Wet-Etching Characteristics of Thin Films for Phase-Change Memory

Etching of phase-change memory thin films is es- sential in the processing for the manufacture of devices. The thin film as a typical material for such purposes can be control-etched by an aqueous solution of 20% nitric acids . It was found that the films in amorphous state could be etched more uniformly than that in crystalline state. The etch rate can be well controlled to be 4.6 nm/s using such a solution, resulting in macroscopic and microscopic uniformity on amorphous films. It is therefore suggested that the crystallization annealing of thin films should be done after a wet etching process in the manufacture of phase-change random access memories. Index Terms—Etching solution, ovonic unified memory (OUM) random access memories (RAMs), phase-change memory, phase- change RAM (PRAM), wet-etching.