Polyallylamine as an Adhesion Promoter for SU-8 Photoresist

Abstract

Resist lithography is an important microfabrication technique in the electronics industry. In this, patterns are transferred by irradiation onto a photosensitive polymer. SU-8 has emerged as a favorite photoresist for High Aspect Ratio (HAR) lithography, showing high chemical and mechanical stability and biocompatibility. Unfortunately, its poor adhesion to substrates is a drawback, with possible solutions being the use of low-viscosity SU-8, surface modification with a low molecular weight adsorbate like hexamethyldisilazane (HMDS), or a commercial adhesion promotion reagent. However, HMDS and the commercial reagent require surface dehydration and/or curing, and a modified form of SU-8 is not always desirable. Here, we demonstrate the use of a water-soluble, amine-containing polymer, polyallylamine (PAAm), which spontaneously adsorbs to silica surfaces, as a simple, easy-to-apply, and reactive adhesion promoter for SU-8. Conditions for the use of PAAm are explored, and the resulting materials are characterized by X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and wetting.

Rapid Prototyping of Soft Lithography Masters for Microfluidic Devices Using Dry Film Photoresist in a Non-Cleanroom Setting

“…For SU-8, a number of optimization or tweaking runs are generally necessary to achieve desired height and vertical sidewalls. In particular, lower height features can only be fabricated with low viscosity SU-8 (e.g., SU-8 TF 6000), which are even more affected by moisture and temperature variations, resulting in a very low adhesion behavior on silicon [27]. Spin coating is highly sensitive to the spinning speed applied for coating, as even a minimum alteration of the speed can lead to a sensible variation in the height of the coating, which may have drastic effects for further application of the master.…”

Linear shrinkage of hydrogel coatings exposed to flow: interplay between dissolution of water and advective transport

“…Double functional groups were first introduced onto the SU-8 photoresist-based micropillar array surface via a reaction involving allylamine (ALAm). 33,34 A 5% v/v solution of allylamine in water was prepared and put under stirring for 10 minutes. The thus-prepared solution was poured into a glass box containing the SU-8 micropillar arrays and left for 30 minutes.…”

Towards environmentally friendly processing of ionic liquid-based photoresists with a boosted lithography performance

“…In general, most photoresists are hydrophobic. Chatterjee et al 8 used polyallylamine as an adhesion promoter for the SU-8 photoresist and an organic solvent was used as a developer. Horibe et al 9 modified the substrate with HMDS before spin-coating and developed it with an alkaline solution.…”