Chemical vapor deposition of chalcogenide materials for phase-change memories

Abstract

Films of chalcogenide Ge–Sb–Te materials were grown by pulsed liquid injection chemical vapor deposition (CVD) technique. Simple thermal CVD without additional process activation and CVD with remote activation of precursor decomposition process by a hot-wire were investigated and compared. Ge(NMe 2) 4, Sb(NMe 2) 3 and Te(i-Pr) 2 precursors in a form of diluted solutions in toluene were used for depositions. Film composition was controlled by injection parameters, while the thickness was directly related with number of pulses. Hot-wire activated CVD process allows the growth of chalcogenide films of clearly better quality compared to films grown by standard thermal CVD. Uniform, smooth, crystalline Ge 2Sb 2Te 5 films were grown at substrate/wire temperature 300 °C/550 °C and pressure ⩽ 15 Torr, using nitrogen as a carrier gas, on Si, Si/SiO 2, Si/Si 3N 4 and glass substrates. Forty to forty five nanometer thick films on Si/SiO 2 substrates showed reversible electrical and optical phase switching behavior.