Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2003-08-27
2004-08-17
Gurley, Lynne A. (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S635000, C438S637000, C438S638000, C438S639000, C438S658000, C438S700000, C438S707000, C438S723000, C438S725000, C438S743000, C438S911000, C438S976000
Reexamination Certificate
active
06777333
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to methods for fabricating a semiconductor device, and more particularly relates to a method for forming an interconnect of a semiconductor device.
In recent years, copper has been commonly used as an interconnect material for semiconductor devices. In process steps for processing an interconnect formed by using copper as an interconnect material, used is a damascene process in which an interconnect groove is formed by a dry etching technique and then an interconnect material is filled into the interconnect groove (see, e.g., Japanese Unexamined Patent Publication No. 2001-196371).
Hereinafter, a method for forming an interconnect in a known semiconductor device will be described with reference to the accompanying drawings.
FIGS. 8A through 8D
are cross-sectional views illustrating respective process steps for fabricating a known semiconductor device.
First, as shown in
FIG. 8A
, a silicon oxide film
102
is formed on a semiconductor substrate
101
of silicon and then an interconnect groove is formed in the silicon oxide film
102
. Next, a conductive pattern
103
of copper is formed so as to be filled in the interconnect groove formed in the silicon oxide film
102
. Subsequently, an insulating film
104
is formed on the silicon oxide film
102
and the conductive pattern
103
, and then a resist pattern
105
having an opening
105
a
is formed on the insulating film
104
.
Next, as shown in
FIG. 8B
, the insulating film
104
is etched by plasma dry etching using the resist pattern
105
as a mask to form an opening
104
a
in the insulating film
104
. In this manner, the surface of the conductive pattern
103
is exposed. The plasma dry etching is performed using a parallel plate RIE system under the conditions where the flow rate of a CF
4
gas as an etching gas is 50 mL/min (normal state), the flow rate of an O
2
gas as a control gas for a deposit to be etched is 10 mL/min (normal state), the substrate temperature is 25° C., the RF output power is 1000 W, and the inside chamber pressure is 5 Pa.
Next, as shown in
FIG. 8C
ashing using an oxygen gas is performed to remove the resist pattern
105
. The ashing is performed using a microwave plasma ashing system under the conditions where the flow rate of an oxygen gas is 1000 mL/min (normal state), the microwave output power is 2000 W, the discharge time is about 1 minute, the substrate temperature is about 250° C. and the pressure is about 100 Pa. By the ashing, a copper oxide layer
103
a
having a thickness of about 40 nm is formed on the surface of the conductive film
103
.
Next, as shown in
FIG. 8D
, the copper oxide layer
103
a
which has been formed during the ashing is removed by cleaning using an organic acid cleaning agent containing aluminum fluoride, and Ar sputtering. Thereafter, a conductive film
106
is formed on part of the conductive pattern
103
from which the copper oxide layer
103
a
has been removed and the insulating film
104
.
In the method for fabricating a known semiconductor device, however, the thickness of the copper oxide layer
103
a
formed on the surface of the conductive pattern
103
is about 40 nm. That is to say, the copper oxide layer
103
a
is relatively thick. Accordingly, the copper oxide layer
103
a
can not be entirely removed by an organic acid cleaning and Ar sputtering, and thus the copper oxide layer
103
a
is left between the conductive pattern
103
and the conductive film
106
, as shown in FIG.
8
D. This results in an increase in contact resistance between the conductive pattern
103
and the conductive film
106
or variations in contact resistance therebetween the conductive pattern
103
and the conductive film
106
.
SUMMARY OF THE INVENTION
The present invention aims to prevent the progress of oxidation of a conductive pattern in removing a resist pattern and also to prevent the formation of a thick oxide film which is difficult to be removed on the surface of the conductive pattern.
To solve the above-described problems, a first method for fabricating a semiconductor device according to the present invention is characterized by comprising the steps of: forming an insulating film on a conductive pattern formed on a substrate; forming a resist pattern on the insulating film; performing etching to the insulating film using the resist pattern as a mask to form in the insulating film an opening at which part of the surface of the conductive pattern is exposed; forming an antioxidant layer on the part of surface of the conductive pattern exposed while removing the resist pattern; and depositing a conductive film on the conductive pattern from which the antioxidant layer has been removed.
In the first method for fabricating a semiconductor device, an antioxidant layer for preventing oxidation of an conductive pattern is formed on the surface of the conductive pattern while a resist pattern is removed. Thus, it is possible to prevent the progress of oxidation of the conductive pattern in removing the resist pattern and also to prevent the formation of a thick oxide film which is difficult to be removed. Moreover, the antioxidant layer formed on the surface of the conductive pattern can be removed in a simple manner, and thus it is possible to prevent an oxide film from being interposed between the conductive pattern and the conductive film. Therefore, the contact resistance between the conductive pattern and the conductive film can be reduced and variations in the contact resistance therebetween can be suppressed.
In the first method for fabricating a semiconductor device, it is preferable that the conductive pattern contains Cu and the antioxidant layer contains CuO as a main component.
Thus, since an antioxidant layer containing CuO is passive, it prevents oxidation of part of a conductive pattern located under the antioxidant layer. Therefore, it is possible to prevent the formation of a thick oxide film which is difficult to be removed. Accordingly, the antioxidant layer formed on the surface of the conductive layer can be removed in a simple manner.
In the first method for fabricating a semiconductor device, it is preferable that the step of forming an antioxidant layer includes performing oxygen plasma treatment with a substrate temperature of 120° C. or less.
Thus, the proportion of CuO in an antioxidant layer formed on the surface of the conductive pattern is increased while the proportion of Cu
2
O therein is reduced. Accordingly, oxidation of the conductive pattern located under the antioxidant layer can be further suppressed and thus the formation of a thick oxide film which is difficult to be removed on the surface of the conductive pattern can be reliably prevented. Therefore, the antioxidant layer formed on the surface of the conductive pattern can be removed in a more simple manner.
In the first method for fabricating a semiconductor device, it is preferable that the step of forming an antioxidant layer includes performing oxygen plasma treatment with a chamber pressure of 40 Pa or less.
Thus, the proportion of CuO in an antioxidant layer formed on the surface of the conductive pattern is increased while the proportion of Cu
2
O therein is reduced. Accordingly, oxidation of the conductive pattern located under the antioxidant layer can be further suppressed and thus the formation of a thick oxide film which is difficult to be removed on the surface of the conductive pattern can be reliably prevented. Therefore, the antioxidant layer formed on the surface of the conductive pattern can be removed in a more simple manner.
A second method for fabricating a semiconductor device according to the present invention is characterized by comprising the steps of: forming an insulating film on a conductive pattern formed on a substrate; forming a resist pattern on the insulating film; performing etching to the insulating film using the resist pattern as a mask to form in the insulating film an opening at which part of the surface of the conductive pattern is exposed; forming an antioxidant layer
Gurley Lynne A.
McDermott Will & Emery LLP
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