Characterization of hollow cathode plasma for etching and ashing processes

Abstract

Plasma etching and ashing processes have been utilized to remove coating material from substrate; e.g. the used diamond coating for dry milling of CFRP (carbon fiber reinforced plastic) parts and members must be ashed away before recoating processes for reuse of WC (Co) tool substrates. Perfect ashing of every diamond film on the skewed teeth of tools with fast ashing rate becomes an issue in practice. Hollow cathode plasma ashing was proposed in the present paper as a promising means to solve it. After a spectroscopic analysis, this plasma consisted of ionized and activated oxygen atoms with high ion density. It concentrated only around the hollow cathode. Quantitative plasma diagnosis was performed to measure and investigate the oxygen ion and electron densities in this hollow cathode plasma; i.e. high ion density ranged from 1017 to 1018 m-3 and electron density from 1016 to 1017 m-3 . This high ion and electron density effect on the ashing process of diamond coating was discussed with aid of theoretical modeling and simulation.