Angular micropositioner for disk drives

Rotary electrostatic microactuators suitable for use in a two-stage servo system for magnetic disk drives have been fabricated using the HexSil process. A 2.6 mm diameter device is shown to be capable of producing 0.17 mN-mm of output torque, corresponding to a predicted actuation bandwidth of 1.6 kHz. The structures are formed from LPCVD polysilicon deposited into deep trenches etched into a silicon mold wafer. Upon release, these structures are transferred to a target wafer using a solder bond. The solder bonding process will provide easy integration of mechanical structures with integrated circuits, allowing separate optimization of the circuit and structure fabrication processes. An advantage of HexSil is that once the mold wafer has undergone the initial plasma etching, it may be re-used for subsequent polysilicon depositions, amortizing the cost of the deep trench etching over many structural runs and thereby significantly reducing the cost of finished actuators. Further, 100 mu m high structures may be made from a 3 mu m deposition of polysilicon, increasing overall fabrication speed.