layer is made of an inorganic silicon material, and the inorganic silicon material comprises silicon dioxide, polycrystalline silicon and silicon nitride.
Optionally, the thickness of the base layer 3 is 1 μm to 1000 μm, preferably 20 μm to 800 μm, for example, 100 μm to 500 μm, so that the base layer 3 can provide sufficient support for the composite piezoelectric substrate.
In this embodiment, the thickness of the glaze layer 1 can be reduced to 2-20 μm, for example, 5-10 μm, so as to reduce the total thickness of the composite piezoelectric substrate, reduce the volume of the composite piezoelectric substrate, and increase the application range thereof.
In this example, the specific structure and parameters of the glaze layer 1 are the same as those of the glaze layer 1 in the composite piezoelectric substrate shown in fig. 1, and the specific structure and parameters of the piezoelectric thin film layer 2 are the same as those of the piezoelectric thin film layer 2 in the composite piezoelectric substrate shown in fig. 1, which may be referred to as the composite piezoelectric substrate shown in fig. 1, and are not described herein again.
Fig. 4 shows a flowchart of a method for manufacturing the aforementioned composite piezoelectric substrate, which includes the following steps 1 'to 3', as shown in fig. 4:
step 1', coating glaze on the surface of the piezoelectric wafer and/or the substrate material.
In this example, the glaze may be coated on only the surface of the piezoelectric wafer or the substrate material, or the glaze may be coated on both the surfaces of the piezoelectric wafer and the substrate material.
The glaze can be directly coated on the surface of the piezoelectric wafer and/or the substrate material, and the implementation manner of directly coating the glaze on the surface of the piezoelectric wafer and/or the substrate material can be referred to as step 1, which is not described herein again.
A quasi-junction layer can be prepared between the glaze and the surface of the piezoelectric wafer, a quasi-junction layer can be prepared between the glaze and the surface of the substrate material, and the implementation manner of preparing the quasi-junction layer can be referred to step 1, which is not described herein again.
The implementation manner of coating the glaze on the quasi-junction layer is the same as that of directly coating the glaze on the surface of the piezoelectric wafer and/or the substrate material, and the description is omitted here.
In this example, if only the glaze is coated on the surface of the piezoelectric wafer or the base material, the base material or the surface of the piezoelectric wafer may or may not be provided with the pre-bonding layer.
And 2', flattening the glaze to obtain a glaze layer.
The implementation manner of the planarization in this step is the same as that in step 2, and reference may be made to the relevant implementation manner in step 2, which is not described herein again.
In this step, the glaze of the glaze layer may be uncured, i.e., have a semi-fluidity, or may be a cured glaze layer.
And 3 ', attaching a substrate material and/or a piezoelectric wafer to the glaze layer obtained in the step 2' to obtain a piezoelectric wafer-substrate material assembly, heating and applying pressure to the piezoelectric wafer-substrate material assembly, and cooling after heat preservation and pressure maintaining.
In this example, one top surface of the resulting piezoelectric wafer-substrate material assembly is a piezoelectric wafer and the other top surface is a substrate material, and the quasi-junction layer, glaze, etc. prepared on the piezoelectric wafer and/or the substrate material are sandwiched between the piezoelectric wafer and the substrate material.
In this step, the melting points of the piezoelectric wafer and the substrate material are both higher than the melting point of the glaze, so that only the glaze is in a molten state, the piezoelectric wafer is in a solid state, and the lattice structure of the piezoelectric wafer can be kept unchanged in order to ensure the piezoelectric performance of the composite piezoelectric substrate.
In this example, after a glaze layer with semi-fluidity is formed on the surface of the piezoelectric wafer, a substrate material is attached to the glaze layer, and mechanical pressure is applied to the substrate material, so that the substrate material is closely attached to the glaze layer, thereby forming a piezoelectric wafer-substrate material assembly.
Specifically, a pressure perpendicular to the joint surface is applied to the piezoelectric wafer-substrate material assembly, and the pressure can be 20-5000g/cm2Preferably 200 to 500g/cm2And preserving heat and pressure for 0.5-10h at the temperature and the pressure so that the piezoelectric wafer, the glaze and the piezoelectric wafer can be fully combined to form a composite piezoelectric substrate with uniform thickness and stable combination.
In this example, the heating in step 3' is carried out at a heating rate of (1-20) ° c/min, up to the melting point temperature of the glaze. The specific temperature rise rate is determined by the piezoelectric crystal, and if the temperature rise rate is too high, the piezoelectric wafer may be broken, and the yield is reduced.
In this example, after the substrate material is pressed onto the glaze layer, the temperature of the formed composite body is reduced, for example, to room temperature, so that the glaze is solidified to form a solid glaze layer, thereby forming the composite piezoelectric substrate.
In this example, the cooling rate may be 1-5 ℃/min, for example, 4 ℃/min, and the applicant finds that the interior of the glaze layer obtained by cooling at the cooling rate is uniform, compact, and free from crack and other defects.
In this example, the thicknesses of the piezoelectric thin film layer and the substrate layer in the composite piezoelectric substrate may also be trimmed, for example, the piezoelectric thin film layer and the substrate layer may be respectively thinned by grinding, polishing, and the like, so that the substrate layer and the piezoelectric thin film layer respectively reach the target thicknesses.
In the embodiment, glaze which has semi-fluidity at normal temperature and can be converted into a solid state through high-temperature re-cooling is used as an adhesive to bond the piezoelectric wafer and the substrate material together, and optionally, the piezoelectric wafer and/or the substrate material are trimmed into a target thickness by using mechanical methods such as grinding and the like to finally form the composite piezoelectric substrate, wherein the maximum temperature of the whole process of the method provided by the application is not more than 550 ℃, generally about 450 ℃, so that the substrate material and the piezoelectric wafer are not damaged basically; moreover, the price of equipment used by the method is lower than that of equipment used by the traditional bonding process, and one piece of equipment can be used for simultaneously preparing a plurality of groups of composite piezoelectric substrates, so that the production efficiency is improved, the preparation cost is greatly reduced, and the method is suitable for industrial batch production; in addition, the method provided by the application has low requirements on the material properties of the piezoelectric wafer, and the lattice constants of the piezoelectric wafer and the substrate material can be different, so that the range of applicable materials is enlarged; further, the method provided by the application can conveniently control the thickness of the glaze layer to be the target thickness according to the requirement.
The applicant finds that the performance of the device manufactured by the composite piezoelectric substrate is directly influenced by the material of the piezoelectric film and the material of the quasi-joint layer, and the influence of the selected glaze material on the performance of the subsequent device is small, so that the method provided by the application can increase the selectable range of the material of the substrate layer, has strong process flexibility, and avoids the scheme that the piezoelectric film layer and the substrate material need to be bonded together by the conventional bonding method. In addition, the bonding process has high requirements on the processing precision, the processing environment, the surface quality of a sample and the like, and only two materials with close lattice constants can realize a good bonding effect, otherwise, a bonded body is easy to break along a bonding surface, and further, the required equipment cost is high, so that the method is not suitable for mass production.
Examples
The glaze used in this example was purchased from 07M-SL31 glass paste from Shenzhen Spanish electronic paste Co.
EXAMPLE 1 preparation of composite Single Crystal piezoelectric Crystal (without substrate)
In this example, the piezoelectric wafer is a homogeneous lithium niobate.
The preparation process comprises the following steps:
(1) taking a lithium niobate wafer to carry out double-sided grinding and polishing until the thickness is 350 mu m and the surface flatness is less than 2 nm;
(2) depositing a silicon dioxide film with uniform thickness on the surface of a lithium niobate wafer by adopting a PECVD (plasma enhanced chemical vapor deposition) method, taking the silicon dioxide film as a quasi-junction layer with the thickness of 3 mu m, and finely polishing the surface of the silicon dioxide film to ensure that the flatness of the silicon dioxide film layer is less than 2nm, wherein the PECVD coating parameters are as follows: the temperature is 50 ℃, the vacuum degree is 1500mTorr, the power is 50W, and the time is 100 min;
(3) coating a layer of glass glaze with the thickness of 200 mu m on the surface of the silicon dioxide film layer by using a screen printing method, flattening the glaze film by using a scraper, heating the sample to 300 ℃, and preserving heat for 30 minutes to completely volatilize a solvent in the glaze;
(4) heating the lithium niobate wafer to 450 ℃ to melt the coated glaze to form a glaze film, cooling the lithium niobate wafer to room temperature at a cooling rate of 4 ℃/min to solidify the glaze liquid film, and forming the composite piezoelectric substrate.
(5) And thinning the lithium niobate wafer layer to 5 mu m, and polishing the surface of the lithium niobate wafer layer to obtain the film thickness and the surface quality meeting the preparation requirement of the device.
The performance of the composite piezoelectric substrate is as follows: the thickness of the silicon dioxide layer is 3000 +/-50 nm, and the thickness difference of different areas is less than 1%; the thickness of the lithium niobate layer is 5000 +/-500 nm, the thickness difference of different areas is less than 1.5%, and the surface roughness is 2 nm.
EXAMPLE 2 preparation of composite Single Crystal piezoelectric substrate (with substrate)
In this example, the piezoelectric wafer is isoconstituent lithium niobate (wafer a) and the base material is also isoconstituent lithium niobate (wafer B).
The preparation process comprises the following steps:
(1) taking the wafer A and the wafer B to respectively carry out double-sided grinding and polishing until the thickness is 350 mu m, so that the surface flatness of the two wafers is less than 2 nm;
(2) depositing a layer of silicon dioxide film with uniform thickness on the surface of the wafer A by adopting a PECVD method, wherein the thickness is 3 microns, and finely polishing the surface of the silicon dioxide film to ensure that the flatness of the silicon dioxide film is less than 2nm, wherein the PECVD film coating parameters are as follows: the temperature is 50 ℃, the vacuum degree is 1500mTorr, the power is 50W, and the time is 100 min;
(3) coating a layer of glaze with the thickness of 200 mu m on the surface of the wafer B by a screen printing method, flattening by a scraper, heating the sample to 300 ℃, and preserving heat for 30min to completely volatilize the solvent in the glaze;
(4) heating the wafer B to 450 ℃, melting the glaze to form a uniform glaze film, cooling the wafer B to room temperature, and flattening the glaze layer to ensure that the flatness of the glaze layer is less than 2 nm;
(5) bonding the silicon dioxide film surface of the wafer A and the glaze surface of the wafer B, placing the wafer A on a heating plate and the wafer B on the heating plate, and applying 200g/cm to the wafer A2The pressure of the pressure is used for ensuring that the two wafers are completely jointed, the temperature is slowly heated to 450 ℃, the glaze surface of the wafer B is completely bonded with the silicon dioxide film surface of the wafer A, the temperature is slowly reduced to normal temperature after the temperature is maintained for 3 hours, wherein the temperature rising rate is 2 ℃/min, and the temperature reduction rate is 3 ℃/min;
(6) and thinning the surface of the wafer A to reduce the thickness of the wafer A to a target thickness (300 mu m), and polishing the surface of the wafer A to obtain the film thickness and the surface quality meeting the preparation requirement of the device.
The performance of the composite piezoelectric substrate is as follows: the thickness of the silicon dioxide layer is 3000 +/-50 nm, and the thickness difference of different areas is less than 1%; the thickness of the lithium niobate layer is 5000 +/-500 nm, the thickness difference of different areas is less than 1.5%, and the surface roughness is 3 nm.
The present application has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to limit the application. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the presently disclosed embodiments and implementations thereof without departing from the spirit and scope of the present disclosure, and these fall within the scope of the present disclosure. The protection scope of this application is subject to the appended claims.
Claims (10)
1. A composite piezoelectric substrate, comprising: the piezoelectric ceramic tile comprises a glaze layer (1) and a piezoelectric thin film layer (2), wherein the glaze layer (1) is formed by coating glaze on the piezoelectric thin film layer (2).
2. The composite piezoelectric substrate of claim 1,
the main component of the glaze layer (1) is silicon dioxide, and the auxiliary materials comprise aluminum oxide, zinc oxide and ethyl cellulose; and/or
The thickness of the glaze layer (1) is 2-500 μm, and the thermal expansion coefficient is 3.0 × 10-7K-1～8.0×10-6K-1A refractive index of 1.4 to 1.7 and a Young's modulus of 5.0X 1010Pa(N/m2)～9.0×1010(N/m2) The melting temperature is 200-550 ℃; and/or
The porosity of the glaze layer (1) is less than 0.5%.
3. The composite piezoelectric substrate according to claim 1 or 2, wherein the surface roughness of the bonding surface of the piezoelectric thin film layer (2) is 0.1nm to 5 nm.
4. The composite piezoelectric substrate according to any one of claims 1 to 3, wherein the components in the glaze layer (1) are uniformly distributed from the bonding face to the substrate face.
5. A method of making the composite piezoelectric substrate of any one of claims 1 to 4, comprising:
step 1, coating glaze on the surface of a piezoelectric wafer;
and 2, carrying out planarization treatment and sizing on the glaze to obtain the composite piezoelectric substrate.
6. The method according to claim 5, wherein the glaze in step 1 mainly comprises silicon dioxide, and the auxiliary materials comprise: alumina, zinc oxide, ethyl cellulose, the solvent comprises: esters and at least two of ethers, alcohols and hydrocarbon compounds; and/or
The viscosity of the glaze is 50 Pa.s-400 Pa.s, the main component is high-purity silicon dioxide, and the melting point of the glaze is lower than that of the piezoelectric wafer;
preferably, the glaze is glass slurry, wherein the sintering temperature of the glass slurry is 400-550 ℃, the fineness of the glass slurry is less than 8 mu m, and the viscosity of the glass slurry is 100-200 Pa s.
7. The method according to claim 5 or 6, characterized in that before step 1, the method further comprises:
step 1-1, preparing a quasi-junction layer on a bonding surface of the piezoelectric wafer;
step 1-2, carrying out planarization treatment on the alignment layer;
the quasi-junction layer comprises at least one quasi-junction layer, each quasi-junction layer is prepared from at least one of metal, metal compound and inorganic nonmetal, wherein the metal comprises at least one of gold, platinum, copper, aluminum, chromium, nickel and the like, the metal compound comprises at least one of gallium nitride, aluminum oxide, aluminum nitride, gallium arsenide and the like, the inorganic nonmetal comprises at least one of silicon dioxide, silicon carbide, polycrystalline silicon and silicon nitride, and the thickness of the quasi-junction layer is 0.1 nm-10 μm, preferably 1-3 μm.
8. The method according to any one of claims 5 to 7, wherein step 2 comprises:
heating the piezoelectric wafer coated with the glaze to the volatilization temperature of a glaze solvent, and preserving heat;
and continuously heating to the melting point of the glaze, and cooling after heat preservation.
9. A composite piezoelectric substrate, comprising: the piezoelectric ceramic film comprises a substrate layer (3), a glaze layer (1) and a piezoelectric film layer (2), wherein the substrate layer (3) and the piezoelectric film layer (2) are bonded through the glaze layer (1).
10. A method of making a composite piezoelectric substrate, comprising:
step 1', coating glaze on the surface of a piezoelectric wafer and/or a substrate material;
step 2', carrying out planarization treatment on the glaze to obtain a glaze layer;
and 3 ', attaching a substrate material and/or a piezoelectric wafer to the glaze layer obtained in the step 2' to obtain a piezoelectric wafer-substrate material assembly, heating and applying pressure to the piezoelectric wafer-substrate material assembly, and cooling after heat preservation and pressure maintaining.
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