Materials for phase-change memory with elevated temperature stability

Thermal stability is one of the key issues in phase-change memory. We try to tackle it by developing new compositions based on Ga-Te-Sb system. Thermal stability is exemplified using Ga18Te12Sb70 which shows crystallization-temperature (T-x) 248 degrees C and activation energy of non-isothermal crystallization 5.9 eV. Films were isothermally soaked at 5 similar to 30 degrees C below T-x to estimate the failure-time when electrical resistance dropped to a half of the original. Arrhenius plot attained using logarithm failure-time versus reciprocal temperature were extrapolated to the temperature corresponding to 10-year failure (T-10y) as 183 degrees C. Pre-crystallization structure upon heating to 2 similar to 5 degrees C below Tx reflects stable amorphous phase of the alloy up to at least 240 degrees C. Memory-cells made of Ga18Te12Sb70 can be set-reset at 20 similar to 500 ns with electrical currents around 66% those of our Ge2Sb2Te5 cells. We suggest that compositions Ga18-25Te8-12Sb67-70 are optimal to ensure T-x > 240 degrees C, T-10y > 180 degrees C and with low operation-currents. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4714711]