Investigation on Chemical Mechanical Polishing of GeSbTe for High Density Phase Change Memory

Phase change memory (PCM) is considered to be a prospective candidate to replace flash for next generation non-volatile memory. In this paper, we studied GST chemical mechanical polishing (CMP) process characterization and optimization on 8-inch wafers. CMP experiment was performed on GST blanket and pattern wafers. GST CMP process optimization experiment was made in both chemical (slurry) and mechanical (pressure) aspects. AFM data shows that the RMS of roughness has been reduced from 2.151 nm to 1.276 nm after GST CMP on the blanket wafer. On the other hand, high density (40%) GST pattern wafer was polished to evaluate the CMP capability. SEM and EDS results demonstrate that GST via array has been achieved by GST CMP process while the element stoichiometric proportion in GST via is not changed. This work paved the way for PCM development to the commercial high density PCM devices in the future.