Microsystem Technologies

, Volume 19, Issue 7, pp 971–978 | Cite as

Process variability in surface roughening of SU-8 by oxygen plasma

  • Nagaraju Oruganti
  • Michel Goedert
  • Sang-Joon John Lee
Technical Paper

Abstract

This study investigates variability in the topography of SU-8 photoresist subject to surface roughening by oxygen plasma treatment. Surface roughness (expressed as root mean square deviation from the mean) under the range of experimental conditions varied from 8 nm for an untreated baseline to as high as 472 nm. At 200 W RF-power and 200 mTorr chamber pressure, the mean surface roughness was 295 nm with standard deviation less than 10 nm across the specimen and 15 nm across the plasma chamber. The standard deviation in surface roughness at higher power and pressure combinations including 500 W and 800 mTorr was as high as 80 nm, with mean surface roughness less than 200 nm. Replicate runs under identical conditions revealed that run-to-run repeatability can be compromised by chamber conditions, evidenced by second runs having higher standard deviation by nearly 20 % over first runs without intermediate chamber cleaning.

References

  1. Abgrall P, Conedera V, Camon H, Gue A, Nguyen NT (2007) SU-8 as a structural material for labs-on-chips and microelectromechanical systems. Electrophoresis 28:4539–4551. doi:10.1002/elps.200700333 CrossRefGoogle Scholar
  2. Chan CM, Ko TM, Hiraoka H (1996) Polymer surface modification by plasmas and photons. Surf Sci Rep 24:1–54. doi:10.1016/0167-5729(96)80003-3 CrossRefGoogle Scholar
  3. Chang T, Tsai T, Yang H, Huang J (2012) “Effect of ultra-fast laser texturing on surface wettability of microfluidic channels”, Microelectronic Engineering; Special issue MNE 2011—Part II, vol 98, no 0, pp 684–688. doi:10.1016/j.mee.2012.05.057
  4. Cheong FC et al (2007) Direct removal of SU-8 using focused laser writing. App Phys A Mater Sci Process 87:71–76. doi:10.1007/s00339-006-3846-z CrossRefGoogle Scholar
  5. Collaud M, Groening P, Nowak S, Schlapbach L (1994) Plasma treatment of polymers: the effect of the plasma parameters on the chemical, physical, and morphological states of the polymer surface and on the metal-polymer interface. J Adhes Sci Technol 8:1115–1127. doi:10.1163/156856194X00979 CrossRefGoogle Scholar
  6. Duffy DC, McDonald JC, Schueller OJA, Whitesides GM (1998) Rapid prototyping of microfluidic systems in poly(dimethylsiloxane). Anal Chem 70:4974–4984. doi:10.1021/ac980656z CrossRefGoogle Scholar
  7. Erickson D, Li D (2004) Integrated microfluidic devices. Anal Chim Acta 507:11–26. doi:10.1016/j.aca.2003.09.019 CrossRefGoogle Scholar
  8. Gottscho RA, Jurgensen CW, Vitkavage DJ (1992) Microscopic uniformity in plasma etching. J Vac Sci Technol B Microelectron Process Phenom 10:2133–2147. doi:10.1116/1.586180 CrossRefGoogle Scholar
  9. Hong G, Holmes AS, Heaton ME (2004) SU8 resist plasma etching and its optimisation. Microsyst Technol 10:357–359. doi:10.1007/s00542-004-0413-4 CrossRefGoogle Scholar
  10. Joshi M, Kale N, Lal R, Ramgopal Rao V, Mukherji S (2007) A novel dry method for surface modification of SU-8 for immobilization of biomolecules in bio-MEMS. Biosens Bioelectron 22:2429–2435. doi:10.1016/j.bios.2006.08.045 CrossRefGoogle Scholar
  11. Lai J, Sunderland B, Xue J, Yan S, Zhao W, Folkard M, Wang Y (2006) Study on hydrophilicity of polymer surfaces improved by plasma treatment. Appl Surf Sci 252:3375–3379. doi:10.1016/j.apsusc.2005.05.038 CrossRefGoogle Scholar
  12. Lee C, Hsu W (2003) Method on surface roughness modification to alleviate stiction of microstructures. J Vac Sci Technol B Microelectron Nanom Struct 21:1505–1510. doi:10.1116/1.1592809 CrossRefGoogle Scholar
  13. Li G, Zhang X, Kawi S (1999) Relationships between sensitivity, catalytic activity, and surface areas of SnO2 gas sensors. Sens Actuators B Chem 60:64–70. doi:10.1016/S0925-4005(99)00245-2 CrossRefGoogle Scholar
  14. Lorenz H, Despont M, Fahrni N, LaBianca N, Renaud P, Vettiger P (1997) SU-8: a low-cost negative resist for MEMS. J Micromech Microeng 7:121–124. doi:10.1088/0960-1317/7/3/010 CrossRefGoogle Scholar
  15. Melai J, Salm C, Smits S, Blanco Carballo VM, Schmitz J, Hageluken B (2007) Considerations on using SU-8 as a construction material for high aspect ratio structures. Paper presented at the 10th Annual Workshop on Semiconductor Advances for Future Electronics and Sensors (SAFE), pp 529–534Google Scholar
  16. Nabesawa H, Hitobo T, Wakabayashi S, Asaji T, Abe T, Seki M (2008) Polymer surface morphology control by reactive ion etching for microfluidic devices. Sens Actuators B Chem 132:637–643. doi:10.1016/j.snb.2008.01.050 CrossRefGoogle Scholar
  17. Natrajan V, Christensen K (2010) The impact of surface roughness on flow through a rectangular microchannel from the laminar to turbulent regimes. Microfluid Nanofluid 9:95–121. doi:10.1007/s10404-009-0526-2 CrossRefGoogle Scholar
  18. Palumbo F, Mundo DR, Cappelluti D, d’Agostino R (2011) Superhydrophic and supershydrophilic polycarbonate by tailoring chemistry and nano-texture with plasma processing. Plasma Process Polym 8:118–126. doi:10.1002/ppap.201000098 Google Scholar
  19. Prentner S, Allen D, Larcombe L, Marson S, Jenkins K, Saumer M (2010) Effects of channel surface finish on blood flow in microfluidic devices. Microsyst Technol 16:091–1096. doi:10.1007/s00542-009-1004-1 CrossRefGoogle Scholar
  20. Qiao R (2007) Effects of molecular level surface roughness on electroosmotic flow. Microfluid Nanofluid 3:33–38. doi:10.1007/s10404-006-0103-x CrossRefGoogle Scholar
  21. Shadpour H, Allbritton LN (2010) In situ roughening of polymeric microstructures. ACS Appl Mater Interfaces 2:1086–1093. doi:10.1021/am900860s CrossRefGoogle Scholar
  22. Stalder AF, Kulik G, Sage G, Barbieri L, Hoffmann P (2006) A snake-based approach to accurate determination of both contact points and contact angles. Colloids Surf A Physicochem Eng Aspects 286(1–3):92–103CrossRefGoogle Scholar
  23. Tominaka S, Nakamura Y, Osaka T (2010) Nanostructured catalyst with hierarchical porosity and large surface area for on-chip fuel cells. J Power Sour 195:1054–1058. doi:10.1016/j.jpowsour.2009.08.082 CrossRefGoogle Scholar
  24. Tserepi A, Gogolides E, Constantoudis V, Cordoyiannis G, Raptis I, Valamontes ES (2003) Surface roughness induced by plasma etching of si-containing polymers. J Adhes Sci Technol 17:1083–1091CrossRefGoogle Scholar
  25. Tsougeni K, Petrou PS, Tserepi A, Kakabakos SE, Gogolides E (2011) Plasma nanotextured polystyrene for intense DNA microarrays. Procedia Eng 25:1573–1576CrossRefGoogle Scholar
  26. Tsougeni K, Petrou PS, Papageorgiou DP, Kakabakos SE, Tserepi A, Gogolides E (2012) Controlled protein adsorption on microfluidic channels with engineered roughness and wettability. Sensors Actuators B Chem 161:216–222CrossRefGoogle Scholar
  27. Ullal SJ, Singh H, Daugherty J, Vahedi V, Aydil ES (2009) Maintaining reproducible plasma reactor wall conditions: SF6 plasma etching of films deposited on chamber walls during Cl2/O2 plasma etching of Si. J Vac Sci Technol A Vac Surf Films 20(4):1195–1201. doi:10.1116/1.1479733 CrossRefGoogle Scholar
  28. Waghmare PR, Mitra SK (2008) Investigation of combined electro-osmotic and pressure-driven flow in rough microchannels. J Fluid Eng Trans ASME 130:061204–061210. doi:10.1115/1.2928333 CrossRefGoogle Scholar
  29. Wagterveld RM, Berendsen CWJ, Bouaidat S, Jonsmann J (2006) Ultralow hysteresis superhydrophobic surfaces by excimer laser modification of SU-8. Langmuir 22:10904–10908. doi:10.1021/la0620298 CrossRefGoogle Scholar
  30. Walther F, Heckl WM, Stark RW (2008) Evaluation of nanoscale roughness measurements on a plasma treated SU-8 polymer surface by atomic force microscopy. Appl Surf Sci 254:7290–7295. doi:10.1016/j.apsusc.2008.05.323 CrossRefGoogle Scholar
  31. Williams JA, Le HR (2006) Tribology and MEMS. J Phys D Appl Phys 39:R201–R214. doi:10.1088/0022-3727/39/12/R01 CrossRefGoogle Scholar
  32. Wu T, Suzuki H, Yomo T (2011) Bio-inspired 3D self-patterning of functional coatings for PDMS microdluidics. Transducers 2311–2314. doi: 10.1109/TRANSDUCERS.2011.5969541
  33. Yang D, Liu Y (2008) Numerical simulation of electroosmotic flow in microchannels with sinusoidal roughness. Coll Surf A Physicochem Eng Aspects 328:28–33. doi:10.1016/j.colsurfa.2008.06.029 CrossRefGoogle Scholar
  34. Young PL, Kandlikar SG (2008) Surface roughness effects on heat transfer in microscale single phase flow: a critical review. In: Proceedings of the 6th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM2008, June 2008, pp 189–201Google Scholar
  35. Zhang X, Yu S, He Z, Miao Y (2004) Wetting of rough surfaces. Surf Rev Lett 11:7–13. doi:10.1142/S0218625X04005925 CrossRefGoogle Scholar
  36. Zhang J, Zhou WX, Chan-Park M, Conner SR (2005) Argon plasma modification of SU-8 for very high aspect ratio and dense copper electroforming. J Electrochem Soc 152:716–721. doi:10.1149/1.2034519 CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Nagaraju Oruganti
    • 1
    • 3
  • Michel Goedert
    • 1
  • Sang-Joon John Lee
    • 2
  1. 1.Biomedical, Chemical, and Materials EngineeringSan José State UniversitySan JoséUSA
  2. 2.Mechanical and Aerospace EngineeringSan José State UniversitySan JoséUSA
  3. 3.Coherent Inc.Santa ClaraUSA

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