Design and Simulation of a Microwave Plasma Enhanced Chemical Vapor Deposition System Using Multiphysics Fluid Modeling*

One of the promising thin film plasma-based manufacturing methods for growth of diamonds is microwave plasma-enhanced chemical vapor deposition (MPECVD). This paper discusses the design of a 3-D MPECVD chamber operated at a 2.45 GHz frequency using the multiphysics fluid modeling based on a finite element method (FEM) that incorporates many physical interfaces including laminar flow, heat transfer in fluids, plasma, and electromagnetic waves (EM) to give more self-consistent and accurate simulation results. The geometrical design of MPECVD consists of a coaxial waveguide connected by slots to a cylindrical plasma chamber at the center to produce TM₀₁₁ mode. If the coupling between the EM in the waveguide and the plasma in the chamber is not good then the power deposited to the chamber is very low, hence good optimized design is needed. Hence the input microwave power and deposited power on the plasma are relatively different. A high power is initially required to ignite the plasma ball and it is possible to sustain the plasma at lower power after the ignition. It is found that the ignition and deposited power of the plasma chamber at 2.45 GHz with the argon pressure at 1 atm and the plasma density of ~1.0e17 1/m³ reaching steady-state at around 5 msec could be obtained. Detailed analysis of the dependence of the MPECVD operation over the critical operating density of the driving frequency and the relation between input power to the waveguide and deposited power to the camber will be presented and discussed.