Oxide Semiconductors TFTs Integration in CMOS BEOL: Device Considerations for Enabling Novel Applications

The tremendous surge in the interest in oxide semiconductors for applications such as Flash memories, 3D DRAM, RF circuits, displays, flexible electronics, is driven by the advantages of these materials over conventional choices [1]. Their CMOS back end of line (BEOL) compatibility helps enable novel complex functionalities without an overhead in the footprint. Additionally, these large band gap materials give an ultra-low off-current for reduced standby power. The application spectrum is growing, and multiple control knobs provide a large design space. Understanding of the device fundamentals, stack engineering and processing, and reliability assessment and modeling are vital to achieve the specifications for the targeted applications. Here, we focus on thin film transistors (TFTs) and use In-Ga-Zn-O (IGZO) as a representative material to discuss the different aspects. These device design and assessment guidelines can be extended to other oxide semiconductors.