An Investigation of Fusion Bonding Process for Mems Piezoresitive Pressure Sensor

This work presents the fabrication and characterization of a high-pressure piezoresistive MEMS pressure sensor using silicon-to-silicon fusion bonding. Traditional anodic bonding techniques, which involve bonding silicon to borosilicate glass, are commonly used for sensor encapsulation. However, the mismatch in the coefficient of thermal expansion (CTE) between silicon and glass can introduce significant thermal stress, potentially affecting device reliability under high-temperature or long-term operation. To overcome these limitations, fusion bonding was employed, which enables direct covalent bonding between silicon wafers, eliminating CTE mismatch and allowing high-temperature annealing. The fusion bonding process was optimized by tuning parameters such as bonding temperature, surface preparation, and annealing conditions. The fabricated pressure sensor, designed for a 400 bar operating range, exhibited a sensitivity of ~ 50 mV/bar under 5 V excitation, with a full-scale output of ~ 100 mV. The device demonstrated excellent linearity within ± 0.2% across a wide temperature range (–40°C to 80°C), highlighting the effectiveness of fusion bonding for high-performance, thermally stable MEMS sensor applications.