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Multiple Word Line Selection for Reducing Semiconductor Memory Test Time

IP.com Disclosure Number: IPCOM000102152D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Dollinger, CP: AUTHOR [+3]

Abstract

A technique is disclosed for reducing dynamic random-access memory (DRAM) test time, test cost, and improve product reliability.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 57% of the total text.

Multiple Word Line Selection for Reducing Semiconductor Memory Test Time

       A technique is disclosed for reducing dynamic
random-access memory (DRAM) test time, test cost, and improve product
reliability.

      Numerous tests have been developed to locate defects in
semiconductor memory arrays. Several of the tests are time consuming
due to details of the failure. An example of such a test is one where
a word line is activated and allowed to be active for long durations
to find leakage defects in adjacent storage cells. In a 4 million-bit
chip, there are typically 1024 word line addresses. If each address
requires 20 milliseconds of accumulated time, then the total test
time exceeds 20 seconds for the entire address space. By selecting
multiple word lines, many array structures may be tested in parallel,
thus saving considerable test time.

      The ability to select multiple word lines is facilitated by
constructing word line address decoders that cannot only select the
usual 1 out of 128 or 256 word lines, but also can select multiple
word lines, i.e., 1 out of 4 or 8 or other multiple. To control the
word line decoder operation between normal use and multiple word line
select use, extra pads on the chip, unique external bias on pads,
test mode, etc., may be used. Actual circuit implementation depends
on the type of word line decoder used and whether or not the
addresses are multiplexed between word line and bit line selection.

      A typical test...