Procedural Detailed Compaction for the Symbolic Layout Design of CMOS Leaf Cells


IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E77-A   No.11   pp.1957-1969
Publication Date: 1994/11/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: Computer Aided Design (CAD)
symbolic layout,  compaction,  design rule,  leaf cell,  constraint graph,  

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This paper describes a procedural detailed compaction method for the symbolic layout design of CMOS leaf cells and its algorithmic aspects. Simple symbolic representations that are loosely designed by users in advance are automatically converted into densely compacted physical patterns in two phases: symbolic–to–pattern conversion and segment–based detailed compaction. Both phases are executed using user-defined procedures and a specified set of design rules. The detailed compaction utilizes a segment–based constraint graph generated by an extended plane sweep method where various kinds of design rules can be applied. Since various kinds of basic operations can be applied to the individual segments of patterns in the procedures, the detailed procedure for processing can be described in accordance with fabrication process technologies and the corresponding sets of design rules. This combined stepwise procedure provides a highly flexible framework for the symbolic layout of CMOS leaf cells. The proposed approach was implemented in a symbolic layout system called CAMEL. To date, more than 300 kinds of symbolic representations of CMOS leaf cells have been designed and are stored in the database. Using several different sets of design rules, symbolic representations have been automatically converted into compacted patterns without design rule violations. The areas of those generated patterns were averaged at 98% of the manually designed patterns. Even in the worst case, the increases in area were less than about 10% of the manually designed ones. Furthermore, since processing times are much shorter than manual design periods, for example, 300 kinds of symbolic representations can be converted to corresponding physical patterns in only a day. It is evident, through these practical design experiences with CAMEL, that our approach is more flexible and process–tolerant than conventional ones.