Multiple Programming Method and Circuitry for a Phase Change Nonvolatile Random Access Memory(PRAM)(Phase Change RAM)(<Special Section>New Era of Nonvolatile Memories)

概要

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A novel multiple programming method for a phase change nonvolatile random access memory (NVRAM) is proposed. The resistance of the chalcogenide semiconductors (phase change materials, e.g. SeSbTe) stacked on the memory cell is controlled by the number of the applied current pulses, and we have observed experimentally 4-valued resistance in the range of 42k-2.1kΩ at the SeSbTe discrete memory cell. On the basis of this experimental results, the 4-valued memory circuit was designed with CMOS 0.35μm process. It has been confirmed with a circuit simulation that the multi-bit read circuit proposed works successfully under a read cycle operation over 100MHz at 3.3V supply voltage and the read operationis completed within 3 nsec.
社団法人電子情報通信学会の論文
2004-10-01