Simultaneous in-situ measurement of film thickness and temperature by using multiple wavelength pyrometric interferometry (MWPI)

An optical in situ method for simultaneous film thickness and temperature measurements is discussed. Multiple-wavelength pyrometric interferometry (MWPI) is capable of high resolution (0.5 nm for thickness and 0.05 K for temperature) and real-time data evaluation. It can be used for process control as well as in situ quality inspection without time delay or additional handling mechanisms and is suitable for monitoring single films as well as multilayer structures. MWPI is insensitive to vibration, rotation and misalignment of the wafer. Due to its optical basis it is also insensitive to hostile environments like high temperature and/or chemically reactive gases. The physical basis of MWPI is outlined as well as the necessary steps of the evaluation procedure. Simultaneous film thickness and temperature measurement during the thermal oxidation of Si is presented. The potential technical impact of MWPI on automation, reliability and long-term performance of semiconductor manufacturing is discussed