TW201337021A - Sputtering target - Google Patents

Abstract

The purpose of the present invention is to provide a sputtering target that prevents the occurrence of coarse clusters such as particles, splashes, and dust during sputtering of a target and that enhances the uniformity of the thickness of a thin film formed by sputtering. The sputtering target is composed primarily of copper of a purity of 99.9 mass% or more and is characterized by containing 10 ppm or less of sulfur (S) and 2 ppm or less of lead (Pb), and is preferably characterized in that the purity of the copper is 99.96 mass% or more.

Description

Sputter target

The present invention relates to a sputtering target made of high-purity copper for forming, for example, a metal thin film constituting a flat panel display element typified by a liquid crystal display, and a photomask for manufacturing a semiconductor element. A light-shielding film, a metal wiring constituting a semiconductor element such as an LSI, and a copper thin film constituting a magnetic recording medium.

A sputtering method is used to form the copper thin film or the like on the object to be sputtered.

The sputtering method is a film formation method of forming a thin film having the same composition as that of a target on a sputtering target by the following steps: sputtering the target (hereinafter referred to as "target") to face a substrate or the like In a form, a gas such as Ar is introduced under a vacuum condition, and a voltage is applied between the sputtered surface of the target and the object to be sputtered by applying a voltage, and the ionized Ar is struck against the target.

Such a sputtering method is used in various fields such as a semiconductor element, a magnetic recording medium, a photomask for manufacturing a semiconductor element, and a liquid crystal display, etc., in accordance with a program for various purposes.

However, the sputtering material from the target is originally adhered to a sputtering target object such as a substrate facing the sputtering target, but is not necessarily limited to vertical sputtering, and is splashed in various directions.

Such a spattery substance is referred to as a granule, and when it is clustered and directly adhered to a substrate, or when it is attached to a device in a sputtering apparatus other than the substrate, it may be peeled off and suspended to adhere to the substrate.

In the sputtering method, such various phenomena are the main cause of coarse clusters such as particles, splashes, and dust, and the problem of uniformity of film thickness is impaired.

In order to solve such a problem, various literatures have been proposed to review the sputtering conditions such as the gas pressure, the input power, and the distance between the target and the substrate in the sputtering process.

It is considered that the problem of abnormal film formation such as occurrence of coarse clusters is caused by the surface state such as the orientation of the target itself and the surface roughness, in addition to the sputtering treatment conditions.

For example, if there is a crack (瑕疵) on the surface of the target, the electric charge will concentrate on the edge (end) of the crack portion, and an abnormal discharge (arc) will occur. As a result, the occurrence of spatter due to the arc increases, and film formation abnormality occurs, and the failure of the film formation to the wiring pattern increases, which causes a problem of a decrease in yield.

From this background, the number or size of cracks on the target surface should be reduced, and in recent years there have been various proposals for the state of the target surface.

For example, "sputter target and its manufacturing method" of Patent Document 1 is also one of them.

Patent Document 1 discloses that a specific surface roughness which can reduce the generation of nodules and particles can be adjusted by applying, for example, machining, polishing, chemical etching, or the like to the sputtering target as a sputtering target. Sputter target and its manufacturing method.

As in the above-described Patent Document 1, in order to improve the surface state of the target itself, it is proposed to have the surface roughness or the tissue alignment of the target itself. However, it hardly understands the literature on the composition of the target itself or its content, and has little focus on the composition of the target element to increase the uniformity of the film thickness.

Specifically, the previous technology for focusing on the composition of target elements is just to understand In order to reduce the unstable characteristics of the MOS characteristics, the following techniques are proposed: a technique for reducing the content of an alkali metal such as sodium or potassium as an impurity contained in the target itself, or a technique for reducing the content of heavy metals such as iron and nickel in order to prevent oxidation; In the present state, there is a problem that the film formation abnormality may not be sufficiently prevented from occurring along with the crack of the target surface.

[Patent Document 1] Japanese Patent Laid-Open No. Hei 11-1766

Accordingly, the present invention provides a sputtering target, which aims to prevent spatter from occurring during sputtering of a target and to improve uniformity of film thickness formed by sputtering.

The present invention is a sputtering target containing copper having a purity of 99.9% by mass or more as a main component, and is characterized by containing 10 ppm or less of sulfur (S) and 2 ppm or less of lead (Pb). The ppm here means the mass ppm.

In one aspect of the invention, the purity of the copper is 99.96 mass% or more.

According to the above configuration, it is possible to form a target in which the crack (瑕疵) having a width larger than the specific size of the sputtering surface and the inside is greatly reduced, so that abnormal discharge (arc) during the sputtering process can be prevented from occurring.

Thereby, it is possible to provide a sputtering target which prevents spattering during sputtering of the target and improves the uniformity of the film thickness of the thin film formed by sputtering.

In the present embodiment, the sputtering target is preferably 99.96 mass% or more, and more preferably 99.99 mass% or more. However, the sputtering target is not particularly limited as long as it is 99.9% by mass or more.

That is, the main component copper of the sputtering target of the present invention contains not only oxygen-free copper (99.96% or more of high-purity copper) but also refined copper.

In the sputtering target, at least the average crystal grain size of the sputtering surface is preferably 200 μm or less, but the average crystal grain size of the sputtering surface is not particularly limited.

The shape of the sputtering target of the present invention is not limited, and examples thereof include a cylindrical shape, a plate shape, and a strip shape.

The method for producing the target of the present invention is also not particularly limited. In other words, the method of adjusting the content of sulfur (S) to 10 ppm or less and the content of lead (Pb) to 2 ppm or less is not particularly limited.

For example, in copper refining, sulfur (S) or lead (Pb) may be removed as much as possible, and then sulfur (S) and lead (Pb) may be added during casting of the ingot to make sulfur (S) and lead ( The content of Pb) is adjusted so as to satisfy a range of a specific weight% or less.

Here, the method of removing sulfur (S) or lead (Pb) during copper refining (copper refining method) is also not limited. For example, sulfur (S) can be deoxygenated, for example, by blowing oxygen, desulfurization, and then producing oxygen-free. When copper is used, it is removed.

Lead (Pb) can be removed, for example, by electric refining. However, when copper is desired to be more highly purified, it can be removed by using a zone melting method or the like.

According to the present invention, it is possible to provide a sputtering target which prevents spattering during sputtering of a target and improves uniformity of film thickness formed by sputtering.

Fig. 1 is a graph showing the relationship between the number of cracks corresponding to the sulfur content of the target and the lead content.

Fig. 2 is a graph showing the relationship between the number of cracks corresponding to the sulfur content of the target and the lead content.

Fig. 3 is a graph showing the relationship between the number of cracks and the number of arcs.

Fig. 4 is a photograph showing a crack portion conforming to the definition of the crack of the target surface.

Figure 5 is a photograph showing a small flaw that does not conform to the definition of the crack of the target surface.

An embodiment of the present invention will be described below.

In the present embodiment, the sputtering target contains copper having a purity of 99.9 (3N)% by mass or more as a main component, and contains 10 ppm or less of sulfur (S) and 2 ppm or less of lead (Pb).

Others include chemical components such as bismuth (Bi), selenium (Se), and tellurium (Te) at a suitable mass% concentration.

Further, at least the sputtering target surface of the sputtering target has an average crystal grain size of 200 μm or less, for example, a cylindrical large-sized cylindrical target having an outer diameter of 150 mm or more and a wall thickness of 20 mm or more.

The method for producing the above-described sputtering target will be described below.

Cokes or the like as a copper raw material is added and cokeed in a melting furnace, whereby an intermediate product mainly obtained by removing copper from copper matte is obtained. Next, the matte is placed in a revolving furnace, oxygen is blown in, and impurities such as sulfur are oxidized to refine the blister copper (the copper content is about 98%). At this time, the crude copper can be reduced by performing a high temperature exceeding 2000 °C.

Thereafter, the blister copper can be refined into 99.99% or more of pure copper by electrolytic refining in a nitric acid bath or a sulfuric acid bath.

In this way, in addition to reducing sulfur (S) and lead (Pb) as much as possible, copper is also reduced in the amount of other impurities such as bismuth (Bi), selenium (Se), and strontium (Te), and vacuum induction melting is performed. . Further, sulfur (S) and lead (Pb) are added to control the content of sulfur (S) to be 10 ppm or less, and the content of lead (Pb) is 2 ppm or less, thereby obtaining a purity of 99.9 (3N). An ingot having a mass% or more of copper as a main component and containing 10 ppm or less of sulfur (S) and 2 ppm or less of lead (Pb).

Next, the ingot is cut into a specific size to prepare a billet for thermal processing.

In particular, for example, an embryo having a diameter of 300 mm and a mass of 300 kg to 400 kg is produced to manufacture a large-sized target.

Further, the embryo which is a material for hot working may be formed into a cylindrical shape or a plate shape and the like which is suitable for the subsequent processing operation, but the embryo is formed into a cylindrical shape in order to obtain a cylindrical sputtering target.

The sputtering target system is formed by using the above-described hot extrusion embryo and sequentially subjected to a thermal processing step, a cold working, and a strain removal annealing step.

In detail, the hot working is a step of performing appropriate processing such as hot extrusion processing, hot press processing, hot forging or hot rolling on an embryo made of high-purity copper by means of the hot working to give strain. The embryo is subjected to thermal processing in a fixed amount of processing.

Then, the above-described processing amount is appropriately defined by a ratio of the thickness reduction (depression amount) to the initial thickness multiplied by 100% or by a shear strain amount.

In particular, when the hot extrusion step is performed as a hot working, the hot working is prepared in advance, and even if the hot working embryo exceeds a temperature of 500 ° C, it is then hot extruded at 600 to 900 ° C.

The subsequent cold working is a step of performing suitable processing such as cold rolling, cold forging, cold extrusion, etc. on the hot-worked material, and cooling processing at a temperature of 80 to 120 ° C / sec for the hot-worked material, for example, by cold rolling. Cooling to about room temperature, reducing the diameter under the following conditions: under atmospheric conditions, the cylindrical hot-worked material is subjected to a reduction ratio of strain of 15% or more at least once per cold drawing; The final thickness of the target is required.

Then, the above-mentioned reduction ratio is defined by a ratio obtained by multiplying the ratio of the thickness reduction amount (depression amount) to the initial thickness by 100%, or by a shear strain amount.

In the second strain annealing step, the cold drawn material after cold working is subjected to annealing, for example, at a temperature ranging from 300 ° C to 600 ° C to be re-synthesized as copper.

More preferably, the residual stress (strain) of the target can be removed by annealing at a temperature ranging from 300 ° C to 500 ° C for about 1 hour.

Furthermore, the strain relief annealing step is performed under atmospheric conditions, or the target is annealed in a protective environment in order to minimize oxidation of the target.

Since the strain present in the sputter target has an effect on the splash of the target material, the strain-removal annealing step is effective in that it can remove the internal stress causing the main cause of the strain. However, if the annealing temperature is too low, recrystallization does not occur. If the annealing temperature is too high, excessive growth of the particles occurs. Therefore, if this point is considered, it is necessary to set an appropriate annealing temperature of, for example, 250 ° C or higher.

By the above-described steps, a sputtering target containing copper (S) having a purity of 99.9% by mass or more and containing 10 ppm or less of sulfur (S) and 2 ppm or less of lead (Pb) can be produced.

When the content of sulfur (S) and lead (Pb) is 10 ppm or less and 2 ppm or less, the sputtering target can be produced, and the thickness can be reduced to less than the specific surface size (sputtered surface) and the internal size of the sputtering target. After that.

In detail, the heat of the hot working step of the embryo is caused to cause the crystal grain size of the embryo to become large and surface roughness such as cracks to be generated, but it has been previously known to prevent such a phenomenon by adding sulfur (S). And so on. On the other hand, it is also known that when sulfur (S) is added to, for example, 18 ppm or more, adverse damage such as fine cracks occurs in the tissue.

Therefore, it is important to set the content of sulfur (S) to a specific mass% or less, and it has been found that the target of the present embodiment is not limited to the sulfur (S) content, and the sulfur (S) content is also set to 10 ppm or less. The content of lead (Pb) is set to 2 ppm or less, whereby the target surface and the inside can be reduced.

Thereby, the number of occurrences of the arc generated from the target can be reduced during the sputtering process, and the prevention The occurrence of coarse clusters such as splashing is prevented, and the uniformity of the film thickness formed by sputtering is improved.

In particular, in recent years, it has been used as a liquid crystal display for large televisions. For example, a substrate size such as a substrate size of more than 2 m is required to be enlarged, and accordingly, it is necessary to form a film onto a large substrate or wafer in the sputtering step of forming wiring.

Therefore, the sputtering target itself is also enlarged, and each part of the target is sputtered. The organization is prone to non-uniformity, and has a problem that the film thickness accuracy and the occurrence of coarse clusters become large.

Furthermore, large-scale sputtering targets are sputtered for film formation onto large substrates or wafers. In the case of treatment, the applied voltage applied during the sputtering process must also be increased. Therefore, in the case where there is a flaw (crack) of a specific size or more on the sputtering surface, there is a problem that the number of arc generations increases.

In this way, when using a large sputtered object, the following will occur. A significant problem is that the occurrence of spatter due to an arc increases, and film formation abnormality occurs, and the film formation to the wiring pattern fails.

On the other hand, the sputtering target of the present embodiment has a sulfur (S) content of 10 ppm. By setting the content of lead (Pb) to 2 ppm or less, the target surface and the inside of the target can be reduced, and the number of occurrences of arcing from the target can be reduced during the sputtering process, so that the substrate can be prevented in particular. Or the problem that the number of arc occurrences becomes obvious when the wafer is enlarged, and a large substrate or wafer can also improve the film formation accuracy.

Hereinafter, an effect confirmation experiment will be described.

(Effect confirmation experiment 1)

In the effect confirmation experiment 1, sulfur is used as an unavoidable impurity contained in the ingot. The difference between the content ratio of (S) and lead (Pb) to produce the target of the prior art and the target of the present embodiment, and the number of cracks on the target surface generated by the sputtering treatment of each separately manufactured target The number of occurrences of the arc is detected.

Further, the sputtering treatment was performed by using a DC magnetron sputtering apparatus, and was treated as a sputtering condition with the following settings: a vacuum plating of 4 × 10 ^-5 Pa was reached, an argon pressure was 0.3 Pa, and an oxygen partial pressure was 1 × 10 ^-3 Pa, and the input electric quantity is 2 W/cm ² .

Further, in the effect confirmation experiment 1, a plate-shaped sputtering target having a thickness of 30 mm was used.

In the target of the prior art, the chemical component contained in the target and the content thereof are oxygen-free copper for an electron tube satisfying the specifications of JIS H3100-C1020.

In detail, the target system has a sulfur (S) of 18 ppm or less, a lead (Pb) of 10 ppm or less, a bismuth (Bi) of 3 ppm or less, and a true (Te) of 5 ppm or less, and a copper purity of 99.9% by mass or more. Main ingredient.

However, the previous target is a sulfur (S) content of 10 ppm or less, but a lead (Pb) content of more than 2 ppm, a lead (Pb) content of 2 ppm or less, but a sulfur (S) content of more than 10 ppm, or The content of sulfur (S) is greater than 10 ppm and the content of lead (Pb) is greater than 2 ppm.

Specifically, six samples of the previous examples 1 to 5 and the comparative examples were prepared as targets of the prior examples, and the contents of sulfur (S) and lead (Pb) are shown in Table 1, respectively. 15 ppm and 5 ppm, the former example 2 was 15 ppm and 2 ppm, the former example 3 was 15 ppm and 1 ppm, the previous example 4 was 10 ppm and 5 ppm, the previous example 5 was 5 ppm, 5 ppm, and the comparative example was 8 ppm and 5 ppm.

Further, the target of the comparative example used the same chemical composition as the copper ingot of the example disclosed in "Patent No. 3975414".

【Table 1】

On the other hand, the target of the example has copper having a purity of 99.9% by mass or more as a main component, and contains 10 ppm or less of sulfur (S) and 2 ppm or less of lead (Pb).

Specifically, four kinds of samples of Examples 1 to 4 were produced as targets of the present example, and the contents of sulfur (S) and lead (Pb) were as shown in Table 1, and Example 1 was 10 ppm. 2 ppm, Example 2 was 10 ppm and 1 ppm, Example 3 was 5 ppm and 2 ppm, and Example 4 was 5 ppm and 1 ppm.

Further, Table 1 shows the contents of sulfur (S) and lead (Pb) in each of the previous examples, comparative examples, and examples, and the experimental results described later show cracks in the target surfaces of each of the prior examples and examples. The number of arcs that occur during the sputtering process.

Regarding the experimental results, the number of cracks on the target surface of the previous examples 1 to 5, the comparative examples, and the examples 1 to 4 [one/100 mm ² ], and the number of arc occurrences in the sputtering process are as shown in Table 1, FIG. 1, FIG. 2, and Figure 3 shows.

Further, the number of cracks on the target surface of the comparative example [one/100 mm ² ] and the number of arc occurrences in the sputtering treatment are shown only in Table 1.

Here, the number of cracks (number / 100 mm ² ) indicates the number of cracks in the inspection area of 100 mm ² of the surface (or section) of the sputtering target; the number of arcs indicates a plate-shaped target having a thickness of 30 mm, and the thickness thereof is 20 mm. That is, the number of arc occurrences occurring when the thickness direction (depth direction) is 10 mm by sputtering.

Further, the number of arcs generated during the sputtering process is measured using an arc counter. As the arc counter, a data storage device manufactured by LANDMARK TECHNOLOGY is used. Further, as the number of visual arcs, it is considered that when the number of arcs exceeds 30 times, the increase in the product loss rate due to an increase in abnormal film formation on the counter substrate or the like is apparent.

Further, Fig. 1 shows the concentration of sulfur (S) and lead (Pb) in each of Examples 1-4 and Previous Examples 1 to 5 in the case where the sulfur (S) content rate [ppm] is plotted on the horizontal axis. Diagram of the number of cracks [/100mm ² ]. 2 is a graph showing the concentration and crack of sulfur (S) and lead (Pb) in each of Examples 1-4 and Previous Examples 1 to 5 in the case where the lead (Pb) content (ppm) is plotted on the horizontal axis. A graph of the number [/100mm ² ]. Fig. 3 is a graph showing the relationship between the number of cracks and the number of arc occurrences in each of Examples 1 to 4 and Previous Examples 1 to 5.

In addition, if the cracking of the crucible is large, the electric charge will concentrate on the edge portion of the crucible, and an arc will occur during the sputtering. Therefore, in the effect confirmation experiment 1, the crack size in the range influencing the occurrence of the arc is as shown in Fig. 4 ( A) and (b) are defined as those in which the width of the crucible (cracking of crucible) is 0.003 mm or more, and the crack is counted.

Here, as shown in FIG. 4(a), the crucible has a width of at most 0.3 mm, and FIG. 4(b) is a crucible having a width of at most 0.004 mm, since the width directions are both 0.003 mm. Therefore, the 瑕疵 corresponds to the definition of the crack in the embodiment.

Further, in Fig. 4(a), the length in the longitudinal direction is 3.34 mm; and in Fig. 4(b), the length in the longitudinal direction is 0.031 mm.

On the other hand, the crucible shown in Fig. 5 is smaller than the width of 0.003 mm and is the same size as the grain boundary, and therefore is not defined by the definition of the crack.

That is, when the width of the crucible is less than the above-mentioned 0.003 mm, the length of the long side direction of the crucible is not more than 4 mm as shown in FIG. 5, and does not affect the occurrence of the arc, and therefore, as shown in FIG. It is not in accordance with the definition of the crack in this embodiment.

As shown in Table 1, Figure 1, Figure 2 and Figure 3, in the case of the previous examples 1 to 5 and the comparative example, the number of cracks on the surface of the sputtering target (sputtered surface) was more than 50 [/100 mm ² ]. On the other hand, in the case of Examples 1 to 4, it was confirmed that it was 50 [pieces/100 mm ² ] or less.

Meanwhile, in the cases of the previous examples 1 to 5 and the comparative examples, the number of occurrences of the arc was more than 30 times, whereas it was confirmed that the number of occurrences of the examples 1 to 4 was less than 30 times.

Therefore, as shown in Table 1 and FIG. 3, when the number of cracks is 50 [/100 mm ² ] or less, the number of arc generations can be suppressed to 30 or less.

From the above, it can be confirmed that the sputtering target has a purity of 99.9% by mass or more of copper as a main component, and a content of sulfur (S) of 10 ppm or less and a content of lead (Pb) of 2 ppm or less. Thereby, the number of occurrences of the arc can be made less than 30 times, and it can be remarkably suppressed as compared with the targets of the previous examples 1 to 5 in which the contents of sulfur (S) and lead (Pb) do not satisfy the above conditions, respectively.

Further, in the case of the previous examples 1 to 5, the comparative examples, and the examples 1 to 4, when the substrate subjected to the sputtering treatment of the target was confirmed, when the sputtering targets of the previous examples 1 to 5 and the comparative examples were used, the substrate occurred. In contrast to the coarse clusters such as splashes, the sputtering targets of Examples 1 to 4 are used. In the case where a large cluster such as a splash does not occur, a film having a uniform film thickness can be formed on the substrate.

Next, a sputtering target which can maintain a low resistance while improving the film formation speed and a method for manufacturing the same will be described.

In detail, the sputtering method is a film forming method of forming a film having the same composition as that of the sputtering target on the sputtered material as described above, but in the sputtering method, the cost of the final product is reduced, and thus productivity is improved ( The demand for improvement in throughput has increased, and the sputtering conditions during the sputtering process have been further reviewed, and attempts have been made to increase the film formation speed during sputtering.

However, the film formation rate at the time of sputtering depends on the sputtering conditions such as the gas pressure, the input power, and the distance between the target and the substrate, and the sputtering conditions affect not only the film formation speed but also the film characteristics such as the uniformity of the film thickness. Thereafter, the sputtering conditions are set only in view of the improvement of the film formation speed, and when the film thickness uniformity is impaired, for example, an increase in electrical resistance or coarse clusters such as particles, splashes, and dust may occur.

The increase in resistance is the main cause of the delay in processing the signal, and the generation of coarse clusters also causes problems with disconnection.

That is, in order to maintain the film quality and at the same time to improve the film formation speed at the time of sputtering, there is a limit not only in the study of the sputtering conditions.

Therefore, in recent years, in order to maintain the quality of the film, it is also required to further increase the film formation speed during sputtering. In addition to the sputtering conditions, attention is also paid to the characteristics of the sputtering material itself, that is, the crystal orientation or crystal grain size of the sputtering. Various proposals such as the content of impurities contained in the sputtered material.

For example, the "Processing Method of Copper Sputtering Target" of JP-A-2002-220759 (hereinafter referred to as "Citation of Technical Document 1") is also one of them.

The prior art document 1 discloses a method for processing a copper sputtering target, which is at least 99.999% high-purity copper, with an average particle size of 10~30μm, containing crystal orientation (111), (200), (220) and (311) alignment, and having a crystal orientation with less than 50% of the particles in each alignment. Further, it is revealed that a film excellent in uniformity can be sputtered onto a wafer by using such a copper sputtering target.

In this way, the sputtering characteristics are changed by the crystal orientation, the crystal grain size, the copper purity, and the like of the sputtering. Therefore, with the progress of various research and development in this respect, it is ensured that the electrical resistance is lower than the previous resistance. At the same time, the effect of increasing the film formation speed is also sought.

However, the size of a substrate such as a liquid crystal display for a large-sized television is increased to a size of, for example, a substrate of more than 2 m, and it is necessary to form a film onto a large substrate or wafer in the sputtering step of forming a wiring. The sputtering target itself is also large in size, and the copper structure is easily uneven in each part of the sputtering target, and the influence on the film thickness precision and the occurrence of coarse clustering becomes large.

Further, with the increase in speed and high performance of information processing such as semiconductor devices in recent years, gates and wirings have been made finer and more complicated. However, if a large current flows through the miniaturized wiring for high speed, the current density increases, and an increase in current density causes an increase in resistance, and such an increase in the resistance value may cause a delay in processing signals or a decrease in reliability. This has become an obstacle to the speeding up of semiconductor devices.

Therefore, the following description can maintain a low resistance, and at the same time, a sputtering target having an improved film formation speed and a method of manufacturing the same are also described.

Such a sputtering target is composed of high-purity copper having a purity of 99.9% (3N) or more, and is characterized in that the crystal orientation satisfies the following [Formula 1] and [Math 2]; the crystal orientation is performed by sputtering. The Miller indices of the crystal structure in the sputtered surface are (111) X-ray diffraction peak intensities I(111), I(200), I(220), I(311) of the respective alignment planes shown on the surface, (200) plane, (220) plane, and (311) plane; Mathematical Formula 1] I(111)/[I(111)+I(200)+I(220)+I(311)]≧0.40; and [Math 2] I(111)>I(200); I (111)>I(220); I(111)>I(311).

Further, it is preferable that the sputtering target satisfies the following [Formula 1'] in [Formula 1]: [Math 1'] I(111)/[I(111)+I(200)+I(220) +I(311)〕≧0.55.

Further, the sputtering target is characterized by satisfying the following relationship of [Formula 3a], [Formula 3b], and [Formula 4]: [Math 3a] I(200)>I(220); [Math 3b] I(200)>I(311); and [Math 4] I(200)≧0.42×I(111).

Here, the left side of [Formula 1] and [Formula 1'] indicates the alignment ratio of I (111), I (200), I (220), and I (311) all I (111) ( Hereinafter, the "alignment ratio of the (111) plane" is referred to as "the mathematical expression 1" and the left side of the mathematical expression 1'.

Further, as described above, the (111) plane can be made by satisfying [Equation 2]. Among the (200) plane, (220) plane, and (311) plane, the (111) plane is the most crystallographic alignment ratio. The atomic density of the FCC metal such as copper is among the above four alignment planes, and is also the highest on the (111) plane, and the (111) plane is the densest. Under such a relationship, as shown in the relationship of [Formula 1], the alignment ratio of the (111) plane ([Formula 1L)) is 40% or more, whereby the surface of the sputtering target can be splashed. Copper atoms are more than before.

In the sputtering target of the present embodiment, [Formula 1L], that is, the alignment ratio of the (111) plane is 40% or more, and the copper atom having the (111) plane can be effectively used with a higher emission density than the other alignment planes. characteristic.

As a result, the film formation speed can be improved. Further, a large amount of copper atoms from the surface of the sputtering target are densely splashed, whereby film formation of a copper film having a uniform film thickness can be performed, and low resistance can be secured.

Therefore, even if the size of the substrate or the wafer is increased, or the gate or wiring of the semiconductor device is made finer or more complicated, the signal processing can be speeded up and high reliability can be achieved, and the final product can be improved due to the increase in yield. The cost is reduced.

Further, let the denominator of [Math 1L] be [I(111) + I(200) + I(220) + I(311)], that is, the sum of the peak intensities of the X-ray diffractions of the four alignment faces, The reason is as follows.

The reason for this is that when recrystallization is performed by an annealing step described later, the (111) plane, the (200) plane, the (220) plane, and the (311) plane are likely to be generated in the case of pure copper, and the main four are used. The sum of the peak intensities of the alignment faces is the denominator of [Math. 1L], and the correct alignment ratio in accordance with the actual copper crystal orientation can be calculated.

In other words, in [Equation 1], the relationship between the peak intensity of the four main alignment faces included in the actual copper crystal orientation is used as the denominator (Formula 1L), and the relationship is 40% or more. Therefore, compared to one of the four main alignment planes, for example, 2 The sum of the peak intensities of the alignment faces is used as the denominator of [Equation 1L], and the correct alignment ratio in accordance with the actual copper crystal orientation can be calculated.

Further, by satisfying the crystal orientations of the following [Formula 3a] and [Formula 3b] as described above, the (200) plane may be next to the (111) plane in each of the above-mentioned alignment surfaces. It is the second highest crystal orientation ratio; [Math 3a] I(200)>I(220); [Math 3b] I(200)>I(311).

Then, among the FCC metals such as copper, the atomic density of the (200) plane in the (111) plane, the (200) plane, the (220) plane, and the (311) plane is second only to the (111) plane. The second highest, so the (220) surface and the (311) surface are more likely to splash copper atoms densely.

Therefore, since the copper atoms can be densely sputtered from the surface of the sputtering target simultaneously with the (111) plane, the film formation speed can be improved, and a uniform film thickness can be formed with low electrical resistance.

Further, as described above, since the (200) plane is at an atomic density lower than the (111) plane, it can be splashed from the surface of the sputtering target with low energy, and thus compared with the case where only the crystal orientation ratio of the (111) plane is increased. It can suppress the sputtering energy of copper atoms as a whole and can cause a decrease in voltage (hereinafter referred to as "sputtering voltage") at the time of sputtering.

Further, as described above, at the time of sputtering, the (111) plane can densely scatter copper atoms, and on the other hand, the (200) plane is less likely to be densely scattered than the (111) plane, but it can ensure lower copper. The nature of the atom's splashing energy.

Therefore, as described above, the sputtering target is made to satisfy the following [Formula 4] The crystal orientation of the system, whereby the alignment characteristics of the (111) plane and the (200) plane can be effectively utilized, and the crystal orientation ratio is improved to the highest (111) plane, and the crystal orientation of the (200) plane can also be made. The rate is higher than the other alignment planes; [Math 4] I (200) ≧ 0.42 × I (111).

Therefore, the high film formation speed can be ensured by causing the copper atoms to be densely scattered, and the energy of the splash can be suppressed lower than when only the crystal orientation ratio of the (111) plane is higher than that of the other alignment faces ( Sputtering voltage).

Further, by satisfying the crystal orientation of the following [Formula 4'], the crystal orientation ratio of I(200) can be made higher than that of the other alignment surface by [Formula 4], so that a high film formation speed can be ensured. At the same time, it is also preferable to further suppress the splash energy (sputtering voltage) to be lower;

[Math 4'] I (200) ≧ 0.80 × I (111).

Further, the sputtering target is characterized in that the crystal grain has a particle diameter of 65 to 200 μm.

When the particle size of the sputtering target is large, the sputtering target must have high energy in order to fly copper atoms out of the target surface. Therefore, by setting the particle size of the crystal grains to a range of a small value of 65 to 200 μm, the energy for causing the copper atoms to fly out from the target surface can be suppressed to be low.

Therefore, since the sputtering target of the present embodiment is aligned with the (111) plane and the (200) plane which require high energy to cause copper atoms to fly out from the target surface, the particle size of the crystal grain is set. Setting it to a smaller value is particularly effective in minimizing the energy used to fly copper atoms out of the target surface.

Further, it is preferable that the particle size of the crystal grain is a small value of 65 to 160 μm. The sputtering method forms a sputtering target.

Thereby, the energy for causing the copper atoms to fly out from the target surface can be suppressed to be lower than when the particle size of the crystal grains is in the range of 65 to 200 μm.

The method of manufacturing the above-described sputtering target will be described below.

First, ordinary electrolytic copper is electrolytically refined in a nitric acid bath or a sulfuric acid bath, and copper which is extremely low in impurity content is subjected to vacuum induction dissolution to obtain an ingot composed of high purity copper of 99.9% (3N) or more. The ingot is cut into a specific size to prepare a preform for hot working.

The sputtering target system is formed by using the above-described hot extrusion embryo and sequentially subjected to a hot extrusion step, a cold working, and an annealing step.

In detail, in the hot extrusion step, the hot working is prepared in advance, and even if the hot working embryo exceeds 500 ° C, the hot extrusion is performed at 500 to 900 ° C, preferably at 660 to 800 ° C. Hot extrusion.

Thereafter, in the cold working, the temperature is cooled to about room temperature at a cooling rate of 50 ° C /sec or more, more preferably 80 ° C / sec to 120 ° C / sec.

In the annealing step, the recrystallization of copper is carried out, for example, at a temperature of from 250 ° C to 400 ° C, more preferably from 300 ° C to 400 ° C. If the temperature is too low, recrystallization does not occur, and if the temperature is too high, excessive growth of the particles occurs. The strain existing in the copper material affects the flying of the target material, so it is effective to perform the annealing step to remove the internal stress which is the main factor causing the strain, and the internal stress can be removed by the annealing step.

It can be produced by the above-described production method of the present embodiment, and is manufactured such that the alignment ratio of I(111) is 40% or more.

Further, as described above, since the sputtering target is satisfied [Math. 1L] ≧ 0.55 Compared with the case of [Formula L] ≧ 0.40, the orientation of the (111) plane having a high areal density in each alignment plane can be increased, and a large amount of copper atoms can be self-sputtered. The surface flies out.

Thereby, the film formation speed can be further improved, and at the same time, a copper film can be densely sputtered from the surface of the sputtering target to form a film having a low electric resistance and a uniform film thickness.

The effect confirmation experiment will be described below.

(Effect confirmation experiment 2)

In the effect confirmation experiment 2, the sputtering targets of Examples 5 to 10 were fabricated as an example of the above-described sputtering target, and the sputtering targets of Comparative Examples 1A and 2A which are comparative controls of the present example were produced, and the films were respectively compared. Resistivity, film formation speed.

The sputtering targets of Examples 5 to 10 and Comparative Examples 1A and 2A were composed of copper materials each having the purity shown in Table 2.

The sputtering targets of Comparative Examples 1A and 2A are produced by a conventional manufacturing method which has been conventionally performed. More specifically, the ingots made of high-purity copper are subjected to hot working such as hot rolling and hot pressing, and then After the cold working such as cold rolling is applied, the final heat treatment is performed, but the hot rolling is performed, for example, by heating to a temperature of 930 °, and is also different from Examples 5 to 10. The cold working and heat treatment steps are carried out under the manufacturing conditions.

On the other hand, the targets of Examples 5 to 10 were produced by the following steps: in the order of the hot extrusion step, the cold working step, and the annealing step, and in the manufacturing conditions of the sputtering target of the present embodiment described above, respectively. Go on.

Each of the sputtering targets of Examples 5 to 10 and Comparative Examples 1A and 2A is produced by the above-described steps, and is additionally processed to a desired target shape by any machining or the like such as a lathe. use.

Table 2 shows the alignment ratio, average crystal grain size, and film resistivity of the (111) plane of the sputtering target.

Here, the alignment ratio of the (111) plane is less than 40% with respect to the sputtering targets of Comparative Examples 1A and 2A, and the sputtering targets of Examples 5 to 10 are manufactured by the above-described manufacturing method of the present embodiment, The sputtering targets of Examples 5 to 8 were all 40% or more, and further, the sputtering targets of Examples 9 and 10 were both 55% or more.

Further, in order to calculate the X-ray diffraction of each of the (111) plane, the (200) plane, the (220) plane, and the (311) plane of the (111) plane alignment ratio shown in [Formula 1] The peak intensity is obtained by injecting X-rays from a surface used as a sputtering target, measuring the intensity from each diffraction surface, and calculating a (111) plane and a (200) plane in which a particularly high peak is displayed. The peak intensity of the X-ray diffraction of the (220) plane and the (311) plane.

Further, under the X-ray irradiation conditions, the X-ray type was CuKα1, the tube voltage was 40 kV, and the tube current was 20 mA.

In addition, the crystal grain size in the copper material sheet is in each of the above-mentioned portions, and the microstructure is observed on the surface used as the sputtering target, and the crystal grain is measured based on JIS H 0501 (cutting method). The diameter is calculated from the average crystal grain size.

The additional processing of the sputtering after the annealing process is performed to eliminate the influence of the roughness of the obtained sputtering target, and the roughness is uniformly ground to 0.5 to 0.8 μm.

The sputtering target of the above-described Examples 5 to 10 and the sputtering targets of Comparative Examples 1A and 2A were used for sputtering, and the film resistivity and film formation rate of the copper film formed into the object to be sputtered were measured, and the results are shown in the table. 2 results.

In addition, sputtering was carried out by using a sputtering target as described above, and sputtering was performed on a OA-10 glass substrate manufactured by Nippon Electric Glass Co., Ltd. having a thickness of 0.7 mm by a DC magnetron sputtering apparatus to form a copper wiring having a film thickness of 0.3 μm. . The sputtering conditions were such that the Ar gas pressure was 0.3 Pa and the discharge power was 500 W.

First, focusing on the results of the film resistivity, Comparative Examples 1A and 2A were 2.1 [μΩcm] and 2.2 [μΩcm], respectively, and Examples 5, 6, and 8 to 10 were substantially the same as the respective values. It is 2.2 [μΩcm], 2.2 [μΩcm], 2.1 [μΩcm], 2.1 [μΩcm], and 2.0 [μΩcm]. In the case of Example 9, it was 1.8 [μΩcm], which was a lower value than the case of Comparative Examples 1A and 2A.

The main reason is that the sputtering target of Example 7 is composed of high-purity copper having a purity of 5 N (99.999%) or more, and therefore, the average crystal grain size is also smaller than that of other sputtering targets.

Further, in view of the film formation rate, Comparative Examples 1A and 2A were both 8 [Å/s], whereas Examples 5 to 10 were 12 [Å/s], 11 [Å/s], and 12 [Å/s], 10 [Å/s], 14 [Å/s], and 15 [Å/s], either of them were faster than Comparative Examples 1A and 2A. especially, Examples 9, 10 were indeed faster relative to Comparative Examples 1A, 2A, and also significantly faster than the other Examples 5 through 8.

From the above, it can be proved that by setting the alignment ratio of the (111) plane to 40% or more, the copper atom having I(111) can be splashed intensively, and therefore, an excellent film resistivity can be secured, and at the same time, it is possible to achieve Increase the film formation speed.

In particular, it has been confirmed that the ratio of the (111) plane is 55% or more, and the effect of I(111) is more remarkable, and the film resistivity is excellent, and the film formation speed is further improved.

The sputtering target of the present embodiment is not limited to the above embodiment, and can be manufactured by various embodiments and production methods.

For example, in the sputtering target of the present embodiment, I (111), I (200), I (220), and I (311) satisfy the relationship of, for example, [Formula 3], that is, I(200)>I is satisfied. (220), I(200)>I(311), but if the relationship between [Mathematical Formula 1] and [Mathematical Formula 2] is satisfied, a configuration that does not necessarily satisfy the relationship of [Mathematical Formula 3] is also included.

Similarly, in the sputtering target of the present embodiment, I (111), I (200), I (220), and I (311) satisfy the relationship of, for example, [Formula 4], that is, I(200) is satisfied. In the relationship of 0.42 × I (111), as long as the relationship between [Mathematical Formula 1] and [Mathematical Formula 2] is satisfied, a configuration that does not necessarily satisfy the relationship of [Mathematical Formula 4] is also included.

Furthermore, the present invention is not limited to the above embodiments, and can be formed in other various embodiments.

Claims (2)

A sputtering target contains copper having a purity of 99.9% by mass or more as a main component, and contains 10 ppm or less of sulfur (S) and 2 ppm or less of lead (Pb). The sputtering target according to claim 1, wherein the copper has a purity of 99.96 mass% or more.