Fiber optic instrument measuring layer thicknesses of e.g. photo-lacquer on semiconductor wafer, limits measurement channel by selectable restriction of measurement zone

摘要

To carry out the measurement, the measurement channel (34) can be restricted to a partial zone (42). The restriction is selectable by limiting evaluation in the zone. The zone has a width less than half or a third that of the measurement channel. The width is especially less than 1.5 mm. Limitation is by selection of specific optical fibers (28) to illuminate the measurement channel. The selected optical fibers have a defined relationship with respect to the reflected beam (20). An independent claim is included for the corresponding method.