Static information storage and retrieval – Read/write circuit – Bad bit
Reexamination Certificate
2002-11-13
2004-06-29
Le, Vu A. (Department: 2824)
Static information storage and retrieval
Read/write circuit
Bad bit
C365S225700
Reexamination Certificate
active
06757204
ABSTRACT:
PRIORITY OF OTHER APPLICATIONS
This application claims priority from German Patent Application No. 101 55 620.9-53, filed Nov. 13, 2001, and entitled CIRCUIT DEVICE HAVING A CENTRAL FUSE.
TECHNICAL FIELD
The invention relates to a circuit device, and in particular, to a semiconductor memory device having a fuse.
BACKGROUND
Fuse boxes have widely been used to activate redundancies on chips or integrated circuits, mostly for memory design. Specifically, redundancies have been used in DRAM design since the 256 k generation to improve yield and profitability. In redundancy, spare elements such as rows and columns are used as logical substitutes for defective elements. The substitution is commonly controlled by a physical encoding scheme. As memory density and size increase, redundancy continues to gain importance. Modern DRAM designs typically employ both row and column redundancy concept. Thus, memory fault repair is a reconfiguration of the memory circuit that inhibits the use of faulty circuit elements and enables the use of operating spare (redundant) elements. Circuit elements, which are repaired in a memory, include rows, columns, blocks (clusters), subarrays and arrays of memory cells.
The repair procedure typically consists of three phases: (1) detection and location of faulty (defect) elements, (2) assignment of operating spare (redundant) elements, and (3) disconnection of the faulty elements and integration of the assigned redundant elements with the memory operation.
Disconnection of faulty elements and engagement of spare elements may be implemented externally by laser, fuse and antifuse programming or by on-chip repair circuit applying electrical fuse, antifuse, EPROM, EEPROM, FRAM, SRAM or other by stable programmable circuit elements which, in the following, are simply referred to as fuse elements. These fuse elements are provided in a fuse box (or fuse repository) which is able to activate the redundant circuit elements provided as spare elements in the circuit to be repaired.
Besides the application of fuse boxes in defect repairable circuit designs, it is also possible to use fuse boxes in electrical circuit modules which contain adjustable circuit elements which can be adjusted by an appropriate programming of the fuse elements contained in the fuse box. For example, fuse boxes could also be employed in analogue circuits for trimming purposes; wherein adjustable circuit elements are adjusted such that the circuit meets predetermined circuit specifications.
In commonly known modern circuit devices, such as semiconductor memories, each individual semiconductor circuit is provided with a local fuse box connected thereto. This fuse box serves the associated circuit in that it enables the activation of adjustable circuit elements therein. If a semiconductor memory chip, for example, contains six memory circuits thereon, then at least six separate local fuse boxes connected to these memory circuits are commonly provided.
Integrated logic and, particularly, memory circuits are constantly miniaturized in order to constantly increase the memory density per unit chip area. Employing fuse box layout concepts, however, requires additional chip area since the commonly used laser programmable fuse elements have minimum sizes defined by the laser programming process. Consequently, there exists a trade-off between memory density and yield improvement when using fuse box concepts.
In view of these drawbacks encountered in the prior art, the problem to be solved by the invention is to provide a circuit device, in particular a semiconductor memory device, which employs a fuse box concept having programmable fuse elements adapted to adjust adjustable elements, which consumes less chip area.
SUMMARY
According to one aspect of the invention, a semiconductor memory device includes a plurality of integrated circuit modules each having a plurality of module elements and at least one adjustable module element. At least one fuse box is electrically connected to the plurality of integrated circuit modules. The fuse box has a plurality of programmable fuse elements, that, when programmed, adjust the adjustable module element.
Thus, the at least one fuse box or fuse repository (which can contain several fuse boxes and which can be partitioned in the layout to have several fuse box blocks) is associated with a plurality of integrated circuit modules. The integrated circuit modules have to be understood as independent integrated circuits, i.e., autonomous integrated circuits, such as different memory circuits on a semiconductor memory chip. Therefore, the term integrated circuit modules refers to independent integrated circuits on a chip and not to parts of a single integrated circuit on this chip.
According to another aspect of the invention, several of the independent integrated circuit modules are connected to a single fuse box or fuse repository, which constitutes a central fuse box of the circuit device. This central fuse box serves different integrated circuit modules by enabling an adjustability of the integrated circuit modules by adjusting the adjustable module elements thereof. This is achieved by a suitable programming of the fuse elements of the fuse box.
Preferably, all components of the at least one fuse box are clustered or grouped in one designated region within the circuit device, e.g., a designated region of the chip. In particular, the programmable (or adjustable) fuse elements of the fuse box are concentrated in a designated fuse element area. In case that laser-programmable fuse elements are used within the fuse box, such clustering or grouping of the programmable fuse elements greatly facilitates the positioning and programming of the laser-programmable fuse elements by the laser programming tool.
In the prior art, local fuse boxes have been widely employed in circuit devices. These local fuse boxes only serve adjacent or close by integrated circuits and are not adapted to configure adjustable module elements, for example, the whole chip. In contrast to the prior art, the control logic provided within the fuse box according to the invention does not linearly increase in its complexity when the number of programmable fuse elements is increased. The inventive (centralized) fuse box requires less chip area compared to several local fuse boxes. This will lead to a considerable reduction of production costs.
According to a preferred embodiment, the number of the programmable fuse elements is not sufficient to adjust all of the adjustable module elements of all of the integrated circuit modules. Thus, the invention proposes to intentionally select the number of programmable fuse elements such that it does not allow to configure all of the adjustable module elements of all of the integrated circuit modules simultaneously. Instead, the number of the programmable fuse elements is only sufficient to adjust a fraction of the adjustable module elements. For example, the number of the programmable fuse elements could be selected such that only up to 90%, preferably only up to 75% and even more preferably only up to 50% of the adjustable module elements of all the integrated circuit modules could be adjusted therewith.
Surprisingly, this substantial reduction of the number of the programmable fuse elements does not greatly affect the overall yield in the production of circuit devices according to the invention. This is essentially due to the fact that in many applications only adjustable module elements in a specific region of the circuit device need to be adjusted. If, for example, the adjustable module element is a redundant module element adapted to replace a defect module element, then only the redundant module elements in certain areas of the circuit device need to be activated. In this context, it has to be borne in mind that defects (defect module elements) in circuit devices are very often clustered leading to fault-free circuit device areas and faulty circuit device areas.
Since one aspect of the invention provides a circuit device with a centralized fuse box, it is very oft
Di Ronza Mario
Picot Olivier
Schöber Volker
Fish & Richardson P.C.
Infineon - Technologies AG
Le Vu A.
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