JPH01309356A - Wiring structure of semiconductor device and its formation - Google Patents

Abstract

PURPOSE:To obtain a wiring part rich in thermal resistance by a method wherein a high m.p. metal silicide film is formed on a titanium nitride film and a high m.p. metal film is formed on the high m.p. metal silicide film. CONSTITUTION:A titanium nitride film 10 is formed continuously on an insulating film 5 and a contact part 6. A high m.p. metal silicide film 11 is formed on the nitride film 10. A high m.p. metal film 7 is formed on the silicide film 11. The nitride film 10 acts as a barrier layer used to prevent the contact part from becoming a silicide. The silicide film 11 and the nitride film 10 in working conjunction with each other act as a close contact layer which brings the metal film 7 formed on them into contact with the insulating film 5 formed under them. Accordingly, the metal film 7 is not stripped off from the insulating film 5. By this setup, a wiring part rich in thermal resistance can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wiring structure of a semiconductor device and a method of forming the same, and particularly relates to a wiring structure for electrically connecting a semiconductor device including an insulating film and a contact portion. It relates to structures and methods of forming them.

[Prior Art 1] FIG. 3 is a schematic cross-sectional view of a conventional LSI, such as a three-dimensional device. The three-dimensional device is the upper layer], the middle layer 2,
It consists of a lower layer 3. Each layer is provided with an active layer, and each active layer has an element formed therein. Electrical connections between elements (between the same layer and between different layers) are made using metal wiring. As a metal for LSI wiring,
Currently, exclusively aluminum and aluminum-silicon.

Aluminum-based metals such as aluminum-silicon-copper or high-melting point metal silicides such as molybdenum silicide and tungsten silicide are used. However, these wiring metals are not considered to be materials that can continue to be used satisfactorily in the future. This is because there are problems described below. That is, although there are steps that require high temperatures in the manufacturing process of the three-dimensional device described above, aluminum-based metals have insufficient heat resistance. Furthermore, high melting point metal silicides have insufficient resistivity. Furthermore, the sputtering method, which is currently the only practical method for forming these wiring materials, has poor step coverage and is expected to become a major hindrance in LSI fabrication in the future. The above are the major problems.

Therefore, there is a strong need for a wiring material that is heat resistant, has a sufficiently low resistivity, and can be used for chemical vapor deposition (abbreviated as CVD) with good step coverage during formation. Hydrogen (H2) of tungsten hexafluoride (WFs) or silane (
CVD tungsten thin films by SiH4) reduction are currently showing some promise. Specifically, 300-500℃
WF6°SiH4 and H2 were heated for 50 to 200 sec each at a temperature of about 0.2 Torr and a pressure of about 0.2 Torr.

If 0 to 200 sccm and 500 to 2000 seconds are supplied, about 10
A CVD tungsten thin film with a low resistivity of μΩcm is deposited on the substrate with very good step coverage.

[Problems to be Solved by the Invention] However, this method has two important problems. These problems will be explained with reference to FIGS. 4A, 4B, and 4C. FIG. 4C shows that in FIG.
For example, it is an enlarged view of part A. Note that FIG. 4C shows a case where tungsten is used as the wiring metal. Before explaining the problems, the steps from FIG. 4A to FIG. 4C will be explained.

Referring to FIG. 4A, a silicon oxide film 5 is formed on a silicon substrate 4, and a contact hole 6 is formed. Next, a tungsten thin film 7 is deposited thereon by reducing WF6 with H2 or SiH4. FIG. 4B is a cross-sectional view of the tungsten thin film 7 in its early stage of deposition, and FIG. 4C is a cross-sectional view of the tungsten thin film 7 after deposition.

Next, problems with this method will be explained.

One of the drawbacks of the CVD method is the problem of adhesion between the substrate and the deposited film before and after heat treatment. That is, the 4th C
Referring to the figure, tungsten thin film 7 deposited by CVD method.
The problem is that the adhesion between the silicon oxide film 5 and the silicon oxide film 5 (the silicon oxide film 5 is the most common insulating film between wirings) is extremely poor. Therefore, C
Even if an attempt is made to deposit the VD tungsten thin film 7 on the base of the silicon oxide film 5 by a simple method, a phenomenon that the tungsten thin film 7 usually peels off during the deposition occurs. In the figure, a portion indicated by reference numeral 8 represents an interface that is about to peel off.

Furthermore, even if good contact between the silicon substrate 4 and the CVD tungsten thin film 7 can be obtained by devising the thin film deposition conditions before heat treatment, the CVD tungsten thin film 7 may be 7 was observed to be completely peeled off.

The second drawback of the CVD method is that the substrate and the deposited film react with each other during heat treatment, resulting in deterioration of the quality of the deposited film. CV
As mentioned above, the D tungsten thin film lacks adhesion to the silicon oxide film 5, but it adheres extremely well to the silicon 4. This is due to the following reasons. That is, WF6
is reduced with a reducing agent such as H2 or StH, and CV
D When a tungsten thin film is deposited on a silicon substrate,
In the exposed portion of the silicon surface, WF6 is reduced by silicon, and tungsten is generated as shown in the following equation.

2WFG+3St→2W+3SiF4 ↑Referring to FIG. 4B, the above reaction is a reaction that erodes the silicon substrate 4 and replaces the silicon with tungsten.As a result of the tungsten-silicon interface 9 sinking into the silicon substrate 4, this reaction This results in extremely good adhesion between the parts. However, if such a tungsten-silicon interface 9 exists, during the subsequent heat treatment, the reaction between tungsten and the underlying silicon, that is, silicidation of tungsten (silicidation proceeds at a temperature of about 700° C. or higher). becomes a serious problem.

This is because the resistivity of the tungsten thin film 7 increases due to the silicidation of tungsten, and furthermore, impurities doped in the substrate are sucked out into the tungsten silicide at the contact portion, resulting in a rapid increase in contact resistance. be.

This invention was made to solve the above-mentioned problems, and provides a wiring structure for a semiconductor device that can prevent silicidation at the tungsten-silicon interface and exhibits good adhesion with an insulating film, and its manufacture. The purpose is to provide a method.

[Means for Solving the Problems] The present invention relates to wiring 1, 1.7 for electrical connection of a semiconductor device including a contact portion formed through an insulating film. In order to achieve the above object, a titanium nitride film is continuously formed on the insulating film and the contact portion, and a high melting point metal silicide film is formed on the titanium nitride film; and a high melting point metal film formed on the high melting point metal silicide film.

When considering step coverage, the high melting point metal silicide film and the high melting point metal film employed in the present invention are CVD
Those formed by a method are preferable.

The high melting point metal used in the present invention is not particularly limited as long as it has a high melting point, and is generally tungsten, molybdenum, or titanium. and tungsten,
Molybdenum is particularly preferably used. As the high melting point metal silicide, the above-mentioned high melting point metal silicides are preferably used.

As a method for forming wiring for electrical connection in a semiconductor device including a contact portion formed through an insulating film, a titanium nitride film is continuously formed on the insulating film and the contact portion. There is a method comprising the steps of forming a high melting point metal silicide film on the titanium nitride film; and forming a high melting point metal film on the high melting point metal silicide film. .

The formation of the high melting point metal silicide film and the high melting point metal film employed in the present invention is preferably performed by a CVD method. This is because the CVD method provides good step coverage.

In addition, when forming the high melting point metal silicide film and the high melting point metal film by the CVD method, after forming the high melting point metal silicide film, continuously using the same apparatus,
Preferably, a high melting point metal film is formed.

As the process of forming the high melting point metal film, a process of forming a tungsten film by reducing tungsten hexafluoride is preferably adopted, but other tungsten compounds may be used as necessary.

The process of forming a high-melting point metal silicide film is particularly preferably a process of forming a tungsten silicide film by reducing a mixed gas consisting of tungsten hexafluoride and silane blended in a predetermined ratio. Other tungsten compounds and other silane compounds may also be employed.

[Operation] The titanium nitride film formed continuously on the insulating film and the contact portion acts as a barrier layer to prevent silicidation in the contact portion.

In addition, two types of high melting point metal silicide/titanium nitride
The layers work together to act as an adhesion layer that brings the refractory metal film formed thereon and the insulating film formed below into close contact. Therefore, the high melting point metal film does not peel off from the underlying insulating film.

Furthermore, since these high melting point metal films have a high melting point, they are highly heat resistant.

[Example] Next, an embodiment of the present invention will be described with reference to the drawings.

FIGS. 1A, 1B, and 1C are cross-sectional views showing steps for realizing an embodiment of the present invention.

Referring to FIG. 1A, an insulating film, such as a silicon oxide film 5, is formed on a semiconductor substrate, such as a silicon substrate 4, and a contact hole 6 is formed.

Next, referring to FIG. 1B, a titanium nitride film 10 is continuously formed on silicon oxide film 5 and contact hole 6 by sputtering. The titanium nitride film 10 is formed by sputtering pure Ti.
This was done by depositing the film and nitriding it by lamp annealing it in N2 at 800°C. The thickness of the obtained titanium nitride film 10 was 500 to 800 mm. Note that the titanium nitride film 10 can also be formed by sputtering TiN as a target.

Next, with reference to FIG. 1C, titanium nitride film 1
A high melting point metal silicide film, such as a tungsten silicide film 11, and a high melting point metal film, such as a tungsten thin film 7, were formed on the wafer 0. Tungsten silicide film 11
The tungsten thin film 7 was formed by CVD. FIG. 2 shows a conceptual diagram of the CVD apparatus used. The CVD apparatus includes a reaction vessel 12. The reaction vessel 12 has an exhaust port 13, a WF6 gas inlet 14, and a SiH
4 gas inlet 15 and N2 gas inlet 16. A substrate support stand 17 is installed inside the reaction vessel 12, and the substrate support stand 17 is equipped with a heating means 18.

Next, a method for forming the tungsten silicide film 11 and the tungsten thin film 7 will be described.

Second, referring to the figure, the silicon substrate 4 on which the titanium nitride film is formed is placed on the substrate support stand 17. Next, the inside of the reaction vessel 12 is exhausted from the exhaust port 13. and,
The silicon substrate 4 is heated to 450° C. by the heating means 18. Next, WF6 gas is introduced into the reaction vessel 12 from the WF6 gas inlet 14 at a flow rate of 1 Qcc/min, and S
iH, gas is SiH, 1600cc from gas inlet 15
is introduced into the reaction vessel 12 at a flow rate of /min. The gas atmosphere pressure within the reaction vessel 12 was maintained at 0.2 Torr.

As a result, 500 people's tungsten silicide film 11
was formed.

Thereafter, the inside of the reaction vessel 12 is exhausted from the exhaust port 13. Then, the silicon substrate 4 is heated to 450° C., WF6 gas is introduced into the reaction vessel 12 from the WF6 gas inlet 14 at a flow rate of 1500 cc/min, and the SiH4 gas is
N2 was introduced into the reaction vessel 12 from the gas inlet 15 at a flow rate of 50 cc/min, and N2 was introduced from the N2 gas inlet 16 at a flow rate of 150 cc/min.
It is introduced into the reaction vessel 12 at a flow rate of 0 cc/min. The gas atmosphere pressure within the reaction vessel 12 was maintained at 0.2 Torr. Under these conditions, a tungsten thin film 7 having a thickness of 1,500 to 2,000 layers was formed on the tungsten silicide film 11.

The wiring thin film obtained in this way is made of tungsten.
No silicidation occurred at the silicon interface. Further, even when the heat treatment conditions were raised to about 950° C., these wiring thin films showed good adhesion to the silicon oxide film 5.

For comparison, wiring thin films having various thin film structures were prepared and the presence or absence of peeling was determined. The results are summarized in Table 1.

Although not shown in Table 1, all of the contact areas showed good adhesion.

Table 1 1) Peeling test: The presence or absence of peeling is determined during heat treatment (approximately 80
After heat treatment (0°C) and heat treatment, the results were visually observed.

2) O: No peeling was observed.

3) ×: Peeling was observed.

As is clear from the data of Comparative Example 2 and Comparative Example 3 in Table 1, peeling of these thin films was observed on the silicon oxide film. On the other hand, in the case of Example 1, no peeling was observed. From this, referring to FIG. 1C, in order to prevent the tungsten thin film 7 from peeling off on the silicon oxide film 5, two layers of WS ix/TiN must be interposed between the tungsten 7 and the silicon oxide film 5. It turns out that it is essential to do so.

According to the present invention, it appears that the wiring structure becomes complicated and the number of manufacturing steps increases. However, in reality, W/W
The two layers of S ix can be deposited sequentially in one CVD apparatus by simply switching the gas flow rates of WF6, S iH4°H2. Here, the gas flow rates of WF6, SiH4, and H2 can be easily switched by using the cocks (not shown) of the WF6 gas inlet 14, SiH4 gas inlet 15, and H2 gas inlet 16, as shown in FIG. can be carried out. Therefore, in the manufacturing process of the present invention, the number of steps for forming the titanium nitride film 10 is only increased;
Manufacturing costs will not increase much.

Although the wiring structure of the semiconductor device of the present invention and the method of forming the same have been described above with reference to specific embodiments, the present invention may be modified in various other forms without departing from its spirit or main characteristics. It can be implemented. therefore,
The above embodiments are merely illustrative in all respects and should not be construed as limiting. The scope of the present invention is indicated by the claims, and is not restricted in any way by the main text of the specification. Furthermore, all modifications and changes that come within the scope of equivalents of the claims are intended to be within the scope of the present invention.

[Effects of the Invention] As explained above, according to the wiring structure of a semiconductor device according to the present invention, since a high melting point metal is used, wiring with high heat resistance can be obtained.

Further, the titanium nitride film continuously formed on the insulating film and in the contact portion acts as a barrier layer that prevents silicidation in the contact portion, so that wiring with low contact resistance can be realized.

Furthermore, the two layers of high melting point metal silicide/titanium nitride work together to act as a dense tube layer that brings the high melting point metal film formed thereon into intimate contact with the underlying insulating film. The melting point metal thin film will no longer peel off from the insulating film.

By employing the above-described forming method as a method for forming the wiring structure of the semiconductor device according to the present invention, wiring can be easily manufactured without increasing the number of steps.

In this case, if the high melting point metal film and the high melting point metal silicide film are formed by the CVD method, a thin film with good step coverage can be obtained.

[Brief explanation of the drawing]

FIGS. 1A, 1B, and 1C are cross-sectional views showing the process of forming a wiring structure of a semiconductor device according to an embodiment of the present invention. Figure 2 shows the C
It is a conceptual diagram of a VD device. FIG. 3 is a schematic cross-sectional view of a conventional three-dimensional device. FIGS. 4A, 4B, and 4C are diagrams showing problems in the conventional CVD tungsten thin film formation method. In the figure, 4 is a silicon substrate, 5 is a silicon oxide film,
6 is a contact hole, 7 is a tungsten thin film, 10 is a titanium nitride film, and 11 is a tungsten silicide film. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A wiring structure for electrical connection of a semiconductor device including a contact portion formed through an insulating film, the titanium nitride film being continuously formed on the insulating film and the contact portion. A wiring structure for a semiconductor device, comprising: a high melting point metal silicide film formed on the titanium nitride film; and a high melting point metal film formed on the high melting point metal silicide film. (2) A method for forming wiring for electrical connection in a semiconductor device including a contact portion formed through an insulating film, the method comprising: continuously forming a titanium nitride film on the insulating film and the contact portion; a step of forming a high melting point metal silicide film on the titanium nitride film; and a step of forming a high melting point metal film on the high melting point metal silicide film. wiring formation method.