N-doped Sb 2Te phase change materials for higher data retention

Abstract

Crystallization temperatures of the Sb 2Te films increase remarkably from 139.4 °C to 223.0 °C as the N 2 flow rates increasing from 0 sccm to 1.5 sccm. Electrical conduction activation energies for amorphous and crystalline states increase by doping nitrogen. A small amount of nitrogen atoms can locate at interstitial sites in the hexagonal structure, generating a strain field, and improving the thermal stability of amorphous state. The best 10-years lifetime at temperature up to 141 °C is found in Sb 2TeN 1 films. Doping excessively high nitrogen in Sb 2Te film will form nitride and make Te separate out. As a result, the activation energy for crystallization decreases instead, accompanying with the deterioration of thermal stability. The power consumption of PCRAM test cell based on Sb 2TeN 1 film is ten times lower than that of PCRAM device using Ge 2Sb 2Te 5 films.