A method for preparing a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance

Abstract

The present invention discloses a method for preparing a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance, wherein a polished self-supporting gallium nitride wafer is used as a substrate and placed on a rotating sample stage of a magnetron sputtering coating device; after the chamber is evacuated, argon and nitrogen are introduced, and a high-purity target material is used as a radio frequency sputtering target to deposit a dielectric layer film on the polished surface of the substrate; then, an MPCVD device is used in combination with a bias-enhanced nucleation technology to pretreat the surface of the dielectric layer; after the bias is turned off, a diamond heat dissipation layer with high thermal conductivity is deposited on the surface of the pretreated dielectric layer, thereby obtaining a gallium nitride wafer structure with a diamond heat dissipation layer. The present invention prepares a gallium nitride / diamond composite heat dissipation layer by regulating the bias and diamond growth process, and the interface thermal resistance is controllable, and it has the characteristics of low interface thermal resistance, good bonding, and high thermal conductivity of the diamond film, which is of significant significance for promoting the application and promotion of high-frequency and high-power gallium nitride power devices.

Description

Technical Field

[0001] The invention relates to a method for preparing a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance, belonging to the technical field of semiconductor materials. Background Art

[0002] The bandgap width of GaN can reach 3.4eV, which is three times that of traditional Si semiconductor materials. It is an excellent wide bandgap semiconductor material. Compared with Si devices, it has smaller transistor size, lower on-resistance and capacitance, faster operating frequency and response speed. GaN has high resistance to ionizing radiation and stable chemical properties, which enables it to serve in more severe environments. It shows excellent prospects as a high-temperature, high-power device and high-frequency microwave device. Theoretically, the power density of GaN can reach 10 5 W / cm 2 , However, in actual use, due to its own thermal effect, the power density of GaN-based high electron mobility transistor devices is only 3~5 W / mm, and its own advantages are far from being fully utilized. The main reason is that excessive power dissipation causes the device to heat up, while the traditional low thermal conductivity substrate and heat dissipation path have limited heat dissipation capacity, which hinders the heat from diffusing to the surrounding environment and causes the static IV characteristics of the device to decay. Diamond has the highest thermal conductivity of known materials, which can reach 2100W / m·K. With the rapid development of chemical vapor deposition (CVD) diamond preparation technology, the thermal conductivity of artificially synthesized CVD diamond has reached the level of natural diamond, and the preparation efficiency and cost have been greatly reduced, making it one of the excellent packaging materials for the next generation of high-power electronic devices.

[0003] Depositing diamond on the back of the GaN wafer can achieve the combination of high-power GaN devices and high thermal conductivity diamond, further improving the power density of GaN devices. GaN is easily decomposed in a high-temperature hydrogen plasma environment, so SiN needs to be inserted between diamond and GaN. x The diamond nucleation and growth on the surface of the non-diamond dielectric layer substrate are the key. In the Chinese invention patent CN 104328390 A "A method for preparing a GaN / diamond film composite sheet", the carbon atom groups CH activated by the jet arc plasma are used. * 、CH2 * and CH3 *The gallium nitride substrate is bombarded to achieve annihilation passivation of the gallium nitride substrate surface and rapid nucleation of the diamond film. Although a high thermal conductivity diamond film is directly grown on the gallium nitride, the gallium nitride substrate is damaged by the plasma bombardment. In the Chinese invention patent CN 107523828 A "A method for preparing a GaN and diamond composite heat dissipation structure", a spin-coated nano-diamond suspension is used to establish auxiliary nucleation points on the surface of a gallium nitride wafer with a transition layer. Although a high thermal conductivity diamond layer is deposited, the bonding strength between the nucleation layer and the transition layer is poor, which affects the interface thermal resistance. In addition, electrostatic seeding of nanoparticles and seed seeding can achieve a higher nucleation density (ACS Nano, Vol 4, 2010, 4824; ACS Appl. Mater. Interfaces, Vol 11, 2019, 40826). However, this method requires strict control of the distribution of diamond nanoparticles by adjusting process parameters. The process is complicated and it is easy to form holes at the interface between diamond and dielectric layer, which is not conducive to the heat dissipation of GaN / diamond composite layer.

[0004] Biasing enhances the nucleation process and produces high-quality polycrystalline diamond films. Biasing the nucleation process to adjust the non-diamond substrate (SiN x Therefore, adjusting the bias voltage can tune the transition region and thus the interfacial thermal resistance of the GaN / diamond interface. Summary of the invention

[0005] The present invention aims to provide a method for preparing a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance, increase the nucleation sites of diamond by bias voltage enhanced nucleation technology, promote the growth of subsequent polycrystalline diamond heat dissipation coating and improve the quality of polycrystalline diamond and film-base bonding strength, reduce the interface thermal resistance by adjusting the bias voltage and diamond growth process, thereby obtaining a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance.

[0006] The present invention utilizes the high thermal conductivity of diamond materials. On the one hand, based on the diamond bias enhanced nucleation process, the surface of gallium nitride with a dielectric layer is pretreated. By changing the bias power supply parameters and the diamond nucleation process parameters, the nucleation density of the diamond deposition in the early stage on the surface of the dielectric layer is regulated, so as to quickly obtain an effective nucleation zone for diamond growth. At the same time, the thickness and composition of the transition zone formed by the dielectric layer and the nucleation layer are adjusted to reduce the non-diamond carbon-containing surface layer and the grain boundary between the interface, thereby achieving the purpose of reducing the interface thermal resistance. On the other hand, in the subsequent growth stage of diamond, by regulating the diamond growth process parameters, the grain size and growth rate of the polycrystalline diamond film are adjusted, and under the premise of protecting the gallium nitride substrate from being etched, a diamond coating with high thermal conductivity and low interface thermal resistance is deposited, thereby realizing the preparation of a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance. The present invention effectively solves the problems that the gallium nitride substrate is easily etched by plasma during the deposition process, the diamond heat dissipation coating is difficult to grow, the coating has poor bonding strength, and is easy to peel off, and is of great significance for improving the high-frequency and high-power performance of gallium nitride power devices.

[0007] The invention provides a method for preparing a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance. First, a polished self-supporting gallium nitride wafer substrate is placed on a sample table in a magnetron sputtering chamber; after the chamber is evacuated, argon and nitrogen protective gases are introduced, and a high-purity target material is used as a radio frequency sputtering target to deposit a dielectric layer film on the surface of the substrate; an MPCVD device and its auxiliary bias power supply are used to perform bias-enhanced nucleation pretreatment on the surface of the dielectric layer to increase diamond nucleation points on the surface of the dielectric layer; finally, after turning off the bias, the diamond growth temperature and methane concentration are adjusted to epitaxially grow a diamond polycrystalline film with high thermal conductivity on the surface of the dielectric layer film; the method obtains a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance by adjusting the enhanced nucleation bias and the diamond growth process.

[0008] The present invention provides a method for preparing a diamond-based gallium nitride wafer material with low interface thermal resistance, which specifically comprises the following steps:

[0009] (1) First, rinse the GaN substrate with deionized water, then place it in acetone and anhydrous ethanol solution for ultrasonic cleaning for 5 min respectively, and then blow dry after cleaning;

[0010] (2) Place the cleaned GaN wafer substrate on the rotating sample stage in the magnetron sputtering chamber, install the high-purity target material on the target body of the RF magnetron sputtering, and adjust the distance between the substrate and the RF sputtering target;

[0011] (3) Evacuate the chamber to a vacuum degree of 1×10 4Pa; introduce argon and nitrogen protective gases to stabilize the gas pressure at 0.6~0.8 Pa; turn on the substrate heating device, and stabilize the substrate temperature at 200~800 ℃; turn on the RF sputtering power supply to deposit a dielectric layer on the substrate surface for 5~30 min;

[0012] (4) Turn off the magnetron sputtering equipment, place the GaN substrate covered with the dielectric layer in the MPCVD equipment, turn on the bias, perform bias nucleation treatment in a hydrogen / methane plasma atmosphere, adjust the flow rate of methane and hydrogen, the volume concentration of methane in the mixed gas is 4-10%, the nucleation layer deposition pressure is 2-5 Pa, and the bias voltage is 100-1000 V. Deposit a sp-rich layer on the surface of the dielectric layer. 3 Bonded carbon film;

[0013] (5) Turn off the bias voltage, deposit a layer of polycrystalline diamond on the surface of the substrate that has been subjected to bias nucleation treatment, adjust the flow rates of methane and hydrogen, the volume concentration of methane in the mixed gas is 5-15%, and the diamond growth pressure is 4-8 Pa, thereby obtaining a gallium nitride / diamond composite heat dissipation layer;

[0014] In the above preparation method, in step (2), the distance between the substrate and the sputtering target is 5 to 15 cm.

[0015] In the above preparation method, in step (3), the dielectric layer material is an amorphous or microcrystalline silicon nitride film or a high c-axis oriented aluminum nitride crystal film; the dielectric layer should completely cover the surface of the gallium nitride wafer to protect the gallium nitride from being etched by plasma; the dielectric layer film growth thickness is 5 to 100 nm.

[0016] In the above preparation method, in step (4), the bias power supply used for the nucleation treatment is a DC power supply, a DC pulse, a radio frequency power supply or a bipolar pulse power supply; the methane flow rate is 5-30 sccm, and the hydrogen flow rate is 200-400 sccm; the microwave power is 1-10 kW, the nucleation layer deposition temperature is 500-1000 °C, the bias duty cycle is 0-100%, and the bias treatment time is 0.5-1h;

[0017] In the above preparation method, in step (5), a polycrystalline diamond film is grown using an MPCVD device, with a methane flow rate of 8 to 50 sccm and a hydrogen flow rate of 200 to 400 sccm; a microwave power of 1 to 10 kW, a growth temperature of 700 to 1000 °C, and a deposition time of 0.5 to 3 h.

[0018] The beneficial effects of the present invention are as follows:

[0019] (1) The present invention uses bias-enhanced nucleation technology to assist in the deposition of a gallium nitride-based diamond composite heat dissipation layer, which solves the problem of low diamond nucleation density on the gallium nitride surface and difficulty in spreading vapor-deposited diamond into a film, and is beneficial to improving the performance of gallium nitride-based power devices;

[0020] (2) The present invention reduces the thickness of the diamond film nucleation zone and improves the diamond quality in the nucleation zone by designing and optimizing the bias nucleation process parameters, thereby reducing the interfacial thermal resistance of the gallium nitride-based diamond heat dissipation film;

[0021] (3) The present invention solves the problems of easy etching of gallium nitride during diamond deposition, poor bonding between diamond coating and gallium nitride, and high interface thermal resistance by increasing the crystal nucleus density of diamond on the surface of the dielectric layer and improving the film formation speed during diamond deposition. This is of great significance for improving the high-frequency and high-power performance of gallium nitride power devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope cross-sectional morphology image of the gallium nitride / diamond composite heat dissipation layer prepared in Example 1;

[0023] Figure 2 This is a scanning electron microscope cross-sectional morphology image of the gallium nitride / diamond composite heat dissipation layer prepared in Example 2;

[0024] Figure 3 This is a scanning electron microscope cross-sectional morphology image of the gallium nitride / diamond composite heat dissipation layer prepared in Example 3;

[0025] Figure 4 This is a transmission electron microscope interface morphology image of the gallium nitride / diamond composite heat dissipation layer prepared in Example 1;

[0026] Figure 5 This is a transmission electron microscope interface morphology image of the gallium nitride / diamond composite heat dissipation layer prepared in Example 2;

[0027] Figure 6 This is a transmission electron microscope interface morphology image of the gallium nitride / diamond composite heat dissipation layer prepared in Example 3;

[0028] Figure 7 This is a transient thermal reflection graph of the gallium nitride / diamond composite heat dissipation layer prepared in Example 1;

[0029] Figure 8 This is a transient thermal reflection graph of the gallium nitride / diamond composite heat dissipation layer prepared in Example 2;

[0030] Fig. 9 This is a transient thermal reflection graph of the gallium nitride / diamond composite heat dissipation layer prepared in Example 3. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing a gallium nitride / diamond composite heat dissipation layer based on low interface thermal resistance, which specifically comprises the following steps:

[0032] (1) First, rinse the GaN substrate with deionized water, then place it in acetone and anhydrous ethanol solutions for ultrasonic cleaning for 5 min respectively, and then blow dry after cleaning.

[0033] (2) The cleaned gallium nitride wafer substrate is placed on the rotating sample stage in the magnetron sputtering chamber, the high-purity target material is mounted on the target body of the RF magnetron sputtering, and the distance between the substrate and the RF sputtering target is adjusted; in the step (2), the distance between the substrate and the sputtering target material is 5 to 15 cm.

[0034] (3) Evacuate the chamber to a vacuum degree of 1×10 4 Pa; introduce argon and nitrogen protective gas to stabilize the gas pressure at 0.6~0.8 Pa; turn on the substrate heating device, and stabilize the substrate temperature at 200~800 ℃; turn on the RF sputtering power supply to deposit a dielectric layer film on the substrate surface for 5~30 min; in the step (3), the dielectric layer material is an amorphous or microcrystalline silicon nitride film or a high c-axis oriented aluminum nitride crystal film. The dielectric layer should completely cover the surface of the gallium nitride wafer to protect the gallium nitride from being etched by plasma. The dielectric layer film growth thickness is 5~100 nm.

[0035] (4) Turn off the magnetron sputtering equipment, place the GaN substrate covered with the dielectric layer in the MPCVD equipment, turn on the bias, perform bias nucleation treatment in a hydrogen / methane plasma atmosphere, adjust the flow rate of methane and hydrogen, the methane concentration in the mixed gas is 4-10%, the nucleation layer deposition pressure is 2-5 Pa, and the bias voltage is 100-1000 V. Deposit a sp-rich layer on the surface of the dielectric layer. 3 The carbon film is bonded; in the step (4), the bias power supply used for the nucleation treatment is a DC power supply, a DC pulse, a radio frequency power supply or a bipolar pulse power supply. The methane flow rate is 5-30 sccm, the hydrogen flow rate is 200-400 sccm; the microwave power is 1-10 kW, the nucleation layer deposition temperature is 500-1000 °C, the bias duty cycle is 0-100%, and the bias treatment time is 0.5-1h.

[0036] (5) Turning off the bias, depositing a layer of polycrystalline diamond on the surface of the substrate after bias nucleation treatment, adjusting the flow rates of methane and hydrogen, the methane concentration in the mixed gas is 5-15%, and the diamond growth pressure is 4-8 Pa, thereby obtaining a gallium nitride / diamond composite heat dissipation layer; in the step (5), an MPCVD device is used to grow a polycrystalline diamond film, the methane flow rate is 8-50sccm, the hydrogen flow rate is 200-400sccm; the microwave power is 1-10 kW, the growth temperature is 700-1000°C, and the deposition time is 0.5-3 h.

[0037] The present invention is further illustrated by the following examples, but is not limited to the following examples. Example 1

[0038] (1) First, rinse the GaN substrate with deionized water, then place it in acetone and anhydrous ethanol solution for ultrasonic cleaning for 5 min respectively, and then blow dry after cleaning;

[0039] (2) Place the cleaned GaN wafer substrate on the rotating sample stage in the magnetron sputtering chamber, install the high-purity silicon nitride target on the RF magnetron sputtering target, and adjust the distance between the substrate and the RF sputtering target to 8 cm.

[0040] (3) Evacuate the chamber to a vacuum degree of 1×10 4 Pa; introduce argon and nitrogen protective gases to stabilize the gas pressure at 0.7 Pa; turn on the substrate heating device and stabilize the substrate temperature at 400 °C; turn on the RF sputtering power supply to deposit a layer of amorphous silicon nitride dielectric layer film on the substrate surface. The dielectric layer should completely cover the surface of the gallium nitride wafer to protect gallium nitride from plasma etching. The deposition time is 7 min, and the dielectric layer film growth thickness is about 45 nm.

[0041] (4) Turn off the magnetron sputtering equipment, place the GaN substrate covered with the silicon nitride dielectric layer in the MPCVD equipment, turn on the pulsed DC bias power supply, and perform bias nucleation treatment in a hydrogen / methane plasma atmosphere. The flow rates of methane and hydrogen are adjusted to 20 sccm and 360 sccm, respectively. The methane concentration in the mixed gas is 5.2%. The nucleation layer deposition pressure is 2.2 Pa. The applied bias voltage is 700 V, the bias duty cycle is 30%, the microwave power is 4.4 kW, the nucleation layer deposition temperature is 700 °C, and the bias treatment time is 1 h. A layer of sp-rich SiO2 is deposited on the surface of the dielectric layer. 3 Bonded carbon film.

[0042] (5) Turn off the bias and deposit a layer of polycrystalline diamond on the surface of the substrate after bias nucleation treatment. The flow rates of methane and hydrogen are adjusted to 40 sccm and 360 sccm, respectively. The methane concentration in the mixed gas is 10%. The diamond growth pressure is 6.4 Pa, the microwave power is 3.2 kW, the growth temperature is 740 °C, and the deposition time is 1.5 h, thereby obtaining a gallium nitride / diamond composite heat dissipation layer. Example 2

[0043] (1) First, rinse the GaN substrate with deionized water, then place it in acetone and anhydrous ethanol solution for ultrasonic cleaning for 5 min respectively, and then blow dry after cleaning;

[0044] (2) Place the cleaned GaN wafer substrate on the rotating sample stage in the magnetron sputtering chamber, install the high-purity silicon nitride target on the RF magnetron sputtering target, and adjust the distance between the substrate and the RF sputtering target to 10 cm.

[0045] (3) Evacuate the chamber to a vacuum degree of 1×10 4 Pa; introduce argon and nitrogen protective gases to stabilize the gas pressure at 0.7 Pa; turn on the substrate heating device and stabilize the substrate temperature at 450 ℃; turn on the RF sputtering power supply to deposit a layer of amorphous silicon nitride dielectric layer film on the substrate surface. The dielectric layer should completely cover the surface of the gallium nitride wafer to protect gallium nitride from plasma etching. The deposition time is 5 min, and the dielectric layer film growth thickness is about 35 nm.

[0046] (4) Turn off the magnetron sputtering equipment, place the GaN substrate covered with the silicon nitride dielectric layer in the MPCVD equipment, turn on the pulsed DC bias power supply, and perform bias nucleation treatment in a hydrogen / methane plasma atmosphere. The flow rates of methane and hydrogen are adjusted to 40 sccm and 400 sccm, respectively, the methane concentration is 9%, the nucleation layer deposition pressure is 2.0 Pa, the applied bias voltage is 650 V, the bias duty cycle is 30%, the microwave power is 5 kW, the nucleation layer deposition temperature is 700 °C, the bias treatment time is 1 h, and a layer of sp-rich SiO2 is deposited on the surface of the dielectric layer. 3 Bonded carbon film.

[0047] (5) Turn off the bias and deposit a layer of polycrystalline diamond on the surface of the substrate after bias nucleation treatment. Adjust the flow rates of methane and hydrogen to 60 sccm and 400 sccm, respectively, the plasma methane concentration to 13%, the diamond growth gas pressure to 6 Pa, the microwave power to 3.2 kW, the growth temperature to 800 °C, and the deposition time to 1.5 h to obtain a gallium nitride / diamond composite heat dissipation layer. Example 3

[0048] (1) First, rinse the GaN substrate with deionized water, then place it in acetone and anhydrous ethanol solution for ultrasonic cleaning for 5 min respectively, and then blow dry after cleaning;

[0049] (2) Place the cleaned GaN wafer substrate on the rotating sample stage in the magnetron sputtering chamber, install the high-purity AlN target on the RF magnetron sputtering target, and adjust the distance between the substrate and the RF sputtering target to 8 cm.

[0050] (3) Evacuate the chamber to a vacuum degree of 1×10 4 Pa; introduce argon and nitrogen protective gases to stabilize the gas pressure at 0.6 Pa; turn on the substrate heating device and stabilize the substrate temperature at 400 °C; turn on the RF sputtering power supply to deposit a layer of amorphous silicon nitride dielectric layer film on the substrate surface. The dielectric layer should completely cover the surface of the gallium nitride wafer to protect gallium nitride from plasma etching. The deposition time is 10 min, and the dielectric layer film growth thickness is about 40 nm.

[0051] (4) Turn off the magnetron sputtering equipment, place the GaN substrate covered with the silicon nitride dielectric layer in the MPCVD equipment, turn on the pulsed DC bias power supply, and perform bias nucleation treatment in a hydrogen / methane plasma atmosphere. The flow rates of methane and hydrogen are adjusted to 40 sccm and 360 sccm, respectively. The methane concentration in the mixed gas is 10%. The nucleation layer deposition pressure is 2.4 Pa. The applied bias voltage is 720 V, the bias duty cycle is 40%, the microwave power is 4.4 kW, the nucleation layer deposition temperature is 750 °C, and the bias treatment time is 1 h. A layer of sp-rich SiO2 is deposited on the surface of the dielectric layer. 3 Bonded carbon film.

[0052] (5) Turn off the bias and deposit a layer of polycrystalline diamond on the surface of the substrate after bias nucleation treatment. The flow rates of methane and hydrogen are adjusted to 60 sccm and 360 sccm, respectively. The methane concentration in the mixed gas is 14.3%. The diamond growth pressure is 6.4 Pa, the microwave power is 3.2 kW, the growth temperature is 860 °C, and the deposition time is 1.5 h, thereby obtaining a gallium nitride / diamond composite heat dissipation layer.

[0053] Figure 1~Figure 3 The scanning electron microscope cross-sectional morphologies of the GaN / diamond composite heat dissipation layers prepared in Examples 1 to 3 are shown respectively. It can be seen from the figure that there are no obvious defects such as cracks and holes at the interface between the GaN substrate and the diamond heat dissipation layer, and the diamond is dense and well bonded to the substrate.

[0054] Figure 4~Figure 6The transmission electron microscope interface morphology photos of the gallium nitride / diamond composite heat dissipation layer prepared in Examples 1 to 3 are shown respectively. It can be seen from the figure that the interface contour between the gallium nitride substrate and the diamond heat dissipation layer is clear, and the transition layer formed by the dielectric layer and the diamond nucleation layer is clearly visible and closely connected to the gallium nitride substrate and the diamond heat dissipation layer, which is conducive to reducing the interface thermal resistance of the composite layer.

[0055] Figure 7~Figure 9 The transient thermal reflection curves of the GaN / diamond composite heat dissipation layer successfully prepared in Examples 1 to 3 are shown respectively. From the figure, the interface thermal resistance of the GaN / diamond composite heat dissipation layer can be obtained, which is 66±10 m 2 K / GW, 26±10 m 2 K / GW and 53±8 m 2 K / GW, which is of the same order of magnitude as the interface thermal resistance of the GaN / diamond composite heat dissipation structure obtained by the bonding process, but the preparation process is much simpler and easier to control than the latter.

[0056] According to the bottom cooling scheme of the single-finger heterostructure field effect transistor, a finite element structural model of diamond as a heat dissipation substrate for a gallium nitride chip was established. The model was solved by finite element analysis. It was found that when no diamond substrate was added, the maximum temperature of the chip active area was 185°C. After the diamond composite scattering layer structure prepared in Examples 1-3 was introduced, the maximum temperature of the active area decreased to 152.2°C, 142.3°C and 148.5°C, respectively, and the temperature decreased by 17.8%, 23% and 20%, respectively. The heat dissipation effect changed with the change of the interface thermal resistance and the thermal conductivity of the diamond. The smaller the interface thermal resistance and the larger the thermal conductivity of the diamond, the enhanced the heat diffusion capacity near the active area.

[0057] The present invention can effectively regulate the thickness and composition of the transition zone formed by the dielectric layer and the nucleation layer by changing the bias voltage to enhance the diamond nucleation process and growth process, thereby affecting the interfacial thermal resistance of the gallium nitride / diamond composite heat dissipation layer, and realizing the application and promotion of gallium nitride-based high-frequency and high-power devices.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that there are many practical solutions that can be adopted in the preparation method, and any equivalent modifications or substitutions made in accordance with the claims of the present invention and the essence of the corresponding technical solutions belong to the scope of the present invention.

Claims

1. A method for preparing a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance, characterized in that The method comprises the following steps: firstly, placing a polished self-supporting gallium nitride wafer substrate on a sample stage in a magnetron sputtering chamber; after the chamber is evacuated, argon and nitrogen protective gases are introduced, and a dielectric layer thin film is deposited on the surface of the substrate using a high-purity target material as a radio frequency sputtering target; using an MPCVD device and its auxiliary bias power supply to perform bias-enhanced nucleation pretreatment on the surface of the dielectric layer to increase diamond nucleation sites on the surface of the dielectric layer; finally, after turning off the bias, adjusting the diamond growth temperature and methane concentration to epitaxially grow a diamond polycrystalline thin film with high thermal conductivity on the surface of the dielectric layer thin film; the method prepares a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance by adjusting the nucleation bias and the diamond growth process; The method for preparing the gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance comprises the following steps: (1) First, rinse the GaN substrate with deionized water, then place it in acetone and anhydrous ethanol solution for ultrasonic cleaning for 5 min respectively, and then blow dry after cleaning; (2) Place the cleaned GaN wafer substrate on the rotating sample stage in the magnetron sputtering chamber, install the high-purity target material on the target body of the RF magnetron sputtering, and adjust the distance between the substrate and the RF sputtering target; (3) Evacuate the chamber to a vacuum degree of 1×10 4 Pa; introduce argon and nitrogen protective gas to stabilize the gas pressure at 0.6~0.8 Pa; turn on the substrate heating device, and stabilize the substrate temperature at 200~800 ℃; turn on the RF sputtering power supply to deposit a dielectric layer film on the substrate surface for 5~30 min; the dielectric layer material is an amorphous or microcrystalline silicon nitride film or a high c-axis oriented aluminum nitride crystal film; the dielectric layer should completely cover the surface of the gallium nitride wafer to protect gallium nitride from plasma etching; the dielectric layer film growth thickness is 5~100 nm; (4) Turn off the magnetron sputtering equipment, place the GaN substrate covered with the dielectric layer in the MPCVD equipment, turn on the bias, perform bias nucleation treatment in a hydrogen / methane plasma atmosphere, adjust the flow rate of methane and hydrogen, the volume concentration of methane in the mixed gas is 4-10%, the nucleation layer deposition pressure is 2-5 Pa, and the bias voltage is 100-1000 V. Deposit a sp-rich layer on the surface of the dielectric layer. 3 Bonded carbon film; (5) Turn off the bias voltage, deposit a layer of polycrystalline diamond on the surface of the substrate after bias nucleation treatment, adjust the flow rate of methane and hydrogen, the volume concentration of methane in the mixed gas is 5~15%, and the diamond growth pressure is 4~8 Pa, thereby obtaining a gallium nitride / diamond composite heat dissipation layer.

2. The method for preparing a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance according to claim 1, characterized in that: In the step (2), the distance between the substrate and the RF sputtering target is 5 to 15 cm.

3. The method for preparing a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance according to claim 1, characterized in that: In the step (4), the bias power supply used for the nucleation treatment is a DC power supply, a DC pulse, a radio frequency power supply or a bipolar pulse power supply; The methane flow rate is 5~30 sccm, the hydrogen flow rate is 200~400 sccm; the microwave power is 1~10 kW, the nucleation layer deposition temperature is 500~1000 ℃, the bias duty cycle is 0~100%, and the bias treatment time is 0.5~1 h.

4. The method for preparing a gallium nitride / diamond composite heat dissipation layer with low interface thermal resistance according to claim 1, characterized in that: In the step (5), a polycrystalline diamond film is grown using an MPCVD device, with a methane flow rate of 8-50 sccm and a hydrogen flow rate of 200-400 sccm; a microwave power of 1-10 kW, a growth temperature of 700-1000°C, and a deposition time of 0.5-3 h.

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