Patent ID: 7386161
Filing Date: 2008-06-10
Classification: G01N,G06T

Abstract:
1. A method for detection of defects, concurrent with on-the-fly review and classification of defect candidates in a flat patterned object under test comprising the following parallel operations: acquiring images of the object; detecting a first defect of said object; assigning review worthiness values to said first defect through a defect detection sub-system having a plurality of defect detection sub-system modules operative according to a first relatively lower operating resolution; detecting a second defect of said object and assigning review worthiness values to said second defect acquiring images of smaller areas around said first defect reviewing said first defect, and classifying said first defect through a defect review sub-system having a plurality of defect review sub-system modules operative according to a second relatively higher resolution, wherein the detection of said second defect is performed concurrently with the review of the first defect; maximizing a number of higher priority defect candidates captured by said defect review sub-system modules and minimizing distance traveled by said defect review sub-system modules using a dynamic defect review sub-system module dispatching algorithm for optimizing motion in said concurrent higher resolution reviewing, wherein said dispatching algorithm further comprises: constructing, for each defect review sub-system and at each iteration of said motion optimization, a forward feasible motion graph in a Graph Theory sense with nodes corresponding to each defect candidate and current position of its associated module, and with arcs corresponding to feasible motions in between said nodes; associating costs for each said arc signifying a module movement from the first defect to the second defect according to a suitable cost function selected from functions representing the cost of missing other defects, distance of required motion and review worthiness of a target defect candidate, and thereby obtaining a resulting graph; solving the resulting graph for finding a minimum cost path, represented by an ordered sequence of defect to defect transitions, from the current location of the defect review sub-system module to the end of a window considered along scanning direction; and computing motion data for the defect review sub-system module for controlling motion of the defect review sub-system module.