Absolute dynamic measurements of temperature changes in electronic components from a thermoreflectance optical test probe

The authors have developed an optical laser probe for the measurement of absolute surface temperature changes in integrated circuits. The experimental method is based upon thermoreflectance, which is the change in reflectance due to surface temperature changes of the device. A laser beam is focused upon a small spot of an operating circuit. The reflected intensity is recorded upon a photodiode in synchronism with the circuit periodic excitation signal. The authors calibrated the device by developing a simple analytical model to calculate the surface temperature behaviour of a silicon resistive structure. The value derived for the relative reflectance temperature coefficient of silicon is in excellent agreement with the value from the literature. The results show that the laser probe to be a fast surface thermometer (DC to 10 MHz), with excellent lateral resolution (1 μm), with high sensitivity (10^-3 °C) and large dynamics (ΔT:10² to 10^-3 °C)