JP2003179061A - Method of forming wirings of semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming wirings of a semiconductor element which enables prevention of contamination by the aging of wiring materials resulting from ordinary high temperature surface reaction and thermal diffusion by reducing or substantially eliminating chemical reaction with the circumferential atmosphere and/or movement by thermal diffusion of atoms of wiring materials after formation of electronic circuit wirings. <P>SOLUTION: In the method of forming wirings of a semiconductor element in which ultra-fine electronic circuit wirings are formed, the electronic circuits are formed by embedding conductor materials including at least Cu layer into the substrate material and only the open surface of the electronic circuits is covered with a material for preventing movement by thermal diffusion of the conductor material. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming wiring of an electric circuit such as a semiconductor element, and more particularly to a structure for coating a surface of a conductor material arranged in a semiconductor substrate for forming fine electric circuit wiring. Regarding

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for surface coating of conductive materials forming fine electric circuits such as semiconductor devices. For example, conventionally, an Al alloy material forming a wiring network as a conductive line of a semiconductor element must be provided with a barrier layer for preventing mutual diffusion of constituent elements between the material and an SiO ₂ layer which is an insulating layer. . Therefore, conventionally, TiN has been used as a barrier layer for preventing diffusion.
The layers may be arranged to intervene between 500 and 1,000 Angstroms.

[0003]

However, in recent years, the demand for the surface coating of a conductive material forming a fine electric circuit tends to become more and more severe. In particular, in the wiring process of semiconductor elements, there is a strong demand for establishment of a fine pattern forming technique using a low electric resistance material which can be replaced with an aluminum alloy due to a demand for further increasing the degree of integration.

This is because the current density increases as the degree of integration increases, causing thermal stress and temperature rise.
This is also caused by the increased risk of wire breakage due to stress migration and electromigration in the l-alloy. In order to avoid this, addition of Cu to the Al alloy and lamination with a refractory metal are being carried out, but this is not a perfect thing.

Therefore, in order to avoid excessive heat generation due to energization, it is inevitably required to employ a material having good conductivity, which is fundamentally different from the conventional Al alloy, for wiring formation. Among the current materials, Cu and Ag are materials having a smaller electric resistance than Al-based materials. Even if such a low electrical resistance material is used, the wiring will be heated by the high temperature process performed after the wiring process and the temperature rise of the wiring material itself and the surrounding material due to the heat generation due to the high current density flowing during the operation after completion. It is unavoidable that the atoms of the material constituent elements chemically react with the surrounding atmosphere or move by diffusion to move inside the surrounding material.

If this becomes remarkable, the wiring material itself and the surrounding insulating material itself are deteriorated, and there is a great possibility that the function of the main body is impaired. If such an adverse effect occurs, it will be difficult to make full use of its usefulness even if a material having a low electrical resistance is used. Therefore, it is necessary to take measures to prevent the chemical reaction of the constituent atoms of the wiring material with the surroundings at high temperature and the migration due to diffusion.

The present invention was devised as a means for solving the above-mentioned need, and after the formation of electric circuit wiring, the wiring material constituting atoms are chemically reacted with the ambient atmosphere and / or moved by thermal diffusion. It is an object of the present invention to provide a method for forming a wiring of a semiconductor element, which can reduce or effectively prevent the deterioration of a wiring material over time due to a normal high temperature surface reaction or thermal diffusion.

[0008]

SUMMARY OF THE INVENTION The present invention provides a wiring forming method for a semiconductor device for forming fine electric circuit wiring,
An electric circuit is formed by embedding a conductor material containing at least a Cu layer in a base material, and only the open surface of the electric circuit is covered with a material that prevents thermal diffusion transfer of the conductor material. .

[0009]

When the surface of the semiconductor material has relatively low reactivity with the surrounding environment, such as contact, deposition, lamination, or mounting, even if exposed to a high temperature process or a high temperature environment during circuit operation, Since it is possible to prevent or reduce the movement of the conductive material due to the chemical reaction on the surface and the thermal diffusion of atoms, it is possible to suppress or prevent the deterioration of the wiring structure, that is, the electric circuit with time.

[0010]

EXAMPLES Specific means for achieving the above-mentioned object will be described using published data examples. The coating structure of an electric circuit according to the present invention is characterized in that the wiring is covered with a metal having good corrosion resistance from the outside of the electric circuit at a high temperature and hardly causing thermal diffusion of metal atoms inside itself. Here, the metal used for the coating has good corrosion resistance and oxidation resistance at high temperatures, and has a very small diffusion coefficient of atoms of a metal element having good electric conductivity such as Cu and Ag inside the bulk. Is used.

FIG. 3 shows the temperature dependence of the electrical resistivity of Al, Cu, Ag and Au. As is clear from FIG.
Since the electric resistance of Cu and Ag is relatively small in the region up to 800 ° C., it is suitable for forming the wiring of an electric circuit as a single conductor material. In addition, Fig. 3 shows the Metals Ref.
erence Book, 5th ed, 1976 Bu
It was drawn from the data described in

On the other hand, FIG. 4 shows the diffusion coefficient of each atom of Cu in various metals, and FIG. 5 shows the diffusion coefficient of each atom of Ag in various metals. 4 and 5 are also Metals Ref.
erence Book, 5th ed. 1976, B
It is plotted from the data described in the Uterworths). As is clear from FIGS. 4 and 5, since the diffusion coefficients of Cu and Ag in various medium metals vary depending on the combination of the conductor metal for wiring and the medium metal,
A medium metal that is chemically stable at high temperatures and that is suitable for each wiring material can be selected and applied for coating.

In order to form the barrier layer for preventing the diffusion, for example, a method using a liquid phase, a gas phase, a molten metal, a powder or the like by a conventional method is used, that is, a barrier is formed on the surface of the conductor material. Layered materials can be contacted, deposited, laminated, and mounted. An example of a typical coating method, that is, a method of contacting, depositing, laminating, and placing materials is shown in Table 1. As a matter of course, methods other than those shown in Table 1 may be used.

[Table 1]

According to the present invention having the above-described structure, the elements which are stable in high temperature from the outside of the conductor material, which is the wiring material forming the electric circuit, and which are inside the conductor material, are formed. By coating a metal with a slow diffusion of atoms, high-temperature processes during the manufacturing of the member and Joule heat generation during circuit operation prevent high-temperature chemical reactions on the surface and migration due to thermal diffusion of atoms even when exposed to a high-temperature environment. Since it can be prevented or reduced, deterioration of the wiring material with time can be suppressed or prevented.

Next, an embodiment of the coating structure on the surface of a conductor material constituting an electric circuit according to the present invention will be described with reference to FIG.

FIG. 1 shows a sectional view of a coating structure for an electric circuit according to a first embodiment of the present invention. A wiring having a two-layer structure in which a Cu layer 2 and an Ag layer 1 are embedded on an insulating or semiconductor base material 4, that is, a conductor layer cross section is shown. The outside of the conductor material of this electric circuit wiring is added to NiSO ₄ -6H ₂ O with a complexing agent and a reducing agent, and the mixture is brought into contact with a mixed solution to perform electroless plating. B alloy 3 is deposited. As is clear from the data in FIGS.
Ag and Cu have extremely small diffusion coefficients in Ni. Further, the Ni-B alloy originally has the property of being chemically stable even at high temperatures. Therefore, the Ni-B alloy is A, which is a conductor material.
For the g layer and the Cu layer, it plays a role as a barrier layer that blocks and reduces the high temperature chemical reaction on the surface and the movement of atoms due to thermal diffusion.

FIG. 2 is a cross-sectional view of a covering structure for an electric circuit according to a second embodiment of the present invention, which is a wiring material embedded in a base material near the surface of the base material, in which the center of the wiring is recessed from the surface to form a groove. Shows what is in shape. Similar to the embodiment shown in FIG. 1, the wiring is composed of a Cu layer 2 and an Ag layer 1 on an insulating or semiconductor substrate 4.
It has a two-layer structure with embedded.

The wiring surface is made of Ni as in the first embodiment.
A complexing agent and a reducing agent are added to SO ₄ -6H ₂ O, and the mixture is brought into contact with a mixed solution to perform electroless plating, so that Ni-B is deposited on the Cu layer 2 and the Ag layer 1 as shown in FIG. Alloy 3
Are deposited. Regarding the method for producing a conductor material having a two-layer structure of an Ag layer and a Cu layer, see Japanese Patent Application No. 4-917.
Details are disclosed in the '78 patent application.

[0019]

As described above, according to the present invention,
The conductor surface of the electric circuit wiring material is mainly coated on the surface of the conductor material on the side opposite to the base with a metal that is stable at high temperatures and does not easily cause thermal diffusion inside the conductor material. React with the surrounding environment, and the constituent elements thereof can be suppressed or prevented from moving by thermal diffusion. As a result, it is possible to suppress or prevent the deterioration of the electric circuit, the parts using the electric circuit, the process of forming the product, or the wiring material during the operation after the product is completed, that is, the electric circuit, with time.

[Brief description of drawings]

FIG. 1 is a sectional view of a coating structure for an electric circuit according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a covering structure for an electric circuit according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing the relationship between the temperature and the electrical resistivity of a metal material having a relatively low electrical resistance.

FIG. 4 is an explanatory diagram showing a relationship between a diffusion coefficient of Cu, which is one of metal materials having a relatively small electric resistance, in a medium metal and an inverse number of an absolute temperature.

FIG. 5 is an explanatory diagram showing the relationship between the diffusion coefficient of Ag, which is another metal material having a relatively small electric resistance, in the medium metal and the reciprocal of the absolute temperature.

[Explanation of symbols]

1 Ag layer 2 Cu layer 3 Ni-B alloy coating layer 4 base materials

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroaki Inoue             11-1 Haneda Asahi-cho, Ota-ku, Tokyo Co., Ltd.             Inside the EBARA CORPORATION F term (reference) 4K022 AA05 AA42 BA04 BA14 BA32                       DA03 DB01                 5F033 HH07 HH11 HH14 MM01 MM05                       MM08 MM12 MM13 PP28 RR04                       XX03 XX05 XX06 XX10 XX18                       XX19 XX20 XX28

Claims (3)

[Claims] 1. A wiring method for a semiconductor device for forming a fine electric circuit wiring, wherein an electric circuit is formed by embedding a conductor material containing at least a Cu layer in a base material, and thermal diffusion transfer of the conductor material is performed. A method for forming a wiring of a semiconductor device, which comprises covering only an open surface of the electric circuit with a preventing material. 2. The wiring forming method for a semiconductor device according to claim 1, wherein the surface of the electric circuit is coated by electroless plating. 3. The method for forming a wiring of a semiconductor element according to claim 2, wherein a material containing Ni is used as a material for preventing thermal diffusion movement of the conductor material.