Silicon-on-insulator (SOI) by bonding and ETCH-back

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. A preferential etch-back process is used to produce Silicon-on-insulator (SOI) whose electrical quality is equal to that of bulk silicon. Capacitor measurements show a 27 µsec minority carrier lifetime and low Q
ss
at the SOI-"bottom oxide" interface, in addition, there is negligible charge within the bonding oxide. N-channel and p-channel FET devices show threshold voltages and mobilities equal to bulk controls. The subthreshold leakage is less than 1 fA per micron of channel width.