Downscaling Metal-Oxide Thin-Film Transistors to Sub-50 nm in an Exquisite Film-Profile Engineering Approach

We report an exquisite, film-profile-engineering approach for producing nanometer-scale channel-length (L) ZnO thin-film transistors (TFTs). The scheme is based on a unique laminated structure in conjunction with a well-designed etching process for building a slender, suspending bridge that shadows the subsequent deposition of pivotal thin films of ZnO and gate oxide as well as simultaneously defines L of the TFTs. With the approach, we have ingeniously downscaled L of ZnO TFTs to as short as 10 nm. The experimental ZnO TFTs of L = 50 and 30 nm, respectively, exhibit excellent performance in terms of high on/off current ratio of 7.9 × 10⁷ and 4.2 × 10⁷, superior subthreshold swing of 92 and 95 mV/decade, and small drain induced barrier lowering of 0.1 and 0.29 V/V. Remarkably the nanometer-scale ZnO TFTs possess excellent device uniformity. Furthermore, the precise control over the geometrical sizes for the channel length enables the fabrication of ultrashort ZnO TFTs of L as short as 10 nm with reasonable gate transfer characteristics.