Microsystem Technologies

, Volume 14, Issue 9–11, pp 1233–1243 | Cite as

High throughput projection UV lithography of high-aspect-ratio thick SU-8 microstructures

  • Ren YangEmail author
  • Chuck Mullen
  • Mark Schaline
  • Karl Reithmaier
  • Ron Sheets
Technical Paper


This paper presents a method and an ultra-violet (UV) lithography system to fabricate high-aspect-ratio microstructures (HARMS) with good sidewall quality and nice dimension control to meet the requirement for industrial high throughput and high yield production of micro devices. The advantages, equipment, working principle of UV projection scanning exposure, and scanning exposure strategies are introduced first. Following the numerical simulation for the UV projection scanning exposure of thick SU-8 photoresist, experiment results are demonstrated for different exposure strategies. With Continually Changing Focus Projection Scanning (CCFPS), SU-8 microstructures with 860 μm high and 15 μm feature size are demonstrated. For microstructure with 866 μm height, 20 μm width, from the top layer to the bottom layer, the dimension can be controlled in the range of +0.7 to −1.7 μm; also, the vertical sidewall angle can be controlled inside 90 ± 0.16°. It approves that the CCFPS exposure for HARMS can achieve much straighter and more vertical sidewall compared with UV contact print or UV projection exposure with focusing image on the resist surface or an optimized depth.


Mask Pattern Vertical Sidewall Energy Contour Projection Lens Sidewall Angle 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



The authors would like to thank Tamarack Scientific Co., Inc. and its support for this project. The authors also would like to thank other engineers from Tamarack Scientific for their supports and helpful discussions in optics, mechanics, electrical hardware, software program, and motion control.


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Ren Yang
    • 1
    Email author
  • Chuck Mullen
    • 1
  • Mark Schaline
    • 1
  • Karl Reithmaier
    • 1
  • Ron Sheets
    • 1
  1. 1.Tamarack Scientific Co., IncCoronaUSA

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