Patent ID: 6366690
Filing Date: 2002-04-02
Classification: G01N

Abstract:
A method for the analysis of patterned semiconductor wafers, which comprises the steps of:(a) irradiating each wafer with a laser beam; (b) causing a relative motion of each wafer with respect to said beam, to cause said beam to scan the wafer; (c) sensing, in an array of fixed directions, the light scattered by the wafer; (d) for each fixed direction, converting said scattered light of step (c) into an electric signal; (e) sampling said electric signal at a predetermined sampling frequency to determine an array of values with each sampling, wherein each value of the array corresponds to one of the fixed directions, such that the sampling defines a pixel of the wafer; (f) defining a pixel signature from said array of values of step (e); (g) defining conditions for a predetermined number of pixel signatures, such that the pixel signature conditions must be satisfied to consider the wafer faultless; (h) determining whether the pixel signatures of each wafer meet the conditions of step (g); and (i) perfoming pixel-based inspections, without requiring reference pattern data, to classify the pixels which meet the conditions of step (g) as acceptable pixels and to classify the remaining pixels as â€œsuspectâ€  pixels.