Active solid-state devices (e.g. – transistors – solid-state diode – Integrated circuit structure with electrically isolated... – Passive components in ics
Reexamination Certificate
2002-10-29
2004-02-03
Eckert, George (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Integrated circuit structure with electrically isolated...
Passive components in ics
C257S381000, C257S508000, C257S510000, C257S774000, C257S637000
Reexamination Certificate
active
06686645
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuse structure, and in particular the fuse structure of a third conductive layer, that can avoid damage to the adjacent fuse structure from the laser blow process in the laser spot of the fuse structure.
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 with programmed capabilities wherein fuses are selectively “blown” by 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 a 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 sectional view of a traditional fuse structure, and
FIG. 1
shows a cross section B-B′ of FIG.
3
.
FIG. 2
is a sectional view of a traditional fuse structure, and
FIG. 2
shows a cross section C-C′ of FIG.
3
.
FIG. 3
is a top view of a traditional fuse structure.
Referring to
FIG. 1
, symbol
100
shows a substrate. A first dielectric layer
120
is formed on the substrate
100
. A metal layer M
0
is formed on part of the first dielectric layer
120
. A second dielectric layer
150
is formed on part of the metal layer M
0
and part of the first dielectric layer
120
. A metal layer M
1
is formed on part of the second dielectric layer
150
. At least one conductive plug
130
is defined through the second dielectric layer
150
, for electrically connecting the M
0
layer and the M
1
layer.
Referring to
FIG. 2
, is a sectional view of a traditional fuse structure, and
FIG. 2
shows the cross section C-C′ of FIG.
3
.
FIG. 3
is a top view of FIG.
1
and FIG.
2
. There are plural fuse structures
210
,
220
,
230
,
240
,
250
,
260
in fuse window
140
. Each fuse structure comprises the M
0
layer, the conductive 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 comprises its own optimal of a laser spot
110
. To give an example, a laser beam
296
blows the position
110
of the fuse structure
240
. Because of misalignment of the laser beam
290
or thermal scattering of the laser beam
290
, thermal shock from the laser blow process can damage the M
0
layer. This can cause the fuse structures to crack, seriously affecting device reliability and yield.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to provide a fuse structure, and in particular a fuse structure of the third conductive layer that can avoid damage to the adjacent fuse structure from the laser blow process in the laser spot thereof.
The present invention provides a fuse structure. An optimal position of laser spot is defined above a substrate. A first dielectric layer is formed on the substrate. A first conductive layer is formed on part of the first dielectric layer. A second dielectric layer is formed on part of the first dielectric layer and part of the first conductive layer. A second conductive layer is formed on part of the second dielectric layer. A third dielectric layer is formed on part of the second conductive layer and part of the second dielectric layer. A third conductive layer is formed on the third dielectric layer and does not electrically connect the first conductive layer and second conductive layer, wherein the third conductive layer and third dielectric layer have an opening to reveal part of the second conductive layer, and define a laser spot of the fuse structure.
At least one conductive plug penetrates the second dielectric layer, to electrically connect the first conductive layer and the second conductive layer, to function as a fuse.
The advantage of the present invention is a third conductive layer placed on top of the second conductive layer. The third conductive layer has an opening to reveal part of the second conductive layer and define a laser spot of the fuse structure.
When a laser beam blows the fuse structure of a laser spot in the second conductive layer, the third conductive layer can obstruct or absorb superfluous laser energy, to prevent damage to the adjacent first conductive layer. The fuse structure of the prior art has no conductive layer or dielectric layer on the top of fuse structure.
REFERENCES:
patent: 6472253 (2002-10-01), Bothra
patent: 2003/0094670 (2003-05-01), Hung et al.
Eckert George
Nanya Technology Corporation
Nguyen Joseph
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