DEFECT FORMATION DURING ANNEALING OF THIN OXIDES ON SILICON

Defect structures resulting from the high-temperature inert gas annealing of thin SiO2 films have been investigated. Czochralski [100] silicon substrates with a 300 angstrom thermal oxide were subjected to a 60 h anneal in argon at 1100-degrees-C. Following the anneal, the wafers were characterized via scanning electron microscope, ellipsometer, scanning Auger microprobe, and atomic force microscope. The defect structures included rounded octagonal voids as well as octagonal and rounded pyramidal etch-pits as reported previously. In addition, deep faceted pits covered by fractured or perforated surface films were observed. The defect morphology depended strongly on location, with the features near the wafer periphery being deeper and more strongly faceted. Based on these and previous experiments, we propose mechanisms for the development of the observed defects.