Preventing unwanted atomic layer deposition by liquid sealing

Abstract

Atomic layer deposition (ALD) is an essential thin film fabrication technique widely used in electronic and energy systems, but avoiding ALD in untargeted areas has been a long-standing challenge that excludes the possibility of creating patterns through bottom-up processes. We present a liquid sealing strategy to prevent unwanted ALD by combining shadow masks with viscous perfluoropolyether oil that conformally fulfills all gaps between the mask and substrate down to the molecular level. Due to the anti-adsorption and non-defective nature of the liquid sealant, ALD molecules are forced away from the masking areas, resulting in order-of-magnitude improvements in the patterning resolution compared with conventional shadow masks. The liquid sealant does not change the growth rate and film properties of ALD oxides and can be easily removed by solvents. This liquid sealing strategy applies to a variety of shadow masks (e.g., curved mask and anodic aluminum oxide), substrates (e.g., silicon, plastic, and elastomer), patterning materials (e.g., oxide and metal), and deposition methods (e.g., sputtering and thermal evaporation), providing new insights for bottom-up pattern fabrications.