Patent ID: 6493063
Filing Date: 2002-12-10
Classification: G03F

Abstract:
A method for reducing critical dimension variation in a resist exposure system having a lens and a reticle, comprising:A) creating from the resist exposure system an exposure pattern with a distribution of the exposure pattern across an exposure field; B) measuring the distribution of the exposure pattern across the exposure field by generating an illumination beam with a cross section in the shape of a band with a length and a width which passes to the reticle, scanning the illumination beam across the reticle in a scan direction, wherein the length of the band is perpendicular to the scan direction and wherein the width of the band is parallel to the scan direction, and focusing the illumination beam onto a layer of resist on a semiconductor wafer; and C) correcting exposure from the resist exposure system according to the measured distribution of the exposure pattern across the exposure field by calculating local exposure energies from the distribution of the exposure pattern across the exposure field, determining a nominal exposure energy, and comparing the local exposure intensities with the nominal exposure energy by deriving an exposure function from the local exposure energies, and comparing the value of the exposure function at a location with the nominal exposure energy by separating the exposure function into a first function which is a function of a distance along the scan direction and is independent of a distance along a direction perpendicular to the scan direction, and a second function which is a function of the distance along the direction perpendicular to the scan direction and independent of the distance along the scan direction, comparing the nominal exposure energy with the first function at a location along the scan direction, and comparing the nominal exposure energy with the second function at a location along the direction perpendicular to the scan direction.