Electrical Properties of Ag-Doped Ge 2 Sb 2 Te 5 Films Used for Phase Change Random Access Memory

Ag-doped Ge2Sb2Te5 films were deposited by rf magnetron sputtering on SiO2/Si substrates. The content of Ag ranging from 4.5 to 11.3 at.% is determined by inductively coupled plasma atomic emission spectrometry. The crystallization temperature of Ag-doped Ge2Sb2Te5 increases with the increasing Ag content and the stability of phase change film is improved greatly. Structures were measured by x-ray diffraction and the face-centered-cubic structure was more stable after Ag doping. Four-point probe was used to measure the sheet resistance of Ag-doped Ge2Sb2Te5 films annealed at different temperatures and it is indicated that Ag atoms increase the sheet resistance of Ge2Sb2Te5 thin film when the annealing temperature is higher than about 360 degrees C, which is beneficial for reducing the reset current. Current-voltage curves were tested and it is demonstrated that 4.5 at.% Ag doping into the Ge2Sb2Te5 film can reduce the threshold current from 1.46 mA to 0.25 mA and can only increase the threshold voltage slightly, which is very useful for low energy consumption.