Crystallographic anisotropy of growth and etch rates of CVD diamond

The investigation of orientation dependent crystal growth and etch processes can provide deep insights into the underlying mechanisms and thus helps to validate theoretical models. Here, we report on homoepitaxial diamond growth and oxygen etch experiments on polished, polycrystalline CVD diamond wafers by use of electron backscatter diffraction (EBSD) and white-light interferometry (WLI). Atomic force microscopy (AFM) was applied to provide additional atomic scale surface morphology information. The main advantage of using polycrystalline diamond substrates with almost random grain orientation is that it allows determining the orientation dependent growth (etch) rate for different orientations within one experiment. Specifically, we studied the effect of methane concentration on the diamond growth rate, using a microwave plasma CVD process. At 1% methane concentration a maximum of the growth rate near <100> and a minimum near <111> is detected. Increasing the methane concentration up to 5% shifts the maximum towards <110> while the minimum stays at <111>. Etch rate measurements in a microwave powered oxygen plasma reveal a pronounced maximum at <111>. We also made a first attempt to interpret our experimental data in terms of local micro-faceting of high-indexed planes.