JP2001279433A - METHOD FOR MANUFACTURING PURE Al TARGET PREVENTING ABNORMAL DISCHARGE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a pure Al target with which splash or abnormal discharge and the resultant development of particles can be prevented an deposition of a pure Al film by sputtering. SOLUTION: Machining is carried out after control of the hardness Hv of the sputter surface to >=20, to suppressed the development of surface defects due to working and to prevent abnormal discharges. Moreover, the contents of O and N as finely dispersed oxides and nitrides of Al are limited to >=1 ppm in total to increase the hardness of the target, by which machinability is improved and the of burr is suppressed to prevent abnormal discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a pure Al target used for sputtering a pure Al film.

[0002]

2. Description of the Related Art Pure Al films are widely used as materials for electrode films and reflection films because of their high conductivity and high reflectance in the visible light range. Typical methods for forming a pure Al film include a vapor deposition method and a sputtering method. The former has a feature that the film formation rate is high and the production efficiency is high, and the latter has a film formation rate that is inferior to the former, but the energy of the sputtered particles is low. Because of its high properties, the film is excellent in crystallinity. In particular, a sputtering method is used for forming an electrode of a semiconductor integrated circuit, an electrode of a liquid crystal panel, and a reflective film which require high film quality. The sputtering method is a thin film forming method using a glow discharge of an inert gas.Rare gas ions generated by a glow discharge of a rare gas are accelerated by a potential gradient generated on a target surface,
A film is formed by colliding with the target surface, and the sputter particles are beaten out and adhere to the substrate. In the sputtering method, various improvements have been proposed since the quality of the target affects the uniformity and productivity of the film.

[0003] As described above, since the target is a base material of the film and at the same time functions as an electrode for the glow discharge, a defect in the target causes abnormal discharge during the glow discharge. For example, if the target structure contains defects such as voids, cracks generated in inclusions, and gaps generated near the interface between the matrix and the inclusions, the cooling of the target in the vicinity of the defect becomes insufficient and one of the targets may be damaged. The part is overheated and becomes a liquid phase, and a splash which adheres to the substrate is generated. Further, when the target contains an inclusion such as an oxide, abnormal discharge occurs due to a difference in conductivity from the matrix, and the inclusion itself ruptures to generate particles that adhere to the substrate. Since the above phenomenon causes a reduction in product yield, various target improvement methods have been proposed to reduce defects in the target.

For example, Japanese Patent Application Laid-Open No. 9-25564 discloses a pure A
It is disclosed that splash can be reduced by setting the number of inclusions per unit area to 40 / cm ² or less in a target material made of 1 or Al alloy.

Also, Japanese Patent Application Laid-Open No. 11-315373 discloses that splash can be reduced by setting the maximum length of inclusions included in the target to 20 μm or less in a target material made of pure Al or Al alloy. ing.

[0006] Further, the present applicant has disclosed in Japanese Patent Application Laid-Open No. 9-23566.
In No. 6, the splash in the pure Al and Al alloy targets was heated by the collision of Ar atoms during sputtering, and the strain remaining on the target surface was released.
It discloses that it is presumed to be caused by emission from the target surface as an atomic group, and that the splash can be reduced by adjusting the surface hardness to Hv25 or less.

[0007]

The inventor of the present invention has conducted intensive studies on the cause of abnormal discharge, which is the cause of the splash of the pure Al target. As a result, since pure Al has a low hardness, fine Al is hardly formed during machining. Burrs occur and abrasive grains are entrapped during polishing, and abnormal discharge frequently occurs, especially immediately after the start of sputtering, and a projection called a nodule is generated on the target surface, which becomes a starting point of abnormal discharge later and a new nodule It was found that the number of abnormal discharges increased during the target life due to a vicious cycle in which was generated. Particles such as film fragments peeled around the target during sputtering and dust generated from sliding parts of the sputtering apparatus are also adsorbed on the active target surface, which also causes the generation of nodules. I also understood.

[0008] All of the above-mentioned improvement methods aim at reducing the amount of inclusions which are the starting points of abnormal discharge, and improve the properties of the very surface of the target which affects the abnormal discharge immediately after the start of the above-mentioned sputtering, as well as the particle generation. It was also found that there was no adsorption prevention effect, and no effect was obtained for abnormal discharge due to the above-mentioned causes. An object of the present invention is to provide a method for producing a pure Al target for sputtering, which realizes a stable discharge from immediately after the start of sputtering to the life end.

[0009]

The inventors of the present invention have conducted studies to solve the above-mentioned problems. As a result, by adjusting the hardness of the surface of the pure Al target to Hv 20 or more, fine burrs and abrasives generated by machining are obtained. It has been found that surface defects such as grain penetration are reduced, and abnormal discharge immediately after the start of sputtering when a film is formed using the target is reduced. Further, the present inventors have found that by adjusting the total content of elements selected from O and N contained in the target to be 1 ppm or more, nodules are not generated during sputtering and stable discharge is realized. Reached.

That is, the present invention is a method for producing a pure Al target in which the hardness on the sputter surface side is adjusted to Hv 20 or more, and then the finish sputtering is performed on the sputter surface side.

In the method of manufacturing a target according to the present invention, the total content of O and N is preferably adjusted to 1 ppm or more.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, an important feature of the present invention is that after adjusting the hardness of a sputter surface to Hv20 or more,
To perform finish machining. Sputtered surface hardness is H
The reason for adjusting to v20 or more is that the machinability during machining is particularly improved, and the occurrence of fine burrs and the incorporation of abrasive grains during polishing can be reduced. Thus, when a film is formed from the target, abnormal discharge immediately after the start of sputtering can be reduced. The surface hardness of the sputtered surface is Hv25.
It is preferable to adjust the above, more preferably, H
v30 or more.

In the method for producing a pure Al target of the present invention, the total content of O and N is preferably adjusted to 1 ppm or more. When O and N are added to a pure Al target, oxides and nitrides with Al are generated, and these are finely dispersed in the target structure, thereby increasing the hardness of the target. As a result, the machinability during machining is further improved, and the occurrence of fine burrs and the penetration of abrasive grains during polishing can be further reduced. In addition, the above-mentioned oxides and nitrides both act as release materials, and have an effect of preventing adsorption of particles.

[0014] The total content of O and N is more preferably at least 10 ppm, and even more preferably at least 50 ppm. On the other hand, if the total content of O and N is too large, the electric conductivity of the film may be reduced.
It is preferably at most 000 ppm. The preferred upper limit of the hardness is Hv35.

As the pure Al raw material used in the present invention, a pure Al ingot obtained by a zone melt method, a three-layer electrolytic method, a Ziegler method, an AlCl ₃ bath electrolytic refining method or the like can be used. In the present invention, pure Al means O, N, H,
This is Al having an impurity content of 1% by mass or less, excluding elements such as rare gases. In addition, as a method for producing a billet, a method such as a vacuum melting casting method or a spray forming method can be applied. Alternatively, a method in which a powder obtained by applying a method such as a gas atomizing method or an arc melting method to a pure Al ingot is subjected to pressure sintering by a method such as hot pressing, hot isostatic pressing, hot extrusion shaping, or the like. Can be applied.

Next, the billet is subjected to plastic working with a total working ratio of 50% or more by upsetting forging, rolling, or the like, and is adjusted so as to roughly obtain a sheet material having a desired target size. In addition, the total working rate at the time of plastic working is preferably 60% or more, and more preferably 80% or more. If the hardness of the material surface does not reach Hv20, the material is subjected to cold rolling at a working rate of 10% or less and a strain rate of 0.5 / s or more, so that the hardness of the material surface is adjusted to Hv20 or more. be able to. Further, the surface can be hardened by a method such as shot peening instead of cold rolling. The thickness of the work hardened layer is adjusted so as to exceed at least the thickness of the work layer removed by machining. A pure Al target for forming a pure Al film can be obtained by subjecting the material obtained through the above steps to machining into a desired shape.

In addition, in order to add O and N to the target, in the case of vacuum melting, a method of bubbling a gas composed of these elements into the molten metal, or adding and introducing an oxide or nitride of Al into the molten metal are introduced. can do. In the powder sintering method and the spray forming method, in addition to the above methods, the atmosphere can be introduced by setting the atmosphere to an oxygen atmosphere, a nitrogen atmosphere, or an Ar atmosphere.

When sputtering the target, the target manufactured in the present invention is subjected to a heat treatment or the like.
It is also possible to reduce the hardness of the target surface.

[0019]

EXAMPLES (Example 1) A pure Al lump having a purity of 99.99% was melted in a vacuum and cast into an iron mold having a diameter of 150 mm x 300 mm. Next, this ingot was heated to 200 ° C., and subjected to upsetting forging at a working ratio of 66% to 100 mm by pressing.
It was approximately φ250 mm × 100 mm. This pure Al lump was rolled using a skin pass roll at a rolling reduction of 0.5%. The hardness at the center of the surface corresponding to the sputtered surface of this material was measured with a Vickers hardness meter under a load of 0.98 N, and the hardness before finishing was determined. Subsequently, the target was spun on the sputter surface side as finish machining to obtain a target (sample No. 1) of φ125 × 5 mm. Further, a target whose surface was polished with a # 400 waterproof paper was obtained. (Sample No. 2)

(Example 2) A pure Al lump having a purity of 99.99% was melted in a vacuum, Al ₂ O ₃ and AlN were added to the molten metal, and oxygen and nitrogen were introduced into the molten metal.
Cast into an iron mold. Next, this ingot was heated to 200 ° C., subjected to upsetting forging at a working ratio of 66% to 100 mm by a press, and was set to approximately φ250 mm × 100 mm. Then, the hardness before finishing was measured in the same manner as in Example 1. Subsequently, machining was performed, and the sputter surface side of the target was lathe-finished as finish machining to obtain a target (sample Nos. 3, 4, and 5) of φ125 × 5 mm.

Example 3 Pure Al powder having a purity of 99.99% was atomized with Ar gas to obtain pure Al powder. This powder was classified with a # 32 sieve to remove coarse-grained powder, and then filled into a soft iron HIP can having a diameter of 200 mm x 15 mm and a thickness of 2 mm, and a lid welded.
While evacuating with an oil diffusion pump connected to a degassing pipe, degassing was performed by heating at 400 ° C. or more for 1 h, and 550 at a pressure of 120 MPa using a hot isostatic press.
After pressure sintering at 1 ° C. × 1 h, the hardness before finishing was measured in the same manner as in Example 1. Subsequently, the HIP can was removed by machining, and the sputter surface side of the target was lathe-finished as finish machining to obtain a φ125 × 5 mm target (sample N).
o. 6) was obtained.

Example 4 A billet having a size of φ150 mm × 300 mm was prepared by applying a spray forming method using nitrogen gas as an atomizing gas to a pure Al lump having a purity of 99.99%. This billet was heated to 200 ° C., and subjected to upsetting forging at a working ratio of 66% up to 100 mm by a press to make it approximately φ250 mm × 100 mm. Then, the hardness before finishing was measured in the same manner as in Example 1. Subsequently, the sputtering surface side of the target was lathe-finished as finish machining to obtain a target (sample No. 7) of φ125 × 5 mm.

(Example 5) Pure Al lump having a purity of 99.99% was atomized with H ₂ gas to obtain a pure Al powder. This powder was classified with a # 32 sieve to remove coarse powder, and the size of the powder filling portion was φ150 × 300 mm.
Filled into a soft iron HIP can with a thickness of 2 mm, welded the lid, and degassed by heating at 400 ° C or higher for 1 h while evacuating with an oil diffusion pump connected to a degassing pipe. After sintering at 550 ° C. × 1 h under a pressure of 120 MPa using a hydrostatic press, the HIP can was removed.
Next, it is heated to 200 ° C. and subjected to upsetting forging with a processing rate of 66% up to 100 mm by pressing.
After having a size of mx 100 mm, this pure Al lump was rolled using a skin pass roll at a rolling reduction of 0.5%, and then machined. Thereafter, the hardness before finishing was measured in the same manner as in Example 1, and subsequently, the sputtering surface side of the target was subjected to lathe finishing as finish machining to obtain a target (sample No. 8) of φ125 × 5 mm.

(Comparative Example 1) Pure aluminum ingot having a purity of 99.99% was melted in vacuum, cast into an iron mold having a diameter of 250 mm x 100 mm, and the pure aluminum ingot was subjected to machining and finished in the same manner as in Example 1. Pre-hardness is measured, finish machining is performed and φ12
A 5 × 5 mm target (sample No. 9) was obtained.

(Comparative Example 2) A pure aluminum lump having a purity of 99.99% was vacuum-melted and cast into an iron mold having a diameter of 150 mm x 300 mm. The billet was heated to 600 ° C and pressed to 200 mm by pressing to maintain a processing rate of 33%. After ingot forging was performed to form a pure Al lump having a diameter of about 180 mm x 200 mm, and then machined, the hardness before finishing was measured in the same manner as in Example 1. Subsequently, the target surface was subjected to lathe finishing for finish machining, and a target of φ125 × 5 mm (sample No. 1)
0) was obtained.

The above target was mounted on a sputtering apparatus having a magnetron cathode, and the ultimate vacuum degree was 8.0 × 1.
0 ^-5 Pa after it evacuated to below, by introducing a high-purity Ar gas to 0.4 Pa, voltage 500 by the DC power supply
V and a current of 1 A were applied to perform sputtering. At this time, an arc monitor was attached between the cathode and the power supply, and a setting was made so that a case where the amount of decrease in the absolute value of the voltage exceeded 200 V was detected as an arc, and the number of arcs generated was counted. Table 1 shows the relationship between the above results and the hardness before finishing.

[0027]

[Table 1]

Table 1 shows that the sample No. Since the abnormal discharge occurred frequently immediately after the start of discharge for the targets 9 and 10,
It can be seen that the number of arcs generated is large over the entire measurement time, and that the target manufactured according to the present invention has extremely little abnormal discharge, especially immediately after the start of sputtering, as compared with the target of the comparative example. Further, in all the samples listed in Table 1, burrs at the time of machining and embedding of abrasive grains at the time of polishing were confirmed by a scanning electron microscope. As a result, the sample N of the present invention example
o. Regarding Samples Nos. 1 to 8, it was not possible to confirm burrs at the time of machining and embedding of abrasive grains at the time of polishing. Burrs during machining for 9 and 10,
Abrasion of abrasive grains during polishing was confirmed. This is considered to be caused by abnormal discharge that occurred frequently immediately after the start of sputtering.

[0029]

According to the present invention, it is possible to reduce burrs at the time of machining during the production of a pure Al target, and to reduce the penetration of abrasive grains at the time of polishing, thereby significantly reducing abnormal discharge generated at the time of sputtering. Pure A from what you can do
This is an indispensable technique in the manufacture of a product using the l film.

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[Procedure amendment]

[Submission date] April 11, 2000 (2004.1.
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0023

[Correction method] Change

[Correction contents]

Example 5 Pure Al powder having a purity of 99.99% was atomized with N ₂ gas to obtain pure Al powder. This powder was classified with a # 32 sieve to remove coarse powder, and the size of the powder filling portion was φ150 × 300 mm.
Filled into a soft iron HIP can with a thickness of 2 mm, welded the lid, and degassed by heating at 400 ° C or higher for 1 h while evacuating with an oil diffusion pump connected to a degassing pipe. After sintering at 550 ° C. × 1 h under a pressure of 120 MPa using a hydrostatic press, the HIP can was removed.
Next, it is heated to 200 ° C. and subjected to upsetting forging with a processing rate of 66% up to 100 mm by pressing.
After having a size of mx 100 mm, this pure Al lump was rolled using a skin pass roll at a rolling reduction of 0.5%, and then machined. Thereafter, the hardness before finishing was measured in the same manner as in Example 1, and subsequently, the sputtering surface side of the target was subjected to lathe finishing as finish machining to obtain a target (sample No. 8) of φ125 × 5 mm.

Claims (2)

[Claims] 1. A method for producing a pure Al target, comprising: adjusting the hardness on the sputter surface side to Hv 20 or more; and performing finish machining on the sputter surface side. 2. The method for producing a pure Al target according to claim 1, wherein the total content of O and N is adjusted to 1 ppm or more.