Elimination of OISF in large-size Si substrate for low warpage and crack-free GaN epitaxial wafer

The oxygen induced stacking fault (OISF) in heavy boron-doping Si substrates causes severe warpage and surface cracks of GaN epitaxial wafers, which will lower the production yield of GaN-based power devices. In this work, high-quality 8-inch Si substrates were fabricated by using rapid thermal annealing (RTA) to eliminate OISF, and thus GaN-epitaxial wafers with low warpage and no surface cracks were obtained. The results show that RTA at 1200 oC can effectively eliminate OISF in Si substrate. Furthermore, the surface morphology and defect measurements indicated that surface cracks of 8-inch epitaxial wafers were removed fully, and its bow value was decreased markedly from 45.7μm to 14.3μm. Consequently, the yields of high electron mobility transistors based on GaN wafers were improved up to 97%.