Design of MEMS-Based Piezoresistive Pressure Sensor Using Two Concentric Wheatstone bridge Circuits for Intracranial Pressure Measurement

Intracranial pressure monitoring plays a crucial role in the diagnosis of neurosurgical and neurological patients. Intracranial pressure measuring devices must have small high precision, fast response time and high functionality. The piezoresistive pressure sensor design proposed in this paper has a diaphragm of n-type single crystal silicon which is diffused to form p-type single crystal silicon in its central region. Eight piezoresistors are used to form two concentric Wheatstone bridge circuits. Four n-type single crystal silicon piezoresistors placed on the surface of p-type silicon in the central region of the diaphragm in Wheatstone bridge configuration and the other four p-type single crystal silicon piezoresistors are placed the surface of n-type silicon region to form another Wheatstone bridge circuit. The simulation results obtained using COMSOL Multiphysics shows that this structure provides a very sensitivity of 127 mV/V/MPa for the entire intracranial pressure range. Due to opposite signs of the piezoresistive coefficients of p-type and n-type single crystal silicon piezoresistors at a constant doping level, the output voltage their respective Wheatstone bridge configured circuits are opposite signs. This increases the overall output voltage of proposed structure thus making it adaptable to measure intracranial pressure with high accuracy.