Microwave Plasma Chemical Vapor Deposition System Research

Diamond has a series of excellent physical and chemical properties, such as its extreme hardness, thermal conductivity, wide band gap, low dielectric constant, resistance to radiation. For its unique advantages, microwave plasma chemical vapor deposition (MPCVD) becomes one of the most promising high-quality diamond film deposition. The content of this paper is the development of a3KW microwave plasma chemical vapor deposition system.This paper introduces the principle of the microwave plasma chemical vapor deposition. The resonant cavity without internal electrodes can avoid the pollution generated by the electrode discharge, and its operating pressure range is wide, the plasma has high density, large area and stability. Without contact with the vacuum wall, it can avoid pollution from the wall of the contaminationFollowed by MPCVD system development process, from the initial quartz tube of MPCVD to a higher power quartz cover of MPCVD, then the stainless steel resonator cavity, and finally enhanced ECR-MPCVD system. On the MPCVD system research, of thed our country is backward from other countries, we still have lots of problems.Introduced the generation mechanism of the microwave plasma, microwave plasma is generated by a microwave discharge. Compare with DC discharge and radio frequency (RF) discharge It have advantages and broader application. Analyze the interaction between microwave and plasma, including the relationship between the microwave power and microwave, as well as to infer the plasma state by the change of microwave power. In addition to the analysis of microwave propagation in the plasma model, the plasma modeling analysis of the incident microwave transmission and reflection. Finally, introduce the characterization of some basic parameters of the plasma.In the aspects of the cavity of MPCVD system, Because of the strong interaction between the microwave and the plasma in the cavity, it is difficult to improve the cavity only based on experience. This article use ANSOFT software simulated the MPCVD cavity system. First we analyzed the type and perturbation of the cylindrical cavity field, select the TEio mode as the microwave transmission mode, select the TMoi mode as the resonant mode in a cylindrical cavity; we introduced the method of the inhibition of TE11mode. Then we modeled the electric field distribution of the resonant cavity, and by the simplified model to calculate the plasma distribution, through the analysis of the plasma density distribution, the main dimensions of the cavity, including the radius of the cavity, the height and the length of the antenna has been optimized. Optimized cavity parameters of the cavity are:height427mm, cavity radius90mm, the optimal value of the antenna37mm. Provide a reference design of the cavity.Introduce the composition of MPCVD device; it’s making up by the microwave source and transmission system, the mode converter and the plasma discharge chamber, vacuum and air system, cooling system and temperature measurement system. Analyze the microwave generation and transfer process, using the method of controlling the anode current stable to control the output power of microwave. Introduce the field in the rectangular waveguide and single mode transmission conditions. Also introduced the principle of the microwave coupled to the cylindrical cavity by the mode converter. You can use silica method to analyze the mode of the cavity; diamond film characterization methods were introduced, including by XRD, SEM, Raman spectroscopy, energy dispersive spectroscopy and so on.Diamond film deposition experiments were carry out in the MPCVD system. In the case of other fixed parameters, discuss the substrate pretreatment, the gas source composition and deposition temperature on film quality. Diamond films by XRD, SEM and Raman spectroscopy to characterize the results were analyzed to optimize the growth conditions of diamond films. The optimization parameters are as follows: substrate:<100> oriented monocrystalline silicon, substrate approach:0.5μm diamond powder grinding and ultrasonic cleaning, microwave source power:2500W (frequency2.45GHz), deposition pressure:4KPa gas flow, CH4:4SCCM, H2:400SCCM, deposition temperature:726℃.