相变存储器单元脉冲I-V特性测量方法及分析

发布时间：2018-01-16 07:11

本文关键词：相变存储器单元脉冲I-V特性测量方法及分析　出处：《华中科技大学》2013年硕士论文　论文类型：学位论文

【摘要】：相变存储器（PCRAM）具有功耗低、速度快、擦写次数高、稳定性好、与MOS工艺兼容良好、可多值存储等优点，被视为下一代主流存储器中最具竞争力的新型非易失性半导体存储器。PCRAM单元的电学性能一直是半导体信息存储领域的重要研究内容，而电流-电压（I-V）特性是它最重要的电学特性之一。通常，PCRAM单元的I-V特性曲线是采用直流扫描的方式测量得到的，直流I-V存在自热和能量累积效应，因为阶梯状电流或电压激励会对PCRAM单元持续地输入能量，相变材料具有储热能特性，那么前面所有历史台阶产生的热量会叠加到下一个台阶产生的热量上。实际上，这种效应不仅存在PCRAM单元的直流I-V测量中，还存在脉冲I-V及电阻-电流和电阻-电压（R-I/R-V）测量中，其导致的直接后果就是破坏它的内部特性。实验证明，经过多次I-V测量后的大部分样品都无法继续正常工作，受到不可逆的损坏。所以开展PCRAM单元的自热和能量累积效应的研究是非常有意义的。本论文采用的方法就是研究PCRAM单元的脉冲I-V特性。由于相变材料以Ge2Sb2Te5（GST）的性能最佳且被最广泛研究，所以采用存储介质为GST的PCRAM样品。利用4200-SCS半导体特性分析仪、高精度泰克数字示波器DPO70064和自主设计的PCB板搭建一个测量系统，开关速度快的MOS管、BNC头、开关、PCRAM芯片等都集成在PCB板上。通过调节PCB板上的开关，测量系统不仅可以测量PCRAM单元的脉冲I-V特性，，还能测量它的一般电学性能。采用以上装置分别测量了相变层厚度为150nm、75nm和25nm的PCRAM单元的直流I-V特性曲线和脉冲I-V特性曲线。对比曲线发现脉冲I-V测量得到的阈值电压比直流I-V的大很多，同时也得出脉冲宽度和脉冲周期都是表征PCRAM单元脉冲I-V特性不可或缺的参变量结论。假设PCRAM单元活动区域的温度上升引起电子活跃性和势垒的改变，就提出了由自热效应建立的物理模型。
[Abstract]:Phase change memory (PCRAM) has the advantages of low power consumption, high speed, high erasing times, good stability, good compatibility with MOS process, multi-value storage and so on. The electrical performance of a new type of nonvolatile semiconductor memory, PCRAM, which is regarded as the most competitive in the next generation mainstream memory, has been an important research content in the field of semiconductor information storage. The current-voltage I-V) characteristic is one of the most important electrical properties. The I-V characteristic curve of PCRAM cells is usually measured by direct current scanning. DC I-V has the effect of self-heating and energy accumulation, because the step current or voltage excitation will continuously input energy to the PCRAM cell, and the phase change material has the characteristics of thermal energy storage. Then all the heat generated by the historical steps in the front will be superimposed on the heat generated by the next step. In fact, this effect exists not only in the DC I-V measurements of PCRAM cells. There are also pulse I-V and resistance-current and resistance-voltage R-I / R-V measurements, the direct result of which is to destroy its internal characteristics. After several I-V measurements, most of the samples could not continue to work normally. It is very meaningful to study the self-heating and energy accumulation effects of PCRAM elements. The method used in this thesis is to study the pulse I-V characteristics of PCRAM elements. Because the phase change material Ge2Sb2Te5GSTs has the best performance and has been widely studied. Therefore, the storage medium for the GST PCRAM sample, using 4200-SCS semiconductor characteristics analyzer. DPO70064 and PCB board designed by ourselves are used to set up a measurement system with high precision Tak digital oscilloscope. The MOS tube with high switching speed is equipped with BNChead and switch. The PCRAM chip is integrated on the PCB board. By adjusting the switch on the PCB board, the measurement system can not only measure the pulse I-V characteristics of the PCRAM cell. The thickness of phase transition layer is 150 nm. The DC I-V characteristic curves and pulse I-V characteristic curves of 75nm and 25nm PCRAM cells are obtained. The comparison curves show that the threshold voltage obtained by pulse I-V measurement is much larger than that of DC I-V cells. It is also concluded that both pulse width and pulse period are indispensable parameters to characterize the pulse I-V characteristics of PCRAM units. It is assumed that the rise of temperature in the active region of PCRAM cells leads to electron activity and potential. Change of base. A physical model based on the self-heating effect is proposed.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TP333

【参考文献】