Method for redundancy replacement in a memory device

摘要

The method of making a fault-tolerant memory device employs a variable domain redundancy replacement (VDRR) arrangement. The method includes the steps of: subdividing the memory into a plurality of primary memory arrays; defining a plurality of domains, at least one of the domains having at least a portion common to another domain to form an overlapped domain area. and wherein at least one of the domains overlaps portions of at least two of the primary arrays; allocating redundancy means to each of the domains to replace faults contained within each of the domains; and replacing at least one of the faults within one of the domains with the redundancy means coupled to the one domain, and at least one other fault of the one domain is replaced by the redundancy means coupled to another of the domains, if the at least one other fault is positioned within the overlapped domain area. Each redundancy unit supporting the primary memory arrays includes a plurality of redundant elements. Unlike the conventional fixed domain redundancy replacement scheme, redundancy units are assigned to at least two variable domains, wherein at least a portion of the domain is common to that of another domain. VDRR makes it possible to choose the most effective domain, and in particular, a smaller domain for repairing a random fault or a larger domain for repairing a clustered faults. <IMAGE> <IMAGE> <IMAGE>