Integrated Octagonal Mechanical Stress Sensor With Temperature Compensation

This paper shows a temperature-compensated piezotransducer device specially designed to be used in a sensor matrix to calculate and map the stress state along the chip surface. This sensor matrix can be a suitable tool to investigate the stress induced by packaging, supporting the back-end process development. The core of this sensor is an eight terminal silicon piezotransduzer (8TSP). This multi-terminal device allows the switch of the bias direction and measure in different orientations. The set of measurements is useful to estimate both angle and magnitude of uniaxial stress in the piezotransducer active area. An integrated solution to compensate the thermal drift of the sensor characteristics based on the theoretical models of the temperature effect in the piezoresistivity of silicon was implemented on-chip. The sensor was characterized under mechanical stress [0, 65] MPa and in the temperature range [268, 353] K. The devices were used to determine the angle of stress with an error of less than 5°, showing that 8TSP is suitable to be used in the sensor matrix to map the stress on semiconductor.