Quality assessment of in situ plasma etched diamond surfaces for CVD overgrowth

TL;DR

This paper introduces a high-resolution X-ray diffraction method to evaluate the effectiveness of in situ plasma etching on diamond surfaces, optimizing pretreatment parameters for improved epitaxial overgrowth quality.

Contribution

It presents a practical, qualitative assessment technique for plasma-etched diamond surfaces, highlighting the influence of process duration and oxygen-to-hydrogen ratio on structural quality and roughness.

Findings

Optimal etching time is around 20 minutes for best results.

Rising oxygen percentage increases roughness without affecting quality gain.

Process duration significantly impacts structural quality improvement.

Abstract

In situ plasma etching is a common method to prepare diamond substrates for epitaxial overgrowth to effectuate higher quality. However, there is no practical, direct, qualitative method established so far to assess the performance of the etching pretreatment. We propose an optimization of the pretreatment process on grounds of high-resolution X-ray diffraction measurements to judge the structural quality gain of the diamond substrates and the effectiveness of the polishing-induced subsurface damage removal. The obtained data shows, that parameters like thickness nor misorientation angle of the diamond substrates seem to influence the gain of the structural quality. The process duration, however, is an important key factor, when the amount of material removal and the arising roughness are discussed. Furthermore, the impact of the oxygen-to-hydrogen ratio is examined. And with rising oxygen percentage, the structural quality gain remains similar, only the overall as well as local mean roughness increases exponentially. Within the utilized reactor setup, the best results are obtained after a 20-minute in situ hydrogen plasma-etching step. The optimal pretreatment process, however, will always embody a tradeoff and needs to be optimized for each reactor type. Due to the introduced method a better evaluation and comparison of the achievements is accomplishable.