Use of starburst patterns in optical lithography

Abstract

We propose to use a starburst pattern as a powerful diagnostic tool in optical lithography. A starburst pattern of constant line/pitch ratio versus radius can be used as a quick diagnostic tool for various off-axis illumination techniques, in particular those that have non-isotropic illumination shapes. Because such a starburst features a multitude of pitches at a multitude of angles, a large area of the pupil is sampled. Careful analysis of the image of the starburst, gives information on the kind of illumination that is used, the resolution limit for all angles, and can be used to find the best focus position. We perform an analysis of the characteristic regions of a starburst image for a given illumination and interpret the images accordingly. Aerial image simulations of the starburst patterns are analyzed and compared to the experimental results.