Vacuum ultraviolet (VUV) and vapor-combined surface modification for hybrid bonding of SiC, GaN, and Si substrates at low temperature and atmospheric pressure

Homo- and heterogeneous bonding of SiC (Si-related semiconductors), and GaN was found feasible at the temperatures lower than 200 °C and atmospheric pressure, utilizing a single vacuum ultraviolet (VUV) and vapor - combined surface modification method. Hybrid bonding of these materials will be of practical use in obtaining high reliability and performance in thin power devices. The water vapor, which was included in VUV irradiation atmosphere (N₂) at the tuned amount of exposure ((g/m³)·s), helped generate hydrogen and hydroxyl radicals, then resulted in the elimination of surface contaminant, partial deoxidization of native oxide, and the formation of hydrate bridging layers at the same time. According to the change in the generation ratio of bridging layers, the exposure of around 4 × 10³ (g/m³)·s was chosen as an optimum parameter. Upon heating at 150 - 200 °C, the hydrogen bonds, which were followed by the dehydration inside the bridging layers, formed tight adhesion between the surfaces. Although the bond area was limited due to the partial contact at the touchdown, the interface did not contain readily visible voids.