Characterization of indium and nitrogen co-implant of NMOSFET for advanced DRAM technologies with dual-gate oxide

Indium and nitrogen implant were used to form the NMOSFET retrograde channel and low-threshold thin-oxide devices respectively. These two impurities are implanted into the same channel before gate oxidation for an advanced sub-0.12/spl mu/m DRAM technology. In this paper, the impacts of nitrogen and indium implant on the current-voltage, Qbd of the ultra-thin gate oxides and hot carrier lifetime of the NMOSFET were investigated. It was found that high dose of the indium implant degrades the oxide integrity. Furthermore, enhanced GOI degradation, such as increasing ratio of the A-mode oxide breakdown was observed for the nitrogen and indium co-implantation. However, based on our investigation, TDDB of gate oxides and hot-carrier lifetime of NMOSFET can reach lifetime criteria for a current 0.12/spl mu/m trench DRAM technology if proper process conditions are selected.