A large-size diamond deposition table, a large-size diamond growth method

Abstract

The application belongs to the field of semiconductors, and specifically discloses a large-size diamond deposition table and a large-size diamond growth method. The large-size diamond deposition table comprises a substrate, a buffer layer, a molybdenum ring and a base, the substrate, the buffer layer and the base are sequentially arranged from top to bottom, and the center lines of the substrate, the buffer layer and the base overlap; the molybdenum ring is sleeved on the substrate, the buffer layer and the base at the same time, and the molybdenum ring and the base are threadedly connected; the top end of the molybdenum ring is fixedly connected with a baffle, and the top surface of the substrate is provided with a mounting groove for mounting the baffle. In the deposition table, the molybdenum ring provides stable and rigid constraint at high temperature, cooperates with the buffer layer to relieve the interface thermal expansion stress, the baffle and the mounting groove are accurately positioned, the plasma and the temperature field distribution are optimized, the warping generated in the growth process can be effectively inhibited, and the uniformity and quality consistency of crystal growth are ensured.

Description

Technical Field

[0001] This invention belongs to the field of semiconductors and relates to a diamond deposition process, specifically to a large-size diamond deposition stage and a method for growing large-size diamonds. Background Technology

[0002] Diamond, with its ultra-high thermal conductivity, ultra-wide bandgap, and excellent optical transmittance, has expanded from traditional grinding applications to core fields such as heat dissipation, semiconductors, and high-end optics, becoming a key material for cutting-edge industries such as AI chips, 5G base stations, and quantum devices. The current market presents a three-way balance between heat dissipation, semiconductors, and high-end grinding. While the heat dissipation sector is experiencing explosive demand growth and semiconductor-grade large-size substrates have achieved technological breakthroughs, high-end applications continue to demand higher requirements for the size, purity, and uniformity of diamond. The bottleneck in the preparation of large-size, high-quality polycrystalline diamond still restricts its large-scale application in optics and other fields. The industry urgently needs to solve these technical challenges to unleash market potential.

[0003] The artificial preparation of diamond has formed two main routes: high-temperature high-pressure (HPHT) and chemical vapor deposition (CVD). HPHT technology simulates the natural diamond formation environment, using a catalyst to convert carbon sources under high temperature and pressure, and has the advantages of large scale and low cost. It is mainly used for the production of industrial-grade single crystal and polycrystalline diamond. CVD technology, on the other hand, uses energy input to dissociate and epitaxially grow carbon-containing precursors under low pressure. Among them, microwave plasma CVD (MPCVD) has become the first choice for the preparation of high-quality diamonds due to the absence of electrode contamination and high energy density. It is further subdivided into two types of equipment: 2450MHz and high-power 915MHz. The former has an effective growth area of ​​only about 3 inches, while the latter is the core equipment for the preparation of large-size polycrystalline diamonds. Conventional CVD technologies such as hot filament CVD and DC arc CVD are difficult to meet the purity requirements of high-end applications due to electrode contamination problems.

[0004] In existing fabrication processes, the non-uniformity and stress accumulation of the diamond growth environment can easily lead to problems such as warping, growth partitioning, and poor uniformity in large-size, high-quality polycrystalline diamonds. Although high-power 915MHz MPCVD can support large-size growth, the electric field distribution within the resonant cavity is easily affected by the design of the molybdenum stage structure. An unreasonable molybdenum stage structure can cause uneven plasma density and distribution of active groups, resulting in differences in crystal growth rate and grain morphology between the center and edge regions, forming growth partitions. At the same time, differences in temperature stages and chemical composition in different regions during growth will generate internal stress. As the diamond film thickness increases, stress accumulates continuously, eventually leading to material warping and deformation. In addition, factors such as the flatness difference of large-size substrates and plasma boundary effects further exacerbate the non-uniformity of the crystal structure, affecting the overall quality of polycrystalline diamonds. Summary of the Invention

[0005] In view of the defects and deficiencies of the existing technology, the present invention provides, firstly, a deposition stage for large-size diamonds; and secondly, a method for growing large-size diamonds.

[0006] In a first aspect, the present invention provides a deposition stage for large-size diamond, comprising a substrate, a buffer layer, a molybdenum ring, and a base, wherein the substrate, the buffer layer, and the base are arranged sequentially from top to bottom, and the center lines of the substrate, the buffer layer, and the base overlap. The molybdenum ring is simultaneously sleeved on the sidewalls of the substrate, the buffer layer, and the base, and the molybdenum ring and the base are threaded together. A baffle is fixedly connected to the top end of the molybdenum ring, and a mounting groove for mounting the baffle is provided on the top surface of the substrate.

[0007] Through research, the inventors discovered that the coaxial nested deposition stage of the present invention, through the concentric arrangement of the substrate, buffer layer and base, combined with the integrated nesting and threaded fastening of the three by the molybdenum ring, utilizes the high-temperature stability and rigid constraint of the molybdenum material to suppress the deformation caused by the accumulation of internal stress during the growth of the substrate and diamond, avoids the temperature difference caused by the deformation of the substrate and diamond, ensures the uniformity of the temperature of the substrate and diamond during the growth process, and ensures the consistency of crystal growth rate and crystal quality.

[0008] Preferably, the end of the baffle located inside the molybdenum ring has a rounded corner, the arc-shaped convex surface of the rounded corner faces the mounting groove, and the side of the mounting groove away from the molybdenum ring is provided with an arc-shaped transition surface, the arc-shaped concave surface of the arc-shaped transition surface and the rounded corner are arranged opposite to each other.

[0009] Through research, the inventors discovered that by setting rounded corners on the inner side of the baffle and providing arc-shaped transition surfaces at corresponding positions in the mounting groove, the edge effects caused by microwaves can be effectively eliminated, preventing cracks, chipping, or localized deformation at sharp corners. This further improves temperature uniformity, further suppresses warping of the substrate and diamond film at high temperatures, and enhances the uniformity and structural integrity of crystal growth.

[0010] Preferably, an annular gap is formed between the baffle and the mounting groove.

[0011] Preferably, the upper surface of the baffle is higher than the upper surface of the substrate.

[0012] Preferably, the substrate is made of silicon carbide, with a warpage ≤50μm, roughness ≤2nm, thickness ≥5mm, and resistivity ≤1000Ω·cm.

[0013] Preferably, the buffer layer is any one or two of copper and silver; the thickness of the buffer layer is 0.01~0.02mm.

[0014] Through research, the inventors discovered that by utilizing the ultra-high thermal conductivity of the buffer layer, the heat on the substrate surface can be rapidly homogenized, eliminating local hot spots and temperature stages. At the same time, relying on its thermal expansion coefficient, which is between that of the substrate and the base, it can serve as a stage buffer layer to alleviate the stress caused by the difference in thermal expansion at the interface, thereby reducing the causes of warping from both the thermal field and stress field perspectives.

[0015] Secondly, the present invention provides a method for growing large-size diamonds, comprising the following steps: Step 1: Place the above deposition stage into the bias MPCVD equipment to perform bias etching, bias nucleation and growth processes in sequence; Step 2: After growth is complete, proceed to the annealing process and cooling to obtain the crude product; Step 3: Place the crude product into a static pressure device for secondary annealing and cooling to obtain the large-size diamond.

[0016] Preferably, during the bias etching process, hydrogen gas is continuously introduced into the reaction system at a flow rate of 1000~4000 sccm; the bias voltage is (-300)~(-250) V; the bias pressure is 24~30 kPa; the temperature in the reaction system is 750~850℃; and the bias etching time is 1~2 h.

[0017] Through research, the inventors discovered that controllable physical bombardment and chemical etching can be achieved by high-flow hydrogen plasma driven by negative bias. This can precisely remove oxide layers, impurities, and damaged layers from the substrate surface, while simultaneously constructing uniform micro-defects and highly active silicon dangling bonds in a directional manner, forming high-density nucleation sites. This lays a clean and highly active interface foundation for the subsequent uniform and dense nucleation of diamond, avoiding substrate damage caused by excessive etching and ensuring the quality of crystal growth.

[0018] Preferably, during the bias nucleation process, methane and hydrogen are simultaneously introduced into the reaction system, and the volume ratio of methane to hydrogen in the reaction system is controlled to be 3.5%~8%; the hydrogen flow rate is 1000~4000 sccm; the bias voltage is (-200)~(-150) V; the bias pressure is 21-25 kPa; the temperature in the reaction system is 700~780℃; and the bias nucleation time is 1~2 h.

[0019] Preferably, when the growth process includes a control stage and a stable growth stage, the growth temperature, methane concentration and pressure are adjusted to the target parameters sequentially during the control stage, and then oxygen is introduced to carry out the stable growth stage.

[0020] Further optimization involves using the target temperature of the bias nucleation process as the initial temperature during the control phase, gradually increasing the temperature in the reaction system from 700~780℃ to 780~950℃. The temperature gradient for each phase is 40~60℃, the heating rate is 2℃ / min, and each phase is maintained at this temperature for 0.4~0.6h.

[0021] Further optimization involves using the methane and hydrogen concentrations from the bias nucleation process as initial concentrations during the regulation phase. The volume ratio of methane to hydrogen is reduced from (3.5%~8%):1 to (2.5%~3.5%):1, with a regulation gradient of 0.4%~0.6% for each stage. Each stage lasts 0.5~1 hours, and the growth pressure is 20~25 kPa.

[0022] Through research, the inventors discovered that by using a phased, gradual process of varying temperature and methane concentration, the growth environment can be smoothly transitioned, avoiding thermal stress and lattice mismatch caused by sudden parameter changes. This effectively reduces crystal defects, internal stress, and warpage, while simultaneously improving grain uniformity and density, thereby producing large-size, low-warpage, and high-optical-quality diamond windows.

[0023] Preferably, during the stable growth stage, the oxygen concentration in the reaction system is 0.01~0.1 vol%, the growth time is 300~500 h, and the growth pressure is 20~25 kPa.

[0024] Preferably, during annealing and cooling, methane is stopped from being introduced, and argon is introduced after the methane concentration reaches 0. The volume ratio of argon to hydrogen in the reaction system is controlled to be 10%~20%:1. The annealing temperature is 1000~1100℃, and the annealing time is 0.3~1h. After annealing is completed, the mixture is cooled to room temperature.

[0025] Preferably, the heating rate during annealing is 2~5℃ / min; the cooling rate is 2~5℃ / min.

[0026] Preferably, the secondary annealing is carried out in an argon atmosphere, with an annealing temperature of 1000~1500℃, an annealing pressure of 100~150MPa, and an annealing time of 4~5h.

[0027] Further optimization is to use an annealing temperature of 1300~1500℃ during the second annealing.

[0028] Compared with the prior art, one or more technical solutions provided by the present invention have at least one of the following beneficial effects: (1) The present invention adopts a coaxial nested deposition stage, in which the substrate, buffer layer and base are concentrically arranged, and the outer side is fitted with a molybdenum ring and threaded fastening. The molybdenum ring provides stable rigid constraint at high temperature, and together with the buffer layer, it relieves the thermal expansion stress at the interface. At the same time, the baffle and mounting groove are precisely positioned to optimize the plasma and temperature field distribution, which can effectively suppress the warping generated during the growth process and ensure the uniformity and quality consistency of crystal growth.

[0029] (2) During the growth of polycrystalline diamond, polycrystalline diamond is grown on the baffle. The annular gap can prevent the polycrystalline substrate from sticking together with the polycrystalline baffle, reducing the probability of diamond cracking during the cooling process.

[0030] (2) This invention uses hydrogen plasma bias etching to efficiently clean and activate the substrate surface, remove impurities and directionally etch silicon in silicon carbide to construct high-density nucleation sites, providing a stable interface for uniform diamond nucleation; on this basis, bias nucleation is performed using appropriate parameters to achieve high-density and high-uniformity crystal nucleation; in the subsequent growth stage, temperature and methane concentration are gradually controlled in stages to ensure a smooth transition of process conditions, effectively reduce internal stress and lattice defects caused by parameter mutations, suppress film warping and uneven growth, and finally obtain large-size, low-warping, and high-crystal-quality diamond optical window material. Attached Figure Description

[0031] Figure 1 The overall structure of the deposition stage for large-size diamonds provided in Example 1; Figure 2 for Figure 1 A magnified structural diagram of part A in the middle.

[0032] The reference numerals in the attached diagram are as follows: 1. Substrate; 2. Buffer layer; 3. Base; 4. Molybdenum ring; 5. Baffle; 6. Mounting groove; 7. Rounded corner; 8. Arc transition surface; 9. Annular gap. Detailed Implementation

[0033] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0034] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0035] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0036] Example 1: A deposition stage for large-sized diamonds, reference Figure 1 The system comprises a substrate 1, a buffer layer 2, a molybdenum ring 4, and a base 3. The substrate 1 is made of silicon carbide, with a warpage ≤50μm, a roughness ≤2nm, a thickness ≥5mm, and a resistivity ≤1000Ω·cm. The substrate 1, buffer layer 2, and base 3 are all cylindrical, with their centerlines overlapping. The substrate 1, buffer layer 2, and base 3 are arranged sequentially from top to bottom.

[0037] The molybdenum ring 4 is simultaneously fitted onto the substrate 1, the buffer layer 2, and the base 3, and the molybdenum ring 4 and the base 3 are threadedly fixedly connected. A baffle 5 is fixedly connected to the top of the molybdenum ring 4. The baffle 5 and the sidewall of the molybdenum ring 4 are perpendicular to each other, and the baffle 5 is located on the inner side of the molybdenum ring 4.

[0038] Reference Figure 1-2 The substrate 1 has a mounting groove 6 for mounting the baffle 5. The baffle 5 has a rounded corner 7 on the side away from the molybdenum ring 4, and the arc-shaped convex surface of the rounded corner 7 faces the mounting groove 6. The mounting groove 6 has an arc-shaped transition surface 8 on the side away from the molybdenum ring 4. When the baffle 5 is installed in the mounting groove 6, an annular gap 9 is formed between the rounded corner 7 and the arc-shaped transition surface 8, and the upper surface of the baffle 5 is flush with or higher than the upper surface of the substrate 1.

[0039] In this specific embodiment, two transition layers are provided. In practical applications, the thickness of the transition layer can be selected according to actual needs. Generally speaking, the larger the size of the diamond to be deposited, the thicker the transition layer should be, which can increase the temperature range in the radial direction of the diamond and alleviate the stress caused by the difference in thermal expansion at the interface.

[0040] The upper surface of the baffle 5 is 0~0.7mm higher than the upper surface of the substrate 1, forming a closed molybdenum stage under the height difference, which optimizes the distribution of electromagnetic field and plasma field on the surface of the substrate 1, making them more uniform and conducive to the growth of high-quality diamond.

[0041] The diameter of substrate 1 is set as d1, and the height of substrate 1 is set as h1; the diameter of buffer layer 2 is set as d2, and the height of buffer layer 2 is set as h2; the diameter of base 3 is set as d3, and the height of base 3 is set as h3; the inner diameter of molybdenum ring 4 is the same as the diameter of base 1, the thickness of molybdenum ring 4 is 20mm, and the height of molybdenum ring 4 is set as h4; the inner diameter of baffle 5 is set as r1, and the height of baffle 5 is set as h5; the height of mounting groove 6 is h6, and the width of mounting groove 6 is d6. In a specific embodiment of the present invention, d1=d2=6 inches, d3=(d1+0.4)mm, h1=5mm, h2=0.02mm, h3=15mm, h4=(h1+h2+h3), r1=(d1-1.6)mm, h5=(h6+0.4)mm; h6=0.3mm, d6=1mm.

[0042] In other embodiments, the substrate 1, buffer layer 2, and base 3 of appropriate size and thickness can be selected according to the diamond of different sizes to be prepared. The thickness of the molybdenum ring 4 can be set according to the actual situation, as long as the molybdenum ring 4 has stable rigidity. The height of the molybdenum ring 4 can also be less than or greater than the sum of the heights of the substrate 1, buffer layer 2, and base 3, as long as the molybdenum ring 4 and baffle 5 can stably fix the substrate 1, buffer layer 2, and base 3.

[0043] When assembling the deposition stage, first stack the base 3, buffer layer 2, and substrate 1 coaxially and align them from bottom to top; then put the molybdenum ring 4 in and rotate it to lock it with the threaded base 3 until the baffle 5 is embedded in the mounting groove 6 of the substrate 1, thus completing the fixed assembly of the overall structure.

[0044] Example 2: A method for growing large-size diamonds includes the following steps: Step 1: Select a double-polished silicon carbide wafer with a diameter d=6 inches, thickness h=5 mm, PV value=50 μm, roughness<2 nm, thickness≥5 mm, resistivity≤1000 Ω·cm, and R of the arc transition surface is 0.5 mm; Clean the substrate with acetone, anhydrous ethanol, and ultrapure water in sequence using ultrasonic cleaning, and then assemble the substrate, buffer layer, molybdenum ring and base into the deposition stage described in Example 1.

[0045] Step 2: Place the deposition stage into the bias MPCVD equipment and continuously introduce hydrogen gas into the MPCVD equipment for bias etching. Control the bias voltage at -300V, the bias pressure at 24kPa, the temperature in the reaction system at 750℃, the hydrogen flow rate at 1000sccm, and the bias time at 2h.

[0046] Step 3: After the bias voltage is applied, the nucleation stage begins. Methane is introduced into the MPCVD equipment, and the volume ratio of methane to hydrogen in the MPCVD equipment is controlled at 3.5 vol%:1. The nucleation voltage is -200V, the nucleation pressure is 21 kPa, the temperature in the reaction system is 700℃, the hydrogen flow rate is 1000 sccm, and the nucleation time is 1 h.

[0047] Step 4: After nucleation, the process enters the regulation stage. The temperature in the reaction system is increased to 750℃ at a rate of 2℃ / min and maintained at this temperature for 0.5h. Then, the temperature is increased to 850℃ in two stages, with each stage increasing by 50℃ within 30min, and each stage is held for 0.5h after the initial increase. Next, the flow rate of methane into the reaction system is reduced, and the methane concentration in the reaction system is adjusted from 3.5%:1 to 2.5%:1 (volume ratio of methane to hydrogen) in two stages. The methane concentration is reduced by 0.5% within 1h, and this concentration is maintained for 0.5h after each reduction. Finally, the pressure in the reaction system is reduced from 21kPa to 20kPa and maintained at this pressure for growth.

[0048] Then, it enters the stable growth stage, maintaining a volume ratio of 2.5%:1 and continuously introducing methane and hydrogen into the reaction chamber, while also introducing oxygen into the reaction system. The oxygen concentration in the reaction system is controlled at 0.01%, the volume ratio of methane to hydrogen is 2.5%, the temperature is 750℃, and the pressure is 20kPa, and the growth is carried out for 500h.

[0049] Step 5: After growth is complete, stop the methane supply. When the methane concentration in the reaction chamber reaches 0, introduce argon gas, controlling the volume ratio of argon to hydrogen in the reaction system to be 10%. Increase the temperature to 1000℃ at 2℃ / h and hold for 0.3h. After annealing, cool to room temperature at 2℃ / min to obtain the crude product.

[0050] Step 6: Transfer the crude product to a hot isostatic pressing (HIP) apparatus for secondary annealing. Anneal at 1000°C and 100MPa for 4 hours under an argon atmosphere, followed by natural cooling to obtain the diamond.

[0051] Example 3: A method for growing large-size diamonds includes the following steps: Step 1: Select a double-polished silicon carbide wafer with a diameter d=6 inches, thickness h=5 mm, warpage of 30 μm, roughness of 1 nm, thickness of 5 mm, resistivity of 100 Ω·cm, and radius R of 0.5 mm for the arc transition surface; ultrasonically clean the substrate sequentially with acetone, anhydrous ethanol, and ultrapure water, and then assemble the substrate, buffer layer, molybdenum ring, and base into the deposition stage described in Example 1.

[0052] Step 2: Place the deposition stage into the bias MPCVD equipment and continuously introduce hydrogen gas into the MPCVD equipment for bias etching. Control the bias voltage at -270V, the bias pressure at 27kPa, the temperature in the reaction system at 800℃, the hydrogen flow rate at 4000sccm, and the bias time at 1h.

[0053] Step 3: After the bias voltage is applied, the nucleation stage begins. Methane is introduced into the MPCVD equipment, and the volume ratio of methane to hydrogen in the MPCVD equipment is controlled at 5.5%. The nucleation voltage is -175V, the nucleation pressure is 23kPa, the temperature in the reaction system is 750℃, the hydrogen flow rate is 1100sccm, and the nucleation time is 1h.

[0054] Step 4: After nucleation, the process enters the regulation stage. The temperature in the reaction system is raised to 800℃ in 25 minutes and grown for 0.5 hours. Then, the temperature is raised to 850℃ again in 25 minutes and held. Next, the flow rate of methane into the reaction system is reduced, and the methane concentration in the reaction system is adjusted from 5.5%:1 to 3.5%:1 (volume ratio of methane to hydrogen) in three stages. The methane concentration is reduced by 0.5% within 1 hour, and then maintained at this concentration for 0.5 hours. Then, the pressure in the reaction system is reduced from 24 kPa to 22 kPa in two stages, with each stage reducing the pressure by 1 kPa and growing for 0.5 hours.

[0055] Then, it enters the stable growth stage, maintaining a volume ratio of 3.5%:1 and continuously introducing methane and hydrogen into the reaction chamber, while also introducing oxygen into the reaction system. The oxygen concentration in the reaction system is controlled at 0.05 vol%, the volume ratio of methane to hydrogen is 3.5 vol%:1, the temperature is 850℃, and the pressure is 22 kPa, and the growth is carried out for 500 hours.

[0056] Step 5: After growth is complete, argon gas is introduced when the methane concentration in the reaction chamber reaches 0, controlling the volume ratio of argon to hydrogen in the reaction system to be 15%. The temperature is then increased to 1050℃ at 3.5℃ / h and held for 0.6h. After annealing, the temperature is cooled to room temperature at 3.5℃ / min to obtain the crude product.

[0057] Step 6: Transfer the crude product to a hot isostatic pressing (HIP) apparatus for secondary annealing. Anneal at 1300°C and 120MPa for 5 hours under an argon atmosphere, followed by natural cooling to obtain the diamond.

[0058] Example 4: A method for growing large-size diamonds includes the following steps: Step 1: Select a double-polished silicon carbide wafer with a diameter d=6 inches, thickness h=5 mm, warpage 20 μm, roughness <2 nm, thickness ≥5 mm, resistivity 80 Ω·cm, and radius R of the arc transition surface 0.5 mm; ultrasonically clean the substrate sequentially with acetone, anhydrous ethanol, and ultrapure water, and then assemble the substrate, buffer layer, molybdenum ring, and base into the deposition stage described in Example 1.

[0059] Step 2: Place the deposition stage into the bias MPCVD equipment and continuously introduce hydrogen gas into the MPCVD equipment for bias etching. Control the bias voltage to -250V, the bias pressure to 30kPa, the temperature in the reaction system to 850℃, the hydrogen flow rate to 4000sccm, and the bias time to 1h.

[0060] Step 3: After the bias voltage is applied, the nucleation stage begins. Methane is introduced into the MPCVD equipment, and the volume ratio of methane to hydrogen in the MPCVD equipment is controlled at 8%. The nucleation voltage is -150V, the nucleation pressure is 25kPa, the temperature in the reaction system is 780℃, the hydrogen flow rate is 4000sccm, and the nucleation time is 1h.

[0061] Step 4: After nucleation, the process enters the regulation stage. The temperature in the reaction system is raised from 800℃ to 950℃ in three stages. In each stage, the temperature is increased by 50℃ within 25 minutes, and then maintained at this temperature for 0.5 hours. Then, the flow rate of methane into the reaction system is reduced, and the methane concentration in the reaction system is adjusted from 8%:1 to 3.5%:1 in seven stages. The methane concentration is reduced by 0.5% within 1 hour, and this concentration is maintained for 0.5 hours after each reduction.

[0062] Then, it enters the stable growth stage, maintaining a volume ratio of 3.5%:1 and continuously introducing methane and hydrogen into the reaction chamber, while also introducing oxygen into the reaction system. The oxygen concentration in the reaction system is controlled at 0.1%, the volume ratio of methane to hydrogen is 3.5%, the temperature is 950℃, and the pressure is 25kPa, and the growth is carried out for 500h.

[0063] Step 5: After growth is complete, argon gas is introduced when the methane concentration in the reaction chamber reaches 0, controlling the volume ratio of argon to hydrogen in the reaction system to be 20%; the temperature is increased to 1500℃ at 5℃ / h and held for 1h. After annealing, the temperature is cooled to room temperature at 5℃ / min to obtain the crude product.

[0064] Step 6: Transfer the crude product to a hot isostatic pressing (HIP) apparatus for secondary annealing. Anneal at 1500°C and 150MPa for 4.5 hours under an argon atmosphere, followed by natural cooling to obtain the diamond.

[0065] Comparative Example 1: A deposition stage for large-size diamonds differs from Example 1 in that the baffle height h5 is less than the mounting groove height h6, where h5 is 0.5 mm and h6 is 1 mm.

[0066] Diamond growth was performed using the deposition stage described above, and steps 1 to 6 were the same as in Example 2.

[0067] Comparative Example 2: A deposition stage for large-size diamonds, which differs from Example 1 in that it has rounded corners and arc transition surfaces that are fitted together without gaps.

[0068] Diamond growth was performed using the deposition stage described above, and steps 1 to 6 were the same as in Example 2.

[0069] Comparative Example 3: A deposition stage for large-size diamonds differs from Embodiment 1 in that the baffle is not rounded and the mounting groove is not provided with a rounded transition surface; otherwise, it is the same as Embodiment 2.

[0070] Diamond growth was performed using the deposition stage described above, and steps 1 to 6 were the same as in Example 2.

[0071] Comparative Example 4: A method for growing large-size diamonds differs from Example 2 in that, in step 4, after the nucleation stage is completed, the process directly enters the stable growth stage. Oxygen is introduced into the reaction system, and the oxygen concentration in the reaction system is controlled at 0.01 vol%, the volume ratio of methane to hydrogen is 2.5 vol%:1, the temperature is 750°C, and the pressure is 20 kPa for 500 h.

[0072] Steps 1-3 and steps 5-6 are the same as in Example 2.

[0073] Comparative Example 5: A method for growing large-size diamonds differs from Example 2 in that the secondary annealing process in step 6 is not included, and the rough product obtained in step 5 is the final product.

[0074] Comparative Example 6: A method for growing large-size diamonds, differing from Example 2 in that, in step 2, the deposition stage is placed into a biased MPCVD apparatus, and hydrogen gas is continuously introduced into the MPCVD apparatus for bias etching. The bias voltage is controlled at -100V, the bias pressure at 18kPa, the temperature within the reaction system at 700℃, the hydrogen flow rate at 400sccm, and the bias time at 2h.

[0075] Steps 1 and 3-6 are the same as in Example 2.

[0076] Comparative Example 7: A method for growing large-size diamonds differs from Example 2 in that, in step 3, after the bias voltage is applied, the nucleation stage begins. Methane is introduced into the MPCVD equipment, and the volume ratio of methane to hydrogen in the MPCVD equipment is controlled at 10 vol%:1. The nucleation voltage is -100V, the nucleation pressure is 27 kPa, the temperature in the reaction system is 850°C, the hydrogen flow rate is 1000 sccm, and the nucleation time is 0.3 h.

[0077] Steps 1-2 and steps 4-6 are the same as in Example 2.

[0078] The diamonds obtained in Examples 2-4 and Comparative Examples 1-7 were subjected to performance tests. The test parameters are shown in Table 1.

[0079] Table 1 Performance parameters of diamonds obtained in Examples 2-4 and Comparative Examples 1-7 As shown in Table 1, using the coaxial constrained molybdenum ring deposition stage structure of this invention, combined with bias etching, segmented temperature and pressure concentration-controlled growth, in-situ annealing, and hot isostatic pressing secondary annealing processes to prepare large-size diamonds, the full width at half maximum (FWHM) of the Raman characteristic peaks were all controlled within the range of 2.3–2.8 cm. -1 Within this range, the thickness difference is only 31.5~36.2μm, the substrate warpage is maintained at 25.1~30.4μm, and all samples are free from cracks and abnormal edge protrusions. This indicates that the rigid constraint structure of the deposition stage and the segmented progressive growth process of this invention can stably prepare large-sized diamonds with high crystal quality, low warpage and uniform thickness within a wide parameter window. Furthermore, moderate parameter improvement can effectively improve deposition efficiency while ensuring crystal quality.

[0080] In Comparative Example 1, the top surface of the baffle is lower than the substrate mounting groove, which disrupts the edge electromagnetic field and plasma field constraint, causing diamond edge protrusion distortion, thickness variation, substrate warping, and Raman half-width at half-maximum deterioration. Thickness uniformity and stress control capability are significantly reduced, confirming that the upper surface of the baffle is not lower than the top surface of the substrate, which is a necessary structural design for balancing the edge temperature field and suppressing abnormal growth.

[0081] Comparative Example 2: The annular gap between the rounded corner of the baffle and the arc surface of the mounting groove was removed. The microwave energy at the corner could not be released, which caused the electric field and thermal stress to concentrate. The sample cracked and was scrapped. Even though the intrinsic crystal quality of the crystal did not deteriorate, it proved that the annular gap can effectively eliminate the microwave edge effect and relieve local stress. It is a key structure to avoid the failure of the finished product.

[0082] Comparative Example 3 lacks a baffle rounded corner and a mounting groove arc transition surface. The sharp corner forms an electric field singularity and stress concentration point, resulting in a significant deterioration in film thickness uniformity and substrate warpage. The sample cracks and lattice defects increase slightly, demonstrating the important role of the arc pairing structure in optimizing edge growth consistency and preventing stress cracking.

[0083] Comparative Example 4 omits the multi-level gradual control process of temperature, methane concentration, and pressure. The direct abrupt change in parameters causes lattice mismatch and internal stress accumulation, resulting in a significant increase in Raman half-width, an increase in crystal defects, and a slight deterioration in film thickness uniformity. This indicates that the segmented and gradual transition process can smoothly connect the growth environment, reduce lattice stress, and improve crystal integrity.

[0084] Comparative Example 5 omitted the hot isostatic pressing secondary annealing. Relying solely on in-situ annealing could not fully release the residual stress inside the film, resulting in cracking of the product. The Raman half-width was significantly higher than that of the example, proving that high-temperature and high-pressure secondary annealing can deeply eliminate the internal stress of thick films and prevent cracking, which is indispensable for improving the structural integrity of diamond.

[0085] Comparative Example 6 shows that the bias etching parameters deviated from the preferred range, the removal of impurities and damaged layers on the substrate surface was incomplete, the nucleation sites were uneven, the diamond growth rate was the lowest among all groups, the Raman full width at half maximum (FWHM) increased significantly, and the crystal defects increased dramatically. This indicates that high-flow-rate hydrogen and strong negative bias etching within the standard range are the prerequisites for efficient nucleation and obtaining high crystal quality.

[0086] In Comparative Example 7, the high methane content, insufficient bias voltage, and short duration during the nucleation stage resulted in uneven nucleation and the formation of polycrystalline inclusions. Although the growth rate was high, the thickness was extremely poor, the substrate warping was severely excessive, the Raman full width at half maximum (FWHM) reached the maximum value of each group, and the crystal quality deteriorated significantly. This confirms that strict control of the carbon-hydrogen ratio, bias voltage, and duration during nucleation is the core process condition for achieving uniform nucleation across the entire domain and reducing defects and substrate deformation.

[0087] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A deposition stage for large-size diamonds, characterized in that, It includes a substrate (1), a buffer layer (2), a molybdenum ring (4), and a base (3), wherein the substrate (1), the buffer layer (2), and the base (3) are arranged sequentially from top to bottom, and the center lines of the substrate (1), the buffer layer (2), and the base (3) overlap; The molybdenum ring (4) is simultaneously sleeved on the sidewalls of the substrate (1), the buffer layer (2) and the base (3), and the molybdenum ring (4) and the base (3) are threaded together; A baffle (5) is fixedly connected to the top end of the molybdenum ring (4), and a mounting groove (6) for mounting the baffle (5) is provided on the top surface of the substrate (1).

2. The deposition stage for large-size diamonds as described in claim 1, characterized in that, The baffle (5) has a rounded corner (7) at one end inside the molybdenum ring (4). The arc-shaped convex surface of the rounded corner (7) faces the mounting groove (6). The mounting groove (6) has an arc-shaped transition surface (8) on the side away from the molybdenum ring (4). The arc-shaped concave surface of the arc-shaped transition surface (8) is opposite to the rounded corner (7).

3. The deposition stage for large-size diamonds as described in claim 1 or 2, characterized in that, An annular gap (9) is formed between the baffle (5) and the mounting groove (6); The upper surface of the baffle (5) is higher than the upper surface of the substrate (1).

4. The deposition stage for large-size diamonds as described in claim 1, characterized in that, The substrate (1) is made of silicon carbide, with warpage ≤50μm, roughness ≤2nm, thickness ≥5mm, and resistivity ≤1000Ω·cm; The buffer layer (2) is any one or two of copper and silver, and the thickness of the buffer layer (2) is 0.01~0.02mm.

5. A method for growing large-size diamonds, characterized in that, Includes the following steps: Step 1: Place the above deposition stage into a bias MPCVD device to perform bias etching, bias nucleation and growth processes in sequence; Step 2: After growth is complete, proceed to the annealing process and cooling to obtain the crude product; Step 3: Place the crude product into a static pressure device for secondary annealing and cooling to obtain the large-size diamond.

6. The method for growing large-size diamonds as described in claim 5, characterized in that, During the bias etching process, hydrogen gas is continuously introduced into the reaction system at a flow rate of 1000~4000 sccm; the bias voltage is (-300)~(-250) V; the bias pressure is 24~30 kPa; the temperature in the reaction system is 750~850℃; and the bias etching time is 1~2 h. During the bias nucleation process, methane and hydrogen are simultaneously introduced into the reaction system, and the volume ratio of methane to hydrogen in the reaction system is controlled to be (3.5%~8%):1; the flow rate of hydrogen is 1000~4000 sccm; and the bias voltage is (-200)~(-150) V. The bias pressure is 21-25 kPa; the temperature in the reaction system is 700-780℃; and the bias nucleation time is 1-2 h.

7. The method for growing large-size diamonds as described in claim 5, characterized in that, When the growth process includes a regulation stage and a stable growth stage, the growth temperature, methane concentration and pressure are adjusted to the target parameters in sequence during the regulation stage, and then oxygen is introduced to carry out the stable growth stage.

8. The method for growing large-size diamonds as described in claim 7, characterized in that, During the control phase, the initial temperature of the bias nucleation process is used as the initial temperature for the phased heating, raising the temperature in the reaction system from 700~780℃ to 780~950℃. The heating gradient for each phase is 40~60℃, the heating rate is 2℃ / min, and each phase is maintained at the temperature for 0.4~0.6h. The methane and hydrogen concentrations in the bias nucleation process were used as the initial concentrations for regulation. The volume ratio of methane to hydrogen was reduced from (3.5%~8%):1 to (2.5%~3.5%):

1. The regulation gradient for each stage was 0.4%~0.6%, and the growth time for each stage was 0.5~1h.

9. The method for growing large-size diamonds as described in claim 7, characterized in that, During the stable growth stage, the oxygen concentration in the reaction system is 0.01~0.1 vol%, the growth time is 300~500 h, and the growth pressure is 20~25 kPa.

10. The method for growing large-size diamonds as described in claim 5, characterized in that, During annealing and cooling, stop the introduction of methane. When the methane concentration reaches 0, introduce argon gas and control the volume ratio of argon to hydrogen in the reaction system to be 10%~20%:

1. The annealing temperature is 1000~1100℃ and the annealing time is 0.3~1h. After annealing, cool to room temperature. The secondary annealing is carried out in an argon atmosphere at a temperature of 1000-1500℃, an annealing pressure of 100-150MPa, and an annealing time of 4-5 hours.

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