相变存储器单元皮秒测试信号完整性研究

Signal integrity of picosecond test pulse applied on phase change memory cells

针对相变存储器皮秒测试系统由于矩阵开关电路分布参数以及信号通道中阻抗突变所引起的反射,严重影响了皮秒脉冲信号的完整性,使施加在相变单元上的皮秒脉冲信号严重失真,为了消除失真,改善信号完整性,从2个方面提出了解决方案:一是采用性能优良的高频继电器构成矩阵开关;二是减小反射,采取了源端阻抗匹配、负载分支端阻抗补偿、菊花链双线拓扑结构等措施,使得反射的影响减小到最小.理论分析与仿真结果表明:皮秒脉冲信号波形质量良好,满足测试要求.本测试系统为研究皮秒编程脉冲作用下相变存储器的存储机理、速度、可靠性等提供了良好的平台,也可作为电阻式随机擦写存储器单元测试系统.

Distributed parameters of the switch array and the reflections induced by the impedance discontinuities along the signal channel has serious influence on the signal integrity of the picosecond pulse applied on phase change memory（PCM） cells,which results in the distortion of the picosecond pulse signal used to apply on the cell of PCM.In order to reduce the distortion and make sure the picosecond pulse valid in the proceeding of test,two methods were proposed to solve these problems.One was to build the switch array with highly performance relays;and the other was to reduce the reflections as follows：impedance matching was acquired at the source term,the impedance discontinuities were compensated at the branches,and double daisy-chain topology structure was introduced.The theory analysis and simulation results indicate that less distortion on the picosecond pulse waveform received on the cells,and the testing system fulfills the need of high speed testing.This picosecond pulse testing system provides a good platform for studying the working speed,reliability and physical nature of PCM cells,and it also can be utilized to test resistive random access memory（RRAM） cells.