Kla Corporation

Yonatan Vaknin

Amnon Manassen

Andrew V Hill

Vladimir Levinski

Daria Negri

Yoram Uziel

Nadav Gutman

Yuri Paskover

Avi Abramov

Anna Golotsvan

Yossi Simon

Nireekshan K Reddy

Nir BenDavid

Nachshon Rothman

Dror Yaacov

Yuval Lubashevsky

Itay Gdor

Avner Safrani

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.

Scanning scatterometry overlay metrology

An overlay metrology system may include an illumination source to generate illumination including two or more spectral bands having two or more center wavelengths. The system may include an optical sub-system to illuminate and image a sample, where the sample in accordance with the metrology recipe includes one or more cells with grating-over-grating structures formed as overlapping gratings with different pitches in different sample layers. The system may include collection pupil components to exclusively pass, for each of the two or more center wavelengths, two diffraction lobes from each of the different pitches of the grating-over-grating structures. A controller may receive images of the sample from the detectors generated in accordance with the metrology recipe and generate overlay measurements between at least some of the different layers of the sample based on the images.

Grating-over-grating overlay measurement with parallel color per layer

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.

Single grab overlay measurement of tall targets

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.

Imaging overlay with mutually coherent oblique illumination

A method includes generating a sequence of images of a semiconductor wafer from first and second detectors. The first detector images the wafer with first imaging parameters and the second detector images the wafer with second imaging parameters. The first or second imaging parameters are varied across the sequence of images to provide variation at sites across the wafer. The method includes providing a metric indicative of center-of-symmetry variations of first and second target features as a function of the varied imaging parameters based on the sequence of images. The method includes identifying a landscape of values of the varied image parameters for which the metric are below a predefined limit. The method includes generating a recipe for metrology measurements in which the varied imaging parameters are set to values within the landscape. The method includes generating metrology measurements from a production wafer based on the recipe.

Enhancing performance of overlay metrology

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.

Multi-directional overlay metrology using multiple illumination parameters and isolated imaging

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.

Growing community of inventors

Migdal Haemek, Israel

Yonatan Vaknin