Improvement of CD uniformity in 180 nm LSI manufacturing by optimizing illumination system

Line width control is a key factor in LSI manufacturing. This paper describes the relationship between line width uniformity and the illumination system of an exposure tool. Variation in the local value of partial coherence a is the cause of the optical proximity effect (OPE) variation across the image field of an exposure tool. By quantifying partial coherence /spl sigma/ and decreasing a variation, OPE variation within the image field was improved from 21.2 nm to 8.8 nm. We reduced OPE variation among tools by setting up these tools with agreeing a values. This paper also discusses the effect of illumination source uniformity on line width. Nonuniformity of an illumination source induces a line width difference between pair lines. We improved the treatment for these problems by adjusting the illumination source uniformity.