Chip structure metallization impact on thermally induced faults in power IC devices

IC's power devices are widely used in many applications like switched-mode power supplies, power drivers for mechanical actuators, etc., being subjected to repetitive power pulses. The Active Power Cycling (APC) influences the reliability of IC's, hence the failure rate. The failure mechanisms observed in MOSFETs power devices based on contacting clip technology [3] are solder fatigue and metallization layer degradation. The difference between the Coefficient of Thermal Expansion (CTE) of different materials can induce high deformations in chip metallization, like wrinkles at the top power metal layers. It is well known that the temperature swing is responsible for the IC's degradation, but many other parameters e.g. geometrical dimensions, material properties etc., have an important impact too. This paper studies the impact of geometrical dimensions on thermal-induced stress and deformations by a contact clip on a typical MOSFET metalization structure.