Method for Fabricating a Diffusion Barrier Metal Layer in a Semiconductor Device

The present invention relates to a method for fabricating a diffusion barrier metal layer in a semiconductor device capable of preventing the substance of a metal wiring from being diffused into its underlayer during the formation of the metal wiring of the semiconductor device, and more particularly, to a method for fabricating a diffusion barrier metal layer which can be used in a deep and narrow contact.

Generally, a ruthenium oxide layer (RuO.sub.2) is used as a diffusion barrier metal layer in a highly integrated semiconductor device above 256M DRAM, and used as a glue layer of a metal wiring formed of aluminum, tungsten or copper. In prior arts, the ruthenium oxide layer is formed by the physical vapor deposition (PVD) or the chemical vapor deposition (CVD) method. In case of the PVD method, ruthenium and oxygen are compounded to form the ruthenium oxide layer. In case of the CVD method, ruthenium source gas and oxygen are compounded to form the ruthenium oxide layer through the metal organic chemical vapor deposition (MOCVD) method.

However, in case where the ruthenium oxide layer is formed by the CVD method, impurities are introduced into the ruthenium oxide layer. This increases the resistance value of the layer. In case that PVD is used, the step coverage of the ruthenium oxide layer is poor, and a silicide layer may be formed by the reaction of the ruthenium oxide layer and silicon. Furthermore, during the deposition of the ruthenium oxide layer, the oxidation rate is too low to form a stable ruthenium oxide layer.

It is an object of the present invention to provide a method for fabricating a diffusion barrier metal layer in a semiconductor device, capable of preventing a silicide layer from being formed at the interface between of ruthenium and silicon layer, and forming a stable ruthenium oxide layer at a high temperature.

To accomplish the object of the present invention, there is provided a method for fabricating a diffusion barrier metal layer in a semiconductor device for preventing a material of a metal wiring in said semiconductor device from being diffused into a silicon layer under said metal wiring, the method including the steps of: exposing the surface of said silicon layer to oxygen plasma, to prevent a silicide from being formed at the interface between said silicon layer and diffusion barrier metal layer; forming a first diffusion barrier metal layer on said silicon layer; implanting oxygen ions into said first diffusion barrier metal layer; and forming a second diffusion barrier metal layer on said first diffusion barrier metal layer.

Other objects and aspects of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings, in which:

FIGS. 1A to 1F are cross-sectional views showing processes for forming a diffusion barrier metal layer in accordance with an embodiment of the present invention.

A preferred embodiment of the present invention will be described below referring to the accompanying drawings. FIGS. 1A to 1F are cross-sectional views showing processes for forming a ruthenium oxide layer as a diffusion barrier metal layer.

As shown in FIG. 1A, an insulating layer 3 is formed on a silicon substrate 1 and a field oxide layer 2, and a conducting layer 4 is formed on the field oxide layer 2. Then, an insulating layer 5 is formed on the overall surface of substrate 1, and the insulating layers 3 and 5 are selectively removed to form a contact hole, thereby exposing a predetermined portion of the silicon substrate 1 and the conducting layer 4.

As shown in Fig. 1B, the overall surface of the substrate 1 is exposed to O.sub.2 plasma 6. Here, the O.sub.2 plasma 6 adheres to the overall surface of the substrate 1 on which the conducting layer 4 and the insulating layer 5 are formed. The O.sub.2 plasma is formed at a low power of below 50W, and at a gas flow of 5 sccm to 50 sccm in plasma enhanced chemical vapor deposition (PECVD) chamber. As described above, by carrying out the O.sub.2 plasma treatment, it is possible to prevent a silicide from being formed at the interface of ruthenium and silicon during the following heat treatment, and form a stable ruthenium oxide layer at a high temperature.

As shown in Fig. 1C, a first ruthenium layer 7 is formed to a thickness of 100 .ANG. to 500 .ANG. in PVD sputter camber on the overall surface of the substrate 1 on which the conducting layer 4 and the insulating layer 5 are formed. Then, O.sub.2 is implanted into the overall surface of the first ruthenium layer 7. Here, O.sub.2 implantation is carried out, considering the projection range Rp according to the thickness of the first ruthenium layer 7. For example, if the thickness of the first ruthenium layer is 200 .ANG., O.sub.2 is implanted at a dose of 10.sup.15 -10.sup.19 ions/cm.sup.2 and at an energy level of 50 keV.

As shown in FIG. 1D, a second ruthenium layer 9 is formed under the same condition as that for the first ruthenium layer 7. Then, the substrate 1, on which the first and second ruthenium layers 7 and 9 are formed, is heat-treated in a tube in which argon and oxygen, or nitrogen and oxygen are mixed for one to five hours. By doing so, as shown in FIG. 1E, an ultimate ruthenium oxide layer 10 is formed. Here, the flow of argon/oxygen or nitrogen/oxygen introduced into the tube is approximately 100 sccm/10 sccm to 2000 sccm/300 sccm, and the temperature in the tube is approximately 400.degree. C. to 700.degree. C. As described above, O.sub.2 is implanted into between the first and second ruthenium layers and a heat treatment is carried out in the tube, so that the stable ruthenium oxide layer can be formed. FIG. 1F is a cross-sectional view showing a device in which a metal wiring 11 is formed using ruthenium oxide layer 10 as a diffusion barrier. The metal wiring 11 is formed of aluminum, tungsten or copper.

According to the present invention described above, it is possible to prevent the silicide from being formed at the interface between the ruthenium layer and silicon layer. Thus, the stable ruthenium oxide layer can be obtained. By using the stable ruthenium oxide layer as a diffusion barrier, it is able to prevent the substance of the metal wiring from being diffused, and form a metal plug having low resistance.

Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.