High reliability of piezoresistive pressure sensors by wafer to wafer direct bonding at room temperature

As a micro-component for detecting and acquiring pressure data, piezoresistive pressure sensors are widely used in the microelectronic industry. Enhancing the sensitivity and reliability of piezoresistive pressure sensors can be achieved with optimized fabrication process and advanced techniques. However, in previous studies, there is limited information and knowledge of the relationship between the sensor performances and their fabrication process. In this study, we further optimized the fabrication process for piezoresistive pressure sensors, achieving a significantly higher stability of the pressure sensor compared with that of the commercial products obtained based on the standard test of "Pressure & High temperature Operating Life Test." A detailed analysis revealed that both the designed structure of the piezoresistive pressure sensor and the preliminary thermal treatment conditions for tetraethylorthosilicate (TEOS) oxide substrate are critical factors that contribute to the improved performance of the pressure sensors. After low-temperature annealing, the atomic scale characterization of the interfaces between different material layers of the sensor showed well-proportioned interfaces. Furthermore, reducing water content in the sensors through high-temperature annealing is crucial for improving the stability of the piezoresistive pressure sensors.