SUPPRESSION OF BORON PENETRATION IN P-MOSFETS USING LOW-TEMPERATURE GATE-OXIDE N2O ANNEAL( POLYSILICON GATE P)

It has been reported that high-temperature (similar to 1100 degrees C) N2O-annealed oxide can block boron penetration from poly-Si gates to the silicon substrate. However, this high-temperature step may be inap propriate for the low thermal budgets required of deep-submicron ULSI MOSFET's. In this study, we show that low-temperature (900 similar to 950 degrees C) N2O-annealed gate oxide is also a good barrier to boron penetration. For the first time, the change in channel doping profile due to compensation of arsenic and boron ionized impurities was resol ved using MOS C-V measurement techniques. It was found that the higher the nitrogen concentration incorporated at Si/SiO2 interface, the mor e effective is the suppression of boron penetration. The experimental results also suggest that, for 60 similar to 110 Angstrom gate oxides, a certain amount of nitrogen (similar to 2.2%) incorporated near the Si/SiO2 interface is essential to effectively prevent boron diffusing into the underlying silicon substrate.