UV-LIGA process for fabricating a multilayer metal structure having adjacent layers that are not entirely superposed, and the structure obtained

A process for the UV-LIGA fabrication of a multilayer metal structure comprising a first layer having a recess, at least a second layer adjacent to a first layer and not entirely superposed therewith, said second layer overhanging the recess, which process comprises the following steps:

• a) spreading a photoresist layer over a flat substrate made of bulk metal;
• b) heating the photoresist layer, if necessary to evaporate the solvent;
• c) exposing the photoresist layer through a mask corresponding to the desired impression, to UV irradiation of 100 to 2000 mJ/cm2 measured at a wavelength from 365 nm;
• d) if necessary to complete the photocuring or photodecomposition of the irradiated parts, carrying out an annealing operation on the layer obtained from the step c);
• e) carrying out a development step by dissolving the parts that have not undergone photocuring or photodecomposition, so as to obtain a cured photoresist mold having open parts;
• f) electrodepositing a first layer of a metal or alloy in the open parts of the mold, which is a first mold, and levelling the metal structure and the first mold by machining so as to obtain a planar upper surface;
• g) depositing a metal tie layer by vacuum evaporation on the planar upper surface of the metal or alloy and the mold, and then repeating steps a), b), c), d) and e) so as to form a second mold having open parts, wherein an open part of the second mold extends over a non-open part of the first mold;
• h) electrodepositing a second layer of a metal or alloy in the open parts of the second mold in the presence of the metal tie layer, and levelling the metal structure and the second mold by machining so as to obtain a planar upper surface;
• i) if necessary, repeating steps g) and h) so as to form the desired multilayer metal structure;
• and
• j) detaching the substrate by delaminating the multilayer metal structure obtained and the cured photoresist, separating the photoresist so as to free the multilayer metal structure, then removing that part of the metal tie layer or layers which has not been inserted between two electrodeposited metal layers, so as to obtain the detached multilayer metal structure in which the first layer has a recess and the second layer adjacent the first layer overhangs the recess.