Ultrathin nitrided gate dielectrics: Plasma processing, chemical characterization, performance, and reliability

The incorporation of nitrogen (N) atoms into ultrathin gate dielectrics 1) at monolayer levels at Si-SiO2interfaces reduces tunneling current and defect generation; 2) in bulk nitrides, as in oxide-nitride-oxide (ONO) or oxide-nitride (ON) composite structures, allows the use of physically thicker films without reduced capacitance compared to single-layer oxides; and 3) in nitrided layers at the polycrystalline Si-dielectric interface or in ON dielectrics reduces boron (B) atom out-diffusion from heavily doped p+polycrystalline silicon gate electrodes into oxide gate dielectrics. The results presented in this review demonstrate that N atoms can be selectively and independently incorporated into different parts of the gate dielectric by low-temperatureremote-plasma-assisted processing. When combined with low-thermal-budget rapid thermal annealing, this yields ultrathin gate dielectrics with performance and reliability which generally exceeds that of single-layer thermally grown oxides. The devices addressed in this paper include n-MOS and p-mos field-effect transistors (FETs) with oxide-equivalent thicknesses of less than 2 nm.