Patent ID: 8982347
Filing Date: 2015-03-17
Classification: G01B,G03F

Abstract:
1. A method to estimate a value representative for a level of alignment mark deformation on a processed substrate using an alignment system comprising an alignment sensor system that is able to emit light at different measuring frequencies to reflect from an alignment mark on the substrate and to detect a diffraction pattern in the reflected light in order to measure an alignment position of the alignment mark, the method comprising: providing a substrate with N alignment marks, wherein each alignment mark is provided in a predetermined alignment position; processing the substrate; for each of the N alignment marks, measuring an alignment position after processing of the substrate using the alignment sensor system, wherein the light is emitted at the respective two or more measuring frequencies towards the alignment mark; for each of the two or more measuring frequencies, detecting a corresponding diffraction pattern from the alignment mark reflected light; determining an alignment position from the detected two or more diffraction patterns, such that for each of the N alignment marks a set of alignment positions is obtained corresponding to the two or more measuring frequencies of the alignment sensor system; for each of the N alignment marks, determining an alignment position deviation for each alignment position of the set of alignment positions by comparing the alignment positions with the predetermined alignment position, thereby obtaining a set of alignment position deviations per alignment mark; for each of the N alignment marks, determining a value which is representative for a spread in the set of alignment position deviations to estimate the level of deformation of the alignment mark; and for each of the N alignment marks, determining a weighing factor based on the value, such that the weighing factor is high for alignment marks having minimal alignment mark deformation and low for alignment marks having a relatively large alignment mark deformation.