Oxide Electronics by Spatial Atomic Layer Deposition

We report on zinc oxide (ZnO)-based devices produced by a fast, open-air atomic layer deposition (ALD) process relying upon the spatial isolation of reactive gases. At deposition rates of greater than 100 Aring per minute, ZnO-based thin-film transistors by spatial atomic layer deposition (S-ALD) show mobility above 15 cm ² /Vs and excellent stability. Measurement and modeling of the gas isolation in the deposition head is discussed. Saturation curves obtained for aluminum oxide (Al ₂ O ₃ ) growth using trimethylaluminum and water are shown to be consistent with chamber ALD systems. Finally, the ability of this new ALD process to leverage patterning by using poly(methyl methacrylate) (PMMA) as a growth inhibitor for selective area deposition is discussed. Relatively thin films of PMMA (~ 40 Aring) are shown to be capable of inhibiting the growth of ZnO for at least 1200 ALD cycles.