INTELLIGENT DESIGN SPLITTING IN THE STENCIL MASK TECHNOLOGY USED FOR ELECTRON-BEAM AND ION-BEAM LITHOGRAPHY

Over the last ten years, projection lithography techniques have been developed for exposing sub-half-micron patterns by electron- or ion-beam irradiation. Most of these systems use a mask with physical holes, the so-called ''stencil'' or ''transmission'' mask, to avoid scattering of the corpuscular beam by the atomic lattice of the mask material. This article presents a topological solution of the well-known mask stencil problem. The basic idea is to synthesize a pattern by overlaying the projected images of a pair of complementary half-patterns. Partitioning ground rules are summarized which ensure manufacturability and mechanical stability of the two complementary half-patterns. All the steps necessary for implementing the ground rules in APL2 (a programming language) are given. They comprise generation and selection of cutting vectors, partitioning of the shape network into meshes, and distribution to two different mask levels. The method is applicable to arbitrary polygonal sets. No double exposures are generated.