Fabrication of a Micromachined Two-Dimensional Wind Sensor by Au–Au Wafer Bonding Technology

The design, fabrication, and performance of a micromachined 2-D wind sensor are presented. The sensor operates based on the detection of temperature and flow-dependent heat distribution on a hot sensing surface. It consists of a silicon sensing chip and a ceramic packaging substrate, in which the sensing chip is bonded to the front side of the ceramic packaging substrate through wafer-level gold bumps. The backside of the ceramic substrate provides a smooth surface for the sensor exposed to the wind flow. A silicon diaphragm was fabricated by wet etching to minimize its heat capacity, resulting in the improvement of the power consumption, response time, and resolutions. Experimental results show that the measurement of wind flow speed is demonstrated in the range from 0.5 to 40 m/s with the sensitivity more than 2.73 mW/ms^-1. The sensor requires only 2 mW initial heating power, and in constant-temperature difference mode, the response time less than 1.4 s is obtained. By measuring temperature difference in two directions perpendicular to each other, the detection of direction in a full range of 360 has been achieved. The errors in the measured wind speed and direction after calibration are ±4% and ±2°, respectively.