JP2862727B2 - Sputtering target for forming metal thin film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering target for forming a metal thin film suitable for, for example, forming a metal thin film used as electric wiring by a sputtering method, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Heretofore, in semiconductor devices such as LSIs,
Al (aluminum) alloys have been widely used as wiring materials. In the field of high-frequency hybrid ICs, whose demand has increased due to the spread of satellite broadcasting and automobile communications, demands for high-speed signal processing and high-density wiring have led to shortening of wiring lengths and the use of thin-film technology. Therefore, the internal wiring and the like of the high-frequency hybrid IC are required to have a low-resistance wiring material such as C.
A thin film of u (copper) is widely used.

A Cu thin film usually has a purity of 99.9.
It is formed using 9% pure copper. However, since the adhesion strength to an element substrate such as SiO ₂ is weak, conventionally, a thin film of Cr (chromium) is formed on a substrate in advance and the Cr is used.
A thin film of Cu is formed on the film. Also,
In order to form a metal thin film used as an electric wiring, not only a conventional printing technique but also a sputtering method using a molded body made of a wiring material as a target has been applied.

[0004]

However, recent LSIs
The progress of manufacturing technology is remarkable, and the realization of finer wiring width has led to rapid development from LSI to ultra-LSI and further to ultra-super LSI. Then, a problem such as a signal delay due to an increase in resistance has become a concern.

In particular, in a logic semiconductor device having a large wiring area with respect to a chip area, signal delay due to an increase in resistance is becoming a serious problem. Therefore, next generation VLS
In order to realize I, a wiring material having lower resistance and higher reliability is required.

As described above, at present, Al alloys and C
u thin film is widely used as a wiring material.
The wiring made of the alloy has a higher specific resistance than pure metal Al. In addition, there are uneasy materials such as disconnection due to electromigration and stress migration, precipitation of Si (silicon) at contact portions, and generation of hillocks due to heat treatment. There are many problems in promoting high integration and high speed in the future.

High melting point metals and Cu have been reconsidered as wiring materials that can be converted to such Al alloys, but high melting point metals generally have a problem of high specific resistance. On the other hand, C
u has low adhesion strength to SiO _{2 serving as} an element substrate,
As described above, conventionally, a film is formed on an element substrate via a Cr thin film.
It has also been pointed out that the thin film of u is affected by high-resistance Cr, making it difficult to improve the frequency characteristics. Also, C
The problem that the u thin film has poor corrosion resistance has also been pointed out.

However, Cu has excellent properties as a wiring material, such as low bulk resistance and resistance to electromigration and the like as compared with Al, and Cu is not easily discarded. Therefore, alloying and the like have been studied to improve the corrosion resistance of Cu and the adhesion strength to the element substrate, but segregation of additional elements in the ingot when casting the alloy, shrinkage cavities during casting, Since many problems such as coarsening of the crystal grains of the lump were left, they were not put to practical use.

The present invention has been made in view of the above circumstances, and when forming a metal thin film to be used as an electric wiring by a sputtering method, it has a high corrosion resistance, a high adhesion strength to an element substrate, etc. An object of the present invention is to provide a sputtering target for forming a metal thin film and a method for manufacturing the same, which can form a copper alloy thin film that is resistant to migration and the like, and is suitable as a wiring material for miniaturization of wiring of semiconductor elements and the like in the future. And

[0010]

The sputtering target for forming a metal thin film according to claim 1 has a purity of 99.
High-purity copper of 9999% by weight or more is used as a base metal, and titanium having a purity of 99.9% by weight or more is added to the base metal by 0.04%.
It is characterized in that a target material made of a high-purity copper alloy is obtained by adding about 0.15% by weight.

[0011] The sputtering target for forming a metal thin film according to the second aspect is characterized in that high purity copper having a purity of 99.9999% by weight or more is used as a base metal, and the base metal has a purity of 9%.
9.9999% by weight or more of zinc in 0.014 to 0.02
A target material made of a high-purity copper alloy is obtained by adding 1% by weight.

According to a third aspect of the present invention, there is provided a method for manufacturing a sputtering target for forming a metal thin film, comprising mixing and melting a base metal and an additive element in accordance with the composition ratio of the high-purity copper alloy according to the first or second aspect. A target base material having a predetermined cross-sectional shape is formed by charging the molten metal in a tank and continuously casting the molten metal in a vacuum or under an inert gas atmosphere, and processing the target base material into a sputtering target for forming a metal thin film. It is characterized by the following.

[0013]

The sputtering target for forming a metal thin film according to the first and second aspects has a high corrosion resistance when used for forming a metal thin film to be used as an electric wiring by a sputtering method, and furthermore, has a high resistance to element substrates and the like. It is possible to provide a copper alloy thin film having a high adhesion strength and a high resistance to electromigration and the like, and it is a wiring material suitable for miniaturization of wiring of semiconductor elements and the like in the future.

Further, according to the method for manufacturing a sputtering target for forming a metal thin film according to the third aspect, casting defects such as segregation of an additional element and shrinkage cavities are prevented. It is possible to manufacture a high quality sputtering target for forming a metal thin film.

[0015]

【Example】

[First Embodiment] FIG. 1 shows a processing procedure of a first embodiment of a method of manufacturing a sputtering target for forming a metal thin film according to the present invention, and FIG. 2 is a schematic diagram of an apparatus used in the first embodiment. It is shown.

The first embodiment has a purity of 99.99999.
% Or more of high-purity copper as a base metal, and 0.04% by weight of Ti (titanium) having a purity of 99.9% by weight or more.
A sputtering target for forming a metal thin film made of a high-purity copper alloy to which 0.15% by weight is added.

First, an apparatus to be used will be described with reference to FIG. This device is a casting device for continuous casting.
In FIG. 2, reference numeral 1 denotes a carbon crucible as a melting tank for obtaining a molten copper alloy, 2 denotes a heater for melting the alloy material charged in the carbon crucible 1, and 3 denotes the carbon for continuous casting. A carbon mold placed in the lower part of the crucible 1, 4 is a starter bar (dummy bar) for guiding the molten metal in the carbon crucible 1 to the carbon mold 3 at the time of starting casting, and 5 is to promote cooling of the molten molten metal. A water-cooled jacket, 6 is a drawer roll for gradually drawing a cast product (continuous plate-shaped ingot) cast with the carbon mold 3, and 8 is a hermetically-sealed periphery for performing continuous casting under a predetermined atmosphere. The main body of the device. Device body 8
Is equipped with a vacuum seal 9 as a casting outlet.
Further, a vacuum connection unit 10 for providing a vacuum atmosphere in the enclosed space and an inert gas supply unit 11 for providing an inert gas atmosphere are connected via a valve 12.

Next, the manufacturing method of the first embodiment will be described with reference to FIG. First, high-purity copper having a purity of 99.9999% by weight or more and Ti having a purity of 99.9% or more are mixed according to the composition ratio of the high-purity copper alloy described above (step 101). Then, the mixed material is put into the carbon mold 3 and is placed under an inert gas atmosphere with an Ar gas (degree of vacuum: 1).
A target base material having a predetermined cross-sectional shape is formed by continuously casting a molten metal at (× 10 ⁻⁴ Torr) (Step 102).

Generally, it has been very difficult to obtain a copper alloy as a target material in which an additive element is uniformly dispersed by a casting method. However, segregation of additional elements can be prevented by rapidly solidifying the molten metal by the cooling effect of the water cooling jacket 5 and the like.
Continuous casting makes it possible to prevent casting defects such as shrinkage cavities and coarse crystal grains.
In fact, the target base material (ingot) obtained by the above-mentioned manufacturing process was a sound material having no shrinkage cavities and preventing the segregation of added elements.

Next, if necessary, mechanical processing such as rolling or grinding is performed (step 103), and a sputtering target for forming a metal thin film is cut out from the target base material (step 104).

In the first embodiment, a sputtering target for forming a metal thin film having a diameter of 5 inches and a thickness of 5 mm was obtained by the above manufacturing steps. Then, this target was mounted on a sputtering apparatus, and sputtering was performed under the conditions of an Ar gas pressure of 3 × 10 ⁻³ Torr and an input power of 1500 W, and a high-purity Cu—Ti alloy film (hereinafter referred to as “SiO _2” ) was formed on an element substrate such as SiO _2. , Simply referred to as a Cu-Ti film). The film thickness was 3000 Å.

The resistivity (unit: μΩcm) of the thus formed Cu—Ti film was measured. Also,
In order to investigate the effect of the addition of Ti on the resistivity, the inventors of the present application varied the addition ratio of Ti variously in the range of 0.02 to 0.2% by weight, and Sputtering targets for forming a metal thin film were manufactured by the same manufacturing method, and a Cu—Ti film was formed on those sputtering targets in the same manner, and the resistivity was measured. The measurement of the resistivity was performed by applying a current of 4 mA at 20 ° C. Table 1 below shows the measurement results. In this resistivity measurement, the annealing condition was set at 250 ° C. in an Ar gas atmosphere.
1 hour. Further, Table 1 shows the measurement results when the addition ratio of Ti is 0.029% by weight, 0.040% by weight, and 0.110% by weight as the metal composition of the sputtering target. Further, for reference, pure copper having a purity of 99.99% by weight (described as 4N in Table 1), pure copper having a purity of 99.9999% by weight (described as 6N in Table 1), pure copper The measurement results of the metal Al under the same conditions were also shown.

[0023]

[Table 1] As shown in Table 1, Cu formed by a sputtering target obtained by adding Ti to high-purity copper.
-In the case of the Ti film, under the annealing conditions, the resistivity tends to increase in accordance with the increase in the addition rate of Ti, but at any addition rate, a better resistivity than that in the case of Al is obtained. Was confirmed.

Further, for each of the above-mentioned Cu-Ti films,
After performing a heat treatment at 250 ° C. for 1 hour in an Ar gas atmosphere, the sample is immersed in a 1N saline solution at a liquid temperature of 35 ° C. for a certain period of time, and the change with time of the reflectance at that time is measured. The corrosion resistance of each of the different Cu—Ti films was evaluated. FIG. 3 shows the evaluation results of the corrosion resistance.

In FIG. 3, the vertical axis indicates the change in the reflectance (the ratio between the reflectance Rc after immersion in a saline solution and the reflectance Ri before the evaluation test), and the horizontal axis indicates the passage of time. I have. In the figure, curve 20 is for a metal thin film made of pure metal Al, and curve 21 is for the case where the Ti addition rate is 0.1 mm.
Curve 22 is for a Cu-Ti film formed with a target having a Ti addition rate of 0.040% by weight, and curve 23 is for a Cu-Ti film formed with an 11% by weight target. Curve 24 for a Cu-Ti film formed with a target having a Ti addition rate of 0.029% by weight;
Curve 25 is for a metal thin film of high purity pure copper having a purity of 99.9999% by weight, and curve 26 is for a Cu—Ti film formed with a target having a Ti addition rate of 0.26% by weight.

As shown in FIG. 3, the Cu—Ti films formed with the targets having the Ti addition rates of 0.040% by weight and 0.11% by weight all have a purity of 99.9%.
It shows higher corrosion resistance than a metal thin film formed by 9% by weight of pure copper, and at a Ti addition rate of 0.11% by weight, it is quite close to a metal thin film of pure metal Al. However, when the addition ratio of Ti was further increased to 0.26% by weight, the corrosion resistance was reduced.

In order to further investigate the relationship between the Ti addition rate and the corrosion resistance, the present inventors conducted similar evaluations of the corrosion resistance by changing the Ti addition rate more finely. As a result, a high-purity copper alloy obtained by using high-purity copper having a purity of 99.9999% by weight or more as a base metal and adding 0.04 to 0.15% by weight of Ti having a purity of 99.9% by weight or more to the base metal In the case of a sputtering target for forming a metal thin film made of a metal, the corrosion resistance is superior to that of a metal thin film made of pure copper having a purity of 99.99% by weight, and a metal thin film having a corrosion resistance close to that of a metal thin film made of pure metal Al is obtained. I confirmed that

High purity copper having a purity of 99.9999% by weight or more is used as a base metal, and the base metal has a purity of 99.9999% by weight or more.
For a sputtering target for forming a metal thin film made of a high-purity copper alloy to which 0.04 to 0.15% by weight of Ti of 9% by weight or more is added, a Cu—Ti film is formed on a glass substrate by a sputtering method. The adhesion strength of the Cu—Ti film was evaluated by a tensile method.
The adhesion strength of a metal thin film made of pure copper having a purity of 99.99% by weight was about 89 kg / cm ² , and the adhesion strength of a metal thin film made of pure copper having a purity of 99.9999% by weight was about 102 kg / cm ^2. In the case of the Ti film, an adhesion strength of 150 kg / cm ² or more was obtained at any addition ratio, and it was confirmed that the adhesion strength was significantly improved. Table 2 below summarizes the above evaluation results. In Table 2, "4N" indicates a metal thin film made of pure copper having a purity of 99.99% by weight, and "6N" indicates a metal thin film having a purity of 99.99% by weight.
A metal thin film made of 9.9999% by weight pure copper is shown.
"u-Ti" refers to a Cu-Ti film formed with a target having a Ti addition rate of 0.04 to 0.15% by weight, and "Cu-Ti film"
"-Zn" indicates a metal thin film formed using a target containing Zn as an additional element described in a second embodiment described later.

[0029]

[Table 2] As described above, the sputtering target for forming a metal thin film manufactured in the first embodiment has high corrosion resistance when used for forming a metal thin film to be used as an electric wiring by a sputtering method, and furthermore has an element substrate and the like. It is possible to provide a copper alloy thin film which has a high adhesive strength to the substrate and is resistant to electromigration and the like, and is a wiring material suitable for miniaturization of wiring of semiconductor elements and the like in the future.

[Second Embodiment] The present inventors of the present invention, as a second embodiment of the method of manufacturing a sputtering target for forming a metal thin film according to the present invention, use Zn (zinc) as an additive element.
A sputtering target for forming a metal thin film made of a high-purity copper alloy using the above method was manufactured.

In the case of the second embodiment, the sputtering target for forming a metal thin film to be manufactured has a purity of 99.9.
High-purity copper of 999% by weight or more is used as a base metal, and Zn having a purity of 99.9999% by weight or more is added to the base metal by 0.0%.
14 to 0.021% by weight was added.

Except that the additive element is Zn having a purity of 99.9999% by weight or more and the addition rate is changed to 0.014 to 0.021% by weight, other conditions in the production are as follows.
All were manufactured according to the first embodiment.

That is, first, the purity is 99.9999% by weight.
The high-purity copper and Zn having a purity of 99.9999% or more are mixed in accordance with the composition ratio of the high-purity copper alloy described above.
Next, the mixed material is put into the carbon mold 3, and Ar
A target base material having a predetermined cross-sectional shape is formed by continuously casting a molten metal under an inert gas atmosphere.

Then, if necessary, mechanical processing such as rolling or grinding is performed to cut out a sputtering target for forming a metal thin film from the target base material.

In the second embodiment, a sputtering target for forming a metal thin film having a diameter of 5 inches and a thickness of 5 mm was obtained by the above manufacturing steps. Then, wearing the target in a sputtering apparatus, Ar gas pressure 3 × 10 ^-3 Torr, a sputtering input power under the condition of 1500 W, a high-purity Cu-Zn alloy layer on the element substrate of SiO ₂ or the like (hereinafter , Simply referred to as a Cu-Zn film). The film thickness was 3000 Å.

The resistivity (unit: μΩcm) of the Cu—Zn film thus formed was measured in the same manner as in the first embodiment. In order to investigate the effect of the addition of Zn on the resistivity, only the Zn addition rate was set to 0.005 to 0.050.
The sputtering target for forming a metal thin film is manufactured by the same manufacturing method as that of the second embodiment while changing variously in the range of the weight%, and the Cu-Zn film is similarly formed on those sputtering targets. After the formation, the resistivity was measured. The measurement of the resistivity was performed by applying a current of 4 mA at 20 ° C. Table 3 below shows the measurement results. In this resistivity measurement, the annealing condition was set to 250 under an Ar gas atmosphere.
C. and 1 hour. In Table 3, sputtering
As the metal composition of the target, the addition rate of Zn is 0.01
4% by weight, 0.021% by weight, 0.0%
The measurement results at 40% by weight are shown. Further, for reference, pure copper having a purity of 99.99% by weight (in Table 3,
4N), pure copper having a purity of 99.9999% by weight (described as 6N in Table 3), and pure metal Al also showed measurement results under the same conditions.

[0037]

[Table 3] As shown in Table 3, Cu formed by a sputtering target obtained by adding Zn to high-purity copper.
It was confirmed that the -Zn film provided higher resistivity than that of pure copper but better resistivity than that of Al at any addition ratio.

Further, for each of the aforementioned Cu-Zn films,
After performing a heat treatment at 250 ° C. for 1 hour in an Ar gas atmosphere, the sample is immersed in a 1N saline solution at a liquid temperature of 35 ° C. for a certain period of time, and the time-dependent change in the reflectance at that time is measured. The corrosion resistance of each of the Cu—Zn films different from each other was evaluated. FIG. 4 shows the evaluation results of the corrosion resistance.

In FIG. 4, the vertical axis indicates the change in the reflectance (the ratio between the reflectance Rc after immersion in a saline solution and the reflectance Ri before the evaluation test), and the horizontal axis indicates the passage of time. I have. In the figure, a curve 30 is for a thin metal film made of pure metal Al, and a curve 31 is for a case where the Zn addition rate is 0.1 mm.
Curve 32 for a Cu—Zn film formed with a target of 014% by weight shows that the Zn addition rate is 0.021% by weight.
Curve 33 is for a Cu—Zn film formed with a target having a Zn addition rate of 0.040% by weight, and curve 34 is for a Cu—Zn film formed with the target No.
Formed with a target having an addition rate of 0.009% by weight of C
For the u-Zn film, curve 35 shows a purity of 99.99.
Curve 36 is for a thin metal film of pure copper with a purity of 99.9999% by weight, for a metal thin film of pure copper at weight%.

As shown in FIG. 4, the Cu—Zn film formed by the targets having the Zn addition ratios of 0.009% by weight and 0.040% by weight has a purity of 99.99% by weight.
Shows higher corrosion resistance in part of the elapsed time than the metal thin film formed of pure copper. On the other hand, the Cu—Zn film formed by using targets having Zn addition rates of 0.014% by weight and 0.021% by weight has a longer elapsed time than a metal thin film formed by pure copper having a purity of 99.99% by weight. , A high corrosion resistance was exhibited in the entire region, and an appearance close to that of a metal thin film made of pure metal Al was confirmed.

In order to further investigate the relationship between the Zn addition rate and the corrosion resistance, the present inventors conducted similar evaluations of the corrosion resistance by changing the Si addition rate more finely. As a result, high-purity copper having a purity of 99.9999% by weight or more is used as the base metal, and the purity of the base metal is 99.9999% by weight.
In the case of a sputtering target for forming a metal thin film made of a high-purity copper alloy to which 0.014 to 0.021% by weight of Zn is added, the corrosion resistance is higher than that of a metal thin film made of pure copper having a purity of 99.99% by weight. It was confirmed that a metal thin film having excellent corrosion resistance and a corrosion resistance close to that of a metal thin film made of pure metal Al was obtained.

Further, high-purity copper having a purity of 99.9999% by weight or more is used as a base metal.
For a sputtering target for forming a metal thin film made of a high-purity copper alloy to which 0.014 to 0.021% by weight of Zn of 9999% by weight or more is added, a Cu—Zn film is formed on a glass substrate by a sputtering method. The Cu
-The adhesion strength of the Zn film was evaluated by a tensile method. In the case of the Cu—Zn film, an adhesive strength of 150 kg / cm ² or more was obtained at any of the addition rates (see Table 2 above), and it was confirmed that the adhesive strength was also significantly improved. Was.

As described above, the sputtering target for forming a metal thin film manufactured in the second embodiment has high corrosion resistance when used for forming a metal thin film to be used as an electric wiring by a sputtering method, and has a high corrosion resistance. Strong copper alloy thin film with high adhesion strength to element substrate etc.
It is a wiring material suitable for miniaturization of wiring of semiconductor elements and the like in the future.

[0044]

According to the first and second aspects of the present invention, the sputtering target for forming a metal thin film has high corrosion resistance when used for forming a metal thin film used as an electric wiring by a sputtering method, and furthermore, an element substrate or the like. It is possible to provide a copper alloy thin film which has a high adhesive strength to the substrate and is resistant to electromigration and the like, and is a wiring material suitable for miniaturization of wiring of semiconductor elements and the like in the future.

Further, according to the method for manufacturing a sputtering target for forming a metal thin film according to the third aspect, casting defects such as segregation of additional elements and shrinkage cavities are prevented. It is possible to manufacture a high quality sputtering target for forming a metal thin film.

[Brief description of the drawings]

FIG. 1 shows a sputtering method for forming a metal thin film according to the present invention.
It is a process explanatory view of a manufacturing method of a target.

FIG. 2 shows a sputtering method for forming a metal thin film according to the present invention.
It is a block diagram of the casting apparatus used by the manufacturing method of a target.

FIG. 3 is a diagram showing the corrosion resistance of the high-purity copper alloy manufactured in the first embodiment of the present invention.

FIG. 4 is a diagram showing the corrosion resistance of the high-purity copper alloy manufactured in the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon crucible 2 Heater 3 Carbon mold 4 Starter bar 5 Water cooling jacket 6 Drawer roll 8 Main unit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Nagatoshi Nagata 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd. (56) References JP-A-5-125523 (JP, A) JP-A-1 JP-A-96376 (JP, A) JP-A-1-96374 (JP, A) JP-A-61-272371 (JP, A) JP-A-2-311394 (JP, A) JP-A-64-75144 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 14/34 C22C 9/00

Claims (3)

(57) [Claims] 1. A high purity copper having a purity of 99.9999% by weight or more is used as a base metal, and 0.04 to 0.15% by weight of titanium having a purity of 99.9% by weight or more is added to the base metal. A sputtering target for forming a metal thin film, wherein the sputtering target is a high-purity copper alloy target material. 2. High purity copper having a purity of 99.9999% by weight or more is used as a base metal, and the base metal has a purity of 99.99% by weight.
0.014 to 0.021% by weight of 99% by weight or more of zinc
A sputtering method for forming a metal thin film, characterized in that a high-purity copper alloy target material is obtained by adding
target. 3. A base metal and an additive element are mixed in accordance with the composition ratio of the high-purity copper alloy according to claim 1 or 2, and the mixture is put into a melting tank, and the molten metal is placed in a vacuum or under an inert gas atmosphere. A method of manufacturing a sputtering target for forming a metal thin film, comprising forming a target base material having a predetermined cross-sectional shape by continuous casting, and processing the target base material into a sputtering target for forming a metal thin film.