Fabrication of multi-layer SU-8 microstructures

Abstract

The fabrication of multi-level SU-8 microstructures using multiple coating and exposure steps and a single developing step has been achieved for up to six layers of SU-8. Alternating layers of SU-8 2010 (thin) and SU-8 2100 (thick) photoresist films were spin coated, followed by soft-bake, ultraviolet (UV) exposure and post-exposure bake steps. The multiple SU-8 layers were simultaneously developed to create patterned microstructures with overall thicknesses of up to 500 µm and minimum lateral feature size of 10 µm. The use of a single developing step facilitated fabrication of complex multi-level SU-8 microstructures that might be difficult, or even impossible, to achieve by sequential processing of multiple SU-8 layers that are individually coated, baked, exposed and developed.

Wettability transition of plasma-treated polystyrene micro/nano pillars-aligned patterns

“…On the other hand, geometric structures including rough structures and regular micro/nano patterns are also crucial [13,14]. To obtain polymer regular micro/ nano geometric surfaces, various nanoprocessing approaches can be employed, including nanoporous template wetting [15], capillary lithography [16], nanoimprint lithography [17], microstereolithography [18], template rolling press [19], and water spreading of carbon nanotubes [20]. A number of theoretical and experimental studies indicated that polymer aligned nanopillar arrays or carbon nanotube arrays could exhibit hydrophobic or surperhydrophobic feature [21][22][23][24].…”

Fabrication of multi-layer polymeric micro-sieve having narrow slot pores with conventional ultraviolet-lithography and micro-fabrication techniques

“…To avoid excessive stress, adhesion failure, and pattern dimensional change, exposure dose must be adjusted according to the substrate or under layer reflectivity. 16 For this case, finding the optimum dose for the second layer was a serious challenge, because an extra or not sufficient dosage could lead to the pore occlusion and pattern failure. After exposing the second layer, wafer was kept again on the hotplate at 95 C for the FIG.…”

“…We utilized SU-8 (MicroChem Corp., Newton, MA) as a potential material for membrane fabrication because it is an epoxy-type photoresist with suitable chemical and mechanical properties that have been used widely for the development of complex features like multi-level microstructures. 15,16 Technically, fabrication of small micro-holes (i.e., 0.5-5 lm) inside a thick SU-8 film is impossible due to the tapering effect, 17,18 which normally happen during UV exposure (i.e., usually top layer is overexposed and tends to be wider than the bottom layer which is relatively underexposed, resulting in the variation of the lateral dimensions). To overcome this impediment, we employed multi-level lithography technique to fabricate polymeric membrane using multiple coating and exposure steps and a single developing process.…”

PDMS microfluidics developed for polymer based photonic biosensors

“…2) utilizing multi-layered SU-8 epoxy based negative photoresist [13,14,15] as a master replica for PDMS moulding [3]. The SU-8 layers were patterned by subsequent spin-coatings and lithographic exposures and a final development step.…”