Effect of implant damage on the gate oxide thickness

Large area capacitors were fabricated with doping and oxide thickness representative of an n-MOSFET channel region. Capacitance–voltage (C–V) measurements on these capacitors showed a systematic change in the accumulation capacitance when additional implant damage is introduced by a 1×1014 cm−2 40 keV silicon implant. The oxide thickness values extracted from the C–V data increase by 1–4 A with the additional implant damage. This trend is confirmed by additional high resolution TEM and X-ray reflectivity measurements. We postulate that the implant damage increased the oxidation rate, due either to the interstitial flux during TED, or to an increase in surface roughness. For channels doped with boron implantation, the increase in thickness does not change with a 5× increase in the doping dose. In contrast, with BF2-implanted channels, the effects are smaller for higher doping dose.