Multilevel Storage in Phase-Change Memory

Yang HONG  Yinyin LIN  Ting-Ao TANG  Bomy CHEN  

IEICE TRANSACTIONS on Electronics   Vol.E90-C   No.3   pp.634-640
Publication Date: 2007/03/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.3.634
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Storage Technology
1T1R,  2T2R,  PCM,  multilevel storage,  one-dimensional ratio space,  ECC,  

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A novel ratio-oriented definition based on 2T2R (Two transistors & two phase change resistors) phase change memory (PCM) cell structure is proposed to gain a high density by multilevel storage. In this novel solution, no reference is needed and good robustness remains still as conventional 2T2R, which is crucial when feature size scales to nanometer technology node. A behavioral SPICE model together with a preliminary simulation proves the idea to be feasible, and further optimization has been carried out. In addition, based on the ratio-oriented definition, a simpler and faster Error Control Coding (ECC) can be realized with n-Error-detection feasible.