MULTI-PHASE TEST POINT INSERTION FOR BUILT-IN SELF TEST OF INTEGRATED CIRCUITS

Method and apparatus for providing high quality Built-in-Self-Test (BIST) of integrated circuits, while guaranteeing convergence and reducing area-overhead and power dissipation during test mode. A divide and conquer approach is used to partition the test into multiple phases during which a number of test patterns are applied to a circuit under test (CUT). The design of each phase (the selection of control and observation points) is guided by a progressively reduced list of undetected faults. Within a phase, a set of control points maximally contributing to the fault coverage achieved so far is identified using a unique probabilistic fault simulation (PFS) technique. The PFS technique accurately computes a propagation profile of the circuit and uses it to determine the impact of a new control point in the presence of control points selected so far. In this manner, in each new phase a group of control points, driven by fixed values and operating synergistically, is enabled. Observation points are selected in a similar fashion to further enhance the fault coverage. The sets of control and observation points are then inserted into the circuit under test and a new, reduced list of undetected faults is determined through exact fault simulation. This process is iterative and continues until the number of undetected faults is less than or equal to an acceptable threshold, a pre-specified number of control and observation points have been inserted, or the maximum number of specified test phases has been reached.