  Rigorous computer simulations of propagating electromagnetic fields have
become an important tool for optical metrology and design of nanostructured
optical components. A vectorial finite element method (FEM) is a good choice
for an accurate modeling of complicated geometrical features. However, from a
numerical point of view solving the arising system of linear equations is very
demanding even for medium sized 3D domains. In numerics, a domain decomposition
method is a commonly used strategy to overcome this problem. Within this
approach the overall computational domain is split up into smaller domains and
interface conditions are used to assure continuity of the electromagnetic
field. Unfortunately, standard implementations of the domain decomposition
method as developed for electrostatic problems are not appropriate for wave
propagation problems. In an earlier paper we therefore proposed a domain
decomposition method adapted to electromagnetic field wave propagation
problems. In this paper we apply this method to 3D mask simulation.
