Fabrication Of Micro Inertial Switch And Process Of Thick Positive Photoresist

With the development of micro-fabrication technique, micro metal devices with specific function are widely used in signal detection, disease analysis, weapon system, aerospace, bio-engineering and other fields because of its small size, low cost, superior performance. Based on UV lithography and micro-electroforming, UV-LIGA process is an effective way to fabricate micro devices. This paper studied the fabrication process of a cross-scale metal inertial switch with high aspect ratio by multi-layer UV-LIGA process, explored the influence of honeycomb structure on the delamination of large-area electroforming layers and researched the fabrication process of thick positive photoresist AZ 50XT.A cross-scale inertial switch with high aspect ratio was fabricated by multi-layer UV-LIGA process on metal substrate and its dynamic performance was tested. During the fabrication process, to increase the aspect ratio of microstructures fabricated by UV-LIGA process, a multi-layer stacking method was used to fabricate micro devices with the aspect ratio of 17:1. To solve the weak adhesive strength problem of multi-layer metal microstructures, small current density activation, plasma treatment were used to improve adhesion property and solved the detachment problem of electroforming layers. To solve the difficulty in removal of SU-8 photoresist in microstructures with high aspect ratio, a wet chemical method was used to remove SU-8 photoresist and microstructures with clean profiles were obtained. Based on above research, a cross-scale inertial switch with high aspect ratio was fabricated successfully. The overall size of the inertial switch is 14×11×0.6mm, the smallest linewidth is 29.8?m and the highest aspect ratio is 17:1. At last, dynamic performance of the micro inertial switch was tested on turntable table equipment and the results show that the inertial switch could achieve design requirements.To reduce the detachment risk of metal microstructures from substrate, the effect of honeycomb structure on the delamination of electroforming layers with large area was studied based on experiment and simulation. The result shows that under the condition of same geometry shape, layout form and number of honeycomb holes, the delamination extent of the electroforming layers is reduced with the decrease of the electroforming area. For the square electroforming layer with 7mm in length, honeycomb structure with 60% area removed can effectively reduce the delamination extent of electroforming layers. Increasing the number of honeycomb holes and adopting rectangular holes can distribute the electroforming area more evenly and result in lower delamination extent of the electroforming layers. Finally, the structure of frame panel was optimally designed based on above research and the frame panel was successfully fabricated.In order to solve the SU-8 removal problem during fabrication of metal microstructures with high aspect ratio, fabrication process of AZ 50XT positive photoresist was studied. Plasma cleaning method was used to clean apolar contamination on the photoresist surface during multilayer lithography process, and the cleanliness of photoresist surface was improved. The effect of exposure time on the surface quality and dimensional error was studied based on experiments. Experiment results show that with the increase of exposure time, the remaining photoresist thickness decreases. And when the exposure time exceeds 9min, the surface quality of photoresist deteriorates with the increase of the exposure time. At the same time, linewidth error of microstructures is magnified with the increase of the exposure time. Copper microstructures were electroformed with AZ 50XT as mold and this experiment proved good compatibility between AZ 50XT and copper electroforming process.