Are Circular Shaped Masks Adequate in Adaptive Mask Overlay Topology Synthesis Method?

Abstract

Previous versions of the material mask overlay strategy (MMOS) for topology synthesis primarily employ circular masks to simulate voids within the design region. MMOS operates on the photolithographic principle by appropriately positioning and sizing a group of negative masks and thus iteratively improves the material layout to meet the desired objective. The fundamental notion is that a group of circular masks can represent a local void of any shape. The question whether masks of more general shapes (e.g., any two-dimensional closed, nonself intersecting polygon) would offer significant enhancements in efficiently attaining the appropriate topological features in a continuum remains. This paper investigates the performance of two other mask types; elliptical and rectangular masks are compared with that of the circular ones. These are the respective modest representatives of closed curves and their polygonal approximations. First, two mean compliance minimization examples under resource constraints are solved. Thereafter, compliant pliers are synthesized using the three mask types. It is observed that the use of elliptical or rectangular masks do not offer significant advantages over the use of circular ones. On the contrary, the examples suggest that less number of circular masks are adequate to model the topology design procedure more efficiently. Thus, it is postulated that using generic simple closed curves or polygonal masks will not introduce significant benefits over circular ones in the MMOS based topology design algorithms.