LAUSR

Although silicon substrate temperature is known to be important in many plasma processes, measuring it involves various difficulties due to the complexity of plasmas. In previous work, the authors proposed an optical-interference contactless thermometer (OICT) for interferometric temperature measurements with high temporal resolution and the ability to measure a substrate surface from behind. In the present work, the OICT is improved with accurate values of the thermo-optic coefficient (TOC) of silicon and more realistic simulations. The TOC of silicon is measured precisely from room temperature to 800 K. Transient temperature of a silicon wafer during a thermal plasma jet (TPJ) annealing is measured by the OICT and a thermocouple simultaneously to evaluate the absolute temperature accuracy and response speed of the OICT. The wafer is heated with the TPJ under a wide range of annealing speed from 10 to 105 K/s. The absolute temperature accuracy of the OICT is determined as being around ±1 K in comparison with the thermocouple and the OICT can measure to within around ±2 K even under heating at 105 K/s.