Method for producing a composite film and composite film

Abstract

The application belongs to the technical field of semiconductor material or device preparation, and particularly relates to a preparation method of a composite film and the composite film. The method comprises the following steps: preparing a composite film precursor, wherein the composite film precursor comprises a substrate and a thin film layer located on the substrate; performing etching treatment on a thin film layer side exposed surface of the composite film precursor based on a preset target surface type, so as to obtain a composite film intermediate body with the preset target surface type; wherein, the preset target surface type is obtained in the following manner: taking any composite film precursor as a sample, performing polishing treatment on a thin film layer side exposed surface of the sample, so as to form a sample processing surface, and a vertical mirror image surface type of the sample processing surface is recorded as the preset target surface type; and performing polishing treatment on a thin film layer side exposed surface of the composite film intermediate body, so as to obtain the composite film. The composite film prepared by the preparation method has good thickness uniformity, high surface quality and stable performance.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material or device fabrication technology, and in particular to a method for preparing a composite thin film and the composite thin film. Background Technology

[0002] In the semiconductor industry, the development of electronic components such as chips, memory, and filters plays a crucial role in securing a leading position. The development of various electronic components is increasingly attracting industry attention, placing higher demands on upstream key materials. As a core component of these devices, the thickness uniformity of composite thin films directly affects the final performance and yield of the devices. Therefore, how to prepare composite thin films with excellent thickness uniformity has become a pressing technical problem to be solved in this field.

[0003] In existing technologies, the fabrication of composite thin films typically employs ion implantation and bond-stripping processes. First, a functional single-crystal wafer is ion-implanted to obtain an ion-implanted wafer containing a thin film layer, a separation layer, and a residual mass layer. Implanted ions accumulate in the separation layer. Then, the ion-implanted wafer is bonded to a substrate to form a bonded body. The bonded body undergoes annealing. The implanted ions in the separation layer form gas, generating bubbles. When these bubbles coalesce, the residual mass layer separates from the thin film layer from the separation layer, and the thin film layer transfers to the substrate, forming a composite thin film precursor. This precursor includes the substrate and the thin film layer bonded to it. Residual separation layer material remains on the exposed surface of the thin film layer; without treatment, this will degrade the performance of the composite thin film. Currently, the traditional approach is to use chemical mechanical polishing (CMP) to remove the residual separation layer material to obtain the composite thin film.

[0004] However, when using chemical mechanical polishing (CMP) to remove residual separation layers, the uniformity of the composite film thickness gradually deteriorates with increasing removal volume due to factors such as polishing pressure and edge deformation, thus affecting the performance of the composite film. Some researchers have attempted to perform CMP followed by ion beam etching, but ion beam etching damages the film surface, producing amorphous surfaces and other defects, which also degrade the performance of the composite film. Summary of the Invention

[0005] This invention provides a method for preparing a composite film and a composite film, thereby solving the technical problems of deterioration of film thickness uniformity and degradation of composite film performance caused by surface damage when removing residual separation layer on the surface of the film layer in existing processes.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a composite thin film, comprising: preparing a composite thin film precursor, the composite thin film precursor including a substrate and a thin film layer located on the substrate; etching the exposed surface of the thin film layer side of the composite thin film precursor based on a preset target surface shape to obtain a composite thin film intermediate having the preset target surface shape; wherein, the preset target surface shape is obtained as follows: taking any composite thin film precursor as a sample, polishing the exposed surface of the thin film layer side of the sample to form a sample processing surface, the perpendicular mirror surface shape of the sample processing surface shape is denoted as the preset target surface shape; polishing the exposed surface of the thin film layer side of the composite thin film intermediate to obtain a composite thin film.

[0007] Preferably, the specific methods of etching and polishing are not limited. For example, the etching process is ion beam etching trimming, and the polishing process is chemical mechanical polishing (CMP).

[0008] As can be seen from the above technical solution, the present invention uses an etching process followed by polishing to process the exposed surface of the film layer side of the composite film precursor. Specifically, an arbitrary composite film precursor is first used as a sample. The exposed surface of the film layer side of the sample is directly polished to remove the separation layer residue, resulting in a sample treatment surface (the surface shape of this surface corresponds to the amount of polishing removal at different positions on the entire exposed surface of the film layer side after the polishing process). Then, a preset target surface shape is determined based on the perpendicular mirror surface shape of the sample treatment surface. After etching the exposed surface of the film layer side of the composite film precursor, a composite film intermediate with the preset target surface shape is constructed. Then, polishing is performed. When polishing is completed, the different positions on the entire film layer side are polished to almost the same horizontal plane, avoiding the degradation of thickness uniformity caused by the traditional CMP process. It also avoids the amorphous surface damage introduced by etching during the process of first chemical mechanical polishing and then ion beam etching, thus avoiding the degradation of the composite film performance.

[0009] Preferably, before polishing the exposed surface of the thin film layer side of the sample, the exposed surface of the thin film layer side of the sample is first etched to form a plane. The specific process parameters of this etching process are not limited, as long as the exposed surface of the thin film layer side of the sample can be etched into a plane.

[0010] As can be seen from the above technical solution, the method of treating the exposed surface of the thin film layer side of the sample in this invention is "first etching into a plane and then polishing to remove the separation layer residue". The starting surface for polishing the sample is a plane, which can avoid the polishing differences introduced by the different states of the exposed surface of the thin film layer of different composite thin film precursors (the composite thin film precursors are prepared by ion implantation and bonding peeling processes, and the exposed surface of the thin film layer side is generated by the splitting of the separation layer. For different composite thin film precursors, the surface state of the separation surface caused by splitting may be different, that is, the state of the exposed surface of the thin film layer is different). The surface shape of the sample after polishing is more referential and can more accurately reflect the deterioration of the thickness uniformity caused by polishing. Therefore, the preparation method of this invention is applicable to the processing of any composite thin film precursor manufactured in the same batch or different batches, without having to repeatedly go through the process of obtaining the preset target surface shape through the sample for composite thin film precursors manufactured in different batches, thus saving costs. In addition, the starting surface for polishing the sample is the exposed surface of the residual separation layer after the etching process damage, and the starting surface for polishing the composite film precursor is also the exposed surface of the residual separation layer after the etching process damage. From this perspective, the two are in the same state and will not produce polishing deviation due to the difference in the state of the polishing starting surface.

[0011] Preferably, when etching the exposed surface of the film layer side of the composite film precursor to form a preset target surface shape, the exposed surface of the film layer side of the composite film precursor is first etched into a plane, and then the preset target surface shape is etched further; or, the exposed surface of the film layer side of the composite film precursor is directly etched into the preset target surface shape. The specific process parameters of this etching process are not limited, as long as the exposed surface of the film layer side of the composite film precursor can be etched into the desired state.

[0012] As can be seen from the above technical solutions, directly etching into the preset target surface shape can match the polishing speed at different positions during the entire polishing process, improving the thickness uniformity when polishing is completed. In addition, the etching amount can be minimized, reducing etching costs. Etching into a plane first and then etching into the preset target surface shape can better match the sample. While matching the preset target surface shape with the polishing speed at different positions during the entire polishing process, it also makes the polishing thickness of the entire polishing process better match the polishing thickness of the sample polishing process, preventing the deterioration of thickness uniformity caused by over-polishing or under-polishing due to different polishing thicknesses.

[0013] Preferably, the polishing process parameters for the exposed surface of the film layer side of the composite film intermediate are the same as those for the polishing process parameters for the sample, or differ only in the polishing time.

[0014] As can be seen from the above technical solutions, the polishing process parameters for the bare surface of the film layer side of the sample and the composite film intermediate are consistent. Therefore, the polishing speed at each position during the polishing process can be better kept consistent, the polishing degree is consistent, and the thickness uniformity is better improved. In addition, the polishing time can be slightly different to avoid insufficient polishing caused by using the same polishing time when the residual amount of the separation layer after etching is inconsistent with the polishing amount of the sample, resulting in residual separation layer or over-polishing.

[0015] Preferably, when the method of first etching the exposed surface of the film layer side of the composite film precursor into a plane and then continuing to etch out the preset target surface shape to form the preset target surface shape is adopted, the polishing treatment of the sample meets the following conditions: polishing is stopped when the lowest point of the polished surface formed during the polishing process reaches the upper surface of the film layer. Furthermore, when etching the exposed surface of the film layer side of the composite film precursor to form the preset target surface, the following conditions must be met simultaneously: after etching, the amount of material to be removed by polishing on the exposed surface of the film layer side is the same as the amount of material removed by polishing when polishing the sample. Furthermore, the polishing process parameters for the exposed surface of the film layer side of the composite film intermediate are the same as those for the polishing process of the sample.

[0016] As can be seen from the above technical solution, when polishing the sample, polished surfaces are continuously formed during the polishing process. The height of the polished surfaces varies at different positions. Polishing stops when the lowest point reaches the upper surface of the thin film layer. That is, polishing stops when the separation layer residue is completely removed at one position. At this point, the polishing does not go into the thin film layer, but it also results in the separation layer residue not being completely removed at other positions. In other words, the surface shape of the treated surface is actually the surface shape of the upper surface of the separation layer residue after polishing. Based on this, when etching the composite thin film precursor, the thickness of the remaining separation layer residue to be polished is first controlled by the planar etching process to ensure that this thickness is consistent with the remaining thickness to be polished after the sample is etched out of the plane. Then, the preset target surface shape is etched out. Thus, the size and shape of the remaining separation layer residue to be polished are completely consistent with the polishing amount of the sample. Using the same polishing process parameters as the sample to polish the exposed surface of the thin film layer side of the composite thin film intermediate can completely remove the separation layer residue without polishing into the thin film layer. The thin film layer is completely preserved, and the thickness uniformity is optimally optimized.

[0017] Preferably, the sample treatment surface profile is obtained in the following way: The initial surface profile of the polished sample thin film layer was obtained by the first measurement. Based on the initial surface shape, regions whose morphological changes exceed a preset threshold are selected, and dense data collection points are set in the regions for a second measurement. Based on the second measurement data, the first measurement data is corrected to obtain the corrected surface shape, which is denoted as the sample treatment surface shape. The sample treatment surface is transformed by a vertical mirror image to obtain the preset target surface.

[0018] Preferably, the measurement method for the thin film layer side of the sample is not limited; any method that yields the surface shape is acceptable. Measurements can be taken using various measuring devices, such as a white light interferometer or an ellipsometer. Furthermore, the preset threshold value is not limited and can be freely set according to actual conditions. For example, after obtaining the initial surface shape, areas where the data differs significantly from other locations can be identified as correction areas.

[0019] As can be seen from the above technical solution, the present invention performs two measurements when obtaining the surface profile of the sample processing surface. The first measurement is a full-surface measurement of the thin film layer of the sample. Then, based on the areas with large morphological changes in the initial surface profile obtained in the first measurement, dense data acquisition points are set up, and a second measurement is performed on the areas with large morphological changes. The first measurement data is corrected based on the second measurement data to improve the data accuracy. As a result, the surface profile of the sample processing surface obtained is more accurate, the preset target surface profile is more precise, and the thickness uniformity is less likely to deteriorate after subsequent etching and polishing.

[0020] Preferably, the method for preparing the composite thin film precursor includes: Prepare a functional single-crystal wafer, and perform ion implantation on the functional single-crystal wafer to obtain an ion-implanted wafer; the ion-implanted wafer includes a thin film layer, a separation layer and a residual mass layer in sequence from the ion implantation surface. The ion-implanted sheet is bonded to the substrate to obtain a bonded body; The bonded body is annealed, and the implanted ions in the separation layer form gas, generating bubbles. When the bubbles merge into a sheet, the ion implantation sheet peels off from the separation layer, and the residual layer and the thin film layer separate from the separation layer. The thin film layer is transferred to the substrate to form a composite thin film precursor. The composite thin film precursor includes a substrate and a thin film layer located on the substrate. Separation layer residue remains on the upper surface of the thin film layer. The separation layer residue is removed by etching the composite thin film precursor and polishing the composite thin film intermediate.

[0021] Preferably, the material of the functional single-crystal wafer is not limited and can be lithium niobate, lithium tantalate, silicon carbide, silicon, gallium nitride, or gallium arsenide. During ion implantation, the implanted ions, implantation dose, and implantation energy are not particularly limited and can be reasonably adjusted as needed. For example, the implanted ions can be one or more of hydrogen ions, helium ions, nitrogen ions, oxygen ions, or argon ions; the ion implantation dose is 1 × 10⁻⁶. 16 ions / cm 2 Up to 3×10 17 ions / cm2 The ion implantation energy ranges from 30 keV to 5 MeV.

[0022] Preferably, the substrate material is not limited and can be one or more of lithium niobate, lithium tantalate, quartz, silicon, sapphire, silicon carbide, silicon nitride, gallium arsenide or indium phosphide.

[0023] Preferably, before bonding, the method further includes: performing surface activation treatment on at least one of the two bonding surfaces; and performing bonding after surface activation treatment to obtain a bonded body. Preferably, the specific method of surface activation treatment is not limited, and can be plasma activation treatment.

[0024] Preferably, the annealing temperature during the annealing process is between 100°C and 600°C, and the annealing time is between 1 hour and 24 hours.

[0025] Preferably, before bonding the ion implantation sheet to the substrate, the method further includes: An isolation layer is disposed on the substrate and / or the thin film side of the ion implantation sheet, and then the ion implantation sheet is bonded to the substrate through the isolation layer.

[0026] Preferably, the method for preparing the isolation layer is not limited. For example, it can be prepared by deposition on the thin film side of the substrate and / or ion-implanted wafer, or, for example, by thermal oxidation of the bonding surface side of a silicon substrate when the substrate is silicon. The material of the isolation layer can be one or more of silicon dioxide, silicon nitride, or aluminum oxide.

[0027] Preferably, before setting the isolation layer, the method further includes: A trap layer is formed on the substrate so that after bonding, the trap layer is located between the substrate and the isolation layer.

[0028] Preferably, the method for preparing the trap layer is not limited, for example, it can be prepared by deposition between the substrate and the isolation layer. The material of the trap layer can be polycrystalline silicon or amorphous silicon.

[0029] Secondly, the present invention provides a composite film prepared by the method of the first aspect of the composite film preparation. The composite film of the present invention exhibits excellent thickness uniformity, with a total thickness television (TTV) of 1 to 2 nanometers. Attached Figure Description

[0030] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0031] Figure 1 This is a flowchart illustrating the method for preparing the composite thin film provided in the embodiments of this application; Figure 2This is a flowchart illustrating the preparation of the composite thin film precursor in the method provided in the embodiments of this application; Figure 3 A breakdown flowchart of step S200 in the method provided in the embodiments of this application; Figure 4 A flowchart showing the breakdown of step S202 in the method provided in the embodiments of this application; Figure 5 A breakdown flowchart of step S300 in the method provided in the embodiments of this application; Figure 6 This is a schematic flowchart illustrating the preparation of the composite film precursor in the composite film preparation method provided in Embodiment 1 of this application. Figure 7 The schematic flowchart of the composite film preparation method provided in Embodiment 1 of this application is based on the processing of the composite film precursor sample to obtain the preset target surface shape. The enlarged part of the dashed line shows the uneven surface of the separation layer residue generated when the separation layer on the upper surface of the film layer is split. Figure 8 This is a schematic flowchart illustrating the process of etching and polishing the composite film precursor based on a preset target surface shape in the composite film preparation method provided in Embodiment 1 of this application. Detailed Implementation

[0032] The embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described below do not represent all embodiments consistent with this application. They are merely examples of systems and methods consistent with some aspects of this application.

[0033] It should be noted that the brief descriptions of terms in this application are only for the convenience of understanding the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise stated, these terms should be understood in their ordinary and common meaning.

[0034] In the following description, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0035] The terms “comprising” and “having”, and any variations thereof, are intended to cover but not exclude inclusion, for example, a product or device that includes a range of components is not necessarily limited to all of the components that are clearly listed, but may include other components that are not clearly listed or that are inherent to such product or device.

[0036] In the field of semiconductor material or device fabrication technology, existing technologies for preparing composite thin films typically employ ion implantation and bond-stripping processes. First, ion implantation is used to implant functional single-crystal wafers, resulting in an ion-implanted wafer containing a thin film layer, a separation layer, and a residual mass layer. Implanted ions accumulate in the separation layer. Then, the ion-implanted wafer is bonded to a substrate to form a bonded body. The bonded body undergoes annealing. Implanted ions in the separation layer form gas, generating bubbles. When these bubbles coalesce, the separation layer splits, and the residual mass layer separates from the thin film layer. The thin film layer transfers to the substrate, forming a composite thin film precursor. This precursor includes the substrate and the thin film layer bonded to it. Residual separation layer material remains on the exposed surface of the thin film layer; without treatment, this will degrade the performance of the composite thin film. Currently, the traditional approach is to use chemical mechanical polishing (CMP) to remove the residual separation layer material to obtain the composite thin film. However, when using CMP to remove residual separation layer material, factors such as polishing pressure and edge deformation affect the uniformity of the composite thin film thickness as the amount of material removed increases, thus impacting the composite thin film's performance. Some researchers in the field have attempted to perform chemical mechanical polishing followed by ion beam etching, but ion beam etching can damage the surface of the thin film, resulting in amorphous surfaces and other damage, which also degrades the performance of the composite thin film and makes it difficult to meet the requirements of high-end device applications.

[0037] To solve the above problems, see [link to relevant documentation]. Figure 1 Some embodiments of the present invention provide a method for preparing a composite thin film, comprising: S100. Prepare a composite thin film precursor, the composite thin film precursor including a substrate and a thin film layer located on the substrate.

[0038] In some embodiments, see Figure 2 The preparation methods of the composite thin film precursor include: S101. Prepare a functional single-crystal wafer and perform ion implantation on the functional single-crystal wafer to obtain an ion-implanted wafer; the ion-implanted wafer includes a thin film layer, a separation layer and a residual mass layer in sequence from the ion implantation surface.

[0039] Specifically, ion implantation is performed on a functional single-crystal wafer to obtain an ion-implanted wafer. The purpose of ion implantation is to form a separation layer rich in implanted ions inside the single-crystal wafer. Through ion implantation, a thin film layer, a separation layer, and a residual mass layer are sequentially formed on the single-crystal wafer from the ion implantation surface. The thin film layer is located above the separation layer, and the residual mass layer is located below the separation layer. The material of the single-crystal wafer is not limited and can be lithium niobate, lithium tantalate, silicon carbide, silicon, gallium nitride, or gallium arsenide. The implanted ions are not limited and can be one or more of hydrogen ions, helium ions, nitrogen ions, oxygen ions, or argon ions. The implantation dose and implantation energy are not particularly limited and can be reasonably adjusted as needed; for example, the implantation dose can be controlled at 1×10⁻⁶.16 ions / cm 2 Up to 3×10 17 ions / cm 2 Within this range, the injected energy can be controlled within the range of 30keV to 5MeV.

[0040] S102. Bond the ion implantation sheet to the substrate to obtain a bonded body.

[0041] Specifically, the ion implantation sheet is bonded to a substrate to obtain a bonded body. The substrate material is not limited and can be one or more of lithium niobate, lithium tantalate, quartz, silicon, sapphire, silicon carbide, silicon nitride, gallium arsenide, or indium phosphide.

[0042] In some embodiments, prior to bonding the ion-implanted sheet to the substrate, the method further includes: An isolation layer is disposed on the substrate and / or the thin film side of the ion implantation sheet, and then the ion implantation sheet is bonded to the substrate through the isolation layer.

[0043] Specifically, an isolation layer is formed on the thin film layer side of the substrate and / or the ion implantation sheet, and then the ion implantation sheet and the substrate are bonded through the isolation layer. The method of fabricating the isolation layer is not limited; for example, it can be formed by deposition on the thin film layer side of the substrate and / or the ion implantation sheet, or, for example, by thermally oxidizing the bonding surface side of a silicon substrate. The material of the isolation layer can be one or more of silicon dioxide, silicon nitride, or aluminum oxide. The purpose of forming the isolation layer is to provide good interfacial bonding performance during subsequent bonding, while also serving as electrical isolation or optical buffering.

[0044] In some embodiments, prior to bonding, the method further includes: At least one of the two bonding surfaces is subjected to surface activation treatment; bonding is then performed after surface activation treatment to obtain a bonded body. In this embodiment, the bonding surface refers to the surface on which the substrate and the ion implantation sheet are actually bonded. For example, when the substrate and the ion implantation sheet are directly bonded, the bonding surface is the upper surface of the substrate and the surface on the thin film layer side of the ion implantation sheet; when the substrate and the ion implantation sheet are bonded through an isolation layer, if the isolation layer is only formed on the substrate, the bonding surface is the side of the isolation layer facing away from the substrate and the surface on the thin film layer side of the ion implantation sheet; if the isolation layer is only formed on the thin film layer of the ion implantation sheet, the bonding surface is the upper surface of the substrate and the side of the isolation layer facing away from the thin film layer; if the isolation layer is formed on both the substrate and the thin film layer of the ion implantation sheet, the bonding surface is the sides of the two isolation layers facing away from the substrate and the thin film layer side, respectively. In this embodiment, the specific method of surface activation treatment is not limited; plasma activation can be used. The plasma activation equipment generates oxygen plasma, nitrogen plasma, argon plasma, etc., to bombard the bonding surface, causing dangling bonds or active groups to form on the surface, thereby enhancing the chemical reactivity of the surface. The purpose of surface activation treatment is to improve the interfacial bonding strength during subsequent bonding.

[0045] In some embodiments, prior to setting the isolation layer, the method further includes: A trap layer is formed on the substrate so that after bonding, the trap layer is located between the substrate and the isolation layer.

[0046] Specifically, a trap layer is formed on the substrate, such that after bonding, the trap layer is located between the substrate and the isolation layer. The method for fabricating the trap layer is not limited; for example, it can be formed on the substrate by deposition. The material of the trap layer can be polycrystalline silicon or amorphous silicon. The purpose of forming the trap layer is to create a defect-trapping layer between the substrate and the subsequently formed isolation layer, which absorbs and fixes free charge carriers at the substrate surface or interface, thereby suppressing the influence of interface charge on the thin film performance. After the trap layer is formed, an isolation layer is formed on top of it, covering the surface of the trap layer.

[0047] S103. Annealing is performed on the bonded body. The implanted ions in the separation layer form gas and generate bubbles. When the bubbles merge into one piece, the ion implantation sheet peels off from the separation layer. The residual material layer and the thin film layer separate from the separation layer. The thin film layer is transferred to the substrate to form a composite thin film precursor. The composite thin film precursor includes a substrate and a thin film layer located on the substrate. Separation layer residue remains on the upper surface of the thin film layer. The separation layer residue is removed by subsequent etching of the composite thin film precursor and polishing of the composite thin film intermediate.

[0048] Specifically, the bonded material undergoes annealing. The purpose of annealing is to allow the implanted ions in the separation layer to form gas under heating conditions, and the generated gas accumulates within the separation layer to form bubbles. The annealing temperature can be controlled within the range of 100℃ to 600℃, and the annealing time can be controlled within the range of 1 hour to 24 hours. The annealing temperature and annealing time can be adjusted according to the type and dosage of implanted ions to ensure that the implanted ions in the separation layer fully form gas, split the separation layer, and achieve complete peeling of the film layer.

[0049] During the annealing process, the implanted ions in the separation layer gradually form gas and generate bubbles. These bubbles grow and coalesce. When the bubble aggregation reaches a critical state, the separation layer fractures, and the residual mass layer and the thin film layer instantly separate from the separation layer. The thin film layer detaches from the ion implantation sheet and transfers to the substrate. Because the separation occurs inside the separation layer, the bonding interface between the thin film layer and the substrate remains intact, and the thin film layer remains intact on the substrate surface.

[0050] After annealing, a composite thin film precursor is formed. The composite thin film precursor includes a substrate and a thin film layer bonded to the substrate. Separation layer residue remains on the surface of the thin film layer facing away from the substrate. These separation layer residues originate from the remaining material adhering to the surface of the thin film layer after the separation layer breaks down and need to be removed in subsequent processes.

[0051] S200. Obtaining the preset target surface shape includes: taking any composite film precursor as a sample, polishing the exposed surface of the film layer side of the sample to remove the separation layer residue, forming a sample processed surface; obtaining the surface shape of the sample processed surface, and the perpendicular mirror surface shape of the sample processed surface shape is recorded as the preset target surface shape. By collecting and analyzing the surface shape of the sample processed surface, the surface shape on which the etching process is based in the formal production process can be determined, so that the film layer of the composite film precursor in the formal production process forms a surface morphology with the preset target surface shape after the etching process, preparing for the subsequent polishing process.

[0052] In some embodiments, see Figure 3 Obtaining the preset target surface shape specifically includes: S201. Take any composite film precursor as a sample, polish the exposed surface of the film layer side of the sample to remove the separation layer residue and form a sample treatment surface.

[0053] In some embodiments, before polishing the exposed surface of the thin film layer side of the sample, the exposed surface of the thin film layer side of the sample is first etched to form a plane, and then polished to remove the residual separation layer. The specific process parameters of this etching process are not limited, as long as the exposed surface of the thin film layer side of the sample can be etched into a plane. The specific methods of etching and polishing are not limited; for example, the etching process can be ion beam etching and the polishing process can be chemical mechanical polishing.

[0054] The surface morphology of the sample treatment surface is the morphological characteristics presented after polishing the exposed surface of the thin film layer side that has been smoothed by etching under the polishing process parameters. This morphology reflects the influence of the polishing process itself on the amount of polishing removal at different positions during the entire polishing process to remove the residual separation layer. This surface morphology data will be used to subsequently determine the preset target surface morphology.

[0055] S202. Obtain the surface profile of the sample treatment surface, and determine the preset target surface profile based on the surface profile of the sample treatment surface.

[0056] The preset target surface shape is a perpendicular mirror image of the sample treatment surface shape.

[0057] Specifically, the preset target surface shape is a vertical mirror image of the sample processing surface shape. A vertical mirror image shape refers to the surface shape obtained by flipping the sample processing surface shape up and down relative to the horizontal plane, with the horizontal plane as the plane of symmetry. The preset target surface shape will be used for subsequent etching of the exposed surface of the thin film layer side of the composite thin film precursor.

[0058] In some embodiments, see Figure 4 The method for obtaining the surface profile of the sample treatment surface is as follows: S2021. The first measurement is performed on the thin film layer side of the polished sample to obtain the initial surface shape.

[0059] Specifically, a first measurement is performed on the thin film layer side of the polished sample. This first measurement can be performed using a white light interferometer or an ellipsometer. The white light interferometer scans the entire surface of the thin film layer side of the sample in a non-contact manner to obtain the relative height data of each spatial point, generating the initial surface profile of the thin film layer side of the sample. This initial surface profile reflects the initial height distribution of each point on the exposed surface of the thin film layer side of the sample, serving as the basis for subsequent data correction.

[0060] S2022. Based on the initial surface shape, select areas where the shape changes exceed a preset threshold, and set up dense data collection points in these areas for a second measurement.

[0061] Specifically, based on the initial surface profile of the sample's thin film layer, regions where morphological changes exceed a preset threshold are selected, and a second measurement is performed on these regions using densely packed data acquisition points. Regions where morphological changes exceed the preset threshold are typically located at the edges of the sample's thin film layer or at local undulations; the surface profile data of these regions significantly impacts the accuracy of the subsequent target surface profile. The preset threshold is a value pre-set based on the overall morphological characteristics of the initial surface profile of the sample's thin film layer and the accuracy of the measuring equipment. It is used to distinguish the degree of morphological change, ensuring that regions with significant morphological changes can be identified for precise measurement. The second measurement uses the same measuring equipment as the first measurement, with densely packed data acquisition points set up in these regions for precise measurement, obtaining high-density local surface profile data.

[0062] S2023. Based on the second measurement data, the first measurement data is corrected to obtain the corrected surface shape, which is denoted as the sample treatment surface shape.

[0063] Specifically, the first measurement data is corrected based on the second measurement data. During correction, the high-density data obtained from the second measurement is fused with the initial surface profile data obtained from the first measurement. The low-precision data in the corresponding areas of the initial surface profile are replaced with the high-density data, thus obtaining the corrected surface profile of the thin film layer side of the sample, denoted as the sample treated surface profile. This corrected surface profile data more accurately reflects the true morphology of the exposed surface of the thin film layer side of the sample.

[0064] S2024. Perform a vertical mirror transformation on the corrected sample treatment surface to obtain the preset target surface.

[0065] Specifically, a vertical mirror transformation is performed on the surface profile of the sample after correction. The vertical mirror transformation is to flip the surface profile of the sample processing surface up and down relative to the horizontal plane as the plane of symmetry. The surface profile obtained after the transformation is the preset target surface profile, which will be used for subsequent etching of the thin film layer of the composite thin film precursor.

[0066] S300. Based on the preset target surface shape, the exposed surface of the film layer side of the composite film precursor is etched to obtain a composite film intermediate with the preset target surface shape; the exposed surface of the film layer side of the composite film intermediate is polished to obtain a composite film.

[0067] The treatment of the exposed surface of the composite thin film precursor includes sequential etching and polishing.

[0068] Specifically, based on a preset target surface shape, the exposed surface of the thin film layer side of the composite thin film precursor is etched. The etching process removes material from the exposed surface of the thin film layer side of the composite thin film precursor according to the preset target surface shape, ensuring that the surface morphology of the exposed surface of the thin film layer side of the composite thin film precursor is consistent with the preset target surface shape. Ion beam etching can be used for the etching process.

[0069] After etching, the exposed surface of the film layer side of the composite film intermediate obtained after etching is polished to remove any remaining separation layer and achieve a smooth surface, thus obtaining the composite film. Chemical mechanical polishing (CMP) can be used for polishing.

[0070] This step is based on the preset target surface shape determined by polishing or etching and polishing the composite film precursor used as the surface shape measurement sample in steps S100 and S200. The composite film precursor used in formal production is then subjected to etching and polishing.

[0071] In some embodiments, see Figure 5 Based on the preset target surface shape, the exposed surface of the thin film layer side of the composite thin film precursor is sequentially etched and polished, including: S301. Based on the preset target surface shape, the exposed surface of the thin film layer side of the composite thin film precursor is etched to obtain a composite thin film intermediate with the preset target surface shape.

[0072] Specifically, when etching the exposed surface of the thin film layer side of the composite thin film precursor to form a preset target surface shape, the exposed surface of the thin film layer side of the composite thin film precursor is directly etched into the preset target surface shape. The specific process parameters of this etching process are not limited, as long as the exposed surface of the thin film layer side of the composite thin film precursor can be etched into the desired state.

[0073] Specifically, based on a preset target surface shape, the exposed surface of the thin film layer of the composite thin film precursor is etched. The etching process removes material from the thin film layer of the composite thin film precursor according to the preset target surface shape, gradually bringing the surface morphology of the exposed surface of the thin film layer closer to the preset target surface shape. The purpose is to ensure that the peak-valley difference of the morphology etched by the etching process matches the thickness change caused by the polishing process itself, thereby enabling precise compensation in subsequent polishing. Ion beam etching can be used for the etching process. After etching, a composite thin film intermediate is obtained, and the exposed surface of the thin film layer of the composite thin film intermediate has been pre-constructed with a preset target surface shape that matches the degradation pattern of the polishing process.

[0074] Alternatively, when etching the exposed surface of the composite film precursor to form a predetermined target surface shape, the exposed surface of the composite film precursor on the thin film layer side is first etched into a plane, and then the predetermined target surface shape is etched further. The specific process parameters of this etching process are not limited, as long as the exposed surface of the composite film precursor on the thin film layer side can be etched into the desired state.

[0075] Specifically, the exposed surface of the thin film layer side of the composite thin film precursor is first etched into a plane. Then, using a preset target surface shape as a control, the exposed flat surface of the thin film layer side of the composite thin film precursor is etched. This latter etching process removes material from the thin film layer of the composite thin film precursor according to the preset target surface shape, gradually bringing the surface morphology of the exposed surface of the thin film layer side of the composite thin film precursor closer to the preset target surface shape. The purpose is to ensure that the peak-valley difference of the morphology etched by the etching process matches the thickness change caused by the polishing process itself, thereby enabling precise compensation in the subsequent polishing process. Ion beam etching can be used for the etching process. After the etching process, a composite thin film intermediate is obtained, and the exposed surface of the thin film layer side of the composite thin film intermediate has been pre-constructed with a preset target surface shape that matches the degradation law of the polishing process.

[0076] S302. Polish the exposed surface of the film layer side of the composite film intermediate to obtain the composite film.

[0077] The exposed surface of the film layer side of the composite film intermediate is polished. This polishing process uses the same parameters as the polishing process for the sample, including the same polishing slurry composition, polishing pad material, polishing pressure, polishing speed, and polishing time. The purpose of using the same process parameters is to ensure that the effect of this polishing process on thickness uniformity is completely consistent with that of the sample polishing process. This allows the pre-etched target surface shape on the exposed surface of the film layer side of the composite film intermediate to precisely cancel out the degradation caused by the polishing process. Chemical mechanical polishing (CMP) can be used for this polishing process. During polishing, the inherent non-uniform removal effect of the polishing process interacts with the pre-etched target surface shape on the exposed surface of the film layer side of the composite film intermediate. Areas with higher surface morphology on the exposed surface of the film layer side have more material removed, while areas with lower morphology have less material removed. These two effects cancel each other out. Upon completion of polishing, all locations are polished to almost the same horizontal plane, resulting in a flat and uniformly thick film surface, thus obtaining the composite film.

[0078] Alternatively, the exposed surface of the film layer side of the composite film intermediate can be polished. This polishing process differs from the polishing of the sample only in the polishing time. This slight difference in polishing time avoids insufficient polishing or excessive polishing caused by using the same polishing time when the residual separation layer after etching the exposed surface of the film layer side of the composite film precursor is inconsistent with the polishing amount of the sample.

[0079] In a more preferred embodiment, when S301 forms the preset target surface by first etching the exposed surface of the film layer side of the composite film precursor into a plane, and then continuing to etch the preset target surface shape, the polishing process performed on the sample satisfies the following conditions: polishing stops when the lowest point of the polished surface formed during the polishing process reaches the upper surface of the film layer; and when etching the exposed surface of the film layer side of the composite film precursor to form the preset target surface shape, the following conditions are also satisfied: after etching, the remaining amount to be removed by polishing on the exposed surface of the film layer side is the same as the amount removed by polishing when polishing the sample; and the process parameters (including polishing time) of the polishing process performed on the exposed surface of the film layer side of the composite film intermediate are the same as the process parameters (including polishing time) of the polishing process performed on the sample. The purpose of this setup is to polish the sample, continuously creating polished surfaces with varying heights. Polishing stops when the lowest point reaches the upper surface of the thin film layer, meaning polishing stops when a certain location is completely free of separation layer residue. At this point, polishing doesn't penetrate the thin film layer, but it also results in incomplete removal of separation layer residue in other locations. In other words, the processed surface shape is actually the upper surface shape of the polished separation layer residue. Based on this, when etching the composite thin film precursor, the thickness of the remaining separation layer residue to be polished is first controlled through a planar etching process, ensuring this thickness matches the remaining thickness after etching the plane from the sample. Then, the preset target surface shape is etched. Thus, the size and shape of the remaining separation layer residue to be polished are completely consistent with the polishing amount of the sample, only they are perpendicular mirror images. Using the exact same polishing process parameters as the sample, the exposed surface of the thin film layer side of the composite thin film intermediate is polished, completely removing the separation layer residue without polishing into the thin film layer. The thin film layer is preserved intact, and thickness uniformity is optimally optimized.

[0080] To more clearly illustrate the preparation method of the composite thin film in the embodiments of this application, several specific embodiments are described below. It should be understood that the specific embodiments described below are merely illustrative of the present invention and are not exhaustive examples, nor are they intended to limit the specific scope of the present invention. All equivalent variations based on the technical content of the present invention should be included within the protection scope of the present invention. Example 1: This embodiment provides a composite thin film and its preparation method. The preparation method of the composite thin film includes the following steps: Figure 6As shown, a lithium niobate single-crystal wafer is prepared, and ion implantation is performed on the lithium niobate single-crystal wafer to obtain an ion-implanted wafer. The ion-implanted wafer includes a thin film layer, a separation layer, and a residual mass layer in sequence from the ion implantation surface. The implanted ions are mainly concentrated in the separation layer, where the implanted ions are helium ions, and the ion implantation dose is 1×10⁻⁶. 16 ions / cm 2 The ion implantation energy was 5 MeV. Plasma activation was performed on the bonding surface between the thin film layer of the ion implantation wafer and the silicon substrate. Then, the ion implantation wafer and the silicon substrate were bonded together through the thin film layer to obtain a bonded body. The bonded body was annealed at 100°C for 24 hours. The implanted ions in the separation layer formed gas, generating bubbles. When the bubbles coalesced, the separation layer split, and the residual layer separated from the thin film layer at the separation layer. The thin film layer remained on the silicon substrate, forming a composite thin film precursor. Separation layer residue remained on the upper surface of the thin film layer. This residue needed to be removed through subsequent etching of the composite thin film precursor and polishing of the composite thin film intermediate. Figure 7 As shown, a composite thin film precursor was taken as a sample, and the exposed surface of the thin film layer side of the sample was etched by ion beam etching to etch the exposed surface of the thin film layer side of the sample into a plane (i.e., as shown). Figure 7 The enlarged view (shown by dashed lines) shows the uneven surface of the separation layer residue on the upper surface of the thin film layer after splitting (the surface is smoothed). Simultaneously, the remaining thickness to be polished after etching the plane is recorded. Then, chemical mechanical polishing is performed. Polished surfaces are continuously formed during the polishing process, with varying heights at different locations. Polishing stops when the lowest point of the polished surface reaches the upper surface of the thin film layer, completing the removal of the separation layer residue and forming the sample treatment surface. Based on the sample treatment surface shape, a preset target surface shape is determined. The preset target surface shape is obtained as follows: a white light interferometer is used to perform a first measurement on the sample treatment surface to obtain the initial surface shape; based on the initial surface shape, areas with morphological changes exceeding a preset threshold are selected, and dense data acquisition points are set in these areas for a second measurement; the first measurement data is corrected based on the second measurement data to obtain the corrected surface shape, which is recorded as the sample treatment surface shape; a vertical mirror transformation is performed on the corrected surface shape to obtain the preset target surface shape. Figure 8As shown, another composite film precursor is used as the production part. Based on the preset target surface shape, the exposed surface of the film layer side of the production part is etched and trimmed by ion beam etching. Specifically, the exposed surface of the film layer side of the composite film precursor is first etched into a plane. While etching into a plane, it is ensured that the remaining thickness of the separation layer to be removed on the exposed surface of the film layer side after etching is consistent with the remaining thickness to be polished after etching the plane of the previously recorded sample. Then, the preset target surface shape is etched again. Thus, after etching, the amount of material to be polished off the exposed surface of the film layer side is exactly the same as the amount of material polished off when polishing the sample, resulting in a production part intermediate with the preset target surface shape. The exposed surface of the film layer side of the production part intermediate is then chemically and mechanically polished. This polishing process uses the same process parameters (including polishing time) as the polishing process of the sample. Thus, all separation layer residues can be completely removed without polishing into the film layer, and the film layer is completely preserved. After polishing, the final composite film production part is obtained. Tests showed that the TTV of the lithium niobate thin film layer in the composite thin film production part prepared in this embodiment is 1 nanometer.

[0081] Example 2: This embodiment provides a composite thin film and its preparation method. The preparation method of the composite thin film includes the following steps: preparing a lithium tantalate single crystal wafer, performing ion implantation on the lithium tantalate single crystal wafer to obtain an ion-implanted wafer, the ion-implanted wafer including a thin film layer, a separation layer and a residual layer sequentially from the ion implantation surface, the implanted ions are mainly concentrated in the separation layer, wherein the implanted ions are hydrogen ions, and the ion implantation dose is 3×10⁻⁶. 17 ions / cm 2The ion implantation energy was 30 keV. A silicon substrate was prepared, and a polycrystalline silicon trap layer was deposited on the substrate. A silicon dioxide isolation layer was deposited on the trap layer. Plasma activation treatment was performed on the thin film layer side of the ion implantation wafer and the side of the isolation layer facing away from the substrate. Then, the ion implantation wafer and the silicon substrate were bonded through the thin film layer and the isolation layer to obtain a bonded body. The bonded body was annealed at 600℃ for 1 hour. The implanted ions in the separation layer formed gas, generating bubbles. When the bubbles merged, the separation layer split, and the residual layer separated from the thin film layer at the separation layer. The thin film layer remained on the silicon substrate, forming a composite thin film precursor. Separation layer residue remained on the upper surface of the thin film layer. The separation layer residue needed to be removed by subsequent etching of the composite thin film precursor and polishing of the composite thin film intermediate. A composite thin film precursor was taken as a sample, and the exposed surface of the thin film layer side of the sample was chemically and mechanically polished to remove the separation layer residue, forming a sample treated surface. Based on the surface shape of the sample treated surface, a preset target surface shape was determined. The method for obtaining the preset target surface shape is as follows: An ellipsometry is used to perform a first measurement on the sample treatment surface to obtain the initial surface shape; based on the initial surface shape, regions whose morphological changes exceed a preset threshold are selected, and dense data acquisition points are set in these regions for a second measurement; the first measurement data is corrected based on the second measurement data to obtain the corrected surface shape, which is recorded as the sample treatment surface shape; a vertical mirror transformation is performed on the corrected surface shape to obtain the preset target surface shape. Another composite thin film precursor is taken as the production part. Based on the preset target surface shape, the exposed surface of the thin film layer side of the production part is etched and trimmed with an ion beam to form the preset target surface shape, resulting in a production part intermediate with the preset target surface shape. The exposed surface of the thin film layer side of the production part intermediate is chemically mechanically polished. This polishing treatment uses the same process parameters as the polishing treatment of the sample, or only differs in polishing time, to remove the separation layer residue. After polishing, the final composite thin film production part is obtained. Testing shows that the TTV of the lithium tantalate thin film layer in the composite thin film production part prepared in this embodiment is 2 nanometers.

[0082] In some embodiments, the present invention also provides a composite film prepared by the composite film preparation method provided in the above embodiments.

[0083] The composite film includes a substrate and a thin film layer bonded to the substrate. The substrate is derived from the substrate of the composite film precursor, and the thin film layer is formed from the thin film layer of the composite film precursor through etching and polishing processes. Specifically, any composite film precursor is taken as a sample. The exposed surface of the thin film layer side of the sample is polished, or first etched to create a plane before polishing to remove any remaining separation layer, forming a sample processing surface. A perpendicular mirror image of this sample processing surface is obtained, denoted as the preset target surface. Based on the preset target surface, the exposed surface of the thin film layer side of the composite film precursor is etched to obtain a composite film intermediate with the preset target surface. Then, polishing is performed to remove any remaining separation layer, resulting in the final composite film. Thus, the remaining separation layer on the exposed surface of the thin film layer side of the composite film precursor is removed, forming the thin film layer of the final composite film. The substrate of the composite film precursor is the substrate of the final composite film.

[0084] Similar parts between the embodiments provided in this invention can be referred to mutually. The specific embodiments provided above are merely examples under the overall concept of this invention and do not constitute a limitation on the scope of protection of this invention. For those skilled in the art, any other embodiments extended from the solution of this invention without creative effort are within the scope of protection of this invention.

Claims

1. A method for preparing a composite thin film, characterized in that, include: Prepare a composite thin film precursor, the composite thin film precursor comprising a substrate and a thin film layer located on the substrate; Based on a preset target surface shape, the exposed surface of the film layer side of the composite film precursor is etched to obtain a composite film intermediate with a preset target surface shape; wherein, the preset target surface shape is obtained as follows: take any composite film precursor as a sample, polish the exposed surface of the film layer side of the sample to form a sample processing surface, and the perpendicular mirror surface shape of the sample processing surface is denoted as the preset target surface shape. The exposed surface of the film layer side of the composite film intermediate is polished to obtain the composite film.

2. The method for preparing the composite thin film according to claim 1, characterized in that, Before polishing the exposed surface of the thin film layer of the sample, the exposed surface of the thin film layer of the sample is first etched to form a plane.

3. The method for preparing the composite thin film according to claim 2, characterized in that, When etching the exposed surface of the film layer side of the composite film precursor to form a preset target surface, the exposed surface of the film layer side of the composite film precursor is first etched into a plane, and then the preset target surface is etched out. Alternatively, the exposed surface of the film layer side of the composite film precursor can be directly etched into the preset target surface shape.

4. The method for preparing the composite thin film according to any one of claims 1-3, characterized in that, The polishing process parameters for the exposed surface of the film layer side of the composite film intermediate are the same as those for the polishing process parameters for the sample, or differ only in the polishing time.

5. The method for preparing the composite thin film according to claim 3, characterized in that, When the method of first etching the exposed surface of the film layer side of the composite film precursor into a plane, and then continuing to etch out the preset target surface shape, the polishing treatment of the sample meets the following conditions: polishing is stopped when the lowest point of the polished surface formed during the polishing process reaches the upper surface of the film layer. Furthermore, when etching the exposed surface of the film layer side of the composite film precursor to form the preset target surface, the following conditions must be met simultaneously: after etching, the amount of material to be removed by polishing on the exposed surface of the film layer side is the same as the amount of material removed by polishing when polishing the sample. Furthermore, the polishing process parameters for the exposed surface of the film layer side of the composite film intermediate are the same as those for the polishing process of the sample.

6. The method for preparing the composite thin film according to claim 1, characterized in that, The method for obtaining the surface profile of the sample treatment surface is as follows: The initial surface profile of the polished sample thin film layer was obtained by the first measurement. Based on the initial surface shape, regions whose morphological changes exceed a preset threshold are selected, and dense data collection points are set in the regions for a second measurement. Based on the second measurement data, the first measurement data is corrected to obtain the corrected surface shape, which is denoted as the sample treatment surface shape. The sample treatment surface is transformed by a vertical mirror image to obtain the preset target surface.

7. The method for preparing the composite thin film according to claim 1, characterized in that, The method for preparing the composite thin film precursor includes: A functional single-crystal wafer is prepared, and ion implantation is performed on the functional single-crystal wafer to obtain an ion-implanted wafer; the ion-implanted wafer includes a thin film layer, a separation layer and a residual mass layer in sequence from the ion implantation surface. The ion-implanted sheet is bonded to the substrate to obtain a bonded body; The bond is annealed to separate the residual material layer of the ion implantation sheet from the separation layer. The thin film layer is transferred to the substrate to form the composite thin film precursor. The composite thin film precursor includes a substrate and a thin film layer on the substrate. Separation layer residue remains on the upper surface of the thin film layer. The separation layer residue is removed by etching the composite thin film precursor and polishing the composite thin film intermediate.

8. The method for preparing the composite thin film according to claim 7, characterized in that, Before bonding the ion-implanted sheet to the substrate, the process further includes: An isolation layer is provided on the substrate and / or on the thin film side of the ion implantation sheet, and the ion implantation sheet is bonded to the substrate through the isolation layer.

9. The method for preparing the composite thin film according to claim 8, characterized in that, Also includes: A trap layer is formed on the substrate such that after bonding, the isolation layer is located between the trap layer and the thin film layer.

10. A composite film, characterized in that, It is prepared by the method of any one of claims 1-9.

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