A Polyurethane‐Based Positive Photoresist

Abstract

Polyurethane (PU) monomer mixtures containing commercially available o-nitrobenzyl-based photocleavable monomers have been formulated and tested as low-cost positive tone photoresists. The photolysis reaction is studied by UV spectroscopy. Well-defined micropatterns on 2 μm thick photodegradable PU films are obtained using 365 nm light exposure. This strategy is also extended to improved formulations based on synthesized o-nitrobiphenylpropyl derivatives with enhanced photochemical properties for single photon excitation and high two-photon absorption cross-sections. Improved pattern resolution in 2D and the capability of 3D resolution using a scanning laser at 780 nm is demonstrated. This work demonstrates the potential of PUs as readily available, versatile, and easy-to-use photoresist materials for low-cost lithography applications.

Clip Chemistry: Diverse (Bio)(macro)molecular and Material Function through Breaking Covalent Bonds

“…For example, caged dimethylpiperidine can catalyze the cross-linking of poly­(hydroxyl amide) with bis­(activated esters) or bis­(vinyl sulfone) as a negative tone resist. Finally, polymers can also be cleaved directly with light − or heat, , eliminating the need for additional reagents. For example, Ionov and co-worker have shown how temperature-dependent polymer solubility can be modulated by photocleavage reactions of o -nitrobenzyl esters, enabling patterning under mild and entirely aqueous conditions …”

Fundamentals of Two-Photon Fabrication

“…Nevertheless, positive-tone photoresists have been used in a number of interesting applications of two-photon fabrication [67][68][69]. However, there are a number of practical limitations to the use of positivetone photoresists in two-photon fabrication.…”

Hexaarylbiimidazole-based polyurethane positive photoresists for UV lithography

“…The light-mask pattern was obtained due to the difference of solubility between irradiated area and unirradiated region. 28,29 In previous work, HABI was introduced into the polymer skeleton by covalent connection, and the designed polymer can undergo color change, solid-liquid transition, photo-controlled anisotropic swelling and morphological change under light irradiation.…”