Browse Prior Art Database

Metal Personalizable Timing Chain Technique for Static Random Access Memory Design

IP.com Disclosure Number: IPCOM000117472D
Original Publication Date: 1996-Mar-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Aipperspach, AG: AUTHOR [+2]

Abstract

A technique is described to do physical layout of Static Random Access Memory (SRAM) critical timing chains that allow for metal changes if a timing problem is discovered with the early hardware.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 92% of the total text.

Metal Personalizable Timing Chain Technique for Static Random Access
Memory Design

      A technique is described to do physical layout of Static
Random Access Memory (SRAM) critical timing chains that allow for
metal changes if a timing problem is discovered with the early
hardware.

      The physical area of the timing circuits of an SRAM generally
consumes a small portion the physical design.  These circuits are
used to provide timing of other circuits that allow the SRAM to work.
Often an SRAM is sufficiently complex that accurate modeling is
difficult and these timing circuits may not be designed correctly
when first pass hardware is submitted to the processing line.  A way
to "fix" these timing circuits quickly by making Back End Of the Line
(BEOL) metal fixes is needed.

      When designing the geometrical mask data for the timing
circuits, the devices should be located in a special area where the
initial design point is constructed.  The interconnect of the devices
are made only with the back end levels, much like a gate array.
Further, additional devices are added in the same circuit location
and are tied off.  These devices should be placed such that with a
metal change, the device could be reconnected into the circuit to fix
a timing problem.  The number and size of these devices are
determined by the amount of timing flexibility that is desired.

      Full advantage of the Front End Of the Line (FOEL) ground
rules may not be taken advanta...