Integrated Isothermal Atomic Layer Deposition/Atomic Layer Etching Supercycles for Area-Selective Deposition of TiO2

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 <200 degrees C to achieve ASD of TiO2 thin films on common Si/SiO2-patterned surfaces without the use of organic nucleation inhibitors. We show that ALD/ALE "supercycles" (where one supercycle comprises, e.g., 30 ALD cycles followed by 5 ALE cycles) can be reliably repeated to yield more than 12 nm of TiO2 while maintaining a selectivity fraction S > 0.9, nearly a 10X improvement over previous reports of inherent TiO2 ASD. After ALD/ALE (=30/5) 14 supercycles at 170 degrees C, X-ray photoelectron spectroscopy data show a small Ti 2p signal on Si-H (hydrogen fluoride-cleaned Si), with no Ti 2p signal detected after additional "postetch" ALE cycles. At 150 degrees C, extended supercycles lead to unwanted particles visible by electron microscopy, which is ascribed to the formation of unreactive mixed silicon/titanium oxide nuclei. The number density of visible particles is consistent with modeled film growth trends. Overall, this work provides new insights into the capabilities for ASD of dielectric materials and a starting point to realize more complex atomic-scale processes using ALD, ALE, and other self-limiting reaction schemes.