Characteristics of phase transition in boron-implanted Ge2Sb2Te5 thin films for phase change memory applications



Phase change memory has been considered as one of the most promising alternatives for next-generation nonvolatile semiconductor memory. Modification of phase change materials by impurity doping has been proved to be an effective way to improve phase change memory device performance. In this study, the most common phase change material, Ge2Sb2Te5 (GST), was employed, and its intrinsic properties were modified using boron–ion implantation. The GST films were implanted with 20 keV boron ions to fluences of 5 × 1014 and 5 × 1015 ions/cm2. The characteristics of the virgin and boron-implanted GST films were investigated by SIMS, XRD, and in situ resistance measurement. The kinetics of the thermally activated phase transition was also analyzed on the basis of the Arrhenius relationship. The results revealed that both crystallization temperature and activation energy of crystallization increase with increasing the boron fluence. The data retention capability is also enhanced from 83 to 88 °C, corresponding to a criterion of 10-year archival lifetime. In addition, the XRD spectra indicated that high-fluence boron–ion implantation partially inhibits the transition of the GST films from face-centered cubic phase to hexagonal close-packed phase. In conclusion, the thermal stability of the GST films can be improved through boron–ion implantation. Copyright © 2014 John Wiley & Sons, Ltd.