Oxygen ambient annealing-driven contact engineering and channel property modulation in tungsten/InGaZnO thin-film transistors for BEOL-compatible integration

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This study investigates the effect of oxygen ambient post-metallization annealing (O 2 PMA) on the interfacial and electrical properties of amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs). Devices were fabricated with tungsten (W) source/drain electrodes and subjected to O 2 PMA at 300, 350, 400, and 450 °C. Structural and chemical analyses confirmed that interfacial reactions between W and IGZO vary significantly with annealing temperature, affecting both the formation of a WO x interlayer and the crystallization of the IGZO channel. At 400 °C, a thin WO x layer is formed at the interface, leading to improved contact quality and minimal degradation of the IGZO properties. As a result, the device annealed at 400 °C exhibited enhanced performance, including an on/off current ratio of approximately 9 × 10 6 , a subthreshold swing of 105 mV/dec at V D = 0.05 V, a field-effect mobility of 14.1 cm 2 /V·s, and a width-normalized contact resistance of 7.85 Ω·cm. In contrast, annealing at 450 °C induced excessive oxygen diffusion, degrading the channel properties and reducing mobility. These results demonstrate that O 2 PMA at 400 °C offers an effective approach to optimize both interfacial contact and channel properties for BEOL-compatible oxide TFTs.