Thin film and preparation method thereof
By obtaining thickness distribution data and setting preset ion implantation reference surfaces during the thinning process of thin film wafers, adjusting the ion implantation energy for thin film preparation, the problems of poor thickness uniformity and lattice damage in the prior art are solved, and the preparation of high-quality films is achieved.
Patent Information
- Application Number
- CN202510122437.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-26
- Publication Date
- 2025-05-02
AI Technical Summary
It is difficult to prepare high-quality films with controllable thickness and excellent thickness uniformity in the prior art, and lattice damage is easily introduced in traditional methods.
By providing a thin film wafer and thinning along its first surface, thickness distribution data is obtained, preset ion implantation reference surface is set, ion implantation energy is adjusted according to the thickness to be peeled at different locations, ion implantation and peeling treatment are performed, and film with excellent thickness uniformity is finally obtained by polishing.
The high-quality film preparation with controllable thickness and excellent thickness uniformity is achieved, which avoids lattice damage, simplifies the process flow and improves the preparation efficiency.
Smart Images
Figure CN119920686A_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the field of semiconductor technology, and specifically relates to a thin film and a method for preparing the same. Background Art
[0002] Thin film materials are becoming increasingly important materials in the semiconductor industry because they can meet the requirements of electronic components to develop in the direction of miniaturization, low power consumption and high performance. Thin film materials usually include self-supporting films (self-supporting films refer to thin film materials that can maintain their own shape and properties without relying on the support of a macroscopic solid substrate) and composite films. Self-supporting films are films of specific thickness customized by users from manufacturers. Manufacturers cut them from wafer ingots according to user requirements and grind and polish them. When users have other requirements for the thickness of self-supporting films, they can only be re-customized from manufacturers due to the lack of independent processing technology. Composite films usually include substrates and film layers. Existing composite film preparation methods usually include grinding and intelligent peeling. In the grinding method, the substrate and the film wafer are first bonded, and the side of the film wafer facing away from the substrate is ground and thinned to obtain a film layer. The film layer obtained by the grinding method has poor thickness uniformity (surface fluctuations are 0.8μm and above), and the composite film based on this deteriorates device performance when used in devices. The smart stripping method first implants ions into a thin film wafer to form a thin film layer, an implantation layer, and a residual material layer. The thin film wafer is bonded to a substrate through the thin film layer. After annealing and heat treatment, the implanted ions in the implantation layer become gas molecules or atoms and produce tiny bubbles. When the bubbles gather and connect into one piece, the residual material layer is peeled off from the implantation layer, and the thin film layer remains on the substrate to form a composite film. The thickness uniformity of the composite film prepared by the smart stripping method is better than that of the grinding method, but the lattice damage introduced by ion implantation in the thin film layer is difficult to eliminate, and the ion implantation energy commonly used on the market is limited, and only thin film layers (2μm and below) can be prepared. Therefore, there is an urgent need in this field for a preparation method that can prepare high-quality thin films with controllable thickness, excellent thickness uniformity, and no lattice damage. Summary of the invention
[0003] Technical issues
[0004] The object of the present invention is to provide a method for preparing a high-quality thin film with controllable thickness, excellent thickness uniformity and no lattice damage, and a thin film prepared by the method.
[0005] Technical Solution
[0006] The first aspect of the present invention provides a method for preparing a thin film, comprising the following steps: providing a thin film wafer, the thin film wafer having a first surface and a second surface relative to each other; thinning the thin film wafer along the first surface, the thin film wafer having a thinned surface and a second surface relative to each other; acquiring thickness distribution data of the thin film wafer after thinning, and setting a preset ion implantation reference plane for the thin film wafer after thinning; obtaining the thickness to be peeled off at different positions corresponding to the thinning surface based on the preset ion implantation reference plane and the thickness distribution data; performing ion implantation from the thinning surface to the thin film wafer after thinning, and implanting ions into the preset ion implantation reference plane, the ion implantation energy of the ion implantation corresponding to different positions of the thinning surface is determined based on the thickness to be peeled off at different positions of the thinning surface; peeling the thin film wafer after ion implantation from the preset ion implantation reference plane, the thin film wafer having a thinned surface and a second surface relative to each other; polishing the peeling surface to obtain the thin film. The preparation method of the present invention can prepare a thin film product with excellent thickness uniformity. This is because although grinding or wet etching can quickly thin the film, the surface state of the thin film wafer after thinning is poor, the surface undulation is large, and the thickness difference at different positions is large. Conventional ion implantation methods are difficult to achieve peeling on the same reference plane. The present invention obtains the thickness to be peeled at different positions corresponding to the thinning surface of the thin film wafer after thinning through the thickness distribution data of the thin film wafer after thinning and the preset ion implantation reference plane, and then adjusts the ion implantation energy at different positions of the thinning surface of the thin film wafer after thinning based on the thickness to be peeled at different positions, so that the implanted ions at different positions all reach the preset ion implantation reference plane, and the peeling is triggered at the preset ion implantation reference plane, so that the thickness uniformity of the film after peeling is more excellent. At the same time, the present invention performs ion implantation from the thinning surface, avoiding the lattice defects introduced when the thin film layer is prepared by ion implantation from the bonding surface of the thin film wafer when the traditional preparation of composite thin film products is carried out, thereby avoiding the heat treatment step to eliminate the defects and avoiding high temperature annealing, so that the thin film layer has no ion implantation lattice defects and has better performance. In addition, the present invention prepares a thin film by grinding and thinning or wet etching combined with ion implantation. The thinning is combined with ion implantation to control the thickness, and is suitable for preparing thin film products of various thicknesses, and the product thickness is controllable. It is worth mentioning that the preparation method of the present invention improves the thinning efficiency by grinding and thinning the thin film wafer or wet etching; the thickness uniformity can be improved by ion implantation, and the method is simple; by avoiding the heat treatment step to eliminate defects, the process is simplified, and the annealing and stripping steps can be carried out in batches to improve efficiency, thereby shortening the preparation cycle of the thin film product of the present invention.
[0007] In some embodiments, the thinning method includes grinding thinning or wet etching.
[0008] In some embodiments, the preset ion implantation reference plane is parallel to the second surface. When the preset ion implantation reference plane is parallel to the second surface, the thickness uniformity is better.
[0009] In some embodiments, the target thickness of the thin film wafer during thinning is H0, the target product thickness of the film is H, the polishing thickness during polishing is H1, and the distance from the preset ion implantation reference plane to the highest point of the thinning surface is the maximum thickness to be peeled off H2; wherein, H0=H+H1+H2. The present invention sets the target thickness of the thin film wafer during thinning to H0, the target product thickness of the film to H, the polishing thickness during polishing to H1, the distance from the preset ion implantation reference plane to the highest point of the thinning surface to the maximum thickness to be peeled off H2, and the design of H0=H+H1+H2 can regulate the thinning thickness, peeling thickness and polishing thickness, minimize the thickness that needs to be peeled off by ion implantation, so that the ion implantation energy that can be provided by the ion implantation equipment commonly used in the market can realize the implanted ions reaching the preset ion implantation reference plane and peeling at the preset ion implantation reference plane, avoiding the cost increase and energy loss problems caused by replacing the ion implantation equipment that can provide high ion implantation energy; and can make the actual thickness of the film obtained after peeling and polishing more consistent with the product target thickness, thereby improving the thickness accuracy.
[0010] In some embodiments, the height of the preset ion injection reference plane is lower than the height of the highest point of the thinning surface, and the height of the preset ion injection reference plane is not lower than the height of the lowest point of the thinning surface. When the height of the preset ion injection reference plane is lower than the height of the highest point of the thinning surface and higher than the height of the lowest point of the thinning surface, the thickness peeled off by ion injection is smaller, and the thickness uniformity can be improved regardless of the degree to which the peeling surface is polished after the peeling treatment; when the height of the preset ion injection reference plane is equal to the height of the lowest point of the thinning surface, the peeling can completely remove the surface undulations introduced by thinning, and the effect of improving the thickness uniformity is better. Since the surface undulations introduced during thinning are mostly between 0.8 and 2 μm, the peeling thickness meets the injection depth that can be achieved by conventional ion injection equipment, and there is no need to introduce ion injection equipment that can provide high ion injection energy. In addition, the height of the preset ion injection reference plane can also be lower than the height of the lowest point of the thinning surface, which can also greatly improve the thickness uniformity.
[0011] In some embodiments, the sum of the distance from the preset ion implantation reference plane to the highest point of the thinned surface and the polishing thickness is equal to the height difference between the highest point of the thinned surface and the lowest point of the thinned surface. At this time, the stripping and polishing just completely remove the surface undulations introduced by thinning, which can greatly improve the thickness uniformity, avoid the waste of materials caused by excessive removal of the thin film wafer, and better control the thickness of the actual thin film product.
[0012] In some embodiments, the specific method for obtaining the thickness distribution data of the thin film wafer after thinning is not limited, and any method that can obtain the thickness distribution data thereof is acceptable. For example, the thickness distribution data defined by the thinning surface and the second surface of the thin film wafer after thinning can be obtained by an optical film thickness detection device or a probe film thickness measuring instrument.
[0013] In some embodiments, the specific method of determining the ion implantation energy corresponding to different positions of the thinning surface based on the thickness to be peeled off at different positions of the thinning surface is not limited, and any achievable method can be adopted. For example, it can be performed through various simulation software, which fits the fitting curve of ion implantation energy and implantation depth according to its ion implantation energy and implantation depth data, and then the ion implantation energy at different positions of the thinning surface can be obtained on the fitting curve based on the thickness to be peeled off at different positions of the thinning surface obtained by the present invention.
[0014] In some embodiments, the material of the thin film wafer is one or more of lithium niobate, lithium tantalate, quartz, silicon carbide, silicon or silicon nitride. The material of the thin film wafer of the present invention is not limited thereto.
[0015] In some embodiments, after thinning the thin film wafer, before obtaining the thickness distribution data of the thin film wafer after thinning, the thinned surface is polished. The polishing after thinning in the embodiment of the present invention makes the adjacent position of the thinned surface relatively smooth, and the thickness distribution data of the thin film wafer after thinning can be obtained more easily.
[0016] In some embodiments, the implanted ions are one or more of hydrogen ions, helium ions, nitrogen ions, oxygen ions or argon ions, preferably hydrogen ions or helium ions, and the implantation dose is 1×10 16 ions / cm 2 ~3×10 17 ions / cm 2 .
[0017] In some embodiments, the stripping treatment is an annealing treatment, and the temperature during the stripping treatment is 100-600°C.
[0018] In some embodiments, the film is a self-supporting film. The preparation method of the present invention is applicable to self-supporting films, and users can independently process the self-supporting films of specific thickness purchased from manufacturers according to actual thickness requirements to prepare high-quality self-supporting films of the required thickness with excellent thickness uniformity and no lattice damage.
[0019] In some embodiments, the film is a composite film; after providing the film wafer and before thinning the film wafer, the following steps are further included: providing a substrate layer, and bonding the surface to be bonded of the substrate layer and the second surface of the film wafer. The preparation method of the present invention is suitable for the preparation of a composite film, and can obtain a high-quality composite film with a desired thickness, excellent thickness uniformity, and no lattice damage.
[0020] In some embodiments, before bonding the surface to be bonded of the substrate layer and the second surface of the thin film wafer, the surface to be bonded of the substrate layer and the second surface of the thin film wafer are activated. Activation can achieve ultra-clean cleaning of the surface of the object, remove organic contamination and oxides on the surface, activate the surface, and enhance bonding ability.
[0021] In some embodiments, the activation treatment is a plasma activation treatment.
[0022] In some embodiments, the material of the substrate layer is selected from one or more of lithium niobate, lithium tantalate, quartz, silicon, sapphire, silicon carbide, silicon nitride, gallium arsenide or indium phosphide. The substrate layer material of the present invention is not limited thereto.
[0023] In some embodiments, before bonding the surface to be bonded of the substrate layer and the second surface of the thin film wafer, an isolation layer is first prepared on the surface to be bonded of the substrate layer and / or the second surface of the thin film wafer, and then the substrate layer and the thin film wafer are bonded via the isolation layer.
[0024] In some embodiments, the isolation layer is prepared by deposition.
[0025] In some embodiments, the deposition method is one of chemical vapor deposition, physical vapor deposition or magnetron sputtering.
[0026] In some embodiments, when the material of the substrate layer is silicon, the isolation layer is prepared by thermal oxidation, and the specific steps are: thermal oxidation is performed from the to-be-bonded surface of the substrate layer to the inside of the substrate layer.
[0027] In some embodiments, after preparing the isolation layer, an activation treatment is performed on a side of the isolation layer facing away from the substrate layer and a second surface of the thin film wafer, and then the substrate layer and the thin film wafer are bonded via the isolation layer.
[0028] In some embodiments, the isolation layer is made of one or more of silicon dioxide, silicon nitride, aluminum oxide or aluminum nitride.
[0029] In some embodiments, before preparing the isolation layer, a trap layer is first prepared on the surface to be bonded to the substrate layer.
[0030] In some embodiments, the trap layer is made of polysilicon or amorphous silicon.
[0031] In some embodiments, the trap layer is prepared by deposition.
[0032] A second aspect of the present invention provides a thin film prepared by any one of the preparation methods described above, with a TTV of 10 nm to 60 nm and excellent thickness uniformity. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 This is a flow chart for preparing the self-supporting film product of Example 1;
[0034] Figure 2 It is a schematic diagram of a thin film wafer after thinning of Example 1, which is marked with a thinning target thickness H0, a product target thickness H, a polishing thickness H1, and a maximum thickness to be peeled off H2;
[0035] Figure 3 is a fitting curve of ion implantation energy and implantation depth when He ions are implanted into lithium niobate in Example 1;
[0036] Figure 4 This is a flow chart for preparing the composite film product of Example 2;
[0037] Figure 5 It is a schematic diagram of a bonding body of a thin film wafer and a substrate after thinning, which is marked with a thinning target thickness H0, a product target thickness H, a polishing thickness H1, and a maximum thickness to be peeled off H2 in Example 2;
[0038] Figure 6 This is a flow chart for preparing the composite film product of Example 3;
[0039] Figure 7 It is a schematic diagram of a bonding body of a thinned thin film wafer, an isolation layer and a substrate marked with a thinning target thickness H0, a product target thickness H, a polishing thickness H1 and a maximum thickness to be peeled off H2 in Example 3;
[0040] Figure 8 This is a flow chart for preparing the composite film product of Example 4;
[0041] Fig. 9 It is a schematic diagram of a bonding body of a thinned thin film wafer, an isolation layer, a trap layer and a substrate, marked with a thinning target thickness H0, a product target thickness H, a polishing thickness H1 and a maximum thickness to be peeled off H2 according to Example 4;
[0042] Fig.10 This is a fitting curve of ion implantation energy and implantation depth when H ions are implanted into lithium tantalate in Example 4. DETAILED DESCRIPTION
[0043] To facilitate the technical solution of the application, the following first provides a general description and definition of the terms and expressions involved in the application.
[0044] The terms "comprises", "includes" or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a list of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus. In the absence of more restrictions, an element defined by the phrase "comprises a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus that includes the element.
[0045] TTV (Total Thickness Variation) is the difference between the maximum thickness and the minimum thickness of the film, and is an important indicator used to measure thickness uniformity. When the film is a self-supporting film, TTV is the difference between the maximum thickness and the minimum thickness of the self-supporting film product; when the film is a composite film, TTV is the difference between the maximum thickness and the minimum thickness of the film layer in the composite film product.
[0046] In each group of comparative experiments provided in this application, unless otherwise specified, except for the differences indicated in each group, other experimental conditions, materials, etc. are kept consistent to ensure comparability.
[0047] Unless otherwise specified, the reagents and instruments used in the embodiments of the present invention can be purchased from the market.
[0048] The following is a further description of a film and a preparation method thereof provided in the present application.
[0049] Example 1 Preparation of high-quality self-supporting film with controllable thickness
[0050] like Figure 1 and Figure 2 As shown, the following steps are included:
[0051] A lithium niobate thin film wafer is prepared; the lithium niobate thin film wafer has a first surface (an upper surface of the lithium niobate thin film wafer) and a second surface (a lower surface of the lithium niobate thin film wafer) that are opposite to each other;
[0052] S1, grinding and thinning: grinding and thinning the lithium niobate thin film wafer along the first surface with the target thinning thickness H0 as the target; wherein the thin film wafer after grinding and thinning has a relative thinning surface (corresponding to the first surface before thinning) and a second surface; after thinning, the thinning surface can be polished;
[0053] S2, obtaining the thickness to be peeled off at different positions corresponding to the thinning surface: obtaining the thickness distribution data of the thinned lithium niobate thin film wafer by a probe-type film thickness measuring instrument; setting a preset ion implantation reference plane for the thinned lithium niobate thin film wafer, preferably making the preset ion implantation reference plane parallel to the second surface; based on the thickness distribution data and the preset ion implantation reference plane, obtaining the thickness to be peeled off at different positions corresponding to the thinning surface; in this step, there is no limitation on the order of obtaining the thickness distribution data and setting the preset ion implantation reference plane, and the thickness distribution data can be obtained first and then the preset ion implantation reference plane can be set, or the preset ion implantation reference plane can be set first and then the thickness distribution data can be obtained;
[0054] S3, ion implantation: Helium ion implantation is performed on the thinned lithium niobate thin film wafer at a rate of 3×10 17 ions / cm 2 The helium ions are implanted into the preset ion implantation reference plane with an implantation dose; wherein, before the ion implantation, the ion implantation energy corresponding to the ion implantation at different positions of the thinning surface is determined based on the thickness to be peeled off at different positions of the thinning surface. The specific method is not limited and can be performed by any achievable existing technology, such as by various simulation software, such as combining the ion implantation energy and implantation depth data of the SRIM software to fit the fitting curve of the ion implantation energy and the implantation depth (such as Figure 3 As shown), based on the fitting curve, find the ion implantation energy corresponding to the thickness to be peeled off at different positions of the thinned lithium niobate thin film wafer, and perform ion implantation based on the obtained ion implantation energy;
[0055] S4, stripping treatment: performing a stripping treatment (i.e., annealing treatment) at 100° C. on the ion-implanted lithium niobate thin film wafer, the ion-implanted lithium niobate thin film wafer is stripped from a preset ion implantation reference plane, and the portion of the lithium niobate thin film wafer from the preset ion implantation reference plane to the second surface is used as the stripped lithium niobate thin film wafer for subsequent further processing; the stripped lithium niobate thin film wafer has a relative stripping surface (corresponding to the thinning surface before stripping) and a second surface;
[0056] S5. Polishing: polishing the peeled surface of the lithium niobate thin film wafer to obtain a lithium niobate self-supporting thin film.
[0057] In this embodiment, the target product thickness of the lithium niobate self-supporting film is H, the polishing thickness during polishing is H1, and the distance from the preset ion implantation reference plane to the highest point of the thinning surface is the maximum thickness to be peeled off H2; preferably, H0=H+H1+H2.
[0058] In this embodiment, the height of the preset ion implantation reference surface is preferably lower than the height of the lowest point of the thinning surface.
[0059] The high-quality lithium niobate self-supporting film with controllable thickness prepared by the preparation method of this embodiment has a TTV of 10.13 nm.
[0060] Example 2 Preparation of high-quality composite film with controllable thickness
[0061] like Figure 4 and Figure 5 As shown, the following steps are included:
[0062] A silicon carbide substrate and a lithium niobate thin film wafer are prepared; the lithium niobate thin film wafer has a first surface (an upper surface of the lithium niobate thin film wafer) and a second surface (a lower surface of the lithium niobate thin film wafer) that are opposite to each other;
[0063] S1, bonding the thin film wafer and the substrate layer: performing plasma surface activation treatment on the surface to be bonded of the silicon carbide substrate and the second surface of the lithium niobate thin film wafer, and then bonding the surface to be bonded of the activated silicon carbide substrate and the second surface of the lithium niobate thin film wafer to form a bonded body including the thin film wafer and the substrate layer in order from top to bottom;
[0064] S2, grinding and thinning: grinding and thinning the lithium niobate thin film wafer along the first surface with the target thinning thickness H0 as the target; wherein the thin film wafer after grinding and thinning has a relative thinning surface (corresponding to the first surface before thinning) and a second surface; after thinning, the thinning surface can be polished;
[0065] S3, obtaining the thickness to be peeled off at different positions corresponding to the thinning surface: obtaining the thickness distribution data of the thinned lithium niobate thin film wafer by a probe-type film thickness measuring instrument; setting a preset ion implantation reference plane for the thinned lithium niobate thin film wafer, preferably making the preset ion implantation reference plane parallel to the second surface of the lithium niobate thin film wafer, and the height of the preset ion implantation reference plane is lower than the height of the highest point of the thinning surface, and higher than the height of the lowest point of the thinning surface; based on the thickness distribution data and the preset ion implantation reference plane, obtaining the thickness to be peeled off at different positions corresponding to the thinning surface;
[0066] S4, ion implantation: hydrogen ion implantation is performed on the thinned lithium niobate thin film wafer at a rate of 1×10 16 ions / cm 2The hydrogen ions are implanted into the preset ion implantation reference plane with an implantation dose; wherein, before the ion implantation, the ion implantation energy corresponding to the ion implantation at different positions of the thinning surface is determined based on the thickness to be peeled off at different positions of the thinning surface. The specific method is not limited, and any feasible existing technology can be used for the method, such as by various simulation software, such as fitting a fitting curve of the ion implantation energy and the implantation depth in combination with the ion implantation energy and the implantation depth data of the SRIM software, and finding the ion implantation energy corresponding to the thickness to be peeled off at different positions of the thinned lithium niobate thin film wafer based on the fitting curve, and performing ion implantation based on the obtained ion implantation energy;
[0067] S5, stripping treatment: the lithium niobate thin film wafer after ion implantation is subjected to a stripping treatment (i.e., annealing treatment) at 600° C. from a preset ion implantation reference plane, the lithium niobate thin film wafer after ion implantation is stripped from the preset ion implantation reference plane, and the portion of the lithium niobate thin film wafer from the preset ion implantation reference plane to the second surface is retained on the silicon carbide substrate as the lithium niobate thin film wafer after stripping; the lithium niobate thin film wafer after stripping has a relative stripping surface (corresponding to the thinning surface before stripping) and a second surface;
[0068] S6. Polishing: polishing the peeled surface of the peeled lithium niobate thin film wafer to obtain a composite thin film including a silicon carbide substrate layer and a lithium niobate thin film layer bonded to the silicon carbide substrate layer.
[0069] In this embodiment, the product target thickness of the composite film is H (for the composite film, its product target thickness H represents the target thickness of the lithium niobate film layer in the composite film), the polishing thickness during polishing is H1, and the distance from the preset ion implantation reference plane to the highest point of the thinning surface is the maximum thickness to be peeled off H2; preferably, H0=H+H1+H2, so that the actual thickness of the film layer in the obtained composite film is more consistent with the product target thickness H, thereby improving the thickness accuracy.
[0070] The high-quality composite film with controllable thickness obtained by the preparation method of this embodiment includes a silicon carbide substrate layer and a lithium niobate film layer located above the silicon carbide substrate layer, and the TTV of the film layer is 26.05 nm.
[0071] Example 3 Preparation of high-quality composite film with controllable thickness
[0072] like Figure 6 and Figure 7 As shown, the following steps are included:
[0073] A silicon substrate and a lithium tantalate thin film wafer are prepared; the lithium tantalate thin film wafer has a first surface (an upper surface of the lithium tantalate thin film wafer) and a second surface (a lower surface of the lithium tantalate thin film wafer) that are opposite to each other;
[0074] S1. preparing an isolation layer: thermally oxidizing the silicon substrate from the surface to be bonded to the inside of the silicon substrate to obtain a silicon dioxide isolation layer;
[0075] S2, bonding the thin film wafer and the substrate: performing plasma surface activation treatment on the side of the silicon dioxide isolation layer facing away from the silicon substrate and the second surface of the lithium tantalate thin film wafer, and then bonding the side of the activated silicon dioxide isolation layer facing away from the silicon substrate and the second surface of the lithium tantalate thin film wafer to form a bonded body including the lithium tantalate thin film wafer, the silicon dioxide isolation layer and the silicon substrate layer from top to bottom;
[0076] S3, grinding and thinning: grinding and thinning the lithium tantalate thin film wafer along the first surface with the target thinning thickness H0 as the target; wherein the thin film wafer after grinding and thinning has a relative thinning surface (corresponding to the first surface before thinning) and a second surface; after thinning, the thinning surface can be polished;
[0077] S4, obtaining the thickness to be peeled off at different positions corresponding to the thinning surface: obtaining the thickness distribution data of the thinned lithium tantalate thin film wafer by an optical film thickness detection device; setting a preset ion injection reference plane for the thinned lithium tantalate thin film wafer, preferably making the preset ion injection reference plane parallel to the second surface of the lithium tantalate thin film wafer, and the height of the preset ion injection reference plane is lower than the height of the highest point of the thinning surface, and is equal to the height of the lowest point of the thinning surface; based on the thickness distribution data and the preset ion injection reference plane, obtaining the thickness to be peeled off at different positions corresponding to the thinning surface;
[0078] S5, ion implantation: Helium ion implantation is performed on the thinned lithium tantalate thin film wafer with a density of 1×10 17 ions / cm 2 The helium ions are implanted into the preset ion implantation reference plane with an implantation dose; wherein, before the ion implantation, the ion implantation energy corresponding to the ion implantation at different positions of the thinning surface is determined based on the thickness to be peeled off at different positions of the thinning surface. The specific method is not limited, and any feasible existing technology can be used for the method, such as by various simulation software, such as fitting a fitting curve of the ion implantation energy and the implantation depth in combination with the ion implantation energy and the implantation depth data of the SRIM software, and finding the ion implantation energy corresponding to the thickness to be peeled off at different positions of the thinned lithium tantalate thin film wafer based on the fitting curve, and performing ion implantation based on the obtained ion implantation energy;
[0079] S6, stripping treatment: performing a stripping treatment (i.e., annealing treatment) at 200° C. on the lithium tantalate thin film wafer after ion implantation, the lithium tantalate thin film wafer after ion implantation is stripped from a preset ion implantation reference plane, and a portion of the lithium tantalate thin film wafer from the preset ion implantation reference plane to the second surface is retained on the silicon dioxide isolation layer as the lithium tantalate thin film wafer after stripping; the lithium tantalate thin film wafer after stripping has a relative stripping surface (corresponding to the thinning surface before stripping) and a second surface;
[0080] S7, polishing treatment: polishing the peeled surface of the lithium tantalate thin film wafer after peeling to obtain a composite thin film including a silicon substrate layer, a silicon dioxide isolation layer and a lithium tantalate thin film layer from bottom to top.
[0081] In this embodiment, the product target thickness of the composite film is H (for the composite film, its product target thickness H represents the target thickness of the lithium tantalate thin film layer in the composite film), the polishing thickness during polishing is H1, and the distance from the preset ion injection reference plane to the highest point of the thinning surface is the maximum thickness to be peeled off H2; preferably, H0=H+H1+H2, so that the actual thickness of the thin film layer in the obtained composite film can be more consistent with the product target thickness H, thereby improving the thickness accuracy.
[0082] The high-quality composite film with controllable thickness obtained by the preparation method of this embodiment includes a silicon substrate layer, a silicon dioxide isolation layer and a lithium tantalate film layer stacked from bottom to top, and the TTV of the film layer is 43.63 nm.
[0083] Example 4 Preparation of high-quality composite film with controllable thickness
[0084] like Figure 8 and Fig. 9 As shown, the following steps are included:
[0085] A silicon substrate and a lithium tantalate thin film wafer are prepared; the lithium tantalate thin film wafer has a first surface (an upper surface of the lithium tantalate thin film wafer) and a second surface (a lower surface of the lithium tantalate thin film wafer) that are opposite to each other;
[0086] S1, depositing a trap layer and an isolation layer: depositing a polysilicon trap layer on the surface to be bonded with the silicon substrate, and depositing a silicon dioxide isolation layer on the polysilicon trap layer;
[0087] S2, bonding the thin film wafer and the substrate: performing plasma surface activation treatment on the side of the silicon dioxide isolation layer facing away from the silicon substrate and the second surface of the lithium tantalate thin film wafer, and then bonding the side of the activated silicon dioxide isolation layer facing away from the silicon substrate and the second surface of the lithium tantalate thin film wafer to form a bonded body including, from top to bottom, the lithium tantalate thin film wafer, the silicon dioxide isolation layer, the polysilicon trap layer and the silicon substrate layer;
[0088] S3, grinding and thinning: grinding and thinning the lithium tantalate thin film wafer along the first surface with the target thinning thickness H0 as the target; wherein the thin film wafer after grinding and thinning has a relative thinning surface (corresponding to the first surface before thinning) and a second surface; after thinning, the thinning surface can be polished;
[0089] S4, obtaining the thickness to be peeled off at different positions corresponding to the thinning surface: obtaining the thickness distribution data of the thinned lithium tantalate thin film wafer by an optical film thickness detection device; setting a preset ion implantation reference plane for the thinned lithium tantalate thin film wafer, preferably making the preset ion implantation reference plane parallel to the second surface of the lithium tantalate thin film wafer; obtaining the thickness to be peeled off at different positions corresponding to the thinning surface based on the thickness distribution data and the preset ion implantation reference plane;
[0090] S5, ion implantation: hydrogen ion implantation is performed on the thinned lithium tantalate thin film wafer at a rate of 5×10 16 ions / cm 2 The hydrogen ions are implanted into the preset ion implantation reference plane with an implantation dose; wherein, before the ion implantation, the ion implantation energy corresponding to the ion implantation at different positions of the thinning surface is determined based on the thickness to be peeled off at different positions of the thinning surface. The specific method is not limited and can be performed by any achievable existing technology, such as by various simulation software, such as combining the ion implantation energy and implantation depth data of the SRIM software to fit the fitting curve of the ion implantation energy and the implantation depth (such as Fig.10 As shown), based on the fitting curve, find the ion implantation energy corresponding to the thickness to be peeled off at different positions of the thinned lithium tantalate thin film wafer, and perform ion implantation based on the obtained ion implantation energy;
[0091] S6, stripping treatment: performing a stripping treatment (i.e., annealing treatment) at 400° C. on the lithium tantalate thin film wafer after ion implantation, the lithium tantalate thin film wafer after ion implantation is stripped from a preset ion implantation reference plane, and a portion of the lithium tantalate thin film wafer from the preset ion implantation reference plane to the second surface is retained on the silicon dioxide isolation layer as the lithium tantalate thin film wafer after stripping; the lithium tantalate thin film wafer after stripping has a relative stripping surface (corresponding to the thinning surface before stripping) and a second surface;
[0092] S7, polishing treatment: polishing the peeled surface of the lithium tantalate thin film wafer after peeling to obtain a composite thin film including a silicon substrate layer, a polysilicon trap layer, a silicon dioxide isolation layer and a lithium tantalate thin film layer from bottom to top.
[0093] In this embodiment, the product target thickness of the composite film is H (for the composite film, its product target thickness H represents the target thickness of the lithium tantalate thin film layer in the composite film), the polishing thickness during polishing is H1, and the distance from the preset ion injection reference plane to the highest point of the thinning surface is the maximum thickness to be peeled off H2; preferably, H0=H+H1+H2, so that the actual thickness of the thin film layer in the obtained composite film can be more consistent with the product target thickness H, thereby improving the thickness accuracy.
[0094] In this embodiment, the sum of the distance H2 from the preset ion implantation reference plane to the highest point of the thinned surface and the polishing thickness is equal to the height difference between the highest point of the thinned surface and the lowest point of the thinned surface. At this time, the stripping and polishing just completely remove the surface undulations introduced by thinning, which can greatly improve the thickness uniformity, avoid the waste of materials caused by excessive removal of the thin film wafer, and better control the thickness of the actual thin film product.
[0095] The high-quality composite film with controllable thickness obtained by the preparation method of this embodiment includes a silicon substrate layer, a polysilicon trap layer, a silicon dioxide isolation layer and a lithium tantalate film layer stacked from bottom to top, and the TTV of the film layer is 51.24 nm.
[0096] Comparative Example 1 Composite film product obtained by conventional grinding and thinning and polishing
[0097] preparing lithium tantalate thin film wafers and silicon substrates;
[0098] S1, subjecting the surface to be combined of the silicon substrate and the surface to be bonded of the lithium tantalate thin film wafer to plasma surface activation treatment, and then bonding them to form a bonded body including the lithium tantalate thin film wafer and the silicon substrate layer from top to bottom;
[0099] S2, grinding and thinning the side of the lithium tantalate thin film wafer away from the silicon substrate layer;
[0100] S2. Polishing the thinned surface of the thinned lithium tantalate thin film wafer to obtain a composite film including a silicon substrate layer and a lithium tantalate thin film layer.
[0101] The composite film prepared by the preparation method of Comparative Example 1 has a TTV of 2.1383 μm. Comparative Examples 1-4 show that the film product prepared by the preparation method of the present invention has a better TTV.
[0102] The above specific implementation methods further illustrate the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above are only specific implementation methods of the present application and are not used to limit the protection scope of the present application. Any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solutions of the present application should be included in the protection scope of the present application.
Claims
1. A method for preparing a thin film, characterized in that: The following steps are involved: providing a thin film wafer having a first surface and a second surface opposite to each other; Thinning the thin film wafer along the first surface, the thin film wafer having an opposite thinning surface and a second surface after thinning; Acquiring thickness distribution data of the thin film wafer after thinning, and setting a preset ion implantation reference plane for the thin film wafer after thinning; Based on the preset ion implantation reference plane and the thickness distribution data, obtaining the thickness to be peeled off at different positions corresponding to the thinning surface; Performing ion implantation from the thinning surface to the thin film wafer after thinning, implanting the ions into a preset ion implantation reference plane, wherein the ion implantation energy corresponding to different positions of the thinning surface is determined based on the thickness to be peeled off at different positions of the thinning surface; The ion-implanted thin film wafer is subjected to a peeling process from a preset ion-implanted reference surface, and the peeled thin film wafer has an opposite peeling surface and a second surface; The peeled surface is polished to obtain the film.
2. The preparation method according to claim 1, characterized in that: The thinning method includes grinding thinning or wet etching.
3. The preparation method according to claim 1, characterized in that: The preset ion implantation reference plane is parallel to the second surface.
4. The preparation method according to claim 1, characterized in that: The target thickness of the thin film wafer during thinning is H0, the target product thickness of the thin film is H, the polishing thickness during polishing is H1, and the distance from the preset ion implantation reference plane to the highest point of the thinning surface is the maximum thickness to be peeled off H2; Among them, H0=H+H1+H2.
5. The preparation method according to claim 1, characterized in that: The height of the preset ion injection reference plane is lower than the height of the highest point of the thinning surface, and the height of the preset ion injection reference plane is not lower than the height of the lowest point of the thinning surface; or, the height of the preset ion injection reference plane is lower than the height of the lowest point of the thinning surface.
6. The preparation method according to claim 1, characterized in that: The sum of the distance from the preset ion implantation reference plane to the highest point of the thinning surface and the polishing thickness is equal to the height difference between the highest point of the thinning surface and the lowest point of the thinning surface.
7. The preparation method according to claim 1, characterized in that: The material of the thin film wafer is selected from one or more of lithium niobate, lithium tantalate, quartz, silicon carbide, silicon or silicon nitride.
8. The preparation method according to claim 1, characterized in that: After thinning the thin film wafer, the thinned surface is polished before obtaining the thickness distribution data of the thin film wafer after thinning.
9. The preparation method according to claim 1, characterized in that: The implanted ions 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 .
10. The preparation method according to claim 1, characterized in that: The temperature during the peeling treatment is 100 to 600°C.
11. The preparation method according to claim 1, characterized in that: The film is a self-supporting film.
12. The preparation method according to claim 1, characterized in that: The film is a composite film; after providing the film wafer and before thinning the film wafer, the method further comprises the following steps: providing a substrate layer, and bonding the surface to be bonded of the substrate layer to the second surface of the film wafer.
13. The preparation method according to claim 12, characterized in that: The material of the substrate layer is selected from one or more of lithium niobate, lithium tantalate, quartz, silicon, sapphire, silicon carbide, silicon nitride, gallium arsenide or indium phosphide.
14. The preparation method according to claim 12, characterized in that: Before bonding the surface to be bonded of the substrate layer and the second surface of the thin film wafer, an isolation layer is prepared on the surface to be bonded of the substrate layer and / or the second surface of the thin film wafer, and then the substrate layer and the thin film wafer are bonded via the isolation layer.
15. The preparation method according to claim 14, characterized in that: The material of the isolation layer is one or more of silicon dioxide, silicon nitride, aluminum oxide or aluminum nitride.
16. The preparation method according to claim 14, characterized in that: Before preparing the isolation layer, a trap layer is first prepared on the surface to be bonded to the substrate layer.
17. The preparation method according to claim 16, characterized in that: The trap layer is made of polysilicon or amorphous silicon.
18. A film, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 17.