A thermally robust phase change memory by engineering the Ge/N concentration in (Ge, N)xSbyTe z phase change material

Abstract

Phase change memory (PCRAM) is an ideal embedded memory due to its simple BEOL process and low voltage operation. Industrial and automotive applications of PCRAM, however, have not been realized because of poor high temperature properties of the conventional Ge₂Sb₂Te₅ phase-change material [1-3]. We have previously reported a special Ge_xSb_yTe_z material along the Ge and Sb₂Te₃ tie line that showed superior high temperature performance. In this work we have further enhanced our previous “golden” material by incorporating nitrogen and engineering the Ge/N concentration. In order to rapidly explore a range of new materials a fast method to test retention behavior by laser melt-quenching is adopted which yields retention data on blanket films consistent with device results. A new material with special Ge/N concentration with excellent high temperature retention is discovered. The new material demonstrated nearly 100% yield in a 256 Mb test chip after 160 °C, 84 hrs baking, with projected 10-year retention at 120 °C. (> 9,000 years at 85 °C.).