Investigation on the effect of silicon doping in Sb₂Te₃ phase change materials

The crystallization behavior and physical properties of Si-doped Sb₂Te₃(Si: ST) materials applicable to phase change random access memory (PCRAM) was studied with the purpose of overcoming their current weaknesses regarding use in PCRAM. Phase change materials were prepared by DC magnetron sputtering. Si-doped Sb₂Te₃materials have anSb₂Te₃(ST) rhombohedral structure regardless of Si content and a segregated region consisting of Si was founded. The Si amorphous phase located at grain boundaries interrupted grain growth, therefore the grain size became smaller. These crystal structures and their bonding characteristics were confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Increasing the amount of Si in Sb₂Te₃ increased the sheet resistance, crystallization temperature (T_c) and crystallization activation energy (E_a), which was confirmed by a 4-point probe measurement. Furthermore, Metal-Insulator-Metal (MIM) devices based on ST and Si : ST were fabricated and the measured threshold voltage (V_th) of Si: ST was higher than ST. These results showed that Si doping improved thermal stability.