Effect of Postannealing on the Oxygen Precipitation and Internal Gettering Process in N/N+ (100) Epitaxial Wafers

Abstract

N/N+ (100) epitaxial silicon wafers having substrate wafers doped with antimony to a resistivity between 0.005 and 0.3 Ω‐cm were annealed at 750°C in a nitrogen ambient for times up to 48h prior to a high‐temperature anneal at 1050°C in dry oxygen. After these heat‐treatments, the bulk defect and electrical properties of the material were characterized. Dependence of the bulk defect size and density as well as the denuded zone width on the postannealing time and resistivity of the substrate wafers were observed. The quality of a gate oxide grown on these wafers and their minority carrier generation lifetime were found to improve after postannealing. An extended postannealing can, however, cause degradation of the oxide integrity and lifetime. This phenomenon is hypothesized to be caused by the microdefects in the epitaxial layer as a result of lack of a denuded zone and/or lack of gettering effectivness after a completion of oxygen precipitation.