SU-8

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(300- 400nm)
• - promotes cross-linking reaction

lthttp//www.zurich.ibm.com/st/mems/su8.htmlgt
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 gt 98 at wave lengths of
  500 to 850 nm.
• lthttp//www.ee.ucla.edu/jjudy/classes/ee250a/lect
  ures/EE250A_Lecture_09_
• Thick-Film_Lithography_SU-8_files/frame.htmgt

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 gt 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.
• lthttp//www.zurich.ibm.com/st/mems/su8.htmlgt
• Judy, Jack. Thick film Lithography SU-8.
  2003.
• lthttp//www.ee.ucla.edu/jjudy/classes/ee250a/
  lectures/EE250A_Lecture_09_Thick-Film_Lithography_
  SU-8_files/frame.htmgt
• Ruhmen,R, Pfeiffer,K. et.al. SU-8 a high
  performance material for Mems appilcation.
  Polymer in Mems. http//www.microchem.com/resource
  s/tok_ebeam_resist.pdf
• 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.
• lthttp//ej.iop.org/links/q61/JY4hey4mG8dIMzUo0E8OJ
  A/jm3112.pdfgt