Technical method of improving overload of pressure sensitive chip based on sacrificial layer technology

For pressure sensitive chips made by sacrificial layer technology, their overload capacity can be significantly improved through accurate control over the thickness of the sacrificial layer and the pressure sensitive diaphragm. Based on the analysis for the simulation of the stress distribution of the pressure sensitive structure, the relationship between sizes of the sensitive structure and the overload capacity is elaborated in virtue of the influence of sensitive structure sizes on fracture strength of the polysilicon sensitive diaphragm; and then a design method in improving overload capacity is proposed. Our simulation and analysis indicate that the overload can exceed thirty one-fold of the full scale pressure when properly reducing the thickness of the sacrificial layer and the diaphragm. A sample pressure sensor chip is fabricated with a full scale range of 2 MPa. The test results show that the overpressure of the sample is 18MPa, and its full scale output voltage is 288 mV under 5 V power supply.