Design and Multiphysics Simulation of a Mo/Cu/W Composite Substrate Stage for MPCVD Diamond Deposition

Abstract In the process of preparing high-quality diamond films via microwave plasma chemical vapor deposition (MPCVD), non-uniform substrate temperature distribution and the resulting film residual stress are key factors leading to film warpage and quality degradation. To address this, this paper designs a novel molybdenum/copper/tungsten (Mo/Cu/W) composite substrate stage. Based on COMSOL Multiphysics coupling simulations, it systematically investigates the synergistic effects of the external geometry, internal material composition, and heat-sink grooves of the substrate stage on the plasma characteristics, temperature field, and stress distribution. Simulation results demonstrate that the optimized rounded-edge frustum (RFSS) external geometry effectively improves the uniformity of both electric field and electron density distribution. The combined use of material composites and heat-sink grooves shows a significant synergistic effect: the Mo/Cu/W composite structure alone reduces the center-to-edge temperature difference from 9.1 °C (for the pure Mo structure) to 5.6 °C. Furthermore, with the introduction of heat-sink grooves, the peak tensile stress at the edge of the polycrystalline diamond film decreases from 0.52 GPa to 0.31 GPa, markedly improving the residual stress profile. This study clarifies that the external geometry of the substrate stage dominates the plasma distribution, while the material composite and heat-sink grooves jointly regulate the temperature field and stress distribution, providing a feasible design reference for enhancing the deposition uniformity and mechanical stability of MPCVD diamond films.