JPH06275621A - Wiring structure of semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To provide the wiring structure of a semiconductor integrated circuit wherein the diffusion of Cu to an insulating film or a substrate is prevented, when Cu wiring is used. CONSTITUTION:A BPSG insulating film 12 of 5000Angstrom in thickness is formed on the surface of an Si substrate 10, and a Ta50W50 film 14 is grown to be 600Angstrom thick on the whole surface of the insulating film 12. A Cu film 16 is grown to be 5000Angstrom thick on the surface of the Ta50W50 film 14. Abase film 14a and a wiring 16a are formed by pattern the Ta50W50 film 14 and the Cu film 16. By a CVD method, W is selectively grown to be 400Angstrom thick only on the outer surface of the Cu wiring 16a, and a W coating film 18 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a semiconductor integrated circuit (LS).
The wiring structure of I).

[0002]

2. Description of the Related Art At present, as a wiring material of a semiconductor integrated circuit, Al or Al obtained by adding Si or Cu to Al is used.
Alloys are used. Since Al is mainly used for such wiring, the allowable current density of the wiring is limited to (2 to 3) × 10 ⁵ A / cm ² or less.
The reason for this is that if a current exceeding the permissible current density is applied to this wiring, the wiring will be broken due to electromigration. In order to pass a current with a high current density, 0.1 to 5% Cu is contained in Al as a wiring material.
An Al-Cu alloy added with may be used. 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.

On the other hand, in order to improve the electromigration resistance of the wiring, it has been proposed to replace the Al wiring or the Al alloy wiring with Cu wiring which is substantially made of Cu and has high electromigration resistance.

[0004]

However, Cu is more likely to diffuse into Si (substrate) or SiO ₂ (insulating film) than Al, which causes a problem that the normal operation of the transistor is hindered. In order to solve this problem, a technique of preventing Cu diffusion by a metallic barrier film has been proposed (for example, barrier material = TiN: 1992 Spring Applied Physics Society 30p-ZH-6, JP-A-53-53). 11608
No. 9, JP-A-63-73645, JP-A-63.
No. 156341, JP-A-1-204449), it is not possible to completely prevent Cu from diffusing into Si or SiO ₂ through the metallic barrier film, and a sufficient effect is not obtained. .

In view of the above circumstances, it is an object of the present invention to provide a wiring structure for a semiconductor integrated circuit which prevents diffusion of Cu into an insulating film or a substrate when Cu wiring is used.

[0006]

The present inventor has conducted various experiments and researches in order to achieve the above-mentioned object. As a result, (1) a Cu-W alloy film is coated on the upper or side surface of a Cu wiring. Alternatively, the diffusion of Cu into the insulating film or the substrate can be prevented by using the Ta-W alloy film as the base of the Cu wiring. (2) Mo, Nb, P in Ta, W, or Ta-W alloy.
By using an alloy film to which an element such as d or Pb is added as a base of the Cu wiring or covering the upper or side surface of the Cu wiring,
The inventors have found that Cu can be prevented from diffusing into the insulating film and the substrate, and have completed the present invention.

Specifically, the wiring structure of the first semiconductor integrated circuit according to the present invention is characterized in that the Ta-W alloy film is used as an underlayer or coating of Cu wiring. The wiring structure of the second semiconductor integrated circuit according to the present invention is Mo and / or
Alternatively, Ta obtained by adding Nb to Ta-W alloy in an amount of 15 atomic% or less
It is characterized in that the --W-based alloy film is used as a base of Cu wiring or as a coating on the upper or side surfaces.

Further, the third semiconductor integrated circuit wiring structure of the present invention comprises a Ta-based alloy film in which one or more metals selected from Mo, Nb and Ti are added to Ta in an amount of 15 atomic% or less. It is characterized in that the base of the Cu wiring or the coating of the upper portion or the side surface portion is formed. Furthermore, the wiring structure of the fourth semiconductor integrated circuit according to the present invention is Mo, N
A W-based alloy film in which one or more metals selected from b, Pd, and Pb are added to W in an amount of 15 atomic% or less is used as a base of Cu wiring or a coating on the upper or side surface of the Cu wiring. Is.

[0009]

First, the operation of the wiring structure of the first semiconductor integrated circuit according to the present invention will be described. Since W and Ta have a very small reaction with Cu during heat treatment and Cu is difficult to form a solid solution, it is possible to suppress an increase in the specific resistance of Cu wiring. Furthermore, the self-diffusion coefficient of W and Ta is Ti, Cr, Mo, N
It is smaller than the self-diffusion coefficient of the transition metals that have been studied up to now, such as b, and is superior to these transition metals in the effect of preventing diffusion of Cu. By the way, the Ta-W binary alloy forms a solid solution alloy in all compositions. When a thin film is formed from such a binary alloy, the thin film has finer crystal grains and a higher film density than a thin film formed from Ta or W alone. Moreover, since many compounds are formed in a normal binary alloy, this compound segregates in the thin film, and the segregated compound becomes a defect of the barrier layer and Cu easily diffuses. In the case of an alloy, since such a compound is not formed, Cu cannot easily diffuse and the problem of deterioration of the barrier effect does not occur. Therefore, in the wiring structure of the first semiconductor integrated circuit of the present invention,
The effect of preventing diffusion of Cu is dramatically improved.

Next, the operation of the wiring structure of the second to fourth semiconductor integrated circuits of the present invention will be described. Mo, Nb
Etc. are completely dissolved in W, Ta, and W-Ta alloys, so that no compound is formed. Therefore, the segregation of the compound does not occur in the thin film formed of W, Ta, or W-Ta alloy, while the crystal grains of the thin film formed of Ta, W, or W-Ta alloy are such as Mo or Nb. It is considered that the addition makes the particles finer, increases the film density, and improves the effect of preventing diffusion of Cu. In addition, it is considered that the increase in the grain boundary diffusion length as the crystal grains become finer is also a factor for improving the barrier property. However, the self-diffusion coefficient of added Mo, Nb, etc. is smaller than that of W, Ta, and the addition of a large amount of Mo, Nb, etc. causes deterioration of the diffusion prevention effect.
The addition amount of Mo, Nb, etc. is limited to 15 atomic% or less.
As explained above, M is added to Ta, W, or W-Ta alloy.
By adding o, Nb, etc., the effect of preventing diffusion of Cu is improved.

[0011]

EXAMPLES Examples of the present invention will be described below. First, Table 1 shows the experimental results comparing the barrier properties against Cu of the Ta-W alloy film, the Ta film, and the W film. In this experiment, Cu / M / Si (M is Ta, Ta _99.9 W
_0.1 , Ta ₅₀ W ₅₀ , Ta _0.1 W _99.9 , or W is represented. )
The laminated film is subjected to diffusion heat treatment, and the Cu concentration on the Si surface is measured by SIMS.
(Secondary-Ion Mass Spec
Roscopy secondary ion mass spectrometry). These multilayer films are Ta film on Si substrate,
A W film or a Ta-W alloy film was deposited by RF magnetron sputtering to 600 L, respectively, and Cu was further deposited on the Ta film, W film or Ta-W alloy film by RF magnetron sputtering to form 5000 L. Then, this multilayer film was heat-treated at 600 ° C. for 1 h in an H ₂ gas atmosphere, and the Cu concentration on the surface of the Si substrate was measured.

[0012]

[Table 1] ──────────────────────────────────── Barrier material Cu concentration (relative value) Comparative example 1 Ta 3.39x10 ⁴ Example 1 Ta _99.9 W _0.1 1.05x10 ⁴ Example 2 Ta ₅₀ W ₅₀ 5.44x10 ³ Example 3 Ta _0.1 W _99.9 9.01x10 ³ Comparative Example 2 W 2.19x10 ⁴ ─── ───────────────────────────────── As is clear from Table 1, compared with Ta and W alone, Ta-
It can be seen that the W alloy has an excellent barrier effect.

Next, with reference to FIG. 1, an example of the wiring structure of the present invention and a method of manufacturing the same will be described. FIG. 1 is a sectional view showing an example of a method for manufacturing a wiring structure according to the present invention. Figure 1
As shown in (a), 500 is formed on the surface of the Si substrate 10.
0Å BPSG (Borophosphosilica
te glass) insulating film 12 is formed, and Ta ₅₀ W ₅₀ film 14 is formed on the entire surface of this insulating film 12 at a total pressure of 2 mTorr.
In an Ar atmosphere of r, 600 Å is grown at a film forming rate of 10 Å / s by RF magnetron sputtering. A Cu film 16 is formed on the surface of the Ta ₅₀ W ₅₀ film 14 at a total pressure of 2 mTo.
Growing 5000 Å at a film forming rate of 60 Å / s by RF magnetron sputtering in an Ar atmosphere of rr.
Then, as shown in FIG. 1 (b), Ta ₅₀ W ₅₀ film 1
4 and the Cu film 16 are patterned to form the base film 14a and the Cu film.
The wiring 16a was formed. After that, as shown in FIG. 1C, W is selectively grown by 400 Å only on the outer surfaces of the base film 14a and the Cu wiring 16a by the CVD method.
The W coating film 18 is formed. The W coating film 18 has a sample temperature of 200 to 400 ° C. and supplies a mixed gas of WF ₆ gas and H ₂ gas to the film forming chamber, and the gas pressure of the mixed gas is 1 To.
It is formed below rr. According to this film forming method, the interface reaction becomes rate-determining, and W can be selectively grown only on the outer surfaces of the Cu wiring 16a and the base film 14a. Here, in order to make this wiring structure multi-layered, an insulating film such as SiO ₂ is provided on the W coating film 18, and the above wiring structure is formed on this insulating film by the same method. Good.

Next, referring to FIG. 2, W, Ta ₅₀ W ₅₀ alloy and M
The experimental result which compared the barrier property with respect to Cu of the film formed by adding various ratios of o and Nb is shown. This experiment
Cu / M / Si (M = W _100-x Mo _x , W _100-x Nb
_x , W _{100- x} (Mo ₅₀ Nb ₅₀ ) _x , (Ta ₅₀ W ₅₀ )
_100-x Mo _x , (Ta ₅₀ W ₅₀ ) _100-x Nb _x , (Ta _{50
W 50) 100-x (Mo} 50 Nb 50) x) laminated film to diffusion heat treatment, the Cu concentration of the Si surface was carried out by measuring by SIMS. These multilayer films were formed by depositing a barrier material alloy film on the Si substrate by RF magnetron sputtering by 600 Å and further by depositing Cu by RF magnetron sputtering on 5000 Å. Then, this multilayer film was heat-treated at 600 ° C. for 1 h in an H ₂ atmosphere, and the Cu concentration on the Si surface was measured.

As is clear from this figure, W, Ta-W
The effect of adding Nb and Mo to the alloy is recognized. Also, N
When b and Mo were added in an amount of 15 atomic% or more, the Cu concentration increased again, and deterioration of the barrier property against Cu was observed. Also, Mo, N for Ta-based alloys containing one or more metals selected from Mo, Nb, and Ti in an amount of 15 atomic% or less.
A similar tendency is observed in the effect of adding b and Ti and the effect of adding Pd and Pb to W.

Next, referring to FIG. 3, the wiring structure of the present invention.
Another example of the body and the manufacturing method thereof will be described. FIG. 3 shows the present invention.
FIG. 6 is a cross-sectional view showing another example of the method for manufacturing the wiring structure by
It As shown in FIG. 3A, the surface of the Si substrate 20.
5,000 Å BPS insulation film 22 is formed on the
The entire surface of the film 22 serves as the base of the Cu film (Ta₅₀W ₅₀)
₉₅(Mo₅₀Nb₅₀)_Five Membrane 24 is A with a total pressure of 2 mTorr.
RF magnetron sputtering in an atmosphere
Grow at 600Å at a film forming rate of 10Å / s. This (Ta
₅₀W₅₀)₉₅(Mo₅₀Nb₅₀)_Five Cu film on the surface of the film 24
26 RF magnet in Ar atmosphere with total pressure of 2 mTorr
50 at a deposition rate of 60Å / s by long sputtering
00Å Grow. Then, as shown in FIG.
To (Ta₅₀W₅₀)₉₅(Mo₅₀Nb₅₀)_Five Membrane 24 and Cu
The film 26 is patterned to form the base film 24a and the Cu wiring 26.
a is formed. After that, as shown in Fig. 3 (c).
As described above, W is formed by the CVD method on the base film 24a and the Cu wiring 2.
The W coating film is selectively grown only on the outer surface of 6a by 400Å.
28 is formed. The W coating film 28 has a sample temperature of 20.
0 ~ 400 ℃ and WF₆ Gas and H₂ Gas mixture
The gas pressure of this mixed gas is 1 Torr or less.
To form. According to this film forming method, the interface reaction is controlled.
The speed becomes W and the W of the outer surface of the Cu wiring 26a and the base film 24a is changed.
It can be selectively grown. Where this wiring structure
To make the structure multi-layered, SiO is formed on the W coating film 28.₂ 
An insulating film such as the above is provided, and the wiring structure described above is provided on this insulating film.
The body may be made similarly.

[0017]

As described above, the wiring structure of the semiconductor integrated circuit according to the present invention is a Ta-W alloy having a good barrier property,
Since a Ta-based alloy, a W-based alloy, or a Ta-W-based alloy is used as the underlayer or coating of the Cu wiring, it is a wiring structure in which Cu diffusion is sufficiently suppressed. Therefore, according to the present invention,
It is possible to realize a Cu wiring having a specific resistance smaller than that of Al and excellent in electromigration resistance and having a great industrial significance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a method for manufacturing a wiring structure of the present invention.

FIG. 2 is a graph showing experimental results comparing barrier properties against Cu of films formed by adding Mo and Nb to W and Ta ₅₀ W ₅₀ alloys at various ratios.

FIG. 3 is a cross-sectional view showing another example of the method for manufacturing the wiring structure of the present invention.

[Explanation of symbols]

10, 20 Si substrate 12, 22 Insulating film 14 Ta ₅₀ W ₅₀ film 14a, 24a Underlayer film 16, 26 Cu film 16a, 26a Cu wiring 18, 28 W coating film 24 (Ta ₅₀ W ₅₀ ) ₉₅ (Mo ₅₀ Nb) ₅₀ ) ₅ membranes

Claims (4)

[Claims] 1. A wiring structure for a semiconductor integrated circuit, wherein a Ta—W alloy film is used as an underlayer or a coating of Cu wiring. 2. A Ta-W alloy containing Mo and / or Nb 1
A wiring structure for a semiconductor integrated circuit, comprising a Ta-W alloy film added at 5 atomic% or less as an underlayer or coating of Cu wiring. 3. A semiconductor integrated device characterized in that a Ta-based alloy film, in which one or more metals selected from Mo, Nb, and Ti are added to Ta in an amount of 15 atomic% or less, is used as a base or coating of Cu wiring. Circuit wiring structure. 4. A W-based alloy film in which one or more metals selected from Mo, Nb, Pd, and Pb are added to W in an amount of 15 atomic% or less is used as a base or coating of Cu wiring. A wiring structure for a semiconductor integrated circuit.