Patent ID: 6741076
Filing Date: 2004-05-25
Classification: G01B

Abstract:
A method for thickness estimation of a conductive top layer of a substrate sample, said method comprising:(a) receiving said substrate sample after said substrate sample has undergone a top layer removal process removing a portion of said conductive top layer of said substrate sample; (b) obtaining initial resistance and reactance measurements from said substrate sample using an eddy current probe positioned at an initial distance relative to said substrate sample; (c) obtaining terminating resistance and reactance measurements from said substrate sample using said eddy current probe positioned at a modified distance relative to said substrate sample; (d) calculating an intersecting line using said initial and terminating resistance and reactance measurements; (e) determining an intersecting point between a previously defined natural intercepting curve and said intersecting line, wherein said natural intercepting curve is defined by a plurality of initial resistance and reactance measurements obtained from at least one calibration sample individually or collectively having a known range of top layer thicknesses; (f) locating a reactance voltage of said intersecting point along a digital calibration curve to identify a closest-two of said known range of top layer thicknesses, wherein said digital calibration curve is defined by a plurality of initial reactance measurements and corresponding top layer thicknesses of said at least one calibration sample; and (g) estimating a thickness of said conductive top layer of said substrate sample by approximating a location of said reactance voltage relative to said closest-two of said known range of top layer thicknesses of said at least one calibration sample.