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Shorter Wires for VLSI

IP.com Disclosure Number: IPCOM000109152D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 1 page(s) / 70K

Publishing Venue

IBM

Related People

Frank, DJ: AUTHOR

Abstract

Described is a way to shorten the wires on integrated circuit chips, and hence increase the speed, without any change in the fabrication processes except for altering the wafer dicing procedure. The reduction is achieved in two ways: use of wiring planes at angles other than 90~ and use of different die geometries for the integrated circuit chips. Either of these two techniques could be used by itself to achieve some reduction in wire length, but the best advantage is obtained by using them together.

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Shorter Wires for VLSI

      Described is a way to shorten the wires on integrated circuit
chips, and hence increase the speed, without any change in the
fabrication processes except for altering the wafer dicing procedure.
The reduction is achieved in two ways: use of wiring planes at angles
other than 90~ and use of different die geometries for the integrated
circuit chips.  Either of these two techniques could be used by
itself to achieve some reduction in wire length, but the best
advantage is obtained by using them together.

      Advanced VLSI of necessity contain many layers of wiring and
these layers are conventionally arranged as x-y plane pairs.  If
there are enough layers of wiring, however, the use of solely x and y
wiring directions is not the most advantageous approach.  Rather, the
wiring planes should be directed in angles that more uniformly cover
all possible angles.  Thus, if n wiring planes are to be used, they
should be directed at angles that are multiples of 180~/n. To be
specific, if 3 wiring planes are available, the wires should be at
0~, +60~, and -60~.  For wires which must connect endpoints with a
uniform angular distribution, the use of the 3 wiring planes results
in a 13% decrease in the average wire length compared to the use of
only x and y oriented wires.

      Altering the die geometry of a chip does not in general alter
the wiring length for wires such as above, where the angular
distribution is uniform.  It can, howev...