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Mechanical Behavior and Anisotropy of Spin-Coated SU-8 Thin Films for MEMS

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Title Mechanical Behavior and Anisotropy of Spin-Coated SU-8 Thin Films for MEMS
 
Creator ROBIN, CJ
VISHNOI, A
JONNALAGADDA, KN
 
Subject Anisotropy
digital image correlation
cross-linking
strain-rate
SU-8
GLASSY-POLYMERS
POLYIMIDE FILMS
WAVE-GUIDE
PHOTORESIST
NANOINDENTATION
DEFORMATION
LITHOGRAPHY
TEMPERATURE
 
Description Spin-coated SU-8 thin films used in Microelectromechanical Systems (MEMS) devices are investigated using tensile experiments on freestanding microscale specimens to understand their mechanical response. Modified in situ optical microscope experiments are performed on 2 mu m thick transparent SU-8 films in the strain rate range of 2 x 10(-5) /s to 2 x 10(-2) /s and accurate strain measurements are extracted using Digital Image Correlation. The effects of strain rate and anisotropy, on mechanical properties, in hard baked and non-hard baked films were studied in conjunction with Fourier Transform Infrared Spectroscopy. The Young's modulus and tensile strength were found to increase with strain rate significantly, with the stress vs. strain behavior changing from viscoelastic to linear elastic. Hard baking of the films resulted in better mechanical properties, viz., elastic modulus and tensile strength, due to increased cross-linking density. The average moduli for hard baked and non-hard baked films were 3.48 +/- 0.57 GPa and 2.92 +/- 0.43 GPa, respectively, obtained from 30 experiments each, over the entire strain rate range. Furthermore, the spin-coat process used to make the films developed anisotropy in the plane of the films due to molecular orientation, which was independent of hard baking temperature and duration.
 
Publisher IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
 
Date 2014-12-29T04:30:55Z
2014-12-29T04:30:55Z
2014
 
Type Article
 
Identifier JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, 23(1)168-180
1057-7157
1941-0158
http://dx.doi.org/10.1109/JMEMS.2013.2264341
http://dspace.library.iitb.ac.in/jspui/handle/100/17081
 
Language English