新型阻变存储器材料及其电阻转变机理研究

发布时间：2018-03-19 23:26

本文选题：阻变存储器　切入点：非易失性　出处：《清华大学》2013年博士论文　论文类型：学位论文

【摘要】：阻变存储器是下一代存储器的有力竞争者之一，是一种同时具备高速和高密度存储潜力的非易失性存储器。寻找适合于阻变存储器的介质材料，，完善电阻转变的物理机制，并制备性能优异的阻变存储器一直是半导体工业界和科学界关注的热点之一。本文采用磁控溅射技术沉积了AlN、Ta2O5和ZnO薄膜，并制备了阳离子迁移型和阴离子迁移型两类阻变存储器器件，系统研究了存储介质厚度、器件尺寸、上电极材料、限流值、工作温度等因素对阻变存储器性能的影响，并结合对存储介质薄膜及其与电极界面的显微结构和化学状态的分析，重点澄清各项工艺参数对不同类型阻变存储器的电阻转变行为的影响，以期获得高性能的阻变存储器器件。研究结果表明，AlN薄膜是一种性能优良的阻变存储器介质材料，基于Ag或Cu离子迁移的(Ag，Cu)/AlN/Pt双极性阻变器件的电阻转变陡峭，高低阻态之间的窗口值超过103，数据保持时间超过106s。器件高低阻态的温度特性证明了其电阻转变基于Ag/Cu金属导电细丝的形成和断开。通过在AlN薄膜中引入弥散分布的Cu原子获得了Pt/AlN:Cu/Pt单极性阻变存储器，该器件响应速度高，能够在100ns的短脉冲激励下完成擦写操作。而通过串联反接两个双极性AlN阻变器件还成功构造了相应的互补型阻变存储器，从而获得了基于AlN薄膜的双极性、单极性和互补型阻变存储器，将阻变存储器的选材范围扩展到了氮化物体系。基于Ta2O5薄膜的阻变存储器中氧离子的迁移对于电阻转变有重要作用，实验利用X射线光电子能谱表征了W/Ta2O5/Pt器件分别处于高阻态和低阻态时W/Ta2O5界面与Ta2O5/Pt界面处Ta的化学价态的变化，表明了在正负电场作用下氧离子的迁移运动是器件发生电阻转变的微观机理。通过电极优化工程，研究了不同化学活性的上电极材料对Ta2O5基阻变存储器性能的影响，结果表明与Ta化学活性相近的Al，Ti，W等金属做上电极时，器件的阈值电压和高低电阻态的分布表现出较小的分散性，是Ta2O5基阻变存储器上电极的最佳选择。在优化电极后的Ta2O5基阻变存储器中成功观察到了量子导电现象，证明了量子导电行为不依赖于导电细丝的种类，是原子级别导电细丝的一种本征现象。实验还获得了具有自整流效应的Al/ZnO/Si阻变存储器，验证了电场作用下氧离子的迁移运动导致Al/ZnO界面处AlOx的变化是器件发生电阻转变的物理机制。该器件0.5V时的存储窗口值达到103，低阻态时在±0.5V的整流比超过102。
[Abstract]:Resistive memory is one of the most powerful contenders for next generation memory. It is a kind of nonvolatile memory with high speed and high density storage potential. The fabrication of high performance resistive memory has been one of the hot topics in semiconductor industry and scientific field. In this paper, AlNN- Ta _ 2O _ 5 and ZnO thin films were deposited by magnetron sputtering. Two kinds of impedance memory devices, cationic migration type and anionic migration type, are prepared. The effects of storage medium thickness, device size, material of upper electrode, current limiting value and working temperature on the performance of the impedance memory are systematically studied. Based on the analysis of the microstructure and chemical state of the film and its interface with the electrode, the influence of various process parameters on the resistance transition behavior of different types of resistive memory is clarified. In order to obtain high performance resistive memory devices. The results show that AlN thin film is an excellent dielectric material for resistive memory. The resistance transition of Ag-CuN / AlN / AlN / Pt bipolar impedance devices based on Ag or Cu ion migration is steep. The window value between the high and low resistance states is more than 103 and the data retention time is more than 106 s. The temperature characteristics of the high and low resistance state of the device prove that the resistance transition is based on the formation and disconnection of the Ag/Cu metal conductive filament. The dispersion distribution is introduced into the AlN thin film. The Pt/AlN:Cu/Pt unipolar resistive memory is obtained. The device has high response speed and can finish the writing operation under the excitation of 100ns short pulse. The corresponding complementary resistive memory is also constructed successfully by the series reverse connection of two bipolar AlN devices, thus the bipolar device based on AlN thin film is obtained. Monopole and complementary resistive memory extend the selection range of resistive memory to nitride system. The migration of oxygen ions in resistive memory based on Ta2O5 thin film plays an important role in resistance transition. The chemical valence states of Ta at the interface of W / Ta _ 2O _ 5 and Ta2O5/Pt were characterized by X-ray photoelectron spectroscopy (XPS) when the W / Ta _ 2O _ 5 / Pt devices were in high resistance state and low resistance state, respectively. It is shown that the migration of oxygen ions under positive and negative electric field is the microcosmic mechanism of the resistance transition of the device. The influence of the materials with different chemical activity on the performance of Ta2O5 based impedance memory is studied by electrode optimization engineering. The results show that the distribution of the threshold voltage and the high and low resistance states of the device shows a small dispersion when the metal such as Al _ (Ti) Ti _ W is used as the upper electrode, which is similar to Ta's chemical activity. It is the best choice of electrode in Ta2O5 basic impedance memory. Quantum conduction phenomenon has been observed successfully in Ta2O5 base impedance memory after optimized electrode. It is proved that the quantum conduction behavior is independent of the type of conductive filament. It is an intrinsic phenomenon of conducting filament at atomic level. The Al/ZnO/Si resistive memory with self-rectifying effect is also obtained. It is proved that the change of AlOx at the interface of Al/ZnO due to the migration of oxygen ions under the action of electric field is the physical mechanism of resistance transition of the device. The storage window value of the device reaches 103 at 0.5 V and the rectifier ratio of 卤0.5V at 卤0.5 V in the low resistance state is more than 102.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TB383.2;TP333

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