A new surface micromachining technology called '3D UV-microforming' was applied to fabricate three-dimensional components on silicon substrates. The technology consists of an advanced resist preparation process, a UV lithographic step, resist development, a galvanic moulding procedure for filling up the resist patterns and finally stripping and cleaning for finishing the structures. During resist preparation, layers up to 200 mu m thickness were obtained. By using a standard UV mask aligner as an exposure tool and followed by immersion development, thick resist layers up to 100 mu m could be patterned in a single shot on pre-processed silicon wafers. Repeated exposure and development were successfully used for structuring resist layers of up to 200 mu m thickness. High aspect ratios of more than 10 as well as steep edges of more than 88 degrees could be fabricated. The resist patterns were moulded by using pulse or d.c. electroplating. For microactuator applications gold, copper and nickel-iron alloys were deposited. NiFe has excellent, stainless-steel-like mechanical properties and is, additionally, ferromagnetic. The magnetic and mechanical characteristics depend on the composition and can be varied with the process parameters. Some magnetically driven microcomponents, e.g. cantilevers for reeds and membranes for valves, were fabricated as demonstrators for the new technique.
