High-efficiency Planarization of GaN Wefers by Catalyst-Referred Etching Employing Photoelectrochemical Oxdation

Abstract:
In this study, a gallium nitride (GaN) substrate was planarized using catalyst-referred etching (CARE). Typical removal rate of GaN substrate is several nm/h, which is not enough value. To improve the removal rate, the GaN substrate was processed using CARE-assisted by PEC reaction (PEC CARE); the removal rate was 77 nm/h. However, the surface was embossed because of subsurface scratches introduced during preprocessing. These scratches were removed when the PEC CARE process was conducted under an applied potential of 1.5 V; The removal rate was 800 nm/h. In addition, a smooth surface of surface roughness 0.4 nm rms was obtained. After subsequent CARE process using a Pt catalyst and deionized water without assist of PEC reaction, a surface with step-terrace structure of the surface roughness of 0.11 nm rms was obtained.; in this case, the surface roughness was 0.11 nm rms and the removal rate was 5 nm/h. Keywords: Planarization, Catalyst-referred etching, Chemical-mechanical Polishing, CARE, Gallium Nitride, Photoelectrochimical reaction, Catalyst