Electrostatic micro actuators with high-aspect-ratio driving gap for hard disk drive application

Micro actuators are developed for hard disk drive application. The aim is high density data storage by positioning the read and write head element precisely. The desired specifications are displacement of ±1 μm, operating voltage of 20 V and structural resonance frequency of 151 Hz. We fabricated a metallic actuator by using thick photoresist lithography and nickel electroplating. The electrostatic gap between the mover and the stator has high aspect ratio to achieve low voltage operation. We introduce a vertical sacrificial layer of copper to make the electrostatic gap. We utilize photoresist with thickness of 10 μm. We completed the process and operated the actuator successfully. We also developed a silicon actuator using silicon deep etching and deposition technology. We use ICP-RIE for silicon etching and LPCVD for deposition of the vertical sacrificial layer of SiO₂ and the mover structure of polysilicon. We obtained an actuator which had thickness of 100 μm with electrode gap of aspect ratio of 50