Laser and electron beam based LIGA processes

Lithographic techniques adopted from the semiconductor industry are capable of defining the x and y dimensions over a very large range eg. 0.1 μm to 10⁵ μm. However, the height or thickness of the structure is limited to a few microns using conventional resist exposure, etching and/or deposition methods. As a typical micromechanical structure may require a height of 50-1000 μm, alternative techniques have been developed. One such technology is known as LIGA (lithographie, galvanoformung, abformung) based upon deep-etch lithography, electroplating and moulding processes. The cost of entry into the LIGA technology is high, mainly because of the hard X-ray radiation that is required to expose deep resist. Alternatives are being considered using high voltage electron beams or excimer laser image projection, that could reduce the costs of the exposure steps by orders of magnitude. The paper concentrates on the exposure step of the LIGA process and illustrates how the alternative techniques might be used. The subsequent steps of electroplating and moulding would remain the same as for the standard LIGA process