Assembly and packaging technologies for high-temperature SiC sensors

Silicon carbide is a promising semiconductor material for sensor applications in harsh environments. To operate SiC-MEMS at high temperature, reliable assembly and packaging technologies are needed. In this paper, packaging technologies for die-attachment and interconnection suitable for SiC-Sensors are presented. They are investigated on their stability, reliability and their thermo-mechanical influence on the sensor element. Active metal brazing, glass soldering and ceramic bonding are used as mounting technologies and Platinum and Palladium wires for electrical interconnection. Different material combinations were examined. Silicon test-chips processed in thin film technology with a metallization suitable for harsh environments were used for conducting and characterization of the technologies. The test-chips were mounted on Al₂O₃, AlN and Si₃N₄ substrates to examine the influence of the sensor substrate. The mechanical stress in the chip induced by the packaging process was analyzed by an optical measurement of the chips surface, correlated to an analytical approach and compared to FEM-simulations. The investigation of the mechanical stability of the material compounds was carried out by shear-tests before and after 100 hours storage at 500°C. In this study the glass-solder process with an AlN sensor substrate is the most suited technology in case of the reliability of SiC-MEMS.