HIGH-PRESSURE HIGH-TEMPERATURE STEAM OXIDATION POLY BUFFER LOCOS (HP-HTPBL) FIELD ISOLATION PROCESS FOR REDUCED ENCROACHMENT AND LOW-STRESS

The characterization of High Pressure-High Temperature Poly Buffer LOG OS (HP-HTPBL) isolation for 0.2 mu m design rules Non Volatile Memorie s is presented. Reduced bird's beak and improved charge to breakdown ( Q(bd)) are obtained by combining High Pressure (25 atmospheres) 1100 d egrees C steam oxidation and 30 degrees C/min ramp-up and 12 degrees C /min ramp-down temperature rates. The fast temperature ramp-up inhibit s the crystallization of the amorphous silicon (a-Si) buffer layer int o large grain and limits the grain boundaries oxygen diffusion during the field oxidation process. Low warpage variations are obtained on 20 0 mm diameter wafers by the reduction of the cumulative oxidation indu ced stress.