Active solid-state devices (e.g. – transistors – solid-state diode – Contacts or leads including fusible link means or noise...
Reexamination Certificate
1999-11-12
2001-04-10
Abraham, Fetsum (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Contacts or leads including fusible link means or noise...
C257S209000, C257S299000, C257S304000, C257S311000
Reexamination Certificate
active
06215173
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a redundancy fuse block having a small occupied area and, more particularly, to a redundancy fuse block for use in a semiconductor memory device, such as DRAM, having a redundancy function.
(b) Description of a Related Art
A semiconductor memory device such as DRAM generally has a redundancy function, wherein a row (or column) of memory cells including one or more of defective memory cells is replaced by a redundancy row (column) including redundancy cells in number corresponding to the number of the memory cells to be replaced. If it is found that a memory device has a defective memory cell in a product test, the address of the defective row is stored in a redundancy circuit by selectively cutting a plurality fuses in a fuse block by a laser beam. Each pair of fuse elements in the fuse block represents a bit of row address by the on- or off-states of the fuse elements.
In operation of the semiconductor memory device, if the redundancy decoder detects that an input row address coincides with the address of the replaced row, the input row address is replaced with the redundancy row address by switching the input row address, whereby the defective row is replaced by the redundancy row.
FIG. 1
shows a conventional semiconductor device having a fuse block including fuse elements
33
, made of polycrystalline silicon (polysilicon), in number corresponding to the number of bits of row address. The fuse block is received in a rectangular window
31
having longer sides perpendicular to the extending direction of each elongate fuse element
33
. In this example, eight fuse elements
33
are arranged in the direction parallel to the longer sides of the rectangular window
31
with a specified space disposed between each two of the fuse elements
33
. Both ends of each fuse element
33
are connected to signal lines
34
and
36
made of aluminum at the contacts
35
and
37
disposed outside the window
31
. The fuse elements
33
are to be selectively cut by the laser beam within the window
31
, for detecting a defective row address in the redundancy address decoder.
During cutting the fuse element
33
, the laser beam is irradiated within a circular area “A” receiving therein the bridge section
33
a
of the single fuse element
33
, whereby the specified fuse element
33
is cut at the bridge section
33
a
without cutting the adjacent fuse elements
33
.
In the arrangement of the fuse elements
33
, the circular area “A” for assuring a sufficient space between each two of the fuse elements
33
provides safe cutting of a specified fuse element
33
without miss-cutting of the adjacent fuse elements. However, the sufficient space for the fuse elements
33
enlarges the pitch of the signal lines
34
and
36
and associated transistors (not shown), thereby enlarging the overall chip size for the semiconductor device.
Patent Publication JP-A-6-310603 describes a fuse block having a reduced occupied area, such as shown in
FIG. 2
, wherein two out of three fuse elements
33
have parallel offsets therein. A first pair of fuse elements
33
shown at the left side, fore example, of the window
31
have right-wise offsets, whereas second pair of fuse elements
33
disposed adjacent to the first pair of fuse elements
33
, with a straight fuse element
33
sandwiched between the pairs, have left-wise offsets. By deviating the circular areas “A” of the pair of fuse elements
33
from each other in the direction of the elongate fuses
33
, the longer sides of the window
31
are reduced in length with the shorter sides being somewhat increased,. The circular area “A” has a radius of 3.5 micrometers (&mgr;m), for example.
In the fuse block described in the publication, however, the advantage in reduction of the area for the window
31
is relatively limited, wherein the longer sides of the window
31
may be reduced from 35 &mgr;m to 29 &mgr;m, for example.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide a window for a fuse block having a reduced occupied area while assuring safe selective-cutting of the fuse elements received therein.
The present invention provides a semiconductor device including a plurality of signal lines and a plurality of associated fuse elements arranged in a window for selectively cutting the fuse elements for a redundancy function of the semiconductor device, each of the fuse elements including a pair of lead sections extending parallel to each other, each of the lead sections having a first end connected to a corresponding one of the signal lines and a second end, and a bridge section connected between the second ends of the pair of lead sections.
In accordance with the semiconductor device of the present invention, since two out of the bridge sections of the fuse elements can be arranged adjacent to each other in the direction of the shorter sides of the window while assuring a sufficient space therebetween, the longer sides of the window receiving therein the fuse elements can be reduced while assuring a safe selective-cutting of the fuse elements.
The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings.
REFERENCES:
patent: 61-168242 (1986-07-01), None
patent: 63-127549 (1988-05-01), None
patent: 63-198354 (1988-08-01), None
patent: 5-136271 (1993-06-01), None
patent: 6-310603 (1994-11-01), None
patent: 9-17872 (1997-01-01), None
Abraham Fetsum
NEC Corporation
Sefer Ahmed N.
Young & Thompson
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