Abstract: A method for inspecting a patterned surface employs reference data related to the pattern to provide a map for identifying regions which are expected to generate equivalent images. These regions are then compared in an image-to-image comparison to identify possible defects. In a first implementation, the regions are related by local symmetry operators. In a second, disjoint corner features or other features are classified and similar features compared.

Abstract: A method for inspecting a patterned surface employs reference data related to the pattern to provide a map for identifying regions which are expected to generate equivalent images. These regions are then compared in an image-to-image comparison to identify possible defects. In a first implementation, the regions are related by local symmetry operators. In a second, disjoint corner features or other features are classified and similar features compared.

Abstract: A method for comparing periodic structures, such as wafer dies, by obtaining signals from the images of two swaths of the wafer dies. The signals for each wafer die are then compared to at least the signals from the two nearest neighbor dies. Preferably, these two neighbor dies are located on either side of the die, in the same row as that die. However, for edge dies, at least one neighbor die is located in another row, preferably an adjacent row. Since images are taken from an even number of swaths by the camera in a first row of dies before images are taken from a similar number of swaths in a second row of dies, the camera (and hence the resultant image) is correctly oriented for obtaining signals from the swaths in the second row of dies. This permits the correct comparison of signals obtained from the first swath of the first row of dies to signals obtained from the first swath of the second row of dies.

Abstract: A method to compare similar physical areas of an inspection area using a scanning arrangement. The inspection area has a periodic pattern having a repeat vector. The scanning arrangement has a stage, a drive mechanism and at least one circular scanner. The circular scanner has a scanning head and an axis of rotation about which the scanning head performs a circular scanning motion. The drive mechanism is configured to provide relative movement between the stage and the axis of rotation. The method includes the steps of: scanning the inspection area by a combination of circular scanning of the scanning head and by generating relative movement between the stage and the axis of rotation such that pairs of curved scanning paths are related by an integer multiple of the repeat vector; and comparing at least one of said pairs of the curved scanning paths by a pixel to pixel comparison.

Abstract: A method to compare similar physical areas of an inspection area using a scanning arrangement. The inspection area has a periodic pattern having a repeat vector. The scanning arrangement has a stage, a drive mechanism and at least one circular scanner. The circular scanner has a scanning head and an axis of rotation about which the scanning head performs a circular scanning motion. The drive mechanism is configured to provide relative movement between the stage and the axis of rotation. The method includes the steps of: scanning the inspection area by a combination of circular scanning of the scanning head and by generating relative movement between the stage and the axis of rotation such that pairs of curved scanning paths are related by an integer multiple of the repeat vector; and comparing at least one of said pairs of the curved scanning paths by a pixel to pixel comparison.

Abstract: A Cartesian scanning system for scanning a surface of a sample. The scanning system includes a light source assembly configured to produce at least one collimated beam of light, a light sensing system, a stage configured for mounting the sample thereon and a linear track having a direction of elongation. The linear track and the stage are configured to move relative to each other. The scanning system also includes a scanning head having a reflecting system which is configured to direct the collimated beam of light onto the surface and to direct a beam of light reflected from the surface to the light sensing system. The scanning head is slidably associated with the linear track so as to be moveable in a direction parallel to a direction of elongation of the linear track. Also included are a position determination system and a scan displacement correction system.

Abstract: A method to scan a surface having a periodic pattern using a scanner. The periodic pattern has a first direction of periodicity having a periodic length. The scanner is configured to produce an image having a plurality of pixels, each of the pixels having a pixel origin. The method includes the steps of positioning the first direction of periodicity of the periodic pattern at an angle relative to the scanning direction of the scanner and scanning the surface by generating relative movement between the scanner and the surface.