Thermal assembly of polysilicon microactuators with narrow-gap electrostatic comb drive

Surface micromachined, polysilicon fuse and weld microstructures are modeled, fabricated, and characterized. The current required to cut the thin, 2000 AA fuse is 30 mA, compared to 80 mA for a 2 mu m-thick fuse. For large currents, a simple model shows that the time to cut a fuse is inversely proportional to the square of the current. An aluminum microbridge is used to form a robust weld, connecting two polysilicon structures. The surface tension of the molten Al produces a force of approximately 15 mu M, which is about 100 times larger than electrostatic comb drive forces. A series of current pulses is used to melt the Al without destroying the weld joint.<>