Diagnostics of the diamond depositing inductively coupled plasma by electrostatic probes and optical emission spectroscopy

Abstract

Electrostatic probe methods and optical emission spectroscopy have been used for diagnostics of the low-pressure inductively coupled radio frequency plasma at pressures between 5 and 80 mTorr under real environments of diamond deposition. The single, triple, and emissive probe methods were used alone or combined to obtain electron temperature (Te) and electron density (ne). The single or triple probe method combined with the emissive probe method allowed the determination of ne with high reliability as confirmed by cross-checking. Comparison with the grown deposits suggested the existence of a critical ne value of around 2×1010 cm−3, which was responsible for the drastic decrease in diamond growth rate observed below 10 mTorr and the resulting no growth at around 5 mTorr. The energy distribution of excitation levels of the H atom Balmer series was almost constant and the distribution equilibrium was not established except the case of 5 mTorr, which was ascribed to the difference in the excitation process of H atoms.