Method for reducing stress of diamond

Abstract

The invention relates to a method for reducing stress of diamond, which comprises the following steps: carrying out first annealing treatment on diamond in a hydrogen-rich atmosphere, using a tantalum material in the first annealing treatment step, and controlling the temperature of the tantalum material to be greater than or equal to 1500 DEG C and less than the melting point of the tantalum material; and then carrying out secondary annealing treatment on the diamond in an inert atmosphere. According to the method, the graphite phase in the diamond can be removed as much as possible, the grain size is increased, the grain size is larger and more complete, the grain becomes smoother through dislocation motion, and lattice gaps are filled, so that the stress of the diamond is fully removed under the non-contact condition, the machinability of the diamond is improved, and the diamond is not damaged.

Description

Technical Field

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

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

[0003] Based on this, it is necessary to provide a method for reducing diamond stress in order to solve the above problem, wherein the method can reduce the diamond stress under non-contact conditions without damaging the diamond.

[0004] A method for reducing diamond stress comprises 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 step, 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; The diamond is then subjected to a second annealing treatment in an inert atmosphere.

[0005] In one embodiment, in the first annealing step, the temperature of the tantalum material is controlled at 1700°C-2600°C.

[0006] In one embodiment, in the first annealing step, the temperature of the diamond is controlled at 500° C.-1000° C.; And / or, the holding time is controlled within 15min-30min; And / or, the cooling rate of the diamond is controlled at 1°C / min-20°C / min.

[0007] In one embodiment, in the second annealing step, 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 first annealing step; And / or, the heat preservation time of the diamond is controlled within 10 min-30 min.

[0008] In one embodiment, in the first annealing step, when the temperature of the diamond drops to 200° C.-350° C., the temperature drop is stopped and a second annealing is performed.

[0009] In one embodiment, in the first annealing step, the diamond is heated by a thermal field provided by the tantalum material; And / or, the distance between the diamond and the tantalum material is 5 mm-30 mm.

[0010] In one embodiment, in the second annealing step, the diamond is heated by using a thermal field provided by the tantalum material; And / or, the distance between the diamond and the tantalum material is 5 mm-30 mm.

[0011] In one embodiment, hydrogen gas is introduced to form a hydrogen-rich atmosphere, and the flow rate of the hydrogen gas is 100 sccm-500 sccm; And / or, in the first annealing step, the pressure is less than or equal to 10 kPa.

[0012] 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; And / or, the inert atmosphere is selected from at least one of a nitrogen atmosphere and an argon atmosphere; And / or, in the second annealing step, the pressure is controlled at 3 kPa-10 kPa.

[0013] In one embodiment, the steps include: The diamond is placed on the sample stage of the hot wire CVD equipment, and then the tantalum wire is arranged on the hot wire holder; Close the vacuum chamber and evacuate the hot wire CVD device to a vacuum state; Passing hydrogen gas, turning on the power to heat the tantalum wire, and performing a first annealing treatment on the diamond using the heat field provided by the tantalum wire; Then the hydrogen gas is turned off, an inert gas is introduced, the tantalum wire is heated, and the diamond is subjected to a second annealing treatment using the heat field provided by the tantalum wire.

[0014] 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, wherein the hydrogen-rich atmosphere can prevent the tantalum material from undergoing oxidation or carbonization reactions, and the tantalum material can be better evaporated of tantalum atoms and diffused more evenly into the diamond through temperature control, promoting the transformation of the graphite phase in the diamond to the diamond phase, and at the same time, hydrogen can generate hydrogen ions under the excitation of the thermal field provided by the tantalum material, and the hydrogen ions can etch the graphite phase in the diamond, thereby promoting the transformation of the graphite phase to the diamond phase and the etching of the graphite phase by the tantalum atoms, and the graphite phase in the diamond can be removed as much as possible, and the grains in the diamond are prompted to produce dislocation movement, self-adjust, fill the lattice gaps and increase the grain size. Then, a second annealing treatment is carried out in an inert atmosphere to fully release the hydrogen ions and tantalum atoms mixed in the diamond lattice, and the grains in the diamond are caused to produce dislocation movement again, further self-adjust, fill the lattice gaps and increase the grain size.

[0015] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 This is a scanning electron microscope image of the diamond after stress relief treatment in Example 1; Figure 2 This is a scanning electron microscope image of the diamond after stress relief treatment in Comparative Example 1; Figure 3 This is a scanning electron microscope photo of the diamond after stress relief treatment in Comparative Example 2; Figure 4 This is the Raman spectrum of diamond after stress relief treatment in Example 1; Figure 5 This is the Raman spectrum of diamond after stress relief treatment in Example 2; Figure 6 This is the Raman spectrum of diamond after stress relief treatment in Example 3; Figure 7 This is the Raman spectrum of diamond after stress relief treatment in Example 4; Figure 8 This is the Raman spectrum of diamond after stress relief treatment in Example 5; Fig. 9 This is the Raman spectrum of diamond after stress relief treatment in Comparative Example 1; Fig.10 This is the Raman spectrum of diamond after stress relief treatment in Comparative Example 2; Fig.11 This is the Raman spectrum of the diamond after stress relief treatment in Comparative Example 3. DETAILED DESCRIPTION

[0018] 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 of the present invention more thorough and comprehensive.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope 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 related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.

[0020] In the present invention, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0021] The method for reducing diamond stress provided by the present invention comprises the following steps: S1, performing a first annealing treatment on the diamond in a hydrogen-rich atmosphere, wherein a tantalum material is also used in the first annealing step, 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; S2, then subjecting the diamond to a second annealing treatment in an inert atmosphere.

[0022] The method of the present invention is used to remove stress in diamond in a targeted manner and improve the machinability of diamond. Therefore, the present invention has no requirements for the preparation method of diamond. For example, diamond is prepared by chemical vapor deposition methods such as hot wire CVD method, DC jet CVD method, DC discharge CVD method, radio frequency CVD method and microwave plasma CVD method, and can also be prepared by other methods such as high temperature and high pressure synthesis method.

[0023] In the method of the present invention, the first annealing treatment of step S1 is carried out in a hydrogen-rich atmosphere, and tantalum material is also used, wherein the hydrogen-rich atmosphere can prevent the tantalum material from undergoing reactions such as oxidation or carbonization, and through temperature control, the tantalum material can better evaporate tantalum atoms and diffuse more evenly into the diamond, promoting the transformation of the graphite phase in the diamond to the diamond phase. At the same time, hydrogen can generate hydrogen ions under the stimulation 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 and the etching of the graphite phase by tantalum atoms, the graphite phase in the diamond can be removed as much as possible, and the grains in the diamond are prompted to produce dislocation movement, self-adjust, fill the lattice gaps and increase the grain size, thereby reducing the stress of the diamond.

[0024] It should be noted that the present invention has no requirements on the tantalum material used, and it can be tantalum wire, etc., and can be selected according to specific needs.

[0025] In step S1, the diamond and tantalum materials are preferably placed in the device simultaneously or successively, and then the device is evacuated to a vacuum, for example, to a vacuum degree of 10 -2 Pa-10 -3 Pa, thereby removing impurity elements in the device cavity, and then performing the first annealing treatment.

[0026] In the first annealing step, hydrogen gas may be introduced to form a hydrogen-rich atmosphere. Preferably, the flow rate of the hydrogen gas is 100 sccm-500 sccm, for example, 100 sccm, 150 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm, 450 sccm, 500 sccm, etc., or a range consisting of any two of these values. At the same time, the pressure is adjusted to be less than or equal to 10 kPa, for example, 0.5 kPa, 1 kPa a, 1.5kPa, 2kPa, 2.5kPa, 3kPa, 3.5kPa, 4kPa, 4.5kPa, 5kPa, 5.5kPa, 6kPa, 6.5kPa, 7kPa, 7.5kPa, 8kPa, 8.5kPa, 9kPa, 9.5kPa, 10kPa, etc., or a range consisting 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 diamond.

[0027] Further, the temperature of the tantalum material is preferably 1700°C-2600°C, for example, 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 a range consisting of any two of these values; meanwhile, the temperature of the diamond is controlled at 500°C-1000°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, etc., or a range consisting of any two of these values, and the insulation time is controlled at 15min-30min, for example, 15min, 18min, 20min, 22min, 25min, 28min, 30min, etc., or a range consisting of any two of these values, so that, through the temperature control of tantalum material and diamond, sufficient tantalum atoms can evaporate and diffuse into diamond, and at the same time, the thermal field of tantalum material and diamond can better excite hydrogen to produce hydrogen ions.

[0028] It should be noted that in the first annealing step, a separate heat source can be used to heat the diamond and tantalum materials so that the temperatures of the diamond and tantalum materials are controlled within different ranges. At the same time, the temperatures of the diamond and tantalum materials are monitored using instruments such as infrared thermometers to maintain the temperatures within the required range.

[0029] Since the temperature of the tantalum material is higher than the temperature 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.

[0030] Preferably, in the step of the first annealing treatment, 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 diffuse better into the diamond. At the same time, when the diamond is heated by the thermal field provided by the tantalum material, the thermal field can be more fully utilized.

[0031] 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. In this way, the diamond grains can undergo dislocation movement during the cooling process and perform sufficient self-tuning.

[0032] Since the first annealing treatment in step S1 is carried out in a hydrogen-rich atmosphere, hydrogen ions are mixed in 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 in the diamond lattice. The presence of hydrogen ions can make the diamond brittle and its machinability deteriorate.

[0033] 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-adjust, fill the lattice gaps and increase the grain size, thereby further reducing the stress of the diamond.

[0034] 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.

[0035] In the step of performing the second annealing treatment in an inert atmosphere, an inert gas may be introduced to form an inert atmosphere, wherein the inert gas is preferably at least one of nitrogen and argon, and the flow rate of the inert gas is 300sccm-800sccm, for example, 300sccm, 350sccm, 400sccm, 450sccm, 500sccm, 550sccm, 600sccm, 650sccm, 700sccm, 750sccm, 800sccm, etc., or any of these values. The pressure in the cavity is adjusted to a range of 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 a range 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 diamond.

[0036] In the step of the second annealing treatment, the temperature of the diamond is controlled at 800°C-1000°C, for example, 800°C, 850°C, 900°C, 950°C, 1000°C, etc., or a range consisting of any two of these values, and the holding time is controlled at 10min-30min, for example, 10min, 12min, 15min, 18min, 20min, 22min, 25min, 28min, 30min, etc., or a range consisting of any two of these values, so that the hydrogen ions and tantalum atoms contained in the diamond lattice can be fully precipitated.

[0037] Furthermore, it is preferred that the temperature of the diamond in the second annealing step is greater than or equal to the temperature of the diamond in the first annealing step, which is more conducive to the complete precipitation of hydrogen ions and tantalum atoms contained in the diamond lattice.

[0038] Because in the first annealing step, when the temperature of the diamond drops to 200°C-350°C, for example, 200°C, 230°C, 250°C, 280°C, 300°C, 320°C, 350°C, etc., or a range consisting of any two of these values, the grains in the diamond have been fully self-adjusted. At this time, it is preferred to stop further cooling and then perform a second annealing treatment, which can save energy consumption and process time.

[0039] Furthermore, after the first annealing step, most of the graphite phase in the diamond has been removed, or is substantially completely removed, and the second annealing step is performed under an inert atmosphere, so that the tantalum atoms are fully removed from the diamond and will not re-enter the diamond. Therefore, it is preferred that the second annealing step and the first annealing step are performed in the same equipment, which can reduce equipment investment and simplify the operating steps.

[0040] Furthermore, during the second annealing treatment, the heating method is preferably the same as the first annealing treatment, using a heat source to heat the tantalum material, and then using the thermal field provided by the tantalum material to heat the diamond. At this time, the distance between the diamond and the tantalum material is the same as the first annealing treatment and remains unchanged, which can greatly simplify the operating steps.

[0041] For example, in one embodiment, the method is performed in a hot-wire CVD device, which is a diamond growth device and does not require additional equipment investment. Specifically, when using the hot-wire CVD device to reduce the stress of diamond, the method includes the following steps: Placing the diamond on the sample stage of the hot wire CVD equipment, and then arranging the tantalum wire on the hot wire rack; preferably, the spacing of the tantalum wire is 0.5mm-2mm, the thickness is 0.35mm-1mm, and the tantalum wire is kept parallel to the sample stage, so as to provide a uniform thermal field for the diamond; Close the vacuum chamber and evacuate the hot wire CVD device to a vacuum state, for example, 10 -2 Pa-10 -3 Pa, removes impurity elements in the equipment cavity; Hydrogen is introduced, and the power is turned on to heat the tantalum wire, and the diamond is subjected to a first annealing treatment using the thermal field provided by the tantalum wire; preferably, when heating the tantalum wire, the current is increased at a rate of 1A / min-10A / min, and the temperature of the tantalum wire is monitored by an infrared thermometer. When the tantalum wire reaches a preset temperature, it is first maintained for a certain time, such as 2h-3h, and then the sample stage is raised, and the distance between the diamond and the tantalum wire (wire-base distance) is adjusted to 5mm-30mm, and the diamond is heated using the thermal field of the tantalum wire, and the temperature of the diamond is monitored by a thermocouple inside the sample stage. After the insulation is completed, the tantalum wire is controlled to slowly cool down by reducing the current, thereby indirectly controlling the diamond to cool down for self-tuning; Then the hydrogen gas is turned off, an inert gas is introduced, the tantalum wire is reheated, and the diamond is subjected to a second annealing treatment using the heat field provided by the tantalum wire.

[0042] Hereinafter, the method for reducing diamond stress will be further described through the following specific examples.

[0043] Example 1 The diamond prepared by hot-filament CVD method was washed with acetone, alcohol and deionized water in sequence and dried in an oven.

[0044] The diamond was placed on the sample stage of the hot wire CVD equipment, the sample stage was lowered to the lowest position, and tantalum wires were arranged on the hot wire rack at a spacing of 0.75 mm. The thickness of the tantalum wires was 0.5 mm.

[0045] Close the vacuum chamber and pump the vacuum degree of the equipment to 2×10 -2 Pa.

[0046] 300 sccm of hydrogen was introduced, and the pressure in 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 wire was monitored with an infrared thermometer, and the temperature of the tantalum wire was made to reach 1700°C and maintained for 2 hours.

[0047] The sample stage was raised, and the distance between the diamond and the tantalum wire (wire-base distance) was controlled to be 15 mm. The thermal field of the tantalum wire was used to heat the diamond. The temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to be 800°C and maintained for 15 minutes.

[0048] Then, the tantalum wire is controlled to slowly cool down 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, the cooling is stopped.

[0049] The hydrogen gas was turned off and 500 sccm of argon gas was introduced to maintain the pressure in the chamber at 5 kPa.

[0050] The current was increased to heat up the tantalum wire again, and the temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to 900°C and maintained for 15 minutes.

[0051] Then the tantalum wire current was reduced at a rate of 5 A / min until the current dropped to 0 A. The diamond was taken out after being left to stand for 4 hours.

[0052] Example 2 The diamond prepared by microwave plasma CVD method was washed with acetone, alcohol and deionized water in sequence and dried in an oven.

[0053] The diamond is placed on the sample stage of the hot wire CVD equipment, the sample stage is lowered to the lowest position, and tantalum wires are arranged on the hot wire rack at a spacing of 1 mm. The thickness of the tantalum wires is 0.75 mm.

[0054] Close the vacuum chamber and pump the vacuum degree of the equipment to 2×10 -2 Pa.

[0055] 300 sccm of hydrogen was introduced, and the pressure in 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 wire was monitored with an infrared thermometer, and the temperature of the tantalum wire was made to reach 2100°C and maintained for 2 hours.

[0056] The sample stage was raised, and the distance between the diamond and the tantalum wire (wire-base distance) was controlled to be 18 mm. The thermal field of the tantalum wire was used to heat the diamond. The temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to be 850°C and maintained for 15 minutes.

[0057] Then, the tantalum wire is controlled 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, the cooling is stopped.

[0058] The hydrogen gas was turned off and 500 sccm of argon gas was introduced to maintain the pressure in the chamber at 5 kPa.

[0059] The current was increased to heat up the tantalum wire again, and the temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to 950°C and maintained for 10 minutes.

[0060] Then the tantalum wire current was reduced at a rate of 5 A / min until the current dropped to 0 A. The diamond was taken out after being left to stand for 4 hours.

[0061] Example 3 The diamond prepared by hot-filament CVD method was washed with acetone, alcohol and deionized water in sequence and dried in an oven.

[0062] The diamond was placed on the sample stage of the hot wire CVD equipment, the sample stage was lowered to the lowest position, and tantalum wires were arranged on the hot wire rack at a spacing of 1.5 mm. The thickness of the tantalum wires was 1 mm.

[0063] Close the vacuum chamber and pump the vacuum degree of the equipment to 2×10 -2 Pa.

[0064] 300 sccm of hydrogen was introduced, and the pressure in 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 wire was monitored with an infrared thermometer, and the temperature of the tantalum wire was made to reach 2300°C and maintained for 2 hours.

[0065] The sample stage was raised, and the distance between the diamond and the tantalum wire (wire-base distance) was controlled to be 20 mm. The thermal field of the tantalum wire was used to heat the diamond. The temperature of the diamond was monitored by the thermocouple inside the sample stage, and the temperature of the diamond was controlled to be 900°C for 15 minutes.

[0066] Then, the tantalum wire is controlled to cool down slowly 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.

[0067] The hydrogen gas was turned off and 500 sccm of argon gas was introduced to maintain the pressure in the chamber at 5 kPa.

[0068] The current was increased to heat up the tantalum wire again, and the temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to 1000°C and maintained for 15 minutes.

[0069] Then the tantalum wire current was reduced at a rate of 5 A / min until the current dropped to 0 A. The diamond was taken out after being left to stand for 4 hours.

[0070] Example 4 The diamond prepared by hot-filament CVD method was washed with acetone, alcohol and deionized water in sequence and dried in an oven.

[0071] The diamond was placed on the sample stage of the hot wire CVD equipment, the sample stage was lowered to the lowest position, and tantalum wires were arranged on the hot wire rack at a spacing of 0.75 mm. The thickness of the tantalum wires was 0.5 mm.

[0072] Close the vacuum chamber and pump the vacuum degree of the equipment to 2×10 -2 Pa.

[0073] 300 sccm of hydrogen was introduced, and the pressure in 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 wire was monitored with an infrared thermometer, and the temperature of the tantalum wire was made to reach 1700°C and maintained for 2 hours.

[0074] The sample stage was raised, and the distance between the diamond and the tantalum wire (wire-base distance) was controlled to be 15 mm. The thermal field of the tantalum wire was used to heat the diamond. The temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to be 800°C and maintained for 30 minutes.

[0075] Then, the tantalum wire is controlled to cool down slowly 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.

[0076] The hydrogen gas was turned off and 500 sccm of argon gas was introduced to maintain the pressure in the chamber at 5 kPa.

[0077] The current was increased to heat up the tantalum wire again, and the temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to 900°C and maintained for 15 minutes.

[0078] Then the tantalum wire current was reduced at a rate of 5 A / min until the current dropped to 0 A. The diamond was taken out after being left to stand for 4 hours.

[0079] Example 5 The diamond prepared by hot-filament CVD method was washed with acetone, alcohol and deionized water in sequence and dried in an oven.

[0080] The diamond is placed on the sample stage of the hot wire CVD equipment, the sample stage is lowered to the lowest position, and tantalum wires are arranged on the hot wire rack at a spacing of 1 mm. The thickness of the tantalum wires is 0.75 mm.

[0081] Close the vacuum chamber and pump the vacuum degree of the equipment to 2×10 -2 Pa.

[0082] 300 sccm of hydrogen was introduced, and the pressure in 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 wire was monitored with an infrared thermometer, and the temperature of the tantalum wire was made to reach 2100°C and maintained for 2 hours.

[0083] The sample stage was raised, and the distance between the diamond and the tantalum wire (wire-base distance) was controlled to be 18 mm. The thermal field of the tantalum wire was used to heat the diamond. The temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to be 850°C and maintained for 30 minutes.

[0084] Then, the tantalum wire is controlled to slowly cool down by reducing the current, thereby reducing the temperature of the diamond. The cooling rate is controlled at 20°C / min. When the temperature of the diamond drops to 300°C, the cooling is stopped.

[0085] The hydrogen gas was turned off and 500 sccm of argon gas was introduced to maintain the pressure in the chamber at 5 kPa.

[0086] The current was increased to heat up the tantalum wire again, and the temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to 950°C and maintained for 30 minutes.

[0087] Then the tantalum wire current was reduced at a rate of 5 A / min until the current dropped to 0 A. The diamond was taken out after being left to stand for 4 hours.

[0088] Comparative Example 1 First, the diamond wafer is prepared by the hot wire CVD method, including: placing the single crystal silicon substrate in an ethanol suspension containing diamond micropowder for ultrasonic oscillation, so that a large amount of diamond micropowder is attached to the surface of the single crystal silicon; then the single crystal silicon substrate is placed in the hot wire CVD equipment, the hot wire is a tantalum wire, and methane and hydrogen are introduced in a ratio of 1:25. The current of each hot wire is increased to 18A and maintained for 4 hours to completely carbonize the tantalum wire; then the current of the carbonized tantalum wire is increased to 26A, the distance between the hot wire and the substrate (wire-to-substrate distance) is adjusted to 5mm, the ratio of methane to hydrogen is 1:50, and it is maintained for 200 hours to deposit a thick diamond film on the silicon substrate, and the silicon substrate is removed with HF to obtain a self-supporting diamond.

[0089] The diamond prepared by hot-filament CVD method was washed with acetone, alcohol and deionized water in sequence and dried in an oven.

[0090] The diamond was placed on the sample stage of the hot wire CVD equipment, the sample stage was lowered to the lowest position, and tungsten wires were arranged on the hot wire rack at a spacing of 0.75 mm. The thickness of the tungsten wires was 0.5 mm.

[0091] Close the vacuum chamber and pump the vacuum degree of the equipment to 2×10 -2 Pa.

[0092] 300 sccm of hydrogen was introduced, and the pressure in 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 tungsten filament was monitored with an infrared thermometer, and the temperature of the tungsten filament was made to reach 1700°C and maintained for 2 hours.

[0093] The sample stage was raised, and the distance between the diamond and the tungsten wire (wire-base distance) was controlled to be 15 mm. The thermal field of the tungsten wire was used to heat the diamond. The temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to be 800°C and maintained for 15 minutes.

[0094] Then, the tungsten wire is controlled 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, the cooling is stopped.

[0095] The hydrogen gas was turned off and 500 sccm of argon gas was introduced to maintain the pressure in the chamber at 5 kPa.

[0096] The current was increased to heat up the tantalum wire again, and the temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to 900°C and maintained for 15 minutes.

[0097] Then the tungsten wire current was reduced at a rate of 5 A / min until the current dropped to 0 A. The diamond was left to stand for 4 hours and then taken out.

[0098] Comparative Example 2 The diamond prepared by hot-filament CVD method was washed with acetone, alcohol and deionized water in sequence and dried in an oven.

[0099] The diamond was placed on the sample stage of the hot wire CVD equipment, the sample stage was lowered to the lowest position, and tantalum wires were arranged on the hot wire rack at a spacing of 0.75 mm. The thickness of the tantalum wires was 0.5 mm.

[0100] Close the vacuum chamber and pump the vacuum degree of the equipment to 2×10 -2 Pa.

[0101] 300 sccm of hydrogen was introduced, and the pressure in 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 wire was monitored with an infrared thermometer, and the temperature of the tantalum wire was made to reach 1700°C and maintained for 2 hours.

[0102] The sample stage was raised, and the distance between the diamond and the tantalum wire (wire-base distance) was controlled to be 15 mm. The thermal field of the tantalum wire was used to heat the diamond. The temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to be 800°C and maintained for 15 minutes.

[0103] Then, the tantalum wire is controlled to slowly cool down 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, the cooling is stopped.

[0104] Then the tantalum wire current was reduced at a rate of 5 A / min until the current dropped to 0 A. The diamond was taken out after being left to stand for 4 hours.

[0105] Comparative Example 3 The diamond prepared by hot-filament CVD method was washed with acetone, alcohol and deionized water in sequence and dried in an oven.

[0106] The diamond was placed on the sample stage of the hot wire CVD equipment, the sample stage was lowered to the lowest position, and tantalum wires were arranged on the hot wire rack at a spacing of 0.75 mm. The thickness of the tantalum wires was 0.5 mm.

[0107] Close the vacuum chamber and pump the vacuum degree of the equipment to 2×10 -2 Pa.

[0108] 300 sccm of nitrogen was introduced, and the pressure in 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 wire was monitored with an infrared thermometer, and the temperature of the tantalum wire was made to reach 1700°C and maintained for 2 hours.

[0109] The sample stage was raised, and the distance between the diamond and the tantalum wire (wire-base distance) was controlled to be 15 mm. The thermal field of the tantalum wire was used to heat the diamond. The temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to be 800°C and maintained for 15 minutes.

[0110] Then, the tantalum wire is controlled to slowly cool down 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, the cooling is stopped.

[0111] The nitrogen gas was turned off and 500 sccm of argon gas was introduced to maintain the pressure in the chamber at 5 kPa.

[0112] The current was increased to heat up the tantalum wire again, and the temperature of the diamond was monitored by the thermocouple inside the sample stage. The temperature of the diamond was controlled to 900°C and maintained for 15 minutes.

[0113] Then the tantalum wire current was reduced at a rate of 5 A / min until the current dropped to 0 A. The diamond was taken out after being left to stand for 4 hours.

[0114] The diamonds obtained in the above examples and comparative examples were tested for performance. The results are as follows: Figure 1-Figure 11 And as shown in Table 1. Among them, Figure 4-Figure 11 In the Raman spectrum of the diamond phase, peak 1 is the characteristic peak of the diamond phase, and peak 2 is the characteristic peak of the graphite phase. In addition, the central peak position of peak 1 of the diamond phase Raman spectrum should be 1332.00 cm -1 If there is stress in diamond, the Raman spectrum peak will shift, and the larger the shift range, the greater the stress.

[0115] Table 1 from Figure 1-Figure 3 It can be seen that the diamond grains in Example 1 are larger and more complete. Figure 4-Figure 11 As shown in Table 1, the peak 1 of the diamond phase in the embodiment is closer to the standard diamond phase peak 1332.00 cm -1 Therefore, the method of the present invention can fully reduce the stress of diamond.

[0116] In addition, from Figure 4-Figure 11 It can be seen that the peak 1 characteristic peak of the diamond phase of the embodiment is high and narrow, and the peak 2 characteristic peak of the graphite phase tends to be smooth, indicating that the content of graphite phase in the diamond is very small, and it is basically all diamond phase and the quality is good.

[0117] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0118] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A method for reducing diamond stress, characterized in that: The following steps are involved: Performing a first annealing treatment on the diamond in a hydrogen-rich atmosphere, wherein a tantalum material is also used in the first annealing step, 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; The diamond is then subjected to a second annealing treatment in an inert atmosphere.

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

3. The method for reducing diamond stress according to claim 1, characterized in that: In the first annealing step, the temperature of the diamond is controlled at 500° C.-1000° C.; And / or, the holding time is controlled within 15min-30min; And / or, the cooling rate of the diamond is controlled at 1°C / min-20°C / min.

4. The method for reducing diamond stress according to claim 1, characterized in that: In the second annealing step, 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 first annealing step; And / or, the heat preservation time of the diamond is controlled within 10 min-30 min.

5. The method for reducing diamond stress 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., the temperature drop is stopped and the second annealing treatment is performed.

6. The method for reducing diamond stress according to claim 1, characterized in that: In the first annealing step, the diamond is heated by using a thermal field provided by the tantalum material; And / or, the distance between the diamond and the tantalum material is 5 mm-30 mm.

7. The method for reducing diamond stress according to claim 1, characterized in that: In the step of the second annealing treatment, the diamond is heated by utilizing the thermal field provided by the tantalum material; And / or, the distance between the diamond and the tantalum material is 5 mm-30 mm.

8. The method for reducing diamond stress according to claim 1, characterized in that: Introducing hydrogen gas to form a hydrogen-rich atmosphere, wherein the flow rate of the hydrogen gas is 100 sccm-500 sccm; And / or, in the first annealing step, the pressure is less than or equal to 10 kPa.

9. The method for reducing diamond stress according to claim 1, characterized in that: Inert gas is introduced to form an inert atmosphere, wherein 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 second annealing step, the pressure is controlled at 3 kPa-10 kPa.

10. The method for reducing diamond stress according to any one of claims 1 to 9, characterized in that: The following steps are involved: The diamond is placed on the sample stage of the hot wire CVD equipment, and then the tantalum wire is arranged on the hot wire holder; Close the vacuum chamber and evacuate the hot wire CVD device to a vacuum state; Passing hydrogen gas, turning on the power to heat the tantalum wire, and performing a first annealing treatment on the diamond using the heat field provided by the tantalum wire; Then the hydrogen gas is turned off, an inert gas is introduced, the tantalum wire is heated, and the diamond is subjected to a second annealing treatment using the heat field provided by the tantalum wire.

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