Gas-phase silicon oxide selective etch

Abstract

A method of etching silicon oxide on patterned heterogeneous structures is described and includes a gas phase etch using anhydrous vapor-phase HF. The HF is combined with an additional precursor in the substrate processing region. The HF may enter through one channel(s) and the additional precursor may flow through another channel(s) prior to forming the combination. The combination may be formed near the substrate. The silicon oxide etch selectivity relative to silicon nitride from is selectable from about one to several hundred. In all cases, the etch rate of exposed silicon, if present, is negligible. No precursors are excited in any plasma either outside or inside the substrate processing region according to embodiments. The additional precursor may be a nitrogen-and-hydrogen-containing precursor such as ammonia.