Investigation of implantation-induced defects in thin gate oxides using low field tunnel currents

Abstract

The influence of through the gate implantation (TGI) on MOS structures with an oxide thickness of 4.0 nm is investigated comparing implantation related trap assisted tunneling currents to leakage currents induced by electrical stress. Although the steady-state J-V characteristics show a similar behavior of the differently generated defects, trap filling experiments and electrical stress tests suggest different physical properties of either kind of defect. Also a decrease in trap generation rate with increasing TGI dose is detected, probably due to a TGI induced reduction of precursor sites for stress induced traps. As overall defect density is formed by the superposition of implantation induced and stress induced defects, this is not contradictory to a reduction of reliability with increasing TGI dose found earlier.