JPH11219953A - Manufacture of copper wiring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve adhesion between a copper wiring and a diffusion barrier layer made of a metallic material having a high melting point or the like. SOLUTION: The method for manufacturing a copper wiring includes a step of forming a wiring material layer 2 of copper or copper alloy on an underlying film (e.g. titanium nitride film) 1 made of metallic material having columnar crystals and a high melting point or made of a metallic compound material having columnar crystals and a high melting point. In the method, prior to formation of a wiring material layer 2 after formation of the underlying film 1, sputter etching is carried out over the surface of the underlying film 1. The sputter etching process uses an argon gas or a gas containing at least a nitrogen gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing copper wiring, and more particularly, to a method for manufacturing copper wiring for improving the adhesion of copper wiring.

[0002]

2. Description of the Related Art Aluminum alloys have been widely used as wiring materials for LSIs. However, as the demand for miniaturization and high-speed LSI increases, it has become difficult to secure sufficient wiring reliability and low wiring resistance with aluminum alloy wiring. As a countermeasure, a copper wiring technique which has higher electromigration resistance and lower resistance than an aluminum alloy has recently received a great deal of attention and is being studied intensively for practical use.

As a technique for processing a copper wiring, a method using a so-called grooved wiring is expected to be promising, because generally, dry etching of copper is not easy. Groove wiring is a method in which a predetermined groove is formed in an interlayer insulating film such as silicon oxide in advance, a wiring material is buried in the groove, and then excess wiring material outside the groove is subjected to chemical mechanical polishing (hereinafter referred to as CMP). CM
P denotes a wiring formed by removing by chemical mechanical polishing or the like. As a method for embedding the wiring material, a method of performing reflow after forming a film by sputtering, an electrolytic plating method, and the like are being studied.

[0004] Copper has the property of diffusing into silicon oxide by heat treatment. In order to prevent such copper diffusion, as shown in FIG.
It is necessary to form some kind of diffusion barrier layer 131 at the interface between the copper wiring 121 and the silicon oxide film 111 in the substrate 2. As a material of the diffusion barrier layer 131,
Generally, a material selected from titanium nitride (TiN), tantalum (Ta), a tantalum alloy, tungsten (W), a tungsten alloy and the like is used. Titanium nitride is a material that has been used since the time of aluminum alloy wiring, and thus has the advantage of easy handling. However, it is said that a tantalum alloy or a tungsten alloy has a higher diffusion barrier property. The diffusion barrier material has not only a function of preventing diffusion into silicon oxide, but also a function of improving the embedding property when embedding copper by a reflow method.

[0005]

However, the poor adhesion between copper and the diffusion barrier layer causes a problem that the copper wiring 121 is peeled off from the diffusion barrier layer 131 as shown in FIG. For example, during the CMP step, a portion having insufficient adhesion is peeled off, causing a scratch called a scratch on the copper surface due to the peeled portion, or the copper wiring itself being peeled off due to a manufacturing process after forming the copper wiring. This will severely affect the performance and reliability of the wiring. On the other hand, for example, when the diffusion barrier layer is formed of a titanium film having excellent adhesion to copper, the diffusion barrier property against copper becomes insufficient, and titanium and copper react by a later heat treatment to form a copper wiring. A problem arises in that the resistance of the wire is increased.

[0006]

SUMMARY OF THE INVENTION The present invention is a method for manufacturing a copper wiring which has been made to solve the above-mentioned problems. That is, a method for manufacturing a copper wiring comprising a step of forming a wiring material layer made of copper or a copper alloy on a base film made of a high melting point metal material having columnar crystals or a high melting point metal compound material having columnar crystals, After forming the base film and before forming the wiring material layer, a sputter etching process is performed on the surface of the base film.

In the above-described method for manufacturing a copper wiring, a sputter etching process is performed on a surface of a base film made of a high melting point metal material having columnar crystals or a high melting point metal compound material having columnar crystals. Is preferentially etched in the vicinity of the crystal grain boundary, so that the surface of the base film has a rough surface having irregularities. This is because the vicinity of the grain boundary is easily etched. Thereafter, when copper is formed on the underlayer, the surface of the underlayer is roughened and the contact area with copper increases, so that the adhesion of copper is improved. Thus, the adhesion to copper can be improved while ensuring the diffusion barrier property to copper.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIG.
Will be described with reference to a schematic configuration diagram of FIG.

FIG. 1A schematically shows the crystal structure of a base film 1 made of titanium nitride formed by a normal DC magnetron sputtering method. In general, when a high-melting point metal material such as titanium nitride, which is a diffusion barrier material for copper, is formed by sputtering, the crystal structure has a fibrous columnar structure. The crystal grain size in this case is approximately 10 nm
It is about.

Next, the surface of the underlayer 1 is subjected to an argon sputter etching process. As a result, as shown in FIG. 1B, the vicinity of the crystal grain boundary 1G on the surface of the base film 1 is preferentially etched by the argon sputter etching process, and the surface of the base film 1 has a rough surface having irregularities. Occurs. The reason why the vicinity of the crystal grain boundary 1G of the base film 1 is easily etched is that the atomic bonds in the grain boundary portion in the titanium nitride crystal of the base film 1 are weak.

Thereafter, as shown in FIG. 1C, when a wiring material layer 2 made of copper or a copper alloy is formed on the base film 1, the surface of the base film 1 is not subjected to sputter etching. The adhesion to the wiring material layer 2 is improved as compared with the case where This is because the surface of the base film 1 is roughened by the sputter etching process, so that the contact area with the wiring material layer 2 is increased.

Next, an example in which the above embodiment is applied to forming a copper trench wiring will be described below with reference to a manufacturing process diagram of FIG.

As shown in FIG. 2A, an element (not shown) is formed on a substrate (not shown), and a lower wiring 1 is formed.
1 and the insulating film 12 are formed, and the surface of the insulating film 12 is flattened by a flattening process.
1 is exposed. And for example plasma CVD
(CVD is an abbreviation of Chemical Vapor Deposition and refers to chemical vapor deposition.) A silicon oxide (hereinafter referred to as PE-SiO ₂ ) is formed as an interlayer insulating film on the insulating film 12 by a method.
The film 13 is formed to a thickness of, for example, 800 nm. Further, a silicon nitride (hereinafter, referred to as PE-SiN) film 14 is formed to a thickness of, for example, 50 nm.

Next, a conventional lithography technique and reactive ion etching (hereinafter referred to as RIE)
For example, the lower wiring 1 is formed on the PE-SiN film 14 and the PE-SiO ₂ film 13 by an active ion etching technique.
A connection hole 15 leading to 1 is opened. The pore diameter was, for example, 0.3 μm.

Next, a plug 16 is formed in the connection hole 15 with, for example, tungsten by a normal plug formation process using tungsten. This plug 16
Is formed, a titanium nitride (TiN) film 17 is formed before burying tungsten in the connection hole 15.

Next, the above PE is formed by a plasma CVD method.
A PE as an insulating film covering the plug 16 on the SiN film 14
Forming the SiO ₂ film 18 to a thickness of, for example, 500 nm; And by lithography technology and RIE technology,
A groove 19 is formed in the PE-SiO ₂ film 18 so that, for example, the upper surface of the plug 16 is exposed at the bottom of the groove 19. The width of the groove 19 was, for example, 0.4 μm. At the time of the RIE, the PE-SiN film 14 functions as an etching stopper.

Next, as shown in FIG. 2B, a natural oxide film (not shown) formed on the plug 16 is removed by ordinary argon sputter etching. Thereafter, a titanium film 20 having a thickness of, for example, 20 nm is formed on the inner wall of the groove 19 by DC magnetron sputtering, and then a titanium nitride film 21 (corresponding to the titanium nitride film 1 described with reference to FIG. 1) is formed, for example, to a thickness of 80 nm. To form a base film. At that time, PE-Si
The titanium film 20 and the titanium nitride film 21 are also formed on the O ₂ film 18. The titanium film 20 is necessary for obtaining good electrical connection with the lower plug 16 made of tungsten.

An example of the conditions for forming the titanium film 20 and the titanium nitride film 21 will be described below. Titanium film 20
As the film forming conditions, argon (for example, 50 sccm) [hereinafter, sccm represents a volume flow rate (cm ³ / min) in a standard state] as a process gas, a DC power of 6 kW,
The pressure of the sputtering atmosphere is 0.2 Pa and the deposition temperature is 200
Set to ° C. The conditions for forming the titanium nitride film 21 include argon (for example, 20 sccm) and nitrogen (for example, 70 sccm) as a process gas, a DC power of 12 kW,
The pressure of the sputtering atmosphere is 0.36 Pa and the deposition temperature is 20
It was set to 0 ° C. Usually, the titanium nitride film 21 is a film having columnar crystals.

Next, the surface of the titanium nitride film 21 is subjected to sputter etching using argon gas. As a result of this processing, the crystal grain boundary portion of the titanium nitride film 21 is preferentially etched, and the surface of the titanium nitride film 21 is formed unevenly. As an example of the condition of the sputter etching process, a DC magnetron sputter etching apparatus is used as an example, and argon (for example, 50 sc) is used as a process gas.
cm), the DC power was set to 1 kW, the pressure of the sputtering atmosphere was set to 0.2 Pa, the processing temperature was set to 200 ° C., and the sputter etching time was set to 30 seconds.

Next, the titanium film 20 is buried in the groove 19 by DC magnetron sputtering.
A wiring material layer 22 (corresponding to the wiring material layer 2 described with reference to FIG. 1) is formed on the PE-SiO ₂ film 18 via the titanium nitride film 21 by depositing, for example, copper to a thickness of 500 nm. . Continue at 400 ° C
By performing a heat treatment for 0 minutes, the groove 19 is filled with the wiring material layer 22. This heat treatment was performed by heating the furnace in argon gas. Then, as shown in (3) of FIG.
Normal CMP (CMP stands for Chemical Mechanical Polishin
g, which means chemical mechanical polishing) to remove an extra wiring material layer (not shown) formed outside the groove 19 and leave the titanium film 20 and the titanium nitride film 2 in the groove 19.
1 is a copper wiring 2 made of a wiring material layer 22 made of copper
Form 3 In this CMP, the PE-SiO ₂ film 18
The above titanium film 20 and titanium nitride film 21 are also removed.

In the above-described method of manufacturing the copper wiring, the surface of the titanium nitride film 21 having columnar crystals serving as the base film of the copper wiring 23 is subjected to the sputter etching treatment. The vicinity of the crystal grain boundary is preferentially etched. Therefore, the surface of the titanium nitride film 21 has a rough surface having irregularities. This is because the vicinity of the crystal grain boundary on the surface of the titanium nitride film 21 is easily etched. After that, the wiring material layer 22 to be the copper wiring 23 is formed on the titanium nitride film 21 in the groove 19, so that the contact area between the wiring material layer 22 and the titanium nitride film 21 increases. Therefore, the adhesion of the copper wiring 23 is improved. Moreover, the barrier property against copper is also ensured by the titanium nitride film 21.

It is desirable that the processes from the sputter etching process to the copper sputter film formation in the above manufacturing method be continuously performed in an industrial vacuum without being opened to the atmosphere by a multi-chamber apparatus.

In the above example of forming the copper trench wiring, the titanium nitride film 21 is used as a copper diffusion barrier material constituting a part of the base film.
However, as a diffusion barrier material of copper, for example, a high melting point metal material such as tantalum (Ta) and tungsten (W) can be used. For example, tantalum nitride (TaN), It is also possible to use a refractory metal compound material such as tantalum silicide (TaSiN), tungsten nitride (WN), and tungsten nitride silicide (WSiN).

In the above sputter etching method, D
C magnetron sputtering method was used, but ICP (Induct
ive Coupled Plasma) Inductively coupled plasma method, ECR
(Electron Cycrotron Resonance) Sputter etching by another plasma generation method such as an electron cyclotron resonance method is also possible.

In the above-described sputter etching, an argon gas is used. However, for example, nitrogen, a mixed gas of argon and nitrogen, or the like can be used. Thus nitrogen gas,
When a gas containing nitrogen is used, nitridation of the surface of the titanium nitride film proceeds, and the diffusion barrier property of copper is improved.

An example of sputter etching conditions using a mixed gas of argon and nitrogen will be described below. As a processing condition, a DC magnetron sputter etching apparatus is used, and argon (for example, 50 scc) is used as a process gas.
m) and nitrogen (20 sccm) using a gas mixture
C power 1kW, sputtering atmosphere pressure 0.28P
a, a processing temperature of 200 ° C. and a sputter etching time of 3
It was set to 0 seconds.

As a method of embedding copper, it is also possible to use a high-pressure reflow method, an electrolytic plating method, or the like, in addition to the above method. Further, as the wiring material, a copper alloy such as zirconium copper (ZrCu) can be used in addition to copper.

Next, a second embodiment will be described below with reference to the manufacturing process diagram of FIG. FIG. 3 illustrates a case where a copper wiring is formed by a normal lithography technique and a dry etching technique. In FIG. 3, the same components as those described below with reference to FIG. 2 are denoted by the same reference numerals.

As shown in FIG. 3A, an element (not shown) is formed on a semiconductor substrate (not shown), and a lower wiring 11 and an insulating film 12 are formed. The surface of the insulating film 12 is flattened to expose the upper surface of the lower wiring 11. Then, a silicon oxide (hereinafter referred to as PE-SiO ₂ ) film 13 serving as an interlayer insulating film is formed to a thickness of, for example, 800 nm on the insulating film 12 by, for example, a plasma CVD method.

Next, a connection hole 15 communicating with, for example, the lower wiring 11 is formed in the PE-SiO ₂ film 13 by a usual lithography technique and a reactive RIE technique. The pore diameter was, for example, 0.3 μm.

Next, a plug 16 is formed in the connection hole 15 by, for example, tungsten by a normal plug forming process using tungsten. This plug 16
Is formed, a titanium nitride (TiN) film 17 is formed before burying tungsten in the connection hole 15.

Next, a natural oxide film (not shown) formed on the plug 16 is removed by ordinary argon sputter etching. Thereafter, a titanium film 20 covering the plug 16 is formed to a thickness of, for example, 20 nm on the PE-SiO ₂ film 13 by DC magnetron sputtering, and then a titanium nitride film 21 (the titanium nitride film described with reference to FIG. Is formed to a thickness of, for example, 80 nm to form a base film. The above titanium film 20
Is necessary to obtain a good electrical connection with the plug 16 made of tungsten in the lower layer.

Then, the surface of the titanium nitride film 21 was subjected to sputter etching using argon gas in the same manner as in the manufacturing method described with reference to FIG. By this process, the crystal grain boundary portion of the titanium nitride film 21 is preferentially etched, and irregularities are formed on the surface of the titanium nitride film 21.

Thereafter, a wiring material layer 22 (FIG. 1) is formed on the titanium nitride film 21 by DC magnetron sputtering.
(Corresponding to the copper film 2 described above), for example,
It is formed by depositing to a thickness of m. Next, the wiring material layer 22 is processed by a dry etching technique using silicon oxide as a mask. Here, for example, an etching apparatus equipped with a helicon wave plasma source was used to etch the wiring material layer 22 using chlorine gas as an etching gas. Further, the above titanium nitride film 21 and titanium film 20
Is also etched. As a result, as shown in FIG. 3B, a copper wiring 23 composed of a wiring material layer 22 connected to the plug 16 is obtained. The titanium nitride film 21 and the titanium film 20 are left under the copper wiring 23.

[0035]

As described above, according to the present invention,
Since the sputter etching process is performed on the surface of the base film made of a high melting point metal material having columnar crystals or a high melting point metal compound material having columnar crystals, the surface of the base film may have uneven surface roughness. it can. Thereafter, when copper is formed on the base film, the contact area with copper increases due to the rough surface of the base film, so that the adhesion of copper is improved. As described above, the adhesion between the copper film and the underlying film serving as a diffusion barrier material can be improved without deteriorating the diffusion barrier properties of the underlying film. Therefore, it is possible to prevent a decrease in the performance and reliability of the copper wiring due to the peeling of the copper wiring.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of a method for manufacturing a copper wiring using the embodiment.

FIG. 3 is a manufacturing process diagram of another method for manufacturing a copper wiring using the embodiment.

FIG. 4 is an explanatory diagram of a conventional copper wiring structure.

FIG. 5 is an explanatory diagram of peeling of a copper wiring.

[Explanation of symbols]

 1. Underlayer film 2. Wiring material layer

Claims (4)

[Claims] 1. A method for manufacturing a copper wiring, comprising: forming a wiring material layer made of copper or a copper alloy on a base film made of a high melting point metal material having columnar crystals or a high melting point metal compound material having columnar crystals. 5. The method of manufacturing a copper wiring according to claim 1, wherein after forming the base film and before forming the wiring material layer, a sputter etching process is performed on a surface of the base film. 2. The method for manufacturing a copper wiring according to claim 1, wherein the gas used for the sputter etching process is an argon gas. 3. The method of manufacturing a copper wiring according to claim 1, wherein the gas used for the sputter etching process contains at least a nitrogen gas. 4. The method of manufacturing a copper wiring according to claim 2, wherein the gas used for the sputter etching process contains at least a nitrogen gas.