Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Fusible link or intentional destruct circuit
Reexamination Certificate
1998-09-28
2001-03-06
Zweizig, Jeffrey (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Fusible link or intentional destruct circuit
Reexamination Certificate
active
06198338
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of constructing a fuse means for a semiconductor device and a circuit adapted to utilize the same.
A fuse means is widely used in a semiconductor device to restore a memory cell through repair, to adjust transistor dimensions, to provide a desired transmission delay for a signal, and to control the pulse-width of a signal.
One commonly-used type of fuse means comprises a one-piece fuse set. A problem with this fuse means is that when the fuse of the fuse means is imperfectly cut one cannot obtain the expected and desired circuit operation.
For example, a fuse means may be utilized as a means for repairing a circuit by replacing an impaired main cell with a redundancy cell in order to improve the production yield of a memory device. In such a case, replacement is usually performed by cutting a fuse of a redundancy decoder in accordance with the address of the main cell to be replaced by utilizing a laser beam cutting device.
FIG. 1
is a circuit diagram illustrating a portion of a redundancy decoder which is constructed by using a conventional fuse construction method. It illustrates the portion of the redundancy decoder comprising one master fuse portion F
M
and decoding fuse portions F
D
's with each of the decoding fuses corresponding to a row address.
In such a redundancy decoder it is generally necessary to perform repairs by cutting the master fuse F
M
and then selectively cutting a decoder fuse F
D
corresponding to the address of an impaired main cell. However, performing such repairs normally cannot be done very easily in such a manner as to avoid imperfect cutting of the fuses and subsequently impaired operation of the circuit.
A repair operation involving a master fuse portion is described in more detail as follows.
During a repair, when a signal RCS
X
B is maintained at a low level of potential and the master fuse is cut properly, the potential of a node N
1
is raised to a high level. However, when master fuse F
M
is not completely cut, the master fuse will then serve as a resistance, thus turning off a PMOS transistor T
2
, which in turn decreases the potential of node N
1
to a low level.
Similarly, incomplete cutting of decoding fuse F
D
has undesired consequences. Such improper repair attempts bring about current leakage through a ground which should be prevented in normal operation.
FIGS. 2A
to
2
C are photos illustrating the imperfect cut of a fuse having the construction of a conventional fuse means and the result of a structural analysis of the cut portion.
FIG. 2A
is a photo showing the cut portion of a fuse, while
FIG. 2B
is a photo showing a magnification of the cut portion of the fuse shown in FIG.
2
A. Each of
FIGS. 2A and 2B
indicate that the fuse is not completely cut through.
FIG. 2C
is a photo showing the result of the structural analysis of the fuse portions remaining as a result of the incomplete cutting attempt.
FIG. 2C
indicates that silicon, which is identical to that constructing the fuse, remains in the cut section of the fuse portion.
Imperfect cutting of a fuse also imposes constraints on use of the fuse for the adjustment of transistor dimensions, the transmission delay of a signal and the control of the pulse-width of a signal. In the case of a fuse fabricated for the transmission delay of a signal, for example, the imperfect cut of the fuse serves as a principal factor to deteriorate reliability of a semiconductor device. The phenomenon of speed-push, that is, causing less delay than is expected to happen, is one undesired consequence that frequently arises.
SUMMARY OF THE INVENTION
It is an object of this invention is to provide a method of constructing a fuse means for a semiconductor device which is adapted to permit an effective repair by cutting of a fuse contained within the fuse means.
It is another object to provide a method of constructing such a fuse means which may be repaired by cutting a fuse using a laser beam cutting device.
It is yet another object of the present invention to provide a method of constructing a fuse means in a semiconductor circuit wherein the method comprises the step of connecting a plurality of fuses in at least one series arrangement.
In a preferred method for constructing a fuse means, fuses are provided in pairs of two, if such is permitted by constraints imposed by the area that the fuse means comprising the arrangement of fuses will occupy.
It is a further object of the present invention to provide a semiconductor circuit comprising at least one fuse means wherein, the fuse means comprises a plurality of fuses which are connected in series.
It is a yet further object of the present invention to provide a semiconductor circuit wherein a fuse means is located in a redundancy circuit.
It is still another object of the invention to provide a circuit adapted to utilize a fuse means comprising a plurality of fuses.
Thus, it is an object of the present invention to provide such a circuit and to provide a repair method with an improved probability that a proper fuse cut is obtained. A further object of the invention is to provide a circuit with a fuse means adapted to comprise a plurality of fuses connected in series to yield such an improved probability of a proper repair. One further object is to provide a fuse means with a plurality of fuses which may each be cut using a laser beam cutting device.
REFERENCES:
patent: 4686384 (1987-08-01), Harvey et al.
patent: 5387823 (1995-02-01), Ashizawa
patent: 5424672 (1995-06-01), Cowles et al.
patent: 5748031 (1998-05-01), Best
Han Eui-gyu
Kim Eun-han
Kim Young-gun
Jones Volentine, L.L.C.
Samsung Electronics Co,. Ltd.
Zweizig Jeffrey
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