TOPIC : Introduction to Faults UNIT 2: Modeling and Simulation Module 1 : Logical faults due to physical faults

Fault Fault is any deficiency in the system either during design or manufacturing which ultimately results in the deviation in the expected value. Faults need to be identified and corrected. A faulty sub-part in a chip might ask for the entire reconstruction of the chip.

Why to model faults? To verify the interconnections of the circuit Real defects are difficult to analyze A fault model identifies targets for testing A fault model makes fault analysis easy

Causes of faults Faults due to materials Faults due to masks Faults due to improper order of process steps Faults due to error in the design rules It is difficult to simulate these faults. So there is a need to visualize these faults as logical faults so that the analysis become easier.

Contd … Material defects ◦ Surface impurities ◦ Body defects Processing defects ◦ Missing contact windows ◦ Parasitic transistors ◦ Oxide breakdown Packaging defects ◦ Contact degradation ◦ Seal leaks

Physical faults  Logical faults Any physical fault can be represented by logical fault. Advantages ◦ Fault analysis becomes logical analysis rather than a physical problem ◦ Many physical faults can be modeled by one logical fault ◦ Logical fault models are technology independent ◦ Some physical faults are too complex to be analyzed