JP2008087999A - Apparatus for supplying raw material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for supplying a raw material, with which production of a gap between a raw material supply pipe and a bottom lid can be prevented by making a support member be a hardly stretchable material and/or adjusting the length of the support member. <P>SOLUTION: The apparatus 1 for supplying a raw material is installed in a single crystal pulling apparatus for supplying a lumpy raw material and provided with a nearly cylindrical raw material supply pipe 3 for holding the lumpy raw material, a conical bottom lid 5 detachably installed at the lower end opening part of the raw material supply pipe 3, and a support member for suspending the bottom lid 5. The support member includes a shaft member made of a material hardly stretched by heat and/or has a length adjusting mechanism capable of adjusting the length in the axial direction of the support member. Thereby, the production of a gap between the lower end opening part and the bottom lid 5 can be prevented even when the apparatus 1 for supplying the raw material is disposed under a high temperature. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a single crystal pulling apparatus for manufacturing a single crystal ingot, and more particularly to a raw material supply apparatus for supplying a polycrystalline raw material.

  A specular wafer used as a substrate for manufacturing a semiconductor device is obtained by slicing a single crystal ingot into thin plate members and grinding and polishing the front and back surfaces thereof. This single crystal ingot can be manufactured by, for example, the Czochralski (CZ) method (including the MCZ method). A general method for producing a single crystal ingot using the Czochralski method will be briefly described below.

  In the Czochralski method, a raw material polycrystalline silicon (polycrystalline raw material) is filled in a quartz crucible installed in a furnace of a single crystal pulling apparatus, and the quartz crucible is heated by a heater provided around the quartz crucible. Thus, polycrystalline silicon is melted to obtain a raw material melt. A single crystal with the same orientation as the seed crystal is grown by immersing a single crystal (seed crystal), which is a seed, and slowly pulling up the seed crystal using the crystal pulling mechanism. Finish into an ingot. Then, the single crystal ingot grown to the required size is taken out of the furnace.

  After stopping the heating by the heater, the inside of the single crystal pulling apparatus is cooled, and a new quartz crucible and polycrystalline silicon as a raw material are recharged. Usually, when silicon is cooled below the melting point while the raw material melt remains in the quartz crucible, the quartz crucible is broken due to expansion during solidification of the melt, so that only one single crystal ingot is produced from one quartz crucible. It was not possible to increase the cost. Therefore, in order to reduce costs, the raw material used for the production of the next single crystal ingot is prevented without cooling the apparatus after the production process of one single crystal ingot is completed and preventing the raw material melt in the quartz crucible from solidifying. There has been proposed a single crystal ingot manufacturing method in which additional polycrystalline silicon is added, the added polycrystalline silicon is melted, and the single crystal ingot is pulled up again. The following techniques are disclosed for supplying polycrystalline silicon as a raw material.

  For example, in Patent Document 1, a single crystal production apparatus (single crystal pulling apparatus) can be easily taken out and taken out, and a nugget-like and / or granular (hereinafter, collectively referred to as “lumb-like”) raw material is solidified and melted in a crucible. A recharge tube is disclosed that is charged directly to the liquid surface. This recharge tube realizes a supply rate suitable for recharge and can improve the productivity of single crystals by performing recharge smoothly and efficiently in a short time.

  In Patent Document 2, the lamp material is melted and stuck on the bottom lid by heating the lamp material (raw material polycrystalline silicon) caused by radiant heat from the raw material melt, or a bridge is formed by thermal expansion. Thus, a recharging device for a single crystal pulling device that improves the problem of no longer falling is disclosed.

  Furthermore, Patent Document 3 discloses a raw material supply apparatus and a supply method that can supply solid raw materials evenly and in a large amount in the circumferential direction without causing crystal contamination.

In each disclosed technique, a recharge apparatus (also referred to as a raw material supply apparatus) including a substantially cylindrical raw material supply pipe (also referred to as a hopper main body or a recharge pipe main body) and a conical bottom lid is used. The material is made of polycrystalline silicon, which is covered with a bottom cover, and is opened and closed by moving the bottom cover up and down to drop the material polycrystalline silicon in the material supply pipe into the quartz crucible.
Republished WO2002 / 068732 JP 2004-244236 A JP 2006-89294 A

  However, in the single crystal pulling process, since the recharge device (or “raw material supply device for recharging”) is inserted into the furnace of the single crystal pulling device in the middle of the melting process of the single crystal silicon pulling, The lower part tends to be hot (several hundred degrees). For this reason, in (or outside) the recharge device, the shaft (or wire) that suspends the bottom cover extends and the bottom cover is lowered, and the recharge pipe (or “a member corresponding to the raw material supply apparatus or the raw material supply pipe of the recharge apparatus”). ) And the bottom lid, there is a possibility that the polycrystalline silicon in the recharge tube falls from the gap.

  For example, if the material supply pipe is made of quartz and the shaft is made of metal, the metal generally has a higher coefficient of thermal expansion than quartz, and even if the length is the same at room temperature, the metal shaft is made of the material at high temperatures. It may be longer and longer than the supply pipe, and a gap may be formed between the raw material supply pipe and the bottom cover. For example, if a raw material supply device is suspended in a furnace of a single crystal pulling device, even if it is quickly operated, it takes a certain amount of time, and the temperature of the shaft may rise from 400 ° C to 500 ° C. Is estimated to occur. In this gap, not all of the lump-like raw material is necessarily dropped, but it is a granular one, and fragments or small pieces generated by friction between nugget-like raw materials (hereinafter collectively referred to as “raw material powder”) ) May fall from such a gap. The raw material powder dropped from this gap may splash the melt when falling into the crucible, and the splashed melt adheres to the in-furnace product and then falls into the crucible during pulling and adheres to the crystal. This may cause dislocation of the crystal, or adversely affect the quality of the single crystal silicon as a future contamination. Also, when such raw material powder (including the above-mentioned broken pieces and granular pieces) falls when the lower end of the raw material supply pipe is above the gate, the dropped raw material powder rides on the gate or gate flange. As a result, there is a risk that the chamber leaks or the gate cannot be opened or closed.

  Here, the raw material powder is a material obtained by pulverizing a raw material solid such as small pieces, granules, granules, etc. of the raw material having a size that can be dropped from the gap between the raw material supply pipe and the bottom cover as described above. It may mean any shape, including spherical shapes, elliptical spheres such as rugby balls. The arithmetic average diameter based on the number when the sphere is approximated may be about 0.1 mm to about 5.0 mm.

Also, the shape index F can be 1 to 10. Here, the shape index is defined as follows. The equivalent sphere diameter (Deq) is obtained from the volume of the raw material powder, and the ratio F to the maximum distance (Lmax) obtained for the shape of the raw material powder is obtained. For example, as shown in FIG.
Sphere with diameter D: Since Deq and Lmax (diameter) are the same, F = Lmax / Deq = 1.
Cube with side D: Lmax is diagonal length, F = √3 / (6 / π) ^1/3 = 1.396.
A square prism with a side of D and a height of 2D: Lmax is the diagonal length, F = √6 / (12 / π) ^1/3 = 1.57.
A cylinder whose height is twice the diameter D: Lmax is the length of the oblique line connecting the upper and lower bases, and F = √5 / 3 ^1/3 = 1.55.
Cone whose height is the same as the diameter D: Lmax is the length along the conical surface, F = √5 / 4 ^1/3 = 1.41.
Flat plate with thickness D, width 4D and length 8D: Lmax is the diagonal length, F = 9 / (192 / π) ^1/3 = 2.28.

  On the other hand, in order to prevent the falling raw material powder from splashing up the melt and adhering the melt to the parts of the single crystal pulling device, etc. You will be exposed to high temperatures. In this case, it is considered that the angle is about 600 degrees or more. In this case, it is assumed that the generated gap is 10 millimeters or more. Therefore, it may fall to a larger raw material powder and further cause problems such as liquid splashing.

  The present invention has been made in view of such circumstances, and the length of the support member in the axial direction is adjusted to the change in the length of the raw material supply pipe (changed when the length of the raw material supply pipe is unchanged). It is an object of the present invention to provide a raw material supply apparatus that prevents the formation of a gap between the raw material supply pipe and the bottom cover by adjusting the adjustment.

  In order to solve the above-described problems, a raw material supply apparatus according to the present invention includes a substantially cylindrical raw material supply pipe that holds a raw material, and a conical bottom that can be attached to and detached from a lower opening end of the raw material supply pipe. A lid and a support member for suspending the bottom lid, the support member comprising length adjusting means.

  More specifically, the present invention can provide the following.

(1) A raw material supply apparatus for supplying a raw material for growing a single crystal, a substantially cylindrical raw material supply pipe for holding the raw material, and a conical bottom provided detachably at a lower opening end of the raw material supply pipe A lid,
A support member that suspends the bottom lid, and the raw material held in the raw material supply pipe having the lower opening end closed by the mounting of the bottom lid is opened by the loading and unloading of the bottom lid The raw material supply apparatus can be provided in which the support member is discharged from a lower opening end and the support member includes a length adjusting unit.

(2) It is possible to provide the raw material supply apparatus according to (1) above, wherein the length adjusting means is an expansion / contraction mechanism using an elastic body.

  Here, the elastic body is a member having elasticity utilizing shape and / or structure, such as a helical spring, a spring, a flat spring, and other springs, metal, elastomer (including rubber), resin, etc. An elastic body that directly utilizes the elastic properties of the material itself such as a polymer material is included. Moreover, a mechanical thing like an air cylinder which can be used for suspension can also be included. Furthermore, these are examples, and if it has an elastic property, it will not be restricted to these.

(3) Providing the raw material supply apparatus according to the above (1) or (2), wherein the length adjusting means is arranged above the axial length of the support member. it can.

  Here, “above” may be above at least half of the length of the support member. Moreover, it may be above the raw material supply pipe filled with the raw material. Since the upper part is milder in terms of heat, the reliability and durability of the length adjusting means are higher. In addition, it becomes easier to use a material, structure, mechanism or the like having low heat resistance. Further, when installed on the raw material supply pipe, the volume of the raw material supply pipe can be used more effectively for filling the raw material. Therefore, if these are taken into consideration, it may be at least 3/4 or more of the length of the support member.

(4) The said length adjustment means can be arrange | positioned in the said raw material supply pipe | tube, The raw material supply apparatus as described in said (1) or (2) characterized by the above-mentioned can be provided.

  When the length adjusting means is long in the axial direction of the support member, the volume of the raw material supply pipe can be used more effectively for filling the raw material than on the raw material supply pipe. That is, if the total length of the raw material supply apparatus is defined to be equal to or less than a predetermined length, it is preferable that the length adjusting means provided on the raw material supply pipe is short. For example, if the length adjusting means is not on the raw material supply pipe, the length of the raw material supply pipe can be increased accordingly. Further, when the length adjusting means is elongated, it can be provided in the raw material supply pipe without sacrificing the volume of the raw material supply pipe so much. In addition, when the adjustment allowance (adjustable length) of the length adjusting means is proportional or positively correlated with the length of the length adjusting means, the longer length adjusting means can be arranged in the raw material supply pipe. Arranging is preferred.

(5) The material according to any one of (1) to (4), wherein the length adjusting means includes a spring and biases when the bottom cover is attached to the lower opening end. A feeding device can be provided.

  For example, the support member can be divided into two shafts, and length adjusting means can be provided between the shafts. This length adjusting means may function to shorten the overall length of the support member when the divided shafts are arranged substantially in series to constitute the support member as a whole. That is, it can have a function of drawing these shafts toward each other. More specifically, an intermediate member that is slidable in the axial direction with respect to each shaft may be provided between the shafts, and at least one shaft may be pulled toward the intermediate member. Note that any shaft is provided with a connecting member (or stopper) so as not to be separated from the intermediate member. For example, the helical spring is applied to the connecting member, and when the at least one shaft is to be separated from the intermediate member, the helical spring uses the force due to the expansion and contraction of the spring, and the resistance force depends on the separated distance. It can have an increasing mechanism. More specifically, a helical spring is mounted between one of the shafts and a pair of connecting members provided on the intermediate member, and the helical spring is compressed when the shaft and the intermediate member are pulled apart. You may do it. This mechanism can be similarly provided for the other shaft and the intermediate member.

(6) From the above (1), wherein the support member includes a shaft member extending along the axial direction, and the length adjusting means includes the shaft member including a metal having a small coefficient of thermal expansion. 5) The raw material supply apparatus according to any one of the above can be provided. When the shaft member, which is a main component of the support member, is made of a metal having a small coefficient of linear thermal expansion, it is preferable because the elongation of the shaft member of the support member is small even when the temperature is high.

(7) From the above (1), wherein the support member includes a shaft member extending along the axial direction, and the length adjusting means includes the shaft member including a metal having a low thermal diffusivity. The raw material supply apparatus according to any one of 5) can be provided. When the shaft member, which is the main component of the support member, is made of a metal having a low thermal diffusivity, even if the bottom cover side of the support member becomes high temperature, it is difficult for heat to be transferred to the upper lifting device side, and the support member becomes high The length of the shaft member becomes shorter. Accordingly, the entire support member is preferable because the elongation due to heat is reduced. In addition, since heat is difficult to be transmitted, when another type of length adjusting means is added, its reliability, durability, and the like are increased.

(8) Any of the above (1) to (5), wherein the support member includes a shaft member extending along the axial direction, and the length adjusting means includes the shaft member including metallic molybdenum. The raw material supply apparatus described above can be provided. The shaft member that is a main component of the support member may be made of molybdenum metal or may be made of a composite material containing molybdenum.

(9) Any of the above (1) to (5), wherein the support member includes a shaft member extending along an axial direction, and the length adjusting means includes the shaft member including a CC composite. The raw material supply apparatus described above can be provided. The shaft member that is a main component of the support member may be made of a CC composite or may be made of a composite material including the CC composite.

  According to the present invention, it is possible to prevent the occurrence of a gap between the opening of the lower end portion of the raw material supply pipe and the bottom lid by making the length of the support member constant or adjusting it appropriately. Become. Thereby, it can prevent that raw material powder falls from the clearance gap which arises between opening of the lower end part of a raw material supply pipe | tube, and a bottom cover.

  Next, embodiments of the present invention will be described with reference to the drawings. In the drawings, components having the same configuration or function and corresponding parts are denoted by the same reference numerals and description thereof is omitted. Moreover, in the following description, only an example of the embodiment according to the present invention is shown, and can be appropriately changed without exceeding the scope of the present invention based on the common general knowledge of those skilled in the art. Therefore, the scope of the present invention is not limited to these specific examples. Also, these drawings are emphasized for the purpose of explanation, and may differ from actual dimensions.

  1A to 1C are cross-sectional views showing an example of a raw material supply apparatus 1 according to the present invention. As shown in FIG. 1A, a raw material supply apparatus 1 includes a substantially cylindrical raw material supply pipe (or hopper body) 3 that holds a raw material (for example, polycrystalline silicon), and a lower end opening of the raw material supply pipe 3. A conical bottom lid 5 that opens and closes the portion 3a and a lower shaft 7a that suspends the bottom lid 5 are configured. Here, the lower shaft 7 a is connected to a length adjusting mechanism 50 that is a length adjusting means, and the length adjusting mechanism 50 that is a length adjusting means is further connected to the upper shaft 7. The shaft 7 and the lower shaft 7a constitute a support member. The shaft 7 is further connected to the seed shaft 16 above, and the whole raw material supply device 1 is suspended by a suspension device (not shown). The bottom cover 5 is fixed to the lower shaft 7a, is attached to the opening 3a at the lower end of the raw material supply pipe 3, and closes the opening 3a. The lower shaft 7a made of metal or other material is inserted through a hole formed in a cylindrical frame of a length adjusting mechanism 50 which is a length adjusting means, and a disk-shaped head 52 is fixed. . A helical spring 53 is arranged coaxially with the lower shaft 7a in a space sandwiched between the disc-shaped head 52 and the cylindrical lower frame of the length adjusting mechanism 50 serving as a length adjusting means. This helical spring is compressed in the state of FIG. 1A, and conversely, the bottom lid 5 is attached to the opening 3a by a force resulting from this compression.

  That is, the lower shaft 7a is pulled upward in the drawing by the helical spring 53. The reaction force of the pulling force acts on the head 51 of the shaft 7 disposed above via the cylindrical frame of the length adjusting mechanism 50 that is the length adjusting means, so that the shaft 7 itself is pushed down. And On the other hand, the shaft 7 is directly connected to a seed shaft 16 further above, and the seed shaft 16 is suspended by a pulling device (not shown). As long as the reaction force (tensile force) of the helical spring 53 does not resist the weight of the raw material supply device, the shaft 7 itself does not fall down. In other words, an attempt is made to pull up the cylindrical frame of the length adjusting mechanism 50, which is the length adjusting means, through the head 51.

  Here, it is assumed that the shaft 7 is pulled upward by the pulling device. Accordingly, the stopper 71 that is caulked and fixed to the shaft 7 comes into contact with the second top plate 9b and supports the second top plate 9b. Since the second top plate 9b is fixed to the raw material supply pipe 3 which is the main body of the raw material supply device 1, the raw material supply device 1 is supported by the pulling device, that is, is suspended. Here, when the stopper 71 comes into contact with the second top plate 9b, the length of the lower shaft 7a is adjusted slightly shorter than the bottom lid 5 is just attached to the opening 3a. Thus, the spring 53 is compressed, and some of the force contributes as a mounting force for pressing the bottom lid 5 and the opening 3a.

  The first top plate 9 a has a hole through which the shaft 7 is inserted while preventing contamination from entering the raw material supply pipe 3. Further, the bottom cover 5 connected to the lower shaft 7 a is guided so as to be the center of the raw material supply pipe 3. A second top plate 9b is provided fixed to the first top plate 9a. Between the first top plate 9a and the second top plate 9b, and above the length adjusting mechanism 50, which is the length adjusting means, from the diameter of the hole opened for inserting the shaft 7. A stopper 71 having a larger diameter is provided, and the raw material supply pipe 3 fixed to the first top plate 9a is suspended by the stopper 71 and the second top plate 9b. A locking portion 42 is fixed to the first top plate 9a via a clamp-shaped fastener. The locking portion 42 has a cylindrical shape extending in the vertical direction as a whole, and is a fastener that is fastened to the first top plate 9a, a cylindrical length adjusting mechanism, and a contact portion with the flange portion. It is mainly comprised from the cushion member etc. with which a lower end part is equipped. Although the two locking portions 42 are provided symmetrically around the raw material supply pipe 3, three or four rotationally symmetrical portions may be provided. In addition, the shape is not limited to a cylindrical shape, and a simple rod-shaped object (regardless of the cross-sectional shape) filled with the contents may be arranged axially symmetrically with three or more in the circumferential direction. The locking portion 42 is used for an opening / closing mechanism of the bottom lid 5 described later.

  FIG. 1B shows a state in which the raw material supply device 1 of FIG. 1A is inserted into the pulling device, the temperature rises, and the support member including the metal lower shaft 7a extends. At this time, although the raw material supply pipe 3 is also extended, it is remarkably small, and therefore, in this figure, it is handled as having no such extension. As shown in FIG. 1B, the combined length of the seed shaft 16, the shaft 7, a length adjusting mechanism 50 (not adjusted here) that is a length adjusting means, and the lower shaft 7a , D is extended. Therefore, a gap is formed between the opening 3 a at the lower end of the raw material supply pipe 3 and the bottom cover 5.

  FIG.1 (c) has shown the state which the raw material supply apparatus 1 of FIG.1 (b) closed the clearance gap automatically. That is, the lower shaft 7a is pulled upward by the extension force of the spring 53, and the gap is automatically removed from the state shown in FIG. 1B, and the bottom cover 5 is remounted on the opening 3a. Is shown. As can be seen, the spring 53 extends by D and absorbs D that has been extended due to a difference in thermal expansion or the like. Therefore, it is preferable that the amount of compression of the elastic body (for example, the spring 53) is ensured to be equal to or more than the expected elongation.

  Here, the diameter of the bottom surface of the bottom cover 5 is substantially the same as or slightly larger than the diameter of the raw material supply pipe 3. A part of the conical surface of the bottom cover 5 engages with the lower end of the raw material supply pipe 3 to close the lower end opening 3a.

  Thus, the raw material supply apparatus 1 is provided between the raw material supply pipe 3 and the bottom cover 5 by the support member (including the shaft 7 and the lower shaft 7a) having a length adjusting mechanism for adjusting the length of the support member. Generation of a gap can be prevented. Thereby, it can prevent that raw material powder falls from the clearance gap which arises between the raw material supply pipe | tube 3 and the bottom cover 5. FIG.

  2 (a) to 2 (c) show, in a sectional view, another embodiment using two helical springs 53 for the present invention. Since the basic structure is the same as that in FIG. FIG. 2A shows a state where the two springs 53 are compressed and set. The two springs 53 are respectively between the head 52 of the shaft 7 and the cylindrical upper frame of the length adjusting mechanism 50 which is the length adjusting means, and are the head 52 and the length adjusting means of the lower shaft 7a. It is compressed between the cylindrical lower frame of the length adjusting mechanism 50.

  FIG. 2B shows a state in which the raw material supply device 1 of FIG. 2A is inserted into the pulling device, the temperature rises, and the support member including the metal lower shaft 7a extends. As shown in the figure, the combined length of the seed shaft 16, the shaft 7, the length adjusting mechanism 50 (which is not adjusted here) as a length adjusting means, and the lower shaft 7a is only D. It is growing. Therefore, a gap is formed between the opening 3 a at the lower end of the raw material supply pipe 3 and the bottom cover 5.

  FIG. 2 (c) shows a state where the raw material supply apparatus 1 of FIG. 2 (b) automatically closes the gap. That is, the cylindrical frame of the length adjusting mechanism 50 that is the length adjusting means is pulled upward by the extension force of the spring 53, and the lower shaft 7a is pulled upward by the extension force of the spring 53. . This is advantageous because the compression allowance of the two elastic bodies can be used when the displacement is large, for example, the thermal expansion is particularly large. Further, it is easy to apply a residual pressure between the bottom lid 5 and the opening 3a, and it is difficult to make a gap between the bottom lid 5 and the opening 3a.

  Next, based on FIG. 3, the whole structure of the single crystal pulling apparatus 10 which pulls the single crystal silicon to which the raw material supply apparatus 1 which is an example of embodiment of this invention is applied is demonstrated easily. FIG. 3 represented by a cross section shows a state in which the raw material supply device 1 is installed in the furnace of the single crystal pulling apparatus 10 during the melting process of single crystal silicon pulling. A single crystal pulling apparatus 10 shown in FIG. 3 mainly includes a chamber 12 and a subchamber 14. In the chamber 12, a heat insulating material 26 surrounding the quartz crucible 20, the graphite crucible 22, and the heater 24 is disposed. The sub-chamber 14 is provided in the upper part of the chamber 12 with a gate valve 18 that can open and close the opening 18a. In the crystal growth step, the single crystal is pulled from the raw material melt 48, separated, and then a single crystal ingot. Is used to hold and take out the single crystal pulling apparatus 10. The seed shaft 16 latches a seed crystal (not shown) or the raw material supply apparatus 1.

  First, the chamber 12 will be described. As shown in FIG. 3, the bottomed cylindrical chamber 12 is provided with a rotary shaft 28 that can move up and down in a state of being directed vertically upward from the center of the bottom. A bowl-shaped graphite crucible 22 is fixed to the upper end of the rotating shaft 28, and a bowl-shaped quartz crucible 20 is fitted inside the graphite crucible 22. The double structure of the quartz crucible 20 and the graphite crucible 22 is because the crucible directly in contact with the raw material melt is preferably the quartz crucible 20 in order to prevent contamination of silicon. On the other hand, quartz is softened at a high temperature and has a property of being brittle and easily damaged, and therefore, the periphery thereof is surrounded by a graphite crucible 22.

  The graphite crucible 22 is surrounded by a heater 24, and the heater 24 melts the polycrystalline silicon lamp material 46 put into the quartz crucible 20. A cylindrical heat insulating material 26 is disposed around the heater 24 concentrically with the chamber 12. The heat insulating material 26 prevents heat from the heater 24 from being directly radiated to the chamber 12.

  As shown in FIG. 3, a substantially cylindrical sub-chamber 14 is connected to the upper portion of the chamber 12 via a gate valve 18. The chamber 12 and the sub-chamber 14 can be communicated or blocked by the gate valve 18. On the other hand, although not shown, the upper end of the sub-chamber 14 is sealed with a top plate. Further, as shown in FIG. 3, a ring-shaped flange portion 40 that protrudes toward the central axis is provided on the inner peripheral surface of the sub-chamber 14.

  A seed shaft pulling device (not shown) is provided on the upper portion of the sub chamber 14. The seed shaft lifting device holds the seed shaft 16 so as to be movable up and down, and is suspended along the central axis of the subchamber 14. A seed crystal is suspended from the lower end of the seed shaft 16 during the single crystal ingot pulling process, and the raw material supply apparatus 1 is suspended during the raw material supply process.

  Next, the structure of the raw material supply apparatus 1 that is hooked on the seed shaft 16 in the raw material supply process will be described. A shaft 7 is coupled to the seed shaft 16, and the shaft 7 is coupled to the bottom lid 5 through a hole formed in the second top plate 9 b and the first top plate 9 a. In the raw material supply apparatus 1, as described with reference to FIG. 1, the raw material supply pipe 3 is held by the shaft 7 via the stopper 71 locked to the second top plate 9b. On the other hand, the bottom lid 5 attached to the lower end opening 3a of the raw material supply pipe 3 is coupled to the lower shaft 7a and coupled to the frame of the length adjusting mechanism 50, which is a length adjusting means, via a spring 53. Yes.

  The raw material supply pipe 3 is made of quartz in order to prevent contamination of silicon as a raw material so as not to contaminate a silicon single crystal as a product. Further, by configuring the raw material supply tube 3 with transparent quartz, it is possible to confirm whether or not all the polycrystalline silicon lamp material 46 loaded in the raw material supply device 1 has fallen. In addition, the raw material supply pipe 3 is provided with a locking portion 42 that is hooked on the flange portion 40 and stops the lowering of the raw material supply pipe 3 that is fixed to the first top plate of the raw material supply apparatus 1. Since the locking portion 42 is supported by the flange portion 40 and stops the lowering of the raw material supply pipe 3, when the shaft 7 and the lower shaft 7a are further lowered, only the bottom lid 5 is lowered.

  The bottom cover 5 is fixed to the lower shaft 7a, and tries to push up the raw material supply pipe 3 with the above-described residual pressure. However, since the pressing force due to the weight of the raw material supply pipe 3 and the like is larger, the stopper 71 is fixed via the first top plate 9a and the second top plate 9b for fixing the raw material supply pipe 3. The raw material supply pipe 3 is substantially supported by the shaft 7. Here, the lower shaft 7a is made of metal (for example, stainless steel, tungsten, molybdenum, etc.) or CC composite. As described with reference to FIG. 1, the stopper 71 is fixed to the shaft 7, and the shaft 7 is disposed under the second top plate 9 b with a hole through which the shaft 7 is inserted. In the state where the raw material supply apparatus 1 is suspended, the stopper 71 contacts the second top plate 9b, and the raw material supply pipe 3 fixed to the second top plate 9b is suspended via the first top plate 9a. Lowering and lowering is restricted.

  4 and 5 show a state in which raw material supply is started. When supplying polycrystalline silicon as a raw material, first, the gate valve 18 is opened, and the chamber 12 and the sub-chamber 14 become one space. At this time, heat is applied from the melt 48 in the crucible 20 by radiation, and the temperature of the raw material supply apparatus 1 rises. Further, the entire raw material supply apparatus 1 is lowered, and the locking portion 42 is supported by the flange portion 40, so that the lowering of the raw material supply pipe 3 is stopped. Further, by lowering the shaft 7 and the lower shaft 7a without lowering the position of the raw material supply pipe 3, the bottom cover 5 is finally detached and the opening 3a at the lower end of the raw material supply pipe 3 is opened. Since the bottom cover 5 is pulled up by the residual pressure of the spring 53, the removal of the bottom cover 5 from the opening 3a is delayed.

  However, when the shaft 7 and the lower shaft 7a are further lowered, as shown in FIG. 6, the bottom lid 5 is detached from the opening 3a, the opening 3a at the lower end of the raw material supply pipe 3 is opened, and the raw material supply device From 1, massive polycrystalline silicon is supplied to the raw material melt 48 of the quartz crucible 20.

  When the raw material supply apparatus 1 is installed in the sub-chamber 14 in a high temperature state, or when the raw material supply apparatus 1 installed in the sub-chamber 14 descends and moves into the chamber 12, the raw material supply apparatus 1 becomes high temperature. Will be exposed. As a result of the raw material supply apparatus 1 being exposed to a high temperature and the lower shaft 7a extending as compared with the raw material supply pipe 3, the bottom lid 5 is relatively lowered (FIG. 4). However, at this time, by releasing the compression amount of the spring 53, the lower shaft 7a is pulled up, and a gap can be prevented from being generated between the lower end opening 3a and the bottom lid 5 (FIG. 5). Therefore, the generation of gaps due to thermal expansion can be prevented, and the bulk polycrystalline silicon lamp material 46 filled in the raw material supply pipe 3 or the raw material powder generated by the friction thereof can be prevented from falling.

  Thus, by providing the support member (the shaft 7 and the lower shaft 7a) with the length adjusting mechanism (as the “length adjusting means”) by the spring 53 as described above, the raw material supply pipe 3 and the bottom lid 5 are provided. It is possible to prevent an unintended gap from occurring between them. As a result, the raw material powder is prevented from falling from the gap formed between the raw material supply pipe 3 and the bottom cover 5, and the occurrence of a malfunction due to the dropping of the raw material powder (for example, adhesion of liquid splashing in the furnace) is avoided. It becomes possible. In addition, it is possible to prevent the occurrence of a leak failure caused by adhering to the seal (O-ring) portion or the like of the gate valve 18. Further, even when the temperature in the furnace of the single crystal pulling apparatus 10 (in the chamber 12 or the subchamber 14) is high, the raw material supply apparatus 1 can be installed in the single crystal pulling apparatus 10, and The raw material supply apparatus 1 can be kept in the single crystal pulling apparatus 10 for a long time with the gate valve 18 opened.

  FIGS. 7 (a) to (c) show another embodiment in which the length adjusting mechanism 50, which is a length adjusting means, is arranged substantially in the center in the length direction of the support member including the shaft 7 and the lower shaft 7a. The form is shown in a cross-sectional view. Since the basic structure is the same as that in FIG. FIG. 7A shows a state at room temperature. A length adjusting mechanism 50 that is a length adjusting means is disposed in the raw material supply pipe 3. Although the installation position of the length adjusting mechanism 50, which is the length adjusting means, is different, it performs substantially the same function. Therefore, the helical spring 53 is the same as the head 52 of the lower shaft 7a and the length adjusting means as in FIG. It is compressed between the cylindrical lower frame of the length adjusting mechanism 50.

  FIG. 7B shows a state in which the raw material supply device 1 of FIG. 7A is inserted into the pulling device, the temperature rises, and the support member including the metal lower shaft 7a extends. As shown in the figure, the combined length of the seed shaft 16, the shaft 7, the length adjusting mechanism 50 (which is not adjusted here) as a length adjusting means, and the lower shaft 7 a is only D. It is growing. Therefore, a gap is formed between the opening 3 a at the lower end of the raw material supply pipe 3 and the bottom cover 5.

  FIG.7 (c) has shown the state which the raw material supply apparatus 1 of FIG.7 (b) closed the clearance gap automatically. That is, the lower shaft 7 a is pulled upward by the extension force of the spring 53. As described above, when the length adjusting mechanism 50, which is a length adjusting means, is disposed in the raw material supply pipe 3, the raw material supply pipe 3 can be lengthened while keeping the entire length the same, It is also possible to enlarge the filling volume. In addition, the length adjusting mechanism 50, which is a length adjusting means, can function as a thermal resistance that lowers the heat conduction in the axial direction of the support member. It is also possible to configure with a low material.

  FIG. 8 shows another embodiment in a longitudinal sectional view. Since the basic structure is the same as that of FIG. 1, duplicate description is omitted. In this embodiment, the length adjusting mechanism 50 as the length adjusting means is not attached to the shaft 7 as the support member. Therefore, when the shaft 7 is made of a normal metal, the raw material supply pipe 3 is made of quartz. Therefore, from the difference in thermal expansion between them, the opening 3a at the lower end of the raw material supply pipe 3 and the bottom cover 5 are provided. There will be a gap between them.

  However, the shaft 7 prevents the formation of such a gap by using a material that takes into consideration the following thermal expansion coefficient. That is, a shaft made of a specific material becomes the length adjusting means.

  Table 1 summarizes the properties of the various materials. It can be seen that quartz glass has a particularly low thermal expansion and a low thermal diffusivity, so that it is difficult for heat to be transmitted and the elongation due to thermal expansion is extremely small. Accordingly, the thermal expansion of the quartz glass can be almost ignored, and it is preferable to use a material having a low thermal expansion as much as possible for the shaft 7. For example, it is more preferable to use molybdenum, tungsten, carbon, or a carbon composite material than SUS304, which is a typical austenitic stainless steel. Since carbon and carbon composite materials can have a smaller thermal expansion coefficient, it is more preferable if characteristics such as mechanical strength are satisfied.

  Note that molybdenum and tungsten have a larger thermal diffusivity and heat is more easily transmitted than SUS304, so it is more preferable to provide a thermal barrier in the middle of the shaft 7. For example, as shown in FIG. 1, it is more preferable that a length adjusting mechanism as a length adjusting means is provided in the middle. Furthermore, in this case, it is more preferable to further provide such a length adjusting mechanism when molybdenum or tungsten having a thermal expansion coefficient that is an order of magnitude larger than that of quartz glass is used. Nor.

  Incidentally, how heat is transferred can be estimated by assuming one-dimensional unsteady heat conduction of a semi-infinite solid. Here, if the temperature is converted as in [Equation 1], the one-dimensional equation of unsteady heat conduction becomes as in [Equation 2].

  Here, a is the thermal diffusivity, t is time (S), and x is distance (m). The initial condition and boundary condition are set to 600 ° C. and the initial temperature is 0 ° C. as shown in [Formula 3]. At this time, it is assumed that the temperature is forcibly raised to 600 ° C. with x = 0. The shaft heat flow approximates adiabatic and further assumes infinity.

  The solution in this case can be obtained analytically, and becomes an error function as shown in [Equation 3]. FIG. 9 shows how the error function changes.

From FIG. 9, in order to consider the time and place where θ / θ ₁ is ½, ie, 300 ° C., z is about 0.47. Accordingly, if a position at 300 ° C. when standing for 1 hour is obtained, the position of stainless steel is 100 mm, and the position of molybdenum is about 400 to 500 mm as shown in Table 2.

  From Table 2, it is possible to predict the approximate thermal gradient, which is effective for making predictions. However, since it is approximated by many assumptions, the absolute value is not accurate and should be confirmed by experiments. To. When the SUS shaft was actually put in the furnace and the size of the gap was measured, it was about 9.2 mm open. Since this is a 900 mm shaft, the average shaft temperature was about 600 ° C. Further, it was about 2.9 mm for molybdenum, and about 2.5 mm to 3.4 mm for tungsten. Moreover, in the carbon material, it was about 2.2 mm to about 2.8 mm. As can be seen from this result, it can be seen that tungsten and molybdenum are less vacant and the gap is narrower, so that the raw material powder is less likely to fall inadvertently.

  In particular, if molybdenum or tungsten is used and further the length adjusting mechanism as the above-described length adjusting means is used, it is expected that there is substantially no gap between the bottom lid 5 and the opening 3a.

  Furthermore, the length adjusting mechanism used for the support member shown in the above embodiment is merely an example, and other means may be used. Even if there is a gap as described above due to non-uniform changes in the length of the support member and the raw material supply pipe, the length can be adjusted by aligning the thermal expansion characteristics and other thermal characteristics. A desired raw material supply apparatus can be provided by using the means for the support member or by appropriately combining these means.

  Moreover, the raw material supply apparatus 1 and the single crystal pulling apparatus 10 shown in the above embodiment are examples, and are not limited to these. The raw material supply apparatus of the present invention can be applied to any apparatus having a function of opening and closing a lower end opening of a raw material supply pipe (hopper body) by attaching and removing a conical bottom lid. In addition, although the above-described embodiment has been described by taking the shape of the material supply pipe of the material supply device 1 as an example of a cylindrical shape, the shape is not limited to the cylindrical shape, and may be other shapes such as a rectangular cylindrical shape. Needless to say, it may be. Further, the shape of the bottom lid is not limited to the conical shape or the truncated cone shape, and it is needless to say that the bottom lid may have another shape such as a pyramid or a prism.

It is sectional drawing which showed the example of the raw material supply apparatus about embodiment of this invention. (A) shows the state at normal temperature, (b) shows the state at high temperature, and (c) shows the state when the length adjusting mechanism functions. It is sectional drawing which showed another example of the raw material supply apparatus about embodiment of this invention. (A) shows the state at normal temperature, (b) shows the state at high temperature, and (c) shows the state when the length adjusting mechanism functions. It is sectional drawing which showed the example of the single crystal pulling apparatus which has arrange | positioned the raw material supply apparatus which is an example of this embodiment. FIG. 4 is a cross-sectional view illustrating the single crystal pulling apparatus of FIG. 3 in a state in which raw material supply is about to start. FIG. 5 is a cross-sectional view showing a state when the raw material supply apparatus as an example of the present embodiment functions in the single crystal pulling apparatus of FIG. 4. FIG. 5 is a cross-sectional view showing a state in which the raw material supply apparatus as an example of the present embodiment releases the bulk polycrystalline silicon of the raw material in the single crystal pulling apparatus of FIG. 4. It is sectional drawing which showed another example of the raw material supply apparatus about embodiment of this invention. (A) shows the state at normal temperature, (b) shows the state at high temperature, and (c) shows the state when the length adjusting mechanism functions. It is sectional drawing which showed another embodiment of the raw material supply apparatus which concerns on this invention. It is the graph which showed the behavior of an error function. It is explanatory drawing of a figure index.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw material supply apparatus 3 Raw material supply pipe 3a Opening part 5 Bottom cover 7 Shaft 7a Lower shaft 9a, 9b 1st and 2nd top plate 10 Single crystal pulling apparatus 12 Chamber 14 Subchamber 16 Seed shaft 18 Gate valve 20 Quartz crucible 22 Graphite crucible 24 Heater 26 Heat insulating material 28 Rotating shaft 40 Flange portion 42 Locking portion 46 Lamp material 48 Raw material melt 71 Stopper

Claims (9)

A raw material supply apparatus for supplying a raw material for growing a single crystal,
A substantially cylindrical raw material supply pipe for holding the raw material;
A conical bottom lid detachably provided at a lower opening end of the raw material supply pipe;
A support member for suspending the bottom lid,
The raw material held in the raw material supply pipe having the lower open end closed by the mounting of the bottom lid is discharged from the lower open end opened by the loading and unloading of the bottom lid,
The raw material supply apparatus, wherein the support member includes length adjusting means.   The raw material supply apparatus according to claim 1, wherein the length adjusting means is an expansion / contraction mechanism using an elastic body.   The raw material supply apparatus according to claim 1, wherein the length adjusting unit is disposed above the axial length of the support member.   The raw material supply apparatus according to claim 1, wherein the length adjusting unit is disposed in the raw material supply pipe.   The raw material supply apparatus according to any one of claims 1 to 4, wherein the length adjusting means includes a spring and biases when the bottom cover is attached to the lower opening end. The support member includes a shaft member extending along the axial direction,
The raw material supply apparatus according to any one of claims 1 to 5, wherein the length adjusting means includes the shaft member including a metal having a low coefficient of thermal expansion. The support member includes a shaft member extending along the axial direction,
The raw material supply apparatus according to any one of claims 1 to 5, wherein the length adjusting means includes the shaft member including a metal having a low thermal diffusivity. The support member includes a shaft member extending along the axial direction,
The raw material supply apparatus according to any one of claims 1 to 5, wherein the length adjusting means includes the shaft member containing metallic molybdenum. The support member includes a shaft member extending along the axial direction,
The raw material supply apparatus according to any one of claims 1 to 5, wherein the length adjusting means includes the shaft member including a CC composite.

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