Structure of Piezoresistive Sensor

In this sensor, the resistor strip is integrated on the monocrystalline silicon diaphragm by integration process to make a silicon piezoresistive chip, and the periphery of this chip is fixedly packaged in the shell, and the electrode leads are led out. Piezoresistive pressure sensor, also known as solid-state pressure sensor, is different from adhesive strain gauge, which needs to feel the external force indirectly through elastic sensitive elements, but directly feels the measured pressure through silicon diaphragm.

One side of the silicon diaphragm is a high-pressure cavity communicating with the measured pressure, and the other side is a low-pressure cavity communicating with the atmosphere. Generally, the silicon diaphragm is designed as a circle with fixed periphery, and the ratio of diameter to thickness is about 20 ~ 60. Four P impurity resistance strips are diffused locally on the circular silicon diaphragm and connected into a full bridge, two of which are in the compressive stress zone and the other two are in the tensile stress zone, which are symmetrical with respect to the center of the diaphragm.

In addition, there are also square silicon diaphragm and silicon column sensor. The silicon cylindrical sensor is also made of resistive strips by diffusion in a certain direction of a crystal plane of the silicon cylinder, and two tensile stress resistive strips and two compressive stress resistive strips form a full bridge.

Piezoresistive sensor is a device made by diffusion resistance on the substrate of semiconductor material according to the piezoresistive effect of semiconductor material. Its substrate can be directly used as a measuring sensor, and the diffusion resistance is connected in the substrate in the form of a bridge.

When the substrate is deformed by external force, the resistance values will change and the bridge will produce corresponding unbalanced output. The substrates (or diaphragms) used as piezoresistive sensors are mainly silicon wafers and germanium wafers. Silicon piezoresistive sensors made of silicon wafers as sensitive materials have attracted more and more attention, especially the solid-state piezoresistive sensors for measuring pressure and speed are the most widely used.