Growth method of high-quality self-supporting diamond thick film

Abstract

The invention belongs to the technical field of polycrystalline diamond growth, and particularly relates to a growth method of a high-quality self-supporting diamond thick film. Compared with the prior art, the polycrystalline diamond film is obtained on the substrate through multiple times of growth and annealing treatment, accumulation of stress accumulated in the polycrystalline film can be reduced, and the quality self-supporting diamond thick film is obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polycrystalline diamond growth, and particularly relates to a growth method of high-quality self-supporting diamond thick film. BACKGROUND

[0002] With the development of science and technology, the performance of electronic equipment is improved, and the heat dissipation problem is increasingly prominent. Polycrystalline diamond leads the heat management technology revolution in the new energy field due to its excellent thermal conductivity, chemical stability and unique physical properties.

[0003] At present, the main means of growing polycrystalline diamond film is chemical vapor deposition (CVD) technology. Among them, microwave plasma assisted chemical vapor deposition (MPCVD) has become a common method for preparing high-quality polycrystalline diamond film due to its advantages of no electrode pollution and precise control of reaction parameters. Through this technology, polycrystalline diamond film can be grown on substrate materials, providing a basis for large-size growth. However, the existing chemical vapor deposition (MPCVD) technology for growing polycrystalline diamond film usually adopts a single growth to the target thickness (a schematic diagram of a composite substrate material prepared by traditional single growth is shown in Figure 1 As shown, 06 is a molybdenum support for growth, 07 is a substrate wafer, and 08 is a polycrystalline diamond film), when the target thickness of the polycrystalline diamond film is prepared, the stress accumulated in the continuously thickening polycrystalline film becomes larger and larger, which is prone to cracking at the end of growth or the quality of the prepared diamond film is poor. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to provide a growth method of high-quality self-supporting diamond thick film.

[0005] The present application provides a growth method of high-quality self-supporting diamond thick film, comprising the following steps:

[0006] S1) first growth: placing a substrate in a reaction chamber, introducing hydrogen under vacuum conditions, adjusting the chamber pressure and microwave power, and then simultaneously increasing the chamber pressure and microwave power, and then at least introducing methane and oxygen, and performing first film growth when the temperature is increased to above 700℃;

[0007] S2) first annealing: at least stop introducing methane and oxygen, and perform a segmented annealing process; the segmented annealing process at least includes: first reducing the microwave power and the chamber pressure simultaneously, and then maintaining at least 0.5h when the temperature is reduced to below 800℃; and then secondly reducing the microwave power and the chamber pressure simultaneously, and then maintaining at least 0.5h when the temperature is reduced to below 600℃;

[0008] S3) Secondary growth: simultaneously increasing the chamber pressure and the microwave power, and at least introducing methane and oxygen, until the temperature is above 700℃, to perform secondary film growth;

[0009] S4) Secondary annealing: at least stopping the introduction of methane and oxygen, to perform a segmented annealing process; the segmented annealing process at least includes: first simultaneously decreasing the microwave power and the chamber pressure, until the temperature is below 800℃, and maintaining for at least 0.5h; and then second simultaneously decreasing the microwave power and the chamber pressure, until the temperature is below 600℃, and maintaining for at least 0.5h;

[0010] S5) Repeating the operations of step S3) and step S4) until the self-supporting diamond thick film reaches a target thickness, to obtain a high-quality self-supporting diamond thick film.

[0011] Preferably, the flow rate of hydrogen in step S1) is 120-2000sccm; the chamber pressure is adjusted to 50-200Torr; and the microwave power is adjusted to 2kW to perform the temperature rising operation and the ignition operation in the reaction chamber.

[0012] Preferably, the gradient of simultaneously increasing the chamber pressure and the microwave power in step S1) is 1-13Torr / 200W; the flow rate of methane is 10-200sccm; the flow rate of oxygen is 1-20sccm; and the time of the primary film growth is 5-20h.

[0013] And / or, nitrogen is also introduced simultaneously with methane and oxygen; the flow rate of nitrogen is 1-80sccm.

[0014] Preferably, the gradient of first simultaneously decreasing the microwave power and the chamber pressure in step S2) is 1-13Torr / 200W; and the gradient of second simultaneously decreasing the microwave power and the chamber pressure is 1-13Torr / 200W.

[0015] The gradient of first simultaneously decreasing the microwave power and the chamber pressure in step S4) is 1-13Torr / 200W; and the gradient of second simultaneously decreasing the microwave power and the chamber pressure is 1-13Torr / 200W.

[0016] Preferably, the segmented annealing process in step S2) at least includes: first simultaneously decreasing the microwave power and the chamber pressure, until the temperature is 600-800℃, and maintaining for 1-2h; and then second simultaneously decreasing the microwave power and the chamber pressure, until the temperature is 400-600℃, and maintaining for 1-2h.

[0017] And / or, the step S4) includes at least: the first time, the microwave power and the chamber pressure are simultaneously reduced, and when the temperature is reduced to 600-800℃, the temperature is maintained for 1-2h; then the second time, the microwave power and the chamber pressure are simultaneously reduced, and when the temperature is reduced to 400-600℃, the temperature is maintained for 1-2h.

[0018] Preferably, the step S2) includes: the third time, the microwave power and the chamber pressure are simultaneously reduced, and the temperature is reduced to below 300℃.

[0019] And / or, the step S4) includes: the third time, the microwave power and the chamber pressure are simultaneously reduced, and the temperature is reduced to below 300℃.

[0020] Preferably, the step S2) includes: the third time, the microwave power and the chamber pressure are simultaneously reduced, and the temperature is reduced to 150-300℃.

[0021] And / or, the step S4) includes: the third time, the microwave power and the chamber pressure are simultaneously reduced, and the temperature is reduced to 150-300℃.

[0022] Preferably, the gradient of the step S3) is 1-13Torr / 200W; the flow rate of the methane is 10-200sccm; the flow rate of the oxygen is 1-20sccm.

[0023] And / or, the time of the second film growth is 5-20h.

[0024] Preferably, the step S3) further includes: the nitrogen is introduced; the flow rate of the nitrogen is 1-80sccm.

[0025] And / or, the step S5) includes: the step S3) and the step S4) are repeated until the self-supporting diamond thick film reaches the target thickness, then the microwave power and the chamber pressure are continuously reduced until the plasma disappears, the hydrogen supply is stopped, the chamber pressure is adjusted to the standard atmospheric pressure, and the temperature is cooled to the room temperature, thereby obtaining the high-quality self-supporting diamond thick film.

[0026] Preferably, the thickness of the high-quality self-supporting diamond thick film is greater than or equal to 100μm.

[0027] The half-height width of the (111) crystal orientation XRD diffraction peak of the high-quality self-supporting diamond thick film is less than 0.15, the half-height width of the (220) crystal orientation XRD diffraction peak is less than 0.11, and the half-height width of the (311) crystal orientation XRD diffraction peak is less than 0.15.

[0028] Compared with existing technologies, this invention reduces the accumulation of stress within the polycrystalline diamond film by obtaining a polycrystalline diamond film through multiple growth and annealing processes on a substrate, resulting in a high-quality, self-supporting thick diamond film. During the growth of a polycrystalline diamond film, as the thickness increases, the grain size gradually enlarges, leading to grain boundaries and other defects. These defects affect the nucleation of new grains, resulting in poor crystallinity. This invention, through annealing the polycrystalline diamond film, repairs lattice defects and removes stress, improving the crystallinity of the newly grown polycrystalline film and thus obtaining a high-quality diamond film of appropriate thickness.

[0029] Experimental results show that the full width at half maximum (FWHM) of the XRD pattern of the high-quality self-supporting diamond thick film prepared by this invention is significantly reduced compared to the normal single-growth process, and the uniformity of grain size is improved, which proves that the crystal quality of the composite material is improved. Attached Figure Description

[0030] Figure 1 A schematic diagram of a composite substrate material prepared by traditional single-stage growth;

[0031] Figure 2 A schematic diagram of the structure of a high-quality self-supporting diamond thick film obtained by the growth method provided in this invention.

[0032] Figure 3 This is a photograph of the substrate of the composite diamond film obtained in Example 1 of the present invention;

[0033] Figure 4 A microscope image of the substrate of the composite diamond film obtained in Example 1 of the present invention;

[0034] Figure 5 The image shows the XRD pattern of the substrate of the composite diamond film obtained in Example 1 of this invention.

[0035] Figure 6 This is a photograph of the substrate of the composite diamond film obtained in Example 2 of the present invention;

[0036] Figure 7 This is a microscope image of the substrate of the composite diamond film obtained in Example 2 of the present invention;

[0037] Figure 8 The image shows the XRD pattern of the substrate of the composite diamond film obtained in Example 2 of this invention.

[0038] Figure 9 A photograph of the substrate of the composite diamond film obtained in Comparative Example 1 of this invention;

[0039] Figure 10 This is a microscope image of the substrate of the composite diamond film obtained in Comparative Example 1 of the present invention.

[0040] Figure 11The image shows the XRD pattern of the substrate of the composite diamond film obtained in Comparative Example 1 of this invention. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] This invention provides a method for growing high-quality self-supporting diamond thick films, comprising the following steps: S1) Primary growth: The substrate is placed in a reaction chamber, hydrogen is introduced under vacuum conditions, and the chamber pressure and microwave power are adjusted to perform heating and ignition operations within the reaction chamber. Then, the chamber pressure and microwave power are simultaneously increased until the temperature reaches above 700°C, at least methane and oxygen are introduced to perform primary film growth; S2) Primary annealing: At least the introduction of methane and oxygen is stopped, and segmented annealing is performed. The segmented annealing process includes at least: a first simultaneous reduction of microwave power and chamber pressure until the temperature drops below 800°C, and holding for at least 0.5 hours; then a second simultaneous reduction of microwave power and chamber pressure until the temperature drops below 800°C, and holding for at least 0.5 hours. S3) Secondary growth: Simultaneously increase the chamber pressure and microwave power, and when the temperature rises to above 700°C, introduce at least methane and oxygen to perform secondary film growth; S4) Secondary annealing: Stop introducing at least methane and oxygen, and perform segmented annealing treatment; The segmented annealing treatment includes at least: first, simultaneously reducing the microwave power and chamber pressure, and when the temperature drops to below 800°C, maintaining it for at least 0.5 hours; then, second, simultaneously reducing the microwave power and chamber pressure, and when the temperature drops to below 600°C, maintaining it for at least 0.5 hours; S5) Repeat steps S3) and S4) until the self-supporting diamond thick film reaches the target thickness, and obtain a high-quality self-supporting diamond thick film.

[0043] See Figure 2 , Figure 2 This is a schematic diagram of the structure of a high-quality self-supporting diamond thick film obtained by the growth method provided by the present invention, wherein 01 is a molybdenum support for growth, 02 is a substrate wafer, 03 is a polycrystalline diamond film grown in the first stage, 04 is a polycrystalline diamond film grown in the second stage, and 05 is a polycrystalline diamond film grown in the third stage.

[0044] In this invention, there are no special restrictions on the source of any raw materials; they can be commercially available.

[0045] In one specific embodiment of the present invention, the substrate can be any substrate known to those skilled in the art, and there are no special limitations. In the present invention, a silicon carbide substrate is preferred.

[0046] In one specific embodiment of the present invention, the substrate is preferably pretreated to obtain a substrate with a good surface condition, and then placed in a reaction chamber to grow a high-quality self-supporting diamond thick film using microwave plasma chemical vapor deposition.

[0047] In one specific embodiment of the present invention, a surface-treated substrate is placed in a reaction chamber, and hydrogen gas is introduced under vacuum conditions; the vacuum degree is preferably less than 1 Torr; the flow rate of the hydrogen gas is preferably 120 to 2000 sccm; optionally, the flow rate of the hydrogen gas is 120 sccm, 200 sccm, 300 sccm, 500 sccm, 600 sccm, 800 sccm, 1000 sccm, 1200 sccm, 1500 sccm, 1800 sccm, 2000 sccm or any two of the above values.

[0048] Hydrogen gas is introduced and the chamber pressure and microwave power are adjusted to perform heating and ignition operations within the reaction chamber. In a specific embodiment of the present invention, the chamber pressure is adjusted to 50–200 Torr; optionally, the chamber pressure is adjusted to 50 Torr, 60 Torr, 70 Torr, 75 Torr, 80 Torr, 90 Torr, 100 Torr, 120 Torr, 140 Torr, 150 Torr, 160 Torr, 180 Torr, 200 Torr, or any range between two of the above values. In a specific embodiment of the present invention, the microwave power is adjusted to 2 kW.

[0049] After the initial heating and ignition, the chamber pressure and microwave power are simultaneously increased to maintain plasma stability. In a specific embodiment of the present invention, the gradient of simultaneously increasing the chamber pressure and microwave power is preferably 1 to 13 Torr / 200W. Optionally, the gradient of simultaneously increasing the chamber pressure and microwave power is 1 Torr / 200W, 2 Torr / 200W, 3 Torr / 200W, 4 Torr / 200W, 5 Torr / 200W, 6 Torr / 200W, 7 Torr / 200W, 8 Torr / 200W, 9 Torr / 200W, 10 Torr / 200W, 11 Torr / 200W, 12 Torr / 200W, 13 Torr / 200W, or any range between two of the above values.

[0050] By increasing the microwave power, the chamber temperature and plasma state can be controlled. Once the temperature reaches above 700°C, at least methane and oxygen are introduced to perform one thin film growth. In a specific embodiment of this invention, it is preferable to raise the temperature to 700°C–1000°C, more preferably to 800°C–1000°C, and even more preferably to 900°C–1000°C, while introducing at least methane and oxygen. The methane flow rate is preferably 10–200 sccm. Optionally, the methane flow rate can be 10 sccm, 30 sccm, 40 sccm, 50 sccm, 80 sccm, 100 sccm, 110 sccm, 115 sccm, 120 sccm, 140 sccm, 150 sccm, 160 sccm, 170 sccm, 180 sccm, 190 sccm, 200 sccm, or any range between two of the above values. The oxygen flow rate is preferably 1–20 sccm; optionally, the oxygen flow rate is 1 sccm, 3 sccm, 5 sccm, 7 sccm, 9 sccm, 10 sccm, 12 sccm, 14 sccm, 15 sccm, 16 sccm, 17 sccm, 18 sccm, 19 sccm, 20 sccm or any two of the above values; the film growth time is preferably 5–20 h; optionally, the film growth time is 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h or any two of the above values; and during the film growth process, the pressure and temperature are kept stable, and the temperature variation range is controlled within 0℃ to 150℃, more preferably within 0℃ to 100℃.

[0051] In one specific embodiment of the present invention, during a single film growth process, nitrogen gas is introduced simultaneously with methane and oxygen; the nitrogen gas flow rate is preferably 1 to 80 sccm; optionally, the nitrogen gas flow rate is 1 sccm, 2 sccm, 3 sccm, 4 sccm, 5 sccm, 6 sccm, 7 sccm, 8 sccm, 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm, 80 sccm, or any two of the above values; introducing nitrogen gas can reduce the flow rate of methane and oxygen, and by introducing nitrogen gas during the film growth process, a wider range of gradient control for simultaneously increasing or decreasing chamber pressure and microwave power during growth and annealing can be achieved, which is beneficial for control.

[0052] After one thin film growth cycle, the introduction of methane and oxygen should be stopped at least. If nitrogen was introduced during the growth cycle, the nitrogen introduction should also be stopped after growth, and a segmented annealing process should be performed. The segmented annealing process includes at least the following steps: first, simultaneously reducing microwave power and chamber pressure until the temperature drops below 800°C and maintaining this temperature for at least 0.5 hours; then, simultaneously reducing microwave power and chamber pressure a second time until the temperature drops below 600°C and maintaining this temperature for at least 0.5 hours. The gradient of the first simultaneous reduction in microwave power and chamber pressure is preferably 1–13 Torr / 200W to maintain plasma stability. Optionally, the gradient of the first simultaneous reduction in microwave power and chamber pressure can be 1 Torr / 200W, 1.5 Torr / 200W, 2 Torr / 200W, 3 Torr / 200W, 4 Torr / 200W, 5 Torr / 200W, 6 Torr / 200W, 7 Torr / 200W, or 8 Torr / 200W. The values ​​are 1 to 13 Torr / 200W, 9 Torr / 200W, 10 Torr / 200W, 11 Torr / 200W, 12 Torr / 200W, 13 Torr / 200W, or any two of the above values. The gradient for the second simultaneous reduction of microwave power and chamber pressure is preferably 1 to 13 Torr / 200W to maintain plasma stability. Optionally, the gradient for the second simultaneous reduction of microwave power and chamber pressure is 1 Torr / 200W, 1.5 Torr / 200W, 2 Torr / 200W, 3 Torr / 200W, 4 Torr / 200W, 5 Torr / 200W, 6 Torr / 200W, 7 Torr / 200W, 8 Torr / 200W, 9 Torr / 200W, 10 Torr / 200W, 11 Torr / 200W, 12 Torr / 200W, 13 Torr / 200W, or any two of the above values.

[0053] In a specific embodiment of the present invention, the segmented annealing process in a single annealing includes at least the following: first, simultaneously reducing the microwave power and the chamber pressure, and holding the temperature at 600°C to 800°C for 1 to 2 hours; then, simultaneously reducing the microwave power and the chamber pressure for a second time, and holding the temperature at 400°C to 600°C for 1 to 2 hours.

[0054] In a specific embodiment of the present invention, the segmented annealing process in a single annealing includes at least the following: first, simultaneously reducing the microwave power and the chamber pressure, and holding the temperature at 700°C for 1 to 2 hours; then, simultaneously reducing the microwave power and the chamber pressure for a second time, and holding the temperature at 500°C for 1 to 2 hours.

[0055] In a specific embodiment of the present invention, the segmented annealing process in the first annealing preferably further includes: a third simultaneous reduction of microwave power and chamber pressure to lower the temperature to below 300°C; the gradient of the third simultaneous reduction of microwave power and chamber pressure is preferably 1 to 13 Torr / 200W to maintain plasma stability; optionally, the gradient of the third simultaneous reduction of microwave power and chamber pressure is 1 Torr / 200W, 1.5 Torr / 200W, 2 Torr / 200W, 3 Torr / 200W, 4 Torr / 200W, 5 Torr / 200W, 6 Torr / 200W, 7 Torr / 200W, 8 Torr / 200W, 9 Torr / 200W, 10 Torr / 200W, 11 Torr / 200W, 12 Torr / 200W, 13 Torr / 200W, or a range between any two of the above values.

[0056] In a specific embodiment of the present invention, the segmented annealing process in the first annealing preferably further includes: a third simultaneous reduction of microwave power and chamber pressure, so that the temperature is reduced to 150°C to 300°C.

[0057] In a specific embodiment of the present invention, the segmented annealing process in the first annealing preferably further includes: a third simultaneous reduction of microwave power and chamber pressure, so that the temperature is reduced to 150°C to 200°C.

[0058] In one specific embodiment of the present invention, the microwave power and chamber pressure are simultaneously reduced for the third time, so that the temperature is reduced to below 300°C, and then the secondary growth can be carried out directly.

[0059] After the first annealing, a second growth is performed: the chamber pressure and microwave power are simultaneously increased, and the temperature is raised to above 700°C. At least methane and oxygen are introduced to perform a second film growth. In a specific embodiment of the present invention, the gradient of simultaneously increasing the chamber pressure and microwave power is preferably 1 to 13 Torr / 200W. Optionally, the gradient of simultaneously increasing the chamber pressure and microwave power is 1 Torr / 200W, 2 Torr / 200W, 3 Torr / 200W, 4 Torr / 200W, 5 Torr / 200W, 6 Torr / 200W, 7 Torr / 200W, 8 Torr / 200W, 9 Torr / 200W, 10 Torr / 200W, 11 Torr / 200W, 12 Torr / 200W, 13 Torr / 200W, or any two of the above values.

[0060] By increasing the microwave power, the chamber temperature and plasma state can be controlled. Once the temperature reaches above 700°C, at least methane and oxygen are introduced for secondary thin film growth. In a specific embodiment of this invention, the temperature is preferably raised to 700°C–1000°C, more preferably to 800°C–1000°C, and even more preferably to 900°C–1000°C, with at least methane and oxygen introduced. The methane flow rate is preferably 10–200 sccm. Optionally, the methane flow rate can be 10 sccm, 30 sccm, 40 sccm, 50 sccm, 80 sccm, 100 sccm, 110 sccm, 115 sccm, 120 sccm, 140 sccm, 150 sccm, 160 sccm, 170 sccm, 180 sccm, 190 sccm, 200 sccm, or any range between two of the above values. The oxygen flow rate is preferably 1–20 sccm; optionally, the oxygen flow rate is 1 sccm, 3 sccm, 5 sccm, 7 sccm, 9 sccm, 10 sccm, 12 sccm, 14 sccm, 15 sccm, 16 sccm, 17 sccm, 18 sccm, 19 sccm, 20 sccm or any two of the above values; the secondary film growth time is preferably 5–20 h; optionally, the secondary film growth time is 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h or any two of the above values; and during the secondary film growth process, the pressure and temperature are kept stable, and the temperature variation range is controlled within 0℃ to 150℃, more preferably within 0℃ to 100℃.

[0061] In one specific embodiment of the present invention, during the secondary film growth process, nitrogen gas is introduced simultaneously with methane and oxygen; the nitrogen gas flow rate is preferably 1 to 80 sccm; optionally, the nitrogen gas flow rate is 1 sccm, 2 sccm, 3 sccm, 4 sccm, 5 sccm, 6 sccm, 7 sccm, 8 sccm, 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm, 80 sccm or any two of the above values; introducing nitrogen gas can reduce the flow rate of methane and oxygen.

[0062] After the secondary thin film growth is completed, the introduction of methane and oxygen should be stopped at least. If nitrogen was introduced during the secondary thin film growth, the nitrogen introduction should also be stopped after the growth is completed, and a segmented annealing process should be performed. The segmented annealing process includes at least the following steps: first, simultaneously reducing the microwave power and chamber pressure, and maintaining the temperature below 800°C for at least 0.5 hours; then, simultaneously reducing the microwave power and chamber pressure a second time, and maintaining the temperature below 600°C for at least 0.5 hours. The gradient of the first simultaneous reduction of microwave power and chamber pressure is preferably 1–13 Torr / 200W to maintain plasma stability. Optionally, the gradient of the first simultaneous reduction of microwave power and chamber pressure can be 1 Torr / 200W, 1.5 Torr / 200W, 2 Torr / 200W, 3 Torr / 200W, 4 Torr / 200W, 5 Torr / 200W, 6 Torr / 200W, 7 Torr / 200W, or 8 Torr / 200W. The values ​​are 1 to 13 Torr / 200W, 9 Torr / 200W, 10 Torr / 200W, 11 Torr / 200W, 12 Torr / 200W, 13 Torr / 200W, or any two of the above values. The gradient for the second simultaneous reduction of microwave power and chamber pressure is preferably 1 to 13 Torr / 200W to maintain plasma stability. Optionally, the gradient for the second simultaneous reduction of microwave power and chamber pressure is 1 Torr / 200W, 1.5 Torr / 200W, 2 Torr / 200W, 3 Torr / 200W, 4 Torr / 200W, 5 Torr / 200W, 6 Torr / 200W, 7 Torr / 200W, 8 Torr / 200W, 9 Torr / 200W, 10 Torr / 200W, 11 Torr / 200W, 12 Torr / 200W, 13 Torr / 200W, or any two of the above values.

[0063] In a specific embodiment of the present invention, the segmented annealing process in the secondary annealing includes at least the following steps: first, simultaneously reducing the microwave power and the chamber pressure, and holding the temperature at 600°C to 800°C for 1 to 2 hours; then, simultaneously reducing the microwave power and the chamber pressure for 1 to 2 hours, and holding the temperature at 400°C to 600°C for 1 to 2 hours.

[0064] In a specific embodiment of the present invention, the segmented annealing process in the secondary annealing includes at least the following: first, simultaneously reducing the microwave power and the chamber pressure, and holding the temperature at 700°C for 1 to 2 hours; then, simultaneously reducing the microwave power and the chamber pressure for 1 to 2 hours, and holding the temperature at 500°C for 1 to 2 hours.

[0065] In a specific embodiment of the present invention, the segmented annealing process in the secondary annealing preferably further includes: a third simultaneous reduction of microwave power and chamber pressure to lower the temperature to below 300°C; the gradient of the third simultaneous reduction of microwave power and chamber pressure is preferably 1 to 13 Torr / 200W to maintain plasma stability; optionally, the gradient of the third simultaneous reduction of microwave power and chamber pressure is 1 Torr / 200W, 1.5 Torr / 200W, 2 Torr / 200W, 3 Torr / 200W, 4 Torr / 200W, 5 Torr / 200W, 6 Torr / 200W, 7 Torr / 200W, 8 Torr / 200W, 9 Torr / 200W, 10 Torr / 200W, 11 Torr / 200W, 12 Torr / 200W, 13 Torr / 200W, or a range between any two of the above values.

[0066] In a specific embodiment of the present invention, the segmented annealing process in the secondary annealing preferably further includes: a third simultaneous reduction of microwave power and chamber pressure, so that the temperature is reduced to 150°C to 300°C.

[0067] In a specific embodiment of the present invention, the segmented annealing process in the secondary annealing preferably further includes: a third simultaneous reduction of microwave power and chamber pressure, so that the temperature is reduced to 150°C to 200°C.

[0068] In one specific embodiment of the present invention, the microwave power and chamber pressure are simultaneously reduced for the third time, so that the temperature is reduced to below 300°C, which allows the next growth process to proceed directly or the growth process to be terminated.

[0069] Repeat steps S3) and S4) until the self-supporting diamond thick film reaches the target thickness. Preferably, continuously reduce the microwave power and chamber pressure until the plasma disappears, stop the hydrogen supply, adjust the chamber pressure to standard atmospheric pressure, and cool to room temperature to obtain a high-quality self-supporting diamond thick film.

[0070] In one specific embodiment of the present invention, the thickness of the high-quality self-supporting diamond thick film is greater than or equal to 100 μm;

[0071] In a specific embodiment provided by the present invention, the full width at half maximum (FWHM) of the XRD diffraction peaks of the (111) crystal plane orientation of the high-quality self-supporting diamond thick film is less than 0.15, the FWHM of the XRD diffraction peaks of the (220) crystal plane orientation is less than 0.11, and the FWHM of the XRD diffraction peaks of the (311) crystal plane orientation is less than 0.15.

[0072] In a specific embodiment provided by the present invention, the full width at half maximum (FWHM) of the XRD diffraction peaks of the (111) crystal plane orientation of the high-quality self-supporting diamond thick film is less than 0.12, the FWHM of the XRD diffraction peaks of the (220) crystal plane orientation is less than 0.103, and the FWHM of the XRD diffraction peaks of the (311) crystal plane orientation is less than 0.14.

[0073] To further illustrate the present invention, the following describes in detail a method for growing high-quality self-supporting diamond thick films provided by the present invention, in conjunction with embodiments.

[0074] All reagents used in the following examples are commercially available.

[0075] Example 1

[0076] Diamond deposition on a 2-inch silicon carbide surface (2.45GHz device):

[0077] First growth: The surface-treated silicon carbide substrate is placed in the CVD chamber, and the vacuum pump is turned on to evacuate the gas to a vacuum level below 1 Torr. H2 is introduced at a flow rate of 200 SCCM, and the chamber pressure is controlled at 80 Torr. At the same time, the microwave power supply is turned on to 2 kW to start heating and ignition. The gas pressure and power supply are increased simultaneously at a gradient of 5 Torr / 200W to maintain plasma stability. The temperature is raised to 900℃, and CH4, O2, and N2 are introduced, with CH4 flow rate of 40 SCCM, O2 flow rate of 1 SCCM, and N2 flow rate of 4 SCCM. The pressure and temperature are kept stable, and the first growth time is 15 hours.

[0078] First annealing: Stop the supply of CH4, O2 and N2, while reducing the power and gas pressure at a gradient of 5 Torr / 200 W to maintain plasma stability; reduce the temperature to 700℃ and hold for 1 hour; continue to reduce the power and gas pressure at a gradient of 5 Torr / 200 W to maintain plasma stability, and reduce the temperature to 500℃ and hold for 1 hour; subsequently, continue to reduce the power and gas pressure at a gradient of 5 Torr / 200 W to maintain plasma stability, and reduce the temperature to around 200℃ to proceed with secondary growth.

[0079] Secondary growth: Set the pressure / power gradient to 5 Torr / 200 W to maintain plasma stability. Heat to 900℃ and introduce CH4, O2, and N2, with CH4 flow rates of 40 SCCM, O2 flow rates of 1 SCCM, and N2 flow rates of 4 SCCM. Maintain stable pressure and temperature; secondary growth time is 18 hours.

[0080] Secondary annealing: Stop the supply of CH4, O2, and N2, while reducing the power and pressure at a gradient of 5 Torr / 200 W to maintain plasma stability. Lower the temperature to 700℃ and hold for 1 hour. Continue to reduce the power and pressure at a gradient of 5 Torr / 200 W to maintain plasma stability, lowering the temperature to 500℃ and holding for 1 hour. Subsequently, continue to reduce the power and pressure at a gradient of 5 Torr / 200 W until the plasma disappears. Turn off the hydrogen supply, adjust the chamber pressure to the standard pressure, and open the reaction chamber after cooling.

[0081] Figure 3 This is a photograph of the substrate of the composite diamond film obtained in Example 1. Figure 4 This is a microscope image of the substrate of the composite diamond film obtained in Example 1. Figure 3 and Figure 4 It can be seen that the substrate is fully formed and the surface grain size is uniformly distributed.

[0082] The substrate of the composite diamond film obtained in Example 1 was examined using X-ray diffraction, and its XRD pattern is shown below. Figure 5 As shown in Table 1, the results are as follows.

[0083] Example 2

[0084] 8-inch silicon carbide surface-deposited diamond (915MHz equipment):

[0085] First growth: The surface-treated silicon carbide substrate is placed in the CVD chamber. The vacuum pump is turned on to evacuate the gas to a vacuum level below 0.1 Torr. H2 is introduced at a flow rate of 600 SCCM, and the chamber pressure is controlled at 75 Torr. Simultaneously, the microwave power supply is turned on to 2 kW to start heating and ignition. The gas pressure is gradually reduced, and the plasma sphere volume is increased while the power is changed at a gradient of 1.25 Torr / kW to maintain plasma stability. The temperature is raised to 900℃, and CH4 and O2 are introduced, with a CH4 flow rate of 115 SCCM and an O2 flow rate of 9 SCCM. The pressure and temperature are kept stable (900℃~1000℃), and the first growth time is 20 hours.

[0086] First annealing: Prioritize stopping the supply of CH4 and O2, while simultaneously reducing power and pressure at a gradient of 1.5 Torr / kW to maintain plasma stability. Reduce the temperature to 700℃ and hold for 2 hours. Continue reducing power and pressure at a gradient of 1.5 Torr / kW to maintain plasma stability, then reduce the temperature to 500℃ and hold for 2 hours.

[0087] Secondary growth: Set the pressure / power gradient to 1.5 Torr / kW to maintain plasma stability. Heat to 900℃ and introduce CH4 and O2, with a CH4 flow rate of 115 SCCM and an O2 flow rate of 9 SCCM. Maintain stable pressure and temperature; secondary growth time is 20 hours.

[0088] Secondary annealing: First, stop the supply of CH4 and O2, while reducing the power and pressure to a gradient of 1.5 Torr / kW to maintain plasma stability. Reduce the temperature to 700℃ and hold for 2 hours. Continue to reduce the power and pressure to a gradient of 1.5 Torr / kW to maintain plasma stability, then reduce the temperature to 500℃ and hold for 2 hours.

[0089] Third growth: Set the pressure / power gradient to 1.5 Torr / kW to maintain plasma stability. Heat to 900℃ and introduce CH4 and O2, with a CH4 flow rate of 115 SCCM and an O2 flow rate of 9 SCCM. Maintain stable pressure and temperature, and allow the second growth time to be 20 hours.

[0090] Three-stage annealing: First, stop the supply of CH4 and O2, while simultaneously reducing the power and pressure at a gradient of 1.5 Torr / kW to maintain plasma stability. Lower the temperature to 700℃ and hold for 2 hours. Continue reducing the power and pressure at a gradient of 1.5 Torr / kW to maintain plasma stability, lowering the temperature to 500℃ and holding for 2 hours. Reduce the hydrogen supply until the plasma disappears, then shut off the hydrogen supply, adjust the chamber pressure to standard pressure, and open the reaction chamber after cooling.

[0091] Figure 6 This is a photograph of the substrate of the composite diamond film obtained in Example 2. Figure 7 This is a microscope image of the substrate of the composite diamond film obtained in Example 2. Figure 6 and Figure 7 It can be seen that the substrate is fully formed and the surface grain size is uniformly distributed.

[0092] The substrate of the composite diamond film obtained in Example 2 was examined using X-ray diffraction, and its XRD pattern is shown below. Figure 8 As shown in Table 1, the results are as follows.

[0093] Comparative Example 1

[0094] Thick film growth using conventional single-stage growth processes:

[0095] The surface-treated silicon carbide substrate was placed in the CVD chamber. The vacuum pump was turned on to evacuate the gas to a vacuum level below 1 Torr. H2 was introduced at a flow rate of 200 SCCM, and the chamber pressure was controlled at 80 Torr. Simultaneously, the microwave power supply was turned on to 2 kW to initiate heating and ignition. The gas pressure and power were increased at a gradient of 5 Torr / 200 W to maintain plasma stability. The temperature was raised to 900℃, and CH4, O2, and N2 were introduced, with CH4 at a flow rate of 40 SCCM, O2 at 1 SCCM, and N2 at 4 SCCM. Pressure and temperature were kept stable, and the growth time for one cycle was 33 hours.

[0096] After growth is complete, stop the supply of CH4, O2, and N2, reduce the power and pressure to a gradient of 5 Torr / 200W, and maintain plasma stability. Once the temperature drops below 500℃, change the gradient to 8 Torr / 200W until the plasma disappears. Then, shut off the hydrogen supply, adjust the chamber pressure to the standard pressure, and open the reaction chamber after cooling.

[0097] Figure 9 This is a photograph of the substrate of the composite diamond film obtained in Comparative Example 1. Figure 10 This is a microscope image of the substrate of the composite diamond film obtained in Comparative Example 1. Figure 9 and Figure 10 It can be seen that cracks appeared on the surface of the diamond film, the surface grain size was much larger than that in the application example, and the growth process was uneven.

[0098] The substrate of the composite diamond film obtained in Comparative Example 1 was examined using X-ray diffraction, and its XRD pattern was obtained as follows. Figure 11 As shown in Table 1, the results are as follows.

[0099] Table 1 Comparison of XRD full width at half maximum (FWHM) results between Examples 1-2 and Comparative Example 1

[0100] Peak position 2 theta Crystal plane orientation Example 1 Example 2 FWHM-comparative example 43.9 Diamond (111) 0.120 0.091 0.192 75.3 Diamond (220) 0.064 0.103 0.130 91.5 Diamond (311) 0.115 0.138 0.249

[0101] Depend on Figure 5 , Figure 8 and Figure 11 It can be seen that the full width at half maximum (FWHM) of the XRD tests in Examples 1 and 2 is smaller than that in Comparative Example 1, indicating that the crystallization quality has been improved. The full width at half maximum (FWHM) of the XRD tests in Comparative Example 1 is larger, indicating that the crystallization quality is slightly worse.

[0102] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for growing high-quality self-supporting diamond thick films, characterized in that, Includes the following steps: S1) Primary growth: The substrate is placed in the reaction chamber, hydrogen is introduced under vacuum conditions, and the chamber pressure and microwave power are adjusted to carry out the heating and ignition operation in the reaction chamber. Then, the chamber pressure and microwave power are increased simultaneously. When the temperature reaches above 700°C, at least methane and oxygen are introduced to carry out the first film growth. S2) Single annealing: At least stop the introduction of methane and oxygen, and perform segmented annealing treatment; the segmented annealing treatment includes at least the following: first, simultaneously reduce microwave power and chamber pressure, wait until the temperature drops below 800°C, and maintain for at least 0.5h; then, second, simultaneously reduce microwave power and chamber pressure, wait until the temperature drops below 600°C, and maintain for at least 0.5h. S3) Secondary growth: Simultaneously increase the chamber pressure and microwave power, and when the temperature reaches above 700°C, at least methane and oxygen are introduced to carry out secondary film growth. S4) Secondary annealing: At least stop the introduction of methane and oxygen, and perform segmented annealing treatment; the segmented annealing treatment includes at least: first, simultaneously reducing microwave power and chamber pressure, and waiting for the temperature to drop below 800°C, and maintaining it for at least 0.5h; then, second, simultaneously reducing microwave power and chamber pressure, and waiting for the temperature to drop below 600°C, and maintaining it for at least 0.5h. S5) Repeat steps S3) and S4) until the self-supporting diamond thick film reaches the target thickness, and obtain a high-quality self-supporting diamond thick film.

2. The growth method according to claim 1, characterized in that, In step S1), the hydrogen flow rate is 120–2000 sccm; the chamber pressure is adjusted to 50–200 Torr; and the microwave power is adjusted to 2 kW to perform heating and ignition operations within the reaction chamber.

3. The growth method according to claim 1, characterized in that, In step S1), the gradient of increasing chamber pressure and microwave power is 1–13 Torr / 200W; the flow rate of methane is 10–200 sccm; the flow rate of oxygen is 1–20 sccm; and the time for the first thin film growth is 5–20 h. And / or, nitrogen is introduced simultaneously with methane and oxygen; the nitrogen flow rate is 1–80 sccm.

4. The growth method according to claim 1, characterized in that, In step S2), the gradient of simultaneously reducing microwave power and chamber pressure for the first time is 1-13 Torr / 200W; the gradient of simultaneously reducing microwave power and chamber pressure for the second time is 1-13 Torr / 200W. In step S4), the gradient of simultaneously reducing microwave power and chamber pressure for the first time is 1 to 13 Torr / 200W; the gradient of simultaneously reducing microwave power and chamber pressure for the second time is 1 to 13 Torr / 200W.

5. The growth method according to claim 1, characterized in that, The segmented annealing process in step S2) includes at least the following: first, simultaneously reducing the microwave power and the chamber pressure, and holding the temperature at 600℃~800℃ for 1~2 hours; then, simultaneously reducing the microwave power and the chamber pressure for a second time, and holding the temperature at 400℃~600℃ for 1~2 hours. And / or, the segmented annealing process in step S4) includes at least the following: first, simultaneously reducing the microwave power and the chamber pressure, and holding the temperature at 600℃~800℃ for 1~2 hours; then, simultaneously reducing the microwave power and the chamber pressure for a second time, and holding the temperature at 400℃~600℃ for 1~2 hours.

6. The growth method according to any one of claims 1 to 5, characterized in that, The segmented annealing process in step S2) also includes: a third simultaneous reduction of microwave power and chamber pressure to lower the temperature to below 300°C. And / or, the segmented annealing process in step S4) further includes: simultaneously reducing the microwave power and the chamber pressure for the third time, so that the temperature is reduced to below 300°C.

7. The growth method according to claim 6, characterized in that, The segmented annealing process in step S2) also includes: a third simultaneous reduction of microwave power and chamber pressure to lower the temperature to 150℃~300℃; And / or, the segmented annealing process in step S4) further includes: simultaneously reducing the microwave power and the chamber pressure for the third time, so that the temperature is reduced to 150℃~300℃.

8. The growth method according to claim 1, characterized in that, In step S3), the gradient of increasing chamber pressure and microwave power is 1-13 Torr / 200W; the methane flow rate is 10-200 sccm; and the oxygen flow rate is 1-20 sccm. And / or, the secondary film growth time is 5 to 20 hours.

9. The growth method according to claim 8, characterized in that, In step S3), nitrogen gas is also introduced; the flow rate of the nitrogen gas is 1-80 sccm. And / or, in step S5), repeat the operations of steps S3) and S4) until the self-supporting diamond thick film reaches the target thickness, then continuously reduce the microwave power and chamber pressure until the plasma disappears, stop the hydrogen supply, adjust the chamber pressure to standard atmospheric pressure, cool to room temperature, and obtain a high-quality self-supporting diamond thick film.

10. The growth method according to claim 1, characterized in that, The thickness of the high-quality self-supporting diamond thick film is greater than or equal to 100 μm; The full width at half maximum (FWHM) of the XRD diffraction peaks of the high-quality self-supporting diamond thick film with (111) crystal plane orientation is less than 0.15, the FWHM of the XRD diffraction peaks of (220) crystal plane orientation is less than 0.11, and the FWHM of the XRD diffraction peaks of (311) crystal plane orientation is less than 0.15.

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