SU-8: Thick Photo-Resist for MEMS

Editor F. Chollet

since 01/1999, modified 09/2018

Introduction

We hope this page will eventually contain all the known data about the SU-8 photoresist. Thus, we need your help! Send all your data number 4206, and I will include it in this page, with credits, of course!

The SU-8 is a negative, epoxy-type, near-UV photoresist based on EPON SU-8 epoxy resin (from Shell Chemical) that has been originally developed, and patented (US Patent No. 4882245 (1989) and others) by IBM. gear in SU8

This photoresist can be as thick as 2 mm and aspect ratio >20 and higher have been demonstrated with a standard contact lithography equipment (picture courtesy of R. Yang).

These astounding results are due to the low optical absorption in the UV range which only limits the thickness to 2 mm for the 365nm-wavelength where the photo-resist is the most sensitive (i.e., for this thickness very little UV light reach the bottom of the structure).

Of course LIGA still yield better results but low-cost application will undoubtedly benefit from this resist that is well suited for acting as a mold for electroplating because of its relatively high thermal stability (Tg>200°C for the cross-linked (i.e., exposed) resist).

Two companies have now bought a license from IBM to sell the photoresist :

Physical properties

Using the litterature reference, the following tables, based on an original compilation from Loren St Clair, gives some properties of the resist. We begin with the known mechanical properties:

Table 1 : Mechanical properties of the SU-8 photoresist.
Characteristics Value Conditions Reference
Modulus of elasticity : E 4.02 GPa in tension, postbaked at 95°C, screw tensile testing machine Lorenz97
4.95 ± 0.42 GPa hardbaked at 200°C, beam deflexion test Dellmann97
4.4 GPa postbake at 95°C, SM blend SOTEC MICRO
3.48 ± 0.57 GPa hardbake, 2µm film Robin13
2.92 ± 0.43 GPa no hardbake, 2µm film Robin13
Bi-axial modulus of elasticity : E/(1 - n) 5.18 +/- 0.89 GPa postbaked at 95°C, thermal cycling test on Si wafer Lorenz98c
Poisson ratio 0.22 postbaked at 95°C, SM blend SOTEC MICRO
Film stress 19 - 16 Mpa for 0 - 400 mic. thick SU-8 film coated on a 3" 375 mic. thick Si wafer, prebaked, illuminated, postbaked at 95°C and brought back to room temperature (20°C) Lorenz98c
Max stress 34 Mpa hardbaked at 200°C, lateral deflexion FEM analysis Dellmann97
Max sheer 0.009 hardbaked at 200°C, lateral deflexion FEM analysis Dellmann97
Plastic domain limit 'no' plastic domain observed hardbaked at 200°C, sample pulled until fracture Lorenz97
Friction coefficient : μ 0.19 postbaked at 95°C, pin-on-disc installation (10 g load) Lorenz97
Bond strength
(see comments below)
4.8 +/- 1.2 MPa on Au, Instrom pull test Nordstrom05
5.6 +/- 2.5 MPa on Ti, Instrom pull test
12.1 +/- 2.8 MPa on Al, Instrom pull test
20.7 +/- 4.6 MPa on Si, pull test

The next table gives data about physical properties of the polymerized SU-8:

Table 2 : Physical properties of the SU-8 photoresist.
Characteristics Value Conditions Reference
Glass temperature: Tg
(see comments below)
~50°C unexposed film (not polymerized) LaBianca95a
>200°C fully crosslinked film (hard baked)
~55°C MCC blend before PEB MCC
Degradation temperature: Td
(see comments below)
~380°C fully crosslinked film (hard baked) LaBianca95a
Coefficient of thermal expansion : CTE 102.0 +/- 5.1 ppm/K SU-8 25 hard baked at 200�C for 10 min (in-plane). Feng02
52.0 +/- 5.1 ppm/K SM10#0 postbaked at 95°C, thermal cycling test on Si wafer Lorenz98c
30 ppm/K SM2050 with 50% filler in the blend SOTEC MICRO
21 ppm/K SM2070 with 70% filler in the blend
Thermal conductivity 0.2 W/mK general value for thermoplastic not for SU-8 Guerin97
Specific heat 1.5 kJ/kg K source not specified Elali04
Polymer shrinkage 7.5% postbaked at 95°C Guerin97
Density: ρ 1200 kg/m3 (or 1.2 g/cm3) Density of the raw SU8 resin (not for the PR) Resins.com
Viscosity (Dynamic or Absolute): η or μ 0.06 Pa.s = 6 cP SM1040 (40% solid + GBL), DIN53019 Lorenz97
J-L Guerin.
1.5 Pa.s = 1500 cP SM1060 (60% solid + GBL), DIN53019
15 Pa.s = 15000 cP SM1070 (70% solid + GBL), DIN53019
Kinematic viscosity: ν (we have ν ρ= η) 0.000045 m2/s = 45 cSt SU-8 2 MCC
0.000290 m2/s = 290 cSt SU-8 5 (52% solid + GBL), density 1.1641, 20°C
0.001050 m2/s = 1050 cSt SU-8 10 (59% solid + GBL), 20°C
0.0025 m2/s = 2500 cSt SU-8 25 (63% solid + GBL), 20°C
0.01225 m2/s = 12250 cSt SU-8 50 (69% solid), 20°C
0.0515 m2/s = 51500 cSt SU-8 100 (73% solid), 20°C

And this table gives data about the electromagnetic properties of the polymerized SU-8:

Table 3 : Electromagnetic properties of the SU-8 photoresist.
Characteristics Value Conditions Reference
refractive index: n 1.67 at 365 nm, not crosslinked (during exposure before PEB) MCC
1.67 at 408 nm, idem
1.596 at 633 nm, crosslinked PR after proton beam exposure, prism-coupling technique Sum03
1.575 at 1550 nm, idem
1.7 at 1.6 THz, postbaked at 100°C (+8 hours at 65°C in KOH), THz time domain spectroscopy Arscott99
1.8 at 100 GHz, idem
absorption coefficient: α ~2 cm-1 at 100 GHz, postbaked at 100°C (+8 hours at 65°C in KOH), THz time domain spectroscopy Arscott99
~40 cm-1 at 1.6 THz, idem
loss tangent: tan δ 0.08 at 100 GHz, postbaked at 100°C (+8 hours at 65°C in KOH), THz time domain spectroscopy Lucyszyn01
0.14 at 1 THz, idem
relative dielectric constant: εr 4 at 10 MHz, postbaked at 100°C, may be valid between 20 GHz and 40 GHz Thorpe98
4.5 at 10 MHz James Thorpe
4.2 at 10 GHz
3 at 10 MHz, postbaked at 95°C, SM blend SOTEC MICRO
Breakdown voltage 1.1 105 V/m electrical breakdown 1.2V for an 11 μm thick SU8(10) film James Thorpe
>4 107 V/m electrical breakdown did not happen at 1000V for a 25 μm thick SU8 film Eric Codner
4.43 ± 0.16 108 V/m SU-8 2 and SU-8 in the range of 2-15 μm Melai09

Other properties

Here are some general properties that can not fit in a table, and are deducted mostly from experiment. They should not be taken for more than that :-)

Process Tips

Here are all the data gathered over the years pertaining to the SU-8 processing. These datas complete the general information you may obtain from the literature, and are mostly tricks. But they do help a lot :-) Contact in bracket gives the source of the info. The text is almost verbatim from the source, with only very slight edition when it was needed. When some details are 'not available', it is mostly because of some proprietary information that could not be divulged openly. Sometimes, SU-8 processing looks more like an art than like an exact science :-)

Research Links

Here is a list of further links to more information on research done with the resist. Enjoy.

Bibliography

Further very useful information (and the previous one :-) from the IBM and the EPFL teams (and a few others...) may be found in the following papers (please contact us if you know other references - specially historical ones :-) This list was established with the help of Loren St CLAIR, Hubert LORENZ, Arnaud BERTSCH, Marc HEUSCHKEL, Patrick MOUNAIX, LING Zhong-Geng, Stepan LUCYSZYN, SUM Tze Chien, Paul DENTIGER, ZHANG Jun, YANG Ren, TEH Weng Hong and David WOOD (it is available as a BibTex database).

  1. D. Stumbo and J. Wolfe, "Ion exposure characterization of a chemically amplified epoxy resist", J. Vac. Scien. Technol. B 11 (1993) : 2432-2435 [an early paper for those interested in proton exposure with SU-8 (thin layer).]
  2. N. LaBianca and J. Delorme, "High aspect ratio resist for thick film applications", in Proc. SPIE vol. 2438, SPIE 11 (1995) : 846-852 [the first (?) attempt to use thick layer of SU-8. By the IBM team.]
  3. N. LaBianca, J. Gelorme, K. Lee, E. Sullivan and J. Shaw, "High aspect ratio optical resist chemistry for MEMS applications", in Proc. 4th Int. Symp. on Magnetic Materials and Processes and Devices and The Electrochem. Soc. 95- 18 (1995) : 386-396 [the first (?) attempt to use thick layer of SU-8. By the IBM team.]
  4. K. Lee, N. LaBianca, S. Rishton, S. Zohlgharnain, J. Gelorme, J. Shaw and T.-P. Chang, "Micromachining applications for a high resolution ultra-thick photoresist", J. Vac. Scien. Technol. B 13 (1995) : 3012-3016 [the first (?) attempt to use thick layer of SU-8 for micromachining and describing the use as a mask for deep silicon etching and as a mold for nickel electroplating. By the IBM team.]
  5. H. Lorenz, M. Despont, N. Fahrni, N. Labianca, P. Vettiger and P. Renaud, "EPON SU-8: A low-cost negative resist for MEMS", in Proc. of Micro Mechanics Europe'96 and Barcelona 13 (1996) : 32-35 [first paper of the IBM/EPFL team.]
  6. L. Dellmann, S. Roth, C. Beuret, G. Racine, H. Lorenz, M. Despont, P. Renaud, P. Vettiger and N. de Rooij, "Fabrication process of high aspect ratio elastic structures for piezoelectric motor applications", in Proc. Transducers 1997 and Chicago 7 (1997) : 641-644 [First journal paper of the EPFL team and from the work presented at the Micro Mechanics Europe'96 conference. Gives some deposition parameters and a simple mechanical characterization.]
  7. M. Despont, H. Lorenz, N.Fahrni, J. B. P. Renaud and P. Vettiger, "High aspect ratio ultrathick and negative-tone near-UV photoresist for MEMS applications", in Proc. MEMS'97 and IEEE and Nagoya 41 (1997) : 518-522 [... and the SU-8 is reveled to an incredulous MEMS world :-)]
  8. L. Guerin, M. Bossel, M. Demierre, S. Calmes and P. Renaud, "Simple and low cost fabrication of embedded microchannels by using a new thick-film photoplastic", in Proc. Transducers 1997 Chicago and 7 (1997) : 1419-1422 [First journal paper of the EPFL team and from the work presented at the Micro Mechanics Europe'96 conference. Gives some deposition parameters and a simple mechanical characterization.]
  9. H. Lorenz, M. Despont, M. Fahrni, N. LaBianca, P. Vettiger and P. Renaud, "SU-8: a low-cost negative resist for MEMS", J. Micromech. Microeng 7 (1997) : 121-124 [First journal paper of the EPFL team and from the work presented at the Micro Mechanics Europe'96 conference. Gives some deposition parameters and a simple mechanical characterization.]
  10. J. M. Shaw, J. D. Gelorme, N. C. LaBianca, W. E. Conley and S. J. Holmes, "Negative photoresists for optical lithography", IBM Journal of Research and Development 41 (1997) : 81-94 [entertaining paper about the genesis of the chemistry for the SU-8 and some application written by the inventors of the resist (online paper and great!)]
  11. A. Bertsch, H. Lorenz and P. Renaud, "Combining microstereolithography and thick resist UV lithography for 3D microfabrication", in Proc. MEMS'98 IEEE and Heidelberg 7 (1998) : 18-23 [The title explains it all...]
  12. L. Dellmann, S. Roth, C. Beuret, L. Paratte, G.-A. Racine, H. Lorenz, M. Despont, P. Renaud, P. Vettiger and N. de Rooij, "Two steps micromoulding and photopolymer high-aspect ratio structuring for applications in piezoelectric motor components", Microsyst. Technol. 4 (1998) : 147-150 [complex use of the SU-8 with a detailed process.]
  13. B. Eyre, J. Blosiu and D. Wiberg, "Taguchi optimization for the processing Epon SU-8 resist", in Proc. MEMS'98 IEEE and Heidelberg 7 (1998) : 218-222 [gives optimized process variables such as softbake time and exposure time and post-exposure time and develop time and substrate type for SU-8 with 73% solvent that were obtained with the Taguchi method for three typical thickness 50mic. and 100 mic. and 220 mic.]
  14. W. Flack, W. Fan and S. White, "Optimization and characterization of ultrathick photoresist films", in Proc. Advances in Resist Technology and Processing XV Proc. SPIE 3333 (1998) : 1288-1303 [a paper from Ultratech Stepper describing experiment with the SU-8 and their 1Xstepper. They concluded that SU-8(25) showed no photo-sensitivity in the gh-line spectrum (390-450 nm) and they used i-line stepper (355-375 nm) to pattern line with an aspect ratio of 1.2 (sic) in a 25mic. thick layer giving a fully detailed process... (online paper and great!)]
  15. M. Heuschkel, L. Guérin, B. Buisson, D. Bertrand and P. Renaud, "Buried microchannels in polymer for delivering of solutions to neurons in a network", Sensors & Actuators: B. Chemical 48 (1998) : 43160 [356-361]
  16. H. Lorenz, M. Despont, N.Fahrni, J. B. P. Renaud and P. Vettiger, "High aspect ratio ultrathick and negative-tone near-UV photoresist and its applications for MEMS", Sens. & Act. A A 64 (1998) : 33-39 [Expanded version of the MEMS'97 paper. It describes process and results (aspect ratio up to 18 and thickness up to 1.2 mm) and application of the SU-8 (including the use of the resists as a structural material (photoplastic) and multi-level patterning).]
  17. H. Lorenz, M. Despont, P. Vettiger and P.Renaud, "Fabrication of photoplastic high-aspect ratio microparts and micromolds using SU-8 UV resist", Microsyst. Technol. 4 (1998) : 143-146 [more example of photoplastic use and complete description of the patented MIMOTEC process where the SU-8 is used to create metallic multilevel mold by repeated coating and patterning followed by electroplating and removal of the resist.]
  18. H. Lorenz, M. Laudon and P. Renaud, "Mechanical characterization of a new high-aspect-ratio near UV-photoresist", Microelec. Engin. 41/ 42 (1998) : 371-374 [first attempt at a comprehensive mechanical characterization of the SU-8.]
  19. C. Malek, "Mask prototyping for ultra-deep X-ray lithography: preliminary studies for mask blanks and high-aspect-ratio absorber patterns", in Proc. SPIE 3512 (1998) : 277-285 [investigates the SU-8 for electroplating thick X-LIGA mask absorber. They also patterned SU-8 with X-ray and found it 'over one order of magnitude' more sensible than PMMA (X 25 with 50 mic. thick film) and and to present thickness-independent incident dose. An interesting point to note and with X-ray you don't have reflection from the substrate and hence no standing wave in the resist and yielding really smooth sidewalls...]
  20. J. Thorpe, D. Steenson and R. Miles, "High frequency transmission line using micromachined polymer dielectric", Electron. Lett. 34 (1998) : 1237-1238 [using SU-8 as insulation dielectric for mm-wave transmission line in copper between 20 GHz and 40 GHz.]
  21. S. Arscott, F. Garet, P. Mounaix, L. Duvillaret, J.-L. Coutaz and D. Lippens, "Terahertz time-domain spectroscopy of films fabricated from SU-8", Electron. Lett. 35 (1999) : 243-244 [measurement of the refractive index (n) and the absorption coefficient (α) of the SU-8 between 100 GHz and 1.6 THz (see the abstract below). Moreover they show results of an interesting double exposure experiment and allowing to expose different thickness of photoresist from a single layer!]
  22. Y. Cheng, C.-Y. Lin, D.-H. Wei, B. Loechel and G. Gruetzner, "Wall profile of thick photoresist generated via contact printing", IEEE Journal of Microelectromechanical Systems 8 (1999) : 243-244 [measurement of the refractive index (n) and the absorption coefficient (a) of the SU-8 between 100 GHz and 1.6 THz (see the abstract below). Moreover they show results of an interesting double exposure experiment and allowing to expose different thickness of photoresist from a single layer!]
  23. W. W. Flack, S. White and B. Todd, "Process characterization of 100µm thick photoresist films", in Proc. SPIE 3678 (1999) : 243-244 [A comparison between 3 thick photoresists (novolak based AZ PLP-100 and polyhydroxy styrene based NR9-8000 and epoxy based SU8-10) by Ultratech... and for 100um films SU-8 is the clear winner :-)]
  24. A. L. Bogdanov and S. S. Peredkov, "Use of SU8 photoresist for very high aspect ratio x-ray lithography", Microelectronic Engineering 53 (2000) : 493-496 [more of the above...]
  25. M. Campbell, D. N. Sharp, M. T. Harrison, R. G. Denning and A. J. Turberfield, "Fabrication of photonic crystals for the visible spectrum by holographic lithography", Nature 404 (2000) : 5356 [the title says it: fabrication of 3-D photonic bandgap crystal working in the visible spectrum... but omits to tell it is using the SU-8! Will it be the killer application? :-)]
  26. H.-K. Chang and Y. Kim, "UV-LIGA process for high aspect ratio structure using stress barrier and C-shape etch hole", Sensors and Actuators 84 (2000) : 342-350
  27. E. L'Hostis, P. E. Michel, G. C. Fiaccabrino, D. J. Strike, N. F. de Rooij and M. Koudelka-Hep, "Microreactor and electrochemical detectors fabricated using Si and EPON SU-8", Sensors and Actuators B: Chemical 64 (2000) : 56-162 [a description of MeV proton irradiation and a maskless technique allowing to reach 1:100 aspect ratio.]
  28. Z.-g. Ling, K. Lian and L. Jian, "Improved patterning quality of SU-8 microstructures by optimizing the exposure parameters", in and Proc. SPIE vol. 3999 and SPIE 84 (2000) : 1019-1027 [at last and a thorough investigation of the SU-8 absorption in the UV and up to the NIR and leading to many process improvements (aspect ratio 25 with 360um thick layer). Very interesting!]
  29. T. Osipowicz, van Kan J.A., T.C. Sum, J.L. Sanchez and F. Watt, "The use of proton microbeams for the production of microcomponents", Nuclear Instruments & Methods in Physics Research and Section B 83 (2000) : 161-163 [more of the above...]
  30. J. A. van Kan, J. L. Sanchez, T. Osipowicz and F. Watt, "Proton micromachining: a new technique for the production of three-dimensional microstructures", Microsystem Technologies 6 (2000) : 82 [a description of MeV proton irradiation and a maskless technique allowing to reach 1:100 aspect ratio.]
  31. R. K. Vestergaard and S. Bouwstra, "Electroplated compliant metal microactuators with small feature sizes using a removable SU-8 mould", Microsystem Technologies 6 (2000) : 214-217 [at last and a thorough investigation of the SU-8 absorption in the UV and up to the NIR and leading to many process improvements (aspect ratio 25 with 360um thick layer). Very interesting!]
  32. F. Watt, J.A. Van Kan and T. Osipowicz, " Three-dimensional microfabrication using maskless irradiation with MeV ion beams: proton-beam micromachining", MRS Bulletin 25 (2000) : 33 [and another one...]
  33. T. Akiyama, U. Staufer, N. F. de Rooij, L. Howald and L. Scandella, "Lithographically defined polymer tips for quartz tuning fork based scanning force microscopes", Microelectronic Engineering 57- 58 (2001) : 769-773 [a critical review of the paper by Arscott et al. and that correct the values of the loss tangent - to a higher one! No, SU8 won't be the new low-loss millimeter-wave dielectric...]
  34. C. Cremers, F. Bouamrane, L. Singleton and R. Schenk, "SU-8 as resist material for deep x-ray lithography", Microsystem Technologies 7 (2001) : 42675 [... its complement.]
  35. M. K. Ghantasala, J. P. Hayes, E. C. Harvey and D. K. Sood, "Patterning and electroplating and removal of SU-8 moulds by excimer laser micromachining", Journal of Micromechanics and Microengineering 11 (2001) : 133-139 [and another one...]
  36. S. Lucyszyn, "Comment : Terahertz time-domain spectroscopy of films fabricated from SU-8", Electron. Lett. (2001) : 1267 [a critical review of the paper by Arscott et al., that correct the values of the loss tangent - to a higher one! No, SU8 won't be the new low-loss millimeter-wave dielectric...]
  37. S. H. Oh, K.-C. Lee, J. Chun, M. Kim and S. S. Le, "Micro heat flux sensor using copper electroplating in SU-8 microstructures", Journal of Micromechanics and Microengineering 11 (2001) : 221-225 [... its complement.]
  38. F. E. H. Tay, J. A. vanKan , F. Watt and W. O. Choong, "A novel micro-machining method for the fabrication of thick-film SU-8 embedded micro-channels", Journal of Micromechanics and Microengineering 11 (2001) : 27-32 [... its complement.]
  39. F. G. Tseng, Y. J. Chuang and W. K. Lin, "Reduction of diffraction effect of UV exposure on SU-8 negative thick PR by air gap elimination", in Proc. HARMST 4th Workshop on High Aspect Ratio Micro-structure Technology (Baden-Baden and Germany) (2001) : 73-74 [... its complement.]
  40. J. Zhang, K. Tan and H. Gong, "Characterization of the polymerization of SU-8 photoresist and its applications in micro-electro-mechanical systems (MEMS)", Polymer Testing 20 (2001) : 693-701 [... its complement.]
  41. J. Zhang, K.L. Tan, G.D. Hong, L.J. Yang and H.Q. Gong, "Polymerization optimization of Su-8 photoresist and its applications in microfluidic systems and MEMS", J. Microm. and Microeng. 8 (2001) : 20-26 [A serious study and quite complete.]
  42. Y. Ansel, F. Gindele, J. Scheurer and F. Schmitz, "Optical waveguide device realised using two SU-8 layers", in Proc. Optical MEMS 2002 (2002) : 123-124 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet, give it a try before throwing money out!]
  43. A. A. Bettiol, I. Rajta, E. J. Teo, J. A. van Kan and F. Watt, "Proton beam micromachining: electron emission from SU-8 resist during ion beam irradiation", Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 190 (2002) : 154-159 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet and give it a try before throwing money out!]
  44. Y. Choi, K. Kim and M. G. Allen, "Continuously-varying and three-dimensional SU-8 structures: fabrication of inclined magnetic actuators", in Proc. MEMS 2002 7 (2002) : 176-179 [or how to obtain sloped surface by tilting the wafer and using the reflow properties of the SU-8. Nice trick!]
  45. Y.-J. Chuang, F.-G. Tseng, J.-H. Cheng and W.-K. Lin, "A novel fabrication method of embedded micro-channels by using SU-8 thick-film photoresists", Sensors and Actuators A: Physical 2 (2002) : 969-972 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet and give it a try before throwing money out!]
  46. Y.-J. Chuang, F.-G. Tseng and W.-K. Lin, "Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination", Microsystem Technologies 8 (2002) : 308-313 [a funny method to obtain conical shape in very thick SU-8 layer and that could possibly be extended to other shape - but involves rather non conventional steps!]
  47. E. H. Conradie and D. F. Moore, "SU-8 thick photoresist processing as a functional material for MEMS applications", Journal of Micromechanics and Microengineering 12 (2002) : 368-374 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet and give it a try before throwing money out!]
  48. P. M. Dentinger, W. M. Clift and S. H. Goods, "Removal of SU-8 photoresist for thick film applications", Microelectronic Engineering 61 62 (2002) : 993-1000 [the companion paper describing the removal techniques aluded above in the process part.]
  49. P. M. Dentinger, K. L. Krafcik, K. L. Simison, R. P. Janek and J. Hachman, "High aspect ratio patterning with a proximity ultraviolet source", Microelectronic Engineering 61- 62 (2002) : 1001-1007 [A sound study focused on thick layer and electroplating and discussing problems and limitation by a team at Sandia labs. It shows an astounding 66:1 aspect ration in a 700um thick layer!]
  50. Feng, R., Farris and J., "The characterisation of thermal and elastic constants for an epoxy photoresist SU8 coating.", J. Mater. Sci. 37 (2002) : 47934799 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet and give it a try before throwing money out!]
  51. C.-H. Ho, K.-P. Chin, C.-R. Yang, H.-M. Wu and S.-L. Chen, "Ultrathick SU-8 mold formation and removal and its application to the fabrication of LIGA-like micromotors with embedded roots", Sensors and Actuators A 35- 33 (2002) : 43344 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet and give it a try before throwing money out!]
  52. J. A. van Kan, I. Rajta, K. Ansari, A. A. Bettiol and F. Watt, "Nickel and copper electroplating of proton beam micromachined SU-8 resist", Microsystem Technologies 8 (2002) : 383-386 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet and give it a try before throwing money out!]
  53. G. M. Kim, B. Kim, M. Liebau, J. Huskens, D. N. Reinhoudt and J. Brugger, "Surface modification with self-assembled monolayers for nanoscale replication of photoplastic MEMS", Journal of Microelectromechanical Systems 11 (2002) : 175-181 [the companion paper describing the removal techniques aluded above in the process part.]
  54. G.-B. Lee, C.-H. Lin and G.-L. Chang, "Micro flow cytometers with buried SU-8/SOG optical waveguides", Sensors and Actuators A: Physical 2 (2002) : 969-972 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet and give it a try before throwing money out!]
  55. C.-J. Lin and F.-G. Tseng, "A high sensitive fabry-perot shear stress sensor employing flexible membrane and double su-8 structures", in Proc. Sensors 2002 2 (2002) : 969-972 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet and give it a try before throwing money out!]
  56. 35.. C.-H. Lin, G.-B. Lee, B.-W. Chang and G.-L. Chang, "A new fabrication process for ultra-thick microfluidic microstructures utilizing SU-8 photoresist", Journal of Micromechanics and Microengineering 12 (2002) : 590-597 [a funny method to obtain conical shape in very thick SU-8 layer and that could possibly be extended to other shape - but involves rather non conventional steps!]
  57. W. Y. Liu, S. Mohammadi, L. P. B. Katehi, H. Khalkhali and K. Korabayashi, "Micro-heat-pipe for InP/InGaAs Microwave Integrated Circuits", and in roc. EDMO 2002 and IEEE 7 (2002) : 176-9 [a funny method to obtain conical shape in very thick SU-8 layer and that could possibly be extended to other shape - but involves rather non conventional steps!]
  58. C. Luo, J. Garra, T. Schneider, R. White, M. Paranjape and J. Currie, "A new method to release SU-8 structures using polystyrene for MEMS applications", in Proc. Eurosensors 25 (2002) : 101-105 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet and give it a try before throwing money out!]
  59. C. G. K. Malek, "SU8 resist for low-cost X-ray patterning of high-resolution and high-aspect-ratio MEMS", Microelectronics Journal 33 (2002) : 101-105 [the companion paper describing the removal techniques aluded above in the process part.]
  60. Ouchi, T., Imada, A., Sato, T., Sakata and H., "Direct coupling of VCSELs to plastic optical fibers using guide holes patterned in a thick photoresist", IEEE Photonics Technology Letters 14 (2002) : 263-265 [the companion paper describing the removal techniques aluded above in the process part.]
  61. C.-T. Pan, H. Yang, S-CShen, M.-C. Chou and H.-P. Chou, "A low-temperature wafer bonding technique using patternable materials", Journal of Micromechanics and Microengineering 12 (2002) : 611-615 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet and give it a try before throwing money out!]
  62. V. Seidemann, S. Butefisch and S. Buttgenbach, "Fabrication and investigation of in-plane compliant SU8 structures for MEMS and their application to micro valves and micro grippers", Sensors and Actuators A 97- 98 (2002) : 457-461 [a cheap way to obtain a good sacrificial layer for SU8 - toluene as solvent and a polystyrene sheet and give it a try before throwing money out!]
  63. Feng, R., Farris and J., "Influence of processing conditions on the thermal and mechanical properties of SU8 negative photoresist.", J. Micromech. Microeng. 13 (2003) : 8088 [a thorough study of the thermal properties of SU8 and showing some surprising behaviour depending heavily on the resist baking strategy.]
  64. V. Kudryashov, X.-C. Yuan, W.-C. Cheong and K. Radhakrishnan, "Grey scale structures formation in SU-8 with e-beam and UV", Microelectronic Engineering 67 68 (2003) : 306311 [a thorough study of the thermal properties of SU8 and showing some surprising behaviour depending heavily on the resist baking strategy.]
  65. S. Li, C. B. Freidhoff, R. M. Young and R. Ghodssi, "Fabrication of micronozzles using low-temperature wafer-level bonding with SU-8", Journal of Micromechanics and Microengineering 13 (2003) : 732-738 DOI [using SU8 to bond wafers together and a strong glue you can easily pattern.]
  66. T. C. Sum, A. A. Bettiol, J. A. van Kan, F. Watt, E. Y. B. Pun and K. K. Tung, "Proton beam writing of low-loss polymer optical waveguides", Applied Physics Letters 83 (2003) : 1707-1709 [a thorough study of the thermal properties of SU8 and showing some surprising behaviour depending heavily on the resist baking strategy.]
  67. M. C. Cheng, A. P. Gadre, J. A. Garra, A. J. Nijdam, C. Luo, T. W. Schneider, R. C. White, J. F. Currie and M. Paranjape, "Dry release of polymer structures with anti-sticking layer", Journal of Vacuum Science & Technology A: Vacuum and Surfaces and Films 22 (2004) : 837-841 [using a teflon layer to release SU8 structure by simple peeling and thus allowing wafer wide structures without the 'release holes' needed for wet release methods, nifty!]
  68. J. El-Ali, I. R. Perch-Nielsen, C. R. Poulsen, D. D. Bang, P. Telleman and A. Wolff, "Simulation and experimental validation of a SU-8 based PCR thermocycler chip with integrated heaters and temperature sensor", Sensors and Actuators A 110 (2004) : 310 [two-photon absorption works also with SU8 and produce 3D structures.]
  69. W. H. Teh, U. Dürig, G. Salis, R. Harbers, U. Drechsler, R. F. Mahrt, C. G. Smith, H.-J. Güntherodt, "SU-8 for real three-dimensional subdiffraction-limit two-photon microfabrication", Applied Physics Letters 84 (2004) : 4095-4097 [two-photon absorption works also with SU8 and produce 3D structures.]
  70. R. Yang and W. Wang, "Fabrication of out-of-plane SU-8 refractive microlens using directly lithography method", in SPIE 5346 (2004) : 151-159 [using SU8 to bond wafers together and a strong glue you can easily pattern.]
  71. R. Yang, J. D. Williams and W. Wang, "A Rapid Micro-mixer/reactor Based on Arrays of Spatially Impinging Micro-jets", Journal of Micromechanical and Microsystem 14 (2004) : 1345-1351 [two-photon absorption works also with SU8 and produce 3D structures.]
  72. R. Yang and W. Wang, "Out-of-plane Polymer Refractive Microlens Fabricated Based on Direct Lithography of SU-8", Sensor and Actuators A: Physical 113 (2004) : 71-77 [using SU8 to bond wafers together and a strong glue you can easily pattern.]
  73. R. Yang and W. Wang, "Numerical and Experimental Study on an Out-of-Plane Pre-aligned Refractive Microlens Fabricated Using UV Lithography Method", Optical Engineering 43 (2004) : - [two-photon absorption works also with SU8 and produce 3D structures.]
  74. M. Agarwal, R. Gunasekaran, P. Coane and K. Verahramyan, "Scum-free patterning of SU-8 resist for electroforming applications", J. Micromech. Microeng. 15 (2005) : 130-135 [using controlled acetone rinse to remove SU8 scum after developement, why not?!]
  75. C. Chung and M. Allen, "Uncrosslinked SU-8 as a sacrificial material", J. Micromech. Microeng. 15 (2005) : N1-N5 [using SU8 as a sacrificial material is hard to think at first - but it is uncrosslinked SU8 and dissolves in PGMEA and allowing really thick sacrificial layers.]
  76. M. P. Larsson, R. R. A. Syms and A. G. Wojcik, "Improved adhesion in hybrid Si-polymer MEMS via micromechanical interlocking", J. Micromech. Microeng. 15 (2005) : 20742082 [a study on improving the adhesion of Su8 to the substrate by using interlocking mechanical structure and showing some success even during KOH etching!]
  77. B. Li, M. Liu and Q. Chen, "Low-stress ultra-thick SU-8 UV photolithography process for MEMS", J. Microlith. and Microfab. and Microsyst. 4 (2005) : 43252 [a thorough investigation at lowering stress and revealing that a PEB just above 55°C makes sense and help reduce stress enormously.]
  78. M. Nordström, A. Johansson, E. S. Nogueron, B. Clausen, M. Calleja and A. Boisen, "Investigation of the bond strength between the photo-sensitive polymer SU-8 and gold", Microelectronic Engineering 78-79 (2005) : 152-157 [a study of adhesion of SU8 on metals (Au and Ti and Al) and Si with an optimized process for gold using adhesion promoter and exposure control.]
  79. R. Yang, D. L. Feeback and W. Wang, "Microfabrication and Test of Three-Dimensional Polymer Hydro-focusing Unit for Flow Cytometry Applications", Sensors and Actuators A: Physical 118 (2005) : 83-91 [two-photon absorption works also with SU8 and produce 3D structures.]
  80. R. Yang, S. A. Soper and W. Wang, "Out-of-plane Microlens ArrayFabricated Using Ultraviolet-lithography", Applied Physics Letter 5097 (2005) : 83-91 [two-photon absorption works also with SU8 and produce 3D structures.]
  81. R. Yang and W. Wang, "Application of Optical Refractive Index Liquid and Wavelength Selection for Ultra-hight-aspect-ratio UV-lithography of Thick SU-8 Resist", Sensor and Actuator B: Chemical article in press and available online March and 2005 (2005) : 83-91 [two-photon absorption works also with SU8 and produce 3D structures.]
  82. K.-H. Jeong, J. Kim and L. P. Lee, "Biologically inspired artificial compound eyes", Science 312 (2006) : 557-561 [an impressive work using SU8 as a self aligned 3D waveguide to mimic the eye of the fly.]
  83. K. K. Seet, V. Mizeikis, K. Kannari, S. Juodkazis, H. Misawa, N. Tétreault and S. John, "Templating and Replication of Spiral Photonic Crystals for Silicon Photonics", IEEE J. Select. Top. Quant. Electro. 14 (2008) : 1064-1073 [using direct laser writing in SU8 to produce spiral photonic crystal after replication of the template in Si.]
  84. B. Solano, S. Rolt and D. Wood, "Thermal and mechanical analysis of an SU8 polymeric actuator using IR thermography", in Proc Inst Mech Engrs part C 222 (2008) : 73-86
  85. J. Melai, C. Salm, S. Smits, J. Visschers and J. Schmitz, "The electrical conduction and dielectric strength of SU-8", J. Micromech. Microeng. 19 (2009) : 65012 [at last a thorough study that shows SU8 has a very high dielectric strength and that leakage is dominated by thermionic conduction.]
  86. J. Melai, C. Salm, R. Wolters and J. Schmitz, "Qualitative and quantitative characterization of outgassing from SU-8", Microelectronic Engineering 86 (2009) : 761-764 [a first study at SU8 outgasing in vacuum and showing the importance of the hard bake step in UHV.]
  87. M. Jamal, A. M. Zarafshar and D. H. Gracias, "Differentially photo-crosslinked polymers enable self-assembling microfluidics", Nature Communications 2 (2011) : 527 DOI [a self-folding 2D SU8 layer assembles in 3D - cool :-)]
  88. C. Robin, A. Vishnoi and K. Jonnalagadda, "Mechanical Behavior and Anisotropy of Spin-Coated SU-8 Thin Films for MEMS", Journal of Microelectromechanical Systems 2 (2013) : 527 DOI [study of thin film SU8 mechanical properties]
  89. M. Gaudet and S. Arscott, "A user-friendly guide to the optimum ultraviolet photolithographic exposure and greyscale dose of SU-8 photoresist on common MEMS, microsystems, and microelectronics coatings and materials", Analytical Methods 9 (2017) : 2495-2504 DOI [A thorough study and modeling of SU8 exposure - with clear and detailed practical information. A must read !]

Commercial Solution

Here is a list of commercial products or commercial application related to the SU-8. If you don't have time to develop your own process... it is a very good alternative :-) Still, you may want to contact the companies cited to get some tricks for free... or sell yours :-) Oh, BTW, they are of course listed at no charge, so if you want to be there just drop me a line :-)

Vendors

This list of local vendor for SU-8 is not maintained actively, but only 'reactively' - when someone tells that a new vendor exists or that he changed then a link is added or updated. Thus don't expect the list to be accurate, but to help you I listed the date when the link has been added or changed :-)