Effect of Multilayer versus Monolayer Dodecanethiol on Selectivity and Pattern Integrity in Area-Selective Atomic Layer Deposition

Monolayer and multilayer dodecanethiols (DDT) can be assembled onto a copper surface from the vapor phase depending on the initial oxidation state of the copper. The ability of the copper-bound dodecanethiolates to block atomic layer deposition (ALD) and the resulting behavior at the interfaces of Cu/SiO₂ patterns during area-selective ALD (AS-ALD) are compared between mono- and multilayers. We show that multilayer DDT is ∼7 times more effective at blocking ZnO ALD from diethylzinc and water than is monolayer DDT. Conversely, monolayer DDT exhibits better performance than does multilayer DDT in blocking of Al₂O₃ ALD from trimethylaluminum and water. Investigation into interfacial effects at the interface between Cu and SiO₂ on Cu/SiO₂ patterns reveals both a gap at the SiO₂ edges and a pitch size-dependent nucleation delay of ZnO ALD on SiO₂ regions of multilayer DDT-coated patterns. In contrast, no impact on ZnO ALD is observed on the SiO₂ regions of monolayer DDT-coated patterns. We also show that these interfacial effects depend on the ALD chemistry. Whereas an Al₂O₃ film grows on the TaN diffusion barrier of a DDT-treated Cu/SiO₂ pattern, the ZnO film does not. These results indicate that the structure of the DDT layer and the ALD precursor chemistry both play an important role in achieving AS-ALD.