03_fault_model_p6

03_fault_model_p6 - 1 K.T. Tim Cheng, 03_fault_model, v1.0...

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Unformatted text preview: 1 K.T. Tim Cheng, 03_fault_model, v1.0 1 Outline Fault Modeling Why Model Faults Single Stuck-at Faults Fault Collapsing Fault Detection and Redundancy K.T. Tim Cheng, 03_fault_model, v1.0 2 Fault Detection and Redundancy Other Common Fault Models Transistor faults Bridging faults Delay faults Memory faults Why Model Faults? I/O function tests inadequate for manufacturing (functionality vs. component & interconnection testing) Fault model identifies target faults K.T. Tim Cheng, 03_fault_model, v1.0 3 Fault model identifies target faults Fault model makes analysis possible Effectiveness measurable by experiments Some Real Faults In Chips Processing faults Missing contact windows Parasitic transistors Oxide breakdown Material defects Bulk defects (Cracks, Crystal imperfections) K.T. Tim Cheng, 03_fault_model, v1.0 4 Surface impurities (Ion migration) Time-dependent failures Dielectric breakdown Electromigration Packaging failures Contact degradation Seal leaks Some Fault Models Single stuck-at faults Transistor open/short faults Bridging faults Delay faults K.T. Tim Cheng, 03_fault_model, v1.0 5 Memory faults Analog faults Single Stuck-At Faults 1 1 1 0 (1) TEST VECTOR TRUE RESPONSE FAULTY RESPONSE K.T. Tim Cheng, 03_fault_model, v1.0 6 Assumptions: 1. Only one line is faulty 2. Faulty line permanently set to 0 or 1 3. Fault can be at an input or output of a gate 0 (1) STUCK - AT - 1 2 Single Stuck-At Fault Most widely studied and used It represents many different physical faults It is independent of technology K.T. Tim Cheng, 03_fault_model, v1.0 7 Experience has shown that tests that detect SSFs detect many nonclassical faults as well The number of SSFs in a circuit is small. Moreover, the number of faults to be explicitly analyzed can be reduced by fault collapsing techniques. An Example y Single Stuck-at-1 o Single stuck-at-0 K.T. Tim Cheng, 03_fault_model, v1.0 8 Role of Fault Collapsing DUT Generate fault list Fault Model K.T. Tim Cheng, 03_fault_model, v1.0 9 Collapse fault list Generate test vectors Required fault coverage Ack: Bushnell and Agrawal, Essential of Electronic Testing, 2000 Definitions Given T1 is set of all tests for fault F1 T2 is set of all tests for fault F2 K.T. Tim Cheng, 03_fault_model, v1.0 10 F2 dominates F1 F1 and F2 are equivalent T2 T1 T1=T2 Fault Equivalence Two equivalent faults are detected by exactly the same tests s - a - 0 s - a - 1 K.T. Tim Cheng, 03_fault_model, v1.0 11 Example : Three faults shown are equivalent s - a - 1 Equivalence Fault Collapsing s - a - 1 s - a - 1 s - a - 1 s - a - 0 K.T. Tim Cheng, 03_fault_model, v1.0 12 N+2 faults in N-input gate s - a - 1 s - a - 0 s - a - 0 s - a - 0 3 Equivalent Fault Collapsing ( a K.T. Tim Cheng, 03_fault_model, v1.0 13 ( a ) ( b ) x x f s. a. 0s....
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03_fault_model_p6 - 1 K.T. Tim Cheng, 03_fault_model, v1.0...

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