MPCVD equipment and preparation method for large-size polycrystalline diamond thin films

Abstract

This invention relates to the field of microwave plasma chemical vapor deposition (MPCVD) technology, specifically to an MPCVD apparatus and method for preparing large-size polycrystalline diamond thin films. The reaction chamber contains a quartz ring, topped by a water-cooled copper substrate stage. A molybdenum ring is placed atop the water-cooled copper substrate stage, with a water-cooled copper-based sample stage at the center of the molybdenum ring. A riser tube is connected to the bottom of the water-cooled copper-based sample stage, and a molybdenum support is placed atop the water-cooled copper-based sample stage. A sample ring is placed atop the molybdenum support. Two infrared temperature sensors are installed outside the temperature observation window of the reaction chamber, respectively aligned with the edge and center of the sample ring. The water-cooled copper-based sample stage contains interlaced cooling water channels and thermal resistance wires. The thermal resistance wires are electrically connected to an electric heating control device, which is electrically connected to a dual infrared temperature measurement device. This invention can improve the temperature uniformity of the internal and external regions during the deposition of large-size polycrystalline diamond thin films.

Description

Technical Field

[0001] This invention relates to the field of microwave plasma chemical vapor deposition technology, specifically to MPCVD equipment and preparation method for preparing large-size polycrystalline diamond thin films. Background Technology

[0002] Methods for preparing polycrystalline diamond films using CVD (Chemical Vapor Deposition) include high-power DC arc plasma jet CVD, hot-wire CVD, and MPCVD (Microwave Plasma Chemical Vapor Deposition). The preparation of optical-grade and electronic-grade polycrystalline diamond films requires ideal deposition rates and extremely low or controllable defect densities. MPCVD, with its electrode-free discharge, has thus become the ideal method for preparing electronic-grade and optical-grade polycrystalline diamond films.

[0003] Compared to the demanding optical and electronic grade polycrystalline diamond film preparation and application, polycrystalline diamond film has a wider range of applications, greater demand, and is more urgent as a heat sink for semiconductor power devices. It has great application potential for improving the near-junction heat dissipation capability of third-generation semiconductor materials silicon carbide and gallium nitride devices under high power density conditions.

[0004] However, in existing MPCVD equipment for preparing polycrystalline diamond thin films, the shape and distribution of the plasma above the deposition stage cause the plasma energy to be strong in the center and weak at the edges, resulting in a temperature decrease from the center to the edge of the deposited sample during deposition. This phenomenon becomes more pronounced with increasing microwave power and prolonged operation. Simultaneously, uneven heat dissipation from the deposition stage compromises the uniformity of the deposited polycrystalline diamond film, leading to height differences between the inner and outer layers, high crystal stress, severe warping and breakage after crystal peeling, significantly impacting crystal quality. This makes it unsuitable for subsequent processing steps such as cutting, grinding, and polishing, as breakage and fragmentation are highly likely, thus hindering the application of polycrystalline diamond in semiconductor device fabrication. Therefore, existing MPCVD equipment for preparing polycrystalline diamond thin films is insufficient for producing high-quality polycrystalline diamond thin films of 2 inches and above. Summary of the Invention

[0005] To address the technical problem that existing MPCVD equipment for preparing polycrystalline diamond films suffers from uneven temperature distribution due to temperature gradients between the inner and outer regions of the deposited sample caused by plasma shape and distribution, thus preventing the preparation of high-quality polycrystalline diamond films of 2 inches or larger, this invention provides both an MPCVD device for preparing large-size polycrystalline diamond films and a method for preparing large-size polycrystalline diamond films.

[0006] To achieve the above objectives, the technical solution adopted by the MPCVD equipment for preparing large-size polycrystalline diamond thin films in this invention is as follows:

[0007] An MPCVD apparatus for preparing large-size polycrystalline diamond thin films includes a reaction chamber containing a quartz ring. A water-cooled copper substrate stage is positioned at the top center of the quartz ring. A molybdenum ring is positioned at the top center of the water-cooled copper substrate stage. A water-cooled copper-based sample stage is positioned at the center of the molybdenum ring, with the inner diameter of the molybdenum ring larger than the outer diameter of the water-cooled copper-based sample stage. A lifting tube is connected to the bottom center of the water-cooled copper-based sample stage, allowing it to move up and down. The lifting tube passes through the water-cooled copper substrate stage and the quartz ring before exiting the reaction chamber. A molybdenum support is coaxially positioned at the top of the water-cooled copper-based sample stage, and a sample ring is coaxially positioned at the top of the molybdenum support. The reaction chamber is equipped with a temperature measuring device. The observation window is equipped with two infrared temperature sensors, which are positioned at the edge and center of the sample ring, respectively. The water-cooled copper-based sample stage has interwoven cooling water channels and thermal resistance wires. The cooling water channels and thermal resistance wires extend from the riser tube into the reaction chamber. The cooling water channels connect to a chiller after extending into the reaction chamber, and the thermal resistance wires connect to an electric heating control device. The electric heating control device is electrically connected to a dual infrared temperature measuring device, which in turn connects to two infrared temperature sensors.

[0008] The aforementioned structural design, with its staggered cooling water channels and thermal resistance wires within the water-cooled copper-based sample stage, effectively regulates the temperature of the molybdenum support and the substrate sample within the sample ring above it. The internal cooling water channels dissipate excess heat, preventing overheating. Combined with an infrared temperature sensor and an electric heating control device, the staggered cooling water channels and thermal resistance wires precisely adjust the temperature of the water-cooled copper-based sample stage based on temperature feedback from the sample ring's edge and center. This reduces the temperature gradient from the center to the edge during deposition, resulting in a more uniform temperature distribution and providing a stable temperature environment for preparing large-size, high-quality polycrystalline diamond films.

[0009] As a preferred implementation of MPCVD equipment for preparing large-size polycrystalline diamond films, when the temperature difference detected by two infrared temperature sensors exceeds the set temperature difference range, the electric heating control device controls the heating of the thermal resistance wire.

[0010] By adopting the above structural scheme, real-time monitoring and automatic adjustment of the temperature of the sample deposited in the sample ring are realized. It can quickly respond to temperature changes, maintain the relative stability of the temperature inside and outside the sample deposited in the sample ring, avoid the degradation of polycrystalline diamond film deposition quality due to excessive temperature difference, effectively improve the uniformity and stability of film deposition, and ensure the quality of large-size polycrystalline diamond films.

[0011] As a preferred implementation of MPCVD equipment for preparing large-size polycrystalline diamond thin films, the water-cooled copper substrate stage is equipped with a copper substrate stage cooling water channel. The pipes of the copper substrate stage cooling water channel extend from the central hole of the quartz ring into the reaction chamber, and are connected to the chiller after extending out of the reaction chamber.

[0012] With the above structural design, the cooling water channel inside the water-cooled copper substrate stage can remove excess heat and prevent the water-cooled copper substrate stage from overheating. Through heat conduction, the temperature of the molybdenum support and the substrate sample in the sample ring above it can be further effectively regulated.

[0013] As a preferred implementation method for MPCVD equipment for preparing large-size polycrystalline diamond thin films, the thickness of the molybdenum ring is 14-18 mm, the outer diameter of the molybdenum ring is the same as the outer diameter of the water-cooled copper substrate stage, and the inner diameter of the molybdenum ring is 0.5-3 mm larger than the outer diameter of the water-cooled copper substrate sample stage.

[0014] The above structural design optimizes the heat conduction path while ensuring the structural strength of the molybdenum ring. An appropriate thickness helps to distribute heat evenly, avoiding uneven heat conduction caused by an excessively thin or thick molybdenum ring.

[0015] As a preferred implementation method for MPCVD equipment for preparing large-size polycrystalline diamond thin films, the thickness of the molybdenum support is 1-5 mm, and the radial dimension of the molybdenum support is the same as that of the water-cooled copper-based sample stage.

[0016] The above structural design allows for a tight fit between the molybdenum support and the water-cooled copper-based sample stage, achieving excellent synergy during heat transfer. The molybdenum support can more evenly transfer the temperature of the water-cooled copper-based sample stage to the deposited sample, while also buffering the stress caused by temperature changes between the water-cooled copper-based sample stage and the deposited sample to a certain extent. This ensures the temperature consistency of the deposited sample during the deposition process, which is beneficial for improving the deposition quality and stability of large-size polycrystalline diamond films.

[0017] As a preferred implementation of MPCVD equipment for preparing large-size polycrystalline diamond thin films, a water-cooled copper-based sample stage with a radial dimension of 1-5 inches is used.

[0018] The above structural design enables the equipment to adapt to the preparation of large-size polycrystalline diamond films with different size requirements.

[0019] As a preferred implementation method for MPCVD equipment for preparing large-size polycrystalline diamond thin films, the temperature observation window is a microwave emission window with a microwave power adjustment range of 0.6KW-12KW and a usable microwave source frequency of 2450MHz or 915MHz.

[0020] The aforementioned structural design allows the equipment to more flexibly adjust microwave power and frequency according to different polycrystalline diamond film fabrication process requirements. Different microwave parameters affect plasma generation, distribution, and energy, thus influencing the film deposition rate, quality, and crystal structure. The wide range of microwave power adjustment and multiple frequency selections provides more possibilities for optimizing polycrystalline diamond film fabrication processes, helping to meet diverse research and production needs.

[0021] As a preferred implementation of MPCVD equipment for preparing large-size polycrystalline diamond thin films, when the riser tube is at its zero point of travel, the height difference between the water-cooled copper-based sample stage and the water-cooled copper substrate stage below is 1 mm.

[0022] By adopting the above structural scheme, the appropriate height difference helps to establish reasonable heat conduction and heat exchange conditions between the water-cooled copper-based sample stage and the water-cooled copper substrate stage in the initial stage of equipment startup. This avoids abnormal temperature distribution caused by the distance between the two being too close or too far, laying a good foundation for the subsequent stable polycrystalline diamond thin film deposition process and improving the repeatability and stability of thin film deposition.

[0023] As a preferred implementation of MPCVD equipment for preparing large-size polycrystalline diamond thin films, a lifting motor is installed outside the reaction chamber. The output end of the lifting motor is coaxially connected to a worm gear. The worm gear is horizontally positioned and meshes with a worm wheel. The worm wheel is fixedly installed outside the reaction chamber. A connecting hole is opened in the center of the worm wheel. An internal thread is opened on the inner circumferential surface of the connecting hole. An external thread is opened on the outer circumferential surface of the lifting tube. One end of the lifting tube extending out of the reaction chamber is threadedly connected to the connecting hole. The top end of the lifting tube is rotatably connected to the bottom of a water-cooled copper-based sample stage.

[0024] The above-described structural design incorporates a self-locking worm gear drive, ensuring the stability of the lifting tube after adjustment to the designated position and preventing height variations in the water-cooled copper-based sample stage due to unforeseen factors. Furthermore, the worm gear drive offers high precision, allowing for flexible adjustment of the water-cooled copper-based sample stage height according to deposition process requirements. This optimizes the interaction between the plasma and the deposited sample, improving the quality and uniformity of thin film deposition, while also facilitating equipment operation and maintenance.

[0025] The technical solution adopted in the preparation method of large-size polycrystalline diamond thin films in this invention is as follows:

[0026] The method for preparing large-size polycrystalline diamond films, using the MPCVD equipment described above, includes the following steps:

[0027] The substrate sample was placed in a methanol suspension containing diamond micro powder for ultrasonic treatment. After treatment, it was transferred to alcohol for ultrasonic cleaning. After cleaning, the substrate sample was placed in a sample ring selected according to the specifications of the substrate sample after it was naturally dried.

[0028] The lifting tube is raised to elevate the water-cooled copper-based sample stage to a position where the molybdenum support and molybdenum ring are level.

[0029] Adjust the positions of the two infrared temperature sensors so that they are aligned with the edge and center of the sample ring, respectively, and so that the two infrared temperature sensors can focus and detect the temperature of the inner and outer regions of the deposited sample through the temperature observation window;

[0030] Adjust the chamber pressure, run the chiller, introduce the polycrystalline growth atmosphere after mixing in proportion into the reaction chamber, run the microwave source, adjust the microwave power, and control the deposition temperature;

[0031] The dual infrared temperature measurement device feeds back the temperature parameters of the deposited sample detected by the two infrared temperature sensors to the electric heating control device. When the temperature difference between the inner and outer regions of the sample exceeds the set temperature difference range, the electric heating control device controls the heating of the thermal resistance wire to keep the temperature difference between the inner and outer regions of the sample within the set temperature difference range.

[0032] As the growth process progresses, the lifting tube is controlled to raise and lower the water-cooled copper-based sample stage, adjusting the height required for sample deposition.

[0033] The beneficial effects of this invention include:

[0034] This invention provides a large-size polycrystalline diamond growth device with high heat conduction efficiency, small temperature gradient between the inner and outer regions of the deposited sample, uniform and continuous temperature field distribution, and precise controllability of the deposition process. This device can effectively reduce the large thermal stress caused by the uneven temperature between the inner and outer regions of the deposited sample during MPCVD deposition of polycrystalline diamond films, reduce the probability of sample cracking and collapse in subsequent processing steps, effectively improve the uniformity and crystal quality of the deposited polycrystalline diamond film, and can directly prepare high-precision, high-quality, large-size polycrystalline diamonds that can directly meet the application requirements of semiconductor device fabrication after preparation. Attached Figure Description

[0035] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the internal structure of the MPCVD equipment used to prepare large-size polycrystalline diamond thin films in a specific embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the worm gear and worm in a specific embodiment of the present invention.

[0038] List of components and reference numerals:

[0039] 1. Reaction chamber; 2. Quartz ring; 3. Water-cooled copper substrate stage; 4. Molybdenum ring; 5. Water-cooled copper-based sample stage; 6. Lifting pipe; 7. Molybdenum support; 8. Sample ring; 9. Infrared temperature sensor; 10. Cooling water circuit for copper substrate stage; 11. Cooling water circuit for copper-based sample stage; 12. Thermal resistance wire; 13. Chiller; 14. Electric heating control device; 15. Dual infrared temperature measuring device; 16. Lifting motor; 17. Worm gear; 18. Worm wheel; 19. Temperature measurement observation window. Detailed Implementation

[0040] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0041] Reference Figure 1This embodiment proposes an MPCVD apparatus for preparing large-size polycrystalline diamond thin films, including a reaction chamber 1, a quartz ring 2 inside the reaction chamber 1, a water-cooled copper substrate stage 3 at the top center of the quartz ring 2, a molybdenum ring 4 at the top center of the water-cooled copper substrate stage 3, and a water-cooled copper-based sample stage 5 at the center of the molybdenum ring 4. The radial dimension of the water-cooled copper-based sample stage 5 is 1-5 inches, and the thickness is 7 mm. The inner diameter of the molybdenum ring 4 is larger than the outer diameter of the water-cooled copper-based sample stage 5, the thickness of the molybdenum ring 4 is 14-18 mm, the outer diameter of the molybdenum ring 4 is the same as the outer diameter of the water-cooled copper substrate stage 3, and the inner diameter of the molybdenum ring 4 is 0.5-3 mm larger than the outer diameter of the water-cooled copper-based sample stage 5. A lifting pipe 6 is connected to the center of the bottom of the water-cooled copper-based sample stage 5. The lifting pipe 6 can move up and down, passing through the water-cooled copper substrate stage 3 and the quartz ring 2, and then exiting the reaction chamber 1. A molybdenum support 7 is coaxially mounted on the top of the water-cooled copper-based sample stage 5, and a sample ring 8 is coaxially mounted on the top of the molybdenum support 7. The molybdenum ring 4, molybdenum support 7, and sample ring 8 are all made of molybdenum with a surface roughness of Ra0.2. Molybdenum has characteristics such as high melting point, good thermal stability, and chemical stability. It is not easily deformed or chemically reacted in the high-temperature MPCVD deposition environment. At the same time, the low surface roughness provides a relatively flat and smooth substrate for the growth of polycrystalline diamond films, which is conducive to the uniform nucleation and growth of diamond crystals, reduces crystal defects, and thus improves the quality and crystallization performance of polycrystalline diamond films, helping to prepare high-quality, large-size polycrystalline diamond films. The thickness of the molybdenum support 7 is 1-5 mm, and the radial dimension of the molybdenum support 7 is the same as that of the water-cooled copper-based sample stage 5. The sample ring 8 is designed with multiple sizes, and different sample rings 8 can be used depending on the radial size and deposition thickness of the sample to be deposited.

[0042] The reaction chamber 1 is equipped with a temperature observation window 19, and two infrared temperature sensors 9 are installed outside the observation window 19. The two infrared temperature sensors 9 are respectively aligned with the edge and center area of ​​the sample ring 8. The temperature measurement range of the infrared temperature sensors 9 is 300-1400℃. The temperature observation window 19 is a microwave emission window, and the microwave power adjustment range is 0.6KW-12KW. The frequency of the microwave source that can be used is 2450MHz or 915MHz.

[0043] The water-cooled copper substrate stage 3 has a copper substrate stage cooling water channel 10 inside. The water-cooled copper-based sample stage 5 has a copper-based sample stage cooling water channel 11 and a thermal resistance wire 12 arranged in an alternating pattern inside. The pipes of the copper substrate stage cooling water channel 10 extend from the central hole of the quartz ring 2 into the reaction chamber 1. The pipes of the copper-based sample stage cooling water channel 11 and the wires of the thermal resistance wire 12 extend from the inside of the riser pipe 6 into the reaction chamber 1. After extending out of the reaction chamber 1, the pipes of the copper substrate stage cooling water channel 10 and the copper-based sample stage cooling water channel 11 are connected to the chiller 13. After extending out of the reaction chamber 1, the wires of the thermal resistance wire 12 are electrically connected to the electric heating control device 14. The electric heating control device 14 is electrically connected to the dual infrared temperature measuring device 15, and the dual infrared temperature measuring device 15 is electrically connected to two infrared temperature sensors 9. When the temperature difference detected by the two infrared temperature sensors 9 exceeds the set temperature difference range, the electric heating control device 14 controls the thermal resistance wire 12 to heat up. The heating temperature range of the thermal resistance wire 12 is 50-300℃, and the heating temperature is regulated by the electric heating control device 14.

[0044] The temperature of the cooling water in the copper substrate stage cooling water circuit 10 and the copper sample stage cooling water circuit 11 is 10-35℃, with an adjustment accuracy of 0.1℃. The cooling water flow rate is greater than or equal to 50L / min, and the flow rate can be adjusted by the chiller 13.

[0045] When the lifting tube 6 is at the zero point of its stroke, the height difference between the water-cooled copper-based sample stage 5 and the water-cooled copper substrate stage 3 below it is 1 mm.

[0046] Reference Figure 1 and 2 In order to realize the lifting of the lifting tube 6, a lifting motor 16 is provided outside the reaction chamber 1 in this embodiment. The output end of the lifting motor 16 is coaxially connected to the worm 17. The worm 17 is set horizontally and meshes with the worm wheel 18. The worm wheel 18 is fixedly installed outside the reaction chamber 1. A connecting hole is opened in the center of the worm wheel 18. The inner circumferential surface of the connecting hole is threaded. The outer circumferential surface of the lifting tube 6 is threaded. One end of the lifting tube 6 extending out of the reaction chamber 1 is threadedly connected to the connecting hole. The top end of the lifting tube 6 is rotatably connected to the bottom of the water-cooled copper-based sample stage 5.

[0047] This embodiment effectively improves the quality of polycrystalline deposition. By controlling the lifting of the water-cooled copper-based sample stage 5, combined with the dual infrared temperature measurement device 15 linked to the electric heating control device 14, the heating of the internal thermal resistance wire 12 of the water-cooled copper-based sample stage 5 is controlled. This reduces the internal and external temperature gradient of the deposited sample during deposition, ensuring a uniform temperature field distribution. It precisely controls the deposition parameters of the polycrystalline substrate within the required process range, avoiding problems such as substrate and deposited sample damage, low polycrystalline quality, and low processing yield caused by thermal stress due to uneven heat transfer during deposition. The sample ring 8 reduces plasma edge effects, preventing plasma adsorption at the substrate sample edges and thus ensuring low crystal quality at the substrate sample edges. The MPCVD equipment used in this embodiment for preparing large-size polycrystalline diamond films can achieve high-precision deposition of 1-4 inch large-size polycrystalline diamond films.

[0048] The MPCVD equipment used in this embodiment for preparing large-size polycrystalline diamond films has a relatively simple structure, which can effectively meet the needs of industrial production and provide a high-quality and reliable solution for industrial production and laboratory growth research.

[0049] This embodiment also proposes a method for preparing large-size polycrystalline diamond films, using one of the MPCVD equipment described above. Taking a 3mm thick two-inch silicon substrate sample as an example, the method for preparing large-size polycrystalline diamond films includes the following steps:

[0050] The silicon substrate sample was placed in a methanol suspension containing 1000-6000 mesh diamond powder and ultrasonically treated for 30 minutes. After treatment, it was transferred to alcohol and ultrasonically cleaned for 20 minutes. After cleaning, it was allowed to air dry naturally and then placed in the sample ring 8 selected according to the substrate sample specifications on the molybdenum support 7.

[0051] The lifting motor 16 is operated to raise the lifting tube 6, thereby raising the water-cooled copper-based sample stage 5 to a position where the molybdenum support 7 and the molybdenum ring 4 are level.

[0052] Adjust the positions of the two infrared temperature sensors 9 so that they are aligned with the edge and center of the sample ring 8 respectively, thereby enabling the detection of the temperature inside and outside the deposited sample.

[0053] Adjust the chamber pressure to 10-300 Torr, run the chiller 13 to set the cooling circulating water temperature to 10-35℃, introduce a polycrystalline growth atmosphere containing hydrogen, nitrogen, methane and oxygen after mixing in proportion, run the microwave source, adjust the microwave power to 0.5KW-12KW, and control the deposition temperature to 600-1000℃.

[0054] The dual infrared temperature measuring device 15 feeds back the temperature parameters of the deposited sample detected by the two infrared temperature measuring sensors 9 to the electric heating control device 14; when the temperature difference between the inner and outer regions of the deposited sample exceeds 10-100℃, the electric heating program is started to control the thermal resistance wire 12 to heat, so as to control the temperature difference between the inner and outer regions of the deposited sample within 10-100℃.

[0055] As the growth process progresses, the height of the grown sample continuously increases. The lifting motor 16 controls the lifting tube 6 to move up and down, thereby moving the water-cooled copper-based sample stage 5 and the molybdenum support 7, adjusting the appropriate height required for the deposition of the sample, so that the deposited sample is always in the optimal position.

[0056] In this embodiment, the growth rate of the deposited sample is 0.1-100 μm / h, the lifting speed of the lifting motor 16 is 0.1-1000 μm / h, and the height of the water-cooled copper-based sample stage 5 is adjustable from 0 to 5000 μm with an adjustment accuracy of 0.1 μm.

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An MPCVD apparatus for preparing large-size polycrystalline diamond thin films, comprising a reaction chamber (1), characterized in that, A quartz ring (2) is provided in the reaction chamber (1). A water-cooled copper substrate stage (3) is provided at the top center of the quartz ring (2). A molybdenum ring (4) is provided at the top center of the water-cooled copper substrate stage (3). A water-cooled copper-based sample stage (5) is provided in the center of the molybdenum ring (4). The inner diameter of the molybdenum ring (4) is larger than the outer diameter of the water-cooled copper-based sample stage (5). A lifting pipe (6) is connected to the bottom center of the water-cooled copper-based sample stage (5). The lifting pipe (6) can be raised and lowered. The lifting pipe (6) passes down through the water-cooled copper substrate stage (3) and the quartz ring (2) and then passes out of the reaction chamber (1). A molybdenum support (7) is coaxially provided at the top of the water-cooled copper-based sample stage (5). A sample ring (8) is coaxially provided at the top of the molybdenum support (7). The reaction chamber (1) is equipped with a temperature observation window (19), and two infrared temperature sensors (9) are provided outside the temperature observation window (19). The two infrared temperature sensors (9) are respectively aligned with the edge and center area of ​​the sample ring (8); The water-cooled copper-based sample stage (5) is equipped with a copper-based sample stage cooling water channel (11) and a thermal resistance wire (12) interlaced inside. The pipes of the copper-based sample stage cooling water channel (11) and the wires of the thermal resistance wire (12) extend out of the reaction chamber (1) from the inside of the riser pipe (6). The pipes of the copper-based sample stage cooling water channel (11) are connected to the chiller (13) after extending out of the reaction chamber (1). The wires of the thermal resistance wire (12) are electrically connected to the electric heating control device (14) after extending out of the reaction chamber (1). The electric heating control device (14) is electrically connected to the dual infrared temperature measuring device (15). The dual infrared temperature measuring device (15) is electrically connected to two infrared temperature sensors (9).

2. The MPCVD equipment for preparing large-size polycrystalline diamond thin films according to claim 1, characterized in that, When the temperature difference detected by the two infrared temperature sensors (9) exceeds the set temperature difference range, the electric heating control device (14) controls the thermal resistance wire (12) to heat.

3. The MPCVD equipment for preparing large-size polycrystalline diamond thin films according to claim 1, characterized in that, The water-cooled copper substrate stage (3) is equipped with a copper substrate stage cooling water channel (10). The pipe of the copper substrate stage cooling water channel (10) extends out of the reaction chamber (1) from the central hole of the quartz ring (2). After the pipe of the copper substrate stage cooling water channel (10) extends out of the reaction chamber (1), it is connected to the chiller (13).

4. The MPCVD equipment for preparing large-size polycrystalline diamond thin films according to claim 1, characterized in that, The thickness of the molybdenum ring (4) is 14-18 mm. The outer diameter of the molybdenum ring (4) is the same as the outer diameter of the water-cooled copper substrate stage (3). The inner diameter of the molybdenum ring (4) is 0.5-3 mm larger than the outer diameter of the water-cooled copper substrate sample stage (5).

5. The MPCVD equipment for preparing large-size polycrystalline diamond thin films according to claim 1, characterized in that, The thickness of the molybdenum support (7) is 1-5 mm, and the radial dimension of the molybdenum support (7) is the same as that of the water-cooled copper-based sample stage (5).

6. The MPCVD equipment for preparing large-size polycrystalline diamond thin films according to claim 5, characterized in that, The radial dimension of the water-cooled copper-based sample stage (5) is 1-5 inches.

7. The MPCVD equipment for preparing large-size polycrystalline diamond thin films according to claim 1, characterized in that, The temperature observation window (19) is a microwave emission window. The microwave power adjustment range is 0.6KW-12KW, and the frequency of the microwave source that can be used is 2450MHz or 915MHz.

8. The MPCVD equipment for preparing large-size polycrystalline diamond thin films according to claim 1, characterized in that, When the lifting tube (6) is at the zero point of its stroke, the height difference between the water-cooled copper-based sample stage (5) and the water-cooled copper substrate stage (3) below is 1 mm.

9. The MPCVD equipment for preparing large-size polycrystalline diamond thin films according to claim 1, characterized in that, A lifting motor (16) is provided outside the reaction chamber (1). The output end of the lifting motor (16) is coaxially connected to the worm (17). The worm (17) is set horizontally and meshes with the worm wheel (18). The worm wheel (18) is fixedly installed outside the reaction chamber (1). A connecting hole is opened in the center of the worm wheel (18). An internal thread is opened on the inner circumferential surface of the connecting hole. An external thread is opened on the outer circumferential surface of the lifting tube (6). One end of the lifting tube (6) extending out of the reaction chamber (1) is threadedly connected to the connecting hole. The top end of the lifting tube (6) is rotatably connected to the bottom of the water-cooled copper-based sample stage (5).

10. A method for preparing large-size polycrystalline diamond thin films, characterized in that, The MPCVD equipment for preparing large-size polycrystalline diamond thin films according to any one of claims 1-9 includes the following steps: The substrate sample was placed in a methanol suspension containing diamond micro powder for ultrasonic treatment. After treatment, it was transferred to alcohol for ultrasonic cleaning. After cleaning, it was allowed to air dry naturally before placing the substrate sample in the sample ring (8) selected according to the substrate sample specifications. The lifting tube (6) is raised to lift the water-cooled copper-based sample stage (5) to a position where the molybdenum support (7) and the molybdenum ring (4) are level. Adjust the position of the two infrared temperature sensors (9) so that the two infrared temperature sensors (9) are aligned with the edge and center area of ​​the sample ring (8) respectively, so that the two infrared temperature sensors (9) can focus on detecting the temperature of the inner and outer areas of the deposited sample through the temperature observation window (19); Adjust the chamber pressure, run the chiller (13), introduce the polycrystalline growth atmosphere after mixing in proportion into the reaction chamber (1), run the microwave source, adjust the microwave power, and control the deposition temperature; The dual infrared temperature measuring device (15) feeds back the temperature parameters of the deposited sample detected by the two infrared temperature measuring sensors (9) to the electric heating control device (14); when the temperature difference between the inner and outer regions of the deposited sample exceeds the set temperature difference range, the electric heating control device (14) controls the thermal resistance wire (12) to heat, so as to control the temperature difference between the inner and outer regions of the deposited sample within the set temperature difference range. As the growth process progresses, the lifting tube (6) is raised and lowered to drive the water-cooled copper-based sample stage (5) to rise and fall, adjusting the height required for the deposition of the sample.

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