Effects of Tetramethyl Silane Concentration on Amorphous SiCN Films Deposited by Microwave Sheath-Voltage Combination Plasma at High Substrate Temperatures

Amorphous silicon carbon nitride (a-SiCN) films are known for their exceptional mechanical properties. This study explores the impact of tetramethylsilane (TMS) concentration on the deposition of a-SiCN films utilizing a microwave sheath-voltage combination plasma (MVP) source. A mixture of TMS and N2 gases served as the reaction medium. The substrate temperatures were maintained between 905°C and 981°C. We observed that the deposition rate escalated with an increase in TMS concentration, reaching a peak rate of approximately 270 µm/h at a 20% TMS concentration. Concurrently, as TMS concentration increased, the carbon content rose from 11 at% to 51 at%, while nitrogen and silicon contents decreased to 15 and 18 at%, respectively. Hence, at lower TMS concentrations, the a-SiCN film predominantly comprised Si-N bonds, but at higher TMS concentrations, it transformed into a composite of Si-N, Si-C, C=N, and C=C bonds. The film hardness also augmented with rising TMS concentrations, achieving a maximum of 28 GPa in 20% TMS films. The friction coefficient for the film with 20% TMS concentration was approximately 0.29. In summary, the study successfully deposited a high-hardness a-SiCN film at an accelerated deposition rate using MVP from a high TMS concentration.