An ionic liquid-based photoresist with expandable applications: direct patterning from small molecules via thiol-ene photopolymerization

The photoresist composed of small molecules was developed. • The photoresist was directly patterned in a one-step process via in situ reactions. • The ionic liquid improves interfacial compatibility between PR and silicon wafer. • Photoresists based on the thiol-ene reaction exhibited preferable sensitivity. • The photoresist was utilized in quantum dot lithography and 3D printing. To circumvent the complex synthesis procedures associated with conventional polymeric photoresists (PRs), we developed an in situ polymerization and crosslinking strategy for small molecules based on thiol-ene free-radical photopolymerization. Ionic liquid (IL), commonly used to modulate interfacial interactions and polymerization reactions, was therefore introduced as one of the monomers to improve the patterning performance. The film-forming ability was improved by the addition of the hydrophilic IL 1-vinyl-3-butylimidazolium bromide (VBIMBr) without the use of toxic hexamethyldisilazane (HMDS) vapor. The lithographic performance with varying IL content was studied, achieving line resolutions of 0.8 μm for deep ultraviolet (DUV) lithography and 100 nm for electron beam lithography (EBL), respectively. Furthermore, the effects of IL on the lithographic kinetics and mechanism were systematically investigated. The homogeneous network induced by thiol-ene photopolymerization enables a uniform distribution of quantum dots (QDs) through effective immobilization, highlighting its potential for QD lithography. It was found that the PR enables the fabrication of multicolor luminescent patterns over a wide scale range (from the micrometer to the millimeter scale) on diverse substrates, with an impressive resolution of 1 μm, demonstrating its potential for applications in additive manufacturing. Additionally, the PR is also applicable to 3D printing owing to its unique formation process. Download: Download high-res image (347KB) Download: Download full-size image