Wafer bonding using parylene and wafer-level transfer of free-standing parylene membranes

This paper describes the development of a wafer bonding technology utilizing a thin Parylene film and its application as a wafer-level freestanding Parylene membrane transfer method. First, a low-temperature (/spl sim/230C/spl deg/) and simple polymer bonding process utilizing very thin (/spl sim/4000/spl Aring/) Parylene intermediate layer has been developed and characterized. Parylene bonding has been performed at 230/spl deg/C in a vacuum of /spl sim/0.15 mTorr under 800 N force on a 4" wafer. The pull-tests on Parylene bonded samples indicate a 3.6 MPa bonding strength. A 1 /spl mu/m-thick Parylene membrane with or without patterns has been successfully transferred over to the device wafer at the wafer-level. This transferred thin film seals over patterns on the device side of a second wafer spanning 10 mm-long and 28 /spl mu/m-deep square-shaped trenches. A yield of more than 65% across a 4" wafer has been achieved. Fluidic micro-channels and flat-surface electrostatic actuators have been successfully fabricated using this method.