Patent ID: 11879853
Assignee: KLA CORPORATION
Field: Measurement (Instruments)
Classification: CPC G  H | IPC G  H

Claim 0:
1. A system comprising:
an illumination source configured to generate an illumination beam;
one or more illumination optics to direct the illumination beam to a sample at an off-axis angle along an illumination direction;
one or more collection optics to collect scattered light from the sample in response to the illumination beam in a dark-field mode, wherein the scattered light from the sample collected by the one or more collection optics includes surface haze associated with light scattered from a surface of the sample, wherein at least a portion of the surface haze has elliptical polarizations;
one or more optical elements located at one or more pupil planes of the one or more collection optics comprising:
a first polarization rotator providing a first spatially-varying polarization rotation distribution to rotate the surface haze to a selected orientation direction, wherein rotation of the surface haze includes rotation of long axes of the elliptical polarizations to the selected orientation direction;
a quarter-wave plate to convert the surface haze from the first polarization rotator to linear polarizations; and
a second polarization rotator providing a second spatially-varying polarization rotation distribution to rotate the linear polarizations of the surface haze from the quarter-wave plate to a selected haze orientation direction;

a linear polarizer aligned to reject light polarized parallel to the selected haze orientation direction to reject the surface haze from the second polarization rotator; and
a detector to generate a dark-field image of the sample based on scattered light from the sample passed by the linear polarizer, wherein the scattered light from the sample passed by the linear polarizer includes at least a portion of light scattered by one or more particles on the surface of the sample.