Oxide thin-film transistors based on i-line stepper process for high PPI displays

Indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs) with a 1 um channel length were successfully fabricated by i-line lithography with a stepper process, resulting in high throughput. The a-IGZO TFT with a channel length of 1 μm exhibits high mobility of 8.77 cm2/Vs with an on/off current ratio of >3 × 1010. The stepper lithography process is capable of defect-free patterning given its precise layer-to-layer alignment and high image resolutions of the types required for large-area high-PPI displays. Consequently, IGZO TFTs can be fabricated on an 8-inch wafer with only minor electrical property deviations in the turn-on voltage, mobility, and on/off ratio. These results indicate that i-line lithography with a stepper process is a promising process for use in cutting-edge large-area electronics industries.