Inspection system utilizing dark-field illumination
First Claim
1. Apparatus for inspecting corresponding portions of patterns that comprise features defined on a substrate and for providing an indication of defects in said portions, said apparatus comprisingmeans for illuminating said corresponding portions in a dark-field mode to scatter light from illuminated feature or defect edges,and means responsive only to light scattered from edges in said corresponding portions for generating difference signals representative of defects in said illuminated portions.
1 Assignment
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Accused Products
Abstract
Integrated-circuit wafers and the lithographic masks and reticles used in their fabrication must be inspected for defects. Conventional systems accomplish such inspection by bright-field illumination and comparison of corresponding portions of two supposedly identical patterns on the workpiece. The minimum-size defect that can be so detected is set by misalignment between the patterns. Dark-field illumination of the portions to be compared significantly enhances the detection capabilities of such an inspection system. For a given misalignment, dark-field illumination permits the detection of defects at least four times smaller than those detectable in a conventional bright-field-illuminated system.
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Citations
28 Claims
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1. Apparatus for inspecting corresponding portions of patterns that comprise features defined on a substrate and for providing an indication of defects in said portions, said apparatus comprising
means for illuminating said corresponding portions in a dark-field mode to scatter light from illuminated feature or defect edges, and means responsive only to light scattered from edges in said corresponding portions for generating difference signals representative of defects in said illuminated portions.
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10. Defect-detecting apparatus for inspecting a workpiece that includes features on a substrate, the features constituting at least two patterns that are intended to be identical, said apparatus comprising
two photodetector arrays, two lens assemblies respectively associated with said arrays, each assembly being responsive to incident scattered light from a respective corresponding pattern portion for directing said light onto its respective array, means for illuminating corresponding portions of said patterns only at a glancing angle in a dark-field mode to cause light to be scattered from edges in said portions and towards said respective lens assemblies, and means responsive to electrical signals provided by said photodetector arrays for in effect comparing the light scattered from said illuminated portions and thereby providing an indication of defects in said portions.
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15. A method of inspecting a workpiece for defects, the workpiece comprising a substrate having features thereon, the features constituting at least two supposedly identical patterns, said method comprising the steps of
illuminating corresponding portions of said patterns in a dark-field mode to cause light to be scattered from edges of features and defects included in said portions, collecting substantially only said scattered light, and utilizing only said collected light to generate output signals representative of the defect condition of said illuminated portions.
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21. Apparatus for inspecting a workpiece to determine whether or not a region thereof is patterned in accordance with prescribed design standards, said apparatus comprising
means for illuminating said region to cause light to be scattered from feature or defect edges in said region, means for collecting only light scattered from the entire extent of said edges and for providing an output signal representative thereof, means for providing a comparison signal derived from a pattern supposedly identical to the one in said region, and means for comparing said signals to provide an indication of whether or not said region is patterned in accordance with said prescribed design standards.
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25. A method of inspecting a workpiece to determine whether or not a region thereof is patterned in accordance with prescribed design standards, said method comprising the steps of
illuminating said region to cause light to be scattered from feature or defect edges in said region, collecting only light scattered from the entire extent of said edges and for providing an output signal representative thereof, providing a comparison signal derived from a pattern supposedly identical to the one in said region, and comparing said signals to provide an indication of whether or not said region is patterned in accordance with said prescribed design standards.
Specification