Design and optimization of a microwave plasma enhanced chemical vapor deposition system for low-pressure operations

Microwave plasma-enhanced chemical vapor deposition (MPECVD) is widely employed in applications such as thin-film deposition, diamond synthesis, and surface modification, owing to its ability to generate uniform, high-density plasmas under low-pressure conditions. In this work, an MPECVD system operating at 2.45 GHz has been designed and optimized for stable argon plasma generation at pressure levels ranging from 75 to 100 mTorr and input power levels from 80 to 100 W. The system features a coaxial WR-340 waveguide, a quartz ring, and glass-filled quartz slots, engineered to enhance plasma confinement and uniformity. To evaluate and refine the system, 3-D finite element method (FEM) simulations have been performed, integrating electromagnetic wave propagation, plasma transport, and heat transfer in a multiphysics framework. Simulation results demonstrate that the inclusion of the quartz ring and optimized slot geometry effectively mitigates the localization of over-dense plasmas while improving uniformity at the chamber center. Adjustments to slot dimensions further minimize electron losses to chamber walls and ensure efficient power conservation. The optimized design can achieve a stable plasma discharge with a central electron density of ~5e17 m^-3, demonstrating its suitability for advanced material processing in lower pressure regimes. This study underscores the significance of 3-D FEM simulations in optimizing an MPECVD system and highlights structural modifications, such as quartz components, as the key to achieving scalable, efficient plasma processing systems. This work demonstrates the potential of advanced simulation-driven design in optimizing an MPECVD system for precise and efficient plasma-based material processing, paving the way for broader applications in semiconductor manufacturing, thin-film deposition, and surface engineering.