Quantitative evaluation of dopant loss in 5-10 keV as ion implantation forlow-resistive, ultrashallow source/drain formation

The effectiveness of low-energy 5-10 keV As ion implantation for sub-0.1 mu m metal-oxide-semiconductor field-effect-transistors (MOSFETs) has been in vestigated. When implantation energy is lowered to 5 keV at a dose of 1 x 1 0(14) cm(-2) the sheer resistance of the diffused layer increases steeply. The origin of the sheet resistance increase in 5-10 keV As ion implantation has been quantitatively studied paying attention to dopant loss. We found that 43% of implanted As remains in a 5 nm screen oxide when implantation e nergy is lowered to 5 keV. Moreover 50-70% of As in Si is lost by dopant pi leup at the SiO2/Si interface during 850 degrees C annealing. The pileup pr oblem becomes more severe with junction depth reduction. By optimizing the implantation energy and the ion dose, both low sheet resistance and ultrash allow junction depth have been simultaneously achieved.