JP2001214261A - METHOD FOR REFINING STRUCTURE OF Al SERIES TARGET MATERIAL FOR SPUTTERING - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for refining the structure of an Al series sputtering target material capable of preventing structural segregation and the formation of coarse compounds. SOLUTION: The method for refining the structure of an Al series target material for sputtering in which a molten alloy containing one or more elements selected from transition metals by 10 atomic % or less, essentially containing the group 3A elements as the above transition elements and the balance substantial by Al is subjected to rapid cooling treatment to finely disperse and form compounds in the target structure is applied.

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 more particularly to an Al-based sputtering target material used for thin-film electrodes and thin-film wiring of a liquid crystal display (hereinafter abbreviated as LCD).
This is a method related to miniaturization of the structure of a system sputtering target material.

[0002]

2. Description of the Related Art Conventionally, a pure Cr film, a pure Ta film, which is a high melting point metal, and an electric wiring film and an electrode used for an LCD, a thin film sensor, etc. for producing a thin film device on a glass substrate, 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 and low stress and to stabilize their characteristics in order to prevent signal delay. For example, for electrodes used in large color LCDs of 12 inches or more, 15μ
Ωcm or less is required. However, the conventional C
r, Ta-based high melting point alloy films have excellent film stability, but have high resistance, about 30μΩcm for Cr and about l80μΩ for Ta.
cm, about 60 μΩcm for Ti. For this reason, Al-based films having lower resistance than these metals are used.

In addition, as the size of the substrate increases, the size of the target material for forming the metal film is also required to increase. For example, in order to stably produce a high-quality metal film in accordance with the high definition of LCDs, a sputtering device used for forming a metal film is a conventional very large substrate transport type in-line type device. Therefore, a single-wafer type apparatus for forming a film while keeping the substrate stationary has come to be widely used. In this single-wafer 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 a required target material size,
Target materials manufactured in two- or three-part sizes have been used by bonding.However, in the case of target materials that have been split for high definition, foreign matter is generated from the joints, resulting in failure. There is a demand for a target material.

[0005] At present, the mainstream substrate size is 370 x 470 mm, and a target material for a single-wafer sputtering apparatus for forming a metal film on this substrate is a large target material having a sputtering surface of about 550 x 650 mm. Must be manufactured integrally. In general, a target material for Al-based sputtering is often manufactured by casting an Al alloy to produce an ingot, and machining the ingot to obtain a target material. However, an alloy mainly composed of Al is excellent in plastic workability in the cold state, so that it is easier to manufacture a large target material integrally as compared with the case of manufacturing a target material of a high melting point metal such as Cr or Ta. In some cases, forging, cold rolling, or the like is performed on the cast ingot to perform machining on the shape of the target material. For example, in order to manufacture a large-sized target material having a flat area of 0.3 m ² or more for a single wafer type corresponding to 550 x 650 mm, the ingot should be large, and a high cold working rate (about 80% or more) should be obtained. It has been manufactured by performing plastic working and mechanical working so that an integrated target material can be manufactured by applying the same.

There have also been many proposals 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, and thus a TFT (Thin-Film-Tr
In the heating step (about 250 to 400 ° C.) after the formation of the electrode film, which is inevitable in the manufacturing process, there is a problem that minute projections called hillocks are formed on the surface.
This hillock is considered to be generated by stress migration, thermal migration, and the like. When this hillock occurs, an insulating film, a protective film, and the like are formed on the Al wiring film, and further, a wiring film, an electrode film, and the like will be formed. In this case, there is a problem in that an electrical short circuit (short) or an etchant or the like invades through the hillock and the Al wiring film is corroded.

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

[0008]

As described above, the conventional Al-based sputtering target materials include those to which an additional element is added to prevent hillocks and a casting method for preventing segregation thereof. The emphasis was on. In a method of obtaining a target material by a melt casting method by a conventional improvement method, macrosegregation of Al and an additive element in an ingot structure can be prevented by, for example, quenching as much as possible. However, in the case of the casting method, since agglomeration portions of compounds such as flakes are generated in the structure and micro segregation inevitably remains, a problem of segregation still exists for a minute thin film such as an LCD wiring. .

As a method of preventing macroscopic segregation of the target material, a method of mixing powder and sintering the mixture 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 zone, it is conceivable to use fine raw material powder. However, the fine Al powder and the additive element powder have not been able to obtain a satisfactory target material having a uniform structure due to handling problems such as measures against oxidation and ignition and manufacturing problems such as agglomeration of the powder during mixing. Further, as pointed out in JP-A-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 reduced due to the difference in sputtering efficiency of each element. There is a problem that it fluctuates over time.

Also, in the case of an Al-based target material, when an ingot is enlarged and sputtering is performed using a target material that has been plastically worked at a high working rate in a cold state, there is a problem that abnormal splash called splash occurs from the target material. is there. Splash is abnormal droplets generated from the target material, and is larger than ordinary sputtered particles. If this splash adheres to the substrate, there is a possibility of causing short-circuit between wires, disconnection, etc. And there is a problem that the yield of the manufactured liquid crystal display is greatly reduced.

The generation of the splash from the Al target material is a serious problem since it directly leads to defects when used for forming wiring. In particular, when a large-sized target material having a flat area of 0.3 m2 or more, which is necessary for obtaining a large-sized LCD, is applied, countermeasures are urgently required as a cause of failure of an expensive large-sized liquid crystal display.

The present inventors have intensively studied the cause of the splash. As a result, they found that the cause of the splash was a minute void in the target material. As a result of further investigation, one of the causes of the generation of this minute void is
When manufacturing a large ingot by the melt casting method, it was found that Al was in a shrinkage cavity generated due to a large thermal shrinkage of Al. Another cause is that although the Al melt dissolves hydrogen, it releases hydrogen when it cools and solidifies, and this hydrogen tends to generate fine voids. Particularly, in order to prevent segregation, if the solidification is carried out by quenching as quickly as possible, the voids are easily included in the ingot.

Further, an Al compound generated by an additive element other than Al may be broken during processing into a target material, and may cause voids. The present inventor studied to suppress the generation of minute voids in the target material structure. As long as the melt casting method was applied, it was difficult to suppress the generation of voids due to shrinkage cavities and dissolved hydrogen. Therefore, the inventor tried to apply the powder sintering method. When the powder sintering method is applied, the above-described shrinkage cavities and the generation of voids due to dissolved hydrogen can be suppressed. However, when 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 the reaction with Al, and this compound is also formed by a melting casting method. It was found that, like the compound to be prepared, it was liable to crack during processing and formed voids that caused splash.

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

[0015]

Means for Solving the Problems The present inventor has found that even in the case of containing a Group 3A element which easily forms a flaky compound with Al, the compound can be uniformly dispersed by quenching treatment such as gas atomization. The inventors have found that a fine structure can be obtained, and have reached the present invention.

That is, the present invention contains 10 atomic% or less of any one or more of the elements selected from transition elements, essentially contains a Group 3A element as the transition element, and substantially contains Al This is a method for refining the structure of an Al-based sputtering target material in which a compound in a target structure is finely dispersed and formed by quenching a molten alloy consisting of: In the present invention, it is preferable to apply a gas atomizing method to the quenching process.

The inventors of the present invention have studied the ingot structure of an Al alloy to which a Group 3A element has been added. As a result, the Group 3A element tends to form a flaky compound with Al. It has been found that voids are likely to be generated which cause the above.

Further, it has been found that by applying a quenching treatment, which has not been conventionally used, to the production of an Al alloy target essentially containing a group 3A element, the structure can be refined even when the group 3A element is included. . Specifically, the structure obtained by the present invention has a reduced Al region (hereinafter, referred to as an “Al uneven distribution region”) containing no compound with Al having a major axis of 0.5 μm or more. Further, the compound to be dispersed can be made as fine as 5 μm or less in circumscribed circle diameter.

In the present invention, the transition element is S
3A called rare earth element consisting of c, Y, lanthanoid
Group, 4A group of Ti, Zr, Hf, 5A of V, Nb, Ta
Group, Cr, Mo, W 6A group, Mn, Tc, Re 7A
Group, Fe, Co, Ni, Ru, Rh, Pd, Os, I
It belongs to 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 deposited in the structure as an intermetallic compound by performing a heat treatment at a heating temperature of 150 ° C to 400 ° C.
The precipitated compound becomes a pinning point for suppressing the growth or flow of Al crystal grains due to heat or potential difference,
Hillock is prevented from being generated in the thin film.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the most significant feature is
It has been found that a method of finely dispersing and forming a compound with Al in the target material structure has been found. This fine structure
The molten metal quenching method can be performed by using an atomizing method such as a gas atomizing method. The application of the molten metal quenching method is intended not only to prevent Al segregation by the conventional melting and casting method but also to achieve unprecedented uniformity of the concentration distribution of the formed thin film by a 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.
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 cross-sectional structure of the target material may be 10 or less, preferably less than 5. Further, the Al unevenly distributed region which does not contain the compound having a major axis of 0.5 μm or more may have an inscribed circle diameter of 10 μm or less with respect to the compound.

As a method for introducing an element for preventing such hillocks into the Al-based target material, a sintering method is preferably applied. If the additive element is powdered and introduced as it is,
It reacts with Al during the sintering process and typically forms a coarse flaky compound such as a rose flower or a dendritic coarse compound in many cases. When a coarse compound is present, cracks easily occur in the structure due to a load such as rolling. A void is generated in the cracked portion, and a splash occurs during sputtering.

According to the study of the present inventor, the generation of the voids causing the splash depends on the form of the compound in the tissue, and is made as small as possible, preferably by a spherical shape having an aspect ratio close to 1, It has been found that the occurrence can be prevented. As described above, in the present invention, the aspect ratio defined by the major axis / minor axis of the compound having a size of 0.5 μm or more in the cross-sectional structure of the target material can be set to less than 5, and even if rolling or the like is applied, the splash ratio can be reduced. This is preferable because it is difficult to generate the void.

As a result of further study, when powder is produced, for example, by the spray quenching method, among the powder, small particles having a high solidification rate, typically particles having a diameter of 200 μm or less, show that the compound does not grow into a thin plate. By sintering this, a target material that can further prevent the generation of voids that cause splash even by processing such as rolling can be obtained. Further, in the present invention, the reason why the circumscribed circle diameter of the compound is preferably 5 μm or less is that even if the total processing rate is 50% or more by dispersing fine particles of less than or equal to 50 μm, it is caused by cracking of the compound. This is because no voids were generated and no increase in splash was confirmed.

When, for example, a powder is produced by the spray quenching method of the present invention, it is desirable that the powder be sintered at 400 ° C. or more and 600 ° C. or less. If the temperature is lower than 400 ° C., sintering hardly proceeds, and if the temperature exceeds 600 ° C., there is a risk that Al is dissolved. 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 cause splashes in the target material, and must be avoided as much as possible.

When rolling at a working ratio of 50% or more, cracking during working can be reduced by increasing the working temperature. Substantially higher than the recrystallization temperature of Al 4
The temperature is desirably set to 00 ° C. or higher, and 550 ° C. or lower which does not exceed the melting point of Al due to a local temperature rise due to processing such as rolling.

[0027]

(Example 1) An ingot of an Al alloy system shown in Table 1 was melt-cast, and the ingot was formed into a rapidly solidified powder by a gas atomizing method in a nitrogen gas atmosphere, and then classified to have a volume average diameter of 60 µm. 133mm inside diameter
It was filled in a 15 mm-high iron can, and heated and degassed while evacuating to a pressure of 10 ⁻³ Pa or less. Next, under pressure of 100 MPa and temperature of 550 ° C., the material is pressed and sintered by HIP (Hot Isostatic Press) and then machined to be processed into a target material having a diameter of 100 mm and a thickness of 4 mm. Wood was obtained.

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

The structure of the target material obtained according to the present invention and the comparative example was observed with a 400 × optical microscope.
The maximum major axis (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 in the Al region were measured. Table 1 shows the results. Further, as a typical structure obtained by the present invention and a comparative example, in a sample having a composition of Al-2 atomic% Nd, a sample No. FIG. 1 shows a photograph of the structure of FIG.
Sample No. of the simple sintered target material according to the comparative example. FIG. 2 shows a photograph of the structure of Sample No. 12 of the smelting target material sample No. 14 are shown in FIG. FIG.
FIG. 3 to FIG. 3 are optical microscope photographs at 400 × magnification.
Further, the surface of the target material obtained by the present invention and the comparative example was mirror-polished, and voids of 1 μm or more were detected by the dye penetrant inspection method.

[0030]

[Table 1]

As is clear from Table 1 and FIGS.
The sample No. obtained according to the present invention. 1 to No. No. 7 is a structure in which the fine compound is dispersed in the structure. on the other hand,
The simple sintered target material obtained in the comparative example has a structure in which a coarse compound exists. In the ingot target material obtained by another comparative example, the compound is finer than the simple sintered target material, but the aspect ratio of the compound is increased, and the compound is flat, It can be seen that there is a wide Al region where no compound exists. In addition, in the voids obtained by the dye penetrant inspection method, the target material of the melting method tends to be slightly increased.

An Ar pressure of 0.3 Pa and a DC magnetron sputtering method using the obtained target material.
An Al alloy film having a thickness of 200 nm is formed on a 4-inch Si wafer under the condition of an input power of 0.5 kW, and after using all target materials at an input power of 0.5 kW for about 1 hour,
After about 20 hours of use, changes in the composition of the films formed were examined. Further, 10 films were formed for each target material under the above-mentioned film forming conditions, and 5 μm was observed on the film surface.
A foreign substance of m or more was regarded as a splash, and the average number per substrate was calculated. Table 2 shows the results.

[0033]

[Table 2]

As shown in Table 2, the target material sample no. 1 to No. 1 In No. 7, the concentration of the transition metal hardly changes during the sputtering period. On the other hand, the simple sintered target material sample No. obtained in the comparative example. 11 and No. In No. 12, the transition metal concentration in the formed thin film tends to increase, which is not preferable. In addition, in the smelted target material obtained by another comparative example, the change in the concentration of the transition metal in the formed thin film is smaller than that of the single sintered target material,
It is larger than the target material obtained by the present invention. In addition, in the case of the smelting target material, the number of splashes increases in response to the large number of defects, which is not preferable.

Example 2 An ingot of an Al alloy system shown in Table 3 was melt-cast, and the ingot was formed into a rapidly solidified powder by a gas atomizing method in a nitrogen gas atmosphere, and then classified to have a volume average diameter of 60 μm. 330mm ×
Fill 530mm x 50mm iron cans, 10 minus 3 P
Heating was performed while evacuating to a pressure equal to or lower than a to perform degassing. Next, at a pressure of 100 MPa and a temperature of 550 ° C., HI
After sintering under pressure by P (Hot isostatic press), rolling,
The target material of 550 mm × 690 mm × 6 mm was machined to obtain a target material.

As a comparative example, pure A having a volume average diameter of 60 μm was used.
1 powder and an additive element metal powder having a volume average diameter of 35 μm were mixed with a rocking mixer, and this powder was filled in a 330 mm × 530 mm × 50 mm iron can and subjected to degassing in the same manner as the sample of the present invention. Next, after pressure sintering by HIP in the same manner as in the present invention, rolling and machining were performed to form a target material of 550 mm × 690 mm × 6 mm, and a single sintered target material shown in Table 3 (sample No. 31) , Sample No. 32). Further, as another comparative example, a molten metal whose alloy composition was adjusted was 330 mm × 530 mm.
Cast into a flat plate mold of iron of mm × 50 mm, roll it, and then machine it to form 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 target material structures obtained by the present invention and the comparative example were observed, and the maximum major axis of the compound present in the structures (substantially equivalent 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 l region was measured. Further, as a typical structure obtained by the present invention and a comparative example, Al-2 atomic%
In the sample having the composition of Nd, the target material sample No. FIG. 4 shows a photograph of the structure of Sample No. 23 of the sample No. of the single sintered target material obtained in the comparative example. FIG. 5 shows a photograph of the structure of the ingot target material sample No. 32 obtained by another comparative example. FIG. 6 shows photographs of the structure of each of the 34 samples. 4 to 6 are 400 times optical microscope photographs. Further, the surface of the target material obtained by the present invention and the comparative example was mirror-polished, and 1 μm
The gaps of m or more were detected, and the numbers are shown in Table 3.

[0038]

[Table 3]

As is clear from Table 3 and FIGS.
The target material sample no. 21-N
o. Reference numeral 27 denotes a structure in which a fine compound is dispersed in the structure. On the other hand, the simple sintered target material obtained in the comparative example has a structure in which a coarse compound exists.
Also, in this single-piece sintered target material, a large gap corresponding to the black portion in the photograph of FIG. 5 is formed. This is because the compound was cracked by rolling and voids were generated. In the smelted target material obtained in another comparative example, the compound is finer than that of the single sintered target material, but a wide Al region in which no compound is present remains. Further, the number of defects is slightly increased as compared with the first embodiment. This was presumed to be due to the fact that the compound having a large aspect ratio was cracked to form voids.

An Ar pressure of 0.3 Pa and a DC magnetron sputtering method using the obtained target material.
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 a power supply of 11 kW. With respect to all the target materials, the composition change 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. In addition, 10 films were formed for each target material under the above film forming conditions, and a foreign substance of 5 μm or more observed on the film surface was regarded as a splash, and the average number per substrate was calculated. Table 4 shows the results.

[0041]

[Table 4]

As shown in Table 4, the target material sample no. 21 to No. 21 No. 27 shows that the transition metal concentration hardly changes during the sputtering period. On the other hand, the simple sintered target material sample No. obtained in the comparative example. 31 and No. 31. Sample No. 32 has a tendency that the transition metal concentration in the formed thin film tends to increase significantly, which is not preferable. Further, as shown in Table 3, the application of rolling caused many voids in the target material, which significantly increased the number of splashes, which is not preferable. Further, in the smelted target material obtained in another comparative example, the change in the concentration of the transition metal in the formed thin film was smaller than that of the simple sintered target material, as in Example 1, but was obtained by the present invention. It is larger than the target material. In addition, although the smelting target material is not as large as the single sintered target material, the number of defects is larger than that of the target material obtained according to the present invention, and it can be seen that the number of splashes is increased accordingly.

[0043]

According to the present invention, fluctuations in the film composition can be eliminated and defects can be reduced with respect to an Al-based target material for LCDs having a flat area of 0.3 m2 or more, in which the occurrence of slash is a major problem. As a result, it became possible to suppress the splash. Therefore, the present invention is extremely effective in achieving an improvement in LCD quality as a target material corresponding to an LCD that needs to be further enlarged.

[Brief description of the drawings]

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

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

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

FIG. 4 is a photograph showing the metal microstructure of a target material that has been rolled after applying the present invention.

FIG. 5 is a photograph showing a metal microstructure of a simple sintered target material subjected to a rolling process of a comparative example.

FIG. 6 is a photograph showing a metal microstructure of a rolled smelted target material of a comparative example.

Claims (2)

[Claims] 1. An alloy melt containing 10 atomic% or less of one or more elements selected from transition elements, essentially including a Group 3A element as the transition element, and substantially the remainder of Al Wherein the compound in the target structure is finely dispersed and formed by quenching the structure of the target material. 2. The method according to claim 1, wherein the quenching treatment is a gas atomization method.