Patent ID: 6310684
Filing Date: 2001-10-30
Classification: G01M,G03F

Abstract:
A method of measuring spherical aberration in a projection system in which a mask pattern is projected in a reduced scale with a light having a wavelength of .lambda., comprising the steps of:(a) projecting a first mask pattern onto a photosensitive object in a reduced scale, said first mask pattern being defined by light-permeable portions and light-impermeable portions each sandwiched between said light-permeable portions, each of said light-permeable portions having a width equal to said wavelength .lambda.;(b) projecting a second mask pattern onto said photosensitive object in a reduced scale, said second mask pattern being defined by light-permeable portions and light-impermeable portions each sandwiched between said light-permeable portions, each of said light-permeable portions having a width equal to .lambda./2;(c) exposing said photosensitive object to said light having a wavelength of .lambda., and developing said photosensitive object;(d) measuring a first location of said photosensitive object at which a width of said light-impermeable portions of said first mask pattern is focused in a minimum, and a second location of said photosensitive object at which a width of said light-impermeable portions of said second mask pattern is focused in a minimum; and(e) measuring spherical aberration, based on said first and second locations.