PYROMETRIC INTERFEROMETRY FOR REAL-TIME MOLECULAR-BEAM EPITAXY PROCESS MONITORING

Pyrometric interferometry (PI) has recently been demonstrated for simu ltaneous real time wafer temperature and thickness measurement during the molecular beam epitaxy process. Both parameters of the thin film l ayer can be determined from the changing interference conditions in th e layer. We used a reflection assisted version of PI to follow the the rmal history of the wafer under different conditions and were able to resolve temperature to less than 1-degrees-C. For thickness measuremen ts, a parabolic fitting algorithm was used to accurately determine the endpoints of the GaAs/AlAs quarter wave stacks. Compared to other non contact methods this technique can be used for very thick layers and i s unaffected by the layer absorption and optical effects.