Patent ID: 6594002
Filing Date: 2003-07-15
Classification: G01B,H01L

Abstract:
A method of determining the symmetric error of a measurement instrument that measures features of a semiconductor wafer, the method comprising;collecting sensor data from a number of measurement runs on a front and back surfaces of a wafer wherein the wafer is oriented at a different angle relative to the instrument for each run, yielding a front data set and a back data set for each angle; organizing the data in each set into a wafer-fixed coordinate frame; reflecting all back surface data about a diameter of the wafer creating a reflected back data set; for each wafer angle, subtracting the reflected back data from the front data and dividing the result by two, yielding an angled wafer average; for each wafer angle, adding the reflected back data to the front data and dividing the result by two, yielding an angled instrument average; and calculating a symmetric error signature by taking the average of all angled instrument averages.