Etching of CoFeB Using CO ∕ NH3 in an Inductively Coupled Plasma Etching System

Abstract

A CoFeB thin film composing a magnetic tunneling junction of was etched in an inductively coupled plasma (ICP) etching system using gas mixtures, and its etch characteristics were compared with those of the CoFeB thin film etched using . When was used to etch the CoFeB thin film, even though its etch rate was faster than that of the CoFeB thin film etched using , a rough CoFeB surface could be observed due to the corrosion of the CoFeB surface during exposure to the air in addition to the significant change of surface composition. On the other hand, no corrosion of the CoFeB thin film was observed after the etching using . When the ratio of was varied, the highest etch rate of could be observed at the ratio of 1:3 compared to about for CO or at the ICP source power of , bias power of , and of operating pressure. The highest etch rate was related to the formation of volatile metal carbonyls between metal and CO, where appeared to assist the easier formation of metal carbonyl by preventing the dissociation of CO into C and .