JPH09142990A - Method for lowering oxygen concentration in silicone single crystal and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to lower the concn. of the oxygen included in a silicon single crystal to an extremely low level by controlling the convection of the silicon melt in a quartz crucible. SOLUTION: A cylindrical block member 26 is inserted between the outer peripheral surface of the silicon single crystal 25 and the inner peripheral surface of the quartz crucible 13. The bottom end of the block member extends near to the surface of the silicon melt 12, thereby segmenting the inside of a chamber 11 to the silicon single crystal side and the inner peripheral surface side of the crucible. A flow regulating member 27 connected to the bottom end of the block member covers the silicon melt surface. A suction port 27a formed near the silicon single crystal of the rear surface of the flow regulating member communicates with a passage 30 formed from the inside of the flow regulating member to the inside of the block member. The inert gas supplied to the inner peripheral surface side of the crucible by a gas feeding and discharging means 34 flows between the flow regulating member and the silicon melt surface from the outer peripheral edge toward the inner peripheral edge of the flow regulating member. The gas is further discharged outside the chamber through the suction port and the passage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for reducing the oxygen concentration in a silicon single crystal manufactured by a silicon single crystal pulling method.

[0002]

2. Description of the Related Art Conventionally, as this type of apparatus, as shown in FIGS. 6 and 7, a quartz crucible 3 in which a silicon melt 2 is stored is housed in a chamber 1 and an outer peripheral surface of a silicon single crystal 5 is formed. Silicon single crystal 5 between the inner surface of the quartz crucible 3 and
A device for pulling a high-purity semiconductor rod from a melt is disclosed in which a heat cap 6 is inserted to surround the heat cap 6 and an annular rim 7 is projected outward from the upper end of the heat cap 6 in a substantially horizontal direction ( Japanese Patent Publication No. 57-40119). In this apparatus, the heat cap 6 is formed in a tubular shape whose diameter decreases as it goes downward, its lower end extends to the vicinity of the surface of the silicon melt 2, and its upper end extends to substantially the same height as the upper end of the heat retaining tube 9. When the heat cap 6 and the annular rim 7 are inserted into the chamber 1 and the lower surface of the annular rim 7 is brought into contact with the upper surface of the heat insulating cylinder 9, the inside of the chamber 1 is closed by the heat cap 6 and the annular rim 7 on the silicon single crystal side. It is divided into the inner surface of the crucible. Further, when an inert gas is supplied into the chamber 1 by a gas supply / exhaust means (not shown) connected to the chamber 1, this inert gas flows down the outer peripheral surface of the silicon single crystal 5 as shown by the solid arrow in FIG. Then, the heat is discharged to the outside of the quartz crucible 3 through the gap between the lower end of the heat cap 6 and the surface of the silicon melt 2.
In the apparatus configured as described above, oxygen in the silicon melt 2 becomes SiO gas or the like to evaporate and drop after adhering in the chamber 1, but at this time, the presence of the heat cap 6 heats the inert gas. Since the gap between the lower end of the cap 6 and the surface of the silicon melt 2 flows vigorously from the outer peripheral surface side of the silicon single crystal 5 toward the inner peripheral surface side of the quartz crucible 3, the above-mentioned fallen object is kept away from the silicon single crystal 5. As a result, it is possible to prevent the falling matter from being taken into the silicon single crystal 5 and generating dislocations which are lattice defects in the silicon single crystal 5. Further, since the heat cap 6 efficiently shields heat, the productivity of the silicon single crystal 5 can be improved.

[0003]

However, in the above-mentioned conventional apparatus for pulling a high-purity semiconductor rod from a melt, an inert gas passes between the lower end of the heat cap and the surface of the silicon melt to form a silicon melt. At the same time as generating the convection as shown by the broken line arrow in FIG. 6, the convection as shown by the alternate long and short dash line arrow from the vicinity of the bottom surface of the quartz crucible to the vicinity of the growth lower surface of the silicon single crystal without passing through the surface of the silicon melt is generated. . As a result, the oxygen in the silicon melt is changed to Si.
The silicon melt with a low oxygen concentration near the surface that has evaporated as O gas, etc. moves away from the silicon single crystal, and SiO ₂ which is a component of the quartz crucible is dissolved in the silicon melt. There is a problem that the oxygen concentration in the silicon single crystal becomes high because it reaches the vicinity of the growth lower surface of the silicon single crystal from the bottom of the silicon and is taken into the silicon single crystal. The object of the present invention is to control the convection of the silicon melt in the quartz crucible, whereby the oxygen concentration contained in the silicon single crystal can be suppressed to an extremely low level.
It is an object of the present invention to provide a method and an apparatus for reducing the oxygen concentration in a silicon single crystal.

[0004]

The invention according to claim 1 is
As shown in FIG.
When the silicon melt 12 stored in the quartz crucible 13 therein is pulled up, the inert gas supplied into the chamber 11 is guided to the surface of the silicon melt 12 so that the surface of the silicon melt 12 causes the inside of the quartz crucible 13 to be removed. Silicon single crystal from the peripheral side 2
5 is a method of reducing the oxygen concentration in the silicon single crystal by controlling the convection direction of the silicon melt 12 by causing an inert gas to flow to the outer peripheral surface side of 5. In this reduction method, the silicon melt 12 that has been subjected to the convection flows from the inner peripheral surface side of the quartz crucible 13 toward the outer peripheral surface side of the silicon single crystal 25 in the process.
Since the oxygen in the silicon becomes SiO gas or the like and evaporates from the surface of the silicon melt 12, the oxygen concentration in the silicon melt 12 reaching the vicinity of the growth lower surface of the silicon single crystal 25 becomes extremely low. As a result, the silicon melt 12 having a low oxygen concentration grows as the silicon single crystal 25, so that the oxygen concentration contained in the silicon single crystal 25 becomes extremely low.

The invention according to claim 2 is, as shown in FIGS. 1 and 4, a silicon single crystal 2 pulled up from a silicon melt 12 stored in a quartz crucible 13 in a chamber 11.
5 is inserted so as to surround the silicon single crystal between the outer peripheral surface of the quartz crucible 5 and the inner peripheral surface of the quartz crucible, and the lower end extends to the vicinity of the silicon melt surface 13 and the inner peripheral surface of the crucible is located inside the chamber 11 on the silicon single crystal side. And a cylindrical partition member 26 that is partitioned into, and covers the surface of the silicon melt 12 that is connected to the lower end of the partition member 26 at a predetermined interval and that the silicon single crystal
5, a flow regulating member 27 having a suction port 27a formed therein, a passage 30 formed from the inside of the flow regulating member 27 to the inside of the partition member 26 and communicating with the suction port 27a, and an inert gas is supplied to the inner peripheral surface of the crucible. A gas supply / exhaust means 34 for causing an inert gas to flow between the surfaces of the rectifying member 27 and the silicon melt 12 from the outer peripheral edge of the rectifying member 27 toward the inner peripheral edge thereof and further to the outside of the chamber 11 via the suction port 27a and the passage 30. And a device for reducing the oxygen concentration in a silicon single crystal. In this reduction device, when pulling up the silicon single crystal 25,
By flowing the inert gas between the lower surface of the flow regulating member 27 and the surface of the silicon melt 12 by the gas supply / discharge means 34 from the outer peripheral edge of the flow regulating member 27 toward the inner peripheral edge, the inner periphery of the quartz crucible 13 is formed on the surface of the silicon melt 12. A convection current is generated in the silicon melt 12 from the surface toward the growth lower surface of the silicon single crystal 25.
Oxygen in the melt 12 becomes SiO gas or the like in the process in which the silicon melt 12 moves from the inner peripheral surface of the quartz crucible 13 on the surface of the melt 12 to the vicinity of the growth lower surface of the silicon single crystal 25 by this convection. Since it evaporates from the surface, the oxygen concentration in the silicon melt 12 that has reached the vicinity of the growth lower surface of the silicon single crystal 25 becomes extremely low. As a result, the silicon melt 12 having a low oxygen concentration grows as the silicon single crystal 25, so that the oxygen concentration contained in the silicon single crystal 25 becomes extremely low. The invention according to claim 3 is the invention according to claim 2, characterized in that the partition member and the rectifying member are formed of carbon, quartz, molybdenum, tungsten, niobium, or tantalum.

[0006]

Next, a first embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIGS. 1 to 4, a quartz crucible 13 for storing a silicon melt 12 is provided in a chamber 11 of a single crystal pulling apparatus 10, and an outer surface of the quartz crucible 13 is covered with a graphite susceptor 14. . The lower surface of the quartz crucible 13 is the graphite susceptor 14
It is fixed to the upper end of the support shaft 16 via the, and the lower part of the support shaft 16 is connected to the crucible drive means 17 (FIG. 4). The crucible driving means 17 has a first rotation motor (not shown) for rotating the quartz crucible 13 and a lifting motor for raising and lowering the quartz crucible 13, and these motors can rotate the quartz crucible 13 in a predetermined direction. At the same time, it can be moved up and down. A heater 18 is provided outside the quartz crucible 13 at a predetermined interval from the quartz crucible 13, and a heat insulating cylinder 19 is provided between the heater 18 and the chamber 11. 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, the chamber 11
A cylindrical casing 21 having a smaller diameter is provided (FIG. 4). The casing 21 is provided with a pulling means 22. The pulling means 22 is a pulling head (not shown) provided at the upper end of the casing 21 so as to be pivotable in a horizontal state.
A second rotation motor (not shown) for rotating the head, a wire cable 23 suspended from the head toward the center of rotation of the quartz crucible 13, and a wire cable 23 provided in the head and wound up Or, it has a pulling motor (not shown) for feeding. At the lower end of the wire cable 23 is attached a seed crystal 24 for dipping in the silicon melt 12 to pull up the silicon single crystal 25.

A partition member 26 is inserted between the outer peripheral surface of the silicon single crystal 25 and the inner peripheral surface of the quartz crucible 13 so as to surround the silicon single crystal 25, and the silicon melt 12 is placed at the lower end of the partition member 26. A rectifying member 27 that covers the surface is connected (FIGS. 1 and 4). The partition member 26 is a cylindrical tubular portion 2
6a, and a disc-shaped flange portion 26b protruding outward from the upper end of the tubular portion 26a in a substantially horizontal direction (see FIG. 1).
~ FIG. 4). The lower end of the cylindrical portion 26a extends to the vicinity of the surface of the silicon melt 12, and the upper end extends to substantially the same height as the upper end of the heat retaining cylinder 19. The outer diameter of the flange portion 26b is formed slightly smaller than the inner diameter of the chamber 11. When the partition member 26 is inserted into the chamber 11, the flange portion 26
The lower surface of b contacts the upper surface of the heat insulation cylinder 19, and the partition member 26 partitions the chamber 11 into the silicon single crystal side and the crucible inner peripheral surface side (FIGS. 1 and 4).

The rectifying member 27 is provided above the surface of the silicon melt 12 at a predetermined distance and substantially parallel to the surface of the silicon melt 12. A ring-shaped suction port 27 is provided on the lower surface of the rectifying member 27 near the silicon single crystal 25.
a is formed (FIGS. 1 and 3), and a passage 30 communicating from the inside of the flow regulating member 27 to the inside of the partition member 26 with the suction port 27a is formed (FIGS. 1 and 4). Above passage 30
Is a first passage 31 formed by hollowing the inside of the flow regulating member 27 communicating with the suction port 27a, and a second passage formed by communicating the first passage 31 with a hollow inside of the tubular portion 26a. 32, and a third passage 33 that is formed by hollowing the inside of the flange portion 26b that communicates with the second passage 32. Here, the inside of the tubular portion 26b means the tubular portion 2
It refers to a portion between the outer peripheral surface and the inner peripheral surface of the peripheral wall forming part 6. The partition member 26 and the rectifying member 27 are preferably made of carbon, quartz, molybdenum, tungsten, niobium, or tantalum. The suction port may not be a ring-shaped hole, but may be a large number of small holes formed at a predetermined interval on the same circumference centered on the silicon single crystal.

Gas supply / exhaust means 3 for supplying an inert gas such as argon gas or nitrogen gas into the chamber 11 and discharging the inert gas from the chamber 11.
4 are connected (FIGS. 1 to 4). The gas supply / discharge means 34 has a main supply pipe 36 having one end connected to a tank (not shown) for storing an inert gas and the other end penetrating the chamber 11 and the flange portion 26b and protruding toward the inner peripheral surface of the crucible, The main discharge pipe 37 has one end connected to the flange portion 26b so as to communicate with the third passage 33 and the other end connected to the suction port (not shown) of the vacuum pump. It is preferable to provide two main supply pipes 36 (FIGS. 1 to 3) or three or more, and the other end of these pipes 36 is the flange portion 2
6b are penetrated at equal intervals on the same circumference centered on the silicon single crystal 25. It is preferable to provide two main discharge pipes 37 (FIGS. 1 and 2) or three or more,
These pipes 37 are connected to the flange portion 26b at equal intervals on the same circumference centered on the silicon single crystal 25. In addition, the main supply pipe 36 and the main discharge pipe 3
The main flow rate adjusting valves 38 and 39 for adjusting the flow rates of the inert gas are provided at 7.

Reference numeral 41 designates the inside of the crucible for adjusting the pressure of the inert gas on the silicon single crystal side in the chamber 11 and preventing the upward flow of the inert gas from occurring along the outer peripheral surface of the silicon single crystal 25. Reference numeral 42 is an auxiliary supply pipe for supplying an inert gas to the peripheral surface side, and 42 is for adjusting the pressure of the inert gas on the inner peripheral surface side of the crucible in the chamber 11 and is supplied from the main supply pipe 41 to the inner peripheral surface side of the crucible. The auxiliary discharge pipes 43 and 44 are provided in the auxiliary supply pipe 41 and the auxiliary discharge pipe 42 for adjusting the flow rate of the inert gas, respectively. It is a flow control valve (Fig. 4). The flow rate of the inert gas supplied from the main supply pipe to the inner peripheral surface side of the quartz crucible is 0 to 100 liters / minute, more preferably 10 to 50 liters / minute. The flow rate of the inert gas supplied to the outer peripheral surface side is 5 to 100 liters / minute, and more preferably 5 to 1
0 liter / min, and the distance from the outer peripheral surface of the silicon single crystal of the inlet provided on the lower surface of the rectifying member is 10 to 15
It is 0 mm, more preferably 10 to 50 mm.

A rotary encoder (not shown) is connected to the 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 vertical position of the support shaft 16 are provided. Each detection output of the rotary encoder, weight sensor, and linear encoder is a controller (not shown)
The control output of the controller is connected to the pulling motor of the pulling means 22 and the lifting motor of the crucible driving means 17, respectively. A memory (not shown) is provided in the controller, and the wire cable 23 for the detection output of the rotary encoder is provided in this memory.
The winding length, that is, the pulling length of the silicon single crystal 25 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 uses the silicon melt 12 in the quartz crucible 13 based on the detection output of the weight sensor.
The raising / lowering motor of the crucible driving means 17 is controlled so that the liquid surface of the crucible is always kept at a constant level.

The operation of the device for reducing the oxygen concentration in the silicon single crystal thus configured will be described. By adjusting the main flow rate adjusting valves 38, 39 and the auxiliary flow rate adjusting valves 43, 44 when pulling up the silicon single crystal 25, the inert gas on the silicon single crystal side in the chamber 11 and on the inner peripheral surface side of the crucible is adjusted. Adjust each flow rate. The inert gas supplied from the main supply pipe 36 to the inner peripheral surface side of the crucible flows down between the inner peripheral surface of the quartz crucible 13 and the outer peripheral surface of the cylindrical portion 26a of the partition member 26 as indicated by the solid line arrow in FIG. Between the lower surface of the member 27 and the surface of the silicon melt 12 flows from the outer peripheral edge of the rectifying member 27 toward the inner peripheral edge, and further flows into the inside of the rectifying member 27 through the suction port 27a and passes through the first to third passages 31 to 33 to the main. It is discharged from the discharge pipe 37 to the outside of the chamber 11. Also, from the auxiliary supply pipe 41 to the silicon single crystal 2
The inert gas supplied to the No. 5 side flows down the outer peripheral surface of the silicon single crystal 25 as shown by the one-dot chain line arrow, and flows into the rectifying member 27 from the suction port 27a.

When the inert gas flows between the lower surface of the rectifying member 27 and the surface of the silicon melt 12 from the outer peripheral edge of the rectifying member 27 toward the inner peripheral edge, this inert gas flow is generated by the silicon melt 1.
Since it is in contact with the surface 2 of the silicon melt 12,
The convection is generated as indicated by the broken arrow, the two-dot chain line arrow and the one-dot chain line arrow. When the silicon melt 12 flows from the inner bottom surface of the quartz crucible 13 along the inner peripheral surface as shown by the one-dot chain line arrow, SiO ₂ which is a component of the quartz crucible 13 melts into the silicon melt 12. Oxygen dissolved in the melt 12 is converted into Si in the process in which the melt 12 moves to the vicinity of the growth lower surface of the silicon single crystal 25 on the surface of the melt 12 as indicated by a dashed arrow.
Since it becomes O gas or the like and evaporates from the surface of the melt 12, and the evaporated SiO gas or the like is discharged to the outside of the chamber 11 by the inert gas flow, the silicon melt 12 that has reached near the growth lower surface of the silicon single crystal 25. The oxygen concentration in it becomes extremely low. As a result, the silicon melt 12 having a low oxygen concentration grows as the silicon single crystal 25, so that the oxygen concentration contained in the silicon single crystal 25 becomes extremely low.

FIG. 5 shows a second embodiment of the present invention.
5, the same reference numerals as those in FIG. 4 indicate the same parts. In this device, the tubular portion 66a of the partition member 66 extends upward, the upper end of which is loosely inserted into the lower portion of the casing 61, and the flange portion 66b is provided so as to project substantially horizontally outward from the upper end of the tubular portion 66a. . A ring-shaped receiver 61a is projectingly provided on the lower inner peripheral surface of the casing 61, and the lower surface of the flange portion 66b abuts on the upper surface of the receiver 61a, so that the partition member 66 moves the inside of the chamber 11 toward the silicon single crystal side. It is designed to be divided into the inner surface of the crucible. The other end of the main supply pipe 36 of the gas supply / discharge means 34 penetrates through the chamber 11 and projects toward the inner peripheral surface of the crucible, and the main discharge pipe 3
One end of 7 is a tubular portion 6 of the partition member 66 in the passage 70 formed from the inside of the flow regulating member 27 to the inside of the partition member 66.
It is connected to the tubular portion 66a so as to communicate with the second passage 72 formed inside 6a. The configuration other than the above is the same as that of the first embodiment. The operation of the oxygen concentration reducing apparatus in the silicon single crystal configured as described above is substantially the same as the operation of the reducing apparatus of the first embodiment, and therefore the repetitive description will be omitted.

[0016]

EXAMPLES Examples of the present invention will now be described in detail with reference to comparative examples with reference to the drawings. <Embodiment 1> As shown in FIGS. 1 to 4, a partition member 26 is inserted between the outer peripheral surface of the silicon single crystal 25 and the inner peripheral surface of the quartz crucible 13, and the chamber 11 is inserted by the partition member 26.
The inside was divided into the silicon single crystal side and the crucible inner peripheral surface side, and a rectifying member 27 covering the surface of the silicon melt 12 was connected to the lower end of the dividing member 26. The gas supply / exhaust means 34 for supplying and discharging the argon gas into the chamber 11 is the main supply pipe 3 for supplying the argon gas to the inner peripheral surface side of the quartz crucible 13 and the outer peripheral surface side of the silicon single crystal 25, respectively.
6 and the auxiliary supply pipe 41, and the main discharge pipe 37 and the auxiliary discharge pipe 42 for discharging the argon gas in the chamber 11. The pipes 36, 37, 41,
The main flow rate adjusting valves 38, 39 and the auxiliary flow rate adjusting valves 43, 44 are provided at 43. By controlling the gas supply / discharge means 34, the inert gas supplied to the inner peripheral surface side of the quartz crucible 13 moves from the outer peripheral edge of the rectifying member 27 toward the inner peripheral edge between the surfaces of the rectifying member 27 and the silicon melt 12. It is configured to be discharged to the outside of the chamber 11 from the suction port 27a on the lower surface of the rectifying member 27 through the passage 30 inside the rectifying member 27 and the partitioning member 26. The inner diameter of the quartz crucible 13 was 406 mm, and the weight of the silicon melt 12 stored in the quartz crucible 13 was 35 kg. Further, the inner diameter of the tubular portion 26a of the partition member 26 and the inner diameter of the rectifying member 27 are 380 mm and 170 mm, respectively, and the silicon single crystal 2 of the suction port 27a formed on the lower surface of the rectifying member 27 is used.
5 was 20 mm from the outer peripheral surface, and the distance between the flow regulating member 27 and the surface of the silicon melt 12 was 20 mm.

<Comparative Example 1> Although not shown, the same construction as that of the above-mentioned Example 1 was carried out except that the partition member, the rectifying member, the main supply pipe and the main discharge pipe of the above-mentioned Example 1 were not used. By controlling the flow rate adjusting valves of the auxiliary supply pipe and the auxiliary discharge pipe of the gas supply / discharge means, the argon gas supplied into the chamber moves above the silicon melt of the quartz crucible from the outer peripheral surface of the silicon single crystal to the inner periphery of the quartz crucible. It was designed to flow toward the surface. Comparative Example 2 As shown in FIGS. 6 and 7, a heat cap 6 was inserted between the outer peripheral surface of the silicon single crystal 5 and the inner peripheral surface of the quartz crucible 3 so as to surround the silicon single crystal 5. An annular rim 7 is projected outward from the upper end of the heat cap 6 in a substantially horizontal direction. The heat cap 6 is formed in a tubular shape whose diameter decreases as it goes downward, its lower end extends to the vicinity of the surface of the silicon melt 2, and its upper end extends to substantially the same height as the upper end of the heat retaining tube 9. When the heat cap 6 and the annular rim 7 are inserted into the chamber 1, the annular rim 7
The lower surface of the chamber abuts on the upper surface of the heat insulating cylinder 9, and the inside of the chamber 1 is partitioned by the heat cap 6 and the annular rim 7 into the silicon single crystal side and the crucible inner peripheral surface side. Although not shown, as the gas supply / discharge means, only the auxiliary supply pipe and the auxiliary discharge pipe were used without using the main supply pipe and the main discharge pipe of the first embodiment. By controlling the gas supply / discharge means, the inert gas flows down the outer peripheral surface of the silicon single crystal 5 as indicated by the solid arrow in FIG.
It was configured to be discharged to the outside of the quartz crucible 3 through the gap between the lower end and the surface of the silicon melt 2. Except for the above, the configuration was the same as in Example 1. <Comparative Test and Evaluation> In the apparatus of Example 1, Comparative Example 1 and Comparative Example 2, the diameter and length of the chamber were changed to 152 mm and 600, respectively, by changing the flow rate and pressure of the argon gas in the chamber.
mm silicon single crystals were grown, and the oxygen concentration contained in the silicon single crystals at a position 250 mm from the shoulders of these silicon single crystals was measured. Table 1 shows the results.

[0018]

[Table 1]

As is clear from Table 1, the oxygen concentration in the silicon single crystal grown by the apparatus of Example 1 is lower than the oxygen concentration in the silicon single crystal grown by the apparatuses of Comparative Examples 1 and 2. I understood.

[0020]

As described above, according to the present invention, when the silicon single crystal is pulled up from the silicon melt in the quartz crucible, the inert gas supplied into the chamber is guided to the surface of the silicon melt. Since the inert gas is caused to flow from the inner peripheral surface side of the quartz crucible to the outer peripheral surface side of the silicon single crystal on the surface of the silicon melt to control the convection direction of the silicon melt, oxygen in the silicon melt is changed to SiO gas or the like. Then, it evaporates from the surface of the silicon melt, and the silicon melt having a low oxygen concentration rides on the convection and goes from the inner peripheral surface side of the quartz crucible toward the outer peripheral surface side of the silicon single crystal. As a result, the silicon melt having a low oxygen concentration grows as a silicon single crystal, and the oxygen concentration contained in the silicon single crystal becomes extremely low.

Further, a cylindrical partition member is inserted between the outer peripheral surface of the silicon single crystal and the inner peripheral surface of the quartz crucible, and the partition member partitions the chamber into the silicon single crystal side and the inner peripheral surface side of the crucible. Then, a rectifying member that covers the surface of the silicon melt is connected to the lower end of the partitioning member, and the inert gas supplied to the inner peripheral surface of the crucible by the gas supply / discharge means is provided between the rectifying member and the surface of the silicon melt outside the rectifying member. If it is configured to flow from the peripheral edge toward the inner peripheral edge and to be discharged to the outside of the chamber from the inlet of the lower surface of the rectifying member through the passage inside the rectifying member and inside the partitioning member, by flowing the inert gas as described above, Convection is generated in the silicon melt from the inner peripheral surface of the quartz crucible toward the growth lower surface of the silicon single crystal. As a result, due to the above convection, the silicon melt melts from the inner surface of the quartz crucible toward the vicinity of the growth lower surface of the silicon single crystal on the surface of this melt, and oxygen in the melt evaporates into SiO gas or the like. Since the silicon melt of oxygen concentration grows as a silicon single crystal,
The oxygen concentration contained in the silicon single crystal is extremely low.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of a portion A of FIG. 4 showing a device for reducing oxygen concentration in a silicon single crystal according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a partitioning member and a rectifying member of the reducing device when viewed obliquely from above.

FIG. 3 is a perspective view of a partition member and a rectifying member as seen obliquely from below.

FIG. 4 is a cross-sectional configuration diagram of the reduction device.

FIG. 5 is a sectional configuration diagram corresponding to FIG. 4 showing a second embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a conventional example and corresponding to FIG.

FIG. 7 is a perspective view of the straightening cylinder.

[Explanation of symbols]

 11 chamber 12 silicon melt 13 quartz crucible 25 silicon single crystal 26,66 partitioning member 27 rectifying member 27a inlet port 30,70 passage 34 gas supply / discharge means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoki Ono 1-297 Kitabukuro-cho, Omiya-shi, Saitama Mitsubishi Materials Corporation Research Institute (72) Keisei Abe 1-297 Kitabukuro-cho, Omiya-shi, Saitama Mitsubishi Materials Research Institute, Inc.

Claims (3)

[Claims] 1. An inert gas supplied into the chamber (11) when pulling a silicon single crystal (25) from a silicon melt (12) stored in a quartz crucible (13) in the chamber (11). The gas is introduced to the surface of the silicon melt (12), and the surface of the silicon melt (12) moves from the inner peripheral surface side of the quartz crucible (13) to the outer peripheral surface side of the silicon single crystal (25). A method for reducing the oxygen concentration in a silicon single crystal, which comprises flowing an active gas to control the convection direction of the silicon melt (12). 2. An outer peripheral surface of a silicon single crystal (25) pulled from a silicon melt (12) stored in a quartz crucible (13) in a chamber (11) and an inner peripheral surface of the quartz crucible (13). Is inserted so as to surround the silicon single crystal (25), and the lower end extends to the vicinity of the surface of the silicon melt (12) and the chamber.
(11) a cylindrical partition member (26, 66) that partitions the inside into a crucible inner peripheral surface side that takes the silicon single crystal side, and the silicon melt (12) connected to the lower end of the partition member (26, 66) ) A rectifying member (27) which covers the surface at a predetermined interval and has an inlet port (27a) formed in the lower surface in the vicinity of the silicon single crystal (25), and the partition member from the inside of the rectifying member (27). (26,66) Passageways (30,70) formed inside to communicate with the suction port (27a)
And supplying an inert gas to the inner peripheral surface side of the crucible, the inert gas from the outer peripheral edge of the rectifying member (27) to the inner peripheral edge between the rectifying member (27) and the silicon melt (12) surface. Reduction of oxygen concentration in a silicon single crystal provided with a gas supply / exhaust means (34) which flows toward the outside and is exhausted to the outside of the chamber (11) through the suction port (27a) and the passages (30, 70) apparatus. 3. An apparatus for reducing oxygen concentration in a silicon single crystal according to claim 2, wherein the partition member and the rectifying member are formed of carbon, quartz, molybdenum, tungsten, niobium or tantalum.