Electrostatic microactuators fabricated using deep RIE and wafer bonding for hard disk drives

A bulk micromachined three-dimensional electrostatic microactuator, used for a hard disk drive dual-stage positioning system, was developed using deep RIE and wafer bonding technologies. The actuators, arranged as vertical comb drives, thereby enhance the electrostatic driving force. By using the proper flexures, the secondary stage actuator drives the R/W magnetic head with a high frequency and accuracy. Micro fabrication of the actuators starts with a 150 μm thick n-type silicon wafer being bonded to a Pyrex glass substrate. Deep RIE and wafer bonding techniques were studied and developed to form the bulk-machined microactuators. This approach is more cost-effective than the process using SOI wafers, and the thick microactuators with high aspect ratio also have better mechanical reliability. The displacement and resonant frequency of fabricated microactuators have been successfully measured and are found to satisfy the design requirement.