Browse Prior Art Database

Improved Detection of Stud Opens in Harper PNP Memory

IP.com Disclosure Number: IPCOM000108694D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Patel, K: AUTHOR [+3]

Abstract

In a Harper PNP memory cell, the drain line and cross-over (NPN collector) defects, as shown in FIG. 1, are very difficult to detect. These defects, under certain conditions, have no effect on the circuit. However, these same defects have a tendency to cause fails under other conditions and for applications. These defects may pass through the tester environment but fail in the system environment. This creates very high expenses associated with field repair, diagnostics and system down time.

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Improved Detection of Stud Opens in Harper PNP Memory

       In a Harper PNP memory cell, the drain line and
cross-over (NPN collector) defects, as shown in FIG. 1, are very
difficult to detect.  These defects, under certain conditions, have
no effect on the circuit.  However, these same defects have a
tendency to cause fails under other conditions and for applications.
These defects may pass through the tester environment but fail in the
system environment.  This creates very high expenses associated with
field repair, diagnostics and system down time.

      By changing the Harper PNP cell to the K&P cell, as shown in
FIG. 2, there are two drain lines which can be biased at different
voltages/ currents.  During testing, the ability to bias one of the
voltage/current sources ON allows improved detection of certain
defects, in particular the Drain Line open and the NPN collector
open.  The biasing does not affect the operation of non-defective
cell.  One way of implementing the above technique (as shown in FIG.
3) is by placing the voltage/current source in the Word Decoder.