Inductively coupled plasma etching for phase-change material with superlattice-like structure in phase change memory device

Phase change material with superlattice-like structure (SLL) is one of the most emerging materials for phase change memory device. A rough etching profile, isotropic, and serious surface damage limit the application of the conventional lift-off process. A well controlled etching process to achieve high etch rate, smooth surface, vertical and nanometer-sized pattern for SLL is required for the mass production of the phase change memory devices. In this study, the etch rates, surface roughness and sidewall angles of SLL GeTe/Sb2Te3 films were investigated by the inductively coupled plasma etching process with various etch parameters including gas ratio, chamber pressure, bias power and coil radio frequency (RF) power. The etch selectivity of SLL to SiO2 and to photo-resist were characterized. The X-ray photoelectron spectroscopy (XPS) of etched surfaces confirmed the etch mechanism of the SLL films in Cl2/Ar chemistry. 86 nm-sized patterns of SLL were fabricated using optimized etching parameters. In addition, an etched SLL film was integrated into a "T" type PCRAM cell, with a 50 nm feature size. This cell operated successfully and a RESET current of only 145 μA was obtained.