Spectral overlay target

Abstract

A metrology system including a measurement sub-system to collect zero-order double diffraction from a metrology target in response to an illumination beam, where the metrology target includes one or more grating-over-grating structures, having common pitches on two sample layers. The system may further include a controller to generate an after-develop inspection (ADI) metrology measurement of the metrology target at an ADI process step, generate an after-etch inspection (AEI) metrology measurement of the metrology target at an AEI process step, determine a non-zero offset (NZO) measurement based on a difference of the ADI metrology measurement and the AEI metrology measurement, and control one or more process tools based on at least one of the ADI metrology measurement, the AEI metrology measurement, or the NZO measurement.

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