Etching of iridium thin films in chlorine- and fluorine-based inductively coupled plasmas

Abstract

The etch characteristics of Ir thin films were investigated in an inductively coupled plasma chamber, using a variety of chlorine gas chemistries, which included Cl2/Ar, Cl2/O2/Ar, and BCl3/Ar, as well as fluorine-based plasmas consisting of mixtures such as SF6/Ar, SF6/He, NF3/Ar, and CF4/O2. Under our experimental conditions, we found that the etch rates of Ir were considerably faster in fluorine-containing plasmas (~30 nm/min) compared to chlorine-based mixtures (<15 nm/min). The patterning of 100 nm line/space features has been demonstrated using an organic mask. Although they show the fastest etching rates, SF6-based plasmas result in significant redeposition. In contrast, etching in CF4/O2 leads to etch profiles that are free of redeposition or residues. The poor selectivity of the mask over Ir under the different tested conditions results in shallow sidewall angles, hence highlighting the need for an alternative mask.