JPH11102911A - Semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce contact resistance and increase bonding strength in an electrode for external connection, by preventing a metal oxide film from being formed on the surface of the electrode for external connection. SOLUTION: After a recessed part for wiring and a recessed part for an external electrode are formed on an interlayer insulating film 101 on a semiconductor substrate 100, a tantalum film 104 is deposited. After that, a copper film 105 is so formed that the recessed part for wiring is filled and a space exists above the recessed part for an external electrode. After an aluminum film 106 restraining oxidation of the copper film 105 is deposited on the copper film 105, chemical mechanical polishing is performed until the interlayer insulating film 101 is exposed. Then, a metal wiring 107 constituted of the copper film 105 and the tantalum film 104, and an electrode 108 for external connection which is constituted of the aluminum film 106, the copper film 105 and the tantalum film 104 are formed. After a protective film constituted of a silicon nitride film 109 and a silicon oxide film 110 is deposited, an aperture part 111 for external connection is formed on the protective film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor device having metal wiring and an electrode for external connection formed on an uppermost wiring layer on a semiconductor substrate, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor device including a metal wiring formed on an uppermost wiring layer on a semiconductor substrate and an electrode for external connection, a material forming the metal wiring and the electrode for external connection is an electric material. Aluminum or an aluminum alloy has been mainly used in consideration of a low electrical resistance and an easy forming process.

In recent years, however, demands for higher integration, higher speed, and higher reliability of semiconductor integrated circuits have been increasing. Therefore, volume resistivity smaller than aluminum-based metal and higher electromigration than aluminum-based metal have been demanded. (EM) -resistant copper or copper alloy has attracted attention as a next-generation wiring material.

Incidentally, it is difficult to perform dry etching on a copper film.
No. 282, a copper film is deposited over the entire surface of the interlayer insulating film including the wiring recesses and the external electrode recesses formed in the interlayer insulating film. For example, chemical mechanical polishing (CMP)
There has been proposed a method of forming a buried wiring of copper by performing ishing).

Hereinafter, a conventional method for forming a copper embedded wiring will be described with reference to FIGS. 13 (a) to 13 (d).

First, as shown in FIG. 13A, a known lithography technique is applied to an interlayer insulating film 11 deposited on a semiconductor substrate 10 on which a semiconductor element (not shown) is formed. Then, the wiring concave portion 12 and the external electrode concave portion 13 are formed by using an etching technique.

Next, as shown in FIG. 13B, a titanium nitride film 14 serving as a copper film barrier layer is formed on the interlayer insulating film 11.
After that, a metal film and a copper film 15 to be an electrode for external connection are sequentially deposited on the entire surface of the titanium nitride film 14, and then a heat treatment is performed on the semiconductor substrate 10.
The copper film 15 is filled in the wiring recess 12 and the external electrode recess 13.

[0008] Next, as shown in FIG.
5 and the titanium nitride film 14 are subjected to chemical mechanical polishing until the interlayer insulating film 11 is exposed, so that the metal wiring 16 comprising the copper film 15 and the titanium nitride film 14 and the external connection electrode 1
7 is formed.

Next, as shown in FIG. 13D, a silicon nitride film 18 and a silicon oxide film 1 are formed over the entire surface of the interlayer insulating film 11, the metal wiring 16, and the external connection electrode 17.
9 are sequentially deposited to form a protective film composed of the silicon nitride film 18 and the silicon oxide film 19, and then the external connection electrode formation region in the protective film is selectively removed to form the external connection opening 20. Form.

Next, although not shown, the external connection electrode 1 is heated while the semiconductor substrate 10 is heated to about 200 ° C.
Bonding the bonding wire to 7 enables the semiconductor element formed on the semiconductor substrate 10 to be electrically connected to the outside.

[0011]

However, the conventional semiconductor device has the following problems. That is, when wire bonding is performed to the external connection electrode 17 in a state where the semiconductor substrate 10 is heated to about 200 ° C., a copper oxide film is formed in a region of the external connection electrode 17 exposed to the external connection opening 20. Will be formed. When a copper oxide film is formed on the surface of the external connection electrode 17, the contact resistance increases and the bonding strength decreases. In other words, despite the fact that the wiring material is changed from aluminum to copper to lower the resistance and improve the reliability by alleviating the electromigration,
New problems such as an increase in contact resistance and a decrease in bonding strength in the external connection electrode occur.

In view of the foregoing, it is an object of the present invention to reduce the contact resistance and improve the bonding strength of an external connection electrode by preventing a metal oxide film from being formed on the surface of the external connection electrode.

[0013]

In order to achieve the above object, a semiconductor device according to the present invention comprises a semiconductor device having a metal wiring and an external connection electrode formed on an uppermost wiring layer on a semiconductor substrate. Assuming the device, the metal wiring is made of a first metal, the external connection electrode is formed on a first metal film made of the first metal, and the first metal film is formed on the first metal film. And a second metal film made of a second metal having better oxidation resistance.

According to the semiconductor device of the present invention, the external connection electrode has the first metal film made of the first metal and the oxidation resistance of the first metal formed on the first metal film which is lower than that of the first metal film. Therefore, the bonding wire or the bump is bonded to the second metal film having excellent oxidation resistance.

In the semiconductor device of the present invention, the metal wiring and the electrode for external connection are preferably formed so as to be respectively buried in an interlayer insulating film formed below the uppermost wiring layer.

In the semiconductor device of the present invention, it is preferable that the second metal film is formed on a region of the first metal film excluding a peripheral portion.

In the semiconductor device according to the present invention, the metal wiring and the electrode for external connection are formed between the uppermost wiring layer and an interlayer insulating film formed below the uppermost wiring layer, and are connected to the first metal interlayer insulating film. It is preferable to have a barrier layer for preventing the diffusion of

In the semiconductor device of the present invention, the first metal is preferably copper or an alloy of copper, and the second metal is preferably aluminum or an alloy of aluminum.

According to a first method of manufacturing a semiconductor device according to the present invention, there is provided a recess forming step of forming a recess for wiring and a recess for external electrodes in an interlayer insulating film formed on a semiconductor substrate; On the interlayer insulating film including the recess for
A first metal film depositing step of depositing a first metal film made of the metal described above such that the wiring recess is filled and a space remains above the external electrode recess; A second metal film depositing step of depositing a second metal film made of a second metal having better oxidation resistance than the first metal; and interposing the second metal film and the first metal film in an interlayer. By removing the insulating film so as to be exposed, the metal wiring made of the first metal film is formed in the wiring recess, and the external wiring made of the first metal film and the second metal film is formed in the external electrode recess. Forming a connection electrode.

According to the first method of manufacturing a semiconductor device, the first metal film made of the first metal is formed on the interlayer insulating film in which the wiring recess and the external electrode recess are formed. After being filled so as to leave a space above the external electrode recess, a second metal made of a second metal having better oxidation resistance than the first metal is formed on the first metal film. In order to remove the second metal film and the first metal film so that the interlayer insulating film is exposed, a buried wiring made of the first metal film can be formed, A buried external connection electrode having a second metal film having excellent oxidation resistance at the top can be formed.

In the first method for fabricating a semiconductor device, the first metal film deposition step comprises: depositing the first metal film by a sputtering method, and then flowing the first metal film by heat treatment to form a wiring recess. It is preferable to include a step of filling the liquid.

In the first method of manufacturing a semiconductor device, the first metal film deposition step preferably includes a step of depositing the first metal film by a CVD method or a plating method.

In the first method for fabricating a semiconductor device, the step of forming a recess includes the step of forming a contact hole below the wiring recess, and the step of depositing a first metal film comprises contacting the first metal film with a first metal film. Preferably, the method includes a step of depositing the holes so that the holes are filled.

In the first method of manufacturing a semiconductor device, the first metal film deposition step prevents the first metal from diffusing into the interlayer insulating film between the interlayer insulating film and the first metal film. It is preferable to include a step of forming a barrier layer.

In the first method for fabricating a semiconductor device, the step of depositing the second metal film includes a step of depositing a second metal film on the first metal film via an insulating film. It is preferable that the method further includes a step of bonding a bonding wire or a bump to the electrode so that the insulating film is broken.

According to a second method of manufacturing a semiconductor device according to the present invention, there is provided a recess forming step of forming a recess for wiring and a recess for external electrodes in an interlayer insulating film formed on a semiconductor substrate; On the interlayer insulating film including the recess for
A first metal film depositing step of depositing a first metal film made of the above-mentioned metal so as to fill the recesses for wiring and the recesses for external electrodes, and a step of depositing the first metal film so that an interlayer insulating film is exposed. By removing, the metal wiring forming step of forming the metal wiring made of the first metal film in the wiring recess, and the acid resistance of the first metal film remaining in the external electrode recess is lower than that of the first metal. External connection electrode for forming an external connection electrode composed of a first metal film and a second metal film by selectively depositing a second metal film made of a second metal having excellent chemical properties Forming step.

According to the second method for manufacturing a semiconductor device, the first metal film made of the first metal is deposited on the interlayer insulating film having the wiring recess formed therein so as to fill the wiring recess. After that, since the first metal film is removed so that the interlayer insulating film is exposed, a buried wiring made of the first metal film can be formed. After depositing a first metal film made of a first metal on the interlayer insulating film in which the external electrode concave portion is formed so that the external electrode concave portion is filled,
The first metal film is removed so that the interlayer insulating film is exposed, and then a second metal having better oxidation resistance than the first metal is formed on the first metal film remaining in the external electrode recess. Since the second metal film is selectively deposited, an external connection electrode having a second metal film having excellent oxidation resistance on the top can be formed.

In the first or second method for fabricating a semiconductor device, the first metal is preferably copper or a copper alloy, and the second metal is preferably aluminum or an aluminum alloy.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment Hereinafter, a semiconductor device according to a first embodiment and a method for manufacturing the same will be described with reference to FIGS. 1 (a) to 1 (c) and 2 (a) to 2 (c). In the following embodiments, a contact hole for connecting a transistor element or the like formed on a semiconductor substrate and a metal wiring, and a via hole for connecting a lower metal wiring and an upper metal wiring are formed as contact holes for convenience. Collectively called holes.

First, as shown in FIG. 1A, a semiconductor substrate 10 on which LSI components (not shown) such as a transistor element, a capacitor element and a metal wiring are formed.
After an interlayer insulating film 101 made of a silicon oxide film is deposited on the substrate 0, the interlayer insulating film 101 is subjected to lithography and dry etching to form a wiring recess 102 and an external electrode recess 103. In this case, the depth d ₁ of the wiring concave portion 102 and the external electrode concave portion 103 can take various values depending on device design or the like, but is usually about 0.5 to 2 μm. Although not shown in FIG. 1A, the bottom of any of the plurality of wiring recesses 102 is buried in a lower wiring, or a contact hole communicating with the lower wiring or the LSI component. Exposed plug is exposed.

Next, as shown in FIG. 1B, the interlayer insulating film 1 including the wiring recess 102 and the external electrode recess 103 is formed.
After a tantalum film 104 serving as a barrier layer for preventing diffusion of copper into the interlayer insulating film 101 is deposited on the entire surface of the tantalum film 01, an uppermost metal wiring and an electrode for external connection are formed on the tantalum film 104. Copper film 105 as a first metal film to be formed
Is deposited by a sputtering method.

Next, as shown in FIG. 1C, the semiconductor substrate 100 is subjected to a heat treatment to improve the crystallinity of the copper constituting the copper film 105 and to form the copper film 105 into the wiring recess 102. And into the external electrode recess 103. In this case, the copper recess 105 is filled in the wiring recess 102, while a space is formed above the external electrode recess 103.

When the width of the wiring recess 102 is smaller than about twice the total thickness t ₁ of the tantalum film 104 and the copper film 105, the tantalum film 104 and the copper film 105 are formed in the wiring recess 102. Will be filled. Further, the total thickness t _{1 of} the tantalum film 104 and the copper film 105 is smaller than the depth d ₁ of the external electrode recess 103 and the external electrode recess 1
When the width is smaller than の of the width of 03, the external electrode concave portion 103 is not filled with the tantalum film 104 and the copper film 105. For example, the depth d ₁ of the wiring recess 102 is 0.8 μm and the width W ₁ is 1.0 μm, and the depth d ₁ of the external electrode recess 103 is 0.8 μm and the width W ₂ is 1 μm.
Assuming that the total thickness t _{1 of the} tantalum film 104 and the copper film 105 is 0.6 μm, the width W ₁ : 0.8 μm of the wiring recess 102 is equal to the total thickness t ₁ : 0.6 μm.
m is smaller than twice (1.2 μm), the wiring concave portion 102 is filled with the tantalum film 104 and the copper film 105, but the width W ₂ : 100 μm of the external electrode concave portion 103 has a total film thickness t ₁ : The external electrode recess 103 is not filled with the tantalum film 104 and the copper film 105 because it is larger than twice of 0.6 μm.

In order to reduce the resistance of the metal wiring as much as possible, it is necessary to reduce the thickness of the tantalum film 104, and the thickness of the tantalum film 104 is preferably 50 nm or less.

Since the flow characteristics vary depending on the composition of copper or copper alloy constituting the copper film 105, the total film thickness t
_{Even when 1} is equal to or less than の of the width W ₁ of the wiring recess 102 and smaller than the depth d ₁ of the wiring recess 102,
It is preferable to set the total film thickness t ₁ according to the composition of copper or a copper alloy so that the wiring recess 102 is filled with the tantalum film 104 and the copper film 105.

Next, as shown in FIG.
5, an aluminum film 106 as a second metal film for suppressing oxidation of the copper film 105 is deposited. In this case, the tantalum film 104, the copper film 105, and the aluminum film 106
Total thickness t ₂ of so larger than the depth d ₁ of the outer electrode recess 103, to set the thickness of the aluminum film 106. By doing so, the external electrode concave portion 103 becomes the tantalum film 104, the copper film 105, and the aluminum film 106.
Filled by

Next, as shown in FIG. 2B, chemical mechanical polishing is performed on the aluminum film 106, the copper film 105, and the tantalum film 104 until the interlayer insulating film 101 is exposed. The uppermost metal wiring 107 made of the film 104, the aluminum film 106, and the copper film 10
5 and external connection electrode 108 made of tantalum film 104
Are formed respectively.

Next, as shown in FIG. 2C, a silicon nitride film 109 and a silicon oxide film 110 are sequentially deposited on the entire surface of the interlayer insulating film 101, the metal wiring 107 and the external connection electrode 108. Then, after forming a protective film composed of the silicon nitride film 109 and the silicon oxide film 110, the external connection electrode forming region in the protective film is selectively removed to form the external connection opening 111. in this case,
The size of the external connection electrode 108 is usually 50 μm to 100 μm.
If the size of the external connection opening 111 is smaller than the size of the external electrode recess 103 by about 5 μm, the area of the external connection electrode 108 that is not covered with the aluminum film 106 is silicon nitride. Membrane 1
09 and the silicon oxide film 110.

Since the total thickness t ₁ of the tantalum film 104 and the copper film 105 is generally about 0.5 to 2.0 μm, as shown in FIG. It is easy to process so that the copper film 105 is not exposed to the external connection opening 111 while being exposed to the portion 111.

In the semiconductor device according to the first embodiment, since the uppermost metal wiring 107 is constituted by the copper film 105 and the tantalum layer 104, the resistance is reduced and the electromigration is reduced. The external connection electrode 108 includes an aluminum film 106, a copper film 105, and a tantalum layer 104. Since the aluminum film 106, which has higher oxidation resistance than the copper film 105, exists on the surface, The wire bonding step or the bump bonding step in flip chip mounting can be reliably performed in an atmosphere at a temperature of about 200 ° C.

Therefore, according to the semiconductor device of the first embodiment, it is possible to increase the contact resistance and improve the bonding strength while reducing the resistance of the metal wiring and suppressing the electromigration.

Further, according to the method of manufacturing a semiconductor device according to the first embodiment, the number of photolithography steps is not increased as compared with the conventional method of manufacturing a semiconductor device.
Since the surface portion of the external connection electrode can be constituted by a metal film having high oxidation resistance, without increasing the manufacturing cost,
It is possible to increase the contact resistance and the bonding strength.

Further, since the wire bonding step or the bump bonding can be performed in the air, it is possible to suppress an increase in manufacturing cost caused when performing the bonding under a special atmosphere.

In the first embodiment, the region of the external connection electrode 108 that is not covered by the aluminum film 106 is covered by the silicon nitride film 109 and the silicon oxide film 110. At least the region of the external connection electrode 108 to which the bonding wire or bump is bonded is the aluminum film 10
6 may be sufficient. That is, in FIG. 2C, the peripheral portion of the copper film 105 may be exposed to the opening 111 for external connection.

In the first embodiment, the copper film 1
05 was deposited by a sputtering method and then filled by heat treatment. Alternatively, the copper film 1 may be formed by a chemical vapor deposition (CVD) method using a source containing a copper film or a plating method.
05 may be deposited.

Second Embodiment Hereinafter, a semiconductor device according to a second embodiment and a method for manufacturing the same will be described with reference to FIGS. 3, 4A to 5C, and 5A to 5C. It will be described with reference to FIG. FIG. 3 shows a planar structure of the semiconductor device according to the second embodiment without a protective film, and FIG.
FIGS. 5A to 5C and FIGS. 5A to 5C show the cross-sectional structures taken along line XX in FIG.

First, as shown in FIG. 4A, after a first interlayer insulating film 201 is deposited on a semiconductor substrate 200,
A first metal wiring 202 is formed on the first interlayer insulating film 201, and then a second interlayer insulating film 203 is formed on the entire surface of the first metal wiring 202 and the first interlayer insulating film 201.
Is deposited. Next, on the second interlayer insulating film 203, the first
After the formation of the resist pattern 204, the second interlayer insulating film 2 is formed using the first resist pattern 204 as a mask.
03 is etched to form a wiring recess 205 and an external electrode recess 206 in the second interlayer insulating film 203. In this case, the depth d ₁ of the wiring concave portion 205 and the external electrode concave portion 206 can take various values depending on device design and the like, but is usually about 0.5 to 2 μm.

Next, as shown in FIG. 4B, after a second resist pattern 207 is formed on the second interlayer insulating film 203, the second resist pattern 207 is used as a mask to form a second resist pattern. Interlayer insulating film 203 and first interlayer insulating film 2
Then, the first metal wiring 20 is etched on the second interlayer insulating film 203 as shown in FIG.
In addition to forming a contact hole (depth: d ₂ ) 208 connecting to the second electrode 2, the external electrode recess 206 is dug down to the second interlayer insulating film 203.

Next, as shown in FIG. 5A, the second interlayer insulating film of copper is formed on the entire surface of the second interlayer insulating film 203 including the recesses 205 for wiring and the recesses 206 for external electrodes. After depositing a titanium nitride film 209 serving as a barrier layer for preventing diffusion into the film 203, a copper film serving as a first metal film serving as an uppermost metal wiring and an external connection electrode is formed on the titanium nitride film 209. 210 is deposited by a CVD method, and thereafter, heat treatment is performed on the semiconductor substrate 200 to improve the crystallinity of the copper film 210.

Incidentally, the titanium nitride film 209 and the copper film 2
The total thickness t ₁ of 10, larger than the depth d ₁ of the interconnect recesses 205, interconnect recesses 205 and the contact hole 2
Total depth of 08 if (d ₁ + d ₂₎ is larger than 1/2 of the small and the diameter of the contact hole 208 than,
Since the total film thickness t ₁ is sufficiently smaller than the width of the external electrode concave portion 206, the wiring concave portion 205 and the contact hole 2 are formed.
08 is filled with the titanium nitride film 209 and the copper film 210, while the external electrode recess 206 is filled with the titanium nitride film 20.
9 and the copper film 210 are not filled.

Next, on the copper film 210, an aluminum film 21 as a second metal film for suppressing oxidation of the copper film 210 is formed.
1 is deposited. In this case, the titanium nitride film 209 and the copper film 2
The thickness of the aluminum film 211 is set so that the total thickness t ₂ of the aluminum film 211 and the thickness of the aluminum film 211 is greater than the depth of the recessed external electrode recess 103. By doing so, the concave portion 103 for the external electrode becomes the titanium nitride film 2
09, a copper film 210 and an aluminum film 211. For example, the depth d ₁ of the wiring concave portion 205 = 0.
8 μm, depth d ₂ of contact hole 208 = 1.0 μm
When the total thickness t ₁ of the titanium nitride film 209 and the copper film 210 is 1.0 μm and the thickness of the aluminum film 211 is 1.0 μm, the wiring recess 205 is nitrided irrespective of the width dimension. The external electrode concave portion 206 is filled with the titanium nitride film 209, the copper film 210, and the aluminum film 211 while being filled with the titanium film 209 and the copper film 210.

In order to reduce the resistance of the metal wiring as much as possible, it is necessary to reduce the thickness of the titanium nitride film 209, and the thickness of the titanium nitride film 209 is preferably 50 nm or less.

In the second embodiment, the thickness of the aluminum film 211 is set to 1.0 μm, and the external electrode recess 206 is filled with the titanium nitride film 209, the copper film 210, and the aluminum film 211. The aluminum film 211 is thinned by chemical mechanical polishing performed later, and the bonding wires or bumps are
If there is no possibility of peeling from the external electrode 11, the external electrode recess 20
6 need not be completely filled.

Next, as shown in FIG. 3 and FIG.
Aluminum film 211, copper film 210 and titanium nitride film 2
09 is subjected to chemical mechanical polishing until the second interlayer insulating film 203 is exposed, to thereby form the copper film 210 and the titanium nitride film 2.
An external connection electrode 213 made of a metal wiring 212 and an aluminum film 211, a copper film 210, and a titanium nitride film 209, which are the uppermost layer made of the metal wiring 212, is formed.

Next, as shown in FIG. 5C, the second interlayer insulating film 203, the metal wiring 212, and the external connection electrode 2 are formed.
13, a silicon nitride film 214 and a silicon oxide film 215 are sequentially deposited over the entire surface to form a silicon nitride film 21.
After forming the protective film composed of the silicon oxide film 4 and the silicon oxide film 215, the external connection electrode forming region in the protective film is selectively removed to form the external connection opening 216.

In the semiconductor device according to the second embodiment, since the uppermost metal wiring 212 is constituted by the copper film 210 and the titanium nitride film 209, the resistance is reduced and the electromigration is eased. The external connection electrode 213 is composed of an aluminum film 211, a copper film 210, and a titanium nitride film 209. Since the aluminum film 211 having higher oxidation resistance than the copper film 210 exists on the surface, In addition, the wire bonding step or the bump bonding step in flip chip mounting can be reliably performed in an air atmosphere at a temperature of about 200 ° C.

Therefore, according to the semiconductor device of the second embodiment, it is possible to increase the contact resistance and improve the bonding strength while reducing the resistance of the metal wiring and suppressing the electromigration.

Further, according to the method of manufacturing a semiconductor device according to the second embodiment, the number of photolithography steps is not increased as compared with the conventional method of manufacturing a semiconductor device.
Since the surface portion of the external connection electrode can be constituted by a metal film having high oxidation resistance, without increasing the manufacturing cost,
It is possible to increase the contact resistance and the bonding strength.

Further, since the wire bonding step or the bump bonding can be performed in the air, it is possible to suppress an increase in manufacturing cost caused when the bonding is performed in a special atmosphere.

In the second embodiment, the copper film 21
0 is formed by the CVD method. Alternatively, the copper film 210 may be deposited by a sputtering method and then filled by performing a heat treatment, or the copper film 210 may be formed by a plating method.

(Third Embodiment) A semiconductor device and a method of manufacturing the same according to a third embodiment will be described with reference to FIG.
This will be described with reference to (a) to (c) and FIGS. 7 (a) to (c).

First, as shown in FIG. 6A, after depositing a first interlayer insulating film 301 on a semiconductor substrate 300,
A first metal wiring 302 is formed on the first interlayer insulating film 301, and then a second interlayer insulating film 303 is formed over the entire surface of the first metal wiring 302 and the first interlayer insulating film 301.
Is deposited. Next, a first layer is formed on the second interlayer insulating film 303.
After the resist pattern 304 is formed, the second interlayer insulating film 3 is formed using the first resist pattern 304 as a mask.
03 is etched to form a contact hole 305 connected to the first metal wiring 302 and a concave portion 306 for an external electrode in the second interlayer insulating film 303, respectively.

Next, as shown in FIG. 6B, after forming a second resist pattern 307 on the second interlayer insulating film 303, the second resist pattern 307 is used as a mask to form a second resist pattern 307. Interlayer insulation film 303 and first interlayer insulation film 3
6C, an interconnect recess 308 is formed in the second interlayer insulating film 303, and an external electrode recess 306 is formed in the second interlayer insulating film 303, as shown in FIG. Dig all the way down.

Next, as shown in FIG. 7A, the second interlayer insulating film of copper is formed on the entire surface of the second interlayer insulating film 303 including the recess 308 for wiring and the recess 306 for external electrodes. After depositing a titanium nitride film 309 serving as a barrier layer for preventing diffusion into the film 303, a copper film serving as a first metal film serving as an uppermost metal wiring and an electrode for external connection is formed on the titanium nitride film 309. 310 is deposited by a CVD method, and thereafter, a heat treatment is performed on the semiconductor substrate 300 to improve the crystallinity of the copper film 310. Then, the copper film 310 is formed on the copper film 310.
An aluminum film 311 as a second metal film that suppresses oxidation of is deposited.

Next, as shown in FIG. 7B, the aluminum film 311, the copper film 310, and the titanium nitride film 309 are subjected to chemical mechanical polishing until the second interlayer insulating film 303 is exposed. Metal wiring 312 and aluminum film 31 of the uppermost layer comprising film 310 and titanium nitride film 309
1. An external connection electrode 313 made of a copper film 310 and a titanium nitride film 309 is formed.

Next, as shown in FIG. 7C, the second interlayer insulating film 303, the metal wiring 312 and the external connection electrode 3 are formed.
A silicon nitride film 314 and a silicon oxide film 315 are sequentially deposited over the entire surface of
After the formation of the protection film including the silicon oxide film 4 and the silicon oxide film 315, the external connection electrode formation region in the protection film is selectively removed to form the external connection opening 316.

The semiconductor device and the method of manufacturing the same according to the third embodiment are different from the second embodiment only in the order of the wiring recess forming step and the contact hole forming step. The same effects as those of the second embodiment can be obtained.

(Fourth Embodiment) A semiconductor device and a method of manufacturing the same according to a fourth embodiment will be described with reference to FIG.
This will be described with reference to (a) to (d).

First, as in the second embodiment, FIG.
As shown in (1), after depositing a first interlayer insulating film 401 on a semiconductor substrate 400, a first metal wiring 402 is formed on the first interlayer insulating film 401. Next, after depositing a second interlayer insulating film 403 over the entire surface of the first metal wiring 402 and the first interlayer insulating film 401, contact holes and wiring recesses are formed in the second interlayer insulating film 403. And a concave portion for an external electrode. Next, the second interlayer insulating film 4
, A second interlayer insulating film 403 made of copper
Nitride film 404 serving as a barrier layer for preventing diffusion into silicon
After that, a copper film 405 as a first metal film serving as an uppermost metal wiring and an external connection electrode is deposited on the titanium nitride film 404 by a CVD method. The heat treatment is performed to improve the crystallinity of the copper film 405.

Next, after an insulating film 406 made of a silicon nitride film or the like is deposited on the copper film 405, an aluminum film as a second metal film for suppressing oxidation of the copper film 405 is formed on the insulating film 406. A film 407 is deposited.

By the way, as in the second embodiment, the first
When a second metal film such as an aluminum film for suppressing oxidation of the first metal film is deposited on a metal film such as a copper film,
Since the first metal film and the second metal film are simultaneously immersed in the polishing agent or the cleaning liquid in the chemical mechanical polishing step or the cleaning step, the types of the polishing agent, the cleaning liquid, the first metal film, and the second metal film Depending on the battery effect, the first metal film or the second
Metal film may be corroded.

Therefore, in the fourth embodiment, the first
An insulating film 406 is interposed between a copper film 405 as a metal film and an aluminum film 407 as a second metal film. Thus, the copper film 405 and the aluminum film 4
Since no current flows between the first metal film and the second metal film, corrosion of the first metal film or the second metal film can be prevented.

Next, as shown in FIG. 8B, chemical mechanical polishing is performed on the aluminum film 407, the insulating film 406, the copper film 405, and the titanium nitride film 404 until the second interlayer insulating film 403 is exposed. Go to the aluminum film 407,
The uppermost metal wiring 408 composed of the insulating film 406, the copper film 405 and the titanium nitride film 404 and the external connection electrode 409 composed of the copper film 405 and the titanium nitride film 404 are formed. The insulating film 406 forming the metal wiring 408
A method for removing the adverse effects associated with the insulating properties of the above will be described later.

Next, as shown in FIG. 8C, the second interlayer insulating film 403, the metal wiring 408, and the external connection electrode 4 are formed.
09, a silicon nitride film 410 and a silicon oxide film 411 are sequentially deposited over the entire surface to form a silicon nitride film 41.
After forming a protective film made of O and the silicon oxide film 411, an external connection electrode forming region in the protective film is selectively removed to form an external connection opening 412.

Next, as shown in FIG. 8D, a bonding wire 413 is bonded to the external connection electrode 409.
In this bonding step, heat, vibration, or impact is applied to the insulating film 406, so that the insulating film 406 is broken, so that the aluminum film 407 and the copper film 405 are brought into a conductive state.
From such a viewpoint, the thickness of the insulating film 406 is 5 n
m to 30 nm is preferred. With this thickness, the battery effect does not occur even when the copper film 405 and the aluminum film 407 are simultaneously immersed in an abrasive or a cleaning solution, and the insulating film is formed in the step of bonding the bonding wire 413 to the external connection electrode 409. 406 can be reliably broken.

(Fifth Embodiment) Hereinafter, a semiconductor device according to a fifth embodiment and a method for manufacturing the same will be described with reference to FIG.
This will be described with reference to (a) to (c) and FIGS. 10 (a) to (d).

First, as shown in FIG. 9A, after an interlayer insulating film 501 is deposited on a semiconductor substrate 500, the interlayer insulating film 501 is subjected to lithography and dry etching to form a wiring recess 502. And concave portion 5 for external electrode
03 is formed. In this case, the depth d ₁ of the wiring concave portion 502 and the external electrode concave portion 503 can take various values depending on device design or the like, but is usually about 0.5 to 2 μm.

Next, as shown in FIG. 9B, after forming a resist pattern 503 on the interlayer insulating film 501,
Using the resist pattern 503 as a mask, the interlayer insulating film 5
9 is etched to form a contact hole 5 under the wiring recess 502, as shown in FIG.
04 is formed.

Next, as shown in FIG. 10A, copper is diffused into the interlayer insulating film 501 over the entire surface of the interlayer insulating film 501 including the wiring recesses 502 and the external electrode recesses 503. After depositing a titanium nitride film 505 serving as a barrier layer to block, a copper film 506 serving as a first metal film serving as an uppermost metal wiring and an external connection electrode is deposited on the titanium nitride film 505 by a CVD method. And then the semiconductor substrate 5
Heat treatment is performed on the copper film 506 to improve the crystallinity of the copper film 506 and fill the wiring concave portion 502 and the contact hole 504 with the copper film 506. In this case, the total thickness t ₁ of the titanium nitride film 505 and the copper film 506 is smaller than the depth d _{1 of the} concave portion 503 for the external electrode,
2 which is larger than 1/2 of the width of 2 and the concave portion 503 for external electrodes.
The width of the wiring recesses 502 and the contact holes 504 are smaller than １ ／ of the width of the titanium nitride film 5.
The external electrode recess 503 is not filled with the titanium nitride film 505 and the copper film 506 while being filled with the copper film 505 and the copper film 506.

Next, as shown in FIG.
An aluminum film 507 as a second metal film for suppressing the oxidation of the copper film 506 is deposited on the substrate 06.

Next, as shown in FIG. 10C, the aluminum film 507, the copper film 506, and the titanium nitride film 505 are subjected to chemical mechanical polishing until the interlayer insulating film 501 is exposed. The uppermost metal wiring 508 and the contact 510 made of the titanium nitride film 505, and the aluminum film 507, the copper film 506, and the titanium nitride film 5
Then, an external connection electrode 509 made of a material 05 is formed.

Next, as shown in FIG. 10D, an interlayer insulating film 501, a metal wiring 508, and an external connection electrode 509 are formed.
After a silicon nitride film 511 and a silicon oxide film 512 are sequentially deposited over the entire surface to form a protective film including the silicon nitride film 511 and the silicon oxide film 512,
An external connection electrode forming region in the protective film is selectively removed to form an external connection opening 513.

The semiconductor device and the method of manufacturing the same according to the fifth embodiment differ from the second embodiment only in the structure of the contact hole, and have the same effects as the second embodiment. can get.

In the fifth embodiment, the copper film 50
6 was deposited by the CVD method, but may be deposited by a plating method instead. When the copper film 506 is deposited by a plating method, the titanium nitride film 505 and the copper film 506 are used.
May be formed by a sputtering method. When the copper film 506 is deposited by a CVD method or a plating method, a copper film 506 having excellent crystallinity is obtained. When the copper film 506 is deposited by a CVD method, the titanium nitride film 505 may be deposited by a sputtering method.

(Sixth Embodiment) A semiconductor device according to a sixth embodiment and a method of manufacturing the same will now be described with reference to FIG.
This will be described with reference to (a) to (c) and FIGS. 12 (a) and 12 (b).

First, as shown in FIG. 11A, after an interlayer insulating film 601 is deposited on a semiconductor substrate 600, the interlayer insulating film 601 is subjected to lithography and dry etching to form a wiring recess 602. Then, a concave portion 603 for an external electrode is formed. In this case, the depth d ₁ of the wiring recess 602 and the external electrode recess 603 can take various values depending on device design or the like, but is usually 0.5 to 2 μm.
It is about.

Next, as shown in FIG. 11B, copper is diffused into the interlayer insulating film 601 over the entire surface of the interlayer insulating film 601 including the wiring recess 602 and the external electrode recess 603. After depositing a titanium nitride film 604 serving as a barrier layer to block, a copper film 605 serving as a first metal film serving as an uppermost metal wiring and an external connection electrode is deposited on the titanium nitride film 604 by a sputtering method. Thereafter, a heat treatment is performed on the semiconductor substrate 600 to improve the crystallinity of the copper film 605 and fill the wiring concave portion 602 and the external electrode concave portion 603 with the copper film 605. In this case, when the total thickness t ₁ of the titanium nitride film 604 and the copper film 605 is larger than the depth d _{1 of} the wiring recess 602 and the external electrode recess 603, the wiring recess 602 and the external electrode recess 603 are formed.
Can be reliably filled with the titanium nitride film 604 and the copper film 605.

Next, as shown in FIG.
05 and the titanium nitride film 604 to the interlayer insulating film 601
After chemical mechanical polishing was performed until the surface was exposed, FIG.
As shown in (a), an interlayer insulating film 601 and a copper film 605
A silicon nitride film 606 and a silicon oxide film 607 are sequentially deposited over the entire surface to form a protective film composed of the silicon nitride film 606 and the silicon oxide film 607.
An external connection electrode forming region in the protective film is selectively removed to form an external connection opening 608.

Next, as shown in FIG.
When an aluminum film 609 as a second metal film for suppressing oxidation of the copper film 605 is selectively deposited on the region exposed on the external connection opening 608 on the silicon film 605 by, for example, a CVD method, the copper film 605 And titanium nitride film 604
Uppermost metal wiring 610 and aluminum film 6
09, a copper film 605 and a titanium nitride film 604 are obtained.

The semiconductor device according to the sixth embodiment has the first
Since it has the same structure as that of the first embodiment, the same effect as that of the first embodiment can be obtained.

According to the method of manufacturing the semiconductor device according to the sixth embodiment, the aluminum film 60 is formed on the copper film 605 in a region exposed to the external connection opening 608.
Since 9 is selectively deposited, it is not necessary to match a mask for forming the external connection opening 608 with the aluminum film 609, so that the manufacturing process is facilitated.

In the sixth embodiment, the copper film 60
5 was deposited by sputtering, but instead of CV
It may be deposited by the D method or the plating method.

In the first to sixth embodiments,
A barrier layer made of a titanium nitride film or a tantalum film was formed below the copper film. Instead of this, a titanium film, a zirconium film, a hafnium film, a tungsten film, or a nitride film or a carbide film thereof is appropriately used. When a material that does not diffuse copper is used as the material of the interlayer insulating film deposited below the copper film, the barrier layer may not be provided.

In the first to sixth embodiments,
Although the aluminum film is used as the metal film for preventing the oxidation of the copper film, a metal film having excellent oxidation resistance, for example, a silver film or a palladium film may be used instead.

If there is a possibility that a first metal film such as a copper film and a second metal film such as an aluminum film react with each other to cause a defect in bonding characteristics or contact characteristics, the first metal film may be used. It is preferable to interpose a barrier film such as TiN film or TiW between the film and the second metal film to prevent a reaction between them.

As the first metal film, a low-resistance metal film can be appropriately used in place of the copper film or the copper alloy film.

In the first to sixth embodiments,
Although the wiring concave portion and the external electrode concave portion are formed at the same depth in the same step, they may be formed at different depths and at different steps.

Further, in the first to sixth embodiments, the entire region of the external connection electrode exposed to the external connection opening is covered with the aluminum film, but the entire region is not necessarily covered. Is also good.

[0099]

According to the semiconductor device of the present invention, the bonding wire or the bump is bonded to the second metal film having excellent oxidation resistance constituting the external connection electrode.
Even if bonding wires or bumps are bonded to the external connection electrodes while the semiconductor substrate is heated to about 200 ° C.,
Since it is difficult to form a metal film on the surface of the external connection electrode, the contact resistance of the external connection electrode is reduced and the bonding strength is improved. In addition, as the first metal, a metal which is inferior in oxidation resistance to the second metal but has low resistivity and high electromigration resistance can be used, so that the resistance of the semiconductor device is reduced. And reliability can be improved.

In the semiconductor device of the present invention, if the metal wiring and the electrode for external connection are formed so as to be embedded in the interlayer insulating film formed below the uppermost wiring layer,
The step of forming a protective film formed on the metal wiring and the external connection electrode and the step of bonding a bonding wire or a bump to the external connection electrode are facilitated.

In the semiconductor device according to the present invention, if the second metal film is formed in a region other than the peripheral portion of the first metal film, the second metal film is formed while preventing oxidation of the region where the bonding wire or the bump is bonded. Resistance can be achieved.

In the semiconductor device of the present invention, when the metal wiring and the external connection electrode have a barrier layer formed between the metal wiring and the external connection electrode, the first metal wiring and the external connection electrode constituting the metal connection and the external connection electrode are formed. The situation where metal diffuses into the interlayer insulating film can be prevented.

In the semiconductor device of the present invention, when the first metal is copper or an alloy of copper and the second metal is aluminum or an alloy of aluminum, the surface of the external connection electrode is prevented from being oxidized and contact is made. The resistance of the metal wiring can be reduced and the electromigration resistance can be improved while reducing the resistance and improving the bonding strength.

According to the first method for fabricating a semiconductor device, a buried wiring made of a first metal film can be formed, and a buried type external having a second metal film excellent in oxidation resistance on the top. Since the connection electrode can be formed, even if a bonding wire or a bump is bonded to the external connection electrode, a metal film is hardly formed on the surface of the external connection electrode, so that the contact resistance of the external connection electrode is reduced. As a result, a semiconductor device having improved bonding strength can be reliably manufactured.

In the first method for fabricating a semiconductor device, the first metal film deposition step may include a step of depositing the first metal film by a sputtering method and then flowing the same by heat treatment to fill the wiring recess. In addition, the embedded wiring can be surely formed by using a versatile device.

In the first method for manufacturing a semiconductor device, if the first metal film depositing step includes a step of depositing the first metal film by a CVD method or a plating method, the first metal film having excellent crystallinity is obtained. A film can be deposited.

In the first method for manufacturing a semiconductor device, the step of forming the recess includes the step of forming a contact hole below the wiring recess, and the first metal film depositing step includes contacting the first metal film with the contact. Including the step of depositing the hole so as to fill the hole, the connecting portion for connecting the metal wiring and the semiconductor element or the wiring layer below the metal wiring can be formed in the same step as the metal wiring. Can be achieved.

In the first method for manufacturing a semiconductor device, if the step of depositing the first metal film includes the step of forming a barrier layer between the interlayer insulating film and the first metal film, the step of depositing the metal wiring and the external connection A semiconductor device in which the first metal forming the electrode does not easily diffuse into the interlayer insulating film can be manufactured.

In the first method for fabricating a semiconductor device, the second metal film deposition step may include a step of depositing a second metal film on the first metal film via an insulating film. In the step of removing the first metal film and the second metal film, even if the first metal film and the second metal film are simultaneously immersed in an abrasive or a cleaning agent, the first metal film and the second metal film are removed. Since a battery effect does not occur between the first metal film and the second metal film, a situation in which the first metal film or the second metal film is corroded can be avoided. In addition, when a step of bonding a bonding wire or a bump to the external connection electrode so that the insulating film is broken is provided, conduction between the first metal film and the second metal film can be ensured.

According to the method of manufacturing the second semiconductor device, the buried wiring made of the first metal film can be formed, and the external connection electrode having the second metal film excellent in oxidation resistance on the top. Therefore, even if a bonding wire or a bump is bonded to the external connection electrode, it is difficult to form a metal film on the surface of the external connection electrode. A semiconductor device with improved strength can be reliably manufactured.

In the first or second method for manufacturing a semiconductor device, when the first metal is copper or an alloy of copper, and the second metal is aluminum or an alloy of aluminum, the resistance of the metal wiring can be reduced and A semiconductor device having improved electromigration resistance, reduced contact resistance of external connection electrodes, and improved bonding strength can be reliably manufactured.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views illustrating respective steps of a manufacturing process of a semiconductor device according to a first embodiment.

FIGS. 2A to 2C are cross-sectional views illustrating respective steps of a manufacturing process of the semiconductor device according to the first embodiment.

FIG. 3 is a plan view showing a state where a protective film of a semiconductor device according to a second embodiment is removed.

FIGS. 4A to 4C are cross-sectional views taken along the line XX in FIG. 3, illustrating respective steps of a manufacturing process of the semiconductor device according to the second embodiment.

FIGS. 5A to 5C are cross-sectional views taken along line XX in FIG. 3 showing respective steps of a manufacturing process of the semiconductor device according to the second embodiment.

FIGS. 6A to 6C are cross-sectional views illustrating respective steps of a manufacturing process of a semiconductor device according to a third embodiment.

FIGS. 7A to 7C are cross-sectional views illustrating respective steps of a manufacturing process of a semiconductor device according to a third embodiment.

FIGS. 8A to 8D are cross-sectional views illustrating respective steps of a manufacturing process of a semiconductor device according to a fourth embodiment.

FIGS. 9A to 9C are cross-sectional views illustrating respective steps of a manufacturing process of a semiconductor device according to a fifth embodiment.

FIGS. 10A to 10D are cross-sectional views illustrating respective steps of a manufacturing process of a semiconductor device according to a fifth embodiment.

FIGS. 11A to 11C are cross-sectional views illustrating respective steps of a manufacturing process of a semiconductor device according to a sixth embodiment.

FIGS. 12A and 12B are cross-sectional views illustrating respective steps of a manufacturing process of a semiconductor device according to a sixth embodiment.

FIGS. 13A to 13D are cross-sectional views illustrating respective steps of a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 semiconductor substrate 101 interlayer insulating film 102 wiring recess 103 external electrode recess 104 tantalum film 105 copper film 106 aluminum film 107 metal wiring 108 external connection electrode 109 silicon nitride film 110 silicon oxide film 111 external connection opening 200 semiconductor substrate Reference Signs List 201 first interlayer insulating film 202 first metal wiring 203 second interlayer insulating film 204 first resist pattern 205 concave portion for wiring 206 concave portion for external electrode 207 second resist pattern 208 contact hole 209 titanium nitride film 210 copper Film 211 aluminum film 212 metal wiring 213 external connection electrode 214 silicon nitride film 215 silicon oxide film 216 external connection opening 300 semiconductor substrate 301 first interlayer insulating film 302 first metal wiring 303 second interlayer Edge film 304 First resist pattern 305 Contact hole 306 External electrode concave portion 307 Second resist pattern 308 Wiring concave portion 309 Titanium nitride film 310 Copper film 311 Aluminum film 312 Metal wiring 313 External connection electrode 314 Silicon nitride film 315 Silicon Oxide film 316 External connection opening 400 Semiconductor substrate 401 First interlayer insulating film 402 First metal wiring 403 Second interlayer insulating film 404 Titanium nitride film 405 Copper film 406 Insulating film 407 Aluminum film 408 Metal wiring 409 External connection Electrode 410 Silicon nitride film 411 Silicon oxide film 412 External connection opening 500 Semiconductor substrate 501 Interlayer insulating film 502 Wiring recess 503 External electrode recess 504 Contact hole 505 Titanium nitride film 506 Copper film 50 Aluminum film 508 Metal wiring 509 External connection electrode 510 Contact 511 Silicon nitride film 512 Silicon oxide film 513 External connection opening 600 Semiconductor substrate 601 Interlayer insulating film 602 Wiring recess 603 External electrode recess 604 Titanium nitride film 605 Copper film 606 Silicon nitride film 607 Silicon oxide film 608 Opening for external connection 609 Aluminum film 610 Metal wiring 611 Electrode for external connection

Claims (13)

[Claims] 1. A semiconductor device comprising a metal wiring and an external connection electrode formed on an uppermost wiring layer on a semiconductor substrate, wherein the metal wiring is made of a first metal, and the external connection electrode is A first metal film made of the first metal, and a second metal formed on the first metal film and made of a second metal having better oxidation resistance than the first metal And a film. 2. The semiconductor device according to claim 1, wherein the metal wiring and the electrode for external connection are formed so as to be embedded in an interlayer insulating film formed below the uppermost wiring layer. 13. The semiconductor device according to claim 1. 3. The semiconductor device according to claim 1, wherein the second metal film is formed on a region of the first metal film excluding a peripheral portion. 4. The semiconductor device according to claim 1, wherein the metal wiring and the external connection electrode are formed between the metal wiring and an interlayer insulating film formed below the uppermost wiring layer. The semiconductor device according to claim 1, further comprising a barrier layer for preventing diffusion. 5. The semiconductor device according to claim 1, wherein the first metal is copper or an alloy of copper, and the second metal is aluminum or an alloy of aluminum. 6. A recess forming step of forming a wiring recess and an external electrode recess in an interlayer insulating film formed on a semiconductor substrate; and forming a wiring recess and an external electrode recess on the interlayer insulating film including the wiring recess and the external electrode recess. A first metal film depositing step of depositing a first metal film made of a first metal so that the wiring recess is filled and a space remains above the external electrode recess; A second metal film deposition step of depositing a second metal film made of a second metal having better oxidation resistance than the first metal on the first metal film; and And removing the first metal film so that the interlayer insulating film is exposed, thereby forming a metal wiring made of the first metal film in the wiring recess,
Forming a wiring for forming an external connection electrode comprising the first metal film and the second metal film in the external electrode recess. 7. The method according to claim 7, wherein the step of depositing the first metal film comprises:
After depositing a metal film by sputtering,
7. The method for manufacturing a semiconductor device according to claim 6, further comprising a step of flowing the metal film by heat treatment to fill the wiring recess. 8. The method according to claim 1, wherein the first metal film depositing step comprises:
7. The method according to claim 6, further comprising the step of depositing said metal film by a CVD method or a plating method. 9. The step of forming a recess includes the step of forming a contact hole below the recess for the wiring, and the step of depositing a first metal film fills the first metal film with the contact hole. 7. The method according to claim 6, further comprising the step of depositing the semiconductor device. 10. The step of depositing a first metal film includes forming a barrier layer between the interlayer insulating film and the first metal film, the barrier layer preventing diffusion of the first metal into the interlayer insulating film. 7. The method of manufacturing a semiconductor device according to claim 6, comprising a step of forming. 11. The step of depositing the second metal film includes the step of depositing the second metal film on the first metal film via an insulating film, and bonding a wire to the external connection electrode. 7. The method according to claim 6, further comprising a step of joining the bump so that the insulating film is broken. 12. A recess forming step of forming a wiring recess and an external electrode recess in an interlayer insulating film formed on a semiconductor substrate; and forming a recess on the interlayer insulating film including the wiring recess and the external electrode recess. A first metal film depositing step of depositing a first metal film made of a first metal so that the wiring recesses and the external electrode recesses are filled; Forming a metal wiring made of the first metal film in the wiring recess by removing the film so that the film is exposed; and removing the first metal film remaining in the external electrode recess. By selectively depositing a second metal film made of a second metal having better oxidation resistance than the first metal,
An external connection electrode forming step of forming an external connection electrode comprising the first metal film and the second metal film. 13. The semiconductor device according to claim 6, wherein the first metal is copper or an alloy of copper, and the second metal is aluminum or an alloy of aluminum. Production method.