Overview of plasma induced damage after dry etch processing

Abstract

Plasma induced charging has been identified as a cause for uncontrolled pattern-dependent etch rate modification and physical damage of the etching pattern. Undercutting (notching) of metal lines and underlayer-dependent oxide etch have been studied using a noncontact oxide charging monitor technique. It is shown that the dry etching process is strongly affected by plasma induced wafer charging and by underlying conducting films. The undercutting of metal lines occurs when the metal pattern is electrically connected to the substrate. Specially designed oxide monitor wafers with an metal pattern underlayer were used for charging distribution studies. It was demonstrated that the connection of a metal underlayer to the silicon substrate causes strong accumulation of positive charges in the wafer center. Strong metal line undercutting occurred under these conditions. The resulting pattern of plasma induced charge correlates to the undercutting pattern.