Oxide-Free SiC-SiC Direct Wafer Bonding and Its Characterization

Abstract

In this study, the feasibility of oxide-free room temperature wafer bonding process was demonstrated for 4H-SiC wafers with in situ surface oxide removal. The investigations covered three areas: incoming metrology of the original wafer, characterization of activated single wafer and analysis of bonded wafer pairs. The focus was on compositional, chemical, mechanical and morphological analysis of the surfaces and of the bonded interfaces. Incoming wafers were inspected whether they fulfill the requirements of wafer bonding, and activated wafers were characterized to measure the surface modifications. The quality of the bonded wafers and the bonding energy were verified using scanning acoustic microscopy measurements as well as the Maszara blade test. Furthermore, cross-section transmission electron microscopy was used to investigate the amorphous layer at the bonding interface. The work reported is a demonstration of the capability of different characterization methods regarding SiC-SiC wafer bonding.