Area-Selective Deposition by Cyclic Adsorption and Removal of 1-Nitropropane

The ever-greater complexity of modern electronic devices requires a larger chemical toolbox to support their fabrication. Here, we explore the use of 1-nitropropane as a small molecule inhibitor (SMI) for selective atomic layer deposition (ALD) on a combination of SiO₂, Cu, CuO, and Ru substrates. Results using water contact angle goniometry, Auger electron spectroscopy, and infrared spectroscopy show that 1-nitropropane selectively chemisorbs to form a high-quality inhibition layer on Cu and CuO at an optimized temperature of 100 °C, but not on SiO₂ and Ru. When tested against Al₂O₃ ALD, however, a single pulse of 1-nitropropane is insufficient to block deposition on the Cu surface. Thus, a new multistep process is developed for low-temperature Al₂O₃ ALD that cycles through exposures of 1-nitropropane, an aluminum metalorganic precursor, and coreactants H₂O and O₃, allowing the SMI to be sequentially reapplied and etched. Four different Al ALD precursors were investigated: trimethylaluminum (TMA), triethylaluminum (TEA), tris(dimethylamido)aluminum (TDMAA), and dimethylaluminum isopropoxide (DMAI). The resulting area-selective ALD process enables up to 50 cycles of Al₂O₃ ALD on Ru but not Cu, with 98.7% selectivity using TEA, and up to 70 cycles at 97.4% selectivity using DMAI. This work introduces a new class of SMI for selective ALD at lower temperatures, which could expand selective growth schemes to biological or organic substrates where temperature instability may be a concern.