相变存储器的高可靠性多值存储设计

A Novel Design for Multilevel Storage and Superb Reliability in Phase-Change Memory

基于相变存储器(PCM)已有的2T2R结构,提出一种以比值为导向的状态定义方法,以实现2T2R结构下PCM的多值存储.它在相变电阻具有4态可编写的能力下,可以实现单元内8态存储,同时对小尺寸验证,而对PCM存储电路的优化将使得PCM更具竞争力.同样基于这种以比值为导向的状态定义,一种软硬件相结合的新型纠错码方法使得对全部数据位的错误监测成为可能.

A novel ratio-oriented definition based on 2T2R （two transistors ＆ two phase change resistors（PCR）） 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 superb reliability 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 Correction Codes （ECC） can be realized with AlL-Error-Detection （AED） feasible.