Browse Prior Art Database

Optimum Wiring Connections for Single-Metal Level Integrated Circuits

IP.com Disclosure Number: IPCOM000047401D
Original Publication Date: 1983-Nov-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 64K

Publishing Venue

IBM

Related People

Caldwell, LB: AUTHOR [+4]

Abstract

Circuit systems (macros) are positioned in long, parallel lines separated by sufficient space for location of interconnecting lines on an integrated circuit substrate. Primary wiring is by long, metal connections in those spaces. Non-metal connections perpendicular to those lines are short and pass as few of the long lines as possible. This is particularly valuable for technologies in which only a single metal layer is available. Commonly, where two planes are available for wiring, a "two-plateau" approach is used in which wires run up-down on one plane, left-right on the other. Often, however, it is desirable to keep wires on one of the planes as short as possible because its electrical characteristic would penalize longer nets.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 3

Optimum Wiring Connections for Single-Metal Level Integrated Circuits

Circuit systems (macros) are positioned in long, parallel lines separated by sufficient space for location of interconnecting lines on an integrated circuit substrate. Primary wiring is by long, metal connections in those spaces. Non-metal connections perpendicular to those lines are short and pass as few of the long lines as possible. This is particularly valuable for technologies in which only a single metal layer is available. Commonly, where two planes are available for wiring, a "two-plateau" approach is used in which wires run up-down on one plane, left-right on the other. Often, however, it is desirable to keep wires on one of the planes as short as possible because its electrical characteristic would penalize longer nets. Hence, to obtain a substantial majority of wires on the desirable plane, a plan must be followed in which the "two-plateau" approach is abandoned for one in which wires run systematically in both directions on both planes. If the classes of circuit systems (macros) are variable in size, and access to the macros is at the perimeter, utilizing space efficiently and minimizing wires on the undesirable plane can be complicated. The class of structures as set forth in the following description will achieve both purposes. This is achieved by the avoidance of certain shapes and the deliberate introduction of others. This discussion refers to two terms, "intersection" and "street." As shown in Fig. 1, a "street" is the area flanked on both sides by macros. As also indicated in Fig. 1, an "intersection" is the area that is neither streets nor macros. Intersections are bounded by macros and streets. Streets may be considered crosswalk zones because, as later described, crossing a metal line is made in the streets, avoiding intersections. The first characteristic of the integrated circuit technology employed is that wires can flow in both directions on both metal and non-metal planes.

The metal plane is, of course, much more effective. Accordingly, the percentage of wires on the desired metal plane is maximized, and the percentage of wires on the less desired plane (non-metal) is minimized. Wires run in parallel through the street on metal and use the non-metal planes almost exclusively for access to nodes and crossing a street. Fig. 2 illustrates this. In all of the drawings, a solid line indicates a metal line, a dashed line indicates a non-metal line, and a square indicates a via connection between a metal level and a non-metal level. If there is no waste space in streets so that (on average) they are as narrow a...