Piezoelectric composite structure, method of manufacture and acoustic wave device

Abstract

The application relates to a piezoelectric composite structure, a preparation method and an acoustic wave device, and the piezoelectric composite structure comprises a supporting substrate layer, an insulating medium layer located on the supporting substrate layer, and a piezoelectric functional layer located on the insulating medium layer; the piezoelectric functional layer comprises an upper defect-free layer and a first defect layer distributed in an upper and lower mode; in the first defect layer, a surface close to the insulating medium layer is a rough surface; and the piezoelectric functional layer is separated from an original piezoelectric substrate comprising an upper defect-free layer and a second defect layer distributed in an upper and lower mode. In the embodiment of the application, the second defect layer of the original piezoelectric substrate is recycled to form the first defect layer with the rough surface in the piezoelectric composite structure, the processing cost is reduced, and unnecessary waste of the piezoelectric material is avoided. Moreover, the introduction of the rough surface in the piezoelectric composite structure improves the structural performance.

Description

Technical Field

[0001] This invention belongs to the field of acoustic device technology, specifically a piezoelectric composite structure, its preparation method, and an acoustic device. Background Technology

[0002] Lithium niobate and lithium tantalate are currently the most widely used piezoelectric transducer materials. They possess excellent piezoelectric, ferroelectric, acousto-optic, pyroelectric, and electro-optic effects, and are widely used in the fabrication of radio frequency front-end resonators, filters, and electro-optic modulators. Emerging fields such as 5G, big data, and augmented / virtual reality are placing higher demands on information transmission rates, power consumption, and signal quality. Due to limitations in material properties, devices based on lithium niobate or lithium tantalate bulk materials struggle to meet the higher requirements of communication systems. To improve device performance, piezoelectric composite substrate device technology based on heterogeneous substrate piezoelectric thin film materials has emerged. The combination of lithium niobate or lithium tantalate thin films with heterogeneous substrates concentrates acoustic wave energy in acoustic devices and optical wave energy in optical devices more effectively in the piezoelectric thin film, improving device performance and facilitating miniaturization and integration.

[0003] The common method for transferring lithium niobate or lithium tantalate films onto a heterogeneous substrate to form a piezoelectric composite structure involves ion implantation onto the polished surface of a lithium niobate or lithium tantalate wafer, bonding the polished surface to the target substrate through an insulating dielectric layer, and then transferring the lithium niobate or lithium tantalate film onto the target substrate via heat treatment, resulting in a piezoelectric composite structure and the stripped piezoelectric substrate. Typically, the surface lattice of the stripped piezoelectric substrate is damaged. Recycling the stripped piezoelectric substrate requires grinding and polishing to remove a significant amount of piezoelectric layer, consuming substantial amounts of material during mass production, increasing production costs, and increasing the risk of wafer fragmentation, thus affecting production yield. Without recycling, production costs also increase significantly. Therefore, there is a need to develop a new piezoelectric composite structure and its fabrication method that can recycle piezoelectric substrates with damaged lattices. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a piezoelectric composite structure, a preparation method, and an acoustic device.

[0005] In a first aspect, embodiments of this application disclose a piezoelectric composite structure, comprising:

[0006] Support substrate layer;

[0007] An insulating dielectric layer located on the supporting substrate layer;

[0008] A piezoelectric functional layer is located on an insulating dielectric layer; the piezoelectric functional layer includes a defect-free layer and a first defect layer distributed vertically; in the first defect layer, the surface near the insulating dielectric layer is a rough surface; the piezoelectric functional layer is obtained by separating the original piezoelectric substrate, which includes a defect-free layer and a second defect layer distributed vertically.

[0009] In some possible embodiments,

[0010] The surface roughness of the first defect layer near the insulating dielectric layer is 2 to 25 nanometers;

[0011] The thickness of the first defect layer is 5 to 80 nanometers;

[0012] The unit atomic displacement (DPA) value of the first defect layer ranges from 0.01 to 0.81;

[0013] The defect concentration in the first defect layer decreases linearly from bottom to top.

[0014] In some possible embodiments,

[0015] The materials of the piezoelectric functional layer and the original piezoelectric substrate include at least one of lithium niobate and lithium tantalate;

[0016] The thickness of the piezoelectric functional layer is 100 to 10,000 nanometers.

[0017] In some possible embodiments,

[0018] The insulating dielectric layer is made of at least one of silicon dioxide and silicon nitride;

[0019] The thickness of the insulating dielectric layer is 100 to 1000 nanometers.

[0020] In some possible embodiments,

[0021] The materials supporting the substrate include at least one of silicon, silicon oxide, silicon-on-insulator (SOI), sapphire, silicon carbide, silicon-on-insulator (SiC), quartz, aluminum nitride, gallium nitride, and diamond.

[0022] The thickness of the supporting substrate layer is 0.2 to 2 millimeters.

[0023] In some possible embodiments,

[0024] The piezoelectric composite structure also includes a carrier trap layer located between the insulating dielectric layer and the supporting substrate layer;

[0025] The carrier trap layer is made of at least one of polycrystalline silicon, amorphous silicon, and porous silicon.

[0026] The thickness of the carrier trap layer is 200 to 2000 nanometers;

[0027] The surface in contact between the charge carrier trap layer and the insulating dielectric layer is either rough or smooth.

[0028] Secondly, this application discloses a method for preparing a piezoelectric composite structure, comprising the following steps:

[0029] Provide a pristine piezoelectric substrate and a support substrate; the pristine piezoelectric substrate includes a defect-free layer and a second defect layer distributed on the top and bottom; the pristine piezoelectric substrate is a recycled piezoelectric substrate, or a piezoelectric substrate that has been internally implanted with ions and then heat-treated, or a piezoelectric substrate whose surface has been irradiated with ions.

[0030] The original piezoelectric substrate is subjected to a first heat treatment to obtain a treated piezoelectric substrate; the treated piezoelectric substrate includes a defect-free layer and a first defect layer that is restored by the lattice quality of the second defect layer.

[0031] An insulating dielectric layer is prepared on the surface of the first defect layer of the piezoelectric substrate, and the insulating dielectric layer is planarized to obtain the first composite.

[0032] Ion implantation is performed on the surface of the insulating dielectric layer in the first conjugate to form a second defect layer inside the defect-free layer of the processed piezoelectric substrate;

[0033] The insulating dielectric layer in the first composite is bonded to the supporting substrate to obtain the second composite;

[0034] The second composite is subjected to a second heat treatment to dissociate the second defect layer inside the piezoelectric substrate, resulting in the piezoelectric substrate to be recycled and the piezoelectric composite structure precursor.

[0035] The piezoelectric composite structure precursor is subjected to a third heat treatment and planarization treatment to remove the second defect layer, thereby obtaining the piezoelectric composite structure; wherein, the retained portion of the treated piezoelectric substrate forms the piezoelectric functional layer.

[0036] In some possible embodiments,

[0037] The insulating dielectric layer is prepared by chemical vapor deposition (CVD) or physical vapor deposition (PVD).

[0038] The planarization process removes 50 to 200 nanometers of the insulating dielectric layer.

[0039] In some possible embodiments,

[0040] The ion types for ion implantation or ion irradiation are at least one of hydrogen ions, helium ions, nitrogen ions, and argon ions.

[0041] The energy of ion beam or ion irradiation is 5 to 500 kiloelectron volts;

[0042] The dose of ion implantation or ion irradiation is 10.13 Up to 10 17 pcs / square centimeter

[0043] In some possible embodiments,

[0044] The first heat treatment is performed at a temperature of 250 to 550 degrees Celsius for 2 to 6 hours in an atmosphere of at least one of nitrogen, argon, and vacuum, and the atmosphere is rich in lithium ions.

[0045] The second heat treatment is performed at a temperature of 100 to 300 degrees Celsius for 5 to 30 hours in an atmosphere of at least one of nitrogen, argon, and vacuum.

[0046] The third heat treatment is performed at a temperature of 250 to 600 degrees Celsius for 2 to 10 hours in an atmosphere of at least one of nitrogen, argon, and vacuum.

[0047] In some possible embodiments,

[0048] Before preparing an insulating dielectric layer on the surface of a piezoelectric substrate, the piezoelectric substrate can be chamfered.

[0049] The chamfering method is a T-shaped chamfer;

[0050] The width of the chamfered edge is 0.5 to 3.5 mm.

[0051] The chamfering process removes edges to a depth of 5 to 30 micrometers.

[0052] In some possible embodiments,

[0053] Before bonding, a carrier trapping layer can be prepared on the surface of the supporting substrate to obtain a third conjugate.

[0054] The carrier trap layer in the third composite is bonded to the insulating dielectric layer in the first composite to obtain the second composite.

[0055] In some possible embodiments,

[0056] The carrier trap layer can be prepared by chemical vapor deposition (CVD) or physical vapor deposition (PVD).

[0057] The surface of the carrier trap layer away from the supporting substrate is a smooth surface. After planarization of the smooth surface of the carrier trap layer, bonding is performed.

[0058] Alternatively, the surface of the carrier trap layer away from the supporting substrate can be a smooth surface. An insulating dielectric layer can be prepared on the smooth surface of the carrier trap layer, and then bonded after planarization treatment.

[0059] Alternatively, the surface of the carrier trap layer away from the supporting substrate can be rough. An insulating dielectric layer can be prepared on the rough surface of the carrier trap layer, and then bonded after planarization treatment.

[0060] Thirdly, embodiments of this application disclose an acoustic wave device, including any of the above-mentioned piezoelectric composite structures and interdigitated electrodes;

[0061] Interdigitated electrodes are disposed on the upper surface of the piezoelectric functional layer.

[0062] The technical solution provided in this application has the following technical effects:

[0063] The piezoelectric composite structure of this application includes: a supporting substrate layer; an insulating dielectric layer located on the supporting substrate layer; and a piezoelectric functional layer located on the insulating dielectric layer. The piezoelectric functional layer includes a defect-free layer and a first defect layer distributed vertically. In the first defect layer, the surface near the insulating dielectric layer is a rough surface. The piezoelectric functional layer is obtained by separating the original piezoelectric substrate, which includes the vertically distributed defect-free layer and the second defect layer. In this application embodiment, by recycling the second defect layer of the original piezoelectric substrate, a first defect layer with a rough surface is formed in the piezoelectric composite structure, reducing processing costs and avoiding unnecessary waste of piezoelectric materials. Moreover, the introduction of a rough surface in the piezoelectric composite structure improves structural performance. Attached Figure Description

[0064] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0065] Figure 1 This is a schematic diagram of a piezoelectric composite structure provided in an embodiment of this application;

[0066] Figure 2 This is a schematic diagram of the structure of a primitive piezoelectric substrate provided in an embodiment of this application;

[0067] Figure 3 This is a schematic diagram of another piezoelectric composite structure provided in the embodiments of this application;

[0068] Figure 4 This is a schematic flowchart of a method for preparing a piezoelectric composite structure provided in an embodiment of this application;

[0069] Figure 5 This is a schematic diagram of the structural flow of the first piezoelectric composite structure preparation method provided in the embodiments of this application;

[0070] Figure 6 This is a schematic diagram of the structural flow of the second piezoelectric composite structure preparation method provided in the embodiments of this application;

[0071] Figure 7 This is a schematic diagram of the structural process of the third piezoelectric composite structure preparation method provided in the embodiments of this application. Detailed Implementation

[0072] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0073] It should be noted that the term "an embodiment" or "embodiment" in the specification of the embodiments of this application refers to a specific feature, structure, or characteristic that can be included in at least one implementation of this application. It should be understood that in the specification, claims, and accompanying drawings of the embodiments of this application, the terms "upper," "lower," "top," "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, in the description of this embodiment, unless otherwise stated, "a plurality of" means two or more. Additionally, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, or product that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0074] It should be understood that when a device or component is referred to as being "on," "adjacent to," or "connected to" other devices or components, it may be directly on, adjacent to, or connected to other devices or components, or there may be intervening devices or components. Conversely, when a device or component is referred to as being "directly on," "directly adjacent to," or "directly connected to" other devices or components, there are no intervening devices or components. It should be understood that although the terms first, second, third, etc., may be used to describe various components, areas, layers, and / or parts, these components, areas, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one component, area, layer, or part from another component, area, layer, or part. Therefore, without departing from the teachings of this application, the first component, area, layer, or part discussed below may be referred to as the second component, area, layer, or part. And the discussion of the second component, area, layer, or part does not imply that the first component, area, layer, or part necessarily exists in this application.

[0075] To make the objectives, technical solutions, and advantages disclosed in the embodiments of this application clearer, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of this application and are not intended to limit the embodiments of this application.

[0076] This application provides a piezoelectric composite structure 1. Figure 1 This is a schematic diagram of a piezoelectric composite structure 1 provided in an embodiment of this application, as shown below. Figure 1 As shown, the piezoelectric composite structure 1 includes: a supporting substrate layer 11; an insulating dielectric layer 12 located on the supporting substrate layer 11; and a piezoelectric functional layer 13 located on the insulating dielectric layer 12.

[0077] In this embodiment, the piezoelectric functional layer 13 includes a defect-free layer 131 and a first defect layer 132 distributed vertically. The surface of the first defect layer 132 near the insulating dielectric layer 12 is a rough surface.

[0078] Figure 2 This is a schematic diagram of the structure of a primitive piezoelectric substrate 2 provided in an embodiment of this application, as shown below. Figure 2 As shown, the original piezoelectric substrate 2 includes a defect-free layer 131 and a second defect layer 21 distributed vertically. The piezoelectric functional layer 13 in the piezoelectric composite structure 1 is obtained by separating the original piezoelectric substrate 2, which is a recycled piezoelectric substrate 3 obtained during the fabrication of the piezoelectric composite structure 1. The second defect layer 21 in the original piezoelectric substrate 2 is transformed into the first defect layer 132 in the piezoelectric composite structure 1.

[0079] In this embodiment, both the piezoelectric functional layer 13 and the original piezoelectric substrate 2 are made of piezoelectric materials. After ion implantation, a second defect layer 21 with lattice defects is formed inside the piezoelectric material, and the portion of the piezoelectric material without lattice defects is the defect-free layer 131. After high-temperature annealing, the lattice quality of the piezoelectric material containing the second defect layer 21 is restored, and the second defect layer 21 is transformed into a first defect layer 132. Specifically, after ion implantation, a second defect layer 21 is introduced into the piezoelectric material. After heat treatment, the second defect layer 21 dissociates to obtain the original piezoelectric substrate 2. After heat treatment to restore the lattice quality of the original piezoelectric substrate 2, the second defect layer 21 transforms into a first defect layer 132, resulting in a processed piezoelectric substrate 4 comprising a defect-free layer 131 and a first defect layer 132 distributed vertically. After ion implantation, the processed piezoelectric substrate 4 introduces a second defect layer 21 into the defect-free layer 131. The second defect layer 21 dissociates internally after heat treatment, yielding a recycled piezoelectric substrate 3, i.e., the new original piezoelectric substrate 2. In this process, the piezoelectric material with lattice defects caused by ion implantation is no longer discarded as waste but is transformed into part of the piezoelectric composite structure 1. Recycling piezoelectric materials with lattice defects reduces processing costs and avoids unnecessary waste of piezoelectric materials. Moreover, the recycled piezoelectric material becomes the first defect layer 132 in the piezoelectric composite structure 1, giving the interface between the piezoelectric functional layer 13 and the insulating dielectric layer 12 of the piezoelectric composite structure 1 a certain roughness. This can effectively scatter the bulk acoustic waves propagating to this interface and the incident light waves, preventing the smooth interface in the acoustic device from reflecting bulk acoustic waves and introducing interference signals to the device. It can also prevent reflections caused by the flat interface during the photolithography process from affecting the resolution of the fabricated device.

[0080] In this embodiment, the materials of the piezoelectric functional layer 13 and the original piezoelectric substrate 2 include at least one of lithium niobate and lithium tantalate. The thickness of the piezoelectric functional layer 13 is 100 to 10,000 nanometers. Optionally, the thickness of the piezoelectric functional layer 13 can be 100 nanometers, 5050 nanometers, or 10,000 nanometers.

[0081] In this embodiment, the surface roughness of the first defect layer 132 near the insulating dielectric layer 12 is 2 to 25 nanometers, specifically 2 nanometers, 13.5 nanometers, or 25 nanometers. The thickness of the first defect layer 132 is 5 to 80 nanometers, specifically 5 nanometers, 42.5 nanometers, or 80 nanometers. The unit atomic displacement (DPA) value of the first defect layer 132 is 0.01 to 0.81, specifically 0.01, 0.81, or 0.41. The defect concentration of the first defect layer 132 decreases linearly from bottom to top.

[0082] In this embodiment, the material of the insulating dielectric layer 12 includes at least one of silicon dioxide and silicon nitride. The thickness of the insulating dielectric layer 12 is 100 to 1000 nanometers, and can be 100 nanometers, 1000 nanometers, or 550 nanometers.

[0083] In this embodiment, the material of the supporting substrate layer 11 includes at least one selected from silicon, silicon oxide, silicon-on-insulator (SOI), sapphire, silicon carbide, silicon-on-insulator (SiC), quartz, aluminum nitride, gallium nitride, and diamond. The thickness of the supporting substrate layer 11 is 0.2 to 2 mm, and can be 0.2 mm, 2 mm, or 1.1 mm.

[0084] Figure 3 This is a schematic diagram of another piezoelectric composite structure 1 provided in an embodiment of this application. The piezoelectric composite structure 1 includes a carrier trapping layer 14 located between an insulating dielectric layer 12 and a supporting substrate layer 11. The material of the carrier trapping layer 14 includes at least one of polycrystalline silicon, amorphous silicon, and porous silicon. The thickness of the carrier trapping layer 14 is 200 to 2000 nanometers, and can be 200 nanometers, 1100 nanometers, or 2000 nanometers.

[0085] Optionally, the surface in contact between the charge carrier trap layer 14 and the insulating dielectric layer 12 is either a rough surface or a smooth surface.

[0086] This application also provides a method for preparing a piezoelectric composite structure 1. Figure 4 This is a schematic flowchart illustrating a method for preparing a piezoelectric composite structure 1 according to an embodiment of this application. Figure 4 As shown, the preparation method includes:

[0087] S1: Provides the original piezoelectric substrate 2 and the support substrate.

[0088] In the embodiments of this application, Figure 5 A schematic diagram of the structural flow of the preparation method of the first piezoelectric composite structure 1 is provided, as follows: Figure 5 As shown, the original piezoelectric substrate 2 includes a defect-free layer 131 and a second defect layer 21 distributed vertically. The defect-free layer 131 is a piezoelectric material without lattice defects, while the second defect layer 21 is a piezoelectric material with lattice defects caused by ion implantation. The original piezoelectric substrate 2 is a recycled piezoelectric substrate 3 obtained during the fabrication of the piezoelectric composite structure 1.

[0089] In this embodiment, the material of the original piezoelectric substrate 2 includes at least one of lithium niobate and lithium tantalate.

[0090] Optionally, before obtaining the recycled piezoelectric substrate 3, the original piezoelectric substrate 2 can also be obtained by heat treatment after ion implantation of piezoelectric material. Specifically, after ion implantation, a second defect layer 21 with lattice defects is introduced into the piezoelectric material. After heat treatment, the second defect layer 21 dissociates to obtain the original piezoelectric substrate 2. The ion implantation includes at least one of hydrogen ions, helium ions, nitrogen ions, and argon ions; the ion implantation energy is 5 to 500 keV; and the ion implantation dose is 10... 13 Up to 10 17 The heat treatment is carried out at a temperature of 100 to 250 degrees Celsius for 5 to 30 hours in an atmosphere of at least one of nitrogen, argon, and vacuum.

[0091] Optionally, before obtaining the recycled piezoelectric substrate 3, the original piezoelectric substrate 2 can also be obtained by ion irradiation of the piezoelectric material. Specifically, the surface of the defect-free piezoelectric material is directly etched to obtain a piezoelectric material with surface defects, i.e., the original piezoelectric substrate 2 including a defect-free layer 131 and a second defect layer 21. The ion types used for ion irradiation include at least one of hydrogen ions, helium ions, nitrogen ions, and argon ions, the ion irradiation energy is 5 to 500 kiloelectron volts, and the ion irradiation dose is 10... 13 Up to 10 17 The support substrate is formed as a support substrate layer 11 in the piezoelectric composite structure 1. The material of the support substrate layer 11 includes at least one selected from silicon, silicon oxide, silicon on insulator (SOI), sapphire, silicon carbide, silicon carbide on insulator (SiC), quartz, aluminum nitride, gallium nitride, and diamond. The thickness of the support substrate layer 11 is 0.2 to 2 mm, and can be 0.2 mm, 2 mm, or 1.1 mm.

[0092] S2: Perform a first heat treatment on the original piezoelectric substrate 2 to obtain the treated piezoelectric substrate 4.

[0093] In this embodiment of the application, after the original piezoelectric substrate 2 undergoes the first heat treatment, the lattice quality of the second defect layer 21 is restored and it is transformed into the first defect layer 132, resulting in a processed piezoelectric substrate 4 including a defect-free layer 131 and a first defect layer 132.

[0094] In the embodiments of this application, the temperature of the first heat treatment is 250 to 550 degrees Celsius, the time is 2 to 6 hours, and the atmosphere is at least one of nitrogen, argon and vacuum environment.

[0095] In this embodiment of the application, when the material of the original piezoelectric substrate 2 is at least one of the piezoelectric materials lithium niobate and lithium tantalate, the first heat treatment also needs to be carried out in an atmosphere rich in lithium ions so that the original piezoelectric substrate 2 can restore its lattice quality after the heat treatment.

[0096] In some optional embodiments, the processed piezoelectric substrate 4 can also be chamfered, cutting the edges of the processed piezoelectric substrate 4 into a certain bevel. Optionally, the chamfering method is a T-shaped chamfer, with the width of the chamfered edge being 0.5 to 3.5 mm and the depth of the chamfered edge being 5 to 30 micrometers.

[0097] S3: An insulating dielectric layer 12 is prepared on the surface of the first defect layer 132 of the piezoelectric substrate 4, and the insulating dielectric layer 12 is planarized to obtain the first composite 5.

[0098] In this embodiment, the insulating dielectric layer 12 is prepared by chemical vapor deposition (CVD) or physical vapor deposition (PVD).

[0099] In this embodiment, after planarization, an insulating dielectric layer 12 with a polished surface is obtained. The polished surface facilitates bonding of the insulating dielectric layer 12 to other materials. The planarization process removes 50 to 200 nanometers of the thickness of the insulating dielectric layer 12.

[0100] S4: Ion implantation is performed on the surface of the insulating dielectric layer 12 in the first composite 5 to form a second defect layer 21 inside the defect-free layer 131 of the processed piezoelectric substrate 4.

[0101] In this embodiment, the ion implantation type includes at least one of hydrogen ions, helium ions, nitrogen ions, and argon ions; the ion implantation energy is 5 to 500 kiloelectron volts; and the ion implantation dose is 10. 13 Up to 10 17 pcs / square centimeter

[0102] S5: Bond the insulating dielectric layer 12 in the first composite 5 to the supporting substrate to obtain a second composite 6 in which the insulating dielectric layer 12 and the supporting substrate layer 11 are bonded.

[0103] Figure 6 This is a schematic diagram of the structural flow of the preparation method of the second piezoelectric composite structure 1 provided in the embodiments of this application. Figure 7 This is a schematic diagram of the structural flow of the preparation method of the third piezoelectric composite structure 1 provided in the embodiments of this application, as shown below. Figure 6 and Figure 7As shown, before bonding, a carrier trapping layer 14 can be prepared on the surface of the supporting substrate to obtain a third composite 7 consisting of the supporting substrate layer 11 and the carrier trapping layer 14. The carrier trapping layer 14 in the third composite 7 is then bonded to the insulating dielectric layer 12 in the first composite 5 to obtain a second composite 6. In the second composite 6, the carrier trapping layer 14 is located between the supporting substrate layer 11 and the insulating dielectric layer 12.

[0104] In this embodiment, during the fabrication of the insulating dielectric layer 12, some fixed charges, trapped charges, and other charge carrier impurities are inevitably introduced. When the device fabricated based on the control layer operates at high frequencies, these mobile charge carriers will move towards the supporting substrate layer 11, forming a conductive layer on the surface of the supporting substrate layer 11, reducing its effective resistivity. This will increase high-frequency losses, cause impedance mismatch, and increase substrate crosstalk in the device. By adding a charge carrier trapping layer 14 between the supporting substrate layer 11 and the insulating dielectric layer 12, the influence of charge impurities on the piezoelectric composite structure 1 and the device performance can be effectively reduced. Among them, the charge carrier trapping layer 14, made of amorphous silicon and polycrystalline silicon, has a high density of defects and interface states between its bands, which can pin the mobile charge carriers in the insulating dielectric layer 12 through the potential barrier between grain boundaries; the charge carrier trapping layer 14, made of porous silicon, can capture the charge carriers in the insulating dielectric layer 12 through its composite pores.

[0105] Optionally, the carrier trap layer 14 can be prepared by chemical vapor deposition (CVD) or physical vapor deposition (PVD).

[0106] Optionally, the material of the carrier trap layer 14 includes at least one of polycrystalline silicon, amorphous silicon, and porous silicon. The thickness of the carrier trap layer 14 is 200 to 2000 nanometers, and can be 200 nanometers, 1100 nanometers, or 2000 nanometers.

[0107] Optionally, the surface of the carrier trap layer 14 in contact with the insulating dielectric layer 12 can be either a rough surface or a smooth surface. The carrier trap layer 14 with either a smooth or rough surface is selected based on specific requirements. A smooth surface can improve the yield of subsequent processes while reducing fabrication difficulty; a rough surface can scatter incident sound waves and light waves, effectively preventing reflected waves from affecting device performance or the fabrication process.

[0108] In an optional embodiment, the surface of the carrier trapping layer 14 away from the supporting substrate layer 11 is a smooth surface, such as... Figure 6 As shown. The smooth surface of the carrier trap layer 14 is planarized, and the carrier trap layer 14 in the third bond 7 is bonded to the insulating dielectric layer 12 in the first bond 5.

[0109] Optionally, the thickness of the carrier trap layer 14 removed by the planarization process is 50 nanometers to 150 nanometers, which can be 50 nanometers, 150 nanometers, or 100 nanometers.

[0110] In another alternative embodiment, the surface of the carrier trap layer 14 away from the supporting substrate layer 11 is a smooth surface or a rough surface, such as... Figure 7 As shown. An insulating dielectric layer 12 is prepared on the smooth or rough surface of the carrier trap layer 14. After planarization treatment of the insulating dielectric layer 12, the insulating dielectric layer 12 on the carrier trap layer 14 in the third bond 7 is bonded to the insulating dielectric layer 12 in the first bond 5.

[0111] Optionally, the insulating dielectric layer 12 prepared on the smooth or rough surface of the carrier trapping layer 14 may be made of at least one of silicon dioxide and silicon nitride. The thickness of the insulating dielectric layer 12 prepared on the smooth or rough surface of the carrier trapping layer 14 may be 100 to 200 nanometers, specifically 100 nanometers, 150 nanometers, or 200 nanometers.

[0112] S6: Perform a second heat treatment on the second composite 6 to dissociate the second defect layer 21 in the processed piezoelectric substrate 4, and obtain the piezoelectric substrate 3 to be recycled and the piezoelectric composite structure precursor 8.

[0113] In this embodiment, the piezoelectric substrate 3 to be recycled includes a defect-free layer 131 and a second defect layer 21 distributed vertically, which is equivalent to a new original piezoelectric substrate 2 for the fabrication of the next piezoelectric composite structure 1. The second defect layer 21 in the piezoelectric substrate 3 to be recycled is transformed into the first defect layer 132 of the next piezoelectric composite structure 1.

[0114] In this embodiment of the application, the portion of the piezoelectric substrate 4 retained in the piezoelectric composite structure precursor 8 further includes a second defect layer 21.

[0115] In this embodiment, the temperature of the second heat treatment is 100 to 300 degrees Celsius, the time is 5 to 30 hours, and the atmosphere is at least one of nitrogen, argon and vacuum.

[0116] S7: Perform a third heat treatment and planarization on the piezoelectric composite structure precursor 8 to remove the second defect layer 21, and obtain the piezoelectric composite structure 1.

[0117] In this embodiment, the second defect layer 21 remaining in the piezoelectric composite structure precursor 8 is removed by a third heat treatment and planarization treatment, so that the remaining portion of the processed piezoelectric substrate 4 forms a piezoelectric functional layer 13 including a defect-free layer 131 and a first defect layer 132 distributed vertically.

[0118] In this embodiment, the temperature of the third heat treatment is 250 to 600 degrees Celsius, the time is 2 to 10 hours, and the atmosphere is at least one of nitrogen, argon and vacuum.

[0119] This application also provides an acoustic wave device, which includes the piezoelectric composite structure 1 described above and interdigitated electrodes. The interdigitated electrodes are disposed on the upper surface of the piezoelectric functional layer 13.

[0120] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired result. Additionally, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0121] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0122] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0123] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a piezoelectric composite structure, characterized in that, Includes the following steps: A pristine piezoelectric substrate and a support substrate are provided; the pristine piezoelectric substrate includes a defect-free layer and a second defect layer distributed vertically; the pristine piezoelectric substrate is a recycled piezoelectric substrate, or a piezoelectric substrate that has been internally ion-implanted and then heat-treated, or a piezoelectric substrate whose surface has been ion-irradiated; the second defect layer is formed by internally ion-implanted and then heat-treated or by surface ion-irradiated; the material of the pristine piezoelectric substrate includes at least one of lithium niobate and lithium tantalate. The original piezoelectric substrate is subjected to a first heat treatment to obtain a treated piezoelectric substrate; the treated piezoelectric substrate includes the defect-free layer and a first defect layer that is restored by lattice quality from the second defect layer; the atmosphere of the first heat treatment is rich in lithium ions. An insulating dielectric layer is prepared on the surface of the first defect layer of the piezoelectric substrate, and the insulating dielectric layer is planarized to obtain a first composite. Ion implantation is performed on the surface of the insulating dielectric layer in the first conjugate to form a new second defect layer inside the defect-free layer of the treated piezoelectric substrate; The insulating dielectric layer in the first composite is bonded to the supporting substrate to obtain the second composite; The second composite is subjected to a second heat treatment to dissociate the new second defect layer inside the piezoelectric substrate, resulting in a piezoelectric substrate to be recycled and a piezoelectric composite structure precursor. The piezoelectric composite structure precursor is subjected to a third heat treatment and planarization treatment to remove the residual new second defect layer, thereby obtaining the piezoelectric composite structure, wherein the first defect layer and the defect-free layer together form a piezoelectric functional layer.

2. The method for preparing the piezoelectric composite structure according to claim 1, characterized in that, The insulating dielectric layer is prepared by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The planarization process of the insulating dielectric layer removes 50 to 200 nanometers of the thickness of the insulating dielectric layer.

3. The method for preparing the piezoelectric composite structure according to claim 1, characterized in that, The types of ions implanted or irradiated include at least one of hydrogen ions, helium ions, nitrogen ions, and argon ions. The energy of the ion implantation or ion irradiation is 5 to 500 kiloelectron volts; The dose of the ion implantation or ion irradiation is 10 13 to 10 17 per square centimeter.

4. The method for preparing the piezoelectric composite structure according to claim 1, characterized in that, The first heat treatment is performed at a temperature of 250 to 550 degrees Celsius for 2 to 6 hours, in an atmosphere of at least one of nitrogen, argon, and vacuum. The second heat treatment is performed at a temperature of 100 to 300 degrees Celsius for 5 to 30 hours in an atmosphere of at least one of nitrogen, argon, and vacuum. The third heat treatment is performed at a temperature of 250 to 600 degrees Celsius for 2 to 10 hours in an atmosphere of at least one of nitrogen, argon, and vacuum.

5. The method for preparing the piezoelectric composite structure according to claim 1, characterized in that, Before the insulating dielectric layer is prepared on the surface of the piezoelectric substrate, the piezoelectric substrate is chamfered. The chamfering method is a T-shaped chamfer; The width of the chamfered edge is 0.5 to 3.5 mm; The depth of the chamfered edge removal is 5 to 30 micrometers.

6. The method for preparing the piezoelectric composite structure according to claim 1, characterized in that, Prior to the bonding, a carrier trapping layer is prepared on the surface of the supporting substrate to obtain a third bond; The carrier trap layer in the third composite is bonded to the insulating dielectric layer in the first composite to obtain the second composite.

7. The method for preparing the piezoelectric composite structure according to claim 6, characterized in that, The carrier trap layer is prepared by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The surface of the carrier trap layer away from the supporting substrate is a smooth surface. The smooth surface of the carrier trap layer is planarized before bonding. Alternatively, the surface of the carrier trap layer away from the supporting substrate is a smooth surface, an insulating dielectric layer is prepared on the smooth surface of the carrier trap layer, and the insulating dielectric layer is planarized and then bonded. Alternatively, the surface of the carrier trap layer away from the supporting substrate is a rough surface, an insulating dielectric layer is prepared on the rough surface of the carrier trap layer, and the insulating dielectric layer is planarized and then bonded.

8. A piezoelectric composite structure, characterized in that, The piezoelectric composite structure is prepared by the method for preparing the piezoelectric composite structure according to any one of claims 1-7, and the piezoelectric composite structure comprises: Support substrate layer; An insulating dielectric layer located on the supporting substrate layer; A piezoelectric functional layer is located on the insulating dielectric layer; the piezoelectric functional layer includes a defect-free layer and a first defect layer distributed vertically; in the first defect layer, the surface near the insulating dielectric layer is a rough surface; the piezoelectric functional layer is obtained by separating the original piezoelectric substrate, which includes a defect-free layer and a second defect layer distributed vertically.

9. The piezoelectric composite structure according to claim 8, characterized in that, The surface roughness of the first defect layer near the insulating dielectric layer is 2 to 25 nanometers; The thickness of the first defect layer is 5 to 80 nanometers; The unit atomic displacement (DPA) value of the first defect layer is 0.01 to 0.81; The defect concentration of the first defect layer decreases linearly from bottom to top.

10. The piezoelectric composite structure according to claim 8, characterized in that, The materials of the piezoelectric functional layer and the original piezoelectric substrate include at least one of lithium niobate and lithium tantalate; The thickness of the piezoelectric functional layer is 100 to 10,000 nanometers.

11. The piezoelectric composite structure according to claim 8, characterized in that, The material of the insulating dielectric layer includes at least one of silicon dioxide and silicon nitride; The thickness of the insulating dielectric layer is 100 to 1000 nanometers.

12. The piezoelectric composite structure according to claim 8, characterized in that, The material of the supporting substrate layer includes at least one of silicon, silicon oxide, silicon on insulator (SOI), sapphire, silicon carbide, silicon carbide on insulator (SiC), aluminum nitride, gallium nitride, and diamond. The thickness of the supporting substrate layer is 0.2 to 2 millimeters.

13. The piezoelectric composite structure according to claim 8, characterized in that, The piezoelectric composite structure further includes a carrier trapping layer located between the insulating dielectric layer and the supporting substrate layer; The carrier trap layer is made of at least one of polycrystalline silicon, amorphous silicon, and porous silicon. The thickness of the carrier trap layer is 200 to 2000 nanometers; The surface in contact between the charge carrier trap layer and the insulating dielectric layer is either a rough surface or a smooth surface.

14. An acoustic wave device, characterized in that, Includes the piezoelectric composite structure as described in any one of claims 8-13 and the interdigitated electrode; The interdigitated electrodes are disposed on the upper surface of the piezoelectric functional layer.

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