Planarization of Phosphorus‐Doped Silicon Dioxide

Abstract

A process has been developed for smoothing surfaces of phosphorus‐doped silicon dioxide (P‐glass). Samples are coated with a positive photoresist which flows during application to form a relatively smooth surface. The photoresist is etched in a plasma using conditions that etch the photoresist and the P‐glass at nearly the same rates. Since the surface profile of the photoresist is preserved during etching, the P‐glass is left with a relatively smooth surface. This process reduces step heights, usually by at least 50%, and decreases the angles at abrupt steps to 5°–30°. In contrast to the flowed P‐glass process, planarization does not require high temperatures and is independent of phosphorus concentration.