Fabrication and Characterization of Hafnium Oxide Based Resistive Random Access Memory Devices.

摘要

Current technology is dependent on the usage of a memory hierarchy. Primary components include SRAM, DRAM, and Flash. The ordering of these components in the memory hierarchy is dictated by both the cost and the performance of the components. These devices all share two distinct problems in that they are all charge based memories containing at least one transistor. Scaling of transistors with accordance to Moore's law is becoming even more difficult as we stretch the limitations of lithography. A universal memory component could simplify the memory hierarchy and allow for even higher levels of performance. Resistive Random Access Memory (ReRAM) is a leading candidate to be the first universal memory. As a two-terminal device with 3D capability, DRAM-like latency, and non-volatile storage, it essentially meets the requirements. Higher endurance and higher yield are the two most pressing needs in terms of performance. However, our understanding of these devices is severely lacking.;This dissertation presents characterization on three different HfO 2-based ReRAM devices. Devices showed promising results, particularly when the device area was scaled down. ReRAM switching was shown to be filamentary due to the non-dependency on the device area. A one-time forming step is required to achieve switching characteristics. A compliance current was necessary during forming to contain the conductance of the filament. An enlarged filament would require even higher reset current, which is generally dictated by the compliance current. Parasitics can affect the on-state resistance due to an inability to control the maximum current through the ReRAM device. Alternative forming techniques such as slow forming and multi-step forming can be used to avoid this effect. Joule heating was shown to be the catalyst to reset the device, which was a polarity dependent process. Devices showed a gradual reset trend, which was both temperature dependent and time dependent. Resetting devices at cryogenic temperatures with fast pulses showed insufficient reset, this can be understood by the temperature dependency in LRS. This work illustrates some unique testing to demonstrate the working principals of ReRAM devices. Further understanding of ReRAM devices is necessary to fully understand the working mechanism.