The present invention can include a method and system for testing IC chips,
including the steps of performing a binary search to a first failing
pattern, determining a failing sink latch, performing a back cone trace to
determine all source latches, determining source latch logic states,
positioning the source latch logic states in a scan chain, exercising a
chip scan path by applying logic transitions on the source latches in the
absence of a system L1 clock, and observing an exercised failing circuit.
The invention can include the use of PICA techniques to observe the
exercised failing circuit. In another embodiment, the invention can
include using LBIST or a WRP technique to search for the failing pattern.
In yet another it includes the step of using an algorithm to exercise the
exercised failing circuit. In another embodiment, the method includes the
step of creating a net pattern to be scanned including a sum of an
original pattern causing a failing circuit to be exercised, and one or
more shifted versions of the original pattern. The algorithm can include a
step where one of the shifted versions is shifted a number of clocks
wherein the number of clocks is equal to the length of the original
pattern. In one embodiment, one of the shifted versions is shifted a
number of clocks, wherein the number of clocks is chosen so that the sum
of the original pattern and the one of the shifted versions does not cause
a scan conflict. In another embodiment the method further includes the
step of using an algorithm to densify the pattern set.