Analysis of small deflection touch mode behavior in capacitive pressure sensors

Due to an increasing need for devices with low power consumption, capacitive pressure sensors have become good substitutes for the well known piezoresistive pressure sensors. Mathematical models are necessary to design and characterize the device, preferably the model is analytical such that geometrical scalings are revealed. We show that, in the case of linear elastic behavior, a simple analytical model can be found for a touch mode capacitive pressure sensor (TMCPS). With this model it is possible to readily evaluate the main features of a TMCPS such as: sensitivity (both in normal and touch mode), touch point pressure and parasitic capacitance. Therefore, the desired device can be designed without using finite element modeling (FEM). This reduces the effort needed to design a micromachined TMCPS. Finally, the model has been compared with a micromachined TMCPS showing an excellent agreement with the experimental data.