Exploiting structure in fast aerial image computation for integrated circuit patterns

Modeling aerial images has recently become a crucial component of semiconductor manufacturing. As all steppers employ partially coherent illumination, such modeling has been computationally intensive for all but elementary patterns. In this paper we describe a fast computational method for calculating aerial images of integrated circuit masks produced by a partially coherent optical projection system. The method described relies on two tools to realize fast computation: (1) coherent decompositions of partially coherent imaging system models as proposed by Pati and Kailath (1994), and (2) the use of "basis" (or building block) images that are well-suited to describe integrated circuit patterns. Examples are presented in which aerial images are computed for large mask areas. The proposed method represents a speed improvement of several orders of magnitude over a more traditional, and more general, approach (SPLAT from the University of California, Berkeley).