Forming-free nitrogen-doped aluminum oxide resistive random access memory [electronic resource]

The persistent request for smaller, faster, cheaper, more capable electronic devices continues to drive the development of technology and to drive the exploration of unique materials to overcome the limits of conventional Si-based technology. Since many modern electronic devices become mobile and multifunctional, they need a new high-density nonvolatile memory overcoming density limitations of currently used flash memory. Bi-stable switching is reported to be observed in a variety of next-generation non-volatile memory technologies such as a resistive random access memory (RRAM), a phase-change random access memory (PRAM), a magnetoresistive random access memory (MRAM) and a ferroelectric random access memory (FeRAM). Among these nonvolatile memories, resistive random access memory (RRAM) is a promising candidate for next-generation nonvolatile memory with higher density than that of flash memory since it is based on a low-temperature grown oxide thin film with bi-stable resistance states and is compatible with three-dimensional stack structure. Among various oxide films exhibiting the resistive switching phenomenon, aluminum oxide (AlOX) is one of the most promising materials because of its simple constituents, clear switching characteristics, and moderate on/off ratio. In addition, since AlOX has a simple binary system, it has an advantage for the industrial fabrication. However, there are some challenges that need to be addressed for the AlOX based RRAM. One of the challenges is that AlOX RRAM cells have been reported to require a high voltage forming process. So, making good quality aluminum oxide film with a moderate amount of defects is a main issue for realizing AlOX RRAM devices. In this dissertation, we present a simple nitrogen-doped AlOX (N-AlOX) RRAM cell that has a moderate amount of defects. The main contribution of this dissertation is a new type of RRAM (N-AlOX RRAM) that does not require a forming process and shows small programming currents. Some switching mechanisms have been proposed to explain the resistance switching phenomenon of AlOX RRAM. However, the underlying mechanism of resistance switching behavior of N-AlOX RRAM has not been understood. So, we perform some material analyses of N-AlOX RRAM in detail to understand the switching mechanism. Next, we discuss various electrical characteristics of N-AlOX RRAM. Based on the electrical characteristics, we present a Frenkel-Poole model for the current conduction mechanism of N-AlOX RRAM. The last topic of this dissertation is titanium oxide (TiOX) based RRAM. We focus on evaluating many electrodes and understanding the impact on the switching characteristics of TiOX RRAM. As a result, we find iridium oxide (IrO2) as a viable electrode for TiOX RRAM. In addition, we successfully improve the uniformity of switching parameters by inserting two hafnium (Hf) interfacial layers. Finally, we conclude this dissertation with a summary of the main points and some suggestions for future work on this topic.

Keywords: Electrical Engineering
Advisor: Wong S. Simon primary advisor. Thesis advisor
Nishi Yoshio
Wong Hon-Sum Philip