Use of 22 nm Litho SEM non-visual defect data as a process quality indicator

This paper proposes that the non-visual defect rate for Litho layers is an indicator of the quality of the process up to and including Litho. “Non-visual” (NV) defects are those detected by optical defect inspection systems but not re-detected by the SEM review tool. The defects are occurring either on or below the surfaces of the films deposited immediately prior to lithography, or buried within the actual lithographic films. Rather than ignore the non-visual data obtained during defect inspection post lithography, the NV rate can be used as a quality indicator to trigger immediate action for root cause determination. This paper presents a new strategy for responding to Litho SEM NV defects based on a detailed study of the origin of these defects.