Fabrication methods for high aspect ratio microstructures

Two methods for fabricating high aspect ratio (depth/width) microstructures were developed and compared. The first method is a modified deep X-ray lithography process with thick negative resist. For preventing pattern collapse caused by surface tension while the rinse liquid is evaporated, some post-rinse drying processes were investigated. The second method is a directional etching of polyimide by O₂ reactive ion etching (RIE). The advantage of the latter method is that the surface tension of liquids does not affect the microstructure in a dry atmosphere. In both methods, aspect ratio of 10 was achieved in polymer molds for electroplating at pattern width of 5 μm without collapse.