Flip-chip packaging using micromachined conductive polymer bumps and alignment pedestals for MOEMS

Using hip-chip bonding techniques with micromachined conductive polymer bum ps and passive alignment techniques with electroplated side alignment pedes tal bumps, a prototype microoptoelectromechanical systems (MOEMS) structure for optical input/output (I/O) couplers has been designed, fabricated and characterized. A top MOEMS substrate has through holes, contact metal pads, and side alignment pedestals with electroplated NiFe to align GaAs metal-s emiconductor-metals (MSM's). Conductive polymer bumps have been formed on c ontact metal pads of GaAs MSM's using thick photoresist bump-holes as moldi ng patterns. A diced GaAs photodetectors die with micromachined conductive polymer bumps was aligned to the side alignment pedestals and flip-chip bon ded onto the substrate. This conductive polymer flip-chip bonding technique allowed a very low contact resistance (similar to 10 m Ohm), a lower bondi ng temperature (similar to 170 degrees C), and simple processing steps. The GaAs MSM photodetectors flip-chip mounted on the top of OE-MCM substrate s howed a low dark current of about 10 nA and a high responsivity of 0.33 A/W .