Fabrication of novel MEMS inertial switch with six layers on a metal substrate

MEMS inertial switches have great potential to be widely used in toys, accessories, automotive, military weapons and industrial applications in recent years. Combining with UV-LIGA technology, a new fabrication method of multilayer movable microstructures on metal substrates is presented in this paper, by which a kind of MEMS omnidirectional inertial switch with six layers has been fabricated on metal substrate directly. The method consists of double alignment marks etching process on the back of metal substrates, SU-8 thick photoresist with high aspect ratio lithography process, micro electroforming process, no back plate growing process and SU-8 photoresist sacrificial layer process. Some problems in the fabrication process, such as poor adhesion property among electroforming deposit layers, high stress in electroforming layers, difficulty of preparing the SU-8 mould with high aspect ratio, have been solved effectively. The smallest dimension of the switch is 15 μm, the highest aspect ratio achieves 6:1, the total height of the switch is 210 μm and the outline size is 2.8 × 2.8 mm. The fabrication method presented in this paper provides a new option for the development of multi-layers micro metal devices and is helpful for the fabrication of similar kinds of micro devices.