Improvements in Thermal Stability of Sb₂Te₃by Modulation of Microstructure via Carbon Incorporation

Phase-change memory (PCM) is the most promising candidate for next-generation memory devices to replace both dynamic random-access memory and flash memory. Sb2Te3 is a promising phase-change material because of its fast operation speed; however, it has poor thermal stability. The operation mechanism of PCMs is based on the Joule heating process; consequently, sufficient thermal stability is one of the most important factors for scaling PCMs in commercialized devices. Herein, a remarkable increase in the thermal stability of C-incorporated Sb2Te3 is reported. The crystallization and 10-year retention temperatures of C-incorporated Sb2Te3 increased to 66% and 52%, respectively, while a reliable operation speed was maintained as compared to that of Ge2Sb2Te5, an existing commercialized phase-change material for 3D Xpoint memory. Regions with highly incorporated C were observed in the Sb2Te3 crystal grains by transmission electron microscopy. Ellipsometry and X-ray photoelectron spectroscopy revealed increased electron localization caused by interstitial C atoms located between Sb and Te, which effectively hindered grain growth and significantly increased thermal stability. The thermal stability can be further enhanced by adjusting the C content, although some of the device operation characteristics are slightly degraded. This study suggests that Sb2Te3 can be easily and effectively utilized as a suitable material for practical applications involving PCM devices with high thermal stability.