Plasma process induced physical damage on ultra thin gate oxide

In this paper, plasma process induced physical damage such as oxide pitting, notching and ion-bombardment induced Si damage has been investigated. Local plasma charging is the main cause for oxide pitting and residual Cl atoms cause notching at the bottom corner of the feature. SiO2 hard mask in combination with a Br/O-2 chemistry provides an oxide pitting and notching free gate patterning process on ultra thin gate oxides. Amorphisation of the underlying Si-substrate can only observed by means of TEM analysis and is explained as an effect of the ion-bombardment. With decreasing the gate oxide thickness below 5nm, the physical damage seems to be more concern than the electrical charging damage from the gate polysilicon patterning.