Design And Research Of 20kW/915 MHz Microwave Plasma Device

The chemical vapor deposition method used in the microwave plasma reactor to prepare synthetic diamond films is currently one of the ideal methods for preparing high-quality diamond films.And the MPCVD method is currently the most ideal method for preparing high-quality diamond films.Until now,many scientific research institutions and enterprises conducted a lot in deposition equipment as well as technology.However,due to foreign technology blockade,the diamond film growth rate of existing equipment is low and the quality is not high,which severely limits the application of diamond film.In this paper,a new 915MHz high-power microwave plasma chemical vapor deposition reactor is developed on the basis of previous work.From the earliest quartz tube development to the current large-scale microwave resonator,the diamond grown by the MPCVD method has also developed from the initial granular shape to the current film shape.Various types of diamond deposition equipment had been studied in this paper.A microwave plasma reactor with a resonance mode of TMO21 and a frequency of 915MHz was designed independently after analyzing and comparing the electromagnetic field distribution and discharge performance of different equipment.According to the excitation coupling theory of the microwave resonator,a novel frustum-conical ring-gap coupling structure is designed for the reactor in this paper.The comparison with traditional structures shows that the new structure can effectively enhance the resonant electric field strength at the center while reducing that of the secondary.This coupling structure enhances the electric field separation of the resonant cavity and can effectively increase the power capacity of the reactor.In order to verify the discharge performance of this new type of microwave plasma reactor,the phenomenological model of hydrogen plasma commonly used in China is used in this paper to study the influence of power and pressure on the plasma discharge state of the reactor.The simulation results show that the new reactor achieves a larger plasma area and higher power input than the same type of resonant reactor under the pressure and temperature conditions required by the diamond deposition process.In order to better study the discharge results of hydrogen plasma in this reactor,the collision reactions of hydrogen plasma are studied in detail in this paper,and a set of hydrogen discharge models suitable for diamond film deposition is summarized based on the experimental data of the existing literature.And the completeness of this model is verified by the one-dimensional local field approximation method.Finally,using this model,the spatial distribution results of the discharge particles in the reactor are obtained.According to the simulation results of the microwave electromagnetic field,the structural design of the reactor is completed,combined with the microwave,vacuum,and water-cooling systems,the microwave plasma chemical vapor deposition platform was accomplished.Then the various subsystems of the experimental platform were tested.Finally,a preliminary discharge experiment was conducted on this platform.