Method for growing oversized diamond polycrystalline film

Abstract

The invention provides a method for growing an oversized diamond polycrystalline film. The method comprises the following steps: S1, cleaning and drying a monocrystalline silicon wafer at room temperature; s2, carrying out pretreatment seed crystal on the monocrystalline silicon wafer, covering a diamond nanocrystalline layer on the silicon surface, and putting the monocrystalline silicon wafer into MPCVD (Microwave Plasma Chemical Vapor Deposition) equipment; s3, the cavity is vacuumized, then hydrogen is introduced for purging, and then vacuumizing is conducted again; then hydrogen is introduced, the air pressure is regulated and controlled to be 5-8 torr, and starting is started to ignite the plasma; s4, the microwave power is increased to 70 KW to 75 KW at the speed of 4.5 KW / min to 5.5 KW / min, the air pressure is increased to 165 torr to 180 torr at the speed of 10 torr / min to 30 torr / min, and the temperature is increased to 900 DEG C to 950 DEG C at the speed of 60 DEG C / min; s5, introducing growth gas, wherein the flow rate of hydrogen is 5000-6000 sccm, the flow rate of methane is 100-150 sccm, the flow rate of oxygen is 5-8 sccm, the flow rate of nitrogen is 1-2 sccm, and the flow rate of argon is 800-1000 sccm; and S6, after the growth is finished, cooling at a rate of 30 DEG C / min, and introducing nitrogen into the cavity for vacuum breaking until the temperature is reduced to room temperature, so as to obtain the oversized diamond polycrystalline film. The size of the oversized diamond polycrystalline film reaches 12 inches.

Description

Technical Field

[0001] The invention relates to a method for growing an ultra-large-size diamond polycrystalline film, belonging to the technical field of semiconductor materials. Background Art

[0002] Silicon devices refer to semiconductor electronic devices made of silicon as the main material. As the requirements for performance and functionality of modern electronic devices continue to increase, the power density of silicon devices is also increasing. Under high power density, the heat generated per unit area or unit volume increases significantly. However, the thermal conductivity of silicon is relatively low, generally around 100-120W / (m·K), which means that the heat conduction speed inside the silicon device is slow, which is not conducive to the rapid dissipation of heat. When the silicon device is in a high-power working state, the heat generated is difficult to conduct quickly to the heat dissipation medium, which can easily cause the internal temperature of the silicon device to rise, affecting its performance and reliability.

[0003] Diamond has the highest thermal conductivity among known materials, up to 22W / (cm·K), far exceeding traditional heat dissipation materials such as copper and aluminum. If a diamond polycrystalline film can be grown on a silicon device, it will be able to quickly conduct the heat generated by the silicon device to ensure stable operation of the device, solving the problem of insufficient heat dissipation of traditional heat dissipation materials in high-power, high-frequency devices and greatly improving heat dissipation efficiency.

[0004] At present, the main method for growing diamond polycrystalline films is chemical vapor deposition (CVD) technology. Among them, microwave plasma assisted chemical vapor deposition (MPCVD) has become a common method for preparing high-quality diamond polycrystalline films because of its advantages such as no electrode pollution and the ability to accurately control reaction parameters. Through this technology, diamond polycrystalline films can be grown on substrate materials, providing a basis for achieving large-scale growth. However, the existing chemical vapor deposition (MPCVD) technology for growing diamond polycrystalline films has the following defects: (1) The current growth rate of diamond polycrystalline films is relatively low, especially for high-quality large-size films, which have a long growth cycle, which to a certain extent limits their large-scale production and application. The longer growth time will also increase production costs and reduce their market competitiveness; (2) Although diamond polycrystalline films of a certain size, such as two inches, can be prepared at present, compared with traditional semiconductor materials such as silicon wafers, their size is still relatively small, and it is difficult to meet the needs of large-size wafers such as large-scale integrated circuits; (3) It is difficult to achieve thickness uniformity and performance uniformity of diamond polycrystalline films within a large size range, which may lead to inconsistent performance in different areas on the same film, affecting its application effect in large-area devices; (4) Even if large-sized diamond polycrystalline films can be grown, their quality is poor and it is difficult to meet the application requirements of large-area devices. Summary of the invention

[0005] The present invention provides a method for growing an ultra-large-sized diamond polycrystalline film, which can effectively solve the above-mentioned problem.

[0006] The present invention is achieved in that:

[0007] A method for growing an ultra-large-sized diamond polycrystalline film comprises the following steps:

[0008] S1, cleaning and drying the single crystal silicon wafer at room temperature;

[0009] S2, pre-treating the single crystal silicon wafer to form a seed crystal, so that the silicon surface is covered with a diamond nanocrystal layer, and placing it in an MPCVD device; the MPCVD device is a 915MHZ or 433MHZ MPCVD device;

[0010] S3, evacuate the chamber, then introduce hydrogen to purge, and then evacuate again; then introduce hydrogen and adjust the pressure to 5-8 torr to start igniting the plasma;

[0011] S4, increase the microwave power to 70-75KW at a rate of 4.5-5.5KW / min, increase the gas pressure to 165-180torr at a rate of 10-30torr / min, and increase the temperature to 900-950°C at a rate of 60°C / min;

[0012] S5, introducing growth gas: hydrogen flow rate 5000-6000sccm, methane flow rate 100-150sccm, oxygen flow rate 5-8sccm, nitrogen flow rate 1-2sccm, argon flow rate 800-1000sccm;

[0013] S6, after the growth is completed, the temperature is lowered at a rate of 30°C / min until it reaches room temperature, and then nitrogen is introduced into the cavity to break the vacuum, thereby obtaining the ultra-large-sized diamond polycrystalline film.

[0014] In some embodiments, the cleaning is to use acetone, alcohol, and deionized water to ultrasonically treat the single crystal silicon wafer for 15 to 30 minutes in sequence.

[0015] In some embodiments, the drying is to use an inert gas to blow dry the single crystal silicon wafer to dry its surface.

[0016] In some embodiments, the diamond nanocrystal layer has a thickness of 10 to 50 nm.

[0017] In some embodiments, the vacuum degree of the vacuum pumping is less than 5 mtorr, and the number of vacuum pumping is 3 to 5.

[0018] In some embodiments, after step S6, the method further includes: S7, grinding and polishing the diamond surface of the super-large-sized diamond polycrystalline film to make its ra less than 1 nm.

[0019] In some embodiments, step S7 further includes: S8, chemically removing silicon from the polished ultra-large-sized diamond polycrystalline film to remove all silicon bases and obtain a pure diamond film.

[0020] In some embodiments, step S8 further includes: S9, scribing the pure diamond film using a picosecond laser to obtain a high-quality diamond sheet.

[0021] In some embodiments, after step S6, the method further includes: grinding and polishing the silicon surface of the ultra-large-sized diamond polycrystalline film to remove part of the silicon base and retain the silicon base with a thickness of 5 nm to 10 μm.

[0022] An ultra-large-sized diamond polycrystalline film prepared by the method.

[0023] The beneficial effects of the present invention are:

[0024] The method of the present invention can grow a 12-inch polycrystalline diamond film with high thermal conductivity through a specific process flow, which is much larger than the same size in the prior art, directly solving the problem of insufficient size, providing a basis for its application in large-area electronic devices, optical elements and other fields, making it more likely to be compatible with existing silicon-based semiconductor technology, and promoting the large-scale application of diamond films in related fields. With the expansion of production scale and the maturity of technology, it is expected to reduce the production cost per unit area to a certain extent, thereby improving the competitiveness of large-size diamond polycrystalline films in the market and accelerating its industrialization process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, 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 invention 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.

[0026] Figure 1 This is a size measurement diagram of the ultra-large-sized diamond polycrystalline film prepared in Example 1.

[0027] Figure 2 This is a thermal conductivity test diagram of the ultra-large-sized diamond polycrystalline film prepared in Example 1.

[0028] Figure 3 This is a thermal conductivity test diagram of the ultra-large-sized diamond polycrystalline film prepared in Example 4.

[0029] Figure 4 This is a thermal conductivity test diagram of the ultra-large-sized diamond polycrystalline film prepared in Example 5. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] An embodiment of the present invention provides a method for growing an ultra-large-sized diamond polycrystalline film, the method comprising the following steps:

[0032] S1, at room temperature, the single crystal silicon wafer is first thoroughly cleaned and then dried. The purpose of this process is to ensure the cleanliness of the substrate to avoid contamination in the subsequent growth process.

[0033] S2, next, the single crystal silicon wafer is pre-treated and seeded to form a diamond nanocrystal seed layer on its surface. This seed layer will help to grow a high-quality polycrystalline diamond film in the future, and can ensure the uniform and high-quality growth of the diamond polycrystalline film. In this step, the seeded silicon wafer is placed in the MPCVD device to prepare for the growth of diamond polycrystalline film. The MPCVD device can be a quartz bell MPCVD, the microwave power supply can be a magnetron or a solid-state power supply, and the operating frequency can be 915MHz or 433MHz.

[0034] S3, then the chamber is evacuated, hydrogen is introduced for purging, and then evacuated again. The purpose of this series of operations is to clean the environment inside the chamber. Subsequently, hydrogen is introduced and the pressure is adjusted to 5-8 torr, and the plasma is started. In this step, the flow rate of hydrogen is set to 50 sccm.

[0035] S4, in the next experimental steps, the experimental parameters will be gradually adjusted to optimize the growth conditions of the diamond film. First, the microwave power will be gradually increased at a rate of 4.5 to 5.5 kilowatts (KW) per minute until it reaches a range of 70 to 75 kilowatts (KW). This process requires careful control to ensure a steady increase in microwave power to provide a uniform energy environment for the experiment. At the same time, the gas pressure will be gradually increased at a rate of 10 to 30 torr per minute until it reaches a range of 165 to 180 torr. The gradual increase in gas pressure helps maintain a stable state in the reaction chamber and ensures that the reactants are evenly distributed in the chamber.

[0036] In addition, the temperature needs to be gradually increased at a rate of 60 degrees Celsius (℃) per minute until it reaches 900 to 950 degrees Celsius (℃). This heating rate is critical to the growth of diamond films because it ensures that the temperature reaches the required high temperature in a short time while avoiding damage to the experimental equipment due to sudden temperature changes. In this process, higher microwave power and lower gas pressure work together to significantly increase the volume of the plasma. The increase in plasma volume helps to cover a larger reaction area, thereby promoting the uniform growth of large-area diamond films.

[0037] In summary, microwave power, gas pressure and temperature increase rate have a decisive influence on the growth of large-area diamond films. By precisely controlling the adjustment rate of these parameters, the growth conditions of diamond films can be effectively optimized, thereby obtaining high-quality large-area diamond film products.

[0038] S5, after that, the growth gas is introduced, including hydrogen flow rate of 5000-6000sccm, methane flow rate of 100-150sccm, oxygen flow rate of 5-8sccm, nitrogen flow rate of 1-2sccm, and argon flow rate of 800-1000sccm. Among these gases, the larger hydrogen flow rate is to ensure that the gas flow can evenly fill the entire cavity. Methane is the main growth gas, while oxygen, nitrogen and argon are auxiliary growth gases. When the temperature rises to the rated temperature, the process gas flow rate is continuously increased from 0 over time within 10 minutes until the rated flow rate is reached, and then maintained for 5-10 minutes after reaching the rated flow rate. These parameters of the growth gas introduced are very critical to the growth quality of the diamond film. If they are not properly regulated, the thermal conductivity of the diamond film will be greatly reduced.

[0039] S6, when the growth process is completed, the temperature is lowered at a rate of 30°C / min until the temperature drops to room temperature. Subsequently, nitrogen is introduced into the cavity to break the vacuum, thereby obtaining the super-large-sized diamond polycrystalline film. After the cavity reaches normal temperature and pressure, the chamber can be opened to take out the silicon-based diamond polycrystalline film that has completed growth. By the method of the present invention, a super-large-sized diamond polycrystalline film with a size of up to 12 inches can be obtained, which is much larger than the size of similar diamond films in the prior art.

[0040] In certain specific embodiments, the cleaning process includes ultrasonically cleaning the single crystal silicon wafer in sequence using acetone, alcohol and deionized water, and the ultrasonic time of each cleaning agent is set between 15 and 30 minutes. First, the single crystal silicon wafer is placed in acetone for ultrasonic cleaning to remove organic pollutants and grease on the surface. Then, the wafer is transferred to alcohol for a second ultrasonic cleaning to further remove residual organic matter and particles. Finally, the wafer is placed in deionized water for a third ultrasonic cleaning to remove residual alcohol and other possible impurities. Through this ultrasonic cleaning method using different cleaning agents in sequence, the cleanliness of the surface of the single crystal silicon wafer can be ensured, providing a clean substrate for subsequent process steps.

[0041] In some specific embodiments, the drying process can be achieved by using an inert gas to blow dry the single crystal silicon wafer, which can effectively remove moisture from the surface of the wafer to make it dry. Specifically, inert gases such as nitrogen or argon, etc., due to their stable chemical properties, will not react with the single crystal silicon wafer, so they can be safely used in the drying process. In this way, the dryness of the wafer surface can be ensured, thereby avoiding the adverse effects caused by moisture in the subsequent manufacturing process.

[0042] In some specific embodiments, the thickness of the diamond nanocrystalline layer is set between 10 nanometers and 50 nanometers. By accurately controlling this thickness range, the performance of the seed layer can be effectively ensured to be optimal. Such a seed layer thickness not only helps to achieve uniform growth of the polycrystalline diamond film, but also significantly improves its quality, ensuring that the grown diamond film has excellent physical and chemical properties. The selection of this thickness range is based on a deep understanding of the diamond growth mechanism and a detailed study of the interaction between the seed layer and the diamond film. By optimizing the thickness of the seed layer, defects that may occur during the growth process can be effectively avoided, thereby obtaining a high-quality polycrystalline diamond film.

[0043] In some specific embodiments, the vacuum degree of the evacuation is less than 5mtorr, that is, less than 5 millitorr (a unit of vacuum degree), and the number of evacuations is 3 to 5 times. The purpose of this process is to clean the environment in the cavity and ensure that there are no excess impurities and gas residues in the cavity. By evacuating the cavity multiple times, the pressure in the cavity can be effectively reduced, thereby achieving a highly clean and pure environment. Such an environment is crucial for the growth of polycrystalline diamond film because it helps to ensure that the polycrystalline diamond film can be grown under uniform and high-quality conditions. In this way, the quality and performance of the polycrystalline diamond film can be significantly improved, so that it exhibits better stability and reliability in various applications.

[0044] In some specific embodiments, after step S6, step S7 is further included. In step S7, the diamond surface of the aforementioned super-large-sized diamond polycrystalline film is finely ground and polished to achieve a surface roughness of less than 1 nanometer (ra < 1nm). Such treatment can significantly improve the surface quality of the diamond film, making it smoother, thereby meeting the requirements of certain high-precision applications.

[0045] In these embodiments, after completing step S7, step S8 is further included. In step S8, the polished super-large-sized diamond polycrystalline film is subjected to chemical desiliconization treatment, the purpose of which is to completely remove all silicon-based components therein, thereby obtaining a pure diamond film composed entirely of diamond. Such a pure diamond film will have extremely broad application prospects due to its excellent physical and chemical properties, such as in the fields of high-performance electronic devices, high-precision optical components, and wear-resistant materials in extreme environments.

[0046] In these embodiments, after completing step S8, step S9 is further included. In step S9, the obtained pure diamond film is subjected to precise slicing by picosecond laser, in order to obtain high-quality diamond sheets. Such diamond sheets will have extremely high application value due to their high purity and excellent physical properties, especially in fields requiring high precision and high stability, such as semiconductor manufacturing, precision optics, and high-end decorative materials.

[0047] In some specific embodiments, after step S6, the silicon surface of the oversized diamond polycrystalline film is further subjected to detailed grinding and polishing. The purpose of this process is to remove part of the silicon-based material so as to retain a silicon-based layer with a thickness between 5 nanometers and 10 microns in the final product. Through this thinning process, the heat dissipation efficiency of the device can be significantly improved. Specifically, the thinned silicon-based layer can conduct heat more effectively, thereby accelerating the speed at which heat is transferred from the inside of the device to the external environment. This improvement is particularly important for electronic devices that generate a lot of heat during operation, because it helps to keep the device operating within a safe and efficient temperature range.

[0048] The present invention introduces a method for preparing an ultra-large-sized diamond polycrystalline film. Through a unique process flow, the method successfully grows a polycrystalline diamond film with a diameter of 12 inches. This size far exceeds the existing technology, directly overcomes the problem of size limitation, and lays the foundation for the application of diamond films in large-area electronic devices and optical components. This technology meets the heat dissipation needs of high-power density devices: as electronic devices develop towards miniaturization and high performance, the power density of devices such as chips continues to increase. Diamond heat sinks can effectively cope with the heat dissipation challenges under high power density, ensuring that the device can still maintain a low temperature when working under high load, thereby improving the performance and reliability of the device and extending its service life. For example, the power density of diamond heat sinks manufactured using chemical vapor deposition (CVD) technology is expected to be three times or more higher than the most advanced gallium nitride (GaN) devices currently, and is particularly suitable for high-power, high-frequency switching application scenarios such as wireless communications and radar systems.

[0049] In addition, diamond heat dissipation technology can also optimize the performance and life of the chip. During the operation of the chip, excessively high temperature will lead to performance degradation, such as reduced carrier mobility, increased leakage current, reduced breakdown voltage, etc., and will also shorten the service life of the chip. Diamond heat dissipation can effectively control the temperature of the chip, reduce the performance degradation and shortened life caused by overheating, and ensure that the chip operates stably and efficiently under high frequency and high power conditions, giving full play to its performance advantages.

[0050] The high thermal conductivity of diamond also makes the design of the heat dissipation system simpler and more efficient. Compared with traditional heat dissipation solutions, the diamond heat dissipation system does not require complex heat dissipation structures and a large number of heat dissipation components, thereby reducing the volume, weight and cost of the heat dissipation system, while improving the integration and reliability of the entire system, helping to achieve miniaturization and lightweighting of electronic equipment.

[0051] Diamond heat sinks not only have good thermal conductivity, but also have excellent insulation properties, mechanical strength and thermal stability. They can maintain stable performance in harsh environments such as high temperature, high pressure, and high humidity, and are not prone to deformation, damage or performance degradation. Therefore, in fields such as aerospace, military equipment, and industrial control that require high environmental adaptability, diamond heat sinks can provide reliable heat dissipation for electronic devices and ensure the normal operation of equipment under extreme conditions.

[0052] Finally, diamond heat dissipation technology breaks through the limitations of traditional heat dissipation materials. Traditional heat dissipation materials such as copper and aluminum have certain limitations in terms of heat dissipation performance, physical properties or cost. For example, although copper has high thermal conductivity, it has high density, high cost, and may have electromagnetic compatibility issues in certain specific applications; aluminum has relatively weak heat dissipation performance and is difficult to meet the heat dissipation requirements of high-power devices. Diamond heat dissipation overcomes the shortcomings of these traditional materials and provides a more ideal solution to solve the heat dissipation problems of high-computing chips, high-frequency power devices, etc.

[0053] Example 1

[0054] A method for growing an ultra-large-sized diamond polycrystalline film comprises the following steps:

[0055] S1, cleaning and drying the single crystal silicon wafer at room temperature; the cleaning is to use acetone, alcohol, and deionized water to ultrasonically treat the single crystal silicon wafer for 20 minutes in sequence. The drying is to use an inert gas to blow dry the single crystal silicon wafer to dry its surface.

[0056] S2, pre-treating the single crystal silicon wafer to make the silicon surface covered with a layer of diamond nanocrystal layer, and putting it into the MPCVD equipment (UP-575 high-power MPCVD equipment of Shenzhen Youpulai Plasma Technology Co., Ltd.) to prepare for the growth of diamond film; the thickness of the diamond nanocrystal layer is about 30nm.

[0057] S3, evacuate the cavity, then introduce hydrogen for purging, and then evacuate again; then introduce hydrogen and adjust the gas pressure to 6 torr to start igniting the plasma; the vacuum degree of the evacuation is less than 5 mtorr, and the number of evacuations is 3.

[0058] S4, increase the microwave power to 75 KW at a rate of 5 KW / min, increase the gas pressure to 170 torr at a rate of 15 torr / min, and increase the temperature to 920°C at a rate of 60°C / min.

[0059] S5, introduce growth gas: hydrogen flow 5500sccm, methane flow 125sccm, oxygen flow 6sccm, nitrogen flow 1.5sccm, argon flow 900sccm. When the temperature rises to the rated temperature, the process gas flow is continuously increased from 0 over time within 10 minutes until the rated flow is reached, and then maintained for 8 minutes after reaching the rated flow. .。

[0060] S6, after the growth is completed, the temperature is lowered at a rate of 30°C / min until it reaches room temperature, and then nitrogen is introduced into the cavity to break the vacuum, thereby obtaining the ultra-large-sized diamond polycrystalline film.

[0061] The size of the super-large diamond polycrystalline film is measured, such as Figure 1 As shown. Figure 1 It can be seen that the size of the super-large-sized diamond polycrystalline film is about 12 inches (30.48 cm).

[0062] Comparative Example 1

[0063] The difference from Example 1 is step S4. The operation of Example 1 is: increasing the microwave power to 75 KW at a rate of 2 KW / min, increasing the gas pressure to 220 torr at a rate of 30 torr / min, and increasing the temperature to 920°C at a rate of 100°C / min. Other operations are the same as Example 1.

[0064] The size of the diamond polycrystalline film was measured and found to be approximately 5 inches.

[0065] Comparative Example 2

[0066] The difference from Example 1 is step S4. The operation of Comparative Example 2 is: increasing the microwave power to 75 kW at a rate of 2 kW / min, increasing the gas pressure to 240 torr at a rate of 30 torr / min, and increasing the temperature to 920°C at a rate of 100°C / min. Other operations are the same as in Example 1.

[0067] The size of the diamond polycrystalline film was measured and found to be approximately 4 inches.

[0068] Comparative Example 3

[0069] The difference from Example 1 is step S4. The operation of Comparative Example 2 is: increasing the microwave power to 75 kW at a rate of 2 kW / min, increasing the gas pressure to 200 torr at a rate of 30 torr / min, and increasing the temperature to 920°C at a rate of 100°C / min. Other operations are the same as in Example 1.

[0070] The size of the diamond polycrystalline film was measured and found to be approximately 7 inches.

[0071] Comparative Example 4

[0072] The difference from Example 1 is step S5. The operation of Example 2 is as follows: the growth gas is introduced with a hydrogen flow rate of 2500 sccm, a methane flow rate of 50 sccm, an oxygen flow rate of 6 sccm, a nitrogen flow rate of 1.5 sccm, and an argon flow rate of 900 sccm. Other operations are the same as in Example 1.

[0073] The size of the diamond polycrystalline film was measured and found to be approximately 12 inches.

[0074] Comparative Example 5

[0075] The difference from Example 1 is step S5. The operation of Example 2 is as follows: the growth gas is introduced with a hydrogen flow rate of 5500 sccm, a methane flow rate of 125 sccm, an oxygen flow rate of 15 sccm, a nitrogen flow rate of 5 sccm, and an argon flow rate of 900 sccm. Other operations are the same as in Example 1.

[0076] The size of the diamond polycrystalline film was measured and found to be approximately 12 inches.

[0077] Example 2

[0078] In the embodiment 1, after step S6, the following further comprises: S7, grinding and polishing the diamond surface of the super-large-sized diamond polycrystalline film to make its ra < 1 nm.

[0079] After step S7, the method further includes: S8, chemically removing silicon from the polished super-large-sized diamond polycrystalline film to remove all silicon bases and obtain a pure diamond film.

[0080] The step S8 also includes: S9, using an ultraviolet picosecond laser to scribing the pure diamond film, and using a splitting machine to split the pure diamond film to obtain high-quality diamond sheets.

[0081] Example 3

[0082] In Example 1, after step S6, the method further includes: grinding and polishing the silicon surface of the ultra-large-sized diamond polycrystalline film to remove part of the silicon base and retain the silicon base with a thickness of 5 nm to 10 μm.

[0083] The thermal conductivity of the diamond polycrystalline films of Example 1 and Comparative Examples 4 and 5 was tested using the 3ω electrical test technique at a test temperature of 25°C ± 10°C. The test results are shown in Table 1. Figure 2-4 And as shown in Table 1.

[0084] Table 1

[0085] Example Thermal conductivity / W / (m·K) Example 1 1993.2 Comparative Example 4 1236.6 Comparative Example 5 1283.5

[0086] It can be clearly seen from the comparative analysis of Example 1 and Comparative Examples 1-3 that the diamond polycrystalline film prepared in Example 1 significantly surpasses the samples 1-3 in the comparative experiment in size. This result fully demonstrates that in the growth process of diamond polycrystalline film, key process parameters such as microwave power and gas pressure have a crucial influence on its growth area. Specifically, by appropriately reducing the gas pressure in the reaction chamber and simultaneously increasing the microwave power, the volume of the plasma can be effectively expanded, thereby promoting the uniform growth of the diamond polycrystalline film over a larger area, and ultimately achieving a significant expansion of the growth area.

[0087] Furthermore, it can be observed from the data listed in Table 1 that the diamond polycrystalline film of Example 1 is comparable in size to the samples of Comparative Examples 4-5, but in terms of the key performance indicator of thermal conductivity, Example 1 shows a significant advantage, which is much higher than the samples of Comparative Examples 4-5. This phenomenon reveals an important fact, that is, in the growth process of diamond polycrystalline film, the optimization of ventilation parameters plays a decisive role in ensuring its formation quality. Although the samples of Comparative Examples 4-5 can also prepare large-sized diamond polycrystalline films, due to the failure to reasonably control the ventilation parameters, their thermal conductivity has dropped significantly, and even failed to meet the qualified standards, which greatly limits their performance and scope of application in practical applications. Therefore, optimizing the ventilation parameters is a key link in improving the comprehensive performance of diamond polycrystalline films.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for growing an ultra-large-sized diamond polycrystalline film, characterized in that: The following steps are involved: S1, cleaning and drying the single crystal silicon wafer at room temperature; S2, pre-treating the single crystal silicon wafer to form a seed crystal, so that the silicon surface is covered with a diamond nanocrystalline layer, and placing it in an MPCVD device; the MPCVD device is a 915MHZ / 433MHZ MPCVD device; S3, evacuate the chamber, then introduce hydrogen to purge, and then evacuate again; then introduce hydrogen and adjust the pressure to 5-8 torr to start igniting the plasma; S4, increase the microwave power to 70-75KW at a rate of 4.5-5.5KW / min, increase the gas pressure to 165-180torr at a rate of 10-30torr / min, and increase the temperature to 900-950°C at a rate of 60°C / min; S5, introducing growth gas: hydrogen flow rate 5000-6000sccm, methane flow rate 100-150sccm, oxygen flow rate 5-8sccm, nitrogen flow rate 1-2sccm, argon flow rate 800-1000sccm; S6, after the growth is completed, the temperature is lowered at a rate of 30°C / min until it reaches room temperature, and then nitrogen is introduced into the cavity to break the vacuum, thereby obtaining the ultra-large-sized diamond polycrystalline film.

2. The method for growing an ultra-large-size diamond polycrystalline film according to claim 1, characterized in that: The cleaning is to use acetone, alcohol and deionized water to ultrasonically clean the single crystal silicon wafer for 15 to 30 minutes in sequence.

3. The method for growing an ultra-large-size diamond polycrystalline film according to claim 1, characterized in that: The drying is to use an inert gas to blow dry the single crystal silicon wafer to make its surface dry.

4. The method for growing an ultra-large-size diamond polycrystalline film according to claim 1, characterized in that: The thickness of the diamond nanocrystal layer is 10-50 nm.

5. The method for growing an ultra-large-size diamond polycrystalline film according to claim 1, characterized in that: The vacuum degree of the vacuum pumping is less than 5 mtorr, and the number of vacuum pumping is 3 to 5.

6. The method for growing an ultra-large-size diamond polycrystalline film according to claim 1, characterized in that: After step S6, the method further includes: S7, grinding and polishing the diamond surface of the super-large-size diamond polycrystalline film to make its ra less than 1 nm.

7. The method for growing an ultra-large-size diamond polycrystalline film according to claim 6, characterized in that: After step S7, the method further includes: S8, chemically removing silicon from the polished super-large-sized diamond polycrystalline film to remove all silicon bases and obtain a pure diamond film.

8. The method for growing an ultra-large-sized diamond polycrystalline film according to claim 7, characterized in that: The step S8 also includes: S9, scribing the pure diamond film using a picosecond laser to obtain a high-quality diamond sheet.

9. The method for growing an ultra-large-sized diamond polycrystalline film according to claim 1, characterized in that: After step S6, the following steps are further performed: grinding and polishing the silicon surface of the super-large-sized diamond polycrystalline film to remove part of the silicon base and retain the silicon base with a thickness of 5 nm to 10 μm.

10. An ultra-large-sized diamond polycrystalline film prepared by the method according to any one of claims 1 to 9.

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