A high-precision polishing method for small-sized GaN / diamond integrated wafers

Abstract

This invention provides a high-precision polishing method for small-sized GaN / diamond integrated wafers, belonging to the field of semiconductor device technology. The method includes the following steps: pre-treatment of the substrate layer of the GaN / diamond integrated wafer to remove impurities; forming a first photocurable resin protective layer on each of the four sides of the GaN / diamond integrated wafer; performing chemical mechanical polishing on the substrate layer of the GaN / diamond integrated wafer; forming a second photocurable resin protective layer on the diamond layer surface of the GaN / diamond integrated wafer; etching the GaN / diamond integrated wafer; and performing heat treatment on the GaN / diamond integrated wafer. This invention can complete the polishing and etching of GaN / diamond integrated wafers without damaging the Si bonding layer. The method is relatively simple and combines the advantages of high precision and low-cost protection found in 3D printing. The GaN / diamond integrated wafers processed by this invention have better performance and higher quality.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, and more specifically, relates to a high-precision polishing method for small-sized GaN / diamond integrated wafers. Background Technology

[0002] Gallium nitride (GaN), representing third-generation semiconductors, is widely used in aerospace and 5G communications due to its advantages such as wide bandgap, high thermal conductivity, and excellent electron mobility and saturation drift velocity. GaN power chips can withstand temperatures up to 600℃, possessing both high energy efficiency and sufficient stability, and are expected to completely replace traditional Si-based power devices in the future. With industrialization, chip sizes are continuously shrinking, and the performance requirements for power devices are constantly increasing. GaN power devices often use sapphire, Si, or other materials as substrates, with a buffer layer added between GaN and the substrate, increasing interfacial thermal resistance. Therefore, limited by traditional substrate materials and buffer layers, even with good heat dissipation performance, it is still difficult to meet the rapid heat dissipation requirements of GaN power devices during operation, severely reducing device performance. Diamond, as the material with the highest thermal conductivity in nature, possesses extremely excellent thermal conductivity (22 W / cm·K). Its application to assist in heat dissipation of GaN power devices, i.e., GaN / diamond integration, is a common method in the semiconductor field today.

[0003] Unlike heteroepitaxial growth, which uses either GaN or diamond as a base to grow the other, GaN-diamond bonding technology integrates separately grown GaN and diamond together through bonding. This avoids the impact of high-temperature growth environment on the intermediate layer between GaN and diamond. At the same time, the technology of growing GaN and diamond separately is mature, has good quality, and can be post-processed.

[0004] However, domestic technology still faces certain limitations in etching GaN / diamond integrated wafers. This is mainly because large-size diamonds cannot currently be grown on a large scale in China. Domestic semiconductor etching technology is primarily designed for first- and second-generation semiconductors, such as Si and InP, with sizes typically around 6, 8, and 12 inches. Due to the limitations of diamond growth size, GaN / diamond integrated wafers are generally smaller than 2 inches, making them unsuitable for domestic etching instruments and requiring additional processing, such as using fixtures and assembling multiple wafers. However, GaN / diamond integrated wafers are mainly used in high-precision packaging, and using fixtures can lead to uneven stress on the wafers during etching, resulting in wafer breakage and deformation. Furthermore, assembling and bonding multiple GaN / diamond integrated wafers onto a large substrate for etching can cause stress concentration issues. Additionally, uneven etching can occur at the seams between adjacent wafers, impurity accumulation can affect etching quality, and etching solution can penetrate and corrode the bonding layer, leading to failure. The multi-piece assembly and bonding method requires a certain number of GaN / diamond integrated wafers, and the bonding and disassembly process increases the number of operation steps, which seriously affects the etching efficiency.

[0005] Chemical mechanical polishing (CMP) is a key technology for achieving wafer surface planarization in integrated circuit manufacturing. This technology removes impurities and oxides from the wafer surface through the synergistic effect of chemical etching and mechanical polishing, achieving sub-nanometer-level flatness. The process includes steps such as surface preparation, chemical reaction, mechanical polishing, cleaning, and inspection cycles. However, high-precision polishing still requires substrate etching at the end. The bonding intermediate layer of GaN / diamond integrated circuits typically uses a Si layer. Polishing and etching solutions can corrode this intermediate layer, leading to structural damage and performance degradation of the GaN / diamond integrated circuit. Therefore, a method needs to be developed to solve the polishing and etching problems of small-sized GaN / diamond integrated circuits. Summary of the Invention

[0006] The purpose of this invention is to provide a high-precision polishing method for small-sized GaN / diamond integrated wafers, so as to complete the polishing and etching of GaN / diamond integrated wafers without damaging the Si bonding intermediate layer of the GaN / diamond integrated wafers.

[0007] To achieve the above objectives, this invention provides a high-precision polishing method for small-sized GaN / diamond integrated wafers, wherein the GaN / diamond integrated wafer includes a Si bonding layer connecting the GaN layer and the diamond layer, and includes the following steps:

[0008] S1. Perform a pre-treatment to remove impurities from the substrate layer of the GaN / diamond integrated wafer;

[0009] S2. Perform a first stereolithography on the GaN / diamond integrated wafer to form a first photocurable resin protective layer on all four sides of the GaN / diamond integrated wafer.

[0010] S3. Perform chemical mechanical polishing on the substrate layer of the GaN / diamond integrated wafer to remove part of the substrate layer;

[0011] S4. Perform a second stereolithography on the GaN / diamond integrated wafer to form a second photocurable resin protective layer on the surface of the diamond layer of the GaN / diamond integrated wafer.

[0012] S5. The GaN / diamond integrated wafer is etched to completely remove the substrate layer;

[0013] S6. Perform heat treatment on the GaN / diamond integrated wafer to remove the first photocurable resin protective layer and the second photocurable resin protective layer.

[0014] Furthermore, the first and second photocurable resin protective layers each contain the following components: 50-60 wt% hydroxyethyl methacrylate, 6-16 wt% polyethylene glycol diacrylate, 21.5-23.5 wt% diphenoxyethanol, 10-12 wt% 2,4,6-trimethylbenzoyl, and 0.4-0.6 wt% Sudan Red G.

[0015] Furthermore, the scanning rate during the first stereolithography and the second stereolithography is 2000~4000mm / s, and the printing power is 75~85%.

[0016] Furthermore, the thickness of the first photocurable resin protective layer and the second photocurable resin protective layer are each 50~100μm.

[0017] Furthermore, the preprocessing includes the following steps:

[0018] The substrate layer of the GaN / diamond integrated wafer was ultrasonically cleaned in an aqueous solution containing ammonia and hydrogen peroxide, and then rinsed with water and ethanol in sequence and dried.

[0019] The substrate layer of the GaN / diamond integrated wafer was ultrasonically cleaned in an aqueous solution containing hydrochloric acid and hydrogen peroxide, and then rinsed with water and ethanol in sequence and dried.

[0020] Furthermore, the polishing solution for the chemical mechanical polishing is an aqueous solution containing potassium hydroxide and hydrogen peroxide.

[0021] Furthermore, the etching solution used in the etching process is a tetramethylammonium hydroxide solution.

[0022] Furthermore, the heat treatment is carried out under air conditions at a temperature of 50~150°C.

[0023] Furthermore, the substrate layer is any one of sapphire, SiC, and Si.

[0024] Furthermore, a buffer layer is provided between the substrate layer and the GaN layer.

[0025] Compared with the prior art, the present invention has the following technical effects:

[0026] This invention provides a high-precision polishing method for small-sized GaN / diamond integrated wafers. Before chemical mechanical polishing and etching, a photocurable resin protective layer is 3D printed around the GaN / diamond integrated wafer using stereolithography. This is followed by chemical mechanical polishing, which avoids corrosion damage to the Si bonding layer caused by the polishing solution. After chemical mechanical polishing, another photocurable resin protective layer is 3D printed on the diamond layer before etching. The resin protective layer formed by the two photocuring processes effectively inhibits the penetration of etching solution into the GaN / diamond integrated wafer, providing effective protection for the Si bonding layer. Furthermore, the photocurable resin protective layer can be completely removed by heat treatment. The high-precision polishing method of this invention can complete the polishing and etching of GaN / diamond integrated wafers without damaging the Si bonding intermediate layer of small-sized GaN / diamond integrated wafers. The method is relatively simple and combines the advantages of high precision and low cost protection of 3D printing. Compared with other polishing methods, the porosity of the bonding layer of the GaN / diamond integrated wafers processed by the method of this invention is significantly reduced, indicating that the method of this invention has the least impact on the GaN / diamond integrated wafers, and the resulting GaN / diamond integrated wafers have better performance and higher quality. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of a small-sized GaN / diamond integrated wafer provided in an embodiment of the present invention;

[0029] Figure 2 Porosity test diagram of the Si bonding layer of the original GaN / diamond integrated wafer provided in the embodiments of the present invention;

[0030] Figure 3This is a porosity test image of the Si bonding layer of the GaN / diamond integrated wafer after processing according to Example 1 of the present invention;

[0031] Figure 4 This is a porosity test diagram of the Si bonding layer of the GaN / diamond integrated wafer after being treated by Comparative Example 1 of the present invention.

[0032] Figure 5 This is a porosity test diagram of the Si bonding layer of the GaN / diamond integrated wafer after being treated by Comparative Example 2 of this invention.

[0033] Figure 2-5 In the image, the red portion represents the location where pores appear.

[0034] in, Figure 1 The labels for the attached figures are as follows:

[0035] 1. Substrate layer, 2. Buffer layer, 3. GaN layer, 4. Si bonding layer, 5. Diamond layer. Detailed Implementation

[0036] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0037] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0038] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. For example, without departing from the scope of embodiments of the invention, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0039] This invention provides a high-precision polishing method for small-sized GaN / diamond integrated wafers, the GaN / diamond integrated wafer including a Si bonding layer connecting a GaN layer and a diamond layer, comprising the following steps:

[0040] S1. Perform a cleanup pretreatment on the substrate layer of the GaN / diamond integrated wafer;

[0041] S2. Perform the first stereolithography on the GaN / diamond integrated wafer to form a first photocurable resin protective layer on all four sides of the GaN / diamond integrated wafer.

[0042] S3. Perform chemical mechanical polishing on the substrate layer of the GaN / diamond integrated wafer to remove part of the substrate layer;

[0043] S4. Perform a second stereolithography on the GaN / diamond integrated wafer to form a second photocurable resin protective layer on the diamond layer surface of the GaN / diamond integrated wafer.

[0044] S5. Etch the GaN / diamond integrated wafer to completely remove the substrate layer;

[0045] S6. Perform heat treatment on the GaN / diamond integrated wafer to remove the first and second photocurable resin protective layers.

[0046] This invention provides a high-precision polishing method for small-sized GaN / diamond integrated wafers, applicable to GaN / diamond integrated wafers containing Si bonding layers. Specifically, the GaN / diamond integrated wafer includes a Si bonding layer connecting the GaN layer and the diamond layer. "Small-sized" refers to a size of less than 2 inches. Further, a buffer layer is provided between the substrate layer and the GaN layer of the GaN / diamond integrated wafer. For example, in one specific embodiment, the GaN / diamond integrated wafer includes a substrate layer 1, a buffer layer 2, a GaN layer 3, a Si bonding layer 4, and a diamond layer 5, sequentially stacked. Figure 1 As shown, this GaN / diamond integrated wafer is fabricated using existing GaN-diamond bonding technology. For example, a Si-based GaN wafer (with an AlN buffer layer) and a diamond wafer are placed in a bonding machine, and Si is used as an intermediate layer. Bonding is then performed using existing bonding technology to obtain the desired product. Figure 1 The GaN / diamond integrated wafer shown is illustrated. The substrate layer 1 can be any of sapphire, SiC, or Si. For example, in one specific embodiment, the substrate layer 1 is Si, and the buffer layer 2 is AlN.

[0047] In step S1 above, in one specific embodiment, the preprocessing includes the following steps:

[0048] (1) The substrate of the GaN / diamond integrated wafer is ultrasonically cleaned in an aqueous solution containing ammonia and hydrogen peroxide, followed by rinsing with water and ethanol (alcohol) and drying. Specifically, the volume ratio of the three components in the aqueous solution containing ammonia and hydrogen peroxide is ammonia:hydrogen peroxide:water = 1:1:5. This ultrasonic cleaning step can remove organic impurities from the surface of the GaN / diamond integrated wafer.

[0049] (2) The substrate layer of the GaN / diamond integrated wafer is ultrasonically cleaned in an aqueous solution containing hydrochloric acid and hydrogen peroxide, followed by rinsing with water and ethanol and drying. Specifically, the volume ratio of hydrochloric acid to hydrogen peroxide to water in the aqueous solution is hydrochloric acid:hydrogen peroxide:water = 1:1:6. This ultrasonic cleaning step can remove metallic impurities from the surface of the GaN / diamond integrated wafer.

[0050] In this embodiment of the invention, the above-mentioned pretreatment steps remove metallic and organic impurities from the surface of the GaN / diamond integrated wafer, so as to ensure that subsequent processes such as forming a photocurable resin protective layer and chemical mechanical polishing can be carried out smoothly.

[0051] In steps S2 and S4 above, this embodiment of the invention uses stereolithography (SLA) to form a first photocurable resin protective layer and a second photocurable resin protective layer on the four sides of the GaN / diamond integrated wafer and the surface of the diamond layer, respectively. Stereolithography enables the photocurable resin to be cured layer by layer on the surface of the GaN / diamond integrated wafer, ensuring the accuracy and efficiency of the entire 3D printing process. The formed photocurable resin can coat the four sides of the GaN / diamond integrated wafer and the surface of the diamond layer, protecting the GaN / diamond integrated wafer from the effects of subsequent polishing and etching solutions. The composition and structure of the first and second photocurable resin protective layers can be completely identical, i.e., 3D printing can be performed using the same formula of photocurable resin solution.

[0052] In this embodiment of the invention, a photocurable resin formulation is selected that can adhere well to the four sides of the GaN / diamond integrated wafer and the surface of the diamond layer, and form a dense resin protective layer after photocuring. This allows the first and second photocurable resin protective layers formed by 3D printing to provide good protection for the GaN / diamond integrated wafer inside, effectively preventing polishing fluid and etching fluid from penetrating into the interior of the GaN / diamond integrated wafer.

[0053] The formulation of the first and second photocurable resin protective layers, as well as the control of scanning rate and printing power during 3D printing, are crucial to the formation of an effective protective layer on the surface of the GaN / diamond integrated wafer. Through experimental design and screening, the embodiments of this invention have optimally selected the following formulations for the first and second photocurable resin protective layers, each containing the following components: 50-60 wt% hydroxyethyl methacrylate, 6-16 wt% polyethylene glycol diacrylate, 21.5-23.5 wt% diphenoxyethanol, 10-12 wt% 2,4,6-trimethylbenzoyl, and 0.4-0.6 wt% Sudan Red G; simultaneously, a suitable scanning rate of 2000-4000 mm / s and a printing power of 75-85% are also preferred.

[0054] In one embodiment, the thickness of the first photocurable resin protective layer and the second photocurable resin protective layer are each 50~100μm. By forming a protective layer of appropriate thickness on the four sides of the GaN / diamond integrated wafer and the surface of the diamond layer, the GaN / diamond integrated wafer can be effectively protected.

[0055] In step S3 above, the polishing solution used in the chemical mechanical polishing of this embodiment of the invention is an aqueous solution containing potassium hydroxide and hydrogen peroxide. In one specific embodiment, the polishing pad is a foamed polyurethane abrasive, and the polishing solution consists of potassium hydroxide and hydrogen peroxide solution in a volume ratio of potassium hydroxide:hydrogen peroxide:water = 2:4:1. Chemical mechanical polishing removes most of the substrate layer, while a small portion is retained for subsequent etching. This combination of chemical mechanical polishing and etching processes allows for efficient removal of the substrate layer of the GaN / diamond integrated wafer, while ensuring that the GaN / diamond integrated wafer is not subjected to destructive damage.

[0056] In step S5 above, the etching solution used in this embodiment of the invention is tetramethylammonium hydroxide solution. Etching is performed using tetramethylammonium hydroxide (TMAH) solution to remove residual Si at the interface between the GaN and Si substrate layers.

[0057] In step S6 above, the heat treatment in this embodiment of the invention is performed under air conditions at a temperature of 50-150°C. The heat treatment completely burns away the first and second photocurable resin protective layers. Preferably, the heat treatment temperature is 100-120°C, which allows for rapid burning away of the photocurable resin protective layer on the GaN / diamond integrated wafer surface with low energy consumption.

[0058] In this embodiment of the invention, after completing the high-precision polishing process of the GaN / diamond integrated wafer, the GaN / diamond integrated wafer is placed under an ultrasonic scanning microscope to test the porosity of the Si bonding layer of the GaN / diamond integrated wafer. By comparing the change in porosity of the Si bonding layer of the GaN / diamond integrated wafer before and after the treatment, the impact of the polishing process on the performance and quality of the GaN / diamond integrated wafer is evaluated.

[0059] This invention discloses a high-precision polishing method for small-sized GaN / diamond integrated wafers. Before chemical mechanical polishing and etching, a photocurable resin protective layer is 3D printed around the GaN / diamond integrated wafer using stereolithography. Chemical mechanical polishing is then performed, which avoids corrosion damage to the Si bonding layer by the polishing solution. After chemical mechanical polishing, another photocurable resin protective layer is 3D printed on the diamond layer before etching. The resin protective layer formed by the two photocuring processes can comprehensively inhibit the penetration of etching solution into the GaN / diamond integrated wafer, effectively protecting the Si bonding layer. Furthermore, the photocurable resin protective layer can be completely removed by heat treatment. The high-precision polishing method of this invention can complete the polishing and etching of GaN / diamond integrated wafers without damaging the Si bonding intermediate layer of small-sized GaN / diamond integrated wafers. The method is relatively simple and combines the advantages of high precision and low cost protection of 3D printing. Compared with other polishing methods, the porosity of the bonding layer of the GaN / diamond integrated wafer obtained by the method of this invention is significantly reduced, indicating that the method of this invention has the least impact on the GaN / diamond integrated wafer, and the resulting GaN / diamond integrated wafer has better performance and higher quality.

[0060] The following examples illustrate a high-precision polishing method for small-sized GaN / diamond integrated wafers according to embodiments of the present invention.

[0061] Example 1

[0062] Embodiment 1 of the present invention provides a high-precision polishing method for small-sized GaN / diamond integrated wafers, comprising the following steps:

[0063] S1. Sample pretreatment: ... Figure 1The GaN / diamond integrated wafer shown (substrate layer 1 is Si, 725 μm thick; buffer layer 2 is AlN, 500 nm thick; GaN layer 3 is 1.5 μm thick) is placed in a 600 μm deep groove. The groove is filled with ammonia and hydrogen peroxide solution in a volume ratio of ammonia:hydrogen peroxide:water = 1:1:5. The groove is placed in an ultrasonic cleaner and cleaned at 75°C for 12 min to remove organic impurities. After rinsing with water, it is cleaned in alcohol for 20 s, then removed and dried with argon gas. After cleaning, it is placed back into the 600 μm deep groove, which is filled with hydrochloric acid and hydrogen peroxide solution in a volume ratio of hydrochloric acid:hydrogen peroxide:water = 1:1:6. The groove is then placed in an ultrasonic cleaner and cleaned at 75°C for 12 min to remove metallic impurities. After rinsing with water, it is cleaned in alcohol for 20 s, then removed and dried with argon gas.

[0064] S2. Preparation of the UV-curing agent: The UV-curing agent consists of: 60 wt% hydroxyethyl methacrylate (HEMA), 6 wt% polyethylene glycol diacrylate (TEGDA), 21.5 wt% diphenoxyethanol (POE), 12 wt% 2,4,6-trimethylbenzoyl (TPO), and 0.5 wt% Sudan Red G. The above materials are prepared according to the specified proportions, stirred in a water bath at 10°C, and then placed in a vacuum mixer to remove air bubbles.

[0065] S3. Preparation of the photocurable resin protective layer: The GaN / diamond integrated wafer is placed on the circular lifting platform of the SLA. The platform has a rectangular notch in the middle, allowing the GaN / diamond integrated wafer to be placed upright and lowered until the side of the integrated wafer is flush with the platform surface. The relevant preparation parameters are as follows: scanning path spacing 70μm, laser spot diameter 30μm, platform descent layer spacing 0.5μm, scanning rate 3000mm / s, printing power 85%, feed delay 200ms, squeegee speed 40mm / s, laser wavelength 405nm, and number of printing layers 100. The photocurable agent from S2 is used to cure each of the four sides of the GaN / diamond integrated wafer once, forming a 50μm thick first photocurable resin protective layer on each of the four sides. The thickness of the first cured layer is 18~20μm. Afterwards, the wafer is removed, and any residual liquid organic matter on the GaN / diamond integrated wafer is dried using an argon gas gun.

[0066] S4. Chemical Mechanical Polishing: The GaN / diamond integrated wafer is fixed in the polishing area using vacuum suction, ensuring a tight fit between the bottom diamond layer and the base. A polyurethane foam abrasive pad is used for polishing, and the polishing slurry consists of potassium hydroxide and hydrogen peroxide solution in a volume ratio of 2:4:1. Simultaneously, the laser is turned on, and the distance between the base and the polishing disc is calibrated to determine the polishing position. During the pre-polishing stage, the polishing disc pressure is 1.5 psi, and the rotation speed is 30 rpm to avoid impact damage. The pressure is then gradually increased to 4.5 psi, the rotation speed is 115 rpm, the polishing slurry input flow rate through the multi-hole nozzle is 260 ml / min, and the polishing temperature is maintained at 25°C. Using a laser thickness gauge, polishing is stopped when the Si substrate layer is polished to only 0.5 μm. The GaN / diamond integrated wafer is then removed, rinsed thoroughly with water, and dried with an argon gas gun.

[0067] S5. Secondary preparation of photocurable resin protective layer: Using the same parameters and methods, the GaN / diamond integrated wafer with the Si substrate facing down is placed on the circular lifting platform of SLA. A second photocurable resin protective layer with a thickness of 50μm is prepared on the diamond layer using the photocuring agent of S2. The residual liquid organic matter on the GaN / diamond integrated wafer is dried using an argon gas gun.

[0068] S6. Etching and Heat Treatment: With the chemically mechanically polished Si substrate facing upwards, etching is performed using tetramethylammonium hydroxide (TMAH) solution to remove residual Si at the interface between the GaN layer and the Si substrate. Afterwards, the surface is rinsed with water, and the GaN / diamond integrated wafer with the resin protective layer is placed in a tube furnace for heat treatment at 120°C in air for 10 minutes to ensure complete combustion of the protective resin. After natural cooling, it is cleaned with water and alcohol.

[0069] S7. Testing: The cleaned GaN / diamond integrated wafer was dried with argon gas and placed under an ultrasonic scanning microscope to test the porosity of the Si bonding layer. Simultaneously, the porosity of the Si bonding layer of the original GaN / diamond integrated wafer, i.e., the GaN / diamond integrated wafer before polishing, was also tested. The test results showed that the porosity of the Si bonding layer of the original GaN / diamond integrated wafer was 3.79%, as shown in the test image. Figure 2 As shown; in this embodiment, the porosity of the Si bonding layer of the GaN / diamond integrated wafer after polishing is 8.31%, as shown in the test image. Figure 3 As shown, compared to the original GaN / diamond integrated wafer, the porosity of the Si bonding layer is increased by 119.26%.

[0070] Examples 2-9 below examine the effects of different scanning rates and printing power on the formed photocurable resin protective layer during 3D printing. The formulation of the photocurable agent is the same as in Example 1, and other process conditions are the same as in Example 1. The formation of the photocurable resin protective layer and the strength of its adhesion to the GaN / diamond integrated wafer are evaluated by the thickness of the first cured layer. The greater the thickness of the first cured layer, the tighter the adhesion between the photocurable resin protective layer and the GaN / diamond integrated wafer, and the better the subsequent protection effect on the GaN / diamond integrated wafer.

[0071] The scanning rate, printing power, first-layer curing thickness, and evaluation results of Examples 1-9 are shown in Table 1 below.

[0072] Table 1

[0073] ;

[0074] Examples 10-17 below examine the effects of different photocuring agent formulations on the formed photocurable resin protective layer. The scanning rate, printing power, and other process conditions are the same as in Example 1. The formation of the photocurable resin protective layer and the strength of its adhesion to the GaN / diamond integrated wafer are evaluated by the thickness of the first cured layer.

[0075] The formulation composition, first-layer curing thickness, and evaluation results of the photocuring agents in Examples 1, 10-17 are shown in Table 2 below.

[0076] Table 2

[0077] ;

[0078] In Tables 1 and 2 above, "failure of the bottom layer due to scraper damage" indicates that the stability of the photocurable resin after molding is very poor. An evaluation result of "excellent" means that the photocurable resin protective layer can form a good and effective protective effect on the GaN / diamond integrated wafer. An evaluation result of "average" means that the photocurable resin protective layer can form a certain protective effect on the GaN / diamond integrated wafer, but the protective effect is average. An evaluation result of "poor" means that a photocurable resin protective layer cannot be formed on the surface of the GaN / diamond integrated wafer.

[0079] Comparative Example 1

[0080] S1. Sample pretreatment: The pretreatment steps are the same as in Example 1.

[0081] S2, Chemical Mechanical Polishing: The chemical mechanical polishing steps are the same as those in Example 1.

[0082] S3. Etching: The etching steps are the same as in Example 1.

[0083] S4. Testing: The cleaned GaN / diamond integrated wafer was dried with argon gas and placed under an ultrasonic scanning microscope to test the porosity of the Si bonding layer. The test results showed that the porosity of the Si bonding layer in the polished GaN / diamond integrated wafer of this comparative example was 40.43%. The test results are shown in the figure below. Figure 4 As shown, compared to the original GaN / diamond integrated wafer, the porosity of the Si bonding layer is increased by 966.75%.

[0084] Comparative Example 2

[0085] S1. Sample pretreatment: The pretreatment steps are the same as in Example 1.

[0086] S2, Chemical Mechanical Polishing: The chemical mechanical polishing steps are the same as those in Example 1.

[0087] S3. Precision Polishing: The GaN / diamond integrated wafer is placed on a nanosecond pulsed fiber laser for fine polishing. The GaN / diamond integrated wafer is fixed in the polishing area using vacuum suction. The stage is tilted at an angle of 3.5°. The laser is perpendicular to the stage base, with a wavelength of 355nm, a pulse length of 10ns, a repetition frequency of 60kHz, an exposure time of 100μs, and a power of 600mW.

[0088] S4. Testing: After polishing with a nanosecond pulsed fiber laser, the GaN / diamond integrated wafer was removed, rinsed with water, and dried with argon gas. It was then placed under an ultrasonic scanning microscope to test the porosity of the Si bonding layer. The test results showed that the porosity of the Si bonding layer in the polished GaN / diamond integrated wafer of this comparative example was 20.83%. The test results are shown in the figure below. Figure 5 As shown, compared to the original GaN / diamond integrated wafer, the porosity of the Si bonding layer is increased by 449.60%.

[0089] The porosity test results of Example 1 and Comparative Examples 1 and 2 show that the method of Example 1 has the least impact on the Si bonding layer of the original GaN / diamond integrated wafer, and the resulting GaN / diamond integrated wafer has better performance and higher quality.

[0090] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A high-precision polishing method for small-sized GaN / diamond integrated wafers, wherein the GaN / diamond integrated wafer includes a Si bonding layer connecting a GaN layer and a diamond layer, characterized in that, Includes the following steps: S1. Perform a pre-treatment to remove impurities from the substrate layer of the GaN / diamond integrated wafer; S2. Perform a first stereolithography on the GaN / diamond integrated wafer to form a first photocurable resin protective layer on all four sides of the GaN / diamond integrated wafer. S3. Perform chemical mechanical polishing on the substrate layer of the GaN / diamond integrated wafer to remove part of the substrate layer; S4. Perform a second stereolithography on the GaN / diamond integrated wafer to form a second photocurable resin protective layer on the surface of the diamond layer of the GaN / diamond integrated wafer. S5. The GaN / diamond integrated wafer is etched to completely remove the substrate layer; S6. Perform heat treatment on the GaN / diamond integrated wafer to remove the first photocurable resin protective layer and the second photocurable resin protective layer.

2. The high-precision polishing method for small-sized GaN / diamond integrated wafers as described in claim 1, characterized in that, The first and second photocurable resin protective layers each contain the following components: 50-60 wt% hydroxyethyl methacrylate, 6-16 wt% polyethylene glycol diacrylate, 21.5-23.5 wt% diphenoxyethanol, 10-12 wt% 2,4,6-trimethylbenzoyl, and 0.4-0.6 wt% Sudan Red G.

3. The high-precision polishing method for small-sized GaN / diamond integrated wafers as described in claim 1, characterized in that, The scanning rate for the first and second stereolithography processes is 2000-4000 mm / s, and the printing power is 75-85%.

4. The high-precision polishing method for small-sized GaN / diamond integrated wafers as described in claim 2, characterized in that, The thickness of the first and second photocurable resin protective layers is 50~100μm respectively.

5. The high-precision polishing method for small-sized GaN / diamond integrated wafers as described in claim 1, characterized in that, The preprocessing includes the following steps: The substrate layer of the GaN / diamond integrated wafer was ultrasonically cleaned in an aqueous solution containing ammonia and hydrogen peroxide, and then rinsed with water and ethanol in sequence and dried. The substrate layer of the GaN / diamond integrated wafer was ultrasonically cleaned in an aqueous solution containing hydrochloric acid and hydrogen peroxide, and then rinsed with water and ethanol in sequence and dried.

6. The high-precision polishing method for small-sized GaN / diamond integrated wafers as described in claim 1, characterized in that, The polishing solution used in the chemical mechanical polishing is an aqueous solution containing potassium hydroxide and hydrogen peroxide.

7. The high-precision polishing method for small-sized GaN / diamond integrated wafers as described in claim 1, characterized in that, The etching solution used in the etching process is a tetramethylammonium hydroxide solution.

8. The high-precision polishing method for small-sized GaN / diamond integrated wafers as described in claim 1, characterized in that, The heat treatment is carried out in air at a temperature of 50-150°C.

9. A high-precision polishing method for small-sized GaN / diamond integrated wafers as described in any one of claims 1-8, characterized in that, The substrate layer can be any one of sapphire, SiC, or Si.

10. The high-precision polishing method for small-sized GaN / diamond integrated wafers as described in claim 9, characterized in that, A buffer layer is provided between the substrate layer and the GaN layer.

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