ELECTRICAL CHARACTERISTICS OF RAPID THERMAL NITRIDED-OXIDE GATE N-MOSFETS AND P-MOSFETS WITH LESS-THAN 1 ATOM-PERCENT NITROGEN CONCENTRATION

The characteristics and reliability of nitrided-oxide gate n- and p-MOSFET's with less than 1 atom%nitrogen concentration in the gate films were investigated in detail. These very light nitridations were accomplished using NH3 gas at low temperatures-from 800-degrees-C to 900-degrees-C. Nitrogen concentrations as low as 0.13 atom% were successfully measured by SIMS and AES. The region of optimum nitrogen concentration for deep-sub-micron devices is discussed. We explain how good drivability and good hot-carrier reliability were attained simultaneously with a nitrogen concentration of around 0.5 atom%, which is equivalent to that of oxynitride gate MOSFETs using N2O gas. The suppression of boron penetration is also discussed. Light nitridation by ammonia gas is particularly desirable for deep-sub-micron processes because it can be accomplished at a relatively low temperature of about 900-degrees-C.