Simultaneously Defined Semiconducting Channel Layer Using Electrohydrodynamic Jet Printing of a Passivation Layer for Oxide Thin-Film Transistors

Abstract

A simple fabrication method for homojunction-structured Al-doped indium-tin oxide (ITO) thin-film transistors (TFTs) using an electrohydrodynamic (EHD) jet-printed Al₂O₃ passivation layer with specific line (<i>W</i>_Al₂O₃) is proposed. After EHD jet printing, the specific region of the ITO film below the Al₂O₃ passivation layer changes from a conducting electrode to a semiconducting channel layer simultaneously upon the formation of the passivation layer during thermal annealing. The channel length of the fabricated TFTs is defined by <i>W</i>_Al₂O₃, which can be easily changed with varying EHD jet printing conditions, i.e., no need of replacing the mask for varying patterns. Accordingly, the drain current and resistance of the fabricated TFTs can be modified by varying the <i>W</i>_Al₂O₃. Using the proposed method, a transparent n-type metal-oxide-semiconductor (NMOS) inverter with an enhancement load can be fabricated; the effective resistance of load and drive TFTs is easily tuned by varying the processing conditions using this simple method. The fabricated NMOS inverter exhibits an output voltage gain of 7.13 with a supply voltage of 10 V. Thus, the proposed approach is promising as a low-cost and flexible manufacturing system for multi-item small-lot-sized production of Internet of Things devices.