JP3509011B2 - Method for Refining Production Materials for Target Material for Al-based Sputtering - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al-based sputtering target material mainly composed of Al, and particularly to an Al for LCD used for thin film electrodes and thin film wiring of a liquid crystal display (hereinafter referred to as LCD).
This is a method for reducing the structure of a sputtering target material.

[0002]

2. Description of the Related Art Conventionally, a pure Cr film, a pure Ta film, which is a refractory metal, has mainly been used for an electric wiring film, an electrode, etc. used for an LCD for manufacturing a thin film device on a glass substrate, a thin film sensor, etc.
A pure metal film such as a pure Ti film or an alloy film thereof is used. With the increase in size and definition of LCDs, wiring films and electrode films are required to have low resistance, low stress, and stable characteristics thereof in order to prevent signal delay. For example, 15μ for electrodes used in large color LCDs of 12 inches or more.
It is required to be Ωcm or less. But conventional C
The r, Ta-based high melting point alloy film is excellent in film stability, but has a high resistance value, about 30 μΩcm for Cr and about 80 μΩ for Ta.
cm, Ti is about 60 μΩcm. Therefore, an Al-based film having a lower resistance than these metals is used.

Further, as the size of the substrate is increased, the target material for forming the metal film is also required to be increased in size. For example, a sputter apparatus used for forming a metal film in order to stably manufacture a metal film of high quality as the LCD becomes finer is a conventional very large substrate transfer type in-line system. Therefore, a single-wafer type apparatus for forming a film while the substrate is stationary has come to be widely used. In this single-wafer type sputtering apparatus, a target material larger than the substrate size is required in order to form a film while standing still on the substrate.

Conventionally, for the required target material size
Target materials manufactured in 2 or 3 sizes were used by bonding, but in the case of divided target materials for higher definition, foreign matters are generated from the joints and they become defective, so they are integrated. Target materials for materials are required.

The substrate size that is currently the mainstream is 370 × 470 mm, and a large target material having a sputtering surface of about 550 × 650 mm is used as a target material for a single-wafer sputtering apparatus for forming a metal film on this substrate. Need to be manufactured integrally. A general Al-based sputtering target material is often manufactured by casting an Al alloy to produce an ingot, and machining this ingot to obtain a target material. However, since an alloy mainly composed of Al is excellent in cold plastic workability, it is easy to integrally manufacture a large target material as compared with the case of manufacturing a target material of a metal having a high melting point such as Cr or Ta. In some cases, the cast ingot is subjected to forging, cold rolling, etc., and is machined into the shape of the target material. For example, in order to manufacture a large target material with a sputter flat area of 0.3 m ² or more of a single-wafer type corresponding to 550 x 650 mm, the ingot is made large and a high cold working rate (about 80% or more) is achieved. It was manufactured by performing plastic working and machining so that it could be applied to manufacture an integrated target material.

Many proposals have been made for improving the composition of the target material. For example, a pure Al film has a low specific resistance but has a problem in heat resistance.
There is a problem that minute projections called hillocks are formed on the surface in the heating step (about 250 to 400 ° C.) after the electrode film formation, which is unavoidable in the manufacturing process.
This hillock is considered to occur due to stress migration, thermal migration, etc. When this hillock occurs, an insulating film, a protective film, etc. should be formed on the Al wiring film, and further a wiring film, an electrode film, etc. should be formed. In such a case, there is a problem that an electrical short circuit (short) occurs and an etching solution or the like enters through the hillocks to corrode the Al wiring film.

Therefore, instead of pure Al, a metal having a high melting point is added for the purpose of solving these problems. For example,
In Japanese Patent Laid-Open No. 4-323872, Mn, Zr, and Cr are added in an amount of 0.05 to 1.0 at%
It is stated that the addition is effective. In addition, in Japanese Examined Patent Publication No. 4-48854, B is 0.002 to 0.5 wt% and H is
It discloses a method of adding 0.002 to 0.7 wt% of f, Nb, Ta, Mo, and W, and a method of adding 0.5 to 1.5 wt% of Si. Further, in JP-A-5-65631, Ti, Zr,
It is described that the addition of 0.2 to 10 at% of Ta is effective in suppressing the generation of hillocks. Furthermore, JP-A-6-29
As described in 9354 and JP-A-7-45555, Fe, C
0.1 to 10 at% for o, Ni, Ru, Rh and Ir, and 0.0 for rare earth elements.
The method of adding 5 to 15 at% or Al as described in JP-A-5-335271.
-0.01 to 3 wt% of Cu, Ti, Pd, Zr, Hf, Y and Sc in Si alloy
A method of adding is known. Such additional elements are
A compound is formed with Al and dispersed in the matrix of Al, but the formed compound has a specific gravity different from that of Al, and thus segregation is likely to occur. Therefore, JP-A-5-335271 and JP-A-6-33
There is also a proposal of a casting technique for preventing segregation, as described in 6673.

[0008]

As described above, the conventional Al-based sputtering target materials include additive elements added to prevent hillocks and casting methods for preventing their segregation. Emphasis was placed. In the method of obtaining the target material by the melt casting method by the conventional improved method, macro segregation between Al and the additional element in the ingot structure can be prevented by, for example, quenching as much as possible. However, in the case of the casting method, agglomerated portions of the compound such as flakes occur in the structure and microscopic segregation remains inevitably, so that the problem of segregation still exists for minute thin films such as LCD wiring. .

As a method of preventing the macroscopic segregation of the target material, a method of mixing powders and sintering can be considered. However, according to our study, when pure Al powder is used as a raw material, the segregation region becomes large when the size of the Al powder raw material is large. In order to reduce the segregation area, it is possible to use fine raw material powder. However, a fine Al powder and additive element powder have not been able to provide a target material having a satisfactory uniform structure because of handling problems such as measures against oxidation and ignition and manufacturing problems such as agglomeration of powder during mixing. Further, as pointed out in Japanese Patent Laid-Open No. 6-299354, which discloses a melting method, in a sintered target material in which Al powder and alloying element powder are mixed, the alloy element concentration in the Al film is different due to the difference in sputtering efficiency of each element. There is a problem that it changes over time.

Further, in the case of an Al-based target material, if the ingot is made large and sputtering is performed using a target material that has been cold-plasticized at a high processing rate, spattering from the target material may cause abnormal droplets called splash. is there. Splash is an abnormal droplet generated from the target material, which is larger than ordinary sputtered particles, and if this splash adheres to the substrate, it may cause shorts between wires, disconnection, etc. There is a problem that the yield becomes high and the yield of the manufactured liquid crystal display is greatly reduced.

The generation of splash from the Al target material is a serious problem because it directly leads to a defect when used for forming wiring. In particular, when a large target material having a sputtering flat area of 0.3 m 2 or more, which is necessary for obtaining a large LCD, is applied, countermeasures against it are urgently required as a cause of failure of an expensive large liquid crystal display.

The present inventors diligently investigated the cause of the splash. As a result, it was found that the cause of the splash was the minute voids in the target material. As a result of further study, one of the causes of the generation of this minute void is
It has been found that when a large ingot is manufactured by the melting and casting method, the heat shrinkage of Al is large, and the shrinkage cavities occur. Another cause is that although the molten aluminum dissolves hydrogen, it releases hydrogen when it cools and solidifies, so that minute voids are easily generated by this hydrogen. Especially, in order to prevent segregation, when the material is rapidly cooled and solidified, voids are easily included in the ingot.

Further, an Al compound produced by an additive element other than Al may be cracked during processing into a target material and cause voids. The present inventor studied to suppress the generation of minute voids in the target material structure, but it was difficult to suppress the generation of voids due to shrinkage cavities or dissolved hydrogen as long as the melt casting method was applied. Therefore, the inventor has tried to apply the powder sintering method. When the powder sintering method is applied, it is possible to suppress the generation of voids due to the shrinkage cavities and dissolved hydrogen described above. However, if a powder of an element for preventing hillocks as described above is simply mixed with Al powder and sintered, a coarse compound may be formed by a reaction with Al, and this compound is also produced by the melt casting method. It was found that, like the compound described above, it easily cracks during processing and forms voids that cause splash.

It is an object of the present invention to provide a method of refining the structure of an Al-based target material which can prevent the segregation of the structure and the formation of coarse compounds.

[0015]

Means for Solving the Problems Even when the present inventor contains a Group 3A element that easily forms a flaky compound with Al, the compound is uniformly dispersed by a rapid cooling treatment such as a gas atomizing method. The present invention has been accomplished by discovering that the above fine structure can be obtained.

That is, the present invention contains 10 atomic% or less of any one or more elements selected from the transition elements, contains a Group 3A element as the transition element as an essential element, and the balance is substantially Al. Al alloy sputter with uniform and fine structure by quenching molten alloy consisting of
Al-based spatter as a raw material for the ring target material
This is a method of refining a manufacturing raw material for a target material for tarring . Further, in the present invention, it is preferable to apply a gas atomizing method to the quenching treatment.

The inventor of the present invention examined the Al alloy ingot structure to which the group 3A element was added, and the group 3A element easily forms a flaky compound with Al, and the compound cracks and splashes in the process of manufacturing the target material. It was found that the voids that cause

It has been found that by applying a quenching treatment which has not been used conventionally to the production of an Al alloy target containing a 3A group element as an essential element, the structure can be made finer even when the 3A group element is contained. . Specifically, the structure obtained by the present invention is a structure in which an Al region having a major axis of 0.5 μm or more and not containing a compound with Al (hereinafter referred to as Al unevenly distributed region) is reduced. Further, it is possible to make the compound to be dispersed as fine as the circumscribed circle diameter is 5 μm or less.

In the present invention, the transition element is S
3A called rare earth element consisting of c, Y and lanthanoid
Group, 4A group of Ti, Zr, Hf, 5A of V, Nb, Ta
Group 6A of Cr, Mo, W, 7A of Mn, Tc, Re
Group, Fe, Co, Ni, Ru, Rh, Pd, Os, I
They are group 8 of r and Pt, and group 1B of Cu, Ag, and Au. After forming a thin film by sputtering, these transition elements are typically subjected to heat treatment at a heating temperature of 150 ° C. to 400 ° C. to precipitate in the structure as an intermetallic compound.
The precipitated compound becomes a pinning point that suppresses the growth or flow of Al crystal grains due to heat or a potential difference,
It prevents the formation of hillocks in the thin film.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The greatest feature of the present invention is that
The inventors have found a method for forming a fine dispersion of a compound with Al on a target material structure. This fine structure is
As the molten metal quenching method, for example, an atomizing method such as a gas atomizing method can be used. The application of the melt quenching method is for preventing not only the segregation of Al by the conventional melt casting method but also for achieving the unprecedented uniformity of the concentration distribution of the formed thin film by the finely dispersed compound.

When the spray quenching method, which is important in the present invention, is applied, the circumscribed circle diameter of the above compound is substantially 5 μm.
It can be m or less. Further, the aspect ratio defined by the major axis / minor axis of the compound of 0.5 μm or more in the sectional structure of the target material can be 10 or less, preferably less than 5. Further, the unevenly distributed region of Al having a major axis of 0.5 μm or more and not containing the compound may be 10 μm or less in the inscribed circle diameter with respect to the compound.

As a method of introducing such an element for preventing hillocks into the Al-based target material, it is desirable to apply the sintering method. If the additive element is powdered and introduced as it is,
In the sintering process, it often reacts with Al to form a coarse flaky compound such as a rose flower or a dendritic coarse compound in many cases. When a coarse compound is present, cracking easily occurs in the structure due to the load such as rolling. Voids are generated in this cracked portion, and a splash is generated during sputtering.

According to the study by the present inventor, the generation of voids that cause splash depends on the morphology of the compound in the tissue, and by making the spheres as fine as possible, preferably close to an aspect ratio of 1, We have found that it can be prevented. As described above, in the present invention, the aspect ratio defined by the major axis / minor axis of the compound of 0.5 μm or more in the cross-sectional structure of the target material can be less than 5, and even if rolling or the like is applied, the splash It is preferable because it is difficult to generate voids.

As a result of further examination, when a powder is produced by the spray quenching method, for example, among the powders, particles having a small diameter with a fast solidification rate, typically a diameter of 200 μm or less, do not grow the compound into a thin plate shape. It can be finely solidified, and if it is sintered, it is possible to obtain a target material that can further prevent the formation of voids that cause splash even by processing such as rolling. Further, in the present invention, the circumscribed circle diameter of the compound is preferably 5 μm or less, because the fine particles of less than this size are dispersed to cause cracking of the compound even if the total processing rate is 50% or more. This is because it was confirmed that voids did not occur and splash did not increase.

When a powder is produced by the spray quenching method of the present invention, for example, the powder is desirably sintered at 400 ° C. or higher and 600 ° C. or lower. This is because if the temperature is lower than 400 ° C., the sintering is difficult to proceed, and if the temperature exceeds 600 ° C., there is a risk of Al being dissolved. The pressure sintering is preferably performed at a pressure of 50 MPa or more in order to obtain a dense sintered body without voids. Remaining voids during this sintering causes splashes in the target material, so it must be avoided as much as possible.

When rolling at a working rate of 50% or more, it is possible to reduce cracks during working by raising the working temperature. Substantially 4 above the recrystallization temperature of Al
It is desirable to set the temperature to 00 ° C. or higher, and the temperature to 550 ° C. or lower, which does not exceed the melting point of Al due to local temperature increase due to processing such as rolling.

[0027]

Example 1 An Al alloy ingot shown in Table 1 was melt-cast, and this ingot was rapidly cooled and solidified by a gas atomizing method in a nitrogen gas atmosphere, and then classified to have a volume average diameter of 60 μm. This powder has an inner diameter of 133 mm
It was filled in an iron can having a height of 15 mm, and heated at a pressure of 10 ⁻³ Pa or less while being exhausted to perform degassing treatment. Next, under the conditions of a pressure of 100 MPa and a temperature of 550 ° C., pressure sintering is performed by HIP (hot isostatic pressing), and then machining is performed to form a target material having a diameter of 100 mm and a thickness of 4 mm. I got the material.

As a comparative example, pure A having a volume average diameter of 60 μm is used.
1 powder and an additive element metal powder having a volume average diameter of 35 μm were mixed by a rocking mixer, and this powder was filled in an iron can having an inner diameter of 133 mm and a height of 15 mm, and degassing was performed in the same manner as the sample of the present invention. Next, as in the case of the present invention, pressure sintering was performed by HIP, and then machining was performed to obtain a target material having a diameter of 100 mm and a thickness of 4 mm, and the single sintered target material shown in Table 1 (Sample No. 11, Sample No. 12) was obtained. Further, as another comparative example, a molten metal having an adjusted alloy composition has a diameter of 150 mm.
It is cast in a cylindrical mold having a height of 100 mm, machined to be processed into a target material having a diameter of 100 mm and a thickness of 4 mm, and the molten target material shown in Table 1 (Sample No. 13, Sample No. 1).
4, sample No. 15) was obtained.

The structures of the target material structures obtained in the present invention and the comparative examples were observed with a 400 × optical microscope.
The maximum major axis of the compound present in the tissue (approximately equivalent to the circumscribed circle diameter of the compound), the maximum aspect ratio = the maximum (major axis / minor axis) value, and the maximum inscribed circle diameter of the Al region were measured. The results are shown in Table 1. Further, as a typical structure obtained by the present invention and the comparative example, in a sample having a composition of Al-2 atomic% Nd, the sample No. Fig. 1 shows the organizational photograph of 3
Sample No. of the single-body sintering target material according to the comparative example. 2 is a photograph of the structure of No. 12, and FIG. Fig. 3 shows photographs of 14 structures. Figure 1
3 to 400 are optical microscope photographs of 400 times.
Further, the surfaces of the target materials obtained in the present invention and the comparative examples were mirror-polished, and voids of 1 μm or more were detected by the dye penetrant flaw detection method, and the number is shown in Table 1.

[0030]

[Table 1]

As is clear from Table 1 and FIGS.
Sample No. obtained according to the present invention. 1-No. No. 7 has a structure in which fine compounds are dispersed in the structure. on the other hand,
The simple substance sintering target material obtained by the comparative example has a structure in which a coarse compound is present. Further, in the ingot target material obtained by another comparative example, the compound is finer than the simple substance sintered target material, but the aspect ratio of the compound is increased, and it is a flat compound, It can be seen that there is a wide Al region where no compound is present. It should be noted that the number of voids formed by the dye penetrant inspection tends to increase slightly with the target material produced by the melting method.

By using the obtained target material by a DC magnetron sputtering method, Ar pressure 0.3 Pa,
An Al alloy film with a film thickness of 200 nm is formed on a 4-inch Si wafer under the condition of an applied power of 0.5 kW, and after all the target materials are used at an applied power of 0.5 kW for about 1 hour,
The composition change of the formed film was examined for each of the films after use for about 20 hours. In addition, 10 films were formed for each target material under the above-mentioned film forming conditions, and 5 μm was observed on the film surface.
Foreign matter of m or more was regarded as splash, and the average number per substrate was calculated. The results are shown in Table 2.

[0033]

[Table 2]

As shown in Table 2, target material sample No. 1 obtained according to the present invention. 1 to No. In No. 7, the transition metal concentration hardly changed during the sputtering period. On the other hand, the simple substance sintering target material sample No. obtained by the comparative example. 11 and No. No. 12 is not preferable because the transition metal concentration in the formed thin film tends to increase. Further, in the melting target material obtained by another comparative example, the concentration variation of the transition metal in the formed thin film is smaller than that of the simple substance sintering target material,
It is larger than the target material obtained by the present invention. In addition, it can be seen that in the case of the melted target material, the number of defects is large and the number of splashes is large, which is not preferable.

Example 2 Al alloy ingots shown in Table 3 were melt-cast, and the ingots were rapidly cooled and solidified by a gas atomizing method in a nitrogen gas atmosphere and classified to have a volume average diameter of 60 μm. 330mm x this powder
Fill a 530mm x 50mm iron can and fill 10 minus 3 power P
Degassing was performed by heating while exhausting to a pressure of a or less. Next, under the conditions of pressure 100MPa and temperature 550 ℃, HI
After pressure sintering with P (hot isostatic press), rolling,
A target material of 550 mm × 690 mm × 6 mm was obtained by machining.

As a comparative example, pure A having a volume average diameter of 60 μm is used.
1 powder and an additive element metal powder having a volume average diameter of 35 μm were mixed by a rocking mixer, and this powder was filled in an iron can of 330 mm × 530 mm × 50 mm, and degassing was performed in the same manner as the sample of the present invention. Then, after pressure-sintering with HIP in the same manner as in the example of the present invention, rolling and machining were performed to form a target material of 550 mm × 690 mm × 6 mm, and the single-piece sintered target material shown in Table 3 (Sample No. 31). , Sample No. 32) were obtained. In addition, as another comparative example, a molten metal whose alloy composition is adjusted is 330 mm × 530
It is cast in a steel flat plate mold of mm × 50 mm, rolled, and then machined into a target material of 550 mm × 690 mm × 6 mm.
o. 33, sample No. 34, sample No. 35) was obtained.

As in Example 1, the structures of the target materials obtained according to the present invention and Comparative Example were observed, and the maximum major axis of the compound existing in the structure (corresponding to the circumscribed circle diameter of the compound),
Maximum aspect ratio = maximum (major axis / minor axis) value, and A
The maximum inscribed circle diameter in the 1 region was measured. Further, as a typical structure obtained by the present invention and the comparative example, Al-2 atomic%
In the sample having the composition of Nd, the target material sample No. The structure photograph of No. 23 is shown in FIG. Fig. 5 shows a photograph of the structure of No. 32, which is a melting target material sample No. 3 obtained by another comparative example. The structure photographs of 34 are shown in FIG. 6, respectively. 4 to 6 are 400 times optical microscope photographs. The surface of the target material obtained in the present invention and the comparative example was mirror-polished, and 1 μm was obtained by a dye penetrant flaw detection method.
The voids of m or more were detected and the number thereof was added to Table 3.

[0038]

[Table 3]

As is clear from Table 3 and FIGS. 4 to 6,
Target material sample No. obtained by the present invention. 21-N
o. No. 27 has a structure in which fine compounds are dispersed in the structure. On the other hand, the simple substance sintering target material obtained in the comparative example has a structure in which a coarse compound is present.
In addition, in this single-piece sintered target material, large voids corresponding to the black portion in the photograph of FIG. 5 are formed. This is because the compound was cracked by rolling and voids were formed. Further, in the ingot target material obtained by another comparative example, the compound is finer than that of the simple substance sintered target material, but a wide Al region where the compound does not exist remains. In addition, the number of defects is slightly increased as compared with Example 1. It is presumed that this is because the compound having a large aspect ratio was cracked to generate voids.

By using the obtained target material by a DC magnetron sputtering method, an Ar pressure of 0.3 Pa,
An Al alloy film having a thickness of 200 nm was formed on a glass substrate having a size of 370 mm × 470 mm × 1.1 mm under the condition of an applied power of 11 kW. With respect to all the target materials, a change in composition of the formed film was examined after using for about 1 hour at an input power of 0.5 kW and after using for about 20 hours. Further, 10 films were formed for each target material under the above-mentioned film forming conditions, and the foreign matter of 5 μm or more recognized on the film surface was regarded as splash, and the average number per substrate was calculated. The results are shown in Table 4.

[0041]

[Table 4]

As shown in Table 4, target material sample No. 1 obtained according to the present invention. 21 to No. In No. 27, the transition metal concentration hardly changes during the sputtering period. On the other hand, the simple substance sintering target material sample No. obtained by the comparative example. 31 and No. 31. 32 is not preferable because the transition metal concentration in the formed thin film tends to increase significantly. Further, as shown in Table 3, it is found that a large number of voids are generated in the target material due to the application of rolling, and the number of splashes is remarkably increased accordingly, which is not preferable. Further, in the ingot-produced target material obtained by another comparative example, the variation in the concentration of the transition metal in the formed thin film is smaller than that of the single-sintered target material as in Example 1, but obtained by the present invention. It is larger than the target material. Further, it can be seen that the ingot target material has a larger number of defects than that of the target material obtained by the present invention, though the number of defects is larger than that of the target material obtained by the present invention, and the number of splashes increases accordingly.

[0043]

EFFECTS OF THE INVENTION According to the present invention, it is possible to eliminate fluctuations in film composition and reduce defects in an Al-based target material for LCD having a sputter flat area of 0.3 m 2 or more, which has been a major problem in occurrence of slush. As a result, the splash can be suppressed as a result. Therefore, the present invention is extremely effective in achieving an improvement in the quality of the LCD as a target material corresponding to the LCD which is required to be further increased in size in the future.

[Brief description of drawings]

FIG. 1 is a photograph showing a metal microstructure of a target material produced by applying the present invention.

FIG. 2 is a photograph showing a metal microstructure of a simple substance sintering target material of a comparative example.

FIG. 3 is a photograph showing a metal microstructure of a molten target material of a comparative example.

FIG. 4 is a photograph showing a metal microstructure of a target material subjected to a rolling treatment after applying the present invention.

FIG. 5 is a photograph showing a metal microstructure of a rolling-treated single-piece sintered target material of a comparative example.

FIG. 6 is a photograph showing a metal microstructure of a melt-processed target material subjected to rolling in a comparative example.

Claims (2)

(57) [Claims] 1. A molten alloy containing at least 10 atomic% of one or more elements selected from transition elements, essentially containing a Group 3A element as the transition element, and the balance substantially consisting of Al. Uniform by quenching
Target for Al-based sputtering with fine structure
Al-based sputter characterized by being used as a raw material for a material
A method of refining a manufacturing raw material for a ring target material . 2. The method of refining a manufacturing raw material for an Al-based sputtering target material according to claim 1, wherein the quenching process is a gas atomizing method.