Optical monitoring of substrate temperature and etching speed of multilayered structures during plasmochemical etching

Using weakly coherent tandem interferometry, the possibility of simultaneous temperature and film thickness measurements in plasmochemical etching processes of silicon on insulator structure is demonstrated. It is shown that changes of the structure’s total optical thickness related to temperature variation can be separated from a change of the physical film thickness. For that purpose we have to take in account changes of zeros interference peak amplitude caused by changes of the interferentional conditions inside the film when its thickness is changing. Temperature measurement precision is ±1°C. Thickness measurement precision is ±10 nm. The results of process monitoring closely correlate with the results of a stair’s profile obtained with a profilometer.