JPH05198577A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a nitrified titanium layer having a heavy film thickness as compared with a silicide layer and creating no grain boundary diffusion due to a crystal grain boundary on the bottom plane of a contact hole. CONSTITUTION:On a substrate 1 having a part of a silicon plane exposed, a thin titanium film 8 and a titanium film 9 containing nitrogen (the atomic ratio N/Ti 0.8 or less) are successively deposited and heated in a nitrogen atmosphere, thereby obtaining a laminated structure composed of a titanium silicide layer 4 and a nitrified titanium layer 5a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a titanium nitride film provided at the bottom of a contact hole.

[0002]

5 and 6 show a sectional structure of a contact portion of a semiconductor device manufactured by a conventional method for manufacturing a semiconductor device. In the figure, 1 is a Si substrate, 2 is the substrate 1
An impurity diffusion layer 3 formed on the surface of the interlayer insulating film is an interlayer insulating film, a contact hole is formed above the impurity diffusion layer 2 of the interlayer insulating film 3, and the impurity diffusion layer exposed at the bottom of the contact hole is diffused. A titanium silicide (TiSi ₂ ) layer 4 is formed on the surface of the layer 2, and a thermal titanium nitride layer 5a is formed on the inner peripheral surface of the contact hole. These titanium silicide (TiSi ₂ ) layer 4 and thermal titanium nitride layer 5a are formed. The Al alloy layer 6 or the W layer 7 to be the wiring is formed via the interposition.

FIGS. 7 and 8 are process sectional views showing a method of forming the titanium nitride film 4 shown in FIGS. 5 and 6. In the figure, 8 is a titanium film and 5b is a titanium nitride layer. Next, the role of each component will be described. Figure 5
In the contact structure of FIG. 3, when the Al alloy layer 6 is used as a wiring between semiconductor elements, but titanium nitride (TiN) 5a is used to prevent mutual diffusion of both in the contact portion with the impurity diffusion layer 2. There are many. Further, the titanium silicide layer 4 on the impurity diffusion layer 2 exposed in the contact hole is formed in order to realize good ohmic contact.

FIG. 6 shows an example in which the W layer 7 is used as wiring. In this case, the W layer 7 is often formed by a vapor phase growth method using WF ₆ gas as a raw material. Titanium nitride (TiN) 5a is used for the purpose of preventing damage to the impurity diffusion layer 2 at that time and for strengthening the adhesion of the W layer 7. Also, the W wiring 7 is 6
When subjected to a high temperature heat treatment of 50 ° C. or higher, the titanium nitride (TiN) 5a also has a function of blocking the silicide reaction between the W layer 7 and the silicon substrate 1. Also in this case, in order to realize good ohmic contact, the titanium silicide layer 4 is often formed on the impurity diffusion layer 2 of the contact.

Conventionally, two methods have been used to form the titanium nitride (TiN) 5 and titanium silicide layers 4 as described above. That is, the first method is a method using thermal nitriding, as shown in FIG. This is Figure 7
As shown in (a), the Si substrate 1 is sputtered to 40
A titanium film 8 having a thickness of about m to 100 nm is deposited, and this is 60
Heat treatment is performed in a nitriding atmosphere at 0 ° C to 900 ° C. At this time, a nitriding reaction occurs from the surface of the titanium film 8 and a silicidation reaction occurs from the Si substrate 1 side to form a laminated structure of titanium nitride 5a and titanium silicide layer 4 as shown in FIG. 7B. .. At this time, the film thickness of the titanium nitride 5a is determined by the competition between the nitriding reaction and the silicidation reaction, and depends on various conditions such as the temperature and the atmosphere of the heat treatment. Become. Also,
The reaction described above occurs at a position in contact with the Si substrate 1, and a silicide reaction does not occur on the interlayer insulating film.
Will be changed to.

As a second method in addition to the method utilizing thermal nitridation of the titanium film as described above, there is also a method of pre-depositing the titanium nitride film itself as shown in FIG. This is shown in Figure 8 (a).
, A thin titanium film 8 having a thickness of about 5 to 20 nm is deposited on the Si substrate 1, and then nitrogen gas is mixed in argon to react with Ti atoms in the sputtering process to form a TiN film. The titanium nitride film 5b is deposited by using a technique such as sputtering. By performing heat treatment in this state, the lower titanium film 8 is silicidized to form a laminated structure of titanium nitride 5b and titanium silicide 4. In this case, the film thickness of the titanium nitride film 5b is determined by the film thickness of the titanium nitride film 8 formed first.

By the way, the film quality of the titanium nitride 5a formed by the thermal nitriding method by the above-mentioned two methods and the titanium nitride 5b formed by the reactive sputtering method are different.
That is, while the titanium nitride 5b formed by the reactive sputtering method has columnar crystals and the crystal grain boundaries run in the film thickness direction, the titanium nitride 5a formed by the thermal nitriding method has clear crystal grain boundaries. It is not allowed. The purpose of using titanium nitride is to prevent the reaction between the Al alloy layer and the Si substrate or the W layer and the Si substrate as described above. The thermal titanium nitride film 5a formed by the first method, which has no clear grain boundary, is advantageous in terms of film quality because it is most likely to occur in the portion where the heat treatment is performed.

Regarding the film thickness ratio between titanium nitride and titanium silicide layer, it is advantageous that the titanium nitride layer is thick. The reason is that for the purpose of preventing the above-mentioned reaction, it is advantageous that titanium nitride is thick, and the thickness of the titanium silicide layer necessary for ohmic contact may be extremely thin. The amount of Si in the substrate consumed by the silicidation reaction may be too large, which may adversely affect the device characteristics. From this point, the titanium nitride 5b formed by the sputtering method according to the second method is more advantageous. I can say.

[0009]

The conventional method for manufacturing a semiconductor device is configured as described above. Titanium nitride formed by the thermal nitriding method is titanium nitrided in contact with the impurity diffusion layer. The film is as small as about 20 to 40% of the whole film, and there is a problem that the film thickness of the titanium nitride layer with respect to titanium silicide cannot be made large. On the other hand, in the method of forming the titanium nitride layer in advance by the reactive sputtering method, the formed titanium nitride film has columnar crystals, and grain boundary diffusion easily occurs along the crystal grain boundaries. However, there is a problem that particles are likely to be generated in the film and the yield of the semiconductor device is significantly reduced.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to increase the film thickness of the titanium nitride layer with respect to titanium silicide and to reduce the diffusion of grain boundaries due to crystal grain boundaries. It is an object to provide a method for manufacturing a semiconductor device having a layer.

[0011]

A method of manufacturing a semiconductor device according to the present invention comprises a step of forming a titanium film having a predetermined thickness on a substrate having a portion where a silicon surface is exposed,
And a step of depositing a nitrogen-containing titanium film containing a predetermined amount of nitrogen on the titanium film, and a step of heat-treating the titanium film and the nitrogen-containing titanium film laminated on the substrate in a nitriding atmosphere. is there.

[0012]

In the present invention, the titanium film and the nitrogen-containing titanium film are sequentially laminated on the substrate having the exposed silicon surface, and the heat treatment is performed in the nitriding atmosphere. It becomes a titanium nitride layer without being converted, and only the lower titanium film is silicidized.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings. In FIG.
The same reference numerals as those in FIG. 8 indicate the same or corresponding portions, and 9 is a titanium film containing a certain amount of nitrogen.

Next, the manufacturing method will be described. Figure 1 (a)
As shown in, a thin titanium film 8 and a titanium film 9 containing nitrogen are sequentially deposited on the substrate 1. Titanium nitride is usually Ti
The nitrogen-containing titanium film 9 is a compound in which N atoms are bonded at a ratio of 1: 1. A film in which the content ratio of N atoms to Ti atoms is 0.8 or less is used.

Subsequently, when heat treatment is performed in a nitriding atmosphere containing nitrogen or ammonia, a silicidation reaction occurs from the substrate 1 side, and the thin titanium film 8 reacts with the substrate 1 to be silicidized to form titanium silicide 4. However, in the titanium film 9 containing nitrogen, the silicide reaction is suppressed because nitrogen is contained in the titanium film, and the film thickness of the titanium silicide layer 4 finally formed is almost defined by the film thickness of the thin titanium film 8. Will be done. Then, the titanium film 9 containing nitrogen that is not silicified becomes titanium nitride 5a by thermal nitriding.

Therefore, the thickness of the titanium film 9 containing nitrogen is
If it is formed to be larger than the lower titanium film 8, the titanium silicide 4 of the titanium nitride 5a formed by the thermal nitriding method.
The film thickness ratio can be increased.

By the way, as a method for forming the titanium film 9 containing nitrogen, reactive sputtering using a Ti target (sputtering with a mixed gas of argon and nitrogen) is often used. Figures 3 and 4 are the Journal of V respectively.
accuum Science Technology.A3 (4), p.1797, (1985)
T produced by the reactive sputtering method described in
FIG. 6 is a graph showing the resistivity of the iN film, the deposition rate, and the atomic ratio of N / Ti.
The atomic ratio of N / Ti is about 1.0 or more, and a titanium nitride film having columnar crystals is formed.

From this, it is suitable to use the titanium film 9 containing nitrogen as a titanium film (N / Ti atomic ratio of 0.8 or less) formed in a region where the proportion of nitrogen gas is about 10 to 23%. I understand that

As described above, according to this embodiment, since the thin titanium film 8 and the titanium film 9 containing a predetermined amount of nitrogen are sequentially laminated on the substrate 1, the heat treatment is performed in the nitriding atmosphere. The silicide reaction is suppressed by the titanium film 9 containing nitrogen and occurs only in the titanium film 8, and most of the titanium film 9 containing nitrogen becomes titanium nitride 5a. The thickness of the titanium nitride 5a can be reduced and the thickness of the titanium nitride 5a can be increased. Further, since the titanium nitride film formed by thermal nitriding does not have a clear grain boundary, defects such as grain boundary diffusion do not occur.

In the above embodiment, the titanium nitride 5a is obtained by determining only the thickness of the titanium film 9 containing nitrogen, but as shown in FIG. 2, the titanium film 10 is added to the uppermost layer. It may have a three-layer structure. In this case, by appropriately selecting the film thickness of the titanium layer 9 containing nitrogen serving as the intermediate layer, the silicide reaction from the substrate during the heat treatment can be stopped in this layer 9, and at this time, the uppermost titanium film is formed. Since all of 10 are thermally nitrided, the formed titanium nitride 5a can have a large film thickness.

[0021]

As described above, according to the method of manufacturing a semiconductor device of the present invention, the titanium film and the nitrogen-containing titanium film are sequentially laminated on the substrate having the exposed portion of the silicon surface, and the titanium film is exposed in the nitriding atmosphere. Since the heat treatment is performed, the nitrogen-containing titanium film becomes a titanium nitride layer without being silicified during the heat treatment, and only the lower titanium film is silicidized to become a titanium silicide layer. There is an effect that a semiconductor device having a titanium nitride film with a small diffusion and a large film thickness can be obtained with high yield.

[Brief description of drawings]

FIG. 1 is a sectional structural view showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a sectional structural view showing a method for manufacturing a semiconductor device according to another embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the specific resistance and deposition rate of a TiN film and the nitrogen partial pressure for explaining the reactive sputtering method suitable for forming the film used in the above examples.

FIG. 4 is a diagram showing an atomic ratio of N / Ti for explaining a reactive sputtering method suitable for forming a film used in the above examples.

FIG. 5 is a sectional structural view of a semiconductor device showing the use of titanium nitride formed by the present invention or the conventional method for manufacturing a semiconductor device.

FIG. 6 is a sectional structural view of a semiconductor device showing an application of titanium nitride formed by the present invention or a conventional method for manufacturing a semiconductor device.

FIG. 7 is a sectional structural view showing a conventional method for manufacturing a semiconductor device.

FIG. 8 is a cross-sectional structure diagram showing another conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Si substrate 2 Impurity diffusion layer 3 Interlayer insulating film 4 Titanium silicide layer 5a Thermal titanium nitride film 5b Titanium nitride film 6 Al alloy wiring 7 W wiring 8 Titanium film 9 Titanium film containing nitrogen 10 Titanium film

Claims (1)

[Claims] 1. A semiconductor device in which a titanium silicide layer and a titanium nitride layer are sequentially formed on a substrate having a portion where a silicon surface is exposed, and a wiring layer is connected through the titanium silicide layer and the titanium nitride layer. In the manufacturing method, a step of forming a titanium film having a predetermined thickness on the substrate, a step of forming a nitrogen-containing titanium film containing a predetermined amount of nitrogen on the titanium film, and laminating the titanium film on the substrate. And a step of heat-treating the titanium film and the titanium film containing nitrogen in a nitriding atmosphere.