Etch Characteristics of CoFeSiB Magnetic Films by Inductively Coupled Plasma Reactive Ion Etching for Magnetic Random Access Memory

초록

Recently, magnetic random access memory (MRAM) has drawn great attention as a prospective semiconductor memorybecause it can provide nonvolatility, fast access time, unlimited read/write endurance, low operating voltage, and high storage density [1-3]. MRAM contains MTJ (magnetic tunnel junction) stack and CMOS. The etching of MTJ stack is one of the key processes for the realization of high density MRAM. The MTJ stackis composed of various magnetic materials, metals, and a tunneling barrier layer. Since magnetic materials and metals in MTJ stack rarely react with chemically active species in a plasma, it is known that dry etching of magnetic materials and metal films is hard to achieve. Initially, ion milling was applied to etch the magnetic materials. Since ion milling is limited by factors such as its slow etch rate, sidewall redeposition and etching damages, new etching technique needs to be developed [4-6]. In this study, the reactive ion etching of CoFeSiB magnetic films isinvestigated in an inductively coupled plasma (ICP) of a Cl2/O2/Ar gas mix. Thin TiN hard mask is employed and the etching proceeds at ambient temperature.Among various etch parameters, the effect of O2 gas on etch characteristics is explored, and the surface analysis of etched films will be performed to elucidate the etching mechanism of the magnetic film at ambient temperature.