Structured Illumination for Contrast Enhancement in Overlay Metrology

摘要

Contrast enhancement in a metrology tool may include generating a beam of illumination, directing a portion of the generated beam onto a surface of a spatial light modulator (SLM), directing at least a portion of the generated beam incident on the surface of the SLM through an aperture of an aperture stop and onto one or more target structures of one or more samples, and generating a selected illumination pupil function of the illumination transmitted through the aperture utilizing the SLM in order to establish a contrast level of one or more field images of the one or more target structures above a selected contrast threshold, and performing one or more metrology measurements on the one or more target structures utilizing the selected illumination pupil function.

主权项

1. An apparatus, comprising:
an illumination source; a spatial light modulator (SLM); a beam splitter configured to direct a portion of light emanating from the illumination source along an illumination path to a surface of the spatial light modulator (SLM); an aperture stop disposed substantially at a pupil plane of the illumination path, the aperture stop having an aperture configured to transmit at least a portion of light directed from the surface of the SLM to a surface of one or more specimens; and a metrology tool configured to measure one or more characteristics of one or more metrology target structures of the one or more specimens, the metrology tool comprising:
an entrance pupil configured to receive illumination directed from the surface of the SLM and transmitted through the aperture of the aperture stop;a beam splitter configured to receive illumination received through the entrance pupil of the metrology tool, the beam splitter further configured to direct at least a portion of the illumination passed through the entrance pupil to the one or more samples;an objective lens configured to focus the at least a portion of the illumination onto one or more target structures of the one or more samples; anda detector configured to collect a portion of illumination scattered from the one or more target structures of the one or more samples, wherein the SLM is configured to control an illumination pupil function of the illumination transmitted through the aperture, the illumination pupil function controlled by controlling a profile of illumination impinging on the surface of the SLM from the illumination source.