Effects of oxide exposure, photoresist and dopant activation on the plasma damage immunity of ultrathin oxides and oxynitrides

Plasma-induced damage study has been performed on ultrathin oxides and oxynitrides. Effects of oxide exposure, photoresist and gate dopant activation on the electrical and reliability characteristics were investigated. It was found that the sidewall exposed structures show less degradation in Qbd and trapping compared with fully covered MOSCAP structures after O₂ plasma exposure. A model for the damage mechanism was proposed which considers the radiation effect and photo-annealing effect, in addition to the well-known charging effect. Note that the damage induced might be very different in other plasma conditions because the photo-anneal effect is strongly dependent on the plasma condition. These results indicate that plasma damage evaluation using fully-covered capacitors alone cannot be used to predict the actual damages in CMOS integrated circuits. It was also found that photoresist overlayer protects the gate from charging and the induced damages will be reduced by activating the gate after the gate etch