Patent ID: 6456736
Filing Date: 2002-09-24
Classification: G01R,G03F,G06T,H01L

Abstract:
A method of inspecting the surface of an article having a plurality of comparable pattern units, each pattern unit having a feature, which method comprises:(a) selecting for measurement a number of the plurality of pattern units; (b) measuring a critical dimension (CD) of the feature in each of the selected pattern units to produce a first plurality of CDs; (c) calculating a statistical function using the first plurality of CDs to produce a first statistical function value; (d) selecting for measurement at least one additional pattern unit of the plurality of pattern units; (e) measuring the CD of the feature in the at least one additional pattern unit; (f) calculating the statistical function using the first plurality of CDs and the CD of the feature in the at least one additional pattern unit to produce a current statistical function value; and (g) comparing the first and current statistical function values to produce a first differential statistical function value, and terminating the inspection when the first differential statistical function value is less than or equal to a predetermined differential statistical function value; wherein when the first differential statistical function value is greater than the predetermined differential statistical function value, the method further comprises:(h) selecting a further additional pattern unit of the plurality of pattern units for measurement; (i) measuring the CD of the feature in the further additional pattern unit; (j) calculating the statistical function using the first plurality of CDs and the CDs of the features in all the additional pattern units to produce an updated statistical function value; (k) comparing the current and updated statistical function values to produce a current differential statistical function value; and (l) terminating the inspection when the current differential statistical function value is less than or equal to the predetermined differential statistical function value.