Bonding Mechanisms and Electrical Properties of Ge/Si and Si/Si Bonded Wafers Achieved by Thin Microcrystalline Ge Interlayer

High-quality Si/Si and Ge/Si wafer bonding is achieved by introducing an ultra-thin microcrystalline Ge interlayer on Si substrate. The bonded wafer with a high-crystallinity Ge interlayer can effectively transfer and absorb bubbles, achieving high bonding strength of Ge/Si and Si/Si bonded wafers with bubble-free and oxide-free bonded interface after low-temperature annealing. Different from the tunneling model appropriated for the bonded wafers with low-crystallinity interlayer, a carrier recombination model is constructed for these with high-crystallinity interlayer to describe the carrier migration behaviors at the bonded interface. Furthermore, five carrier transport models are established to illustrate the effect of different crystallinity of the Ge interlayer on the carrier transport. This work provides a practical and simple method to fabricate high-quality bonding materials, which is of great significance for the development of micro-electronics devices.