Generation of Au micropatterns on two sidewalls of a Si channel through a PDMS shadow mask

Abstract

Conventional lithographic approaches are good at patterning the top surface of a substrate, but not suited to producing patterns on the sidewalls of microstructures. We have previously developed an approach to generate Au micropatterns on a single Si sidewall using a polydimethylsiloxane (PDMS) shadow mask. In this work, we have modified the previously developed approach for the purpose of fabricating patterns on two vertical sidewalls of a Si channel. In the modified approach, instead of bonding a PDMS shadow mask to a channel sidewall, the PDMS shadow mask was suspended above a Si channel. Two processes of thermal evaporation (instead of one process) were subsequently employed to produce Au sidewall patterns. In these two processes, the two sidewalls of the Si channel were tilted toward the Au source, respectively, to ensure that Au vapors went through the PDMS shadow mask and deposited on both sidewalls. Finally, after the removal of the PDMS membrane, Au patterns were generated on the channel sidewalls. In this work, we first established 3D geometric models for the modified approach. Based on the understanding gained from these geometric models, we then applied this approach to produce 10 µm Au dots and 20 µm wide Au lines on the sidewalls of Si microchannels. The maximum error was 0.9 µm when the geometric models were used to predict the dimensions and distances of these generated patterns. The modified approach might also be applied to produce patterns on multiple sidewalls of a microstructure.