Preparation method of diamond gallium nitride composite wafer

Abstract

The invention discloses a preparation method of a diamond gallium nitride composite wafer, which belongs to the field of semiconductors, and comprises the following steps: providing a temporary wafer and an SOI substrate, the SOI substrate comprising a first silicon layer, an insulating layer and a second silicon layer which are stacked in sequence; growing a gallium nitride epitaxial layer on the surface of the second silicon layer; bonding the temporary wafer with the gallium nitride epitaxial layer; preparing a first groove structure on the surface of the first silicon layer; the first groove structure is filled with corrosive liquid or ultrasonic cleaning liquid to remove the insulating layer in the bonding sheet, and the first silicon layer is driven to fall off when the insulating layer is removed; growing diamond on the surface of the second silicon layer; preparing a second groove structure on the surface of the temporary wafer; the first groove structure is filled with corrosive liquid, the bonding layer in the first wafer is removed through corrosion of the corrosive liquid, the temporary wafer is driven to fall off when the bonding layer is removed, the diamond gallium nitride composite wafer is obtained, and therefore the quality and the yield of the diamond gallium nitride composite wafer can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a method for preparing a diamond gallium nitride composite wafer. Background Art

[0002] Gallium nitride (GaN) semiconductor materials have excellent properties such as large bandgap, high breakdown field strength, high carrier mobility, and easy formation of heterostructures. They are very suitable for the development of high-power electronic devices and high-frequency microwave devices, and play an important role in national defense science and technology, aerospace, 5G communication applications and other fields.

[0003] Diamond material has the advantages of high thermal conductivity, small specific heat capacity, significant heat dissipation effect at high temperatures and no heat accumulation. When diamond is used as the substrate material for gallium nitride, it can improve the heat dissipation performance of the gallium nitride wafer, thereby improving the service life and reliability of the gallium nitride wafer.

[0004] At present, the common process for preparing diamond gallium nitride composite wafers includes a transfer bonding process, that is, first bonding the gallium nitride with a native substrate to a temporary substrate, then removing the native substrate and preparing a diamond substrate on the gallium nitride, and finally removing the temporary substrate. In this way, diamond gallium nitride composite wafers can be prepared, but when removing the native substrate and the temporary substrate, a mechanical thinning and polishing process is required to remove the native substrate and the temporary substrate. Since the gallium nitride is easily broken during the mechanical thinning and polishing process, the quality and yield of the diamond gallium nitride composite wafer are reduced. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a method for preparing a diamond gallium nitride composite wafer. The technical problem to be solved by the present invention is achieved by the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a diamond gallium nitride composite wafer, comprising:

[0007] Step 1: providing a temporary wafer and an SOI substrate, wherein the SOI substrate comprises a first silicon layer, an insulating layer, and a second silicon layer stacked in sequence, wherein the thickness of the first silicon layer is greater than the thickness of the second silicon layer;

[0008] Step 2: growing a gallium nitride epitaxial layer on the surface of the second silicon layer in the SOI substrate to obtain a gallium nitride epitaxial wafer;

[0009] Step 3: Prepare a bonding layer, and use a wafer bonding process to stack and bond the temporary wafer, the bonding layer, and the GaN epitaxial layer in sequence;

[0010] Step 4: preparing a first groove structure on the surface of the first silicon layer in the bonding wafer, the first groove structure comprising a plurality of first grooves distributed transversely and a plurality of second grooves distributed longitudinally, and the depth of the first groove structure is equal to the thickness of the first silicon layer;

[0011] Step 5: Filling the first groove structure with an etching solution or an ultrasonic cleaning solution, removing the insulating layer in the bonding wafer by etching with the etching solution, or removing the insulating layer in the bonding wafer by ultrasonic impact, and driving the first silicon layer to fall off when the insulating layer is removed, so as to obtain a first wafer;

[0012] Step 6: growing diamond on the surface of the second silicon layer in the first wafer to obtain a second wafer;

[0013] Step 7: preparing a second groove structure on the surface of the temporary wafer in the second wafer, the second groove structure comprising a plurality of third grooves distributed transversely and a plurality of fourth grooves distributed longitudinally, and the depth of the second groove structure is equal to the thickness of the temporary wafer;

[0014] Step eight: Fill the first groove structure with an etching solution, and remove the bonding layer in the first wafer by etching with the etching solution. When the bonding layer is removed, the temporary wafer is driven off to obtain a diamond gallium nitride composite wafer.

[0015] In one embodiment of the present invention, step 2 includes:

[0016] The SOI substrate is placed in a growth device with the first silicon layer facing downward and the second silicon layer facing upward, and a gallium nitride epitaxial layer is grown on the surface of the second silicon layer using a MOCVD process.

[0017] In one embodiment of the present invention, after step 2 and before step 3, the method further includes:

[0018] Acetone, anhydrous ethanol and deionized water are used in turn to ultrasonically clean and dry the GaN epitaxial wafer and the temporary wafer, wherein the power of the ultrasonic cleaning is 80W to 100W and the cleaning time is 10 minutes to 20 minutes.

[0019] In one embodiment of the present invention, step three includes:

[0020] Step 301: using an electron beam evaporation process to deposit bonding layers on the surface of the GaN epitaxial wafer and the surface of the temporary wafer respectively;

[0021] Step 302: stack the bonding layer in the temporary wafer onto the bonding layer in the GaN epitaxial wafer, clamp the temporary wafer and the GaN epitaxial wafer with a clamp and place them in a wafer bonding machine for hot pressing bonding, wherein the bonding temperature is 350° C. and the pressing time is 60 to 90 minutes.

[0022] In one embodiment of the present invention, step 4 includes:

[0023] The bonding wafer is placed in a laser scribing machine with the first silicon layer facing upward, and a first groove and a second groove intersecting horizontally and vertically are scratched on the surface of the first silicon layer using a laser scribing process, wherein the spacing between two adjacent first grooves is 2 mm, and the spacing between two adjacent second grooves is 2 mm, and the depth of the first groove and the depth of the second groove are both equal to the thickness of the first silicon layer.

[0024] In one embodiment of the present invention, step five includes:

[0025] The bonding sheet is immersed in a hydrofluoric acid solution with a concentration of 5% to 10%. The hydrofluoric acid solution flows along the first groove and the second groove to corrode the insulating layer. After the insulating layer is corroded and dissolved, the first silicon layer is driven to fall off to obtain a first wafer, wherein the insulating layer is made of silicon dioxide.

[0026] In one embodiment of the present invention, step five includes:

[0027] The bonding wafer is placed in a cleaning tank in an ultrasonic cleaning device, wherein deionized water is provided in the cleaning tank. The bonding wafer is immersed in the deionized water, and the upper surface of the bonding wafer is lower than the water surface of the deionized water. Ultrasonic waves are used to impact the insulating layer along the first tank and the second tank to cause the insulating layer to fall off and drive the first silicon layer to detach, thereby obtaining a first wafer, wherein the insulating layer is made of silicon dioxide, the ultrasonic frequency is 40kHz, the ultrasonic power is 100W, and the cleaning time is 10 minutes.

[0028] In one embodiment of the present invention, step six includes:

[0029] Step 601: preparing a diamond powder suspension solution with a diamond particle size of 3 nm to 50 nm as an ultrasonic solution;

[0030] Step 602: placing the first wafer in an ultrasonic solution for ultrasonic treatment for 25 minutes to form uniformly distributed diamond seeds on the first wafer;

[0031] Step 603: placing the first wafer on a hot plate at 100° C. and heating for 10 minutes for drying;

[0032] Step 604: Place the first wafer into the MPCVD equipment with the second silicon layer facing upward, and deposit 200 μm thick diamond on the surface of the second silicon layer to obtain a second wafer, wherein the methane-hydrogen ratio in the MPCVD equipment is set to 8%, the power is 4000 W, and the temperature is 800°C.

[0033] In one embodiment of the present invention, step seven includes:

[0034] Place the second wafer in the laser scribing machine with the temporary wafer facing up, and use the laser scribing process to scratch the third and fourth grooves that intersect horizontally and vertically on the surface of the temporary wafer, wherein the spacing between two adjacent third grooves is 2 mm, and the spacing between two adjacent fourth grooves is 2 mm, and the depth of the third groove and the depth of the fourth groove are both equal to the thickness of the temporary wafer.

[0035] In one embodiment of the present invention, step eight includes:

[0036] The second wafer is placed in a potassium iodide solution, and the potassium iodide solution flows along the third groove and the fourth groove to corrode the bonding layer. After the bonding layer is corroded and dissolved, the temporary wafer is driven to fall off to obtain a diamond gallium nitride composite wafer, wherein the bonding layer is made of gold.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] In the above scheme of the present application, first, by preparing a first groove structure on the surface of the first silicon layer, and the depth of the first groove structure is equal to the thickness of the first silicon layer, the etching liquid or ultrasonic cleaning liquid can flow into the first groove structure, and pass through the first groove structure and contact the insulating layer, so that the insulating layer can be removed by etching the insulating layer with the etching liquid or ultrasonic impacting the insulating layer, avoiding the risk of gallium nitride cracking when the insulating layer and the first silicon layer are removed by mechanical thinning and polishing process, thereby improving the quality and yield of the diamond gallium nitride composite wafer. Moreover, when the insulating layer is removed, the first silicon layer can be driven off together, making the removal of the insulating layer and the first silicon layer more convenient. In addition, when the first groove structure includes a plurality of first grooves distributed laterally and a plurality of second grooves distributed longitudinally, the etching liquid or ultrasonic cleaning liquid can flow through the first groove and the second groove to various positions of the insulating layer, making the removal of the insulating layer more efficient and more uniform.

[0039] Secondly, by preparing a second groove structure on the surface of the temporary wafer in the second wafer, and the depth of the second groove structure is equal to the thickness of the temporary wafer, the etching liquid can flow into the second groove structure, and pass through the second groove structure and contact the bonding layer, so that the bonding layer can be removed by etching the bonding layer with the etching liquid, avoiding the risk of gallium nitride cracking when the bonding layer and the temporary wafer are removed by mechanical thinning and polishing, thereby improving the quality and yield of the diamond gallium nitride composite wafer. Moreover, when the bonding layer is removed, the temporary wafer can be driven off together, making the removal of the bonding layer and the temporary wafer more convenient. In addition, when the second groove structure includes a plurality of third grooves distributed laterally and a plurality of fourth grooves distributed longitudinally, the etching liquid can flow through the third groove and the fourth groove to various positions of the bonding layer, making the removal of the bonding layer more efficient and more uniform.

[0040] Furthermore, when an SOI substrate is used, the gallium nitride epitaxial layer is grown using the second silicon layer on the SOI substrate, which can make the growth of the gallium nitride epitaxial layer more convenient and with better growth quality. At the same time, when growing diamond, the second silicon layer on the SOI substrate can serve as a growth substrate for diamond and can also protect the gallium nitride epitaxial layer during the diamond growth process to avoid damage to the gallium nitride epitaxial layer, thereby further improving the quality and yield of diamond gallium nitride composite wafers.

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a schematic diagram of a method for preparing a diamond gallium nitride composite wafer provided by an embodiment of the present invention;

[0043] Figure 2 is a schematic diagram of an SOI substrate in an embodiment of the present invention;

[0044] Figure 3 is a schematic diagram of a gallium nitride epitaxial wafer in an embodiment of the present invention;

[0045] Figure 4 is a schematic diagram of a bonding sheet in an embodiment of the present invention;

[0046] Figure 5 is a schematic diagram of providing a first groove structure on a bonding wafer in an embodiment of the present invention;

[0047] Figure 6 is a top view of the first silicon layer in an embodiment of the present invention;

[0048] Figure 7 is a schematic diagram of the etching liquid entering the first groove structure in an embodiment of the present invention;

[0049] Figure 8 is a schematic diagram of an ultrasonic cleaning liquid entering a first groove structure in an embodiment of the present invention;

[0050] Fig. 9 is a schematic diagram of a first wafer in an embodiment of the present invention;

[0051] Fig.10 is a schematic diagram of a second wafer in an embodiment of the present invention;

[0052] Fig.11 is a schematic diagram of providing a second trench structure on a second wafer in an embodiment of the present invention;

[0053] Fig.12 is a top view of a temporary wafer in an embodiment of the present invention;

[0054] Fig.13Schematic diagram of a diamond gallium nitride composite wafer in an embodiment of the present invention. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0056] See also Figures 1 to 13 The present invention provides a method for preparing a diamond gallium nitride composite wafer, comprising:

[0057] Step 1: providing a temporary wafer and an SOI substrate, wherein the SOI substrate comprises a first silicon layer, an insulating layer, and a second silicon layer stacked in sequence, wherein the thickness of the first silicon layer is greater than the thickness of the second silicon layer;

[0058] Step 2: growing a gallium nitride epitaxial layer on the surface of the second silicon layer in the SOI substrate to obtain a gallium nitride epitaxial wafer;

[0059] Step 3: Prepare a bonding layer, and use a wafer bonding process to stack and bond the temporary wafer, the bonding layer, and the GaN epitaxial layer in sequence;

[0060] Step 4: preparing a first groove structure on the surface of the first silicon layer in the bonding wafer, the first groove structure comprising a plurality of first grooves distributed transversely and a plurality of second grooves distributed longitudinally, and the depth of the first groove structure is equal to the thickness of the first silicon layer;

[0061] Step 5: Filling the first groove structure with an etching solution or an ultrasonic cleaning solution, removing the insulating layer in the bonding wafer by etching with the etching solution, or removing the insulating layer in the bonding wafer by ultrasonic impact, and driving the first silicon layer to fall off when the insulating layer is removed, so as to obtain a first wafer;

[0062] Step 6: growing diamond on the surface of the second silicon layer in the first wafer to obtain a second wafer;

[0063] Step 7: preparing a second groove structure on the surface of the temporary wafer in the second wafer, the second groove structure comprising a plurality of third grooves distributed transversely and a plurality of fourth grooves distributed longitudinally, and the depth of the second groove structure is equal to the thickness of the temporary wafer;

[0064] Step eight: Fill the first groove structure with an etching solution, and remove the bonding layer in the first wafer by etching with the etching solution. When the bonding layer is removed, the temporary wafer is driven off to obtain a diamond gallium nitride composite wafer.

[0065] In some embodiments of the present application, SOI substrate (Silicon-On-Insulator) is a semiconductor technology that grows a single crystal silicon layer on an insulator. Its basic structure includes a top silicon layer, an insulating layer (such as silicon dioxide) and a bottom silicon layer. This structure achieves dielectric isolation of components by introducing an insulating layer between the active silicon layer and the substrate, thereby improving the performance and reliability of the chip.

[0066] In some embodiments of the present application, the temporary wafer includes but is not limited to a silicon wafer, a sapphire wafer, and a silicon carbide wafer, and the size of the temporary wafer is consistent with the size of the SOI substrate.

[0067] In some embodiments of the present application, the insulating layer in the SOI substrate includes but is not limited to silicon dioxide, sapphire, silicon nitride, or a stacked structure of two or more thereof.

[0068] In some embodiments of the present application, the wafer bonding method in step three can be dielectric bonding, metal bonding or adhesive bonding. When dielectric bonding is used, the bonding layer cannot be made of the same material as the insulating layer of the SOI substrate to prevent the temporary wafer serving as a support from falling off during the removal of the first silicon layer of the SOI substrate.

[0069] In some embodiments of the present application, when preparing the first groove structure and the second groove structure, a laser cutting machine may be used for scribing or a photolithography machine may be used for groove pattern transfer and subsequent etching.

[0070] In some embodiments of the present application, the process for growing diamond may be a microwave plasma chemical vapor deposition (MPCVD) process.

[0071] In the above scheme of the present application, first, by preparing a first groove structure on the surface of the first silicon layer, and the depth of the first groove structure is equal to the thickness of the first silicon layer, the etching liquid or ultrasonic cleaning liquid can flow into the first groove structure, and pass through the first groove structure and contact the insulating layer, so that the insulating layer can be removed by etching the insulating layer with the etching liquid or ultrasonic impacting the insulating layer, avoiding the risk of gallium nitride cracking when the insulating layer and the first silicon layer are removed by mechanical thinning and polishing process, thereby improving the quality and yield of the diamond gallium nitride composite wafer. Moreover, when the insulating layer is removed, the first silicon layer can be driven off together, making the removal of the insulating layer and the first silicon layer more convenient. In addition, when the first groove structure includes a plurality of first grooves distributed laterally and a plurality of second grooves distributed longitudinally, the etching liquid or ultrasonic cleaning liquid can flow through the first groove and the second groove to various positions of the insulating layer, making the removal of the insulating layer more efficient and more uniform.

[0072] Secondly, by preparing a second groove structure on the surface of the temporary wafer in the second wafer, and the depth of the second groove structure is equal to the thickness of the temporary wafer, the etching liquid can flow into the second groove structure, and pass through the second groove structure and contact the bonding layer, so that the bonding layer can be removed by etching the bonding layer with the etching liquid, avoiding the risk of gallium nitride cracking when the bonding layer and the temporary wafer are removed by mechanical thinning and polishing, thereby improving the quality and yield of the diamond gallium nitride composite wafer. Moreover, when the bonding layer is removed, the temporary wafer can be driven off together, making the removal of the bonding layer and the temporary wafer more convenient. In addition, when the second groove structure includes a plurality of third grooves distributed laterally and a plurality of fourth grooves distributed longitudinally, the etching liquid can flow through the third groove and the fourth groove to various positions of the bonding layer, making the removal of the bonding layer more efficient and more uniform.

[0073] Moreover, when an SOI substrate is used, the gallium nitride epitaxial layer is grown using the second silicon layer on the SOI substrate, which can make the growth of the gallium nitride epitaxial layer more convenient and with better growth quality. At the same time, when growing diamond, the second silicon layer on the SOI substrate can be used as a growth substrate for diamond, and can also protect the gallium nitride epitaxial layer during the diamond growth process to avoid damage to the gallium nitride epitaxial layer, thereby further improving the quality and yield of diamond gallium nitride composite wafers. In addition, SOI substrates have obvious advantages over bulk silicon materials, and the technology for preparing gallium nitride materials using SOI as a growth substrate is mature and its integration with IC processes is constantly improving. At the same time, the above method of the present application does not have strict requirements on the bonding strength of the bonding sheet, and there are multiple choices for bonding layer materials. The above method of the present application is well compatible with semiconductor process production lines, and can prepare large-size, high-efficiency, low-cost and high-performance diamond gallium nitride composite wafers, providing core materials for high-power density gallium nitride microwave power devices, so that the high-power advantages of gallium nitride devices can be fully utilized. It has high research value and can generate good social and economic benefits, promoting the development of related industrialization.

[0074] In some embodiments of the present application, Figure 2 and Figure 3 As shown, step two includes:

[0075] The SOI substrate is placed in a growth device with the first silicon layer facing downward and the second silicon layer facing upward, and a gallium nitride epitaxial layer is grown on the surface of the second silicon layer using a MOCVD process. This method facilitates the growth of a gallium nitride epitaxial layer on the surface of the second silicon layer.

[0076] In some embodiments of the present application, the MOCVD process (Metal-Organic Chemical Vapor Deposition) is a new vapor phase epitaxial growth technology developed on the basis of vapor phase epitaxy (VPE). It uses metal organic compounds and hydrides as crystal growth source materials, performs vapor phase epitaxy on a substrate through thermal decomposition reaction, and grows thin-layer single crystal materials of various III-V group, II-VI group compound semiconductors and their multi-component solid solutions.

[0077] In some embodiments of the present application, after step 2 and before step 3, the following steps are further included:

[0078] Acetone, anhydrous ethanol and deionized water are used to ultrasonically clean and dry the GaN epitaxial wafer and temporary wafer respectively, wherein the power of ultrasonic cleaning is 80W to 100W and the cleaning time is 10 minutes to 20 minutes. This method can fully clean the GaN epitaxial wafer and temporary wafer before bonding them, improve the cleanliness of the GaN epitaxial wafer and temporary wafer during bonding, and thus make the bonding effect of the GaN epitaxial wafer and temporary wafer better.

[0079] In some embodiments of the present application, when acetone, anhydrous ethanol and deionized water are used to ultrasonically clean the GaN epitaxial wafer and the temporary wafer respectively, contaminants and dust particles on the surfaces of the GaN epitaxial wafer and the temporary wafer can be washed away.

[0080] In some embodiments of the present application, Figure 4 As shown, step three includes:

[0081] Step 301: using an electron beam evaporation process to deposit bonding layers on the surface of the GaN epitaxial wafer and the surface of the temporary wafer respectively;

[0082] Step 302: stack the bonding layer in the temporary wafer onto the bonding layer in the GaN epitaxial wafer, clamp the temporary wafer and the GaN epitaxial wafer with a fixture and place them in a wafer bonding machine for hot pressing bonding, wherein the bonding temperature is 350°C and the pressing time is 60 minutes to 90 minutes. In this way, the temporary wafer can be bonded to the GaN epitaxial wafer by wafer bonding.

[0083] In some embodiments of the present application, the bonding layer is made of gold, the thickness of the bonding layer is 300nm to 500nm, and when the bonding layer in the temporary wafer is stacked on the bonding layer in the gallium nitride epitaxial wafer, it is ensured that the edges of the temporary wafer and the gallium nitride epitaxial wafer completely overlap. After applying pressure for 60 minutes to 90 minutes, the pressure is removed, and the bonded wafer is taken out after slowly cooling to room temperature.

[0084] In some embodiments of the present application, Figure 5 and Figure 6 As shown, step four includes:

[0085] The bonding wafer is placed in a laser scribing machine with the first silicon layer facing upward, and the first and second grooves intersecting horizontally and vertically are scratched on the surface of the first silicon layer by laser scribing, wherein the spacing between two adjacent first grooves is 2 mm, the spacing between two adjacent second grooves is 2 mm, and the depth of the first groove and the depth of the second groove are both equal to the thickness of the first silicon layer. This method facilitates the preparation of the first groove structure on the first silicon layer by laser scribing, and can make the removal of the insulating layer more uniform.

[0086] In an alternative approach, Figure 7 and Fig. 9 As shown, step five includes:

[0087] The bonding wafer is immersed in a hydrofluoric acid solution with a concentration of 5% to 10%. The hydrofluoric acid solution flows along the first groove and the second groove to corrode the insulating layer. After the insulating layer is corroded and dissolved, the first silicon layer is driven to fall off, thereby obtaining a first wafer, wherein the insulating layer is made of silicon dioxide. In this method, the insulating layer can be corroded and dissolved by the hydrofluoric acid solution with a concentration of 5% to 10%, so that the insulating layer can be dissolved and detached. When the insulating layer falls off, the first silicon layer can be driven to fall off together, thereby removing the insulating layer and the first silicon layer.

[0088] In some embodiments of the present application, the hydrofluoric acid solution reaches the surface of the silicon dioxide layer through the vertical and horizontal grooves, and simultaneously corrodes the silicon dioxide vertically and laterally. After the silicon dioxide layer is corroded and dissolved, the first silicon layer naturally falls off due to the lack of a bonding layer, thereby obtaining a wafer supported by a temporary wafer.

[0089] In another alternative, such as Figure 8 and Fig. 9 As shown, step five includes:

[0090] The bonding sheet is placed in a cleaning tank in an ultrasonic cleaning device, wherein deionized water is provided in the cleaning tank, the bonding sheet is immersed in the deionized water, the upper surface of the bonding sheet is lower than the water surface of the deionized water, and ultrasonic waves are used to impact the insulating layer along the first and second grooves to cause the insulating layer to fall off and drive the first silicon layer to detach, thereby obtaining a first wafer, wherein the material of the insulating layer is silicon dioxide, the ultrasonic frequency is 40kHz, the ultrasonic power is 100W, and the cleaning time is 10 minutes. In this method, when ultrasonic waves propagate in deionized water, a cavitation effect is generated, and tiny vacuum bubbles (cavitation bubbles) are formed inside the deionized water. These cavitation bubbles will continue to grow, shrink, and collapse under the periodic pressure changes of ultrasonic waves. The strong energy impact generated by the collapse of the cavitation bubbles can loosen and detach silicon dioxide, thereby achieving the removal of the first silicon layer. The upper surface of the bonding sheet is lower than the water surface of the deionized water, which can ensure that the bonding sheet can be fully immersed in the deionized water, thereby improving the efficiency and effect of removing the insulating layer and the first silicon layer.

[0091] In some embodiments of the present application, after step five and before step six, the following steps are further included:

[0092] Cleaning the first wafer: placing the first wafer in acetone, anhydrous ethanol and deionized water in turn for ultrasonic cleaning to wash away residual solution and other contaminants. The power of ultrasonic cleaning can be selected from 80 to 100 W, and the time can be selected from 10 to 20 minutes.

[0093] In some embodiments of the present application, Fig.10 As shown, step six includes:

[0094] Step 601: preparing a diamond powder suspension solution with a diamond particle size of 3 nm to 50 nm as an ultrasonic solution;

[0095] Step 602: placing the first wafer in an ultrasonic solution for ultrasonic treatment for 25 minutes to form uniformly distributed diamond seeds on the first wafer;

[0096] Step 603: placing the first wafer on a hot plate at 100° C. and heating for 10 minutes for drying;

[0097] Step 604: Place the first wafer into the MPCVD device with the second silicon layer facing upward, and deposit diamond with a thickness of 200 μm on the surface of the second silicon layer to obtain a second wafer, wherein the methane-hydrogen ratio in the MPCVD device is set to 8%, the power is 4000 W, and the temperature is 800° C. In this way, diamond can be grown on the second silicon layer of the first wafer, and the growth quality of diamond is improved.

[0098] In some embodiments of the present application, Fig.11 and Fig.12 As shown, step seven includes:

[0099] The second wafer is placed in a laser scribing machine with the temporary wafer facing upward, and the third and fourth grooves intersecting horizontally and vertically are scratched on the surface of the temporary wafer by laser scribing, wherein the spacing between two adjacent third grooves is 2 mm, the spacing between two adjacent fourth grooves is 2 mm, and the depth of the third groove and the depth of the fourth groove are both equal to the thickness of the temporary wafer. This method facilitates the preparation of the second groove structure on the temporary wafer by laser scribing, and can make the removal of the bonding layer more uniform.

[0100] In some embodiments of the present application, Fig.11 and Fig.13 As shown, step eight includes:

[0101] The second wafer is placed in a potassium iodide solution, and the potassium iodide solution flows along the third and fourth grooves to corrode the bonding layer. After the bonding layer is corroded and dissolved, the temporary wafer is driven to fall off, thereby obtaining a diamond gallium nitride composite wafer, wherein the bonding layer is made of gold. In this method, the bonding layer can be corroded and dissolved by the potassium iodide solution, so that the bonding layer can be dissolved and detached. When the bonding layer falls off, the temporary wafer can be driven to fall off together, thereby removing the bonding layer and the temporary wafer.

[0102] In some embodiments of the present application, after obtaining the diamond gallium nitride composite wafer, the diamond gallium nitride composite wafer can be placed in flowing deionized water for cleaning to remove residual potassium iodide solution.

[0103] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0104] In addition, the terms "first", "second", "third", and "fourth" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third", and "fourth" may explicitly or implicitly include one or more of the feature. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0105] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0106] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for preparing a diamond gallium nitride composite wafer, characterized in that: include: Step 1: providing a temporary wafer and an SOI substrate, wherein the SOI substrate comprises a first silicon layer, an insulating layer, and a second silicon layer stacked in sequence, wherein the thickness of the first silicon layer is greater than the thickness of the second silicon layer; Step 2: growing a gallium nitride epitaxial layer on the surface of the second silicon layer in the SOI substrate to obtain a gallium nitride epitaxial wafer; Step 3: preparing a bonding layer, and using a wafer bonding process to sequentially stack and bond the temporary wafer, the bonding layer, and the gallium nitride epitaxial layer to obtain a bonding wafer; Step 4: preparing a first groove structure on the surface of the first silicon layer in the bonding wafer, wherein the first groove structure includes a plurality of first grooves distributed laterally and a plurality of second grooves distributed longitudinally, and the depth of the first groove structure is equal to the thickness of the first silicon layer; Step 5: Filling the first groove structure with a corrosive liquid or an ultrasonic cleaning liquid, and removing the insulating layer in the bonding wafer by corroding the corrosive liquid, or removing the insulating layer in the bonding wafer by ultrasonic impact, wherein the first silicon layer is driven to fall off when the insulating layer is removed, so as to obtain a first wafer; Step six: growing diamond on the surface of the second silicon layer in the first wafer to obtain a second wafer; Step 7: preparing a second groove structure on the surface of the temporary wafer in the second wafer, wherein the second groove structure comprises a plurality of third grooves distributed transversely and a plurality of fourth grooves distributed longitudinally, and the depth of the second groove structure is equal to the thickness of the temporary wafer; Step eight: Filling the first groove structure with an etching liquid, and removing the bonding layer in the first wafer by etching with the etching liquid, and driving the temporary wafer to fall off when the bonding layer is removed, so as to obtain a diamond gallium nitride composite wafer.

2. The method for preparing a diamond gallium nitride composite wafer according to claim 1, characterized in that: The second step comprises: The SOI substrate is placed in a growth device with the first silicon layer facing downward and the second silicon layer facing upward, and a gallium nitride epitaxial layer is grown on the surface of the second silicon layer using a MOCVD process.

3. The method for preparing a diamond gallium nitride composite wafer according to claim 1, characterized in that: After step 2 and before step 3, the following steps are also included: Acetone, anhydrous ethanol and deionized water are used in sequence to ultrasonically clean and dry the gallium nitride epitaxial wafer and the temporary wafer, wherein the power of the ultrasonic cleaning is 80W to 100W and the cleaning time is 10 minutes to 20 minutes.

4. The method for preparing a diamond gallium nitride composite wafer according to claim 1, characterized in that: The step three comprises: Step 301: using an electron beam evaporation process to deposit bonding layers on the surface of the gallium nitride epitaxial wafer and the surface of the temporary wafer respectively; Step 302: stack the bonding layer in the temporary wafer onto the bonding layer in the GaN epitaxial wafer, clamp the temporary wafer and the GaN epitaxial wafer with a clamp and place them in a wafer bonding machine for hot pressing bonding, wherein the bonding temperature is 350°C and the pressing time is 60 minutes to 90 minutes.

5. The method for preparing a diamond gallium nitride composite wafer according to claim 1, characterized in that: The fourth step comprises: The bonding sheet is placed in a laser scribing machine with the first silicon layer facing upward, and the first groove and the second groove intersecting horizontally and vertically are scratched on the surface of the first silicon layer using a laser scribing process, wherein the spacing between two adjacent first grooves is 2 mm, the spacing between two adjacent second grooves is 2 mm, and the depth of the first groove and the depth of the second groove are both equal to the thickness of the first silicon layer.

6. The method for preparing a diamond gallium nitride composite wafer according to claim 1, characterized in that: The step five comprises: The bonding sheet is immersed in a hydrofluoric acid solution with a concentration of 5% to 10%. The hydrofluoric acid solution flows along the first groove and the second groove to corrode the insulating layer. After the insulating layer is corroded and dissolved, the first silicon layer is driven to fall off to obtain a first wafer, wherein the insulating layer is made of silicon dioxide.

7. The method for preparing a diamond gallium nitride composite wafer according to claim 1, characterized in that: The step five comprises: The bonding sheet is placed in a cleaning tank in an ultrasonic cleaning device, wherein deionized water is provided in the cleaning tank, and the bonding sheet is immersed in the deionized water. The upper surface of the bonding sheet is lower than the water surface of the deionized water, and ultrasonic waves are used to impact the insulating layer along the first tank and the second tank to cause the insulating layer to fall off and drive the first silicon layer to detach, thereby obtaining a first wafer, wherein the insulating layer is made of silicon dioxide, the ultrasonic frequency is 40kHz, the ultrasonic power is 100W, and the cleaning time is 10 minutes.

8. The method for preparing a diamond gallium nitride composite wafer according to claim 1, characterized in that: The step six comprises: Step 601: preparing a diamond powder suspension solution with a diamond particle size of 3 nm to 50 nm as an ultrasonic solution; Step 602: placing the first wafer in the ultrasonic solution for ultrasonic treatment for 25 minutes to form uniformly distributed diamond seeds on the first wafer; Step 603: placing the first wafer on a hot plate at 100° C. and heating for 10 minutes for drying; Step 604: Place the first wafer into the MPCVD equipment with the second silicon layer facing upward, and deposit 200 μm thick diamond on the surface of the second silicon layer to obtain a second wafer, wherein the methane-hydrogen ratio in the MPCVD equipment is set to 8%, the power is 4000 W, and the temperature is 800°C.

9. The method for preparing a diamond gallium nitride composite wafer according to claim 1, characterized in that: The step seven comprises: The second wafer is placed in a laser scribing machine with the temporary wafer facing upward, and the third groove and the fourth groove intersecting horizontally and vertically are scratched on the surface of the temporary wafer using a laser scribing process, wherein the spacing between two adjacent third grooves is 2 mm, and the spacing between two adjacent fourth grooves is 2 mm, and the depth of the third groove and the depth of the fourth groove are both equal to the thickness of the temporary wafer.

10. The method for preparing a diamond gallium nitride composite wafer according to claim 4, characterized in that: The step eight comprises: The second wafer is placed in a potassium iodide solution, and the potassium iodide solution flows along the third groove and the fourth groove to corrode the bonding layer. After the bonding layer is corroded and dissolved, the temporary wafer is driven to fall off to obtain a diamond gallium nitride composite wafer, wherein the bonding layer is made of gold.

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