SU-8 - Gary Rubloff

• is a polymer
- a negative epoxy based
photoresist containing 8epoxy groups.
- a single molecule contains 8
epoxy groups in a bisphenolA novalac glycidyl ether.
- dissolved in a organic
solvent along with photoacid
- is photosensitive(300- 400nm)
- promotes cross-linking
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)
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.
Features of SU-8
High thermal resistance
High chemical resistance
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 SU8.
Modulus of elasticity is 4.02 GPa for tensile testing
due to
• Silicon(Si) is a semi-conductor
• Used as a Substrate.
• It is cheap and convenient for microelectronic process like lithography.
• Adhesive to SU-8.
• IBM Research -Zurich Research Laboratary. “ Epon SU-8
• Judy, Jack. “Thick film Lithography & SU-8”. 2003.
• Ruhmen,R, Pfeiffer,K. “ 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. Dec4 .2002.

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