Nanoindentation Analysis of SU-8 Coated Wafers at Different Baking Phases

Tarjányi, Tamás and Gulyás, Gábor and Bali, Krisztián and Sámi, Márton and Kiss, Rebeka Anna and Beiler, Barbara and Fürjes, Péter and Szabó, Tibor (2025) Nanoindentation Analysis of SU-8 Coated Wafers at Different Baking Phases. POLYMERS, 17 (24). No. 3337. ISSN 2073-4360

Preview	Text polymers-17-03337.pdf - Published Version Available under License Creative Commons Attribution. Download (3MB) | Preview
	Text (graphical abstract) polymers-17-03337-ag.png - Published Version Available under License Creative Commons Attribution. Download (75kB)

Abstract

SU-8 photoresist is extensively used as a structural and passivation layer in microelectromechanical systems, microfluidic devices, and related microscale technologies. The long-term reliability of these devices critically depends on the mechanical integrity and viscoelastic behaviour of the SU-8 coating. In this study, the mechanical and viscoelastic behaviour of SU-8 polymer thin films was systematically investigated using nanoindentation at different baking stages representative of standard photolithographic processing. SU-8 layers were spin-coated on silicon wafers and subjected to pre-bake, post-bake, and hard-bake treatments to evaluate the effects of progressive cross-linking. Static nanoindentation revealed that the elastic modulus did not change significantly during the baking phases and remained near 6.2 GPa; however, a significant change in hardness was observed from 0.173 ± 0.012 GPa after pre-bake to 0.365 ± 0.011 GPa and 0.364 ± 0.016 GPa after post- and hard bake, respectively. Creep tests analysed by the Burgers viscoelastic model showed a significant increase in both the retarded modulus and viscosity parameters with thermal curing, indicating the suppression of long-term viscoelastic deformation. The combined results demonstrate that nanoindentation provides a sensitive, nondestructive tool for monitoring the evolution of cross-linking and viscoelastic stability in SU-8 films, offering valuable insight for process optimization and mechanical reliability in MEMS and microfluidic applications.

Actions (login required)

Edit Item