Fabrication of electrostatic micro-actuators for a hard disk drive application

Abstract

Micro-actuators are developed for a hard disk drive application. The aim is to obtain a high density of data storage by positioning the read and write head element precisely. The desired specifications are a displacement of ±0.5 μm, operating voltage of 20 V and a structural resonance frequency of 15 kHz. We manufactured the metallic actuator by using thick photoresist lithography and nickel electroplating. The electrostatic gap between the mover and the stator has a high aspect ratio, in order to achieve low voltage operation. We deposited a copper layer by electroplating as a vertical sacrificial layer. Then we removed the copper layer at last process step to make the electrostatic gap with high aspect ratio. We utilize a photoresist which has a thickness of 10 μm as the first trial. We completed the process and operated the actuator successfully. We also developed a silicon actuator using the silicon deep etching and deposition technology. We use an Inductive Coupled Plasma-Reactive Ion Etching (ICP-RIE) machine for silicon etching and a Low Pressure Chemical Vapor Deposition (LPCVD) machine for deposition of the vertical sacrificial layer of SiO2 and the mover structure of polySi. We obtained an actuator which had thickness of 100 μm with the electrode gap having a aspect ratio of 50.