Inspection system utilizing dark-field illumination
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United States of America Patent
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Jun 17, 1986
Grant Date -
N/A
app pub date -
Jan 25, 1984
filing date -
Jan 25, 1984
priority date (Note) -
Expired
status (Latency Note)
Importance
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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