JP2841439B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] The present invention relates to the formation of a tungsten (W) film used for internal wiring of a semiconductor integrated circuit (IC), etc., which chemically functions as a barrier and is mechanically an adhesive material. The purpose of this study is to make it possible to deposit W by chemical vapor deposition on a titanium nitride (TiN) film that functions as a TiN film. A step of depositing a film, a step of depositing a polycrystalline or amorphous Si film on the TiN film, and a chemical vapor deposition method of reducing tungsten hexafluoride (WF ₆ ) with hydrogen (H ₂ ) (CVD) including a step of depositing a W layer on the Si film.

[Industrial applications]

The present invention relates to CVD of a W film used for forming an internal wiring of an IC.
The present invention relates to the formation, and particularly to a processing method for forming a W film on a non-Si surface by H ₂ reduction of WF ₆ .

The internal wiring of the IC is usually formed by applying an Al or Al alloy film and patterning. IC
When formed on a Si substrate, if an Al contact is provided in the Si element region, there is a disadvantage that Si and Al react or migration of Si occurs.Therefore, a barrier film is sandwiched between Al / Si to remove it. Preventing.

This barrier film needs to be a chemically stable conductor, but in addition, SiO ₂ or PS used for interlayer insulation
Good adhesion to G and good adhesion to Al are required. TiN to satisfy such conditions
It is widely used because of its superior properties and other advantages in processing steps as compared with other similar materials.

Although the use of Al-based wiring materials in combination with a TiN barrier film can be said to be a well-established technique, some problems have arisen with the progress of high integration of ICs and miniaturization of patterns.

One of them relates to the poor coverage of the Al film formed by sputtering or vapor deposition. Normally, the contact with the element region of the substrate and the interlayer connection of the multilayer wiring are formed simultaneously with the wiring pattern by forming a hole in the insulating coating layer and applying a wiring material film. With the miniaturization, the cross-sectional shape of the connection hole became deeper than the opening width, making it difficult to apply a sufficiently thick Al film to the wall surface of such a connection hole. It is. If the wiring film thickness is locally small, the electric field concentrates on that portion, which may cause disconnection.

Another problem with Al-based wiring materials is that the mechanical strength is not sufficient. When the width of the wiring pattern and the size of the connection hole become finer, the wiring film thickness also becomes smaller, and the wiring film is broken due to the stress due to the difference in thermal expansion coefficient from the insulating material layer to which the wiring film is adhered. Although the situation is easy to do, especially Al
Since the system material breaks at the crystal grain boundary, it is vulnerable to tensile stress.

Because of such a problem, W has been used as a wiring material instead of an Al-based material. Since the W film can be deposited by the CVD method with good coating properties and has high mechanical strength, the above problem can be solved if the W film can be used for the internal wiring of the IC. Become.

Since W has a lower chemical activity than Al, it is not necessary to interpose a barrier film in the sense of suppressing the reaction with Si, but the adhesion to the underlying material SiO ₂ or PSG is sufficient. Instead, it is necessary to perform a treatment for firmly bonding the two. For this purpose, it would be advantageous if the established technology could be used as an adhesion layer of a TiN film.

[Problems to be solved by conventional technology and invention]

For CVD deposition of W, WF ₆ is reduced by SiH ₄ and WF ₆ and H
There is a method of reducing with ₂ . Comparing the two, SiH ₄ is strongly reducing, to react directly with WF _6, while the reaction is the supply rate-limiting, reduction with H ₂ is first in H ₂ acts as the active surface dissociation However, since the generated nascent H proceeds through the process of reacting with WF ₆ , this reaction is surface-limited.

Since the reduction by SiH ₄ is rate-controlled, the reaction proceeds irrespective of the material of the base and W is deposited. However, depending on the geometrical shape of the base surface, a portion where a large amount is deposited and a portion where a small amount are deposited occur. That is, as a general evaluation, although it has good coverage, which is a feature of the CVD method, it cannot be said that it has sufficient coverage for fine connection holes of high-density ICs.

On the other hand, since the reduction by H ₂ is surface-limited, there is little variation in the film thickness due to the geometrical shape of the base, and the W film formed by this method has sufficient coverage even for fine connection holes of high-density ICs. Will have. However, since the method includes the step of H ₂ is released by the active surface, the underlying surface is Ti
In the case of an inert material such as N, there is a fundamental problem that the reaction hardly proceeds.

An object of the present invention is to solve the above problems and to provide a method for depositing and forming a W film on a TiN film by a treatment method for reducing WF ₆ with H ₂ , thereby reducing the risk of disconnection of an IC.
Is to realize the internal wiring.

[Means for solving the problem]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention includes the following steps: 1. a step of depositing a titanium nitride (TiN) film on a substrate, and a step of depositing polycrystalline or amorphous Si on the TiN film. The method includes a step of depositing a film and a step of depositing a tungsten (W) layer on the Si film by a chemical vapor deposition method of reducing tungsten hexafluoride (WF ₆ ) with hydrogen (H ₂ ).

2. a step of forming an insulating coating layer having connection holes on the substrate; a step of applying a titanium nitride (TiN) film on the insulating coating layer including the continuous holes; A polycrystalline or amorphous Si film is deposited, and tungsten (W) is deposited on the Si film by a chemical vapor deposition method of reducing tungsten hexafluoride (WF ₆ ) with hydrogen (H ₂ ). And depositing a layer.

3. The polycrystalline or amorphous Si film in the method for manufacturing a semiconductor device includes a thickness of 200 to 600 °.

(Operation)

According to the above process, since the surface on which W is deposited is covered with polycrystalline or amorphous Si (hereinafter, referred to as poly-Si), WF ₆ reaching the surface is reduced by Si. A process occurs and W is deposited on the poly-Si surface. Poly Si
After the entire surface of the film is covered with W, H ₂ acts on the W surface to dissociate, and the resulting nascent H reduces WF ₆ .

That is, W deposition on the TiN film by H ₂ reduction of WF ₆ which has been almost impossible in the past can be realized by interposing a thin film of poly-Si as in the present invention.

In addition, as an active surface for precipitating W in the initial stage, there is a material exhibiting an effect other than Si, but it can be formed by a low-pressure CVD method with excellent coverage, Taking into account the advantage that it is a material commonly used in manufacturing and that a new processing apparatus is not required, the use of a poly-Si film is the most utilized.

〔Example〕

1 (a) to 1 (d) are schematic sectional views showing processing steps of an embodiment of the present invention. Hereinafter, the embodiment will be described with reference to the drawings.

1A shows a state in which a PSG layer 2 serving as an insulating coating is provided on the surface of a substrate 1 and a connection hole 3 is opened. The substrate 1 is a convenient expression, and the substance is an element region formed on a Si substrate or a lower layer wiring of a multilayer wiring.

As shown in FIG. 2B, a TiN film 4 is deposited on the entire surface by a known sputtering method. This processing method is, for example, Ar
This is high-frequency sputtering using Ti as a target in a + N ₂ atmosphere, and the thickness of TiN is 500 °. The sputtering may be direct-current sputtering, and both are performed under reduced pressure conditions, so that the coverage of the TiN film is good.

Next, as shown in FIG. 1C, a poly-Si film 5 is entirely deposited on the TiN film 4. The formation of the poly-Si layer is caused by the thermal decomposition of SiH _4, is a processing temperature of 650 to 750 ° C., coverage be carried the process at reduced pressure condition becomes good. This poly Si
The film is for reducing W first as described above, and it is sufficient that the film covers the entire surface even if the thickness is uneven, and a process with good coverage such as a low pressure CVD method is used. In the case of using the method, it is sufficient that the thickness of the Si film is about 200 to 600 °.

After coating the substrate surface with poly-Si by the above processing, the substrate temperature was kept at 600 ° C, and the source gas was WF ₆ / H ₂ = 4/100
Is supplied to advance the reduction reaction. Under these conditions, the deposition rate of W is 1500-2000 ° / min, and the time is controlled to deposit and form a W film 6 of 5000 °. This state is shown in FIG.

Since the formation of the W film is surface-limited as described above, the coatability is sufficiently good. If the W film is patterned and used as an internal wiring, the W film has a sufficient film thickness even in the connection hole portion, and has a disconnection. Internal wiring without fear is realized.

〔The invention's effect〕

As described above, formed by the method of the present invention
The internal wiring of the IC has sufficient mechanical strength and coverage, and the risk of disconnection due to thermal stress or electric field concentration is greatly reduced.

[Brief description of the drawings]

1 (a) to 1 (d) are schematic cross-sectional views showing the steps of the embodiment, in which 1 is a substrate, 2 is a PSG layer, 3 is a connection hole, 4 is a TiN film, and 5 is poly-Si. It is a membrane.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/28-21/288 H01L 29/40-29/43 H01L 21/768

Claims (3)

(57) [Claims] A step of depositing a titanium nitride (TiN) film on a substrate; a step of depositing a polycrystalline or amorphous Si film on the TiN film; and tungsten hexafluoride (WF ₆ ). A step of depositing a tungsten (W) layer on the Si film by a chemical vapor deposition method of reducing hydrogen with hydrogen (H ₂ ). 2. A step of forming an insulating coating layer provided with a connection hole on a substrate; and forming titanium nitride (TiN) on the insulating coating layer including the continuous hole.
A step of depositing a film, a step of depositing a polycrystalline or amorphous Si film on the TiN film, and a chemical vapor deposition of reducing tungsten hexafluoride (WF ₆ ) with hydrogen (H ₂ ) A method of depositing a tungsten (W) layer on the Si film by a method. 3. The polycrystalline or amorphous Si film has a thickness of 200 to 6
3. The method for manufacturing a semiconductor device according to claim 1, wherein the thickness is 00 °.