Fabrication and electrical properties of advanced thin film materials for resistive switching memories

The exponential growth of electronics and computing capacity has dramatically changed the way we live and can be envisioned even more in the future. This growth trend of electronics was predicted by Moore’s law and driven by the device scaling down to 10 nm node. However, with the impending fundamental physical limits and increased fabrication cost, new technology routes need to be proposed to empower the development of even smaller, faster, and more energyefficient devices. For memory devices, two technology routes were proposed. One is based on the 3D stacks of the traditional mainstream floating-gate based FLASH memory. The other is the new memory devices based on different storage mechanisms, such as resistive random access memory (RRAM). Compared to other emerging new memory technologies, such as ferroelectric random access memory (FeRAM), magnetoresistive random access memory (MRAM), and phase change memory (PCM), RRAM devices feature simple device structure, low fabrication cost, and easy 3D integration. RRAM devices were also reported to exhibit fast switching speed of less than 1 ns, superior endurance of 1012 cycles, and power consumption at several hundred pW. Yet combining all the excellent features within one material system is still an open challenge. The performances that can be achieved in devices are determined by the materials. Understanding how to grow and control the properties of the materials is of great importance. Tantalum oxide (TaOx) has been widely studied and reported to exhibit the fastest switching speed and the most superior endurance in RRAM applications. The use of pulsed laser deposition (PLD) technique to grow and control the TaOx thin film materials for RRAM devices are less reported. In this thesis, I first describe the stoichiometry of the TaOx thin films controlled by varying PLD conditions at room temperature and how it is related to the electrical properties, such as resistivity and resistive switching behaviour, of the TaOx thin films. Second, I present how annealing effect can influence the TaOx material and trigger the resistive switching behaviour in the TiN/TaOx/W structured RRAM devices. Also, the effect of strain on the Pt/TaOx/Ta structured RRAM devices were studied. The thesis ends with my view on how the understanding and the experiments can be improved further.