Patent ID: 6978215
Filing Date: 2005-12-20
Classification: G01Q,G02B,H01J

Abstract:
1. A method of determination of true nonlinearity of scan along a selected direction X or Y in scan microscope, comprising the steps of orienting a test object on a microscope space so that a direction of strips of periodic pressure is perpendicular to a scanning line; scanning of the test object along the axis X and Y for forming a first two dimensional array of signal value; line by line measuring of pitch values between two strips of a diffraction grating and conversion of a first two dimensional array of signal values into a first two dimensional array of pitch values; averaging of the pitch values along all lines of a frame along a direction perpendicular to the scanning line and converting of the first two dimensional of array of pitch values into a first one dimensional profile of dependence of the average pitch from a coordinate along the scanning line; displacement of the test object along the scanning line by a value of one pitch along or opposite to a probe movement; another scanning of the test object along the axis X and Y for forming a second, displaced array of signal values; line by line measuring of pitch values between two neighboring strips of the grating and converting of the second two dimensional array of signal values into a second two dimensional array of pitch values; averaging of the pitch values along all lines of the frame along a direction perpendicular to the scanning line and converting the second two dimensional array of pitch values into a second one dimensional profile of dependence of the average pitch of the coordinate along the scanning line; calculating of a differential nonlinearity of scan along the selected scanning direction in accordance with the expression wherein DNL (I) is a differential nonlinearity of scan on a portion of a field of view with number I+1 relative to the portion with number I; P′(I) is an average pitch with number I measured in accordance with the second, shifted one dimensional profile P(I) is an average value of the same pitch with I measured in accordance with the first, initial one dimensional profile, with selecting a plus sign if a displacement was performed along the scanning line and minus sign if the test object was displaced opposite to the movement of the probe along the scanning line, with I from 1 to N wherein N is a number of fixed pitches along the line of scanning; calculated an integrated nonlinearity along a whole field of view in accordance with the formula wherein INL(I+1) is an integral nonlinearity of scan on the portion of the field of view with number I+1; DNL(k) is a differential nonlinearity on the portion of the field of view with the number k, and performing summation on all portions on the field of view preceding the portion with number I+1; calculating a differential non uniformity of the test object in accordance with the expressions DNU(I,J)=±{P(I)−P′(J)} and I=J±1, wherein DNU(I,J) is a differential non uniformity of the pitch of test object on the portion between the pitch with a number I and the pitch with the number J; P(I) is an average pitch with the number I in the first, initial one dimensional profile; P′(J) is an average pitch with the number J on the second, shifted one dimensional profile, with selection of a plus sign when the displacement was performed along the displacement of the probe and the minus sign where the displacement was performed in an opposite direction; and calculation of an integrated non uniformity of the test object in accordance with the formula where I=J+1 is a corrected, true value of the pitch with number I+1; P(1)− is a base value of the pitch with number 1; and performing summation on all pitches preceding the pitch with the number I+1.