JP3846145B2 - Crucible lid and silicon polycrystal melting method using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lid used for a quartz crucible of a silicon single crystal growing apparatus and a silicon polycrystal melting method using the lid.
[0002]
[Prior art]
Conventionally, an apparatus for growing a silicon single crystal includes a carbon susceptor that is provided in a chamber and surrounds and supports a quartz crucible, and melts polycrystalline silicon in the quartz crucible that surrounds the susceptor and is provided in the chamber. A carbon heater for heating the silicon melt stored in the quartz crucible. This apparatus is provided with a crucible lifting / lowering means for raising or lowering the quartz crucible via the support shaft of the susceptor, and after melting polycrystalline silicon contained in the quartz crucible with a carbon heater, the silicon melt stored in the quartz crucible A seed crystal is brought into contact with the seed crystal, and the seed crystal is pulled up to grow a silicon single crystal below the seed crystal.
On the other hand, the polycrystalline silicon melted by the carbon heater is put in a quartz crucible mounted in the chamber, or is put in a quartz crucible outside the chamber and then mounted in the chamber. The reason why polycrystalline silicon is put outside the chamber is to improve the operating rate of the silicon single crystal growing apparatus. In this case, a quartz crucible containing polycrystalline silicon is stored in advance outside the chamber, and the quartz crucible stored in the apparatus once the growth of the silicon single crystal is prepared so that the stored quartz crucible can be immediately installed in the chamber. . At the time of storage, a lid is put on a quartz crucible containing polycrystalline silicon in order to prevent impurities floating in the air from adhering to the polycrystalline silicon.
[0003]
[Problems to be solved by the invention]
However, if the quartz crucible is simply covered, the quartz crucible opening and lid cannot be completely sealed, and the ambient temperature fluctuates, causing air to flow from the slight gap and the quartz crucible. There is a problem that impurities floating on the outside of the metal enter the inside of the quartz crucible through the gap together with air and adhere to the surface of the polycrystalline silicon. In order to solve this problem, it is necessary to fill the gap after the quartz crucible is covered. However, this work is difficult, and the number of work steps increases, so that the operating rate of the apparatus cannot be substantially improved. There is a problem.
Also, when a quartz crucible containing polycrystalline silicon is installed in the chamber, impurities floating outside the chamber enter the chamber together with the quartz crucible, and the impurities are removed from the quartz crucible after removing the lid. In some cases, it enters the crucible and adheres to the polycrystalline silicon. If such impurities are present in the silicon melt that is subsequently melted from the polycrystalline silicon and stored in the quartz crucible, there is a problem that the free rate of the pulled silicon single crystal is lowered.
An object of the present invention is to provide a crucible lid that can effectively prevent impurities from adhering to polycrystalline silicon simply by covering the quartz crucible.
Another object of the present invention is to provide a method for melting silicon polycrystal using a crucible lid that can improve the freezing rate of a silicon single crystal that is pulled up by reducing impurities in the silicon melt.
[0004]
[Means for Solving the Problems]
As shown in FIG. 1, the invention according to claim 1 includes a flat plate portion 13a that covers an upper opening of a quartz crucible 12 in which polycrystalline silicon 11 is placed, and a quartz crucible 12 that is integrally formed with the flat plate portion 13a. A cover 13 having a surrounding portion 13b surrounding the upper portion and having a ventilation hole 13c formed at a substantially central portion of the flat plate portion 13a ; and a filter attached to the upper portion of the flat plate portion 13a so as to cover the ventilation hole 13c. 14 and a crucible lid .
The characteristic structure is formed so as to cover the peripheral wall 13d surrounding the ventilation hole 13c in the upper part of the flat plate part 13a and having an external thread formed on the outer periphery, and the filter 14 attached to the upper part of the peripheral wall 13d and the flat plate part 13a. There is a mounting lid 16 having an air guide hole 16a corresponding to the vent hole 13c and having an internal thread formed on the inner periphery thereof that can be screwed into the external thread .
According to the first aspect of the present invention, when the quartz crucible 12 sealed with the crucible lid 10 into which the polycrystalline silicon 11 is placed is stored, air is circulated from the ventilation hole 13c. When air is discharged from the inside of the quartz crucible 12 to the outside, impurities do not enter the inside of the quartz crucible 12, but when air is introduced from the outside to the inside of the quartz crucible 12, the air is After passing through the filter 14, the air is introduced into the quartz crucible 12 through the ventilation holes 13 c of the lid 13. At this time, the filter 14 collects the floating impurities and prevents the impurities from being mixed into the air introduced into the quartz crucible 12 from the vent hole 13 c of the lid 13. Thus, impurities are prevented from entering the inside of the quartz crucible 12 and adhering to the polycrystalline silicon 11 placed in the quartz crucible 12.
[0005]
2 to 4, the quartz crucible 12 in which the polycrystalline silicon 11 is put and the upper opening portion is covered with the crucible lid 10 according to the first aspect is disposed in the chamber 21. A step of evacuating the inside of the chamber 21 and circulating an inert gas in the chamber 21, a step of removing the crucible lid 10 from the quartz crucible 12 after setting the inside of the chamber 21 to atmospheric pressure, A process of circulating the inert gas again in the chamber 21 after evacuating the interior, and the chamber 21 in the inert gas atmosphere in a state where the inert gas is circulated or after the inert gas is stopped. And a step of melting the polycrystalline silicon 11 by the carbon heater 26 provided in the method for melting the polycrystalline silicon using a crucible lid.
[0006]
In the second aspect of the present invention, the quartz crucible 12 is covered with the crucible lid 10 and the inside of the chamber 21 is once evacuated to float the quartz crucible 12 when the quartz crucible 12 is attached to the chamber 11. Impurities are discharged to the outside. Thereafter, an inert gas is circulated to discharge impurities adhering to the outer surfaces of the quartz crucible 12 and the crucible lid 10 out of the chamber 21. Thereafter, the crucible lid 10 is removed and an inert gas is allowed to flow inside the chamber 21, whereby impurities that have entered when the crucible lid 10 is removed are discharged to the outside before adhering to the polycrystalline silicon. As described above, when the quartz crucible 12 is attached to the chamber 11 or when the crucible lid 10 is removed from the quartz crucible 12, impurities introduced into the quartz crucible 12 and the crucible lid 10 adhere to the outer surface. Since the polycrystalline silicon 11 is discharged out of the chamber 21 before melting, the polycrystalline silicon 11 is melted and no impurities are present in the silicon melt stored in the quartz crucible 12, and the single silicon to be pulled up is removed. The crystal free rate is improved as compared with the conventional case.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a crucible lid 10 of the present invention includes a lid 13 configured to cover an upper opening of a quartz crucible 12 in which polycrystalline silicon 11 is placed, and a filter 14. A flat plate portion 13 a that covers the opening of the quartz crucible 12 and a surrounding portion 13 b that surrounds the upper periphery of the quartz crucible 12 are integrally formed. The lid body 13 is integrally formed by molding a resin such as polytetrafluoroethylene (trade name; Teflon), polypropylene, polyethylene, and the like, and a vent hole 13c formed of a circular hole is formed at a substantially central portion of the flat plate portion 13a. It is formed. The flat plate portion 13a is formed with a peripheral wall 13d surrounding the ventilation hole 13c at a predetermined distance from the hole edge, and a male screw is formed around the peripheral wall 13d.
[0008]
The filter 14 is disposed above the flat plate portion 13 a so as to cover the ventilation hole 13 c of the lid 13. The filter 14 used in this embodiment is a filter paper made of non-woven fabric, and is formed to a thickness corresponding to the height of the peripheral wall 13d. The filter 14 is capable of collecting particles having a particle diameter of 0.3 μm, and is configured to collect impurities contained in the air from the air that passes through the filter 14. The filter 14 is formed to have an outer diameter corresponding to the inner diameter of the peripheral wall 13 d and is attached to the lid body 13 by an attachment lid 16. The attachment lid 16 is formed so as to cover the peripheral wall, and an air guide hole 16a corresponding to the ventilation hole 13c is formed. The mounting lid 16 is formed with a female screw that can be screwed into the male screw of the peripheral wall 13d, and the filter 14 is screwed into the male screw of the peripheral wall 13d in a state where the filter 14 is disposed on the upper portion of the flat plate portion 13a. It attaches to the upper part of the cover body 13 so that the ventilation hole 13c may be covered.
[0009]
The polycrystalline silicon 11 is placed in the quartz crucible 12 in a space where the amount of floating impurities outside the silicon single crystal growing apparatus is not more than a predetermined amount, that is, in a so-called clean room. The crucible lid 10 is placed on a quartz crucible 12 in which polycrystalline silicon 11 is placed. When the crucible lid 10 is put on the quartz crucible 12, the flat plate portion 13 a of the lid body 13 covers the opening of the quartz crucible 12, and the surrounding portion 13 b of the lid body 13 surrounds the upper periphery of the quartz crucible 12. This prevents the quartz crucible 12 from coming off. Thus, when the quartz crucible 12 containing the polycrystalline silicon 11 is sealed and stored with the crucible lid 10 of the present invention, a pressure difference is generated between the inside and outside of the quartz crucible 12 when the ambient environment temperature fluctuates. From the pressure difference, air flows through the ventilation holes 13c. When air is discharged from the inside of the quartz crucible 12 to the outside, impurities do not enter the inside of the quartz crucible 12, but when air is introduced from the outside to the inside of the quartz crucible 12, the air is After passing through the filter 14, it is introduced into the quartz crucible 12 through the ventilation hole 13 c of the lid 13 as indicated by the solid arrow in FIG. 1. At this time, the filter 14 collects the floating impurities and prevents the impurities from being mixed into the air introduced into the quartz crucible 12 from the vent hole 13 c of the lid 13. This prevents impurities from entering the quartz crucible 12 and adhering to the polycrystalline silicon 11 placed in the quartz crucible 12.
[0010]
Next, the silicon polycrystal pulling apparatus 20 to which the quartz crucible 12 is attached will be described.
As shown in FIGS. 2 to 4, the quartz crucible 12 is provided in a chamber 21 of a silicon single crystal pulling apparatus 20. The outer surface of the quartz crucible 12 is covered with a graphite susceptor 22. The lower surface of the quartz crucible 12 is fixed to the upper end of the support shaft 23 via the graphite susceptor 22, and the lower portion of the support shaft 23 is connected to the crucible driving means 24. Although not shown, the crucible driving means 24 has a first rotating motor for rotating the quartz crucible 12 and a lifting motor for moving the quartz crucible 12 up and down, and the quartz crucible 12 can be rotated in a predetermined direction by these motors. At the same time, it is movable in the vertical direction. The outer peripheral surface of the quartz crucible 12 is surrounded by a heater 26 at a predetermined interval from the quartz crucible 12, and the heater 26 is surrounded by a heat retaining cylinder 27.
[0011]
A cylindrical casing 28 is connected to the upper end of the chamber 21. As shown in FIG. 4, the casing 28 is provided with a pulling means 29. The pulling means 29 is a pulling head (not shown) provided at the upper end of the casing 28 so as to be rotatable in a horizontal state, a second rotating motor (not shown) for rotating the head, and the quartz crucible 12 from the head. And a pulling motor (not shown) provided in the head for winding or unwinding the wire cable 29a. A seed crystal 29b for pulling up the silicon single crystal rod 25 is attached to the lower end of the wire cable 29a. A heat shielding member 31 is provided between the outer peripheral surface of the silicon single crystal rod 25 and the inner peripheral surface of the quartz crucible 12 to surround the outer peripheral surface of the silicon single crystal rod 25.
[0012]
Further, gas supply / discharge means 32 for supplying an inert gas to the silicon single crystal rod side of the chamber 21 and discharging the inert gas from the crucible inner peripheral surface side of the chamber 21 is connected to the chamber 21. The gas supply / discharge means 32 has one end connected to the peripheral wall of the casing 28 and the other end connected to a tank (not shown) for storing the inert gas, and one end connected to the lower wall of the chamber 21. The other end has a discharge pipe 34 connected to a vacuum pump (not shown). The supply pipe 33 and the discharge pipe 34 are provided with first and second flow rate adjusting valves 36 and 37 for adjusting the flow rate of the inert gas flowing through the pipes 33 and 34, respectively.
[0013]
A method for melting silicon polycrystal using the crucible lid in the apparatus configured as described above will be described.
As shown in FIG. 2, first, a quartz crucible 12 in which polycrystalline silicon 11 is placed and an upper opening is covered with a crucible lid 10 is attached to a graphite susceptor 22, so that the quartz crucible 12 together with the crucible lid 10. Is provided in the chamber 21. Next, the air in the chamber 21 is discharged from the discharge pipe 34 to the outside of the chamber 21 by opening the second flow rate adjusting valve 37, and the inside of the chamber 21 is once evacuated. Thereafter, the first flow rate adjusting valve 36 is opened, an inert gas is supplied from the supply pipe 33 into the chamber 21, and the inert gas is discharged from the discharge pipe 34, whereby the inert gas is circulated into the chamber 21. As described above, when the chamber 21 is once evacuated, the floating impurities introduced when the quartz crucible 12 is mounted in the chamber 11 are discharged together with air from the discharge pipe 34 to the outside, and an inert gas is circulated. Impurities adhering to the outer surfaces of the quartz crucible 12 and the crucible lid 10 are discharged out of the chamber 21.
[0014]
Thereafter, the second flow rate adjusting valve 37 is closed, the inside of the chamber 21 is brought to atmospheric pressure by the inert gas supplied from the supply pipe 33, and the first flow rate adjusting valve 36 is closed in this state. Thereafter, as shown in FIG. 3, the chamber 21 is opened, the crucible lid 10 is removed from the quartz crucible 12, the chamber 21 is closed again, and the second flow rate adjusting valve 37 is opened again. As a result, the air that has entered the chamber 21 when released and the inert gas remaining in the chamber 21 are discharged from the discharge pipe 34 to the outside of the chamber 21, and the inside of the chamber 21 is in a vacuum state. Thereafter, the first flow rate adjusting valve 36 is opened again, an inert gas is supplied into the chamber 21 from the supply pipe 33, and the inert gas is circulated into the chamber 21 by exhausting the inert gas from the exhaust pipe 34. As a result, the impurities that have entered with the air when released are discharged from the discharge pipe 34 together with the air or inert gas before adhering to the polycrystalline silicon.
[0015]
The polycrystalline silicon 11 placed in the quartz crucible 12 is melted by the carbon heater 26 in a state where the inert gas is circulated as described above or in an inert gas atmosphere after the flow of the inert gas is stopped. When the polycrystalline silicon 11 is melted, as shown in FIG. 4, the silicon melt 39 is stored in the quartz crucible 12, and the inert gas flowing through the chamber 21 discharges the gas evaporated from the surface of the melted silicon melt 12. The pipe 34 is discharged to the outside. Thereafter, the wire cable 29a of the pulling means is fed out, the tip of the seed crystal 29b is brought into contact with the silicon melt 39, and the silicon single crystal rod 25 is grown under the seed crystal 29b. Impurities that intrude with air when attaching to the chamber 11 or removing the crucible lid 10 from the quartz crucible 12, or impurities adhering to the quartz crucible 12 and the outer surface of the crucible lid 10 enter the polycrystalline silicon 11. Since it is discharged out of the chamber 21 before melting, there is no impurity in the silicon melt 39 stored in the quartz crucible 12, and the free rate of the pulled silicon single crystal 25 is improved as compared with the prior art.
[0016]
【The invention's effect】
As described above, the crucible lid of the present invention is configured to cover the upper opening of the quartz crucible in which polycrystalline silicon is placed, and has a lid body formed with a vent hole in a substantially central portion, and a vent hole. Since the filter attached to the upper part of the lid is provided so as to cover, air is circulated from the ventilation hole. When air is introduced from the outside to the inside of the quartz crucible, the air passes through the filter, and the filter collects floating impurities, so that impurities are not mixed into the inside of the quartz crucible from the ventilation holes. Impurities do not adhere to the polycrystalline silicon placed in the quartz crucible.
Further, in the silicon polycrystal melting method using the crucible lid of the present invention, the chamber is once evacuated while the quartz crucible is covered with the crucible lid, so that the quartz crucible is inserted when the quartz crucible is attached to the chamber. The floating impurities are discharged to the outside, and then the impurities adhering to the outer surface of the quartz crucible and the crucible lid can be discharged out of the chamber by circulating an inert gas. Further, since the inert gas is allowed to flow inside the chamber even after the crucible lid is removed, impurities that have intruded when the crucible lid is removed can be discharged to the outside. As a result, there is no impurity in the silicon melt in which the polycrystalline silicon is melted and stored in the quartz crucible, and the free rate of the silicon single crystal to be pulled can be improved as compared with the prior art.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram showing a state in which a crucible lid of the present invention is put on a quartz crucible.
FIG. 2 is a cross-sectional configuration diagram of a pulling device equipped with a quartz crucible covered with a crucible lid.
FIG. 3 is a cross-sectional configuration diagram of a pulling device in which the crucible lid is removed from a quartz crucible.
FIG. 4 is a cross-sectional configuration diagram of a pulling apparatus in which a silicon single crystal is pulled up from a silicon melt.
[Explanation of symbols]
10 Crucible lid 11 Polycrystalline silicon 12 Quartz crucible 13 Lid 13a Ventilation hole 14 Filter 21 Chamber 26 Carbon heater

Claims (2)

A flat plate portion (13a) covering the upper opening of the quartz crucible (12) containing polycrystalline silicon (11), and the upper periphery of the quartz crucible (12) formed integrally with the flat plate portion (13a) A lid (13) having a surrounding portion (13b) for enclosing, and a vent hole (13c) formed in a substantially central portion of the flat plate portion (13a) ,
A crucible lid comprising: a filter (14) attached to an upper portion of the flat plate portion (13a) so as to cover the ventilation hole (13c) ,
A peripheral wall (13d) surrounding the ventilation hole (13c) at the top of the flat plate portion (13a) and having a male screw formed on the outer periphery ;
An air guide hole (16a) is formed to cover the filter (14) attached to the upper part of the peripheral wall (13d) and the flat plate part (13a) , and corresponds to the ventilation hole (13c) , and the inner periphery. wherein and a male thread can be screwed mounting lid female thread is formed (16) to
A crucible lid characterized by that . Providing a quartz crucible (12) in the chamber (21) in which polycrystalline silicon (11) is placed and the upper opening is covered with a crucible lid (10) according to claim 1;
Circulating an inert gas in the chamber (21) after evacuating the chamber (21);
Removing the crucible lid (10) from the quartz crucible (12) after bringing the chamber (21) to atmospheric pressure;
Recirculating an inert gas into the chamber (21) after evacuating the chamber (21);
The polycrystalline silicon (11) by the carbon heater (26) provided in the chamber (21) in a state where the inert gas is circulated or in an inert gas atmosphere after the flow of the inert gas is stopped A method for melting silicon polycrystal using a crucible lid, comprising the step of melting.

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