Preparation method of GaN / diamond with low interface thermal resistance

Abstract

The invention discloses a preparation method of GaN / diamond with low interface thermal resistance, and aims to solve the bottleneck problems of interface failure, high interface thermal resistance and the like caused by growth of diamond on a GaN substrate. The preparation method of the GaN / diamond with low interface thermal resistance comprises the following steps of: 1, ultrasonically cleaning a GaN substrate; 2, carrying out reverse sputtering cleaning on the GaN substrate; 3, sputtering and depositing a Si3N4 transition layer on the GaN substrate; 4, ultrasonic cleaning; 5, spin-coating the nano-diamond suspension liquid on the GaN substrate; 6, introducing hydrogen, oxygen and methane gas, and depositing a diamond layer in stages; 7, depositing a diamond layer at a first stage under low pressure; and 8, depositing a diamond layer at a second stage under high pressure. The GaN / diamond material with low interface thermal resistance is prepared through a multi-temperature gradient low-temperature growth process in combination with collaborative optimization of air pressure and time, and gradient heat flow control is combined with stress buffering of the Si3N4 transition layer, so that the integrity of the Si3N4 film is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal management of semiconductor materials and devices, and particularly relates to a method for preparing a gallium nitride (GaN) / diamond material with low interface thermal resistance based on a temperature gradient process. Background Art

[0002] As the material with the highest known hardness and the best thermal conductivity in nature, diamond shows great application potential in the field of heat dissipation of semiconductor devices. Especially in high-power GaN-based electronic devices, the heterogeneous integration of diamond and GaN is regarded as a key technical path to break through the heat dissipation bottleneck. The traditional chemical vapor deposition (CVD) method for growing diamond usually needs to be carried out in a high-temperature environment above 800°C to promote the dissociation of carbon-containing precursors and the orderly growth of diamond lattices. However, when this high-temperature process is implemented on a GaN-based substrate, it faces two core challenges: severe etching of GaN by hydrogen plasma and thermal mismatch stress between multi-layer heterogeneous materials, which seriously restrict the reliability of the GaN / diamond composite structure and the stability of device performance.

[0003] In conventional CVD diamond growth, the hydrogen-rich plasma environment is the key to maintaining sp 3 The high reactivity of hydrogen free radicals causes irreversible chemical etching of the GaN surface at high temperatures. When the temperature exceeds 700°C, the etching rate of hydrogen plasma and GaN increases exponentially. Even if silicon nitride (Si3N4) is used as a transition layer, its protective effect decreases significantly. This is mainly attributed to two mechanisms: first, high temperature intensifies the diffusion ability of hydrogen free radicals, allowing them to penetrate the grain boundary defects of the Si3N4 film and directly react with GaN, causing GaN to decompose into volatile products; second, the density of Si3N4 itself degrades under the bombardment of high-temperature plasma, generating microcracks and pores, further weakening its barrier effect, which not only destroys the integrity of the Si3N4 film, but also significantly affects its bonding with the diamond film layer and increases the interfacial thermal resistance.

[0004] In summary, existing high-temperature diamond growth technology faces the dual constraints of etching and thermal mismatch in GaN-based heterojunction integration. Developing a method for preparing GaN / diamond materials with low interfacial thermal resistance based on a temperature gradient process is an inevitable choice to overcome the existing technical barriers. Summary of the Invention

[0005] The present invention addresses bottleneck issues such as interface failure and high interface thermal resistance caused by growing diamond on a GaN substrate. By adjusting the coupling relationship between growth power, gas pressure and temperature, a method for preparing GaN / diamond materials with low interface thermal resistance based on a temperature gradient process is proposed.

[0006] The method for preparing GaN / diamond materials with low interfacial thermal resistance based on the temperature gradient process is realized according to the following steps:

[0007] 1. Ultrasonically clean the GaN substrate to obtain the cleaned GaN substrate;

[0008] 2. Place the cleaned GaN substrate in a magnetron sputtering coating machine, control the Ar flow rate to be 10 - 100 sccm, and the gas pressure to be 0.3 - 1 Pa, and perform reverse sputtering cleaning on the GaN substrate to obtain a clean GaN substrate;

[0009] 3. Sputter-deposit a Si3N4 transition layer on the clean GaN substrate to obtain a GaN substrate coated with the Si3N4 transition layer;

[0010] 4. Ultrasonically clean the GaN substrate coated with the Si3N4 transition layer to obtain the cleaned GaN substrate coated with the Si3N4 transition layer;

[0011] 5. Spin-coat the surface of the cleaned GaN substrate coated with the Si3N4 transition layer with a nanodiamond suspension to obtain a GaN substrate with a nanodiamond seed layer;

[0012] 6. Place the GaN substrate with the nanodiamond seed layer in a microwave plasma chemical vapor deposition (MPCVD) device, introduce hydrogen, oxygen, and methane gases, control the hydrogen flow rate, oxygen flow rate, and methane flow rate, and deposit the diamond layer in stages;

[0013] 7. In the first stage of depositing the diamond layer, control the deposition pressure to be 70 - 80 Torr, the hydrogen flow rate to be 150 - 170 sccm, the methane flow rate to be 25 - 35 sccm, the oxygen flow rate to be 0.2 - 2 sccm, the deposition temperature to be 500 - 600 °C, and the deposition time to be 1 - 10 h;

[0014] 8. In the second stage of depositing the diamond layer, control the deposition pressure to be 120 - 130 Torr, the hydrogen flow rate to be 180 - 190 sccm, the methane flow rate to be 14 - 18 sccm, the oxygen flow rate to be 0.2 - 2 sccm, the deposition temperature to be 800 - 900 °C, and the deposition time to be 10 - 50 h to obtain GaN / diamond with low interfacial thermal resistance, thereby completing the epitaxial growth of diamond on the GaN surface.

[0015] The present invention realizes the preparation of GaN / diamond materials with low interfacial thermal resistance through the temperature gradient growth process and the synergistic optimization of gas pressure and time.

[0016] The method for preparing GaN / diamond materials with low interfacial thermal resistance based on the temperature gradient process of the present invention has the following beneficial effects:

[0017] 1. Through staged kinetic matching, in the low-temperature nucleation stage, through the coordinated regulation of high methane concentration and low pressure, the migration barrier of carbon-based active elements is significantly reduced, promoting the uniform distribution of fine and high-density nuclei, avoiding the coarsening or local agglomeration of nuclei caused by the rapid diffusion of carbon atoms at high temperatures. At the same time, the low-temperature environment can reduce the etching side reaction of hydrogen radicals on the substrate surface.

[0018] 2. The diamond nucleation layer formed at low temperature not only acts as a thermal / chemical barrier during the high-temperature growth stage, blocking the direct erosion of the active hydrogen plasma on the substrate, but also relieves the mismatch of thermal expansion coefficients between diamond and the substrate through its gradient structure, reducing the risk of film cracking induced by interfacial thermal stress.

[0019] 3. In the high-temperature stage, by improving the methane dissociation efficiency and atomic hydrogen concentration, the preferential growth of diamond grains and the annihilation of defects are promoted, thereby obtaining a dense diamond film with high continuity and low grain boundary density.

[0020] The temperature gradient growth of the present invention not only avoids the irreversible damage to the substrate by the direct high-temperature method, but also significantly improves the thermal performance of the composite structure through the synergistic effect of the nucleation layer - growth layer, making the thermal resistance at the interface between the diamond layer and the substrate ≤ 10m 2 K / GW, providing an efficient heat dissipation path for GaN devices, breaking through the inherent bottlenecks of amorphous phase pollution, interface mismatch cracking, and high defect density in high-temperature processes, and providing a diamond heat dissipation solution with high thermal conductivity, low stress, and strong reliability for wide-bandgap semiconductor hetero-integration. Description of the Drawings

[0021] Figure 1 It is a scanning electron microscope image of the diamond film layer grown in the example;

[0022] Figure 2 It is a laser Raman spectrum of the diamond film layer grown in the example. Detailed Description of the Invention

[0023] Detailed Description 1: The method for preparing GaN / diamond materials with low interface thermal resistance by the temperature gradient process of this embodiment is implemented according to the following steps:

[0024] 1. Ultrasonically clean the GaN substrate to obtain the cleaned GaN substrate;

[0025] 2. Place the cleaned GaN substrate in a magnetron sputtering coater, control the Ar flow rate to be 10 - 100 sccm, and the gas pressure to be 0.3 - 1 Pa, and perform reverse sputtering cleaning on the GaN substrate to obtain a clean GaN substrate;

[0026] 3. Sputter-deposit a Si3N4 transition layer on the clean GaN substrate to obtain a GaN substrate coated with a Si3N4 transition layer;

[0027] 4. Ultrasonic cleaning is performed on the GaN substrate coated with the Si3N4 transition layer to obtain a cleaned GaN substrate coated with the Si3N4 transition layer;

[0028] 5. Spin-coating the nano-diamond suspension onto the surface of the cleaned GaN substrate coated with a Si3N4 transition layer to obtain a GaN substrate with a nano-diamond seed layer;

[0029] 6. Placing the GaN substrate with the nanodiamond seed layer in a microwave plasma chemical vapor deposition (MPCVD) device, introducing hydrogen, oxygen, and methane gases, and controlling the hydrogen, oxygen, and methane flow rates to deposit the diamond layer in stages;

[0030] 7. In the first stage of depositing the diamond layer, the deposition pressure is controlled to 70-80 Torr, the hydrogen flow rate is controlled to 150-170 sccm, the methane flow rate is controlled to 25-35 sccm, the oxygen flow rate is controlled to 0.2-2 sccm, the deposition temperature is controlled to 500-600°C, and the deposition time is controlled to 1-10 hours;

[0031] 8. In the second stage of depositing the diamond layer, the deposition pressure is controlled to 120-130 Torr, the hydrogen flow rate is controlled to 180-190 sccm, the methane flow rate is controlled to 14-18 sccm, the oxygen flow rate is controlled to 0.2-2 sccm, the deposition temperature is 800-900°C, and the deposition time is 10-50 hours to obtain GaN / diamond with low interface thermal resistance, thereby completing the epitaxial growth of diamond on the GaN surface.

[0032] In the process of depositing the diamond layer in stages in this embodiment, the microwave power increases from 2.9 kW to 4.5 kW from the first stage to the second stage of depositing the diamond layer.

[0033] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that in step 1, the GaN substrate is ultrasonically cleaned in acetone, anhydrous ethanol and deionized water in sequence, with each ultrasonic cleaning lasting 20 minutes.

[0034] Specific embodiment three: This embodiment differs from specific embodiment one or two in that the reverse sputtering cleaning time in step two is 10 to 20 minutes.

[0035] Specific embodiment 4: The difference between this embodiment and any one of specific embodiments 1 to 3 is that the thickness of the Si3N4 transition layer in step 3 is 10 to 100 nm.

[0036] Specific Embodiment 5: The difference between this embodiment and any one of Embodiments 1 to 4 is that in Step 4, the GaN substrate coated with the Si3N4 transition layer is ultrasonically cleaned successively in acetone, absolute ethanol, and deionized water, with each ultrasonic cleaning lasting for 20 minutes.

[0037] Specific Embodiment 6: The difference between this embodiment and any one of Embodiments 1 to 5 is that in Step 5, the particle size of the nanodiamond in the nanodiamond suspension is 10 - 50 nm.

[0038] Specific Embodiment 7: The difference between this embodiment and any one of Embodiments 1 to 6 is that in Step 7, the deposition pressure is controlled at 70 - 80 Torr, the hydrogen flow rate is controlled at 165 - 170 sccm, the methane flow rate is controlled at 28 - 35 sccm, the oxygen flow rate is controlled at 0.5 - 1 sccm, and the deposition temperature is 500 - 600 °C.

[0039] Specific Embodiment 8: The difference between this embodiment and Embodiment 7 is that in Step 7, the deposition time is 6 - 10 h.

[0040] Specific Embodiment 9: The difference between this embodiment and Embodiment 7 is that in Step 8, the deposition pressure is controlled at 125 - 130 Torr, the hydrogen flow rate is controlled at 180 - 190 sccm, the methane flow rate is controlled at 14 - 16 sccm, the oxygen flow rate is controlled at 0.5 - 1 sccm, and the deposition temperature is 850 - 900 °C.

[0041] Specific Embodiment 10: The difference between this embodiment and any one of Embodiments 1 to 9 is that in Step 8, the total thickness of the diamond layer epitaxially grown is 250 - 400 μm.

[0042] Example: The method for low-temperature epitaxial growth of diamond on the GaN surface with temperature gradient control is implemented according to the following steps:

[0043] 1. The GaN substrate is ultrasonically cleaned in acetone, absolute ethanol, and deionized water for 20 minutes each in sequence to obtain the cleaned GaN substrate;

[0044] 2. The cleaned GaN substrate is placed in a magnetron sputtering coating machine, with the Ar flow rate controlled at 50 sccm and the pressure at 0.5 Pa. Subsequently, the DC power supply is turned on with a power of 60 W, and the GaN substrate is subjected to reverse sputtering cleaning for 10 minutes to remove the residual impurities and contaminants on the substrate surface, obtaining a clean GaN substrate;

[0045] 3. A Si3N4 transition layer is sputter-deposited on the clean GaN substrate, with the Ar gas flow rate controlled at 50 sccm, the RF power supply turned on with an RF power of 60 W, and the deposition pressure at 0.5 Pa, obtaining a GaN substrate coated with a Si3N4 transition layer with a thickness of 20 nm;

[0046] IV. Ultrasonically clean the GaN substrate coated with the Si3N4 transition layer in acetone, absolute ethanol, and deionized water for 20 min each to obtain the cleaned GaN substrate coated with the Si3N4 transition layer;

[0047] V. Spin-coat the surface of the cleaned GaN substrate coated with the Si3N4 transition layer with the nanodiamond suspension to obtain a GaN substrate with a nanodiamond seed layer;

[0048] VI. Place the GaN substrate with the nanodiamond seed layer in a microwave plasma chemical vapor deposition (MPCVD) apparatus, introduce hydrogen, oxygen, and methane gases, control the hydrogen flow rate, oxygen flow rate, and methane flow rate, and deposit the diamond layer in two stages;

[0049] VII. In the first stage of depositing the diamond layer, control the deposition pressure at 75 Torr, the hydrogen flow rate at 170 sccm, the methane flow rate at 30 sccm, the oxygen flow rate at 1 sccm, the microwave power at 2.9 kW, the deposition temperature at 550 °C, and the deposition time at 10 h;

[0050] VIII. In the second stage of depositing the diamond layer, control the deposition pressure at 130 Torr, the hydrogen flow rate at 185 sccm, the methane flow rate at 15 sccm, the oxygen flow rate at 1 sccm, the microwave power at 4.5 kW, the deposition temperature at 880 °C, and the deposition time at 100 h, thereby completing the epitaxial growth of diamond on the GaN surface, and the total thickness of the grown diamond layer is 300 μm.

[0051] In this embodiment, the prepared GaN / diamond is analyzed in combination with the attached drawings, as shown in Figure 1 and Figure 2 This preparation method has the following advantages:

[0052] 1. High crystal quality and low defect density: As shown in Figure 1 (SEM), the film layer presents a continuous and dense columnar crystal structure, with clear grain boundaries and no holes or cracks. The multi-stage temperature gradient effectively inhibits the abnormal growth of grains, realizing the directional fusion and densification of grains.

[0053] 2. Excellent interface bonding and low interface thermal resistance: The low-temperature starting process and the Si3N4 transition layer reduce the thermal decomposition rate of the GaN substrate. The gradient heating strategy greatly reduces the interface thermal stress, improves the bonding strength, reduces the interface thermal resistance, the interface thermal resistance ≤ 10 m 2 K / GW, improves the growth rate and growth quality, and meets the thermal cycle reliability requirements of high-power devices.

[0054] 3. Ultra-high purity and thermal conductivity: As shown in Figure 2 The full width at half maximum of the diamond characteristic peak is only 4.15 cm-1 , indicating that sp 3 has an extremely high carbon content. The deposition of amorphous carbon is inhibited at the low-temperature stage, and the residual defects are removed at the later high-temperature stage, making the thermal conductivity ≥ 1200 W / (m·K). The advantages of the temperature gradient growth process are verified, providing a reliable solution for the heat dissipation of high-power electronic devices.

[0055] Comparative Example: The method for epitaxial growth of diamond on the surface of GaN in this example is implemented according to the following steps:

[0056] I. Ultrasonically clean the GaN substrate in acetone, absolute ethanol, and deionized water for 20 minutes each to obtain a cleaned GaN substrate;

[0057] II. Place the cleaned GaN substrate in a magnetron sputtering coating machine, control the Ar flow rate to be 50 sccm, the gas pressure to be 0.5 Pa, then turn on the DC power supply with a power of 60 W, and perform reverse sputtering cleaning on the GaN substrate for 10 minutes to remove possible residual impurities and contaminants on the substrate surface to obtain a clean GaN substrate;

[0058] III. Sputter-deposit a Si3N4 transition layer on the clean GaN substrate, control the Ar gas flow rate to be 50 sccm, turn on the RF power supply with an RF power of 60 W, and the deposition gas pressure to be 0.5 Pa to obtain a GaN substrate coated with a 20-nm-thick Si3N4 transition layer;

[0059] IV. Ultrasonically clean the GaN substrate coated with the Si3N4 transition layer in acetone, absolute ethanol, and deionized water for 20 minutes each to obtain a cleaned GaN substrate coated with the Si3N4 transition layer;

[0060] V. Spin-coat the surface of the cleaned GaN substrate coated with the Si3N4 transition layer with a nanodiamond suspension to obtain a GaN substrate with a nanodiamond seed layer;

[0061] VI. Place the GaN substrate with the nanodiamond seed layer in a microwave plasma chemical vapor deposition (MPCVD) device, introduce hydrogen, oxygen, and methane gases, control the hydrogen flow rate to be 200 sccm, the oxygen flow rate to be 1 sccm, the methane flow rate to be 20 sccm, the deposition gas pressure to be 130 Torr, the microwave power to be 4.5 kW, the deposition temperature to be 880 °C, and the deposition time to be 110 h, thereby completing the epitaxial growth of diamond on the surface of GaN.

[0062] The GaN / diamond obtained by growing at a high temperature of 880 °C for a long time in this example results in the exponential etching of GaN by hydrogen plasma and penetration of the Si3N4 grain boundary defects, leading to the decomposition of GaN; at the same time, the Si3N4 layer shows microcracks and pores due to the bombardment of high-temperature plasma, significantly reducing the bonding force with diamond and increasing the interfacial thermal resistance.

Claims

1. A preparation method of GaN / diamond with low interfacial thermal resistance, characterized in that The preparation method of the GaN / diamond with low interfacial thermal resistance is realized according to the following steps: I. Ultrasonically clean the GaN substrate to obtain the cleaned GaN substrate; II. Place the cleaned GaN substrate in a magnetron sputtering coating machine, control the Ar flow rate to be 10 - 100 sccm, and the gas pressure to be 0.3 - 1 Pa, and perform reverse sputtering cleaning on the GaN substrate to obtain a clean GaN substrate; III. Sputter-deposit a Si3N4 transition layer on the clean GaN substrate to obtain a GaN substrate coated with a Si3N4 transition layer; IV. Ultrasonically clean the GaN substrate coated with a Si3N4 transition layer to obtain the cleaned GaN substrate coated with a Si3N4 transition layer; V. Spin-coat the surface of the cleaned GaN substrate coated with a Si3N4 transition layer with a nanodiamond suspension to obtain a GaN substrate with a nanodiamond seed layer; VI. Place the GaN substrate with a nanodiamond seed layer in a microwave plasma chemical vapor deposition device, introduce hydrogen, oxygen and methane gases, control the hydrogen flow rate, oxygen flow rate and methane flow rate, and deposit the diamond layer in stages; VII. In the first stage of depositing the diamond layer, control the deposition pressure to be 70 - 80 Torr, control the hydrogen flow rate to be 150 - 170 sccm, the methane flow rate to be 25 - 35 sccm, the oxygen flow rate to be 0.2 - 2 sccm, the deposition temperature to be 500 - 600 °C, and the deposition time to be 1 - 10 h; VIII. In the second stage of depositing the diamond layer, control the deposition pressure to be 120 - 130 Torr, control the hydrogen flow rate to be 180 - 190 sccm, the methane flow rate to be 14 - 18 sccm, the oxygen flow rate to be 0.2 - 2 sccm, the deposition temperature to be 800 - 900 °C, and the deposition time to be 10 - 50 h to obtain the GaN / diamond with low interfacial thermal resistance, thereby completing the epitaxial growth of diamond on the GaN surface.

2. The preparation method of GaN / diamond with low interfacial thermal resistance according to claim 1, wherein In step I, ultrasonically clean the GaN substrate in acetone, absolute ethanol and deionized water in sequence, and ultrasonically clean for 20 min each time.

3. The preparation method of GaN / diamond with low interfacial thermal resistance according to claim 1, characterized in that In step II, the reverse sputtering cleaning time is 10 - 20 min.

4. The preparation method of GaN / diamond with low interfacial thermal resistance according to claim 1, characterized in that In step III, the thickness of the Si3N4 transition layer is 10 - 100 nm.

5. The preparation method of GaN / diamond with low interfacial thermal resistance according to claim 1, characterized in that In step IV, ultrasonically clean the GaN substrate coated with a Si3N4 transition layer in acetone, absolute ethanol and deionized water in sequence, and ultrasonically clean for 20 min each time.

6. The preparation method of GaN / diamond with low interfacial thermal resistance according to claim 1, characterized in that In step V, the particle size of the nanodiamonds in the nanodiamond suspension is 10 - 50 nm.

7. The preparation method of GaN / diamond with low interfacial thermal resistance according to claim 1, characterized in that In step VII, control the deposition pressure to be 70 - 80 Torr, control the hydrogen flow rate to be 165 - 170 sccm, the methane flow rate to be 28 - 35 sccm, the oxygen flow rate to be 0.5 - 1 sccm, and the deposition temperature to be 500 - 600 °C.

8. The preparation method of GaN / diamond with low interfacial thermal resistance according to claim 7, characterized in that In step VII, the deposition time is 6 - 10 h.

9. The preparation method of GaN / diamond with low interfacial thermal resistance according to claim 7, characterized in that In step VIII, control the deposition pressure to be 125 - 130 Torr, control the hydrogen flow rate to be 180 - 190 sccm, the methane flow rate to be 14 - 16 sccm, the oxygen flow rate to be 0.5 - 1 sccm, and the deposition temperature to be 850 - 900 °C.

10. The preparation method of GaN / diamond with low interfacial thermal resistance according to claim 1, characterized in that In step VIII, the thickness of the epitaxially grown diamond layer is 250 - 400 μm.

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