Performance evaluation of a reconfiguration-algorithm for memory arrays containing clustered faults

Reconfiguration of memory arrays using spare rows and columns is useful for yield-enhancement of memories. This paper presents a reconfiguration algorithm (QRCF) for memories that contain clustered faults. QRCF operates in a branch and bound fashion similar to known optimal algorithms that require exponential time. However, QRCF repairs faults in clusters rather than individually. Since many faults are repaired simultaneously, the execution-time of QRCF does not become prohibitive even for large memories containing many faults. The performance of QRCF is evaluated under a probabilistic model for clustered faults in a memory array. For a special case of the fault model, QRCF solves the reconfiguration problem exactly in polynomial time. In the general case, QRCF produces an optimal solution with high probability. The algorithm is also evaluated through simulation. The performance and execution-time of QRCF on arrays containing clustered faults are compared with other approximation algorithms and with an optimal algorithm. The simulation results show that QRCF outperforms previous approximation algorithms by a wide margin and performs nearly as well as the optimal algorithm with an execution-time that is orders of magnitude less.