Etching of RuO2 and Pt thin films with ECR/RF reactor

Abstract

Ferroelectric thin films for memory and MEMS applications require noble metal or refractory metal oxide electrodes. In this paper, physical and chemical parameters during etching of RuO2 and Pt by a dual frequency ECR/RF reactor have been investigated. The removal characteristics of blanket films and films with a patterned mask (photoresist or SiO2 masks) were investigated as a function of gas chemistry (Ar, O2, halogen gases), ion beam energy (ion extraction/acceleration voltages), substrate bias RF power and working pressure (from 5×10-3 to 5×10-1 Pa). The etch processes were characterized in terms of etch rate, selectivity, critical dimension, lateral uniformity and mask stability. High etching rate processes (up to 70 nm/min for RuO2 and 60 nm/min for Pt with removable photoresist mask) were obtained and a micron scale patterns demonstrated. Patterning of a multilayer stack PZT/Pt/SiO2 could be achieved with a single photolithography step.