A composite film and preparation method thereof

Abstract

The embodiment of the present application provides a composite film and a preparation method thereof, wherein the composite film comprises a substrate, a first isolation layer, a second isolation layer and a functional film layer, wherein the first isolation layer, the second isolation layer and the functional film layer are sequentially stacked from bottom to top on the surface of the substrate, and the first isolation layer and the second isolation layer are made of the same material, and the diameter of the second isolation layer is smaller than the diameter of the first isolation layer. The present application will make the bonding force between the first isolation layer and the second isolation layer stronger, so that the bonding body formed by the substrate and the functional substrate has a better bonding effect, and thus the composite film formed by peeling off the bonding body has better structural strength and stability.

Description

Technical Field

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

[0002] Composite thin films are widely used in the fields of nonlinear optics, ferroelectrics, photoelectrics, photoelastics, pyroelectrics, photorefractives and nonlinearity. Composite thin films generally include a functional layer, an isolation layer and a substrate layer. The substrate layer is used to support the isolation layer and the functional layer, the functional layer is used to achieve the conversion between electricity and sound, and the isolation layer is used to cut off the electrical coupling between the functional layer and the substrate layer. Among them, the material of the functional layer is lithium niobate and lithium tantalate. Since lithium niobate and lithium tantalate have the advantages of high Curie temperature, strong spontaneous polarization, high electromechanical coupling coefficient and excellent electro-optical effect, composite lithium niobate thin films and composite lithium tantalate thin films are receiving more and more attention and application, especially in the fields of thin film bulk acoustic wave devices, filters and modulators.

[0003] The preparation methods of composite lithium niobate film and composite lithium tantalate film mainly include epitaxial growth method, thinning and polishing method and ion implantation method. In the epitaxial growth method, it is difficult to obtain a large-area, uniform and complete composite film due to the large lattice mismatch and different expansion coefficients between the film layer made of materials such as lithium niobate and lithium tantalate and the substrate layer material (such as silicon, quartz, etc.); it is difficult to obtain a composite film with nanometer-level thickness by using the thinning and polishing method, and the thinning and polishing process is easy to cause damage to the composite film, which will greatly affect the performance of electronic components. Therefore, in the actual production process of composite films, the ion implantation method is becoming more and more common.

[0004] At present, the ion implantation method generally includes the following steps: first, ion implantation is performed on the lithium niobate / lithium tantalate matrix to obtain an implanted sheet comprising a thin film layer, an implanted layer and a residual material layer; then, the thin film layer of the implanted sheet and the process surface of the substrate wafer are directly bonded at room temperature under atmospheric environment to obtain a bonded body; finally, the bonded body is annealed to peel off the residual material layer from the bonded body along the implanted layer, thereby transferring the thin film layer to the substrate wafer, and finally preparing a composite thin film.

[0005] In the above-mentioned ion implantation method, on the one hand, due to the different materials of the lithium niobate / lithium tantalate matrix and the substrate wafer, the thermal expansion coefficients of the two are quite different, and the expansion strength of the material is linearly related to the heating temperature, so the higher the heating temperature, the greater the expansion difference of the two materials with different thermal expansion coefficients. Therefore, if the lithium niobate / lithium tantalate matrix and the substrate wafer are directly heated and bonded, the two will generate a force due to the expansion difference, causing the bonded body to bend. When the heating temperature reaches the separation temperature, the residual material layer and the film layer will be instantly separated as a whole, and the residual material layer and the film layer will recover from the bent state to the flat state in a short time. In the process of the residual material layer and the film layer returning to the flat state, the force generated when the flatness is restored is large, which easily causes the residual material layer and the film layer to explode, thereby reducing the yield of the composite film. In addition, the separated residual material layer cannot be reused, resulting in serious waste of substrate wafers and increasing the production cost of the composite film.

[0006] On the other hand, the difference in material between the lithium niobate / lithium tantalate matrix and the substrate wafer results in poor bonding force between the two during the actual bonding process, and bonding failure is likely to occur at the edge of the formed bond. Summary of the invention

[0007] The embodiments of the present application provide a composite film and a method for preparing the same, so as to solve the problem of poor bonding effect between substrates of different materials in the current composite film bonding process.

[0008] In a first aspect, an embodiment of the present application provides a composite film, comprising a substrate, a first isolation layer, a second isolation layer and a functional film layer, wherein the first isolation layer, the second isolation layer and the functional film layer are stacked in sequence from bottom to top on the surface of the substrate, and the first isolation layer and the second isolation layer are made of the same material, and the diameter of the second isolation layer is smaller than the diameter of the first isolation layer.

[0009] In some embodiments, a diameter of the functional thin film layer is the same as a diameter of the second isolation layer, and both are smaller than a diameter of the first isolation layer.

[0010] In some embodiments, the difference between the diameter of the second isolation layer and the diameter of the first isolation layer is 5-6 mm.

[0011] In some embodiments, a defect layer is further included between the substrate and the first isolation layer, and the defect layer is used to provide a trap for capturing carriers between the substrate and the first isolation layer.

[0012] In some embodiments, the material of the first isolation layer and the second isolation layer is one of silicon dioxide, silicon oxynitride or silicon nitride.

[0013] In a second aspect, an embodiment of the present application provides a method for preparing a composite film, which is used to prepare the composite film as above, comprising the following steps:

[0014] Preparing a first isolation layer and a second isolation layer on the surfaces of the functional layer of the base substrate and the functional substrate respectively, wherein the diameter of the second isolation layer is smaller than the diameter of the first isolation layer;

[0015] Performing ion implantation on the functional substrate, so that ions pass through the second isolation layer and enter the functional layer of the functional substrate, and sequentially forming a stacked residual layer, an implantation layer and a functional film layer in the functional layer, wherein the functional film layer contacts the second isolation layer, and the implanted particles are distributed in the implantation layer;

[0016] Bonding the second isolation layer to the first isolation layer to obtain a first bonding body;

[0017] The first bonding body is annealed to separate the functional film layer from the residual layer along the injection layer and transfer the functional film layer to the substrate to obtain the composite film.

[0018] In some embodiments, before preparing the first isolation layer on the surface of the substrate, the preparation method further includes: preparing a defect layer on the surface of the substrate.

[0019] In some embodiments, the step of preparing a first isolation layer and a second isolation layer on the surfaces of the functional layers of the base substrate and the functional substrate, respectively, comprises:

[0020] Providing a functional layer and an auxiliary substrate, and preparing a second isolation layer and a third isolation layer on the surfaces of the functional layer and the auxiliary substrate, respectively;

[0021] Bonding the third isolation layer and the surface of the functional layer facing away from the second isolation layer to form the functional substrate in a second bonding body, wherein the functional substrate comprises the auxiliary substrate, the third isolation layer, the functional layer and the second isolation layer stacked in sequence;

[0022] A first isolation layer is prepared on the surface of the substrate.

[0023] In some embodiments, the step of preparing a first isolation layer and a second isolation layer on the surfaces of the functional layers of the base substrate and the functional substrate, respectively, comprises:

[0024] providing functional layers and auxiliary substrates;

[0025] Prepare a second isolation layer and a third isolation layer on two opposite surfaces of the functional layer respectively;

[0026] Bonding the auxiliary substrate to the third isolation layer to form the functional substrate in a third bonding body, wherein the functional substrate comprises the auxiliary substrate, the third isolation layer, the functional layer and the second isolation layer stacked in sequence;

[0027] A first isolation layer is prepared on the substrate.

[0028] In some embodiments, the thermal expansion coefficients of the base substrate, the functional substrate, and the auxiliary substrate are the same or similar.

[0029] Due to the adoption of the above technical solution, the technical effects achieved by this application are:

[0030] The present application provides a composite film, comprising a substrate substrate, a first isolation layer, a second isolation layer and a functional film layer stacked in sequence, and the bonding between the substrate substrate and the functional film layer is realized by the first isolation layer and the second isolation layer. Among them, the first isolation layer and the second isolation layer are set to the same material, so that the first isolation layer and the second isolation layer have the same or similar thermal expansion coefficient, so that during the heating bonding process, the risk of the functional film layer bursting caused by the excessive expansion difference between the two is reduced, which is conducive to the improvement of the yield rate of the composite film. In addition, this setting method of the same material will also make the bonding force between the first isolation layer and the second isolation layer stronger, so that the bonding body formed by the substrate substrate and the functional substrate has a better bonding effect, and then the composite film peeled from the bonding body has better structural strength and stability. In addition, the diameter of the second isolation layer is smaller than the diameter of the first isolation layer. Since the contact area between the first isolation layer and the second isolation layer is reduced, the second isolation layer is entirely located in the bonding surface of the first isolation layer as a whole, which greatly avoids the situation where the edge positions of the two cannot be bonded, which is conducive to further improvement of the bonding effect of the composite film. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure of a composite film provided in an embodiment of the present application;

[0032] Figure 2 is a schematic diagram of the structure of another composite film provided in an embodiment of the present application;

[0033] Figure 3 It is a schematic diagram of a process for preparing a composite film provided in Example 1 of the present application;

[0034] Figure 4 is a schematic diagram of a functional substrate preparation process provided in Example 1 of the present application;

[0035] Figure 5 is a schematic diagram of a composite film preparation process provided in Example 1 of the present application;

[0036] Figure 6 It is a schematic flow chart of a method for preparing an isolation layer provided in Example 2 of the present application;

[0037] Figure 7 is a schematic diagram of a preparation process of a functional substrate in the form of a second bonding body provided in Example 2 of the present application;

[0038] Figure 8 is a schematic diagram of a composite film preparation process provided in Example 2 of the present application;

[0039] Fig. 9 It is a schematic flow chart of a method for preparing an isolation layer provided in Example 3 of the present application;

[0040] Fig.10 is a schematic diagram of a preparation process of a functional substrate presenting a third bonding body provided in Example 3 of the present application;

[0041] Fig.11 is a schematic diagram of a composite film preparation process provided in Example 3 of the present application;

[0042] Fig.12 is a schematic diagram of a composite film preparation process provided in Example 4 of the present application;

[0043] Fig.13 is a schematic diagram of a composite film preparation process provided in Example 5 of the present application;

[0044] Fig.14 This is a schematic diagram of a composite film preparation process provided in Example 6 of the present application.

[0045] Description of reference numerals:

[0046] 100 substrate base plate, 110 first isolation layer;

[0047] 200 functional substrate, 210 base, 220 functional layer, 221 residual layer, 222 injection layer, 223 functional thin film layer, 230 second isolation layer;

[0048] 300 auxiliary substrate, 310 third isolation layer;

[0049] 400 defect layers. DETAILED DESCRIPTION

[0050] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0051] Figure 1 It is a schematic diagram of the structure of a composite film provided in an embodiment of the present application.

[0052] Reference Figure 1 As shown, an embodiment of the present application provides a composite film, including a base substrate 100, a first isolation layer 110, a second isolation layer 230 and a functional film layer 223, the first isolation layer 110, the second isolation layer 230 and the functional film layer 223 are stacked in sequence from bottom to top on the surface of the base substrate 100, and the first isolation layer 110 and the second isolation layer 230 are made of the same material, and the diameter of the second isolation layer 230 is smaller than the diameter of the first isolation layer 110.

[0053] Among them, the function of the base substrate 100 is to provide support for the first isolation layer 110, the second isolation layer 230 and the functional film layer 223; the function of the first isolation layer 110 and the second isolation layer 230 is to isolate the electrical coupling that may be generated between the functional film layer 223 and the base substrate 100; the function of the functional film layer 223 is to enable the composite film to achieve specific electrical properties, such as for achieving the conversion between electricity and sound.

[0054] The present embodiment of the present application does not limit the thickness of the base substrate 100, the first isolation layer 110, the second isolation layer 230 and the functional film layer 223. For example, the thickness of the base substrate 100 can be 0.3-1 mm, the thickness of the first isolation layer 110 and the second isolation layer 230 can both be 200-3000 nm, and the thickness of the functional film layer 223 can be 50-3000 nm.

[0055] In addition, the preparation method of the first isolation layer 110 and the second isolation layer 230 can be a deposition method or a thermal oxidation method, etc., and the embodiment of the present application does not limit this. However, it should be noted that the formation of the first isolation layer 110 can be directly deposited or oxidized on the substrate 100 so that the first isolation layer 110 is formed on the surface of the substrate 100; and the formation of the second isolation layer 230 can be directly deposited or oxidized on the surface of the first isolation layer 110 away from the substrate 100 so that it is formed on the basis of the first isolation layer 110; or, the second isolation layer 230 can also be formed on the basis of the following functional substrate 200, that is, the surface of the functional substrate 200 is deposited or oxidized so that the surface of the functional substrate 200 forms the second isolation layer 230, and then the second isolation layer 230 is transferred to the substrate 100 (or the first isolation layer 110) through bonding, annealing and other processes. The embodiment of the present application does not limit the forming method of the first isolation layer 110 and the second isolation layer 230.

[0056] It should be noted that the surface (or process surface) of the base substrate 100 in the embodiment of the present application refers to the surface of the base substrate 100 that can cooperate with other hierarchical structures (such as the first isolation layer 110, the functional film layer 223, etc.), such as the top surface of the base substrate 100. In addition, the material of the base substrate 100 can be one of quartz, silicon, sapphire, SOI (Silicon On Insulator), diamond, silicon carbide, silicon nitride, gallium arsenide, indium phosphide or germanium, and the embodiment of the present application does not limit the material of the base substrate 100.

[0057] The material of the first isolation layer 110 and the second isolation layer 230 can be one of silicon dioxide, silicon oxynitride or silicon nitride, and the material of the functional film layer 223 can be one of lithium niobate, lithium tantalate, quartz, ceramic, lithium tetraborate, potassium titanyl phosphate, rubidium titanyl phosphate, gallium arsenide or silicon. The embodiments of the present application do not limit the materials of the first isolation layer 110, the second isolation layer 230 and the functional film layer 223.

[0058] The composite film provided in the present application realizes the bonding between the substrate 100 and the functional film layer 223 through the first isolation layer 110 and the second isolation layer 230. Among them, the first isolation layer 110 and the second isolation layer 230 are set to the same material, so that the first isolation layer 110 and the second isolation layer 230 have the same or similar thermal expansion coefficients, thereby reducing the risk of the functional film layer 223 bursting due to the large expansion difference between the two during the heating bonding process, which is conducive to the improvement of the yield rate of the composite film. In addition, this setting method of the same material will also make the bonding force between the first isolation layer 110 and the second isolation layer 230 stronger, so that the bonding body formed by the substrate 100 and the functional substrate 200 has a better bonding effect, and then the composite film peeled off from the bonding body has better structural strength and stability. In addition, the diameter of the second isolation layer 230 is smaller than the diameter of the first isolation layer 110. Since the contact area between the first isolation layer 110 and the second isolation layer 230 is reduced, the second isolation layer 230 is entirely located on the bonding surface of the first isolation layer 110, which greatly avoids the situation where the edges of the two cannot be bonded, which is beneficial to further improve the bonding effect of the composite film.

[0059] It is understandable that, although the diameter of the second isolation layer 230 is set to be smaller than the diameter of the first isolation layer 110 in the embodiment of the present application, there is no specific limitation on the size relationship between the functional film layer 223 and the first isolation layer 110, the second isolation layer 230 and the base substrate 100. In other words, the diameter of the functional film layer 223 may be the same as the diameter of the second isolation layer 230, the diameter of the first isolation layer 110 or the diameter of the base substrate 100, or may be different from the diameters of the three.

[0060] Based on this, the sizes of the base substrate 100, the first isolation layer 110, the second isolation layer 230 and the functional film layer 223 in the embodiment of the present application can be realized in a variety of different ways. For example, the base substrate 100, the first isolation layer 110 and the functional film layer 223 have the same diameter, and the diameter of the second isolation layer 230 is smaller than the diameter of the first isolation layer 110; or, the base substrate 100 and the first isolation layer 110 have the same diameter, the diameter of the second isolation layer 230 is smaller than the diameter of the first isolation layer 110, and the diameter of the functional film layer 223 is smaller than the diameter of the second isolation layer 230; or, the base substrate 100 and the first isolation layer 110 have the same diameter, the second isolation layer 230 and the functional film layer 223 have the same diameter, and both are smaller than the first isolation layer 110. 0 diameter; or, the diameter of the first isolation layer 110 is smaller than the diameter of the base substrate 100, the diameter of the second isolation layer 230 is smaller than the diameter of the first isolation layer 110, and the diameter of the functional film layer 223 is the same as the second isolation layer 230; or even, the diameters of the base substrate 100, the first isolation layer 110, the second isolation layer 230 and the functional film layer 223 decrease in sequence, etc. Other possible size relationships among the base substrate 100, the first isolation layer 110, the second isolation layer 230 and the functional film layer 223 will not be listed one by one here.

[0061] However, for ease of understanding and explanation, the embodiment of the present application will take the case where the diameter of the functional film layer 223 is the same as the diameter of the second isolation layer 230 and both are smaller than the diameter of the first isolation layer 110 as a preferred method to explain the relevant contents of the composite film.

[0062] In this embodiment, since the diameter of the functional film layer 223 is set to be the same as the diameter of the second isolation layer 230, during the preparation process of the composite film, both the second isolation layer 230 and / or the functional film layer 223 can be better peeled off from the functional substrate 200 described below, and the second isolation layer 230 and the functional film layer 223 as a whole have a better bonding effect with the first isolation layer 110 and the base substrate 100 as a whole, are not easy to crack at the edges, and the various hierarchical structures of the composite film are not easy to separate, which is beneficial to improving the overall structural stability of the composite film.

[0063] In some specific examples, the difference between the diameter of the second isolation layer 230 and the diameter of the first isolation layer 110 can be 5-6 mm. Here, the specific difference between the diameter of the second isolation layer 230 and the diameter of the first isolation layer 110 can be reasonably selected according to the specific processing and production requirements of the composite film, and the embodiments of the present application are not limited to this.

[0064] Figure 2 It is a schematic diagram of the structure of another composite film provided in an embodiment of the present application.

[0065] In some embodiments, reference Figure 2 As shown, the composite film also includes a defect layer 400 located between the base substrate 100 and the first isolation layer 110, and the defect layer 400 is used to provide a trap for capturing carriers between the base substrate 100 and the first isolation layer 110. Among them, there are lattice defects of a certain density in the defect layer 400, which can capture carriers existing between the first isolation layer 110 and the base substrate 100, and prevent these carriers from causing carrier aggregation at the interface between the first isolation layer 110 and the base substrate 100, thereby reducing the loss of the composite film. Preferably, the material of the defect layer 400 can be one of polycrystalline silicon, amorphous silicon, and polycrystalline germanium.

[0066] The preparation method of the defect layer 400 may be a deposition method, an etching method, or an ion implantation method, etc. When the deposition method is adopted, for example, polycrystalline silicon, amorphous silicon, and polycrystalline germanium may be deposited to form the defect layer 400, wherein the deposition method may be chemical vapor deposition (CVD), physical vapor deposition (PVD), magnetron sputtering, etc., and the present application does not limit the deposition method; when the etching method is adopted, the substrate 100 may be etched to form the defect layer 400; when the ion implantation method is adopted, the corresponding ions may be implanted into the substrate 100 to form the defect layer 400, and the present application embodiment does not limit the specific forming method of the defect layer 400.

[0067] When the composite film includes a defect layer 400, the first isolation layer 110 can be formed on the surface of the defect layer 400. Specifically, for example, the first isolation layer 110 can be prepared on the defect layer 400 by thermal oxidation. When the defect layer 400 is a polysilicon layer, the polysilicon layer can be oxidized, and the side of the polysilicon layer away from the base substrate 100 is oxidized to form a silicon dioxide layer (i.e., the first isolation layer 110), while the side close to the base substrate 100 is not oxidized. The oxidation temperature when preparing the first isolation layer 110 by thermal oxidation can be 900-1000°C.

[0068] In addition, since the specific structure of the composite film finally prepared by the present application can be reasonably selected according to the requirements of the product, accordingly, the preparation method of the composite film provided by the present application can actually have a variety of different implementation processes. For ease of understanding, several different embodiments will be described below:

[0069] Embodiment 1

[0070] Figure 3 It is a schematic flow chart of a method for preparing a composite film provided in Example 1 of the present application.

[0071] Reference Figure 3 As shown, the embodiment of the present application also provides a method for preparing a composite film, which is used to prepare the composite film as described above. Specifically, the preparation method may include the following steps:

[0072] S110, preparing a first isolation layer and a second isolation layer on the surfaces of the functional layers of the base substrate and the functional substrate respectively.

[0073] Among them, the diameter of the second isolation layer 230 is smaller than the diameter of the first isolation layer 110, the thickness of the functional layer can be 0.3-1mm, and the material of the functional layer 220 can be one of lithium tantalate, quartz, ceramic, lithium tetraborate, potassium titanyl phosphate, rubidium titanyl phosphate, gallium arsenide or silicon.

[0074] It should be noted that, in some embodiments, the functional substrate 200 can be a whole, which has a functional layer 220 that enables the composite film to have a specific function, and a substrate 210 for carrying the functional layer 220, that is, the substrate 210 and the functional layer 220 together constitute the functional substrate 200. In other embodiments, the functional substrate can also be composed only of the functional layer 220, that is, the functional layer 220 serves as the functional substrate 200. Among them, the material of the substrate 210 is the same as that of the base substrate 100, such as quartz, silicon, sapphire, SOI, diamond, silicon carbide, silicon nitride, gallium arsenide, indium phosphide or germanium. In addition, when the second isolation layer 230 is prepared on the surface of the functional layer 220, the second isolation layer 230 can also be used as a part of the functional substrate 200, that is, the functional substrate 200 can include the substrate 210, the functional layer 220 and the second isolation layer 230; or the functional substrate 200 can include the functional layer 220 and the second isolation layer 230. This embodiment does not limit the structure, material, size, etc. of the functional substrate 200 , the base substrate 100 , and the functional layer 220 .

[0075] For ease of understanding, the first embodiment will take the structure of the functional substrate 200 including the base 210 and the functional layer 220 as an example to illustrate the preparation process of the composite film.

[0076] S120, performing ion implantation on the functional substrate, so that the ions pass through the second isolation layer and enter the functional layer of the functional substrate, and sequentially form a stacked residual layer, an implantation layer and a functional thin film layer in the functional layer.

[0077] The functional film layer 223 is in contact with the second isolation layer 230, and the injected particles are distributed in the injection layer 222. When ions are injected into the functional substrate 200 by ion implantation, the present application does not limit the method of ion implantation, and any ion implantation method in the prior art can be used. The injected ions are ions that can generate gas by heat treatment, such as at least one of hydrogen ions, helium ions, oxygen ions, argon ions or neon ions. For example, the injection dose of the ion beam can range from 2×10 16 ions / cm 2 -4×10 16 ions / cm 2 , the injection energy range can be 40keV-600keV.

[0078] It is understood that when performing ion implantation, the depth of the implantation layer 222 can be adjusted by adjusting the ion implantation energy. Specifically, the greater the ion implantation energy, the deeper the depth of the implantation layer 222; conversely, the smaller the ion implantation energy, the shallower the depth of the implantation layer 222. In addition, the diffusion width of the implantation layer 222 can be adjusted by adjusting the ion implantation dose. Specifically, the greater the ion implantation dose, the wider the diffusion width of the implantation layer 222; conversely, the smaller the ion implantation dose, the narrower the diffusion width of the implantation layer 222.

[0079] As a specific example, the functional layer may be a lithium niobate wafer, and the implanted ions may be helium ions. For example, helium ions are implanted into the lithium niobate wafer, and the implantation energy of the helium ions may be 400 KeV, and the implantation dose may be 4×10 16 ions / cm 2 , to form an implantation layer 222 in the lithium niobate wafer.

[0080] S130, bonding the second isolation layer to the first isolation layer to obtain a first bonding body.

[0081] In order to improve the bonding effect between the first isolation layer 110 and the second isolation layer 230, the surfaces of the first isolation layer 110 and the second isolation layer 230 may be polished and cleaned before bonding. In addition, the embodiment of the present application does not specifically limit the bonding method, and any bonding method in the prior art may be used, for example, bonding by surface activation to obtain the first bonded body. Moreover, the present application does not limit the surface activation method, for example, plasma activation or chemical solution activation may be used.

[0082] S140, annealing the first bonding body to separate the functional film layer from the residual layer along the injection layer, and transfer the functional film layer to the substrate to obtain a composite film.

[0083] The purpose of the annealing treatment is to heat the injected ions in the injection layer 222 to form gas and generate bubbles. The bubbles are interconnected in the injection layer 222, so that the residual layer 221 and the functional film layer 223 are instantly separated as a whole to obtain a composite film. The annealing treatment usually includes a primary annealing and a secondary annealing. The temperature range of the primary annealing is 180-300°C, and its purpose is to separate the functional film layer 223 from the residual layer 221 and peel off the residual layer 221; the temperature range of the secondary annealing is 300-600°C, and its purpose is to eliminate the possible injection damage in the functional film layer 223 and the residual layer 221.

[0084] In the actual annealing process, the bonded body can be treated at a temperature of 180-600°C for 1-100h, so that bubbles are formed inside the injection layer 222 in the functional layer. For example, when the injected ions are helium ions, the annealing process can convert the helium ions into helium; when the injected ions are hydrogen ions, the annealing process can convert the helium ions into hydrogen. As the annealing process proceeds, the bubbles in the injection layer 222 are connected together, and finally the injection layer 222 is cracked, so that the residual layer 221 and the functional film layer 223 are separated, so that the residual layer 221 is peeled off from the bonded body, and then a composite film is formed on the base substrate 100.

[0085] The preparation method of the composite film provided in the present application, on the one hand, since the first isolation layer 110 and the second isolation layer 230 are made of the same material and their thermal expansion coefficients are similar, the two have stronger bonding force and better bonding effect when bonded, which is beneficial to the improvement of the structural stability of the composite film prepared subsequently; on the other hand, since the diameter of the second isolation layer 230 is smaller than the diameter of the first isolation layer 110, the bonded body formed by the two is not prone to edge cracking during the annealing process, which makes it difficult for the various hierarchical structures of the composite film to separate, which is beneficial to further improve the structural strength and reliability of the composite film.

[0086] For ease of understanding, the preparation process of the composite film will be described below using a specific example. Figure 4 is a schematic diagram of a functional substrate preparation process provided in Example 1 of the present application, Figure 5 It is a schematic diagram of a composite film preparation process provided in Example 1 of the present application.

[0087] Preparation stage: Before preparing the composite film, first, two 6-inch silicon wafers (i.e., the first silicon wafer and the second silicon wafer, serving as the substrate 100 and the base 210, respectively) and a lithium tantalate wafer (serving as the functional layer 220 of the functional substrate 200) can be prepared. The two silicon wafers and the lithium tantalate wafer are fixed on the porous ceramic chucks of the polishing equipment, and then the silicon wafer and the lithium tantalate wafer are chemically and mechanically polished to make them both have smooth surfaces, and the silicon wafer and the lithium tantalate wafer are cleaned by semiconductor RCA to obtain clean surfaces.

[0088] Functional substrate preparation stage: refer to Figure 4 As shown, the second silicon wafer and the lithium tantalate wafer are contact-bonded after being activated to obtain the functional substrate 200, and then a second silicon dioxide layer (i.e., the second isolation layer 230) having a diameter smaller than that of the lithium tantalate wafer by about 5 mm is deposited on the lithium tantalate wafer. It can be found that after the above treatment process, the functional substrate 200 finally prepared actually has a three-layer structure, i.e., it includes a single crystal silicon layer, a functional layer 220, and a second silicon dioxide layer in sequence from bottom to top.

[0089] Substrate preparation stage: refer to Figure 5 As shown, a first silicon dioxide layer (ie, the first isolation layer 110 ) is formed on the first silicon wafer by thermal oxidation, wherein the oxidation thickness of the first silicon dioxide layer is about 5 μm.

[0090] Ion implantation stage: Helium ions are implanted into the functional substrate 200 by ion implantation, and nitrogen ions are implanted into the lithium tantalate wafer through the second silicon dioxide layer, so that the lithium tantalate wafer is formed into a residual layer 221, an implantation layer 222 and a functional film layer 223 in sequence from the implantation surface, and the implanted nitrogen ions are distributed in the implantation layer 222 to obtain an implanted wafer. The implantation dose parameter can be: the implantation dose is 2×10 16 ions / cm 2 , the injection energy is 200keV.

[0091] Bonding stage: the second silicon dioxide layer in the functional substrate 200 is brought into contact with the first silicon dioxide layer in the base substrate 100 and bonded by a direct bonding method to obtain a first bonded body.

[0092] Annealing treatment stage: the first bond body is placed in an annealing furnace and heat treated at 280°C for 4 hours. The first bond body is disconnected at the injection layer 222, and the second silicon wafer and the residual layer 221 are completely peeled off to obtain a composite film having a structure of a first silicon wafer, a first silicon dioxide layer, a second silicon dioxide layer and a functional film layer 223. The diameter of the second silicon dioxide layer is about 5 mm smaller than the diameter of the silicon wafer and the first silicon dioxide layer, and the diameter of the functional film layer 223 is the same as that of the first silicon dioxide layer. The composite film is then annealed at 350°C for 3 hours to eliminate the injection damage.

[0093] Cleaning stage: the composite film is taken out from the annealing furnace and then fixed on the porous ceramic suction cup of the polishing equipment, the functional film layer 223 is subjected to chemical mechanical polishing, and then semiconductor RCA cleaning is performed to obtain a clean surface, and finally a composite film product is obtained.

[0094] In addition, the second silicon wafer and the residual layer 221 peeled from the bonded body can be reused, such as continuing to deposit a silicon dioxide layer on the residual layer 221, so that the peeled portion is reused as the functional substrate 200 in another preparation cycle. This arrangement can greatly reduce the production cost of the composite film.

[0095] Embodiment 2

[0096] When preparing the isolation layer, there are many different preparation methods according to different preparation processes. For example, an auxiliary substrate 300 may be additionally provided, and a third isolation layer 310 may be prepared on the auxiliary substrate 300, and then a first isolation layer and a second isolation layer 230 may be prepared on the surface of the base substrate 100 and the surface of the functional layer 220, respectively. Figure 6 It is a schematic flow chart of a method for preparing an isolation layer provided in Example 2 of the present application.

[0097] Specifically, refer to Figure 6 As shown, the method for preparing the isolation layer in the second embodiment of the present application includes the following steps:

[0098] S210, providing a functional layer and an auxiliary substrate, and preparing a second isolation layer and a third isolation layer on the surfaces of the functional layer and the auxiliary substrate, respectively.

[0099] The auxiliary substrate 300 may be made of quartz, silicon, sapphire, SOI, diamond, silicon carbide, silicon nitride, gallium arsenide, indium phosphide or germanium. Furthermore, the auxiliary substrate 300 may be made of the same material as the base substrate 100 or different from the base substrate 100 .

[0100] In this step S210, by selecting appropriate materials, the auxiliary substrate 300 and the base substrate 100 can have thermal expansion coefficients with small differences. In this way, even if the functional board and the base substrate 100 are made of different materials, the composite film will not explode during the annealing separation process, which is conducive to ensuring the stability of the composite film structure.

[0101] S220, bonding the third isolation layer and the surface of the functional layer facing away from the second isolation layer to form a functional substrate in the form of a second bonding body.

[0102] The functional substrate 200 in the second bonding body includes an auxiliary substrate 300 , a third isolation layer 310 , a functional layer 220 and a second isolation layer 230 which are stacked in sequence.

[0103] S230, preparing a first isolation layer on the surface of the substrate.

[0104] For ease of understanding, the preparation method of the isolation layer provided in the second embodiment will be combined with a specific example to illustrate the preparation process of the composite film. Figure 7 is a schematic diagram of a preparation process of a functional substrate in the form of a second bonding body provided in the second embodiment of the present application, Figure 8 It is a schematic diagram of a composite film preparation process provided in Example 2 of the present application.

[0105] Preparation stage: prepare two 6-inch silicon wafers (i.e., the first silicon wafer and the second silicon wafer, serving as the base substrate 100 and the auxiliary substrate 300, respectively) and a lithium niobate wafer (serving as the functional layer 220). The two silicon wafers and the lithium tantalate wafer are fixed on the porous ceramic chucks of the polishing equipment, and then the silicon wafer and the lithium tantalate wafer are subjected to chemical mechanical polishing treatment to make both have smooth surfaces, and the silicon wafer and the lithium tantalate wafer are subjected to semiconductor RCA cleaning to obtain clean surfaces.

[0106] Functional substrate preparation stage: refer to Figure 7 As shown, a third silicon dioxide layer (i.e., a third isolation layer 310) is formed by oxidation on a second silicon wafer (i.e., an auxiliary substrate 300) by a thermal oxidation method; the third silicon dioxide layer is contact-bonded with a surface-activated lithium niobate wafer. Then, a second silicon dioxide layer (i.e., a second isolation layer 230) having a diameter smaller than that of the lithium niobate wafer by about 6 mm is deposited on the lithium niobate wafer. It can be found that after the above-mentioned treatment process, the functional substrate 200 in the form of a second bonding body is actually prepared to have a four-layer structure, namely, from bottom to top, it includes a single crystal silicon layer, a third silicon dioxide layer, a functional layer 220, and a second silicon dioxide layer.

[0107] Substrate preparation stage: refer to Figure 8As shown, a first silicon dioxide layer (ie, a first isolation layer) is formed on a first silicon wafer (ie, substrate 100) by thermal oxidation, wherein the oxidation thickness of the first silicon dioxide layer is about 10 μm.

[0108] Ion implantation stage: Helium ions are implanted into the functional substrate 200 in the second bonding body by ion implantation. The helium ions penetrate the second silicon dioxide layer and are implanted into the lithium niobate wafer, so that the lithium niobate wafer forms a residual layer 221, an implantation layer 222 and a functional film layer 223 in sequence from the implantation surface. The implanted helium ions are distributed in the implantation layer 222 to obtain an implanted wafer. The implantation dose parameters can be: the implantation dose is 4×10 16 ions / cm 2 , the injection energy is 100keV.

[0109] Bonding stage: the second silicon dioxide layer is brought into contact with the first silicon dioxide layer and bonded by a direct bonding method to obtain a first bonded body.

[0110] Annealing treatment stage: the first bond body is placed in an annealing furnace and heat treated at 180°C for 6 hours. The first bond body is disconnected at the injection layer 222, and the second silicon wafer, the third silicon dioxide layer and the residual layer 221 are completely peeled off to obtain a composite film having a structure of a first silicon wafer, a first silicon dioxide layer, a second silicon dioxide layer and a functional film layer 223. The diameter of the second silicon dioxide layer is about 6 mm smaller than the diameter of the first silicon wafer and the first silicon dioxide layer, and the diameter of the functional film layer 223 is the same as that of the first silicon dioxide layer. The composite film is then annealed at 400°C for 3 hours to eliminate the injection damage.

[0111] Cleaning stage: the composite film is taken out from the annealing furnace and then fixed on the porous ceramic suction cup of the polishing equipment, the functional film layer 223 is subjected to chemical mechanical polishing, and then semiconductor RCA cleaning is performed to obtain a clean surface, and finally a composite film product is obtained.

[0112] In addition, the second silicon wafer, the third silicon dioxide layer and the residual layer 221 peeled from the first bonding body can be reused, such as continuing to deposit a silicon dioxide layer on the residual layer 221, so that the peeled portion can be reused as a functional substrate 200 to be reused in another preparation cycle.

[0113] Embodiment 3

[0114] Similar to the above-mentioned embodiment 2, the present embodiment 3 provides another method for preparing the isolation layer different from the above-mentioned embodiment 2 according to the different preparation processes of the isolation layer. Fig. 9 A schematic flow chart of a method for preparing an isolation layer provided in Example 3 of the present application.

[0115] Specifically, refer to Fig. 9 As shown, the method for preparing the isolation layer provided in the embodiment of the present application comprises the following steps:

[0116] S310, providing a functional layer and an auxiliary substrate.

[0117] S320, preparing a second isolation layer and a third isolation layer on two opposite surfaces of the functional layer respectively.

[0118] S330, bonding the auxiliary substrate to the third isolation layer to form a functional substrate in the form of a third bonding body.

[0119] The functional substrate 200 in the third bonding body includes an auxiliary substrate 300 , a third isolation layer 310 , a functional layer 220 and a second isolation layer 230 which are stacked in sequence.

[0120] S340, preparing a first isolation layer on the substrate.

[0121] Preferably, in some embodiments, before preparing the first isolation layer 110 on the surface of the base substrate 100 , a defect layer 400 may also be prepared on the surface of the base substrate 100 , and the defect layer 400 is located between the first isolation layer 110 and the base substrate 100 .

[0122] It can be found that the difference between the preparation method of the isolation layer in the third embodiment and the second embodiment is that the second isolation layer 230 and the third isolation layer 310 in the third embodiment are formed on both sides of the functional layer 220, while the second isolation layer 230 and the third isolation layer 310 in the second embodiment are formed on the surfaces of the functional layer 220 and the auxiliary substrate 300, respectively. Based on this, those skilled in the art can select different isolation layer preparation processes according to actual production and processing requirements, so as to make the subsequent preparation process of the composite film more flexible, reduce its process difficulty, and facilitate the improvement of production efficiency. In addition, compared with the above embodiments, the third embodiment can also further improve the performance of the composite film by preparing a defect layer 400 on the base substrate 100.

[0123] The following will combine the preparation method of the isolation layer in the third embodiment and use a specific example to illustrate the preparation process of the composite film in the third embodiment. Fig.10 is a schematic diagram of a preparation process of a functional substrate presenting a third bonding body provided in Example 3 of the present application, Fig.11 This is a schematic diagram of a composite film preparation process provided in Example 3 of the present application.

[0124] Preparation stage: prepare two 3-inch silicon wafers (i.e., the first silicon wafer and the second silicon wafer, serving as the base substrate 100 and the auxiliary substrate 300, respectively) and a lithium niobate wafer (serving as the functional layer 220). Fix the two silicon wafers or lithium niobate wafers on the porous ceramic chucks of the polishing equipment, perform chemical mechanical polishing to obtain a smooth surface, and then perform semiconductor RCA cleaning on the two wafers to obtain a clean surface.

[0125] Functional substrate preparation stage: refer to Fig.10 As shown, a second silicon dioxide layer (i.e., a second isolation layer 230) and a third silicon dioxide layer (i.e., a third isolation layer 310) are deposited on both sides of a lithium niobate wafer, wherein the diameter of the second silicon dioxide layer is about 5 mm smaller than that of the lithium niobate wafer, and the third silicon dioxide layer on the lithium niobate wafer is contact-bonded with a second silicon wafer (i.e., an auxiliary substrate 300) after surface activation to obtain a functional substrate 200 in the form of a third bonding body, and includes, from bottom to top, a single crystal silicon layer, a third silicon dioxide layer, a functional layer 220, and a second silicon dioxide layer.

[0126] Substrate preparation stage: refer to Fig.11 As shown, a polysilicon layer (ie, defective layer 400) is deposited on a first silicon wafer (ie, substrate 100), and a first silicon dioxide layer (ie, first isolation layer) is formed by oxidizing the polysilicon layer through a thermal oxidation method, wherein the oxidation thickness of the first silicon dioxide layer is 10 μm.

[0127] Ion implantation stage: oxygen ions are implanted into the functional substrate 200 in the third bonding body by using an ion implantation method. The oxygen ions are implanted into the lithium niobate wafer through the second silicon dioxide layer, so that the lithium niobate wafer is divided into a residual layer 221, an implantation layer 222 and a lithium niobate thin film layer in sequence from the implantation surface. The implanted oxygen ions are distributed in the implantation layer 222 to obtain an implanted wafer. When the oxygen ions are implanted by using the ion implantation method, the implantation dose parameters can be: the implantation dose is 3×10 16 ions / cm 2 , the injection energy is 400keV.

[0128] Bonding stage: the second silicon dioxide layer is brought into contact with the first silicon dioxide layer and bonded by a direct bonding method to obtain a first bonded body.

[0129] Annealing treatment stage: the first bond body is placed in an annealing furnace and heat treated at 200°C for 2 hours. The first bond body is disconnected at the injection layer 222, and the second silicon wafer, the third silicon dioxide layer and the residual layer 221 are completely peeled off to obtain a composite film having a structure of a first silicon wafer, a polysilicon layer, a first silicon dioxide layer, a second silicon dioxide layer and a functional film layer 223. The diameter of the second silicon dioxide layer is about 5 mm smaller than the diameter of the first silicon wafer and the first silicon dioxide layer, and the diameter of the functional film layer 223 is the same as that of the first silicon dioxide layer. The composite film is then annealed at 600°C for 3 hours to eliminate the injection damage.

[0130] Cleaning stage: the composite film is taken out from the annealing furnace and then fixed on the porous ceramic suction cup of the polishing equipment, the functional film layer 223 is subjected to chemical mechanical polishing, and then semiconductor RCA cleaning is performed to obtain a clean surface, and finally a composite film product is obtained.

[0131] In addition, the second silicon wafer, the third silicon dioxide layer and the residual layer 221 peeled from the first bonding body can be reused, such as continuing to deposit a silicon dioxide layer on the residual layer 221, so that the peeled portion can be reused as a functional substrate 200 to be reused in another preparation cycle.

[0132] Embodiment 4

[0133] Fig.12 This is a schematic diagram of a composite film preparation process provided in Example 4 of the present application.

[0134] The difference between the fourth embodiment and the second embodiment is that the diameters of the functional film layer 223 and the second isolation layer 230 are the same and smaller than the diameter of the first isolation layer, and the fourth embodiment further comprises a defective layer 400 on the base substrate 100 .

[0135] For example, refer to Fig.12 As shown in the figure, the preparation process of the composite film includes the following stages:

[0136] Preparation stage: prepare two 4-inch silicon wafers (i.e., a first silicon wafer and a second silicon wafer, serving as the base substrate 100 and the auxiliary substrate 300, respectively) and a lithium tantalate wafer (serving as the functional layer 220) having a diameter approximately 6 mm smaller than that of the silicon wafer, fix the silicon wafer or the lithium tantalate wafer on the porous ceramic suction cup of the polishing equipment, respectively, perform chemical mechanical polishing to obtain a smooth surface, and then perform semiconductor RCA cleaning on the two wafers to obtain a clean surface.

[0137] Functional substrate preparation stage: a third silicon dioxide layer (i.e., a third isolation layer 310) is formed on the second silicon wafer (i.e., the auxiliary substrate 300) by thermal oxidation, the third silicon dioxide layer is contact-bonded with the surface-activated lithium tantalate wafer, and then a second silicon dioxide layer (i.e., a second isolation layer 230) is deposited on the lithium tantalate wafer. The diameters of the second silicon dioxide layer and the lithium tantalate wafer are about 6 mm smaller than the diameters of the second silicon wafer and the third silicon dioxide layer, thereby obtaining a four-layer functional substrate 200, i.e., a functional substrate 200 including, from bottom to top, the auxiliary substrate 300, the third isolation layer 310, the functional layer 220 and the second isolation layer 230.

[0138] Substrate substrate preparation stage: Argon ions are injected into the first silicon wafer (i.e., substrate 100) by ion implantation to induce damage, thereby forming an amorphous silicon layer (i.e., defect layer 400) on the first silicon wafer, and a first silicon dioxide layer (i.e., first isolation layer) is deposited on the amorphous silicon layer, wherein the oxidation thickness of the first silicon dioxide layer is 15 μm.

[0139] Ion implantation stage: the functional substrate 200 is implanted with argon ions by using the ion implantation method. The argon ions are implanted into the lithium tantalate wafer through the second silicon dioxide layer, so that the lithium tantalate wafer forms a residual layer 221, an implantation layer 222 and a lithium tantalate thin film layer in sequence from the implantation surface. The implanted argon ions are distributed in the implantation layer 222 to obtain an implanted wafer. When the argon ions are implanted by using the ion implantation method, the implantation dose parameters are: the implantation dose is 2×10 16 ions / cm 2 , the injection energy is 225keV.

[0140] Bonding stage: the second silicon dioxide layer is brought into contact with the first silicon dioxide layer and bonded by a direct bonding method to obtain a first bonded body.

[0141] Annealing treatment stage: the first bonding body is placed in an annealing furnace and heat treated at 280°C for 2 hours. The first bonding body is disconnected at the injection layer 222, and the second silicon wafer, the third silicon dioxide layer and the residual layer 221 are completely peeled off to obtain a composite film having a structure of a first silicon wafer, an amorphous silicon layer, a first silicon dioxide layer, a second silicon dioxide layer and a functional film layer 223. The diameters of the functional film layer 223 and the second silicon dioxide layer are the same and are both smaller than the diameters of the first silicon wafer and the first silicon dioxide layer by about 6 mm. The composite film is then annealed at 500°C for 3 hours to eliminate injection damage.

[0142] Cleaning stage: the composite film is taken out from the annealing furnace and then fixed on a porous ceramic suction cup of a polishing device, the functional film layer 223 is subjected to chemical mechanical polishing, and then RCA cleaning is performed to obtain a clean surface, and finally a composite film product is obtained.

[0143] In addition, the second silicon wafer, the third silicon dioxide layer and the residual layer 221 peeled from the first bonding body can be reused, such as continuing to deposit a silicon dioxide layer on the residual layer 221, so that the peeled portion can be reused as a functional substrate 200 to be reused in another preparation cycle.

[0144] Embodiment 5

[0145] Fig.13 This is a schematic diagram of a composite film preparation process provided in Example 5 of the present application.

[0146] The difference between the fifth embodiment and the third embodiment is that the diameters of the functional film layer 223 and the second isolation layer 230 are the same, and both are smaller than the diameter of the first isolation layer.

[0147] For example, refer to Fig.13 As shown in the figure, the preparation process of the composite film includes the following stages:

[0148] Preparation stage: prepare two 3-inch silicon wafers (a first silicon wafer and a second silicon wafer, serving as the base substrate 100 and the auxiliary substrate 300, respectively) and a lithium niobate wafer (serving as the functional layer 220) having a diameter approximately 5 mm smaller than that of the silicon wafer, fix the silicon wafer or the lithium niobate wafer on the porous ceramic suction cup of the polishing equipment, perform chemical mechanical polishing to obtain a smooth surface, and then perform semiconductor RCA cleaning on the two wafers to obtain a clean surface.

[0149] Functional substrate preparation stage: a third silicon dioxide layer (third isolation layer 310) is formed on the second silicon wafer (auxiliary substrate 300) by thermal oxidation, the third silicon dioxide layer is contact-bonded with the surface-activated lithium niobate wafer, and then a second silicon dioxide layer (second isolation layer 230) is deposited on the lithium niobate wafer. The diameter of the second silicon dioxide layer and the lithium niobate wafer are the same, and both are 5 mm smaller than the diameter of the second silicon wafer and the third silicon dioxide layer, so as to obtain a four-layer functional substrate 200, i.e., a functional substrate 200 including, from bottom to top, the auxiliary substrate 300, the third isolation layer 310, the functional layer 220 and the second isolation layer 230.

[0150] Substrate substrate preparation stage: a polycrystalline germanium layer (ie, defect layer 400) is deposited on a first silicon wafer (ie, substrate 100) by a deposition method, and then a first silicon dioxide layer (ie, first isolation layer) is deposited on the polycrystalline germanium layer, wherein the oxidation thickness of the first silicon dioxide layer is 10 μm.

[0151] Ion implantation stage: Helium ions are implanted into the functional substrate 200 by using an ion implantation method. The helium ions penetrate the second silicon dioxide layer and are implanted into the lithium niobate wafer, so that the lithium niobate wafer is divided into a residual layer 221, an implantation layer 222 and a lithium niobate thin film layer in sequence from the implantation surface. The injected helium ions are distributed in the implantation layer 222 to obtain an implanted wafer. When the helium ions are implanted by using the ion implantation method, the implantation dose parameters are: the implantation dose is 3×10 16 ions / cm 2 , the injection energy is 245keV.

[0152] Bonding stage: the second silicon dioxide layer is brought into contact with the first silicon dioxide layer and bonded by a direct bonding method to obtain a first bonded body.

[0153] Annealing treatment stage: the first bond body is placed in an annealing furnace and heat treated at 280°C for 2 hours. A thin film mechanical separation device is used to apply mechanical force to the second bond body during / after the heat treatment, so that the first bond body is disconnected and separated at the injection layer 222. The second silicon wafer, the third silicon dioxide layer and the residual layer 221 are completely peeled off to obtain a composite film with a structure of a first silicon wafer, a polycrystalline germanium layer, a first silicon dioxide layer, a second silicon dioxide layer and a functional thin film layer 223. The diameters of the functional thin film layer 223 and the second silicon dioxide layer are the same, and are both smaller than the diameters of the silicon wafer and the first silicon dioxide layer by about 5 mm. The composite film is then annealed at 500°C for 3 hours to eliminate injection damage.

[0154] Cleaning stage: After the composite film is taken out of the annealing furnace, it is fixed on the porous ceramic suction cup of the polishing equipment, the film layer is subjected to chemical mechanical polishing, and then RCA cleaning is performed to obtain a clean surface, and finally a composite film product is obtained.

[0155] In addition, the second silicon wafer, the third silicon dioxide layer and the residual layer 221 peeled from the first bonding body can be reused, such as continuing to deposit a silicon dioxide layer on the residual layer 221, so that the peeled portion can be reused as a functional substrate 200 to be reused in another preparation cycle.

[0156] Embodiment 6

[0157] Fig.14 This is a schematic diagram of a composite film preparation process provided in Example 6 of the present application.

[0158] The difference between the sixth embodiment and the above embodiments is that the bonding step between the auxiliary substrate 300 and the functional substrate 200 is performed after the ion implantation of the functional substrate 200.

[0159] For example, refer to Fig.14 As shown in the figure, the preparation process of the composite film includes the following stages:

[0160] Preparation stage: prepare two 3-inch silicon wafers (i.e., a first silicon wafer and a second silicon wafer, serving as the base substrate 100 and the auxiliary substrate 300, respectively) and a lithium niobate wafer (serving as the functional layer 220), fix the silicon wafer or the lithium niobate wafer on the porous ceramic suction cup of the polishing equipment, respectively, perform chemical mechanical polishing to obtain a smooth surface, and then perform semiconductor RCA cleaning on the two wafers to obtain a clean surface.

[0161] Functional substrate preparation stage: double-sided deposition is performed on the lithium niobate wafer to prepare a second silicon dioxide layer (i.e., the second isolation layer 230) and a third silicon dioxide layer (i.e., the third isolation layer 310), wherein the diameters of the lithium niobate wafer and the third silicon dioxide layer are the same, and the diameter of the second silicon dioxide layer is 5 mm smaller than the diameters of the lithium niobate wafer and the third silicon dioxide layer.

[0162] Substrate substrate preparation stage: a polysilicon layer (ie, defect layer 400) is deposited on a first silicon wafer (ie, substrate 100) by a deposition method, and then a first silicon dioxide layer (ie, first isolation layer) is deposited on the polysilicon layer, wherein the oxidation thickness of the first silicon dioxide layer is 10 μm.

[0163] Ion implantation stage: Helium ions are implanted into the functional substrate 200 by using the ion implantation method. The helium ions penetrate the second silicon dioxide layer and are implanted into the lithium niobate wafer, so that the lithium niobate wafer is divided into a residual layer 221, an implantation layer 222 and a lithium niobate thin film layer in sequence from the implantation surface. The implanted helium ions are distributed in the implantation layer 222 to obtain an implanted wafer. When the helium ions are implanted by the ion implantation method, the implantation dose parameters are: the implantation dose is 2×10 16 ions / cm 2 , the injection energy is 300keV.

[0164] Bonding stage: the second silicon dioxide layer of the implanted sheet is brought into contact with the first silicon dioxide layer on the first silicon wafer by direct bonding. Then, the second silicon wafer (i.e., the auxiliary substrate 300) is brought into contact with the third silicon dioxide layer for bonding to obtain a first bonded body.

[0165] Annealing treatment stage: the first bonding body is placed in an annealing furnace and heat treated at 280°C for 2 hours, so that the second bonding body is disconnected and separated at the injection layer 222, and the second silicon wafer, the third silicon dioxide layer and the residual layer 221 are completely peeled off to obtain a composite film with a structure of a first silicon wafer, a polysilicon layer, a first silicon dioxide layer, a second silicon dioxide layer and a functional film layer 223. The diameters of the functional film layer 223, the first silicon oxide layer, the polysilicon layer and the first silicon wafer are the same, and the diameter of the second silicon dioxide layer is about 5 mm smaller than the diameters of the first silicon wafer, the polysilicon layer and the first silicon dioxide layer. Then the composite film is annealed at 500°C for 3 hours to eliminate the injection damage.

[0166] Cleaning stage: the composite film is taken out of the annealing furnace and fixed on a porous ceramic suction cup of a polishing device, the functional film layer 223 is subjected to chemical mechanical polishing, and then RCA cleaning is performed to obtain a clean surface, and finally a composite film product is obtained.

[0167] In addition, the second silicon wafer, the third silicon dioxide layer and the residual layer 221 peeled from the first bonding body can be reused, such as continuing to deposit a silicon dioxide layer on the residual layer 221, so that the peeled portion can be reused as a functional substrate 200 to be reused in another preparation cycle.

[0168] In another embodiment, the thermal expansion coefficients of the base substrate 100, the functional substrate 200 and the auxiliary substrate 300 are the same or similar. This arrangement prevents a large expansion difference between the three due to temperature changes during the annealing process, thereby facilitating the separation of different hierarchical structures in the composite film, thereby facilitating the improvement of the yield rate of the composite film.

[0169] It should also be noted that, regarding the preparation process of the composite film in the above-mentioned different embodiments, the preparation sequence of the different stages can be flexibly adjusted according to the actual production and processing needs, and this application does not limit this.

[0170] It is easy to understand that those skilled in the art can combine, split, reorganize, etc. the embodiments of the present application to obtain other embodiments based on the several embodiments provided in the present application, and these embodiments do not exceed the protection scope of the present application.

[0171] The above specific implementation methods further explain in detail the purpose, technical solutions and beneficial effects of the embodiments of the present application. It should be understood that the above are only specific implementation methods of the embodiments of the present application and are not used to limit the protection scope of the embodiments of the present application. Any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solutions of the embodiments of the present application should be included in the protection scope of the embodiments of the present application.

Claims

1. A method for preparing a composite film, characterized in that: The steps include: Preparing a first isolation layer and a second isolation layer on the surfaces of the functional layer of the base substrate and the functional substrate respectively, wherein the diameter of the second isolation layer is smaller than the diameter of the first isolation layer; Ion implantation is performed on the functional substrate, so that the ions pass through the second isolation layer and enter the functional layer of the functional substrate, and a stacked residual layer, an implantation layer and a functional thin film layer are sequentially formed in the functional layer, wherein the functional thin film layer is in contact with the second isolation layer, and the implanted particles are distributed in the implantation layer; wherein the material of the first isolation layer and the second isolation layer is one of silicon dioxide, silicon oxynitride or silicon nitride, and the material of the functional thin film layer is one of lithium niobate, lithium tantalate, quartz, ceramic, lithium tetraborate, potassium titanyl phosphate, rubidium titanyl phosphate, gallium arsenide or silicon; Bonding the second isolation layer to the first isolation layer to obtain a first bonding body; The first bonding body is annealed to separate the functional film layer from the residual layer along the injection layer, and the residual layer is peeled off from the first bonding body to form a composite film on the substrate.

2. The preparation method according to claim 1, characterized in that: Before preparing the first isolation layer on the surface of the substrate, the preparation method further comprises: A defect layer is prepared on the surface of the substrate.

3. The preparation method according to claim 1, characterized in that: The method of preparing a first isolation layer and a second isolation layer on the surfaces of the functional layers of the base substrate and the functional substrate respectively comprises: Providing a functional layer and an auxiliary substrate, and preparing a second isolation layer and a third isolation layer on the surfaces of the functional layer and the auxiliary substrate, respectively; Bonding the third isolation layer and the surface of the functional layer facing away from the second isolation layer to form the functional substrate in a second bonding body, wherein the functional substrate comprises the auxiliary substrate, the third isolation layer, the functional layer and the second isolation layer stacked in sequence; A first isolation layer is prepared on the surface of the substrate.

4. The preparation method according to claim 1, characterized in that: The method of preparing a first isolation layer and a second isolation layer on the surfaces of the functional layers of the base substrate and the functional substrate respectively comprises: providing functional layers and auxiliary substrates; Prepare a second isolation layer and a third isolation layer on two opposite surfaces of the functional layer respectively; Bonding the auxiliary substrate to the third isolation layer to form the functional substrate in a third bonding body, wherein the functional substrate comprises the auxiliary substrate, the third isolation layer, the functional layer and the second isolation layer stacked in sequence; A first isolation layer is prepared on the substrate.

5. The preparation method according to claim 3 or 4, characterized in that: The thermal expansion coefficients of the base substrate, the functional substrate and the auxiliary substrate are the same or similar.

6. A composite film, characterized in that: The composite film is obtained by the preparation method according to any one of claims 1 to 5, and the composite film comprises a substrate (100), a first isolation layer (110), a second isolation layer (230) and a functional film layer (223), wherein the first isolation layer (110), the second isolation layer (230) and the functional film layer (223) are sequentially stacked from bottom to top on the surface of the substrate (100), and the first isolation layer (110) and the second isolation layer (230) are made of the same material, and the diameter of the second isolation layer (230) is smaller than the diameter of the first isolation layer (110).

7. The composite film according to claim 6, characterized in that: The diameter of the functional film layer (223) is the same as the diameter of the second isolation layer (230), and both are smaller than the diameter of the first isolation layer (110).

8. The composite film according to claim 7, characterized in that: The difference between the diameter of the second isolation layer (230) and the diameter of the first isolation layer (110) is 5-6 mm.

9. The composite film according to claim 6, characterized in that: It also includes a defect layer (400) located between the substrate (100) and the first isolation layer (110), wherein the defect layer (400) is used to provide a trap for capturing carriers between the substrate (100) and the first isolation layer (110).

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