A lateral diamond / GaN / diamond substrate for making GaN HEMT and its preparation method

Abstract

The present invention relates to a lateral diamond / GaN / diamond substrate and preparation method for manufacturing GaN HEMTs. The method comprises: obtaining two pieces of polycrystalline diamond and polishing one side of the polycrystalline diamond to a smooth surface; obtaining a GaN single crystal wafer and polishing both sides of the GaN single crystal wafer to smooth surfaces, wherein the smooth surface of the GaN single crystal wafer is a non-polar surface; and bonding the smooth surfaces of the two polycrystalline diamonds to the two smooth surfaces of the GaN single crystal wafer using a low-temperature bonding process to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate. This method improves the heat dissipation capacity of conventional GaN epitaxial substrates, enhances the quality of epitaxial GaN, and further increases the operating life and stability of the device, thereby paving the way for the device to operate at high power. The device can be used to manufacture high-frequency, high-power GaN-based HEMTs.

Description

Technical Field

[0001] The present invention belongs to the field of microelectronics technology and relates to a lateral diamond / GaN / diamond substrate for manufacturing GaN HEMT and a preparation method thereof. Background Art

[0002] As a third-generation semiconductor material, GaN has excellent properties such as wide bandgap, high electron saturation velocity, and high breakdown field strength, and is widely used in high-frequency, high-power devices and circuits. Due to the polarization effect, a two-dimensional electron gas is formed at the AlGaN / GaN interface in the polar direction, which can greatly enhance the electron mobility of GaN devices. Since GaN itself has a high breakdown field strength, this principle can be used to manufacture high electron mobility transistor (HEMT) devices.

[0003] In recent years, as the power density of GaN-based power devices increases, the thermal accumulation effect of the chip increases rapidly, causing various performance indicators to deteriorate rapidly, limiting the full utilization of its high-power characteristics. The thermal conductivity of sapphire, SiC, and Si substrates commonly used for epitaxial GaN is only about 40-400W·m -1 ·k -1 , which cannot meet the heat dissipation requirements of high-power applications. Therefore, the heat dissipation problem has become one of the main problems restricting the further development and widespread application of GaN-based power devices. Diamond is the substrate material with the highest thermal conductivity at present, with a thermal conductivity of 1200 to 2000 W·m -1 ·k -1 , which can effectively solve the heat dissipation problem in high-power applications. However, due to lattice mismatch, the dislocation density of epitaxial GaN on diamond substrates is very high, the crystal quality is poor, and the resulting devices have severe leakage, which also affects the high-power characteristics of GaN materials.

[0004] The most ideal epitaxial substrate for GaN is a GaN homogeneous substrate, which has the characteristics of no lattice mismatch, thus reducing the dislocation density and improving the crystal quality. However, the thermal conductivity of the GaN homogeneous substrate is only 200W·m -1 ·k -1 , which is much lower than that of diamond substrates and cannot meet the heat dissipation requirements of high-power devices. Figure 1 The figure shows a pure GaN wafer.

[0005] In short, the substrates currently used for GaN epitaxy cannot achieve both high thermal conductivity and low dislocation density, which limits GaN power devices, especially GaN HEMT devices, from exerting their high-power characteristics. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, the present invention provides a lateral diamond / GaN / diamond substrate and a method for fabricating a GaN HEMT. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0007] An embodiment of the present invention provides a method for preparing a lateral diamond / GaN / diamond substrate for manufacturing a GaN HEMT, comprising the following steps:

[0008] Obtain two pieces of polycrystalline diamonds, and polish one side of the polycrystalline diamonds into a smooth surface by polishing;

[0009] Obtaining a GaN single crystal wafer, and polishing both sides of the GaN single crystal wafer into smooth surfaces by polishing, wherein the smooth surface of the GaN single crystal wafer is a non-polar surface;

[0010] The smooth surfaces of the two polycrystalline diamonds are bonded to the two smooth surfaces of the GaN single crystal wafer respectively by using a low temperature bonding process to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate.

[0011] In one embodiment of the present invention, polishing one side of the polycrystalline diamond into a smooth surface by polishing comprises:

[0012] One side of the two polycrystalline diamonds is polished to a root mean square roughness of 0.5-3.0 nm to form a smooth surface.

[0013] In one embodiment of the present invention, polishing both sides of the GaN single crystal wafer into smooth surfaces by polishing includes:

[0014] The root mean square roughness of both sides of the GaN single crystal wafer is polished to less than 1 nm by polishing, so that both sides of the GaN single crystal wafer form smooth surfaces.

[0015] In one embodiment of the present invention, the smooth surfaces of two pieces of polycrystalline diamond are bonded to the two smooth surfaces of the GaN single crystal wafer respectively using a low temperature bonding process to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate, comprising:

[0016] Using a CVD process, depositing SiN bonding layers on the smooth surfaces of the GaN single crystal wafer and the polycrystalline diamond respectively;

[0017] Control the temperature to below 150℃ and the pressure to below 10 -5 Under a low vacuum degree of 100 Pa, a pressure of 1-100 N is applied for a duration of 1-10 minutes, so that the two smooth surfaces of the GaN single crystal wafer are bonded to the smooth surfaces of the two polycrystalline diamonds respectively;

[0018] Performing a thermal annealing treatment on the GaN single crystal wafer and the polycrystalline diamond after the bonding treatment at a temperature of 300-500° C., wherein the thermal annealing time is 10-30 minutes;

[0019] The GaN single crystal wafer and the polycrystalline diamond after thermal annealing are longitudinally sliced ​​and mechanically polished to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate.

[0020] In one embodiment of the present invention, the GaN single crystal wafer and the polycrystalline diamond after thermal annealing are longitudinally sliced ​​and mechanically polished to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate, comprising:

[0021] Using a laser cutting process to longitudinally slice the GaN single crystal wafer and the polycrystalline diamond after thermal annealing to obtain a plurality of slices, wherein the slice thickness is 1-10 mm;

[0022] One side or both sides of the slice are mechanically polished to a mirror surface to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate.

[0023] Another embodiment of the present invention provides a lateral diamond / GaN / diamond substrate for fabricating a GaN HEMT. The substrate is prepared by the preparation method described in any of the above embodiments. The device includes: a GaN single crystal wafer, two polycrystalline diamonds, and two SiN bonding layers. The polycrystalline diamonds, the SiN bonding layers, the GaN single crystal wafer, the SiN bonding layers, and the polycrystalline diamonds are arranged in sequence from left to right.

[0024] In one embodiment of the present invention, the lateral size of the polycrystalline diamond is 0.5-5 mm.

[0025] In one embodiment of the present invention, the lateral size of the GaN single crystal wafer is 10-30 mm.

[0026] In one embodiment of the present invention, the lateral dimension of the SiN bonding layer is 40-200 nm.

[0027] In one embodiment of the present invention, the thickness of the substrate formed by the polycrystalline diamond, the SiN bonding layer, the GaN single crystal wafer, the SiN bonding layer and the polycrystalline diamond is 1-10 mm.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention uses polycrystalline diamond as part of the substrate, thereby enhancing the heat dissipation capacity of the substrate.

[0030] 2. Since the dislocation direction of the GaN single crystal is parallel to the substrate, the present invention uses it in the epitaxial process, especially the GaN homoepitaxial process, and the epitaxial crystal will have more ideal crystal quality.

[0031] 3. Since the present invention can slice the polycrystalline diamond / GaN / polycrystalline diamond structure multiple times, it can be produced in large quantities.

[0032] 4. Since epitaxial growth can be performed on both sides of the substrate obtained by the present invention, the Ga side or the N side can be freely selected for epitaxy.

[0033] 5. The substrate prepared by the present invention improves the heat dissipation capability of conventional GaN epitaxial substrates, improves the quality of epitaxial GaN, and further enhances the device's operating life and stability, thereby laying the foundation for the device's operation at high power. It can be used to fabricate high-frequency, high-power GaN-based HEMT devices.

[0034] Other aspects and features of the present invention will become apparent from the following detailed description, which proceeds with reference to the accompanying drawings. It should be understood, however, that the drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention, as reference should be made to the appended claims. It should also be understood that, unless otherwise indicated, the drawings are not necessarily drawn to scale and are intended merely to conceptually illustrate the structures and processes described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the structure of a GaN wafer provided by the prior art;

[0036] Figure 2 A schematic flow chart of a method for preparing a lateral diamond / GaN / diamond substrate for manufacturing a GaN HEMT provided in an embodiment of the present invention;

[0037] Figure 3 A schematic diagram of a process for preparing a lateral diamond / GaN / diamond substrate for a GaN HEMT provided in an embodiment of the present invention;

[0038] Figure 4 A schematic structural diagram of a lateral diamond / GaN / diamond substrate for fabricating a GaN HEMT provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0040] Example 1

[0041] See Figure 2 、 Figure 3 and Figure 4 , Figure 2 A schematic flow chart of a method for preparing a lateral diamond / GaN / diamond substrate for manufacturing a GaN HEMT provided in an embodiment of the present invention. Figure 3 A schematic diagram of a process for preparing a lateral diamond / GaN / diamond substrate for manufacturing a GaN HEMT provided by an embodiment of the present invention. Figure 4 A schematic diagram of the structure of a lateral diamond / GaN / diamond substrate for manufacturing a GaN HEMT according to an embodiment of the present invention. The present invention provides a method for manufacturing a lateral diamond / GaN / diamond substrate for manufacturing a GaN HEMT, the method comprising the following steps:

[0042] Step 1. Please refer to Figure 3 a. Obtain two pieces of polycrystalline diamond and polish one side of the polycrystalline diamond into a smooth surface.

[0043] In a specific embodiment, polishing one side of the polycrystalline diamond into a smooth surface by polishing comprises:

[0044] One side of two polycrystalline diamonds is polished to a root mean square roughness of 0.5-3.0 nm to form a smooth surface.

[0045] Specifically, two pieces of polycrystalline diamond with a thickness of 0.5-5 mm are selected, and one side of each of the two polycrystalline diamonds is polished to a root mean square roughness (RMS) of 0.5-3.0 nm to form a smooth surface. The thickness of the polycrystalline diamond will determine the lateral size of the polycrystalline diamond in the final substrate.

[0046] Step 2: Please refer to Figure 3 (a) Obtain a GaN single crystal wafer, and polish both sides of the GaN single crystal wafer into smooth surfaces by polishing, wherein the smooth surface of the GaN single crystal wafer is a non-polar surface.

[0047] In a specific embodiment, polishing both sides of a GaN single crystal wafer into smooth surfaces includes:

[0048] The root mean square roughness of both sides of the GaN single crystal wafer is polished to less than 1 nm by polishing, so that both sides of the GaN single crystal wafer form smooth surfaces.

[0049] Specifically, a non-polar GaN single crystal wafer with a thickness of 10-30 mm is selected. Through polishing, the RMS of both sides of the GaN single crystal wafer is reduced to below 1 nm, forming smooth surfaces on the upper and lower sides. The thickness of the selected GaN single crystal wafer will determine the lateral size of the GaN single crystal in the final substrate.

[0050] Step 3: Bond the smooth surfaces of two polycrystalline diamonds to the two smooth surfaces of the GaN single crystal wafer using a low-temperature bonding process to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate.

[0051] In a specific embodiment, step 3 includes:

[0052] Step 3.1, please refer to Figure 3 (b) Using CVD (Chemical Vapor Deposition) technology, SiN bonding layers are deposited on the smooth surfaces of the GaN single crystal wafer and polycrystalline diamond, respectively.

[0053] Specifically, a CVD process is used to deposit a 20-100 nm thick SiN bonding layer on the smooth surfaces of GaN single crystal and polycrystalline diamond, respectively.

[0054] Step 3.2: Control the temperature below 150° C. and apply a pressure of 1-100 N for 1-10 minutes under a low vacuum of less than 10-5 Pa to ensure that the two smooth surfaces of the GaN single crystal wafer are closely attached to the smooth surfaces of the two polycrystalline diamonds, thereby achieving pre-bonding.

[0055] Step 3.3: Perform thermal annealing on the bonded GaN single crystal wafer and polycrystalline diamond at a temperature of 300-500° C., wherein the thermal annealing time is 10-30 minutes.

[0056] Specifically, the temperature is raised to 300-500° C. for 10-30 minutes to perform thermal annealing.

[0057] Step 3.4: longitudinally slice and mechanically polish the GaN single crystal wafer and polycrystalline diamond after thermal annealing to obtain a transverse polycrystalline diamond / GaN / polycrystalline diamond substrate.

[0058] In a specific embodiment, step 3.4 includes steps 3.41-3.42, wherein:

[0059] Step 3.41, see Figure 3 (c) Using a laser cutting process to slice the GaN single crystal wafer and polycrystalline diamond after thermal annealing to obtain several slices, wherein the slice thickness is 1-10 mm

[0060] Specifically, the structure produced after the heat treatment is sliced ​​longitudinally using a laser cutting process, with a slice thickness of 1-10 mm. The slice thickness will determine the thickness of the final substrate.

[0061] Step 3.42, see Figure 3(d) Mechanically polishing one or both sides of the slice to a mirror finish to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate.

[0062] Specifically, the slice is placed horizontally, and single-sided or double-sided mechanical polishing is performed to a mirror surface to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate.

[0063] The invention adopts polycrystalline diamond as a part of the substrate, thereby enhancing the heat dissipation capacity of the substrate.

[0064] Since the dislocation direction of the GaN single crystal is parallel to the substrate, the present invention uses it in an epitaxial process, especially a GaN homoepitaxial process, and the epitaxially grown crystal will have a more ideal crystal quality.

[0065] Since the present invention can slice the polycrystalline diamond / GaN / polycrystalline diamond structure multiple times, it can be prepared in large quantities.

[0066] Since epitaxial growth can be performed on both sides of the substrate obtained by the present invention, the Ga side or the N side epitaxial growth can be freely selected.

[0067] The lateral diamond / GaN / diamond substrate fabricated in this invention can improve device thermal conductivity, preventing the negative impact of thermal effects on device performance, thereby increasing device power density. Furthermore, if this structure is used for homoepitaxial GaN growth, it can reduce dislocations in epitaxial wafers.

[0068] The lateral diamond / GaN / diamond substrate prepared by the present invention can be used to manufacture GaN high electron mobility transistor devices.

[0069] Example 2

[0070] This embodiment provides a method for preparing a 1 mm thick single-sided polished lateral diamond / GaN / diamond substrate based on the above embodiment. The preparation method includes the following steps:

[0071] Step 1, such as Figure 3 (a) Two 0.5 mm thick polycrystalline diamond sheets were polished using a mixture of equal weights of 30% H₂O₂ and deionized water as the polishing fluid and W0.5 diamond grit as the abrasive. The polishing speed was set at 20 r / min and the polishing pressure was set at 0.6 MPa. One side of each polycrystalline diamond sheet was polished to a root mean square roughness (RMS) of 0.5 nm, resulting in a smooth surface.

[0072] Step 2, such as Figure 3(a) A 10 mm thick non-polar GaN single crystal wafer was polished using a 0.8% H₂O₂ solution and W0.5 grit SiO₂ as the abrasive. The polishing speed was set at 60 r / min and the polishing pressure was set at 0.10 MPa. The RMS of the GaN single crystal wafer was reduced to 0.5 nm on both sides, resulting in smooth surfaces on both the top and bottom.

[0073] Step three, such as Figure 3 (b) low-temperature bonding the smooth surfaces of two polycrystalline diamond sheets to the smooth surfaces on both sides of a GaN single crystal wafer;

[0074] 3a) using a CVD process with a reaction chamber temperature of 675° C. and a reaction chamber pressure of 320 mTorr, while simultaneously introducing ammonia gas at a flow rate of 20 sccm and a silicon source (SiH2Cl2) at a flow rate of 40 sccm into the reaction chamber, the process was repeated twice to deposit a 20 nm thick SiN bonding layer on each of the two smooth surfaces of the GaN single crystal wafer; and setting the reaction chamber temperature to 750° C. and maintaining the reaction chamber pressure at 150 mTorr, while simultaneously introducing ammonia gas at a flow rate of 22 sccm and a silicon source (SiH2Cl2) at a flow rate of 98 sccm into the reaction chamber to deposit a 20 nm thick SiN bonding layer on each of the smooth surfaces of the two polycrystalline diamond wafers;

[0075] 3b) Control the temperature to 50℃ and the pressure to 10 -7 Under a vacuum degree of 10 Pa, a pressure of 10 N was applied for 1 minute, so that the two smooth surfaces of the GaN single crystal wafer were closely attached to the smooth surfaces of the two polycrystalline diamonds, achieving pre-bonding;

[0076] 3c) raising the temperature to 300° C. for 10 min to perform thermal annealing;

[0077] Step 4: Figure 3 (c) The prepared sample was sliced ​​longitudinally using a laser cutting process, using a laser wavelength of 355 nm, a slice thickness of 1 mm, a cutting power of 50 W, a laser pulse frequency of 30 Hz, a scanning speed of 0.2 mm / min, and cyclic scanning until the slice was completely cut;

[0078] Step five, such as Figure 3 (d) The slice is placed horizontally and mechanically polished to a mirror finish on one side to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate.

[0079] Example 3

[0080] This embodiment provides a method for preparing a 5 mm thick single-sided polished lateral diamond / GaN / diamond substrate based on the above embodiment. The preparation method includes the following steps:

[0081] Step 1, such as Figure 3 (a) Two 2mm thick polycrystalline diamond sheets were polished using an equal-mass mixture of 30% H₂O₂ and deionized water as the polishing fluid and W0.5 diamond grit as the abrasive. The polishing speed was set at 40 r / min and the polishing pressure was set at 0.8 MPa. One side of each polycrystalline diamond sheet was polished to a root mean square roughness of 1.5 nm, resulting in a smooth surface.

[0082] Step 2, such as Figure 3 (a) A 20mm thick non-polar GaN single crystal wafer was polished using a 0.8% H2O2 solution and W0.5 SiO2 abrasive. The polishing speed was set at 75 r / min and the polishing pressure was set at 0.15 MPa. The RMS of the GaN single crystal wafer was reduced to 0.7nm on both sides, resulting in smooth surfaces on both the top and bottom.

[0083] Step three, such as Figure 3 (b) Low-temperature bonding of the smooth surfaces of two polycrystalline diamond sheets to the smooth surfaces on both sides of a GaN single crystal wafer.

[0084] 3a) using a CVD process with a reaction chamber temperature of 750° C. and a reaction chamber pressure of 320 mTorr, while simultaneously introducing ammonia gas at a flow rate of 20 sccm and a silicon source (SiH2Cl2) at a flow rate of 40 sccm into the reaction chamber, the process was repeated twice to deposit a 50 nm thick SiN bonding layer on each of the two smooth surfaces of the GaN single crystal wafer; and setting the reaction chamber temperature to 825° C. and maintaining the reaction chamber pressure at 150 mTorr, while simultaneously introducing ammonia gas at a flow rate of 22 sccm and a silicon source (SiH2Cl2) at a flow rate of 98 sccm into the reaction chamber to deposit a 50 nm thick SiN bonding layer on each of the smooth surfaces of the two polycrystalline diamond wafers;

[0085] 3b) Control the temperature to 100℃ and the pressure to 10 -6 Under a vacuum degree of 1.5 Pa, a pressure of 150 N was applied for 5 minutes, so that the two smooth surfaces of the GaN single crystal wafer were closely attached to the smooth surfaces of the two polycrystalline diamonds, achieving pre-bonding.

[0086] 3c) raising the temperature to 450° C. for 15 minutes for thermal annealing;

[0087] Step 4: Figure 3 (c) The prepared sample was sliced ​​longitudinally using a laser cutting process, using a laser wavelength of 266 nm, a slice thickness of 5 mm, a cutting power of 90 W, a laser pulse frequency of 60 Hz, a scanning speed of 0.6 mm / min, and cyclic scanning until the slice was completely cut;

[0088] Step five, such as Figure 3 (d) The slice is placed horizontally and mechanically polished to a mirror finish on one side to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate.

[0089] Example 4

[0090] This embodiment provides a method for preparing a 1 mm thick single-sided polished lateral diamond / GaN / diamond substrate based on the above embodiment. The preparation method includes the following steps:

[0091] Step 1, such as Figure 3 (a) Two 5mm thick polycrystalline diamond sheets were polished using an equal-mass mixture of 30% H₂O₂ and deionized water as the polishing fluid and W0.5 diamond grit as the abrasive. The polishing speed was set at 60 r / min and the polishing pressure was set at 1.0 MPa. One side of each polycrystalline diamond sheet was polished to a root mean square roughness of 3.0 nm, resulting in a smooth surface.

[0092] Step 2, such as Figure 3 (a) A 30 mm thick non-polar GaN single crystal wafer was polished using a 0.8% H₂O₂ solution and W0.5 grit SiO₂ as the abrasive. The polishing speed was set at 90 r / min and the polishing pressure was set at 0.20 MPa. The RMS of the GaN single crystal wafer was reduced to 1.0 nm on both sides, resulting in smooth surfaces on both the top and bottom.

[0093] Step three, such as Figure 3 (b) Low-temperature bonding of the smooth surfaces of two polycrystalline diamond sheets to the smooth surfaces on both sides of a GaN single crystal wafer.

[0094] 3a) using a CVD process with a reaction chamber temperature of 825° C. and a reaction chamber pressure of 320 mTorr, while simultaneously introducing ammonia gas at a flow rate of 20 sccm and a silicon source (SiH2Cl2) at a flow rate of 40 sccm into the reaction chamber, the process was repeated twice to deposit a 100 nm thick SiN bonding layer on each of the two smooth surfaces of the GaN single crystal wafer; and setting the reaction chamber temperature to 875° C. and maintaining the reaction chamber pressure at 150 mTorr, while simultaneously introducing ammonia gas at a flow rate of 22 sccm and a silicon source (SiH2Cl2) at a flow rate of 98 sccm into the reaction chamber to deposit a 100 nm thick SiN bonding layer on each of the smooth surfaces of the two polycrystalline diamond wafers;

[0095] 3b) Control the temperature to 150℃ and the pressure to 10 -5 Under a vacuum degree of 1.5 Pa, a pressure of 500 N was applied for 10 minutes, so that the two smooth surfaces of the GaN single crystal wafer were closely attached to the smooth surfaces of the two polycrystalline diamonds, achieving pre-bonding.

[0096] 3c) raising the temperature to 500° C. for 30 min to perform thermal annealing;

[0097] Step 4: Figure 3 (c) The prepared sample was sliced ​​longitudinally using a laser cutting process, using a laser wavelength of 157 nm, a slice thickness of 10 mm, a cutting power of 120 W, a laser pulse frequency of 90 Hz, a scanning speed of 1.0 mm / min, and cyclic scanning until the slice was completely cut;

[0098] Step five, such as Figure 3 (d) The slice is placed horizontally and mechanically polished on both sides to a mirror finish to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate.

[0099] Example 5

[0100] See Figure 4 , Figure 4 The present invention provides a schematic diagram of a lateral diamond / GaN / diamond substrate for manufacturing GaN HEMT. A lateral diamond / GaN / diamond substrate for a HEMT is prepared using the method described in the above embodiment. The lateral diamond / GaN / diamond substrate comprises: a polycrystalline diamond 1, a SiN bonding layer 2, a GaN single crystal wafer 3, a SiN bonding layer 4, and a polycrystalline diamond 5. The polycrystalline diamond 1, SiN bonding layer 2, GaN single crystal wafer 3, SiN bonding layer 4, and polycrystalline diamond 5 are arranged in sequence from left to right. The polycrystalline diamond 1 and polycrystalline diamond 5 enhance the substrate's heat dissipation capability and improve the device's performance under high power conditions. The SiN bonding layers 2 and 4 are used in the bonding process between the polycrystalline diamond 1 and polycrystalline diamond 2, respectively, and the GaN single crystal wafer 3. The GaN single crystal wafer 3 is a non-polar epitaxial GaN single crystal wafer. Homoepitaxial growth of GaN improves the crystal quality of the epitaxial layer. Furthermore, due to the adjusted orientation after slicing, the GaN on the substrate surface is polar, making it suitable for fabricating HEMT devices.

[0101] Preferably, the lateral dimensions of the polycrystalline diamond 1 and the polycrystalline diamond 5 are both 0.5-5 mm.

[0102] Preferably, the lateral size of the GaN single crystal wafer 3 is 10-30 mm.

[0103] Preferably, the lateral dimensions of the SiN bonding layer 2 and the SiN bonding layer 4 are both 40-200 nm.

[0104] Preferably, the thickness of the substrate formed by the polycrystalline diamond 1, the SiN bonding layer 2, the GaN single crystal wafer 3, the SiN bonding layer 4, and the polycrystalline diamond 5 is 1-10 mm.

[0105] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0106] In the description of this specification, reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" means that the specific features, structures, materials, or special features 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 special features described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0107] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a lateral diamond / GaN / diamond substrate for manufacturing a GaN HEMT, characterized in that: The following steps are involved: Obtain two pieces of polycrystalline diamonds, and polish one side of the polycrystalline diamonds into a smooth surface by polishing; Obtaining a GaN single crystal wafer, and polishing both sides of the GaN single crystal wafer into smooth surfaces by polishing, wherein the GaN single crystal wafer is a non-polar single crystal wafer, and the smooth surface of the GaN single crystal wafer is a non-polar surface; Using a CVD process, depositing SiN bonding layers on the smooth surfaces of the GaN single crystal wafer and the polycrystalline diamond respectively; Control the temperature to below 150℃ and the pressure to below 10 -5 Under a low vacuum degree of 100 Pa, a pressure of 1-100 N is applied for a duration of 1-10 minutes, so that the two smooth surfaces of the GaN single crystal wafer are bonded to the smooth surfaces of the two polycrystalline diamonds respectively; Performing a thermal annealing treatment on the GaN single crystal wafer and the polycrystalline diamond after the bonding treatment at a temperature of 300-500° C., wherein the thermal annealing time is 10-30 minutes; Using a laser cutting process to longitudinally slice the GaN single crystal wafer and the polycrystalline diamond after thermal annealing to obtain a plurality of slices, wherein the slice thickness is 1-10 mm; Mechanically polishing one or both sides of the slice to a mirror surface to obtain a lateral polycrystalline diamond / GaN / polycrystalline diamond substrate, wherein the lateral diamond / GaN / diamond substrate comprises: polycrystalline diamond (1), SiN bonding layer (2), GaN single crystal wafer (3), SiN bonding layer (4), polycrystalline diamond (5), wherein the polycrystalline diamond (1), SiN bonding layer (2), GaN single crystal wafer (3), SiN bonding layer (4), and polycrystalline diamond (5) are arranged in sequence from left to right; the GaN on the surface of the lateral diamond / GaN / diamond substrate is a polar surface, and both sides of the lateral diamond / GaN / diamond substrate are used for epitaxial growth to respectively realize Ga-face or N-face epitaxy.

2. The method for preparing a lateral diamond / GaN / diamond substrate for manufacturing a GaN HEMT according to claim 1, wherein: Polishing one side of the polycrystalline diamond into a smooth surface by polishing, comprising: One side of the two polycrystalline diamonds is polished to a root mean square roughness of 0.5-3.0 nm to form a smooth surface.

3. The method for preparing a lateral diamond / GaN / diamond substrate for manufacturing a GaN HEMT according to claim 1, wherein: Polishing both sides of the GaN single crystal wafer into smooth surfaces by polishing, comprising: The root mean square roughness of both sides of the GaN single crystal wafer is polished to less than 1 nm by polishing, so that both sides of the GaN single crystal wafer form smooth surfaces.

4. A lateral diamond / GaN / diamond substrate for manufacturing a GaN HEMT, characterized in that: The substrate is prepared using the preparation method according to any one of claims 1 to 3, and the substrate comprises: a GaN single crystal wafer, two polycrystalline diamonds and two SiN bonding layers, wherein the polycrystalline diamonds, the SiN bonding layers, the GaN single crystal wafer, the SiN bonding layers and the polycrystalline diamonds are arranged in sequence from left to right.

5. The lateral diamond / GaN / diamond substrate for fabricating a GaN HEMT according to claim 4, wherein: The lateral size of the polycrystalline diamond is 0.5-5 mm.

6. The lateral diamond / GaN / diamond substrate for fabricating a GaN HEMT according to claim 4, wherein: The lateral size of the GaN single crystal wafer is 10-30 mm.

7. The lateral diamond / GaN / diamond substrate for fabricating a GaN HEMT according to claim 4, wherein: The lateral dimension of the SiN bonding layer is 40-200 nm.

8. The lateral diamond / GaN / diamond substrate for fabricating a GaN HEMT according to claim 4, wherein: The thickness of the substrate formed by the polycrystalline diamond, the SiN bonding layer, the GaN single crystal wafer, the SiN bonding layer and the polycrystalline diamond is 1-10 mm.

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