Scalability and Stability Enhancement in Self-Aligned Top-Gate Indium- Zinc-Oxide TFTs With Al Reacted Source/Drain

A self-aligned fabrication process for top-gate amorphous indium-zinc-oxide (a-IZO) thin-film transistors (TFTs) is demonstrated. Aluminum (Al) thermal treatment is employed to dope the a-IZO layer and thus form the self-aligned source/drain regions. The results show that the sheet resistance of the Al-treated a-IZO layer can be as low as 360 Ω/□. The fabricated top-gate TFTs typically have a mobility of 16.84 cm²/V · s, subthreshold swing of 0.14 V/dec and on/off current ratio of > 10⁹. The Al-treated TFTs show a significant scalability and stability enhancement compared to the conventional Ar plasma-treated ones. This enhancement can be attributed to the thin Al₂O₃ layer formed on source-drain area that blocks the diffusion of hydrogen or H₂O from the passivation layer into the source-drain and channel regions.