Use of a Ti Buffer Layer to Improve the Mechanical Properties of Ge 2 Sb 2 Te 5 Thin Films for Phase-Change Memory

The inclusion of a Ti inter-adhesion and electrode layer is important for the integration of Ge2Sb2Te5 (GST) phase-change materials into device fabrication. The microstructure and mechanical properties of Ge2Sb2Te5 thin films with a Ti buffer layer (GST/Ti) were investigated in this work. The results showed that the Ti layer affects the microstructure of GST thin films due to the diffusion of Ti atoms into the interface of the GST/Ti stack to form Te2Ti phase. A uniform grain distribution was observed in the GST/Ti thin films. Conversely, a nonuniform distribution and “abnormal” growth of {0001}-oriented grains were observed in GST thin films without a Ti buffer layer. Furthermore, the effect of the Ti transition layer on the grain growth mode of the GST, which has a significant influence on its mechanical properties, is discussed: a smaller unbalanced stress and more uniform grain distribution are evident in GST/Ti, thus the homogeneous grain distribution of GST with the addition of a Ti layer contributes to the higher hardness and elasticity modulus values. The improved mechanical properties of such GST/Ti thin films may be a factor ensuring the robustness of phase-change memory.