(Invited, Digital Presentation) Low-Temperature Direct Bonding of Wide-Bandgap Semiconductor Substrates

For the next-generation semiconductor devices, our research group has developed direct bonding techniques of wide-bandgap materials, including SiC, Ga 2 O 3 , and diamond. It is known that the semiconductor substrates activated by oxygen plasma can form atomic bonds at low temperatures. In this case, a thick oxide layer, which may become a thermal and electrical barrier, is formed at the bonding interface. Meanwhile, our research group demonstrated that the OH-terminated Ga 2 O 3 and diamond substrates were directly bonded without an oxide intermediate layer. In addition, the SiC substrate dipped into the HF acid can be bonded with the Ga 2 O 3 substrate with an ~1-nm-thick amorphous layer. The dissimilar substrates bonded through the ultra-thin intermediate layer would contribute to efficient heat dissipation and future heterojunction devices.