Stress control for process optimization of the capacitive pressure sensors for biomedical applications achieved by surface micromachining technology

An integrated structure of capacitive pressure sensor for biomedical applications achieved by surface micromachining technology, consisting in the pressure sensor and a testing component is presented. The test structure permitted to apply the pull-in voltage method for the evaluation of the residual stress in the polysilicon layer on the basis of a new form of the set of two equations describing the beam pull-in voltage effect. The integrated structure allowed the optimization of the phosphorus diffusion process to obtain low stress polysilicon membranes of the capacitive pressure sensors for biomedical applications.