Design of fault-diagnosable and repairable folded PLAs for yield enhancement

A defect-tolerant PLA (programmable logic array) design with a simple column folding technique to enhance the probe yield is presented. The results show that the design requires less die size than a previous design, while still achieving full diagnosability of single and multiple stuck-at, bridging, and crosspoint faults. The design concept is readily extended to other folding techniques. Among the various folding techniques, the trade-offs are the density improvement and regularity, i.e. the density improvement is often paid for as higher irregularity. In fact, the irregularity often results in a higher defect density. It is concluded that a density improvement does not guarantee a higher overall yield