The Buried Oxide of Silicon on Insulator Materials

Doctoral thesis, 1997

The buried oxide of silicon on insulator (SOI) wafers plays an important role in the operation of electronic devices made on such materials. The presence of defects in the buried oxide can seriously degrade the performance of a circuit. This thesis presents results from electrical and structural investigations of buried oxides in bonded SOI (BSOI) wafers and in separation by implanted oxygen (SIMOX) wafers. Direct evidence for large amounts of hydrogen at all solid-solid interfaces in BSOI wafers is presented. The amount of hydrogen depends on the cleaning procedure used prior to wafer bonding and it correlates with structural and electrical defects in the buried oxide of the final SOI wafer. To enhance the thermal conductivity through BSOI wafers, buried aluminum oxide films can be used as an alternative to the commonly used buried silicon dioxide. The aluminum oxide films have sufficiently good electrical properties, but there are problems with film stress as a result of structural transformations during high temperature processing. The nature of internal oxidation of the recently developed low dose SIMOX structure was investigated. It is suggested that oxygen saturation in the SOI film plays an important role during growth of the buried oxide.