Burst Nucleation in Area-Selective Atomic Layer Deposition
Nucleation behavior governs the selectivity of area-selective atomic layer deposition (AS-ALD). Ideally, nontargeted regions should exhibit delayed nucleation or sparse nucleation that can be easily removed by post-treatment. Here, we report a burst nucleation phenomenon during AS-ALD on perfluoroalkyl self-assembled monolayer (SAM)-treated surfaces. Burst nucleation results in discontinuous particle deposition with weak interfacial adhesion on nontargeted regions, in contrast to the progressive nucleation that forms uniform and adherent films on alkyl SAMs. These weakly adhered particles can be completely removed by gentle wiping without affecting the ALD film in targeted areas. The burst window depends on the SAM chain length, the ALD precursor, and the ALD temperature. When applied to Cu/SiO2 substrates, the nucleation control enables 99.9% selectivity after 30 cycles of Al2O3 ALD, while that of alkyl SAMs is 52.2%. The burst nucleation strategy is broadly effective for enhancing the selectivity of AS-ALD oxides (e.g., ZrO2, HfO2, ZnO) and polymers (e.g., polyimide).
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