Monday, February 16, 2009


LIGA is an acronym for the German ‘Lithografie Galvanoformung Abformung’, meaning lithography, electroplating and injection-moulding, as these are the three steps usually involved in the process [2][3].

In the 1980s, a demand for non-silicon structures with high aspect ratio started to arise. In this context a technique called LIGA was invented at the German Kernforschungs Zentrum Karlsruhe (KZK) [1], allowing for the manufacture out of polymers, metals and ceramics of micro components in almost any lateral geometry and structural height. Originally used for the mass production of micro-nozzles for uranium enrichment the technique was quickly adopted by many users for numerous applications.

For the LIGA technique a polymer (photo-resist) sensitive to X-radiation is patterned by the shadow thrown by a special photo mask placed in the beam path. An exact image of the absorber structures on the mask is thereby transferred on to the photo-resist. The areas hit by the radiation change their molecular structure becoming either more or less resistant against certain liquids than the unexposed areas. The area with the lower chemical resistance can then be dissolved selectively by wet chemical methods. If the exposed areas are dissolved, the photoresist is called a positive resist, if the unexposed areas are dissolved, a negative resist. Due to the high energy and parallelism of X-rays, structures with aspect ratios of up to 500 can be produced. Structures with structural details in the area of 0.2 μm have also been reported, owing to the high accuracy with which X-ray masks can be produced and the wavelength of the radiation of 3 – 4 Å [5][6][7][8][9][10][11][12][13].

To produce the necessary X-radiation very expensive set-ups called synchrotrons are used. These consist of a several meter long ring structure in which electrons are accelerated. When reaching a certain velocity the rotating electrons emit X-rays perpendicular to their circular flight path. The emitted radiation is highly collimated and by placing an X-ray mask and substrate into the beam path, the mask structures can be transferred onto the substrate.

As a synchrotron is rather expensive equipment, the production of polymer or metal structures with this technique is not economical for mass production. Therefore a modified method utilizing UV-radiation instead of X-ray radiation, called UV-LIGA has been invented and was first reported by Lawes and Zheng. UV-LIGA has since found a wide range of users throughout the world [4]. The only difference to X-ray- LIGA is the use of a UV light-source instead of a synchrotron, which makes the technique much cheaper and allows for research by a broader group of researchers.

Standard LIGA process. a) Thick photoresist is used to create a positive image of the intended parts. b)A moulding master is produced using electroplating, c) Multiples negatice of the master are produced using a moulding process.


  1. J. Mohr, P. Bley, M. Strohrmann, and U. Wallrabe, "Microactuators fabricated by the LIGA process," Journal of Micromechanics and Microengineering, vol. 2, pp. 234-241, 1992.
  2. E. W. Becker, W. Ehrfeld, G. Krieg, and W. Bier, "Method for producing seperating nozzle elements," US 4351653/1 ed. USA, 1982.
  3. J. V. Collins, A. S. Pabla, and C. W. Ford, "Preliminary results on the use of LIGA in an optoelectronics application," Lasers and Electro-Optics Society Annual Meeting, pp. 42, 1998.
  4. Z. Cui and R. A. Lawes, "Low cost fabrication of micromechanical systems," Microelectronic Engineering, vol. 35, pp. 389-392, 1997.
  5. J. V. Collins, A. S. Pabla, and C. W. Ford, "Preliminary results on the use of LIGA in an optoelectronics application," Lasers and Electro-Optics Society Annual Meeting, pp. 42, 1998.
  6. E. W. Becker, "Development of the seperation nozzle process for the enrichment of uranium," German Chemical Engineering, vol. 9, pp. 204, 1986.
  7. E. W. Becker, "Entwicklung des Trennduesenverfahrens zur Uran- Anreicherung, Development of Nozzle Separation Process for Enrichment of Uranium," vol. 58, pp. 284, 1986.
  8. W. Ehrfeld, P. Bley, F. Gotz, P. Hagmann, A. Maner, J. Mohr, H. O. Moser, D. Munchmeyer, W. Schelb, D. Schmidt, and E. W. Becker, "Fabrication of Microstructures using the LIGA Process," Hyannis, MA, USA, pp. 11, 1987.
  9. E. W. Becker, W. Ehrfeld, P. Hagmann, A. Maner, and D. Muenchmeyer, "Fabrication of Microstructures with high aspect ratios and great structural heights by Synchrotron Radiation Lithography, Galvanoforming, and Plastic Moulding ( LIGA Process)," Microelectronic Engineering, vol. 4, pp. 35, 1986.
  10. W. Ehrfeld, F. Gotz, D. Munchmeyer, W. Schelb, and D. Schmidt, "LIGA process: sensor construction techniques via X-ray lithography," Solid-State Sensor and Actuator Workshop, 1988. Technical Digest., IEEE, pp. 1, 1988.
  11. W. Menz, "Microactuators in LIGA technique," vol. 2, pp. 281, 1992.
  12. W. Menz, W. Bacher, M. Harmening, and A. Michel, "The LIGA technique-A novel concept for microstructures and the combination with Si-technologies by injection molding," Micro Electro Mechanical Systems, 1991, MEMS '91, Proceedings. 'An Investigation of Micro Structures, Sensors, Actuators, Machines and Robots'. IEEE, pp. 69, 1991.
  13. A. Rogner, J. Eicher, D. Munchmeyer, R. P. Peters, and J. Mohr, "LIGA technique - what are the new opportunities," Journal of Micromechanics and Microengineering, vol. 2, pp. 133-140, 1992.