Polyimide Spacers for Flip-Chip Optical MEMS

Multichip integration provides an attractive means to overcome space limitations for large-port-count optical microelectromechanical systems (MEMS) routing systems by allowing actuation and control wiring to be fabricated separately on one chip and then attached beneath a second chip that is populated with a densely packed mirror array. In such systems, vertical as well as horizontal chip alignment is critical when a large but very uniform separation must be maintained across the extent of the array. A technique for creating a structure that simultaneously provides accurate large-gap spacing and acts as a chip-bonding agent is presented here. Specialized processing of an 80- mum thick photoimaged polyimide structure for bonding mirror and electrode chips for a 1296-mirror array is described, along with measurements of height uniformity within 1% and structure characterization demonstrating suitability for production and long-term stability. The process parameters and simplicity of the technique make it suitable for a wide range of applications where MEMS must be integrated with electronic control circuitry. [2006-0042].