1. SU-8 is a polymer EPON SU-8
- a negative epoxy based photoresist containing 8-epoxy groups.
- a single molecule contains 8 epoxy groups in a bisphenol- A novalac glycidyl ether.
- dissolved in a organic solvent along with photoacid generator.
- is photosensitive( nm)
- promotes cross-linking reaction
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2. SU-8 Processing A typical SU-8 process consists of - Spin-coating
- Soft Bake
- Exposure
- Post Exposure bake(PEB)-to cross link exposed regions
of the film
- Development
- Rinse & dry
- Hard Bake (or curing-optional)
- Imaged material
- Remove (optional)

3. Features of SU-8 Why should we use SU-8? Good adhesion
Optical absorption in the UV spectrum is very low allowing patterning of thick coatings.
Broad range of thickness can be obtained from one spin with a conventional spin coater (750 nm to 500 mm)
High aspect ratios ( ~15 for lines and 10 for trenches)- high degree of cross-linking.
Optical transparency is > 98% at wave lengths of 500 to 850 nm.
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Thick-Film_Lithography_SU-8_files/frame.htm>

4. Features of SU-8 High thermal resistance due to
High chemical resistance cross-
linking
SU-8 is compatible with standard silicon micro-electronic processing.
SU-8 is used to create reverse patterns of channels, reservoirs, interconnects
Non-conductive- can be used as dielectric during electroplating.
Tg(glass transition temperature) is > 200 degrees centigrade and
Td(decomposition temperature) is ~ 380 degree centigrade for fully cured SU-8.
Modulus of elasticity is 4.02 GPa for tensile testing

5. Silicon Silicon(Si) is a semi-conductor Used as a Substrate.
It is cheap and convenient for micro-electronic process like lithography.
Adhesive to SU-8.

6. References
IBM Research -Zurich Research Laboratary. “ Epon SU-8 Photoresist”.
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Judy, Jack. “Thick film Lithography & SU-8”
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Ruhmen,R, Pfeiffer,K. et.al. “ SU-8: a high performance material for Mems appilcation. Polymer in Mems.
Feng,Ru. Farris,R. “ Influence of Processing conditions on the thermal and mechanical properties of SU-8 negative Photoresist Coatings”. Journal of micromechanics and microengineering. Dec
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