Mechanisms of Pb(zr_0.53Ti_0.47)O₃ thin film etching with ECR/RF reactor

Abstract

Ferroelectric capacitive devices for memory and MEMS applications require patterned ferroelectric thin films with high anisotropic etched features. In this paper, physical and chemical parameters during etching of Pb(Zr_0.53Ti_0.47)O₃ (PZT) by a dual frequency ECR/RF reactor have been investigated. The removal characteristics of blanket films and films with a patterned mask were investigated as a function of gas chemistry (Ar, halogen gases), substrate bias RF power and working pressure (from 5 × 10⁻⁴ Pa to 1Pa). The etch processes were characterized in terms of etch rate, selectivity and mask stability. High etching rate processes (up to 70 nm/min with removable photoresist mask) were obtained and micron scale patterns were demonstrated. The impact of the etch process on the PZT surface layer modification was characterized by AFM, SEM, TEM and XPS. A strong influence of process chemistry and RF bias power on etching selectivity and surface topography (roughness, involatile residues) was observed. No surface damage layer was detected by Transmission Electron Microscopy. However, XPS revealed fluorine (up to 34%) and chlorine radicals (below 10%) in a 10nm thick surface layer.

Key Words:

• Plasma etching
• PZT
• ECR/RF reactor
• MEMS patterning