Effects of ion implantation on deep-submicrometer, drain-engineered MOSFET technologies

The effects of ion implantation on the reliability of thin-oxide (7-nm) MOS structures using drain engineering, e.g. lightly doped-drain (LDD), Inverse-T, large-angle-tilt-implanted drain (LATID), are examined. High-dose, conventional source/drain implants with no spacer present are seen to degrade oxide integrity severely by increasing the gate-to-diffusion leakage along the gate perimeter. The oxide degradation results in a reduction of the oxide breakdown strength rather than an increase in the perimeter shorting defect density. Gate oxide integrity is improved if oxide spacer technologies are used prior to source/drain implantation. To be fully effective these spacers must be thick enough to stop ion penetration at the edge of the polysilicon gate. Oxide spacers grown by reoxidation to ion-implant-induced gate-oxide degradation than oxide spacers formed by CVD oxide. The bird´s beak which forms during the reoxidation step is thought to improve gate reliability by thickening the gate oxide at the gate-feature edge. No yield loss was observed for the low doses (<10 ¹⁴ As/cm²) used for LDD implants. Inverse-T- and GOLD-type devices exhibit the same edge degradation as conventional devices but are further affected by the implant which penetrates the thin T-bar