Browse Prior Art Database

Three Level Metal Wiring Scheme With Improved Wiring Density

IP.com Disclosure Number: IPCOM000121223D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 34K

Publishing Venue

IBM

Related People

Nishihara, M: AUTHOR

Abstract

A simple but effective global wiring scheme is described to provide better wiring density. First and second level wiring is performed horizontally and third level wiring is performed vertically.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 87% of the total text.

Three Level Metal Wiring Scheme With Improved Wiring Density

      A simple but effective global wiring scheme is described
to provide better wiring density.  First and second level wiring is
performed horizontally and third level wiring is performed
vertically.

      In conventional gate arrays with double layer metal wiring,
first level metal (M1) lines run horizontally and second level metal
(M2) lines run vertically.  The cell density is limited by overflow
of M2 wiring.  This is due to the basic cell dimension which is
narrow in the horizontal direction and wide in the vertical
direction.  In other words, there are fewer M2 wiring channels than
M1 wiring channels per cell.  It is observed in many actual cases
that overflow of global wiring occurs due to the limited M2 channels.

      The above problem becomes more serious if third level metal
(M3) wiring is used.  Since M1 runs horizontally and M2 runs
vertically in conventional gate arrays, it will be an ordinary design
to cause the additional M3 wires to run horizontally.  However, in
this case, the problem of M2 overflow may not be improved.  For
example, when an M3 wire is used to fill a need for horizontal wire,
one M2 channel is also used due to via hole down to M1 even though
there is no need for M2 wire.

      This article proposes a new wiring scheme in which M1 and M2
wires run horizontally and M3 wires run vertically. In this scheme,
all of horizontal wiring requirements can be res...