Damage-free highly efficient plasma-assisted polishing of a 20-mm square large mosaic single crystal diamond substrate

Nian Liu,Kohki Sugawara,Kenichi Fujino,Kentaro Kawai,Naoya Yoshitaka,Yuko Akabane,Kenta Arima,Kazuya Yamamura,Daisuke Takeuchi,Hideaki Yamada

doi:10.1038/s41598-020-76430-6

Abstract

Plasma-assisted polishing (PAP) as a damage-free and highly efficient polishing technique has been widely applied to difficult-to-machine wide-gap semiconductor materials such as 4H-SiC (0001) and GaN (0001). In this study, a 20-mm square large mosaic single crystal diamond (SCD) substrate synthesized by microwave plasma chemical vapor deposition (CVD) was polished by PAP. Argon-based plasma containing oxygen was used in PAP to modify the surface of quartz glass polishing plate, and a high material removal rate (MRR) of 13.3 μm/h was obtained. The flatness of SCD polished by PAP measured by an interferometer was 0.5 μm. The surface roughness measured by both scanning white light interferometer (SWLI) (84-μm square) and atomic force microscope (AFM) (5-μm square) was less than 0.5 nm Sq. The micro-Raman spectroscopy measurement results of mosaic SCD substrate processed by PAP showed that residual stress and non-diamond components on the surface after PAP processing were below the detection limit.

Highlights

Plasma-assisted polishing (PAP) as a damage-free and highly efficient polishing technique has been widely applied to difficult-to-machine wide-gap semiconductor materials such as 4H-SiC (0001) and GaN (0001)
We describe the PAP polishing characteristics of 20-mm square mosaic single crystal diamond (SCD) substrate made by the clone method
To evaluate the surface roughness of the mosaic SCD substrate, seven local areas on the entire substrate were measured by scanning white light interferometer (SWLI)

Summary

Introduction

Plasma-assisted polishing (PAP) as a damage-free and highly efficient polishing technique has been widely applied to difficult-to-machine wide-gap semiconductor materials such as 4H-SiC (0001) and GaN (0001). A 20-mm square large mosaic single crystal diamond (SCD) substrate synthesized by microwave plasma chemical vapor deposition (CVD) was polished by PAP. Argon-based plasma containing oxygen was used in PAP to modify the surface of quartz glass polishing plate, and a high material removal rate (MRR) of 13.3 μm/h was obtained. In this method, it is assumed that the non-diamond component, which is converted by the reaction between the diamond surface and the catalytic metal at high temperature caused by friction, is mechanically or chemically removed. We describe the PAP polishing characteristics of 20-mm square mosaic SCD substrate made by the clone method

Methods

Results

Conclusion