Compressed scan testing techniques

A non-transitory computer-readable medium having instructions stored thereon that are executable by a computing device to perform operations comprising:

• receiving failure information from a first test of a device under test (DUT), wherein the DUT includes a plurality of scan chains that each include a plurality of scan cells and wherein the first test is based on a first compressed test pattern;
• determining that the failure information is not usable to definitively determine a failing scan cell for a failure because of an unknown value for the first test;
• generating a plurality of compressed test patterns that specify identical input values for the plurality of scan chains as the first compressed test pattern, wherein the plurality of compressed test patterns specify test modes in which an output of at least one scan chain of the plurality of scan chains directly controls a scan output independent of other ones of the plurality of scan chains;
• and
• definitively determining the failing scan cell for the failure based on failure information from one or more second tests of the DUT, wherein the one or more second tests of the DUT are performed using the plurality of compressed test patterns.

A system, comprising:

• a failure processing unit, configured to:
• receive failure information from a first test of a device under test (DUT), wherein the DUT includes a plurality of scan chains that each include a plurality of scan cells and wherein the first test is performed using a first compressed test pattern;
• determine that the failure information is not usable to definitively determine a failing scan cell for a failure;
• generate a plurality of compressed test patterns based on the first test pattern, wherein the plurality of compressed test patterns specify different test modes in which an output of at least one scan chain of the plurality of scan chains directly controls a scan output independent of other ones of the plurality of scan chains;
• and
• definitively determine the failing scan cell for the failure based on one or more second tests of the DUT using the plurality of compressed test patterns.