The LIGA technique and its potential for microsystems

The LIGA technique, which is an X-ray lithographic electrodeposition molding process, was developed at the Nuclear Research Centre Karlsruhe. Unlike in the silicon-based technology, the source material is an X-ray sensitive plastic layer of several hundred micrometers thickness which is directly polymerized onto a metallic base plate. The pattern of a mask is transferred into the thick resist layer by means of highly parallel, high intensity synchrotron radiation at a characteristic wavelength of 0.2 to 0.6 nm. Due to breakage in the long chains of molecules the irradiated areas change their chemical stability and can be dissolved with a suitable developer. Techniques involving microelectrodeposition can be used to build up a complementary structure of metal. With the metal structure so generated, almost any number of copies made of plastic can be reproduced with a high accuracy in detail and at relatively little cost using injection molding, reaction injection molding or embossing techniques