Investigation on the etching of thick diamond film and etching as a pretreatment for mechanical polishing

Etching with oxygen plasma produced by DC glow discharge was investigated as a potential technique for etching of diamond films and as a pretreatment technique for mechanical polishing of thick diamond films. The influence of DC power and gas pressure to etched morphology and etching rate were studied using scanning electron microscopy and electronic micro-balance, respectively. The electron temperature and plasma density were measured by Langmuir single probe to explicate the influence mechanism of etching parameters according to an etching model. The effect of etching on mechanical polishing was studied through surface roughness measuring instrument and Raman spectrometer.It was found that at a constant gas pressure the rise of DC power would result in the increase of deepening etch pits overspreading from the protuberant facet to the boundary of diamond crystallites with rising etching rate. And the same tendency was engendered by reducing gas pressure when the DC power remained. The numerous etch pits can be ascribed to etching with a higher rate of dislocations whose edges exist at the film surface. In accordance with an etching model, the measured results of Langmuir probe suggest that the main influence mechanism of etching are the plasma density and electron temperature, and the increase of etching rate and deepening etch pits can be mainly attributed to the enhanced directional etching with rising ion flux and sheath voltage. Appropriate etching with oxygen plasma is an effective pretreatment method for enhancing the efficiency of rough polishing process in mechanical polishing of thick diamond film.