Intrinsic unipolar SiOx-based resistive switching memory: characterization, mechanism and applications

Chang, Ph. D., Yao-Feng
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Floating gate (FG) nonvolatile memory has been the main structure of nonvolatile memory devices, since its invention in 1967 by D. Kahng and S. M. Sze. They have been widely employed in the portable electronic products such as mobile phones, digital cameras, notebook computers, mp3 players and USB flash drives. However, as device size continues to shrink, the typical flash memory device will continue to suffer from issues of retention and endurance. In order to solve the problems, researchers have considered new storage layers and novel structures in nonvolatile memory devices to replace the conventional floating gate device. Therefore, a great deal of potential memory structures have been proposed, with some transferring into a production line, such as phase change memory (PCM), magnetic random access memory (MRAM) and ferroelectric random access memory (FeRAM). In the innovation of memory devices, resistance random access memories (ReRAMs) have gained significant research interest as an alternative for next-generation nonvolatile memory due to its high density, low cost, low power consumption, fast switching speed and simple cell structure. In this dissertation, the intrinsic unipolar silicon oxide (SiOx-based) Resistive-RAM (ReRAM) characterization, mechanism and applications have been presented. I investigate device structures, material compositions and electrical characteristics to realize ReRAM cells with high ON/OFF ratio, low static power consumption, low switching power, and high readout-margin using complementary metal-oxide-semiconductor (CMOS) compatible SiOx-based materials. These ideas are combined with the use of horizontal and vertical device structure designs, composition optimization, electrical controlling and external factors for understanding resistive switching mechanism. Modeling of resistive switching mechanism, including temperature effect, pulse response and carrier transport behaviors are performed, to develop a compact model in energy diagram, trap-level information in SiOx resistive switching layer, even for computer-aided design (CAD) in very-large-scale integration (VLSI) design. Finally, synapse-based neuromorphic system is demonstrated in SiOx-based ReRAM, combining with bio-inspiration and biomimetics process illustrations. This work presents the comprehensively investigation of SiOx-based resistive switching characteristics, mechanisms, applications for future post-CMOS devices era.