TWI573764B - Containers for silicon ingots - Google Patents

Description

矽Ingot manufacturing container

The present invention relates to a container for manufacturing an antimony ingot for use in the manufacture of a solar cell grade crucible.

In the past, as a method for producing a niobium ingot used in a solar cell or the like, the niobium melt is contained in a container made of graphite or quartz (such as a sorghum, a mold, or the like), and the crucible melt is solidified from below to allow the crucible to be solidified. The casting method of crystal growth is well known.

According to this casting method, since the direction in which crystal growth progresses can be made uniform when the crucible melt is solidified, it is possible to manufacture a good quality wafer in which the ratio resistivity of the grain boundary is suppressed. Moreover, if the casting method is used, mass production of the bismuth ingot can also be carried out.

As a large-sized container for the production of a bismuth ingot, a container made of a graphite or quartz plate (a bottom plate and four side plates) that are screwed to each other and detachably assembled is known (for example, Patent Documents 1 and 2). Moreover, in order to improve the take-out property of the bismuth ingot, a mold release material such as tantalum nitride (Si ₃ N ₄ ) is formed on the inner surface of the container. In particular, in Patent Document 2, the initial solidified layer is formed by first solidifying the molten liquid leaked from the gap between the sheets to prevent the ruthenium melt from leaking to the outside of the container.

[Patent Document 1] Japanese Patent Laid-Open No. 62-108515

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2006-83024

When the crucible is manufactured by using the above-described separable assembly type container, the generated ingot can be easily taken out by disassembling the container. In addition, at the high temperature at the time of manufacture of the bismuth ingot, the container may be deformed or deteriorated, and the container may be damaged, and the gap between the sheets may be enlarged to cause the ruthenium melt to leak to the outside. Further, when the crucible melt leaks to the outside of the container, the expensive member or the like around the container disposed inside the crystal growth apparatus is damaged.

Further, in the case of applying the technique described in Patent Document 2, it is possible to prevent the leakage of the ruthenium melt, but the initial solidified layer formed in the gap between the sheets is crystallized from the gap at the corner of the container where the release material is dense. The reason for the crystallization. Therefore, it is impossible to produce a bismuth ingot having good quality and good quality.

The present invention has been made in order to solve the problems described above, and an object of the invention is to provide a container for producing an ingot which can prevent a flawed molten metal from leaking to the outside and which can produce a fine ingot having a good quality.

According to the invention of the first aspect of the invention, there is provided a container for manufacturing a bismuth ingot, comprising: a container body having a bottom plate and a plurality of side plates, which are assembled in a separable manner; and a release material formed on the inner surface of the container body a container for use in solidifying a crucible melt to grow polycrystalline crystals, characterized in that the container is a porous body or a combination of any of tantalum nitride, tantalum carbide, or alumina. Two or more kinds of porous bodies are formed, and the release material is made of tantalum nitride.

The invention according to claim 2, wherein the porous body has an open porosity of 10% or more and 40% or less.

Here, the open porosity refers to the ratio of the volume of the pores communicating with the outside to the sum of the apparent volumes of the porous bodies.

The container according to claim 1 or 2, further comprising a holder having a fixing groove for fixing the side plate, surrounded by the fixing groove In the region where the bottom plate is placed, the side plate is erected in the fixing groove, and a wedge is fitted into the remaining space of the fixing groove, and the bottom plate and the side plate are joined and fixed.

The invention according to claim 3, wherein the container for producing an antimony ingot according to claim 3, wherein a molten liquid collecting material is deposited in the residual space of the fixing groove, and the molten crucible is leaked Melting and mitigating the Si volume expansion stress.

According to the present invention, since the release material having good mold release property is strongly formed on the inner surface of the container body, it is possible to effectively prevent the damage of the release material due to the stress caused by the volume expansion at the time of solidification of the crucible. produce. Therefore, it is possible to prevent the ruthenium melt from leaking to the outside, and it is possible to manufacture a ruthenium ingot having a good quality with good yield. Further, the container can be repeatedly used in the production of bismuth ingots.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

Fig. 1 is a top view of a container for manufacturing a ruthenium ingot according to the present invention, and Fig. 2 is a cross-sectional view taken along line A-A of Fig. 1. As shown in Fig. 1 and Fig. 2, the container for manufacturing an ingot (hereinafter, the container) 10 of the embodiment has a heat-resistant container body 11 and is formed on the inner surface of the container body 11 for lifting the ingot. The mold release material 12; and a holder (sustainer) 13 for holding the container body 11 and the like.

The container body 11 is a box-shaped member that can be assembled in a divided manner by joining the rectangular bottom plate 11a and the four side plates 11b to each other. The four side panels 11b are disposed in an upright state to surround the outer circumference of the bottom plate 11a. For example, as shown in FIGS. 1 and 2, the four side plates 11b have the same shape, and the side surface on one end side in the width direction of the one side side plate 11b and the main surface side edge portion on the one end side in the width direction of the other side plate 11b are in contact with each other. The manners are mutually joined to form a frame of the side of the container body 11.

The bottom plate 11a and the side plate 11b constituting the container body 11 are composed of any one of Si ₃ N ₄ or SiC or Al ₂ O ₃ or a combination of two or more types of porous bodies (porous materials). The thickness of the container body 11 (the bottom plate 11a and the side plate 11b) is desirably equal to or greater than the thickness at which the strength of the warpage is not generated, for example, 5 mm or more.

The bottom plate 11a and the side plate 11b are produced by, for example, sintering Si ₃ N ₄ or SiC powder, and have an open porosity of 10% or more and 40% or less. When the porosity of the porous body constituting the container body 11 is less than 10%, the air bubbles remain in the interior of the mold release material 12, and the mold release material 12 is weakened and easily broken. Moreover, when the open porosity exceeds 40%, the possibility of leakage of the molten liquid increases. Therefore, the porosity of the porous body constituting the container body 11 is preferably 10% or more and 40% or less, and more preferably 20% or more and 30% or less from the viewpoint of easiness of mold release property. .

The container body 11 composed of the porous body described above has better heat resistance than a container made of quartz, and does not deteriorate or deform when the temperature of the bismuth ingot is increased. Therefore, when the production of the bismuth ingot is performed, it is possible to effectively prevent the release material 12 from being damaged due to deterioration or deformation of the container body 11.

The mold release material 12 is composed of a sintered body of Si ₃ N ₄ , and a main surface of the side plate 11 b (the surface which becomes the inner surface of the container main body 11), a main surface of the bottom plate 11a, and the like are formed in advance before the container body 11 is assembled. These adjacent faces of one main face. The mold release material 12 is applied to a main surface of the bottom plate 11a and the side plate 11b by bristles, spray, or the like by, for example, a water-based slurry prepared by mixing a Si ₃ N ₄ powder with a binder such as polyvinyl alcohol. It is formed by firing at 700 to 1550 ° C in an environment or an inert gas atmosphere such as argon. The thickness of the release material 12 is, for example, 200 to 1000 μm, preferably 300 to 600 μm, in the extent that the Si melt does not reach the container side during crystal growth.

Since the slurry applied to the bottom plate 11a and the side plate 11b constitutes the bottom plate 11a and the side plate 11b with a porous body, it gradually penetrates into the pores of the bottom plate 11a and the side plate 11b. Further, the air bubbles in the slurry are defoamed by the bottom plate 11a and the side plate 11b which are made of a porous body. Since the firing is performed in this state, the release material 12 is strongly formed on one main surface of the bottom plate 11a and the side plate 11b. Therefore, when the manufacture of the niobium ingot is performed, the mold release material 12 can be effectively prevented from being damaged.

When the air bubbles remain in the mold release material 12, the mold release material 12 tends to be easily broken when the ruthenium ingot is produced in accordance with the number and size of the remaining air bubbles. Therefore, in the conventional container body, When the release material is formed, a defoaming treatment by a reduced pressure or the like is performed. On the other hand, in the case of the container 10 of the present embodiment, when the release material 12 is formed, it is not necessary to perform the defoaming treatment, and the release material 12 can be easily formed.

Further, since the mold release material 12 is strongly formed on the inner surface of the container body 11, it is not necessary to have a multilayer structure as in the related art. Therefore, the process and cost incurred in the production of the container 10 are not increased, and the film thickness of the release material 12 can be easily increased. Further, when the mold release material 12 is formed, since it is not necessary to use a sintering aid such as cerium oxide or metal oxide, it is possible to prevent a decrease in crystallinity due to an increase in the concentration of impurities in the bismuth ingot.

The holder 13 is, for example, a plate-like member made of graphite, and the fixing groove 13a for fixing the four side plates 11b is formed in a rectangular ring shape. In the holder 13 and a region (protrusion) 13b surrounded by the fixing groove 13a, the bottom plate 11a having the release material 12 is placed. Further, a side plate 11b having a release material 12 is erected in the fixing groove 13a, and a graphite holding plate 14 is disposed outside the side plate 11b. Further, at the four corners of the fixing groove 13a, the wedge 15 is fitted in two places (eight places), and the side plate 11b is pressed inward, whereby the container body 11 is fixed to the holder 13. At this time, the four side plates 11b and the bottom plate 11a are joined without a gap so that the molten metal does not leak.

Further, in the remaining space of the fixing groove 13a, a molten liquid collecting material 16 which is melted with the crucible melt is placed. Thereby, the side plate 11b can be fixed to the fixing groove 13a in a more stable state, and the positional displacement in the lateral direction is restricted. The melt trapping material 16 may be a material which can be reacted and melted with the crucible melt, and is preferably, for example, a carbon felt, a quartz glass wool, a strontium sand, a quartz glass sheet or the like. In order to alleviate the volume expansion stress at the time of solidification of Si, the melt collecting material 16 is desirably formed of a carbon fiber-based or ceramic fiber-based material.

Further, the depth and the width of the fixing groove 13a formed in the holder 13 are such that a residual space is formed in a state in which the side plate 11b and the holding plate 14 are disposed, and when the wedge 15 is fitted into the remaining space, the container body 11 It can be stably fixed to the holder 13 to the extent.

In this way, the container 10 of the embodiment includes a box-shaped container body 11 that is detachably assembled by the bottom plate 11a and a plurality of (for example, four) side plates 11b; and the inner surface of the container body 11 is formed Mold material 12. Further, the container body 11 (the bottom plate 11a and the side plate 11b) is made of a porous body made of any one of tantalum nitride, tantalum carbide, or alumina, or a combination of two or more kinds of porous bodies, and the release material 12 It is made of tantalum nitride. Further, the open porosity of the porous body is 10% or more and 40% or less.

In this container 10, since the release material 12 having a good mold release property is strongly formed on the inner surface of the container body 11, it is possible to effectively prevent the stress release material 12 from being damaged due to volume expansion accompanying solidification of the crucible. . Therefore, it is possible to prevent the krypton melt from leaking to the outside of the container.

Further, since the side plate 11b having the release material 12 is lifted upward by the volume expansion accompanying solidification, the melt liquid which is crystallized from the molten liquid surface is compressed, so that no melt leakage occurs. .

Therefore, the bismuth ingot having good quality can be produced with good yield. Moreover, the container 10 can also be used repeatedly in the manufacture of a bismuth ingot.

Further, the container 10 is provided with a holder 13 having a fixing groove 13a for fixing the side plate 11b. Moreover, the bottom plate 11a is placed in the region (protrusion) 13b surrounded by the fixing groove 13a, and the side plate 11b is erected in the fixing groove 13a, and the wedge is embedded in the remaining space of the fixing groove 13a. 11a is joined and fixed to the side plate 11b.

That is, in the container 10, the bottom plate 11a is pressed by the side plate 11b so that the two are joined, but the fixing is not performed. Therefore, the side plate 11b can be slightly moved in the lateral direction or the longitudinal direction. Of course, it does not cause a large shift in the extent to which the enthalpy melt leaks. Thereby, the stress generated by the volume expansion at the time of solidification of the crucible can be effectively alleviated. Therefore, the mold release material 12 can be effectively prevented from being damaged.

Further, since the side plate 11b protrudes downward from the bottom plate 11a, even when the crystal grows, the side plate 11b is slightly lifted upward, and the state of being joined to the bottom plate 11a can be ensured. Even if, for some reason, a part of the crucible melt leaks from the gap between the side plate 11b and the bottom plate 11a, the crucible melt is stored and solidified in the fixing groove 13a of the holder 13 and sealed. Therefore, it is possible to effectively prevent the krypton melt from leaking to the outside of the container 10.

Further, in the remaining space of the fixing groove 13a, a molten liquid collecting material (sand, quartz glass, carbon felt, quartz glass wool, etc.) which is fused with the leaking cerium melt is placed. The melt trapping material can effectively alleviate the volume expansion stress in the lateral direction by virtue of its deformability. Thereby, an increase in the gap between the side plate and the bottom plate can be suppressed.

Further, even if a part of the crucible melt leaks from the gap between the side plate 11b and the bottom plate 11a, the leaked crucible melt reacts with the melt trapping material 16 and melts, so that no crucible melt leaks into the container. The external situation of 10 is generated.

Fig. 3 is a view showing an example of a crystal growth apparatus using the container 10 of the embodiment. The crystal growth apparatus 1 shown in Fig. 3 is used to produce a ruthenium ingot by Kjeldahl crystal growth. In the crystal growth apparatus 1, a heater 17 is disposed on the outer circumference of the container 10. Further, a crystal pulling shaft 18 is disposed at the center of the container 10, and a seed crystal 19 composed of a single crystal (or polycrystalline crystal) is attached to the tip end.

When the ruthenium ingot is produced by using the crystal growth apparatus 1 and the Kjeldahl crystal, the ruthenium raw material (for example, ruthenium melt) is put into the container 10, and the seed crystal 19 is brought into contact with the surface of the ruthenium melt 20, from the surface. The crucible melt 20 is solidified, and the crucible polycrystal 20a is grown.

At this time, by pulling the seed crystal 19 at an extremely low speed, the polycrystalline crystal is grown, and the longitudinal stress caused by the volume expansion at the time of solidification of the crucible can be alleviated. Specifically, the drawing speed of the seed crystal 19 may be set in accordance with the volume expansion in the longitudinal direction when the crucible melt 20 is solidified.

In the case where the bismuth ingot is produced by Kjeldahl crystal growth, there is a case where the top portion which is solidified near the surface of the ruthenium melt 20 is occluded into the container 10 (release material 12) due to the volume expansion at the time of solidification. When the seed crystal 19 is pulled down in this state, the side plate 11b is lifted upward. However, as described above, even in this case, the container 10 of the present embodiment does not leak out of the crucible melt 20 to the outside of the container 10, and the stress caused by the volume expansion at the time of solidification is also alleviated.

Further, in the case where the bismuth ingot is produced by the Kjeldahl crystal, the upper portion of the side plate 11b may be inclined outward by 3° or more and less than 90° in the portion where the surface of the ruthenium melt 20 is located. Thereby, it is possible to reduce the loss of the crystal which is grown during the pulling of the crystal to the side surface of the container, and to prevent the compression of the lower melting liquid of the crystal due to the volume expansion at the time of solidification of the crucible, and to safely crystallize and grow.

[Examples]

In the examples, a ruthenium ingot was produced using Kelvin crystal growth using the crystal growth apparatus 1. First, the ruthenium melt 20 to which boron (concentration: 1.0 × 10 ¹⁶ atoms/cm ³ ) is added flows into the vessel 10 composed of the vessel body 11 made of Si ₃ N ₄ , and the crucible melt 20 is held to allow the depth direction. The temperature gradient became 10 ° C / cm.

Then, the seed crystal 19 composed of the Si single crystal having a crystal orientation of <100> and 3.5 mm square is brought into contact with the surface of the crucible melt 20, and the crystal 19 is pulled up at 1 mm/h to further crystallize the crucible. growing up. At this time, the container 10 and the seed crystal 19 were rotated at 5 rpm, and the ruthenium polycrystal 20a was concentrically grown centering on the seed crystal 19. The crucible melt 20 was completely cured by the growth of 3 hours to obtain the crucible ingot of the example. In addition, the time point at which the temperature of the bottom of the container 10 (container body 11) becomes 1410 ° C of the freezing point of 矽 is regarded as the end point of crystal growth.

In the manufacture of the bismuth ingot of the embodiment, when the seed crystal is pulled up to correspond to the volume expansion amount, the side plate 11 is vertically lifted inside the susceptor, and the side plate is still held, so that no melt leakage occurs. The situation arises. Moreover, the produced ruthenium ingot can be easily taken out by disassembling the container 10. Further, in the obtained antimony ingot, the crystal grain boundary is uniform in the longitudinal direction, and therefore has a good crystal quality.

Moreover, the release material 12 in the container 10 is not damaged, so that the container can be repeatedly used in the manufacture of the bismuth ingot.

[Comparative example]

The crucible melt was solidified except for the use of the crucible ingot manufacturing container of the structure shown in Fig. 4A, and as a result, as shown in Fig. 4C in which the portion surrounded by the dotted line of Fig. 4B was enlarged, The molten liquid leaks from the gap between the bottom plate 11a and the side plate 11b.

When an operation corresponding to the volume expansion amount is pulled up from the crystal grown on the surface of the molten liquid, the crystal is caught by the side plate of the container and lifted up, which causes a large gap.

Further, as a result of disintegration of the container, only the upper portion of the ingot connected to the seed crystal was obtained, which was separated from the solidified body at the lower portion, and the ingot was not easily produced at a good yield. Further, the leaked molten liquid strongly adheres to the surface on which the side plates and the bottom plate of the release material are not formed, and thus cannot be reused.

The invention developed by the inventors of the present invention has been specifically described above based on the embodiments. However, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the invention.

The container 10 of the embodiment can be used not only in Kjeldahl crystals, but also in the production method of various bismuth ingots. For example, it can also be used in a casting method in which the crucible melt is solidified from the bottom of the container 10 and the polycrystalline crystal grows.

Further, the container body 11 (the bottom plate 11a and the side plate 11b) may be formed of a porous body of alumina or SiC having less impurities than Si ₃ N ₄ . If importance is attached to the release material 12, Si ₃ N _{4 of the} same material as the release material may be selected.

Moreover, the side wall portion of the holder 13 can also be fixed by screws. Specifically, in a portion shown by a dot lock line BB in FIG. 2, the holder 13 is divided, and the screw (bolt) is inserted from the direction indicated by the arrow C and locked, thereby the holder 13 is integrated. The person. In the case where the container 10 is enlarged, the split holder (sustainer) 13 is relatively easy to handle, and is also advantageous in terms of cost reduction.

The contents of the embodiments disclosed above are merely illustrative and are not intended to limit the invention. The scope of the present invention is not limited to the foregoing invention, but all modifications within the meaning and scope of the claims are intended to be included in the invention.

1. . . Crystal growth device

10. . .矽Ingot manufacturing container

11. . . Container body

11a. . . Bottom plate

11b. . . Side panel

12. . . Release material

13. . . Holder

13a. . . Fixed groove

13b. . . Convex

14. . . Holding plate

15. . . wedge

16. . . Melt trap

17. . . Heater

18. . . Pull crystal axis

19. . . Crystallization

20. . .矽 melt

20a. . . Polycrystalline

Fig. 1 is a top view of a container for producing a ruthenium ingot to which the present invention is applied.

Figure 2 is a cross-sectional view taken along line A-A of Figure 1.

Fig. 3 is a view showing an example of a crystal growth apparatus using a container according to an embodiment.

Fig. 4A is a perspective view showing the main body of the container for manufacturing a bismuth ingot used in the comparative example.

Fig. 4B is a front sectional view showing the main body of the container for manufacturing a bismuth ingot shown in Fig. 4A.

Fig. 4C is a partially enlarged view showing, in an enlarged manner, the body of the container for manufacturing an ingot in the portion surrounded by the broken line in Fig. 4B.

10. . .矽Ingot manufacturing container

11. . . Container body

11b. . . Side panel

12. . . Release material

13. . . Holder

13a. . . Fixed groove

14. . . Holding plate

15. . . wedge

16. . . Melt trap

Claims (2)

A container for manufacturing a bismuth ingot, comprising a container body having a bottom plate and a plurality of side plates, which are assembled in a separable manner, and a release material formed on an inner surface of the container body, wherein the mash melt is solidified A container for producing an antimony ingot for use in growing a polycrystalline crystal, wherein the container system is composed of one or a combination of two or more of tantalum nitride, tantalum carbide, and aluminum oxide, and has an open porosity. 10% or more and 40% or less of a porous body, wherein the release material is formed of tantalum nitride, and the container for producing a ruthenium ingot has a holder on which a groove for inserting the side plate is formed. The groove surrounds the central portion of the upper surface, and the bottom plate is placed in a region surrounded by the groove on the upper surface of the holder, and the wedge is fitted between the side surface of the side plate inserted into the groove and the side surface of the groove. The front plate is joined to and fixed to the side plate. The container for producing an ingot according to the first aspect of the invention, wherein the remaining space of the fixing groove is covered with a molten liquid collecting material which is fused with the leaked cerium molten material and has a crucible (Si) The mitigation function of volume expansion stress.