Reliability characterization of LDMOS transistors submitted to multiple energy discharges

In this paper, we show on an example how thermal characterization on test vehicles supported by simulation can be used to define a consistent Accelerated Stress Test for power IC's. We describe the reliability program to access the long-term behavior of LDMOS transistors. After the study of the advantages and limitations of the back body diode thermal measurement method, we have investigated in this work the thermal limits of the tested transistors. Then, using a dedicated test bench, we have evaluated the reliability of the devices submitted to repetitive energy discharges and we have studied the observed failure mechanism. Finally, based on these test results, we have set up a reliability database, which helps us to relate the lifetime of the devices and their working temperature. Thanks to this database, LDMOS design and size will be optimized regarding reliability performances.