Abstract: An overlay metrology system may include an objective lens, illumination optics to illuminate an overlay target including a first grating with a first pitch on a first sample layer and a second grating with a second pitch on a second sample layer, where the first and second sample layers are separated by a layer separation distance greater than a depth of field of the objective lens. The system may further include collection optics with a radially-varying defocus distribution to compensate for the layer separation distance such that the first and second gratings are simultaneously in focus on the detector.

Abstract: A method for metrology includes directing at least one illumination beam to illuminate a semiconductor wafer on which at least first and second patterned layers have been deposited in succession, including a first target feature in the first patterned layer and a second target feature in the second patterned layer, overlaid on the first target feature. A sequence of images of the first and second target features is captured while varying one or more imaging parameters over the sequence. The images in the sequence are processed in order to identify respective centers of symmetry of the first and second target features in the images and measure variations in the centers of symmetry as a function of the varying image parameters. The measured variations are applied in measuring an overlay error between the first and second patterned layers.

Abstract: An optical metrology system may include an overlay metrology tool for characterizing an overlay target on a sample, where the overlay target includes first-direction periodic features in a first set of layers of the sample, and second-direction periodic features in a second set of layers of the sample. The overlay metrology tool may simultaneously illuminate the overlay target with first illumination beams and second illumination beams and may further generate images of the overlay target based on diffraction of the first illumination beams and the second illumination beams by the overlay target, where diffraction orders of the first illumination beams contribute to resolved image formation of only the first-direction periodic features, and where diffraction orders of the second illumination beams contribute to resolved image formation of only the second-direction periodic features. The system may further generate overlay measurements along the first and second measurement directions based on the images.

Abstract: An optical metrology system may include an overlay metrology tool for characterizing an overlay target on a sample, where the overlay target includes first-direction periodic features in a first set of layers of the sample, and second-direction periodic features in a second set of layers of the sample. The overlay metrology tool may simultaneously illuminate the overlay target with first illumination beams and second illumination beams and may further generate images of the overlay target based on diffraction of the first illumination beams and the second illumination beams by the overlay target, where diffraction orders of the first illumination beams contribute to resolved image formation of only the first-direction periodic features, and where diffraction orders of the second illumination beams contribute to resolved image formation of only the second-direction periodic features. The system may further generate overlay measurements along the first and second measurement directions based on the images.

Abstract: An overlay metrology system may include an illumination an illumination source to generate an illumination beam, one or more illumination optics to direct the illumination beam to an overlay target on a sample as the sample is scanned relative to the illumination beam along a scan direction, the target including one or more cells having Moiré structures. The system may also include two photodetectors at locations of a pupil plane associated with Moiré or overlapping diffraction orders from the Moiré structures. The system may then generate overlay measurements based on time-varying interference signals captured by the detector as the sample is scanned.

Abstract: An overlay metrology system may include illumination sources configured to generate one or more pairs of mutually coherent illumination beams and illumination optics to direct the pairs of illumination beams to an overlay target at common altitude incidence angles and symmetrically opposed azimuthal incidence angles, where the overlay target includes two or more grating structures distributed along one or more measurement directions. The system may further include imaging optics to image the overlay target onto detectors when implementing the metrology recipe, where an image of a particular one of the two or more grating structures is generated exclusively with a single non-zero diffraction order of light from each of the illumination beams within the particular one of the pairs of illumination beams. The system may further include a controller to determine overlay measurements based on images of the overlay target.

Abstract: A method for metrology includes directing at least one illumination beam to illuminate a semiconductor wafer on which at least first and second patterned layers have been deposited in succession, including a first target feature in the first patterned layer and a second target feature in the second patterned layer, overlaid on the first target feature. A sequence of images of the first and second target features is captured while varying one or more imaging parameters over the sequence. The images in the sequence are processed in order to identify respective centers of symmetry of the first and second target features in the images and measure variations in the centers of symmetry as a function of the varying image parameters. The measured variations are applied in measuring an overlay error between the first and second patterned layers.

Abstract: An overlay metrology system may include an overlay metrology tool suitable for measurement of an overlay target on a sample, the overlay target including one or more grating structures with patterned features distributed along one or more measurement directions. The overlay metrology tool may include an objective lens and an illumination pathway to illuminate the overlay target with two or more oblique illumination lobes distributed among one or more illumination distributions such that, for each of the measurement directions, diffraction orders of the one or more illumination distributions by the overlay target that are collected by the objective lens exclusively include a 0-order diffraction lobe and a single first-order diffraction lobe from at least one of the two or more illumination lobes. The overlay metrology tool may further include at least one detector to image the sample and a controller to generate overlay measurements based on the images.

Abstract: A method for metrology includes directing at least one illumination beam to illuminate a semiconductor wafer on which at least first and second patterned layers have been deposited in succession, including a first target feature in the first patterned layer and a second target feature in the second patterned layer, overlaid on the first target feature. A sequence of images of the first and second target features is captured while varying one or more imaging parameters over the sequence. The images in the sequence are processed in order to identify respective centers of symmetry of the first and second target features in the images and measure variations in the centers of symmetry as a function of the varying image parameters. The measured variations are applied in measuring an overlay error between the first and second patterned layers.