Abstract: A patterned specimen inspection system achieves the inherent advantages of the die to statistical image (DSI) inspection mode for repetitive and random patterns and simultaneously achieves the inspection speed of the optical pattern filtering (OPF) mode. A preferred embodiment entails producing a patterned specimen wafer image with coherent optical spatial frequency filtering, as in the OPF mode, and carrying out defect detection by pixel comparison, as in the DSI mode. For repetitive and random pattern areas, implementation of the invention increases the inspection speed of the DSI mode to approach that of the OPF mode because image spatial filtering enables the use of a large sized unit pixel. For the repetitive pattern, the ability to use a large unit pixel size results from the complete removal of light energy from the repetitive patterns in the image.

Abstract: An inspection system (2) employs a beam of monochromatic light (12) that travels through a Fourier transform lens (16) before striking a specimen wafer (4) at an angle (.THETA.) with respect to the normal (26) of the specimen wafer (4) to produce diffracted light (28b ) and 28c) that has a broad spatial frequency spectrum which can be selectively filtered to produce a dark field image pattern of the various sized defects in an inspection area (22) of the wafer. The nearly collimated beam of monochromatic light strikes the wafer at an angle (.THETA.) with respect to the normal of the wafer of between zero degrees and a predetermined maximum angle. For the inspection system disclosed, the predetermined maximum angle is the angle formed when the beam of monochromatic light is as far away from the optic axis as possible yet still within the numerical aperture of the Fourier transform lens (16). Moreover, if a specific range of defect sizes is anticipated, the system can be optimized by setting the angle (.THETA.

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: 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: Apparatus provides an incident light beam which illuminates the surface of a resist coated grooved disc, having an exposure pattern of signal elements formed within the groove, with a light spot that spans a plurality of convolutions of the groove. As the resist coating is developed, portions of the resist coating corresponding to the exposure pattern are removed and the emerging structure of the signal elements serves as a diffraction grating which diffracts the incident light beam. Photodetector apparatus positioned to intercept a selected portion of the diffracted beam provides an output corresponding to the light power in the selected portion. Means responsive to the output of the photodetector are provided for directly indicating the achievement of a desired emerging signal element geometry in the region illuminated by the light spot to thereby control the resist development process.

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.