Method to detect systematic defects in VLSI manufacturing
First Claim
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1. A method for detecting systematic defects occurring on wafers having several chips which have a plurality of devices with scannable latches for logic testing comprising:
- testing the logic for each device, and storing the latches that contained an incorrect logic value after completion of any test, as well as the identification of the associated failing tests;
backtracing through a cone of logic from the latches having incorrect values;
assigning a weighting value for objects encountered during backtracing to produce a vector of weights for each failing device;
determining a fail signature based on the vector; and
comparing fail signatures of any two failing devices to determine similarity of the failure.
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Abstract
Defects in manufacturing of IC devices are analyzed by testing the devices for defects using results of LSSD technology to find at least one failing pattern that contains incorrect values. The failing latches are used as a starting point to trace back through combinational logic feeding the failing latches, until controllable latches are encountered. A decision is then made to continue the back tracing or not depending on whether the latter latches were clocked during the application of one of the failing patterns or not.
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Citations
22 Claims
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1. A method for detecting systematic defects occurring on wafers having several chips which have a plurality of devices with scannable latches for logic testing comprising:
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testing the logic for each device, and storing the latches that contained an incorrect logic value after completion of any test, as well as the identification of the associated failing tests;
backtracing through a cone of logic from the latches having incorrect values;
assigning a weighting value for objects encountered during backtracing to produce a vector of weights for each failing device;
determining a fail signature based on the vector; and
comparing fail signatures of any two failing devices to determine similarity of the failure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification