A method for improving the yield of lithium niobate thin film bonded by silicon light heterojunction

Abstract

The present application relates to a kind of method for improving lithium niobate of silicon photo heterojunction bonding thin film yield, belong to integrated photonic device manufacturing technical field.The present application aims to solve the problem of low yield caused by thin film rupture in high-temperature annealing due to lattice mismatch in SOI and thin film lithium niobate heterojunction bonding.The present application transfers the silicon optical functional layer of SOI wafer to lithium niobate substrate by bonding, then bonds thin film lithium niobate on the silicon optical functional layer to form heterojunction bonding body, cuts the surface of heterojunction bonding body into multiple array distributed isolated units before high-temperature annealing, and the cutting depth extends to lithium niobate substrate, finally high-temperature annealing treatment is carried out.The present application replaces silicon substrate with lithium niobate substrate to achieve lattice matching, and releases stress by surface cutting, effectively prevents thin film lithium niobate from breaking during high-temperature annealing process, significantly improves the yield of heterojunction bonding.Mainly used for the manufacture of silicon light and lithium niobate heterojunction integrated photonic device.

Description

Technical Field

[0001] This invention relates to the field of integrated photonic device manufacturing technology, specifically to a method for improving the yield of lithium niobate in silicon photonic heterobonding films, particularly applicable to methods for improving bonding yield in large-size wafer-level silicon photonic heterointegration processes. Background Technology

[0002] Silicon-on-insulator (SOI) is widely used in the fabrication of integrated photonic devices due to its low light absorption at wavelengths above 1200 nm and compatibility with CMOS processes. The SOI platform enables the large-scale production of passive devices such as couplers and waveguide array gratings, as well as active devices such as lasers and detectors. However, silicon, as a centrosymmetric crystal, inherently lacks electro-optic, acousto-optic, and second-order nonlinear optical effects, which limits its application in high-speed electro-optic modulation and frequency conversion. Thin-film lithium niobate (TFLN), with its excellent electro-optic, acousto-optic, and nonlinear optical properties, is considered a promising integrated photonics material platform. Heterogeneous integration of TFLN with SOI can achieve complementary and optimized material properties.

[0003] Currently, heterobonding of SOI and TFLN typically employs a direct bonding process, where TFLN is directly bonded to the SOI wafer surface after SOI wafer fabrication. However, due to the significant lattice mismatch between lithium niobate and silicon, the bonding interface generates substantial thermal stress during high-temperature annealing. For large wafers (e.g., 8-inch wafers), this stress can easily lead to TFLN film cracking, severely limiting the yield of silicon photonic heterobonded lithium niobate films.

[0004] Therefore, there is an urgent need for a method to improve the yield of lithium niobate in silicon photonic heterobonded thin films in order to solve the problems existing in the current technology. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in the prior art by providing a method to improve the yield of lithium niobate in silicon photonic heterobonded thin films. This method involves transferring the silicon photonic functional layer to the lithium niobate target substrate and performing deep stress-relieving cutting before high-temperature annealing to release the internal stress of the heterobonded material through physical isolation.

[0006] To achieve the above-mentioned objectives, the present invention employs the following technical solution: a method for improving the yield of lithium niobate in silicon photonic heterobonded thin films, comprising the following steps:

[0007] An initial wafer containing a silicon photonics functional layer and an initial substrate is obtained. The initial wafer is bonded to a target substrate, and the initial substrate is removed to transfer the silicon photonics functional layer onto the target substrate, wherein the target substrate is a lithium niobate substrate. A donor wafer containing thin-film lithium niobate is bonded to the side of the silicon photonics functional layer away from the target substrate, and the redundant portion of the donor wafer is removed to retain the thin-film lithium niobate, forming a heterobonded composite. Before the high-temperature annealing process, the heterobonded material is stress-relief cut to form multiple array-distributed isolation units. The cutting depth extends from the top surface of the thin-film lithium niobate to at least partially expose the target substrate. High-temperature annealing is performed on the heterogeneous composite after stress-relief cutting to enhance the bonding force between the layers.

[0008] Furthermore, the initial wafer is a silicon-on-insulator wafer, which, from bottom to top, includes a silicon substrate as the initial substrate, a buried oxide layer, and a silicon dioxide layer encapsulating the silicon photonic functional layer; the step of transferring and bonding the silicon photonic functional layer to the target substrate includes: bonding the surface of the silicon dioxide layer away from the buried oxide layer to the surface of the target substrate, and then completely removing the silicon substrate.

[0009] Furthermore, after removing the initial substrate and before bonding the donor wafer, the exposed buried oxide layer is thinned to a thickness that meets the optical waveguide coupling requirements between the silicon photonics functional layer and the thin-film lithium niobate.

[0010] Furthermore, the donor wafer is a lithium niobate-on-insulator thin film wafer, including a donor silicon substrate, a donor buried layer, and a thin film lithium niobate on the surface; the step of bonding the donor wafer and retaining the thin film lithium niobate includes: bonding the surface of the thin film lithium niobate to the surface of the thinned buried oxide layer, and annealing it at a preset temperature; then sequentially removing the donor silicon substrate and the donor buried layer, so that the thin film lithium niobate is exposed on the top layer.

[0011] Furthermore, the target substrate is a single-crystal lithium niobate wafer, and the crystal phase tangent of the target substrate is the same as that of the thin-film lithium niobate.

[0012] Furthermore, the crystal phase tangential of both the target substrate and the thin-film lithium niobate is X-cut.

[0013] Furthermore, the high-temperature annealing temperature is higher than the preset annealing temperature.

[0014] Furthermore, stress-relieving cutting employs a mechanical cutting method to cut the surface of the heterogeneous bond into rectangular blocks with a side length of 1~2cm.

[0015] Furthermore, before bonding the silicon dioxide layer to the target substrate, the surface of the silicon dioxide layer is planarized using chemical mechanical polishing, so that the surface flatness after treatment is less than 0.25 μm and the surface roughness is less than 0.2 nm.

[0016] Furthermore, the steps for removing the silicon substrate or donor silicon substrate include: thinning the substrate by polishing and then removing the remaining substrate material by etching solution; The steps for removing the donor burial layer include: removal using an erosive solution.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses a lithium niobate substrate instead of a silicon substrate as the carrier substrate for the SOI functional layer. Since the lithium niobate substrate and the thin-film lithium niobate have the same or similar crystal structure, the lattice mismatch between the two is much smaller than the mismatch between lithium niobate and silicon, which reduces the inherent stress of the bonding interface from the material source.

[0018] 2. In this invention, after bonding the lithium niobate film and before final annealing, the surface of the bonded body is cut into multiple small pieces, with the cutting depth penetrating the lithium niobate film and extending into the interior of the lithium niobate substrate. This cutting operation divides the large-area continuous film into independent small regions, allowing the film stress within each small piece to be released at the edges, avoiding the accumulation of stress in the large-area film, and effectively preventing the film from cracking during high-temperature annealing.

[0019] 3. This invention combines substrate replacement and surface cutting as two stress relief mechanisms, which significantly improves the yield of silicon photonic heterobonded thin films of lithium niobate under the dual effect, providing a feasible process solution for heterogeneous integration at the large-size wafer level. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of a method for improving the yield of lithium niobate in silicon photonic heterobonded thin films according to the present invention; Figure 2 This is a top view of the heterogeneous bond after stress-relieving cutting in this invention.

[0021] In the figure, 101 is the silicon substrate; 102 is the buried oxide layer; 103 is the silicon photonic functional region; 104 is the silicon dioxide layer; 105 is the target substrate (lithium niobate substrate); and 106 is the thin film lithium niobate. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0023] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0024] Example 1 like Figure 1 As shown, this embodiment provides a method for improving the yield of lithium niobate thin films in silicon photonics heterobonded films. This method uses SOI wafers and LNOI wafers as raw materials. By transferring the SOI functional layer onto a lithium niobate substrate and performing surface dicing before high-temperature annealing, the stress at the heterobonding interface is relieved, thereby improving the bonding yield of the lithium niobate thin film. Specifically, it includes the following steps: Step 1: Wafer Preparation and Surface Pretreatment Provide one completed SOI wafer as the initial wafer, with a size of 8 inches. See also Figure 1 The SOI wafer, from bottom to top, includes a silicon substrate 101 as the initial substrate, a buried oxide layer 102, and a silicon photonic functional region 103. Multiple silicon photonic functional chips are formed within the silicon photonic functional region 103, each chip containing silicon photonic functional structures such as coupling structures, beam splitting / combining structures, detection structures, and thermal modulation structures. After wafer fabrication, a silicon dioxide layer 104 is deposited on the outermost surface of the SOI wafer, which covers each silicon photonic functional chip.

[0025] To meet the stringent surface quality requirements of direct bonding, chemical mechanical polishing (CMP) was used to planarize the surface of the silicon dioxide layer 104. After polishing, the surface flatness of the silicon dioxide layer 104 was less than 0.25 μm (for a 2 cm × 2 cm area), the surface roughness was less than 0.2 nm, and the thickness of the silicon dioxide layer 104 was 3 μm.

[0026] Simultaneously, a lithium niobate wafer is provided as the target substrate 105. This lithium niobate wafer is 8 inches in size, X-shaped, and 500 μm thick. The lithium niobate wafer, as the target substrate 105, is made of the same material as the subsequently bonded thin film lithium niobate 106, and has the same tangent (both X-shaped), thus exhibiting good lattice matching and reducing the inherent stress at the bonding interface at the material level.

[0027] Step 2: Plasma activation and first bonding The silicon dioxide layer 104 surface after CMP treatment in step one and the bonding surfaces of the lithium niobate wafer 105 were respectively subjected to plasma activation treatment. Plasma activation can generate a large number of dangling bonds and active groups on the solid surface, significantly improving the surface chemical activity and creating conditions for direct bonding. The process parameters for plasma activation are: activation power 200W, activation time 120s, reaction gas is oxygen, and oxygen flow rate is 100sccm.

[0028] After activation, the SOI wafer is flipped so that the surface of the silicon dioxide layer 104 faces down towards the lithium niobate wafer 105, and the back side of the silicon substrate 101 faces up. The surface of the silicon dioxide layer 104 is aligned and bonded to the surface of the lithium niobate wafer 105, achieving pre-bonding at room temperature. Subsequently, annealing is performed in an oxygen atmosphere to strengthen the bonding force. The annealing temperature is 200℃, the annealing time is 3 hours, and the heating and cooling rates are both 1℃ / min. After annealing, the first bond is formed.

[0029] Step 3: Remove the silicon substrate The silicon substrate 101 of the SOI wafer in the first bond is removed. First, the silicon substrate 101 is thinned to 50 μm using a polishing method to remove most of the silicon material. Then, the remaining silicon substrate 101 is wet-etched using a TMAH (tetramethylammonium hydroxide) alkaline solution to completely remove it. The TMAH solution exhibits good etching selectivity for silicon but a very low etching rate for silicon dioxide; therefore, the etching automatically stops when the etching front reaches the buried oxide layer 102, achieving selective removal of the silicon substrate 101. After removing the silicon substrate 101, the buried oxide layer 102 is exposed.

[0030] Step 4: Thinning the buried oxide layer The exposed buried oxide layer 102 was thinned. CMP was used to thin the buried oxide layer 102 to 200 nm, resulting in a surface roughness of less than 0.2 nm (for a 2 cm × 2 cm area, the surface smoothness is less than 0.25 μm). The purpose of thinning the buried oxide layer 102 to the submicron level is that a thinner buried oxide layer 102 facilitates evanescent wave coupling between the silicon waveguide in the silicon photonic functional region 103 and the lithium niobate waveguide in the subsequently bonded thin-film lithium niobate 106, thereby achieving efficient transfer of optical signals between the silicon and lithium niobate material platforms. The smaller the thickness of the buried oxide layer 102 and the smaller the spacing between the two waveguides, the higher the coupling efficiency.

[0031] Step 5: LNOI (Lithium Niobate on Insulator) wafer bonding and thin-film lithium niobate transfer An 8-inch LNOI wafer is provided as the donor wafer. From bottom to top, the LNOI wafer comprises a donor silicon substrate (725 μm thick), a donor buried layer (500 nm thick), and a thin film of lithium niobate 106 on the surface. The thin film lithium niobate 106 is X-cut and 400 nm thick. Since the thin film lithium niobate 106 and the target substrate 105 are both X-cut lithium niobate, they exhibit good lattice matching.

[0032] The surfaces of the thin-film lithium niobate 106 and the thinned buried oxide layer 102 from step four were subjected to plasma activation treatment. The activation process parameters were the same as in step two: activation power 200W, activation time 120s, and oxygen flow rate 100sccm. After activation, the surfaces of the thin-film lithium niobate 106 and the thinned buried oxide layer 102 were aligned and bonded together at room temperature. Subsequently, annealing was performed in an oxygen atmosphere to strengthen the bonding force. The annealing temperature was 200℃, the annealing time was 3 hours, and the heating and cooling rates were both 1℃ / min.

[0033] Next, the donor silicon substrate and the donor buried layer were removed sequentially. First, the donor silicon substrate was thinned to 50 μm using a polishing method, and then the remaining silicon material was removed by etching with a TMAH alkaline solution. Subsequently, the donor buried layer was removed by etching with a hydrofluoric acid (HF) solution, completely exposing the thin film lithium niobate 106 to the top layer. This completes the transfer of the thin film lithium niobate 106 to the silicon photonic functional layer, forming a heterobonded composite.

[0034] After steps one through five, the heterobonded structures formed are, from bottom to top, the target substrate 105 (lithium niobate substrate, 500 μm, X-cut), the silicon dioxide layer 104 (3 μm) encapsulating the silicon photonic functional region 103, the buried oxide layer 102 (200 nm), and the thin film lithium niobate 106 (400 nm, X-cut).

[0035] Step Six: Stress Relief Cutting Before high-temperature annealing, the heteropolymer is subjected to stress-relieving cutting. For example... Figure 2 As shown, a mechanical grinding wheel cutting method is used to cut the surface of the heterobonded material into multiple arrayed rectangular blocks. In this embodiment, the side length of the resulting rectangular blocks is 2 cm. The cutting begins from the top surface of the thin film lithium niobate 106 and proceeds downwards, sequentially penetrating the thin film lithium niobate 106 (400 nm), the buried oxide layer 102 (200 nm), and the silicon dioxide layer 104 (3 μm), with a total cutting depth of approximately 50 μm, extending into the interior of the target substrate 105, thus exposing the bottom portion of the cutting trench to the target substrate 105. Figure 2 In the top view shown, the Notch label is placed at the edge of the wafer, indicating that the wafer is an 8-inch standard wafer, and also indicating the crystal orientation information of the lithium niobate substrate.

[0036] After cutting, a grid-like groove structure is formed on the surface of the bond, dividing the originally continuous large-area film into multiple independent small regions. The principle of this cutting operation is that the film in each small section can independently undergo minute thermal expansion deformation during the subsequent high-temperature annealing process. The stress in the film can be released at the free edges of the small sections, thereby effectively avoiding the accumulation and concentration of stress in the large-area film and preventing the film from cracking during high-temperature annealing.

[0037] Step 7: High-temperature annealing treatment The heterogeneous bonded material after stress-relief cutting is subjected to high-temperature annealing to further strengthen the bonding force between the thin film lithium niobate 106 and the buried oxide layer 102. Annealing is performed in an oxygen atmosphere at a temperature of 300°C for 3 hours, with both the heating and cooling rates at 1°C / min. In this invention, "high-temperature annealing" refers to the annealing temperature higher than the second annealing temperature (i.e., the preset temperature) in step five, as opposed to the second annealing treatment.

[0038] Since the initial annealing temperature between the lithium niobate film 106 and the buried oxide layer 102 in step five was 200℃, while the high-temperature annealing temperature in this case is 300℃, the higher annealing temperature provides greater thermal activation energy, which helps to further strengthen the chemical bonding at the bonding interface. Simultaneously, since the bond surface was cut into multiple independent small pieces in step six, each small piece can freely undergo minor thermal expansion deformation during the 300℃ high-temperature annealing process. This effectively alleviates the residual stress caused by lattice mismatch between the lithium niobate film 106 and the underlying layers, as well as the thermal stress caused by the difference in thermal expansion coefficients, thereby preventing the lithium niobate film 106 from cracking.

[0039] The resulting heterobonded structure, from bottom to top, consists of: target substrate 105 (lithium niobate substrate, 500 μm, X-cut), silicon dioxide layer 104 (3 μm) encapsulating silicon photonic functional region 103, buried oxide layer 102 (200 nm), and thin film lithium niobate 106 (400 nm, X-cut).

[0040] Among them, the annealing performed at 200℃ after the first bonding is called the first annealing, the annealing performed at 200℃ after the second bonding is called the second annealing, the annealing performed at 300℃ after cutting is called high-temperature annealing, the temperature of the first annealing (200℃) is called the first temperature, the temperature of the second annealing (200℃) is called the second temperature (i.e. the preset temperature), and the temperature of the high-temperature annealing (300℃) is called the third temperature.

[0041] Example 2 This embodiment provides another method to improve the yield of lithium niobate in silicon photonic heterobonded thin films. Its basic process flow is the same as that in Embodiment 1, except that the size of the isolation unit for stress relief cutting in step six is ​​different.

[0042] In this embodiment, to accommodate the denser wafer layout of silicon photonics functional chips, a smaller cutting size is used to achieve a more thorough stress release effect. A mechanical abrasive wheel cutting method is used to cut the surface of the heterogeneous bond into rectangular blocks with sides of 1 cm. The cutting depth also extends from the top surface of the thin-film lithium niobate 106 through the intermediate layers and partially into the target substrate 105. The smaller isolation unit size further refines the distribution range of thermal stress, making it easier for thermal expansion deformation generated during high-temperature annealing to be absorbed locally. This provides higher fracture resistance redundancy for bonding operations on ultra-large wafers (such as 8-inch and larger).

[0043] Explanation of process parameter changes: Those skilled in the art should understand that the specific process parameters in the above embodiments are preferred values ​​and can be reasonably adjusted as needed in practical applications. The optional ranges for each parameter are given below: 1. Regarding plasma activation parameters: the activation power can be adjusted within the range of 100~300W, the activation time can be adjusted within the range of 60~180s, and the oxygen flow rate can be adjusted within the range of 50~150 sccm.

[0044] 2. Regarding the first temperature: it can be adjusted within the range of 150~250℃, and the annealing time can be adjusted within the range of 2~5 hours.

[0045] 3. Regarding the second temperature (preset temperature): it can be adjusted within the range of 150~250℃, and the annealing time can be adjusted within the range of 2~5 hours.

[0046] 4. Regarding the third temperature: It can be adjusted within the range of 250~350℃, and the annealing time can be adjusted within the range of 2~5 hours. The annealing atmosphere is an oxygen-containing atmosphere. The temperature of the high-temperature annealing treatment is usually higher than that of the initial annealing treatment to ensure that the bonding interface receives sufficient energy to achieve strong bonding. The heating rate and cooling rate can be adjusted within the range of 0.5~2℃ / min.

[0047] 5. Regarding the thinning thickness of the buried oxide layer 102: it can be adjusted within the range of 100~300nm. The surface roughness after thinning should be less than 0.5nm to meet the requirements of optical waveguide coupling.

[0048] 6. Regarding the size of the isolation unit for stress relief cutting: The side length of the rectangular block formed by cutting can be selected within the range of 1~2cm. The cutting depth should ensure that it penetrates the thin film lithium niobate 106 and all its intermediate layers and partially cuts into the target substrate 105. The cutting depth can be adjusted within the range of 30~80μm.

[0049] 7. Regarding the crystal phase tangency: The target substrate 105 and the thin film lithium niobate 106 have the same crystal phase tangency, specifically an X-cut. Consistent tangency between the two facilitates lattice matching and reduces interfacial stress.

[0050] All adjustments to the above numerical ranges are within the scope of protection claimed in this invention, and all the above embodiments can achieve the technical effects of relieving heterogeneous bonding stress and improving the bonding yield of thin film lithium niobate.

[0051] The parts of this invention not described in detail are prior art, therefore they are not described in detail here.

[0052] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0053] Although this document uses a considerable amount of technical terminology, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention.

[0054] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes made to their shape or structure, any technical solution that is the same as or similar to this invention falls within the protection scope of this invention.

Claims

1. A method for improving the yield of lithium niobate in silicon photonic heterobonded thin films, characterized in that, Includes the following steps: An initial wafer containing a silicon photonics functional layer and an initial substrate is obtained, the initial wafer is bonded to a target substrate, and the initial substrate is removed to transfer and bond the silicon photonics functional layer to the target substrate, wherein the target substrate is a lithium niobate substrate. A donor wafer containing a thin film of lithium niobate is bonded to the side of the silicon photonic functional layer away from the target substrate, and the redundant portion of the donor wafer is removed to retain the thin film of lithium niobate, forming a heterobonded composite. Before the high-temperature annealing process, the heterobonded material is subjected to stress-relieving cutting to form multiple arrayed isolation units. The cutting depth extends from the top surface of the thin-film lithium niobate to at least partially expose the target substrate. The heterogeneous composite after stress-relief cutting is subjected to high-temperature annealing to enhance the bonding force between the layers.

2. The method according to claim 1, characterized in that, The initial wafer is a silicon-on-insulator wafer, which, from bottom to top, includes a silicon substrate (101) as the initial substrate, a buried oxide layer (102), and a silicon dioxide layer (104) encapsulating the silicon photonic functional layer (103). The step of transferring and bonding the silicon photonic functional layer to the target substrate includes: bonding the surface of the silicon dioxide layer (104) away from the buried oxide layer (102) to the surface of the target substrate (105), and then completely removing the silicon substrate (101).

3. The method according to claim 2, characterized in that, After the initial substrate is removed and before the donor wafer is bonded, the exposed buried oxide layer (102) is thinned to a thickness that meets the optical waveguide coupling requirements between the silicon photonics functional layer (103) and the thin-film lithium niobate (106).

4. The method according to claim 3, characterized in that, The donor wafer is a lithium niobate thin film wafer on insulator, comprising a donor silicon substrate, a donor buried layer, and the thin film lithium niobate (106) located on the surface. The steps of bonding the donor wafer and retaining the thin film lithium niobate (106) include: bonding the surface of the thin film lithium niobate (106) to the surface of the thinned buried oxide layer (102) and annealing it at a preset temperature; The donor silicon substrate and the donor buried layer are then removed sequentially, exposing the thin film lithium niobate (106) to the top layer.

5. The method according to claim 4, characterized in that, The target substrate (105) is a single-crystal lithium niobate wafer, and the crystal phase tangent of the target substrate (105) is the same as that of the thin-film lithium niobate (106).

6. The method according to claim 5, characterized in that, The crystal phase tangent of both the target substrate (105) and the thin-film lithium niobate (106) is X-cut.

7. The method according to claim 4, characterized in that, The high-temperature annealing process is performed at a temperature higher than the preset temperature.

8. The method according to claim 1, characterized in that, The stress-relieving cutting method employs mechanical cutting to cut the surface of the heterogeneous bond into rectangular blocks with a side length of 1-2 cm.

9. The method according to claim 2, characterized in that, Before the silicon dioxide layer (104) is bonded to the target substrate (105), the surface of the silicon dioxide layer (104) is planarized by chemical mechanical polishing, so that the surface flatness is less than 0.25 μm and the surface roughness is less than 0.2 nm.

10. The method according to claim 4, characterized in that, The step of removing the silicon substrate (101) or the donor silicon substrate includes: thinning the substrate by grinding and then removing the remaining substrate material by etching solution; The step of removing the donor burial layer includes: removing it with an etchant.

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