Abstract: The disclosure is directed to various apodization schemes for pupil imaging scatterometry. In some embodiments, the system includes an apodizer disposed within a pupil plane of the illumination path. In some embodiments, the system further includes an illumination scanner configured to scan a surface of the sample with at least a portion of apodized illumination. In some embodiments, the system includes an apodized pupil configured to provide a quadrupole illumination function. In some embodiments, the system further includes an apodized collection field stop. The various embodiments described herein may be combined to achieve certain advantages.

Abstract: Systems and methods for discrete polarization scatterometry are provided.

Abstract: A system and method for maintaining focus in an imaging device; the imaging device having an objective lens with an optical axis, a stage for supporting a specimen, and a controller for controlling the stage-to-objective distance; the system comprising: one or more image sensors placed at a plurality of substantially different axial focal positions, and at least one computing device executing computer-readable instructions stored in its memory and configured to acquire images from each of the image sensors; the method comprising: computing a quantitative image characteristic for each of the images acquired by the computing device, computing an axial stage-to-objective distance correction based on the computed quantitative image characteristics and the plurality of axial focal positions, and causing the controller to adjust the axial stage-to-objective distance according to the computed axial stage-to-objective distance correction.

Abstract: Systems and methods for blocking specular reflection and suppressing modulation from periodic features on a specimen are provided. One inspection system configured to block specular reflection and suppress modulation in an image of a specimen includes an illumination subsystem configured to illuminate the specimen with a predetermined pattern of spatially incoherent light. The system also includes an optical element configured to block light reflected from periodic features formed on the specimen and at least some light diffracted from the periodic features. The system further includes a detector configured to detect light that passes through the optical element and to generate an image of the specimen in response to the detected light. The optical element blocks specular reflection and at least partially suppresses modulation in the image due to the periodic features. The system also includes a processor configured to detect defects on the specimen using the image.

Abstract: A system is provided herein for inspecting a specimen. In one embodiment, the system may include a dual-channel microscope, two illuminators, each coupled for illuminating a different channel of the dual-channel microscope and two detectors, each coupled to a different channel of the dual-channel microscope for acquiring images of the specimen. Means are provided for separating the channels of the dual-channel microscope, so that the two detectors can acquire the images of the specimen at substantially the same time. In one embodiment, the channels of the dual-channel microscope may be spectrally separated by configuring the two illuminators, so that they produce light in two substantially non-overlapping spectral ranges.

Abstract: A system is provided herein for inspecting a specimen. In one embodiment, the system may include a dual-channel microscope, two illuminators, each coupled for illuminating a different channel of the dual-channel microscope and two detectors, each coupled to a different channel of the dual-channel microscope for acquiring images of the specimen. Means are provided for separating the channels of the dual-channel microscope, so that the two detectors can acquire the images of the specimen at substantially the same time. In one embodiment, the channels of the dual-channel microscope may be spectrally separated by configuring the two illuminators, so that they produce light in two substantially non-overlapping spectral ranges.

Abstract: Serrated Fourier filters and inspection systems are provided. One Fourier filter includes one or more blocking elements configured to block a portion of light from a wafer. The Fourier filter also includes periodic serrations formed on edges of the one or more blocking elements. The periodic serrations define a transition region of the one or more blocking elements. The periodic serrations are configured to vary transmission across the transition region such that variations in the transmission across the transition region are substantially smooth. One inspection system includes a Fourier filter configured as described above and a detector that is configured to detect light transmitted by the Fourier filter. Signals generated by the detector can be used to detect the defects on the wafer.

Abstract: Systems and methods for blocking specular reflection and suppressing modulation from periodic features on a specimen are provided. One inspection system configured to block specular reflection and suppress modulation in an image of a specimen includes an illumination subsystem configured to illuminate the specimen with a predetermined pattern of spatially incoherent light. The system also includes an optical element configured to block light reflected from periodic features formed on the specimen and at least some light diffracted from the periodic features. The system further includes a detector configured to detect light that passes through the optical element and to generate an image of the specimen in response to the detected light. The optical element blocks specular reflection and at least partially suppresses modulation in the image due to the periodic features. The system also includes a processor configured to detect defects on the specimen using the image.

Abstract: Fourier filters and wafer inspection systems are provided. One embodiment relates to a one-dimensional Fourier filter configured to be included in a bright field inspection system such that the bright field inspection system can be used for broadband dark field inspection of a wafer. The Fourier filter includes an asymmetric illumination aperture configured to be positioned in an illumination path of the inspection system. The Fourier filter also includes an asymmetric imaging aperture complementary to the illumination aperture. The imaging aperture is configured to be positioned in a light collection path of the inspection system such that the imaging aperture blocks light reflected and diffracted from structures on the wafer and allows light scattered from defects on the wafer to pass through the imaging aperture.

Abstract: Systems and methods for providing illumination of a specimen for inspection are provided. One system includes one or more first optical elements configured to illuminate a diffuser with a predetermined pattern of coherent light. The system also includes one or more second optical elements configured to image light exiting the diffuser onto an illumination pupil of the system such that the predetermined pattern is reproduced in the illumination pupil. In addition, the system includes an objective lens configured to focus light from the predetermined pattern in the illumination pupil onto a specimen plane. In one embodiment, the light focused onto the specimen plane is not substantially coherent. In another embodiment, the predetermined pattern is selected based on an illumination mode selected for the inspection of the specimen.