Optimizing reactive ion etching to remove sub-surface polishing damage on diamond

Low defect smooth substrates are essential to achieve high quality diamond epitaxial growth and high performance devices. The optimization of the Ar/O2/CF4 reactive ion etching (RIE) plasma treatment for diamond substrate smoothing and its effectiveness to remove subsurface polishing damage are characterized. An O2/CF4 RIE process and the effect of different process parameters (inductively coupled plasma, platen power, and pressure) were initially examined. This process, however, still produced a detrimental effect to surface roughness, with etch pits across the surface of the sample. The addition of argon to the process achieved near-zero surface pit density and reduced roughness by 20%–44% after 6 and 10 μm etching. Iterative high-resolution X-ray diffraction measurements provided a nondestructive tool to examine the effectiveness of polishing damage removal and in this case reduced after removal of 6 μm of material from the surface of the diamond substrate with the smoothing treatment.