Area-Selective Atomic Layer Deposition of SiO₂ on SiO₂ with Alkanethiol Functionalized Cu as the Nongrowth Surface

We report on the area-selective, O₃ and O₂-plasma-assisted atomic layer deposition (ALD) of SiO₂ on plasma-deposited SiO₂ with Cu as the nongrowth surface. Di-sec-butyl-aminosilane (DSBAS) was used as the Si precursor for SiO₂ ALD. We studied the surface functionalization of Cu and the ALD process on bare and functionalized Cu surfaces using in situ reflection-absorption infrared spectroscopy (RAIRS). The Cu surface was functionalized at 100 °C using heptanethiol (HT) supplied from the gas phase. The native oxide on Cu promoted the uptake of HT and led to the formation of a multilayer hydrocarbon passivation layer. Since O₃ and O₂ plasma degraded the organic layer, the inhibitor was redosed during every cycle in a three-step A-B-C-type ALD process (A: HT; B: DSBAS; C: O₃ or O₂ plasma) performed at a substrate temperature of 100 °C. In situ RAIRS and X-ray photoelectron spectroscopy (XPS) show that combustion of the hydrocarbon passivation layer by O₃ and O₂ plasma leads to the formation of surface carbonates, and these were more readily formed during the O₃-based process compared to the O₂ plasma ALD process. Within the sensitivity of the RAIRS setup, for both the ALD processes, surface -SiH₃ groups were not detected after the DSBAS partial cycle. High-resolution XPS indicated some SiO₂ growth and partial oxidation of the Cu surface after theA-B-C ALD processes. Approximately 5 nm of SiO₂ was deposited on the SiO₂ growth surface for both O₃ and O₂ plasma-assisted ALD with high selectivity. However, perfect growth selectivity could not be obtained due to the formation of surface carbonates.