A bird´s beak reduction technique for LOCOS in VLSI Fabrication

The local oxidation of silicon (LOCOS) enhancement technique using a thin nitridized pad oxide formed by thermally nitridizing a thin thermal oxide in ammonia gas ambient has been developed for fabricating a defect-free near-zero bird´s beak field isolation structure. By directly measuring the bird´s beak length from the SEM cross-sectional view of the enhanced LOCOS structure, the process regime for reducing the bird´s beak length down to 0.1 µm with a field oxide thickness of 8000 Å has been exploited.