Etching and micro-optics fabrication in diamond using chlorine-based inductively-coupled plasma

The effect of Inductively-Coupled Plasma (ICP) etching on diamond using chlorine-based plasma has been investigated. The diamond materials studied include type IIa natural diamond, High Pressure and High Temperature (HPHT) diamond and Chemical Vapour Deposition (CVD) diamond. It was found that argon and chlorine (Ar/Cl2) ICP plasma etching can improve the smoothness of the diamond surface. By using this method, a minimum root-mean-squared (rms) surface roughness of 0.19 nm has been achieved. To demonstrate optimized Ar/Cl2 plasma etching, diamond spherical micro-lenses and micro-trenches were fabricated. Compared to argon and oxygen (Ar/O2) plasma etching, Ar/Cl2 plasma etching has a low selectivity with respect to the photo-resist mask, which enables an accurate control over the dimensions of the microstructures fabricated. The surface quality and profiles of these micro-lenses and micro-trenches were characterized by atomic force microscopy (AFM) and were shown to be better than those fabricated by Ar/O2 ICP plasma.