Abstract: Utilizing numerical simulation techniques in combination with COMSOL Multiphysics software, a novel MPCVD system was proposed. The structural parameters of the system was optimized through simulation under a microwave electric field. At the optimal dimensions, the flow field distribution, the plasma and electric field distribution of the device were simulated and calculated. Finally, diamond films were deposited, and the effects of methane and oxygen content on the growth of diamond films were studied. The results show that under the optimal dimensions, the highest electric field intensity is above the substrate holder, reaching 6 430 V/m, and a stable hemispherical plasma completely covering the substrate holder without secondary plasma formation is obtained at an input power of 4.5 kW and a pressure of 80 torr. The optimal air inlet of the device is located directly above, and two exhaust outlets are symmetrically distributed below. The higher CH₄ content leads to a faster deposition rate, but the excessive CH₄ content degrades the crystal quality. When the volume ratio of CH₄ to H₂ is 6%, the crystal quality is better. As the O₂ content increases, the diamond deposition rate increases first and then decreases. When the volume ratio of O₂ to H₂ reaches 2%, the deposition rate approaches 0. When the volume ratio of O₂ to H₂ is 0.5%, the crystal quality is better.

Key words: MPCVD, diamond film, numerical simulation, plasma, microwave resonant cavity