System and method for monitoring the topography of a wafer surface during lithographic processing

摘要

A system for monitoring wafer surface topography during a lithographic process is described that includes projection optics that illuminate a portion of the wafer surface. The system further includes at least one off-axis wafer surface gauge that monitors wafer surface height relative to the projection optics as well as at least one backplane gauge that monitors wafer position relative to a backplane. The system also includes a filter that translates time-domain measurements of off-axis wafer surface gauge and the backplane gauge into space-domain measurements. A coordinate transformer is included that transforms the space-domain measurements into a single coordinate system. A computational element that combines the space-domain measurements with a focus set-point to determine correction data is also included together with a delay line for storing the correction data until the wafer has moved a predetermined distance.