METHODS AND APPARATUS FOR CALCULATING ELECTROMAGNETIC SCATTERING PROPERTIES OF A STRUCTURE USING A NORMAL-VECTOR FIELD AND FOR RECONSTRUCTION OF APPROXIMATE STRUCTURES

摘要

A projection operator framework in the field of lithographic semiconductor processing is described to analyze the concept of localized normal-vector fields within field-material interactions in a spectral basis, in isotropic and anisotropic media, which may be used in for example RCWA (Rigorous Coupled Wave Analysis), the Differential Method, and the Volume-Integral Method. This greatly improves the flexibility of the normal- vector field approach and also leads to significant saving of CPU time to set up these fields. The method has the steps: 1402, generate a localized normal-vector field n in a region of the structure defined by the material boundary, decomposed into sub-regions with a predefined normal-vector field and possibly corresponding closed-form integrals. 1404, construct a continuous vector field F using the normal-vector field to select continuous components E_T and D_n. 1406, localized integration of normal- vector field n over the sub- regions to determine coefficients of, C. 1408, determine components E_x, E_y, E_Z of the electromagnetic field by using field-material interaction operator C to operate on vector field F. 1410, calculate electromagnetic scattering properties of the structure using the determined components of the electromagnetic field.