JP2867537B2 - Method for manufacturing semiconductor integrated circuit device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor integrated circuit device, and more particularly to a method for forming a contact between an aluminum wiring and a semiconductor substrate.

[Prior Art] A method of forming a contact between an aluminum wiring and a semiconductor substrate of a conventional semiconductor integrated circuit device will be described with reference to FIG. Using a photoresist film or an aluminum film as a mask on a semiconductor substrate 1 made of P-type Si,
Is selectively ion-implanted to form an n-type diffusion layer 2 on the surface of the semiconductor substrate 1. The diffusion layer 2 is used as a source / drain portion of a transistor, a resistor on a circuit, and the like in a semiconductor integrated circuit device.

On the semiconductor substrate 1 thus formed, an isolation insulating film 3 is formed for isolation between elements or interconnections.

When the isolation insulating film 3 is etched by reactive ion etching or the like using a photoresist film as a mask, the isolation insulating film 3 on the diffusion layer 2 is removed, and a contact portion 4 is formed. TiW and Al are sputtered on the semiconductor substrate 2 in the contact portion 4 by 0.1 μm each.
When about 1.1 μm is deposited, the barrier metal film 5 and the aluminum wiring 7 are formed. Further, when the barrier metal film 5 and the aluminum wiring 7 are selectively etched, a contact to the n-type diffusion layer 2 having the structure shown in FIG. 3 is formed. The contact thus formed can be subjected to a heat treatment in a hydrogen atmosphere so that the contact resistance between the aluminum wiring 7 and the diffusion layer 2 can be reduced.

[Problems to be solved by the invention]

In the above-described conventional method for forming a contact between an aluminum wiring and a semiconductor substrate, in order to increase the adhesion between the diffusion layer 2, the barrier metal film 5 and the aluminum wiring 7 and to reduce the resistance between the diffusion layer 2 and the aluminum wiring 7. To
In a hydrogen atmosphere, heat treatment at 400-500 ° C is performed.
In order to reduce the resistance value, the contact according to the related art has a problem that the barrier property of TiW is not maintained, and the leakage current of the diffusion layer from the aluminum wiring to the semiconductor substrate increases.

[Means for solving the problem]

According to the method of manufacturing a semiconductor integrated circuit of the present invention, a contact portion is formed by selectively opening a separation insulating film between elements or between layers formed on a semiconductor substrate, and a barrier metal film is formed on the contact portion. Forming a silicon oxide film on the barrier metal film, then forming an aluminum film, and performing a heat treatment to reduce at least a part of the silicon oxide film.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a semiconductor chip shown in the order of steps for explaining one embodiment of the present invention.

As is selectively applied to a semiconductor substrate 1 made of P-type Si by using a photoresist film or an aluminum film as a mask, 30 ke
By ion implantation at an energy of about V, a thin n-type diffusion layer 2 is formed on the surface of the semiconductor substrate 1.
This diffusion layer is used as a source / drain portion of a transistor, a resistor on a circuit, or the like, as in the conventional technology. On the semiconductor substrate 1 thus formed, a PSG film or a silicon oxide film doped with boron or phosphorus is generally provided for separating elements or layers. Here, a 1.0 μm silicon oxide film was deposited by vapor phase growth to form an isolation insulating film 3. This isolation insulating film 3
Is etched by reactive ion etching,
The contact 4 is formed so that the surface of the n-type diffusion layer 2 is exposed. After performing a surface treatment on the surface of the diffusion layer 2, TiW is sputtered to deposit a barrier metal film 5 to a thickness of about 0.1 μm. Further, the silicon oxide film 6 is formed to a thickness of 1 to 2 nm.
It is formed by vapor deposition or sputtering (FIG. 1A).

Further, when the aluminum oxide film 7 is formed by etching the laminated film of the silicon oxide film 6 and the aluminum film using the photoresist as a mask, n of the structure shown in FIG.
A contact with the mold diffusion layer can be formed.

The contact having the above-described structure needs to be subjected to a heat treatment so that the resistance between the aluminum wiring 7 and the diffusion layer 2 is sufficiently reduced. By this heat treatment, silicon oxide is reduced by aluminum, an intermediate layer made of a mixture of aluminum oxide, Si and Al is formed, and a contact with sufficiently low resistance is obtained. For example, 450 ° C for 1nm silicon oxide film
Heat treatment may be performed for 20 minutes.

The contact leakage current (p−
The relationship between the reverse bias current of the n-junction) and the heat treatment temperature is shown by the solid line in FIG. However, the heat treatment time is 20 minutes. At low temperatures, the silicon oxide film remains almost intact, so that the leakage current is naturally small.

Although the formation of the contact between the n-type diffusion layer and the aluminum wiring 7 is described as an example, the present invention can be similarly applied to the formation of the contact between the p-type diffusion layer and the aluminum wiring. Furthermore, not only TiW but also other barrier metals may be used as the barrier metal.

〔The invention's effect〕

As described above, according to the present invention, by forming a silicon oxide film between a barrier metal film and an aluminum wiring, the leakage current can be reduced even when a heat treatment for improving the adhesion between the aluminum wiring and the diffusion layer is performed. Since it can be kept small, a semiconductor integrated circuit device having good contacts can be realized.

[Brief description of the drawings]

1 (a) and 1 (b) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention, and FIG. 2 is a pn junction between a diffusion layer 2 and an aluminum wiring 7. FIG. 3 is a characteristic diagram showing a relationship between a heat treatment temperature and a leakage current when a current flows in the opposite direction, and FIG. 3 is a longitudinal sectional view for explaining a conventional contact forming method. 1 ... semiconductor substrate, 2 ... diffusion layer, 3 ... isolation insulating film,
4 ... contact part, 5 ... barrier metal film, 6 ... insulating film, aluminum wiring film.

Claims (1)

(57) [Claims] A step of forming a contact portion by selectively opening a separation insulating film between elements or between layers formed on a semiconductor substrate, and forming a barrier metal film on the contact portion; A method for manufacturing a semiconductor integrated circuit device, comprising: forming a silicon oxide film on a film, forming an aluminum film, and performing a heat treatment to reduce at least a part of the silicon oxide film.