JPH0745611A - Wiring structure - Google Patents

Abstract

PURPOSE:To increase the strength against electromigration in a multilayer wiring of Al and CVDW. CONSTITUTION:The aluminum film 14 is formed by sputtering over the CVDW film, and is caused to reflow thereby making the surface of the aluminum flat. Thereafter, the conductive layer 15 of titanium, titanium nitride, or tungsten titanate, and the aluminum film 16 are formed by sputtering, and the wiring is formed by standard micromachining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring structure of a semiconductor integrated circuit, and more particularly to a laminated wiring structure of a chemical vapor deposition tungsten film and an aluminum film.

[0002]

2. Description of the Related Art Conventionally, as a wiring structure of an integrated circuit, a laminated structure of Cu-containing Al and a barrier metal formed by a sputtering method is used as a countermeasure for stress migration. Here, the barrier metal is generally titanium nitride or titanium-containing tungsten or tungsten, and these are formed by a sputtering method.

On the other hand, with the high integration of semiconductor integrated circuit devices, the connection holes between the wirings and the connection holes between the diffusion region and the wirings have been miniaturized. As this connection hole is further miniaturized, the coverage of Al containing Cu and the barrier metal formed by the sputtering method may be deteriorated and the wire may be broken.

In order to solve such a problem, "199
0 years VMIC Conference Proceed
ing ", P133-141," Barrier Metal Effects on Electromigration.
Barrier metal effects on
electromigration of layer
ed Aluminum metallizatio
Attention has been paid to the laminated structure wiring of Cu-containing Al and chemical vapor deposition tungsten shown in “n)”.

This structure, as shown in the sectional view of FIG.
An interlayer film 20 is formed on the silicon substrate 10, a tungsten layer 13 is formed by CVD on the interlayer film 21,
An aluminum layer is formed on the tungsten layer 13.

The reason why the chemical vapor deposition tungsten is used here is as shown in FIG.
Since the coating property in the connection hole of No. 3 is excellent, the Al layer 14
This is because even if the wire breaks in the connection hole, the tungsten layer 13 makes a connection and there is no problem in terms of characteristics.

[0007]

In the case of this conventional wiring structure, since the CVDW surface has severe irregularities, the grain size of the Al layer 14 formed thereon is on the barrier metal formed by the sputtering method. The grain size of Al is smaller than that of Al and the electromigration resistance is deteriorated. The actual evaluation results of this electromigration are shown in Table 1 below.

[0008]

[Table 1]

As described above, there is a problem that electromigration resistance is deteriorated when it is laminated with a chemical vapor deposition (CVD) tungsten film. In this case, the storage temperature is 150 ° C. and the current density is 2 × 10 ⁶ A / cm ² .

An object of the present invention is to solve the above problems and provide a wiring structure having improved electromigration resistance.

[0011]

The structure of the wiring structure of the present invention comprises a tungsten film chemically vapor-deposited on a semiconductor integrated circuit substrate and a first aluminum film having a surface flattened on the surface of the tungsten film. And a conductive film other than the aluminum film formed on the surface of the first aluminum film, and a second aluminum film formed on the surface of the conductive film other than the aluminum film.

[0012]

FIG. 1 is a sectional view illustrating an embodiment of the present invention in the order of manufacturing steps. First, as shown in FIG. 1A, a silicon oxide film 11 is formed on a silicon substrate 10. Next, as shown in FIG. 1B, 100 is formed on the silicon oxide film 11.
Tungsten 12 having a thickness of 0 angstrom is formed by the sputtering method. Next, as shown in FIG. 1 (c), C having a thickness of 1000 angstrom is formed on the sputtered tungsten 12.
The VD tungsten 13 is formed. The CVD tungsten 13 is formed by using WF ₆ and H ₂ gas and using a reduced pressure CV.
D.

Further, as shown in FIG. 1D, a Cu-containing aluminum 14 is formed on the CVD tungsten 13 to a film thickness of 200.
It is formed by a sputtering apparatus with a thickness of 0 angstrom. Subsequently, heat treatment at 400 to 500 ° C. is performed in the same sputtering apparatus to reflow aluminum and flatten the surface. Then, on the surface of the aluminum layer 14, as shown in FIG.
As shown in (e), the conductive layer 15 such as titanium, titanium nitride, or angusten is formed to a film thickness of 1000 angstrom by the sputtering method. Finally, the conductive layer 14
As shown in FIG. 1F, aluminum 15 is formed on the surface by a sputtering method to have a film thickness of 2000 angstrom, and then wiring is formed by an ordinary fine processing technique.

As shown in Table 2, the electromigration resistance of this wiring is as follows:
This is improved compared to the case where an aluminum film and a CVDW film are laminated.

[0015]

[Table 2]

In Table 2, the storage temperature is 150 ° C. and the current density is 2 × 16 ⁶ A / cm ² .

Next, a second embodiment of the present invention will be described. In this embodiment, after forming the tungsten layer 13 in FIG. 1C of the first embodiment, the surface of the tungsten layer 13 is etched by plasma etching using SF6 gas. As a result, unevenness on the surface of the tungsten layer 13 is reduced, and thereafter, wiring is formed by the process of FIG.

In the second embodiment, the roughness of the surface of the CVDW layer 13 is smaller than that in the first embodiment, so that the grain size of the first Al film 14 is large.
Therefore, there is an advantage that the electromigration resistance is improved as compared with the case of the first embodiment.

[0019]

As described above, the present invention is a CVDW.
After forming the first aluminum film with a flat surface on the surface of
Since the second aluminum film is formed by providing one conductive layer, the fine grain size of the first aluminum film is increased without reflecting the grain size of the second aluminum film. Therefore, it has an effect of improving electromigration resistance as compared with the laminated wiring of the aluminum film and the CVDW layer.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention in the order of manufacturing steps.

FIG. 2 is a vertical cross-sectional view illustrating a conventional wiring structure.

[Explanation of symbols]

 10 Silicon Substrate 11 Silicon Oxide Film 12 (Sputtering) Tungsten Film 13 CVDW (Tagsten) Film 14 First Aluminum Film 15 Conductive Layer (Titanium Nitride / Tungsten) 16 Second Aluminum Film

Claims (2)

[Claims] 1. A tungsten film chemically vapor-deposited on a semiconductor integrated circuit substrate, a first aluminum film whose surface is flattened on the surface of the tungsten film, and aluminum formed on the surface of the first aluminum film. A wiring structure comprising: a conductive film other than a film and a second aluminum film formed on a surface of the conductive film other than the aluminum film. 2. The wiring structure according to claim 1, wherein the first aluminum is reflowed at a high temperature and the surface thereof is flattened.