Analysis of Subsurface Damage Structures of Gallium Nitride Substrates Induced by Mechanical Polishing with Diamond Abrasives

• Published in: physica status solidi (b) 2024-11, Vol.261 (11), p.n/a
• Main Authors: Omiya, Natsuko, Aida, Hideo, Takeda, Hidetoshi, Kanda, Motoki, Doi, Toshiro
• Format: Article
• Language: English
• Subjects: cathodoluminescence imaging; chemical mechanical polishing; GaN substrate; subsurface damage
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.202400031

Subsurface damage (SSD) structures induced by mechanical polishing of gallium nitride (GaN) substrates are comprehensively investigated using atomic force microscopy, cathodoluminescence (CL) imaging, and cross‐sectional transmittance electron microscopy. The low removal rate of the CMP process is a barrier to high productivity of a GaN wafering process; therefore, reducing the chemical mechanical polishing (CMP) process time by reducing the depth of SSD induced by mechanical processing is an active research area. To better understand the SSD structures, the surface roughness, SSD depth, and SSD distributions induced by mechanical polishing are quantitatively evaluated in this study. The SSD structures induced by mechanical polishing can be quantitatively exhibited as the SSD distribution with the damage strength at the outermost surface and the damage propagation, which are obtained by CMP process time‐resolved CL imaging method. On the basis of the analysis results, a schematic model of the SSD structures for mechanically polished GaN substrates is proposed. Herein, subsurface damage (SSD) structures induced by mechanical polishing of gallium nitride substrates are examined. Investigations on the SSD structures are quite important to improve the productivity of the wafering process. The main findings are that the SSD structures can be quantitatively evaluated as the surface damage strength at the outermost surface and the damage propagation. On the basis of the experimental results, a model of the SSD structure is proposed.