NEW PHENOMENA OF CHARGE DAMAGE IN PLASMA-ETCHING - HEAVY DAMAGE ONLY THROUGH DENSE-LINE ANTENNA

The effect of antenna shape on charge damage has been examined using electron cyclotron resonance (ECR) plasma metal etching and test devices with an 8-nm-thick gate oxide. A dense-line antenna causes capacitor breakdown and the positive shift of the transistor's threshold voltage (V(t)), while a sparse-line antenna does not. This positive V(t) shift corresponds to a positive charge-up of the dense line, and is not dependent on overetching. Such damage is hardly observed when the antenna's top surface is exposed to the plasma, indicating that the plasma is uniform in terms of conventional charge damage. These new phenomena can be explained by a new mechanism consisting of electron shading with photoresist patterns. This shading leads to less neutralization of the ion charge impinging onto the transitory metal which remains between the antenna lines because of the microloading effect, and thus the excess positive charge causes the damage.