Nanomechanical Characterization of Organic Surface Passivation Films on 50 nm Patterns during Area-Selective Deposition

Abstract

Area-selective deposition (ASD) is a "bottom-up" substrate-selective material deposition process, considered as a promising alternative to current "top-down" pattering techniques. The most studied and successful ASD strategies envisage a combination of atomic layer deposition (ALD) and a passivation layer, which prevents material deposition on the non-growth areas. As ASD targets increasingly smaller dimensions, metrology challenges are prominent along with preserving confined film growth. For patterned substrates with nanometric critical dimensions, only a few characterization techniques can be employed to assess the ASD performance. However, these techniques provide no or little insight into the passivation layer. This is a crucial limitation as the blocking film plays a key role in the ASD process. In this work, pulsed force mode atomic force microscopy (AFM) is used to characterize and monitor the quality of the passivation films by measuring the surface energy fluctuations occurring on the patterned substrate undergoing ASD. As the evolution of the relative adhesion force distribution of the sample under ALD conditions is recorded, the octadecanethiol (ODT) coverage on non-growth areas is accurately estimated. The heavily temperature-dependent self-assembled monolayer degradation revealed by the nanomechanical characterization is supported by X-ray photoelectron spectroscopy. As Hf3N4 ALD is performed, the top-down scanning electron microscopy investigation is employed to show the strong relationship between ASD quality upon ALD and pulsed force AFM-derived ODT coverage.