EB Tester Fault Localization Algorithm for Combinational
Circuits by Utilizing Fault Simulation and Test Pattern
Sequence for EB Tester
Koji Nakamae, Takashi Ishimura, and Hiromu Fujioka
Department of Information Systems Engineering, Faculty of Engineering, Osaka Universi ty, Osaka, Japan 565-0871
SUMMARY
An EB tester fault localization algorithm for combi-
national circuits utilizing a fault list generated in concurrent
fault simulation and test pattern sequence is proposed. In
the algorithm, first, an initial fault candidate list and con-
current fault lists on internal signal lines are obtained by
performing concurrent fault simulation on a test pattern for
which the LSI tester detected an error on one of the output
pins. Then, using the concurrent fault lists, the signal line
to be probed is chosen so that the fault candidate list is
narrowed down maximally. One or more random test pat -
terns are generated for a partial circuit with the probing line
as an output terminal without increasing the waveform
measurement time. Under the test pattern sequence com -
posed of the fault-detected test pattern and the generated
random test patterns, the EB tester probes the chosen line.
Then using the probed result and the fault simulation on the
added random test patterns performs the fault localization.
These procedures are iterated until the number of faults
included in the fault candidate list is reduced to one. The
proposed algorithm was applied to eight different IS-
CAS85 benchmark circuits to evaluate its performance.
Results showed that the number of probed lines was re-
duced to about a fifth of that for the guided probed method.
The increase in processing time that resulted from adopting
the proposed algorithms was about 50 seconds for the
circuits with several thousand gates and was less than the
waveform measurement time for one probing line. Concur-
rent fault simulation is the main determinant of the process-
ing time, but it is carried out only once at the initial stage.
Therefore, our proposed fault localization algorithm is an
efficient method relative to the guided probe method.
© 2000 Scripta Technica, Syst Comp Jpn, 31(8): 4148,
2000
Key words: EB tester; fault localization; fault
simulation; test pattern sequence; combinational circuits.
1. Introduction
The CAD-linked electron-beam (EB) tester has be-
come an indispensable instrument for the diagnosis of
faulty VLSI chips [1]. When a VLSI chip is identified as
faulty by the LSI tester, the EB tester localizes the fault by
probing the internal signal lines on the fault propagation
paths from one of the faulty output pins. The internal signal
measurement time occupies the bulk of the fault diagnosis
time. To reduce the diagnosis time, it is essential to reduce
the number of probing lines.
Guided probe (GP) diagnosis [24] is well known as
a fault localization method. The principle is to back trace
an error from one of the faulty output pins. Back tracing is
a method developed to speed up the GP diagnosis process;
it tries to reduce the number of probing lines by considering
the fault probability based on layout analysis [5].
There is also fault diagnosis based on fault dictionar-
ies [2, 6, 7]. The diagnosis uses fault simulation to deter-
© 2000 Scripta Technica
Systems and Computers in Japan, Vol. 31, No. 8, 2000
Translated from Denshi Joho Tsushin Gakkai Ronbunshi, Vol. J82-D-I, No. 7, July 1999, pp. 933939
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