JP2010083685A - Raw material feeding device and apparatus and method for producing single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a raw material feeding device where troubles caused in the device by the hopping of a molten liquid when recharging are suppressed while keeping high productivity by efficiently melting a solid raw material recharged into the molten liquid in a crucible and to provide an apparatus and a method for producing a single crystal. <P>SOLUTION: The raw material feeding device 13 to feed a grain aggregate solid raw material in the crucible 4 holding the molten liquid 5 of the raw material is equipped with a raw material filling vessel 14 in which the raw material is filled and which has an opening openable and closable downward and a cylindrical movable cover 15 which surrounds the outer periphery of the opening at the raw material filling vessel 14, which is set so as to be position-variable in a vertical direction and which goes down in the direction of the crucible 4 when feeding the raw material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a single crystal manufacturing apparatus and manufacturing method used in a Czochralski method for growing a single crystal ingot such as silicon, and more particularly to a raw material supply apparatus suitably used for recharging a raw material in this manufacturing apparatus. Is.

  In general, the Czochralski method (CZ method) is known as a method for growing a silicon single crystal. This is because silicon solid material is heated and melted in a crucible installed in a growing apparatus, seed crystal silicon is immersed in the surface of the raw material melt and then pulled up, and silicon having the same orientation as the seed crystal This is a method for growing a single crystal ingot.

  In the growth of a single crystal by the above-described CZ method, when the solid raw material initially charged in the crucible is melted, the volume is reduced, so that the amount of melt of the obtained raw material is insufficient as compared with the volume of the crucible. Therefore, in order to replenish the shortage of the raw material melt, recharging for additionally supplying a solid raw material after first charging the crucible is widely performed. By this recharging, the volume of the crucible can be effectively utilized, and the productivity in growing a single crystal ingot can be improved.

  Further, a quartz crucible often used for growing a silicon single crystal by the CZ method cannot be used because a solid adhesive layer is formed between the crucible inner wall and the melt once the solid raw material is melted. Therefore, from the viewpoint of improving productivity, multi-pooling in which a plurality of single crystals are pulled up at once is desired. However, this multi-pooling is possible only by the application of recharge. Specifically, after pulling up the single crystal from the crucible, the solid raw material in an amount corresponding to the decrease in the raw material melt is recharged to the residual melt in the crucible, and the single crystal is pulled up again. As a result, a plurality of single crystals can be manufactured from a crucible that can normally be used only once, and the manufacturing yield can be improved and the manufacturing cost can be reduced.

  In this way, recharging is an effective technology, but when recharging a solid raw material, the melt in the crucible jumps due to the impact when the raw material falls and the droplets adhere to the device, shortening the life of the device, or simply There was a problem of adversely affecting the growth of crystals.

  On the other hand, in Patent Document 1, an inner container having an opening and filled with a solid raw material is slidably inserted into an outer container that closes the opening of the inner container, and then these containers are inserted. The technique is described in which the solid material is poured into the raw material melt in the crucible after the container is lowered to the crucible and stopped, the container is slid to open the opening. At this time, by opening the opening using the sliding movement, static raw material can be charged, and further, the fine particle raw material can be dropped at the initial charging stage, thereby preventing liquid splashing. It is said that will increase.

Further, in Patent Document 2, a recharge pipe filled with a solid material, and provided on the lower outer side of the recharge pipe, slidable with respect to the recharge pipe and having a reduced diameter inclined portion toward the opening at the lower end. A recharging device is disclosed that includes a funnel-shaped outer cylinder and a lower end lid that closes the opening. Here, as a state in which the central portion of the melt is partially solidified, the recharge device is lowered toward the melt in the crucible, and the opening reduced in diameter toward the center of the melt is opened. A solid raw material is dropped and supplied to the solidified surface at the center of the melt. Thereby, even if the solidification ratio of the melt surface is low, the splash of the melt is suppressed, and the productivity can be improved.
JP-A-2005-1977 JP 2007-277069 A

  However, when the conventional technique is used, the temperature of the melt is lowered by the recharged solid raw material, so that it takes time until the recharged raw material is remelted, resulting in a problem that productivity is lowered. In order to prevent this, it is conceivable to increase the temperature of the melt sufficiently by increasing the heating output of the crucible from the stage before recharging the solid raw material. Splashing becomes prominent, increasing the risk of damaging the device. Moreover, according to the methods of Patent Documents 1 and 2, in order to suppress the liquid splash, the opening of the recharge device is lowered to the vicinity of the liquid surface, and then the opening is opened to drop the solid raw material. The opening part of the recharge device with a movable mechanism is damaged due to heat and causes a defect. The heat causes a gap between the opening part and the lid, causing unintentional dropping of the raw material. Many problems remain unsolved, such as contamination of impurities from solid materials into the raw material.

  The present invention has been completed in view of the above-mentioned problems in the prior art, and its purpose is to efficiently melt the solid material recharged in the melt in the crucible while maintaining high productivity. An object of the present invention is to provide a raw material supply apparatus, a single crystal manufacturing apparatus, and a single crystal manufacturing method that suppress problems caused in the apparatus due to the splashing of the melt during recharging.

  A raw material supply apparatus according to the present invention is a raw material supply apparatus that supplies agglomerated solid raw material to a crucible that holds a raw material melt, and is filled with a solid raw material and has an opening that can be opened and closed downward. A container and a tubular movable cover which surrounds the outer periphery of the opening of the raw material filling container and is provided so as to be variable in the vertical direction and descends in the direction of the crucible when the raw material is supplied.

  The single crystal production apparatus of the present invention includes the raw material supply apparatus of the present invention, and a crucible that holds the raw material melt and is supplied with agglomerated solid raw material from the raw material supply apparatus.

  Furthermore, the method for producing a single crystal according to the present invention is a method for producing a single crystal in which a solid material in the form of agglomerates is supplied to a crucible using the single crystal production apparatus according to the present invention, and the lower end of the movable cover is The step of lowering the movable cover until it reaches a position near the surface of the raw material melt in the crucible, the step of opening the opening of the raw material filling container and dropping the solid raw material into the raw material melt of the crucible, A step of gradually raising the movable cover as the charged solid material melts.

  Since the raw material supply apparatus of the present invention is configured as described above, when the solid raw material is recharged, the solid raw material passes through the inside of the descending tubular movable cover to the molten melt in the crucible. Supplied. At this time, since the melt heat is taken away by the supplied solid raw material, the surface of the melt is once solidified, but the lowered movable cover serves as a crucible lid and is sandwiched between the movable cover and the crucible. Since the heat is stored in the space, the recharged solid material is efficiently melted in a short time.

  Furthermore, since the solid raw material is supplied with the movable cover lowered, even if the raw material fine powder or melt splash is scattered around when the raw material is dropped, the movable cover can suppress the influence on the outside. Adverse effects on the lifetime and growth of single crystals can be reduced.

  In addition, since the splash of the melt is suppressed by the movable cover, it is not necessary to bring the opening of the raw material filling container closer to the hot melt in the crucible than necessary. Therefore, the movable mechanism of the opening of the raw material filling container is not easily damaged by heat. Further, since the raw material is supplied by opening and closing the opening of the raw material filling container, it is not necessary to provide a lid at the opening of the movable cover, and a simple mechanism can be used, so that troubles due to heat hardly occur. In addition, since the openings and lids of the raw material filling container that accumulates solid raw materials do not reach an unnecessarily high temperature, contamination of the raw materials from the locations (openings and lids) that are actually in contact with the solid raw materials Hard to happen.

  Since the single crystal production apparatus of the present invention includes the raw material supply apparatus of the present invention as described above, the solid crystal recharged in the crucible can be melted in a short time, and the single crystal production apparatus has high productivity. It becomes. Furthermore, since the movable cover can suppress the adverse effect on the life of the apparatus and the growth of the single crystal due to the splashing of the melt at the time of recharging and the scattering of the raw material fine powder, the apparatus has a high productivity and a high yield. In addition, since the solid raw material can be recharged with the opening of the raw material filling device being sufficiently spaced from the melt, it contributes to a longer life of the device and the pulling of a high quality single crystal.

  According to the method for producing a single crystal of the present invention, the step (1) of lowering the movable cover until the lower end of the movable cover comes to a position near the surface of the raw material melt in the crucible, and the opening of the raw material filling container Opening and dropping the solid raw material into the raw material melt of the crucible (2), and gradually separating the distance between the crucible and the movable cover as the solid raw material charged into the crucible melts (3) In particular, at the time of step (2), the movable cover in the lowered state serves as a crucible lid, so that the recharged solid raw material is efficiently melted in a short time. And as it melts, the distance between the crucible and the movable cover is gradually increased so that when there is an undissolved solid material inside the movable cover, it can be efficiently discharged into the crucible. Further, since the movable cover is kept away from the high-temperature melt, it is not necessary to expose the movable cover to higher heat than necessary.

  According to the method for producing a single crystal of the present invention, the effects as described above are exhibited, so that impurities can be prevented from being mixed into the solid raw material, and a single crystal having a high purity can be produced. In addition, since the life and productivity of the apparatus can be kept high, it contributes to cost reduction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in the following description, only an example of the embodiment according to the present invention is shown, and the scope of the present invention is not limited to these specific examples. In addition, the members shown in the drawings and their dimensions and ratios may be emphasized or omitted for the sake of explanation, and do not necessarily correspond to actual ones.

  FIG. 1 is a schematic cross-sectional view showing an example of a single crystal manufacturing apparatus (a silicon single crystal manufacturing apparatus in this example) according to the present invention. 1 is a so-called CZ furnace, and includes a main chamber 1 and a pull chamber 2 as furnace bodies. The pull chamber 2 has a smaller diameter than the main chamber 1 and is superimposed on the center of the main chamber 1. A crucible is disposed at the center of the main chamber 1.

  The crucible has a double structure in which a quartz crucible 4 provided on the inside and a graphite crucible 3 provided on the outside thereof are combined. Quartz constituting the quartz crucible 4 is softened at a high temperature and has the property of being brittle and easily damaged, so the periphery thereof is surrounded by the graphite crucible 3. These crucibles are supported by the support shaft 11 via a crucible receptacle (not shown). The support shaft 11 can be driven to move the crucible up and down or to rotate in the circumferential direction.

  The periphery of the graphite crucible 3 is surrounded by a heater 6. The heater 6 melts a silicon solid material (for example, a polycrystalline lamp material) charged into the quartz crucible 4. A heat insulating material 7 for heat insulation is arranged on the apparatus bottom pedestal 10 concentrically with the main chamber 1 along the inner surface of the main chamber 1 on the outer side of the heater 6. This heat insulating material 7 prevents heat from the heater 6 from being directly radiated to the main chamber 1.

  Further, an opening is provided on the heat insulating material 7, and a heat shielding shield 8 having a circumferential portion extending horizontally on the upper side and on the lower side is provided on the lower side.

  The main chamber 1 is provided with an exhaust port 12 so that an inert gas such as Ar can be supplied into the main chamber 1 from a gas supply pipe (not shown). Specifically, silicon is melted by discharging air from the exhaust port 12 to bring the inside of the main chamber 1 into a decompressed state and flowing an inert gas such as Ar gas to a desired state.

  A wire 9 as a pulling shaft is suspended in the pull chamber 2. The wire 9 is driven up and down by a driving mechanism (not shown) provided at the top of the pull chamber 2. The wire 9 may be rotated by a driving mechanism.

  A raw material supply device 13 according to the present invention is provided below the wire 9 of the pulling shaft. The raw material supply device 13 includes a raw material filling container 14 and a movable cover 15 provided so as to surround the outer periphery thereof.

  The raw material supply apparatus 13 will be described in detail with reference to FIG. FIG. 2 is a schematic cross-sectional view showing an example of a raw material supply apparatus according to the present invention that constitutes the single crystal manufacturing apparatus shown in FIG. 1, and (a) shows a solid raw material with a movable cover positioned above. (B) shows the time when the movable cover is positioned below and the solid material is released.

  The raw material filling container 14 is filled with a solid material 18 of agglomerated silicon and is held at a position where it can be supplied to the silicon raw material melt in the quartz crucible 4. The main body of the raw material filling container 14 is formed of stainless steel or the like, and has a cylindrical shape capable of holding a silicon solid raw material 18 therein. In addition, an opening 14a is provided below, and is configured to freely open and close as necessary. Although details will be described later, by opening the opening 14a, the silicon solid material 18 in the raw material filling container 14 can be charged into the quartz crucible 4 provided below. The solid raw material 18 is, for example, a granule having a particle size of 5 mm to 25 mm, and the amount to be filled at a time is, for example, about 20 kg.

  The movable cover 15 has a pseudo-cylindrical shape having an inner diameter larger than the outer diameter of the raw material filling container 14, and is provided at a position surrounding the periphery of the opening 14 a of the raw material filling container 14. The movable cover 15 is held so that the position of the outer periphery of the raw material filling container 14 is variable in the vertical direction. In this example, the movable cover 15 is configured to be slidable with the outer peripheral portion of the raw material filling container 14, and wires 17 are attached to a plurality of locations of the movable cover 15, and the raw material is moved by moving the wire 17 in the vertical direction. The position of the movable cover 15 can be changed during the process of supplying. It is easy to lower the movable cover 15 by its own weight.

  The operation of the raw material supply apparatus 13 is as follows. First, the raw material supply device 13 is filled with a silicon solid material 18, attached to the wire 9, and lowered from the pull chamber 2 side toward the main chamber 1. Eventually, the locking portion 16 comes into contact with the small diameter portion 1a provided in the main chamber 1, and the lowering of the raw material supply device 13 stops (see FIG. 2A).

  Thereafter, the movable cover 15 suspended by the wire 17 is lowered and stopped at a predetermined position. Thereafter, the opening 14a of the raw material filling container 14 is opened, and the solid raw material 18 is dropped into the melt 5 (see FIG. 2B).

  In this way, the solid raw material 18 is supplied to the melt 5 having a high temperature in the quartz crucible 4 via the inside of the lowered tubular movable cover 15. At this time, since the heat of the melt 5 is taken away by the supplied solid raw material 18, the surface of the melt 5 is once solidified, but the movable cover 15 in the lowered state serves as a lid for the quartz crucible 4. Since the heat is stored in the space sandwiched between the movable cover 15 and the quartz crucible 4, the recharged solid raw material 18 is efficiently melted in a short time.

  In addition, as a standard of the movable range of the movable cover 15, it is preferable that the opening portion 14a of the raw material filling container 14 is positioned inside. This is because the movable cover 15 always exists integrally with the raw material filling container 14 by being configured in this manner, and the effect of heat storage by the movable cover 15 is great.

  Further, since the solid raw material 18 is supplied in a state where the movable cover 15 is lowered, even if the raw material fine powder or the splash of the melt scatters around when the raw material falls, the movable cover 15 can suppress the influence on the outside. The adverse effects on the lifetime in the apparatus and the growth of the single crystal can be reduced. In this way, in order to prevent the splash of the raw material fine powder or melt from affecting the surroundings adversely, the position of the lower end of the movable cover 15 is 50 mm to 200 mm from the surface of the melt 5 in the quartz crucible 4. It is good to be a position.

  The raw material filling container 14 is generally made of stainless steel or the like, and may be deteriorated when approaching a silicon melt exceeding 1410 ° C. However, according to the configuration of the present invention, as described above, since the movable cover 15 can suppress the splashing of the melt droplets, the opening 14 a of the raw material filling container 14 is sufficiently separated from the melt 5. The movable mechanism is not easily damaged by heat, and the life of the apparatus can be extended.

  Furthermore, since the raw material is supplied by the opening / closing operation of the opening 14a of the raw material filling container 14, it is not necessary to provide a lid at the opening of the movable cover as is conventionally done. As described above, according to the configuration of the present invention, the structure of the movable cover 15 itself is a very simple mechanism, so that troubles due to heat hardly occur.

  Moreover, since the opening part 14a and lid | cover of the raw material filling container 14 which accumulate | stored the solid raw material 18 do not become high temperature more than necessary, it is from the location (the opening-and-closing part of the opening part 14a) which is actually contacting the solid raw material 18 to a raw material. On the other hand, contamination of impurities is difficult to occur.

  If the movable cover 15 is formed of a member having excellent heat resistance, the movable cover 15 can be used for a long period of time, and the raw material filling container 14 is sufficiently protected from the high heat of the melt 5. Can do. As such a member having excellent heat resistance, molybdenum, tungsten, boron nitride, or silicon carbide can be used. In addition, since heat is transmitted as light under high temperature conditions exceeding 1000 ° C., the material of the movable cover 15 is preferably one that reflects light, that is, has a low emissivity. The emissivity is preferably 0.4 or less, and examples of such a material include molybdenum and tungsten.

  As described above, the movable cover 15 is exposed to a severe situation in which it is necessary to resist the splash of the melt and to withstand the high temperature of the melt. Therefore, even if it is made of a heat-resistant material, it gradually deteriorates after being used several times. Therefore, it is preferable to have a structure that can be freely attached to and detached from the raw material filling container 14. In this way, for example, when the surface state of the movable cover 15 deteriorates, it can be removed and the surface can be physically and chemically polished for regeneration. Further, when the material of the movable cover 15 is greatly deteriorated, it is easy to replace it. As an example of a structure that can be freely attached and detached, if it is configured by parts divided into a plurality of parts in the vertical direction and these are combined and attached around the side surface of the raw material filling container 14, the structure can be integrated. good.

  As described above, according to the method for producing a single crystal of the present invention, the movable cover 15 is lowered until the lower end of the movable cover 15 comes to a position near the surface of the melt 5 in the quartz crucible 4 (1). And the step (2) of opening the opening 14 a of the raw material filling container 14 and dropping the solid raw material 18 into the melt 5 of the quartz crucible 4. Thereafter, as the solid raw material 18 charged into the quartz crucible 4 is melted, the movable cover 15 is gradually raised or the quartz crucible 4 is gradually lowered to separate the movable cover 15 from the melt 5. It is desirable to add step (3) further. In this way, when there is an undissolved solid raw material 18 inside the movable cover 15, it can be efficiently discharged into the quartz crucible 4, and the movable cover 15 can be exposed to the high heat of the melt 5 more than necessary. This is because.

  In the above, the characteristic part of the manufacturing method of the single crystal using the single crystal manufacturing apparatus based on this invention was explained in full detail. For other steps, a conventionally known method may be used. Hereinafter, the entire process will be briefly described.

  In the case of multi-pooling, the silicon single crystal that has been grown and cooled in the apparatus is taken out of the apparatus, and the raw material supply apparatus 13 of the present invention that has been filled with the solid raw material 18 of polycrystalline silicon is suspended from the wire 9. And housed in the single crystal manufacturing apparatus of the present invention.

  Next, with the crucible rotation speed maintained at, for example, 1 rpm, the output of the heater 6 is lowered to lower the temperature of the remaining silicon melt until the melt surface is close to the solidification temperature. In this state, the temperature of the silicon melt is stabilized, the raw material supply device 13 is lowered from above the pull chamber 2 of the single crystal manufacturing device, and the locking portion 16 of the raw material supply device 13 is brought into contact with the small diameter portion 1 a of the main chamber 1. To stop.

  Thereafter, the wire 17 suspending the movable cover 15 is lowered, the lower end of the movable cover 15 is stopped at a position 100 mm from the surface of the melt 5, the opening 14 a of the raw material filling container 14 is opened, and the solid inside The raw material 18 is dropped and supplied to the melt 5 of the quartz crucible 4 and recharged.

  Here, as the falling supply of the solid raw material 18 proceeds, the quartz crucible 4 is gradually lowered to complete the supply of the solid raw material 18. Thereafter, the wire 9 is raised, and the raw material supply device 13 which has been emptied is moved above the single crystal manufacturing device and taken out of the device.

  Since the volume is reduced when the solid raw material 18 is melted inside the quartz crucible 4, a necessary amount of the solid raw material 18 can be added to the quartz crucible 4 by repeating this operation several times (for example, three times). When the solid raw material 18 is charged, a dopant agent for adjusting the electrical conductivity characteristics to a desired standard range may be added to the single crystal.

  Thereafter, a seed crystal for growing a single crystal is attached to the wire 9 in a predetermined crystal orientation, immersed in the surface of the melt 5 of the silicon raw material, and pulled up by a predetermined method, so that the same orientation as the seed crystal is obtained. A silicon single crystal ingot having an array can be grown.

  According to the method for producing a single crystal of the present invention, the effects as described above are exhibited, so that impurities can be prevented from being mixed into the solid raw material, and a single crystal having a high purity can be produced. In addition, since the life and productivity of the apparatus can be kept high, it contributes to cost reduction.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. For example, the wire 9 that suspends the raw material supply device 13 and the wire 17 that suspends the movable cover 15 may be integrally connected. By adopting such an integrally connected configuration, the raw material supply device 13 is suspended by the wire 9 and lowered, and after stopping the descent by the locking portion 16, the wire 9 is loosened as it is. The movable cover 15 can be lowered by its own weight.

It is typical sectional drawing which showed an example of the single-crystal manufacturing apparatus based on this invention. It is typical sectional drawing which shows an example of the raw material supply apparatus which concerns on this invention, (a) is when a movable cover is located upwards and hold | maintains a solid raw material, (b) is a movable cover located below. The time to release the solid raw material is shown.

Explanation of symbols

1: Main chamber 1a: Small diameter part 2: Pull chamber 3: Graphite crucible 4: Quartz crucible 5: Raw material melt 6: Heater 7: Thermal insulation 8: Heat shield shield 9: Wire 10: Equipment bottom base 11: Support Shaft 12: Exhaust port 13: Raw material supply device 14: Raw material filling container 14a: Opening 15: Movable cover 16: Locking portion 17: Wire 18: Solid raw material

Claims (6)

A raw material supply device for supplying agglomerated solid raw material to a crucible holding a raw material melt,
A raw material filling container filled with the solid raw material and having an opening that can be opened and closed downward;
A raw material supply device comprising: a tubular movable cover that surrounds the outer periphery of the opening of the raw material filling container and is provided so as to be positionally variable in the vertical direction and descends toward the crucible when the raw material is supplied.   The raw material supply apparatus according to claim 1, wherein a movable range of the movable cover is determined so that the opening of the raw material filling container is located inside.   The raw material supply apparatus of Claim 1 or Claim 2 with which the said movable cover is comprised by either molybdenum, tungsten, a boron nitride, or silicon carbide.   The raw material supply apparatus according to any one of claims 1 to 3, wherein the movable cover is provided detachably with respect to the raw material filling container. The raw material supply apparatus according to any one of claims 1 to 4,
A crucible for holding a raw material melt and a crucible for supplying agglomerated solid raw material from the raw material supply device. A method for producing a single crystal in which a solid raw material in the form of agglomerates is supplied to a crucible using the single crystal production apparatus according to claim 5 and melted.
Lowering the movable cover until the lower end of the movable cover comes to a position near the surface of the raw material melt in the crucible;
Opening the opening of the raw material filling container and dropping the solid raw material into the raw material melt of the crucible;
A step of gradually separating the crucible and the movable cover as the solid raw material charged in the crucible melts.