Abstract: In an imaging system (10) for detecting defects in a specimen (14) having a repetitive pattern (16), a spatial filter (50) receives a spatial frequency spectrum produced by a Fourier transform lens (34) and blocks preselected spatial frequency components thereof. The spatial filter includes an array of substantially parallel opaque stripes (70a-70c) that are positioned on a substantially transparent substrate (72). In one embodiment, the stripes are spaced apart by equal distances (78) and are of increasing widths (76a-76c) that correspond to the orders of diffraction of the Fourier transform pattern (45) produced by the Fourier transform lens. The spatial filter can be used to filter light spots forming a Fourier transform pattern for specimens having repetitive pattern sizes included within a specified range of sizes.

Abstract: A method and an apparatus detect in a light pattern the presence of defects (10') in a photomask (10) to which the light pattern corresponds. An inspection area (36) that includes the light pattern is partitioned into stripe regions (72). The width (70) of a stripe region corresponds to the maximum extent of the image window (54) of a charge-coupled camera device (42) that is employed to scan continuously each stripe region at a nominally constant speed. Each stripe region is divided into a first array (90) of pixel elements (92) arranged in rows (94) and columns (96). The camera device comprises plural light detecting elements (84) that are arranged in a second array (82) of rows (86) and columns (88). The camera continuously traverses the columns of the first array in a direction along the length of the stripe region and acquires in row-by-row fashion quantities of charge which correspond to the intensities of the light present in the pixel elements with which the light detecting elements are aligned.

Abstract: An inspection system (10, 100) employs a Fourier transform lens (34, 120) and an inverse Fourier transform lens (54, 142) positioned along an optic axis (48, 144) to produce from an illuminated area of a patterned specimen wafer (12) a spatial frequency spectrum whose frequency components can be selectively filtered to produce an image pattern of defects in the illuminated area of the wafer. Depending on the optical component configuration of the inspection system, the filtering can be accomplished by a spatial filter of either the transmissive (50) or reflective (102) type. The lenses collect light diffracted by a wafer die (14) aligned with the optic axis and light diffracted by other wafer dies proximately located to such die. The inspection system is useful for inspecting only dies having many redundant circuit patterns.

Abstract: An apparatus and a method employ on a subject at least one holographic optical element that develops two beams of focused light whose focal configurations appear in predetermined locations which correspond to the position of the subject in the system. In a first preferred embodiment, two holographic optical elements are recorded on a subject that is to be aligned and supported by a holder assembly. During exposure of the holographic optical elements, the light rays passing through the plate converge of two focal points that have position coordinates which define their locations in the coordinate space of the optical system. Each focused point of light strikes a position sensitive detector which develops output signals that represent the position coordinates of the focused point of light in the system.

Abstract: A translatable and rotatable mechanism is employed in optical processing apparatus for exposing a specimen pattern and inspecting light pattern or image developed from it. The mounting mechanism includes a plate that is rotatably mounted on a linear positioning table assembly. The plate includes a substrate arm and a camera arm that extend in opposite directions from the axis of rotation of the plate. The specimen pattern, such as a photomask, is positioned on the free end of the substrate arm, and a video camera is positioned on the free end of the camera arm. Whenever the plate is rotated to an exposure orientation, the photomask diffracts light rays emanating from a laser. The diffracted light rays interfere with a reference beam to form a hologram. Whenever the plate is rotated 180.degree. to an inspection orientation, a reconstructed imate of the photomask appears at the location where the photomask was positioned during exposure.

Abstract: An inspection system (10, 100) employs a Fourier transform lens (34, 120) and an inverse Fourier transform lens (54, 142) positioned along an optic axis (48, 144) to produce from an illuminated area of a patterned specimen wafer (12) a spatial frequency spectrum whose frequency components can be selectively filtered to produce an image pattern of defects in the illuminated area of the wafer. Depending on the optical component configuration of the inspection system, the filtering can be accomplished by a spatial filter of either the transmissive (50) or reflective (102) type. The lenses collect light diffracted by a wafer die (14) aligned with the optic axis and light diffracted by other wafer dies proximately located to such die. The inspection system is useful for inspecting only dies having many redundant circuit patterns.