Pyrometric Interferometry (PI) for real time MBE process monitoring

Pyrometric Interferometry (PI) has recently been demonstrated for simultaneous real time wafer temperature and thickness measurement during the molecular beam epitaxy (MBE) process. Both parameters of the thin film layer can be determined from the changing interference conditions in the layer. We used a reflection assisted version of PI to follow the thermal history of the wafer under different conditions and were able to resolve temperature to less than 1 deg C. For thickness measurement a parabolic fitting algorithm was used to accurately determine the endpoints of the GaAs/A1As quarter wave stacks. Compared to other noncontact methods this technique can be used for very thick layers and is unaffected by the layer absoprtion and optical effects.