Fabrication of IC-compatible capacitive sensors by polymer processing

A low-temperature (<300 °C) polymer micromachining process has been developed, whereby the sensor can be fabricated directly on substrates containing complete electronic circuits. This approach is strong since any IC process can be selected with no regard to the sensor process. Condenser microphones have been fabricated with a sensitivity of 8. 1 mV/Pa, flat frequency response between 100 Hz and 15 kHz, and an equivalent noise level of 24 dBA SPL. Differential pressure sensors have been made with a nominal sensitivity Δ C/C of 17 %/bar for a pressure range 1 bar. Furthermore, uni-axial accelerometers with a nominal sensitivity of 0.43 %/g have been implemented. From these results it may be concluded that IC-compatible capacitive sensors with good performances can be achieved with this technology, and it is suggested that the use of polymer processing on silicon therefore may become an important issue in smart sensors of the future.