A low-temperature photoresist-based film-profile engineering scheme for fabricating bottom- and double-gated indium-gallium-zinc oxide TFTs

We proposed a novel low-temperature (<110 °C) process scheme based on the film-profile engineering technique for fabricating indium-gallium-zinc oxide thin-film transistors (TFTs) with both bottom-gated (BG) and double-gated (DG) configurations. An organic photoresist (PR) suspended bridge is constructed to shadow the depositing species during the deposition processes of the bottom gate-oxide, channel, and source/drain metal films. An Al₂O₃ layer deposited at 110 °C using atomic-layer deposition is employed as the bottom gate-oxide layer. Such a low-temperature process allows us to deposit the Al₂O₃ layer following the formation of the PR suspended bridge, preventing the formation of organic residues between the gate-oxide and channel layers. As a result, excellent device performance in terms of field-effect mobility of 12.1 cm² V⁻¹ s⁻¹ and subthreshold swing of 141 mV/dec is achieved. Our proposed low-temperature process scheme is readily applicable for fabricating DG TFTs which show substantial enhancements in driving currents.