Abstract: Using the junction temperature distribution as determined from infrared imaging,the thermal spectrum curve is obtained by thermal spectrum analysis for use in creating a "sub-transistors in parallel connection" model.Based on the model,from theoretical calculation and experiment,the validity of the excessive thermotaxis effect of low current is verified.For current passing through a pn junction in a non-uniform temperature distribution,there is much more thermotaxis at low current than at high current,i.e.,with decreasing measured current,the ratio of the current density at high-temperature to that at low-temperature increases,and the effective area decreases.Based on these characteristics,the electro-thermal instability and the degree of uniformity of the junction temperature distribution can be studied.This has great significance for the reliability analysis of semiconductor devices.

Key words: thermal spectrum curve, current density, excessive thermotaxis, effective area