Browse Prior Art Database

Variable Length Cell Rows in an Integrated Circuit

IP.com Disclosure Number: IPCOM000050683D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 72K

Publishing Venue

IBM

Related People

Stoops, EH: AUTHOR

Abstract

Existing integrated circuit chip-image typically have each horizontal row of cells 2 formed beneath predefined horizontal ground and voltage power buses 1 (called power fingers), as shown in Fig. 1. The ground and power fingers will be placed on the integrated circuit chip regardless whether there are cells of circuitry which will also be formed in that row on the final chip. This creates a problem in that if a large macro circuit image is to be formed on one side of a wiring column, the design automation routine must specifically go back and terminate the horizontal extent of the power fingers for those horizontal rows which would otherwise intersect the macro.

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Variable Length Cell Rows in an Integrated Circuit

Existing integrated circuit chip-image typically have each horizontal row of cells 2 formed beneath predefined horizontal ground and voltage power buses 1 (called power fingers), as shown in Fig. 1.

The ground and power fingers will be placed on the integrated circuit chip regardless whether there are cells of circuitry which will also be formed in that row on the final chip. This creates a problem in that if a large macro circuit image is to be formed on one side of a wiring column, the design automation routine must specifically go back and terminate the horizontal extent of the power fingers for those horizontal rows which would otherwise intersect the macro.

In order to improve upon the flexibility of the design for design automation (DA), it is the principle of this invention to make the first level metal power fingers 1 an integral part of the definition of a cell structure 2. This is distinguished from the existing definition of the horizontal power fingers 1 Which are a fixed part of the overall chip image itself. This identification of the horizontal power finger structures with the cell structures themselves permits a variable length of cell rows to be designed, thereby increasing the flexibility of layout and wirability of the resultant integrated circuit.

Reference to Fig. 2 will illustrate the principle. A one four input HDR cell layout is shown. The principle of the invention is to make the ground horizontal power finger a short segment 1 which is uniquely identified with the definition of the four-input NOR cell in the DA library. The segment 1 overlaps the cell boundary 2 by the overlap portion 4 so as to make connection with the next adjacent cell's ground finger segment 1 on the right side of the cell. The segment 1 also overlaps the left boundar...