JP4775911B2 - Method for producing aluminum-lithium alloy target and aluminum-lithium alloy target - Google Patents

Description

  The present invention relates to a method for producing an aluminum-lithium alloy target used in a sputtering apparatus and an aluminum-lithium alloy target produced using the method.

  An organic electroluminescence (organic EL) element is required to have a material that can realize high luminous efficiency and high luminance and has high environmental stability. An Al—Li (aluminum-lithium) alloy is known as a material that satisfies such requirements. Patent Document 1 described below describes that an electron injection electrode (cathode) of an organic EL element is formed of a sputtered film of an Al—Li alloy.

  By the way, uniformity is strongly required for the sputtering target. Specifically, the alloy elements are uniformly dispersed, there are few impurities, there are few inclusions, the crystal structure is uniform, and the resistance value distribution is good. . In an alloy system in which a material (lithium) that easily reacts with oxygen, nitrogen, and moisture is used as an additive element, such as an Al-Li alloy, in the alloying, suppression of slag generation, suppression of moisture, melting furnace / treatment It is necessary to suppress the reaction with the refractory used in the tool.

  As a conventional Al-Li alloy production method, an Al-Li alloy production method by atmospheric melting (see Patent Document 2) and an Al-Li alloy production method by vacuum melting (see Patent Document 3) are known. . Patent Documents 4 and 5 disclose a method for producing a single crystal target of an aluminum-based alloy in which the concentration distribution is made uniform by controlling the addition amount of the additive element and the casting control or solidification control of the molten metal. Yes.

JP 11-329746 A Japanese Patent Publication No. 6-47697 JP-A-6-330203 JP-A-7-300667 Japanese Patent Laid-Open No. 11-12727

  Conventionally, Al-Li alloys have been developed mainly for aircraft applications, and development of melt casting technologies such as atmosphere control, selection of refractories, examination of molten metal cleaning methods, lithium addition methods, etc. are progressing. Has been. Therefore, an ingot for a sputtering target having a high purity and a low inclusion content necessary for thin film production has not been produced.

In order to make an ingot having high cleanliness for a sputtering target for thin film production, it is natural to suppress compound formation with impurities in the dissolved material, but lithium and oxygen, nitrogen and moisture in the atmosphere. The reaction must be suppressed. Lithium has an extremely low melting point of 180 ° C., and its specific gravity is 0.53 g / cm ³ and is the lightest element in the metal. Lithium easily reacts with oxygen and nitrogen, and easily forms hydroxide due to the presence of moisture. For this reason, dissolution for alloying aluminum and lithium is very difficult.

  When melting aluminum for alloying in the atmosphere, disperse the material and place it in a crucible so that the contact efficiency between the aluminum and the material to be alloyed increases, or disperse the material. Thus, a method of charging into molten aluminum is taken. However, the specific gravity is about one-fifth that of aluminum, and dissolution of alloying with metallic lithium, which is very active against oxygen and moisture, is undesirable because lithium oxidation occurs and alloying is hindered.

  On the other hand, during cooling and solidification, when lithium cannot be dissolved in the aluminum crystal phase and crystallized or precipitated as AlLi (β phase) at the grain boundary, the plastic workability is significantly reduced, and forging and rolling into a plate shape. It is difficult to process the sputtering target due to cracking during processing or edge cracking at the edge. In addition, in a target obtained from an ingot in which a molten Al—Li alloy is cast, when AlLi (β phase) crystallizes or precipitates outside the aluminum crystal phase, it becomes a two-phase mixed region with different specific resistance. Causes abnormal discharge during sputtering film formation. Therefore, it is necessary to determine the upper limit value of the lithium content of the Al—Li alloy that minimizes crystallization or precipitation of AlLi (β phase).

  This invention is made | formed in view of the above-mentioned problem, and makes it a subject to provide the manufacturing method and aluminum-lithium alloy target of an aluminum-lithium alloy target with little composition of impurities and inclusions and a uniform composition distribution.

  In solving the above problems, the present invention provides a method for producing an aluminum-lithium alloy target for sputtering composed of an aluminum single phase, which is installed in a melting furnace maintained in a vacuum atmosphere or an inert gas atmosphere. A first step of melting aluminum in the crucible, a second step of forcibly immersing and stirring lithium lump in the molten aluminum in the crucible, and a molten aluminum-lithium alloy in the crucible It has the 3rd process to pour, and the 4th process which performs structure | tissue control of the said aluminum-lithium alloy ingot.

  In the first step, aluminum is melted with a crucible in a melting furnace maintained in a vacuum atmosphere or an inert gas atmosphere. Next, in the second step, the lithium lump is forcibly immersed in molten aluminum and stirred. By performing lithium melting in the melting furnace, oxidation of lithium during alloying is suppressed, and generation of lithium-containing compound slag is prevented. Further, by forcibly immersing lithium in the molten aluminum and stirring it, concentration unevenness due to the specific gravity difference between aluminum and lithium is prevented, and lithium is uniformly dispersed.

  The second step includes a step of immersing the tip of the graphite plunger to which the lithium block is fixed in the crucible, and a step of rotating the plunger to stir the molten metal. The lithium mass is accommodated in an aluminum case. This case is melted together with the lithium block in the molten aluminum. The plunger stands by directly above the crucible, and a heat shielding plate is installed between the crucible and the plunger during melting of aluminum to prevent melting of lithium due to radiant heat. The molten metal is agitated by rotating the plunger around its axis.

  In order to obtain an Al—Li alloy target for sputtering composed of an aluminum single phase, the amount of lithium added is preferably 3% by weight or less. Here, the Al—Li alloy composed of an aluminum single phase means a solid solution of Al element and Li element. According to the Al-Li equilibrium diagram, the maximum solid solubility limit of metal Li with respect to metal Al is 4 wt% at about 600 ° C. However, the maximum solid solubility limit of metallic Li decreases along the solubility curve as the temperature decreases. Therefore, when the amount of Li added exceeds the maximum solid solubility limit, it is impossible to prevent AlLi (β phase) from crystallization into the aluminum phase and precipitation from the supersaturated solid solution during solidification. If there are two-phase mixed compositions having different specific resistances, the plastic workability deteriorates and the processing accuracy decreases. Further, from the viewpoint of a sputtering target, abnormal discharge is induced, the film formation rate becomes unstable, and the film thickness distribution also deteriorates. For the above reasons, the amount of lithium added is 3% by weight or less.

  In the third step, the crucible is tilted in the melting furnace, and a molten aluminum-lithium alloy is poured into a mold installed adjacent to the crucible. Foreign matter such as lithium oxide, nitride or hydroxide by consistently melting aluminum, adding and melting lithium, and casting in a melting furnace maintained in a vacuum or inert gas atmosphere It is possible to obtain an Al—Li alloy ingot with a very small amount. Moreover, in order to suppress precipitation of inclusions in the aluminum phase, it is preferable to solidify at an appropriate cooling rate. For example, a method of casting a molten metal while forcibly cooling the mold is preferred, as well as using a material having high thermal conductivity such as copper for the mold.

  In the fourth step, the structure of the produced aluminum-lithium alloy ingot is controlled. Ingot structure control includes a forging process including rolling and drawing for processing into a desired target shape, and a heat treatment process for removing internal stress and adjusting the crystal structure. These process temperatures are preferably performed at a temperature lower than the eutectic temperature for the purpose of preventing precipitation of lithium inclusions in the aluminum phase, and specifically, performed at a temperature condition of 550 ° C. or lower.

  The aluminum-lithium alloy target produced as described above can obtain a homogeneous aluminum single-phase structure with a small amount of foreign matter and inclusions and a composition distribution within ± 5%. Therefore, the occurrence of abnormal discharge during sputtering film formation can be suppressed, and the film formation rate can be stabilized and the film thickness distribution can be made uniform.

  As described above, according to the present invention, it is possible to obtain an aluminum-lithium alloy target with a small content of foreign matter and inclusions and a uniform composition distribution.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing a configuration of a melting furnace 10 applied to a method for producing an aluminum-lithium (Al—Li) alloy target according to an embodiment of the present invention. The melting furnace 10 includes a vacuum tank 11 having an exhaust port 11c connected to a vacuum pump (not shown), a crucible 12 installed in the inside of the vacuum tank 11 (melting chamber), and a position directly above the crucible 12. A plunger 13 is provided.

  An aluminum block 21 is inserted into the crucible 12, and a lithium block 22 is held at the tip of the plunger 13. The inside of the vacuum chamber 11 is adjusted to a predetermined vacuum atmosphere or an atmosphere replaced with an inert gas. As will be described later, the melting furnace 10 melts the aluminum block 21 in the crucible 12 and then immerses the tip of the plunger 13 in the molten aluminum to melt the lithium lump 22.

  The crucible 12 is a bottomed cylindrical body made of graphite and is accommodated in the movable container 14. A fire-resistant holding member 16 around which a coil 15 is wound around the outer peripheral portion is fixed inside the movable container 14, and the crucible 12 is accommodated inside the holding member 16. The holding member 16 is made of carbon, for example. The movable container 14 is rotatably installed with respect to the base member 17 via a rotation shaft 18. The crucible 12, the holding member 16 and the aluminum block 21 are heated by energizing the coil 15.

  The rotation shaft 18 is connected to a rotation mechanism (not shown) installed outside the vacuum chamber 11, and is configured so that the movable container 14 can rotate with respect to the base member 17. Alternatively, the movable container 14 may be pushed and operated to rotate the movable container 14 around the rotation shaft 18.

  A lip 12A serving as a pouring port is formed at the minimum rotational radius position of the opening peripheral edge of the crucible 12. A plurality of support rods 12B having substantially the same protruding height as the lip 12A are attached to the other region of the opening peripheral edge of the crucible 12. The support rod 12B is formed of a material that can withstand relatively thermal shock, such as graphite or stainless steel.

  And the heat shielding board 19 is mounted on the front-end | tip of these lips 12A and the support bar 12B. The heat shielding plate 19 is for preventing the lithium block 22 from being melted by radiant heat when the aluminum block 21 is melted. The heat shielding plate 19 is made of, for example, graphite, and is configured so as to be able to selectively take the illustrated position for shielding the opening of the crucible 12 and the position for opening the opening of the crucible 12. Specifically, movement control of the shielding plate 19 is performed using, for example, a manipulator (not shown).

  The plunger 13 is made of a compressed graphite material. The plunger 13 is connected to a drive mechanism (not shown) installed outside the vacuum chamber 11, and is configured to be capable of vertical movement along the axial direction and rotational movement around the axis.

  An aluminum case 23 that holds the lithium mass 22 is held at the tip 13 </ b> A of the plunger 13. For example, the case 23 is formed by deforming a foil or a sheet into an appropriate shape. Preferably, the lithium block 22 is vacuum-sealed inside the case 23. In the present embodiment, the case 23 is held at the distal end portion 13 </ b> A of the plunger 13 using an aluminum wire 24. The case 23 and the wire 24 are formed with the same purity as the aluminum block 21.

  A mold 25 is installed in the vacuum chamber 11. The mold 25 is installed adjacent to the movable container 14, and receives the molten Al—Li alloy flowing out from the crucible 12 through the lip 12 </ b> A by rotating around the rotating shaft 18, and at the same time is cooled and solidified. Then, an Al-Li alloy ingot having a predetermined shape is formed. The mold 25 includes a cooling plate 26 provided with a cooling water circulation mechanism therein, a mold 27 installed on the cooling plate 26, and a thin carbon installed between the cooling plate 26 and the mold 27. A sheet 28 is provided. The shape and height of the mold 27 are not particularly limited, and are appropriately selected according to the ingot shape to be formed, such as a circle or a rectangle. The carbon sheet 28 is installed for the purpose of preventing a drop in releasability of the ingot after casting.

  Next, the manufacturing method of the Al-Li alloy target of this embodiment using the melting furnace 10 comprised as mentioned above is demonstrated. 2A to 2C are schematic views of main steps for explaining the method for producing the Al—Li alloy target of the present embodiment.

(First step)
First, the aluminum block 21 is inserted into the crucible 12. The purity of the aluminum block 21 is preferably as high as possible. For example, a purity of 99.99% (4 nines) or more is used. As long as the required amount of molten metal is obtained, the shape and number of aluminum blocks 21 are not particularly limited.

  On the other hand, the case 23 in which the lithium mass 22 is accommodated is held by the tip 13 </ b> A of the plunger 13. The purity of the lithium block 22 is preferably as high as possible, and for example, a purity of 99.9% (3 nines) or more is used. The case 23 is fixed to the distal end portion 13A of the plunger 13 by using an aluminum wire 24. Of course, the case 23 is not limited to this, and the case 23 may be fixed by an engaging action with the distal end portion 13A.

Next, the inside (dissolution chamber) of the vacuum chamber 11 is evacuated and maintained at a predetermined degree of vacuum. The pressure in the melting chamber is not particularly limited, but it is preferable that the degree of vacuum is relatively high from the viewpoint of preventing the oxidation reaction of aluminum and lithium during melting, for example, a pressure of 1.33 Pa (10 ⁻² Torr) or less. Is set.

  On the other hand, the atmosphere in the melting chamber is not limited to a vacuum atmosphere, and may be an atmosphere replaced with an inert gas such as argon (Ar). In this case, the inside of the vacuum chamber 11 is once evacuated to a predetermined pressure, and then argon gas is introduced into the vacuum chamber 11. The pressure in the melting chamber at this time is set to a pressure lower than the atmospheric pressure.

  After the pressure adjustment in the vacuum chamber 11 is completed, the heat shielding plate 19 is installed above the crucible 12, and the coil 15 is energized and the crucible 12 is heated. The heating temperature of the crucible 12 is set higher than the melting point of aluminum (about 660 ° C.). Thereby, the aluminum block 21 is melted in the crucible 12.

  In the present embodiment, since the aluminum block 21 is melted in an atmosphere cut off from the atmosphere, the aluminum reaction at the time of melting can be suppressed, and a molten aluminum with less impurities such as oxides can be obtained. .

  Further, since the lithium block 22 has a lower melting point (180 ° C.) than aluminum, the lithium block 22 may be melted by the radiant heat when the aluminum block 21 is melted. However, in this embodiment, since the upper part of the crucible 12 is covered with the heat shielding plate 19 when the aluminum block 21 is melted, the radiant heat from the crucible 12 does not reach the case 23, and therefore the melting of the lithium lump 22 is avoided. can do.

(Second step)
Subsequently, melting for alloying of aluminum and lithium is performed (FIG. 2A). In this step, first, the heat shielding plate 19 covering the upper part of the crucible 12 is removed. Then, the plunger 13 is lowered by a predetermined amount, and the tip portion 13A is immersed in the molten aluminum to dissolve the lithium lump 22. At this time, both the aluminum case 23 and the wire 24 are also melted.

  Subsequently, the plunger 13 is rotated around its axis to stir the molten metal 20 in the crucible 12 (FIG. 2B). The stirring action can be obtained mainly by the shape effect of the plunger tip 13A. In the present embodiment, the plunger tip portion 13A is formed in a shape in which protrusions (blades) are projected at a plurality of locations on the outer peripheral portion thereof, so that a large stirring action can be obtained only by the rotation of the plunger 13.

  In this embodiment, since the addition of the lithium block 22 to the molten aluminum is performed inside the vacuum tank 11 whose atmosphere is adjusted, the oxidation of lithium during alloying is suppressed, and the lithium-containing compound slag Occurrence can be prevented. Moreover, since the lithium lump 22 is forcibly immersed in the molten aluminum and stirred by the method as described above, the occurrence of uneven density due to the difference in specific gravity between aluminum and lithium is prevented, and lithium is It can be uniformly dispersed in the molten aluminum. Furthermore, since the crucible 12 is made of graphite, it is possible to prevent the crucible 12 from attacking on the surface of the molten aluminum containing lithium and to suppress the formation of lithium-containing compounds.

  Here, the Al—Li alloy used as the sputtering target is preferably an aluminum single phase from the viewpoint of plastic workability and film formation characteristics during use. An Al—Li alloy composed of an aluminum single phase means a solid solution of an Al element and a Li element. When the alloy structure becomes multiphase, the composition distribution (concentration distribution) of the additive element increases, and the plastic workability decreases. Also, resistance distribution occurs on the target surface, causing abnormal discharge, and it becomes impossible to stabilize the film formation rate and make the film thickness distribution uniform.

  In order to obtain an Al—Li alloy target for sputtering composed of an aluminum single phase, the amount of lithium added is preferably 3% by weight or less based on the total alloy component. In the present embodiment, the addition amount of the lithium block 22 is 3% or less of the total weight of the aluminum block 21, the case 23, the wire 24 and the lithium block 22.

  FIG. 3 schematically shows an Al—Li system equilibrium diagram (source: “BINARY ALLOY PHASE DIAGRAMS” Second Edition, T. B Massalski, ASM INTERNATIONAL ISBN: 0-87170-404-8). The maximum solid solubility limit of lithium with respect to aluminum is 4% by weight at 596 ° C. However, the maximum solid solubility limit of lithium decreases along the solubility curve SC with decreasing temperature. Therefore, when the amount of lithium added exceeds the maximum solid solubility limit, crystallization of AlLi (β phase) in the aluminum phase cannot be prevented during solidification. In the present embodiment, the amount of lithium added is suppressed to 3% by weight or less, and an Al—Li alloy target composed of an aluminum single phase is produced by casting a molten metal at a cooling rate of a certain level or higher as described later. Like to do.

(Third step)
Next, a step of casting the molten Al-Li alloy 20 in the crucible 12 into the mold 25 is performed (FIG. 2C). In this step, the crucible 12 is tilted by turning the movable container 14 counterclockwise in FIG. 1 around the turning shaft 18, and the molten metal 20 is poured into the mold 25. Cooling water is circulated inside the cooling plate 26 constituting the mold 25. Therefore, the Al—Li alloy melt 20 flowing out from the crucible 12 is solidified at a constant cooling rate in the mold 25. Thereby, precipitation of AlLi (β phase) in the aluminum phase due to supersaturation of lithium can be prevented, and the aluminum single phase can be maintained even after solidification.

  In the present embodiment, since melting of aluminum, addition / dissolution of lithium, and casting are performed consistently in a melting furnace maintained in a vacuum atmosphere, lithium oxide, nitride, or hydroxylation is performed. It is possible to obtain an Al—Li alloy ingot with very few foreign substances such as objects.

(Fourth process)
Subsequently, the structure control of the obtained Al—Li alloy ingot is performed. Ingot structure control includes a forging process including rolling and drawing for processing into a desired target shape, and a heat treatment process for removing internal stress and adjusting the crystal structure.

  The process temperature here is 550 ° C. or lower. This is because, even when the lithium content is below the maximum solid solubility limit and the alloy structure is a single phase, the β phase may be precipitated by subsequent plastic working / heat treatment depending on the process temperature. For example, even if the process temperature is equal to or lower than the eutectic point, the eutectic line may be exceeded locally due to the uniformity of the heating furnace and overheating of the processed part. Precipitation of the β phase causes abnormal discharge such as increase in voltage and occurrence of arcing when used as a target, resulting in variations in film formation rate. Therefore, in the present embodiment, considering the temperature change of several tens of degrees during the process, the upper limit of the process temperature is set to 550 ° C. or less so as to avoid the multi-phase of the target alloy structure.

  As described above, the Al—Li alloy target according to the present invention is manufactured. According to the Al—Li alloy target of this embodiment, an aluminum single-phase structure with a small content of foreign matter and inclusions and a uniform composition distribution (for example, within ± 5%) can be obtained. Therefore, the occurrence of abnormal discharge during sputtering film formation can be suppressed, and the film formation rate can be stabilized and the film thickness distribution can be made uniform.

Example 1
An Al—Li alloy ingot was produced using the melting furnace 10 described with reference to FIG. As the aluminum block 21, rod-shaped high-purity aluminum (purity 99.99%) of about 30 mm square was used. As the case 23 for housing the lithium lump 22, a high-purity aluminum rolled into a foil having a thickness of 0.2 mm was prepared. For the lithium lump 22, rod-shaped lithium (manufactured by Honjo Metal Co., Ltd., purity 99.9%) having a diameter of 10 mmφ was used.

As the crucible 12, a crucible made of compressed graphite was used. The shape of the crucible 12 was a bottomed cylinder, and as shown in FIG. 4, the one having an inner diameter of 175 mmφ and a depth of 300 mm was used. 7,750 g of high purity aluminum was set in this crucible, the pressure in the melting furnace was reduced to 1.33 × 10 ⁻² Pa, and then the crucible was heated to 750 ° C. by induction heating (40 kW) to obtain high purity aluminum. Dissolved.

  Here, as shown in FIG. 4, the temperature of the molten aluminum was monitored by using a CA sheathed thermocouple inserted in a high-purity graphite thermocouple protection tube 30 installed in the crucible 12. The outer shape of the protective tube 30 was 15 mm in length, 15 mm in width, 310 mm in height, 4 mmφ in inner diameter, and 300 mm in depth.

  3% by weight of lithium was wrapped twice with a high-purity aluminum foil having a thickness of 0.2 mm, and tied and fixed to the tip 13A of the plunger 13 located at the upper part of the crucible with a high-purity aluminum wire (99.99%). A graphite heat shield plate 19 was installed in the opening of the crucible so that the opening of the crucible was opened immediately before the addition of lithium.

Even when the temperature of the molten aluminum was 750 ° C., the pressure in the furnace was maintained at 1.33 × 10 ⁻² Pa. Next, after removing the heat shield at this temperature and opening the crucible opening, the plunger was quickly moved to forcibly immerse the lithium mass held at the tip of the molten aluminum in the molten aluminum and stirred for 1 minute . Thereafter, induction heating of the crucible was stopped, and casting was performed from the crucible to a mold (inner diameter 260 mmφ, height 60 mm) at about 700 ° C. to obtain a disk-shaped aluminum-lithium alloy melt.

  As shown in FIG. 5, a part (point a, point b) 20 mm inside from the center of the top part and bottom part of the obtained ingot, and a part 5 c inside the height direction center part of the side surface of the ingot (c Samples were taken from each point, and the composition of lithium was analyzed by ICP-AES (high frequency plasma emission spectroscopy). The analysis results were 3.08% by weight at point a, 2.90% by weight at point b, 3.02% by weight at point c, and within 3.0% by weight ± 5%.

  The ingot after sampling was subjected to press forging and rolling to obtain a sputtering target having a thickness of 12 mm and a diameter of 200 mmφ. The process temperature of press forging was 550 ° C., rolling after heat treatment, and final heat treatment was performed at 450 ° C. It is bonded to a copper cooling plate (backing plate) with an indium-based brazing material, and this is set in a sputtering device, and sputtering treatment is performed for 1 hour under DC sputtering conditions of a reduced pressure argon gas atmosphere of 0.9 Pa and 1 kW. went. During sputtering, abnormal discharge phenomenon did not appear and was stable.

Thereafter, the target was removed from the apparatus, and surface observation of the target, cross-sectional observation cut into a cross, and composition analysis were performed. A CCD magnifier with a magnification of 50 times was used for surface observation and cross-sectional observation. The target surface after the sputtering test was smooth with no depressions, protrusions, or swellings observed over the entire surface. No voids or the like were observed in the entire cross section cut into a cross. At the central portion of the cross-sectional thickness, samples were taken from the target outer peripheral portion, the intermediate portion, and the central portion as follows, and lithium composition analysis was performed by ICP-AES method.
As a result of the measurement,
4 locations on the outer periphery: 3.08 wt%, 2.98 wt%, 2.88 wt%, 2.86 wt%
4 middle parts: 3.02% by weight, 2.96% by weight, 3.00% by weight, 2.86% by weight
1 central part: 2.88% by weight
It was within 3.0% by weight ± 5% for a total of nine places.

  In addition, for tissue observation, sampling was performed from the vicinity of the sampling position of the sample for composition analysis of the cross-section from two outer peripheral portions, two intermediate portions, and one central portion. From the structure observation result of the Al—Li alloy, it was confirmed that the aluminum single phase was in a state where lithium was dissolved in aluminum.

(Example 2)
An Al—Li alloy target was produced in the same manner as in Example 1 except that the Al—Li alloying was dissolved in an argon gas atmosphere.

The pressure in the melting furnace was 1.33 × 10 ⁻² Pa to melt the aluminum in the crucible. When the temperature of the molten aluminum is 750 ° C., the pressure in the furnace is once reduced to 2.66 Pa, and then high purity aluminum argon gas (purity 99.999%, dew point temperature −70 ° C. or less) is introduced into the furnace. The pressure was reduced to 6.66 × 10 ⁴ Pa in the atmosphere. Next, the crucible lid (heat shielding plate) was opened at this temperature, the plunger was lowered, and the lithium lump was forcibly immersed in the molten aluminum and stirred for 1 minute. After the induction heating of the crucible was stopped, the crucible was cast into a mold having an inner diameter of 260 mmφ and a height of 60 mm and solidified by cooling to obtain an Al—Li alloy ingot. The subsequent steps were the same as in Example 1, and a sputtering target having a thickness of 12 mm and a diameter of 200 mmφ was obtained.

  The obtained sputtering target was subjected to the same sputtering test and composition analysis as in Example 1. Sputtering was possible without abnormal discharge, and the composition analysis result was within m3.0% by weight ± 5%. Moreover, as a result of sampling and sampling from two outer peripheral parts, two intermediate parts, and one central part in the vicinity of the sampling position of the sample for composition analysis of the cross section, as in Example 1, lithium was contained in aluminum. Was confirmed to be a single phase of aluminum in a solid solution state.

(Example 3)
An Al—Li alloy ingot was produced in the same manner as in Example 2 except that the shape of the mold was 220 mm in width, 500 mm in length, and 25 mm in depth. Thereafter, the surface was cut and press forging and rolling were performed, and an ingot having a thickness of 10 mm and a length of 1000 mm could be produced without causing cracks. Further, the shape was processed into a sputtering target having a thickness of 8 mm and a diameter of 200 mmφ, and the same sputtering test and composition analysis as in Example 1 were performed. Sputtering was possible without abnormal discharge, and the compositional analysis result was within 3.0% by weight ± 5%. Moreover, as a result of sampling and sampling from two outer peripheral parts, two intermediate parts, and one central part in the vicinity of the sampling position of the sample for composition analysis of the cross section, as in Example 1, lithium was contained in aluminum. Was confirmed to be a single phase of aluminum in a solid solution state.

(Comparative Example 1)
Using an atmospheric heating furnace (electric furnace) for heating at 1000 ° C., 7,000 grams of high-purity aluminum was set in a magnesia crucible (inner diameter 175 mmφ, depth 300 mm) and dissolved in the atmosphere by overheating. The aluminum oxide generated on the surface was removed with an alumina plate, and a predetermined amount of lithium wrapped in an aluminum foil was quickly put into the molten aluminum as in Example 1. Part of the charge floated as an oxide on the surface of the melt. The oxide (slag) floating on the surface of the molten metal was removed with an alumina plate.

  The Al—Li alloy melt in the crucible was cast into a mold having an inner diameter of 260 mmφ and a height of 60 mm and cooled to obtain an Al—Li alloy ingot. 5 mm inside part (points a and b in FIG. 5) from the center of the top and bottom parts in the height direction of this ingot, and a part 5 mm inside from the center part in the height direction of the side surface of the ingot (in FIG. 5) Samples were taken from each point c), and lithium composition analysis was performed by ICP-AES (high frequency plasma emission spectroscopy). As a result of the analysis, the point a was 2.82% by weight, the point b was 2.56% by weight, the point c was 2.98% by weight, and the maximum was 3.0% by weight-15%.

  The ingot after sampling was press forged and rolled to a thickness of 15 mm. Although a sputtering target having a thickness of 12 mm and a diameter of 200 mmφ was used, foreign matter and voids were observed when the surface was observed. When this sputter target was cut into a cross and observed in a cross section, foreign matter and voids were observed even in the cross section, and could not be used as a sputtering target for film formation.

(Comparative Example 2)
The Al—Li alloying was dissolved in an argon gas atmosphere by a vacuum induction heating furnace. 4% by weight of lithium is wrapped twice in high-purity aluminum foil with a thickness of 0.2mm, lightly fixed to the tip of the plunger (see Fig. 1) with aluminum wire so that it can be easily detached by vibration, and hung on the top of the crucible. . The conditions up to the lithium alloying were the same as in Example 2. However, the addition of lithium was performed by opening the crucible lid and lightly vibrating the plunger to drop the lithium block wrapped with aluminum foil onto the molten aluminum surface.

  Oxide-like suspended matter was observed on the slowly rotating aluminum melt surface. After the induction heating was stopped, it was cast into a mold having an inner diameter of 260 mmφ and a height of 60 mm and cooled to obtain an Al—Li alloy ingot. 5 mm inside part (points a and b in FIG. 5) from the center of the top and bottom parts in the height direction of this ingot, and a part 5 mm inside from the center part in the height direction of the side surface of the ingot (in FIG. 5) Samples were taken from each point c), and lithium composition analysis was performed by ICP-AES (high frequency plasma emission spectroscopy). The analysis results were 3.02% by weight at point a, 2.88% by weight at point b, 2.90% by weight at point c, and within 3.0% by weight ± 5%.

  The subsequent steps were the same as in Example 1, and a sputtering target having a thickness of 12 mm and a diameter of 200 mmφ was obtained. Then, the same sputter test and composition analysis as in Example 1 were performed. In the 1 hour sputter test, five abnormal discharges occurred. The target surface was observed after the sputter test, the cross section was cut into a cross, and the composition was analyzed. On the surface, protrusions that were thought to have occurred during abnormal discharge were confirmed, and 13 holes or dents of about 1 mm were observed over the entire surface. Moreover, in the cross-sectional observation, a lot of voids and the like that seem to be solidified by entraining a part of the oxide were also seen. Further, as a result of sampling and sampling from two outer peripheral parts, two intermediate parts, and one central part in the vicinity of the sampling position of the composition analysis sample, an aluminum phase and an AlLi phase in which lithium is dissolved in aluminum ( It was confirmed that the two phases were composed of (β phase).

  As mentioned above, although embodiment and the Example of this invention were described, of course, this invention is not limited to these, A various deformation | transformation is possible based on the technical idea of this invention.

  For example, in the embodiments and examples described above, aluminum is dissolved in the crucible in a vacuum atmosphere. However, the present invention is not limited to this, and aluminum is dissolved in an inert gas atmosphere such as argon gas. You may make it perform.

  In the above embodiment, the mold 25 is configured by combining the cooling plate 26 and the mold 27. However, a mold in which the cooling plate 26 and the mold 27 are integrally formed may be used.

It is a sectional side view showing a schematic structure of a melting furnace used in an embodiment of the present invention. It is principal part sectional drawing which shows typically the lithium alloying process and casting process which are demonstrated in embodiment of this invention. It is an Al-Li system equilibrium state diagram. It is the top view and side sectional view which show the structure of the graphite crucible used in the Example of this invention. It is a figure which shows the sample collection position for the composition analysis of the Al-Li alloy ingot in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Melting furnace 11 Vacuum tank 12 Crucible 13 Plunger 14 Movable container 18 Rotating shaft 19 Heat shielding plate 20 Al-Li alloy molten metal 21 Aluminum block 22 Lithium lump 25 Mold

Claims (7)

A method for producing a sputtering aluminum-lithium alloy target comprising an aluminum single phase, comprising:
A first step of melting aluminum in a crucible installed in a melting furnace maintained in a vacuum atmosphere or an inert gas atmosphere;
In the aluminum melt in the crucible, a second step of immersing the tip of the graphite plunger lithium mass fixed, for stirring the molten metal by rotating the plunger,
A third step of casting a molten aluminum-lithium alloy in the crucible;
And a fourth step of controlling the structure of the aluminum-lithium alloy ingot. A method for producing an aluminum-lithium alloy target. The method for producing an aluminum-lithium alloy target according to claim 1 , wherein the lithium lump is accommodated in an aluminum case, and the case is melted together with the lithium lump. In the second step, the plunger is located immediately above the crucible,
2. The method for producing an aluminum-lithium alloy target according to claim 1 , wherein a heat shielding plate is installed between the crucible and the plunger during melting of aluminum. 2. The method for producing an aluminum-lithium alloy target according to claim 1 , wherein the amount of the lithium block added is 3% by weight or less. 2. The aluminum-lithium alloy according to claim 1, wherein in the third step, the crucible is tilted, and the molten aluminum-lithium alloy is cast into a mold installed adjacent to the crucible. 3. Target manufacturing method. The method for producing an aluminum-lithium alloy target according to claim 1, wherein the fourth step includes a forging step and a heat treatment step, and the step temperature is 550 ° C or lower. An aluminum-lithium alloy target manufactured by the method for manufacturing an aluminum-lithium alloy target according to claim 1,
An aluminum-lithium alloy target, wherein the lithium content is 3% by weight or less and the composition distribution is within ± 5%.

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