Wet-etching characteristics of Ge/sub 2/Sb/sub 2/Te/sub 5/ thin films for phase-change memory

Etching of phase-change memory thin films is essential in the processing for the manufacture of devices. The Ge/sub 2/Sb/sub 2/Te/sub 5/ thin film as a typical material for such purposes can be control-etched by an aqueous solution of 20% nitric acids (HNO/sub 3/). It was found that the Ge/sub 2/Sb/sub 2/Te/sub 5/ 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 Ge/sub 2/Sb/sub 2/Te/sub 5/ thin films should be done after a wet etching process in the manufacture of phase-change random access memories.