Investigation on the Gallium Nitride Polishing Process Under Hybrid-Field Effects

The third-generation semiconductor material gallium nitride (GaN) has attracted more and more researchers attention due to its excellent performance. In the processing of GaN wafer, surface/subsurface damage would inevitably generate after diamond abrasive lapping. Chemical mechanical polishing (CMP) with soft abrasive is widely used to remove surface/subsurface damage and obtain the ultra-smooth wafer surface. However, traditional CMP of GaN wafer has very low material removal rate (MRR) because of the high hardness and chemical inertness of wafer. To improve GaN polishing MRR, hybrid-field effects polishing methods include photochemical mechanical polishing (PCMP) and photoelectrochemical mechanical polishing (PECMP) were proposed. Experimental results illustrated that both PCMP and PECMP methods could significantly improve MRR and surface quality. Meanwhile, the PCMP and PECMP mechanism were discussed.