TWI448571B - Aluminum-lithium alloy target and manufacturing method of the same - Google Patents

Description

Aluminum-lithium alloy target manufacturing method and aluminum-lithium alloy target

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

An organic electroluminescence (organic EL) device is required to have high luminous efficiency and high luminance, and is a material having high environmental stability. An Al-Li (aluminum-lithium)-based alloy is known as a material that satisfies such requirements. In the following Patent Document 1, an electron injecting electrode (cathode) in which an organic EL element is formed by a sputtering film of an Al—Li-based alloy is described.

However, for targets for sputtering, uniformity is strongly required. Specifically, the alloying elements are required to be uniformly dispersed, the impurities are less, the inclusions are less, the crystal structure is uniform, and the resistance value distribution is good. In an alloy system in which an element (lithium) which is easily reacted with oxygen, nitrogen, or water is used as an additive element in an Al-Li-based alloy, it is necessary to suppress the generation of slag and suppress moisture when it is alloyed. And inhibiting the reaction with the refractory used in the melting furnace or tool.

In the method for producing an Al-Li alloy, a method for producing an Al-Li alloy which is melted in the atmosphere (see Patent Document 2), and a method for producing an Al-Li alloy which is vacuum-melted (refer to the patent document) 3). Further, in Patent Documents 4 and 5, it is disclosed that the uniformity of the concentration distribution is achieved by performing the addition amount of the additive element or the casting control or solidification control of the melt. A method for producing a single crystal target of an aluminum alloy.

Patent Document 1: Japanese Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. 5: Japanese Special Report No. 11-12727

In the past, the development of the Al-Li alloy was mainly carried out for use as an aircraft, and has been developed in terms of environmental casting gas control, selection of refractory materials, review of the cleaning method of the molten metal, and melting casting technology such as the lithium addition method. Therefore, an ingot for a sputtering target having high purity and a small inclusion content required for producing a film has not yet been produced.

In order to produce an ingot with high cleanliness required for sputtering targets for film production, it is of course necessary to inhibit the formation of compounds with impurities in the molten material, but it is necessary to inhibit the reaction of lithium with oxygen, nitrogen and water in the atmosphere. . The melting point of lithium is extremely low to 180 ° C, and its specific gravity is the lightest element in the metal, which is 0.53 g/cm ³ . Further, lithium is liable to react with oxygen or nitrogen, and it is easy to form a hydroxide due to the presence of moisture. Therefore, the melting required for the alloying of aluminum and lithium is extremely difficult to carry out.

In the melting of aluminum alloying in the atmosphere, a method of dissolving the material in a manner of increasing the contact efficiency between the aluminum and the alloyed material, and then heating and melting the mixture, or dispersing the material and putting it into the aluminum melt The method in the middle. However, the specific gravity is about one-fifth of that of aluminum, and it is oxygen and moisture. In the melting of the alloy of highly active metal lithium and aluminum, oxidation of lithium is caused to hinder alloying, which is not preferable.

On the other hand, in the process of cooling and solidification, if lithium cannot be solid-melted in the aluminum crystal phase, lithium crystallizes or precipitates in the grain boundary outside the aluminum crystal phase to become AlLi (β phase). At this time, the plastic workability of the ingot is remarkably lowered, or cracking or edge cracking (cracking near the edge) occurs during forging processing into a plate shape and rolling processing, and it is difficult to perform ingot processing to manufacture sputtering. Target. Further, in the target obtained by casting the ingot of the molten Al-Li alloy, when AlLi (β phase) crystallizes or precipitates out of the aluminum crystal phase, a two-phase mixed region having a specific resistance is formed, and It is the cause of abnormal discharge when it is sputtered. Therefore, it is necessary to specify the upper limit of the lithium content of the AlLi (β phase) crystal or the Al-Li alloy which precipitates very little.

The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing an aluminum-lithium alloy target having an impurity and a small inclusion content and having a uniform composition distribution, and an aluminum-lithium alloy target.

In order to solve the above problems, the present invention is a method for producing an aluminum-lithium alloy target, wherein the aluminum-lithium alloy target for sputtering is composed of a single phase of aluminum, and is characterized by the following steps: Dissolving aluminum in a crucible disposed in a melting furnace maintained in a vacuum environment or an inert gas atmosphere; in the second step, forcibly impregnating the lithium in the aluminum melt in the crucible and stirring; in the third step, the foregoing crucible The molten aluminum-lithium alloy is cast in the mold; and in the fourth step, the microstructure control of the ingot of the aluminum-lithium alloy is performed.

In the first step, aluminum is melted while being maintained in a vacuum furnace or an inert gas atmosphere. Next, in the second step, the lithium block is forcibly immersed in the aluminum melt and stirred. By performing lithium melting in the melting furnace, oxidation of lithium during alloying or the like is suppressed, and generation of lithium-containing compound slag is prevented. Further, by forcibly immersing lithium in the aluminum melt and stirring it, it is possible to prevent the occurrence of density unevenness due to the difference in specific gravity between aluminum and lithium, and to uniformly disperse lithium in the aluminum melt.

The second step includes a step of immersing the end portion of the graphite plug to which the lithium block is fixed in the crucible, and a step of rotating the plug to agitate the melt. The lithium block is housed in an aluminum case. The tank system is melted together with the lithium block in the aluminum melt. The plug is placed in a standby position directly above the crucible, and in the melting of aluminum, a heat shielding plate is provided between the crucible and the plug, thereby preventing melting of lithium due to radiant heat in the first step. The stirring of the melt is performed by the rotation of the plug around the shaft.

In order to obtain an Al—Li alloy target for sputtering composed of a single aluminum phase, the amount of lithium added is preferably 3% by weight or less. Here, the Al-Li alloy composed of a single phase of aluminum means a solid solution of an Al element and a Li element. According to the Al-Li equilibrium state diagram, the maximum solid concentration limit of the metal Li with respect to the metal Al is 4% by weight at about 600 °C. However, the maximum solid melting limit of the metal Li decreases along the melting curve as the temperature decreases. Therefore, when Li is added at a maximum solid concentration or more, it is impossible to prevent AlLi (β phase) from being crystallized in the aluminum phase and precipitated from the supersaturated solid solution during solidification. When such crystallization or precipitation occurs, the plastic workability is deteriorated and the processing accuracy is lowered. In addition, from the viewpoint of the target for sputtering, Since the existence of the two-phase mixed composition having a different specific resistance causes an abnormal discharge to be induced and the film formation rate becomes unstable, 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 the molten aluminum-lithium alloy is cast into a mold provided adjacent to the crucible. In a melting furnace maintained in a vacuum environment or an inert gas atmosphere, it is possible to obtain a foreign matter such as lithium oxide, nitride or hydroxide by performing aluminum alloy melting, lithium addition/melting, and casting. Al-Li alloy ingot. Further, in order to suppress the inclusion of inclusions in the aluminum phase, it is preferred to solidify at a moderate cooling rate. For example, it is preferable to use a material having a high thermal conductivity such as copper in the mold, and it is preferable to carry out the melt casting while forcibly cooling the mold.

In the fourth step, the structure control of the ingot of the obtained aluminum-lithium alloy is performed. The structure control of the ingot includes a forging step including rolling or drawing processing for processing into a desired target shape, and a heat treatment step for removing internal stress and adjusting the crystal structure. The purpose of these process temperatures is to prevent lithium inclusions from being precipitated in the aluminum phase, preferably at a temperature lower than the eutectic temperature, and specifically, at a temperature of 550 ° C or lower.

The aluminum-lithium alloy target manufactured by the above method can obtain a homogeneous aluminum single phase structure in which the content of foreign matter and inclusions is small and the composition is distributed within ±5%. Therefore, the occurrence of abnormal discharge can be suppressed at the time of sputtering film formation, 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, an aluminum-lithium alloy target having a small content of foreign matter and inclusions and a uniform composition distribution can be obtained.

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

Fig. 1 is a schematic cross-sectional view showing the configuration of a melting furnace 10 which is 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 chamber 11 including an exhaust port 11c connected to a vacuum pump (not shown), a crucible 12 disposed inside the vacuum chamber 11 (melting chamber), and a plug 13 located at the crucible 12 Just above it.

The aluminum block 21 is loaded in the crucible 12, and the lithium block 22 is held at the end before the plug 13. The interior of the vacuum chamber 11 is adjusted to a predetermined vacuum environment or an environment in which it is replaced with an inert gas. As will be described later, the melting furnace 10 is formed by melting the aluminum block 21 in the crucible 12, and then immersing the end portion of the plug 13 in the aluminum melt to melt the lithium block 22.

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

The rotating shaft 18 is coupled to a rotating mechanism (not shown) provided outside the vacuum chamber 11, and is configured to freely rotate the movable container 14 with respect to the base member 17. Or can be set to push the movable container to make the movable volume The device 14 is configured to rotate about the rotating shaft 18.

In the position of the minimum rotational radius of the peripheral portion of the opening of the crucible 12, a lip portion 12A as a spout is formed. In the other region of the peripheral portion of the opening of the opening 12, a plurality of support bars 12B having substantially the same protruding height as the lip portion 12A are attached. The support rod 12B is formed of a material that is more resistant to thermal shock such as graphite or stainless steel.

Further, a heat shielding plate 19 is placed on the front end of the lip portion 12A and the support rod 12B. The heat shielding plate 19 is for preventing the lithium block 22 from being melted due to the radiant heat when the aluminum block 21 is melted. The heat shielding plate 19 is formed of, for example, graphite, and is configured to selectively take a position where the opening of the crucible 12 is shielded and a position where the opening of the crucible 12 is opened. Specifically, the movement control of the heat shield plate 19 is performed using, for example, a manipulator (not shown).

The plug 13 is formed of a compressed graphite material. The plug 13 is connected to a drive mechanism (not shown) provided outside the vacuum chamber 11, and is configured to be movable up and down along the axial direction of the drive mechanism and to rotate around the circumference of the shaft.

The end portion 13A holds the aluminum case 23 for accommodating the lithium block 22 before the plug 13. The case 23 is formed by deforming, for example, a foil-like or sheet-like aluminum material into an appropriate shape. It is preferable that the lithium block 22 is vacuum-sealed inside the casing 23. In the present embodiment, the casing 23 is held by the aluminum wire member 24 at the end portion 13A before the plug 13. Further, the casing 23 and the wire 24 are formed of the same purity as the aluminum block 21.

A mold 25 is provided inside the vacuum chamber 11. The mold 25 is disposed adjacent to the movable container 14 and is rotated about the rotation axis 18. The action receives the Al-Li alloy melt flowing from the crucible 12 via the lip portion 12A while cooling and solidifying, thereby forming an ingot of an Al-Li alloy of a predetermined shape. The mold 25 includes a cooling plate 26 having a circulation mechanism for cooling water therein, a mold frame 27 disposed above the cooling plate 26, and a thin carbon sheet 28 disposed on the cooling plate 26 and the mold frame Between 27 and. The shape and height of the mold frame 27 are not particularly limited, and may be appropriately selected into a circular shape, a square shape, or the like depending on the shape of the ingot to be formed. The carbon sheet 28 is provided for the purpose of preventing the mold release property of the ingot after casting from being lowered.

Next, a method of producing the Al-Li alloy target of the embodiment using the melting furnace 10 configured as described above will be described. Figs. 2A to 2C are schematic diagrams showing main steps of a method of manufacturing an Al-Li alloy target according to the embodiment.

(Step 1)

First, the aluminum block 21 is loaded into the crucible 12. The higher the purity of the aluminum block 21, the better, for example, a purity of 99.99% (4 nine) or more can be used. The shape or the number of blocks of the aluminum block 21 is not particularly limited as long as the required amount of melt is available.

On the other hand, the case 23 in which the lithium block 22 is housed is held at the end portion 13A before the plug 13. The higher the purity of the lithium block 22, the better, for example, a purity of 99.9% (3 nine) or more can be used. Although the aluminum body wire 24 is used for fixing the front end portion 13A of the plug 23 to the plug 13, it is of course not limited, and the case 23 can be fixed by cooperation with the front end portion 13A.

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

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

After the pressure regulation of the vacuum chamber 11 is completed, the heat shielding plate 19 is placed above the crucible 12, and the energization control of the coil 15 is further performed to perform the heat treatment of the crucible 12. The heating temperature of 坩埚12 is set to a temperature 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 environment sealed from the atmosphere, the reaction of aluminum during melting can be suppressed, and an aluminum melt having less impurities such as oxide can be obtained.

Further, since the melting point (180 ° C) of the lithium block 22 is lower than that of aluminum, when the aluminum block 21 is melted, the lithium block 22 is melted due to the radiant heat of aluminum. However, in the present embodiment, since the upper portion of the crucible 12 is covered with the heat shielding plate 19 at the time of melting of the aluminum block 21, the radiant heat from the crucible 12 does not reach the case 23, so that the melting of the lithium block 22 can be avoided.

(Step 2)

Next, the melting required for the alloying of aluminum and lithium is carried out (Fig. 2A). In this step, the heat shielding plate 19 covering the upper portion of the crucible 12 is first removed. Then, the plug 13 is lowered by a predetermined amount, and the front end portion 13A thereof is immersed in aluminum. The lithium block 22 is melted in the melt. Further, at this time, the aluminum case 23 and the wire 24 are also melted together.

Next, the plug 13 is rotated about its axis and the melt 20 in the crucible 12 is stirred (Fig. 2B). The stirring action can be mainly obtained by the shape effect of the plug front end portion 13A. In the present embodiment, the plug distal end portion 13A is formed such that the protruding portion (blade) protrudes at a plurality of positions on the outer peripheral portion of the distal end portion 13A, whereby only the rotation of the plug 13 can be obtained. Stirring.

In the present embodiment, the operation of adding the lithium block 22 to the aluminum melt in the vacuum chamber 11 adjusted in the environment is performed, so that oxidation of lithium during alloying and the like can be suppressed, and slag of the lithium-containing compound can be prevented. produce. In addition, since the lithium block 22 is forcibly immersed in the aluminum melt by the above method and stirred, it is possible to prevent the lithium from being uniformly dispersed in the aluminum melt due to the density unevenness caused by the difference in specific gravity between aluminum and lithium. In the liquid. Further, since the crucible 12 is made of graphite, it is possible to prevent the impact of the lithium-containing compound on the surface of the molten aluminum containing lithium, and to suppress the formation of the lithium-containing compound.

Here, the Al-Li alloy used as the target for sputtering is preferably a single aluminum phase from the viewpoint of plastic working and film forming properties at the time of use. The Al-Li alloy composed of a single phase of aluminum means a solid solution of an Al element and a Li element. When the alloy structure becomes multi-phase, the composition distribution (concentration distribution) of the added elements becomes large, and the plastic workability is lowered. Further, the presence of a mixed composition of two phases having different specific resistances causes a discharge distribution on the surface of the target to cause abnormal discharge, and it is impossible to achieve uniformization of the film formation rate and uniformity of the film thickness distribution.

In order to obtain an Al-Li alloy target for sputtering composed of a single phase of aluminum, the amount of lithium added is preferably 3% by weight or less based on the total composition of the alloy. In the present embodiment, the amount of lithium block 22 added 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 is a diagram showing the Al-Li equilibrium state diagram (taken from "BINARY ALLOY PHASE DIAGRAMS" Second Edition, T.B Massalski, ASM INTERNATIONAL ISBN: 0-87170-404-8). The maximum solid solubility limit of lithium relative to aluminum is 596 ° C, 4 wt%. However, the maximum solid solution limit of lithium decreases along the meltability curve SC as the temperature decreases. Therefore, the amount of lithium added above the maximum solid concentration limit cannot prevent AlLi (β phase) from being precipitated into the aluminum phase during solidification. In the present embodiment, the amount of lithium added is reduced to 3% by weight or less, and the melt is cast at a cooling rate of a certain temperature or more as described later, thereby producing Al-Li composed of a single phase of aluminum. Alloy target.

(Step 3)

Next, a step of casting the melt 20 of the Al-Li alloy in the crucible 12 to the mold 25 is carried out (Fig. 2C). In this step, the movable container 14 is rotated in the counterclockwise direction about the rotation shaft 18 in Fig. 1, whereby the crucible 12 is tilted, and the melt 20 is cast to the mold 25. The cooling water is circulated inside the cooling plate 26 constituting the mold 25. Therefore, the Al-Li alloy melt 20 flowing out of the crucible 12 is solidified in the mold 25 at a certain cooling rate. Thereby, AlLi (β phase) crystals can be prevented from being precipitated into the aluminum phase due to supersaturation of lithium, and the aluminum single phase can be maintained after curing.

In this embodiment, the melting furnace is maintained in a vacuum environment. Among them, aluminum is melted, lithium is added, melted, cast, and the like, and an Al-Li alloy ingot having few foreign matters such as lithium oxide, nitride, or hydroxide can be obtained.

(Step 4)

Next, the structure control of the obtained Al-Li alloy ingot is performed. The structure control of the ingot includes a forging step including rolling or drawing processing for processing into a desired target shape, and a heat treatment step for removing internal stress and adjusting the crystal structure.

The process temperature here is set to 550 ° C or lower. This is because even if the lithium content is below the maximum solid concentration limit and the alloy structure is a single phase, the β phase may be precipitated due to subsequent plastic working or heat treatment due to the difference in process temperature. For example, even at a process temperature below the eutectic point, locality exceeds the eutectic line (eutectic temperature) due to the uniformity of the furnace or the overheating of the processed portion. When the β phase is precipitated, it causes a voltage rise and an abnormal discharge such as arcing when used as a target, and the film formation rate is uneven. Therefore, in the present embodiment, the upper limit of the process temperature is set to 550 ° C or less in consideration of the tens of degrees of temperature change at the time of the step, in order to avoid the multiphase of the alloy structure of the target.

By the above manner, the Al-Li alloy target of the present invention is produced. According to the Al-Li alloy target of the present embodiment, an aluminum single phase structure in which the content of foreign matter and inclusions is small and the composition distribution is uniform (for example, within ±5%) can be obtained. Therefore, it is possible to suppress the occurrence of abnormal discharge at the time of sputtering film formation, and to achieve uniformization of the film formation rate and uniformity of the film thickness distribution.

[Examples] (Example 1)

An Al-Li alloy ingot was produced using the melting furnace 10 described with reference to Fig. 1. The aluminum block 21 is a rod-shaped high-purity aluminum (purity of 99.99%) of about 30 mm square. As the case 23 for accommodating the lithium block 22, the high-purity aluminum is rolled and worked into an aluminum foil having a thickness of 0.2 mm. Lithium block 22 is used with a diameter of 10mm Rod-shaped lithium (made by City Metal Co., Ltd., purity 99.9%).

坩埚12 series is made of compressed graphite. The shape of the crucible 12 is a bottomed cylindrical shape, as shown in Fig. 4, the inner diameter is 175 mm. , the depth of 300mm. 7,750 g of high-purity aluminum was placed in the crucible, and after the pressure in the melting furnace was reduced to 1.33 × 10 ^-2 Pa, the high-purity aluminum was melted by heating the crucible to 750 ° C by induction heating (40 kW).

Here, the temperature monitoring of the molten aluminum is as shown in Fig. 4, and a sheath sheath thermocouple mounted on a thermocouple protection tube 30 made of high-purity graphite provided in the crucible 12 is used. The protective tube 30 has a shape of 15 mm in length, 15 mm in width, 310 mm in height, and 4 mm in inner diameter. , and the depth is 300mm.

3 wt% of lithium was coated with 2 layers of high-purity aluminum foil having a thickness of 0.2 mm, and fastened to the front end portion 13A of the plug 13 located at the upper portion of the crucible with a high-purity aluminum wire (99.99%). A heat shield plate 19 made of graphite is provided in the opening of the crucible, and the opening of the crucible is opened before the addition of lithium.

In the case where the aluminum melt temperature was 750 ° C, the furnace pressure was also maintained at 1.33 × 10 ^-2 Pa. Next, after the heat shielding plate was removed at this temperature and the opening of the crucible was opened, the plug was quickly moved and the lithium block held at the tip end portion of the plug was forced to be immersed in the aluminum melt, and stirred for 1 minute. After that, the induction heating of the crucible is stopped, and at about 700 ° C, the alloy melt is poured from the crucible to the mold (the inner diameter is 260 mm). Casting at a height of 60 mm) to obtain a circular aluminum-lithium alloy melt.

As shown in Fig. 5, the distance from the center of the top of the obtained ingot to the center of the bottom of the ingot is 20 mm (a point, b point), and the distance from the center of the side surface of the ingot to the inside of the height of 5 mm. The sample was collected (point c), and the composition of lithium was analyzed by ICP-AES (high-frequency plasma luminescence spectrometry). The analysis results were: 3.08 wt% at point a, 2.90 wt% at point b, and 3.02 wt% at point c, all within 3.0 wt% ± 5%.

The sampled ingot is subjected to stamping forging and rolling, and can be processed to a thickness of 15 mm without cracking, thickness 12 mm, diameter 200 mm. Sputter target. The process temperature for stamping forging was set to 550 ° C, rolled after heat treatment, and final heat treatment was performed at 450 ° C. It was bonded to a copper cooling plate (backing plate) by an indium-based welding material, and placed in a sputtering apparatus, and subjected to a DC sputtering condition of 0.9 Pa, 1 kW under a reduced pressure argon atmosphere for 1 hour. Sputtering treatment. During sputtering, abnormal discharge did not occur and the process was stable.

Thereafter, the target was removed from the apparatus, and the surface observation of the target, the cross-sectional observation of the target, and the composition analysis of the cross-section were performed. Surface observation and section observation were performed using a CCD magnifying glass with a magnification of 50 times. On the surface of the target after sputtering, no depression, protrusion, expansion, etc. were observed on the entire surface, which was quite smooth. No voids or the like were observed in the entire cross-sectional area of the cross cut. In the central portion of the thickness of the cross section, by the following The sample was collected from a portion corresponding to the outer peripheral portion, the intermediate portion, and the central portion of the target, and the composition of lithium was analyzed by the ICP-AES method.

(measurement result)

4 positions in the outer peripheral portion: 3.08 wt%, 2.98 wt%, 2.88 wt%, 2.86 wt% intermediate portion 4 positions: 3.02 wt%, 2.96 wt%, 3.00 wt%, 2.86 wt% center portion 1 position: 2.88 wt % totals 9 positions, within 3.0% by weight ± 5%.

Further, in order to observe the tissue, samples were taken from two positions on the outer peripheral portion in the vicinity of the collection position of the analysis sample for the analysis of the cross section, two positions in the intermediate portion, and one position in the center portion. As a result of observing the structure of the Al-Li alloy, it was confirmed that the aluminum single phase was in a state in which lithium was solid-melted 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 melted in an argon atmosphere.

The pressure in the melting furnace was set to 1.33 × 10 ^-2 Pa to melt the aluminum in the crucible. The temperature of the aluminum melt is 750 ° C, and after the pressure in the furnace is reduced to 2.66 Pa, high-purity aluminum argon gas (purity 99.999%, dew point temperature -70 ° C or lower) is introduced into the furnace to prepare argon. The pressure in the gas environment is 6.66 × 10 ⁴ Pa in a reduced pressure state. Next, the lid (heat shield) of the crucible was opened at this temperature, and the plug was lowered to forcibly immerse the lithium block in the aluminum melt, followed by stirring for 1 minute. After the induction heating of the crucible is stopped, it is cast in an inner diameter of 260 mm. In a mold of 60 mm in height, and solidified by cooling, an Al-Li alloy ingot was obtained. The subsequent steps were carried out in the same manner as in Example 1 to obtain a thickness of 12 mm and a diameter of 200 mm. Sputter target.

The same sputtering test and composition analysis as in Example 1 were carried out for the obtained sputtering target. Sputtering can be performed without abnormal discharge, and the composition analysis result of lithium is also within 3.0% by weight ± 5%. In addition, it was confirmed that the results of the observation were carried out by sampling from two positions in the vicinity of the collection position of the analysis sample of the cross section, two positions in the middle portion, and one position in the center portion, and it was confirmed that the results were the same as those in Example 1. The same lithium solid phase is solidified in the aluminum single phase.

(Example 3)

An Al-Li alloy ingot was produced in the same manner as in the above Example 2 except that the shape of the mold was set to have a width of 220 mm, a length of 500 mm, and a depth of 25 mm. Thereafter, the surface was cut, and press forging and rolling were performed to produce an ingot having a thickness of 10 mm and a length of 1000 mm without cracking. In addition, it is processed into a thickness of 8mm and a diameter of 200mm. The sputtering target shape was sputtered, and the same sputtering test and composition analysis as in Example 1 were carried out. Sputtering can be performed without abnormal discharge, and the composition analysis result of lithium is also within 3.0% by weight ± 5%. In addition, as a result of performing tissue observation from two positions in the vicinity of the vicinity of the collection position of the sample for analysis of the cross section, the two positions in the middle portion, and one position in the center portion, the results were confirmed in the same manner as in the first embodiment. A single phase of aluminum that is solidified in the state of aluminum.

(Comparative Example 1)

Using a heating oven (electric furnace) at 1000 ° C, 7,000 g of high-purity aluminum was placed in a magnesia-made crucible (inner diameter 175 mm) , depth 300mm), and melted in the atmosphere by heating. The aluminum oxide produced on the surface was removed by an alumina plate, and a predetermined amount of lithium coated with aluminum foil was quickly introduced into the aluminum melt in the same manner as in Example 1. One part of the input floats on the surface of the melt to form an oxide. The oxide (slag) floating on the surface of the melt is removed by an alumina plate.

Casting the Al-Li alloy melt in the crucible to an inner diameter of 260 mm A mold having a height of 60 mm was cooled and an Al-Li alloy ingot was obtained. A portion having a distance of 20 mm from the center of the top and the bottom of the ingot in the height direction of the ingot (points a and b in Fig. 5) and a portion on the inner side from the center in the height direction of the side surface of the ingot (Point c in Fig. 5) Samples were taken, and composition analysis of lithium was performed by ICP-AES (High Frequency Plasma Luminescence Spectrometry). The analysis results were: 2.82% by weight at point a, 2.56 wt% at point b, 2.98 wt% at point c, and -15% at a maximum of 3.0% by weight.

The sampled ingot was subjected to stamping forging and rolling, and processed to a thickness of 15 mm. Although made into a thickness of 12mm, diameter 200mm The target is sputtered, but foreign matter and voids can be observed when the surface is observed. As a result of cross-cutting the sputtering target and performing cross-sectional observation, foreign matter and voids were observed in the cross-section, and it was not used as a sputtering target for film formation.

(Comparative Example 2)

The Al-Li alloying is melted in an argon atmosphere by a vacuum induction heating furnace. 4% by weight of lithium is coated with two layers of high-purity aluminum foil having a thickness of 0.2 mm, and is simply fixed by aluminum wire in a manner that the vibration is immediately released at the front end of the plug (refer to FIG. 1). Hang on the top of the raft. As for the conditions of lithium alloying, the same conditions as in the second embodiment are carried out, but the addition of lithium is 坩 The lid of the crucible is opened, and the plug is gently vibrated, and the lithium block covered with the aluminum foil is dropped to the aluminum melt surface.

An oxide-like float is observed on the slowly rotating aluminum melt. After stopping induction heating, cast in an inner diameter of 260mm A mold having a height of 60 mm was cooled and an Al-Li alloy ingot was obtained. A portion having a distance of 20 mm from the center of the top and the bottom of the ingot in the height direction of the ingot (points a and b in Fig. 5) and a portion on the inner side from the center in the height direction of the side surface of the ingot (Point c in Fig. 5) Samples were taken, and composition analysis of lithium was performed by ICP-AES (High Frequency Plasma Luminescence Spectrometry). 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 of 5%.

The subsequent steps were carried out in the same manner as in Example 1 to obtain a thickness of 12 mm and a diameter of 200 mm. Sputter target. Then, the same sputtering test and composition analysis as in Example 1 were carried out. Five abnormal discharges occurred during the one hour sputtering test. The surface of the target after the sputtering test was observed, the cross-section of the cross-cut was observed, and the composition analysis was performed. When the surface was confirmed to have a protruding shape which was considered to be abnormal discharge, it was further confirmed that there were 13 holes or depressions of approximately 1 mm. Further, in the cross-sectional observation, many voids and the like which can be considered to be a part of the oxide and solidified are also observed. Furthermore, it was confirmed that the result of observing the structure was that the lithium was solid-melted in the aluminum state by sampling the two positions at the outer peripheral portion, the two intermediate portions, and the central portion at the position near the collection position of the analysis sample. It consists of two phases consisting of an aluminum phase and an AlLi phase (β phase).

The embodiments and examples of the present invention have been described above, but the present invention Of course, the present invention is not limited to the embodiments and examples, and various modifications can be made based on the technical idea of the present invention.

For example, in the above embodiments and examples, although aluminum is melted in a crucible in a vacuum environment, it is not limited thereto, and aluminum melting may be performed in an inert gas atmosphere such as argon.

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

10‧‧‧ melting furnace

11‧‧‧vacuum tank

11c‧‧‧Exhaust gas

12‧‧‧坩埚

12A‧‧‧Lip

12B‧‧‧Support rod

13‧‧‧ Plug

13A‧‧‧ front end

14‧‧‧ movable container

15‧‧‧ coil

16‧‧‧Retaining components

17‧‧‧Base member

18‧‧‧Rotary axis

19‧‧‧Heat shield

20‧‧‧Al-Li alloy melt

21‧‧‧Aluminum block

22‧‧‧Lithium block

23‧‧‧ cabinet

24‧‧‧Wire

25‧‧‧Molding

26‧‧‧Cooling plate

27‧‧‧Template

28‧‧‧Carbon

30‧‧‧Protection tube

Fig. 1 is a side cross-sectional view showing a schematic configuration of a melting furnace used in an embodiment of the present invention.

2A to C are schematic cross-sectional views showing principal parts of the lithium alloying step and the casting step described in the embodiment of the present invention.

Fig. 3 is a diagram showing the equilibrium state of the Al-Li system.

4A and B are plan and side cross-sectional views showing the constitution of a graphite crucible used in the embodiment of the present invention.

Fig. 5 is a view showing a sample collection position for composition analysis of an Al-Li alloy ingot according to an embodiment of the present invention.

10‧‧‧ melting furnace

11‧‧‧vacuum tank

11c‧‧‧Exhaust gas

12‧‧‧坩埚

12A‧‧‧Lip

12B‧‧‧Support rod

13‧‧‧ Plug

13A‧‧‧ front end

14‧‧‧ movable container

15‧‧‧ coil

16‧‧‧Retaining components

17‧‧‧Base member

18‧‧‧Rotary axis

19‧‧‧Heat shield

21‧‧‧Aluminum block

22‧‧‧Lithium block

23‧‧‧ cabinet

24‧‧‧Wire

25‧‧‧Molding

26‧‧‧Cooling plate

27‧‧‧Template

28‧‧‧Carbon

Claims (7)

A method for producing an aluminum-lithium alloy target, the aluminum-lithium alloy target being used as a sputtering and composed of a single aluminum phase, characterized by the following steps: the first step, being maintained in a vacuum environment Or melting the aluminum in the crucible in the inert gas environment; in the second step, the lithium block is forcibly immersed in the aluminum melt in the crucible and stirred; and in the third step, the aluminum-lithium alloy in the crucible is The molten metal is cast; and in the fourth step, the microstructure control of the ingot of the aluminum-lithium alloy is performed; and the second step is performed by immersing the end portion of the graphite plug (Plunger) to which the lithium block is fixed The steps in the preceding step: and the step of rotating the plug to stir the solution. The method for producing an aluminum-lithium alloy target according to the first aspect of the invention, wherein the lithium block is housed in a case made of aluminum, and the case system is melted together with the lithium block. The method for producing an aluminum-lithium alloy target according to the second aspect of the invention, wherein in the second step, the plug is located directly above the crucible, and in the melting of aluminum, the crucible and the A heat shield plate is disposed between the plugs. The method for producing an aluminum-lithium alloy target according to the third aspect of the invention, wherein the lithium block is added in an amount of 3% by weight or less. The method for producing an aluminum-lithium alloy target according to claim 1, wherein in the third step, the crucible is tilted, and the molten aluminum-lithium alloy is cast adjacent to the crucible. Molding. The method for producing an aluminum-lithium alloy target according to the first aspect of the invention, wherein the fourth step comprises a forging step and a heat treatment step, and the process temperature is 550 ° C or lower. An aluminum-lithium alloy target manufactured by the method for producing an aluminum-lithium alloy target according to claim 1, characterized in that the lithium content is 3% by weight or less, and the lithium is in the aluminum The difference in the content of each position of the lithium alloy target is within ±5%.