High aspect ratio electrostatic micro actuators using LIGA process

High-power electrostatic microactuators using LIGA process have been fabric ated. Comb drive type actuators and a wobble motor were designed and fabric ated. A basic structure of the microactuators was composed of movable and f ixed electrodes of Ni, a sacrificial layer of SiO2 and a Si substrate, and carried out by one mask process. As design rules, a minimum resist width of 2 mum, resist height of 120 mum, maximum width of movable parts of 10 mum, minimum width of fixed parts of 40 mum and driving voltage of about 100 V, were decided. A 120 mum-thick PMMA resist was formed on a Si substrate by a casting method. The PMMA was exposed using a compact SR source "AURORA", using an X-ray mask with 7 mum-thick Au absorber on a 2 mum-thick poly-Si m embrane. The exposed PMMA was developed by a developer. Ni microstructures with 100 mum-height, 2 mum-minimum width, 2 mum-minimum gap, and then maxim um aspect ratio of 50, were made by electroforming. Ni microstructures used 2 for movable electrodes were separated from the substrate by lateral etch ing of SiO2. After lateral etching of SiO2, Au wires were bonded to electro des. Actuation of the comb drive type actuator and rotation of the wobble m otor were confirmed. The applied voltage to the comb drive actuator and the wobble motor were 65 and 125 V.