3D modeling of electron-beam lithographic process from scanning electron microscope images

Computational lithography is typically based on a model representing the lithographic process where a typical model consists of three components, i.e., line spread function, conversion formula (exposure-to-developing rate conversion), and noise process (exposure fluctuation). In our previous study, a practical approach to modeling the e-beam lithographic process by deriving the three components directly from SEM images was proposed. However, a 2D model of a substrate system was employed; i.e., the exposure variation along the resist-depth dimension was not considered. In this study, the possibility of improving the accuracy of modeling using a 3D model is investigated. The 3D model is iteratively determined by modeling the critical dimension estimated based on the model to those measured in SEM images. This paper describes the 3D modeling approach and new optimization procedures and discusses in detail the results from an extensive simulation for an accuracy analysis of the 3D modeling approach.