Wafer bonding for silicon-on-insulator technologies

TLDR

The process involves bonding silicon wafers with only thermally grown oxide between them. The authors propose that wafers are drawn into intimate contact by consuming gaseous oxygen during oxidation, creating a partial vacuum. Bonding occurs after insertion into an oxidizing ambient, driven by oxygen consumption that generates a partial vacuum and polymerization of silanol bonds between wafer pairs. The technique yields SOI by etching away all but a few microns of one wafer, achieving a 27 µs minority‑carrier lifetime, no interface degradation, and negligible bonding‑interface charge, making it suitable for 3D and planar SOI applications.

Abstract

A silicon wafer bonding process is described in which only thermally grown oxide is present between wafer pairs. Bonding occurs after insertion into an oxidizing ambient. It is proposed the wafers are drawn into intimate contact as a result of the gaseous oxygen between them being consumed by oxidation, thus producing a partial vacuum. The proposed bonding mechanism is polymerization of silanol bonds between wafer pairs. Silicon on insulator (SOI) is produced by etching away all but a few microns of one of the bonded pair. Capacitor measurements show a 27 μs minority-carrier lifetime and no degradation of the SOI-insulator interface. In addition, there is negligible charge at the bonding interface making the technique attractive for three-dimensional as well as planar SOI applications.