Wafer level packaging based on AU-AU bonding for a CMOS compatible thermal wind sensor

A CMOS compatible two-dimensional thermal wind sensor, which can measure the wind speed as high as more than 40m/s, was presented by using au-au bonding technology for wafer-level packaging. A ceramic chip, whose front side exposed to the airflow works as the temperature sensing surface, was adapted to protect the temperature sensing silicon chip, while au bumps were used to achieve the thermal interconnection and the electrical interconnection between them. The wet etching technology was utilized to thin the silicon substrate to 50μm thickness and overcome the feed-through problem, simultaneously. The results show that the wind speed measurement range of the sensor is higher than 40m/s with 2mW start heating power, and the transient response time for wind speed is less than 1.4s.