Methods and systems for pattern design with tailored response to wavefront aberration

摘要

The present invention relates to methods and systems for designing gauge patterns that are extremely sensitive to parameter variation, and thus robust against random and repetitive measurement errors in calibration of a lithographic process utilized to image a target design having a plurality of features. The method may include identifying most sensitive line width/pitch combination with optimal assist feature placement which leads to most sensitive CD (or other lithography response parameter) changes against lithography process parameter variations, such as wavefront aberration parameter variation. The method may also include designing gauges which have more than one test patterns, such that a combined response of the gauge can be tailored to generate a certain response to wavefront-related or other lithographic process parameters. The sensitivity against parameter variation leads to robust performance against random measurement error and/or any other measurement error.

主权项

1. A method, implemented by a computer, selecting a set of test patterns for being imaged via a projection lithography system, the set of test patterns having a predetermined characteristic of a lithography response to a predefined wavefront aberration term of the projection lithography system, the predefined wavefront aberration term mathematically representing a characteristic of a wavefront aberration of the lithography system, the method comprising the steps of:
a) generating a mathematical series expansion as an approximation of the lithography response as a function of the predefined wavefront aberration term; b) selecting a set of selected expansion terms from the mathematical series expansion; c) generating a cost function comprising the selected expansion terms; d) solving, using the computer, the cost function to define coefficients corresponding to the predefined wavefront aberration term while constraining at least part of the unselected expansion terms substantially to zero; and e) selecting the set of test patterns from among a group of patterns using the coefficients.