OXIDE-GROWTH ENHANCEMENT ON HIGHLY N-TYPE DOPED SILICON UNDER STEAM OXIDATION

Steam oxidation of silicon, enhanced by arsenic or phosphorus doping a t concentrations higher than 10(19) cm(-3), has been experimentally in vestigated in the temperature range of 700 to 900 degrees C on <100> a nd <111> surface orientations to gain better insight into the enhanced oxide growth and to derive data for possible model improvements. The redistribution of the dopant to the grown oxide, the transition layer, and remaining silicon is mathematically described. The resultant dopa nt concentration in the oxide and the associated dopant accumulation a round the reacting surface follow exponential functions in agreement w ith measurement at least up to 800 degrees C oxidation temperature. Th e oxidation enhancement relative to lightly doped silicon clearly deve lops gradually with the oxide growth as do the oxide doping and the ac cumulation. Only 10 to 30% of the accumulated dopants reside in the si licon and contribute to conductivity there. However, there is an about 5 nm thick conductive layer above the regular silicon that can be etc hed off by HF but seems to change its structure with a rapid thermal a nnealing at 1000 degrees C, rendering it etch resistant.