High-performance annealing-free InGaZnOx thin film transistors by thermal ALD

초록

We report indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) fabricated entirely by thermal atomic layer deposition (TALD) within a low thermal budget (<= 300 degrees C) and without post-deposition annealing. A targeted O-3 overdose step integrated into the Ga2O3 sub-cycles of the IGZO TALD super-cycle raises the local oxygen chemical potential and helps suppress inter-sub-cycle redox reactions and vacancy formation. Structural and chemical analyses confirm smooth, fully amorphous Al2O3/IGZO stacks with abrupt interfaces and reduced oxygen-vacancy signatures, while cation states remain stable. Standard TFTs fabricated from these layer stacks exhibit excellent device performance, including near-ideal subthreshold swing (SS) values of 66.4-70 mV/dec, operation windows within 3 V, field-effect mobilities ranging between mu(FE) = 23.6-25.6 cm(2)/Vs, threshold voltages (V-TH) close to 0 V, and negligible hysteresis. Under positive-bias temperature stress, Delta V-TH remains small across 25-85 degrees C, indicating good device reliability. A holistic comparison with prior ALD-based oxide TFTs shows that the combination of low temperature processing, near-ideal SS, and small drift under stress places our devices on the favorable end of performance-stability trade-off. The O-3 overdose concept presented here provides a generalizable lever for oxygen vacancy control in the TALD of multi-cation oxides and is naturally compatible with BEOL and monolithic 3D integration.

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