Experimental detection of time dependent temperature maps in power bipolar transistors

Abstract In this paper, we present a completely automated experimental set-up for transient temperature distribution measurements on the surface of the semiconductor power devices. Based on direct radiometric measurements, the proposed system is able to acquire, with high spatial (less than 10 μm) and quite good time (less than 10 μs) resolution, the temperature maps of devices biased in critical working conditions without damaging them. As an example of the measurement set-up capability, we show some measurements on the onset of the hot spot in two different kind of cellular BJTs. The obtained results confirm that the electro-thermal instability is mainly dependent on the lay-out of the device under test. Moreover, hot-spot growth is much faster than the heating time constant of the chip. Finally, we obtained the result that the hot-spot size is almost constant, independently from the chip area.