《Semiconductor Wafer Bonding》.pdf

Annu. Rev. Mater. Sci. 1998. 28:215–41 Copyright c 1998 by Annual Reviews. All rights reserved SEMICONDUCTOR WAFER BONDING ¨ U. Gosele Max-Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany; e-mail:goesele@mpi-halle.de Q.-Y. Tong Wafer Bonding Laboratory, School of Engineering, Duke University, Durham, North Carolina 27708-0300 KEY WORDS: silicon-on-insulator, surface energy, UHV bonding, compliant substrate ABSTRACT When mirror-polished, flat, and clean wafers of almost any material are brought into contact at room temperature, they are locally attracted to each other by van der Waals forces and adhere or bond. This phenomenon is referred to as wafer bond- ing. The most prominent applications of wafer bonding are silicon-on-insulator (SOI) devices, silicon-based sensors and actuators, as well as optical devices. The basics of wafer-bonding technology are described, including microclean- room approaches, prevention of interface bubbles, bonding of III-V compounds, low-temperature bonding, ultra-high vacuum bonding, thinning methods such as smart-cut procedures, and twist wafer bonding for compliant substrates. Wafer bonding allows a new degree of freedom in design and fabrication of material combinations that previously would have been excluded because these mate- rial combinations cannot be realized by the conventional approach of epitaxial growth. INTRODUCTION Wafer bonding refers to the phenomenon wherein mirror-polished, flat, and clean wafers of almost any material, when brought into contact at room tem- perature, are locally attracted to each other by van der Waals forces and adhere or bond. Wafer bonding is alternatively also known as direct bonding, fusion bonding, or more colloquially as gluing without glue. In most cases, the wafers