Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-10-26
2001-11-13
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S600000, C438S758000
Reexamination Certificate
active
06316350
ABSTRACT:
FIELD OF THE INVENTION
The invention is generally related to the field of semiconductor processing and more specifically to an etch for removing slag remaining after a blowing a fuse.
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.
FIGS. 1A and 1B
show a fuse
30
before and after the fuse
30
is blown, respectively. During this process, a high power laser is used to “blow” a portion of the capping layer
16
overlying the metal
20
. The capping layer typically comprises silicon nitride or oxide. During this process, the metal
20
of the fuse
30
can reach an extremely high temperature (e.g., 2000° C.). As a result, the metal
20
of the fuse
30
is blown out of the fuse area within interconnect level
14
. Unfortunately, some of the material from the fuse
30
is redeposited on the sidewalls of the fuse
30
and on the surface of the device. This material is referred to a slag
22
. Slag
22
comprises both the metal
20
of the fuse and the liner material
18
of the fuse. To avoid unwanted shorts, the slag
22
must be removed.
Etch sequences to remove aluminum (Al) slag and TiN liners are known in the art. However, copper metal interconnects are being developed to replace aluminum interconnects to improve performance. Accordingly, there is a need to replace the Al-slag and TiN liner etch sequence with a Cu-slag and appropriate liner etch sequence.
SUMMARY OF THE INVENTION
The invention is a post laser blown fuse slag etch for a copper fuse with a barrier metal liner (e.g., Ta
x
N
y
, Ta, Ti, Ti
x
N
y
). After the fuse is blown, copper and copper complexes may be selectively removed, for example, by a nitric acid/H
2
O
2
solution. Then, a corrosion inhibitor is used to passivate the surface of exposed copper. Next, the liner is removed using a strong basic etch chemistry comprising a base plus H
2
O
2
. This solution removes the liner selectively with respect to silicon nitride and oxides. A diluted HF solution may then be used to remove any trace metal or oxidized copper.
An advantage of the invention is providing a copper slag etch sequence that removes the barrier liner material selectively with respect to silicon nitride and oxides.
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: 3794948 (1974-02-01), Linton et al.
patent: 6061264 (2000-05-01), Giust et al.
Eissa Mona M.
Yocum Troy A.
Brady III W. James
Dang Phuc T.
Garner Jacqueline J.
Nelms David
Telecky , Jr. Frederick J.
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