A preconstrained Compaction Method Applied to Direct Design-Rule Conversion of CMOS Layouts


IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E77-A   No.10   pp.1684-1691
Publication Date: 1994/10/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: Computer Aided Design (CAD)
compaction,  design rules,  constraint graph,  strongly-connected-components,  cell layouts,  

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This paper describes a preconstrained compaction method and its application to the direct design-rule conversion of CMOS layouts. This approach can convert already designed physical patterns into compacted layouts that satisfy user-specified design rules. Furthermore, preconstrained compaction can eliminate unnecessarily extended diffusion areas and polysilicon wires which tend to be created with conventional longest path based compactions. Preconstrained compaction can be constructed by combining a longest path algorithm with forward and backward slack processes and a preconstraint generation process. This contrasts with previously proposed approaches based on longest path algorithms followed by iterative improvement processes, which include applications of linear programming. The layout styles in those approaches are usually limited to a model where fixed-shaped rectilinear blocks are moved so as to minimize the total length of rectilinear interconnections among the blocks. However, preconstrained compaction can be applied to reshaping polygonal patterns such as diffusion and channel areas. Thus, this compaction method makes it possible to reuse CMOS leaf and macro cell layouts even if design rules change. The proposed preconstrained compaction approach has been applied to direct design-rule conversion from 0.8-µm to 0.5-µm rules of CMOS layouts containing from several to 10,195 transistors. Experimental results demonstrate that a 10.6% reduction in diffusion areas can be achieved without unnecessary extensions of polysilicon wires with a 39% increase in processing times compared with conventional approaches.