Variation of band-edge position with errors in the monitoring of layer termination level for long- and short-wave pass filters.

Optical monitoring of periodic thin-film stacks by the termination of each layer at the same constant photometric level has certain advantages. One of these principal advantages is the error compensation effect in the vicinity of the monitoring wavelength. In this study, we examine, by simulation, the effect of an error in the knowledge of the absolute value of the photometric termination level on the probable stability in the manufacture of the edge position of a blocked band. The results include equations that allow the determination of the appropriate values of parameters associated with the optimum termination levels to minimize the effects of such errors.