Patent ID: 6526546
Filing Date: 2003-02-25
Classification: G01R

Abstract:
Process for locating a defective element in an integrated circuit whose theoretical layout is known, of the type comprising a succession of steps consisting in:the determination of a measurement point of the integrated circuit; and the testing of the measurement point determined by implementing: the application of a sequence of tests to the inputs of the integrated circuit; the measurement of signals at the determined measurement point of the integrated circuit, during the application of the sequence of tests; and the assessment of the measurement point by comparison of the measured signals with theoretical signals which ought to be obtained at the determined measurement point so as to assess whether the measurement point is faulty or satisfactory; and in which the position of the defective element of the integrated circuit is determined from assessments performed at the various determined measurement points,characterized in that it comprises initially: a step of modelling the theoretical layout of the integrated circuit, in the form of at least one graph comprising a set of nodes and of arcs oriented from the inputs of the circuit to the outputs of the circuit; considering as a search subgraph, a subgraph whose vertex-forming node corresponds to a faulty measurement point; and in that, for the search for the defective element, it comprises the steps of:assigning each node of the search subgraph considered a characteristic variable dependent on the structure of the search subgraph; considering as measurement point the measurement point corresponding to a node of the subgraph considered, obtained by applying a predetermined criterion pertaining to the characteristic variables of the set of nodes of the search subgraph considered; performing a test of the measurement point considered; considering as new search subgraph: either the search subgraph previously considered, while excluding the node corresponding to the measurement point tested and all its parent nodes, if the measurement point is satisfactory or a subgraph whose node corresponding to the measurement point is the vertex, if the measurement point is faulty; and searching for the defective element in the new search subgraph considered, until a predetermined stopping criterion is satisfied.