Development of HFCVD apparatus for synthesizing diamond films with low thermal budget

Abstract

The electrical power consumption, which is approximately equal to the thermal budget, accounts for the majority of the total cost to synthesize diamond films by the hot filament chemical vapor deposition (HFCVD) apparatus. In this study, two strategies, visualizing as certain additional parts in the apparatus, are proposed for reducing the thermal budget and synthesis cost. Detailed effects are proven by the finite volume method (FVM) simulation, temperature measurement and deposition experiments, demonstrating that the reduction of thermal conductivity of the worktable (by changing the worktable material) and the insertion of the circular ring copper shielding will significantly contribute to the reduction of the heat dissipation and substrate temperature rise. Influences of major filament parameters on substrate temperature values and distributions are then clarified, suggesting that in order to control the substrate temperatures in a similar and reasonable range in the modified apparatus, the best choice is to synchronously reduce the filament diameter and the electrical power, while retaining the filament temperature still in a high level (around 2200 °C). Finally, the energy saving ratios are as high as 28.4% (experimental apparatus) and 27.4% (commercial apparatus), and the substrate temperature distributions can also be improved, guaranteeing the uniformity of as-deposited diamond films on mass substrates.