JPH0864597A - Aluminum wiring layer and its forming method - Google Patents

Abstract

PURPOSE: To prevent generation of Si nodules and improve resistance to electromigration. CONSTITUTION: In an aluminum wiring layer which is formed on a substratum and contains Si, a Ti layer is formed which is in contact with the aluminum wiring layer, in at least one position on the aluminum wiring layer or under the layer or in the layer. For example, an Al-1% Si wiring layer 12 of 250nm in thickness is formed by a sputtering method, on a TiN layer 10 which is formed as a barrier metal layer on the substratum W. A Ti layer 14 of 20nm in thickness is formed on the Al-1%, Si wiring layer 12 by a sputtering method. An Al-1% Si wiring layer 16 of 250nm in thickness is formed on the Ti layer 14 by a sputtering method. Thereby an aluminum wiring layer can be obtained. The condition of sputtering for forming the Al-1% Si wiring layer and the Ti layer may be the ordinary sputtering condition for forming each of them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum wiring layer containing Si and a method for forming the same, and more particularly to an aluminum wiring layer which hardly causes electromigration and a method for forming the same.

[0002]

2. Description of the Related Art As a wiring material of a semiconductor device, an aluminum alloy containing Si, for example, Al-1% Si alloy, Al
1% Si-0.5% Cu alloys and the like are often used to prevent alloy spikes in addition to the reason of low electric resistance and low cost. Usually, the aluminum wiring layer containing Si is formed on the substrate by sputtering using an Al target containing Si. By the way, in recent years, in order to ensure prevention of alloy spikes, as shown in FIG. 3, a metal layer such as TiN is first formed as the barrier metal layer 10 on the substrate W, and the aluminum wiring layer 12 is formed thereon. Is formed.

[0003]

When the aluminum wiring layer contains Si, the aluminum wiring layer 1
2 Si nodules often precipitate in the aluminum wiring layer due to the thermal history associated with the formation. In particular, when the barrier metal layer 10 is present in the lower layer, the Si nodules N grow significantly as shown in FIG. 4A, and in an extreme case, as shown in FIG.
In some cases, the Si nodules N grow to a height of 2 or more, and the Si nodules N are exposed above the surface of the aluminum wiring layer.

To further explain, when forming a contact, Si nodules N grow in the aluminum wiring layer 12 as shown in FIG. 5, so that the effective sectional area of the wiring conductor in the contact hole decreases. The resistance to electromigration decreases as the wiring resistance increases. In FIG. 5, reference numeral 20 denotes an interlayer insulating film. In addition, FIG.
As shown in (a), an example will be given in which Si nodules N are grown in the aluminum wiring layer 12 at the contact hole formation position. In this case, when etching is performed to form the contact holes, Si nodules N are etched and voids are generated in the aluminum wiring layer 12 as shown in FIG. 6B, which causes a contact failure. At the same time, Via Contact resistance increases and electromigration resistance decreases. In FIG. 6, 20 is an interlayer insulating film, and 22 is a resist film.

By the way, as the LSI is highly integrated, the aluminum wiring becomes thin and the current flowing through the aluminum wiring becomes large, and electromigration becomes a big problem. Electromigration refers to a phenomenon in which metal atoms move when a large current stress (about 10 ⁵ A / cm ² ) is applied to the metal. As a result, Al is lost on the cathode side to generate voids, and Al is accumulated on the anode side to cause hillocks and whiskers.
Wiring resistance increases and breaks due to voids, and short-circuiting occurs between multilayer wiring due to hillocks and whiskers. Therefore, if the electromigration resistance decreases, the reliability of the wiring decreases.

When the Si nodules are formed in the aluminum wiring layer as described above, the wiring reliability cannot be maintained because the wiring resistance increases, the contact failure, the electromigration resistance decrease, and the like. It is difficult to reduce the wiring thickness and the line width. Therefore, an object of the present invention is to prevent the generation of Si nodules,
An object of the present invention is to provide an aluminum wiring layer having improved electromigration resistance and a method for forming the same.

[0007]

The aluminum wiring layer according to the present invention is an aluminum wiring layer containing Si,
The aluminum wiring layer is contacted with the aluminum wiring layer at at least one position above, below, and in the layer
It is characterized in that a layer is formed.

In the method of forming an aluminum wiring layer according to the present invention, when the aluminum wiring layer containing Si is formed on the substrate, the aluminum wiring layer is formed on at least one position above, below or in the aluminum wiring layer. The feature is that a Ti layer is formed in contact with the aluminum wiring layer.

The aluminum wiring layer containing Si referred to in the present invention is made of S such as Al--Si alloy and Al--Si--Cu alloy.
It is formed of an aluminum alloy containing i.
An example is an l-1% Si alloy or an Al-1% Si-0.5% Cu alloy. The method for forming the aluminum wiring layer and the Ti layer is not particularly limited, and the sputtering method or the CVD method is used. The required film thickness of the Ti layer to be formed is in the range of 1 to 6% of the film thickness of the aluminum wiring layer. The present invention can be applied regardless of whether or not a barrier metal layer is formed under the aluminum wiring layer as long as it is an aluminum wiring layer containing Si.

[0010]

In the present invention, it is considered that Si reacts with Ti to prevent the growth of Si nodules. Also, A
It is considered that the electromigration resistance is improved by the discontinuity of l-Si crystal formation (see FIG. 7) and the excellent heat resistance of the Ti layer. In FIG. 7, I is Al −
The schematic crystal interface of Si crystal is shown.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the accompanying drawings. 1A, 1B and 1C are cross-sectional views each showing a wiring layer cross section in each step when the method for forming an aluminum wiring layer according to the present invention is carried out. As shown in FIG. 1A, an Al-1% Si wiring layer 12 having a film thickness of 250 nm is formed on the TiN layer 10 formed as a barrier metal layer on the substrate W by a sputtering method. Then, as shown in FIG.
A Ti layer 1 with a thickness of 20 nm is formed on the Al-1% Si wiring layer 12.
4 is formed by the sputtering method. Furthermore, FIG.
As shown in (c), an Al-1% Si wiring layer 16 having a film thickness of 250 nm is formed on the Ti layer 14 by a sputtering method to obtain an aluminum wiring layer according to the present invention. The sputtering conditions for forming the Al-1% Si wiring layer and the Ti layer may be the usual sputtering conditions for forming the respective layers.

A disconnection test was conducted to evaluate the aluminum wiring layer of this example. As a result, the aluminum wiring layer of this example had an average life until disconnection significantly higher than that of a conventional aluminum wiring layer. It was confirmed that it became longer.

In the above-described embodiment, the Ti layer 14 is formed on the upper and lower A layers.
Although sandwiched between l-1% Si wiring layers, as shown in FIG. 2A, first, a Ti layer 14 having a thickness of 20 nm is formed on the Ti N layer 10 which is a barrier metal layer. Alternatively, the Al-1% Si wiring layer 18 having a film thickness of 500 nm may be formed, and further, as shown in FIG. 2B, first, as shown in FIG.
1-1% Si wiring layer 18 is formed, and then Al-1% S
A Ti layer having a film thickness of 20 nm may be formed on the i wiring layer 18.

[0014]

According to the present invention, when an aluminum wiring layer containing Si is formed on a substrate, the aluminum wiring layer is contacted with the aluminum wiring layer at at least one position above, below or within the aluminum wiring layer. By forming the layer, it is possible to prevent Si nodules from being generated in the aluminum wiring layer. As a result, it is possible to improve the electromigration resistance of the aluminum wiring layer, reduce the wiring resistance, prevent the occurrence of voids in the aluminum wiring layer, and improve the reliability of the wiring. Further, since the reliability of the wiring is improved, thinning and flattening of the wiring are facilitated. Further, since the current strength per unit cross-sectional area can be increased by improving the electromigration resistance, it is possible to reduce the line width of the wiring.

[Brief description of drawings]

1 (a), (b) and (c) are cross-sectional views each showing a wiring layer cross section in each step when a method for forming an aluminum wiring layer according to the present invention is carried out.

2 (a) and 2 (b) are cross-sectional views each showing a cross section of a wiring layer when the method of the present invention is carried out in a mode different from that of FIG.

FIG. 3 is a cross-sectional view of a wiring layer portion of a semiconductor device.

4A and 4B are schematic cross-sectional views showing a state in which Si nodules are formed in an aluminum wiring layer.

FIG. 5 is a schematic cross-sectional view showing a state where Si nodules are formed on a wiring conductor in a contact hole.

6A and 6B are cross-sectional views of each step of forming a contact hole, which are schematic views for explaining a situation in which a void is generated in an aluminum wiring layer when forming the contact hole. Is.

FIG. 7 is a schematic cross-sectional view for explaining generation of a crystal interface of an Al—Si crystal.

[Explanation of symbols]

 10 Ti N layer 12, 16, 18 Al -1% Si wiring layer 14 Ti layer 20 Interlayer insulating film 22 Resist film

Claims (2)

[Claims] 1. An aluminum wiring layer containing Si, wherein a Ti layer is formed in contact with the aluminum wiring layer at at least one position above, below, or in the layer of the aluminum wiring layer. Aluminum wiring layer. 2. When forming an aluminum wiring layer containing Si on a substrate, a Ti layer is formed in contact with the aluminum wiring layer at at least one position above, below, or in the aluminum wiring layer. And a method for forming an aluminum wiring layer.