Scalable, High-Performance Printed InO_x Transistors Enabled by Ultraviolet-Annealed Printed High-k AlO_x Gate Dielectrics

Abstract

Inorganic transparent metal oxides represent one of the highest performing material systems for thin-film flexible electronics. Integrating these materials with low-temperature processing and printing technologies could fuel the next generation of ubiquitous transparent devices. In this work, we investigate the integration of UV-annealing with inkjet printing, demonstrating how UV-annealing of high-k AlO x dielectrics facilitates the fabrication of high-performance InO x transistors at low processing temperatures and improves bias-stress stability of devices with all-printed dielectrics, semiconductors, and source/drain electrodes. First, the influence of UV-annealing on printed metal–insulator–metal capacitors is explored, illustrating the effects of UV-annealing on the electrical, chemical, and morphological properties of the printed gate dielectrics. Utilizing these dielectrics, printed InO x transistors were fabricated which achieved exceptional performance at low process temperatures (<250 °C), with linear mobility μlin ≈ 12 ± 1.6 cm2/V s, subthreshold slope <150 mV/dec, I on/I off > 107, and minimal hysteresis (<50 mV). Importantly, detailed characterization of these UV-annealed printed devices reveals enhanced operational stability, with reduced threshold voltage (V t) shifts and more stable on-current. This work highlights a unique, synergistic interaction between low-temperature-processed high-k dielectrics and printed metal oxide semiconductors.

Printed, Highly Stable Metal Oxide Thin‐Film Transistors with Ultra‐Thin High‐κ Oxide Dielectric

“…Taking that into account, 1.2 m ink concentration was selected for further tests as this concentration allowed a higher film thickness whilst maintaining good uniformity, which is crucial to prevent high leakage and pinholes probability (see Figure S1, Supporting Information). Notably, by using combustion synthesis in the ink formulation as shown here, a higher viscosity value can be reached due to a higher solute concentration, when compared with conventional sol–gel as reported earlier by Subramanian et al37 This can be beneficial for roll‐to‐roll (R2R) printing of thin oxide films from combustion inks. Thermogravimetry and differential scanning calorimetry (TG‐DSC) was performed on the 1.2 m Al 2 O 3 sol–gel and combustion xerogel, as depicted in Figure 2b.…”

Inkjet‐Printed and Deep‐UV‐Annealed YAlOx Dielectrics for High‐Performance IGZO Thin‐Film Transistors on Flexible Substrates

“…The main drawback of that study, however, was the high PDA temperature of 400 °C, which is not compatible with temperature‐sensitive substrates. Very recently, Subramanian and co‐workers have successfully demonstrated oxide‐based TFTs with printed and DUV annealed AlO x dielectrics on rigid silicon substrates with maximum fabrication temperature of 250 °C . Although the processing temperature is much lower than the previously reported values, it is still not compatible with flexible substrates such as polyethylenenaphtalene and polyethyleneterephthalate.…”

“…This requirement stems from the fact that inks with too low viscosity are jetted with undesirable satellites (artifact drops with smaller volumes than the main drop) in an uncontrollable fashion, whereas inks with too high viscosity are not jettable. An easy way of adjusting the viscosity of the ink is to change the precursor concentration . Viscosity levels of the inks with different precursor concentrations were measured and the results are shown in Figure a.…”

A Review of Low‐Temperature Solution‐Processed Metal Oxide Thin‐Film Transistors for Flexible Electronics

“…d) Schematic illustrating of single and multinozzle printing. c,d) Reproduced with permission . Copyright 2018, American Chemical Society.…”

“…Low‐temperature‐processed inkjet‐printed high‐ k AlO x dielectrics produced via UV annealing were introduced by Subramanian and co‐workers, using a multinozzle printing method (Figure c) . Compared with conventional single‐nozzle printing, multinozzle printing is a rapid process, as an entire film can be deposited in a single pass as shown in Figure d.…”