JP4081901B2 - Single crystal puller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single crystal pulling apparatus used for pulling a single crystal by a CZ method (Czochralski method).
[0002]
[Prior art]
In the manufacture of a silicon single crystal that is a material of a semiconductor device, pulling by the CZ method is frequently used. A pulling apparatus as shown in FIG. 9 is generally used for pulling a single crystal by the CZ method.
[0003]
That is, the crucible 2 is disposed in the main chamber 1 at the center thereof. A heater 3 is disposed outside the crucible 2, and a heat insulating cylinder 4 is disposed along the inner surface of the main chamber 1 further outside the heater 3. The crucible 2 has a double structure in which an inner quartz crucible 2a is held by an outer graphite crucible 2b, and is placed on a support shaft 5 called a pedestal. The support shaft 5 is driven in the circumferential direction and the axial direction for rotation and elevation of the crucible 2.
[0004]
In the pulling of the single crystal, as a first step, the raw material (polycrystalline silicon) charged in the crucible 2 is heated from the outside by the heater 3 and melted. As a second stage, the pulling shaft 7 is lowered into the main chamber 1 through the small-diameter pull chamber 6 connected to the main chamber 1, and the seed crystal attached to the chuck 8 at the lower end thereof is stored in the crucible 2. It is immersed in the raw material melt 10. Then, when the pulling shaft 7 is raised while rotating, the single crystal 11 is grown below the seed crystal and pulled into the pull chamber 6.
[0005]
During operation, the chamber is evacuated to a predetermined reduced pressure, and an inert gas is circulated in the chamber from top to bottom. Also, the crucible 2 rotates in the circumferential direction and rises to offset the liquid level drop due to consumption of the raw material melt 10.
[0006]
Here, the heat insulating cylinder 4 is provided in order to prevent the dissipation of the heater heat and reduce the heater power. In order to enhance this effect, the heat insulating cylinder 4 is often combined with a ring-shaped heat insulating plate 12 extending substantially horizontally inward from the upper end portion thereof. When a gas rectifying cylinder with a flange having an inverted conical shape is disposed above the crucible 2, a flange-shaped holding part that projects outward from the upper end of the gas rectifying cylinder serves as the heat insulating plate 12. The heat insulating plate 12 has a gas rectifying function as well as preventing heat dissipation of the heater.
[0007]
[Problems to be solved by the invention]
In such a single crystal pulling apparatus, when the heating temperature of the crucible 2, particularly the quartz crucible 2 a exceeds about 1500 ° C., the quartz crucible 2 a starts to soften, and when the temperature rises to 1550 ° C. or higher, the quartz crucible 2 a has its own weight. Deformation occurs due to external factors. As this deformation, as shown in FIG. 10 (a), the middle part of the quartz crucible 2a bulges due to bending or sagging, and the upper end of the crucible 2a tilts inward as shown in FIG. 10 (b). There is a fall phenomenon.
[0008]
Such crucible deformation has not been so noticeable until now due to operational improvements. However, with the recent increase in the diameter of single crystals, this deformation has become prominent and has become a particularly serious problem. The reason why crucible deformation becomes conspicuous as the diameter of a single crystal increases is as follows.
[0009]
FIG. 11 shows the temperature distribution at the melt surface level in the crucible when the crucible diameter is small and large. As shown in the figure, the diameter of the crucible 2 is increased by increasing the diameter of the single crystal 11, but the heating temperature at the center of the crucible 2 maintains the silicon melting point (1420 ° C.) regardless of the diameter of the crucible. There is a need. In order to maintain the temperature in the central portion, the heater output increases as the diameter of the crucible 2 increases. As a result, the heating temperature of the side wall portion of the crucible 2 surrounded by the heater 3 rises, and the deformation of the quartz crucible 2a occurs. Become prominent.
[0010]
And when the deformation of the quartz crucible becomes remarkable, the yield level drop due to the melt surface fluctuation and gas turbulence in the crucible becomes a problem, and in the operation of arranging the inverted conical gas rectifying cylinder above the crucible, As the crucible rises, the crucible hits the gas flow straightening cylinder and the pulling may be interrupted.
[0011]
An object of the present invention is to provide a single crystal pulling apparatus capable of effectively suppressing deformation even when a large-diameter crucible is used.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the inventors of the present invention pay attention to the thermal history that the quartz crucible receives during operation because the quartz crucible rises during operation and the positional relationship with respect to the heater and the heat insulating member changes. The influence of the shape of the heat insulating member on the heat history was examined by heat transfer simulation. As a result, the following facts were found.
[0013]
Factors governing the deformation of the quartz crucible relate to the heating temperature and the heating time, and the deformation of the quartz crucible occurs in a short time at a temperature range of 1650 ° C. or higher where the heating temperature exceeds the softening point of the quartz glass, and below the softening point. Even when the temperature is 1500 ° C. or lower, the quartz crucible is deformed when heated for a long time.
[0014]
The main cause of the deformation of the quartz crucible in the conventional single crystal pulling apparatus is that the quartz crucible rises as the pulling progresses, and despite the fact that the portion without the silicon melt inside the quartz crucible protrudes from the upper end of the heater, This part is to be held for a long time in a temperature range slightly lower than the softening point of about 1500 ° C. In order to remove the cause of this deformation, the heat insulating performance is limited in the part above the upper end of the heater of the heat insulating member. It is effective to lower the temperature of the quartz crucible in that portion.
[0015]
However, if the area that degrades the heat insulation performance is extended to a portion below the upper end of the heater, a large amount of heater power is required because of heat dissipation. Especially, the large heater power softens the temperature of the quartz crucible during melting and dipping. It raises the temperature far beyond the point, and conversely causes the quartz crucible to be deformed.
[0016]
The single crystal pulling apparatus of the present invention has been developed based on such knowledge. As a first configuration, the heat insulating performance of the portion located above the vicinity of the upper end of the heater of the heat insulating cylinder disposed outside the heater is provided. It takes measures to lower it.
[0017]
Further, as a second configuration, means for reducing the heat insulation performance without reducing the air flow shielding function of the ring-shaped heat insulating plate extending substantially horizontally inward from the upper end of the heat insulating cylinder is provided.
[0018]
As means for lowering the heat insulation performance in the first configuration, that is, means for lowering the heat insulation performance of the portion located above the vicinity of the upper end of the heater of the heat insulation cylinder, the thickness of the portion located above the vicinity of the upper end of the heater of the heat insulation cylinder T2 is made partially or entirely thinner than the thickness T1 of the portion located below the upper end of the heater in the heat insulating cylinder, or a through opening is provided in a portion located above the upper end of the heater in the heat insulating cylinder. It is also possible to use a combination of a plurality of types of means.
[0019]
When the thickness T2 of the portion positioned above the vicinity of the upper end of the heater of the heat insulating cylinder is made thinner than the thickness T1 of the section positioned below the vicinity of the upper end of the heater of the heat insulating cylinder, T2 is (T1 × 0.2 to 0). .7) The following is preferable. When T2 exceeds (T1 × 0.7), the high temperature state of the crucible continues for a long time, and the effect of suppressing crucible deformation becomes insufficient. When T2 is less than (T1 × 0.2), the increase in heater output becomes remarkable, and although it is a short time, the crucible is heated to a high temperature of 1650 ° C. or more exceeding the softening point at the time of melting or dipping, The effect of suppressing the deformation becomes insufficient.
[0020]
When a through opening is provided in a portion located above the vicinity of the upper end of the heater of the heat insulating cylinder, the total area of the through opening is S2, and the area of the inner peripheral surface of the portion located above the upper end of the heater of the heat insulating cylinder is defined as S1. , S2 is preferably (S1 × 0.2 to 0.8). When S2 is less than (S1 × 0.2), the high temperature state of the crucible continues for a long time, and the effect of suppressing crucible deformation becomes insufficient. When S2 exceeds (S1 × 0.8), the increase in the heater output becomes remarkable, so that the crucible is heated to a high temperature of 1650 ° C. or more exceeding the softening point at the time of melting or dipping. The effect of suppressing deformation is insufficient.
[0021]
When the thickness T2 of the portion located above the vicinity of the upper end of the heater of the heat insulating cylinder is partially made thinner than the thickness T1 of the section positioned below the vicinity of the upper end of the heater of the heat insulating cylinder, or above the vicinity of the upper end of the heater of the heat insulating cylinder. In the case where the through openings are provided in the located portions, it is important that these heat radiation promoting portions are provided evenly in the circumferential direction of the heat insulating cylinder.
[0022]
As a means for lowering the heat insulation performance in the second configuration, that is, a means for lowering the heat insulation performance without lowering the air flow shielding function of the heat insulation board, a part having a low heat insulation performance is formed on the heat insulation board. There are things.
[0023]
As a means of forming a part with low heat insulation performance on the heat insulating plate, the heat insulating plate is partially thinned, or in the case of a box structure in which the heat insulating plate is composed of an outer shell portion and an inner filling portion, There is so-called meat removal or the like in which the inner filling portion is extracted. In any case, it is important to form a portion having a low heat insulating performance, that is, a heat radiation promoting portion, uniformly in the circumferential direction of the heat insulating plate.
[0024]
In the case where the heat insulation plate is thinned, S2 ′ is (S1 ′ × 0.2), where S2 ′ is the total area of the thinned portions and S1 ′ is the surface area of one side of the heat insulation plate protruding from the heat insulation cylinder. ~ 0.7) is preferred. When S2 ′ is less than (S1 ′ × 0.2), the high temperature state of the crucible continues for a long time, and the effect of suppressing crucible deformation becomes insufficient. When S2 ′ exceeds (S1 ′ × 0.7), the heater output increases remarkably, and the crucible is heated to a high temperature of 1650 ° C. or higher, and the effect of suppressing the deformation becomes insufficient.
[0025]
In the second configuration, in order not to change the gas rectifying action by the heat insulating plate, it is necessary not to lower the air flow shielding function of the heat insulating plate. For this reason, the through opening is excluded.
[0026]
The present invention is particularly effective for a single crystal pulling apparatus using a quartz crucible having a diameter of 22 inches or more in which crucible deformation is particularly problematic.
[0027]
The single crystal pulling apparatus of the present invention suppresses the heating temperature at the upper end of the crucible to 1550 ° C. or less where deformation does not become a problem by providing the heat insulating member with a means for reducing the heat insulating performance, in other words, a means for promoting heat dissipation. Can do. It is desirable that various specific means for promoting heat dissipation be designed so that the heating temperature at the upper end of the crucible can be suppressed to 1550 ° C. or lower.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a single crystal pulling apparatus according to the first embodiment of the present invention, FIG. 2 is a longitudinal sectional view of a main part of the single crystal pulling apparatus, and FIG. 3 is a perspective view of the main part.
[0029]
The single crystal pulling apparatus according to the first embodiment differs from the conventional single crystal pulling apparatus shown in FIG. 9 in the structure of the heat insulating cylinder 4. The structure of the other parts is the same as that of the conventional single crystal pulling apparatus shown in FIG.
[0030]
The heat insulation cylinder 4 is a cylindrical body provided along the inner surface of the main chamber outside the annular heater 3 that heats the crucible 2. The upper part of the heat insulating cylinder 4 protrudes upward from the upper end of the heater 3, and the protruding part 42, that is, the part above the heater upper end of the heat insulating cylinder 4 is entirely from the main body part 41 below the heater upper end of the heat insulating cylinder 4. It is said to be thin over the circumference. Specifically, by removing a portion on the outer surface side of the protruding portion 42, the thickness T2 of the protruding portion 42 is set to (0.2 to 0.7) times the thickness T1 of the main body portion 41 over the entire circumference.
[0031]
A ring-shaped heat insulating plate 12 extending substantially horizontally inward is integrally provided at the upper end of the heat insulating cylinder 4. The heat insulating plate 12 and the heat insulating cylinder 4 have a box structure in which carbon fibers are filled in a carbon shell.
[0032]
In such a single crystal pulling apparatus, the thickness T2 of the protruding portion 42 of the heat insulating cylinder 4 is made thinner than the thickness T1 of the main body portion 41, so that the temperature distribution at the position where the crucible 2, particularly the side wall of the quartz crucible 2a passes. Is changed as shown in FIG.
[0033]
That is, FIG. 4 is a temperature distribution diagram in the height direction at the position where the side wall of the quartz crucible passes, and the temperature distribution curve A in the figure is a temperature distribution curve in the case of a conventional apparatus in which the heat insulating cylinder has a constant thickness over the entire height. B shows the temperature distribution curve C in the case of the device of the present invention in which the thickness of the protruding portion is 0.5 times the thickness of the main body portion, and the temperature distribution curve C shows the temperature distribution in the case of the comparison device in which the thickness of the portion above the middle stage of the heater Curve D shows the case of the comparison device in which the thickness of the heater outer portion of the heat insulating cylinder is reduced.
[0034]
The quartz crucible rises as the pulling progresses. In the case of the conventional apparatus (A) in which the heat insulation cylinder has a constant thickness over the entire height, it not only exceeds 1500 ° C. inside the heater but also exceeds 1500 ° C. over a wide region above the upper end of the heater, that is, inside the protruding portion of the heat insulation cylinder. As a result, the side wall portion of the quartz crucible, particularly the upper end portion thereof, is exposed to a high temperature of 1500 ° C. or higher where deformation becomes a problem over a long period of operation.
[0035]
However, in the device (B) of the present invention in which the thickness of the protruding portion of the heat insulating cylinder is thinner than the thickness of the main body portion below, the temperature inside the heater rises slightly due to the increase in the heater output due to the decrease in the overall heat insulating performance, The temperature is extremely lowered above the upper end of the heater, that is, inside the protruding portion of the heat insulating cylinder, and maintained at 1500 ° C. or lower. As a result, the heating temperature of the side wall portion of the quartz crucible, particularly the upper end portion thereof, is suppressed to 1500 ° C. or lower.
[0036]
In the case of the comparative device (C) in which the thickness is reduced above the middle stage of the heater of the heat insulation cylinder, the temperature is lowered above the upper end of the heater, that is, inside the protruding portion of the heat insulation cylinder, but the heater output is reduced due to a decrease in overall heat insulation performance. The increase becomes remarkable, and the temperature inside the heater rises extremely. As a result, deformation of the quartz crucible becomes a problem during melting or dipping. The same tendency occurs when the thickness is extremely thin above the upper end of the heater of the heat insulating cylinder.
[0037]
In the case of the comparison device (D) in which the thickness is reduced outside the heater of the heat insulating cylinder, the temperature rises in a wide region due to a significant increase in the heater output.
[0038]
In the single crystal pulling apparatus of the present invention, the temperature of the quartz crucible 2 located in the inner peripheral region of the heater 3 exceeds 1550 ° C., but a silicon melt exists in the quartz crucible 2, and the silicon melt Due to the internal pressure, the quartz crucible 2 which is a problem is hardly deformed. Thereafter, when the upper end of the quartz crucible 2 exceeds the upper end portion of the heater 3, the temperature of the protruding portion decreases, the time of exposure to the high temperature is shortened, and the deformation is remarkably suppressed.
[0039]
In the first embodiment, the thickness of the protruding portion 42 is reduced over the entire circumference, but it is also possible to reduce the thickness at a plurality of locations in the circumferential direction. That is, it is also possible to provide a plurality of thin heat dissipation promoting portions in the circumferential direction.
[0040]
FIG. 5 is a perspective view of the main part of the single crystal pulling apparatus according to the second embodiment of the present invention.
[0041]
In the single crystal pulling apparatus according to the second embodiment, the thickness of the protruding portion 42 of the heat insulating cylinder 4 is the same as the thickness of the main body portion 41. Instead, the protruding portion 42 has a plurality of through openings 43, 43. -The heat dissipation promotion part which consists of is provided in the circumferential direction at equal intervals. The total area S2 of the through openings 43, 43... Is set to (S1 × 0.2 to 0.8) of the area S1 of the inner peripheral surface of the protruding portion 42. Other structures are the same as those of the single crystal pulling apparatus according to the first embodiment.
[0042]
Also in the single crystal pulling apparatus according to the second embodiment, similarly to the single crystal pulling apparatus according to the first embodiment, the heat radiation is promoted by the projecting portion 42 of the heat insulating cylinder 4 so that the side wall portion of the quartz crucible is heated to a high temperature. The time spent is shortened and its deformation is suppressed. Incidentally, the temperature distribution curve B in FIG. 4 shows the total area S2 of the through openings 43, 43... 0.5 of the area S1 of the inner peripheral surface of the protruding portion 42 in the single crystal pulling apparatus according to the second embodiment. It corresponds approximately when it is doubled.
[0043]
FIG. 6 is a chart showing the influence of the thickness of the protruding portion of the heat insulating cylinder and the total area of the through openings provided in the protruding portion on the deformation amount of the quartz crucible. The crucible deformation amount is the maximum protrusion amount from the normal inner surface due to deformation of the quartz crucible when a silicon single crystal having a diameter of 12 inches is pulled using a quartz crucible having a diameter of 34 inches.
[0044]
If the heat insulating cylinder is of the same thickness over the entire height and the projecting part does not have a through opening, the crucible deformation amount reaches about 40 mm, but the thickness of the projecting part of the heat insulating cylinder is made thinner than the thickness of the body part below it. As a result, the crucible deformation amount becomes small, and the crucible deformation amount is suppressed to 5 mm or less at T2 ≦ 0.7 × T1. Also, the crucible deformation amount is reduced by providing a through opening in the protruding portion, and the crucible deformation amount is suppressed to 5 mm or less when S2 ≧ 0.2 × S1.
[0045]
In the second embodiment, the through opening is square, but it may be circular and the shape is not limited.
[0046]
In the second embodiment, the protruding portion has the same thickness as the main body portion below it. However, the protruding portion can be made thinner than the main body portion, and a through opening can be provided in the protruding portion.
[0047]
FIG. 7 is a longitudinal sectional view of the main part of the single crystal pulling apparatus according to the third embodiment of the present invention.
[0048]
In the single crystal pulling apparatus according to the third embodiment, the ring-shaped heat insulating plate 12 that protrudes inward substantially horizontally from the upper end of the heat insulating cylinder 4 has a partial thinning structure. In other words, the heat insulation plate 12 is partially provided with a lightening portion 12 ′ as a heat dissipation promoting portion formed by extracting the carbon fiber filled inside the carbon shell.
[0049]
In this example, the lightening portions 12 ′ are continuously provided on a part of the heat insulating plate 12 in the radial direction, but may be provided at a plurality of positions in the circumferential direction. Moreover, it can also provide in the whole radial direction in the several position of the circumferential direction.
[0050]
The total area S2 'of the lightening portion 12' is 0.2 to 0.8 in terms of the ratio to the surface area S1 'on one side of the portion of the heat insulating plate 12 protruding inward from the heat insulating cylinder 4.
[0051]
In the single crystal pulling apparatus according to the third embodiment, the heat insulating plate 12 is provided with the thinned portion 12 ', so that the single crystal pulling apparatus is above the heater 3 similarly to the single crystal pulling apparatus according to the first and second embodiments. The heat dissipation in the glass is promoted and the ambient temperature is lowered, so that the time during which the side wall of the quartz crucible is brought to a high temperature is shortened, and deformation thereof is suppressed. Incidentally, the temperature distribution curve B in FIG. 4 shows the total area S2 ′ of the thinned portion 12 ′ in one side of the portion of the heat insulating plate 12 protruding inward from the heat insulating cylinder 4 in the single crystal pulling apparatus according to the third embodiment. This corresponds approximately to 0.4 times the surface area S1 ′.
[0052]
Further, since the shell is left as it is in the lightening portion 12 'and there is no gas flow, the rectification function is unchanged.
[0053]
FIG. 8 is a table showing the influence of the area of the lightening portion provided on the heat insulating plate on the deformation amount of the quartz crucible. The crucible deformation amount is the maximum protrusion amount from the normal inner surface due to deformation of the quartz crucible when a silicon single crystal having a diameter of 12 inches is pulled using a quartz crucible having a diameter of 34 inches.
[0054]
When the heat sink is not provided with the lightening part, the crucible deformation amount reaches about 35 mm. However, by providing the lightening part, the crucible deformation amount becomes small, and S2 ′ ≧ 0.2 × In S1 ′, the crucible deformation amount is suppressed to 5 mm or less. However, when S2 ′> 0.7 × S1 ′, the crucible deformation amount increases again due to an increase in the heater output.
[0055]
In the third embodiment, the protruding portion of the heat insulating cylinder is equal in thickness to the main body portion below it, but it is also possible to make the protruding portion thinner than the main body portion or to provide a through opening in the protruding portion.
[0056]
【The invention's effect】
As described above, the single crystal pulling apparatus of the present invention has a quartz crucible diameter reduced by taking measures to reduce heat insulation performance and promote heat dissipation in a limited manner above the heat insulation member provided outside the heater. Even when it is large, the deformation can be effectively prevented. Therefore, it is possible to avoid the lowering of the yield due to the melt surface fluctuation and gas turbulence in the crucible due to the deformation of the crucible, and the interruption of the pulling which is a problem in the operation of arranging the inverted conical gas rectifying cylinder above the crucible. it can.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a single crystal pulling apparatus according to a first embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of a main part of the single crystal pulling apparatus.
FIG. 3 is a perspective view of the main part.
FIG. 4 is a temperature distribution diagram at a position where a side wall portion of the quartz crucible passes.
FIG. 5 is a perspective view of a main part of a single crystal pulling apparatus according to a second embodiment of the present invention.
FIG. 6 is a table showing the influence of the thickness of the protruding portion of the heat insulating cylinder and the total area of the through openings provided in the protruding portion on the deformation amount of the quartz crucible.
FIG. 7 is a longitudinal sectional view of a main part of a single crystal pulling apparatus according to a third embodiment of the present invention.
FIG. 8 is a chart showing the influence of the area of the lightening portion provided on the heat insulating plate on the deformation amount of the quartz crucible.
FIG. 9 is a longitudinal sectional view of a conventional single crystal pulling apparatus.
FIG. 10 is a schematic diagram for explaining deformation of a quartz crucible.
FIG. 11 is a temperature distribution diagram in the horizontal direction at the melt surface level.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Main chamber 2 Crucible 2a Quartz crucible 2b Graphite crucible 3 Heater 4 Heat insulation cylinder 41 Main-body part 42 Projection part (part above a heater upper end)
43 Through-opening (heat dissipation promoting part)
5 Support shaft 6 Pull chamber 7 Pulling shaft 8 Chuck 10 Raw material melt 11 Silicon single crystal 12 Heat insulation plate 12 ′ Meat removal part (heat dissipation promotion part)

Claims (3)

A CZ comprising a quartz crucible having a diameter of 22 inches or more for containing the raw material, a heater for heating and melting the raw material in the quartz crucible from the outside of the quartz crucible, and a heat insulating cylinder arranged so as to surround them. In the single crystal pulling apparatus according to the method, when the thickness of the portion located above the upper end of the heater of the heat insulating cylinder is T2, and the thickness of the portion located below the upper end of the heater of the heat insulating cylinder is T1, T2 is T1 × A single crystal pulling apparatus characterized in that, as 0.2 to 0.7, the heat insulating performance of a portion located above the upper end of the heater of the heat insulating cylinder is lowered. A CZ comprising a quartz crucible having a diameter of 22 inches or more for containing the raw material, a heater for heating and melting the raw material in the quartz crucible from the outside of the quartz crucible, and a heat insulating cylinder arranged so as to surround them. In the single crystal pulling apparatus according to the method, a through opening is provided in a portion located above the upper end of the heater of the heat insulating cylinder, the total area of the through opening is S2, and the upper end of the heat insulating cylinder is located above the heater upper end. When the area of the inner peripheral surface of the part is S1, S2 is set to S1 × 0.2 to 0.8, and the heat insulating performance of the part located above the upper end of the heater of the heat insulating cylinder is reduced. Single crystal pulling device. A CZ comprising a quartz crucible having a diameter of 22 inches or more for containing the raw material, a heater for heating and melting the raw material in the quartz crucible from the outside of the quartz crucible, and a heat insulating cylinder arranged so as to surround them. In the single crystal pulling apparatus according to the method, when the thickness of the portion located above the upper end of the heater of the heat insulating cylinder is T2, and the thickness of the portion located below the upper end of the heater of the heat insulating cylinder is T1, T2 is T1 × 0.2 to 0.7, and a through-opening is provided in a portion located above the upper end of the heater of the heat insulating cylinder, and the total area of the through-opening is S2, above the upper end of the heater of the heat insulating cylinder. When the area of the inner peripheral surface of the part located at S is S1, the heat insulation performance of the part located above the upper end of the heater of the heat insulation cylinder is lowered by setting S2 to S1 × 0.2 to 0.8. A single crystal pulling apparatus characterized in that

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