Pressure Sensor for Harsh Environments Realized by Triple-Stack Fusion Bonding

Fusion bonding of three separate wafers into a triple stack has been performed to manufacture a pressure sensor for oil well monitoring. A bond strength (Si/SiO2) of 5-15 MPa is achieved after annealing at 1000oC. The aluminum contact pads were applied by sputtering through a mechanical mask prebonded onto the triple stack. The sensor withstands an absolute pressure of 1000 Bar, and it can be operated at 200oC. A zero shift of less than 2,5% of FSO is observed.