Wet etching of Ge2SbTe5 films and switching properties of resultant phase change memory cells

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.