JPH06275620A - Semiconductor integrated circuit wiring structure - Google Patents

Abstract

(57) [Abstract] [Purpose] In a semiconductor integrated circuit, Cu wiring is used and C
A wiring structure is obtained in which the diffusion of u into Si or SiO ₂ is prevented. [Structure] An insulating film 2 of BPSG is provided on the surface of a Si substrate 1, an amorphous layer 3 of Nb-N is grown thereon by RF magnetron sputtering, and C is formed on the surface thereof.
The Cu film 5 is formed by growing the u film 4 by RF magnetron sputtering.

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 (LSI) having Cu wiring.

[0002]

2. Description of the Related Art At present, a wiring material for semiconductor integrated circuits is made of Al or an alloy of Al and Si or Cu. Since Al is used as the main material in such a wiring, the allowable current density that can be flown is limited to (2 to 3) × 10 ⁵ A / cm ² or less. This is because when a current exceeding this is applied, the wiring is broken due to electromigration. In order to flow more current, an alloy containing 2 to 5% Cu in Al may be used as a material for the wiring. However, although the allowable current density is improved, the specific resistance of the wiring is increased, which causes a problem of reliability deterioration due to heat generation. Therefore, it has been proposed to use Cu substantially as a wiring material having a low specific resistance in place of the Al wiring.

[0003]

However, Cu is Al
There is a problem that it is more likely to diffuse into Si or SiO _{2 as} compared with the above, and thus the normal operation of the transistor is hindered. Therefore, it has been proposed to use a crystalline barrier material as the Cu diffusion prevention layer. For example, 1992 Spring Society of Applied Physics 30p-ZN-6, JP-A-53-1160.
89, JP-A-63-73645 and JP-A-6.
There are JP-A-3-156341, JP-A-1-20449, and the like. However, in this case, the diffusion from the crystal grain boundaries occurs and the sufficient effect is not obtained.

Therefore, there is an urgent need to develop a wiring structure of a semiconductor integrated circuit capable of preventing the diffusion of Cu wiring. An object of the present invention is to provide a semiconductor integrated circuit wiring structure that solves this problem.

[0005]

In order to solve the above problems, the present invention uses W, Ta, Nb, Ti and their nitrides as a wiring material, substantially using Cu instead of Al wiring. The present invention proposes a semiconductor integrated circuit wiring structure in which an amorphous barrier layer of one kind of material selected from the above is used as a base of Cu wiring or provided as a coating on the upper portion or side surface portion of Cu wiring.

[0006]

According to the present invention, since Cu is used as the wiring material, the specific resistance is lower than that of Al and the electromigration resistance is good. Moreover, since the Cu wiring is covered with the amorphous barrier layer, it is possible to suppress the grain boundary diffusion of Cu. Materials that can be effectively used as an amorphous barrier include W and T, which have a small Cu solid solution and whose Cu resistivity does not increase even by heat treatment.
Mention may be made of a, Nb, Ti and nitrogen compounds thereof. To form an amorphous layer of these materials, an amorphous layer is directly formed by a sputtering method, an ion plating method, or the like, or a crystalline layer is formed and then made amorphous by a method such as ion irradiation or ion implantation.

By providing the amorphous barrier layer thus formed, the Cu diffusion preventing effect is enhanced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing a manufacturing process of a Cu wiring structure according to the present invention. As shown in FIG. 1A, Si
5000 Å BPSG (Boro-Ph
an insulating film 2 of ospho-Silicate Glass), and an amorphous layer 3 of Nb-N is formed on the surface of the insulating film 2 as an underlayer of Cu by RF magnetron sputtering at a total pressure of 2 mTorr in an Ar atmosphere containing 45% nitrogen. Grow at 600Å at a film speed of 10Å / s.
To form the amorphous layer 3, the substrate temperature is set to Nb-N.
An amorphous layer was obtained by cooling the substrate holder with liquid nitrogen to keep it below the crystallization temperature of. Here, it was confirmed by an X-ray diffraction method that the Nb-N layer had an amorphous structure. A Cu film 4 is grown on the surface thereof by RF magnetron sputtering in an Ar atmosphere of 2 mTorr at a film forming rate of 6000 Å / min and 5000 Å. Next, as shown in FIG. 1B, this is patterned to form Cu wiring 5. Next, as shown in FIG.
Cu wiring 5 by reactive sputtering as well as the base
The periphery of is covered with an amorphous Nb-N layer 6 having a thickness of 500Å to form a Cu wiring 5. After that, unnecessary portions are etched to produce a Cu wiring structure 10 as shown in FIG. Further, when the present wiring structure is formed in multiple layers, an insulating film such as SiO ₂ may be provided on the amorphous Nb-N layer 6 and the wiring structures 3 to 5 may be similarly formed thereon.

Table 1 shows the barrier properties against Cu when various barrier materials are used, SIMS (Secondary).
-Ion Mass Spectroscopy secondary ion mass spectrometry). The sample was a thermal oxide film grown on a Si wafer for 5000 Å, various barrier materials were deposited on it by RF magnetron sputtering for 600 Å, and Cu was laminated for 5000 Å in H ₂ at 600 ° C for 1 h. Heat treatment (heating rate: 100 ° C / h) was performed, and SIMS
This is a comparison of the Cu concentration in the Si wafer by obtaining the Cu depth profile using.
As shown in this table, it is clearly shown that when the amorphous barrier material according to the present invention is used, the diffusion of Cu is remarkably prevented as compared with the crystalline metal film and the nitride film which have been proposed so far. ing. It is considered that this is because the amorphous structure having no crystal grain boundary suppresses diffusion of Cu through the grain boundary.

[0010]

[Table 1]

[0011]

As described above, in the fine wiring structure of the semiconductor integrated circuit, Cu is diffused to the surroundings by forming a structure in which the Cu wiring is surrounded by the amorphous layer or a base body of the Cu wiring. Thus, a semiconductor wiring structure having a lower specific resistance than Al wiring and excellent electromigration could be realized. Therefore, Cu wiring can be used as the wiring of the semiconductor integrated circuit, and the industrial significance of the present technology is great.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a wiring structure of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Si substrate 2 Insulating film 3 Amorphous layer 4 Cu film 5 Cu wiring 6 Amorphous Nb-N layer 10 Cu wiring structure

Claims (1)

[Claims] 1. A semiconductor integrated circuit wiring structure, characterized in that an amorphous barrier layer of one material selected from W, Ta, Nb, Ti and nitrides thereof is provided as an underlayer or coating of Cu wiring. body.