Characterization of Cr-doped Sb2 Te3 films and their application to phase-change memory

Abstract

Phase-change memory (PCM) is regarded as one of the most promising candidates for the next-generation nonvolatile memory. Its storage medium, phase-change material, has attracted continuous exploration. Along the traditional GeTe–Sb2Te3 tie line, the binary compound Sb2Te3 is a high-speed phase-change material matrix. However, the low crystallization temperature prevents its practical application in PCM. Here, Cr is doped into Sb2Te3, called Cr–Sb2Te3 (CST), to improve the thermal stability. We find that, with increase of the Cr concentration, grains are obviously refined. However, all the CST films exhibit a single hexagonal phase as Sb2Te3 without phase separation. Also, the Cr helps to inhibit oxidation of Sb atoms. For the selected film CST_10.5, the resistance ratio between amorphous and crystalline states is more than two orders of magnitude; the temperature for 10-year data retention is 120.8 °C, which indicates better thermal stability than GST and pure Sb2Te3. PCM cells based on CST_10.5 present small threshold current/voltage (4 μA/0.67 V). In addition, the cell can be operated by a low SET/RESET voltage pulse (1.1 V/2.4 V) with 50 ns width. Thus, Cr–Sb2Te3 with suitable composition is a promising novel phase-change material used for PCM with high speed and good thermal stability performances. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)