High density plasma etching of IrRu thin films as a new electrode for FeRAM

The etch characteristics of IrRu thin films with TiN hard mask were studied using a high density inductively coupled plasma of Cl-2/O-2/Ar gas mixture. The etch rate and etch profile were investigated by varying the gas concentrations of O-2 and Cl-2. As the O-2 concentration in a 30% Cl-2/O-2/Ar gas mix increased, the etch selectivity of IrRu to TiN increased, resulting in the vertical etch profile. As the Cl2 concentration increased, the etch profile became worse due to the low etch selectivity. It was revealed that the etch selectivity of IrRu to TiN was closely related to the etch profile. The residue-free IrRu etching with a high degree of anisotropy was achieved using the Cl-2/O-2/ Ar mixture at the optimized etching conditions.