Diamond composite wafer and preparation method thereof
By forming a diamond layer on the side surface of the diamond growth substrate toward the support substrate, and using a nano-sintered metal layer to bond the diamond growth substrate to the support substrate, the problems of peeling and fragmentation of thin substrates due to thermal stress warping, fragmentation and thinning are solved, and the yield of diamond composite wafers is improved.
Patent Information
- Application Number
- CN202311185055.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-08
- Publication Date
- 2025-03-11
AI Technical Summary
During the formation of the diamond layer, the thin substrate is prone to warping and fragmentation due to thermal stress, and when the thick substrate is thinned, stress will be concentrated on the heterogeneous interface between the substrate and the diamond, resulting in peeling and fragmentation.
Using an integrated substrate, including a thinner diamond growth substrate and a thicker support substrate, the two are bonded by a nanosintered metal layer to form a composite structure, and a diamond layer is formed on the surface of the diamond growth substrate on one side facing away from the support substrate. The thinning of the substrate is finally achieved by removing the support substrate.
It effectively avoids warping and fragmentation problems caused by thermal stress, and avoids peeling and fragmentation of diamond growth substrate and diamond layer during thinning, thereby improving the yield of diamond composite wafers.
Smart Images
Figure CN119601457A_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the field of semiconductor technology, and in particular relates to a diamond composite wafer and a preparation method thereof. Background Art
[0002] As the size of ultra-high power devices continues to shrink, the heat dissipation problem of the devices has gradually become prominent. Currently, most of them use high thermal conductivity diamond layers to improve the heat transfer capacity of the devices.
[0003] There is thermal mismatch during the formation of the diamond layer. Thin substrates are prone to warping and fragmentation due to thermal stress. Currently, most methods increase the thickness of the substrate (≥3mm) and use the strength of the thick substrate to reduce the warping and fragmentation rate during the formation of the diamond layer. However, the thickness of the substrate used in the device is currently required to be less than or equal to 50μm. Therefore, after the diamond layer is formed on the thick substrate, the thick substrate needs to be thinned to meet the thickness requirements. However, in the process of thinning the thick substrate, stress will continue to concentrate on the heterogeneous interface between the substrate and the diamond, which can easily cause the substrate and the diamond layer to peel off and break.
[0004] How to avoid warping and cracking of the substrate due to thermal stress when forming a diamond layer on a thin substrate, and at the same time avoid peeling and cracking of the substrate and the diamond layer caused by thinning the substrate, so as to improve the yield of diamond composite wafers, has become an urgent problem to be solved. Summary of the invention
[0005] In response to the above technical problems, the present application provides a diamond composite wafer and a preparation method thereof, which can avoid the warping and breakage of the diamond growth substrate due to thermal stress when a diamond layer is formed on the diamond growth substrate, and at the same time avoid thinning the diamond growth substrate, which causes peeling and breakage of the diamond growth substrate and the diamond layer.
[0006] The present application provides a method for preparing a diamond composite wafer, comprising: providing an integrated substrate, the integrated substrate comprising a diamond growth substrate and a support substrate, one side surface of the diamond growth substrate being bonded to one side surface of the support substrate, the thickness of the diamond growth substrate being less than the thickness of the support substrate; forming a diamond layer on a side surface of the diamond growth substrate facing away from the support substrate to obtain a composite structure of the diamond layer and the integrated substrate; and removing the support substrate from the composite structure to obtain a diamond composite wafer.
[0007] In one embodiment, providing the integrated substrate includes: providing the diamond growth substrate and the supporting substrate; stacking the diamond growth substrate and the supporting substrate, and setting a nano-sintered metal layer between the diamond growth substrate and the supporting substrate; sintering to bond the diamond growth substrate and the supporting substrate through the nano-sintered metal layer to obtain the integrated substrate.
[0008] In one embodiment, the nano-sintered metal layer is nano-silver.
[0009] In one embodiment, the thickness of the diamond growth substrate is 10 μm to 50 μm, and the thickness of the support substrate is 3 mm to 10 mm.
[0010] In one embodiment, the step of forming a diamond layer on the surface of the diamond growth substrate facing away from the supporting substrate to obtain a composite structure of the diamond layer and the integrated substrate comprises: placing the surface of the diamond growth substrate facing away from the supporting substrate in a preset atmosphere, and forming a diamond layer on the surface of the diamond growth substrate facing away from the supporting substrate by high temperature treatment; and obtaining a composite structure of the diamond layer and the integrated substrate.
[0011] In one embodiment, the diamond layer has a thickness of 100 μm to 300 μm.
[0012] In one embodiment, the step of removing the supporting substrate from the composite structure to obtain a diamond composite wafer comprises: placing the composite structure in a corrosive liquid; heating the corrosive liquid to remove the nano-sintered metal layer between the diamond growth substrate and the supporting substrate, so that the supporting substrate falls off from the composite structure; and obtaining the diamond composite wafer.
[0013] In one embodiment, the diamond growth substrate includes any one of a silicon wafer, a silicon carbide wafer, and an SOI wafer, and the support substrate is a silicon wafer.
[0014] In one embodiment, the diamond growth substrate is an SOI wafer; the step of removing the supporting substrate from the composite structure to obtain a diamond composite wafer comprises: removing the supporting substrate from the composite structure; removing the lower silicon layer of the SOI wafer to obtain the diamond composite wafer.
[0015] The present application also provides a diamond composite wafer, which is prepared using the above-mentioned diamond composite wafer preparation method.
[0016] The present application provides a diamond composite wafer and a preparation method thereof, which provides support for a thinner diamond growth substrate by means of a thicker supporting substrate, thereby preventing the diamond growth substrate from warping or breaking due to thermal stress when a diamond layer is formed on the diamond growth substrate. In addition, the substrate thinning effect can be achieved by removing the supporting substrate, without the need to further thin the diamond growth substrate, thereby preventing the diamond growth substrate and the diamond layer from peeling off or breaking during the thinning process. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 It is a schematic diagram of the process of preparing a diamond composite wafer provided in an embodiment of the present application;
[0018] Figure 2 It is a specific schematic diagram of the process of preparing a diamond composite wafer provided in an embodiment of the present application;
[0019] Figure 3 It is a schematic diagram of the effect of forming a diamond layer on an integrated substrate provided in an embodiment of the present application. DETAILED DESCRIPTION
[0020] The specific implementation methods of the present application are further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application but are not intended to limit the scope of the present application.
[0021] Figure 1 FIG. 1 is a flow chart of a method for preparing a diamond composite wafer provided in an embodiment of the present application. Figure 1 As shown, the preparation method of the diamond composite wafer of the present application includes but is not limited to the following steps:
[0022] Step S10: providing an integrated substrate, the integrated substrate comprising a diamond growth substrate and a support substrate, one side surface of the diamond growth substrate is bonded to one side surface of the support substrate, and the thickness of the diamond growth substrate is less than the thickness of the support substrate;
[0023] Step S20: forming a diamond layer on the surface of the diamond growth substrate facing away from the support substrate to obtain a composite structure of diamond and integrated substrate;
[0024] Step S30: removing the supporting substrate from the composite structure to obtain a diamond composite wafer.
[0025] The method for preparing a diamond composite wafer provided in an embodiment of the present application provides support for a thinner diamond growth substrate by using a thicker supporting substrate, which can avoid the diamond growth substrate from warping or breaking due to thermal stress when a diamond layer is formed on the diamond growth substrate, and can reduce the difficulty of growing diamond directly on a thin substrate. In addition, the substrate thinning effect can be achieved by removing the supporting substrate, and there is no need to thin the diamond growth substrate again, which can avoid the diamond growth substrate and the diamond layer from peeling off or breaking during the thinning process, thereby greatly improving the yield of the diamond composite wafer.
[0026] Optionally, the diamond growth substrate includes any one of a silicon wafer, a silicon carbide wafer, and a silicon-on-insulator (SOI) wafer, and the supporting substrate is a silicon wafer. Optionally, the thickness of the diamond growth substrate is 10 μm to 50 μm, and a diamond-ultra-thin silicon composite wafer can be obtained, and the thickness of the supporting substrate is 3 mm to 10 mm, which can effectively provide supporting force.
[0027] In one embodiment, providing an integrated substrate in step S10 includes:
[0028] Providing a diamond growth substrate and a supporting substrate;
[0029] stacking a diamond growth substrate and a supporting substrate, and providing a nano-sintered metal layer between the diamond growth substrate and the supporting substrate;
[0030] Sintering is performed to bond the diamond growth substrate to the support substrate via the nano-sintered metal layer to obtain an integrated substrate.
[0031] Optionally, a nano-sintered metal slurry is uniformly coated on one side surface of the diamond growth substrate and one side surface of the support substrate, and the side surface of the diamond growth substrate coated with the nano-sintered metal slurry is bonded to the side surface of the support substrate coated with the nano-sintered metal slurry to obtain a stacked structure of the diamond growth substrate and the support substrate. The stacked structure of the diamond growth substrate and the support substrate is subjected to a high-temperature annealing treatment under a certain pressure, for example, a high-temperature annealing treatment at 250° C. for 1 hour, so that the nano-sintered metal slurry is sintered in the air, and the nano-sintered metal layer obtained by sintering bonds the diamond growth substrate and the support substrate together to obtain an integrated substrate.
[0032] The nano-sintered metal layer can be nano-copper, nano-gold or nano-silver, wherein nano-silver is preferred. It is worth mentioning that the melting point of nano-silver can reach 960°C after sintering, while the growth temperature of polycrystalline diamond is between 600°C and 900°C. Nano-silver is used to bond the diamond growth substrate and the supporting substrate. In the process of forming a diamond layer on the diamond growth substrate, nano-silver will not melt under the high temperature environment of diamond growth, and the diamond growth substrate and the supporting substrate can still be bonded together, ensuring that in the process of forming a diamond layer on the diamond growth substrate, the supporting substrate can provide support for the diamond growth substrate, avoiding the situation that the diamond growth substrate is warped and broken due to thermal stress. In addition, the nano-sintered metal layer does not contain organic matter. The nano-sintered metal layer is used to bond the diamond growth substrate and the supporting substrate. In the process of forming a diamond layer on the diamond growth substrate, it is possible to avoid the high temperature causing the organic matter to volatilize and cause the diamond layer formed on the diamond growth substrate to produce voids, causing the diamond layer to break due to the huge local stress generated by the voids.
[0033] In one embodiment, step S20: forming a diamond layer on a surface of the diamond growth substrate facing away from the support substrate to obtain a composite structure of the diamond layer and the integrated substrate, comprising:
[0034] Placing the surface of the diamond growth substrate facing away from the support substrate in a preset atmosphere, and forming a diamond layer on the surface of the diamond growth substrate facing away from the support substrate through high temperature treatment;
[0035] A composite structure of a diamond layer and an integrated substrate is obtained.
[0036] Optionally, the integrated substrate is placed in a microwave plasma chemical vapor deposition apparatus, and the diamond growth substrate in the integrated substrate is placed upward, methane and hydrogen are introduced into the microwave plasma chemical vapor deposition apparatus, and high-temperature treatment is performed at 800° C. to form a diamond layer on the surface of the diamond growth substrate facing away from the support substrate, and the diamond layer is ground and polished to obtain a composite structure of the diamond layer and the integrated substrate. Optionally, the thickness of the diamond layer is 100 μm to 300 μm.
[0037] In one embodiment, step S30: removing the support substrate from the composite structure to obtain a diamond composite wafer, comprising:
[0038] placing the composite structure in a corrosive solution;
[0039] The etching liquid is heated to remove the nano-sintered metal layer disposed between the diamond growth substrate and the support substrate, so that the support substrate falls off from the composite structure;
[0040] A diamond composite wafer is obtained.
[0041] Optionally, a nitric acid etching solution is prepared, and the composite structure of the diamond layer and the integrated substrate is immersed in the nitric acid etching solution, and the nitric acid etching solution is heated in a water bath at 80°C, so that the nitric acid etching solution corrodes the nano-sintered metal layer between the diamond growth substrate and the support substrate to remove the nano-sintered metal layer. After the nano-sintered metal layer is removed, the support substrate bonded to the diamond growth substrate by the nano-sintered metal layer will fall off from the composite structure, and the remaining part of the composite structure that has not fallen off is taken out for cleaning, and the surface attachments are removed, and the diamond growth substrate in the remaining part is polished to make its roughness ≤0.2mm, so as to obtain a diamond composite wafer.
[0042] Optionally, the diamond growth substrate is an SOI wafer, and step S30: removing the support substrate from the composite structure to obtain a diamond composite crystal includes:
[0043] removing the supporting substrate from the composite structure;
[0044] The lower silicon layer of the SOI wafer is removed to obtain a diamond composite wafer.
[0045] Specifically, when the diamond growth substrate in the composite structure is an SOI wafer, after the supporting substrate is removed from the composite structure, the SOI wafer can be subjected to inductively coupled plasma (ICP) etching to further remove the lower silicon layer of the SOI wafer, thereby obtaining a diamond composite wafer composed of the upper silicon layer of the SOI wafer and a diamond layer formed on the surface of the upper silicon layer, so as to meet the thickness requirements of high-power devices for the diamond growth substrate.
[0046] Optionally, the diamond growth substrate and the support substrate have the same diameter. Figure 2As shown, first, a thin silicon wafer a with a diameter of 50.8 mm and a thickness of 30 μm and a thick silicon wafer b with a diameter of 50.8 mm and a thickness of 3 mm are provided, and nanosilver slurry is uniformly coated on one side surface of the thin silicon wafer a and one side surface of the thick silicon wafer b, and the side surface of the thin silicon wafer a coated with the nanosilver slurry is bonded to the side surface of the thick silicon wafer b coated with the nanosilver slurry to obtain a stacked structure of the thin silicon wafer a and the thick silicon wafer b. Then, the stacked structure of the thin silicon wafer a and the thick silicon wafer b is subjected to a high temperature annealing treatment of 250° C. for 1 hour, so that the nanosilver slurry is sintered in the air, and the sintered nanosilver layer c bonds the thin silicon wafer a and the thick silicon wafer b together to obtain an integrated substrate. Next, the integrated substrate is placed in a microwave plasma chemical vapor deposition (MPCVD) instrument, and the thin silicon wafer a in the integrated substrate is placed upward, and methane and hydrogen are introduced into the microwave plasma chemical vapor deposition instrument, and a high-temperature treatment is performed at 800° C. to form a 300 μm thick diamond layer d on the surface of the thin silicon wafer a on the side facing away from the thick silicon wafer b, and the diamond layer d is ground and polished to obtain a composite structure of the diamond layer d and the integrated substrate. The composite structure of the diamond layer d and the integrated substrate is immersed in a nitric acid etching solution, and the nitric acid etching solution is heated in a water bath at 80° C., so that the nitric acid etching solution corrodes the nanosilver layer c between the thin silicon wafer a and the thick silicon wafer b, so as to remove the nanosilver layer c and make the thick silicon wafer b bonded to the thin silicon wafer a through the nanosilver layer c fall off from the composite structure. Finally, the remaining part of the composite structure that has not fallen off is taken out for cleaning to remove surface attachments, and the thin silicon wafer a in the remaining part is subjected to mechanical chemical polishing to make its roughness ≤ 0.2 mm to obtain a diamond composite wafer. Figure 3 As shown, a flat diamond layer is formed on the integrated substrate, and the substrate is not warped or broken.
[0047] In other embodiments, a thin silicon wafer with a diameter of 50.8 mm and a thickness of 50 μm and a thick silicon wafer with a diameter of 50.8 mm and a thickness of 3 mm can be bonded together with a nanosilver slurry, and subjected to a high-temperature annealing treatment at 250° C. for 1 h to complete sintering of the nanosilver slurry in air. The nanosilver layer obtained by sintering bonds the thin silicon wafer and the thick silicon wafer together to obtain an integrated substrate. A 300 μm thick diamond layer is formed on the surface of the thin silicon wafer in the integrated substrate that is away from the thick silicon wafer to obtain a composite structure of the diamond layer and the integrated substrate. A nitric acid etching solution is used to remove the nanosilver layer between the thin silicon wafer and the thick silicon wafer in the composite structure, so that the thick silicon wafer bonded to the thin silicon wafer through the nanosilver layer falls off from the composite structure to obtain a diamond composite wafer.
[0048] A thin silicon wafer with a diameter of 101.6 mm and a thickness of 30 μm and a thick silicon wafer with a diameter of 101.6 mm and a thickness of 3 mm can also be used to bond them together with a nanosilver paste, and then annealed at 250° C. for 1 hour to complete sintering of the nanosilver paste in air. The nanosilver layer obtained by sintering bonds the thin silicon wafer and the thick silicon wafer together to obtain an integrated substrate. A 300 μm thick diamond layer is formed on the surface of the side of the thin silicon wafer in the integrated substrate that faces away from the thick silicon wafer to obtain a composite structure of the diamond layer and the integrated substrate. A nitric acid etching solution is used to remove the nanosilver layer between the thin silicon wafer and the thick silicon wafer in the composite structure, so that the thick silicon wafer bonded to the thin silicon wafer through the nanosilver layer falls off from the composite structure to obtain a diamond composite wafer.
[0049] A thin silicon wafer with a diameter of 50.8 mm and a thickness of 30 μm and a thick silicon wafer with a diameter of 50.8 mm and a thickness of 5 mm can also be connected by nanosilver paste, and annealed at 250° C. for 1 hour to complete sintering of the nanosilver paste in air. The nanosilver layer obtained by sintering bonds the thin silicon wafer and the thick silicon wafer together to obtain an integrated substrate. A 300 μm thick diamond layer is formed on the surface of the side of the thin silicon wafer in the integrated substrate that faces away from the thick silicon wafer to obtain a composite structure of the diamond layer and the integrated substrate. A nitric acid etching solution is used to remove the nanosilver layer between the thin silicon wafer and the thick silicon wafer in the composite structure, so that the thick silicon wafer bonded to the thin silicon wafer through the nanosilver layer falls off from the composite structure to obtain a diamond composite wafer.
[0050] A thin silicon wafer with a diameter of 50.8 mm and a thickness of 30 μm and a thick silicon wafer with a diameter of 50.8 mm and a thickness of 3 mm can also be connected by nanosilver paste, and annealed at 250° C. for 1 hour to complete sintering of the nanosilver paste in air. The nanosilver layer obtained by sintering bonds the thin silicon wafer and the thick silicon wafer together to obtain an integrated substrate. A 100 μm thick diamond layer is formed on the surface of the side of the thin silicon wafer in the integrated substrate that faces away from the thick silicon wafer to obtain a composite structure of the diamond layer and the integrated substrate. A nitric acid etching solution is used to remove the nanosilver layer between the thin silicon wafer and the thick silicon wafer in the composite structure, so that the thick silicon wafer bonded to the thin silicon wafer through the nanosilver layer falls off from the composite structure to obtain a diamond composite wafer.
[0051] A SOI wafer with a diameter of 50.8 mm and an upper silicon layer thickness of 10 μm and a thick silicon wafer with a diameter of 50.8 mm and a thickness of 3 mm can also be connected through nanosilver paste, and a high-temperature annealing treatment is performed at 250° C. for 1 hour to complete sintering of the nanosilver paste in air. The nanosilver layer obtained by sintering bonds the SOI wafer and the thick silicon wafer together to obtain an integrated substrate. A 300 μm thick diamond layer is formed on a surface of the SOI wafer in the integrated substrate that faces away from the thick silicon wafer to obtain a composite structure of the diamond layer and the integrated substrate. A nitric acid etching solution is used to remove the nanosilver layer between the SOI wafer and the thick silicon wafer in the composite structure, so that the thick silicon wafer bonded to the SOI wafer through the nanosilver layer falls off from the composite structure. The lower silicon layer of the SOI wafer is removed by ICP etching to obtain a diamond composite wafer.
[0052] The method for preparing a diamond composite wafer provided in an embodiment of the present application uses a nano-sintered metal layer to bond a diamond growth substrate and a support substrate, so that a thicker support substrate provides support for a thinner diamond growth substrate, which can avoid the diamond growth substrate from warping and breaking due to thermal stress when forming a diamond layer on the diamond growth substrate, and can reduce the difficulty of growing diamond directly on a thin substrate. In addition, the nano-sintered metal layer does not contain organic matter, and in the process of forming a diamond layer on the diamond growth substrate, it can avoid the diamond layer from generating voids due to the volatilization of organic matter, which causes the diamond layer to break due to the huge local stress generated by the voids. By corroding the nano-sintered metal layer, the support substrate can be removed to achieve a substrate thinning effect, which can reduce the difficulty of substrate thinning, and there is no need to thin the diamond growth substrate. It can avoid the diamond growth substrate and the diamond layer from peeling off and breaking during the thinning process, thereby greatly improving the yield of the diamond composite wafer.
[0053] The present application also provides a diamond composite wafer, which is prepared using the above-mentioned diamond composite wafer preparation method.
[0054] In this document, unless otherwise specified or limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.
[0055] In this document, the terms "comprises," "comprising," or any other variations thereof, are intended to cover a non-exclusive inclusion of elements other than those listed and may also include additional elements not expressly listed.
[0056] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.
Claims
1. A method for preparing a diamond composite wafer, characterized in that: include: Providing an integrated substrate, the integrated substrate comprising a diamond growth substrate and a support substrate, one side surface of the diamond growth substrate is bonded to one side surface of the support substrate, and the thickness of the diamond growth substrate is less than the thickness of the support substrate; forming a diamond layer on a surface of the diamond growth substrate facing away from the support substrate to obtain a composite structure of the diamond layer and the integrated substrate; The supporting substrate is removed from the composite structure to obtain a diamond composite wafer.
2. The preparation method according to claim 1, characterized in that The integrated substrate is provided, comprising: Providing the diamond growth substrate and the support substrate; stacking the diamond growth substrate and the support substrate, and providing a nano-sintered metal layer between the diamond growth substrate and the support substrate; Sintering is performed to bond the diamond growth substrate to the support substrate via the nano-sintered metal layer to obtain the integrated substrate.
3. The preparation method according to claim 2, characterized in that: The nano-sintered metal layer is nano-silver.
4. The preparation method according to claim 1, characterized in that: The thickness of the diamond growth substrate is 10 μm to 50 μm, and the thickness of the support substrate is 3 mm to 10 mm.
5. The preparation method according to claim 1, characterized in that: The step of forming a diamond layer on a surface of the diamond growth substrate facing away from the support substrate to obtain a composite structure of the diamond layer and the integrated substrate comprises: Placing the surface of the diamond growth substrate facing away from the support substrate in a preset atmosphere, and forming a diamond layer on the surface of the diamond growth substrate facing away from the support substrate through high temperature treatment; A composite structure of the diamond layer and the integrated substrate is obtained.
6. The preparation method according to claim 5, characterized in that: The thickness of the diamond layer is 100 μm to 300 μm.
7. The preparation method according to claim 2, characterized in that: The step of removing the support substrate from the composite structure to obtain a diamond composite wafer comprises: placing the composite structure in a corrosive solution; Heating the etching solution to remove the nano-sintered metal layer between the diamond growth substrate and the support substrate, so that the support substrate falls off from the composite structure; The diamond composite wafer is obtained.
8. The preparation method according to any one of claims 1 to 7, characterized in that: The diamond growth substrate includes any one of a silicon wafer, a silicon carbide wafer, and an SOI wafer, and the supporting substrate is a silicon wafer.
9. The preparation method according to claim 1, characterized in that: The diamond growth substrate is a SOI wafer; The step of removing the support substrate from the composite structure to obtain a diamond composite wafer comprises: removing the support substrate from the composite structure; The lower silicon layer of the SOI wafer is removed to obtain the diamond composite wafer.
10. A diamond composite wafer, characterized in that: The diamond composite wafer is prepared by the method for preparing a diamond composite wafer as described in any one of claims 1 to 9.