JP2000247774A - Pulling apparatus of silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a silicon single crystal rod from being contaminated by impurities mixed in an inert gas, and further to obtain the highly pure silicon single crystal rod. SOLUTION: A silicon molten liquid 12 is stored in a quartz crucible 13 installed in a chamber 11, and a heater 18 surrounding the outer periphery of the quartz crucible 13 heats the silicon molten liquid 12. A heat-shielding member 26 surrounding the outer periphery of a silicon single crystal rod 25 pulled from the silicon molten liquid 12, and positioned so that the lower end thereof may be at the upper side of the silicon molten liquid 12 so as to form a distance therefrom, shields the radiant heat from the heater 18. A gas- supplying and exhausting means allows an inert gas to flow down between the silicon single crystal rod 25 and the heat-shielding member 26, and to pass the surface of the silicon molten liquid 12 and to be exhausted to the exterior of the chamber 11. A short cylindrical body 31 is installed in the lower part of the heat-shielding member 26 so as to form a prescribed distance from the inner periphery surface of the heat-insulating member 26. The short cylindrical body 31 is made of quartz, and attached through plural attaching ribs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for pulling and growing a silicon single crystal rod from a silicon melt.

[0002]

2. Description of the Related Art Conventionally, as this type of apparatus, as shown in FIG. 4, a quartz crucible 3 in which a silicon melt 2 is stored in a chamber 1 is accommodated. A cylindrical heat shield member 6 is inserted between the inner peripheral surface of the heat shield member 3 and the silicon single crystal rod 5, and the upper end of the heat shield member 6 projects outward in a substantially horizontal direction. Are known. In this device, the lower end of the heat shielding member 6 extends to near the surface of the silicon melt 2. Further, the upper end of the heat shielding member 6 is placed on the upper end of the heat retaining cylinder 9, and the radiant heat emitted from the heater 8 to the silicon single crystal rod 5 is blocked by the heat shielding member 6. Further, when an inert gas is supplied into the chamber 1 by gas supply / discharge means (not shown) connected to the chamber 1, the inert gas is supplied to the outer peripheral surface of the silicon single crystal rod 5 as shown by a two-dot chain arrow. Through the gap between the lower end of the heat shielding member 6 and the surface of the silicon melt 2 and the quartz crucible 3.
It is designed to be discharged outside.

In the apparatus configured as described above, oxygen in the silicon melt 2 evaporates as SiO gas or the like. At this time, due to the presence of the heat shielding member 6, the inert gas is removed from the lower end of the heat shielding member 6 and the silicon Since the gas flows vigorously from the outer peripheral surface of the silicon single crystal rod 5 to the inner peripheral surface of the quartz crucible 3 through the gap on the surface of the melt 2, the evaporated matter such as the above-mentioned SiO gas is kept away from the silicon single crystal rod 5. As a result, it is possible to prevent the above-mentioned evaporated substance from being taken into the silicon single crystal rod 5 and generating dislocations, which are lattice defects, in the silicon single crystal rod 5.
In addition, since the heat shielding member 6 efficiently shields heat, the productivity of the silicon single crystal rod 5 can be improved.

[0004]

However, in the above-mentioned conventional silicon single crystal pulling apparatus, impurities may be generated from a member located above the silicon single crystal rod 5 pulled from the silicon melt 2. There is a problem that these impurities are mixed into the inert gas and transported to the outer peripheral surface of the silicon single crystal rod 5. In particular, when the heat shielding member 6 made of carbon, molybdenum, or the like is formed to have a smaller diameter toward the lower side as shown in FIG. 4, impurities generated from the heat shielding member 6 cause silicon impurities to flow due to the flow of the inert gas. The silicon single crystal rod 5 was guided to the lower part of the single crystal rod 5 and was contaminated by the impurities. It is an object of the present invention to provide a silicon single crystal pulling apparatus capable of preventing contamination of a silicon single crystal rod by impurities mixed in an inert gas and obtaining a high purity silicon single crystal rod.

[0005]

The invention according to claim 1 is
As shown in FIG. 1, an outer peripheral surface of a silicon single crystal rod 25 pulled up from a silicon melt 12 stored in a quartz crucible 13 in a chamber 11 is surrounded and a lower end thereof is spaced upward from the surface of the silicon melt 12 and And the heat shielding member 26 that blocks the radiant heat from the heater 18 and the inert gas flows between the silicon single crystal rod 25 and the heat shielding member 26 and passes through the surface of the silicon melt 12 and is discharged out of the chamber 11. This is an improvement of a silicon single crystal pulling apparatus provided with a gas supply / discharge means 27. The characteristic configuration is the short cylinder 31
Are provided at a lower portion of the heat shielding member 26 at a predetermined interval from the inner peripheral surface of the heat shielding member 26. In the apparatus for pulling a silicon single crystal according to the first aspect of the present invention, the inert gas supplied into the chamber 11 by the gas supply / discharge means 27 may be mixed with impurities generated from the upper member in the chamber 11. The impurities flow down along with the flow of the inert gas along the surface of the upper member in the chamber 11, and further flow down along the inner peripheral surface of the heat shielding member 26. The short cylinder 31 guides the inert gas containing the impurity to the surface of the silicon melt 12 without approaching the silicon single crystal rod 25 under the heat shielding member 26, and
Let it drain out. Therefore, the silicon single crystal rod 25 is hardly contaminated by impurities.

According to a second aspect of the present invention, as shown in FIG. 3, as shown in FIG. 3, a portion 26a of the heat shielding member 26 surrounding the silicon single crystal rod 25 has a diameter directed downward. The plurality of mounting ribs 31a, which are formed small and whose distal ends can contact the inner surface of the heat shielding member 26,
1 is a pulling apparatus for pulling a silicon single crystal radially formed on the outer periphery of the silicon single crystal. In the silicon single crystal pulling apparatus according to the second aspect, by inserting the short cylindrical body 31 from above into the portion 26a surrounding the silicon single crystal rod 25,
The distal end of the radially-mounted mounting rib 31a contacts the inner peripheral surface of the lower portion of the heat shielding member 26, and the short cylindrical body 31 is mounted. For this reason, the short cylindrical body 31 according to the present invention can be easily attached to the existing heat shielding member having a smaller diameter toward the lower side.
Can be installed.

On the other hand, the short cylindrical body 31 with the tip of the mounting rib 31a abutting on the inner peripheral surface of the heat shielding member 26 can be easily removed from the heat shielding member 26 by lifting it up. It is also possible to remove only the short cylinder 31 from the pulling device after pulling the single crystal rod 25 and clean it. The invention according to claim 3 is the invention according to claim 1 or 2, wherein the short cylinder 31 is a silicon single crystal pulling apparatus made of quartz. In the silicon single crystal pulling apparatus according to the third aspect, the short cylindrical body 31 is made of quartz that transmits infrared rays. Thus, the temperature distribution around the silicon single crystal rod 25 is not changed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, a quartz crucible 13 for storing a silicon melt 12 is provided in a chamber 11 of a silicon single crystal pulling apparatus 10, and the outer surface of the quartz crucible 13 is covered with a graphite susceptor 14. The lower surface of the quartz crucible 13 is fixed to the upper end of a support shaft 16 via the graphite susceptor 14, and the lower portion of the support shaft 16 is connected to a crucible driving unit 17. Crucible driving means 1
7 has a first rotation motor (not shown) for rotating the quartz crucible 13 and a lifting / lowering motor for moving the quartz crucible 13 up and down. These motors can rotate the quartz crucible 13 in a predetermined direction. It can be moved in any direction. The quartz crucible 1 is located outside the quartz crucible 13.
A heater 18 surrounding the outer peripheral surface of the heater 3 at a predetermined interval is provided, and a heat retaining cylinder 19 surrounding the outer peripheral surface of the heater 18 at a predetermined interval is provided outside the heater 18. The high-purity silicon polycrystal charged into the quartz crucible 13 by the heater 18 is melted to form the silicon melt 12.

On the upper surface of the chamber 11, a chamber 11 is provided.
A cylindrical casing 21 having a smaller diameter is provided. The casing 21 is provided with a pulling means 22. The pulling means 22 includes a pulling head (not shown) rotatably provided at the upper end of the casing 21 in a horizontal state, a second rotation motor (not shown) for rotating the head, and a quartz crucible 13 from the head. And a pulling motor (not shown) provided in the head for winding up or feeding out the wire cable 23. At the lower end of the wire cable 23 is attached a seed crystal 24 for dipping in the silicon melt 12 and pulling up the silicon single crystal rod 25.

A heat shielding member 26 is inserted between the outer peripheral surface of the silicon single crystal rod 25 and the inner peripheral surface of the quartz crucible 13 so as to surround the outer peripheral surface of the silicon single crystal rod 25. The heat shielding member 26 is formed of graphite, and the silicon single crystal rod 2
5, a cylindrical portion 26a having a diameter decreasing downward as it goes down, and a disk-shaped flange portion 2 projecting outward from the upper end of the cylindrical portion 26a in a substantially horizontal direction.
6b. The lower end of the cylindrical portion 26a is the silicon melt 1
It extends to the vicinity of the two surfaces, and the upper end extends until it is substantially the same height as the upper end of the heat retaining cylinder 19. When the lower surface of the flange portion 26b of the heat shielding member 26 is installed on the upper surface of the heat retaining cylinder 19, the cylindrical portion 26a of the heat shielding member 26 partitions the inside of the chamber 11 into the silicon single crystal side and the crucible inner peripheral surface, and The radiant heat applied to the silicon single crystal rod 25 from the heater 18 is shut off.

An inert gas such as an argon gas or a nitrogen gas flows into the chamber 11 between the silicon single crystal rod 25 and the heat shielding member 26 and passes through the surface of the silicon melt 12 to be discharged out of the chamber 11. Discharge means 27 is connected. The gas supply / discharge means 27 has a gas supply pipe 27a having one end connected to the upper peripheral wall of the casing 21 and the other end connected to an air tank (not shown), and a vacuum pump having one end connected to the lower wall of the chamber 11 and the other end. (Not shown) and a gas discharge pipe 27b. Gas supply pipe 2
7a and the gas discharge pipe 27b
First and second flow control valves 27c and 27d for controlling the flow rate of the inert gas flowing through the first and second inert gases a and 27b are provided, respectively.

A rotary encoder (not shown) is connected to an output shaft (not shown) of the pulling motor, and a weight sensor (for detecting the weight of the silicon melt 12 in the quartz crucible 13) is connected to the crucible driving means 17. (Not shown), and a linear encoder (not shown) for detecting the elevation position of the support shaft 16. Each detection output of the rotary encoder, weight sensor and linear encoder is a controller (not shown)
And the control output of the controller is connected to a pulling motor of the pulling means 22 and a lifting motor of the crucible driving means 17, respectively. The controller is provided with a memory (not shown), and the memory has a wire cable 23 for detecting output of the rotary encoder.
Is stored as a map, and the liquid level of the silicon melt 12 in the quartz crucible 13 with respect to the detection output of the weight sensor is stored as a map. The controller controls the silicon melt 1 in the quartz crucible 13 based on the detection output of the weight sensor.
The lifting motor of the crucible driving means 17 is controlled so that the liquid level of No. 2 is always kept at a constant level.

A characteristic configuration of this embodiment is that the short cylindrical body 31 is provided at a lower portion of the heat shielding member 26 at a predetermined interval from the inner peripheral surface of the heat shielding member 26. FIG.
As shown in the figure, four mounting ribs 3
1 a is formed radially, and the tip of the mounting rib 31 a is configured to be able to contact the inner surface of the heat shielding member 26. Short cylinder 31
The mounting rib 31a is integrally formed of transparent quartz, and the short cylindrical body 31 is attached to the heat shielding member 26 by attaching a solid arrow in the figure to the cylindrical portion 26a having a smaller diameter toward the lower side. This is done by inserting as shown.
The short tubular body 31 inserted into the tubular portion 26a from above is provided with a mounting rib 31 formed radially below the tubular portion 26a.
The short cylindrical body 31 is detachably attached to the heat shielding member 26 by lifting the short cylindrical body 31 upward as shown by a broken line arrow in the drawing. Although the figure shows a case where four mounting ribs 31a are formed, the number of the mounting ribs 31a is not limited to four, and may be three or five or more.

The operation of the silicon single crystal pulling apparatus thus constructed will be described. As shown in FIG. 1, when pulling up the silicon single crystal rod 25, by adjusting the first and second flow control valves 27c and 27d, an improper connection between the surface of the silicon melt 12 and the lower end of the heat shielding member 26 is obtained. The active gas is passed through, and evaporates such as SiO gas evaporating from the silicon melt 12 are kept away from the silicon single crystal rod 25.

On the other hand, the inert gas supplied from the gas supply pipe 27a into the chamber 11 sometimes contains impurities of heavy metals such as iron and copper generated from members at the upper portion of the chamber 11. The impurities flow down along with the flow of the inert gas along the surface of the upper member in the chamber 11, and as shown by the dashed-dotted arrow in FIG.
It flows down along the inner peripheral surface. In this case, the short cylindrical body 31 converts the inert gas flowing down along the surface of the heat shielding member 26 out of the inert gas flowing between the silicon single crystal rod 25 and the heat shielding member 26 below the heat shielding member 26 into silicon. It is guided to the surface of the silicon melt 12 while being separated from the single crystal rod 25. That is, the short cylinder 31 guides the inert gas containing impurities to the surface of the silicon melt 12 without approaching the silicon single crystal rod 25, and the inert gas guided to the surface of the silicon melt 12 is then heated. The gas passes through the gap between the lower end of the shielding member 16 and the surface of the silicon melt 12 and is discharged to the outside of the chamber 11 together with the inert gas indicated by the broken arrow containing almost no impurities. As a result, the inert gas around the silicon single crystal rod 25 pulled up from the silicon melt 12 contains almost no impurities, and the silicon single crystal rod 25 is hardly contaminated with impurities. The crystal rod 25 can be manufactured.

[0016]

As described above, according to the present invention, the inert gas containing impurities flowing down along the surface of the heat shielding member among the inert gas flowing between the silicon single crystal rod and the heat shielding member. Is configured so that the short cylinder guides the silicon single crystal rod without approaching the silicon single crystal rod and discharges it outside the chamber.Therefore, the inert gas around the silicon single crystal rod contains almost no impurities, and the silicon single crystal rod is Almost no contamination by impurities. As a result, a high-purity silicon single crystal rod can be manufactured. Further, when the portion surrounding the silicon single crystal rod of the heat shielding member is formed to have a smaller diameter toward the lower side, if the short cylindrical body is mounted via a plurality of mounting ribs formed radially, The short cylinder can be attached by a simple operation simply by inserting the short cylinder from above, and the short cylinder according to the present invention can be easily attached to an existing heat shielding member having a small diameter toward the bottom. be able to. On the other hand, the short cylinder attached via the mounting rib can be removed from the heat shielding member by lifting it upward, so that only the short cylinder is removed from the pulling device after the silicon single crystal rod is pulled and cleaned. Can also.
Furthermore, if the short cylinder is made of transparent quartz, this quartz transmits infrared rays, so even if the short cylinder is attached to the heat shielding member,
The temperature distribution around the silicon single crystal rod is not changed as compared with the case where the rod is not attached.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a pulling device of the present invention.

FIG. 2 is an enlarged sectional view of a portion A in FIG.

FIG. 3 is a cutaway perspective view of a main part of a heat shielding member including a short cylinder of the pulling device.

FIG. 4 is a sectional view showing a conventional example and corresponding to FIG. 2;

[Explanation of symbols]

 Reference Signs List 10 silicon single crystal pulling apparatus 11 chamber 12 silicon melt 13 quartz crucible 18 heater 25 silicon single crystal rod 26 heat shielding member 27 gas supply / discharge means 31 short cylindrical body 31a mounting rib

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisashi Furuya 1-5-1, Otemachi, Chiyoda-ku, Tokyo Within Mitsubishi Materials Silicon Corporation (72) Inventor Hitoshi Sasaki 1-5, Otemachi, Chiyoda-ku, Tokyo No. 1 Mitsubishi Materials Silicon Corporation (72) Inventor Naoki Ono 1-5-1, Otemachi, Chiyoda-ku, Tokyo F-term (reference) 4M077 AA02 BA04 CF00 EG18 EG19 FK18 HA12 PE24 PE27

Claims (3)

[Claims] 1. A silicon single crystal rod (25) which is pulled up from a silicon melt (12) stored in a quartz crucible (13) in a chamber (11) and has a lower end surrounding the silicon melt.
(12) a heat shielding member (26) that is located above at an interval from the surface and blocks radiant heat from the heater (18), and the inert gas is the silicon single crystal rod (25) and the heat shielding member (26). A gas supply / discharge means (27) for discharging the mixture through the surface of the silicon melt (12) and discharging it out of the chamber (11). ) Is provided below the heat shield member (26) at a predetermined distance from the inner peripheral surface of the heat shield member (26). 2. A silicon single crystal rod (25) of a heat shielding member (26).
A plurality of mounting ribs (31a), each of which is formed to have a smaller diameter toward the lower side and a distal end configured to be able to contact the inner surface of the heat shielding member (26), include a short cylindrical body (31). 2. The apparatus for pulling a silicon single crystal according to claim 1, wherein the apparatus is radially formed on the outer periphery of (1). 3. The apparatus for pulling a silicon single crystal according to claim 1, wherein the short cylinder body is made of quartz.