Thermally stable tungsten and titanium doped antimony tellurium films for phase change memory application

Sb₂Te₃ alloy, as one of the representative phase change base materials, is largely limited by its low thermal stability in the practical application. Here, both tungsten and titanium are used to improve the thermal stability of materials. After co-doping, the crystallization temperature is significantly increased, and the increment will be leveled up if more tungsten content was doped in the W–Ti–(Sb₂Te₃). Specifically, the amorphous-to-metastable FCC phase transition temperature is about 120 °C for pure Sb₂Te₃, approximately 230 °C for W_0.03Ti_0.045–(Sb₂Te₃)_0.925, and around 304 °C for W_0.07Ti_0.045–(Sb₂Te₃)_0.885, respectively. Beyond that, the second FCC-to-hexagonal phase transition temperature is also improved due to the addition of tungsten atoms, as obtained from the XRD analysis result. As observed in the bright images of W_0.03Ti_0.045–(Sb₂Te₃)_0.925, tungsten dopant can refine the crystalline grains effectively further, by utilizing transmission electron microscope. In the final, electrical characterization of phase change memory devices proves W_0.03Ti_0.045–(Sb₂Te₃)_0.925 owns excellent operation properties, such as higher-speed reversible write/erase, and better resistance stability of both high and low states, compared with the widely used Ge₂Sb₂Te₅ phase change material.