Optimizing ALD-Deposited IGZO TFT Thermal Stability Through Compositional Adjustments

The integration of metal oxide TFTs is challenged by high BEOL temperatures. Our study evaluated ALD-deposited IGZO TFTs with different composition ratio. These TFTs exhibited mobilities ranging from 30.24 to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$81.60 ~\text{cm}^{2} ~\mathrm{V}^{-1} ~\mathrm{s}^{-1}$</tex>. The optimized-composition <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\operatorname{In}_{0.25} \text{Ga}_{0.26} \text{Zn}_{0.49} \mathrm{O}$</tex> TFT without encapsulation, maintained performance after <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$450^{\circ} \mathrm{C}$</tex> annealing process and exhibited enhanced thermal stability, reducing the threshold voltage shift from over 15 V to −1.5 V. This enhancement is attributed to the stabilization of the amorphous structure, optimization of the coordination number, and reduction of defect states.