Area selective atomic layer deposition of ruthenium with pinacolborane as a small molecule inhibitor

This study investigates the use of pinacolborane as a small molecule inhibitor for the area selective atomic layer deposition (ALD) of Ru on oxide, nitride, and metal surfaces. Pinacolborane selectively chemisorbs and blocks the Ru film growth on native SiO2, TiN, Co, Cu, HfO2, and ZrO2 surfaces while Ru film grows solely on a Pt surface. The surfaces were subjected to eight exposures of 10 s pulses of pinacolborane separated by 30 s of N2 purging, followed by Ru film deposition with bis(cyclopentadienyl)ruthenium (RuCp2) and O2 at 340 °C. The process was tested at various temperatures, and the difference between the growth surface and nongrowth surfaces was the most evident at 340 °C. Energy dispersive x-ray spectroscopy confirmed the selective deposition of Ru film on Pt surfaces. X-ray photoelectron spectroscopy revealed the presence of boron on the HfO2 surface after the pinacolborane exposures. Selectivity of the Ru growth on Pt is greater than 0.9 with respect to native SiO2 up to 300 Ru ALD cycles; TiN, HfO2, and ZrO2 up to 900 Ru ALD cycles; Co up to 700 Ru ALD cycles; and Cu up to 1000 Ru ALD cycles. Additionally, in an ABC-type process where pinacolborane is dosed in every ALD cycle, Ru film grows only on Ru while being effectively suppressed on native SiO2 and Pt surfaces. Our findings can serve as a valuable resource in the fabrication of next-generation interconnects.