ICP Enhanced Cmp for Efficient and Non-Damaging Gan Polishing

Abstract

Gallium nitride (GaN) is one of the representatives of the third-generation semiconductors. However, advanced processing to prepare a non-destructive GaN substrate is a key factor affecting the advanced GaN based device. In this paper, an inductively coupled plasma etching (ICP) technique is proposed to enhance the chemical mechanical polishing (CMP) effective to achieve damage-free processing of GaN. The ICP etching technique is utilized to remove most of the damage layer produced by grinding, followed by a short CMP time to repair the surface and further reduce the roughness, resulting in an atomically smooth surface (Sa=0.104 nm).The entire process was shortened from 15 h for conventional CMP to 1.5 h, and it was also shown that the wet oxidation reaction involved in the CMP process eliminates impurities and defects produced by dry etching. FIB-STEM testing demonstrated that the method is a nondestructive polishing method, as ICP techniques are isotropically etched, and CMP does not cause new damage to the substrate. The improvement of the process accelerates the commercialization of large-size GaN single-crystal substrates and promotes their wide application and development in laser displays, RF devices and power electronics.

Keywords: gallium nitride, ICP etching, subsurface damage, material removal, chemical mechanical polishing