Method for prolonging batch production and growth time of monocrystal diamond

Abstract

The invention discloses a method for prolonging the batch production and growth time of monocrystal diamonds, and belongs to the technical field of diamond preparation. The method comprises the steps that seed crystals are placed in a substrate table and grow in a working cavity, the substrate table is provided with a concave part, the concave part is provided with a groove, the seed crystals are placed in the groove, a single crystal growth face is made to be lower than the upper surface of the substrate table by 0.6 mm or above, and the distance between every two adjacent seed crystals is larger than or equal to 1 mm; the single crystal growth comprises first-stage single crystal growth and second-stage single crystal growth, the first stage and the second stage comprise gas introduction and gas flow adjustment, and the gas introduced in the first stage comprises hydrogen and methane; gas introduced in the second stage comprises hydrogen, methane, oxygen and nitrogen; the volume concentration of the methane introduced in the first stage is smaller than that of the methane introduced in the second stage; the temperature of the first stage is lower than that of the second stage. The method can prolong the time length of batch production and single growth of the single crystal diamond and ensure the quality of the diamond.

Description

Technical Field

[0001] The present application relates to the technical field of diamond preparation, and in particular to a method for extending the growth time of batch production of single crystal diamonds. Background Art

[0002] Microwave plasma vapor deposition (MPCVD) is used to mass produce single crystal diamonds. Especially in the cultivation of diamonds, rough diamonds need to reach a certain weight or thickness, which usually requires multiple growths to meet the weight or thickness requirements, increasing the production cycle and cost. At the same time, multiple growths will inevitably reduce the yield rate of rough diamonds grown in batches. From a technical perspective, there are three main reasons that force companies to adopt this method for batch growth. First, if the growth time of a single single crystal is too long, various defects will appear on the surface, including polycrystalline points and crystal orientation changes, which will eventually affect the quality of the single crystal and the overall yield rate. Secondly, due to the large number of single crystals in batch single crystal growth, the single crystals will be connected to each other after a certain period of growth, and then squeezed and pulled, resulting in a significant increase in the overall temperature. The usual measures are to reduce power and pressure to achieve the purpose of cooling, but this measure will significantly reduce the growth rate of the single crystal. Therefore, based on this situation, the growth time of a single single crystal is usually controlled within 200 hours. Summary of the invention

[0003] The present application provides a method for extending the growth time of single crystal diamond mass production, which can extend the single growth time of single crystal diamond mass production and ensure the quality of diamond.

[0004] This application is implemented as follows: The present application provides a method for extending the growth time of single crystal diamond batch production, comprising: Placing a seed crystal in a substrate stage and growing it in a working chamber, wherein the substrate stage is provided with a recessed portion, the recessed portion is provided with a groove, the seed crystal is placed in the groove and the single crystal growth surface is lower than the upper surface of the substrate stage by more than 0.6 mm, and the distance between two adjacent seed crystals is ≥1 mm; The single crystal growth includes a first-stage single crystal growth and a second-stage single crystal growth. Both the first stage and the second stage include introducing gas and adjusting gas flow. The gas introduced in the first stage includes hydrogen and methane; the gas introduced in the second stage includes hydrogen, methane, oxygen and nitrogen; the volume concentration of methane introduced in the first stage is less than the volume concentration of methane introduced in the second stage; the temperature of the first stage is less than the temperature of the second stage.

[0005] In one embodiment, the distance between two adjacent seed crystals is 1-2 mm.

[0006] In one embodiment, the depth of the recessed portion is 1 to 3 mm.

[0007] In one embodiment, the methane volume concentration in the first stage is 1-5%, and the methane volume concentration in the second stage is 5-10%.

[0008] In one embodiment, the gas introduced in the first stage also includes nitrogen, and the nitrogen flow rate introduced in the first stage is greater than the nitrogen flow rate introduced in the second stage; the nitrogen flow rate in the first stage is 1~5sccm, and the nitrogen flow rate in the second stage is 0.1~1sccm.

[0009] In one embodiment, the temperature of the first stage is 750-900°C, and the temperature of the second stage is 850-1000°C.

[0010] In one embodiment, the microwave powers of the first stage and the second stage are both 4~6kw, the pressure in the working chamber is both 130~170torr, and the flow rate of hydrogen introduced is both 300~500sccm; the gas introduced in the first stage also includes oxygen, the flow rate of oxygen introduced in the first stage is 0.1~1sccm, and the flow rate of oxygen introduced in the second stage is 0.5~1.5sccm.

[0011] In one embodiment, the duration of the first stage single crystal growth is 6 to 24 hours.

[0012] In one embodiment, the lateral expansion rate of the single crystal around the single crystal during the single crystal growth process is 5-7 um / h.

[0013] In one embodiment, during the single crystal growth process, the adjacent seed crystals are connected for 120 to 150 hours.

[0014] The beneficial effects of the embodiments of the present application are at least as follows: The method of extending the growth time of mass production of single crystal diamonds in the present application is, in the first stage, to make the growth surface of the single crystal as flat as possible through a low methane concentration and a suitable temperature, reduce surface defects, ensure that the growth mode is a typical step growth of diamond single crystals, and ensure smooth growth in the next stage; the suitable temperature and methane concentration can inhibit polycrystalline around the single crystal, avoid premature polycrystalline around the single crystal, and cause the growth time to be reduced. In the second stage, a higher methane concentration is used to ensure that the growth speed meets the production requirements, the appropriate amount of nitrogen is used to achieve the color requirements of the cultured diamond, and the appropriate temperature ensures that the crystal orientation of the growth surface can remain unchanged for a long time and reduce the generation of other defects. At the same time, since the distance between two adjacent seed crystals placed in the groove is ≥1mm, the single crystal connection time during the growth process can be extended, and the lateral expansion speed around the single crystal can be controlled in conjunction with the single crystal growth process conditions to ensure that the seed crystal connection time is extended; in addition, the seed crystal is placed in the groove and the single crystal growth surface is made lower than the upper surface of the substrate table by more than 0.6mm, so that the plasma ball is suspended above the substrate table away from the seed crystal, thereby improving the plasma discharge around the seed crystal, and at the same time, in conjunction with the single crystal growth process conditions, improving the severity of polycrystalline around the seed crystal, so that the overall temperature mutation after the seed crystal is connected is improved, ensuring that the power pressure change is small, reducing the expansion speed of the surrounding polycrystalline to the center of the single crystal, and weakening the mutual extrusion and pulling during the single crystal connection process, so that the overall temperature after connection will not jump significantly, and the quality of the single crystal diamond can be guaranteed after the growth time is extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 This is a schematic structural diagram of a substrate stage according to Example 1 of the present application; Figure 2 is a cross-sectional view of the substrate stage of Example 1 of the present application; Figure 3 This is a schematic structural diagram of a substrate stage in Comparative Example 1 of the present application; Figure 4 This is a cross-sectional view of the substrate stage of comparative example 1 of the present application.

[0017] Icons: 11- substrate stage; 111- recessed portion; 112- groove; 113- boss; 12- seed crystal. DETAILED DESCRIPTION

[0018] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0019] The following is a specific description of the method for extending the growth time of single crystal diamond batch production according to the embodiment of the present application: A method for extending the growth time of single crystal diamond batch production, comprising the following steps: (1) Seed screening. The thickness difference of the screened seeds is ≤0.05mm, the side length difference is ≤0.1mm, the color is uniform, the polishing type is consistent (the polishing type of the seeds in the same working chamber can only be single polishing, double polishing or no polishing, that is, the polishing type of the seeds in the same working chamber can be either all single polishing, all double polishing, or no polishing), and there are no surface defects.

[0020] (2) Pretreatment: Pretreatment is performed on the seed crystal, substrate stage and working chamber respectively.

[0021] The seed crystal pretreatment step includes: pickling the seed crystal with concentrated sulfuric acid, heating to 200-300°C, and keeping warm for 30-60 minutes; after acid treatment (i.e., pickling with concentrated sulfuric acid), ultrasonic cleaning with deionized water for 1-3 times, ultrasonic cleaning with anhydrous ethanol for 1-3 times, and ultrasonic cleaning with acetone for 1-3 times, and the ultrasonic cleaning time of each chemical reagent is 5-15 minutes each time.

[0022] The steps of substrate stage pretreatment include: using a wire drawing cloth to treat the working surface and heat dissipation surface of the substrate stage, and then using anhydrous ethanol to ultrasonically clean it 1 to 2 times, each time for 5 to 15 minutes, and then wiping the working surface with acetone.

[0023] Please refer to Figure 1 and Figure 2 The substrate stage 11 is provided with a recessed portion 111, the recessed portion 111 is provided with a groove 112, the groove 112 is provided with a plurality of bosses 113, the bosses 113 are arranged at intervals, and the seed crystal 12 is arranged in the groove 112 and between the bosses 113. When the seed crystal 12 is placed in the groove 112, the single crystal growth surface can be lower than the upper surface of the substrate stage 11 by more than 0.6 mm, and the distance between two adjacent seed crystals 12 is ≥1 mm.

[0024] In some embodiments, the distance between two adjacent seed crystals 12 is 1-2 mm, for example, any one of 1 mm, 1.2 mm, 1.5 mm, 1.8 mm and 2 mm, or a value between any two of them.

[0025] In some embodiments, the depth of the recessed portion 111 is 1-3 mm, for example, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm.

[0026] The steps of pretreatment of the working chamber include: placing the pretreated substrate stage into the working chamber, starting the microwave and introducing hydrogen and oxygen, wherein the microwave power is 5~6kw, the pressure of the working chamber is 140~170torr, the hydrogen flow rate is 300~500sccm, the oxygen flow rate is 3~5sccm, the temperature of the substrate stage is 600~800℃, and the plasma etching time is 3~6h.

[0027] (3) Maintain the pressure in the working chamber, and the pressure rise rate (i.e., the difference in pressure increase per unit time when the working chamber is not evacuated) is ≤2 Pa / h. Maintaining the pressure in the working chamber enables the vacuum inspection of the equipment to verify the sealing performance of the equipment.

[0028] (4) Seed introduction: Measure the thickness of each seed crystal and record it, place the seed crystal of corresponding thickness on the substrate stage, ensure that there is no foreign matter on the surface of the seed crystal, place the substrate stage together with the seed crystal into the working chamber, and then slowly evacuate the working chamber to e -3 Below torr.

[0029] (5) Seed crystal heating: Introduce hydrogen into the working chamber and start the microwave to raise the seed crystal temperature to above 700°C within 10 to 30 minutes.

[0030] (6) Seed etching: hydrogen and oxygen are introduced into the working chamber, the microwave power is 4~6 kW, the pressure in the working chamber is 130~170 torr, the hydrogen flow rate is 300~500 sccm, the oxygen flow rate is 1~5 sccm, the seed temperature is 700~900℃, and the etching time is 10~60 min.

[0031] (7) Single crystal growth: The first stage of single crystal growth: hydrogen and methane are introduced; The second stage of single crystal growth: hydrogen, methane, oxygen and nitrogen are introduced.

[0032] The volume concentration of methane introduced in the first stage is lower than that in the second stage; and the temperature in the first stage is lower than that in the second stage.

[0033] In the first stage, through lower methane concentration and appropriate temperature, the growth surface of the single crystal is made as flat as possible, surface defects are reduced, and the growth mode is guaranteed to be the typical step growth of diamond single crystal, ensuring smooth growth in the next stage. The appropriate temperature and methane concentration can suppress the polycrystal around the single crystal, avoiding the premature appearance of polycrystal around the single crystal, which will reduce the growth time.

[0034] The microwave power in the first stage is 4~6kw, the pressure in the working chamber is 130~170torr, the volume concentration of methane introduced is 1~5%, the hydrogen flow rate is 300~500sccm, and the temperature condition is 750~900℃. The single crystal growth time in the first stage is 6h~24h.

[0035] Optionally, the methane volume concentration in the first stage is 1%, 2%, 3%, 4% or 5%; optionally, the temperature condition in the first stage is any one of 750°C, 780°C, 800°C, 820°C, 850°C, 880°C and 900°C, or a value between any two of them; optionally, the microwave power in the first stage is 4kW, 5kW or 6kW; optionally, the pressure in the working chamber in the first stage is 130torr, 140torr, 150torr, 160torr or 170torr; optionally, the hydrogen flow rate in the first stage is 300sccm, 400sccm or 500sccm.

[0036] Furthermore, the gas introduced in the first stage also includes oxygen; optionally, the flow rate of oxygen introduced in the first stage is 0.1~1sccm.

[0037] In the first stage, a relatively low methane concentration and a suitable temperature are used to make the single crystal growth surface as flat as possible. The introduction of oxygen can further reduce surface defects, ensure that the growth mode is a typical step growth of a diamond single crystal, and ensure smooth growth in the next stage. The suitable temperature and methane concentration can inhibit polycrystalline around the single crystal, avoid premature polycrystalline around the single crystal, and reduce the growth time. Exemplarily, the oxygen flow rate in the first stage is 0.1sccm, 0.2sccm, 0.3sccm, 0.4sccm, 0.5sccm, 0.6sccm, 0.7sccm, 0.8sccm, 0.9sccm or 1sccm.

[0038] Furthermore, the gas introduced in the first stage also includes nitrogen, and the flow rate of the nitrogen introduced in the first stage is greater than the flow rate of the nitrogen introduced in the second stage.

[0039] In the first stage, a lower methane concentration and a higher nitrogen volume are used to make the single crystal growth surface as flat as possible, reduce surface defects, ensure the growth mode is a typical step growth of diamond single crystal, and ensure smooth growth in the next stage; a higher nitrogen volume and a lower temperature can inhibit polycrystalline around the single crystal, avoid premature polycrystalline around the single crystal, and reduce the growth time. Optionally, the nitrogen flow rate is 1~5sccm, for example, the nitrogen flow rate in the first stage is 1sccm, 2sccm, 3sccm, 4sccm or 5sccm.

[0040] In the second stage, a higher methane concentration is used to ensure the growth rate to meet production requirements, a lower nitrogen amount is used to achieve the color requirements of cultured diamonds, and appropriate temperature is used to ensure that the crystal orientation of the growth surface can remain unchanged for a long time and reduce the occurrence of other defects.

[0041] At the same time, since the distance between two adjacent seed crystals is greater than or equal to 1mm, the single crystal connection time during the growth process can be extended. The lateral expansion speed around the single crystal can be controlled to be 5~7um / h in conjunction with the single crystal growth process conditions, so that the connection time of adjacent seed crystals is extended to 120h~150h; in addition, the seed crystal is placed in the groove and the single crystal growth surface is lower than the upper surface of the substrate table by more than 0.6mm, so that the plasma ball is suspended above the substrate table away from the seed crystal, thereby improving the plasma discharge around the seed crystal. At the same time, the single crystal growth process conditions are used to improve the severity of polycrystalline around the seed crystal, so that the overall temperature mutation after the seed crystal is connected is improved, the power pressure change is ensured to be small, the expansion speed of the surrounding polycrystalline to the center of the single crystal is reduced, and the mutual extrusion and pulling are weakened during the single crystal connection process, so that the overall temperature after connection will not jump significantly, and the quality of the single crystal diamond can be guaranteed after the growth time is extended.

[0042] Among them, the microwave power of the second stage is 4~6kw, the pressure in the working chamber is 130~170torr, the volume concentration of methane introduced is 5~10%, the nitrogen flow rate is 0.1~1sccm, the hydrogen flow rate is 300~500sccm, the oxygen flow rate is 0.5~1.5sccm, and the temperature condition is 850~1000℃.

[0043] Optionally, the methane volume concentration in the second stage is 5%, 6%, 7%, 8%, 9% or 10%; optionally, the nitrogen flow rate in the second stage is 0.1sccm, 0.2sccm, 0.3sccm, 0.4sccm, 0.5sccm, 0.6sccm, 0.7sccm, 0.8sccm, 0.9sccm or 1sccm; optionally, the temperature condition of the second stage is any one of 850℃, 880℃, 900℃, 920℃, 950℃, 980℃ and 1000℃, or a value between any two of them. Optionally, the microwave power of the second stage is 4 kW, 5 kW or 6 kW; optionally, the pressure in the working chamber of the second stage is 130 torr, 140 torr, 150 torr, 160 torr or 170 torr; optionally, the hydrogen flow rate of the second stage is 300 sccm, 400 sccm or 500 sccm; optionally, the oxygen flow rate of the second stage is 0.5 sccm, 0.6 sccm, 0.7 sccm, 0.8 sccm, 0.9 sccm, 1 sccm, 1.1 sccm, 1.2 sccm, 1.3 sccm, 1.4 sccm or 1.5 sccm.

[0044] (8) Cooling treatment: After the single crystal growth is completed, turn off all gases except hydrogen, maintain for 30min~60min, and then cool down for 3h~6h to below 300℃.

[0045] (9) Annealing treatment: Keep hydrogen flowing into the working chamber and keep the microwave on. Raise the temperature of the single crystal diamond to 1100~1300℃ within 30~60min and maintain this temperature for 30~180min. Then cool the single crystal diamond to room temperature within 30~60min.

[0046] The method for prolonging the growth time of single crystal diamond mass production of the present application is further described in detail below in conjunction with the embodiments. Example

[0047] This embodiment provides a method for extending the growth time of single crystal diamond batch production, which includes the following steps: (1) Seed crystal screening. The thickness difference of the screened seeds is ≤0.05mm, the side length difference is ≤0.1mm, the color is uniform, the polishing type is consistent, and there are no surface defects.

[0048] (2) Pretreatment: The seed crystal, substrate stage 11 and working chamber are pretreated respectively.

[0049] Among them, the step of seed pretreatment includes: pickling the seed with concentrated sulfuric acid, heating to 250°C, and keeping warm for 50 minutes; after acid treatment (i.e., pickling with concentrated sulfuric acid), ultrasonic cleaning with deionized water twice, ultrasonic cleaning with anhydrous ethanol twice, and ultrasonic cleaning with acetone twice, and the ultrasonic cleaning time of each chemical reagent is 15 minutes each time.

[0050] The steps of pre-treating the substrate stage 11 include: treating the working surface and the heat dissipation surface of the substrate stage with a wire drawing cloth, then ultrasonically cleaning it with anhydrous ethanol twice, each time for 15 minutes, and then wiping the working surface with acetone.

[0051] Please refer to Figure 1 and Figure 2 , wherein the substrate stage 11 is provided with a recessed portion 111, the recessed portion 111 is provided with a groove 112, the groove 112 is provided with a plurality of bosses 113, the bosses 113 are arranged at intervals, and the seed crystal 12 is arranged in the groove 112 and between the bosses 113. When the seed crystal 12 is placed in the groove 112, the single crystal growth surface can be lowered by 1 mm from the upper surface of the substrate stage 11, and the distance between two adjacent seed crystals is 1.5 mm.

[0052] The steps of pretreatment in the working chamber include: placing the pretreated substrate stage 11 into the working chamber, starting the microwave and introducing hydrogen and oxygen, wherein the microwave power is 5 kW, the pressure of the working chamber is 160 Torr, the hydrogen flow rate is 450 sccm, the oxygen flow rate is 4 sccm, the temperature of the substrate stage 11 is 750°C, and the plasma etching time is 5 hours.

[0053] (3) Maintain the pressure in the working chamber, and the pressure rise rate (i.e., the difference in pressure increase per unit time when the working chamber is not evacuated) is ≤2 Pa / h. Maintaining the pressure in the working chamber can be used to check the vacuum of the equipment and confirm that the equipment is well sealed.

[0054] (4) Seed introduction: Measure the thickness of each seed crystal and record it, place the seed crystal of corresponding thickness on the substrate stage, ensure that there is no foreign matter on the surface of the seed crystal, place the substrate stage together with the seed crystal into the working chamber, and then slowly evacuate the working chamber to e ~3 Below torr.

[0055] (5) Seed crystal heating: Hydrogen is introduced into the working chamber and microwaves are started to raise the seed crystal temperature to 850°C within 20 minutes.

[0056] (6) Seed etching: hydrogen and oxygen were introduced into the working chamber. The microwave power was 5 kW, the pressure in the working chamber was 160 torr, the hydrogen flow rate was 450 sccm, the oxygen flow rate was 3 sccm, the seed temperature was 800 °C, and the etching time was 30 min.

[0057] (7) Single crystal growth: The first stage of single crystal growth: hydrogen, methane, oxygen and nitrogen are introduced. The initial microwave power of the first stage is 5 kW, the initial pressure in the working chamber is 160 torr, the volume concentration of methane introduced is 4%, the nitrogen flow rate is 3 sccm, the hydrogen flow rate is 400 sccm, the oxygen flow rate is 0.2 sccm, the temperature condition is 850°C, and the single crystal growth time of the first stage is 18 hours.

[0058] Second stage single crystal growth: adjust the methane flow, oxygen flow and nitrogen flow. The initial microwave power of the second stage is 5.7 kW, the initial pressure in the working chamber is 165 torr, the volume concentration of methane introduced is 7%, the nitrogen flow is 0.6 sccm, the oxygen flow is 0.7 sccm, the hydrogen flow is maintained at 400 sccm, and the temperature condition is 900 °C.

[0059] (8) Cooling treatment: After the single crystal growth is completed, turn off all gases except hydrogen, maintain for 45 minutes, and then cool down for 4 hours.

[0060] (9) Annealing treatment: Hydrogen is introduced into the working chamber and the microwave is kept on. The temperature of the single crystal diamond is raised to 1300°C within 45 minutes and maintained at this temperature for 120 minutes. Then, the temperature of the single crystal diamond is cooled to room temperature within 45 minutes.

[0061] Growth results: After the first stage of single crystal growth, the single crystal growth surface became flat, and the growth mode was the typical step growth of diamond single crystal. During the second stage of single crystal growth, no polycrystalline points appeared on the single crystal surface or the crystal orientation changed. After 140 hours of growth, the seed crystal was fully connected. No large temperature difference occurred during the single crystal connection process. The polycrystalline expansion around the seed crystal was well controlled. After full connection, the power was maintained at 98% of the initial power. Growth continued to 200 hours, at which time the power was still maintained at 90% of the initial power. At the same time, there was little polycrystalline expansion around, achieving high-quality growth of 200 hours in a single time. Example

[0062] Example 2 provides a method for extending the growth time of single crystal diamond mass production. Compared with Example 1, the only difference is that the single crystal growth process conditions in the first stage are different from those in Example 1.

[0063] The process conditions for the first stage single crystal growth of Example 2 are to introduce hydrogen and methane. The initial microwave power is 5 kW, the initial pressure in the working chamber is 160 Torr, the volume concentration of methane introduced is 4%, the hydrogen flow rate is 400 sccm, the temperature condition is 850°C, and the single crystal growth time of the first stage is 18 hours.

[0064] Growth results: After the first stage of single crystal growth, the single crystal growth surface became flat, and the growth mode was the typical step growth of diamond single crystal. During the second stage of single crystal growth, no polycrystalline points appeared on the single crystal surface or the crystal orientation changed. After 140 hours of growth, the seed crystal was fully connected. No large temperature difference occurred during the single crystal connection process. The polycrystalline expansion around the seed crystal was well controlled. After full connection, the power was maintained at 98% of the initial power. Growth continued to 200 hours, at which time the power was still maintained at 90% of the initial power. At the same time, there was little polycrystalline expansion around, achieving high-quality growth of 200 hours in a single time. Example

[0065] Example 3 provides a method for extending the growth time of single crystal diamond mass production. Compared with Example 1, the only difference is that the single crystal growth process conditions in the first stage are different from those in Example 1.

[0066] The process conditions for the first stage single crystal growth of Example 3 are to introduce hydrogen, oxygen and methane. The initial microwave power is 5 kW, the initial pressure in the working chamber is 160 Torr, the volume concentration of methane introduced is 4%, the hydrogen flow rate is 400 sccm, the oxygen flow rate is 0.2 sccm, the temperature condition is 850°C, and the single crystal growth time of the first stage is 18 hours.

[0067] Growth results: After the first stage of single crystal growth, the single crystal growth surface became flat, and the growth mode was the typical step growth of diamond single crystal. During the second stage of single crystal growth, no polycrystalline points appeared on the single crystal surface or the crystal orientation changed. After 140 hours of growth, the seed crystal was fully connected. No large temperature difference occurred during the single crystal connection process. The polycrystalline expansion around the seed crystal was well controlled. After full connection, the power was maintained at 98% of the initial power. Growth continued to 200 hours, at which time the power was still maintained at 90% of the initial power. At the same time, there was little polycrystalline expansion around, achieving high-quality growth of 200 hours in a single time.

[0068] Comparative Example 1 Compared with Example 1, Comparative Example 1 is different in that the structure of the substrate stage 11 of Comparative Example 1 is different from that of Example 1, and the single crystal growth process conditions of Comparative Example 1 are different from those of Example 1.

[0069] Please refer to Figure 3 and Figure 4 , wherein the substrate stage 11 is provided with a recessed portion 111, the recessed portion 111 is provided with a groove 112, the groove 112 is provided with a plurality of bosses 113, the bosses 113 are arranged at intervals from each other, and the seed crystal 12 is arranged in the groove 112 and between the bosses 113. The top surface of the boss 113 is flush with the upper surface of the substrate stage 11, and the distance between two adjacent seed crystals 12 is 0.6 mm.

[0070] The single crystal growth process conditions of Comparative Example 1 are as follows: hydrogen, methane, oxygen and nitrogen are introduced. The initial microwave power is 5.7 kW, the initial pressure in the working chamber is 165 Torr, the volume concentration of methane introduced is 7%, the nitrogen flow rate is 0.6 sccm, the hydrogen flow rate is 400 sccm, the oxygen flow rate is 0.7 sccm, and the temperature condition is 950°C.

[0071] Growth results: Polycrystals began to appear around the single crystal after about 5 hours of growth. After 40 hours, the seed crystals were fully connected. At the same time, the temperature of some seed crystals was abnormally high during the connection process. The polycrystals around the seed crystals were rapidly expanding. After full connection, the power had dropped to 90% of the initial power. Growth continued for 120 hours. Due to the rapid expansion of polycrystals around the single crystal, the area of ​​the single crystal was significantly reduced. At the same time, the power had dropped to 80% of the initial power, which could no longer meet the power required for growth, so the growth had to be stopped.

[0072] This is because the distance between the crystal seeds is relatively close, and under the conditions of the single crystal growth process, the crystal seed connection time is relatively short. The substrate stage is not provided with a recessed portion 111, and is non-sinking. The discharge around the crystal seeds is relatively strong. Under the conditions of the single crystal growth process, the polycrystalline grows rapidly around the crystal seeds. The crystal seeds squeeze and pull each other during the connection process, resulting in a large change in the overall temperature of the crystal seeds, and even abnormally high temperatures of individual crystal seeds. In addition, the inventors of the present application found in their research that the distance between two adjacent crystal seeds 12 is less than 0.8 mm (for example, 0.4~0.8 mm), and it is impossible or difficult to extend the growth time of single crystal diamond.

[0073] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the single crystal growth process conditions of Comparative Example 2 are different from those of Example 1.

[0074] The single crystal growth process conditions of Comparative Example 2 are as follows: hydrogen, methane, oxygen and nitrogen are introduced. The microwave power is 5.7 kW, the pressure in the working chamber is 165 Torr, the methane concentration is 7%, the nitrogen flow rate is 0.6 sccm, the hydrogen flow rate is 400 sccm, the oxygen flow rate is 0.7 sccm, and the temperature condition is 950°C.

[0075] Growth results: Polycrystals began to appear around the single crystal after about 5 hours of growth. After 100 hours, the seed crystals were fully connected. At the same time, the temperature of some seed crystals was abnormally high during the connection process. The polycrystals around the seed crystals were rapidly expanding. After full connection, the power had dropped to 90% of the initial power. Growth continued until 130 hours. Due to the rapid expansion of polycrystals around the single crystal, the area of ​​the single crystal was significantly reduced. At the same time, the power had dropped to 80% of the initial power, which could no longer meet the power required for growth, so the growth had to be stopped.

[0076] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the substrate stage used in Comparative Example 3 is different from that in Example 1. The substrate stage used in Comparative Example 3 is the substrate stage described in Comparative Example 1.

[0077] Growth results: After 60 hours of growth, the seed crystals were fully connected. After full connection, the power had dropped to 90% of the initial power. After 150 hours of growth, the power had dropped to 80% of the initial power, which could no longer meet the power required for growth, so the growth had to be stopped.

[0078] Comparative Example 4 The only difference between Comparative Example 4 and Example 2 is that the substrate stage used in Comparative Example 4 is different from that in Example 2. The substrate stage used in Comparative Example 4 is the substrate stage described in Comparative Example 1.

[0079] Growth results: After 60 hours of growth, the seed crystals were fully connected. After full connection, the power had dropped to 90% of the initial power. After 150 hours of growth, the power had dropped to 80% of the initial power, which could no longer meet the power required for growth, so the growth had to be stopped.

[0080] Comparative Example 5 The only difference between Comparative Example 5 and Example 3 is that the substrate stage used in Comparative Example 5 is different from that in Example 3. The substrate stage used in Comparative Example 5 is the substrate stage described in Comparative Example 1.

[0081] Growth results: After 60 hours of growth, the seed crystals were fully connected. After full connection, the power had dropped to 90% of the initial power. After 150 hours of growth, the power had dropped to 80% of the initial power, which could no longer meet the power required for growth, so the growth had to be stopped.

[0082] The above description is only a specific embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for extending the growth time of single crystal diamond batch production, characterized in that: include: Placing a seed crystal in a substrate stage and growing it in a working chamber, wherein the substrate stage is provided with a recessed portion, the recessed portion is provided with a groove, the seed crystal is placed in the groove and the single crystal growth surface is lower than the upper surface of the substrate stage by more than 0.6 mm, and the distance between two adjacent seed crystals is ≥1 mm; The single crystal growth includes a first-stage single crystal growth and a second-stage single crystal growth. Both the first stage and the second stage include introducing gas and adjusting gas flow. The gas introduced in the first stage includes hydrogen and methane; the gas introduced in the second stage includes hydrogen, methane, oxygen and nitrogen; the volume concentration of methane introduced in the first stage is less than the volume concentration of methane introduced in the second stage; the temperature of the first stage is less than the temperature of the second stage.

2. The method for extending the growth time of single crystal diamond mass production according to claim 1, characterized in that: The distance between two adjacent seed crystals is 1-2 mm.

3. The method for extending the growth time of single crystal diamond mass production according to claim 1, characterized in that: The depth of the recessed portion is 1-3 mm.

4. The method for extending the growth time of single crystal diamond mass production according to any one of claims 1 to 3, characterized in that: The methane volume concentration in the first stage is 1-5%, and the methane volume concentration in the second stage is 5-10%.

5. The method for extending the growth time of single crystal diamond mass production according to any one of claims 1 to 3, characterized in that: The gas introduced in the first stage also includes nitrogen, and the nitrogen flow rate introduced in the first stage is greater than the nitrogen flow rate introduced in the second stage; the nitrogen flow rate in the first stage is 1~5sccm, and the nitrogen flow rate in the second stage is 0.1~1sccm.

6. The method for extending the growth time of single crystal diamond mass production according to any one of claims 1 to 3, characterized in that: The temperature of the first stage is 750-900°C, and the temperature of the second stage is 850-1000°C.

7. The method for extending the growth time of single crystal diamond mass production according to any one of claims 1 to 3, characterized in that: The microwave powers of the first stage and the second stage are both 4~6kw, the pressure in the working chamber is both 130~170torr, and the flow rate of hydrogen introduced is both 300~500sccm; the gas introduced in the first stage also includes oxygen, the flow rate of oxygen introduced in the first stage is 0.1~1sccm, and the flow rate of oxygen introduced in the second stage is 0.5~1.5sccm.

8. The method for extending the growth time of single crystal diamond mass production according to any one of claims 1 to 3, characterized in that: The duration of the single crystal growth in the first stage is 6 to 24 hours.

9. The method for extending the growth time of single crystal diamond mass production according to any one of claims 1 to 3, characterized in that: The lateral expansion speed of the single crystal around the single crystal during the single crystal growth process is 5-7 um / h.

10. The method for extending the growth time of single crystal diamond mass production according to any one of claims 1 to 3, characterized in that: During the single crystal growth process, the adjacent seed crystals are connected for 120 to 150 hours.

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