Layer forming material and wiring forming method

Details Layer forming material and wiring forming method Layer forming material and wiring forming method

1998-01-07

2002-04-16

Nazario-Gonzalez, Porfirio (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heavy metal containing

C556S113000, C427S150000, C430S320000

Reexamination Certificate

active

06372928

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a layer forming material for forming copper wiring on a substrate, and also to a copper wiring forming method.
Conventionally, aluminium has mainly be used as a wiring material of a semiconductor integrated circuit formed on a semiconductor substrate made of Si. Due to the requirements for higher integration and higher speed of a semiconductor integrated circuit, however, attention is now placed, as the wiring material, on copper excellent in resistance to high stress migration and high electromigration.
The following description will discuss, as a first example of prior art, a method of forming copper wiring on a substrate using a sputtering method with reference to FIGS.
6
(
a
) to (
e
).
As shown in FIG.
6
(
a
), an insulating layer
101
of SiO
2
is deposited on the whole surface of a substrate
100
of Si. Then, as shown in FIG.
6
(
b
), a resist pattern
102
is formed on the insulating layer
101
by photolithography. Then, as shown in FIG.
6
(
c
), the insulating layer
101
is etched with the resist pattern
102
serving as a mask, thereby to form a concave portion
103
for wiring.
As shown in FIG.
6
(
d
), a sputtering method is applied with the use of a target of Si-containing Cu, thereby to deposit a Si-containing copper layer
104
on the whole surface of the insulating layer
101
. Then, as shown in FIG.
6
(
e
), that portion of the copper layer
104
which projects from the surface of the insulating layer
101
, is removed by a CMP method for example, thereby to form copper wiring
105
formed by the copper layer
104
. Then, the substrate
100
is thermally treated, as shown in FIG.
6
(
f
), to form a copper silicide layer
106
on the surface of the copper wiring
105
.
The following is the reason of why the copper silicide layer
106
is formed. Copper is liable to be readily oxidized by a heat treatment of about 300° C. in the atmosphere of a trace amount of oxygen since copper is low in resistance to oxidation. Accordingly, when the copper wiring
105
comes in contact with an oxygen-containing layer of SiO
2
or the like forming the insulating layer
101
, the oxidation of copper is advanced with the passage of time in the heating step. Even though the copper wiring
105
does not come in contact with an oxygen-containing layer, the copper wiring
105
comes in contact with the air during the heat treatment. This disadvantageously results in an increase in resistance of the copper wiring
105
. Also, the characteristics of the transistor and the like may be degraded by diffusing copper in the copper wiring
105
into the insulating layer
101
. In addition, direct deposition of the copper wiring
105
onto the insulating layer
101
results in less adhesiveness between the copper wiring
105
and the insulating layer
101
. To prevent the copper wiring
105
from coming in contact with the insulating layer
101
or the air, the copper silicide layer
106
is formed on the surface of the copper wiring
105
.
When the wiring rule is small in depositing the copper layer
104
on the insulating layer
101
by a sputtering method, voids
107
are disadvantageously formed as shown in FIG.
6
(
d
). The voids
107
remain also in the copper wiring
105
. This disadvantageously contributes to disconnection.
Recently, attention is placed on the technology of forming a copper layer and copper wiring by a CVD (Chemical Vapor Deposition) method using an organic copper complex compound as a precursor. In the field of semiconductor device, study has extensively been made on this technology.
With reference to FIGS.
7
(
a
) to (
d
) and FIGS.
8
(
a
) to (
c
), the following description will discuss, as a second example of prior art, a copper wiring forming method by the CVD method.
As shown in FIG.
7
(
a
), an insulating layer
111
of SiO
2
is formed on the whole surface of a substrate
110
of Si. Then, as shown in FIG.
7
(
b
), a resist pattern
112
is formed on the insulating layer
111
by photolithography. Then, as shown in FIG.
7
(
c
), the insulating layer
111
is etched with the resist pattern
112
serving as a mask, thereby to form a wiring concave
113
.
As shown in FIG.
7
(
d
), a first barrier layer
114
made of WSiN for example is deposited on the wall and bottom surfaces of the wiring concave
113
by a sputtering or CVD method. Then, as shown in FIG.
8
(
a
), a copper layer
115
is deposited on the whole surface of the insulating layer
111
by a CVD method. Then, as shown in FIG.
8
(
b
), that portion of the copper layer
115
which projects from the surface of the insulating layer
111
, is eliminated by a CMP method for example, thus forming copper wiring
116
formed by the copper layer
115
. Then, as shown in FIG.
8
(
c
), a second barrier layer
117
of WSiN for example is deposited on the whole surfaces of the copper wiring
116
and the insulating layer
111
by a sputtering or CVD method. The first and second barrier layers
114
,
117
in the second example of prior art, act in the same way as the copper silicide layer
106
acts in the first example of prior art.
To deposit the copper layer
115
by a CVD method, there is known, as the layer forming material to be supplied to the substrate
110
, an organic copper complex compound which is in the form of a liquid or a solid at room temperature. In using a liquid organic copper complex compound in a CVD method, there are known two methods; i.e., a first method in which the organic copper complex compound is caused to pass, in the form of a liquid, through a liquid mass flow meter, the compound is increased in temperature to cause the same to be evaporated by a vaporizer, and the resulting gaseous organic copper complex compound is then introduced into a reaction chamber; and a second method in which a liquid organic copper complex compound is evaporated by bubbling and the resulting gaseous organic copper complex compound is introduced into a reaction chamber through a heated pipe.
As an example of the organic copper complex compound of prior art, there is known, as disclosed by U.S. Pat. No. 5,144,049, L=H
2
C═CH—SiMe
3
((hfac)CU(vinyl trimethyl silane)) in which the ligand is the &bgr; diketone type as shown by the following chemical formula:
When this organic copper complex compound is a solid, the solid organic copper complex compound is dissolved in an organic solvent, e.g., isopropyl alcohol, and the resulting solution is introduced into a reaction chamber in the same manner as done in the liquid organic copper complex compound.
According to the copper wiring forming method using a CVD method, to form a barrier layer on the surface of the copper wiring
116
, the first barrier layer
114
and the second barrier layer
117
are required to be formed at different steps. This increases the number of steps to disadvantageously lengthen the whole process.
Further, when copper wiring is formed using an organic copper complex compound of prior art, carbon is put, as impurity, into the copper wiring. This advantageously increases the copper wiring in resistance.
SUMMARY OF THE INVENTION
In a copper wiring forming technology using a CVD method, it is a first object of the present invention to reduce the number of the steps of forming barrier layers on the surface of the copper wiring. It is a second object of the present invention to lower the copper wiring in resistance.
A first layer forming material according to the present invention comprises a compound which has a structure of six-membered ring coordinated to Cu and containing Si, and of which general formula is represented by the following chemical formula:
(wherein X
1
and X
2
are elements of the VI group of the same or different types which are coordinate-bonded to Cu, at least one of Y
1
, Y
2
and Y
3
is Si, L is a group which has a double or triple bond and which is able to supply electrons to Cu, and each of R
1
and R
2
is an optional element or compound).
According to the first layer forming material, Si is contained in the structu

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