Plasma Diagnostics and Characteristics of Hydrofluorocarbon Films in Capacitively Coupled CF4/H2 Plasmas

Abstract

Plasma diagnostics including electron density, temperature, neutral atomic densities of the $\mathbf{CH}_{4}/\mathbf{H}_{2}$ plasmas were performed in a capacitively-coupled reactor using surface-wave probe, Langmuir probe and vacuum ultraviolet absorption spectroscopy. The plasma density increased monotonically with varying $\mathbf{H}_{2}$ content from 30 to 90 %. The electron temperature first decreased with $\mathbf{H}_{2}$ up to 50 % and then increased at higher $\mathbf{H}_{2}$ concentration. The HF concentration reached a maximum value at a $\mathbf{H}_{2}$ of approximately 50 %, which is probably due to balance between H and F radicals from the plasma. Increasing the $\mathbf{H}_{2}$ content resulted in a higher H concentration and a less cross-linked structure of the amorphous hydrofluorocarbon films, analyzed by using in situ Fourier transformation infrared spectroscopy.