Thin film preparation method suitable for wafer with uneven surface
By presetting the reference surface of the ion implantation surface and preparing the barrier layer on the wafer surface, the process complexity and TTV problems caused by uneven wafer surface are solved, and film preparation with excellent thickness uniformity is achieved.
Patent Information
- Application Number
- CN202510544657.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-28
- Publication Date
- 2025-07-29
AI Technical Summary
When the wafer surface is uneven, the prior art requires different ion implantation energy to be used at different locations, resulting in increased process complexity and poor surface state after peeling. The TTV is too large and cannot meet the requirements of semiconductor devices.
By obtaining wafer thickness distribution data, presetting the ion implantation reference surface, preparing a barrier layer, and concentrating ions on the reference surface under the same ion implantation energy, combining peeling and polishing treatments to achieve film preparation with excellent thickness uniformity.
Under the same ion implantation energy, the implanted ions are concentrated on the preset reference plane. After peeling, the surface state is good, and the TTV is trimmed, reducing the complexity of the ion implantation process and excellent thickness uniformity.
Smart Images
Figure CN120388884A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of semiconductors, and particularly relates to a method for preparing a thin film applicable to wafers with uneven surfaces. Background Art
[0002] In the ion implantation and stripping method, high-energy particles are implanted into the wafer. The ions stay within a certain depth of the wafer to form an ion implantation layer. After heating, the ions form a gas (for example, helium ions will turn into helium gas) and expand in volume. When the gases are connected in a continuous sheet, the wafer breaks from the ion implantation layer to achieve stripping. However, the depth of ion implantation is affected by the ion implantation energy. When the wafer surface is uneven with undulations, especially when the undulations are large, at the same ion implantation energy, the depths reached by the implanted ions corresponding to different positions on the wafer are different. After thermal stripping, the surface state is poor and the TTV is too large, which cannot meet the usage requirements of semiconductor devices. If different ion implantation energies are used for different positions on the wafer during ion implantation, although the depths reached by the implanted ions corresponding to different positions on the wafer are the same, improving the surface state after stripping, it increases the complexity of the ion implantation process to a certain extent.
[0003] Therefore, it is necessary to develop a method for preparing a thin film that can achieve the concentration of implanted ions on the same ion implantation reference plane when using the same ion implantation energy for wafers with uneven surfaces, resulting in a good surface state and a small TTV after thermal stripping, and reducing the complexity of the ion implantation process. Summary of the Invention
[0004] Technical Problem
[0005] The object of the present invention is to develop a method for preparing a thin film that can achieve the concentration of implanted ions on the same ion implantation reference plane when the wafer surface is uneven and the TTV is too large, using the same ion implantation energy, resulting in a good surface state after thermal stripping and a trimmed TTV.
[0006] Technical Solution
[0007] The first aspect of the present invention provides a method for preparing a thin film applicable to a wafer with an uneven surface, which is characterized by including the following steps: preparing an initial wafer having opposite first and second surfaces; obtaining thickness distribution data of the initial wafer and presetting an ion implantation reference plane for the initial wafer; based on the thickness distribution data and the ion implantation reference plane, obtaining the thickness to be peeled at different positions on the first surface of the initial wafer; determining the ion implantation energy based on the maximum value of the thickness to be peeled; preparing a barrier layer on the first surface of the initial wafer; performing ion implantation on the initial wafer through the barrier layer with the ion implantation energy to implant ions to the ion implantation reference plane, obtaining an ion-implanted wafer; performing a peeling process on the ion-implanted wafer from the ion implantation reference plane to obtain a peeled wafer with a peeling surface; and polishing the peeling surface of the peeled wafer to obtain the thin film. The preparation method of the present invention is applicable to preparing a thin film from a wafer with an uneven surface. Under the action of the barrier layer, the sum of the barrier layer and the thickness to be peeled of the initial wafer is coordinated, so that under the same ion implantation energy, the implanted ions can be concentrated on the preset ion implantation reference plane. That is, in the preparation method of the present invention, even if the wafer surface is uneven, a constant ion implantation energy can be used for ion implantation. The implanted ions can be concentrated on the preset ion implantation reference plane, and the peeling is initiated at the preset ion implantation reference plane. After thermal peeling, the surface state is good, and the TTV is trimmed. Compared with using different ion implantation energies at different positions of the wafer during ion implantation, the complexity of the ion implantation process can be reduced.
[0008] In some embodiments, the ion implantation reference plane is parallel to the second surface. The position of the ion implantation reference plane is not limited and can be freely adjusted according to actual needs. The preset ion implantation reference plane of the present invention is parallel to the second surface, which can better improve the TTV and make the thickness uniformity better.
[0009] In some embodiments, the thickness to be peeled is the distance from the ion implantation reference plane to the first surface.
[0010] In some embodiments, the ion implantation energy is greater than or equal to the ion implantation energy required to implant ions from the position on the first surface having the maximum thickness to be peeled to the ion implantation reference plane.
[0011] In some embodiments, the specific method for obtaining the thickness distribution data of the initial wafer of the present invention is not limited, and any method capable of obtaining its thickness distribution data can be used; for example, it can be obtained by an optical film thickness detection device or a probe type film thickness measuring instrument (step gauge).
[0012] In some embodiments, the thicknesses at different positions of the barrier layer are obtained based on the thicknesses to be peeled off at different positions on the first surface of the initial wafer, the constituent elements and density of the initial wafer, the constituent elements and density of the barrier layer, and the ion implantation energy. There is no limitation on the specific method for obtaining the thicknesses at different positions of the barrier layer, and any feasible method can be adopted. For example, the thicknesses at different positions of the barrier layer are obtained by importing the thicknesses to be peeled off at different positions on the first surface of the initial wafer, the constituent elements and density of the initial wafer, the constituent elements and density of the barrier layer, and the ion implantation energy into simulation software (such as SRIM) for simulation. By providing a barrier layer on the first surface of the initial wafer, and based on the thicknesses to be peeled off at different positions on the first surface of the initial wafer, the material properties of the initial wafer, the material properties of the barrier layer, and the ion implantation energy determined based on the maximum value of the thicknesses to be peeled off, the thicknesses corresponding to different positions of the barrier layer are obtained. Based on the design of the barrier layer thickness, the sum of the barrier layer thickness and the thickness to be peeled off of the initial wafer is such that, under the same ion implantation energy, the implanted ions can be concentrated on a preset ion implantation reference plane. After thermal peeling, the surface state is good, and the TTV is trimmed. Compared with using different ion implantation energies at different positions of the wafer during ion implantation, the complexity of the ion implantation process can be reduced.
[0013] In some embodiments, there is no limitation on the material and preparation method of the barrier layer. For example, the material of the barrier layer includes photoresist, and the barrier layer is obtained by photolithography of the photoresist.
[0014] In some embodiments, the preparation method of the barrier layer is as follows: spray photoresist on the first surface of the initial wafer until the thickness of the photoresist reaches a first thickness; based on the difference between the first thickness and the thicknesses at different positions of the barrier layer, obtain the thicknesses to be denatured at different positions on the surface of the photoresist; perform exposure treatment on the photoresist from the surface of the photoresist downward by irradiating a light source, and a denatured layer is formed on the part of the surface of the photoresist that has been exposed; wherein, the exposure depth reached by the irradiating light source at different positions on the surface of the photoresist is consistent with the thickness to be denatured at the corresponding position on the surface of the photoresist; remove the denatured layer to obtain the barrier layer. In the present invention, the first thickness is not less than the maximum value of the thicknesses at different positions of the barrier layer.
[0015] In some embodiments, the specific implementation manner of the exposure treatment is: based on the thicknesses to be denatured at different positions on the surface of the photoresist, obtain the required light intensity corresponding to the corresponding position on the surface of the photoresist; then supply the irradiating light source with the required light intensity at different positions on the surface of the photoresist. The irradiating light sources with different light intensities result in different denaturation rates at different positions on the surface of the photoresist, so that the exposure depth at different positions on the surface of the photoresist is consistent with the thickness to be denatured at the corresponding position on the surface of the photoresist.
[0016] In some embodiments, the specific implementation of the exposure process is as follows: based on the thickness to be denatured at different positions on the photoresist surface, the required light intensity corresponding to the corresponding positions on the photoresist surface is obtained; then a glass carrier is prepared, and an absorbent layer is sprayed on the surface of the glass carrier. The thicknesses at different positions of the absorbent layer satisfy that the light intensity passing through different positions of the glass carrier with the absorbent layer when irradiating a homogenizing light source is consistent with the required light intensity at the corresponding positions on the photoresist surface; finally, the photoresist surface is irradiated with a homogenizing light source through the glass carrier with the absorbent layer. The absorption degree of light at different positions of the absorbent layer is different, the light intensity irradiating the photoresist through the glass carrier and the absorbent layer is different, and the denaturation rate at different positions on the photoresist surface is different, so that the exposure depth at different positions on the photoresist surface is consistent with the thickness to be denatured at the corresponding positions on the photoresist surface. In the present invention, the absorbent layer can be on the outer side or the inner side of the glass carrier.
[0017] In some embodiments, the specific implementation of the exposure process is as follows: based on the thickness to be denatured at different positions on the photoresist surface, the required light intensity corresponding to the corresponding positions on the photoresist surface is obtained; then a light baffle is prepared, and the thickness of the light baffle is processed based on the required light intensity at different positions on the photoresist surface. The thicknesses at different positions of the light baffle satisfy that the light intensity passing through different positions of the light baffle when irradiating a homogenizing light source is consistent with the required light intensity at the corresponding positions on the photoresist surface; finally, the photoresist surface is irradiated with a homogenizing light source through the light baffle with the processed thickness. The absorption degree of light at different positions of the light baffle is different, the light intensity irradiating the photoresist through the light baffle is different, and the denaturation rate at different positions on the photoresist surface is different, so that the exposure depth at different positions on the photoresist surface is consistent with the thickness to be denatured at the corresponding positions on the photoresist surface. In the present invention, the thickness processing can be performed on the inner side or the outer side of the light baffle.
[0018] In some embodiments, the denatured layer is removed by a developer. After obtaining the denatured layer by exposing the photoresist in the present invention, the denatured layer can be easily removed by rinsing with a developer to obtain a barrier layer with the required thickness, and the method is simple.
[0019] In some embodiments, the material of the initial wafer is selected from one or more of lithium niobate, lithium tantalate, quartz, silicon carbide, silicon, or silicon nitride. The material of the initial wafer is not limited thereto.
[0020] In some embodiments, the initial wafer is obtained by preprocessing an initial wafer precursor; wherein, the initial wafer precursor has an opposite surface to be processed and a second surface, and the preprocessing includes sequentially performing grinding and thinning and polishing on the surface to be processed of the initial wafer precursor. The surface to be processed after polishing becomes the first surface of the initial wafer, and the second surface becomes the second surface of the initial wafer. In the present invention, the thickness is regulated by grinding and thinning, and the degree of grinding and thinning can be set based on the thickness requirement. After grinding and thinning, the surface is uneven, with large surface undulations and large thickness differences at different positions. However, the overall process of ion implantation - stripping - polishing in the preparation method of the present invention plays a role in improving the thickness uniformity. Specifically, in the present invention, an ion implantation reference plane is preset for the initial wafer, and a barrier layer is prepared on the first surface of the initial wafer. The sum of the thickness of the barrier layer and the thickness to be stripped of the initial wafer can enable the implanted ions to be concentrated on the preset ion implantation reference plane under the same ion implantation energy, and the stripping is initiated at the preset ion implantation reference plane. The position of the ion implantation reference plane can be freely adjusted, so that the surface undulations introduced by grinding and thinning can be completely removed during stripping. After thermal stripping, the surface state is good, the TTV is trimmed, and the thickness uniformity is excellent, and the thickness can reach 1 - 5 μm.
[0021] In some embodiments, before the preprocessing, the second surface of the initial wafer precursor is pre - bonded with a substrate.
[0022] In some embodiments, before the second surface of the initial wafer precursor is pre - bonded with a substrate, the bonding surface of the substrate and the second surface of the initial wafer precursor are activated. The activation treatment can achieve ultra - clean cleaning of the object surface, activate the surface, and enhance the bonding ability. The way of activation treatment is not limited, for example, plasma activation treatment.
[0023] In some embodiments, before the second surface of the initial wafer precursor is pre - bonded with a substrate, an isolation layer is first prepared on the bonding surface of the substrate and / or the second surface of the initial wafer precursor, and then the substrate layer and the initial wafer precursor are bonded via the isolation layer.
[0024] In some embodiments, before the isolation layer is prepared, a trap layer is first prepared on the bonding surface of the substrate. The method of the present invention is applicable to both self - supporting thin films and composite thin films including a substrate and a thin film layer (corresponding to the initial wafer), substrate - isolation layer - thin film layer, substrate - trap layer - isolation layer - thin film layer, etc., and has strong applicability.
[0025] In some embodiments, the material of the initial wafer precursor is selected from one or more of lithium niobate, lithium tantalate, quartz, silicon carbide, silicon, or silicon nitride; the material of the substrate is selected from one or more of lithium niobate, lithium tantalate, quartz, silicon, sapphire, silicon carbide, silicon nitride, gallium arsenide, or indium phosphide; the material of the isolation layer is selected from one or more of silicon dioxide, silicon nitride, silicon oxynitride (SiON), aluminum oxide, or aluminum nitride. The materials of the initial wafer precursor, substrate, isolation layer, and trap layer in the present invention are not limited thereto.
[0026] In some embodiments, the isolation layer is prepared by deposition.
[0027] In some embodiments, the deposition method is one of chemical vapor deposition, physical vapor deposition, or magnetron sputtering.
[0028] In some embodiments, when the material of the substrate is silicon, the isolation layer is preferably prepared by thermal oxidation. The specific steps are as follows: Thermal oxidation is performed from the bonding surface of the substrate into the substrate. The preparation method of the isolation layer is not limited thereto.
[0029] In some embodiments, the trap layer is prepared by deposition. The preparation method of the trap layer is not limited thereto.
[0030] In some embodiments, the implanted ions for ion implantation are one or more of hydrogen ions, helium ions, nitrogen ions, oxygen ions, or argon ions, and the implantation dose is 1×10 16 ions / cm 2 ~3×10 17 ions / cm 2 。
[0031] In some embodiments, the temperature during the stripping process is 100 - 600 °C.
[0032] The second aspect of the present invention provides a thin film prepared by the preparation method described in any one of the above. The TTV of the thin film prepared by the present invention is 10 nm - 60 nm, and it has excellent thickness uniformity. Description of the Drawings
[0033] Figure 1 It is a flowchart for the preparation of a self-supporting thin film product in Example 1;
[0034] Figure 2A It is a flowchart for the preparation of a barrier layer by non-uniform light in Example 1;
[0035] Figure 2B It is a flowchart for the preparation of a barrier layer by an absorptive layer in Example 1;
[0036] Figure 2C It is the preparation flow chart of the barrier layer prepared by the light baffle in Example 1;
[0037] Figure 3 It is the preparation flow chart of the composite film product including two-layer structure of a substrate and a thin film layer in Example 2;
[0038] Figure 4A It is the preparation flow chart of the barrier layer prepared by non-uniform light in Example 2;
[0039] Figure 4B It is the preparation flow chart of the barrier layer prepared by the light-absorbing layer in Example 2;
[0040] Figure 4C It is the preparation flow chart of the barrier layer prepared by the light baffle in Example 2;
[0041] Figure 5 It is the preparation flow chart of the composite film product including three-layer structure of a substrate, an isolation layer and a thin film layer in Example 3;
[0042] Figure 6 It is the preparation flow chart of the composite film product including four-layer structure of a substrate, a trap layer, an isolation layer and a thin film layer in Example 4. Detailed implementation manners
[0043] For facilitating the implementation of the technical solution of the application, the terms and expressions involved in the present invention are generally described and defined as follows first.
[0044] The term "comprise", "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including the said element.
[0045] TTV (Total Thickness Variation) is the difference between the maximum thickness and the minimum thickness of a thin film, which is an important index for measuring thickness uniformity. When the thin film is a self-supporting thin film, TTV is the difference between the maximum thickness and the minimum thickness of the self-supporting thin film product; when the thin film is a composite thin film, TTV is the difference between the maximum thickness and the minimum thickness of the thin film layer in the composite thin film product.
[0046] In each group of comparative experiments provided by the present invention, unless otherwise specified, except for the differences pointed out in each group, other experimental conditions, materials, etc. are kept consistent for comparability.
[0047] In the embodiments of the present invention, the reagents, instruments and equipment used can be purchased from the market without detailed description.
[0048] The following further describes a thin film preparation method provided by the present invention, which is applicable to wafers with uneven surfaces.
[0049] Example 1: Preparation of a self-supporting thin film using a wafer with an uneven surface
[0050] As Figure 1 shown, it includes the following steps:
[0051] S1. Prepare a silicon initial wafer precursor, which has a surface to be processed and a second surface opposite to the surface to be processed; successively perform grinding and thinning and polishing on the surface to be processed of the silicon initial wafer precursor to obtain a silicon initial wafer; wherein, the surface to be processed after polishing becomes the first surface of the silicon initial wafer, and the second surface becomes the second surface of the silicon initial wafer opposite to the first surface.
[0052] S2. Obtain the thickness distribution data of the silicon initial wafer through a probe type film thickness measuring instrument, and preset an ion implantation reference plane for the silicon initial wafer, and the preset ion implantation reference plane is parallel to the second surface.
[0053] S3. Based on the thickness distribution data and the ion implantation reference plane, obtain the thickness to be peeled off at different positions on the first surface of the silicon initial wafer, and the thickness to be peeled off is equal to the distance from the ion implantation reference plane to the first surface.
[0054] S4. Prepare a barrier layer made of photoresist material on the first surface of the silicon initial wafer; wherein, the thickness of different positions of the barrier layer is obtained by: importing the thickness to be peeled off at different positions on the first surface of the silicon initial wafer, the composition elements and density of the silicon initial wafer, the composition elements and density of the barrier layer, and the ion implantation energy into a simulation software (such as SRIM), and simulating and calculating through the simulation software to obtain the thickness data of different positions of the barrier layer. In this embodiment, the ion implantation energy is determined based on the maximum value of the thickness to be peeled off. The ion implantation energy can be the ion implantation energy that is just equal to the ion implantation energy required to implant ions from the position with the maximum thickness to be peeled off on the first surface to the ion implantation reference plane when there is no barrier layer. At this time, the thickness of the barrier layer corresponding to the position with the maximum thickness to be peeled off is zero, and the ion implantation energy can also be greater than this value. At this time, the thickness of the barrier layer corresponding to the position with the maximum thickness to be peeled off is greater than zero.
[0055] In this embodiment, the barrier layer is obtained by photolithography of photoresist; specifically, the preparation method of the barrier layer made of photoresist material is as follows:
[0056] S41. Spray photoresist on the first surface of the initial silicon wafer until the thickness of the photoresist reaches a first thickness, where the first thickness is not less than the maximum thickness among the thicknesses at different positions of the barrier layer, to obtain a barrier material made of photoresist material adhered to the first surface of the initial silicon wafer.
[0057] S42. Based on the difference between the first thickness and the thicknesses at different positions of the barrier layer, obtain the thicknesses to be modified at different positions on the surface of the barrier material made of photoresist material.
[0058] S43. Expose the barrier material made of photoresist material by irradiating a light source downward from the surface of the barrier material made of photoresist material, so that the exposure depth reached by the irradiated light source at different positions on the surface of the barrier material made of photoresist material is consistent with the thicknesses to be modified at the corresponding positions on the surface of the barrier material made of photoresist material. The exposed part of the barrier material made of photoresist material forms a modified layer. In this embodiment, the specific implementation of S43 can be as Figure 2A shown: Based on the thicknesses to be modified at different positions on the surface of the barrier material made of photoresist material, obtain the required light intensities corresponding to the corresponding positions on the surface of the barrier material made of photoresist material; then supply the irradiated light sources with the required light intensities at different positions on the surface of the barrier material made of photoresist material. The irradiated light sources with different light intensities result in different modification rates at different positions on the surface of the barrier material made of photoresist material, so that the exposure depths at different positions on the surface of the barrier material made of photoresist material are consistent with the thicknesses to be modified at the corresponding positions on the surface of the barrier material made of photoresist material; or, as Figure 2B shown: Based on the thicknesses to be modified at different positions on the surface of the barrier material made of photoresist material, obtain the required light intensities corresponding to the corresponding positions on the surface of the barrier material made of photoresist material; then prepare a glass carrier and spray an absorbing layer on the glass carrier. The thicknesses at different positions of the absorbing layer satisfy that the light intensities passing through the glass carrier with the absorbing layer at different positions when irradiating a uniform light source are consistent with the required light intensities at the corresponding positions on the surface of the barrier material made of photoresist material; finally, use the uniform light source to irradiate the surface of the barrier material made of photoresist material through the glass carrier with the absorbing layer. The absorption degrees of light at different positions of the absorbing layer are different, and the light intensities irradiating the barrier material made of photoresist material through the glass carrier and the absorbing layer are different. The modification rates at different positions on the surface of the barrier material made of photoresist material are different, so that the exposure depths at different positions on the surface of the barrier material made of photoresist material are consistent with the thicknesses to be modified at the corresponding positions on the surface of the barrier material made of photoresist material; or, as Figure 2CAs shown, based on the thickness to be denatured at different positions on the surface of the resist material barrier, the light intensity required at the corresponding positions on the surface of the resist material barrier is obtained; then a light baffle is prepared, and the thickness of the light baffle is processed based on the light intensity required at different positions on the surface of the resist material barrier. The thicknesses at different positions of the light baffle satisfy that the light intensity transmitted through different positions of the light baffle when irradiating a uniform light source is consistent with the light intensity required at the corresponding positions on the surface of the resist material barrier; finally, a uniform light source is used to irradiate the surface of the resist material barrier through the light baffle after thickness processing. The absorption degree of light at different positions of the light baffle is different, the light intensity irradiating the resist material barrier through the light baffle is different, and the denaturation rate at different positions on the surface of the resist material barrier is different, so that the exposure depth at different positions on the surface of the resist material barrier is consistent with the thickness to be denatured at the corresponding positions on the surface of the resist material barrier.
[0059] S44. Remove the denatured layer by rinsing with a developer to obtain a resist material barrier layer.
[0060] S5. Perform helium ion implantation on the initial silicon wafer through the resist material barrier layer at the ion implantation energy determined in S4, with an implantation dose of 3×10 17 ions / cm 2 , and the implanted ions are concentrated at the ion implantation reference plane to obtain an ion-implanted silicon wafer.
[0061] S6. Perform an annealing treatment (peeling treatment) on the ion-implanted silicon wafer at 600 °C. The ion-implanted silicon wafer peels off from the ion implantation reference plane to obtain a peeled silicon wafer with a peeling surface.
[0062] S7. Polish the peeling surface of the peeled silicon wafer to obtain a silicon self-supporting film.
[0063] The TTV of the self-supporting film (silicon self-supporting film) prepared by the method of this embodiment is 15.67 nm, and the thickness uniformity is excellent.
[0064] Example 2 uses a wafer with an uneven surface to prepare a composite film including a substrate and a thin film layer with a two-layer structure
[0065] As Figure 3 shown, it includes the following steps:
[0066] S1. Prepare a lithium niobate initial wafer precursor and a silicon substrate. The lithium niobate initial wafer precursor has a surface to be processed and a second surface opposite to the surface to be processed. Perform plasma activation treatment on the second surface of the lithium niobate initial wafer precursor and the bonding surface of the silicon substrate, and bond through the activated surface to obtain a bonded body including the silicon substrate and the lithium niobate initial wafer precursor bonded to the silicon substrate. Grind and polish the surface to be processed of the lithium niobate initial wafer precursor in sequence to obtain a lithium niobate initial wafer bonded to the silicon substrate. Wherein, the surface to be processed after polishing becomes the first surface of the lithium niobate initial wafer, and the second surface becomes the second surface of the lithium niobate initial wafer opposite to the first surface.
[0067] S2. Obtain the thickness distribution data of the lithium niobate initial wafer through an optical film thickness detection device, and preset an ion implantation reference plane for the lithium niobate initial wafer. The preset ion implantation reference plane is parallel to the second surface.
[0068] S3. Based on the thickness distribution data and the ion implantation reference plane, obtain the thickness to be peeled at different positions on the first surface of the lithium niobate initial wafer. The thickness to be peeled is equal to the distance from the ion implantation reference plane to the first surface.
[0069] S4. Prepare a barrier layer made of photoresist material on the first surface of the lithium niobate initial wafer. Wherein, the thickness of the barrier layer at different positions is obtained by the following method: import the thickness to be peeled at different positions on the first surface of the lithium niobate initial wafer, the composition elements and density of the lithium niobate initial wafer, the composition elements and density of the barrier layer, and the ion implantation energy into simulation software (such as SRIM), and simulate and calculate the thickness data of the barrier layer at different positions through the simulation software. In this embodiment, the ion implantation energy is determined based on the maximum value of the thickness to be peeled. The ion implantation energy can be just equal to the ion implantation energy required to implant ions from the position on the first surface with the maximum thickness to be peeled to the ion implantation reference plane when there is no barrier layer. At this time, the thickness of the barrier layer corresponding to the position with the maximum thickness to be peeled is zero, and the ion implantation energy can also be greater than this value. At this time, the thickness of the barrier layer corresponding to the position with the maximum thickness to be peeled is greater than zero.
[0070] In this embodiment, the barrier layer is obtained by photolithography of photoresist. Specifically, the preparation method of the barrier layer made of photoresist material is as follows:
[0071] S41. Spray photoresist on the first surface of the lithium niobate initial wafer until the thickness of the photoresist reaches a first thickness. The first thickness is not less than the maximum thickness among the thicknesses of the barrier layer at different positions, to obtain a barrier material made of photoresist material attached to the first surface of the lithium niobate initial wafer.
[0072] S42. Obtain the thickness to be denatured at different positions on the surface of the resist material barrier based on the first thickness and the difference in thickness at different positions of the barrier layer.
[0073] S43. Expose the resist material barrier by irradiating a light source downward from the surface of the resist material barrier, so that the exposure depth reached by the irradiated light source at different positions on the surface of the resist material barrier is consistent with the thickness to be denatured at the corresponding positions on the surface of the resist material barrier. The part of the resist material barrier after exposure forms a denatured layer. In this embodiment, the specific implementation of S43 can be as Figure 4A shown: Based on the thickness to be denatured at different positions on the surface of the resist material barrier, obtain the required light intensity corresponding to the corresponding positions on the surface of the resist material barrier; then supply the irradiated light source with the required light intensity at different positions on the surface of the resist material barrier. The irradiated light sources with different light intensities result in different denaturation rates at different positions on the surface of the resist material barrier, so that the exposure depth at different positions on the surface of the resist material barrier is consistent with the thickness to be denatured at the corresponding positions on the surface of the resist material barrier; or, as Figure 4B shown, based on the thickness to be denatured at different positions on the surface of the resist material barrier, obtain the required light intensity corresponding to the corresponding positions on the surface of the resist material barrier; then prepare a glass carrier and spray an absorbent layer on the glass carrier. The thickness at different positions of the absorbent layer satisfies that the light intensity transmitted through the glass carrier with the absorbent layer at different positions when irradiating a uniform light source is consistent with the required light intensity at the corresponding positions on the surface of the resist material barrier; finally, use the uniform light source to irradiate the surface of the resist material barrier through the glass carrier with the absorbent layer. The absorption degree of light at different positions of the absorbent layer is different, and the light intensity transmitted through the glass carrier and the absorbent layer and irradiating the resist material barrier is different. The denaturation rates at different positions on the surface of the resist material barrier are different, so that the exposure depth at different positions on the surface of the resist material barrier is consistent with the thickness to be denatured at the corresponding positions on the surface of the resist material barrier; or, as Figure 4CAs shown, based on the thickness to be denatured at different positions on the surface of the photoresist material barrier, the light intensity required at the corresponding positions on the surface of the photoresist material barrier is obtained; then a light baffle is prepared, and the thickness of the light baffle is processed based on the light intensity required at different positions on the surface of the photoresist material barrier. The thicknesses at different positions of the light baffle satisfy that the light intensity transmitted through different positions of the light baffle when irradiating a uniform light source is consistent with the light intensity required at the corresponding positions on the surface of the photoresist material barrier; finally, the surface of the photoresist material barrier is irradiated with a uniform light source through the light baffle after thickness processing. The absorption degree of light at different positions of the light baffle is different, the light intensity irradiating the photoresist material barrier through the light baffle is different, and the denaturation rates at different positions on the surface of the photoresist material barrier are different, so that the exposure depths at different positions on the surface of the photoresist material barrier are consistent with the thicknesses to be denatured at the corresponding positions on the surface of the photoresist material barrier.
[0074] S44. Remove the denatured layer by rinsing with a developer to obtain a photoresist material barrier layer.
[0075] S5. Perform hydrogen ion implantation on the lithium niobate initial wafer through the photoresist material barrier layer with the ion implantation energy determined in S4, and the implantation dose is 1×10 16 ions / cm 2 , and the implanted ions are concentrated at the ion implantation reference plane to obtain an ion-implanted lithium niobate wafer.
[0076] S6. Perform an annealing treatment (peeling treatment) on the ion-implanted lithium niobate wafer at 300 °C. The ion-implanted lithium niobate wafer peels off from the ion implantation reference plane to obtain a peeled lithium niobate wafer with a peeling surface.
[0077] S7. Polish the peeling surface of the peeled lithium niobate wafer to obtain a composite film including a silicon substrate and a lithium niobate thin film layer.
[0078] The TTV of the lithium niobate thin film layer of the composite film (silicon substrate / lithium niobate thin film layer composite film) prepared by the method of this embodiment is 25.23 nm, and the thickness uniformity is excellent.
[0079] Example 3 uses a wafer with an uneven surface to prepare a composite film including a three-layer structure of a substrate, an isolation layer, and a thin film layer
[0080] The preparation process is as Figure 5 shown. The difference between this embodiment and Example 2 is that:
[0081] S1: Prepare a lithium niobate initial wafer precursor and a silicon substrate. The lithium niobate initial wafer precursor has a surface to be processed and a second surface opposite to the surface to be processed. Thermally oxidize the bonding surface of the silicon substrate downward to oxidize a part of the silicon substrate to form a silicon dioxide isolation layer. Perform plasma activation treatment on the second surface of the lithium niobate initial wafer precursor and the exposed surface of the silicon dioxide isolation layer, and bond through the activated surface to obtain a bonded body including a silicon substrate, a silicon dioxide isolation layer, and a lithium niobate initial wafer precursor bonded on the silicon dioxide isolation layer from bottom to top. Grind and polish the surface to be processed of the lithium niobate initial wafer precursor in sequence to obtain a lithium niobate initial wafer bonded on the silicon dioxide isolation layer. Among them, the surface to be processed after polishing becomes the first surface of the lithium niobate initial wafer, and the second surface becomes the second surface of the lithium niobate initial wafer opposite to the first surface.
[0082] The TTV of the lithium niobate thin film layer of the composite thin film (silicon substrate / silicon dioxide isolation layer / lithium niobate thin film layer composite thin film) prepared by the method of this embodiment is 43.56 nm, and the thickness uniformity is excellent.
[0083] Example 4 uses a wafer with an uneven surface to prepare a composite thin film including four layers of a substrate, a trap layer, an isolation layer, and a thin film layer
[0084] The preparation process is as Figure 6 shown. The difference between this embodiment and Example 2 is that:
[0085] S1: Prepare a lithium niobate initial wafer precursor and a silicon substrate. The lithium niobate initial wafer precursor has a surface to be processed and a second surface opposite to the surface to be processed. Deposit a polysilicon trap layer on the bonding surface of the silicon substrate, deposit a silicon dioxide isolation layer on the upper surface of the polysilicon trap layer, perform plasma activation treatment on the second surface of the lithium niobate initial wafer precursor and the exposed surface of the silicon dioxide isolation layer, and bond through the activated surface to obtain a bonded body including a silicon substrate, a polysilicon trap layer, a silicon dioxide isolation layer, and a lithium niobate initial wafer precursor bonded on the silicon dioxide isolation layer from bottom to top. Grind and polish the surface to be processed of the lithium niobate initial wafer precursor in sequence to obtain a lithium niobate initial wafer bonded on the silicon dioxide isolation layer. Among them, the surface to be processed after polishing becomes the first surface of the lithium niobate initial wafer, and the second surface becomes the second surface of the lithium niobate initial wafer opposite to the first surface.
[0086] The TTV of the lithium niobate thin film layer of the composite thin film (silicon substrate / polysilicon trap layer / silicon dioxide isolation layer / lithium niobate thin film layer composite thin film) prepared by the method of this embodiment is 46.43 nm, and the thickness uniformity is excellent.
[0087] The above specific embodiments have further elaborated in detail the object, technical solution and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made on the basis of the technical solution of the present invention shall be included within the protection scope of the present invention.
Claims
1. A method for preparing a thin film applicable to a wafer with an uneven surface, characterized in that, Including the following steps: Prepare an initial wafer, the initial wafer having opposite first and second surfaces; Obtain thickness distribution data of the initial wafer and preset an ion implantation reference plane for the initial wafer; Based on the thickness distribution data and the ion implantation reference plane, obtain the thickness to be peeled at different positions on the first surface of the initial wafer; Based on the maximum value of the thickness to be peeled, determine the ion implantation energy; Prepare a barrier layer on the first surface of the initial wafer; Perform ion implantation on the initial wafer through the barrier layer with the ion implantation energy, implanting ions to the ion implantation reference plane to obtain an ion-implanted wafer; Perform a peeling process on the ion-implanted wafer from the ion implantation reference plane to obtain a peeled wafer having a peeled surface; Perform a polishing process on the peeled surface of the peeled wafer to obtain the thin film.
2. The method for preparing a thin film applicable to a wafer with an uneven surface according to claim 1, wherein The ion implantation reference plane is parallel to the second surface.
3. The method for preparing a thin film applicable to a wafer with uneven surface according to claim 1, wherein The thickness to be peeled is the distance from the ion implantation reference plane to the first surface.
4. The method for preparing a thin film applicable to a wafer with an uneven surface according to claim 1, wherein The ion implantation energy is greater than or equal to the ion implantation energy required to implant ions from the position on the first surface having the maximum thickness to be peeled to the ion implantation reference plane.
5. The method for preparing a thin film applicable to a wafer with an uneven surface according to claim 1, characterized in that, The thicknesses at different positions of the barrier layer are obtained based on the thicknesses to be peeled at different positions on the first surface of the initial wafer, the composition elements and density of the initial wafer, the composition elements and density of the barrier layer, and the ion implantation energy.
6. The method for preparing a thin film applicable to a wafer with uneven surface according to claim 1, wherein The material of the barrier layer includes photoresist, and the barrier layer is obtained by photolithography of the photoresist.
7. The method for preparing a thin film applicable to a wafer with an uneven surface according to claim 6, characterized in that, The specific method for preparing the barrier layer is as follows: Spray photoresist on the first surface of the initial wafer until the thickness of the photoresist reaches a first thickness; Based on the difference between the first thickness and the thicknesses at different positions of the barrier layer, obtain the thicknesses to be denatured at different positions on the surface of the photoresist; Perform an exposure process on the photoresist by irradiating a light source downward from the surface of the photoresist, and the portion of the photoresist that has been exposed forms a denatured layer; wherein, the exposure depth reached by the light source irradiated on different positions on the surface of the photoresist is consistent with the thickness to be denatured at the corresponding positions on the surface of the photoresist; Remove the denatured layer to obtain the barrier layer.
8. The method for preparing a thin film applicable to a wafer with an uneven surface according to claim 1, characterized in that, The material of the initial wafer is selected from one or more of lithium niobate, lithium tantalate, quartz, silicon carbide, silicon, or silicon nitride.
9. The method for preparing a thin film applicable to a wafer with an uneven surface according to claim 1, wherein The initial wafer is obtained by preprocessing an initial wafer precursor; wherein, the initial wafer precursor has an opposite surface to be processed and a second surface, and the preprocessing includes sequentially performing grinding and thinning and polishing on the surface to be processed of the initial wafer precursor, and the surface to be processed after polishing becomes the first surface of the initial wafer, and the second surface becomes the second surface of the initial wafer.
10. The method for preparing a thin film applicable to a wafer with uneven surface according to claim 9, characterized in that, Before the preprocessing, a substrate is pre-bonded to the second surface of the initial wafer precursor.
11. The method for preparing a thin film applicable to a wafer with an uneven surface according to claim 10, wherein, Before pre-bonding the substrate to the second surface of the initial wafer precursor, first prepare an isolation layer on the surface to be bonded of the substrate and / or the second surface of the initial wafer precursor, and then bond the substrate and the initial wafer precursor via the isolation layer.
12. The method for preparing a thin film applicable to a wafer with an uneven surface according to claim 11, wherein, Before preparing the isolation layer, first prepare a trap layer on the surface to be bonded of the substrate.
13. The method for preparing a thin film applicable to a wafer with uneven surface according to claim 12, wherein, The material of the initial wafer precursor is selected from one or more of lithium niobate, lithium tantalate, quartz, silicon carbide, silicon or silicon nitride; the material of the substrate is selected from one or more of lithium niobate, lithium tantalate, quartz, silicon, sapphire, silicon carbide, silicon nitride, gallium arsenide or indium phosphide; the material of the isolation layer is selected from one or several of silicon dioxide, silicon nitride, silicon oxynitride, aluminum oxide or aluminum nitride; the material of the trap layer is selected from polycrystalline silicon or amorphous silicon.
14. The method for preparing a thin film applicable to a wafer with uneven surface according to claim 1, wherein, The implanted ions for the ion implantation are one or more of hydrogen ions, helium ions, nitrogen ions, oxygen ions or argon ions, and the implantation dose is 1×10 16 ions / cm 2 ~3×10 17 ions / cm 2 ; and / or, the temperature during the stripping treatment is 100 to 600 °C.
15. A thin film prepared by the thin film preparation method applicable to wafers with uneven surfaces according to any one of claims 1-14.