JPH06275725A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing Al interconnections having excellent electromigration resistance in the method for manufacturing the interconnection to be connected to a tungsten plug. CONSTITUTION:A method for manufacturing a semiconductor device comprises the steps of depositing, after an insulating layer 2 opened with a contact hole 3 on a substrate 1 is formed, a diffusion preventive layer 4 on the entire substrate, forming a tungsten plug 5 buried in the hole 3 by etching back a tungsten layer 5a buried in the hole 3, deposited to cover the entire substrate 1 until the layer 4 deposited on the layer 2 is surface-exposed, and forming Al interconnection 6 by depositing Al on the plug 5 and the surface-exposed layer 4. The method further comprises the steps of oxidizing, after the step of forming the plug 6 by etching the layer 5a before the aluminum is deposited, the surface of the surface-exposed layer 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device,
In particular, the present invention relates to a method for manufacturing an aluminum wiring in which tungsten is connected to a contact hole embedded as a plug.

A method of connecting a multilayer wiring in which a contact hole is filled with tungsten and upper and lower Al wirings are connected as a plug is an effective method for solving a corrosion problem in a fine wiring having a high current density, and is expected to be put into practical use. ing.

Therefore, there is a need for a method for forming a contact hole using tungsten as a plug and an Al wiring connected to the contact hole without impairing its characteristics.

[0004]

2. Description of the Related Art When an Al wiring is provided on an insulating layer, for example, a SiO ₂ layer, the insulating layer and the Al wiring are provided to prevent diffusion in a contact region with a semiconductor substrate or to reduce stress migration. A diffusion preventive layer, for example, a diffusion preventive layer containing TiN is provided therebetween.

This diffusion barrier layer is deposited on top of the A
The surface layer is oxidized in order to further reduce electromigration of the 1-wiring. By such oxidation, A
It is possible to prevent the nitrogen contained in the diffusion prevention layer from being degassed into the atmosphere during the deposition of the 1-wiring and refining the Al crystal grains. Therefore, the crystal grains of Al deposited thereon become coarse, and an Al wiring having excellent electromigration resistance can be manufactured.

However, when the contact hole formed in the insulating layer is filled with tungsten and the Al wiring connected thereto is formed, the above-mentioned method of oxidizing the surface of the diffusion preventing layer cannot be applied. Hereinafter, this circumstance will be described with reference to examples.

FIG. 2 is a cross-sectional view of a process of an embodiment of the prior art, showing a manufacturing process of contact holes and wirings connected to the contact holes. First, depositing an insulating layer 2 made of SiO ₂ on a silicon substrate 1, the impurity region 1a is formed on the surface. Next, a contact hole 3 exposing the surface of the impurity region 1a is formed in the insulating layer 2.

Then, as the diffusion prevention layer 4, a Ti thin film 4 is formed.
a and a TiN thin film 4b are sequentially deposited so as to cover the inner surface of the contact hole 3 and the surface of the insulating layer 2. Next, the surface of the diffusion prevention layer 4 is oxidized, and the surface of the diffusion prevention layer 4 is oxidized to form a surface oxide layer 4c.

Next, referring to FIG. 2B, a tungsten layer 5a is buried in the contact hole 3 and deposited on the entire surface of the diffusion preventing layer 4. Then, referring to FIG. 2 (c),
The tungsten layer 5a is etched back to leave the tungsten plug 5 filling the contact hole 3, and the tungsten layer 5a deposited on the insulating layer 2 is removed.

Next, Al is deposited and photo-etched to form an Al wiring 6. In the above process, FIG.
Referring to (c), when the tungsten layer 5a is etched back, overetching is required to completely remove the tungsten layer 5a on the insulating layer 2. Therefore, the surface of the diffusion prevention layer 4 on the insulating layer 2 is etched and the surface oxide layer 4c is removed. as a result,
The Al deposited on the surface of the diffusion prevention layer 4 on the insulating layer 4 has fine crystal grains and is poor in resistance to electromigration.

[0011]

In the conventional method of manufacturing a semiconductor device, even if the surface of the diffusion preventive layer is oxidized, the diffusion preventive layer is etched back when the tungsten plug filling the contact hole is formed thereafter. As a result of the removal of the surface oxide layer formed on the surface, there is a problem that the electromigration resistance of the Al wiring deposited thereon is deteriorated.

According to the present invention, an Al wiring excellent in electromigration resistance is provided in a semiconductor device provided with a contact hole having a tungsten plug by oxidizing a surface of the diffusion preventive layer after forming a tungsten plug filling the contact hole. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can be used.

[0013]

FIG. 1A is a process sectional view of an embodiment of the present invention, which shows a manufacturing process of a contact hole and a wiring connected to the contact hole.

The structure of the present invention for solving the above-mentioned problems is, referring to FIG. 1, a step of forming an insulating layer 2 having a contact hole 3 formed on a substrate 1, an inner surface of the contact hole 3 and A step of depositing a diffusion prevention layer 4 covering the insulating layer 2, and a step of depositing a tungsten layer 5a made of tungsten or an alloy containing tungsten as a main component to fill the contact hole 3 and cover the entire surface of the substrate 1; Etching away the tungsten layer 5a until the diffusion barrier layer 4 deposited on the insulating layer 2 is exposed,
Tungsten plug 5 filling the contact hole 3
And then aluminum (Al) on the tungsten plug 5 and the exposed diffusion preventing layer 4.
Alternatively, an alloy containing aluminum as a main component is deposited to form Al.
In a method of manufacturing a semiconductor device having a step of forming wiring 6, after the step of etching the tungsten layer 5a to form the tungsten plug 5, before depositing the aluminum or an alloy containing aluminum as a main component In addition, it has a step of oxidizing the surface of the diffusion preventing layer 4 exposed.

[0015]

In the structure of the present invention, referring to FIG. 1, after the tungsten plug 5 is formed, the surface of the diffusion preventing layer 4 exposed by etching back the tungsten layer 5a for forming the tungsten plug is oxidized. Then, a surface oxide layer 4c is formed on the surface of the diffusion prevention layer 4. Then, in order to form the Al wiring 6, aluminum or an alloy containing aluminum as a main component is deposited.

In such a structure, the Al wiring 6 disposed on the insulating layer 2 is always made of aluminum or an alloy containing aluminum as a main component, which is deposited on the surface oxide layer 4c formed on the surface of the diffusion preventing layer 4. It is formed. As described above, the aluminum deposited on the diffusion prevention layer 4 having the surface oxide layer 4c has coarse crystal grains and is excellent in electromigration resistance. Therefore, the Al wiring 6 formed by the method of the present invention has excellent migration resistance.

In the above-described structure of the present invention, the oxidation for forming the surface oxide layer 4c can be formed by, for example, heat treatment at 450 ° C. for 30 minutes in a nitrogen atmosphere at 1 atm. Under such conditions, no oxide film is formed on the surface of the tungsten plug 5 to increase the contact resistance with Al or Al alloy deposited thereon. Therefore, good contact using the Al wiring 6 and the tungsten plug 5 can be realized.

The oxidation can also be formed by another method known as a method of oxidizing the diffusion prevention layer, for example, by immersing in a thermal oxidation material such as Rapid Thermal Anneal or nitric acid.

[0019]

EXAMPLES The present invention will be described in detail with reference to examples.
Referring to FIG. 1 (a), is deposited on the surface of the substrate 1, for example, a silicon substrate surface impurity region 1a is formed as a contactor region on the surface, for example, an insulating layer 2 made of SiO ₂ by CVD .

Then, a contact hole 3 exposing the surface of the impurity region 1a is formed in the insulating layer 2. Then, a diffusion preventing layer 4 is deposited to cover the inner surface of the contact hole 3 and the insulating layer 2. The diffusion prevention layer 4 has a Ti thin film 4a as a lower layer, which is deposited by sputtering, for example.
It is possible to have a laminated structure in which the N thin film 4b is the upper layer.
Of course, other methods may be used for deposition if desired.

Next, a tungsten layer 5a which is filled with the contact hole 3 and covers the entire surface of the substrate 1 and which is made of tungsten or a tungsten alloy normally used for contacts is formed.
Are deposited by, for example, the CVD method.

Next, referring to FIG. 1B, the tungsten layer 5a is deposited on the insulating layer 2 by plasma sputtering to form a T film.
Etch back until the iN thin film 4b is exposed. In this step, the tungsten layer 5a on the insulating layer 2 is removed, leaving the tungsten plug 5 filling the contact hole 3.

Next, referring to FIG. 1C, the insulating layer 2
By oxidizing the surface of the TiN thin film 4b exposed above, TiN
A surface oxide layer 4c is formed on the surface of the thin film 4b. Oxidation was performed by heat treatment at 450 ° C. for 30 minutes in a nitrogen atmosphere. As described above, the surface of the tungsten plug 5 is not oxidized under this condition.

Next, referring to FIG. 1D, an aluminum alloy that covers the tungsten plug 5 and the diffusion preventing layer 4 deposited on the insulating layer is deposited by, for example, sputtering. Next, this aluminum alloy is photo-etched to form Al wirings 6.

This aluminum alloy is, for example, Al
-0.15% Ti-0.1% Cu, Al-1% Si-
0.1% Cu, Al-1% Si, or Al-2% Cu can be used. Further, instead of the aluminum alloy, aluminum that does not intentionally contain impurities can be used.

Through the above steps, an Al wiring 6 which contacts the impurity region 1a through the tungsten plug 5 and extends on the insulating layer is formed. No increase in the contact resistance between the Al wiring 6 and the tungsten plug 5 due to the formation of the surface oxide layer 4c was observed.

According to the present embodiment, since the surface oxide layer 4c is formed on the surface of the TiN thin film 4b exposed during Al deposition, the release of nitrogen from the inside of the TiN thin film 4b to the atmosphere is prevented. To be done. Therefore, Al having coarse crystal grains is deposited, and Al wiring having excellent migration resistance is formed.

[0028]

As described above, according to the present invention, the surface of the diffusion preventive layer is oxidized after the tungsten plug filling the contact hole is formed, so that the surface of the diffusion plug is connected to the tungsten plug filling the contact hole and the electromigration resistance is improved. It is possible to provide a method for manufacturing a semiconductor device in which an excellent Al wiring is formed, and this contributes greatly to improving the performance of the semiconductor device.

[Brief description of drawings]

FIG. 1 is a process sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view of a process of an example of a conventional technique.

[Explanation of symbols]

 1 Substrate 1a Impurity region 2 Insulating layer 3 Contact hole 4 Diffusion prevention layer 4a Ti layer 4b TiN layer 4c Surface oxide layer 5 Tungsten plug 5a Tungsten layer 6 Al wiring

Claims (1)

[Claims] 1. A contact hole (3) on a substrate (1).
A step of forming an insulating layer (2) having an opening formed therein, a step of depositing a diffusion prevention layer (4) covering the inner surface of the contact hole (3) and the insulating layer (2), and then the contact hole (3) A step of depositing a tungsten layer (5a) made of tungsten or an alloy containing tungsten as a main component to cover the entire surface of the substrate (1), and depositing the tungsten layer (5a) on the insulating layer (2). Also, the tungsten plug (5) is etched and removed until the diffusion prevention layer (4) is exposed to fill the contact hole (3).
And forming the tungsten plug (5)
And a step of depositing aluminum (Al) or an alloy containing aluminum as a main component on the exposed diffusion prevention layer (4) to form an Al wiring (6), After the step of etching the tungsten layer (5a) to form the tungsten plug (5) and before depositing the aluminum or the alloy containing aluminum as a main component, the diffusion preventing layer (4) exposed is formed. A method of manufacturing a semiconductor device, comprising a step of oxidizing a surface.