Evaluation of phase transition behavior of Ge₂Sb ₂Te₅ thin film for phase change random access memory

The phase transition behavior of Ge₂Sb₂Te₅ (GST) thin film, which is a candidate material of recording layer for phase change random access memory (PRAM), has been evaluated using an in-situ reflectance measurement method. The experimental data have been analyzed by using johnson-mehl-avrami-kolomogorov (JMAK) model. JMAK model can be used only in isothermal state. However, temperature changes with time during the operation of PRAM. To apply JMAK equation to PRAM simulation, it has been assumed that the temperature increases stepwise and isothermally. By using JMAK equation and assumption for the transient state, the phase transition behavior of GST thin film has been predicted under 3°C/min heating rate in this study. The simulation result agrees well with the experimental results. Therefore, it can be concluded that JMAK equation can be used for the PRAM simulation model.