Device and method for correcting deformation of large-size diamond film by loading heat treatment at high temperature

Abstract

The invention relates to a device and a method for correcting deformation of a large-size diamond film by loading heat treatment at high temperature, and belongs to the technical field of high-temperature and high-pressure preparation. The method mainly comprises the following steps: preparing media including but not limited to graphite paper, ceramic powder and the like into mixed powder; putting an 8-inch large-size diamond film into the mixed powder, and preheating; and then applying high-temperature loading to the film in a vacuum environment for treatment. The method has the advantages that bending of the large-size diamond self-supporting film (4-8 inches) is corrected, the phenomenon of uneven stress distribution in the loading process and the annealing process is reduced or eliminated, stress uniform distribution of the large-size diamond self-supporting film is remarkably improved, the deformation of the diamond film is reduced, the deformation correction condition is solved by 90% or above, the warping degree can reach 30 micrometers or below, and the yield of the large-size diamond self-supporting film is improved. And the crack generation probability of the self-supporting film during later grinding and polishing is reduced, so that the whole film rate reaches 80% or above, and meanwhile, the comprehensive mechanical property of the diamond film is also effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature and high-pressure preparation, and particularly relates to a device and method for correcting the deformation of a large-size diamond film by heat treatment under high temperature loading. Technical Background

[0002] Diamond has extremely excellent physical and chemical properties and has gradually become one of the indispensable materials in the fields of thermotics, optics, mechanics, and electricity. With the rapid development of the electronics industry, the third-generation semiconductor materials have been rapidly applied to high-power electronic devices, but their heat dissipation has become a bottleneck restricting the improvement of their performance. In the early 1980s of the last century, the chemical vapor deposition method (CVD) realized the preparation of diamond films, bringing hope for the application of diamond in this field.

[0003] In previous studies, diamond can be used as a passivation layer and a substrate layer of a device due to its ultra-high thermal conductivity, greatly reducing the hot spot temperature of the device and increasing the device power density. For example, integrating diamond with high thermal conductivity with GaN power devices can greatly improve the heat exchange capacity of the system and significantly improve the heat dissipation effect of the device by virtue of the ultra-high thermal conductivity of diamond, so as to reduce the temperature of the device channel. The difficulty in the diamond / GaN bonding technology is that it has extremely high requirements for the surface roughness and warpage of diamond. The diamond film with deformation and warpage is not conducive to the processing of the diamond film, and it is impossible to obtain a low surface roughness that meets the application requirements. Moreover, in the later application, it affects the bonding technology between diamond and semiconductor devices, increases the interface thermal resistance, reduces the bonding strength, etc., which is not conducive to the effective exertion of the excellent performance of diamond and affects the device performance and service life. In order to reduce its production cost and meet the application requirements of high-power devices, it has become extremely important to prepare large-area diamond self-supporting films with low warpage.

[0004] In addition, the residual stress generated during the deposition process has a great impact on the quality and performance of the diamond film. Generally speaking, the residual stress can be divided into internal stress and thermal stress. The former is generated during the film growth process, while the latter is caused by the different thermal contractions of the film and the substrate due to the mismatch of the thermal expansion coefficients between the two materials. The thermal stress is released after the diamond film is detached from the growth substrate. Therefore, the residual stress in the diamond film is basically the internal stress generated during the growth process, and the non-uniformity of the stress distribution will lead to a large deformation phenomenon in the diamond film.

[0005] Patent CN 101054661 A proposes a method for changing the comprehensive performance of a diamond film, reducing or eliminating the elemental impurities such as N, H, O, etc. and micro-defects such as dislocations and stacking faults at the grain boundaries of the diamond film, thereby changing its comprehensive performance. However, it does not involve the correction of the curvature of the large-area diamond self-supporting film and the stress release during annealing and cooling, so as to improve the flatness and the whole film rate of the diamond film.

[0006] Patent CN 113684466 B provides a method for reducing cracks in diamond films. By controlling the separation of the cooling table, the cooling rate of the diamond film is reduced, so that stress is released and the occurrence of cracks is reduced. However, it does not involve how to correct the warping of the diamond film, nor does it involve the annealing of the diamond film during the cooling process.

[0007] How to correct the deformation of the diamond film and release the internal stress during the cooling stage, so as to reduce the occurrence of cracks in the later processing and improve the utilization rate of the self-supporting film is the key issue. Summary of the Invention

[0008] The present invention provides a device and method for correcting the deformation of diamond films, in order to solve the technical problem that the prior art cannot correct the warping of large-size self-supporting diamond films, resulting in low utilization rate of stress release.

[0009] The solution adopted by the present invention is:

[0010] A device for correcting the deformation of large-size diamond films by applying heat treatment under vacuum and high temperature, characterized in that the device includes an upper hydraulic column, a pressure sensing control system, a vacuum chamber, a medium, a diamond film, a mechanical pump, a vacuum detection control system, an observation window, a correction mold, a fixture, a heating wire, a thermocouple, and a temperature detection control system. The pressure sensing control system controls the ejector rod of the upper hydraulic column, which is located above the vacuum chamber and vertically passes through the interior of the chamber, and keeps close contact with the periphery of the chamber to maintain a vacuum environment. The reaction medium is filled between the diamond film and the correction mold, and the diamond film is fixed by the fixture. The mechanical pump is placed outside and evacuates the chamber to vacuum, and is detected by the vacuum detection control system. The observation window is located on the side of the chamber. The heating wires are located on both sides of the fixture, and the thermocouple is located below the fixture. Controlled by the temperature detection system, it can heat the bottom to slow down the cooling rate.

[0011] A method for correcting the deformation of large-size diamond films by applying heat treatment under vacuum and high temperature using the above device, the specific steps are as follows:

[0012] The upper hydraulic push rod initially stays at a distance of not less than 30 cm from the base, and the dielectric is filled into the diamond film on the diamond film fixture. The mechanical pump is turned on through the vacuum detection control system to evacuate the chamber. When the required conditions are met in the vacuum chamber, the chamber is heated by adjusting the heating wire through the temperature detection control system, and real-time detection is performed using a thermocouple. After the temperature conditions are reached, the hydraulic column is pressurized to pressurize the diamond film, and the pressure sensor control system performs loading adjustment. The warping phenomenon is corrected through the reaction between the diamond film and the dielectric under high temperature conditions, and the diamond film is prevented from cracking. After a period of time, the heating is stopped, and annealing is performed to release the stress inside the diamond film. Finally, the diamond film sample is taken out, ground to remove the dielectric, and pickled and cleaned.

[0013] Furthermore, the filling medium includes but is not limited to graphite paper and ceramic powder mixed powder, which covers the surface of the 4-8 inch diamond self-supporting film.

[0014] Furthermore, a mechanical pump was used to evacuate the air to below 0.1 Pa, and the vacuum leakage rate was within 2×10 -5 Pa m 3 / s.

[0015] Furthermore, when the vacuum requirement is met, a heating wire is used to heat the chamber, and when the temperature reaches 1200-2500° C., hydraulic loading is started to correct the diamond film.

[0016] Furthermore, the heating wire includes tungsten wire, molybdenum wire or graphite.

[0017] Furthermore, the pressure range of the pressure sensing control system is 0.05-10GPa, and the horizontal height of the upper hydraulic column push rod after the load is applied is lower than the horizontal height of the self-supporting membrane groove; when the vacuum and temperature requirements are met, the upper hydraulic column push rod continues to pressurize for 0.5-36h, starting from 0.05GPa, each pressurization shall not exceed 500MPa and is a uniform pressurization, and the maximum pressure is 10GPa; after the pressure of the upper hydraulic column push rod reaches the maximum value, it is maintained for 0.5-30h and the pressure is reduced to 0.05GPa in the same steps.

[0018] Furthermore, annealing is started after the upper hydraulic column push rod is separated from the groove, and the specific steps include: heating the self-supporting film in the range of 1-20°C / min each time, turning off the heating system after the heating temperature reaches 1200-2500°C, and keeping the diamond film warm for 0.5-24h; cooling after the insulation is completed, in the range of 1-20°C / min, turning off the temperature when the temperature reaches 50°C, and letting it stand to cool to room temperature.

[0019] Further, the operating steps after taking out the diamond film sample are as follows: Use a tool to take out the diamond film and then grind it with diamond powder for 4 - 12 hours to remove the covering medium; finally, pickle it in a solution prepared from nitric acid and sulfuric acid for 20 - 40 minutes to obtain a complete and pollution-free diamond film.

[0020] The key point in the implementation process of the present invention lies in:

[0021] To achieve the deformation correction of the diamond film, the key lies in filling the medium into the diamond film on the diamond film fixture, evacuating the air and then heating the chamber, applying pressure to the diamond film with a hydraulic column after reaching the temperature condition, and correcting the warping phenomenon through the reaction between the diamond film and the medium under high temperature conditions, while preventing problems such as cracking of the diamond film. After maintaining for a period of time, stop heating and perform annealing to release the internal stress of the diamond film.

[0022] The beneficial effects of the present invention compared with the prior art are as follows:

[0023] This method mainly corrects the deformation of the diamond self-supporting film under high temperature and loading in a vacuum condition and in a medium, which can reduce the interfacial thermal resistance, improve the bonding strength, and make the diamond / GaN bonding technology easier. It is beneficial to the effective exertion of the excellent properties of diamond, greatly extending the device performance and service life. In addition, during the annealing process, the inhomogeneity of the internal stress in the diamond film will be eliminated or improved, thereby reducing the warping degree of the diamond film. It avoids the concentration of stress and the generation of cracks in the diamond film. By using the device and method for correcting the deformation of a large-size diamond film under vacuum and high temperature loading designed by the present invention, the warping degree of the diamond film can be greatly improved, the stress can be fully released, and the probability of crack generation can be reduced, greatly improving the utilization rate of the large-size diamond self-supporting film. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the working state of the device before loading in an embodiment of the present invention.

[0025] In this example, 1 is the upper hydraulic column, 2 is the pressure sensing control system, 3 is the vacuum chamber, 4 is the medium, 5 is the diamond film, 6 is the mechanical pump, 7 is the vacuum detection control system, 8 is the observation window, 9 is the correction mold, 10 is the fixture, 11 is the heating wire, 12 is the thermocouple, and 13 is the temperature detection control system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0027] Embodiment 1

[0028] An apparatus and method for correcting the deformation of large-sized diamond films by heat treatment under vacuum and high temperature. The steps include: directly fixing the diamond film with the fixture (10) and pressurizing the diamond film with the upper hydraulic column ejector rod (1). First, put the medium powder (4) into the groove of the fixture (10), and cover it with another layer after the diamond self-supporting film is fixed; evacuate the apparatus, and the vacuum leakage rate must reach below 2×10 -5 Pa·m3 / s to meet the conditions. Lower the hydraulic column (1) until it touches the medium powder and then stop. Among them, the direct contact between the hydraulic column (1) and the fixture (10) and the medium powder (4) includes: when the hydraulic column (1) descends into the groove, its horizontal height is lower than that of the fixture (10). Before pressure loading, first raise the temperature, and control the temperature at 1400°C. When the temperature is stable, apply a loading pressure of 5 GPa. The hydraulic column (1) continuously applies pressure for 36 h. The upper hydraulic column ejector rod first starts to increase the pressure from 0.05 GPa; after the pressure of the hydraulic column (1) reaches the maximum value, it remains for 28 h and then reduces the pressure to 0.05 GPa in the same steps; after the loading is completed, the hydraulic column (1) separates from the groove and moves above. After the upper hydraulic column ejector rod separates from the groove, heat preservation annealing is started. The specific steps include: each time the temperature increase range is 10°C / min, first heat the self-supporting film; after the temperature reaches 2200°C, turn off the heating system. Keep the diamond film (5) at a constant temperature for 20 h, then cool it down, and the range is 10°C / min; when the temperature drops to 50°C, turn off the cooling, and let it stand and cool to room temperature. After maintaining the pressure for 12 h, open the intake valve to restore the vacuum state, and take out the diamond self-supporting film. Open the chamber body to take out the diamond film, and the whole film rate can reach 80%, and the warpage degree is reduced from 1 mm to 50 μm. There are individual cracks on the surface of the diamond film.

[0029] Example 2

[0030] An apparatus and method for correcting the deformation of large-size diamond films by heat treatment under vacuum and high temperature. The steps include: directly fixing the diamond film with the fixture (10) and pressurizing the diamond film with the upper hydraulic column ejector rod (1). First, put the medium powder (4) into the groove of the fixture (10), and cover it with another layer after the diamond self-supporting film is fixed. Evacuate the apparatus to a pressure below 0.1 Pa. Lower the hydraulic column (1) until it touches the medium powder and then stop. Among them, the direct contact of the hydraulic column (1) with the fixture (10) and the medium powder (4) includes: the hydraulic column (1) descends into the groove and its horizontal height is lower than that of the fixture (10). Before pressure loading, first raise the temperature to 1800 °C. When the temperature is stable, apply a pressure of 7 GPa. The hydraulic column (1) continuously applies pressure for 30 h. The upper hydraulic column ejector rod starts to increase the pressure from 0.05 GPa; after the pressure of the hydraulic column (1) reaches the maximum value, it is maintained for 24 h and then reduced to 0.05 GPa in the same steps; after the loading is completed, the hydraulic column (1) is separated from the groove and moved above. After the upper hydraulic column ejector rod is separated from the groove, heat preservation annealing is carried out. The specific steps include: each time the temperature rise range is 15 °C / min, first heat the self-supporting film; after the temperature reaches 2000 °C, turn off the heating system. Keep the diamond film (5) at a constant temperature for 20 h, then cool it down at a rate of 15 °C / min; when the temperature drops to 50 °C, turn off the cooling, and let it stand and cool to room temperature. After maintaining the pressure for 15 h, open the intake valve to restore the vacuum state, and take out the diamond self-supporting film. Open the chamber body to take out the diamond film. The whole film rate can reach 85%, and the warpage degree is reduced from 1 mm to 40 μm. There are no obvious cracks on the surface of the diamond film.

[0031] Example 3

[0032] An apparatus and method for deforming and correcting large-sized diamond films by heat treatment under vacuum and high temperature. The steps include: directly fixing the diamond film with the fixture (10) and pressurizing the diamond film with the upper hydraulic column ejector rod (1). First, put the medium powder (4) into the groove of the fixture (10), and cover it with another layer after the diamond self-supporting film is fixed; evacuate the apparatus. Lower the hydraulic column (1) until it touches the medium powder and then stop. Among them, the direct contact between the hydraulic column (1) and the fixture (10) and the medium powder (4) includes: the hydraulic column (1) descends into the groove and its horizontal height is lower than that of the fixture (10). Before pressure loading, heat up first, and control the temperature at 2200 °C. When the temperature is stable, load the pressure at 10 GPa. The hydraulic column (1) continuously pressurizes for 26 h. The upper hydraulic column ejector rod starts to increase the pressure from 0.05 GPa; after the pressure of the hydraulic column (1) reaches the maximum value, it remains for 20 h and then reduces the pressure to 0.05 GPa in the same steps; after the loading is completed, the hydraulic column (1) separates from the groove and moves above. After the upper hydraulic column ejector rod separates from the groove, start heat preservation annealing. The specific steps include: the temperature increase range is 20 °C / min each time, and first heat the self-supporting film; after the temperature reaches 1800 °C, turn off the heating system.

[0033] Keep the diamond film (5) at a constant temperature for 16 h, then cool it down, and the range is 20 °C / min; when the temperature drops to 50 °C, turn it off and let it cool to room temperature statically. After maintaining the pressure for 10 h, open the intake valve to restore the vacuum state, and take out the diamond self-supporting film. Open the chamber body to take out the diamond film, and the whole film rate can reach 95%, and the warpage degree is reduced from 1 mm to 30 μm. There are no cracks on the surface of the diamond film. The vacuum degree in the apparatus is lower than 10 -3 Pa, and there is no flowing medium inside at this time. Under the condition of ensuring no oxygen, perform high-temperature loading to correct the diamond self-supporting film to prevent the generation of other carbon phases. After loading and correction, perform high-temperature annealing, which can release the internal stress brought by the loading once again, so that the surface of the large-sized diamond self-supporting film is flat, has low stress and extremely high utilization rate.

Claims

1. A deformation correction device for large-sized diamond films by heat treatment under high temperature loading, characterized in that, It includes upper hydraulic column push rod, pressure sensor control system, vacuum chamber, dielectric, diamond film, mechanical pump, vacuum detection control system, observation window, correction mold, fixture, heating wire, thermocouple, temperature detection control system; The pressure sensing control system controls the upper hydraulic column push rod, which is located above the vacuum chamber and passes vertically through the interior of the chamber, maintaining close contact with the surroundings of the chamber to maintain a vacuum environment; the reaction medium is filled between the diamond film and the correction mold, and the diamond film is fixed by a clamp; the mechanical pump is placed outside to evacuate the chamber to a vacuum, and the vacuum detection control system is used for detection; the observation window is located on the side of the chamber; the heating wires are located on both sides of the clamp, and the thermocouple is located below the clamp. The bottom can be heated to slow down the cooling rate through the temperature detection system.

2. A method for correcting the deformation of a large-sized diamond film by vacuum high-temperature loading heat treatment using the device described in claim 1, characterized in that Includes steps: The upper hydraulic column initially stays at a distance of not less than 30 cm from the base, and the dielectric is filled into the diamond film on the diamond film fixture. The mechanical pump is turned on through the vacuum detection control system to evacuate the chamber. When the required conditions are met in the vacuum chamber, the chamber is heated by adjusting the heating wire through the temperature detection control system, and real-time detection is performed using a thermocouple. After the temperature conditions are reached, the hydraulic column is pressurized to pressurize the diamond film, and the pressure sensor control system performs loading adjustment. The warping phenomenon is corrected through the reaction between the diamond film and the dielectric under high temperature conditions, and the diamond film is prevented from cracking. After a period of time, the heating is stopped, and annealing is performed to release the stress inside the diamond film. Finally, the diamond film sample is taken out, ground to remove the dielectric, and pickled and cleaned.

3. The method for correcting the deformation of a large-sized diamond film by heat treatment under vacuum and high temperature according to claim 2, characterized in that, The filling medium includes but is not limited to graphite paper and ceramic powder mixed powder, which is used to cover the surface of the 4-8 inch diamond self-supporting film.

4. The method for correcting the deformation of a large-sized diamond film by heat treatment under vacuum and high temperature according to claim 2, characterized in that, Use a mechanical pump to evacuate to below 0.1 Pa, with a vacuum leakage rate of 2×10 -5 Pa m 3 / s.

5. The method for correcting the deformation of a large-size diamond film by heat treatment under vacuum and high temperature according to claim 2, wherein When the vacuum requirement is met, a heating wire is used to heat the chamber, and when the temperature reaches 1200-2500°C, hydraulic loading is started to correct the diamond film.

6. The method for correcting the deformation of a large-size diamond film by heat treatment under vacuum and high temperature according to claim 5, characterized in that, The heating wire includes tungsten wire, molybdenum wire or graphite.

7. The method for correcting the deformation of a large-sized diamond film by heat treatment under vacuum and high temperature according to claim 2, wherein The pressure range of the pressure sensing control system is 0.05-10GPa. After the load is applied to the upper hydraulic column push rod, the horizontal height is lower than the horizontal height of the self-supporting membrane groove; when the vacuum and temperature requirements are met, the upper hydraulic column push rod continues to pressurize for 0.5-36h, starting from 0.05GPa. Each pressurization shall not exceed 500MPa and is a uniform pressurization, with a maximum pressure of 10GPa; after the pressure of the upper hydraulic column push rod reaches the maximum value, it is maintained for 0.5-30h and reduced to 0.05GPa in the same steps.

8. The method for correcting the deformation of a large-sized diamond film by heat treatment under vacuum and high temperature according to claim 2, wherein, After the upper hydraulic column push rod is separated from the groove, annealing begins. The specific steps include: heating the self-supporting film in the range of 1-20°C / min each time, turning off the heating system after the heating temperature reaches 1200-2500°C, and keeping the diamond film warm for 0.5-24h; cooling after the insulation is completed, in the range of 1-20°C / min, turning off the temperature when the temperature reaches 50°C, and standing to cool to room temperature.

9. The method for correcting the deformation of a large-sized diamond film by heat treatment under vacuum and high temperature according to claim 2, characterized in that The operating steps after taking out the diamond film sample are as follows: Use tools to take out the diamond film and then grind it with diamond powder for 4 - 12 hours to remove the covered medium; finally, pickle it with a solution prepared from nitric acid and sulfuric acid for 20 - 40 minutes to obtain a complete and pollution-free diamond film.

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