Scum-free patterning of SU-8 resist for electroforming applications

Abstract

A simple approach is developed to obtain scum-free pattern transfer in SU-8 resist by UV-lithography for electroforming applications. SU-8 is an epoxy-based negative resist used in the fabrication of high-aspect ratio microstructures. SU-8 resist poses considerable processing difficulties and tends to leave organic residues of undeveloped resist on the surface of the exposed metallic seed layer. Scum-free pattern transfer in SU-8 resist is important for the subsequent electroplating process used to fabricate the high-aspect ratio metallic microstructures. Dry plasma etching processes are commonly used to remove the SU-8 residue prior to electroplating. However, these processes are complex and not cost-effective. In this work, it is shown that scum-free SU-8 patterns could be achieved by proper selection of process parameters such as soft-bake temperature, exposure time, post-exposure-bake temperature, developing time and rinsing in solvents. The success of this particular process is due to controlled rinsing of the patterned sample in acetone to remove the resist scum. The results of our method for patterning the SU-8 resist to fabricate nickel microstructures using this mold are reported.

A novel design and micro-fabrication for copper (Cu) electroforming bipolar plates

“…1(b and c). However, some roughness and waviness of the sidewall are still found, possibly caused by the use of film mask for exposure (Agarwal et al, 2005). In any case, it is important that one should remove any residual resist layer with no stiction, before attempting electroforming; otherwise, the flatness of the surface would be affected.…”

“…In fact, SU-8 can be also used as an electroplating mould in many applications (Agarwal et al, 2005). The present study aims to develop a copper www.elsevier.com/locate/micron Micron 39 (2008) 263-268 electroforming process by patterning SU-8 negative resist using a deep UV lithography technique to fabricate PEM fuel cell stack bipolar plates.…”

Numerical analyses of peel demolding for UV embossing of high aspect ratio micro-patterning

“…The stress-strain data for a nominal UV cure time of 30 s was used throughout the modeling process. The polymer replication is assumed to have taken place within a rigid nickel mold of the kind that can be fabricated with micromachining and nickel electroforming methods (Agarwal et al 2005).…”

Sidewall slopes and roughness of SU-8 HARMST

“…Earlier some authors (Agarwal et al 2005;Shew et al 2003) had reported the surface roughness of SU-8 microstructures using X-ray lithography to be around 10 nm root mean square (rms), however, no detailed studies were reported that also consider the depth dependent roughness. Accordingly, we undertook detailed theoretical and experimental studies to study the dependence of surface roughness on the incident beam spectrum, along and perpendicular to the direction of beam and on the depth of the resist (Vora et al 2006).…”