Impact of nitrogen implantation on highly reliable sub-quarter-micron metal oxide field-effect transistors (MOSFETs) with lightly doped drain structure

We studied the effects of nitrogen implantation in the SiO₂ sidewall spacer in detail in order to improve in the reliability of lightly doped drain (LDD) metal oxide field-effect transistors (MOSFETs), since the hot carrier degradation of LDD MOSFETs remains one of major issues even in the sub-quarter-micron region. It was found that nitrogen implantation in the SiO₂ sidewall spacer can effectively suppress the hot carrier degradation of the LDD structure because the nitrogen atoms are segregated at the interface between the sidewall SiO₂ and the Si substrate. This segregation can reduce the generation of interface states or electron traps in the sidewall spacer without causing gate depletion or an increase in gate resistance. Highly reliable sub-quarter-micron LDD N-MOSFETs can be realized using this nitrogen implantation technique.