JPH09202685A - Single crystal pulling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent lowering of yield caused by occurrence of segregation and improve yield concerning electrical resistivity by disposing a heat blocking material having a specific height below a heater arranged around a crucible and the upper part of the crucible. SOLUTION: A heat blocking material 21 having 10-500mm height, whose inner wall is positioned more inside than the outside of a heater 12 is installed at a distance of 5-200mm below the heater 12 arranged around a crucible 11 and the upper part of the crucible 11. The crucible 11 is moved to a position at which the heater 12 is most effective to melt all of raw materials for crystal by operating a lifting and lowering device of a supporting shaft 20 and the raw materials for crystal are melted by applying electric current to the heater 12. Then, the crucible 11 is moved so that the heater 12 is positioned at the upper part of the crucible 11 and a melted layer 13 is formed in the upper layer and a solid layer 14 is formed in the lower layer and the melted layer 13 is brought into contact with a seed crystal 17 attached to a seed chuck 16 and a single crystal 18 is pulled up by pulling up the seed crystal 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal pulling apparatus, and more particularly to a single crystal pulling apparatus capable of pulling a high quality Si single crystal used as a semiconductor material.

[0002]

2. Description of the Related Art There are various methods for growing a single crystal, and one of the typical methods is the Czochralski method (hereinafter referred to as the CZ method). FIG. 4 is a cross-sectional view schematically showing a single crystal pulling apparatus used in the conventional CZ method, and 41 in the figure shows a crucible.

The crucible 41 comprises a bottomed cylindrical quartz inner layer holding container 41a and a bottomed cylindrical graphite outer layer holding container 41b fitted to the outside of the inner layer holding container 41a. The crucible 41 is supported by a support shaft 48 that rotates at a predetermined speed in the direction of the arrow in the figure. A resistance heating type heater 42 is provided outside the crucible 41.
However, the heat insulating cylinders 47 are arranged concentrically outside the heater 42, and the heater 42 is provided inside the crucible 41.
The melt 43 of the crystallization raw material melted by the above is filled. A pulling shaft 44 made of a pulling rod, a wire, or the like is hung on the central axis of the crucible 41, and the seed crystal 45 attached to the tip of the pulling shaft 44 via the seed chuck 44a is melted.
3 is brought into contact with the surface of the support shaft 48 and is rotated at the same speed as the support shaft 48 in the same direction or in the opposite direction at a predetermined speed, and
By pulling up 4, the melt 43 is solidified and the single crystal 46 is grown.

By the way, the single crystal 46 made of semiconductor is
In the case of pulling by the Z method, impurities such as phosphorus are often added to the melt 43 before pulling in order to adjust the electric resistivity and electric conductivity type of the single crystal 46. But normal C
In the Z method, there is a problem that a single crystal 46 having a uniform electric resistivity in the growth axis direction of the single crystal 46 cannot be obtained due to a so-called segregation phenomenon occurring between the single crystal 46 and the melt 43. there were.

The above-mentioned segregation phenomenon means the concentration of impurities taken into the single crystal 46 at the interface between the single crystal 46 and the melt 43 when the melt 43 solidifies and the single crystal 46 grows, and the melt 43. However, the effective segregation coefficient Ke (impurity concentration of 46 in single crystal / impurity concentration in melt 43) is often smaller than 1. In this case, since the single crystal 46 grows and the impurity concentration in the melt 43 gradually increases due to the segregation phenomenon, the impurity concentration in the single crystal 46 also gradually increases,
Electric resistance becomes smaller. Therefore, some of the single crystals 46 pulled by the above method do not meet the standard regarding the electrical resistivity, and the yield is lowered.

Therefore, a melt layer method has been developed as a single crystal pulling method for the purpose of preventing the yield from decreasing due to the occurrence of the above-mentioned segregation phenomenon and increasing the yield related to the electrical resistivity.

FIG. 5 is a sectional view schematically showing a single crystal pulling apparatus used in the melt layer method. The basic feature of this melting layer method is that the raw material for crystallization in the crucible 11 having substantially the same structure as that shown in FIG. 4 is once melted by the heater 12, then the melting layer 13 is formed on the upper layer, and the lower layer is formed. Solid layer 14
Is formed, and the solid layer 14 is gradually eluted with the growth of the single crystal 18 to keep the impurity concentration in the molten layer 13 constant.

In this apparatus, since the heater 12 having a short length as shown in the figure is used, before the heater 12 is energized, first, the raising / lowering mechanism of the support shaft 20 is operated to cause the heater 12 to remove all the crystal raw material. The crucible 11 is moved to the most efficient position for melting. Next, the heater 12 is energized to melt all the crystal raw material, and then the supporting shaft 20
The elevating mechanism is operated to move the crucible 11 so that the heater 12 is located above the crucible 11, and the heater power is adjusted to form the solid layer 14 in the lower layer. In this single crystal pulling apparatus, the configuration of members other than the heater 12 is almost the same as the apparatus used in the CZ method,
Except for the above-mentioned part, the pulling method of the single crystal 18 is also CZ.
It is almost the same as the raising method by the law.

In the melt layer method, there are roughly proposed two methods for keeping the impurity concentration in the melt layer 13 constant. That is, there are a melt layer thickness constant method for keeping the volume (depth) of the melt layer 13 constant and a melt layer thickness changing method for changing the volume (depth) of the melt layer 13.

According to the above-mentioned constant melt layer thickness method, the solid layer 14 containing no impurities is melted as the single crystal 18 is pulled up, and the volume of the melt layer 13 is kept constant. There is a method in which the impurity concentration in the melted layer 13 is kept constant by adding it in a desired manner. JP-B-44-8242, JP-B-62-880 and JP-B-3-7405.
The above-mentioned method is disclosed in Japanese Patent Publication No. Further, the solid layer 14 is first made to contain impurities, the impurities are not added to the molten layer 13, the volume of the molten layer 13 is kept constant during the pulling of the single crystal 18, and the impurity concentration of the molten layer 13 is kept constant. A method of keeping the temperature substantially constant is disclosed in JP-B-62-880 and JP-A-63-252989.

In the melt layer thickness changing method, the melt layer 1 is intentionally used.
3 is a method of keeping the impurity concentration in the melted layer 13 constant without adding impurities during the pulling of the single crystal 18 by changing the volume of No. 3 of JP-A-61-20569.
It is disclosed in Japanese Patent Laid-Open No. 61-205692 and Japanese Patent Laid-Open No. 61-215285.

In the above two melt layer methods,
The thickness of the molten layer 13 can be controlled, for example, by the number of heaters 12 as heating elements, length, power, position of the crucible 11, the outer circumference of the heater 12, and a heat insulating cylinder that suppresses heat transfer under the crucible 11. This is performed by appropriately selecting the shape and material of 19a.

As described above, since the impurity concentration in the melted layer 13 can be kept substantially constant in the melted layer method, it is possible to prevent the decrease in the yield due to the conventional change in the electrical resistivity.

[0014]

However, silicon single crystals for manufacturing semiconductor wafers tend to be large in size in order to reduce production costs, and the crucible 11 used tends to have a larger inner diameter accordingly. is there. Therefore, when the raw material for crystallization is melted in the crucible 11, a molten liquid layer having a large liquid surface area and a shallow depth is formed. Therefore, when trying to pull up a single crystal by the fusion layer method, the thickness of the solid layer 14 formed near the bottom surface of the crucible 11 is inevitably thin, which makes the formation of the solid layer 14 itself difficult. There were challenges.

Japanese Unexamined Patent Publication (Kokai) No. 5-21472 discloses a single crystal pulling apparatus which facilitates formation of a solid layer. FIG. 6 is a cross-sectional view showing the single crystal pulling apparatus described in the above publication.

In this single crystal pulling apparatus, the crystal raw material in the crucible 11 is melted by using the two heaters 12a and 12b, and the solid state layer 14 is formed by stopping the energization of the lower heater 12b. After this, the two-stage heater 12
By controlling the powers of a and 12b, the single crystal 18 is pulled up while controlling the elution amount of the solid layer 14. Although the solid layer 14 can be formed more efficiently than the conventional apparatus by the above method, the temperature of the lower heater 12b that has been once heated does not immediately drop, so that the solid layer 14 can be formed quickly. I couldn't say I could.

Therefore, Japanese Unexamined Patent Publication (Kokai) No. 6-85365 discloses a single crystal pulling apparatus in which a heat shield plate is arranged between two heaters so that the heat shield plate can move in and out. According to this single crystal pulling apparatus, after completely melting the raw material for crystallization in the crucible, the heat shield plate is inserted between the upper heater and the lower heater to speed up the formation of the solid layer. be able to.

However, in the above-mentioned single crystal pulling apparatus, since the heat shield plate is inserted from the circumferential side surface, there is a problem that the mechanism for inserting the heat shield plate becomes very complicated.

Further, Japanese Patent Laid-Open No. 12389/1993 discloses that
A single crystal pulling apparatus is disclosed in which a radiant heat shield is provided below the heater mainly for the purpose of blocking radiant heat from the heat retaining cylinder. By using the device, a solid layer is formed faster than in the conventional case. However, since the radiant heat blocker disclosed in the above publication is installed for the purpose of blocking radiant heat from the heat-insulating cylinder, it is a plate-like body made of Mo or W arranged vertically, and the radiant heat blocker is Therefore, the effect of directly blocking the radiant heat from the heater cannot be expected, and even in this case, it cannot be said that the solid layer 14 can be rapidly formed.

The present invention has been made in view of the above problems, and after melting the raw material for crystallization in the crucible, the radiant heat radiated from the heater to the lower part of the crucible is cut off, so that the bottom of the crucible is solidified. It is an object of the present invention to provide a single crystal pulling apparatus capable of rapidly forming a layer.

[0021]

Means for Solving the Problems and Effects Thereof In order to achieve the above object, a single crystal pulling apparatus (1) according to the present invention
Is a single crystal pulling apparatus equipped with a crucible and a heater arranged around the upper part of the crucible.
A heat shield having a height of 10 to 500 mm and an inner wall located inside the outer surface of the heater is disposed at a distance of up to 200 mm.

According to the above single crystal pulling apparatus (1),
Move the crucible so that the heater is at an appropriate position to melt all the crystal raw material in the crucible and efficiently melt the crystal raw material, and then further move the crucible so that the heater is located above the crucible. By moving, the radiant heat radiated to the lower part of the crucible can be blocked by the heat blocker,
A solid layer can be formed quickly.

Single crystal pulling apparatus (2) according to the present invention
In the above single crystal pulling apparatus (1), the heat shield is installed so as to be movable in the vertical direction.

According to the above single crystal pulling apparatus (2),
The melting of the crystal raw material in the crucible by the heater can be performed in a state where the heat shield is located in the lower part of the chamber, so that the crystal raw material is efficiently heated without being disturbed by the heat shield,
It can be melted, while the solid layer can be formed with the heat blocker being moved to the vicinity of the lower part of the heater, so that the radiant heat radiated to the lower part of the crucible can be blocked by the heat blocker. The solid layer can be quickly formed.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment (1) of a single crystal pulling apparatus according to the present invention will be described below.

FIG. 1 is a sectional view schematically showing a single crystal pulling apparatus according to the embodiment (1), and FIG. 2 schematically shows the vicinity of a heat shield 21 in the single crystal pulling apparatus. It is an expanded sectional view. The single crystal pulling apparatus is constructed in the same manner as the conventional single crystal pulling apparatus shown in FIG. 5 except for the heat blocker 21 arranged on the heat retaining wall 19a, and the single crystal pulling method is almost the same. Because there is
Here, detailed description thereof is omitted, and the solid layer 1 using the configuration of the heat shield 21 and the heat shield 21 is omitted.
Processes up to forming 4 will be described.

As shown in FIG. 2, the distance between the lower surface of the heater 12 and the upper surface of the heat shield 21 is L, the height of the heat shield 21 is H, and the extension line of the outer surface of the heater 12 and the heat When the distance from the extension line of the inner wall of the barrier 21 is R, L is 5 to 2
The range is 00 mm, and H is usually in the range of 10 to 500 mm, although it depends on the kind of the heat insulating material. R is 0 mm
20 mm or more is more preferable, but the inner wall of the heat shield 21 should be positioned so as not to collide with the side surface of the crucible 11 when the crucible 11 is moved.

If the distance L between the lower surface of the heater 12 and the upper surface of the heat shield 21 is less than 5 mm, the heater 12 and the heat shield 21 may come into contact with each other. It is difficult for the radiant heat of 12 to reach the lower side, and on the other hand, when L exceeds 200 mm, the heat shield effect by the heat shield 21 becomes weak.

If the height H of the heat shield 21 is less than 10 mm, the thickness of the heat shield 21 is too thin, and the heat shield 21 is too thin.
If the heat insulation effect due to is weak and H exceeds 500 mm, the heat insulating material 21 keeps the vicinity of the lower part of the crucible 11 warm, which makes it difficult to remove heat from the lower part of the crucible 11 and hinders the formation of the solid layer 14. .

When the inner wall of the heat shield 21 is outside the outer surface of the heater 12, the heat shield 21 does not have a heat insulating effect on the lower portion of the crucible 11.

The heat shield 21 needs to be arranged over the entire periphery below the heater 12, and its shape is preferably a ring shape. The cross-sectional shape of the heat shield 21 is not particularly limited, but a rectangular cross-sectional shape is preferable in terms of ease of production. Further, the heat shield 21 has a heat insulating member 21b inside.
Are arranged and the outer peripheral portion is covered with the heat resistant member 21a. The heat insulating member 21b forming the inside preferably has a low thermal conductivity and can efficiently block the heat of the heater 12. Specific examples thereof include carbon fiber and rock wool, and the heat insulating member 21b.
The density is preferably 0.1 to 0.5 g / cm ³ . Further, as a specific example of the heat resistant member 21a forming the outer peripheral portion,
For example, a carbon material such as graphite can be used, but the thickness thereof is preferably 3 to 10 mm.

The heat shield 21 may be formed integrally with the heat insulation wall 19a arranged around it, or the heat shield 21 may be arranged on the surface of the heat insulation wall 19a.
The heat shield 21 is usually arranged by adhesion. The adhesion method is such that a resin or the like that easily carbonizes is applied and adhered as an adhesive, and then the adhesive is carbonized and adhered by high-temperature treatment in a reducing atmosphere. Etc.

Next, a method of forming the solid layer 14 using the single crystal pulling apparatus according to this embodiment will be described.

Up to melting of the raw material for crystallization in the crucible 11, it is almost the same as in the case of the melt layer method using the single crystal pulling apparatus shown in FIG. Since it is formed, the heater 12 easily melts the entire crystal raw material in the crucible 11 even in such a state.
Must be in position. In this case, it is preferable to move the crucible 11 so that the heater 12 is below the crucible 11 as compared with the conventional case.

The solid layer 14 is formed after all of the crystallization raw material in the crucible 11 is melted. In this case, too, the crucible 11 is placed so that the heater 12 is located above the crucible 11 in the same manner as in the conventional case. To move. At this time, since the heat shield 21 exists below the heater 12, the solid layer 14 is formed more quickly than in the conventional case. After that, the single crystal 18 is pulled up by the same method as in the conventional case.

Next, the embodiment (2) of the single crystal pulling apparatus according to the present invention will be described.

FIG. 3 is a sectional view schematically showing a single crystal pulling apparatus according to the embodiment (2). This single crystal pulling apparatus has almost the same configuration as the conventional single crystal pulling apparatus shown in FIG. 5 except that a heat shield raising / lowering device 25 is additionally provided. Therefore, the details of the single crystal pulling apparatus itself will be described here. The description is omitted, and only the heat blocker lifting device 25 and the method for forming the solid layer 14 using the heat blocker lifting device 25 will be described.

The heat shield raising / lowering device 25 moves the heat shield 26 fixed to the upper end of the support rod 27 to a different position for melting the crystal raw material and for forming the solid layer 14. A device for rapidly forming the solid layer 14.

The heat shield 26 is fixed to the upper end of a support rod 27 which is inserted into a through hole 22b formed in the lower wall 22a of the chamber, and the lower end of the support rod 27 is located at the center of the elevator plate 28. It is fixed perpendicular to. The through hole 22b, through which the support rod 27 is inserted to keep the chamber 22 airtight, is hermetically sealed by an O-ring 35. Lift plate 2 fixed to the lower end of the support rod 27
8, a through hole 28 having a thread groove near the left and right ends
a is formed, and two screw rods 30 are screwed in parallel with the left and right through holes 28a. Support plates 29 are provided at the upper and lower ends of the two screw rods 30 to slidably support the screw rod 30. More specifically, two holes 29a are formed in the vicinity of the left and right ends of the two support plates 29.
Two screw rods 30 are rotatably fitted in parallel with each other via a lubricant. The support rod 27 has a through hole 29b formed in a central portion of a support plate 29 arranged on the upper side.
It is also fixed to the elevating plate 28 in a state where it is also inserted.

On the other hand, of the two screw rods 30 supported by the support plate 29, one pulley 32 is fitted and fixed to the lower portion of the right screw rod 30, and the left screw rod 30 is fixed.
Two pulleys 32 are fitted and fixed to the lower part of
One pulley 32 fixed to the left and right screw rods 30 is connected by a belt 31, and when the left screw rod 30 rotates by the connection by the belt 31, the right screw rod 30 also rotates at the same speed. It is supposed to do. In addition, the other pulley 32 fixed to the left screw rod 30
The pulley 32 fixed to the speed reducer 33 is connected to the belt 31 so that the rotation of the speed reducer 33 is transmitted to the screw rod 30 on the left side. Furthermore, this decelerator 33 is a motor 3
4 is connected.

Therefore, when the motor 34 is rotated, the decelerator 33 rotates, and the rotation of the decelerator 33 is transmitted to the left and right screw rods 30 via the pulley 32 and the belt 31, and the left and right screw rods 30 rotate. As a result, the lifting plate 28 screwed onto the screw rod 30 moves up and down. Further, the vertical movement of the lifting plate 28 causes the support bar 2 supported by the lifting plate 28.
7 moves up and down, and the heat shield 26 fixed to the upper end of the support rod 27 also moves up and down. By the mechanism of the heat-shielding object lifting device 25 as described above, the heat-shielding object 26 can be moved in the vertical direction by rotating the motor 34 while controlling the rotation direction.

The material of the heat shield 26 may be the same as that of the embodiment (1), and the position (R) of the inner wall and the height (height (H) of the embodiment (1) are different. (Corresponding) may be the same as in the case of the embodiment (1).

Next, a method of forming the solid layer 14 using the single crystal pulling apparatus according to this embodiment will be described.

First, the heat shield lifting device 25 is used to move the heat shield 26 to the lower portion of the chamber 22. That is, by controlling the rotation direction of the motor 34, the rotation direction of the screw rod 30 is controlled to lower the elevating plate 28, and the heat shield 26 is positioned below the chamber 22.

Next, in the same manner as in the embodiment (1), the crystallization raw material is melted, and then the crucible 11 is moved so that the heater 12 is located above the crucible 11. Next, the motor 34 is rotated in the opposite direction to the above case,
The heat shield 26 is moved to a position directly below the heater 12 by raising the elevating plate 28. By moving the heat shield 26 directly below the heater 12, radiant heat in the downward direction of the heater 12 is blocked, and the lower portion of the crucible 11 is rapidly cooled, whereby the solid layer 14 is quickly formed. After that, the single crystal 18 is formed in the same manner as in the embodiment (1).
Pull up.

[0046]

EXAMPLES AND COMPARATIVE EXAMPLES In this example, the shape (L, H, R) of the heat shield 21 was measured by the single crystal pulling apparatus shown in FIG.
Was changed to a value as shown in Table 1 below, and a single crystal was pulled by the melt layer method. In addition,
The heat resistant member 21a has a thickness of 3 mm.

Quartz inner layer holding container 11 of crucible 11 used
a has an inner diameter of 558 mm (22 inches) and a height of 3
55mm (14 inches), its thickness is 7.0mm,
The resistance heating type heater 12 had an inner diameter of 650 mm, an outer diameter of 700 mm, and a height of 150 mm.

Next, the weight of polycrystalline silicon, which is a raw material for crystallization used when pulling a single crystal, is set to 110 kg,
Phosphorus (P) with an effective partition coefficient of 0.35 was added.
Further, the solid layer 14 was formed after all the raw materials for crystallization were melted, and after confirming that the thickness of the solid layer 14 became constant, the thickness of the solid layer 14 was measured. To measure the thickness of the solid layer 14, a quartz pipe with a mark for dimension measurement is attached to the seed chuck 16, the pulling shaft 15 is lowered, and the quartz pipe is lowered until it hits the solid layer 14,
The depth of the molten layer 13 was obtained from the length of the immersed quartz pipe and the pulling shaft 15, and the thickness of the solid layer 14 was calculated.

Next, the conditions for pulling the single crystal 18 will be described. The single crystal pulling rate is 0.5 mm / min.
Lifting shaft at a speed of 15 rpm, crucible 11 at 8 rpm
Rotate in the opposite direction at a speed of 203 mm (8 inches)
The single crystal 18 having a diameter of 3 mm was pulled up to a length of 300 mm, and the pulled single crystal 18 was used to determine the electrical resistivity deviation (%) and the average oxygen concentration (atom / cm ³ ). In addition, inside the single crystal pulling apparatus, after the crystal raw material was charged into the crucible 11, the pressure was 1333 Ps and the Ar flow rate was 30 liters / until the single crystal pulling was completed.
I kept it to the minute.

First, a method of obtaining the electric resistivity deviation will be described. The pulled single crystal 18 is cut into slices,
About the obtained disc-shaped single crystal 18, 50 m along the crystal central axis to a position where the crystal length is 50 to 300 mm.
The electrical resistivity (R) was measured at a pitch of m. Next, using the obtained electrical resistivity (R), the arithmetic mean value (R _mean )
Was calculated, and the electric resistance deviation was calculated according to the following formula 1. However, in the following formula 1, R _max represents the maximum value in the measured electrical resistivity and R _min represents the minimum value in the measured electrical resistivity.

[0051]

[Equation 1] Electric resistance deviation (%) = (R _max −R _min ) × 1
00 / R _{mean The} electric resistivity deviation calculated by the above formula 1 is 1 crystal 1
8 is related to the yield, and the electrical resistivity deviation is 1
Almost all of those with 0% or less can be used as products, and therefore are indicated by "", and those with an electric resistivity deviation of more than 10% decrease the yield and are indicated by "x" as inferior products.

Next, regarding the average oxygen concentration, the same sample as that used for the measurement of the electrical resistivity was used, the oxygen concentration was measured by the infrared absorption method, and the arithmetic average value of these values was obtained. The average oxygen concentration was used.

The dimensions of the heat shield 21 are shown in Table 1 below, and the initial solid layer thickness (mm), electrical resistivity deviation (%), judgment results regarding pass / fail and average oxygen concentration are shown in Table 1 below. 2 shows.

[0054]

[Table 1]

[0055]

[Table 2]

As is clear from the conditions and results of the examples and comparative examples shown in Tables 1 and 2 above, the inner wall of the heat shield 21 is located outside the outer surface of the heater 12 ( In the case where the R value is −), only the thin solid layer 14 is formed, and the pulled single crystal 18 has inferior characteristics, while the inner wall of the heat blocker 21 is the heater 12. Located inside the outer surface of the
(The value of + is +), the thickness of the formed solid layer 14 is thick and the characteristics of the pulled single crystal 18 are excellent. In order to form a sufficiently thick solid layer 14, R is 2
It is preferably 0 mm or more.

The distance L between the lower surface of the heater 12 and the upper surface of the heat shield 21 is 20 mm,
And 100 mm, a sufficiently thick solid layer 14 is formed, but when the value becomes 250 mm, the effect of radiant heat shielding by the heat shield 21 is not exerted, and only the thin solid layer 14 is formed. The characteristics of the pulled single crystal 18 are also inferior.

Further, with respect to the height H of the heat shield 21 of 40 mm and 200 mm, a sufficiently thick solid layer 14 is formed and the pulled single crystal 18 has excellent characteristics. However, the value of H is 8
If it is too small (mm) or too large (600 mm), the thickness of the solid layer 14 formed is small and the pulled single crystal 18 has poor characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a single crystal pulling apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view schematically showing an enlarged vicinity of a heat shield of the single crystal pulling apparatus according to the embodiment shown in FIG.

FIG. 3 is a cross-sectional view schematically showing a single crystal pulling apparatus according to another embodiment.

FIG. 4 is a cross-sectional view schematically showing a conventional single crystal pulling apparatus by the CZ method.

FIG. 5 is a cross-sectional view schematically showing a conventional single-crystal pulling apparatus equipped with a single-stage heater by a melt layer method.

FIG. 6 is a cross-sectional view schematically showing a conventional single-crystal pulling apparatus equipped with a two-stage heater by a melt layer method.

[Explanation of symbols]

 11 Crucible 12 Heater 21, 26 Heat Shield 25 Heat Shield Lifter

Claims (2)

[Claims] 1. A single crystal pulling apparatus comprising a crucible and a heater disposed around the upper portion of the crucible, wherein a height of 10 to 500 is provided below the heater at a distance of 5 to 200 mm.
An apparatus for pulling a single crystal, characterized in that a heat shield whose inner wall is located inside the outer surface of the heater is provided in mm. 2. The single crystal pulling apparatus according to claim 1, wherein the heat shield is installed so as to be vertically movable.