JP7006573B2 - Single crystal pulling device and method for manufacturing silicon single crystal - Google Patents

Description

The present invention relates to a single crystal pulling device and a method for producing a silicon single crystal.

Conventionally, during the production of a silicon single crystal, the inside is imaged by using an imaging means outside the chamber, and the growth conditions of the silicon single crystal are controlled based on the growth status of the silicon single crystal (for example, a patent). See Document 1).

The single crystal pulling device described in Patent Document 1 includes a purge tube made of quartz. The purge tube has a transparent viewing window. Through this viewing window, the CCD camera can capture the growth status of the silicon single crystal.

Japanese Unexamined Patent Publication No. 2011-246341

However, in the configuration of Patent Document 1, since the surface of the viewing window and the vertical straight line (straight line extending in the direction of gravity) are parallel, the angle of incidence of the optical axis of the CCD camera on the surface of the viewing window is large. Therefore, the reflected image on the surface of the viewing window may be captured by the CCD camera, and the growth state of the silicon single crystal may not be properly captured.

An object of the present invention is to provide a single crystal pulling device capable of appropriately grasping a growing state of a silicon single crystal from the outside of a chamber, and a method for producing a silicon single crystal.

The purge tube of the present invention is a purge tube provided in the chamber of the single crystal pulling device, and is a cylindrical portion formed in a cylindrical shape and guiding an inert gas introduced from the outside of the chamber to the silicon melt side. And a flange portion that protrudes outward from the outer peripheral surface of the cylindrical portion in a flange shape, and at least a part of the flange portion is a silicon single crystal by an optical observation means provided outside the chamber. It is characterized by being provided with a permeation part that enables observation of the growing condition of the.

As for the growth status of the silicon single crystal observed by the optical observation means, the generation status of the annular meniscus existing at the boundary between the silicon single crystal and the liquid surface of the silicon melt, and the heat shield from the liquid surface of the silicon melt. An example is the distance to the lower end (hereinafter, may be referred to as a "gap").
According to the present invention, the purge tube is provided in the single crystal pulling device so that the central axis of the cylindrical portion and the vertical straight line are parallel to each other, so that the angle of incidence of the optical axis of the optical observation means on the upper surface of the transmissive portion can be determined. It can be made smaller than the configuration as in Patent Document 1 (hereinafter referred to as "conventional configuration"). Therefore, it is possible to prevent the reflection component on the upper surface of the transmissive portion from being observed by the optical observation means, and it is possible to appropriately grasp the growth state of the silicon single crystal by the optical observation means.

If the growth status of the silicon single crystal cannot be properly grasped, the problem that the gap during the production of the silicon single crystal cannot be precisely controlled, the problem that the diameter of the silicon single crystal during the production cannot be precisely controlled, and the silicon single crystal It may not be possible to precisely control the pulling speed, which is closely related to the diameter control of the single crystal.
In the present invention, since the growing state of a silicon single crystal can be appropriately grasped, precise gap control, precise diameter control of a silicon single crystal, precise pull-up speed control, or a single silicon for a semiconductor in which these are required at the same time is required. Suitable for producing crystals.

In the purge tube of the present invention, it is preferable that the transmissive portion is formed so that the incident angle of the optical axis of the optical observation means with respect to the upper surface of the transmissive portion is 45 ° or less.

The case where the incident angle is 45 ° or less includes both a case where the angle formed by the outer peripheral surface of the cylindrical portion and the upper surface of the transmissive portion in the side view is an acute angle and a case where the angle is obtuse.
According to the present invention, it is possible to further suppress the reflection component on the upper surface of the transmissive portion from being observed by the optical observation means. It is more preferable that the incident angle is formed so as to be 22.5 ° or less.

In the purge tube of the present invention, it is preferable that the transmission portion is formed so that the incident angle is 0 °.

The case where the incident angle is 0 ° includes the range of −5 ° to 5 ° in addition to 0 °.
According to the present invention, it is possible to prevent the reflected component on the upper surface of the transmissive portion from being observed by the optical observation means.

In the purge tube of the present invention, it is preferable that the transmission portion is made of flat quartz having a uniform thickness.

According to the present invention, distortion of the observation result during two-dimensional observation can be suppressed, and the growth state of the silicon single crystal can be more appropriately grasped by the optical observation means.

In the purge tube of the present invention, it is preferable that the flange portion is formed in the shape of an annular plate extending in a direction orthogonal to the central axis of the cylindrical portion. In particular, it is preferable that the flange portion has a uniform thickness.

According to the present invention, the collar portion can be easily manufactured by making the collar portion a simple shape.

In the purge tube of the present invention, the outer diameter of the flange portion is preferably larger than the inner diameter of the lower end of the cylindrical or truncated cone-shaped heat shield provided in the chamber.

According to the present invention, the purge tube can be easily installed only by the contact between the flange portion and the heat shield.

In the purge tube of the present invention, the cylindrical portion is preferably formed of graphite.

According to the present invention, the weight of the purge tube can be reduced and the cost can be reduced.

The single crystal pulling device of the present invention has a crucible accommodating a silicon melt, a pulling portion for growing a silicon single crystal by bringing the seed crystal into contact with the silicon melt and then pulling the seed crystal, and above the crucible. A cylindrical heat shield provided so as to surround the silicon single crystal, the above-mentioned purge tube, the crucible, the chamber containing the heat shield and the purge tube, and the inside of the chamber from the outside of the chamber. The crucible is provided with a gas introduction portion for introducing the inert gas into the crucible, and an optical observation means provided outside the chamber and for observing the growth state of the silicon single crystal via the transmission portion of the purge tube. It is characterized by.

In the single crystal pulling device of the present invention, it is preferable that the inner peripheral surface of the heat shield is provided with a purge tube support portion that supports the purge tube from below. In particular, it is preferable to support the flange portion of the purge tube from below.

According to the present invention, the purge tube can be easily positioned. In particular, if the collar is supported from below, the purge tube will not tilt and will be stable.

The method for producing a silicon single crystal of the present invention is a method for producing a silicon single crystal using the above-mentioned single crystal pulling device, and controls the growth conditions of the silicon single crystal based on the observation result of the optical observation means. It is characterized by doing.

The schematic diagram of the single crystal pulling apparatus which concerns on 1st Embodiment of this invention. The enlarged view of the main part of the single crystal pulling apparatus in the 1st Embodiment. The purge tube in the first embodiment is shown, (A) is a plan view, (B) is a sectional view, and (C) is a sectional view taken along the line IIIC-IIIC of (B). A purge tube according to a second embodiment of the present invention is shown, (A) is a plan view, and (B) is a cross-sectional view taken along the IVB-IVB line of (A). The schematic diagram of the single crystal pulling apparatus in the 2nd Embodiment. The enlarged view of the main part of the single crystal pulling apparatus in the 2nd Embodiment. An embodiment of the present invention is shown, (A) is a cross-sectional view showing a state near the surface of a silicon melt in an experimental example, and (B) is a perspective view of a purge tube.

[First Embodiment]
Hereinafter, the first embodiment of the present invention will be described with reference to the drawings.

[Related technology]
First, a general configuration of a single crystal pulling device will be described.
As shown in FIG. 1, the single crystal pulling device 1 is a device used in the CZ method (Czochralski method), and includes a pulling device main body 2, an optical observation means 3, and a control unit 4.
The pulling device main body 2 is provided on the chamber 21, the crucible 22 arranged in the chamber 21, the heater 23 for heating the crucible 22, the pulling portion 24, the heat shield 25, and the inner wall of the chamber 21. It is provided with a heat insulating material 26 and a crucible drive unit 27.
As shown by the alternate long and short dash line, the single crystal pulling device 1 is a device used in the MCZ (Magnetic field applied Czochralski) method, and is a pair of electromagnetic coils arranged across the crucible 22 on the outside of the chamber 21. You may have 28.

The chamber 21 includes a main chamber 211 and a pull chamber 213 connected to the upper part of the main chamber 211 via a gate valve 212.
The main chamber 211 is formed in a shape having an upper surface, and includes a main body portion 211A in which a crucible 22, a heater 23, a heat shield 25, and the like are arranged, and a lid portion 211B that closes the upper surface of the main body portion 211A. The lid 211B is provided with an opening 211C for introducing an inert gas such as Ar gas into the main chamber 211, and a quartz window 211D for the optical observation means 3 to observe the inside of the chamber 21. ing. A support portion 211E extending inward is provided between the main body portion 211A and the lid portion 211B.
The pull chamber 213 is provided with a gas introduction port 21A for introducing an inert gas such as Ar gas into the main chamber 211. A gas exhaust port 21B for discharging the gas in the main chamber 211 is provided below the main body portion 211A of the main chamber 211.

The crucible 22 includes a quartz crucible 221 and a graphite crucible 222 accommodating the quartz crucible 221.
The heater 23 is arranged around the crucible 22 and melts the silicon in the crucible 22.
The pull-up unit 24 includes a cable 241 to which the seed crystal SC is attached to one end, and a pull-up drive unit 242 that raises and lowers and rotates the cable 241.

The heat shield 25 is provided so as to surround the silicon single crystal SM, and blocks radiant heat radiated upward from the heater 23. The heat shield 25 has a truncated cone-shaped heat shield main body 251 that decreases in diameter toward the bottom, and a support that extends outward from the upper end of the heat shield main body 251 in a flange shape. It is provided with a unit 252. As shown in FIG. 2, the heat shield main body 251 is provided with a purge tube support portion 251A that continuously projects in the circumferential direction from the inner peripheral surface thereof.
The heat shield 25 is arranged above the crucible 22 by fixing the supported portion 252 on the support portion 211E.
The crucible drive unit 27 includes a support shaft 271 that supports the graphite crucible 222 from below, and rotates and raises and lowers the crucible 22 at a predetermined speed.

The optical observation means 3 observes the generation state of the meniscus existing on the liquid surface of the silicon melt M, the gap G, and the like as the growth state of the silicon single crystal SM. The optical observation means 3 includes an image pickup means 31 and a calculation means 32. The image pickup means 31 is, for example, a two-dimensional CCD camera, and images the liquid surface of the silicon melt M from the outside of the chamber 21 via the window portion 211D. The calculation means 32 calculates and obtains the growth status of the silicon single crystal SM based on the image pickup result of the image pickup means 31.

The control unit 4 manufactures the silicon single crystal SM based on various information stored in the memory 41 and the operation of the operator. Examples of the information stored in the memory 41 include the gas flow rate in the chamber 21, the pressure inside the furnace, the electric power applied to the heater 23, the rotation speed of the crucible 22 and the silicon single crystal SM, and the like.

[Purge tube configuration]
Next, the configuration of the purge tube provided in the single crystal pulling device 1 will be described.
As shown in FIGS. 3A to 3C, the purge tube 5 includes a cylindrical cylindrical portion 51 and a flange portion 52 protruding outward from the lower end of the cylindrical portion 51 in a flange shape. There is.

The flange portion 52 is formed in the shape of a truncated cone cylinder whose diameter increases toward the bottom. The collar portion 52 includes a collar main body portion 521 and a transmission portion 522.
The flange body portion 521 is formed in a substantially C shape in which a part of the shape of a truncated cone having a uniform thickness is cut out in a plan view. That is, the upper surface 521A of the collar main body 521 has a curved surface.
The transmission portion 522 is formed in a flat plate shape having a uniform thickness. That is, the upper surface 522A of the transmission portion 522 is a flat surface. The transmission portion 522 is provided so as to fill the notched portion in the collar main body portion 521. The transmission portion 522 is provided so that the angle θ ₁ formed by the upper surface 522A and the outer peripheral surface 51A of the cylindrical portion 51 is an obtuse angle in the side view. As shown in FIG. 2, the transmission portion 522 is provided so that the incident angle of the optical axis P of the image pickup means 31 with respect to the upper surface 522A (the angle of the optical axis P with respect to the normal line N of the upper surface 522A) is 45 ° or less. ing. In the first embodiment, the incident angle is 0 °, that is, the angle θ ₂ formed by the upper surface 522A and the optical axis P is 90 °.

The cylindrical portion 51, the flange body portion 521, and the transmission portion 522 are each made of transparent quartz, and these are welded so that the central axis of the cylindrical portion 51 and the central axis of the collar body portion 521 coincide with each other. It is integrated. In a plan view, the outer shape of the flange portion 52 is circular, and its outer diameter is larger than the inner diameter of the lower end opening of the heat shield 25. The silicon single crystal SM passes through the inside of the cylindrical portion 51 and is pulled upward.

[Structure of single crystal pulling device equipped with purge tube]
As shown in FIGS. 1 and 3, the purge tube 5 is supported by the purge tube support portion 251A whose flange portion 52 projects from the inner peripheral surface of the heat shield main body portion 251 from below, whereby the silicon melt M is supported. The distance from the liquid surface to the transmission portion 522 is positioned to be L ₁ . By setting this distance to L ₁ , the position of the lower end of the transmission portion 522 becomes higher than the upper end position of the discoloration region A of the purge tube 9 in the embodiment described later. Further, the purge tube 5 is positioned so that the central axis of the cylindrical portion 51 and the central axis of the heat shield 25 coincide with each other and the central axis of the cylindrical portion 51 is parallel to the vertical line V. ..

A draw tube 29 may be provided in the pulling device main body 2. The draw tube 29 is formed of, for example, a metal having an inner diameter larger than the outer diameter of the cylindrical portion 51 of the purge tube 5. The outer peripheral surface of the draw tube 29 is fixed to the inner peripheral surface of the opening 211C of the lid portion 211B, so that the lower end of the draw tube 29 is located inside the heat shield 25 and the upper end of the flange portion 52 is inside the draw tube 29. It can be provided so that the portion is located. In this embodiment, the purge tube 5 and the draw tube 29 are not in contact with each other, but they may be in contact with each other.

[Manufacturing method of silicon single crystal]
Next, a method for manufacturing a silicon single crystal SM using the single crystal pulling device 1 will be described.
By this manufacturing method, a silicon single crystal SM capable of acquiring a silicon wafer of 200 mm, 300 mm, 450 mm or the like may be manufactured.

First, the control unit 4 of the single crystal pulling device 1 determines the quality required for the silicon single crystal SM, for example, the resistivity, the flow rate of the inert gas which is the pulling condition for satisfying the oxygen concentration, the pressure inside the chamber 21. The rotation speed of the crucible 22 and the silicon single crystal SM, the heating conditions of the heater 23, and the like are set. It should be noted that this setting condition may be one input by the operator, or may be calculated and obtained by the control unit 4 based on a target oxygen concentration or the like input by the operator.

Next, the control unit 4 heats the crucible 22 to melt the polysilicon material (silicon raw material) in the crucible 22 to generate a silicon melt M. The silicon melt M may contain a dopant for adjusting the resistivity of the silicon single crystal SM.
After that, the control unit 4 introduces the inert gas into the chamber 21 from the gas introduction port 21A at a predetermined flow rate and reduces the pressure in the chamber 21 to maintain the inside of the chamber 21 in an inert atmosphere under reduced pressure. do.
After that, the control unit 4 immerses the seed crystal SC in the silicon melt M and pulls up the cable 241 while rotating the crucible 22 and the cable 241 in a predetermined direction to grow the silicon single crystal SM.

During the growth of this silicon single crystal SM, the silicon of the silicon melt M may evaporate and react with oxygen to generate SiO. When this SiO adheres to the inner wall of the lid portion 211B of the main chamber 211 and aggregates, the aggregates pass through the inside of the heat shield 25 and fall into the silicon melt M, and the silicon single crystal SM is polycrystal. There is a risk of becoming. However, in the present embodiment, since the entire outer edge of the truncated cone-shaped flange portion 52 is in contact with the inner peripheral surface of the heat shield 25, even if the agglomerates fall inside the heat shield 25, The flange portion 52 can prevent the agglomerates from reaching the silicon melt M.

Further, during the growth of the silicon single crystal SM, the optical observation means 3 captures an image of the silicon melt M or the silicon single crystal SM transmitted through the transmission portion 522 by the image pickup means 31, and the calculation means is based on the image pickup result. At 32, the growth status of the silicon single crystal SM is obtained. Then, the control unit 4 controls the growth conditions such as the diameter and the gap G of the silicon single crystal SM so that the desired silicon single crystal SM is produced based on the growth condition obtained by the optical observation means 3. ..

[Action and effect of the first embodiment]
According to the first embodiment, the following actions and effects can be achieved.
(1) The purge tube 5 composed of the cylindrical portion 51 and the flange portion 52 is positioned in the chamber 21 so that the central axis of the cylindrical portion 51 and the vertical line V are parallel to each other.
Therefore, the incident angle of the optical axis P of the image pickup means 31 with respect to the upper surface 522A of the transmission portion 522 can be made smaller than that of the conventional configuration. As a result, it is possible to suppress the reflection component on the upper surface 522A of the transmission portion 522 from being imaged by the image pickup means 31, and it is possible to appropriately grasp the growth state of the silicon single crystal SM from the outside of the chamber 21.

(2) In particular, since the transmission portion 522 is configured so that the incident angle of the optical axis P with respect to the upper surface 522A is 0 °, it is possible to prevent the reflection component on the upper surface 522A from being imaged by the image pickup means 31.
(3) Further, since the thickness of the flat plate-shaped transmission portion 522 is made uniform, distortion of the observation result during two-dimensional observation can be suppressed.
Due to the effects of these (2) and (3), the imaging means 31 can image an image in which the actual situation of the silicon melt M or the silicon single crystal SM is projected almost accurately and clearly. In particular, the image of the boundary between the silicon melt M and the silicon single crystal SM and its surroundings can be clearly imaged.
As a result, the growing state of the silicon single crystal SM can be grasped almost accurately from the outside of the chamber 21. Then, the diameter and the gap G of the silicon single crystal SM can be precisely controlled based on the grasped growing condition. That is, with a clear image, it is possible to accurately grasp the amount of deviation with respect to the target diameter or the amount of deviation with respect to the target gap G, and control so as to eliminate the amount of deviation.

(4) Since the outer diameter of the flange portion 52 is larger than the inner diameter of the lower end opening of the heat shield 25, the purge tube 5 can be easily installed only by the contact between the collar 52 and the heat shield 25. ..

(5) Since the purge tube 5 is positioned so that the distance from the liquid surface of the silicon melt M to the transmission portion 522 is L ₁ , the transmission portion 522 is discolored by the radiant heat of the silicon melt M. Can be suppressed.
Since this discoloration occurs when silicon oxide (SiOx) adheres to and binds to the transmission portion 522, it can be removed by pickling with hydrofluoric acid or the like, but the removal cost is incurred, which leads to an increase in manufacturing cost. ..
In the above embodiment, the discoloration of the transmissive portion 522 can be suppressed, so that the cost increase can be suppressed.

[Second Embodiment]
Next, the second embodiment of the present invention will be described with reference to the drawings.
The same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted or simplified.

[Purge tube configuration]
First, the configuration of the purge tube will be described.
As shown in FIGS. 4A to 4B, the purge tube 7 includes a cylindrical cylindrical portion 71 and a flange portion 72 protruding outward from the lower end of the cylindrical portion 71. There is. As shown in FIG. 5, the outer diameter of the flange portion 72 is larger than the inner diameter of the lower end opening of the heat shield 25, and further larger than the inner diameter of the upper end opening of the heat shield 25.

The cylindrical portion 71 is formed of graphite.
The collar portion 72 is made of transparent quartz. The flange portion 72 extends in a direction orthogonal to the central axis of the cylindrical portion 71, and is formed in the shape of an annular plate having a uniform thickness. The outer diameter of the flange portion 72 is larger than the inner diameter of the lower end opening of the heat shield 25, and further larger than the inner diameter of the upper end opening of the heat shield 25. When the purge tube 7 is provided in the chamber 21, a part of the flange portion 72 including the portion overlapping the optical axis P of the image pickup means 31 functions as the transmission portion 721. For example, in FIG. 4A, the region surrounded by the alternate long and short dash line functions as the transmission portion 721, but depending on the installation state of the purge tube 7, another region may be the transmission portion 721. With such a configuration, the upper surface 721A of the transmission portion 721 becomes a flat surface.
The upper surface 72A of the flange portion 72 is provided with a circular positioning groove portion 72B along the inner edge of the annular plate shape. By fitting the lower end of the cylindrical portion 71 into the positioning groove portion 72B, both are positioned so that the central axis of the cylindrical portion 71 and the central axis of the flange portion 72 coincide with each other. The transmission portion 721 is provided so that the angle θ ₃ formed by the upper surface 721A and the outer peripheral surface 71A of the cylindrical portion 71 is a right angle in the side view.

[Structure of single crystal pulling device equipped with purge tube]
As shown in FIGS. 5 and 6, the purge tube 7 is provided in the chamber 21 of the single crystal pulling device 1A. Since the purge tube 7 is larger than the inner diameter of the upper end opening of the heat shield 25, it can be placed on the upper surface of the supported portion 252 of the heat shield 25. By placing the flange portion 72 on the upper surface of the supported portion 252 of the heat shield 25, the distance L ₂ from the liquid surface of the silicon melt M to the transmission portion 721 is set from the distance L ₁ of the first embodiment. Can be lengthened, and the position of the lower end of the transmission portion 721 can be surely made higher than the upper end position of the discoloration region A of the purge tube 9. Further, since the purge tube 7 can be prevented from being exposed to a high temperature as compared with the first embodiment, more repeated use becomes possible.
Further, the purge tube 7 is positioned so that the central axis of the cylindrical portion 71 and the central axis of the heat shield 25 coincide with each other and the central axis of the cylindrical portion 71 is parallel to the vertical line V. Further, the purge tube 7 is positioned so that a part on the upper end side thereof is located in the opening 211C of the lid portion 211B. Although the purge tube 7 and the opening 211C are not in contact with each other, they may be in contact with each other.
As described above, by supporting the purge tube 7 in the chamber 21, the incident angle θ ₄ of the optical axis P of the image pickup means 31 with respect to the upper surface 721A of the transmission portion 721 (the optical axis P with respect to the normal line N of the upper surface 721A). The incident angle θ4) is 45 ° or less.

[Manufacturing method of silicon single crystal]
Next, a method for manufacturing a silicon single crystal SM using the single crystal pulling device 1A will be described.
Since the manufacturing process of the silicon single crystal SM is the same as that of the first embodiment, only the difference due to the provision of the purge tube 7 instead of the purge tube 5 will be described.

During the growth of the silicon single crystal SM, agglomerates of SiO may fall inside the heat shield 25 as the silicon melt M evaporates. However, in the present embodiment, the outer edge of the annular plate-shaped flange portion 72 is formed. Since the entire circumference is located outside the upper end opening of the heat shield main body 251, the flange portion 72 can prevent the agglomerates from reaching the silicon melt M.

Further, during the growth of the silicon single crystal SM, the image pickup means 31 of the optical observation means 3 captures an image transmitted through the transmission portion 721. Then, the control unit 4 controls the growth conditions so that the desired silicon single crystal SM is produced based on the growth situation obtained by the optical observation means 3.

[Action and effect of the second embodiment]
According to the second embodiment, in addition to the same effects as in (4) and (5) of the first embodiment, the following effects can be obtained.
(6) The purge tube 7 composed of the cylindrical portion 71 and the flange portion 72 is positioned in the chamber 21 so that the central axis of the cylindrical portion 71 and the vertical line V are parallel to each other.
Therefore, the incident angle θ ₄ of the optical axis P of the imaging means 31 with respect to the upper surface 721A of the transmissive portion 721 can be made smaller than that of the conventional configuration, and the growing condition of the silicon single crystal SM from the outside of the chamber 21 is appropriate. Can be grasped.

(7) Since the flange portion 72 extends in a direction orthogonal to the central axis of the cylindrical portion 71 and is formed in the shape of an annular plate having a uniform thickness, the flange portion 72 can be easily manufactured.

(8) Since the cylindrical portion 71 is made of graphite, the weight of the purge tube 7 can be reduced and the cost can be reduced.

[Modification example]
The present invention is not limited to the above embodiment, and various improvements and design changes can be made without departing from the gist of the present invention.

For example, even if the transmission portion 522 is provided so that the angle θ ₁ formed by the upper surface 522A and the outer peripheral surface 51A of the cylindrical portion 51 is an acute angle and the incident angle of the optical axis P with respect to the upper surface 522A is 45 ° or more. good.
If the angle θ ₁ formed by the upper surface 522A and the outer peripheral surface 51A of the cylindrical portion 51 of the transmission portion 522 is less than 180 °, that is, if it is not 180 ° as in the conventional configuration, the optical axis P is incident on the upper surface 522A. It may be provided so that the angle exceeds 45 °. Even with such a configuration, the incident angle of the optical axis P with respect to the upper surface 522A can be made smaller than that of the conventional configuration, and it is possible to suppress the reflection component in the transmission portion 522 from being imaged by the image pickup means 31.
The transmission portions 522 and 721 may have a plate shape having a non-uniform thickness.
The upper surface 521A of the curved flange body portion 521 may function as a transmissive portion, and in this case, the entire flange portion 52 may be formed into a truncated cone shape.

The cylindrical portion 71 may be formed of a metal such as stainless steel or quartz, or the region other than the cylindrical portion 51, the flange body portion 521, and the region that functions as the transmission portion 721 of the flange portion 72 may be formed of graphite or metal. May be good.
The heat shield main body 251 of the heat shield 25 may be cylindrical, or the purge tube support portion 251A may not be provided on the heat shield main body 251.

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

First, the purge tube 9 as shown in FIG. 7A was placed inside the heat shield 25. As shown in FIG. 1 of the above-mentioned prior art document (Japanese Patent Laid-Open No. 2011-246341), the purge tube 9 is formed in a cylindrical shape by quartz. The lower end 91 of the purge tube 9 is supported by a protrusion 259 protruding inward from the lower end of the heat shield 25.

Using the single crystal pulling device having the configuration of FIG. 7A, a plurality of silicon single crystal SMs are manufactured by a single pulling method (a method of manufacturing one silicon single crystal using one quartz crucible). , The discoloration of the purge tube 9 was observed every time each silicon single crystal SM was manufactured. At this time, the gap G was adjusted while observing the growing condition with the optical observing means 3 through the side surface portion on the lower end side of the purge tube 9.

As shown in FIG. 7B, it was confirmed that discoloration began to occur after the production of the first silicon single crystal SM, and the discoloration color became darker as the number of productions increased. When a silicon single crystal was produced about 50 hours after the start of energization of the heater 23, the purge tube 9 was discolored to a state where it was difficult to observe with the optical observation means 3.
Then, the height H from the lower end 91 of the purge tube 9 to the upper end of the discoloration region A and the discolored position on the inner surface of the heat shield 25 were confirmed.
Based on this confirmation result, the position of the lower end of the transmission portion 522,721 is higher than the upper end position of the discoloration region A of the purge tube 9 and the upper end position of the discoloration region inside the heat shield 25. It was confirmed that there is a possibility that discoloration can be suppressed by installing 5 and 7.
Actually, in the configuration of the first and second embodiments, when the purge tubes 5 and 7 were installed at the positions based on the above confirmation results to manufacture the silicon single crystal SM, it exceeded 50 hours after the start of energization of the heater 23. No discoloration was seen.

1,1A ... Single crystal pulling device, 21 ... Chamber, 22 ... Crucible, 24 ... Pulling part, 25 ... Heat shield, 251A ... Purge tube support part, 3 ... Optical observation means, 5,7 ... Purge tube, 51, 71 ... Cylindrical part, 51A, 71A ... Outer peripheral surface, 52,72 ... Flange part, 522,721 ... Transmission part, 522A, 721A ... Top surface, M ... Silicon melt, SM ... Silicon single crystal.

Claims (9)

A crucible that houses the silicone melt,
A pulling part for growing a silicon single crystal by bringing the seed crystal into contact with the silicon melt and then pulling it up.
A cylindrical or truncated cone-shaped heat shield provided above the crucible so as to surround the silicon single crystal,
A chamber that houses the crucible and the heat shield,
A purge tube provided in the chamber.
A cylindrical portion formed in a cylindrical shape and guiding the inert gas introduced from the outside of the chamber to the silicon melt side, and a cylindrical portion.
It is provided with a collar portion that protrudes outward from the outer peripheral surface of the cylindrical portion in a collar shape.
At least a part of the flange portion includes a purge tube provided with a transmission portion that enables observation of the growth state of a silicon single crystal by an optical observation means provided outside the chamber .
A gas introduction unit that introduces an inert gas from the outside of the chamber into the inside of the chamber,
An optical observation means provided outside the chamber and for observing the growth state of the silicon single crystal via the transmission portion of the purge tube is provided.
A single crystal pulling device characterized in that a purge tube support portion for supporting the purge tube from below is provided on the inner peripheral surface of the heat shield . In the single crystal pulling device according to claim 1,
The single crystal pulling device is characterized in that the transmissive portion is formed so that the incident angle of the optical axis of the optical observation means with respect to the upper surface of the transmissive portion is 45 ° or less. In the single crystal pulling device according to claim 2.
The transmission portion is a single crystal pulling device characterized in that the incident angle is formed to be 0 °. In the single crystal pulling device according to any one of claims 1 to 3.
The transmission portion is a single crystal pulling device characterized in that it is made of flat plate-shaped quartz having a uniform thickness. In the single crystal pulling device according to any one of claims 1 to 4.
The flange portion is a single crystal pulling device characterized in that it is formed in the shape of an annular plate extending in a direction orthogonal to the central axis of the cylindrical portion. In the single crystal pulling device according to claim 5.
The flange portion is a single crystal pulling device characterized in that the thickness is uniformly formed. In the single crystal pulling device according to any one of claims 1 to 6.
A single crystal pulling device characterized in that the outer diameter of the flange portion is larger than the inner diameter of the lower end of a cylindrical or truncated cone-shaped heat shield provided in the chamber. In the single crystal pulling device according to any one of claims 1 to 7.
The single crystal pulling device characterized in that the cylindrical portion is formed of graphite. A method for producing a silicon single crystal using the single crystal pulling device according to any one of claims 1 to 8.
A method for producing a silicon single crystal, which comprises controlling the growth conditions of the silicon single crystal based on the observation result of the optical observation means.

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