A No-Verification Multi-Level-Cell (MLC) Operation in Cross-Point OTS-PCM

We present the first MLC operation for OTS-PCM with comprehensive operation algorithm study. An ADM chip with fast write speed (<300ns) and robust operation (>109 cycles) are shown indicating the potential for high performance MLC OTS-PCM. A desirable 2-bits/cell operation up to 108 cycles without further read verification is achieved based on 100 cells data from 1Mbit crosspoint array. Systematic discussions of MLC operation under “1/2V” scheme is further presented, and threshold voltage (Vt) drift is evaluated accordingly.