A clustered failure model for the memory array reconfiguration problem

Reconfiguration of memory array using spare rows and spare columns, which has been shown to be a useful technique for yield enhancement of memories, is considered. A clustered failure model that adopts the center-satellite approach of F.J. Meyer and D.K. Pradhan (1989) is proposed and utilized to show that the total number of faulty cells that can be tolerated when clustering occurs is larger than when faults are independent. It is also shown that an optimal solution to the reconfiguration problem can be found in polynomial time for a special case of the clustering model. An efficient approximation algorithm is given for the general case of the probabilistic model assumed. It is shown, through simulation, that the computation time required by this algorithm to repair large arrays containing a significant number of clustered faults is small