Patent ID: 6549006
Filing Date: 2003-04-15
Classification: G01B

Abstract:
A method for identifying metal layer thickness of an inspection sample, said method comprising:obtaining initial resistance and reactance measurements from said inspection sample using an eddy current probe positioned at a distance relative to said inspection sample; increasing the relative distance between said eddy current probe and said inspection sample, and when an eddy current on air signal is detected, obtaining terminating resistance and reactance measurements; calculating an inspection sample intersecting line using said initial and terminating resistance and reactance measurements; determining an intersecting point between a previously defined natural intercepting curve and said inspection sample intersecting line, wherein said natural intercepting curve is defined by a plurality of initial resistance and reactance measurements obtained from a plurality of calibration samples having a range of known-thicknesses; locating a reactance voltage of said intersecting point along a digital calibration curve to identify a closest two of said plurality of calibration samples, wherein said digital calibration curve is defined by a plurality of initial reactance measurements and corresponding thicknesses of said plurality of calibration samples; and identifying said metal layer thickness of said inspection sample by performing an interpolation between said closest two of said plurality of calibration samples.