JP2004128109A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device capable of preventing corrosion of Cu wiring that follows galvanic corrosion while keeping the specific resistance of a barrier metal to a low value. <P>SOLUTION: Suppressing galvanic corrosion is thought to be possible if the atomic ratio N/W in WN is 0.7 or higher, as ionization of WN is hard to progress. The specific ratio tends to rise as the atomic ratio N/W becomes higher. The barrier metal film is preferred to be lower in specific ratio for functioning. So, a Wn film is preferred to be 2.0 or below in N/W which is the atomic ratio between N and W. A barrier metal film having such composition as the atomic ratio N/W between N and W is 0.7-2.0 is practical when considering corrosion resistance and specific resistance value. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor device using copper wiring and a method for manufacturing the same, and more particularly to a barrier metal film for copper wiring.
[0002]
[Prior art]
With the recent high integration of LSIs, the importance of wiring process technology is increasing. This is because the increase in wiring delay time has become more remarkable than the reduction in gate delay time due to miniaturization.
In order to suppress the wiring delay, it is necessary to reduce the capacitance between the wirings and to reduce the wiring resistance. Further, since the current density increases with miniaturization, it is necessary to improve electromigration (EM).
In order to improve these problems, it is considered important to introduce a multilayer wiring technology using Cu wiring and a low dielectric constant interlayer film.
[0003]
The Cu wiring has an electric resistance of about two-thirds that of the conventional Al alloy wiring, and is a material capable of realizing a reduction in the wiring resistance. It is a material expected to have higher EM resistance than Al alloy wiring.
Therefore, introduction to actual devices has already begun. As a method for forming a Cu wiring, a damascene method is generally used. A method for forming a Cu wiring using the damascene method will be described below.
First, a wiring trench (Trench) pattern is formed in the interlayer insulating film by using photolithography and etching, and a film (barrier metal film) for preventing diffusion of Cu into the insulating film is formed. Is embedded in a wiring groove, and thereafter, an excess Cu film on the insulating film is removed by using CMP (Chemical Mechanical Polishing) or the like.
[0004]
As the above barrier metal film material, Ta and TaN formed by a sputtering method are generally used.
However, as device miniaturization and integration progress, it becomes more difficult to form a barrier metal film with good coverage inside the connection hole (Via) between wirings. In the next generation device, CVD (chemical vapor) is used. It is considered that a barrier metal film formation by a deposition method is necessary, and research and development have been conducted.
Above all, a WN film using a CVD method is considered to be one of the promising candidates as a next-generation barrier metal film (for example, see Non-Patent Document 1).
[0005]
[Non-patent document 1]
M. Harada, E .; Mizuno and N.M. Gonohe, on Advanced Metallization Conference 2000, pp. 397-402.
[0006]
[Problems to be solved by the invention]
However, it has been reported that when W, WN, Ti, TiN, or the like is used as a barrier metal material, galvanic corrosion occurs during the CMP process.
The galvanic corrosion is a phenomenon in which ionization of the barrier metal progresses due to a local current generated from a potential difference in the liquid between Cu and the barrier metal.
FIG. 4 is an explanatory view showing a galvanic corrosion phenomenon of a barrier metal occurring during the CMP process.
As shown in the drawing, a Cu wiring 14 is formed in a wiring groove provided in the silicon oxide film 10 via a barrier metal film 12 and is arranged in a slurry 16 for CMP processing. WN ionization disappears in the portion exposed to the surface.
[0007]
In particular, it has been reported that corrosion of a substance such as W, WN, Ti, and TiN which has a large difference in potential with respect to Cu (a potential lower than that of Cu) correlates with the value.
As shown in FIG. 5, a phenomenon occurs in which the corrosion 14A of the Cu wiring 14 is caused due to the portion where the WN film has disappeared due to the galvanic corrosion.
On the other hand, the barrier metal film preferably has a low specific resistance value in terms of its function.
[0008]
Accordingly, an object of the present invention is to provide a semiconductor element and a method for manufacturing the same, which can prevent the corrosion of the Cu wiring due to the galvanic corrosion of the barrier metal while maintaining the specific resistance of the barrier metal at a low value. It is in.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has a wiring groove pattern formed in an insulating film, and a Cu wiring provided in the wiring groove pattern via a barrier metal film, wherein the barrier metal film is made of a WN film. The WN film has a composition in which the atomic ratio N / W of N and W is 0.7 or more and 2.0 or less.
[0010]
Also, the present invention provides a step of forming a wiring groove pattern in an insulating film, a step of forming a barrier metal film inside the wiring groove, and a step of forming a Cu wiring in the wiring groove via a barrier metal film. Wherein the barrier metal film is formed of a WN film, and the WN film is formed with a composition in which the atomic ratio N / W of N and W is 0.7 or more and 2.0 or less. I do.
[0011]
In the semiconductor device and the method of manufacturing the same according to the present invention, a WN film is used as a barrier metal film of a Cu wiring, and the WN film has a composition having an atomic ratio N / W of N and W of 0.7 or more and 2.0 or less. Therefore, it is possible to prevent corrosion of the Cu wiring due to galvanic corrosion of the barrier metal while maintaining the specific resistance of the barrier metal at a low value.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a semiconductor device and a method of manufacturing the same according to the present invention will be described.
In the present embodiment, in order to prevent galvanic corrosion in a barrier metal film when Cu wiring is used, a WN film is used as a barrier metal film, and the composition of the WN film is further defined.
[0013]
First, in order to evaluate the galvanic corrosion described above, a Cu material and a barrier metal material were immersed in a slurry, and a current value flowing between Cu and the barrier metal was measured.
FIG. 2 is an explanatory view showing the results of the experiment. The Cu electrode 22 and the barrier metal (WN) electrode 24 are impregnated in the slurry tank 20, and the current value is measured by the ammeter 26.
On the WN electrode 24 side, ionization of W proceeds, and the WN film disappears. At that time, the smaller the current value flowing between Cu and the barrier metal, the smaller the potential difference between Cu and the barrier metal, indicating that galvanic corrosion is less likely to occur.
[0014]
FIG. 3 is an explanatory diagram showing the WN composition-dependent characteristics of the current value between the Cu and the barrier metal (WN). The vertical axis indicates the current, and the horizontal axis indicates the atomic ratio N / W.
As shown in the figure, a result is obtained in which the current value decreases as the ratio of N increases.
Further, the current value in the case where the barrier metal film has been corroded by actually performing the CMP process and the current value in the case where it has not been corroded are also indicated by broken lines α in the figure.
From these results, it is considered that when the atomic ratio N / W in WN is 0.7 or more, the ionization of WN becomes difficult to progress, so that galvanic corrosion can be suppressed (however, the corrosion current value is used). The absolute value of the current value does not need to be defined because it varies depending on the slurry.)
On the other hand, the specific resistance tends to increase as the atomic ratio N / W increases, and the barrier metal film preferably has a low specific resistance in terms of its function. In this regard, the WN film is composed of N and W. Is preferably 2.0 or less.
In consideration of these trade-offs, it is desirable that the barrier metal film has a composition in which the atomic ratio N / W of N and W is 0.7 or more and 2.0 or less.
[0015]
Therefore, in this embodiment, by forming the barrier metal film from a WN film having a composition in which the atomic ratio N / W of N and W is 0.7 or more and 2.0 or less, the specific resistance of the barrier metal is reduced to a low value. It is intended to provide a semiconductor element in which corrosion of Cu wiring is effectively prevented while maintaining the above-mentioned value.
The Cu wiring may include a plug portion of a via plug or a contact plug in some cases, and can be applied to, for example, a manufacturing method by a dual damascene method or a single damascene method.
[0016]
Next, a specific example of the method for manufacturing a semiconductor device according to the present embodiment will be described.
FIG. 1 is a sectional view illustrating the method for manufacturing a semiconductor device according to the present embodiment.
[Step 1]
First, in FIG. 1A, an interlayer insulating film 2 is formed on a semiconductor element substrate 1. Thereafter, a wiring groove pattern 2A having a trench structure is formed by a photolithography and etching process.
Although not shown, a dual damascene structure (a structure including a wiring groove and a hole for a plug) is also included here without depending on the wiring groove pattern of the trench structure, and the pattern shape is not particularly limited.
[0017]
[Step 2]
Next, as shown in FIG. 1B, a WN film 3 as a barrier metal film is formed using, for example, a CVD method.
For example, the film forming conditions are as follows.
(1) Process pressure: 40 Pa
(2) Process gas: WF ₆ = 3.3 sccm, SiH ₄ = 116 sccm, NH ₃ = 7 sccm, Ar = 80 sccm
(3) Substrate heating temperature: 380 ° C
(4) Film thickness: 100 °
Under the above film forming conditions, a WN film having an atomic ratio N / W of N / W of 0.7 was obtained.
[0018]
Alternatively, a WN film 3 as a barrier metal film is formed using, for example, a PVD method.
For example, the film forming conditions are as follows.
(1) Target: W
(2) Power: 4kW
(3) Process gas: Ar = 6 sccm, N2 = 25 sccm
(4) Substrate heating temperature: 150 ° C
(5) Film thickness: 100 °
Under the above film forming conditions, a WN film having an atomic ratio N / W of N / W of 1.06 was obtained.
However, the method of forming the barrier metal does not need to be limited to the above conditions, nor does it need to be limited to the CVD method and the PVD method.
Thereafter, the Cu film 4 is buried in the trench groove by using, for example, a method of forming a Cu film by electrolytic plating after forming a Cu seed layer.
[0019]
[Step 3]
Next, as shown in FIG. 1C, the Cu film 4 and the WN film 3 on the interlayer insulating film 2 are removed by, for example, a CMP (chemical mechanical polishing) method or the like to form a Cu wiring.
[0020]
In the present embodiment as described above, it is possible to suppress galvanic corrosion during the CMP process while maintaining the specific resistance of the barrier metal film at a low value. It is considered that since a wiring can be formed, a highly reliable wiring with improved resistance to EM and stress migration (SM) can be realized.
[0021]
It is known that the specific resistance of the film tends to increase as the N composition in the WN film increases, but the atomic ratio N / W = 1.06 shown by the point β in FIG. At this point, a specific resistance value of about 350 μΩcm was obtained, and a low specific resistance value was obtained.
Therefore, by considering the atomic ratio N / W between N and W within the range of 0.7 or more and 2.0 or less while considering the specific resistance value and the corrosion resistance as described above, A practicable barrier metal film having little influence on the total Cu wiring resistance is provided.
[0022]
The structure and the manufacturing method of the semiconductor element according to the present embodiment as described above are widely applied to various semiconductor elements such as an IC element using a Cu wiring (and a Cu plug) and a solid-state imaging element and the manufacturing method thereof. What you get.
[0023]
【The invention's effect】
As described above, according to the semiconductor device and the method of manufacturing the same of the present invention, a WN film is used as a barrier metal film of a Cu wiring, and the composition of the WN film is set such that the atomic ratio N / W between N and W is 0.1%. Since it is 7 or more and 2.0 or less, it is possible to prevent the corrosion of the Cu wiring due to the galvanic corrosion of the barrier metal while maintaining the specific resistance of the barrier metal at a low value, and to improve the quality and reliability of the semiconductor element. There is an effect that can contribute to improvement.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention.
FIG. 2 shows a case where a Cu material and a barrier metal material are immersed in a slurry and a current value flowing between Cu and the barrier metal is measured in order to evaluate galvanic corrosion in the embodiment of the present invention. It is an explanatory view showing an experimental result.
FIG. 3 is an explanatory diagram showing a WN composition dependent characteristic of a current value between a Cu and a barrier metal (WN) used in the embodiment of the present invention.
FIG. 4 is an explanatory view showing a galvanic corrosion phenomenon of a barrier metal occurring during a CMP process in a conventional Cu wiring forming step.
FIG. 5 is an enlarged sectional view showing a corrosion phenomenon of the Cu wiring 14 due to galvanic corrosion.
[Explanation of symbols]
1 ... Semiconductor element substrate, 2 ... Interlayer insulating film, 3 ... WN film, 4 ... Cu film.

Claims (7)

A wiring groove pattern formed in the insulating film, and a Cu wiring provided in the wiring groove pattern via a barrier metal film;
The barrier metal film is made of a WN film, and the WN film has a composition in which an atomic ratio N / W between N and W is 0.7 or more and 2.0 or less;
A semiconductor element characterized by the above-mentioned. 2. The semiconductor device according to claim 1, wherein the wiring groove pattern includes a hole for a plug, and the Cu wiring includes a plug portion. Forming a wiring groove pattern in the insulating film;
Forming a barrier metal film inside the wiring groove;
Forming a Cu wiring in the wiring groove via a barrier metal film,
The barrier metal film is formed of a WN film, and the WN film is formed with an atomic ratio N / W of N and W of 0.7 or more and 2.0 or less;
A method for manufacturing a semiconductor device, comprising: 4. The method according to claim 3, wherein a hole for a plug is formed with the wiring groove pattern, and a plug portion is formed with the Cu wiring. 4. The method according to claim 3, wherein the Cu wiring is formed by forming a Cu seed layer in the wiring groove via a barrier metal film, and then forming a Cu film by electrolytic plating. 6. The method according to claim 5, wherein after the Cu wiring is formed by the electrolytic plating, the Cu wiring and the barrier metal film are planarized by a CMP method. 4. The method according to claim 3, wherein the barrier metal film is formed by a CVD method or a PVD method.

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