A composite film and preparation method thereof

Abstract

The present invention relates to the field of semiconductor technology, and in particular to a composite film and a preparation method thereof. A composite film comprises a substrate layer and a functional layer bonded above the substrate layer, characterized in that the material of the substrate layer is quartz or quartz glass, a separable structure is temporarily bonded below the substrate layer before the substrate layer is bonded to the functional layer, and the separable structure is thermally separated from the substrate layer after the functional layer is formed; wherein the thermal separation temperature of the separable structure is greater than the temperature of the heat treatment during the formation of the functional layer. The present invention effectively absorbs the thermal stress caused by the thermal expansion difference between the quartz-based substrate and the functional layer during the formation of the functional layer through the temporarily bonded separable structure, and protects the substrate to prevent the problem of fragments. The thermal separation temperature of the separable structure is greater than the temperature of the heat treatment during the formation of the functional layer, and can fully play the role of absorbing stress and protecting the substrate during the entire process of the formation of the functional layer. The process for preparing the composite film of the present invention makes the substrate thickness no longer limited by the influence of the fragments of the preparation process, and the quartz or quartz glass substrate of the required thickness can be selected based on actual needs, without the need for subsequent substrate thinning process, thereby reducing manufacturing costs.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a composite film and a preparation method thereof. Background Art

[0002] In today's information age, the semiconductor industry is in rapid development. The development of devices such as CPU chips, memory, amplifiers, filters, modulators, etc. plays a huge role in seizing the position in the semiconductor industry. The development of various electronic components has attracted more and more attention from the industry. Composite films, as key basic materials for downstream devices, have a significant impact on the development of electronic components.

[0003] At present, the traditional composite thin film structure usually includes a substrate layer and a functional layer composited on the substrate layer. Some devices expect to use quartz as the substrate and piezoelectric materials such as lithium niobate or lithium tantalate as the functional layer. However, quartz is brittle and easy to break, and its thermal expansion coefficient is much lower than that of lithium niobate or lithium tantalate, so it is very easy to break during the preparation process; in addition, it is also very easy to break when processing waveguides on composite thin films; in addition, although the use of a thick substrate can alleviate the fragmentation problem to a certain extent when processing waveguides, the device application has requirements for the thickness of the substrate, and the back of the substrate generally needs to be thinned. The brittleness of quartz makes it easy to break when the substrate is thinned. Therefore, when quartz is used as a substrate, it brings great difficulties to the process, and it is difficult to obtain a complete composite thin film product. Summary of the invention

[0004] Technical issues

[0005] It is expected that quartz will be used as the substrate. However, quartz is brittle and easy to break, and its thermal expansion coefficient is very different from that of lithium niobate and lithium tantalate. During the heat treatment process, large stress will be generated, resulting in fragmentation problems. When processing waveguides on composite films, fragmentation will also occur due to the brittleness of quartz and the difference in thermal expansion coefficients with lithium niobate and lithium tantalate. In order to reduce the fragmentation problem during waveguide processing, a thick substrate is usually used. Although the fragmentation problem can be alleviated to a certain extent when processing waveguides, the device application has requirements for the substrate thickness. After processing the waveguide, the substrate needs to be further thinned, which will inevitably introduce further fragments.

[0006] Technical Solution

[0007] A first aspect of the present invention provides a composite film, comprising a substrate layer and a functional layer bonded above the substrate layer, characterized in that the material of the substrate layer is quartz or quartz glass, and a detachable structure is temporarily bonded under the substrate layer before the substrate layer is bonded to the functional layer, and the detachable structure is thermally separated from the substrate layer after the functional layer is formed; wherein the thermal separation temperature of the detachable structure is greater than the temperature of the heat treatment during the formation of the functional layer.

[0008] The functional layer is a thin film wafer (the thin film wafer is an ion implanted wafer made by ion implantation, which includes a functional layer, an ion implanted layer and a residual material layer from top to bottom.) After bonding with the substrate layer, a thin layer structure is formed on the substrate layer after peeling along the ion implanted layer, eliminating ion implantation defects and polishing. The temperature of the heat treatment during the formation of the functional layer includes the temperature of the first stage heat treatment and the temperature of the second stage heat treatment. The temperature of the first stage heat treatment is the peeling temperature when the residual material layer is peeled off from the ion implanted layer, and the temperature of the second stage heat treatment is the heat treatment temperature for eliminating ion implantation defects.

[0009] In some embodiments, the thermal separation temperature of the separable structure is 220° C. to 380° C., and the temperature of the heat treatment during the formation of the functional layer is 100° C. to 375° C.

[0010] In some embodiments, the separable structure includes a supporting substrate and an intermediate layer, wherein the supporting substrate is temporarily bonded below the substrate layer through the intermediate layer; and the material of the intermediate layer is a thermally separable material.

[0011] In some embodiments, the thermal separation material is selected from One or more of HT-10.10, TB1238, acrylic resin, phenolic resin or silicone resin, preferably HT-10.10 or TB1238.

[0012] In some embodiments, the material of the functional layer is lithium niobate or lithium tantalate.

[0013] In some embodiments, the material of the support substrate is one or more of silicon carbide, sapphire, silicon, lithium niobate or lithium tantalate, preferably silicon carbide or sapphire.

[0014] In some embodiments, the thickness of the substrate layer is 120-200 μm.

[0015] In some embodiments, an isolation layer is further provided between the substrate layer and the functional layer.

[0016] In some embodiments, the material of the isolation layer is one or more of silicon dioxide, silicon nitride, aluminum oxide or aluminum nitride, preferably silicon dioxide.

[0017] In some embodiments, the functional layer has a waveguide structure.

[0018] A second aspect of the present invention provides a method for preparing any of the above-mentioned composite films, the method comprising the following specific steps:

[0019] S1, bonding a separable structure under the substrate layer to obtain a composite substrate including the substrate layer and the separable structure;

[0020] S2, bonding the substrate layer to the thin film wafer to obtain a bonded body including the thin film wafer and the composite substrate in order from top to bottom;

[0021] S3, thinning the thin film wafer to obtain an intermediate including a functional layer and a composite substrate from top to bottom;

[0022] S4. Thermally separating the separable structure from the substrate layer to obtain a composite film including a functional layer and a substrate layer in order from top to bottom.

[0023] In some embodiments, step S1 specifically includes: coating a thermal separation material on the surface of the substrate layer and / or the support substrate, bonding the substrate layer and the support substrate through the thermal separation material, and obtaining a composite substrate having a separable structure including an intermediate layer and a support substrate bonded below the substrate layer, wherein the intermediate layer is located between the substrate layer and the support substrate.

[0024] In some embodiments, the bonding temperature in step S1 is 60-250° C., the bonding pressure is 0.5-25 KN, and the bonding time is 6-60 min.

[0025] In some embodiments, in step S2, before bonding the substrate layer to the thin film wafer, an activation treatment is performed on a surface of the substrate layer opposite to the separable structure and a surface of the thin film wafer to be bonded.

[0026] In some embodiments, the activation treatment in step S2 is achieved by plasma surface activation.

[0027] In some embodiments, the thin film wafer is an ion implanted wafer made by ion implantation, which comprises a functional layer, an ion implanted layer and a residual material layer from top to bottom.

[0028] In some embodiments, the step of thinning the thin film wafer in step S3 is specifically as follows:

[0029] S3-1, performing the first stage heat treatment on the bonded body, stripping off the residual material layer from the ion implantation layer, and retaining the functional layer;

[0030] S3-2, performing the second stage heat treatment to eliminate ion implantation defects;

[0031] S3-3. Polishing the upper surface of the functional layer to remove the residual ion implantation layer.

[0032] In some embodiments, the temperature of the first stage heat treatment is the stripping temperature when the residual material layer is stripped off from the ion implantation layer, the temperature of the second stage heat treatment is the heat treatment temperature for eliminating ion implantation defects, and the thermal separation temperature of the separable structure is greater than the temperature of the second stage heat treatment and greater than the temperature of the first stage heat treatment.

[0033] In some embodiments, the temperature of the first stage heat treatment is 100-200°C, and the temperature of the second stage heat treatment is 200-375°C.

[0034] In some embodiments, the ions implanted by the ion implantation are one of hydrogen ions, helium ions, nitrogen ions, oxygen ions or argon ions, preferably hydrogen ions or helium ions;

[0035] In some embodiments, the implanted ions are hydrogen ions, and the implantation dose is 3×10 16 ions / cm 2 ~8×10 16 ions / cm 2 , the injection energy is 100keV~400keV.

[0036] In some embodiments, the implanted ions are helium ions with an implantation dose of 1×10 16 ions / cm 2 ~1×10 17 ions / cm 2 , the injection energy is 50keV~1000keV.

[0037] In some embodiments, before bonding the substrate layer to the thin film wafer, an isolation layer is first deposited on the side of the substrate layer opposite to the separable structure and / or the bonding side of the thin film wafer, and then the substrate layer and the thin film wafer are bonded via the isolation layer.

[0038] In some embodiments, the deposition method is one of chemical vapor deposition, physical vapor deposition or magnetron sputtering.

[0039] In some embodiments, after polishing the upper surface of the functional layer, waveguide etching is performed on the functional layer before thermally separating the separable structure from the substrate layer.

[0040] In some embodiments, the waveguide etching step is specifically as follows: making a mask on the upper surface of the functional layer based on the pattern of the target waveguide structure, etching the position without the mask on the functional layer, removing the mask, and forming the waveguide structure.

[0041] The third aspect of the present invention provides a method for preparing the above-mentioned composite film, the method comprising the following specific steps:

[0042] S1. Coating a thermal separation material on the surface of the substrate layer and / or the supporting substrate, and bonding the substrate layer to the supporting substrate through the thermal separation material to obtain a composite substrate having a separable structure including an intermediate layer and a supporting substrate bonded to the substrate layer, wherein the intermediate layer is located between the substrate layer and the supporting substrate;

[0043] S2, depositing an isolation layer on the substrate layer and / or the thin film wafer;

[0044] S3, bonding the substrate layer to the thin film wafer via the isolation layer to obtain a bonded body including the thin film wafer, the isolation layer and the composite substrate in order from top to bottom;

[0045] S4, thinning the thin film wafer to obtain an intermediate including a functional layer, an isolation layer and a composite substrate from top to bottom;

[0046] S5, performing waveguide etching on the functional layer to obtain an intermediate having a waveguide structure;

[0047] S6. Thermally separate the separable structure from the substrate layer to obtain a composite film comprising a functional layer, an isolation layer and a substrate layer in order from top to bottom.

[0048] In some embodiments, before bonding in step S3, the bonding surfaces are subjected to plasma surface activation treatment.

[0049] Technical Effects

[0050] The composite film of the present invention comprises a quartz or quartz glass substrate and a functional layer bonded above the substrate layer. A separable structure is temporarily bonded below the substrate layer before bonding. The thermal separation temperature of the separable structure is greater than the temperature of heat treatment during the formation of the functional layer. The separable structure is thermally separated from the substrate layer after the functional layer is formed. The thermal stress caused by the thermal expansion difference between the quartz or quartz glass substrate and the functional layer during the formation of the functional layer is effectively absorbed by the temporarily bonded separable structure, and the substrate layer is protected to prevent the problem of fragmentation. The preparation method of the composite film of the present invention solves the problem of fragments in the preparation process with the help of a separable structure. In addition, the thermal separation temperature of the separable structure is 220°C to 380°C, and the temperature of the heat treatment during the formation of the functional layer is 100 to 375°C (including the temperature of the first stage heat treatment of 100 to 200°C and the temperature of the second stage heat treatment of 200 to 375°C). The thermal separation temperature is basically within the temperature range of the second stage heat treatment for eliminating defects. In the actual annealing process, by cleverly implementing the temperature of the second stage heat treatment to be lower than the thermal separation temperature, the separable structure can be kept intact during the entire process of stripping off the functional layer and eliminating defects and during the waveguide processing to fully play the role of absorbing stress and protecting the substrate. The separable structure can also be separated in time after eliminating defects and processing the waveguide, and the maximum thermal separation temperature is only slightly higher than the temperature for eliminating defects. The separation process will not affect the crystal structure of the composite film. The separable structure is composed of a supporting substrate and an intermediate layer located above the supporting substrate. The intermediate layer has a thermal separation characteristic. When the functional layer is prepared, the intermediate layer and the supporting substrate can be thermally separated from the substrate layer at the thermal separation temperature without affecting the overall structure of the composite film. In addition, the quartz or quartz glass substrate is protected by the separable structure, and its thickness is no longer limited by the influence of the preparation process debris. The quartz or quartz glass substrate of the required thickness can be selected based on actual needs, without the need for subsequent substrate thinning process, reducing manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 FIG. 1 is a schematic structural diagram of a method for preparing a composite film provided in Example 1 of the present invention;

[0052] Figure 2 Shown is a structural schematic diagram of a method for preparing a composite film provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0053] In order to facilitate the understanding of the technical solution of the application, the following first provides a general description and definition of the terms and expressions involved in the present invention.

[0054] The terms "comprises", "includes" or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device that includes the element. The term "from top to bottom" indicates a relative position relationship and does not indicate a specific orientation.

[0055] The term "lattice damage caused by ion implantation" means that during the actual implantation process, ions need to gradually penetrate downward from the upper surface of the crystal and reach a specific depth. During this process, the thin film crystal will also be impacted by ions and produce some loss, destroying the original performance of the crystal.

[0056] The term "thermal separation temperature" refers to heating to the separation temperature of the thermal separation material.

[0057] In each group of comparative experiments provided by the present invention, unless otherwise specified, other experimental conditions, materials, etc., except for the differences indicated in each group, are kept consistent to ensure comparability.

[0058] Unless otherwise specified, the reagents and instruments used in the embodiments of the present invention can be purchased from the market.

[0059] The following is a further description of a composite film and a preparation method thereof provided by the present invention.

[0060] Embodiment 1:

[0061] The present embodiment provides a composite film, including a quartz substrate and a lithium niobate functional layer bonded to the top of the quartz substrate. Wherein, a separable structure is temporarily bonded below the quartz substrate before bonding, and the separable structure is thermally separated from the quartz substrate after the lithium niobate functional layer is formed. The separable structure includes a silicon carbide support substrate and a TB1238 intermediate layer of thermal separation material with thermal separation characteristics, and the silicon carbide support substrate is temporarily bonded to the quartz substrate through the TB1238 intermediate layer. The lithium niobate functional layer is the functional layer after the ion implantation sheet of the thin film wafer is peeled off along the ion implantation layer. The thermal separation temperature of TB1238 is greater than the thermal treatment temperature for peeling and eliminating ion implantation defects during the formation of the lithium niobate functional layer.

[0062] Reference Figure 1 , the preparation method of the composite film comprises the following steps:

[0063] S1. Coating a thermal separation material TB1238 (the thermal separation temperature is 220°C, purchased from Shenzhen Huaxun Semiconductor Materials Co., Ltd.) on a silicon carbide support substrate, and bonding the silicon carbide support substrate to a quartz substrate (thickness is 200 μm) via the thermal separation material TB1238 for 35 minutes at a temperature of 110°C and a pressure of 15KN, to obtain a composite substrate having a separable structure comprising a TB1238 intermediate layer and a silicon carbide support substrate bonded below the quartz substrate, wherein the TB1238 intermediate layer is located between the quartz substrate and the silicon carbide support substrate;

[0064] S2, plasma surface activation is performed on the side of the quartz substrate opposite to the TB1238 intermediate layer and the surface to be bonded of the lithium niobate thin film wafer, and then the two activated surfaces are bonded; wherein the lithium niobate thin film wafer is an ion-implanted wafer that has been ion-implanted, comprising a residual material layer, an ion-implanted layer and a functional layer, and the ions injected during the ion injection process are hydrogen ions, and the injection dose is 8×10 16 ions / cm 2 , the injection energy is 100keV;

[0065] S3, thinning the side of the lithium niobate thin film wafer away from the quartz substrate to obtain an intermediate; wherein, the method of thinning the lithium niobate thin film wafer is: performing a first stage heat treatment at 200° C. on the bonded composite substrate and the lithium niobate thin film wafer, peeling off the residual material layer at the ion implantation layer, separating the residual material layer from the functional layer, and transferring the functional layer to the quartz substrate; then performing a second stage heat treatment at 210° C. to eliminate lattice damage caused by ion implantation; and polishing the upper surface of the functional layer;

[0066] S4. Performing a thermal separation annealing treatment at 220° C. on the intermediate, separating the silicon carbide support substrate and the TB1238 intermediate layer from the quartz substrate, and obtaining a composite thin film.

[0067] Embodiment 2:

[0068] This embodiment provides a composite film, including a quartz glass substrate, a silicon dioxide isolation layer, and a lithium tantalate functional layer bonded to the silicon dioxide isolation layer, which are arranged in order from bottom to top. Before bonding, a separable structure is temporarily bonded below the quartz glass substrate, and after the lithium tantalate functional layer is formed, the separable structure is thermally separated from the quartz glass substrate. The separable structure includes a sapphire support substrate and a thermal separation material having thermal separation properties. HT-10.10 intermediate layer, sapphire support substrate through The HT-10.10 intermediate layer is temporarily bonded to the quartz glass substrate. The lithium tantalate functional layer is the functional layer after the thin film wafer ion implantation sheet is peeled off along the ion implantation layer. The thermal separation temperature of HT-10.10 is greater than the heat treatment temperature for peeling and eliminating peeling defects during the formation of the lithium tantalate functional layer. The lithium tantalate functional layer has a waveguide structure.

[0069] Reference Figure 2 , the preparation method of the composite film comprises the following steps:

[0070] S1. Coating thermal separation material on sapphire support substrate HT-10.10 (thermal separation temperature of 220°C, purchased from Brewer Science) was used to separate the sapphire support substrate and the quartz glass substrate (thickness of 120 μm) through the thermal separation material at a temperature of 180°C and a pressure of 10KN. HT-10.10 was bonded for 42 minutes to obtain a bonded A composite substrate of a separable structure of an HT-10.10 intermediate layer and a sapphire support substrate, wherein The HT-10.10 interlayer is located between the quartz glass substrate and the sapphire support substrate.

[0071] S2, on the quartz glass substrate A silicon dioxide isolation layer is deposited on the opposite side of the HT-10.10 intermediate layer by chemical vapor deposition (CVD), and the silicon dioxide isolation layer and the bonding surface of the lithium tantalate thin film wafer are plasma surface activated, and then the two activated surfaces are bonded; wherein, the lithium tantalate thin film wafer is an ion-implanted wafer that has been ion-implanted, comprising a residual material layer, an ion-implanted layer and a functional layer. The ions injected during the ion implantation process are helium ions, and the implantation dose is 7×10 16 ions / cm 2 , the injection energy is 500keV;

[0072] S3, thinning the side of the lithium tantalate thin film wafer away from the quartz glass substrate to obtain an intermediate; the method of thinning the lithium tantalate thin film wafer is: performing a first-stage heat treatment at 190° C. on the bonded body after step S2, peeling off the residual material layer at the ion implantation layer to separate the residual material layer from the functional layer, and transferring the functional layer to the silicon dioxide isolation layer; then performing a second-stage heat treatment at 215° C. to eliminate lattice damage caused by ion implantation; and polishing the upper surface of the functional layer;

[0073] S4, based on the pattern of the target waveguide structure, a mask is made on the surface of the thinned lithium tantalate thin film wafer (i.e., the functional layer), the position without the mask on the functional layer is etched, and the mask is removed to form a waveguide structure, thereby obtaining an intermediate having a waveguide structure; the intermediate is subjected to a thermal separation annealing treatment at 220° C. to separate the sapphire support substrate and the quartz glass substrate from the quartz glass substrate HT-10.10 intermediate layer to obtain a composite film.

[0074] Embodiment 3:

[0075] The difference from Example 1 is:

[0076] The thermal separation material is acrylic resin (thermal separation temperature is 320°C).

[0077] Step S1: At a temperature of 60°C and a pressure of 5KN, the silicon carbide supporting substrate and the quartz substrate (thickness of 160μm) are bonded for 60 minutes via a thermal separation material acrylic resin to obtain a composite substrate in which a separable structure including an acrylic resin intermediate layer and a silicon carbide supporting substrate is bonded under the quartz substrate.

[0078] Step S3: The temperature of the first stage heat treatment is 100°C, and the temperature of the second stage heat treatment is 250°C.

[0079] Step S4: The intermediate is subjected to a thermal separation annealing treatment at 320°C.

[0080] Embodiment 4:

[0081] The difference from Example 2 is:

[0082] The thermal separation material is silicone resin (thermal separation temperature is 380°C).

[0083] Step S1: At a temperature of 250°C and a pressure of 25KN, the sapphire support substrate and the quartz glass substrate (thickness of 180 μm) are bonded for 8 minutes via a thermal separation material silicone resin to obtain a composite substrate having a separable structure comprising a silicone resin intermediate layer and a sapphire support substrate bonded below the quartz glass substrate.

[0084] Step S3: The temperature of the first stage heat treatment is 200°C, and the temperature of the second stage heat treatment is 360°C.

[0085] Step S4: performing a thermal separation annealing treatment at 380° C. on the intermediate.

[0086] The above specific implementation methods further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solutions of the present invention should be included in the scope of protection of the present invention.

Claims

1. A composite film comprising a substrate layer and a functional layer bonded on the substrate layer, characterized in that: The material of the substrate layer is quartz or quartz glass. Before the substrate layer is bonded to the functional layer, a separable structure is temporarily bonded under the substrate layer. After the functional layer is formed, the separable structure is thermally separated from the substrate layer. Wherein, the thermal separation temperature of the separable structure is greater than the temperature of the heat treatment during the formation of the functional layer.

2. The composite film according to claim 1, characterized in that The thermal separation temperature of the separable structure is 220° C. to 380° C., and the temperature of the heat treatment during the formation of the functional layer is 100° C. to 375° C.

3. The composite film according to claim 1, characterized in that The separable structure comprises a supporting substrate and an intermediate layer, wherein the supporting substrate is temporarily bonded below the substrate layer through the intermediate layer; and the material of the intermediate layer is a thermal separation material.

4. The composite film according to claim 3, characterized in that: The thermal separation material is selected from One or more of HT-10.10, TB1238, epoxy resin, acrylic resin, phenolic resin or silicone resin; the material of the supporting substrate is one or more of silicon carbide, sapphire, silicon, lithium niobate or lithium tantalate.

5. The composite film according to claim 1, characterized in that The material of the functional layer is one of lithium niobate or lithium tantalate; and / or, an isolation layer is further provided between the substrate layer and the functional layer; wherein the material of the isolation layer is one or more of silicon dioxide, silicon nitride, aluminum oxide or aluminum nitride.

6. The composite film according to claim 1, characterized in that: The functional layer has a waveguide structure.

7. A method for preparing a composite film according to any one of claims 1 to 6, characterized in that: The method comprises the following specific steps: S1, bonding a separable structure under the substrate layer to obtain a composite substrate including the substrate layer and the separable structure; S2, bonding the substrate layer to the thin film wafer to obtain a bonded body including the thin film wafer and the composite substrate in order from top to bottom; S3, thinning the thin film wafer to obtain an intermediate including a functional layer and a composite substrate from top to bottom; S4. Thermally separate the separable structure from the substrate layer to obtain a composite film including a functional layer and a substrate layer in order from top to bottom.

8. The method according to claim 7, characterized in that Step S1 specifically includes: coating a thermal separation material on the surface of the substrate layer and / or the supporting substrate, bonding the substrate layer and the supporting substrate via the thermal separation material, and obtaining a composite substrate having a separable structure including an intermediate layer and a supporting substrate bonded below the substrate layer.

9. The method according to claim 7, characterized in that: In step S1, the bonding temperature is 60-250° C., the bonding pressure is 0.5-25 KN, and the bonding time is 6-60 min.

10. The method according to claim 7, characterized in that The thin film wafer is an ion implantation wafer made by ion implantation, and comprises a functional layer, an ion implantation layer and a residual material layer from top to bottom.

11. The method according to claim 10, characterized in that The steps of thinning the thin film wafer in step S3 are specifically as follows: S3-1, performing the first stage heat treatment on the bonded body, stripping off the residual material layer from the ion implantation layer, and retaining the functional layer; S3-2, performing the second stage heat treatment to eliminate ion implantation defects; S3-3, polishing the upper surface of the functional layer; The thermal separation temperature of the separable structure is higher than the temperature of the second stage heat treatment, and the temperature of the second stage heat treatment is higher than the temperature of the first stage heat treatment.

12. The method according to claim 11, characterized in that The temperature of the first stage heat treatment is 100-200°C, and the temperature of the second stage heat treatment is 200-375°C.

13. The method according to claim 7, characterized in that Before bonding the substrate layer to the thin film wafer, an isolation layer is first deposited on the side of the substrate layer opposite to the separable structure and / or the surface to be bonded of the thin film wafer, and then the substrate layer and the thin film wafer are bonded via the isolation layer.

14. The method according to claim 11, characterized in that After polishing the upper surface of the functional layer, waveguide etching is performed on the functional layer before thermally separating the separable structure from the substrate layer.

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