A method for preparing a diamond gallium nitride composite wafer

Abstract

The application discloses a preparation method of a diamond gallium nitride composite wafer, and belongs to the field of semiconductors. The method comprises the following steps: 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 which are sequentially stacked; growing a gallium nitride epitaxial layer on the surface of the second silicon layer; bonding the temporary wafer and the gallium nitride epitaxial layer; preparing a first groove structure on the surface of the first silicon layer; filling the first groove structure with etching liquid or ultrasonic cleaning liquid to remove the insulating layer in the bonding piece, and the insulating layer is removed together with the first silicon layer; growing diamond on the surface of the second silicon layer; preparing a second groove structure on the surface of the temporary wafer; filling the first groove structure with etching liquid to remove the bonding layer in the first wafer by etching, and the bonding layer is removed together with the temporary wafer, so as to obtain the diamond gallium nitride composite wafer, thereby improving the quality and yield of the diamond gallium nitride composite wafer.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductors, and particularly relates to a preparation method of a diamond gallium nitride composite wafer. BACKGROUND

[0002] Gallium nitride (GaN) semiconductor material has excellent characteristics such as large band gap, high breakdown field strength, high carrier mobility, and easy formation of heterostructures, and is very suitable for developing high-power electronic devices and high-frequency microwave devices, and has an important position in the fields of national defense science and technology, aerospace, 5G communication applications, etc.

[0003] Diamond material has the advantages of high thermal conductivity, small specific heat capacity, significant heat dissipation effect at high temperature and no accumulation of heat, etc. When diamond is used as the substrate material of gallium nitride, the heat dissipation performance of the gallium nitride wafer can be improved, and thus the service life and reliability of the gallium nitride wafer are improved.

[0004] The common process for preparing a diamond gallium nitride composite wafer at present includes a transfer bonding process, that is, gallium nitride with a native substrate is first bonded to a temporary substrate, then the native substrate is removed and a diamond substrate is prepared on the gallium nitride, and finally the temporary substrate is removed. By using this method, a diamond gallium nitride composite wafer can be prepared. However, when the native substrate and the temporary substrate are removed, a mechanical thinning and polishing process is needed to remove the native substrate and the temporary substrate. Since the mechanical thinning and polishing process is used for processing, it is easy to cause the gallium nitride to break, and thus the quality and yield of the diamond gallium nitride composite wafer are reduced. SUMMARY

[0005] In order to solve the above problems in the prior art, the application provides a preparation method of a diamond gallium nitride composite wafer. The technical problem to be solved by the application is solved by the following technical scheme:

[0006] In a first aspect, the application provides a preparation method of a diamond gallium nitride composite wafer, comprising:

[0007] Step one: 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 sequentially stacked, the thickness of the first silicon layer being greater than the thickness of the second silicon layer;

[0008] Step two: 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 three: preparing a bonding layer, and sequentially stacking and bonding the temporary wafer, the bonding layer and the gallium nitride epitaxial layer by using a wafer bonding process;

[0010] Step four: 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 transversely distributed first grooves and a plurality of longitudinally distributed second grooves, the depth of the first groove structure being equal to the thickness of the first silicon layer;

[0011] Step five: filling the first groove structure with etching liquid or ultrasonic cleaning liquid, removing the insulating layer in the bonding wafer by etching with the etching liquid or by ultrasonic impact, the insulating layer being removed together with the first silicon layer to obtain a first wafer;

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

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

[0014] Step eight: filling the first groove structure with etching liquid, removing the bonding layer in the first wafer by etching with the etching liquid, the bonding layer being removed together with the temporary wafer to obtain a diamond-gallium nitride composite wafer.

[0015] In an embodiment of the present application, step two comprises:

[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 by using a MOCVD process.

[0017] In an embodiment of the present application, after step two and before step three, the method further comprises:

[0018] The gallium nitride epitaxial wafer and the temporary wafer are sequentially subjected to ultrasonic cleaning with acetone, anhydrous ethanol and deionized water and drying, wherein the power of the ultrasonic cleaning is 80-100 W and the cleaning time is 10-20 minutes.

[0019] In an embodiment of the present application, step three comprises:

[0020] Step 301: depositing a bonding layer on the surface of the gallium nitride epitaxial wafer and the surface of the temporary wafer by using an electron beam evaporation process;

[0021] Step 302: stacking the bonding layer in the temporary wafer on the bonding layer in the gallium nitride epitaxial wafer, clamping and fixing the temporary wafer and the gallium nitride epitaxial wafer by using a clamp and placing them in a wafer bonding machine for thermal compression bonding, wherein the bonding temperature is 350℃ and the pressure application time is 60-90 minutes.

[0022] In one embodiment of the present application, step four comprises:

[0023] The bonding sheet is placed in the laser scribing machine with the first silicon layer facing up, and a laser scribing process is used to scribe first grooves and second grooves intersecting each other on the surface of the first silicon layer, wherein the distance between adjacent two first grooves is 2mm, the distance between adjacent two second grooves is 2mm, and the depth of the first grooves and the depth of the second grooves are equal to the thickness of the first silicon layer.

[0024] In one embodiment of the present application, step five comprises:

[0025] The bonding sheet is soaked in a hydrofluoric acid solution with a concentration of 5% to 10%, and the hydrofluoric acid solution flows along the first grooves and the second grooves to corrode the insulating layer. After the insulating layer is dissolved and corroded, the first silicon layer is removed, and a first wafer is obtained, wherein the material of the insulating layer is silicon dioxide.

[0026] In one embodiment of the present application, step five comprises:

[0027] The bonding sheet is placed in a cleaning tank of an ultrasonic cleaning device, and deionized water is provided in the cleaning tank. The bonding sheet is soaked in the deionized water, and the upper surface of the bonding sheet is below the water surface of the deionized water. Ultrasonic waves are used to impact the insulating layer along the first grooves and the second grooves, so that the insulating layer is removed and the first silicon layer is separated, and a first wafer is obtained, wherein the material of the insulating layer is silicon dioxide, the frequency of the ultrasonic waves is 40kHz, the power of the ultrasonic waves is 100W, and the cleaning time is 10 minutes.

[0028] In one embodiment of the present application, step six comprises:

[0029] Step 601: A diamond powder suspension solution with diamond particles of 3nm to 50nm in size is prepared as an ultrasonic solution;

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

[0031] Step 603: The first wafer is placed on a hot plate with a temperature of 100℃ for heating and drying for 10 minutes;

[0032] Step 604: The first wafer is placed in an MPCVD device with the second silicon layer facing up, and diamond with a thickness of 200μm is deposited 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 4000W, and the temperature is 800℃.

[0033] In one embodiment of the present application, step seven comprises:

[0034] The second wafer is placed in the laser scribing machine in a temporary wafer-up manner, and a third groove and a fourth groove intersecting horizontally and vertically are scribed on the surface of the temporary wafer by using a laser scribing process, wherein the distance between the two adjacent third grooves is 2mm, the distance between the two adjacent fourth grooves is 2mm, and the depth of the third groove and the depth of the fourth groove are equal to the thickness of the temporary wafer.

[0035] In an embodiment of the present application, step eight comprises:

[0036] The second wafer is placed in the 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 detached, and a diamond gallium nitride composite wafer is obtained, wherein the material of the bonding layer is gold.

[0037] Compared with the prior art, the present application has the following advantages:

[0038] In the above-mentioned scheme of the present application, first, the first groove structure is prepared 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, so that the etching liquid or ultrasonic cleaning liquid can flow into the first groove structure and contact the insulating layer through the first groove structure, thereby removing the insulating layer by etching the insulating layer with the etching liquid or impacting the insulating layer with the ultrasonic wave, avoiding the risk of breaking the gallium nitride when the mechanical thinning and polishing process is used to remove the insulating layer and the first silicon layer, and improving the quality and yield of the diamond gallium nitride composite wafer. Moreover, the first silicon layer can be detached together with the insulating layer when the insulating layer is removed, 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 transversely distributed first grooves and a plurality of longitudinally distributed second grooves, the etching liquid or ultrasonic cleaning liquid can flow to each position of the insulating layer through the first grooves and the second grooves, making the removal of the insulating layer more efficient and uniform.

[0039] Secondly, the second groove structure is prepared 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, so that the etching liquid can flow into the second groove structure and contact the bonding layer through the second groove structure, thereby removing the bonding layer by etching the bonding layer with the etching liquid, avoiding the risk of breaking the gallium nitride when the mechanical thinning and polishing process is used to remove the bonding layer and the temporary wafer, and improving the quality and yield of the diamond gallium nitride composite wafer. Moreover, the temporary wafer can be detached together with the bonding layer when the bonding layer is removed, making the removal of the bonding layer and the temporary wafer more convenient. In addition, when the second groove structure includes a plurality of transversely distributed third grooves and a plurality of longitudinally distributed fourth grooves, the etching liquid can flow to each position of the bonding layer through the third grooves and the fourth grooves, making the removal of the bonding layer more efficient and uniform.

[0040] And, when the SOI substrate is adopted, the gallium nitride epitaxial layer is grown on the second silicon layer on the SOI substrate, the growth of the gallium nitride epitaxial layer is more convenient and the growth quality is better, and when the diamond is grown, the second silicon layer on the SOI substrate can be used as the growth substrate of the diamond and can protect the gallium nitride epitaxial layer during the growth of the diamond, so that damage of the gallium nitride epitaxial layer is avoided, and thus the quality and yield of the diamond-gallium nitride composite wafer are further improved.

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

[0042] Figure 1 is a schematic diagram of a preparation method of a diamond-gallium nitride composite wafer provided by an embodiment of the application;

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

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

[0045] Figure 4 is a schematic diagram of a bonding wafer in an embodiment of the application;

[0046] Figure 5 is a schematic diagram of setting a first trench structure on the bonding wafer in an embodiment of the application;

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

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

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

[0050] Figure 9 is a schematic diagram of a first wafer in an embodiment of the application;

[0051] Figure 10 is a schematic diagram of a second wafer in an embodiment of the application;

[0052] Figure 11 is a schematic diagram of setting a second trench structure on the second wafer in an embodiment of the application;

[0053] Figure 12 is a top view of a temporary wafer in an embodiment of the application;

[0054] Figure 13is a schematic diagram of a diamond gallium nitride composite wafer in the embodiment of the present application. DETAILED DESCRIPTION

[0055] The present application will be further described in conjunction with specific embodiments, but the embodiments of the present application are not limited thereto.

[0056] Please refer to Figures 1 to 13 The embodiment of the present application provides a preparation method of a diamond gallium nitride composite wafer, comprising:

[0057] Step one: 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 sequentially stacked, the thickness of the first silicon layer being greater than the thickness of the second silicon layer;

[0058] Step two: 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 three: preparing a bonding layer, and sequentially stacking and bonding the temporary wafer, the bonding layer and the gallium nitride epitaxial layer by wafer bonding process;

[0060] Step four: preparing a first trench structure on the surface of the first silicon layer in the bonded wafer, the first trench structure comprising a plurality of transversely distributed first grooves and a plurality of longitudinally distributed second grooves, the depth of the first trench structure being equal to the thickness of the first silicon layer;

[0061] Step five: filling the first trench structure with etching liquid or ultrasonic cleaning liquid, removing the insulating layer in the bonded wafer by etching liquid or removing the insulating layer in the bonded wafer by ultrasonic impact, the insulating layer being removed together with the first silicon layer to obtain a first wafer;

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

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

[0064] Step eight: filling the first trench structure with etching liquid, removing the bonding layer in the first wafer by etching liquid, the bonding layer being removed together with the temporary wafer to obtain a diamond gallium nitride composite wafer.

[0065] In some embodiments of the present application, the 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 layer of silicon, an insulating layer (such as silicon dioxide), and a bottom layer of silicon. This structure achieves dielectric isolation of the active silicon layer from the substrate by introducing an insulating layer between them, 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 laminated structure of two or more of them.

[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 from falling off during the removal of the first silicon layer of the SOI substrate.

[0069] In some embodiments of the present application, a laser cutting machine can be used for scribing when preparing the first and second trench structures, or a photoetching machine can be used for trench pattern transfer and subsequent etching.

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

[0071] In the above scheme of the present application, first, the first trench structure is prepared on the surface of the first silicon layer, and the depth of the first trench structure is equal to the thickness of the first silicon layer, so that the etching liquid or ultrasonic cleaning liquid can flow into the first trench structure and contact the insulating layer through the first trench structure, thereby removing the insulating layer by etching the insulating layer with the etching liquid or impacting the insulating layer with the ultrasonic wave, avoiding the risk of gallium nitride cracking when the mechanical thinning and polishing process is used to remove the insulating layer and the first silicon layer, and improving the quality and yield of the diamond gallium nitride composite wafer. Moreover, the removal of the insulating layer can drive the first silicon layer to fall off together, making the removal of the insulating layer and the first silicon layer more convenient. In addition, when the first trench structure includes a plurality of first grooves distributed transversely and a plurality of second grooves distributed longitudinally, the etching liquid or ultrasonic cleaning liquid can flow through the first and second grooves to each position of the insulating layer, making the removal of the insulating layer more efficient and uniform.

[0072] Secondly, the second groove structure is prepared 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, so that the etching liquid can flow into the second groove structure and contact the bonding layer through the second groove structure, thereby removing the bonding layer by etching the bonding layer, avoiding the risk of gallium nitride cracking when the mechanical thinning and polishing process is used to remove the bonding layer and the temporary wafer, and improving the quality and yield of the diamond gallium nitride composite wafer. And the temporary wafer can be removed together when the bonding layer is removed, so that the removal of the bonding layer and the temporary wafer is more convenient. In addition, when the second groove structure includes a plurality of third grooves distributed transversely and a plurality of fourth grooves distributed longitudinally, the etching liquid can flow through the third grooves and the fourth grooves to each position of the bonding layer, so that the removal of the bonding layer is more efficient and more uniform.

[0073] In addition, when the SOI substrate is used, the gallium nitride epitaxial layer is grown on the second silicon layer of the SOI substrate, which can facilitate the growth of the gallium nitride epitaxial layer and improve the 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 protect the gallium nitride epitaxial layer during diamond growth, thereby avoiding damage to the gallium nitride epitaxial layer and further improving the quality and yield of the diamond gallium nitride composite wafer. In addition, the SOI substrate has obvious advantages over bulk silicon materials, and the technology for preparing gallium nitride materials using SOI as a growth substrate is mature and continuously improves the integration with IC processes. At the same time, the above-mentioned method of the present application does not have strict requirements for the bonding strength of the bonding sheet, and the bonding layer material can have multiple choices. The above-mentioned method of the present application is compatible with the semiconductor process production line, 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, enabling the full play of the high-power advantage of gallium nitride devices, having high research value, and being able to produce good social and economic benefits, and promoting the development of related industries.

[0074] In some embodiments of the present application, as shown in Figure 2 and Figure 3 Step two includes:

[0075] The SOI substrate is placed in the growth device with the first silicon layer facing down and the second silicon layer facing up, and a gallium nitride epitaxial layer is grown on the surface of the second silicon layer using the MOCVD process. Using this method, it is convenient to grow 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 type of vapor phase epitaxy growth technology developed on the basis of vapor phase epitaxy growth (VPE). It uses metal organic compounds and hydride as crystal growth source materials, and performs vapor phase epitaxy on the substrate through thermal decomposition reaction to grow thin layer single crystal materials of various III-V group, II-VI group compound semiconductors and their multi-element solid solution.

[0077] In some embodiments of the present application, after step two and before step three, further comprising:

[0078] The gallium nitride epitaxial wafer and the temporary wafer are sequentially subjected to ultrasonic cleaning with acetone, anhydrous ethanol and deionized water, and are dried, wherein the power of the ultrasonic cleaning is 80W-100W, and the cleaning time is 10-20 minutes. By using this method, the gallium nitride epitaxial wafer and the temporary wafer can be fully cleaned before they are bonded, the cleanliness of the gallium nitride epitaxial wafer and the temporary wafer during bonding is improved, and thus the bonding effect of the gallium nitride epitaxial wafer and the temporary wafer is better.

[0079] In some embodiments of the present application, when the gallium nitride epitaxial wafer and the temporary wafer are sequentially subjected to ultrasonic cleaning with acetone, anhydrous ethanol and deionized water, contaminants and dust particles on the surfaces of the gallium nitride epitaxial wafer and the temporary wafer can be washed away.

[0080] In some embodiments of the present application, as shown in Figure 4 Step three comprises:

[0081] Step 301: A bonding layer is deposited on the surface of the gallium nitride epitaxial wafer and the surface of the temporary wafer by using an electron beam evaporation process;

[0082] Step 302: The bonding layer in the temporary wafer is stacked on the bonding layer in the gallium nitride epitaxial wafer, the temporary wafer and the gallium nitride epitaxial wafer are clamped and fixed by using a clamp and are placed in a wafer bonding machine for thermal pressure bonding, wherein the bonding temperature is 350℃, and the pressure application time is 60-90 minutes. By using this method, the temporary wafer can be bonded to the gallium nitride epitaxial wafer by wafer bonding.

[0083] In some embodiments of the present application, the material of the bonding layer is gold, the thickness of the bonding layer is 300-500nm, and when the bonding layer in the temporary wafer is stacked on the bonding layer in the gallium nitride epitaxial wafer, the edges of the temporary wafer and the gallium nitride epitaxial wafer are ensured to completely coincide. After 60-90 minutes of pressure application, the pressure is removed, the bonded wafer is slowly cooled to room temperature, and then taken out.

[0084] In some embodiments of the present application, as shown in Figure 5 and Figure 6 Step four includes:

[0085] Place the bonding sheet in the laser scribing machine with the first silicon layer facing up, and use the laser scribing process to scribe the first and second grooves on the surface of the first silicon layer, wherein the distance between two adjacent first grooves is 2 mm, the distance between two adjacent second grooves is 2 mm, and the depth of the first groove and the depth of the second groove are equal to the thickness of the first silicon layer. In this way, the first trench structure can be prepared on the first silicon layer by laser scribing, and the insulation layer can be removed more uniformly.

[0086] In an alternative way, as shown in Figure 7 and Figure 9 Step five includes:

[0087] Soak the bonding sheet in a hydrofluoric acid solution with a concentration of 5% to 10%, and the hydrofluoric acid solution flows along the first and second grooves to corrode the insulation layer. After the insulation layer is corroded and dissolved, the first silicon layer is removed, and a first wafer is obtained, wherein the material of the insulation layer is silicon dioxide. In this way, the insulation layer can be dissolved and removed by using a hydrofluoric acid solution with a concentration of 5% to 10% to corrode and dissolve the insulation layer. When the insulation layer falls off, the first silicon layer can also fall off, thereby removing the insulation 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 longitudinal and lateral grooves, and the silicon dioxide is etched longitudinally and laterally. After the silicon dioxide layer is corroded and dissolved, the first silicon layer naturally falls off without a connecting layer, and a die sheet supported by a temporary wafer is obtained.

[0089] In another alternative way, as shown in Figure 8 and Figure 9 Step five includes:

[0090] Place the bonding wafer in a cleaning tank of an ultrasonic cleaning device, and the cleaning tank is provided with deionized water, the bonding wafer is soaked in the deionized water, and the upper surface of the bonding wafer is lower than the water surface of the deionized water; and ultrasonic waves are used to impact the insulating layer along the first groove and the second groove, so that the insulating layer is separated and the first silicon layer is separated, and a first wafer is obtained, wherein the material of the insulating layer is silicon dioxide, the frequency of the ultrasonic waves is 40 kHz, the power of the ultrasonic waves is 100 W, and the cleaning time is 10 minutes. In this way, when the ultrasonic waves propagate in the deionized water, cavitation effect is generated, and micro vacuum bubbles (cavitation bubbles) are formed in the deionized water; under the periodic pressure change of the ultrasonic waves, the cavitation bubbles continuously grow, shrink and collapse; and the strong energy impact generated by the collapse of the cavitation bubbles can loosen and separate the silicon dioxide, and then the first silicon layer is removed. The upper surface of the bonding wafer is lower than the water surface of the deionized water, so that the bonding wafer can be fully soaked in the deionized water, and the efficiency and effect of removing the insulating layer and the first silicon layer are improved.

[0091] In some embodiments of the present application, after step five and before step six, the method further comprises:

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

[0093] In some embodiments of the present application, as shown in Figure 10 , step six comprises:

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

[0095] 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;

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

[0097] Step 604: placing the first wafer in the MPCVD device with the second silicon layer facing up to 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 the diamond is improved.

[0098] In some embodiments of the present application, as shown in Figure 11 and Figure 12 , step seven comprises:

[0099] The second wafer is placed in the laser scribing machine with the temporary wafer facing up, and a laser scribing process is used to scribe third and fourth grooves intersecting each other on the surface of the temporary wafer, wherein the distance between two adjacent third grooves is 2mm, the distance between two adjacent fourth grooves is 2mm, and the depth of the third groove and the depth of the fourth groove are equal to the thickness of the temporary wafer. In this way, the second groove structure can be prepared on the temporary wafer by laser scribing, and the bonding layer can be removed more uniformly.

[0100] In some embodiments of the present application, as shown in Figure 11 and Figure 13 Step eight includes:

[0101] The second wafer is placed in the 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 removed, and a diamond gallium nitride composite wafer is obtained, wherein the material of the bonding layer is gold. In this way, the bonding layer can be dissolved and separated by using the potassium iodide solution to corrode and dissolve the bonding layer. When the bonding layer falls off, the temporary wafer can be removed together, so as to remove 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 application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0104] In addition, the terms "first", "second", "third", "fourth" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", "third", "fourth" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0105] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate different embodiments or examples described in the specification.

[0106] The above is a further detailed description of the present application in combination with specific preferred embodiments, and cannot be considered as limiting the specific implementation of the present application to these descriptions. For those skilled in the art, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be considered as falling within the protection scope of the present application.

Claims

1. A method for preparing a diamond-gallium nitride composite wafer, characterized in that, include: Step 1: Provide a temporary wafer and an SOI substrate. The SOI substrate includes a first silicon layer, an insulating layer, and a second silicon layer stacked sequentially. The thickness of the first silicon layer is greater than the thickness of the second silicon layer. Step 2: A gallium nitride epitaxial layer is grown on the surface of the second silicon layer in the SOI substrate to obtain a gallium nitride epitaxial wafer; Step 3: Prepare the bonding layer. The temporary wafer, the bonding layer, and the gallium nitride epitaxial layer are sequentially stacked and bonded using a wafer bonding process to obtain a bonded wafer. Step 4: Prepare a first trench structure on the surface of the first silicon layer in the bonding wafer. The first trench structure includes multiple horizontally distributed first trenches and multiple vertically distributed second trenches. The depth of the first trench structure is equal to the thickness of the first silicon layer. Step 5: Fill the first trench structure with an etchant or an ultrasonic cleaning solution to remove the insulating layer in the bonded wafer by etching with the etchant or by ultrasonic impact. When the insulating layer is removed, the first silicon layer is detached to obtain the first wafer. Step 6: Grow diamond on the surface of the second silicon layer in the first wafer to obtain the second wafer; Step 7: Prepare a second trench structure on the surface of the temporary wafer in the second wafer. The second trench structure includes multiple horizontally distributed third trenches and multiple vertically distributed fourth trenches. The depth of the second trench structure is equal to the thickness of the temporary wafer. Step 8: Fill the first trench structure with an etchant to remove the bonding layer in the first wafer by etching. When the bonding layer is removed, the temporary wafer is detached to obtain a gallium diamond nitride composite wafer. Step four includes: The bonding wafer is placed in a laser scribing machine with the first silicon layer facing upwards. The laser scribing process is used to scribing the first and second grooves, which are intersecting horizontally and vertically, on the surface of the first silicon layer. The distance between two adjacent first grooves is 2 mm, the distance between two adjacent second grooves is 2 mm, and the depth of the first groove and the depth of the second groove are equal to the thickness of the first silicon layer. Step seven includes: The second wafer is placed in a laser scribing machine with the temporary wafer facing upwards. The laser scribing process is used to scribing the surface of the temporary wafer with intersecting third and fourth grooves. The distance between two adjacent third grooves is 2 mm, the distance between two adjacent fourth grooves is 2 mm, and the depth of the third groove and the depth of the fourth groove are equal to the thickness of the temporary wafer.

2. The method for preparing a diamond-gallium nitride composite wafer according to claim 1, characterized in that, Step two includes: The SOI substrate is placed in the growth equipment with the first silicon layer facing down and the second silicon layer facing up, and a gallium nitride epitaxial layer is grown on the surface of the second silicon layer using the MOCVD process.

3. The method for preparing a diamond-gallium nitride composite wafer according to claim 1, characterized in that, After step two and before step three, the following also includes: The gallium nitride epitaxial wafer and the temporary wafer were ultrasonically cleaned and dried sequentially using acetone, anhydrous ethanol, and deionized water, respectively. The ultrasonic cleaning power was 80W~100W and the cleaning time was 10 minutes~20 minutes.

4. The method for preparing a diamond-gallium nitride composite wafer according to claim 1, characterized in that, Step three includes: Step 301: Using electron beam evaporation, bonding layers are deposited on the surface of the gallium nitride epitaxial wafer and the surface of the temporary wafer, respectively; Step 302: The bonding layer in the temporary wafer is stacked onto the bonding layer in the gallium nitride epitaxial wafer. The temporary wafer and the gallium nitride epitaxial wafer are clamped and fixed using a jig and placed in a wafer bonding machine for hot-press bonding. The bonding temperature is 350°C and the pressure application time is 60 to 90 minutes.

5. The method for preparing a diamond-gallium nitride composite wafer according to claim 1, characterized in that, Step five includes: 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 and second tanks to corrode the insulating layer. After the insulating layer is corroded and dissolved, it causes the first silicon layer to fall off, resulting in a first wafer. The insulating layer is made of silicon dioxide.

6. The method for preparing a diamond-gallium nitride composite wafer according to claim 1, characterized in that, Step five includes: The bonding wafer is placed in a cleaning tank of an ultrasonic cleaning device. The cleaning tank contains deionized water, and the bonding wafer is immersed in the deionized water with its upper surface below the water surface. Ultrasonic waves are used to impact the insulating layer along the first and second tanks to cause the insulating layer to detach and the first silicon layer to detach, thus obtaining a first wafer. 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.

7. The method for preparing a diamond-gallium nitride composite wafer according to claim 1, characterized in that, Step six includes: Step 601: Prepare a diamond powder suspension with diamond particles of 3nm~50nm size as an ultrasonic solution; Step 602: Place the first wafer in the ultrasonic solution for ultrasonic treatment for 25 minutes to form uniformly distributed diamond seed crystals on the first wafer. Step 603: Place the first wafer on a hot plate at 100°C and heat for 10 minutes to dry it; Step 604: Place the first wafer into the MPCVD equipment with the second silicon layer facing upwards, and deposit a diamond layer with a thickness of 200 μm on the surface of the second silicon layer to obtain the second wafer. The MPCVD equipment is set with a methane-to-hydrogen ratio of 8%, a power of 4000 W, and a temperature of 800 °C.

8. The method for preparing a diamond-gallium nitride composite wafer according to claim 4, characterized in that, Step eight includes: The second wafer is placed in a potassium iodide solution, which flows along the third and fourth grooves to etch the bonding layer. After the bonding layer is etched and dissolved, it causes the temporary wafer to fall off, resulting in a diamond gallium nitride composite wafer. The bonding layer is made of gold.

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