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New approaches for area-selective deposition (ASD) are becoming critical for advanced semiconductor patterning. Atomic layer deposition (ALD) and atomic layer etching (ALE), that is, “inverse ALD”, are considered important for ASD, but to date, direct integration of ALD and ALE for ASD has not been reported. This work demonstrates that self-limiting thermally driven ALE, using WF6 and BCl3, can be directly coupled with self-limiting thermal ALD, using TiCl4 and H2O, in a single isothermal reactor at temperature 0.9, nearly a 10× improvement over previous reports of inherent TiO2 ASD. After ALD/ALE (=30/5) 14 supercycles at 170 °C, X-ray photoelectron spectroscopy da...

A key hallmark of atomic layer deposition (ALD) is that it proceeds via self-limiting reactions. For a good ALD process, long reactant exposure times beyond that required for saturation on planar substrates can be useful, for example, to achieve conformal growth on high aspect ratio nanoscale trenches, while maintaining consistent deposition across large-area surfaces. Area-selective deposition (ASD) is becoming an enabling process for nanoscale pattern modification on advanced nanoelectronic devices. Herein, we demonstrate that during area-selective ALD, achieved by direct coupling of ALD and thermal atomic layer etching (ALE), excess reactant exposure can have a substantially detrimental influence on the extent of selectivity. As an example system, we study ASD of TiO2 on hydroxylated SiO2 (Si–OH) vs hydrogen-terminated (100) Si (Si–H) using TiCl4/H2O for ALD and WF6/BCl3 for ALE. Using in situ spectroscopic ellipsometry and ex situ x-ray photoelectron spectroscopy, we show that unwanted nucleation can be minimized by limiting the water exposure during the ALD steps. Longer exposures markedly increased the rate of nucleation and growth on the desired non-growth region, thereby degrading selectivity. Specifically, transmission electron microscopy analysis demonstrated that near-saturated H2O doses enabled 32.7 nm thick TiO2 patterns at selectivity threshold S > 0.9 on patterned Si/SiO2 substrates. The correlation between selectivity and reactant exposure serves to increase fundamental insights into the effects of sub-saturated self-limiting surface reactions on the quality and effectiveness of ASD processes and methods.