Wiring layer of a semiconductor integrated circuit

Details Wiring layer of a semiconductor integrated circuit Wiring layer of a semiconductor integrated circuit

1999-03-16

2001-11-06

Quach, T. N. (Department: 2814)

Active solid-state devices (e.g., transistors, solid-state diode

Combined with electrical contact or lead

Of specified material other than unalloyed aluminum

C257S761000, C257S763000, C257S767000

Reexamination Certificate

active

06313535

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device of a multilayered wiring structure, and more particularly to a semiconductor device in which a lower wiring layer is made of a material containing Al and upper and lower wiring layers are connected via a barrier metal film interposed therebetween.
In general, barrier metal films are formed above and below a wiring layer in a semiconductor device in order to protect the wiring layer and improve reliability. This matter is described in, for example, “Proceedings of 11th International VLSI Multilevel Interconnection Conference (1994)”, pages 172 to 178.
A method for manufacturing a conventional semiconductor device having barrier metal films will be described with reference to
FIGS. 23 and 24
.
First, as shown in
FIG. 23
, an insulating film
101
is formed on a part or the main surface of an active area having source/drain regions and a gate on a silicon substrate. A Ti film
102
, a TiN film
103
, an AlCu film
104
, a Ti film
105
and a TiN film
106
are formed in this order on the silicon substrate.
The AlCu film
104
constitutes a first wiring layer. The Ti film
102
and the TiN film
103
formed under the AlCu film
104
and the Ti film
105
and the TiN film
106
formed above it are used as barrier metal films of the wiring layer including the AlCu film
104
.
The barrier metal films have a multilevel structure constituted by two layers, each including Ti and TiN films. The TiN film
106
of the upper barrier metal film is also used as anti-reflection layer for lithography. The Ti film
105
is also used to prevent the surface of the AlCu film
104
from being nitrided when the TiN film
106
is deposited.
Then, as shown in
FIG. 24
, an SiO
2
film
107
serving as an interlayer insulating film is deposited on the main surface of the substrate. Thereafter, a resist pattern (not shown) is formed on the substrate by means of the lithography. Using the resist pattern as a mask, the SiO
2
film is selectively etched by the RIE method. Subsequently, the resist pattern is removed, thereby forming a via
108
.
Thereafter, a Ti film
110
, a TiN film
111
, and an AlCu film
109
to be a wiring material, are deposited on the main surface and then patterned. As a result, a second wiring layer
109
, electrically connected to the AlCu film
104
, is formed.
In the conventional method described above, after annealing at 450° for 60 minutes, a sheet resistance of a wiring layer including an AlCu film
104
was increased to about 0.45 (&OHgr;/□). Thus, the conventional method has a problem that an increase in wiring resistance must be suppressed. Further, it is desirable that the overall lower wiring layer including the upper and lower barrier metal films be thin.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in consideration of the aforementioned drawbacks of the prior art. It is therefore an object of the present invention to provide a semiconductor device having a thin and low-resistance wiring layer, which can be used in a refine apparatus, and a method for manufacturing the same.
The object of the present invention is achieved by a semiconductor device comprising: a first conductive film made of a material, such as AlCu, containing Al; a first barrier metal film provided on the first conductive film, the first barrier metal film containing a material, such as W, which reacts with Al at a rate lower than that at which Ti reacts with Al; an interlayer insulating film, such as SiO
2
, provided on the first barrier metal film; an opening provided in the interlayer insulating film so as to expose the first barrier metal film; and a second conductive film, such as AlCu, TiN or Ti, provided to bury the opening and electrically connected to the first conductive film.
With the above structure, when the first barrier metal film is made of W, it satisfactorily functions as an etching stopper, since the etching selectivity of W to SiO
2
is 40. The W film improves the electro-migration resistance of the AlCu film. Furthermore, the W film heat-reacts with Al as a Ti film does, which is conventionally used. However, since the degree of heat reaction of the W film with Al film is fully lower than that of the Ti film with Al film, the increase in sheet resistance of the AlCu film, caused by the heat reaction, is suppressed. Consequently, even if the lower wiring layer is thinner than that of the conventional device, the resistance of the lower wiring layer can be satisfactorily low.
The object of the present invention is also achieved by a method for manufacturing a semiconductor device comprising the steps of: forming a first conductive film made of a material, such as AlCu, containing Al; forming a first barrier metal film on the first conductive film, the first barrier metal film containing a material, such as W, which reacts with Al at a rate lower than that at which Ti reacts with Al; forming a first wiring layer by patterning a multilayered film including the first conductive film and the first barrier metal film to a desired shape; forming an interlayer insulating film on the first barrier metal film; forming an opening in the interlayer insulating film, such as SiO
2
, by selective etching so as to expose the first barrier metal film; and forming a second wiring layer electrically connected to the first wiring layer by burying the opening.
According to the above method, there is provided a semiconductor device having a thin and low-resistance wiring layer, which can be used in a refine apparatus.
Further, the object is achieved by the method, wherein the aforementioned step of forming a second wiring layer includes the steps of: forming a buried layer in the opening by selective growth; forming a second conductive film on a main surface of the multilayered film; and patterning the second conductive film.
This method has the following advantage in addition to that obtained by the first-mentioned method. Since the buried contact is formed in the opening by selectively growing W, the opening of a high aspect ratio can be buried automatically. Therefore, the two wiring layers can be brought into contact with each other easily and satisfactorily.
The object of the present invention is also achieved by a method for manufacturing a semiconductor device comprising the steps of: forming a first conductive film made of a material containing Al; forming a first barrier metal film on the first conductive film, the first barrier metal film containing a material which reacts with Al at a rate lower than that at which Ti reacts with Al; forming an insulating film on the first barrier metal film; forming a first wiring layer by patterning a multilayered film including the first conductive film, the first barrier metal film and the insulating film to a desired shape; forming an interlayer insulating film on the multilayered film; forming an opening in the interlayer insulating film and the insulating film by selective etching so as to expose the first barrier metal film; and forming a second wiring layer electrically connected to the first wiring layer by burying the opening.
This method has the following advantage in addition to those obtained by the aforementioned methods. Since the insulating film is provided on the W film as the first barrier metal film, even if the resist film serving as a mask is not satisfactorily thick, the insulating film under the resist functions as a mask in the step of patterning the multilayered film. Therefore, the semiconductor device can be processed with high accuracy and the margin of process can be improved.
The object of the present invention is also achieved by a method for manufacturing a semiconductor device comprising the steps of: forming a first barrier metal film containing a material which reacts with Al at a rate lower than that at which Ti reacts with Al; forming a first conductive film made of a material containing Al; forming a second barrier metal film on the first conductive film, the second barrier metal film containing a material wh

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