Patent ID: 7042569
Filing Date: 2006-05-09
Classification: G03F,H01L

Abstract:
1. A method of measuring alignment accuracy between two or more patterned layers formed on a substrate comprising: forming a test area as part of the patterned layers, wherein a first diffraction grating is built into a patterned layer A and a second diffraction grating is built into a patterned layer B, the two gratings substantially overlapping, said test area further including one or more additional layers which do not have diffraction gratings formed therein; observing the test area using an optical instrument capable of measuring any one or more of transmission, reflectance, or ellipsometric parameters as a function of any one or more of wavelength, polar angle of incidence, azimuthal angle of incidence, or polarization of the illumination and detection; and determining the geometric parameters of the gratings and the additional layers, said geometric parameters including the offset between the gratings, by fitting the measurements from the optical instrument to an optical model, wherein the optical model accounts for the diffraction of the electromagnetic waves by the gratings and the interaction of the gratings with each other's diffracted field and the effects of the additional layers, wherein the first and second diffraction gratings have different pitches.