CN117702243A

CN117702243A - Single crystal furnace

Info

Publication number: CN117702243A
Application number: CN202311727030.8A
Authority: CN
Inventors: 杨文武; 梁万亮
Original assignee: Xian Eswin Material Technology Co Ltd
Current assignee: Xian Eswin Material Technology Co Ltd
Priority date: 2023-12-15
Filing date: 2023-12-15
Publication date: 2024-03-15

Abstract

The invention relates to a single crystal furnace, which comprises a furnace body and a crucible assembly positioned in the furnace body, wherein a guide cylinder is arranged above the crucible assembly, a crystal bar lifting area is arranged in the guide cylinder, a water cooling jacket is arranged between the crystal bar lifting area and the guide cylinder, the water cooling jacket is of a cylindrical structure, the water cooling jacket comprises an outer surface and an inner surface, the cross section of the outer surface is circular in the radial direction of the water cooling jacket, and the cross section of the inner surface is elliptical. In the radial direction of the water cooling jacket, the cross-sectional shape of the outer surface of the water cooling jacket is circular, and the cross-sectional shape of the inner surface of the water cooling jacket is elliptical. In the crystal pulling process, the crystal bar forms stable and symmetrical temperature fields on the inner periphery of the ellipse during the rotation process, so that heat in the crystal bar is accelerated to radiate to the water cooling jacket and taken away in time, and the heat exchange efficiency is improved.

Description

Single crystal furnace

Technical Field

The invention relates to the technical field of semiconductor product manufacturing, in particular to a single crystal furnace.

Background

Monocrystalline silicon is the base material for most semiconductor components, most of which are produced by the czochralski method. In the method, solid polysilicon silicon material is placed in a crucible and heated to melt the polysilicon material in the crucible, in the process of pulling a single crystal silicon rod, seed crystal is firstly contacted with molten silicon, the molten silicon at a solid-liquid interface is cooled and crystallized along the seed crystal, the seed crystal is slowly pulled out for growth, and after the necking is finished, the crystal growth diameter is amplified by reducing the pulling speed and/or the temperature of a silicon solution until reaching a target diameter; after shoulder turning, crystal growth enters into an equal diameter growth stage by controlling the pulling speed and the melt temperature; finally, the diameter of the crystal growth surface is gradually reduced to form a tail cone by increasing the pulling speed and increasing the temperature of the melt until the crystal leaves the surface of the melt finally, and the growth of the monocrystalline silicon rod is completed.

During the pulling process, a thermal field that affects the heat dissipation of the pulled ingot is very important, as it directly affects the temperature gradient of the ingot, which is the most critical determinant of ingot quality.

In the prior art, all the thermal field components are of symmetrical revolution structures, for example, the radial section of the whole water cooling jacket is circular, and the eccentric assembly condition always exists in each thermal field assembly process, so that the complete symmetrical assembly is not realized, the quality of the crystal bar is greatly influenced in the crystal pulling process, and the radial oxygen content in the crystal is non-uniform.

Disclosure of Invention

In order to solve the technical problems, the invention provides a single crystal furnace, which solves the problem of non-uniform radial oxygen content of a crystal bar caused by eccentric assembly of thermal field components.

In order to achieve the above purpose, the technical scheme adopted by the embodiment of the invention is as follows: the utility model provides a single crystal furnace, includes furnace body and the crucible assembly that is located the furnace body, the top of crucible assembly is provided with the draft tube, the inside of draft tube is provided with the crystal bar and promotes the region, the crystal bar promote the region with be provided with the water cooling jacket between the draft tube, the water cooling jacket is tubular structure, the water cooling jacket includes surface and internal surface on the radial direction of water cooling jacket, the cross-sectional shape of surface is circular, the cross-sectional shape of internal surface is oval.

Optionally, the outer surface is provided with a thermal barrier coating.

Optionally, the inner surface is provided with a heat absorbing coating.

Optionally, the thickness of the heat absorbing coating gradually decreases in the axial direction of the water jacket in a direction from the bottom end to the top end of the water jacket.

Optionally, the thickness of the heat absorbing coating is 200+ -25 um.

Optionally, a gap between the bottom of the water cooling jacket and the guide cylinder is 10-20mm.

Optionally, the inner surface of the guide cylinder is provided with a step structure, so that the inner diameter of the guide cylinder gradually decreases from the top end of the guide cylinder to the bottom end of the guide cylinder.

Optionally, the bottom end of the guide cylinder is provided with a first step, and the cross section of the inner surface of the first step is elliptical.

Optionally, a plurality of notches are arranged on the inner surface of the first step at intervals along the circumferential direction of the guide cylinder.

Optionally, the cross-section shape of the notch in the radial direction of the guide cylinder is arc-shaped.

Optionally, the distance between the bottom of the guide cylinder and the liquid level of the silicon melt in the crucible assembly is 50-80mm.

The beneficial effects of the invention are as follows: in the radial direction of the water cooling jacket, the cross-sectional shape of the outer surface of the water cooling jacket is circular, and the cross-sectional shape of the inner surface of the water cooling jacket is elliptical. In the crystal pulling process, the crystal bar forms stable and symmetrical temperature fields at the inner periphery of the ellipse when in the rotation process, so that heat in the crystal bar is accelerated to radiate to the water cooling jacket and taken away in time, the heat exchange efficiency is improved, the rapid abnormal growth of body micro defects in the crystal bar is effectively inhibited, the crystal bar is kept within a smaller size range (below 19 nm), and the overall quality of the crystal bar is improved.

Drawings

FIG. 1 shows a schematic diagram of a single crystal furnace in an embodiment of the invention;

FIG. 2 shows a schematic view of a guide shell in an embodiment of the invention;

FIG. 3 shows a schematic view of a water jacket in an embodiment of the invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present disclosure more apparent, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present disclosure. It will be apparent that the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments, which can be made by one of ordinary skill in the art without the need for inventive faculty, are within the scope of the present disclosure, based on the described embodiments of the present disclosure.

Unless defined otherwise, technical or scientific terms used in this disclosure should be given the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The terms "first," "second," and the like, as used in this disclosure, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Likewise, the terms "a," "an," or "the" and similar terms do not denote a limitation of quantity, but rather denote the presence of at least one. The word "comprising" or "comprises", and the like, means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof, but does not exclude other elements or items. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", etc. are used merely to indicate relative positional relationships, which may also be changed when the absolute position of the object to be described is changed.

Referring to fig. 1-3, this embodiment provides a single crystal furnace, including furnace body and the crucible assembly that is located the furnace body, the top of crucible assembly is provided with guide cylinder 2, the inside of guide cylinder 2 is provided with the crystal bar and promotes the region, crystal bar promotes the region with be provided with water jacket 1 between the guide cylinder 2, water jacket 1 is tubular structure, water jacket 1 includes surface 12 and internal surface 11 in the radial direction of water jacket 1, the cross-sectional shape of surface 12 is circular, the cross-sectional shape of internal surface 11 is oval.

In the related art, the radial cross section of the whole water cooling jacket 1 is circular, namely, the radial cross section of the outer surface of the water cooling jacket 1 is circular, and the cross section of the inner surface of the water cooling jacket 1 is circular, so that the eccentric assembly always exists in the process of assembling each thermal field, the complete symmetrical assembly is not realized, the quality of the crystal rod is greatly influenced in the process of pulling the crystal, and the radial oxygen content in the crystal is non-uniform.

Referring to fig. 1-3, in this embodiment, in the radial direction of the water jacket 1, the cross-sectional shape of the outer surface 12 of the water jacket 1 is circular, and the cross-sectional shape of the inner surface 11 of the water jacket 1 is elliptical, so that a stable symmetrical temperature field is formed on the inner circumference of the ellipse when the crystal bar 3 rotates, heat radiation of the crystal bar 3 to the water jacket 1 is accelerated and timely carried away, heat exchange efficiency is improved, rapid abnormal growth of bulk micro defects in the crystal bar 3 is effectively inhibited, the bulk quality of the crystal bar 3 is improved, and the bulk quality of the crystal bar 3 is maintained within a smaller size range (below 19 nm).

Compared with the traditional rotary body water-cooled jacket 1 (the water-cooled jacket 1 with a circular section), the cooling rate of the water-cooled jacket 1 with the elliptical section of the inner surface 11 is better, and the supercooling degree is larger, so that the aggregation type abnormal growth of micro defects can be well restrained, and the improvement of the yield of the crystal bars 3 is facilitated.

The cross section of the inner surface 11 of the water cooling jacket 1 in the radial direction is elliptical, the cross section of the outer surface 12 of the water cooling jacket 1 in the radial direction is circular, the elliptical inner surface 11 plays a role in forming a stable and symmetrical temperature field, heat in the crystal bar is accelerated to radiate to the water cooling jacket 1 and is taken away in time, heat exchange efficiency is improved, and the circular outer surface is convenient to assemble with the guide cylinder 2.

In an exemplary embodiment, the outer surface 12 is provided with a thermal barrier coating.

The heat-insulating coating has the functions of reflecting and shielding heat, prevents the transmission of external heat from the outside to the inside of the water-cooled jacket 1, and maintains the constant temperature of the substrate.

In an exemplary embodiment, the thermal barrier coating is a thermal barrier functionally graded coating, i.e., the thickness of the thermal barrier coating decreases gradually from the top end of the water jacket 1 to the bottom end of the water jacket 1.

In an exemplary embodiment, the heat-insulating coating is a high-temperature-resistant high-temperature-barrier zirconia ceramic coating, but not limited thereto.

In an exemplary embodiment, the inner surface 11 is provided with a heat absorbing coating.

The heat absorption coating has a heat absorption effect so as to accelerate heat radiation of the crystal bar 3 to the water cooling jacket 1 and timely take away the heat, and the heat exchange efficiency is improved.

The ceramic heat absorption coating is used as the heat absorption coating, the bonding strength between the heat absorption coating and the substrate (namely the water cooling jacket 1) is high, the thermal stress of a coating interface can be effectively relieved, the thermodynamic performance is stable, and the overall service life of the water cooling jacket 1 is provided.

In an exemplary embodiment, the thickness of the heat absorbing coating gradually decreases in the axial direction of the water jacket 1 in the direction from the bottom end to the top end of the water jacket 1.

In an exemplary embodiment, the thickness of the heat absorbing coating is 200+ -25 um.

In an exemplary embodiment, the gap between the bottom of the water jacket 1 and the guide cylinder 2 is 10-20mm.

In an exemplary embodiment, the length of the water jacket 1 is 900-1000mm.

In an exemplary embodiment, the inner diameter of the water jacket 1 is different along the axial direction of the water jacket 1.

The inner diameter of the water jacket 1 is different along the axial direction of the water jacket 1, i.e., the inner diameter of the water jacket 1 is varied along the axial direction of the water jacket 1, the variation of the inner diameter of the water jacket 1 is used to make the interval between different wall portions of the inner sidewall of the water jacket 1 in the axial direction of the water jacket 1 and the ingot 3 pulled out by the single crystal furnace and moved through the water jacket 1 in parallel with the axial direction different, for example, the interval between the upper portion of the inner sidewall of the water jacket 1 and the ingot 3 is larger than the interval between the lower portion of the inner sidewall of the water jacket 1 and the ingot 3, the difference in the spacing is used to make the cooling rate of the different rod portions of the ingot 3 corresponding to the different wall portions different, it is easy to understand that the cooling rate is faster for the portion of the ingot 3 closer to the inner side wall of the water jacket 1 and slower for the portion of the ingot 3 farther from the inner side wall, for example, the inner side wall of the water jacket 1 includes a first portion closer to the first end and a second portion farther from the first end, the inner diameter of the first portion being larger than the inner diameter of the second portion, at which time the cooling rate of the first portion is slower and the cooling rate of the second portion is faster, the difference in the cooling rates being used to make the temperature gradient of the ingot 3 meet the requirement.

In a specific embodiment, along the axial direction of the water jacket 1, the water jacket 1 includes a first end disposed near the top end of the single crystal furnace and a second end disposed far from the top end of the single crystal furnace, and the inner diameter of the water jacket 11 gradually decreases from the first end to the second end.

From the first end to the second end, the inner diameter of the water cooling jacket 1 gradually decreases, so that the temperature gradient of the crystal bar 3 in the axial direction of the crystal bar is uniformly changed, and the quality of the crystal bar 3 is improved.

In an exemplary embodiment, the water jacket 1 includes a housing and a cooling water pipe wound around a sidewall of the housing.

In an exemplary embodiment, the water inlet and the water outlet of the cooling water pipeline are arranged at one end of the shell close to the top end of the single crystal furnace, so that cooling water can be conveniently injected and discharged.

In an exemplary embodiment, the cooling water pipe may include a first straight portion extending in an axial direction of the water jacket 1 and formed with the water inlet, a second straight portion extending in the axial direction of the water jacket 1 and formed with the water outlet, and a spiral portion surrounding the housing and disposed between the water inlet and the water outlet, such that the cooling water pipe may be distributed throughout the water jacket 1.

The first straight line portion is connected to the start end of the spiral portion, the start end of the spiral portion is disposed near the first end of the water jacket 1, the end of the spiral portion is disposed near the second end of the water jacket 1, and the second straight line portion extends from the second end to the first end, so that the cooling water entering the spiral portion flows from the first end to the second end along the spiral portion.

Illustratively, the diameter of the cooling water pipe in the spiral portion may gradually decrease from the first end to the second end, the bottom portion of the ingot 3 (the portion of the ingot 3 near the bottom of the single crystal furnace) may correspond to a thinner cooling water pipe portion, and the cooling water flows faster in the thinner cooling water pipe portion, so that more heat can be taken away from the bottom portion of the ingot 3, or the cooling rate of the bottom portion of the ingot 3 is increased, which is beneficial to making the temperature of the ingot 3 in the axial direction more uniform and obtaining a smaller axial temperature gradient.

Illustratively, the water cooling jacket 1 may comprise an inner cylinder and an outer cylinder sleeved outside the inner cylinder, with the cooling water pipe being located between the inner cylinder and the outer cylinder.

The outer cylinder plays a role in protecting the cooling water pipeline, and plays a role in heat insulation and preservation.

In an exemplary embodiment, the inner surface of the guide cylinder 2 is provided with a stepped structure such that the inner diameter of the guide cylinder 2 gradually decreases from the top end of the guide cylinder 2 to the bottom end of the guide cylinder 2.

In an exemplary embodiment, the bottom end of the guide cylinder 2 has a first step 21, that is, a step near the bottom end of the guide cylinder 2 in the step structure is the first step 21, and the cross-section of the inner surface of the first step 21 is elliptical.

In the crystal pulling process, the crystal bar 3 forms stable and symmetrical temperature fields at the inner periphery of the ellipse during the rotation process, so that the pulsation change of the interface during the directional solidification process of the melt can be effectively avoided, the generation probability of defects is further reduced, the radial uniformity of oxygen in the crystal bar 3 is ensured, and the crystal bar 3 without defects and with uniform radial oxygen is pulled.

In an exemplary embodiment, the radial cross-sectional shape of the inner surface of the guide cylinder 2 is elliptical.

Because the heat regulation capability of the elliptic cavity is stronger, compared with the circular guide cylinder 2, the elliptic guide cylinder 2 can well transfer heat on the surface of the crystal bar 3, quickens the reaction of vacancy type defects and gap type defects in the area and is beneficial to the defect-free growth of the crystal bar 3.

In an exemplary embodiment, the step structure of the guide shell 2 includes a second step 22, and the water cooling jacket 1 is located above the step surface of the second step 22.

The orthographic projection of the end face of the bottom end of the water jacket 1 on the guide cylinder 2 is positioned on the step surface of the second step 22.

The second step 22 comprises a side surface adjacent to the step surface, and a gap is provided between the guide cylinder 2 and the water jacket 1 in the radial direction of the guide cylinder 2.

Referring to fig. 1, in an exemplary embodiment, the first step 21 and the second step 22 are disposed adjacent to each other.

In an exemplary embodiment, a plurality of notches are provided on the inner surface of the first step 21 at intervals along the circumferential direction of the guide cylinder 2.

The guide cylinder 2 mainly plays a role in isolating heat radiation of the heater on the single crystal in a thermal field, and increasing the temperature gradient of the single crystal, so that the pulling speed is improved, meanwhile, argon flows through the guide cylinder 2 to blow the liquid level, so that oxides are taken away, that is, the faster the argon flows through the lower edge speed of the guide cylinder 2, the more the oxides are taken away, and the lower the oxygen content of the single crystal is. The arrangement of the plurality of notches increases the area through which the shielding gas flows, and in the same time, the speed of the shielding gas flowing through the inner surface of the first step 21 with the notches is greater than that of the existing smooth inner surface, so that the capability of taking away oxide is improved, and the quality of single crystals is improved.

In an exemplary embodiment, along the axial direction of the guide cylinder 2, the guide cylinder 2 includes a first portion and a second portion, one end of the second portion is connected to the first portion, the other end of the second portion is a free end, and the free end of the second portion is disposed near the level of the silicon melt.

The inner surface of the second part is provided with the step structure, and the first step 21 is provided at the free end.

The arrangement of the notches increases the flow rate of the shielding gas flowing through the free end, compared with the free end of the second part of the existing guide cylinder 2, the arrangement of the notches increases the area of the shielding gas flowing through the free end of the second part of the guide cylinder 2, so that more shielding gas flows out of the free end of the second part of the guide cylinder 2, the flow rate of the shielding gas flowing through the free end of the second part of the guide cylinder 2 is increased, and in the same time, the flow rate of the shielding gas is increased, so that more oxides can be taken away by the shielding gas, the capability of taking away the oxides by the shielding gas is improved, the oxygen content of the drawn silicon single crystal is reduced, and the quality of the single crystal is improved.

The number of said notches is a plurality, chosen according to the size of the diameter of the free end of the second portion of the cartridge 2, not specifically required here. The guide cylinder 2 is of an annular structure, the second part of the guide cylinder 2 is a part, close to the silicon solution, of the guide cylinder 2, the free end of the second part of the guide cylinder 2 is close to the liquid level of the silicon solution, the free end of the second part is elliptical, the gaps are arranged along the circumference of the free end of the second part, and when the gaps are arranged, the gaps can be arranged at equal intervals or non-equal intervals, and the gaps are selected according to actual requirements and do not meet specific requirements. Preferably, in this embodiment, a plurality of the notches are equally spaced along the circumference of the free end of the second portion.

When the gap is arranged, the gap is arranged along the radial direction of the free end of the second part, that is, the gap is formed by the inward recession of the end part of the free end of the second part along the radial direction of the second part, and the area of the second part is increased along the radial direction, so that more shielding gas flows through the free end of the second part in the same time, and more oxide can be taken away by the shielding gas.

Illustratively, the recess is a through slot, i.e. in the axial direction of the guide cylinder 2, the recess is arranged through the first step 21. The shielding gas flows through the notch, the flowing area of the shielding gas is increased in different radial directions, the flow rate of the shielding gas flowing through the free end of the second part in unit time is increased, and the capability of the shielding gas for taking away oxides is improved.

Illustratively, the shielding gas is argon.

In an exemplary embodiment, the cross-sectional shape of the recess in the radial direction of the guide cylinder 2 is arc-shaped.

In some embodiments, the cross-sectional shape of the notch in the radial direction of the guide cylinder 2 is semicircular, but not limited thereto.

The notch is mainly used for dispersing the inert gas to flow in a lump, so that the inert gas to flow in a lump is reduced to form a large vortex, and the stability of a solid-liquid interface is greatly influenced by the large vortex, so that the stable growth of the crystal rod 3 is influenced.

In an exemplary embodiment, the inner surface of the first step 21 is recessed to form the notch, and a connection between the notch and the inner surface of the first step 21 is chamfered.

In an exemplary embodiment, the distance between the bottom of the guide cylinder 2 and the level of the silicon melt in the crucible assembly is 50-80mm.

The crucible assembly comprises a quartz crucible 4 and a graphite crucible 5 sleeved outside the quartz crucible 4, the graphite crucible 5 is used for supporting the quartz crucible 4, a silicon solution is contained in the quartz crucible 4, the distance from the bottom of the guide cylinder 2 to the liquid level of the silicon solution is a very important technological parameter, and in order to ensure stable defect-free growth of a crystal rod, the contact angle of a solid-liquid interface is ensured to be 10-15 degrees, and the distance is set to be 50-80mm.

The embodiment of the invention also provides a single crystal furnace, which comprises the water cooling jacket and a lifting structure for controlling the lifting of the water cooling jacket.

Specifically, the single crystal furnace comprises:

the furnace body is used for defining a cavity;

a crucible provided in the chamber, including a quartz crucible 4 for containing a silicon melt formed by pulling the crystal rod, and a graphite crucible 5 provided around the outside of the quartz crucible 4;

the guide cylinder is used for guiding inert gas to the upper part of the silicon melt, and is arranged on the periphery of the water cooling sleeve;

and the lifting structure is used for controlling the lifting of the water cooling jacket.

The embodiment of the invention also provides a crystal bar growth method, which comprises the following steps:

placing the nitrogen-doped polysilicon material in a quartz crucible;

sealing the furnace body of the single crystal furnace, vacuumizing and introducing inert gas;

heating to melt the polysilicon charge;

and lowering the seed crystals into the corresponding sub accommodating cavities, and performing a growth process comprising welding, shouldering, shoulder rotating and constant diameter.

The nitrogen is doped in the polysilicon material, the nitrogen can provide a needed nuclear embryo for oxygen precipitation heterogeneous nucleation, the nucleation work required by oxygen precipitation formation is reduced, BMD generation is promoted, the axial defect distribution of the crystal bar is changed by the nitrogen, the axial Margin region (defect-free region) of the crystal bar can be increased by nitrogen with a certain concentration, and the adjustment threshold value of pull speed is increased according to the V/G theory.

The following points need to be described:

(1) The drawings of the embodiments of the present disclosure relate only to the structures related to the embodiments of the present disclosure, and other structures may refer to the general design.

(2) In the drawings for describing embodiments of the present disclosure, the thickness of layers or regions is exaggerated or reduced for clarity, i.e., the drawings are not drawn to actual scale. It will be understood that when an element such as a layer, film, region or substrate is referred to as being "on" or "under" another element, it can be "directly on" or "under" the other element or intervening elements may be present.

(3) The embodiments of the present disclosure and features in the embodiments may be combined with each other to arrive at a new embodiment without conflict.

It is to be understood that the above embodiments are merely illustrative of the application of the principles of the present invention, but not in limitation thereof. Various modifications and improvements may be made by those skilled in the art without departing from the spirit and substance of the invention, and are also considered to be within the scope of the invention.

Claims

1. The utility model provides a single crystal furnace, includes furnace body and the crucible assembly that is located the furnace body, the top of crucible assembly is provided with the draft tube, the inside of draft tube is provided with the crystal bar and promotes the region, the crystal bar promote the region with be provided with the water cooling jacket between the draft tube, its characterized in that, the water cooling jacket is tubular structure, the water cooling jacket includes surface and internal surface on the radial direction of water cooling jacket, the cross-sectional shape of surface is circular, the cross-sectional shape of internal surface is oval.

2. The single crystal furnace of claim 1, wherein the outer surface is provided with a thermal barrier coating.

3. The single crystal furnace of claim 1, wherein the inner surface is provided with a heat absorbing coating.

4. A single crystal furnace according to claim 3, wherein the thickness of the heat absorbing coating gradually decreases in the axial direction of the water jacket in the direction from the bottom end to the top end of the water jacket.

5. A single crystal furnace according to claim 3, wherein the thickness of the heat absorbing coating is 200±25um.

6. The single crystal growing furnace of claim 1 wherein the gap between the bottom of the water jacket and the guide cylinder is 10-20mm.

7. The single crystal growing furnace of claim 1, wherein the inner surface of the guide cylinder is provided with a stepped structure such that the inner diameter of the guide cylinder gradually decreases from the top end of the guide cylinder to the bottom end of the guide cylinder.

8. The single crystal growing furnace of claim 7 wherein the bottom end of the guide cylinder has a first step, and the inner surface of the first step has an elliptical cross-sectional shape.

9. The single crystal growing furnace of claim 8, wherein a plurality of notches are provided on an inner surface of the first step at intervals along a circumferential direction of the guide cylinder.

10. The single crystal growing furnace of claim 9, wherein the notch has an arc-shaped cross-section in a radial direction of the guide cylinder.

11. The single crystal furnace of claim 1, wherein a distance between a bottom of the guide cylinder and a level of the silicon melt in the crucible assembly is 50-80mm.