Influence of the bonding conditions on the response of capacitive pressure sensors

The behaviour of a capacitive pressure sensor built from a deformable silicon plate bonded to a Pyrex 7740 substrate has been simulated numerically with finite-element calculations. The comparison of 3D simulations with experimental data has shown the validity of the numerical model used for the simulations. By carrying out a structural analysis with these tools, it has also been revealed that silicon and Pyrex exhibit substantial deformations in the neighbourhood of their bonding when a pressure is applied on the sensor. If these deformations did not occur, the sensitivity of the sensor would be divided by 2.1, its measurement range would be multiplied by 1.68 and its linearity would be significantly increased. It is inferred that the response of most pressure sensors is influenced by the deformations of the diaphragm bonding.