N-doped Sb2Te phase change materials for higher data retention

Crystallization temperatures of the Sb2Te films increase remarkably from 139.4 degrees C to 223.0 degrees 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 degrees C is found in Sb2TeN1 films. Doping excessively high nitrogen in Sb2Te 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 Sb2TeN1 film is ten times lower than that of PCRAM device using Ge2Sb2Te5 films. (C) 2011 Elsevier B.V. All rights reserved.