Method of forming embedded copper interconnections and...

Details Method of forming embedded copper interconnections and... Method of forming embedded copper interconnections and...

2000-09-12

2002-05-21

Everhart, Caridad (Department: 2825)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S640000, C438S638000

Reexamination Certificate

active

06391775

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of forming embedded interconnections of copper on a surface of a substrate such as a semiconductor wafer, and a structure of such embedded interconnections of copper.
2. Description of the Related Art
Generally, aluminum alloys have heretofore been used as the materials of interconnections for use in semiconductor devices. For lower electric resistance and greater migration resistance, however, embedded interconnections of copper produced by a damascene process, and such embedded interconnections of copper arranged in multiple layers are employed.
Conventional multilayer embedded interconnections of copper have suffered various problems. Such problems will be described below with reference to
FIGS. 1A through 1C
of the accompanying drawings which illustrate a process of successive steps of forming multilayer embedded interconnections of copper. As shown in
FIG. 1A
, an interconnection
111
of copper is embedded in the upper surface of an insulating layer
110
of silicon dioxide (SiO
2
). Another insulating layer
120
of silicon dioxide (SiO
2
) is disposed on the insulating layer
110
and the interconnections
111
for insulating the interconnections of copper (Cu)
111
in an upper layer. When the insulating layer
120
is deposited on the interconnections layer
111
, an exposed upper surface
111
a
of the interconnections
111
is undesirably oxidized by oxygen.
As shown in
FIG. 1B
, an etchant (etching gas) is applied to etch the insulating layer
120
through a hole
131
defined in a resist layer pattern
130
on the surface of the insulating layer
120
for thereby forming a hole
121
in the insulating layer
120
, which will be filled with a plug for connection to the interconnections
111
. When the insulating layer
120
is thus etched, the exposed upper surface
111
a of the interconnections
111
is undesirably modified in the composition by the etchant.
As shown in
FIG. 1C
, when the resist layer
130
(see
FIG. 1B
) is removed using oxygen, the exposed upper surface
111
a
of the interconnections
111
is undesirably oxidized by the applied oxygen.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of forming embedded interconnections of copper while effectively preventing the exposed surface of an interconnections of copper from being modified or oxidized.
Another object of the present invention is to provide an embedded copper interconnection structure.
According to the present invention, a method of forming embedded interconnections of copper comprises the steps of: forming an insulating layer; forming embedded interconnections of copper in the insulating layer; planarizing (making coplanar) an exposed surface of the insulating layer including an exposed surface of the embedded interconnections of copper; and forming a protective film of silver on the exposed surface of the embedded interconnections of copper. The protective film of silver on the embedded interconnections of copper prevents the embedded interconnections of copper from being oxidized and prevents the surface thereof from being modified.
To form the protective film of silver on the exposed surface of the embedded interconnections of copper, the exposed surface of the embedded interconnections of copper may be plated with silver according to for example, immersion plating. The immersion plating allows the protective film of silver to be selectively formed only on the exposed surface of the embedded interconnections of copper, and also allows the protective film of silver to be formed in a very small thickness. Therefore, the amount of silver in the protective silver film may be relatively small. Since the protective film of silver and the embedded interconnections of copper do not form a solid solution, the electrical resistance of the embedded interconnections remains relatively low even if silver and copper are diffused in each other.
According to the present invention, an embedded copper interconnection structure comprises a substrate, a first insulating layer disposed on the substrate, an embedded interconnection of copper disposed in the first insulating layer, a protective film of silver disposed on the embedded interconnections of copper in the first insulating layer. The structure also includes a second insulating layer disposed on a surface of the first insulating layer including the embedded interconnections of copper having the protective film of silver thereon.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiment of the present invention by way of example.


REFERENCES:
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patent: 5071518 (1991-12-01), Pan
patent: 5250120 (1993-10-01), Takada et al.
patent: 5406120 (1995-04-01), Jones
patent: 5545927 (1996-08-01), Farooq et al.
patent: 5763953 (1998-06-01), IIjima et al.
patent: 6214728 (2001-04-01), Chan et al.
patent: 6291082 (2001-09-01), Lopatin
patent: 06006012 (1994-01-01), None

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