Leveraging the microscale effect to enhance the overload capacity of a piezoresistive differential pressure sensor

The microscale effect has been widely employed in microelectromechanical systems (MEMS) devices due to its unique capabilities to enhance heat transfer efficiency, improve mechanical performance, and significantly amplify electrostatic forces. In this paper, the microscale strength effect of monocrystalline silicon is incorporated into the design of a differential pressure sensor for the first time. To improve the overload capacity of differential pressure sensors, this paper presents a sensor with a combined cross beam island with fillets (CBIF) ultra-thin membrane structure. Firstly, the relationship between membrane thickness and fracture strength is established through burst pressure tests. Secondly, the stress distribution, full-scale output, and maximum stress of the CBIF membrane are analyzed. The influence of structural dimensions on overload capacity is investigated, and the dimensions yielding the highest overload capacity are determined using a size optimization model that incorporates the microscale effect. Finally, the differential pressure sensors are fabricated using MEMS bulk micromachining technology. Measurement results reveal that the sensor with the CBIF membrane achieves a burst pressure of 10.5 ± 0.3 times FS and a sensitivity of 0.16 (mV/V/kPa) over a pressure range of 0-100 kPa. Compared with the conventional C-type membrane sensor, the sensor with the CBIF membrane increased the overload capacity by 66.4% under the same pressure range and sensitivity.