Optimized metal fuse process

Details Optimized metal fuse process Optimized metal fuse process

2001-11-30

2004-02-10

Arbes, Carl J. (Department: 3729)

Metal working

Method of mechanical manufacture

Electrical device making

C029S029000, C029S846000

Reexamination Certificate

active

06687973

ABSTRACT:

FIELD OF THE INVENTION
The invention is generally related to the field of semiconductor processing and more specifically to a metal fuse process.
BACKGROUND OF THE INVENTION
In some integrated circuits, alternate interconnect paths are created to increase yield. For example, in SRAM circuits, after the last interconnect level is formed, the functionality of the device is measured. Defective interconnect paths are severed and replaced, with alternative interconnect paths. The defective interconnect paths are severed by “blowing” a fuse. During this process, a high power laser is directed at fuses that need to be removed. As a result, the fuse is for the most part, vaporized by the high power laser pulse. A wet etch is then used to remove any remaining fuse material from the blown fuse link as well as material from the fuse that may have been redeposited on the surface during the blowing process.
One prior art fuse process is shown in
FIGS. 1A-1D
. The top metal interconnect layer is used to form both fuses, like fuse
30
and probe pads, like probe pad
40
. The top metal interconnect comprises aluminum
42
with an overlying TiN barrier layer
44
. 8000 Å of oxide
52
are deposited using a high-density plasma (HDP) process. A resist pattern
54
is formed exposing the areas of oxide
52
over both the fuses and the probe pads, as shown in
FIG. 1A. A
single etch is then used to expose the fuses
30
and probe pads
40
, as shown in FIG.
1
B. An etch chemistry is used that etches both oxide and TiN. As a result of the etch and overetch required to ensure that all desired areas across the wafer are cleared, the fuse links
30
are degraded.
The circuits are then probed to determine which fuse links should be blown to fix defective circuits.
Next, a 3000 Å conformal oxide layer
56
is deposited over the structure, as shown in FIG.
1
C. Layer
56
completely covers the exposed fuses
30
and provides protection for the exposed aluminum of the probe pads
40
. A laser pulse is then directed towards the fuses that need to be removed. The fuse
30
cracks or breaks off at the weakest point, as shown in
FIG. 1D. A
wet etch is then used to wash away any remaining broken fuses and debris and dissolve fuse links that may be still attached through cracks in the conformal oxide.
Unfortunately, a blown fuse that does not crack correctly can jeopardize adjacent fuses that may still be desired. As a result, this process may result in degraded or even missing fuses.
SUMMARY OF THE INVENTION
The invention is a metal fuse process that uses a thinner (e.g., 6000 Å) oxide over the top interconnect. Because the oxide is thin at the upper corners of the fuse, the oxide cracks over the fuse during a laser pulse. A wet etch is then used to dissolve the exposed fuses.
An advantage of the invention is providing a metal fuse process the offers improved yield by avoiding over etching of fuses.
This and other advantages will be apparent to those of ordinary skill in the art having reference to the specification in conjunction with the drawings.


REFERENCES:
patent: 6214681 (2001-04-01), Yu
patent: 6261873 (2001-07-01), Bouldin et al.
patent: 6476454 (2002-11-01), Suguro
patent: 6617612 (2003-09-01), Zhang et al.
patent: 57-202778 (1982-12-01), None

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