Abstract: A mechanism for localizing a substrate relative to a projection camera or other apparatus over large travel distances is described. The mechanism includes one or more trucks that move with the stage in a primary direction and remain stationary when the stage moves in an ancillary direction. The position of the trucks, together with relative distances between the truck(s) and a stage on which the substrate is supported facilitates alignment.

Abstract: An optical metrology device includes an aperture that can be adjusted based on the thickness of the film on a sample. The aperture is adjusted to have a first aperture configuration or a second aperture configuration, where the second aperture configuration allows more light to pass. The aperture may be adjusted to use the second aperture configuration, e.g., if the thickness of the film produces a lateral shift from each internal reflection in the film at least 80% of the measurement spot size or the film thickness is greater than a predesignated amount, or if the light measured with the first aperture configuration and second aperture configuration differs by more than a predetermined threshold. The aperture may be in the source arm of the optical system, e.g., between the light source and the sample, or the receiver arm of the optical system, e.g., between the sample and the detector.

Abstract: A method for correcting misalignments is provided. An alignment for each device of a group of devices mounted on a substrate is determined. An alignment error for the group of devices mounted on the substrate is determined based on the respective alignment for each device. One or more correction factors are calculated based on the alignment error. The alignment error is corrected based on the one or more correction factors.

Abstract: Optical metrology is used to calibrate the plane-of-incidence (POI) azimuth error by determining and correcting an azimuth angle offset. The azimuth angle offset may be determined by measuring at least a partial Mueller matrix from a calibration grating on a sample held on a stage for a plurality of POI azimuth angles. An axis of symmetry is determined for a curve describing a value of a Mueller matrix element with respect to POI azimuth angle, for each desired wavelength and each desired Mueller matrix element. The axis of symmetry may then be used to determine the azimuth angle offset, e.g., by determining a mean, median or average of all, or a filtered subset, of the axes of symmetry. If desired, an axis of symmetry may be determined for data sets other than Mueller matrix elements, such as Fourier coefficients of measured signals.

Abstract: A surface topography of a sample with a transparent surface layer is measured using surface topographies of a reference sample. The surface topographies of the reference sample are measured before and after the deposition of an opaque film over the surface layer. A surface topography of the sample is measured at the same relative positions as the surface topography measurements of the reference sample. A height difference at multiple corresponding positions on the sample and the pre-opaque film reference sample is determined. The actual surface height of the reference sample at each position is known from the surface topography of the post-opaque reference sample. The actual surface topography of the sample is determined by combining the actual surface heights of the reference sample with the determined height differences. The resulting surface topography of the sample may be used to characterize the sample, such as detecting defects on the sample.