Novel back-channel-etch process flow based a-IGZO TFTs for circuit and display applications on PEN foil.

In this study, we report high-quality amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) fabricated on a polyethylene naphthalate foil using a new back-channel-etch (BCE) process flow. The BCE flow allows a better scalability of TFTs for high-resolution backplanes and related circuits. The maximum processing temperature was limited to less than 165 °C in order to ensure good overlay accuracy (<1 µm) on foil. The presented process flow differs from the previously reported flow as we define the Mo source and drain contacts by dry etch prior to a-IGZO patterning. The TFTs show good electrical performance, including field-effect mobilities in the range of 15.0 cm²/(V·s), subthreshold slopes of 0.3 V/decade, and off-currents <1.0 pA on foil. The threshold voltage shifts of the TFTs measured were less than 1.0 V after a stressing time of 10⁴ s in both positive (+1.0 MV/cm) and negative (−1.0 MV/cm) bias directions. The applicability of this new BCE process flow is demonstrated in a 19-stage ring oscillator, demonstrated to operate at a supply voltage of 10 V with a stage delay time of 1.35 µs, and in a TFT backplane driving a 32 × 32 active-matrix organic light-emitting diode display. [ABSTRACT FROM AUTHOR]