Understanding Selectivity Loss Mechanisms in Selective Material Deposition by Area Deactivation on 10 nm Cu/SiO₂ Patterns

Area-selective deposition (ASD), a “bottom-up” substrate-selective material deposition process, is a promising solution to overcome the current limitations experienced in semiconductor manufacturing processes, which rely on “top-down” patterning techniques. To achieve this selective material growth, atomic layer deposition (ALD) is frequently employed in conjunction with a blocking layer to suppress material nucleation on the nongrowth areas. ASD is suitable on many levels of wafer manufacturing; notably, its “bottom-up” nature makes it more impactful at the smallest critical dimensions (CDs), such as sub-10 nm. Nevertheless, the ASD studies at such relevant nanoscale dimensions are very limited or nonexistent. Therefore, we studied ASD enabled by 1-octadecanethiol (ODT)-derived self-assembled monolayer (SAM) passivation on unprecedented scaled-down Cu/SiO2 patterns, targeting ASD of hafnium nitride on 10 nm-wide dielectric spacings. Pulsed force atomic force microscopy nanomechanical characterization proved the tight confinement of the organic layer to the metal lines even on such high-density patterns. In addition, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy (SEM) measurements reveal the selective and conformal deposition of ∼5.0 nm hafnium nitride film on the 10 nm-wide SiO2 spacings. Nevertheless, it is shown that, as the pattern features shrink, the undesired lateral expansion of the isotropically growing ALD film becomes a more stringent limitation to the ASD resolution. The “monolayer trade-off” associated with the employed passivation to enable ASD is analyzed in this work. In fact, a monolayer-thick blocking film is desired to avoid poisoning of the growth surface, whereas the ASD film lateral expansion could be effectively prevented if thicker passivation films are employed instead.