Method for Reducing Diamond Stress

Abstract

The present invention relates to a method for reducing diamond stress, comprising the following steps: performing a first annealing treatment on the diamond in a hydrogen-rich atmosphere, wherein a tantalum material is also used in the first annealing treatment, and the temperature of the tantalum material is controlled to be greater than or equal to 1500°C and less than the melting point of the tantalum material; and then performing a second annealing treatment on the diamond in an inert atmosphere. The method of the present invention can remove as much graphite phase as possible from the diamond and increase the grain size, making the grains larger and more complete. The grains become flatter through dislocation movement, filling lattice gaps, thereby fully removing the diamond stress under non-contact conditions, improving the diamond's machinability, and preventing damage to the diamond.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond, and particularly to a method for reducing the stress of diamond. Background Art

[0002] The thermal conductivity of diamond can reach 2200 W / mK, and it is expected to be used as a heat dissipation substrate for high-power electronic components. However, the residual stress in diamond results in poor machinability. Currently, heat energy, ultrasonic shock vibration, and the random vibration impact of fillers are usually used to impact diamond to provide external power for the dislocation movement of its crystal grains and reduce the stress of diamond. However, these methods are likely to cause damage to diamond. Summary of the Invention

[0003] Based on this, in view of the above problems, it is necessary to provide a method for reducing the stress of diamond, which can reduce the stress of diamond under non-contact conditions and will not damage diamond.

[0004] A method for reducing the stress of diamond includes the following steps:

[0005] Anneal the diamond for the first time in a hydrogen-rich atmosphere. In the step of the first annealing treatment, tantalum material is also used, and the temperature of the tantalum material is controlled to be greater than or equal to 1500 °C and less than the melting point of the tantalum material;

[0006] Then anneal the diamond for the second time in an inert atmosphere.

[0007] In one embodiment, in the step of the first annealing treatment, the temperature of the tantalum material is controlled at 1700 °C - 2600 °C.

[0008] In one embodiment, in the step of the first annealing treatment, the temperature of the diamond is controlled at 500 °C - 1000 °C;

[0009] And / or, the heat preservation time is controlled at 15 min - 30 min;

[0010] And / or, the cooling rate of the diamond is controlled at 1 °C / min - 20 °C / min.

[0011] In one embodiment, in the step of the second annealing treatment, the temperature of the diamond is controlled at 800 °C - 1000 °C, and is greater than or equal to the temperature of the diamond in the step of the first annealing treatment;

[0012] And / or, the heat preservation time of the diamond is controlled at 10 min - 30 min.

[0013] In one embodiment, in the step of the first annealing treatment, when the temperature of the diamond drops to 200°C - 350°C, the temperature reduction is stopped and the second annealing treatment is carried out.

[0014] In one embodiment, in the step of the first annealing treatment, the diamond is heated by the thermal field provided by the tantalum material;

[0015] And / or, the distance between the diamond and the tantalum material is 5 mm - 30 mm.

[0016] In one embodiment, in the step of the second annealing treatment, the diamond is heated by the thermal field provided by the tantalum material;

[0017] And / or, the distance between the diamond and the tantalum material is 5 mm - 30 mm.

[0018] In one embodiment, hydrogen is introduced to form a hydrogen-rich atmosphere, and the flow rate of the hydrogen is 100 sccm - 500 sccm;

[0019] And / or, in the step of the first annealing treatment, the pressure is less than or equal to 10 kPa.

[0020] In one embodiment, an inert gas is introduced to form an inert atmosphere, and the flow rate of the inert gas is 300 sccm - 800 sccm;

[0021] And / or, the inert atmosphere is selected from at least one of a nitrogen atmosphere and an argon atmosphere;

[0022] And / or, in the step of the second annealing treatment, the pressure is controlled at 3 kPa - 10 kPa.

[0023] In one embodiment, it includes the following steps:

[0024] Place the diamond on the sample stage of the hot filament CVD equipment, and then arrange tantalum wires on the hot filament rack;

[0025] Close the vacuum chamber and evacuate the hot filament CVD equipment to vacuum;

[0026] Introduce hydrogen, turn on the power to heat the tantalum wires, and use the thermal field provided by the tantalum wires to carry out the first annealing treatment on the diamond;

[0027] Then turn off the hydrogen, introduce an inert gas, heat the tantalum wires, and use the thermal field provided by the tantalum wires to carry out the second annealing treatment on the diamond.

[0028] In the method of the present invention, the first annealing treatment is carried out in a hydrogen-rich atmosphere and tantalum material is also used. The hydrogen-rich atmosphere can prevent reactions such as oxidation or carbonization of the tantalum material. And by controlling the temperature, the tantalum material can better evaporate tantalum atoms and more evenly diffuse into diamond, promoting the transformation of the graphite phase in diamond into the diamond phase. At the same time, hydrogen ions can be generated under the excitation of the thermal field provided by the tantalum material. The hydrogen ions can etch the graphite phase in diamond. Thus, by promoting the transformation of the graphite phase into the diamond phase by tantalum atoms and etching the graphite phase by hydrogen ions, the graphite phase in diamond can be removed as much as possible, and dislocation movement can be generated in the grains of diamond, performing self-tuning, filling lattice voids and increasing the grain size. Then, the second annealing treatment is carried out in an inert atmosphere to fully release the hydrogen ions and tantalum atoms trapped in the diamond lattice, and make the grains in diamond generate dislocation movement again, further performing self-tuning, filling lattice voids and increasing the grain size.

[0029] Therefore, the method of the present invention can remove the graphite phase in diamond as much as possible, increase the grain size, make the grain size larger, more complete and smoother through dislocation movement, fill the lattice voids, thus fully removing the stress of diamond under non-contact conditions, improving the machinability of diamond, and without damaging diamond. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to these drawings without creative efforts.

[0031] Figure 1 It is a scanning electron microscope image of the diamond after stress removal treatment in Example 1;

[0032] Figure 2 It is a scanning electron microscope image of the diamond after stress removal treatment in Comparative Example 1;

[0033] Figure 3 It is a scanning electron microscope photograph of the diamond after stress removal treatment in Comparative Example 2;

[0034] Figure 4 It is a Raman spectrum diagram of the diamond after stress removal treatment in Example 1;

[0035] Figure 5 It is a Raman spectrum diagram of the diamond after stress removal treatment in Example 2;

[0036] Figure 6Raman spectrum of diamond after stress relief treatment in Example 3;

[0037] Figure 7 Raman spectrum of diamond after stress relief treatment in Example 4;

[0038] Figure 8 Raman spectrum of diamond after stress relief treatment in Example 5;

[0039] Figure 9 Raman spectrum of diamond after stress relief treatment in Comparative Example 1;

[0040] Figure 10 Raman spectrum of diamond after stress relief treatment in Comparative Example 2;

[0041] Figure 11 Raman spectrum of diamond after stress relief treatment in Comparative Example 3. Detailed implementation manners

[0042] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention. The optional range of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items. The said any and all combinations include any two related listed items, any more related listed items, or all combinations of the related listed items.

[0044] In the present invention, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0045] The method for reducing the stress of diamond provided by the present invention includes the following steps:

[0046] S1. Anneal the diamond for the first time in a hydrogen-rich atmosphere. In the steps of the first annealing treatment, tantalum material is also used, and the temperature of the tantalum material is controlled to be greater than or equal to 1500 °C and less than the melting point of the tantalum material;

[0047] S2. Then anneal the diamond for the second time in an inert atmosphere.

[0048] The method of the present invention is used to specifically remove the stress in the diamond and improve the machinability of the diamond. Therefore, the present invention has no requirements for the preparation method of the diamond. For example, the diamond is prepared by chemical vapor deposition methods such as hot filament CVD method, DC jet CVD method, DC discharge CVD method, RF CVD method, and microwave plasma CVD method, or can also be prepared by other methods such as high temperature and high pressure synthesis method.

[0049] In the method of the present invention, the first annealing treatment in step S1 is carried out in a hydrogen-rich atmosphere and tantalum material is also used. Among them, the hydrogen-rich atmosphere can prevent reactions such as oxidation or carbonization of the tantalum material, and by controlling the temperature, the tantalum material can better evaporate tantalum atoms and more uniformly diffuse into the diamond, promoting the transformation of the graphite phase in the diamond to the diamond phase. At the same time, hydrogen ions can be generated under the excitation of the thermal field provided by the tantalum material, and the hydrogen ions can etch the graphite phase in the diamond. Therefore, by promoting the transformation of the graphite phase to the diamond phase by tantalum atoms and etching the graphite phase by hydrogen ions, the graphite phase in the diamond can be removed as much as possible, and dislocation movement of the grains in the diamond can be promoted, self-tuning can be carried out, lattice voids can be filled, and the grain size can be increased, thereby reducing the stress of the diamond.

[0050] It should be noted that the present invention has no requirements for the tantalum material used, which can be tantalum wire, etc., and can be specifically selected according to needs.

[0051] In step S1, it is preferable to place the diamond and the tantalum material in the equipment simultaneously or successively, and then evacuate the equipment. For example, the vacuum degree reaches 10 -2 Pa - 10 -3 Pa, so as to remove the impurity elements in the equipment cavity, and then carry out the first annealing treatment.

[0052] In the steps of the first annealing treatment, hydrogen can be introduced to form a hydrogen-rich atmosphere. Preferably, the flow rate of the hydrogen is 100 sccm - 500 sccm, such as 100 sccm, 150 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm, 450 sccm, 500 sccm, etc., or the range composed of any two of these values. At the same time, the pressure is adjusted to be less than or equal to 10 kPa, such as 0.5 kPa, 1 kPa, 1.5 kPa, 2 kPa, 2.5 kPa, 3 kPa, 3.5 kPa, 4 kPa, 4.5 kPa, 5 kPa, 5.5 kPa, 6 kPa, 6.5 kPa, 7 kPa, 7.5 kPa, 8 kPa, 8.5 kPa, 9 kPa, 9.5 kPa, 10 kPa, etc., or the range composed of any two of these values. Further, during the first annealing treatment, the pressure is maintained constant to provide a stable environment for the first annealing treatment of the diamond.

[0053] Further, the temperature of the tantalum material is preferably 1700 °C - 2600 °C, such as 1700 °C, 1750 °C, 1800 °C, 1850 °C, 1900 °C, 1950 °C, 2000 °C, 2050 °C, 2100 °C, 2150 °C, 2200 °C, 2250 °C, 2300 °C, 2350 °C, 2400 °C, 2450 °C, 2500 °C, 2550 °C, 2600 °C, etc., or the range composed of any two of these values; at the same time, the temperature of the diamond is controlled within 500 °C - 1000 °C, such as 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, 950 °C, 1000 °C, etc., or the range composed of any two of these values, and the heat preservation time is controlled within 15 min - 30 min, such as 15 min, 18 min, 20 min, 22 min, 25 min, 28 min, 30 min, etc., or the range composed of any two of these values. Thus, through the temperature control of the tantalum material and the diamond, sufficient tantalum atoms can evaporate and diffuse into the diamond. At the same time, the thermal fields of the tantalum material and the diamond can better stimulate hydrogen to generate hydrogen ions.

[0054] It should be noted that in the steps of the first annealing treatment, a separate heat source can be used to heat the diamond and the tantalum material so that the temperatures of the diamond and the tantalum material are controlled within different ranges. At the same time, instruments such as infrared thermometers are used to monitor the temperatures of the diamond and the tantalum material and maintain the temperatures within the required ranges.

[0055] Since the temperature of the tantalum material is higher than that of the diamond in the first annealing step, the tantalum material can be heated by a heat source, and then the diamond can be heated by the thermal field provided by the tantalum material to save energy.

[0056] Preferably, in the first annealing step, the distance between the diamond and the tantalum material is 5 mm-30 mm, for example, 5 mm, 8 mm, 10 mm, 12 mm, 15 mm, 18 mm, 20 mm, 22 mm, 25 mm, 28 mm, 30 mm, etc., or a range consisting of any two of these values. Such an arrangement helps tantalum atoms to better diffuse into the diamond. At the same time, when the diamond is heated using the thermal field provided by the tantalum material, the thermal field can be more fully utilized.

[0057] In the step of the first annealing treatment, after the insulation is completed, the cooling rate of the diamond is controlled at 1°C / min-20°C / min, for example, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min, 16°C / min, 17°C / min, 18°C / min, 19°C / min, 20°C / min, etc., or a range consisting of any two of these values. Such an arrangement can cause dislocation movement of the diamond grains during the cooling process, thereby performing sufficient self-tuning.

[0058] Since the first annealing treatment in step S1 is carried out in a hydrogen-rich atmosphere, hydrogen ions are mixed into the diamond lattice. In addition, hydrogen is also used in some diamond preparation methods, such as chemical vapor deposition, which causes hydrogen ions to be mixed into the diamond lattice. The presence of hydrogen ions can make the diamond brittle and reduce its machinability.

[0059] To this end, the present invention further performs step S2, performing a second annealing treatment in an inert atmosphere, thereby fully releasing the hydrogen ions and tantalum atoms contained in the diamond lattice, and causing the diamond grains to produce dislocation movement again, further self-adjusting, filling the lattice gaps and increasing the grain size, thereby further reducing the stress of the diamond.

[0060] Therefore, the method of the present invention can remove the graphite phase in the diamond as much as possible and increase the grain size, making the grain size larger and more complete and becoming flatter through dislocation movement, filling the lattice gaps, thereby fully removing the stress of the diamond under non-contact conditions, improving the machinability of the diamond, and not damaging the diamond.

[0061] Among them, in the step of performing the second annealing treatment in an inert atmosphere, an inert gas can be introduced to form an inert atmosphere. Among them, the inert gas is preferably at least one of nitrogen and argon. The flow rate of the inert gas is 300 sccm - 800 sccm, such as 300 sccm, 350 sccm, 400 sccm, 450 sccm, 500 sccm, 550 sccm, 600 sccm, 650 sccm, 700 sccm, 750 sccm, 800 sccm, etc., or the range composed of any two of these values. At the same time, the pressure in the cavity is adjusted to be 3 kPa - 10 kPa, such as 3 kPa, 3.5 kPa, 4 kPa, 4.5 kPa, 5 kPa, 5.5 kPa, 6 kPa, 6.5 kPa, 7 kPa, 7.5 kPa, 8 kPa, 8.5 kPa, 9 kPa, 9.5 kPa, 10 kPa, etc., or the range composed of any two of these values. Similarly, during the second annealing treatment, the pressure is maintained constant to provide a stable environment for the second annealing treatment of the diamond.

[0062] In the step of performing the second annealing treatment, the temperature of the diamond is controlled at 800 °C - 1000 °C, such as 800 °C, 850 °C, 900 °C, 950 °C, 1000 °C, etc., or the range composed of any two of these values. The holding time is controlled at 10 min - 30 min, such as 10 min, 12 min, 15 min, 18 min, 20 min, 22 min, 25 min, 28 min, 30 min, etc., or the range composed of any two of these values. Thus, the hydrogen ions and tantalum atoms trapped in the diamond lattice can be fully precipitated.

[0063] Furthermore, it is preferably that the temperature of the diamond in the second annealing treatment step is greater than or equal to the temperature of the diamond in the first annealing treatment step, which is more conducive to the full precipitation of the hydrogen ions and tantalum atoms trapped in the diamond lattice.

[0064] Since in the step of performing the first annealing treatment, when the temperature of the diamond drops to 200 °C - 350 °C, such as 200 °C, 230 °C, 250 °C, 280 °C, 300 °C, 320 °C, 350 °C, etc., or the range composed of any two of these values, the grains in the diamond have been fully self-tuned. At this time, it is preferably to stop further cooling and then perform the second annealing treatment, which can save energy consumption and process time.

[0065] Further, after the step of the first annealing treatment, most of the graphite phase in the diamond has been removed, or basically completely removed, and the step of the second annealing treatment is carried out in an inert atmosphere, so that tantalum atoms can be fully removed from the diamond and will not enter the diamond again. Therefore, preferably, the step of the second annealing treatment and the step of the first annealing treatment are carried out in the same device, which can reduce the equipment investment and simplify the operation steps.

[0066] Furthermore, during the second annealing treatment, the heating method is preferably the same as that of the first annealing treatment. The tantalum material is heated by a heat source, and then the diamond is heated by the heat field provided by the tantalum material. At this time, the distance between the diamond and the tantalum material remains the same as that of the first annealing treatment, which can greatly simplify the operation steps.

[0067] For example, in an embodiment, the method is carried out in a hot filament CVD device, and the hot filament CVD device is a diamond growth device, without the need to increase additional equipment investment. Specifically, when using a hot filament CVD device to reduce the stress of diamond, the following steps are included:

[0068] Place the diamond on the sample stage of the hot filament CVD device, and then arrange tantalum wires on the hot filament rack; preferably, the spacing of the tantalum wires is 0.5 mm - 2 mm, the thickness is 0.35 mm - 1 mm, and the tantalum wires are parallel to the sample stage, so as to provide a uniform heat field for the diamond;

[0069] Close the vacuum chamber, evacuate the hot filament CVD device to a vacuum, such as 10 -2 Pa - 10 -3 Pa, to remove impurity elements in the device cavity;

[0070] Introduce hydrogen, turn on the power to heat the tantalum wires, and use the heat field provided by the tantalum wires to perform the first annealing treatment on the diamond; preferably, when heating the tantalum wires, increase the current at a rate of 1 A / min - 10 A / min, and monitor the temperature of the tantalum wires with an infrared thermometer. When the tantalum wires reach the preset temperature, first maintain for a certain period of time, such as 2 h - 3 h, then raise the sample stage, adjust the distance (wire-base distance) between the diamond and the tantalum wires to 5 mm - 30 mm, heat the diamond with the heat field of the tantalum wires, and monitor the temperature of the diamond through the thermocouple inside the sample stage. After the heat preservation is completed, control the tantalum wires to cool down slowly by reducing the current, so as to indirectly control the diamond to cool down for self-tuning;

[0071] Then close the hydrogen, introduce an inert gas, reheat the tantalum wires, and use the heat field provided by the tantalum wires to perform the second annealing treatment on the diamond.

[0072] Hereinafter, the method for reducing the stress of diamond will be further described through the following specific examples.

[0073] Example 1

[0074] The diamond prepared by the hot filament CVD method was successively washed with acetone, alcohol, and deionized water, and dried in an oven.

[0075] The diamond was placed on the sample stage of the hot filament CVD equipment. The sample stage was lowered to the lowest position. Tantalum wires were arranged on the hot filament holder at a spacing of 0.75 mm, and the thickness of the tantalum wires was 0.5 mm.

[0076] The vacuum chamber was closed, and the vacuum degree of the equipment was pumped to 2×10 -2 Pa.

[0077] 300 sccm of hydrogen was introduced, and the pressure inside the chamber was adjusted to 2 kPa. The power supply was turned on, and the current was increased at a rate of 10 A / min. The temperature of the tantalum wire was monitored with an infrared thermometer to make the temperature of the tantalum wire reach 1700 °C and maintained for 2 hours.

[0078] The sample stage was raised, and the distance (wire-substrate distance) between the diamond and the tantalum wire was controlled to be 15 mm. The diamond was heated by the thermal field of the tantalum wire, and the temperature of the diamond was monitored through the thermocouple inside the sample stage. The temperature of the diamond was controlled to be 800 °C and maintained for 15 min.

[0079] Then, the temperature of the tantalum wire was slowly decreased by reducing the current, so as to lower the temperature of the diamond. The cooling rate was controlled at 10 °C / min. When the temperature of the diamond dropped to 300 °C, the cooling was stopped.

[0080] Hydrogen was turned off, and 500 sccm of argon was introduced to keep the gas pressure inside the chamber at 5 kPa.

[0081] The current was increased to reheat the tantalum wire, and the temperature of the diamond was monitored through the thermocouple inside the sample stage. The temperature of the diamond was controlled to be 900 °C and maintained for 15 min.

[0082] Then, the current of the tantalum wire was decreased at a rate of 5 A / min until the current dropped to 0 A. The diamond was taken out after standing for 4 hours.

[0083] Example 2

[0084] The diamond prepared by the microwave plasma CVD method was successively washed with acetone, alcohol, and deionized water, and dried in an oven.

[0085] The diamond was placed on the sample stage of the hot filament CVD equipment. The sample stage was lowered to the lowest position. Tantalum wires were arranged on the hot filament holder at a spacing of 1 mm, and the thickness of the tantalum wires was 0.75 mm.

[0086] The vacuum chamber was closed, and the vacuum degree of the equipment was pumped to 2×10 -2 Pa.

[0087] Introduce 300 sccm of hydrogen gas and adjust the pressure inside the chamber to 2 kPa. Turn on the power supply and increase the current at a rate of 10 A / min. Monitor the temperature of the tantalum wire with an infrared thermometer to make the temperature of the tantalum wire reach 2100 °C and maintain it for 2 hours.

[0088] Raise the sample stage and control the distance between the diamond and the tantalum wire (wire-substrate distance) to be 18 mm. Heat the diamond using the thermal field of the tantalum wire and monitor the temperature of the diamond through the thermocouple inside the sample stage. Control the temperature of the diamond to be 850 °C and maintain it for 15 min.

[0089] Then, control the tantalum wire to cool down slowly by reducing the current, thereby reducing the temperature of the diamond. The cooling rate is controlled at 12 °C / min. When the temperature of the diamond drops to 300 °C, stop the cooling.

[0090] Turn off the hydrogen gas and introduce 500 sccm of argon gas to keep the pressure inside the chamber at 5 kPa.

[0091] Increase the current to make the tantalum wire heat up again. Monitor the temperature of the diamond through the thermocouple inside the sample stage. Control the temperature of the diamond to be 950 °C and maintain it for 10 min.

[0092] Then, reduce the current of the tantalum wire at a rate of 5 A / min until the current drops to 0 A. After the diamond stands still for 4 hours, take it out.

[0093] Example 3

[0094] Wash the diamond prepared by the hot filament CVD method successively with acetone, alcohol, and deionized water, and dry it in an oven.

[0095] Place the diamond on the sample stage of the hot filament CVD equipment. Lower the sample stage to the lowest position. Arrange the tantalum wires on the hot filament rack at a spacing of 1.5 mm. The thickness of the tantalum wire is 1 mm.

[0096] Close the vacuum chamber and pump the vacuum degree of the equipment to 2×10 -2 Pa.

[0097] Introduce 300 sccm of hydrogen gas and adjust the pressure inside the chamber to 2 kPa. Turn on the power supply and increase the current at a rate of 10 A / min. Monitor the temperature of the tantalum wire with an infrared thermometer to make the temperature of the tantalum wire reach 2300 °C and maintain it for 2 hours.

[0098] Raise the sample stage and control the distance between the diamond and the tantalum wire (wire-substrate distance) to be 20 mm. Heat the diamond using the thermal field of the tantalum wire and monitor the temperature of the diamond through the thermocouple inside the sample stage. Control the temperature of the diamond to be 900 °C and maintain it for 15 min.

[0099] Then, the tantalum wire is slowly cooled by reducing the current, thereby reducing the temperature of the diamond. The cooling rate is controlled at 15 °C / min. When the temperature of the diamond drops to 300 °C, the cooling is stopped.

[0100] Turn off the hydrogen gas and introduce 500 sccm of argon gas to keep the pressure inside the cavity at 5 kPa.

[0101] Increase the current to reheat the tantalum wire. Monitor the temperature of the diamond through the thermocouple inside the sample stage, and control the temperature of the diamond to be 1000 °C and maintain it for 15 minutes.

[0102] Then, reduce the current of the tantalum wire at a rate of 5 A / min until the current drops to 0 A. After the diamond stands still for 4 hours, it is taken out.

[0103] Example 4

[0104] The diamond prepared by the hot wire CVD method is washed successively with acetone, alcohol, and deionized water, and then dried in an oven.

[0105] Place the diamond on the sample stage of the hot wire CVD equipment. The sample stage is lowered to the lowest position. Arrange the tantalum wire on the hot wire rack at a spacing of 0.75 mm. The thickness of the tantalum wire is 0.5 mm.

[0106] Close the vacuum chamber and pump the vacuum degree of the equipment to 2×10 -2 Pa.

[0107] Introduce 300 sccm of hydrogen gas and adjust the pressure inside the cavity to 2 kPa. Turn on the power supply and increase the current at a speed of 10 A / min. Monitor the temperature of the tantalum wire with an infrared thermometer to make the temperature of the tantalum wire reach 1700 °C and maintain it for 2 hours.

[0108] Raise the sample stage and control the distance (wire-substrate distance) between the diamond and the tantalum wire to be 15 mm. Heat the diamond using the thermal field of the tantalum wire. Monitor the temperature of the diamond through the thermocouple inside the sample stage, and control the temperature of the diamond to be 800 °C and maintain it for 30 minutes.

[0109] Then, the tantalum wire is slowly cooled by reducing the current, thereby reducing the temperature of the diamond. The cooling rate is controlled at 5 °C / min. When the temperature of the diamond drops to 300 °C, the cooling is stopped.

[0110] Turn off the hydrogen gas and introduce 500 sccm of argon gas to keep the pressure inside the cavity at 5 kPa.

[0111] Increase the current to reheat the tantalum wire. Monitor the temperature of the diamond through the thermocouple inside the sample stage, and control the temperature of the diamond to be 900 °C and maintain it for 15 minutes.

[0112] Then, the tantalum wire current was decreased at a rate of 5 A / min until the current dropped to 0 A. After the diamond was left standing for 4 hours, it was taken out.

[0113] Example 5

[0114] The diamond prepared by the hot filament CVD method was successively washed with acetone, alcohol, and deionized water, and then dried in an oven.

[0115] The diamond was placed on the sample stage of the hot filament CVD equipment. The sample stage was lowered to the lowest position. Tantalum wires were arranged on the hot wire rack at a spacing of 1 mm, and the thickness of the tantalum wire was 0.75 mm.

[0116] The vacuum chamber was closed, and the vacuum degree of the equipment was pumped to 2×10 -2 Pa.

[0117] 300 sccm of hydrogen was introduced, and the pressure inside the chamber was adjusted to 2 kPa. The power was turned on, and the current was increased at a speed of 10 A / min. The temperature of the tantalum wire was monitored with an infrared thermometer to make the temperature of the tantalum wire reach 2100 °C and maintained for 2 hours.

[0118] The sample stage was raised, and the distance between the diamond and the tantalum wire (the wire-base distance) was controlled to be 18 mm. The diamond was heated using the thermal field of the tantalum wire, and the temperature of the diamond was monitored through the thermocouple inside the sample stage. The temperature of the diamond was controlled to be 850 °C and maintained for 30 min.

[0119] Then, the temperature of the tantalum wire was slowly decreased by reducing the current, so that the temperature of the diamond decreased. The cooling rate was controlled at 20 °C / min. When the temperature of the diamond dropped to 300 °C, the cooling was stopped.

[0120] Hydrogen was turned off, and 500 sccm of argon was introduced to keep the gas pressure inside the chamber at 5 kPa.

[0121] The current was increased to make the tantalum wire heat up again. The temperature of the diamond was monitored through the thermocouple inside the sample stage. The temperature of the diamond was controlled to be 950 °C and maintained for 30 min.

[0122] Then, the tantalum wire current was decreased at a rate of 5 A / min until the current dropped to 0 A. After the diamond was left standing for 4 hours, it was taken out.

[0123] Comparative Example 1

[0124] First, prepare a diamond wafer using the hot filament CVD method, including: placing a single-crystalline silicon substrate in an ethanol suspension containing diamond micropowder and ultrasonically oscillating it to make a large amount of diamond micropowder adhere to the surface of the single-crystalline silicon; then putting the single-crystalline silicon substrate into a hot filament CVD device, selecting a tantalum wire as the hot filament, introducing methane and hydrogen with a ratio of 1:25. Raise the current of each hot filament to 18 A and keep it for 4 hours to completely carbonize the tantalum wire; then raise the current of the carbonized tantalum wire to 26 A, adjust the distance between the hot filament and the substrate (the wire-substrate distance) to 5 mm, and the ratio of methane to hydrogen is 1:50, keep it for 200 h to deposit a thick diamond film on the silicon substrate, and remove the silicon substrate with HF to obtain self-supporting diamond.

[0125] Wash the diamond prepared by the hot filament CVD method successively with acetone, alcohol, and deionized water, and dry it in an oven.

[0126] Place the diamond on the sample stage of the hot filament CVD device, lower the sample stage to the lowest position, arrange tungsten wires on the hot filament rack at a spacing of 0.75 mm, and the thickness of the tungsten wire is 0.5 mm.

[0127] Close the vacuum chamber and pump the vacuum degree of the device to 2×10 -2 Pa.

[0128] Introduce 300 sccm of hydrogen, adjust the pressure in the chamber to 2 kPa. Turn on the power, raise the current at a speed of 10 A / min, monitor the temperature of the tungsten wire with an infrared thermometer, make the temperature of the tungsten wire reach 1700 °C, and keep it for 2 hours.

[0129] Raise the sample stage, control the distance between the diamond and the tungsten wire (the wire-substrate distance) to 15 mm, heat the diamond using the thermal field of the tungsten wire, monitor the temperature of the diamond through the thermocouple inside the sample stage, and control the temperature of the diamond to 800 °C and keep it for 15 min.

[0130] Then control the tungsten wire to cool down slowly by reducing the current, so as to reduce the temperature of the diamond, and control the cooling rate to 10 °C / min. When the temperature of the diamond drops to 300 °C, stop cooling.

[0131] Close the hydrogen, introduce 500 sccm of argon, and keep the air pressure in the chamber at 5 kPa.

[0132] Raise the current to make the tantalum wire heat up again, monitor the temperature of the diamond through the thermocouple inside the sample stage, and control the temperature of the diamond to 900 °C and keep it for 15 min.

[0133] Then reduce the current of the tungsten wire at a rate of 5 A / min until the current drops to 0 A, and take out the diamond after standing for 4 hours.

[0134] Comparative Example 2

[0135] The diamond prepared by the hot filament CVD method was successively washed with acetone, alcohol, and deionized water, and then dried in an oven.

[0136] The diamond was placed on the sample stage of the hot filament CVD equipment. The sample stage was lowered to the lowest position. Tantalum wires were arranged on the hot filament holder at a spacing of 0.75 mm, and the thickness of the tantalum wires was 0.5 mm.

[0137] The vacuum chamber was closed, and the vacuum degree of the equipment was pumped to 2×10 -2 Pa.

[0138] 300 sccm of hydrogen was introduced, and the pressure inside the chamber was adjusted to 2 kPa. The power was turned on, and the current was increased at a rate of 10 A / min. The temperature of the tantalum wires was monitored with an infrared thermometer to make the temperature of the tantalum wires reach 1700 °C and maintained for 2 hours.

[0139] The sample stage was raised, and the distance (wire-substrate distance) between the diamond and the tantalum wires was controlled to be 15 mm. The diamond was heated by the thermal field of the tantalum wires. The temperature of the diamond was monitored through the thermocouple inside the sample stage, and the temperature of the diamond was controlled to be 800 °C and maintained for 15 min.

[0140] Then, the temperature of the tantalum wires was slowly decreased by reducing the current, so as to reduce the temperature of the diamond. The cooling rate was controlled at 10 °C / min. When the temperature of the diamond dropped to 300 °C, the cooling was stopped.

[0141] Then, the current of the tantalum wires was decreased at a rate of 5 A / min until the current dropped to 0 A. The diamond was taken out after standing for 4 hours.

[0142] Comparative Example 3

[0143] The diamond prepared by the hot filament CVD method was successively washed with acetone, alcohol, and deionized water, and then dried in an oven.

[0144] The diamond was placed on the sample stage of the hot filament CVD equipment. The sample stage was lowered to the lowest position. Tantalum wires were arranged on the hot filament holder at a spacing of 0.75 mm, and the thickness of the tantalum wires was 0.5 mm.

[0145] The vacuum chamber was closed, and the vacuum degree of the equipment was pumped to 2×10 -2 Pa.

[0146] 300 sccm of nitrogen was introduced, and the pressure inside the chamber was adjusted to 2 kPa. The power was turned on, and the current was increased at a rate of 10 A / min. The temperature of the tantalum wires was monitored with an infrared thermometer to make the temperature of the tantalum wires reach 1700 °C and maintained for 2 hours.

[0147] Raise the sample stage, control the distance between the diamond and the tantalum wire (wire-base distance) to 15 mm, heat the diamond using the thermal field of the tantalum wire, monitor the temperature of the diamond through the thermocouple inside the sample stage, control the temperature of the diamond to be 800 °C, and maintain it for 15 min.

[0148] Then, control the tantalum wire to cool down slowly by reducing the current, thereby reducing the temperature of the diamond. The cooling rate is controlled at 10 °C / min. When the temperature of the diamond drops to 300 °C, stop the cooling.

[0149] Turn off the nitrogen, introduce 500 sccm of argon, and keep the pressure inside the cavity at 5 kPa.

[0150] Increase the current to make the tantalum wire heat up again, monitor the temperature of the diamond through the thermocouple inside the sample stage, control the temperature of the diamond to be 900 °C, and maintain it for 15 min.

[0151] Then, reduce the current of the tantalum wire at a rate of 5 A / min until the current drops to 0 A. After the diamond stands still for 4 hours, take it out.

[0152] Perform performance tests on the diamonds obtained in the above examples and comparative examples. The results are as Figures 1-11 and shown in Table 1. Among them, Figures 4-11 in the Raman spectrum, peak1 is the characteristic peak of the diamond phase, and peak2 is the characteristic peak of the graphite phase. In addition, the center peak position of the Raman spectrum peak1 of the diamond phase should be 1332.00 cm -1 . If there is stress in the diamond, the Raman spectrum peak will shift, and the larger the shift range, the greater the stress.

[0153] Table 1

[0154]

[0155] From Figures 1-3 it can be seen that the diamond grains in Example 1 are larger and more complete. At the same time, from Figures 4-11 and Table 1, it can be seen that the peak1 of the diamond phase in the examples is closer to the standard diamond phase peak of 1332.00 cm -1 . Therefore, the method of the present invention can sufficiently reduce the stress of the diamond.

[0156] In addition, from Figures 4-11 it can be seen that the peak1 characteristic peak of the diamond phase in the examples is high and narrow, and the peak2 characteristic peak of the graphite phase tends to be smooth, indicating that the content of the graphite phase in the diamond is very small, and it is basically the diamond phase with better quality.

[0157] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0158] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for reducing the stress of diamond, characterized in that, It includes the following steps: Introduce hydrogen to form a hydrogen-rich atmosphere. The flow rate of the hydrogen is 100 sccm - 500 sccm. Anneal the diamond for the first time in the hydrogen-rich atmosphere. In the step of the first annealing treatment, tantalum material is also used. Heat the diamond by the thermal field provided by the tantalum material. The distance between the diamond and the tantalum material is 5 mm - 30 mm. And control the temperature of the tantalum material to be greater than or equal to 1500 °C and less than the melting point of the tantalum material. The temperature of the diamond is controlled at 500 °C - 1000 °C, and the holding time is controlled at 15 min - 30 min; Then anneal the diamond for the second time in an inert atmosphere. In this process, heat the diamond by the thermal field provided by the tantalum material. The temperature of the diamond is controlled at 800 °C - 1000 °C, and it is greater than or equal to the temperature of the diamond in the first annealing treatment step. The holding time of the diamond is controlled at 10 min - 30 min.

2. The method for reducing the stress of diamond according to claim 1, wherein In the step of the first annealing treatment, the temperature of the tantalum material is controlled at 1700 °C - 2600 °C.

3. The method for reducing the stress of diamond according to claim 1, characterized in that, In the step of the first annealing treatment, the cooling rate of the diamond is controlled at 1 °C / min - 20 °C / min.

4. The method for reducing the stress of diamond according to claim 1, characterized in that, In the step of the first annealing treatment, when the temperature of the diamond drops to 200 °C - 350 °C, stop cooling and perform the second annealing treatment.

5. The method for reducing the stress of diamond according to claim 1, characterized in that, In the step of the first annealing treatment, the pressure is less than or equal to 10 kPa.

6. The method for reducing the stress of diamond according to claim 1, characterized in that, Introduce an inert gas to form an inert atmosphere. The flow rate of the inert gas is 300 sccm - 800 sccm; And / or, the inert atmosphere is selected from at least one of a nitrogen atmosphere and an argon atmosphere; And / or, in the step of the second annealing treatment, the pressure is controlled at 3 kPa - 10 kPa.

7. The method for reducing the stress of diamond according to any one of claims 1 to 6, characterized in that, It includes the following steps: Place the diamond on the sample stage of the hot filament CVD equipment, and then arrange tantalum wire on the hot filament rack; Close the vacuum chamber and evacuate the hot filament CVD equipment to vacuum; Introduce hydrogen, turn on the power to heat the tantalum wire, and perform the first annealing treatment on the diamond by the thermal field provided by the tantalum wire; Then close the hydrogen, introduce an inert gas, heat the tantalum wire, and perform the second annealing treatment on the diamond by the thermal field provided by the tantalum wire.

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