KR20200066193A - Purge tube, Single crystal pulling device, silicon single crystal producdtion method - Google Patents

Abstract

A purge tube (5) comprises: a cylindrical unit (51) formed in a cylindrical shape, and guiding inert gas introduced from the outside of a chamber (21) toward a side of silicon melt (M); and a flange unit (52) protruding, in the form of a flange, from an outer circumferential surface of the cylindrical unit (51) toward the outside. At least a part of the flange unit (52) is provided with a transmission unit (522) which enables observation of the growth condition of a silicon single crystal (SM) by an optical observation means (3) provided outside the chamber (21).

Description

Purge tube, single crystal pulling device, and method for manufacturing silicon single crystal {Purge tube, Single crystal pulling device, silicon single crystal producdtion method}

The present invention relates to a purge tube, a single crystal pulling apparatus and a method for manufacturing a silicon single crystal.

Conventionally, during the production of a silicon single crystal, imaging is performed using an imaging means outside the chamber, and control of the growth conditions of the silicon single crystal is performed based on the growth situation of the silicon single crystal (for example, Document 1: Japanese Patent Publication 2011) -246341 publication).

The single crystal pulling apparatus described in Document 1 is equipped with a purge tube made of quartz. The purge tube has a transparent viewing window. Through this observation window, the CCD camera is capable of imaging the growth situation of the silicon single crystal.

However, in the structure of Document 1, since the surface of the observation window and the vertical line (a straight line extending in the direction of gravity) are parallel, the incident angle of the optical axis of the CCD camera with respect to the surface of the observation window is large. For this reason, there is a fear that the reflection image on the surface of the observation window is imaged with a CCD camera, and thus it is impossible to properly image the growth state of the silicon single crystal.

Patent Document 1: Japanese Patent Publication No. 2011-246341

An object of the present invention is to provide a purge tube, a single crystal pulling apparatus, and a method for manufacturing a silicon single crystal, which makes it possible to properly grasp the growth situation of a silicon single crystal from the outside of the chamber.

The purge tube of the present invention is a purge tube provided in a chamber of a single crystal pulling device, formed in a cylindrical shape, and a cylindrical portion guiding an inert gas introduced from the outside of the chamber toward the silicon melt side, and an outer side from the outer circumferential surface of the cylindrical portion. A flange portion protruding toward the flange type is provided, and at least a portion of the flange portion is provided with a transmission portion that enables observation of the growth state of the silicon single crystal by an optical observation means provided outside the chamber. It is characterized by.

The growth conditions of the silicon single crystal observed by the optical observation means are as follows: from the occurrence of the annular meniscus existing at the boundary between the silicon single crystal and the silicon melt, or from the liquid level of the silicon melt. The distance to the bottom of a heat shield (hereinafter sometimes referred to as a "gap") can be exemplified.

According to the present invention, by arranging a purge tube in a single crystal pulling apparatus so that the vertical axis and the central axis of the cylindrical portion are parallel, the angle of incidence of the optical axis of the optical observation means with respect to the upper surface of the transmissive portion is configured as in the above document 1 (hereinafter, "conventional configuration" It can be made small compared with "." Therefore, it is possible to suppress the reflection component on the upper surface of the transmissive part from being observed by the optical observation means, and it is possible to appropriately grasp the growth condition of the silicon single crystal by the optical observation means.

If it is not possible to properly grasp the growth status of the silicon single crystal, the problem that the gap during silicon single crystal manufacturing cannot be precisely controlled, the problem that the diameter of the silicon single crystal being manufactured cannot be precisely controlled, and furthermore, the diameter of the silicon single crystal is controlled. There is a concern that the pulling rate control, which is closely related to, cannot be performed precisely.

Since the present invention can appropriately grasp the growth situation of the silicon single crystal, it is very suitable for precise gap control, precise silicon single crystal diameter control, or precise pulling speed control, or the production of silicon single crystal for semiconductors where they are simultaneously required. .

In the purge tube of the present invention, it is preferable that the transmission 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 transmission portion is 45° or less.

The case where the angle of incidence is 45° or less includes both the case where the angle between the outer circumferential surface of the cylindrical portion and the upper surface of the transmissive portion when viewed from the side becomes an acute angle and an obtuse angle.

ADVANTAGE OF THE INVENTION According to this invention, it can further suppress that the reflection component in the upper surface of a transmission part is observed by optical observation means. In addition, it is more preferable that the angle of incidence is 22.5° or less.

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

When the incident angle is 0°, in addition to 0°, a range of -5° to 5° is also included.

ADVANTAGE OF THE INVENTION According to this invention, it can prevent that the reflection component in the upper surface of a transmission part is observed with an optical observation means.

In the purge tube of the present invention, it is preferable that the permeable portion is formed of a flat plate-shaped quartz.

According to the present invention, deformation of the observation result at the time of two-dimensional observation can be suppressed, and the growth condition 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 a toric plate shape extending in a direction perpendicular 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, by making the flange portion a simple shape, the flange portion can be easily produced.

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 conical cylindrical heat shield provided in the chamber.

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

In the purge tube of the present invention, it is preferable that the cylindrical portion is formed of graphite.

According to the present invention, it is possible to reduce the weight and cost down of the purge tube.

The single crystal pulling apparatus of the present invention includes a crucible that accommodates a silicon melt, an impression portion that fosters a silicon single crystal by pulling after seed crystals are brought into contact with the silicon melt, and the silicon single crystal above the crucible. Cylindrical heat shield provided to surround the, the above-described purge tube, the crucible, the chamber to accommodate the heat shield and the purge tube, and a gas introduction unit for introducing an inert gas from the outside of the chamber into the interior of the chamber And, it is provided on the outside of the chamber, it characterized in that it comprises an optical observation means for observing the growth state of the silicon single crystal through the transmission portion of the purge tube.

In the single crystal pulling apparatus of the present invention, it is preferable that a purge tube support portion for supporting the purge tube from below is provided on the inner circumferential surface of the heat shield. 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, when the flange portion is supported from below, the purge tube is not tilted and is stable.

The method for manufacturing a silicon single crystal of the present invention is a method for manufacturing a silicon single crystal using the above-described single crystal pulling apparatus, and is characterized by controlling the growth conditions of the silicon single crystal based on the observation result of the optical observation means.

According to the embodiment of the present invention, it is possible to appropriately grasp the growth status of the silicon single crystal by means of optical observation. Further, since the growth status of the silicon single crystal can be grasped appropriately, it is very suitable for precise gap control, precise silicon single crystal diameter control, or precise pulling speed control, or the production of silicon single crystals for semiconductors that require them simultaneously.

1 is a schematic view of a single crystal pulling apparatus according to a first embodiment of the present invention.
2 is an enlarged view of a main part of a single crystal pulling device in the first embodiment.
3A is a plan view showing a purge tube in the first embodiment.
3B is a cross-sectional view showing a purge tube in the first embodiment.
3C shows a purge tube in the first embodiment, and is a cross-sectional view taken along line IIIC-IIIC in FIG. 3B.
4A is a plan view showing a purge tube according to a second embodiment of the present invention.
4B shows a purge tube according to a second embodiment of the present invention, and is a cross-sectional view taken along line IVB-IVB in FIG. 4A.
5 is a schematic view of a single crystal pulling device in the second embodiment.
6 is an enlarged view of a main part of a single crystal pulling apparatus in the second embodiment.
7A shows an embodiment of the present invention, and is a cross-sectional view showing a state near the surface of a silicon melt in an experimental example.
7B is a perspective view of a purge tube showing an embodiment of the present invention.

[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 apparatus 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 have.

The pulling device main body 2 includes a chamber 21, a crucible 22 disposed in the chamber 21, a heater 23 heating the crucible 22, a pulling portion 24, and heat A shielding body 25, a heat insulating material 26 provided on the inner wall of the chamber 21, and a crucible driving part 27 are provided.

However, the single crystal pulling device 1 is a device used in a magnetic field applied Czochralski (MCZ) method, as indicated by a chain of dashed lines, as long as the crucible 22 is disposed on the outside of the chamber 21. It may have a pair of electromagnetic coils 28.

The chamber 21 includes a main chamber 211 and a full chamber 213 connected to the upper portion of the main chamber 211 via a gate valve 212.

The main chamber 211 is formed in a shape of the upper surface, and the main body 211A, on which the crucible 22, the heater 23, the heat shield 25, and the like are disposed, and the upper surface of the main body 211A are closed. A cover portion 211B to be provided is provided. The cover portion 211B includes an opening portion 211C for introducing an inert gas such as Ar gas into the main chamber 211, and a window portion made of quartz for the optical observation means 3 to observe the inside of the chamber 21 ( 211D) is provided. A support portion 211E extending inward is provided between the body portion 211A and the cover portion 211B.

The full 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 gas in the main chamber 211 is provided below the main body 211A of the main chamber 211.

The crucible 22 is provided with a quartz crucible 221 and a graphite crucible 222 accommodating the quartz crucible 221.

The heater 23 is disposed around the crucible 22 and melts silicon in the crucible 22.

The pulling unit 24 includes a cable 241 to which a seed crystal SC is attached, and an pulling driving unit 242 for moving the cable 241 up and down and rotating.

The heat shield 25 is provided to surround the silicon single crystal SM, and blocks radiant heat radiated upward from the heater 23. The heat shield 25 includes a heat shield body portion 251 formed in a conical cylindrical shape that decreases in diameter as it goes downward and a supported portion 252 extending in a flange shape toward the outside from the top of the heat shield body portion 251. I have it. As shown in Fig. 2, the heat shield body portion 251 is provided with a purge tube support portion 251A continuously protruding from its inner circumferential direction in the circumferential direction.

The heat shield 25 is disposed above the crucible 22 by fixing the supported portion 252 on the support portion 211E.

The crucible driving unit 27 includes a support shaft 271 supporting the graphite crucible 222 from below, and rotates and elevates the crucible 22 at a predetermined speed.

The optical observing means 3 observes the occurrence condition of the meniscus existing in the liquid surface of the silicon melt M, the gap G, and the like as the growth condition of the silicon single crystal SM. The optical observation means 3 is provided with an imaging means 31 and a computation means 32. The imaging means 31 is, for example, a two-dimensional CCD camera, and photographs the liquid level of the silicon melt M from the outside of the chamber 21 through the window portion 211D. The calculation means 32 calculates and calculates the growth status of the silicon single crystal SM based on the imaging result of the imaging means 31.

The control unit 4 manufactures the silicon single crystal SM based on various information stored in the memory 41 or the operation of the operator. Examples of the information stored in the memory 41 include gas flow rate in the chamber 21, internal pressure of the furnace, electric power input to the heater 23, and the number of rotations of the crucible 22 and the silicon single crystal SM. can do.

〔Composition of purge tube〕

Next, the configuration of the purge tube provided in the single crystal pulling device 1 will be described.

3A to 3C, the purge tube 5 is provided with a cylindrical cylindrical portion 51 and a flange portion 52 protruding in a flange shape from the lower end of the cylindrical portion 51 toward the outside. have.

The flange portion 52 is formed in a conical cylindrical shape that increases in diameter as it goes downward. The flange portion 52 includes a flange 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 a conical cylindrical shape having a uniform thickness is cut off when viewed from a plane. That is, the upper surface 521A of the flange body portion 521 is a curved surface.

The transparent portion 522 is formed in a flat plate shape having a uniform thickness. That is, the upper surface 522A of the transmissive portion 522 is flat. The permeable portion 522 is provided so as to fill the cut-off portion of the flange body portion 521. The transmissive portion 522 is provided so that the angle θ ₁ formed between the upper surface 522A and the outer peripheral surface 51A of the cylindrical portion 51 when viewed from the side is an obtuse angle. As shown in FIG. 2, the transmissive part 522 is the angle of incidence of the optical axis P of the imaging means 31 with respect to the upper surface 522A (the angle of the optical axis P with respect to the normal N of the upper surface 522A) ) Is provided to be 45° or less. In the first embodiment, the angle of incidence is 0°, that is, the angle θ ₂ between the upper surface 522A and the optical axis P is 90°.

The cylindrical portion 51, the flange body portion 521, and the transmissive portion 522 are each formed of transparent quartz, and these are welded so that the central axis of the cylindrical portion 51 and the central axis of the flange body portion 521 coincide. It is integrated by. When viewed in 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 opening of the heat shield 25. The silicon single crystal SM passes through the inside of the cylindrical portion 51 and is pulled upward.

(Configuration of a single crystal pulling device having a purge tube)

1 and 3A to 3C, the purge tube 5 is supported by the purge tube support portion 251A where the flange portion 52 protrudes from the inner circumferential surface of the heat shield body portion 251, It is positioned so that the distance from the liquid surface of the silicon melt M to the permeable portion 522 is L ₁ . By setting this distance as L ₁ , the position of the lower end of the transmissive portion 522 is higher than the upper position of the discoloration region A of the purge tube 9 in the embodiment described later. Further, the purge tube 5 is positioned such that the central axis of the cylindrical portion 51 and the central axis of the heat shield 25 coincide, and the central axis of the cylindrical portion 51 is parallel to the vertical line V. have.

A draw tube 29 may be provided in the pulling device main body 2. The draw tube 29 is formed of a cylindrical shape, for example, of a metal whose inner diameter is larger than the outer diameter of the cylindrical portion 51 of the purge tube 5. The draw tube 29 has its outer circumferential surface fixed to the inner circumferential surface of the opening 211C of the cover portion 211B, so that its lower end is located inside the heat shield 25, and also the upper end of the flange portion 52 is located therein. Can be arranged. Incidentally, in this embodiment, the purge tube 5 and the draw tube 29 are not in contact, but both may be in contact.

(Method for producing silicon single crystal)

Next, a method for manufacturing a silicon single crystal (SM) using the single crystal pulling apparatus 1 will be described.

However, a silicon single crystal (SM) capable of acquiring a silicon wafer of 200 mm, 300 mm, 450 mm or the like can also be manufactured by this manufacturing method.

First, the control unit 4 of the single crystal pulling device 1 is a flow rate of an inert gas that is a pulling condition for satisfying the quality required for the silicon single crystal SM, for example, resistivity and oxygen concentration, inside the chamber 21. The pressure, the number of revolutions of the crucible 22 or the silicon single crystal SM, and the heating conditions of the heater 23 are set. In addition, this setting condition may be input by the operator, or may be calculated and calculated by the control unit 4 based on the target oxygen concentration input by the operator.

Next, the control unit 4 melts the polysilicon material (silicon raw material) in the crucible 22 by heating the crucible 22 to generate a silicon melt (M). In addition, the silicon melt M may contain a dopant for adjusting the resistivity of the silicon single crystal SM.

Thereafter, the controller 4 introduces an inert gas from the gas inlet 21A into the chamber 21 at a predetermined flow rate, and also depressurizes the pressure in the chamber 21 to inert an atmosphere under reduced pressure in the chamber 21. Keep it.

Thereafter, the controller 4 immerses the seed crystal SC into the silicon melt M to rotate the crucible 22 and the cable 241 in a predetermined direction, while pulling the corresponding cable 241 to raise the silicon single crystal ( SM).

During the growth of the silicon single crystal SM, silicon in the silicon melt M may evaporate and react with oxygen to generate SiO. When this SiO adheres to and adheres to the inner wall of the cover portion 211B of the main chamber 211, the aggregate passes through the inside of the heat shield 25 and falls into the silicon melt (M), resulting in silicon single crystal (SM). There is a risk of polycrystallization. However, in this embodiment, since the entire circumference of the outer edge of the conical cylindrical flange portion 52 is in contact with the inner circumferential surface of the heat shield 25, even if aggregates fall inside the heat shield 25, the flange portion ( 52) can prevent the agglomerate from reaching the silicon melt (M).

Further, during the growth of the silicon single crystal (SM), the optical observation means (3) images the image of the silicon melt (M) or the silicon single crystal (SM) passing through the transmission portion (522) with the imaging means (31). , Based on this imaging result, the growth condition of the silicon single crystal SM is calculated by the calculation means 32. Then, the control unit 4 controls the growth conditions such as the diameter of the silicon single crystal SM or the gap G so that the desired silicon single crystal SM is produced based on the growth situation obtained by the optical observation means 3.

(Operational effects of the first embodiment)

According to the first embodiment, the following operational 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 vertical axis V and the central axis of the cylindrical portion 51 are parallel.

For this reason, the angle of incidence of the optical axis P of the imaging means 31 with respect to the upper surface 522A of the transmissive portion 522 can be reduced compared to the conventional configuration. As a result, it is possible to suppress the reflection component on the upper surface 522A of the transmissive portion 522 from being imaged by the imaging means 31, and to properly grasp the growth condition of the silicon single crystal SM outside the chamber 21. Can be.

(2) In particular, since the transmissive portion 522 is configured such that the incident angle of the optical axis P with respect to the upper surface 522A is 0°, the reflection component in the upper surface 522A is imaged by the imaging means 31 Can be prevented.

(3) In addition, since the thickness of the plate-shaped transmission portion 522 is made uniform, deformation (distortion) of the observation result during two-dimensional observation can be suppressed.

By the effects of these (2) and (3), the imaging means 31 can capture an image in which the actual situation of the silicon melt M or the silicon single crystal SM is reflected almost accurately and clearly. In particular, the boundary between the silicon melt (M) and the silicon single crystal (SM) and the surrounding image can be cleared.

As a result, the growth situation of the silicon single crystal SM can be grasped almost accurately from outside the chamber 21. In addition, the diameter and the gap G of the silicon single crystal SM can be precisely controlled based on the grasping situation. That is, it becomes possible to accurately grasp the amount of separation with respect to the desired diameter or the amount of separation with respect to the desired gap G by the cleared image, and to control the amount of separation.

(4) Since the outer diameter of the flange portion 52 is made larger than the inner diameter of the lower opening of the heat shield 25, the purge tube 5 can be easily installed only by contacting the flange portion 52 with the heat shield 25. Can be.

(5) Since the purge tube 5 is positioned so that the distance from the liquid surface of the silicon melt M to the permeable part 522 is L ₁ , the permeable part 522 is discolored by the radiant heat of the silicon melt M. Can be suppressed.

This discoloration occurs because silicon oxide (SiOx) is attached to and bonded to the permeable portion 522, and thus can be removed by acid washing with hydrofluoric acid or the like, but leads to an increase in manufacturing cost because of the removal cost.

In the above embodiment, since discoloration of the transmissive portion 522 can be suppressed, an increase in cost can be suppressed.

[Second Embodiment]

Next, a second embodiment of the present invention will be described with reference to the drawings.

However, the same reference numerals are given to the same configuration as in the first embodiment, and the description is omitted or simplified.

〔Composition of purge tube〕

First, the configuration of the purge tube will be described.

4A and 4B, the purge tube 7 includes a cylindrical cylindrical portion 71 and a flange portion 72 protruding in a flange shape toward the outside from the lower end of the cylindrical portion 71. have. As shown in Fig. 5, the outer diameter of the flange portion 72 is larger than the inner diameter of the lower opening of the heat shield 25, and furthermore, larger than the inner diameter of the upper opening of the heat shield 25.

The cylindrical portion 71 is formed of graphite.

The flange portion 72 is formed 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 a toric plate shape having a uniform thickness. The outer diameter of the flange portion 72 is larger than the inner diameter of the lower opening of the heat shield 25 and further larger than the inner diameter of the upper opening of the heat shield 25. When the purge tube 7 is provided in the chamber 21, a part of the region including the portion overlapping the optical axis P of the imaging means 31 in the flange portion 72 functions as the transmission portion 721. . For example, in FIG. 4A, the region surrounded by the double-dashed line functions as the permeable portion 721, but the other region may be the permeable portion 721 depending on the installation state of the purge tube 7. With this configuration, the upper surface 721A of the transmissive portion 721 becomes a flat surface.

A circular positioning groove portion 72B along the inner edge of the toric plate shape is provided on the upper surface 72A of the flange portion 72. Both are positioned so that the central axis of the cylindrical portion 71 coincides with the central axis of the flange portion 72 by fitting the lower end of the cylindrical portion 71 into the positioning groove portion 72B. The transmissive portion 721 is provided so that the angle θ ₃ between the upper surface 721A and the outer peripheral surface 71A of the cylindrical portion 71 when viewed from the side is a right angle.

(Configuration of a single crystal pulling device having a purge tube)

5 and 6, the purge tube 7 is provided in the chamber 21 of the single crystal pulling apparatus 1A. Since the purge tube 7 is larger than the inner diameter of the upper opening of the heat shield 25, it can be placed on the upper surface of the supported portion 252 of the heat shield 25. When the flange portion 72 is placed on the upper surface of the supported portion 252 of the heat shield 25, the distance L ₂ from the liquid level of the silicon melt M to the permeable portion 721 is the distance of the first embodiment. It can be longer than (L ₁ ), and the position of the lower end of the transmission portion 721 can be reliably higher than the upper position of the discoloration region A of the purge tube 9. Furthermore, since the purge tube 7 can be avoided from being exposed to high temperatures compared to the first embodiment, more repeated use becomes possible.

In addition, the purge tube 7 is positioned so that the central axis of the cylindrical portion 71 coincides with the central axis of the heat shield 25 and the central axis of the cylindrical portion 71 is parallel to the vertical line V. have. Furthermore, the purge tube 7 is positioned such that a portion of its upper side is located in the opening 211C of the cover portion 211B. Although the purge tube 7 and the opening 211C are not in contact, both may be in contact.

As described above, the incidence 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 by the purge tube 7 being supported in the chamber 21 (the upper surface 721A) The angle of incidence (θ ₄ ) of the optical axis P with respect to the normal (N) is 45° or less.

(Method for producing silicon single crystal)

Next, a method of manufacturing the silicon single crystal SM using the single crystal pulling apparatus 1A will be described.

However, since the manufacturing process of the silicon single crystal (SM) is the same as that of the first embodiment, only differences according 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, there is a fear that aggregates of SiO may fall inside the heat shield 25 due to evaporation of the silicon melt M. In this embodiment, the outside of the toric plate flange portion 72 Since the entire circumference of the edge is located outside the upper opening of the heat shield body portion 251, it is possible to prevent aggregates from reaching the silicone melt M by the flange portion 72.

Further, during the growth of the silicon single crystal SM, the imaging means 31 of the optical observation means 3 images the image passing 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.

(Operational effects of the second embodiment)

According to the second embodiment, in addition to the same effects as (4) and (5) of the first embodiment, the following effects can be achieved.

(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 vertical axis V and the central axis of the cylindrical portion 71 are parallel.

For this reason, the angle of incidence 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 silicon is outside the chamber 21. It is possible to properly grasp the single crystal (SM) nurturing situation.

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

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

[Modification example]

However, the present invention is not limited to the above embodiments, and various improvements and design changes are possible without departing from the scope of the present invention.

For example, the angle θ ₁ between the upper surface 522A and the outer peripheral surface 51A of the cylindrical portion 51 becomes an obtuse angle, and the incident angle of the optical axis P with respect to the upper surface 522A is, for example, the transmissive portion 522. It may be provided to be 45° or more.

If the angle θ ₁ between the upper surface 522A and the outer circumferential surface 51A of the cylindrical portion 51 is less than 180°, that is, if the 180° is not 180° as in the conventional configuration, the transmissive part 522 is to the upper surface 522A The incident angle of the optical axis P may be provided to exceed 45°. Even in such a configuration, the angle of incidence 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 imaging means 31. .

The transmissive 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 transmission portion, and in this case, the entire flange portion 52 may be formed in a conical cylindrical shape.

The cylindrical portion 71 may be formed of metal or quartz, such as stainless steel, and graphite or metal other than the region serving as the transmission portion 721 of the cylindrical portion 51 or the flange body portion 521 or the flange portion 72 It can also be formed.

The heat shield body portion 251 of the heat shield body 25 may be cylindrical, or the purge tube support portion 251A may not be provided in the heat shield body portion 251.

Example

Next, the present invention will be described in more detail by examples, but the present invention is not limited by these examples at all.

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

A single pulling method (a method of manufacturing a single silicon single crystal using a single quartz crucible) using a single crystal pulling apparatus having the configuration of FIG. 7A is prepared, and each silicon single crystal (SM) Discoloration of the purge tube 9 was observed each time. At this time, the gap G was adjusted while observing the growth condition with the optical observation means 3 through the side portion of the lower side of the purge tube 9.

After the production of the first silicon single crystal (SM), as shown in FIG. 7B, discoloration began to occur, and it was confirmed that the discoloration color became darker as the number of the productions increased. The purge tube 9 was discolored until the observation with the optical observation means 3 was difficult at the time when the silicon single crystal was produced about 50 hours after the start of energization of the heater 23.

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 position of the inner surface of the heat shield 25 were discolored.

Based on the result of the check, the purge tube (such that the lower positions of the transmissive parts 522 and 721 are higher than the upper position of the discoloration area A of the purge tube 9 and the upper position of the discoloration area inside the heat shield 25. It was confirmed that discoloration could be suppressed by providing 5 and 7).

In fact, in the configuration of the first and second embodiments, the purge tubes 5 and 7 were installed at positions based on the confirmation result to produce silicon single crystals SM, and 50 hours after the energization of the heater 23 was started. Discoloration was not seen even if it exceeded.

Claims (11)

A purge tube provided in a chamber of a single crystal pulling device,
A cylindrical portion formed in a cylindrical shape and guiding an inert gas introduced from the outside of the chamber toward a silicon melt,
It has a flange portion protruding from the outer circumferential surface of the cylindrical portion toward the outside in a flange shape,
A purge tube, characterized in that at least a part of the flange portion is provided with a transmission portion that enables observation of the growth state of the silicon single crystal by an optical observation means provided outside the chamber. The purge tube according to claim 1,
The transmission portion is a purge tube, characterized in that the incidence angle of the optical axis of the optical observation means with respect to the upper surface of the transmission portion is formed to be 45 ° or less. The purge tube according to claim 2,
The transmission portion is a purge tube characterized in that the incidence angle is formed to be 0 °. The purge tube according to claim 1,
The transmission portion is a purge tube characterized in that it is formed of a quartz plate of a uniform thickness. The purge tube according to claim 1,
The flange portion is a purge tube, characterized in that formed in a toric plate shape extending in a direction orthogonal to the central axis of the cylindrical portion. The purge tube according to claim 5,
The flange portion is a purge tube, characterized in that the thickness is formed uniformly. The purge tube according to claim 1,
The outer diameter of the flange portion is a purge tube, characterized in that larger than the inner diameter of the lower end of the cylindrical or conical cylindrical heat shield provided in the chamber. The purge tube according to claim 1,
The cylindrical portion is a purge tube, characterized in that formed by graphite. A crucible to accommodate the silicone melt,
An impression portion for fostering a silicon single crystal by pulling the seed crystal after contacting it with the silicon melt,
And a cylindrical heat shield provided to surround the silicon single crystal in the upper portion of the crucible,
The purge tube according to any one of claims 1 to 8,
A chamber accommodating the crucible, the heat shield, and the purge tube,
A gas introduction unit for introducing an inert gas from the outside of the chamber into the interior of the corresponding chamber;
It is provided on the outside of the chamber, the single crystal pulling device, characterized in that it comprises an optical observation means for observing the growth state of the silicon single crystal through the transmission portion of the purge tube. In the single crystal pulling apparatus according to claim 9,
A single crystal pulling device, characterized in that a purge tube support for supporting the purge tube from below is provided on the inner circumferential surface of the heat shield. A method for producing a silicon single crystal using the single crystal pulling apparatus according to claim 9,
A method for producing a silicon single crystal, wherein the growth conditions of the silicon single crystal are controlled based on the observation result of the optical observation means.

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