Small embedded sensors for accurate temperature measurements in DMOS power transistors

Device temperature is one of the most important limits for the safe operating area and the reliability of power DMOS transistors. Therefore, accurate measurements of their intrinsic device temperature are required. However, standard methods such as IR thermography usually cannot be applied to advanced smart power technologies where a thick power metal layer obscures the - often significantly hotter - active device area. Thus, we propose to embed very small temperature sensors in the active DMOS cell array. These sensors allow for an accurate reading of the intrinsic device temperature while not influencing the DMOS behavior noticeably. The sensors are calibrated up to 600°C, validated by comparison to TIM measurements up to 400°C, and used to investigate thermal runaway. Results from 60 sensors embedded in one large power DMOS with on-chip analog multiplexing are also presented.