US 4,365,163 AGranted

Pattern inspection tool - method and apparatus

AssigneeInternational Business Machines Corporation

InventorsDonald E. Davis, Richard D. Moore, Philip M. Ryan, Edward V. Weber

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Abstract

This describes an automatic defect inspection system as could be applied to metallized masks or other patterns. The system causes each subfield to be individually aligned for inspection irrespective of the previous alignment of the pattern or any other sub-field. This is accomplished by scanning a preselected portion of each sub-field and adjusting the position of the scan based on the resulting signal while scanning a pre-established portion of the sub-field. In this way a portion of each sub-field is used as an alignment mark and stepping errors avoided. Once alignment is achieved a probe, comparable to the size of the minimum defect to be detected is scanned over the sub-field with an overlapping pattern to find defects such as excessive metal, metal in improper places or points where the metal is missing.

Claims13

Dependent claims

A method of positioning and inspecting a patterned workpiece comprising the steps of:

placing a patterned workpiece, provided with a multiplicity of patterns, to be inspected in an inspection apparatus,
directing a beam to scan a selected region overlying a first edge of a selected first pattern of said multiplicity of patterns on said workpiece,
measuring and storing the signal created by the beam scanning said region,
directing the beam to scan a second selected region overlying a second edge of said first pattern,
said second edge being substantially parallel to said first edge,
measuring and storing the signal created by the beam scanning said second region,
directing the beam to scan a third selected region overlying a third edge of said first pattern,
said third edge being at an angle with respect to said first and second edges,
measuring and storing the signal created by the beam scanning said third region,
directing the beam to scan a fourth selected region overlying a fourth edge of said first pattern,
said fourth edge being substantially parallel to said third edge,
measuring and storing the signal created by the beam scanning said fourth region, and
using said measured signals from said first, second, third and fourth regions to align the scanned edges of said first pattern to a predetermined inspection position,
directing the beam to scan over the entire said first pattern, measuring the signals created by the beam scanning said first pattern, and comparing the measured signals from said first pattern to the information used to create the patterned workpiece to detect defects in said pattern, and
directing the beam to scan the area surrounding said first pattern and comparing the measured signal from the area surrounding said one pattern to the information used to create the patterned workpiece to detect defects outside of said first pattern.

12 more elements

A method of inspecting metallized, patterned glass masks comprising the steps of:

placing a glass mask, having a plurality of replicated fields thereon, each field comprising metallized and unmetallized surface portions, on a table positionable in a plane normal with respect to the nominal position of an electron beam,
aligning said mask to a first position with respect to said nominal position using gross alignment marks on said mask,
exposing a metallized portion of one of said fields to said electron beam and measuring the back-scattered electron current from said metallized portion generated by the beam impinging on said metallized portion,
exposing an unmetallized portion of said one of said fields to said beam and measuring the back-scattered electron current from said unmetallized portion generated by the beam impinging on said unmetallized portion,
establishing a threshold level between the measured currents,
traversing, a first region overlapping a first edge of a selected metallized pattern in said one of said fields with said beam and measuring the back-scattered electron current from said region,
moving said beam with respect to said mask an amount equal to the pre-established width of said selected metallized pattern,
traversing a second region overlapping a second edge of said selected metallized pattern, said second edge being parallel to said first edge, with said beam and measuring the back-scattered electron current from said region,
comparing the measured current from the first region with the measured current from the second region,
determining the difference between the measured currents,
positioning said table to resposition said beam with respect to said pattern to eliminate the difference between said measured currents and to compensate for positional error of said beam in said first position with respect to said pattern,
repeating said travserving, moving comparing, and determining steps on parallel edges of said pattern at an angle with respect to said first and second edges,
repositioning said table to a third position to compensate for positional error of said beam in said second position with respect to said pattern, and
traversing said beam over the said selected pattern,
measuring the back-scattered current from said pattern, and
comparing said current with a predetermined level to detect defects in said pattern
directing the beam to the unmetallized portion of said mask surrounding said selected metallized pattern, and
observing the returned signal for a change in level indicative of a defect in said unmetallized portion.

15 more elements

Dependencies are inferred from the claim text.