Multi-physics simulation and experimental optimization of diamond deposition in a cylindrical MPCVD reactor

Résumé fourni par la source

Abstract The uniformity and quality of diamond films deposited in Microwave Plasma Chemical Vapor Deposition (MPCVD) reactors are significantly challenged by non-uniform plasma distributions and low growth rates. This study combines multi-physics numerical simulations with experimental investigations to optimize diamond deposition in a home-built cylindrical resonant-mode MPCVD reactor. A comprehensive multi-physics model coupling electromagnetic fields, fluid dynamics, and hydrogen-methane plasma chemistry was developed to analyze the effects of microwave power, reactor pressure, substrate height, and chamfer geometry on plasma characteristics, particularly electron density, temperature, and electric field uniformity. Experimentally, the influences of methane concentration (2%–6%) and substrate temperature (910 °C–995 °C) on the morphology, crystallinity, and growth rate of polycrystalline diamond films were systematically evaluated. The simulation results identify optimal geometric parameters: a substrate height of 5 mm combined with a 0.8 mm chamfer, and a substrate edge flush with a molybdenum holder (Δh = 0 mm), which minimize the coefficient of variation for electric field uniformity to 3.284%. Experimentally, optimized deposition conditions of 4% methane concentration and a substrate temperature of 935 °C–940 °C yielded dense, phase-pure polycrystalline diamond films with a growth rate of 4 μm h −1 , as confirmed by SEM and Raman spectroscopy (FWHM of 8.9–9.4 cm −1 ). This work provides a validated framework for the coupled optimization of the process and geometric parameters to achieve high-quality, uniform diamond films via MPCVD.

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