Reduction of microtrenching and island formation in oxide plasma etching by employing electron beam charge neutralization

Abstract

During plasma etching of oxide thin-film patterns, nonuniform charge buildup within etching features results in formation of microtrenches. Near the etch endpoint, the underlying film layer adjacent to the feature edges is exposed first, leaving an oxide island in the feature center and potentially causing underlayer damage before the endpoint is reached. Herein, a directional electron flux is added to the plasma ion flux incident on the etching substrate with the goal of minimizing microtrenching and oxide island formation. Scanning electron microscopic images of patterns etched with added electron irradiation show a reduction in microtrenching and oxide island formation as compared to patterns etched under identical conditions without electron irradiation. A computer simulation shows that the added electron irradiation reduces microtrenching by allowing more uniform ion flux to reach the feature bottom.