Direct wafer bonding of Ga₂O₃–SiC at room temperature

Integration of Ga₂O₃ on SiC substrate with a high thermal conductivity is one of the promising solutions to reduce the self-heating of Ga₂O₃ devices. Direct wafer bonding of Ga₂O₃–SiC at room temperature was achieved by surface activated bonding (SAB) using a Si-containing Ar ion beam. An average bonding energy of ~2.31 J/m² was achieved. Both the structure and the composition of the interface were investigated to understand the bonding mechanism. According to the interface analysis, a ~2.2 nm amorphous SiC layer and a ~1.8 nm amorphous β-Ga₂O₃ layer originating from the ion beam bombardment for surface activation were found at the interface. A slight diffusion at the interface might already happen at room temperature, which should contribute to the strong bonding. To confirm the diffusion at a low temperature and investigate the possible interfacial variation during device operation, an annealing process was carried out at 473 K. The same analysis was applied on the annealed bonding interface. The interfacial layer shrank by ~0.5 nm after annealing. The further diffusion of Ga and Si at the interface caused by the annealing was confirmed. Besides, the position of the Ar count peak inside the amorphous Ga₂O₃ layer shifted by ~0.5 nm toward SiC.