一种三维相变存储器1S1R存储单元电路仿真模型

A Circuit Simulation Model of 1S1R for 3D Phase-Change Memory

三维相变存储芯片1S1R存储单元由双向阈值选通管(OTS)和相变存储器件(PCM)串联组成.为了解决现有OTS和PCM电路仿真模型不能准确模拟器件电学特性和物理特性、不适用于限制型PCM等问题,提出了一种采用Verilog-A语言实现的1S1R电路仿真模型.该模型实现了对OTS电学特性和PCM相变过程中电流、温度、熔融比例、晶态比例和非晶比例变化的模拟,具有良好的收敛性和较快的仿真速度,仿真结果与器件实际测试结果吻合.与传统模型相比,该模型针对限制型PCM特点,实现了对PCM熔融过程、晶态非线性、熔融电阻率稳定和OTS亚阈值非线性、双向选通特性的模拟和集成.分析了OTS亚阈值非线性参数和读电压窗口的关系,发现当OTS阈值电流约等于PCM阈值电流时读窗口最大;展示了1S1R单元直流和阵列瞬态仿真结果,为三维相变存储器的电路设计和仿真提供了基础.

The 1 S1 R storage unit of 3 D phase-change memory is composed of ovonic threshold switch selector(OTS)in series with the phase change memory(PCM)device.In order to solve the problems of the current OTS and PCM circuit simulation models,such as not able to accurately simulate the electrical and physical characteristics of devices,and not suitable for confined PCM,a 1 S1 R spice model based on Verilog-A is proposed.The model simulates the electrical characteristics of OTS and the changes of current,temperature,melting proportion,crystallization proportion and amorphous proportion in the crystallization,melting and quenching of the PCM.The model has a good convergence and fast simulation speed.The simulation results are consistent with the actual test results of the device.Compared with the traditional model,the simulation and integration of confined PCM melting process,crystal nonlinearity,melting resistivity stability and subthreshold nonlinearity,and bidirectional switching characteristics of OTS are realized.The relationship between OTS subthreshold nonlinear parameter and read voltage window is analyzed.It is found that the read window reaches its maximum when OTS threshold current is approximately equal to PCM threshold current.The results of DC simulation of 1 S1 R cell and transient simulation of array are displayed,providing the basis for circuit design and simulation of 3 D phase-change memory.