Active solid-state devices (e.g. – transistors – solid-state diode – Integrated circuit structure with electrically isolated... – Passive components in ics
Reexamination Certificate
2002-02-07
2004-07-27
Eckert, George C. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Integrated circuit structure with electrically isolated...
Passive components in ics
C257S209000, C337S290000, C337S293000, C337S295000, C438S281000
Reexamination Certificate
active
06768184
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuse structure used in an integrated circuit device, and more particularly, to a novel fuse structure that can prevent the adjoining fuse structure from being damaged in the laser blow process.
2. Description of the Related Art
Fuses are routinely used in the design of monolithic integrated circuits (IC), and in particular in memory devices as elements for altering the configuration of the circuitry contained therein. As such, memories are commonly built which programmed capabilities wherein fuses are selectively “blown” by, e.g., a laser beam.
It is well known that random access memories (RAM) are designed with redundancies which include spare columns, rows, or even fully functional arrays, wherein when any of these spare elements fails, the defective row, column and the like are replaced by a corresponding element. Disabling and enabling of spare elements is accomplished by fuses which are blown (i.e., melted away) when required, preferably, by the laser beam.
Additionally, the technique of laser fuse deleting (trimming) has been widely used both in the memory and logic IC fabrication industries, as an effective way to improve functional yields and to reduce development cycle time. Yet, fuse blow yield and fuse reliability have been problematic in most conventional fuse designs.
FIG. 1
is a cross-section of a traditional fuse structure.
FIG. 2
is a top view of a traditional fuse structure. And
FIG. 1
shows the cross section C-C′ of FIG.
2
.
Referring to
FIG. 1
, symbol
100
shows an insulated layer substrate. A metal layer M
0
is formed on part of the substrate
100
. An oxide layer
120
is formed on the metal layer M
0
and part of the substrate
100
. A metal layer M
1
having an optimal position of laser spot
110
is formed on part of the oxide layer
120
. At least one conductive plug
130
is defined through the oxide layer
120
, for electrically connecting the M
0
layer and the M
1
layer. A fuse window
140
is formed above part of the M
1
layer comprising the position
110
and part of the oxide layer
120
. Symbol
150
shows a passivation layer.
In
FIG. 2
, there are plural fuse structures
210
,
220
,
230
in the fuse window
140
. Each fuse structure
210
,
220
,
230
comprises the M
0
layer, the plug
130
and the M
1
layer. The solid line area shows the M
1
layer, the dash line area shows the M
0
layer, and each structure
210
,
220
,
230
comprises its own optimal position of laser spot
110
. To give an example, a laser beam
290
blows the position
110
of the fuse structure
220
. Because of misalignment of the laser beam
290
or thermal scattering of the laser beam
290
, this laser blow process can damage the M
0
layer of the fuse structures
210
,
230
which near the fuse structure
220
by thermal shock. This causes the fuse structures
210
,
230
to crack, and seriously affect device reliability and yield.
SUMMARY OF THE INVENTION
An object of the present invention is to provide the first fuse structure. An optimal position of laser spot is defined above a substrate. A first conductive layer is formed on part of the substrate. A dielectric layer is formed on the substrate and the first conductive layer. A second conductive layer comprising the position of laser spot is formed on part of the dielectric layer. A third conductive layer is formed on the part of the dielectric layer placed above the first conductive layer, where the third conductive layer is insulated from the first and second conductive layers. At least one conductive plug penetrates the dielectric layer, to electrically connect the first conductive layer and the second conductive layer.
The second fuse structure of the present invention is also provided. An optimal position of laser spot is defined above a substrate. A first conductive layer is formed on part of the substrate. A dielectric layer is formed on the substrate and the first conductive layer. A second conductive layer comprising the position of laser spot is formed on the dielectric layer. At least one conductive plug penetrates the dielectric layer, to electrically connect the first conductive layer and the second conductive layer.
The present invention improves on the prior art in that the third conductive serving as a floating layer is placed above the first conductive layer; or the second conductive layer is expanded above the first conductive layer. Thus, the invention can prevent both misalignment of the laser beam and thermal scattering of the laser beam from damaging the first layer of the fuse structure in the laser blow process, raises reliability and yield, and ameliorates the disadvantages of the prior art.
REFERENCES:
patent: 5321300 (1994-06-01), Usuda et al.
patent: 5585662 (1996-12-01), Ogawa
patent: 5618750 (1997-04-01), Fukuhara et al.
patent: 6008716 (1999-12-01), Kokubun
patent: 6218721 (2001-04-01), Niwa
patent: 6295721 (2001-10-01), Tsai
patent: 6335229 (2002-01-01), Pricer et al.
patent: 6444544 (2002-09-01), Hu et al.
patent: 6562674 (2003-05-01), Tsuura
patent: 2002/0079552 (2002-06-01), Koike
patent: 4-3-83361 (1991-04-01), None
Hung Jui-Lin
Wang Mang-Shiang
Eckert George C.
Ladas & Parry
Nanya Technology Corporation
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