Thermal effect of Ge₂Sb₂Te₅ in phase change memory device

In the fabrication of phase change random access memory (PRAM) devices, high temperature thermal processes are inevitable. We investigate the thermal stability of Ge₂Sb₂Te₅ (GST) which is a prototypical phase change material. After high temperature process, voids of phase change material exist at the interface between Ge₂Sb₂Te₅ and substrate in the initial open memory cell. This lower region of Ge₂Sb₂Te₅ is found to be a Te-rich phase change layer. Phase change memory devices are fabricated in different process conditions and examined by scanning electron microscopy and energy dispersive X-ray. It is found that hot-chuck process, nitrogen-doping process, and lower temperature inter-metal dielectric (IMD) deposition process can ease the thermal impact of line-GST PRAM cell.