LASER-BEAM THERMOGRAPHY OF CIRCUITS IN THE PARTICULAR CASE OF PASSIVATED SEMICONDUCTORS

Surface temperature changes upon integrated circuits can be observed b y measuring the corresponding reflectance variation. We presented this method for temperature measurement in earlier work [1, 2] for Si inte grated circuits with no passivation layer. We show in this presentatio n how the passivation oxide layer upon integrated circuits increases, with a factor depending upon the oxide thickness, the reflectance resp onse resulting from a temperature change. Absolute temperature changes are derived from reflectance measurements through a temperature coeff icient. This coefficient, known for silicon, is calculated for differe nt oxide thicknesses. We have built a laser probe for reflectance meas urements upon integrated circuits. The probe, which includes a visuali sation set-up, has a lateral resolution of 1 mu m, the size of the las er spot. Absolute temperature changes from 0.05 to 500 K can be determ ined and followed as a function of time as the detection system covers the DC-125 MHz range. The laser probe allows also the precise measure ment of the oxide thickness upon the semiconductor component. This is performed through the measurement of the reflectance at two different angles of incidence.