Measurement and Simulation of Self-Heating in DMOS Transistors up to Very High Temperatures

Self-heating can lead to excessive temperatures in large power DMOS transistors, thus restricting their safe operating area (SOA). To explore that limit, the device temperature must be known with sufficient accuracy, which is difficult in advanced BCD technologies. This is because standard measurement methods such as infrared thermography do not show the true device temperature. Also, most (electro-)thermal simulation approaches have not been experimentally verified close to the SOA limits. In this work, a test chip with novel temperature sensors embedded inside the DMOS cell array will be used for accurate measurements of the device temperature. Moreover, a 3-D numerical temperature simulator is extended to correctly consider the temperature-dependent DMOS behavior. Thus, electro-thermal coupling is taken into account while simultaneously calculating the temperatures with high spatial resolution. The validity of the simulator will be demonstrated experimentally by comparison to measurements for temperatures exceeding 500°C, up to the onset of thermal runaway