A NEW MINORITY-CARRIER SURFACE LIFETIME TECHNIQUE

Comprehensive monitoring of various forms and concentrations of metallic contamination can guard against yield problems in semiconductor devices. Acceptable levels of contamination rapidly decrease with smaller device geometries. Some forms of contamination can be detected by degradation in minority-carrier lifetime, but traditional methods measure lifetime in the bulk silicon rather than at the surface, where device action takes place. A new technique for measuring minority-carrier lifetime at the surface eliminates problems that have prevented this measurement in the past. The technique is sensitive to various forms of metallic contamination. Furthermore, it can be used to measure the surface of epitaxial wafers or wafers with internal gettering because it does not depend on bulk conditions.