Static information storage and retrieval – Read/write circuit – Having fuse element
Reexamination Certificate
1999-11-30
2001-03-27
Dinh, Son T. (Department: 2824)
Static information storage and retrieval
Read/write circuit
Having fuse element
C365S200000
Reexamination Certificate
active
06208578
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to integrated circuit devices and more particularly to the partial replacement of partially defective integrated circuit memory devices.
BACKGROUND OF THE INVENTION
Technological advances have permitted semiconductor integrated circuit memory devices to comprise significantly more circuit elements in a given silicon area. Reducing and eliminating defects in the circuit elements has, however, become increasingly more difficult with the increased number of circuit elements. To achieve higher population capacities, circuit designers strive to reduce the size of individual circuit elements to maximize available die real estate. The reduced size makes these circuit elements increasingly susceptible to defects caused by material impurities during fabrication.
Relying on zero defects in the fabrication of integrated circuit memory devices is an unrealistic goal, however. Therefore, redundant circuit elements are provided on the devices to reduce the number of scrapped devices. If a primary circuit element of a device is determined to be defective, a redundant circuit element is substituted for the defective primary circuit element. Substantial reductions in scrap are achieved by using redundant circuit elements without substantially increasing the cost of the device.
However, occasionally a defective circuit element of a device cannot be repaired by using a redundant element also within the device, or such repair is economically or logistically unfeasible. For example, a single bit failure may be serious enough that it is not internally repairable. In this and other situations, the entire memory device may be replaced by a redundant device. There are drawbacks to this approach, however. Even if the memory device is only partially defective, replacing it with a redundant device means that many of the operational elements are not used and thus wasted. Furthermore, the redundant device must itself be completely operational, or otherwise the replacement will not be successful.
Complete replacement of a defective memory device with a redundant device may therefore be economically undesirable in that a nearly operational device must be scrapped and replaced by a completely operational device. For these reasons, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification as disclosed herein, there is a need for the replacement of a partially defective integrated circuit device without having to completely replace the partially defective device. That is, there is a need to partially replace the defective device such that use is still made of many, most or all of the operational elements of the partially defective device.
SUMMARY OF THE INVENTION
The above-mentioned problems and other problems are addressed by the present invention, which will be understood by reading and studying the following specification. The present invention relates to the partial replacement of partially defective integrated circuit memory devices. A memory device is described which has one or more links having an initial closed configuration, wherein each link is coupled to a data line coupled to a section of the memory array. Each link is configured to open to permit replacement of just the section of the memory array coupled to the data line to which the link is coupled.
In particular, in one embodiment of the invention, a multi-chip module includes a plurality of memory devices mounted on a substrate and a plurality of data lines, each coupled to a memory device. A normally closed link is coupled to each data line. If one of the memory devices is partially defective, the appropriate link is opened. This is the link that is coupled to the data line which is coupled to the defective section of the memory device. A partially or completely operating memory device is coupled to the module at a repair site to replace only the defective section.
The operable sections of the partially defective memory device thus remain in use and are not wasted. Furthermore, the replacement memory device may itself be partially defective, since it is not completely replacing the other memory device. This is economically advantageous because memory devices that might otherwise be scrapped may serve as replacement devices, and in any case completely operable replacement devices are not required. Still other and further aspects, advantages and embodiments of the present invention will become apparent in the following description and by reference to the following drawings.
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patent: 5200652 (1993-04-01), Lee
patent: 5265054 (1993-11-01), McClure
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patent: 5703817 (1997-12-01), Shiratake et al.
patent: 5706231 (1998-01-01), Kokubo
“Micron Technology, Inc. 4 MEG×4 DRAM catalog pages”, 3-33 to 3-48, (1995).
Dinh Son T.
Micro)n Technology, Inc.
Schwegman Lundberg Woessner & Kluth P.A.
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