Two-Step Plasma Treatment Designed for High-Performance Flexible Amorphous ZnAlSnO Thin-Film Transistors Replacing Thermal Annealing

A two-step plasma treatment is designed as a post-process treatment for active layers of flexible thin-film transistors (TFTs) instead of thermal post-annealing. Amorphous zinc-aluminum-tin-oxide (ZATO) is used for active layers of flexible TFTs, which highlights the influence of the two-step plasma treatment on ZATO films and the corresponding TFT devices, because the device performance of ZATO TFTs exhibits significant improvement only after the active layers are annealed at high temperature. The effects of various plasma-treatment of the ZATO active layer on the device performance are studied in detail. The two-step plasma treatment can ameliorate the amorphous film and improve the corresponding device performance. The flexible TFT device with ZATO active layer processed by the two-step plasma treatment exhibits anI(on)/I(off)current ratio of 1.15 x 10(8), a positive threshold voltage of 3.77 V, a field-effect mobility of 13.2 cm(2) V-1 s(-1), and a subthreshold swing of 0.5 V per decade. Meanwhile, a correlation is found that the effect of thetwo-stepplasma treatment as post-process treatment of amorphous ZATO films is almost equivalent to 500 degrees C annealing, by comparing the electrical properties of TFTs with ZATO active layers annealed at different temperature. The two-step plasma treatment may replace high-temperature annealing in the thermosensitive process.