Fabrication and characterization of sealed cavities realized by adhesive wafer bonding with dry etched Cyclotene™

Fabrication and characterization results of sealed cavities formed by adhesive wafer bonding with dry etched Cyclotene 3000™ are presented. The cavities were formed by patterning partially cured Cyclotene 3000™ on an SOI wafer. The cavities were sealed by bonding the patterned layer at low temperature (210 °C) to another partially cured thin Cyclotene 3000™ layer on a bare silicon wafer. The parameters for the vacuum bonding process were determined through an iterative process that involved optical and SEM inspection of the Cyclotene™ layers at the bonding surfaces to ensure a void and wrinkle free strong bond. The fabricated cavities were 28 µm wide and 800 nm high with a 10 µm wide supporting wall. Cavities of other dimensions can also be realized following the same procedure. The cavities can be used to realize MEMS microphones, MEMS pressure sensors, capacitive micromachined ultrasonic transducers (CMUT), resonant cavities, and also for protective encapsulation of MEMS and microelectronic dies.