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/sup 14/ As/cm/sup 2/) 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.<
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