Laser beam thermography of circuits in the particular case of passivated semiconductors
Résumé
Surface temperature changes upon integrated circuits can be observed by measuring the corresponding reflectance variation. We presented this method for temperature measurement in earlier work [1, 2] for Si integrated circuits with no passivation layer. We show in this presentation how the passivation oxide layer upon integrated circuits increases, with a factor depending upon the oxide thickness, the reflectance response resulting from a temperature change. Absolute temperature changes are derived from reflectance measurements through a temperature coefficient. This coefficient, known for silicon, is calculated for different oxide thickness.s. We have built a laser probe for reflectance measurements upon integrated circuits. The probe, which includes a visualisation set-up, has a lateral resolution of 1 μm, the size of the laser spot. Absolute temperature changes from 0.05 to 500 K can be determined and followed as a function of time as the detection system covers the DC-125 MHz range. The laser probe allows also the precise measurement of the oxide thickness upon the semiconductor component. This is performed through the measurement of the reflectance at two different angles of incidence.