Jet-printed fabrication of a-Si:H thin-film transistors and arrays

Phase-change wax-based printed masks, in place of conventional photoresist masks, were used to fabricate a-Si:H thin-film transistors (TFTs). Printed wax-mask features with a minimum feature size of ∼20 μm were achieved using an acoustic-ink-printing process. Both discrete and matrix addressing structured bottom-gate TFTs with source-drain contacts overlapping the channel were created using a four-mask process. The TFTs had I–V characteristics comparable to photolithographically patterned devices, with mobility of 0.6–1 cm2/V s, threshold voltage of 2–3 V, and on/off ratios exceeding 107 for devices with channel lengths below 50 μm. The wax-mask process was also used to fabricate self-aligned TFT devices, eliminating the source-drain contact overlap constraint.