Integrating a CD SEM into an optical system for photomask metrology operations

摘要

In semiconductor wafer dimensional metrology, the critical dimension scanning electron microscope (CD SEM) has long been the instrument of choice for measuring submicron features because of its nanometer-scale resolution and ever-improving throughput. Because photomask features historically have been at least four or five times larger than wafer features, nanometer-scale resolution has not been necessary and optical CD measurement techniques have sufficed to provide lithography and process engineers with information on the effects of certain modes of operation.