Nanostructured High-Performance Thin-Film Transistors and Phototransistors Fabricated by a High-Yield and Versatile Near-Field Nanolithography Strategy

Abstract

Thin-film transistors (TFTs) and field-effect transistors (FETs) are basic units to build functional electronic circuits and investigate transport physics. In conventional TFTs or FETs, performance in terms of current level, on−off ratio, and the sensitivity of detection is limited by homogeneous semiconducting layers. In this paper, we develop TFTs with submicron heterostructures by using a strategy based on near-field photolithography. We use an array of totalreflective polydimethylsiloxane pyramids or trenches as a soft photomask in photolithography to induce multiple reflections and diffractions to focus the light. The textured feature enables the generation of gaps, dots, and grids at the nanoscale, with dimensions as small as sub-100 nm on substrates at the centimeter scale. We demonstrated the very high performance oxide TFTs on the nanoscale and periodic degenerately doped heterojunctions, and they yielded a nearly 20fold increase in transconductance and apparent device mobility. The on−off ratio was higher than 10 9 , with notably enhanced output current and clear scaling effect with channel length. We also built nanostructured wide-gap/narrow-gap heterojunctions to balance the high on−off ratio and sensitive photoresponse in a unidirectional phototransistor. This study shows the viability of programming a variety of nanoscale submicron patterns or interfaces in TFTs and FETs to significantly enlarge the scope of research on multifunctional TFTs and FETs.

Oxide semiconductor thin-film transistors with nano-splitting and field-surrounding channels fabricated by subwavelength photolithography

“…A 30 nm IGZO film was deposited onto the substrate with dielectric layer by radio frequency sputtering. Then, the IGZO layer was patterned by double exposure with subwavelength photolithography [26] and conventional lithography, as shown in figures 1(a), (b). Firstly, a layer of 20% (v/v) diluted positive-tone photoresist was spin-coated at 500 rpm for 10 s and 4000 rpm for 40 s onto IGZO layer.…”

“…In the first exposure, the textured PDMS photomask was placed on sample surface and the samples were exposed for 1 s with UV light of wavelength 365 nm. The light control principle and the detailed procedure of subwavelength photolithography have been reported in the previous work [26]. The samples were subsequently exposed for 20 s with Cr mask as conventional lithography.…”

“…However, these technologies have their shortcomings in resolution, cost of facility, application, and repeatability. Therefore, we apply the newly reported subwavelength photolithography technology to fabricate oxide transistors with nano-splitting channels [26]. In this costeffective strategy, the tips of total-reflective polydimethylsiloxane (PDMS) soft photomask focus the exposure light to generate subwavelength photoresist patterns through ordinary lithography equipment.…”

31‐2: Invited Paper: Nanostructures Oxide Thin‐Film Transistors Fabricated by Near‐Field Nanolithography with Enhanced Device Performance

“…The electrical properties of devices with nanostructured heterojunctions channel or normal IGZO TFT. Data from reference[3].…”

“…Results of TLM and the relation between maximum drain current and channel length. Data from reference[3].…”