Reduction of Plasma Damage in Reactive Ion Etching by Means of Suppressing Self-Bias

Abstract

We discuss a technique for suppressing the sheath voltage of the powered electrode (the self-bias) without introducing a substantial disturbance to the main plasma and reduce plasma damage in the etching of amorphous silicon (a-Si) films. It has been shown experimentally that the sheath voltage can be reduced in a wide voltage range by reducing the floating potential. The plasma density was almost constant at the disk on which the wafer was placed. The damage introduced to a-Si films by ion bombardment was reduced by 41% of that obtained at the sheath voltage of -73 V by suppressing the sheath voltage from -73 V to -36 V. Also, it was ascertained experimentally that a threshold sheath voltage for the ion damage may exist.