Silicon fusion bonding (SFB) is the joining together of two silicon wafers without the use of intermediate adhesives. The technology has been used to fabricate silicon-on-insulator (SOI) substrates and silicon power devices, and also has wide applications in the fabrication of silicon sensors, actuators and other microstructures. This paper reviews the development and current status of SFB. A history of the technology from the early 1960s to the present is presented. Process techniques necessary to incorporate SFB successfully into silicon micromachining processes are discussed, and examples of successful SFB structures are presented. Comparisons to competing techniques are made, and the potential for future development of SFB structures is discussed. Silicon fusion bonding presents major new possibilities in the design of silicon micromachined structures when combined with other available processing techniques. SFB has already been used in novel accelerometers, high-temperature pressure sensors, ultraminiature pressure sensors and high over-range pressure sensors. SFB does not appear to be the technique of choice for VLSI SOI technology, but it is highly viable for use in silicon microstructures, and it is incumbent on the micromachining community to pursue further development of the technology. With the development of 'smart' power devices occurring in parallel with the development of 'smart' sensors, it is to be hoped that evolution of SFB for both microstructures and power devices will continue and will provide cross-fertilization between the two fields. © 1990.
