ECR plasma polishing of CVD diamond films

Polycrystalline diamond films, deposited by MW-plasma CVD, were etched in an air plasma and influences of plasma parameters on the etching behavior were investigated. It was found that the reactivity of plasma species played an important role in the etching behavior of diamond films. The key parameters effecting the etching conditions were gas pressure and microwave power. In air plasmas at pressures >100 Pa, nonuniform etch structures such as etch pits on the grains and at the grain boundaries as well as columnar structures were caused by the selective etching by low-reactivity oxygen species. Diamond films were more uniformly etched in a highly dissociated and ionized low-pressure ECR air plasma. CVD diamond films were polished in an ECR air plasma, the roughness average R(a) being reduced from 800-1000 nm (as deposited) down to 71 nm, with the help of a selectively removed thin gold layer, which was used to confine the reactive etching to the desired asperities of the diamond films.