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Method to Identify Defective, Testable, Redundant Lines in Memory Arrays

IP.com Disclosure Number: IPCOM000107766D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Dewar, DR: AUTHOR

Abstract

By using a conventional repair algorithm to test and bit map a standard memory array, inclusive of its two-dimensional redundant lines and elements, level of usefulness of the redundant lines and elements is determined. This pseudo-repair operation identifies redundant lines falling into categories of "must fix" and "sparse" condition in a single run. Frequently, sufficient information is thereby provided to an operator that incorrect identification of a fixable array as unfixable is avoided.

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Method to Identify Defective, Testable, Redundant Lines in Memory Arrays

       By using a conventional repair algorithm to test and bit
map a standard memory array, inclusive of its two-dimensional
redundant lines and elements, level of usefulness of the redundant
lines and elements is determined.  This pseudo-repair operation
identifies redundant lines falling into categories of "must fix" and
"sparse" condition in a single run.  Frequently, sufficient
information is thereby provided to an operator that incorrect
identification of a fixable array as unfixable is avoided.

      Referring to the figure, a memory array having n columns and m
rows has four redundant lines a through d in each dimension.  Fails
are shown as circles.  Conventional testing and either totalizing
fails or bit mapping redundant lines alone would find faults in all
the redundant lines, and the device would be declared unfixable.

      By including all lines and elements in a pseudo-repair
operation, a table is generated identifying all array and redundant
lines having any fails as "must fix" lines or lines having "sparse
fails".  The result of a pseudo-repair operation is shown below for
the m by n array and its 4 column by 4 row lines of redundancy
shown in the figure.

      MUST FIX (MF)               SPARSE (SP)
                                         ROW          COLUMN
                R1                       R3           Ca
                C2              ...