Gallium precursor reaction pathway-driven low-temperature atomic layer deposition of IGZO for thin-film transistors

Abstract

Indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) fabricated by atomic layer deposition (ALD) are promising for large flat-panel display technology requiring low thermal budgets (<400 °C), which is critical for next-generation displays and back-end-of-line electronics. However, the choice of precursor affects the feasibility of low-temperature processes. In this study, two gallium precursors—triethylgallium (TEGa) and trimethylgallium—were employed to achieve low-temperature fabrication of IGZO TFTs by fully thermal ALD. A high field-effect mobility (μFE) of 40.09 cm2/V s was achieved at 250 °C for the IGZO TFTs fabricated by TEGa, which has a lower thermal budget than other methods. This performance is attributed to the unique β-hydride elimination pathway of TEGa, which not only enables low-temperature deposition but also significantly reduces the defect state density in the IGZO films. The TFT devices exhibited excellent stability under a 30-min positive bias stress test, with a threshold voltage shift (ΔVth) of merely 8 mV. These findings provide a new approach for the low-temperature deposition of metal oxide semiconductor devices.