Lowcost, lowdefect, 2" GaN epiready substrates processed with EGrinding

Gallium nitride substrates are the key to achieving highend, energyefficient semiconductor devices such as power switches, laser diodes and light emitting diodes (LEDs). Significant effort has been exerted to develop costeffective nearequilibrium ammonothermal (NEAT) growth of bulk GaN crystals; however, due to extreme hardness and chemical stability, a lowcost wafering process for bulk GaN crystals has not been established yet. Currently, chemical mechanical polishing (CMP) to achieve a damagefree, atomicallyflat wafer surface is so inefficient that ~150 hours are required to finish the surface. To achieve a time and cost efficient process to make the surface epiready, we need to develop a wafer shaping process which minimizes subsurface damage and therefore CMP time. This project develops a novel grinding method called EGriniding, which creates a smoother surface with reduced damage using less processing time than the conventional polishing process. During Phase I, we demonstrated the feasibility of EGrinding by achieving a mirrorlike surface (RMS roughness ~2 nm) and very thin subsurface damage layer (~0.5 μm, achievement goal was 1 μm) on 10 x 10 mm GaN wafers. In Phase II, we will expand the wafer size to 2"" and incorporate EGrinding to achieve a more than 30% reduction in wafering time. SixPoint is the leading company in GaN boule growth, therefore we can incorporate the EGrinding into our production process without any business obstacles. The successful development of a lowcost wafering process will lead tolowcost, lowdefect GaN substrates needed for energyrelated applications such as power electronic switches and solidstate lighting. Keywords: GaN wafers, Grinding, Lapping, Polishing, CMP, subsurface damage.