Plasma induced charging and physical damage after dry etch processing

Plasma induced charging has been identified as a cause of uncontrolled pattern-dependent etch rate modification and physical etching pattern damage. It is demonstrated that plasma nonuniformity and the pattern distribution of conducting layers under the wafer surface play an important role in the final charging distribution, resulting in physical damage, device damage and etch process failure. Undercut or notching of metal lines and underlayer-dependent oxide etch are studied using a noncontact oxide charging monitor technique. It is shown that the dry etch process is strongly affected by plasma induced wafer charging. Undercutting of metal lines occurs when the metal pattern has an electrical connection to the substrate. Oxide charging monitor wafers with a metal underlayer connected to the silicon substrate have charging redistribution with a strong accumulation of positive charge in the wafer center. The induced charge pattern is correlated to the undercut pattern