JP2730458B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device having a contact hole filled with an aluminum alloy.

[0002]

2. Description of the Related Art As semiconductor devices become more highly integrated, the number of contacts (hereinafter referred to as "contact holes") between impurity diffusion layers and metal wiring for joining the impurity diffusion layers to external elements becomes extremely small. The aspect ratio of the hole (contact depth / contact diameter) is increasing. Conventionally,
A method of forming a metal wiring layer between elements which has been mainly used is a physical vapor deposition method using a sputtering method. If the aspect ratio increases to about 1 due to the reduction of the contact hole, it becomes difficult for this metal wiring layer to secure a sufficient coverage (step coverage) inside the contact hole.
Disconnection of the metal wiring layer occurs.

In order to solve such a problem, attempts have been made to bury a metal wiring layer in a contact hole by various methods. Among them, as a method of filling the contact hole with an aluminum alloy, a method of forming an aluminum alloy by a sputtering method at a high temperature of 400 ° C. or higher, or a method of forming an aluminum alloy at a low temperature by a sputtering method, There is a method of performing a heat treatment at a high temperature of not less than ℃.

FIG. 3 shows an example of such a method, for example, a method proposed in Japanese Patent Application Laid-Open No. 4-65831.
In this method, as shown in FIG.
After opening a contact hole 14 for connecting to the impurity diffusion layer 12 in the upper insulating film 13, an aluminum-based alloy 15 is formed on the surface of the insulating film 13 including the contact hole by a sputtering method, and then heated to 400 ° C. or more. By heat-treating at a high temperature to melt the aluminum-based alloy 15, the contact holes 14 can be filled with the aluminum-based alloy as shown in FIG.

However, in such a method, in a subsequent heat treatment step, the aluminum alloy 1
The reaction between 5 and silicon substrate 11 causes a problem that aluminum diffuses into the silicon substrate and so-called aluminum spike X occurs. For this reason, Japanese Unexamined Patent Publication No. 63-246
In Japanese Patent No. 70, as shown in FIG. 4A, a barrier metal 16 made of titanium tungsten nitride is formed in advance on the inner surface of the contact hole 14, and an aluminum-silicon alloy 17 is formed thereon. In this alloy 1
7 is melted and embedded in the contact hole 14 as shown in FIG. 4B. In this method, the barrier effect of the titanium tungsten nitride barrier metal 16 and the silicon in the aluminum-silicon alloy 17 prevent the aluminum from reacting with the silicon substrate, so that aluminum spikes can be prevented.

[0006]

However, since titanium tungsten nitride as a barrier metal has a lower etching rate as compared with an aluminum-silicon alloy, the titanium tungsten nitride is etched together with the aluminum-silicon alloy in a subsequent step. In addition, the aluminum-silicon alloy is easily peeled off. In order to prevent this, it is necessary to strictly control the film thickness and etching conditions of titanium tungsten nitride, and the production tends to be complicated.

On the other hand, if titanium nitride or the like is used as a barrier metal in order to avoid such complicated manufacturing, as described in the same publication, aluminum penetrates the barrier metal and reacts with the silicon substrate to react with the aluminum. There is a possibility that a spike may occur, which causes a problem that a defect of the semiconductor device occurs. In addition, since the wettability between the aluminum alloy and titanium nitride is low, the aluminum alloy does not adhere to the barrier metal, so that when the aluminum alloy is melted, internal voids (air) are easily entrained. In some cases, the contact between the substrate and the silicon substrate may be reduced. An object of the present invention is to prevent aluminum spikes, avoid complication of production, and bury an aluminum-based alloy in a high-aspect-ratio contact hole to provide a good contact between a metal wiring and an impurity diffusion layer. An object of the present invention is to provide a method of manufacturing a semiconductor device which can be used.

[0008]

According to the manufacturing method of the present invention, after a contact hole is opened in an insulating film provided on a semiconductor substrate, the bottom and side surfaces of the contact hole and the insulating film are formed.
Along the surface of the edge film, a barrier metal consisting of a refractory metal whose surface is a nitride film and a silicon film are successively thinned.
Forming an aluminum alloy sequentially, and then performing heat treatment to bury the aluminum alloy in the contact hole while reacting the aluminum alloy and the silicon film on the bottom surface and side surfaces of the contact hole. An aluminum-based alloy is buried in a state of being closely contacted with the inner surface of the contact hole. Further, another manufacturing method of the present invention, bottom and sides of the contact hole
A barrier metal, a silicon film , and an aluminum-based alloy are sequentially and thinly formed along the surface and the surface of the insulating film , and heat-treated to cause a reaction between the aluminum-based alloy and the silicon film on the bottom and side surfaces of the contact hole. Forming a film of an aluminum-based alloy at a high temperature and embedding it in a contact hole. Further, after forming the silicon film, it is preferable to deposit the aluminum alloy in it in the same vacuum.

[0009]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the present invention in the order of manufacturing steps. As shown in FIG. 1A, phosphorus (P) or boron (B) is diffused on the surface of a silicon substrate 1 to form an impurity diffusion layer 2 of a required conductivity type. Then, an insulating film 3 is formed on the surface of the silicon substrate using a silicon oxide film or the like. Thereafter, as shown in FIG. 1B, a contact hole 4 is formed in the insulating film 3 on the impurity diffusion layer by a photolithography technique. In this example, the contact hole 4 is opened by a wet etching method and a dry etching method.
The opening edge has a gentle cross-sectional structure.

Next, as shown in FIG. 1C, a barrier metal 5 is formed on the surface of the insulating film 3 including the contact hole 4. Here, titanium (Ti) and titanium nitride (Ti
N) in this order by the sputtering method in the same vacuum
It is formed to a thickness of 00 °. After the formation of the barrier metal 5, the silicon substrate 1 is once taken out of the vacuum and heat-treated in a nitrogen atmosphere. Then, as shown in FIG. 1 (d),
On the upper surface of the barrier metal 5, a silicon film 6 is formed to a thickness of 200 ° by a normal temperature sputtering method. Further, an aluminum-copper alloy (Al-0.5% Cu) 7 is deposited on the surface by sputtering at a temperature of 300 [deg.] C. or less in the same vacuum.
Å thickness.

Then, the substrate temperature is set to 430 ° C. to 500 ° C.
By performing the heat treatment for 2 minutes or more by heating at
As shown in (e), the aluminum-copper alloy 7 reacts with the underlying silicon film 8, and the aluminum-copper-silicon alloy is buried in the contact hole 4. After that, the metal layer composed of the aluminum-copper-silicon alloy and the barrier metal 5 is etched into a required pattern to form a wiring layer.

Therefore, in the wiring layer formed by this method, since the aluminum-copper alloy has better wettability to silicon than titanium nitride, the silicon film 6 is formed on the barrier metal 5 formed in the contact hole 4. Aluminum-copper alloy 7 formed by sputtering
Can be formed on the inner surface of the contact hole 4 with good adhesion. Therefore, this aluminum-copper alloy 7
Is heat-treated into the contact hole 4 along the silicon film 6, so that no void is involved in the contact hole 4 and the contact property is not reduced.

When the aluminum-copper alloy is heat-treated, it reacts with the silicon of the silicon film and the silicon concentration does not become insufficient. Therefore, it is possible that aluminum breaks through the barrier metal 5 and reacts with the silicon substrate 1. No aluminum spikes can be prevented. At this time, the silicon film 6 and the aluminum-copper alloy 7
Are formed in the same vacuum, so that a silicon oxide film is not formed on the surface of the silicon film 6 and a suitable reaction with the aluminum-copper alloy 7 is enabled.
As described above, when the aluminum-copper alloy is melted, it is buried in the contact hole while being wet with the silicon film and reacting with the silicon film. It becomes possible.

Here, in the step of FIG. 1E, when the aluminum-copper alloy 7 is formed by sputtering,
After forming a silicon film to a thickness of 200 ° by a normal temperature sputtering method, as shown in FIG. 2A, the aluminum-copper alloy 7a is sputtered at a temperature of 300 ° C. or less to a thickness of 1000 ° in the same vacuum as shown in FIG. Immediately thereafter, heat treatment is performed at a substrate temperature of 430 ° C. to 500 ° C. for about 30 seconds.
Then, while maintaining this temperature, as shown in FIG.
A film may be formed to a thickness of 000 °, and this may be directly buried in the contact hole 4.

In this manner, the aluminum-copper alloys 7a and 7b are formed to a thickness of 5000 mm as in the first embodiment, but the lower layer portion 7a having a thickness of 1000 mm is formed.
Is sputter-formed at a low temperature, and is heated immediately thereafter to react with the silicon film 6, so that the lower layer portion 7a along the aluminum-copper alloy barrier metal is more effectively reacted with the silicon film 7. , Contact hole 4
It is possible to enhance the effect of embedding in the inside and to more effectively prevent aluminum spikes. After that, since the aluminum-copper alloy 7b is deposited by the sputtering method and directly buried in the contact hole 4, a subsequent heat treatment becomes unnecessary, and the number of steps can be reduced. Also in the second embodiment, embedding of an aluminum-copper alloy in a contact hole having an aspect ratio of about 2 can be realized. In each of the above embodiments, an example is shown in which an aluminum-copper alloy is used as the aluminum-based alloy, but it goes without saying that another aluminum-based alloy may be used.

[0016]

As described above, according to the present invention, the bottom and side surfaces of a contact hole having an aspect ratio of 1 or more and
A barrier metal made of a refractory metal having a nitride film formed on the surface of the insulating film and a silicon film are sequentially and thinly formed.
The aluminum alloy reacts with silicon because the aluminum alloy is formed and then heat-treated to bury the aluminum alloy and the silicon film at the bottom and side surfaces of the contact hole while causing the aluminum alloy to react with the silicon film. Thus, the aluminum-based alloy can be buried in a state in which the aluminum-based alloy is in close contact with the surface of the barrier metal, and good contact can be obtained without generating voids or the like at the bottom and side surfaces of the contact hole. Further, by reacting the aluminum alloy with the silicon film, it is possible to prevent the aluminum alloy from piercing the barrier metal and reacting with the silicon substrate, thereby preventing the occurrence of aluminum spikes. Further, at this time, since the nitride film is present on the surface of the barrier metal, the silicon film does not react with the barrier metal, and it is possible to more effectively prevent the barrier metal from being pierced. The metal can be formed thin, which facilitates manufacture.

Also, a barrier metal is provided in the contact hole,
Since a silicon film and a thin aluminum alloy are sequentially formed, heat treatment is performed to react the aluminum alloy with the silicon film, and then an aluminum alloy is formed at a high temperature and embedded in the contact hole. It can be in close contact with the barrier metal by the system alloy, and the aluminum alloy will be embedded directly on it,
Heat treatment can be reduced, and generation of voids and the like can be reliably prevented. When the barrier metal is made of titanium nitride, it is easy to form a wiring pattern by etching simultaneously with the aluminum-based alloy, and the manufacturing process is not complicated. In addition, by forming an aluminum alloy in the same vacuum as it is after forming the silicon film, a silicon oxide film is not formed on the surface of the silicon film, and the reaction with the aluminum alloy is improved. I do.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view showing a part of a process in a manufacturing method according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view showing an example of a conventional manufacturing method in the order of steps.

FIG. 4 is a cross-sectional view showing another example of the conventional manufacturing method in the order of steps.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 silicon substrate 2 impurity diffusion layer 3 insulating film 4 contact hole 5 barrier metal 6 silicon film 7 aluminum-copper alloy

Claims (3)

(57) [Claims] 1. A step of forming a contact hole in an insulating film provided in a semiconductor substrate, and a step of forming a bottom surface of the contact hole.
And along the sides and surface of the insulating film, a step of the surface sequentially and form a thin barrier metal and silicon <br/> con film made of a refractory metal which is a nitride film, on said silicon film semiconductor, characterized in that it comprises a step of forming an aluminum-based alloy, and a step of embedding heating to the contact hole of the bottom and the contact hole while reacting the silicon film and the aluminum-based alloy on the side surface Device manufacturing method. 2. A step of opening a contact hole in an insulating film provided on a semiconductor substrate, and a step of forming a bottom of said contact hole.
And barrier metal along the side and the surface of the insulating film
And a step of sequentially and forming a thin silicon film, forming a thin aluminum-based alloy to said sheet <br/> silicon film, said aluminum-based alloy heat treatment to the bottom surface and a side surface of the contact hole A method of manufacturing a semiconductor device, comprising: a step of reacting with the silicon film; and a step of forming an aluminum-based alloy at a high temperature and filling it in the contact hole. 3. After forming the silicon film, a film of aluminum alloy as it is in the same vacuum claim 1
Or a method for manufacturing a semiconductor device according to item 2.