Wet etching of Ge2Sb2Te5 films and switching properties of resultant phase change memory cells

Abstract

Wet-etching of amorphous Ge2Sb2Te5 films was studied by ICP and XPS spectrometries. It is thought that wet-etching arises from chemical etching that starts with bond breakages, oxidation of each element and subsequent dissolution of the resultant oxides. The Ge element debonds more easily from the Ge–Sb–Te matrix than the Te element, but Ge oxide is more stable than Te oxide. The Te element debonds more sluggishly than Ge, although Te oxide is quite unstable. As a result, Ge is the first leached element that dominates the etching process. Sb is the most difficult element to leach in Ge2Sb2Te5 thin films. Cells of phase-change random access memory (PRAM) were successfully manufactured using the wet-etching process, and studies of the switching properties revealed a low threshold voltage of 0.60 ± 0.15 V.