JP3980934B2 - Gallium purification equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for purifying metallic gallium.
[0002]
[Prior art]
Compound semiconductor GaAs single crystals have about five times the electron mobility of silicon and other simple elements, as well as high frequency characteristics, magnetic conversion functions, light receiving and emitting functions, etc., so high-speed ICs and optoelectronic integrated circuits It is widely used as a substrate for electronic devices such as optical devices.
[0003]
Of the Ga and As raw materials used to make GaAs single crystals, the As raw material is 7N (seven nines, meaning 99.99999%; the same shall apply hereinafter) to obtain high-purity As in the market. Is relatively easy. However, since a wide variety of impurities are mixed in the Ga source depending on the Ga source, and the amount of each impurity is usually fluctuating, a Ga source that does not contain impurities that are inconvenient for the production of GaAs single crystals. Is difficult to obtain stably. Moreover, the actual content of the individual impurity elements in the metal Ga is that the present analysis technique (glow discharge mass spectrometer) cannot obtain a reliable value at 0.01 ppm or less for each component. . For this reason, it is difficult to specify the true content of individual impurity elements contained in a trace amount in a Ga raw material used for the production of a GaAs single crystal.
[0004]
In addition, a compound semiconductor GaP single crystal is excellent in light receiving and emitting functions and is used for substrates for optical devices such as light emitting elements. However, in order to obtain a high luminance light emitting element, impurities in the GaP single crystal substrate are used. It is necessary to keep it to the limit. In particular, impurities that increase the carrier concentration and lower the resistivity during the synthesis of the GaP polycrystal are harmful. And it is said that many such harmful impurities are derived from Ga raw materials as in GaAs. The same applies to other Ga-based compound semiconductors such as GaN single crystals.
[0005]
Conventionally, as a purification method of metallic gallium for removing impurities, an acid treatment method, an electrolytic purification method, a zone melting method, a crystal pulling method, a recrystallization method by solidifying a melt, and the like are known. Of these, recrystallization by melt solidification has advantages over other methods because it can be purified with relatively simple equipment and operation. The principle utilizes the phenomenon that the impurity concentration on the crystal side becomes lower than the impurity concentration in the residual liquid in the process of solidifying the liquid gallium containing impurities.
[0006]
As a method for purifying gallium using this phenomenon, in Japanese Patent Application Laid-Open No. 2000-129372 filed by the same applicant, the solidification interface is gradually reduced so that the solidification interface is gradually reduced in diameter. A gallium purification method and apparatus for efficiently concentrating impurities was proposed. Similarly, in Japanese Patent Laid-Open No. 2001-122623, a method and an apparatus capable of stably producing metallic gallium having a purity of 7N or more by leaving a seed crystal and repeating it when carrying out the same gallium purification method. Proposed.
[0007]
In any case, the gallium purification apparatus described in Japanese Patent Application Laid-Open No. 2000-129372 and Japanese Patent Application Laid-Open No. 2001-122623 includes a container having a cylindrical inner wall and a cooling / heating device attached to the outer peripheral surface of the container. A zone, a suction pipe disposed at the center of the container, and a magnet rotor installed below the container, while stirring the liquid gallium raw material contained in the container by the magnet rotor Solidification proceeds so that the cylindrical solidification interface gradually decreases in diameter from the inner wall surface to the center of the container, and the liquid phase present in the center of the container is solidified by the suction pipe before all of the raw material in the container is solidified. The gist is to suck out of the container.
[0008]
[Problems to be solved by the invention]
Although the present inventors have continued to purify gallium according to the above-mentioned apparatus, a part of the residual liquid remaining on the central side of the cylindrical container during the solidification process sometimes becomes an annular solid phase formed outside of it. I found out that an overflow phenomenon occurred on the surface of (the upper surface of the solid phase parallel to the bottom of the container). Even if a residual liquid with a high impurity concentration is mixed with a solid phase side with a low impurity concentration, even if it is as small as a droplet, this may cause a decrease in the purity of the gallium on the solid phase side to be purified. It is not preferable from the viewpoint of efficiency.
[0009]
Therefore, the present invention aims to solve this problem. The gallium purification apparatus proposed in Japanese Patent Laid-Open No. 2000-129372 and Japanese Patent Laid-Open No. 2001-122623 has been further improved to efficiently achieve high purity. The object is to purify metallic gallium.
[0010]
[Means for Solving the Problems]
According to the present invention, a container having a cylindrical inner wall, a cooling / heating zone attached to the outer peripheral surface of the container, a suction pipe disposed at the center of the container, and a magnet installed below the container The liquid gallium raw material contained in the vessel is stirred by the magnet rotor and solidified so that the cylindrical solidification interface gradually decreases in diameter from the inner wall surface of the vessel toward the center of the vessel. In the gallium refining device that advances and sucks the liquid phase existing in the central part of the container outside the container by the suction pipe before all of the raw materials in the container are solidified, the end point position of the solidification interface at the central part of the container Provided is a gallium purifier characterized by comprising a control means. As this end point position control means, a heat medium such as a coiled heat exchanger through which hot water flows can be used, and this is preferably installed so as to surround the suction pipe.
[0011]
Further, according to the present invention, a container having a cylindrical inner wall, a cooling / heating zone attached to the outer peripheral surface of the container, a suction pipe disposed at the center of the container, and a container installed below the container. The cylindrical solidification interface gradually decreases in diameter from the inner wall surface of the container toward the center of the container while stirring the liquid gallium raw material contained in the container by the magnet rotor. In the gallium purification apparatus that advances the solidification and sucks the liquid phase existing in the center of the container outside the container by the suction pipe before all the raw materials in the container are solidified, a center pole provided with heating means is provided in the suction Provided is a gallium refining apparatus which is installed adjacent to a pipe and has the lower end of the center pole brought close to or in contact with the bottom of the container.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to an improvement of the gallium purification apparatus described in JP-A-2000-129372 and JP-A-2001-122623. FIG. 1 shows a main part of the gallium purification apparatus described in these publications. This gallium refining device comprises a container 2 having a cylindrical inner wall 1 and a cooling / heating zone 3 attached to the outer peripheral surface of the container 2 (a jacket through which cold water or hot water is exchanged). ), A heating zone 4 provided in the container inside the inner wall 1 (consisting of coiled heat exchange through which hot water is passed), a suction pipe 5 disposed in the center of the container, It is comprised from the rotor 6 which consists of a permanent magnet installed under the container. The heating zone 4 is provided as necessary and is mainly used for dissolution. A heating zone 7 through which hot water flows is also provided on the outer periphery of the suction pipe 5, and a heating zone 8 through which hot water passes is also provided at the bottom of the container.
[0013]
Each of these device elements is substantially the same as that described in Japanese Patent Laid-Open No. 2000-129372 and Japanese Patent Laid-Open No. 2001-122623. For example, after the steps (A) to (C) in FIG. Is purified. FIG. 2A shows a state in which the liquid gallium raw material 9 is put in the container 2. In this state, warm water is passed through the cooling / heating zone 3 (jacket 3) and the heating zone 8 (jacket 8) at the bottom of the container to maintain the liquid gallium raw material 9 at a temperature higher than the melting point. The heating zone 7 of the suction pipe continues to pass hot water during the subsequent processing.
[0014]
FIG. 2 (B) shows a state in the middle of solidification where solidification has started from the state (A). In this state, cold water is passed through the jacket 3 while continuing the rotation of the magnet rotor 6. , Hot water to the heating zone 8 is stopped. As a result, the solidification interface B between the liquid phase L and the solid phase S is gradually reduced in diameter toward the center of the container while having a cylindrical shape.
[0015]
FIG. 2 (C) shows an operation of extracting the residual liquid RL at the center of the container from the suction pipe 5, and the water flow state of hot water and cold water is not substantially different from that in FIG. 2 (B), but the residual liquid RL. In order to prevent the water from solidifying at the bottom of the container, warm water may be passed through the heating zone 8 at the bottom of the container.
[0016]
In this way, while solidification is progressed so that the diameter of the solidification interface B gradually decreases from the inner peripheral surface of the cylindrical container 2 toward the central portion while applying swirling flow stirring to the liquid phase L, the liquid phase L remains. The impurity concentration of the liquid phase L increases and a solid phase S with a low impurity concentration is generated. However, as the remaining liquid phase L decreases, the interface is distorted, and the solid cylindrical interface B is not necessarily a perfect cylinder. It may not be. FIG. 3 shows an example of such a state. Since Ga has a lower specific gravity in the solid phase, the remaining liquid portion is pushed up as the solidification progresses, and the upper surface of the solid phase S rises toward the center. It becomes. In this case, some droplets of the liquid phase L overflow or scatter to the upper surface side of the solid phase S and solidify on the solid phase S.
[0017]
That is, solidification does not occur at the solidification interface B between the liquid phase L and the solid phase S, but a part of the liquid phase L scatters and solidifies as it is and joins the solid phase S to form a liquid phase L with a high impurity concentration. The solid phase S is mixed as it is. For this reason, the purity of the solid phase S is lowered and the operation efficiency is lowered. This phenomenon is likely to occur near the end point of solidification as shown in FIG. 2 (C), and the impurity concentration in the residual liquid RL is high at this stage, so that the influence of purity reduction on the solid phase S is also increased accordingly. .
[0018]
The present invention is to improve this point, and the gist of the improvement point according to the present invention is that the gallium purification apparatus is provided with an end position control means for the solidification interface at the center of the container (first improvement). Point), and a center pole provided with heating means was installed adjacent to the suction pipe, and the lower end of the center pole was brought close to or contacted with the bottom of the container (second improvement point) It is in.
[0019]
The first improvement point will be described with reference to FIG. 4. As the end point position control means, a coiled heat exchanger 10 (hereinafter referred to as the central coil 10) is installed so as to surround the suction pipe 5. This central coil 10 is composed of a concentric constant-pitch spiral heat transfer tube, which is installed at the center of the container 2 so as to surround the suction pipe 5 with its central axis aligned with the axis of the container 2. . The central coil 10 is configured to allow warm water to flow.
[0020]
4 has the same configuration as that of the apparatus of FIG. 1 except that the central coil 10 is installed. In FIG. 4, members denoted by the same reference numerals as those of FIG. 1 are the same as those of FIG. I mean.
[0021]
FIG. 5 shows the operating state of the apparatus of FIG. 5A and 5B are the same as the stages of FIGS. 2A and 2B, but warm water is passed through the central coil 10. FIG. For this reason, in addition to the supply of heat from the heating zone 7 of the suction pipe on the liquid phase L side, the supply of heat from the central coil 10 having a larger diameter is performed, so that temperature unevenness at the solidification interface B is eliminated. The solidification interface close to a true cylinder gradually decreases in diameter.
[0022]
FIG. 5C shows a solidification end point stage where the solidification is completed up to where the central coil 10 is located. By providing the central coil 10, it is possible to prevent the solidification from progressing to the inside of the central coil 10 even if the solidification is completed up to the position where the central coil 10 is located. For this reason, the solidification interface is maintained in a shape close to the true cylinder at the solidification completion position.
[0023]
Thus, in the apparatus of FIG. 5, the central coil 10 is provided, so that the solidification interface is prevented from being distorted and the solidification end point position can be accurately controlled. Further, since the progress of solidification is avoided, a phenomenon in which a part of the liquid phase L overflows or splashes on the upper surface of the solid phase S as described with reference to FIG. As a result, it is possible to prevent the residual liquid containing a large amount of impurities from being mixed with the solidified high purity side, thereby improving the purification efficiency of gallium. On the other hand, since the solidification end point position can be accurately controlled, the monitoring load of the solidification end point is reduced. As a result, the operability of the end point control is improved and the operation accuracy of the apparatus can be increased.
[0024]
Next, the second improvement point will be described with reference to FIG. 6. In this case, the center pole 11 provided with heating means is installed adjacent to the suction pipe 12. Then, the lower end 13 of the center pole 11 is brought close to the bottom of the container 2 or brought into contact with the bottom of the container 2. In the illustrated example, the center pole 11 is constituted by a stainless steel double pipe, and warm water is passed through the double pipe to the vicinity of the lower end 13 thereof. Heat can be applied to the bottom surface 14 of the container 2 by bringing the lower end 13 of the center pole 11 into contact with the bottom surface 14 of the container 2.
[0025]
The suction pipe 5 in FIG. 1 sucks the residual liquid having a high impurity concentration from the center thereof, so that the suction load increases when the lower end of the suction pipe 5 is brought into contact with or near the bottom surface of the container. The supply of heat to the bottom of the container by the pipe 5 could not be expected so much. Therefore, in the process in which the solidification interface B moves toward the center, a phase transformation with a latent heat change occurs, and even if heat is supplied from the heating zone 8 at the bottom, the solid phase S and the liquid phase Since a temperature difference occurred in L, it was difficult to keep the temperature at the bottom of the container constant, and this proved that blistering and distortion of the solidification interface B occurred.
[0026]
For this reason, in the second improvement of the present invention, apart from the suction pipe for sucking the liquid phase L, a center pole 11 provided with heating means is installed at the center of the container 2 and its lower end 13 is placed at the bottom of the container. The configuration is such that heat is applied from the center pole 11 to the center of the bottom of the container. As a result, it is considered that the temperature unevenness on the bottom surface of the container has been eliminated. However, a part of the liquid phase L due to the above-mentioned problem, that is, the shape change of the solidification interface B overflows or splashes on the upper surface of the solid phase S. As a result, gallium purification efficiency can be improved.
[0027]
Note that the lower end 13 of the center pole 11 does not necessarily have to be in contact with the bottom of the center of the container. If the lower end 13 is close to the bottom, the same effect can be obtained. This is because heat transfer takes place between the lower end 13 of the center pole 11 and the bottom of the container through the liquid phase of metal gallium present between them, which is not significantly affected by stirring. In addition, as shown in FIG. 6, when a recess 15 is formed at the center of the bottom of the container and this recess 15 is used as a liquid reservoir, the residual liquid is sucked by the suction pipe 12 after the end of solidification. It becomes easier to suck the residual liquid present at the bottom of the container near the end of the suction. The suction pipe 12 provided in the vicinity of the center pole 11 does not necessarily need to coincide with the center axis of the container, and may be installed in a state of being tied to the outside of the center pole 11.
[0028]
FIG. 7 is a combination of the first improvement in FIG. 5 and the improvement in FIG. That is, as the end point position control means, a central coil 10 through which hot water flows is concentrically installed with the center of the container, and a center pole 11 is placed in the center of the central coil 10 with its lower end 13 in contact with or close to the bottom of the container. The suction pipe 12 is attached to the center pole 11 by tying it. According to this combination, the effect of the central coil 10 and the effect of the center pole 11 can avoid the deformation of the solidification interface, such as distortion and blistering, where solidification proceeds while reducing the diameter. Overflow and splash are prevented, and the end point position can be reliably controlled, so that the gallium purification efficiency is further improved.
[0029]
The basic operation itself of the gallium refining apparatus shown in FIGS. 5 to 7 and the repurification operation itself that repeats the purification while leaving the seed crystal are disclosed in Japanese Patent Laid-Open Nos. 2000-129372 and 2001-122623. The apparatus of the present invention can be operated according to the procedures described in these publications. At that time, it is only necessary to appropriately perform the operation of supplying hot water to the central coil 10 and the center pole 11, and the temperature and amount of water supplied to these are determined by the cooling / heating zone 3 or the container attached to the outer peripheral surface of the container. What is necessary is just to manage appropriately in consideration of the coiled heat exchange 4 installed so that it may circulate around the inner wall, and also the warm water temperature and the amount of water flow to the heating zone 8 outside the bottom of the container.
[0030]
【The invention's effect】
As described above, according to the present invention, a liquid phase solid phase that may be generated when the gallium purification apparatus disclosed in Japanese Patent Laid-Open Nos. 2000-129372 and 2001-122623 is operated. Overflow and splash to the side can be prevented. As a result, the gallium purification efficiency by the apparatus is increased and the operability is improved. Moreover, since the end point control of solidification can be performed accurately, operability is improved in this respect as well.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a conventional gallium purification apparatus.
FIG. 2 is a diagram for explaining an operation sequence of the apparatus of FIG. 1;
FIG. 3 is a diagram for explaining the behavior when the apparatus of FIG. 1 is operated;
FIG. 4 is a schematic cross-sectional view showing an example of a gallium purification apparatus according to the present invention.
FIG. 5 is a diagram for explaining the operating status of the apparatus of the present invention.
FIG. 6 is a schematic cross-sectional view showing an example of another gallium purification apparatus according to the present invention.
FIG. 7 is a schematic cross-sectional view showing still another example of a gallium purification apparatus according to the present invention.
[Explanation of symbols]
1 Container inner wall 2 Cylindrical container 3 Cooling / heating zone (jacket) attached to the outer peripheral surface of the container
4 Heating zone (heat exchange coil) provided in the container inside the container inner wall
5 Suction pipe 6 Magnet rotor 7 Heating zone around the suction pipe (hot water pipe)
8 Heating zone at the bottom of the vessel 9 Liquid refined raw material 10 Coiled heat exchanger (central coil)
11 Center pole

Claims (1)

Consists of a container having a cylindrical inner wall, a cooling / heating zone attached to the outer peripheral surface of the container, a suction pipe disposed in the center of the container, and a magnet rotor installed below the container, While the liquid gallium raw material contained in the container is agitated by the magnet rotor, solidification proceeds so that the cylindrical solidification interface gradually decreases in diameter from the inner wall surface of the container toward the center of the container. in refining gallium apparatus for sucking out the vessel the liquid phase present in the container the central part by the suction pipe before the whole is solidified, a coiled heat exchanger heat medium flowing in the central portion of the container above the A gallium refining device , installed so as to surround a suction pipe .

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