Switching operation improvement of phase change memory with nanoscale W plug structure by CMP process

To reduce the reset current for developing reliable high-density phase change random access memory, small bottom electrode contact (BEC) size formation is a critical process. One of the failure modes for the process is the corrosion of the tungsten (W) plug, which is caused by the W chemical mechanical polisher (CMP) process. An ultra-smooth surface of BEC nanoscale W plug structure was successfully fabricated by the CMP process, which reduced the W/phase change material (Ge₂Sb₂Te₅, GST) contact resistance, and gained more homogeneous resistance distribution. Thus, the stability of the device was improved greatly by the acidic buff CMP process compared with that of the device with alkali buff owing to the reduction of W/GST connect resistance fluctuation.