Monolayer-level controlled incorporation of nitrogen in ultrathin gate dielectrics using remote plasma processing:: Formation of stacked "N-O-N" gate dielectrics

A low thermal budget approach to monolayer-level controlled incorporation of nitrogen in ultrathin gate dielectrics using 300 degrees C, remote plasma processing is discussed. Incorporation of approximately 1 ML of nitrogen at the Si-SiO2 interface in an "N-O" structure has been achieved by remote plasma-assisted oxidation of the Si surface followed by N-2/He remote plasma nitridation, each at a process pressure of 0.3 Torr. The Interface nitridation reduces direct and Fowler-Nordheim tunneling by at least one order of magnitude, independent of film thickness. Incorporation of nitrogen at the top surface of the oxide in a concentration equivalent to about 1-2 molecular layers of silicon nitride in an "O-N" structure has been accomplished by N-2/He remote plasma nitridation at 300 degrees C, but at a reduced process pressure of 0.1 Torr. Top surface nitridation has been shown to prevent boron diffusion out of p(+) poly-Si gate electrodes during high-temperature activation anneals, e.g., at 1000 degrees C. Combining interfacial and top surface nitridation processes resulted in a "N-O-N" structure that was effective in reducing tunneling leakage currents and suppressing boron out-diffusion from p(+) poly-Si gate electrodes. (C) 1999 American Vacuum Society. [S0734-211X(99)20506-9].