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Overview

 

Carafe has recently added the capability of extracting compound faults [SS95]. A compound fault is the result of a spot defect simultaneously affecting an arbitrary number of objects in a circuit. Carafe extracts compound faults by first finding fault primitives. A fault primitive tracks the region a single defect must fall in to cause two objects in a circuit to be disrupted. This region is called the critical area for that fault primitive. A fault primitive can be one of the following types:

To extract compound faults, Carafe collects all fault primitives of the same type. The critical areas for these fault primitives are then intersected to find any overlapping. When an overlapping occurs, the region of overlapping is the critical area for a fault that affects all the objects listed in the fault primitives forming that region. This process is repeated for each type of fault primitive. Faults that cause the same change in the circuit's description are considered to be the same fault, even though each failure may occur on different layers of material or in different areas of the circuit.

  
Figure 4.1: Overlapping Critical Areas

Figure 4.1 shows the overlapping of three fault primitive critical areas. Assume that CA 1 causes a fault affecting objects A and B, CA 2 causes a fault affecting objects B and C, and CA 3 causes a fault affecting objects D and E. Specifically how these faults would be reported depends on the type of fault being extracted. However, Carafe places no arbitrary limitations on the number of objects which may be involved in a single fault. The following faults would be reported for the seven regions formed by the overlapping.

Physical defect sizes are specified as the radius of a circular defect. However, for computational simplicity, these circular defects are approximated as squares where the defect radius is one-half the length of a side.



next up previous contents
Next: Space/Time Considerations Up: Compound Faults Previous: Compound Faults



David Dahle Wed Jan 24 11:51:06 PST 1996