High temperature pressure sensor using Cu-Sn wafer level bonding

This paper presents a novel high temperature SOI pressure sensor utilizing Cu-Sn wafer level bonding. Fabrication process and bonding procedure are described in detail. For high temperature operation, heavily doped piezoresistors and TiSi2/Ti/ TiN/Pt/Au ohmic contact electrode are specially designed. To fabricate Cu sealing ring on the wafer with 380pm-deep cavities, spray coating method has been used to coat the wafer and define the pattern. Moreover, in order to calibrate the absolute pressure sensor at high temperatures, a novel calibration setup is designed. The measurement results show that the pressure sensor has a nonlinearity error of 0.11%FS and a sensitivity of 0.28mV/kPa with the measurement range of 30-150kPa at 300°C, which verify the reliability of the Cu-Sn wafer level bonding.