JPH08236623A - Semiconductor device and fabrication thereof - Google Patents

Abstract

PURPOSE: To stabilize the electrical characteristics by enhancing adhesion of tungsten filling a contact hole and an underlying film. CONSTITUTION: Titanium 1, titanium nitride 2, a titanium tungsten alloy 3 and tungsten 4 are deposited sequentially in a contact hole 16. Since the titanium tungsten alloy 3 exhibiting high adhesion to titanium nitride 2 and tungsten 4 is interposed between them, sufficient adhesion is ensured between tungsten 4 and an impurity diffusion layer 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly to connecting upper and lower wirings in a contact hole (connection hole) with a buried structure using a tungsten film.

[0002]

2. Description of the Related Art As the miniaturization of LSI progresses, a technique for surely electrically connecting a lower layer wiring and an upper layer wiring with a contact hole having a smaller aspect ratio is required. Therefore, the tungsten CVD (chemical vapor deposition) technique used for filling a contact hole having a high aspect ratio is indispensable in the process of half micron or later.
However, it is difficult to form a tungsten film on the insulating film, and since there is a problem that the junction leak between the source and the drain increases due to the diffusion of tungsten atoms, a barrier metal film such as titanium nitride is usually formed under the tungsten. By so doing, the diffusion of tungsten into the silicon substrate is effectively suppressed. At this time, a titanium film having a thickness of 20 nm or less is formed below the titanium nitride film in order to prevent an increase in contact resistance due to the direct formation of the titanium nitride film on the source and drain.

Generally, a titanium nitride film is formed by a reactive sputtering method of a titanium target in plasma of a mixed gas of nitrogen and argon. At this time, if the residual oxygen in the sputtering apparatus is mixed in the titanium nitride film formed, the value of the specific resistance of the titanium nitride film tends to vary.
As a result, in-plane variation occurs in the film quality of the tungsten film formed by the CVD method, and its reproducibility becomes low.

Therefore, recently, for example, Japanese Unexamined Patent Publication No. 5-2931
As reported in Japanese Unexamined Patent Application Publication No. 6-74, before filling the contact hole with the tungsten film formed by the CVD method,
A tungsten film formed by sputtering is formed on the surface of the titanium nitride film.

[0005]

However, since titanium nitride and tungsten are materials composed of only different elements from each other, in the above-mentioned conventional example, the titanium nitride film and the tungsten directly formed on the titanium nitride film by the sputtering method. There is a problem in that the adhesion to the film is poor and therefore the electrical characteristics are not stable and the manufacturing yield is reduced.

Therefore, an object of the present invention is to stabilize the electrical characteristics of the contact hole by improving the adhesion of the tungsten film formed to fill the contact hole having a high aspect ratio with the underlying film, for example. It is to improve the manufacturing yield of semiconductor devices.

[0007]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention comprises a step of forming an insulating film on a conductive layer to be a base film, and a step of forming the conductive film on the insulating film. A step of forming a contact hole reaching the layer, a step of forming a titanium film in contact with the conductive layer on the bottom surface of the contact hole, a step of forming a titanium nitride film on the titanium film, and a step of forming the titanium nitride film. The method has a step of forming a titanium-tungsten alloy film thereon and a step of forming a tungsten film filling the contact hole on the titanium-tungsten alloy film.

In one aspect of the present invention, the method further comprises the step of forming a wiring pattern by selectively removing the tungsten film by etching.

In one aspect of the present invention, the method further includes the step of forming a wiring pattern by selectively removing the tungsten film, the titanium-tungsten alloy film, the titanium nitride film, and the titanium film by etching.

In one aspect of the present invention, the conductive layer is an impurity diffusion layer formed on a surface portion of a silicon substrate.

In one aspect of the present invention, the insulating film is a silicon oxide film.

Further, in the semiconductor device of the present invention, the contact hole reaching the conductive layer formed in the insulating film on the conductive layer serving as the base film contacts the titanium film in contact with the conductive layer and the titanium film. It is embedded by a titanium nitride film, a titanium-tungsten alloy film in contact with the titanium nitride film, and a tungsten film in contact with the titanium-tungsten alloy film.

Further, in another aspect of the semiconductor device of the present invention, a titanium film in which the first conductive film and the second conductive film are in contact with the first conductive film and titanium nitride in contact with the titanium film are provided. They are connected through a film, a titanium-tungsten alloy film in contact with the titanium nitride film, and a tungsten film in contact with the titanium-tungsten alloy film.

[0014]

In the present invention, the titanium-tungsten alloy film is interposed between the titanium nitride film and the tungsten film without making direct contact with each other. Since this titanium-tungsten alloy film contains the same kind of element, it has good adhesion to both the titanium nitride film and the tungsten film. Therefore, sufficient adhesion between the tungsten film and the base film can be maintained.

[0015]

EXAMPLES The present invention will be described below with reference to examples.

First, a first embodiment of the present invention will be described with reference to FIG.

First, as shown in FIG. 1A, an N-type impurity diffusion layer 12 is formed by ion-implanting arsenic into the surface portion of a P-type silicon substrate 10. After a while
After the interlayer insulating film 14 made of a silicon oxide film having a film thickness of about 1 μm is formed by the CVD method, the interlayer insulating film 14 is formed.
Then, a contact hole 16 having a diameter of about 0.5 μm is formed by a fine processing technique using a photoresist (not shown) to expose the impurity diffusion layer 12. Further, a titanium (Ti) film 1 having a thickness of about 20 nm is formed on the entire surface by a sputtering method, and the impurity diffusion layer 1 exposed from the surface of the interlayer insulating film 14 including the inner surface of the contact hole 16 and the contact hole 16 is formed.
The surface of 2 is coated with titanium film 1.

Next, as shown in FIG. 1B, a titanium nitride film 2 having a thickness of about 100 nm is formed on the entire surface of the titanium film 1 by a reactive sputtering method using a mixed gas of nitrogen and argon. To do. Note that only nitrogen may be used as the sputtering gas at this time.

Next, as shown in FIG. 1C, a titanium-tungsten alloy (TiW) film 3 having a thickness of about 50 nm is uniformly formed on the entire surface of the titanium nitride film 2 by the sputtering method. The film composition of this titanium-tungsten alloy film 3 is
It is 10 wt% Ti-W.

Next, as shown in FIG. 1D, a tungsten (W) film having a thickness of about 500 nm is formed on the entire surface of the titanium-tungsten alloy film 3 by a CVD method using tungsten hexafluoride and hydrogen as source gases. ) A film (plug) 4 is formed, and the contact hole 16 is buried. Then, the tungsten film 4, the titanium-tungsten alloy film 3, the titanium nitride film 2 and the titanium film 1 on the surface of the interlayer insulating film 14 are etched back by plasma etching. As a result, the tungsten film 4,
The titanium-tungsten alloy film 3, the titanium nitride film 2 and the titanium film 1 remain and the surface is flattened.

In this embodiment, the titanium-tungsten alloy film 3 is interposed between the titanium nitride film 2 and the tungsten film 4 without making direct contact with each other. Since this titanium-tungsten alloy film 3 is a material containing the same kind of element in both the titanium nitride film 2 and the tungsten film 4, it has good adhesion to both the titanium nitride film 2 and the tungsten film 4. Therefore, sufficient adhesion between the tungsten film 4 and the underlying impurity diffusion layer 12 can be maintained, and the electrical characteristics do not become unstable due to the deterioration in the adhesion of the tungsten film 4. In addition, the titanium nitride film 2 allows the tungsten film 4 to cover the silicon substrate 1.
Diffusion of tungsten to 0 can be effectively suppressed, and no junction leak occurs in the impurity diffusion layer 12. Therefore, the manufacturing yield can be improved.

Next, the second embodiment of the present invention will be described with reference to FIG.
Will be described with reference to.

First, as shown in FIG. 2A, an N-type impurity diffusion layer 12 is formed by ion-implanting arsenic into the surface of the P-type silicon substrate 10. After a while
After the interlayer insulating film 14 made of a silicon oxide film having a film thickness of about 1 μm is formed by the CVD method, the interlayer insulating film 14 is formed.
Then, a contact hole 16 having a diameter of about 0.5 μm is formed by a fine processing technique using a photoresist (not shown) to expose the impurity diffusion layer 12. Further, a titanium (Ti) film 1 having a thickness of about 20 nm is formed on the entire surface by a sputtering method, and the impurity diffusion layer 1 exposed from the surface of the interlayer insulating film 14 including the inner surface of the contact hole 16 and the contact hole 16 is formed.
The surface of 2 is coated with titanium film 1.

Next, as shown in FIG. 2B, a titanium nitride film 2 having a thickness of about 100 nm is formed on the entire surface of the titanium film 1 by a reactive sputtering method using a mixed gas of nitrogen and argon. To do. Note that only nitrogen may be used as the sputtering gas at this time.

Next, as shown in FIG. 2C, a titanium-tungsten alloy (TiW) film 3 having a thickness of about 50 nm is formed on the entire surface of the titanium nitride film 2 by the sputtering method. The film composition of the titanium-tungsten alloy film 3 is 10
wt% Ti-W.

Next, as shown in FIG. 2D, a tungsten (W) film with a thickness of about 500 nm is formed on the entire surface of the titanium-tungsten alloy film 3 by the CVD method using tungsten hexafluoride and hydrogen as source gases. ) Forming the film 4 and filling the contact hole 16. After that, the interlayer insulating film 14
The tungsten film 4 on the surface of is etched by a fine processing technique and patterned into a wiring shape. At this time, if necessary, the titanium-tungsten alloy film 3 and the titanium nitride film 2
The titanium film 1 and the titanium film 1 may be simultaneously etched to form a wiring shape. In FIG. 2, the wiring is formed in the direction perpendicular to the paper surface.

In the first and second embodiments described above, the heat treatment was not performed between the formation of the titanium nitride film 2 and the formation of the titanium-tungsten alloy film 3, but nitrogen gas is the main component during this period. You may heat-process in a gas atmosphere. Further, the present invention is not limited to the contact hole, but can be widely applied to a case where two conductive films are connected via a tungsten film.

[0028]

As described above, according to the present invention,
The titanium-tungsten alloy film is interposed between these two films without direct contact between the titanium nitride film and the tungsten film. Since this titanium-tungsten alloy film contains the same kind of element, it has good adhesion to both the titanium nitride film and the tungsten film. Therefore,
Sufficient adhesion between the tungsten film and the base film can be maintained, for example, the electrical characteristics in the contact hole are stabilized, and the manufacturing yield of semiconductor devices is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a semiconductor device of a first embodiment of the present invention in the order of manufacturing steps.

FIG. 2 is a sectional view showing a semiconductor device according to a second embodiment of the present invention in the order of manufacturing steps.

[Explanation of symbols]

 1 Titanium (Ti) Film 2 Titanium Nitride Film 3 Titanium Tungsten Alloy (TiW) Film 4 Tungsten (W) Film 10 Silicon Substrate 12 Impurity Diffusion Layer 14 Interlayer Insulation Film 16 Contact Hole

Claims (7)

[Claims] 1. A step of forming an insulating film on a conductive layer serving as a base film, a step of forming a contact hole reaching the conductive layer in the insulating film, and a bottom surface of the contact hole contacting the conductive layer Forming a titanium film; forming a titanium nitride film on the titanium film; forming a titanium tungsten alloy film on the titanium nitride film; and forming a contact on the titanium tungsten alloy film. And a step of forming a tungsten film filling the holes. 2. The method of manufacturing a semiconductor device according to claim 1, further comprising the step of forming a wiring pattern by selectively removing the tungsten film by etching. 3. The method according to claim 1, further comprising the step of forming a wiring pattern by selectively etching away the tungsten film, the titanium-tungsten alloy film, the titanium nitride film, and the titanium film. A method of manufacturing a semiconductor device according to item 1. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the conductive layer is an impurity diffusion layer formed on a surface portion of a silicon substrate. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the insulating film is a silicon oxide film. 6. A titanium film in contact with the conductive film, the titanium film being in contact with the conductive film, the contact hole being formed in the insulating film on the conductive film serving as the base film and reaching the conductive layer; A semiconductor device comprising a titanium-tungsten alloy film in contact with a titanium film and a tungsten film in contact with the titanium-tungsten alloy film. 7. A titanium film in which the first conductive film and the second conductive film are in contact with the first conductive film, a titanium nitride film in contact with the titanium film, and a titanium-tungsten alloy in contact with the titanium nitride film. A semiconductor device, which is connected via a film and a tungsten film in contact with the titanium-tungsten alloy film.