CN112921395A

CN112921395A - Crystal pulling device

Info

Publication number: CN112921395A
Application number: CN202110088626.2A
Authority: CN
Inventors: 沈伟民
Original assignee: Zing Semiconductor Corp
Current assignee: Zing Semiconductor Corp
Priority date: 2021-01-22
Filing date: 2021-01-22
Publication date: 2021-06-08
Also published as: TW202229665A; TWI746400B

Abstract

The invention discloses a crystal pulling device. The crystal pulling device comprises a guide shell, the guide shell comprises an inner shell, an outer shell and a thermal insulation material arranged between the inner shell and the outer shell, the thermal insulation material comprises a cylindrical solid felt formed by winding fiber materials, wherein the winding direction of the fiber is close to the normal direction perpendicular to the side wall of the inner shell, so that the extending direction of the fiber materials is close to the direction parallel to the side wall of the inner shell of the guide shell. According to the crystal pulling device, the winding direction of the fiber materials for forming the solid felt of the heat insulation material is set to be close to the normal direction perpendicular to the side wall of the inner cylinder, so that the extending direction of the fiber materials is close to the direction parallel to the side wall of the inner cylinder of the guide cylinder, when heat is transmitted to the inner side from the crucible or the silicon melt in the crucible through the side wall of the guide cylinder, the heat transmission efficiency is reduced because the heat transmission direction is perpendicular to the extending direction of the fiber materials, and the heat insulation effect of the heat insulation material is maximized.

Description

Crystal pulling device

Technical Field

The invention relates to the technical field of semiconductors, in particular to a crystal pulling device.

Background

The czochralski method (Cz) is an important method for preparing silicon single crystals for semiconductors and solar energy, and comprises heating and melting a high-purity silicon material placed in a crucible by a thermal field composed of carbon materials, and then immersing seed crystals into the melt and carrying out a series of processes (melting, temperature stabilization, seeding, shouldering, constant diameter, ending and cooling) to finally obtain single crystal rods.

In the ingot growth of semiconductor single crystal silicon or solar single crystal silicon by the CZ method, the temperature distribution of the ingot and the melt directly affects the quality and growth rate of the ingot. During the growth of CZ crystal bar, the guide shell (or reflecting screen) is used as an important part in the crystal pulling thermal field, which prevents the heat of the silicon melt liquid level and the quartz crucible from radiating to the crystal bar, and plays the role of improving the crystal pulling speed and controlling the defects of the crystal.

Referring to FIG. 1, a schematic of a crystal pulling apparatus is shown. As shown in FIG. 1, the crystal pulling apparatus comprises a furnace body 1, a crucible 11 is provided in the furnace body 1, a heater 12 for heating the crucible 11 is provided outside the crucible 11, and a silicon melt 13 is contained in the crucible 11. A pulling device 14 is arranged at the top of the furnace body 1, the seed crystal is pulled out of the crystal rod 10 from the liquid level of the silicon melt under the driving of the pulling device 14, and in order to realize the stable growth of the crystal rod, a driving device 15 for driving the crucible 11 to rotate and move up and down and a magnetic field applying device 17 arranged outside the furnace body for applying a magnetic field to the silicon melt in the crucible are further arranged at the bottom of the furnace body 1. With continued reference to FIG. 1, the crystal pulling apparatus also includes heat shield apparatus disposed about the periphery of the ingot 10. The heat shield device comprises a guide cylinder 16, the guide cylinder 16 is in a barrel shape, and is used as the heat shield device for isolating a quartz crucible and heat radiation generated by silicon melt in the crucible to the surface of a crystal bar in the crystal bar growing process, improving the cooling speed and the axial temperature gradient of the crystal bar and increasing the growth speed of the crystal bar on one hand, and influencing the distribution of a thermal field on the surface of the silicon melt on the other hand, so that the excessive difference of the axial temperature gradients of the center and the edge of the crystal bar is avoided, and the stable growth between the crystal bar and the liquid level of the silicon melt is ensured; meanwhile, the guide cylinder is also used for guiding the inert gas introduced from the upper part of the crystal bar growing furnace to enable the inert gas to pass through the surface of the silicon melt at a larger flow speed, so that the effect of controlling the oxygen content and the impurity content in the crystal bar is achieved. During the growth of a semiconductor crystal rod, the crystal rod 10 vertically passes through the guide shell 16 upwards under the driving of the pulling device 14.

Referring to fig. 2, a schematic cross-sectional structure of a draft tube is shown. As shown in fig. 2, the guide cylinder is provided in an annular cylindrical structure, and is composed of an outer cylinder 161, an inner cylinder 162, and a heat insulating material 163 between the inner and outer cylinders. The heat insulating material has the function of preventing heat entering the outer barrel from being transferred to the inner barrel, so that the temperature of the inner barrel is prevented from rising, and meanwhile, the heat of the crystal facing the inner barrel is not easy to transfer out, so that the temperature gradient of the crystal bar is small. Since the opposing surface between the guide shell 16 and the crucible 11 and the silicon melt 13 in the crucible is constantly changing during the pulling process, as shown in fig. 2, in the bottom position of the guide shell, the heat of the crucible and the silicon melt in the crucible needs to be transferred to the inner shell 162 through the heat insulating material 163 having a thick bottom, and in the upper position of the guide shell, the heat of the crucible and the silicon melt in the crucible needs to be transferred to the inner shell 162 through the heat insulating material 163 having a thin upper.

Current insulation materials are divided into soft and solid felts. The solid felt has stable shape and stable performance, and is widely used in a thermal field for semiconductor crystal growth. The heat insulating material is manufactured by winding graphite fibers into a cylindrical solid felt according to a desired shape and finally performing surface wrapping treatment, and as disclosed in patent application CN102367588A, the graphite felt is widely used as a heat insulating layer of a crystal pulling device, wherein the graphite felt is heat-insulated by being disposed between an outer draft tube and an inner draft tube in a draft tube. The solid felt, because it is formed by winding of fibers, has anisotropic thermal conductivity and thermal expansion properties depending on the fiber direction. In terms of the thermal conductivity, the thermal conductivity along the extending direction of the fibers is 2 to 3 times as large as that along the normal direction perpendicular to the extending direction of the fibers. As shown in fig. 2, the insulation material 163 is wound from fibers in one direction to form one body (lines of the insulation material 163 are shown as fibers in fig. 2), wherein in the bottom region of the draft tube, heat is transferred to the inner tube 162 through the insulation material 163 in the extending direction of the fibers, and in the upper region of the draft tube, heat is transferred to the inner tube 162 through the insulation material 163 in the normal direction perpendicular to the extending direction of the fibers. Because the heat conduction coefficient along the extension direction of the fiber is larger than that along the normal direction vertical to the extension direction of the fiber, the temperature at the bottom of the inner cylinder is higher, the average temperature reaches 1050 ℃, the temperature of the crystal bar is limited to be transmitted out through the inner cylinder, the temperature gradient of the crystal is smaller, the crystal pulling speed is reduced, and the crystal pulling quality is influenced.

To solve the problems in the prior art, the invention provides a crystal pulling device.

Disclosure of Invention

In this summary, concepts in a simplified form are introduced that are further described in the detailed description. This summary of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In order to solve the problems in the prior art, the invention provides a crystal pulling device which comprises a guide cylinder, wherein the guide cylinder comprises an inner cylinder, an outer cylinder and a heat insulation material arranged between the inner cylinder and the outer cylinder, the heat insulation material comprises a cylindrical solid felt formed by winding fiber materials, and the winding direction of the fiber materials is close to the normal direction vertical to the side wall of the inner cylinder, so that the extending direction of the fiber materials is close to the direction parallel to the side wall of the inner cylinder of the guide cylinder.

Illustratively, the draft tube comprises a first part and a second part from top to bottom, the outer tube comprises an outer tube upper part and an outer tube lower part, the inner tube comprises an inner tube upper part and an inner tube lower part, the inner tube upper part and the outer tube upper part and a first solid felt positioned between the inner tube upper part and the outer tube upper part form the first part, and the inner tube lower part and the outer tube lower part and a second solid felt positioned between the inner tube lower part and the outer tube lower part form the second part

Illustratively, the second portion protrudes inwardly of the draft tube relative to the first portion.

Illustratively, the first portion and the second portion have different winding directions of the fiber material.

Illustratively, the first part is provided as a cylindrical barrel, and the winding direction of the fiber material of the first solid felt in the first part is along a direction close to a normal line perpendicular to the upper part of the outer barrel.

Illustratively, the lower part of the inner cylinder comprises a plane arranged horizontally or a slope inclined downwards in the radius direction, and the winding direction of the fiber material of the second solid felt in the second part is along the direction close to the normal perpendicular to the lower part of the inner cylinder.

Illustratively, the direction of extension of the fibrous material of the first solid mat in the first section is in the range of 75-105 ° from a normal to the sidewall of the upper portion of the inner barrel.

Illustratively, the angle between the direction of extension of the fibrous material of the second solid mat in the second section and a normal perpendicular to the lower portion of the inner barrel is in the range of 75-105 °.

Illustratively, the fiber material of the first solid felt in the first section extends in a direction parallel to a sidewall of the upper portion of the inner barrel.

Illustratively, the fiber material of the second solid felt in the second section extends in a direction parallel to the lower portion of the inner barrel.

According to the crystal pulling device, the winding direction of the fiber materials for forming the solid felt of the heat insulation material is set to be close to the normal direction perpendicular to the side wall of the inner cylinder, so that the extending direction of the fiber materials is close to the direction parallel to the side wall of the inner cylinder of the guide cylinder, when heat is transmitted to the inner side from the crucible or the silicon melt in the crucible through the side wall of the guide cylinder, the heat transmission efficiency is reduced because the heat transmission direction is perpendicular to the extending direction of the fiber materials, and the heat insulation effect of the heat insulation material is maximized.

Drawings

The following drawings of the invention are included to provide a further understanding of the invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a schematic diagram of a crystal pulling apparatus according to one embodiment;

FIG. 2 is a schematic view of a draft tube in a crystal pulling apparatus according to one embodiment;

FIG. 3 is a schematic structural view of a crystal pulling apparatus according to one embodiment of the present invention;

FIG. 4A is a schematic structural view of a draft tube in a crystal pulling apparatus according to one embodiment of the present invention;

FIG. 4B is a schematic structural view of a draft tube in a crystal pulling apparatus according to another embodiment of the present invention;

FIG. 4C is a schematic view of a guide shell in a crystal pulling apparatus according to another embodiment of the present invention.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent that the invention may be practiced without limitation to specific details that are within the skill of one of ordinary skill in the semiconductor arts. The following detailed description of the preferred embodiments of the invention, however, the invention is capable of other embodiments in addition to those detailed.

It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular is intended to include the plural unless the context clearly dictates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Exemplary embodiments according to the present invention will now be described in more detail with reference to the accompanying drawings. These exemplary embodiments may, however, be embodied in many different forms and should not be construed as limited to only the embodiments set forth herein. It is to be understood that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of these exemplary embodiments to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity, and the same elements are denoted by the same reference numerals, and thus the description thereof will be omitted.

An exemplary crystal pulling apparatus in accordance with the present invention is described below with reference to fig. 3 and 4A-4C. FIG. 3 is a schematic structural view of a crystal pulling apparatus according to one embodiment of the present invention; FIG. 4A is a schematic structural view of a draft tube in a crystal pulling apparatus according to one embodiment of the present invention; FIG. 4B is a schematic structural view of a draft tube in a crystal pulling apparatus according to another embodiment of the present invention; FIG. 4C is a schematic view of a guide shell in a crystal pulling apparatus according to another embodiment of the present invention.

As shown in fig. 3, the crystal pulling apparatus includes a furnace body 2, a crucible 21 is provided in the furnace body 2, a heater 22 for heating the crucible 21 is provided outside the crucible 21, and a silicon melt 23 is contained in the crucible 21. A pulling device 24 is arranged at the top of the furnace body 2, the seed crystal is pulled out of the crystal rod 20 from the liquid level of the silicon melt under the driving of the pulling device 24, and in order to realize the stable growth of the crystal rod, a driving device 25 for driving the crucible 21 to rotate and move up and down and a magnetic field applying device 27 arranged outside the furnace body for applying a magnetic field to the silicon melt in the crucible are further arranged at the bottom of the furnace body 2. With continued reference to FIG. 3, the crystal pulling apparatus also includes heat shield apparatus disposed about the periphery of the ingot 20. The heat shield device comprises a guide cylinder 26, the guide cylinder 26 is in a barrel shape, and is used as a heat shield device for isolating a quartz crucible and heat radiation generated by silicon melt in the crucible to the surface of a crystal bar in the crystal bar growing process, improving the cooling speed and the axial temperature gradient of the crystal bar and increasing the growth speed of the crystal bar on one hand, and influencing the distribution of a thermal field on the surface of the silicon melt on the other hand, so that the excessive difference of the axial temperature gradients of the center and the edge of the crystal bar is avoided, and the stable growth between the crystal bar and the liquid level of the silicon melt is ensured; meanwhile, the guide cylinder is also used for guiding the inert gas introduced from the upper part of the crystal bar growing furnace to enable the inert gas to pass through the surface of the silicon melt at a larger flow speed, so that the effect of controlling the oxygen content and the impurity content in the crystal bar is achieved. During the growth of a semiconductor crystal rod, the crystal rod 20 is driven by the pulling device 24 to vertically and upwardly pass through the guide cylinder 26.

Referring to FIG. 4A, a schematic of the construction of a draft tube in a crystal pulling apparatus according to the present invention is shown. The guide cylinder is arranged in a cylindrical structure with an upper opening and a lower opening around the silicon crystal rod, and is symmetrical about a central axis. Fig. 4A is a schematic cross-sectional view of the guide cylinder on the silicon ingot side.

Illustratively, the cartridge includes, but is not limited to, a cylindrical cartridge, a conical cartridge, and the like.

As shown in fig. 4A, the guide shell 26 is provided in a cylindrical tubular structure.

The guide cylinder 26 includes a first portion (a portion in a dashed line frame 26 a) and a second portion (a portion in a dashed line frame 26 b), the outer cylinder of the guide cylinder 26 includes an outer cylinder upper portion 261a and an outer cylinder lower portion 261b, the inner cylinder of the guide cylinder 26 includes an inner cylinder upper portion 262a and an inner cylinder lower portion 262b, and the insulation material includes a solid felt formed by winding a fiber material, including a first solid felt 263a and a second solid felt 263 b.

As shown in fig. 4A, the outer cylinder upper part 261a, the inner cylinder upper part 262a, and the first solid felt 263a located between the outer cylinder upper part 261a and the inner cylinder upper part 262a constitute a first portion (portion in the broken-line frame 26 a) of the draft tube 26, and the outer cylinder lower part 261b, the inner cylinder lower part 262b, and the second solid felt 263b located between the outer cylinder lower part 261b and the inner cylinder lower part 262b constitute a second portion (portion in the broken-line frame 26 b) of the draft tube 26.

Illustratively, the material of the inner and outer barrels is provided as graphite.

In the invention, the heat insulation material is set into a cylindrical solid felt formed by winding a fiber material.

Exemplary fibrous materials for wound insulation include fiberglass, graphite fibers, and the like.

In the embodiment, graphite fibers are wound to form a cylindrical solid felt as the heat insulation material.

Illustratively, as shown in fig. 4A, the second portion (the portion in the dashed box 26 b) protrudes toward the inside of the guide cylinder with respect to the portion in the first portion dashed box 26 a).

On one hand, the guide shell is used as a heat shielding device for shielding heat radiated from the crucible and the silicon melt to the silicon crystal bar, and the guide shell is arranged in a way that the second part protrudes towards the inner side of the guide shell relative to the first part, so that the heat radiated from the silicon melt at the bottom of the guide shell and the crucible to the silicon crystal bar can be further shielded, and the shielding effect is improved. The guide cylinder is used as an argon guide device in the second aspect, in the crystal pulling process, the argon introduced into the crystal pulling chamber is guided, the second part is arranged in a protruding mode relative to the first part towards the inner side of the guide cylinder, and the passage of the argon flowing to the liquid level of the silicon melt through the guide cylinder is effectively reduced, so that the flow speed of the argon flowing from the top of the furnace body and flowing back to the liquid level of the silicon melt through the guide cylinder is increased, the shearing force of the liquid level of the silicon melt is increased, accordingly, the flowing structure of the silicon melt is further adjusted, the flowing state of the silicon melt is more uniform along the circumferential direction, the speed uniformity of crystal growth is further improved, and the crystal pulling quality is improved.

Illustratively, the first portion and the second portion have different winding directions of the fiber materials.

Since the solid felt is formed by winding a fiber material, the thermal conductivity and thermal expansion properties of the solid felt are anisotropic according to the direction of the fiber material. In terms of the thermal conductivity, the thermal conductivity along the extension direction of the fiber material is 2-3 times as large as that along the normal direction perpendicular to the extension direction of the fiber material.

In this embodiment, the winding direction of the fiber material used for forming the solid felt of the heat insulating material is set to be close to the direction perpendicular to the normal line of the side wall of the inner cylinder, so that the extending direction of the fiber material is close to the direction parallel to the side wall of the inner cylinder of the guide cylinder.

As shown in fig. 4A, the first portion of the guide shell 26 is provided as a cylindrical shell, wherein the first portion of the guide shell 26 shown in fig. 4A is rectangular in cross-section. Further, with continued reference to fig. 4A, the fiber material of the first solid mat 263a forming the first part of the guide shell 26 is wound in a direction perpendicular to the normal direction of the inner cylinder sidewall (i.e., the inner cylinder upper portion 262a) of the first part such that the extending direction of the fiber material is parallel to the sidewall (i.e., the inner cylinder upper portion 262a) of the inner cylinder of the first part.

Illustratively, the lower part of the inner cylinder comprises a plane horizontally arranged or a slope inclined downwards, and the winding direction of the fiber material of the second solid felt in the second part is along a direction close to a normal line vertical to the lower part of the inner cylinder.

As shown in fig. 4A, the second portion of the guide shell 26 protrudes inward from the first portion, and the inner cylinder lower portion 262b is a horizontally disposed plane, so that the second portion of the guide shell 26 is provided as a cylindrical barrel having an inner diameter smaller than that of the first portion.

Referring to FIG. 4B, a schematic diagram of a draft tube in a crystal pulling apparatus according to another embodiment of the present invention is shown. The draft tube of fig. 4B is similar to the draft tube of fig. 4A, except that a second portion of the draft tube 26 of fig. 4B protrudes inward from the first portion, and the inner tube lower portion 262B is a slope inclined downward in the radial direction, so that the second portion of the draft tube 26 is provided with a cylindrical tube having a smaller inner diameter than the first portion and a top inclined downward in the radial direction.

Referring to FIG. 4C, a schematic diagram of a draft tube in a crystal pulling apparatus is shown, according to another embodiment of the present invention. The draft tube in fig. 4C is similar to the draft tube in fig. 4A and 4B, except that a second portion of the draft tube 26 in fig. 4C protrudes inward from the first portion, and the inner tube lower portion 262B is a slope inclined downward in a radial direction such that the second portion of the draft tube 26 is provided with a tapered tube extending downward.

With continued reference to fig. 4A, the fiber material of the second solid felt 263b forming the second part of the guide shell 26 is wound in a direction perpendicular to the normal line direction of the inner cylinder sidewall (i.e., the inner cylinder lower portion 262b) of the second part such that the extending direction of the fiber material is parallel to the inner cylinder sidewall (i.e., the inner cylinder lower portion 262b) of the second part.

Since the extending direction of the fiber material of the first part of the first fixing felt 263a is parallel to the upper part 262a of the inner cylinder, when the heat of the crucible or the silicon melt is transferred to the inner side of the draft tube 26 through the first part of the draft tube 26, the heat is transferred along the extending direction perpendicular to the fiber material, and the heat resistance effect is good because the heat conduction coefficient is small in the extending direction perpendicular to the fiber material.

Also, since the fiber material of the second portion of the second fixing felt 263b extends in parallel to the inner cylinder lower part 262b, when the heat of the crucible or the silicon melt is transferred to the inner side of the draft tube 26 through the second portion of the draft tube 26, the heat is transferred in the direction perpendicular to the extension direction of the fiber material, so that the heat blocking effect is good since the thermal conductivity coefficient is small in the direction perpendicular to the extension direction of the fiber material.

It should be understood that the above-mentioned winding of the fiber material of the first solid felt 263a of the first part along the direction perpendicular to the normal of the inner cylinder sidewall (i.e. the upper part 262a of the inner cylinder) of the first part and the winding of the fiber material of the second solid felt 263b of the second part along the direction perpendicular to the normal of the inner cylinder sidewall (i.e. the lower part 262b) of the second part are merely exemplary, and in the actual winding process, the winding directions of the fiber materials of the first part and the second part are set to be different, and the winding can be performed along the direction close to the direction perpendicular to the inner cylinder sidewall of the first part or the inner cylinder sidewall of the second part, respectively, so long as the extending direction of the fiber material is as parallel to the plane of the inner wall of the guide cylinder as far as possible, and the heat conduction reducing effect of the present invention can be achieved along the extending direction perpendicular to the extending direction of the fiber material in the heat propagation, the technical effect of heat insulation is enhanced.

In one embodiment according to the invention, the winding direction of the fiber material of the first solid felt in the first section is along a direction close to a normal line perpendicular to the upper part of the inner cylinder, and the extending direction of the fiber material of the first solid felt in the first section is in a range of 75-105 degrees from a normal line perpendicular to the side wall of the upper part of the inner cylinder.

In one embodiment according to the present invention, the winding direction of the fiber material of the second solid felt in the second section is along a direction close to a normal line perpendicular to the lower part of the inner cylinder, and the included angle between the extending direction of the fiber material of the second solid felt in the second section and the normal line perpendicular to the lower part of the inner cylinder is in the range of 75-105 °.

In one embodiment, the guide shell as shown in fig. 2 is adopted, wherein the fixed felt at the bottom of the guide shell and the fixed felt at the upper part of the guide shell are made of fiber materials and are wound along the same direction, so that the temperature at the bottom of the inner cylinder of the guide shell is higher, the average temperature reaches 1050 ℃, and finally the average pulling speed of the crystal pulling process is 1.0 mm/min.

According to an embodiment of the present invention, a draft tube as shown in fig. 4A is used, wherein the fixed felt at the bottom of the draft tube and the fixed felt at the upper part of the draft tube are made of fiber materials and wound in different directions, wherein the fixed felt at the upper part of the draft tube is made of fiber materials and wound in a direction perpendicular to the normal direction of the side wall of the draft tube, so that the extending direction of the fiber materials of the fixed felt at the upper part of the draft tube is parallel to the side wall of the draft tube, and the fixed felt at the bottom of the draft tube is made of fiber materials and wound in a direction perpendicular to the normal direction of the bottom of the draft tube, so that the extending direction of the fiber materials of the fixed felt at the bottom of the draft tube is parallel to the bottom of the draft tube, and finally, the temperature at the bottom of the inner tube of the draft tube in fig. 4A is reduced, specifically reduced to 1000 ℃, so that the average pulling, the pulling speed is improved by 20 percent.

In the crystal pulling apparatus according to the present invention, the winding direction of the fiber material to form the solid mat of the heat insulating material is set to be close to the normal direction perpendicular to the side wall of the inner cylinder so that the extending direction of the fiber material is close to the direction parallel to the side wall of the inner cylinder of the guide cylinder, and when heat is transferred from the crucible or the silicon melt in the crucible to the inside through the side wall of the guide cylinder, the efficiency of heat conduction is reduced because the conduction direction of the heat is perpendicular to the extending direction of the fiber material, so that the heat resistance effect of the heat insulating material is maximized.

The present invention has been illustrated by the above embodiments, but it should be understood that the above embodiments are for illustrative and descriptive purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many variations and modifications may be made in accordance with the teachings of the present invention, which variations and modifications are within the scope of the present invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. The utility model provides a crystal pulling device, its characterized in that includes the draft tube, the draft tube includes inner tube, urceolus and sets up the inner tube with thermal insulation material between the urceolus, thermal insulation material includes the solid felt of tube-shape that adopts the fiber material coiling to form, wherein, the coiling direction of fiber material is close to the perpendicular to the normal direction of inner tube lateral wall, so that the extending direction of fiber material be close to with the parallel direction of inner tube lateral wall of draft tube.

2. A crystal puller as set forth in claim 1 wherein the draft tube includes a first section and a second section from top to bottom, the outer tube includes an outer tube upper portion and an outer tube lower portion, the inner tube includes an inner tube upper portion and an inner tube lower portion, the inner tube upper portion and the outer tube upper portion and a first solid blanket located therebetween constituting the first section, the inner tube lower portion and the outer tube lower portion and a second solid blanket located therebetween constituting the second section.

3. A crystal puller as set forth in claim 2 wherein the second portion projects inwardly of the draft tube relative to the first portion.

4. A crystal puller as set forth in claim 3 wherein the fiber material of the first and second sections is wound in a different direction.

5. A crystal puller as set forth in claim 4 wherein the first section is provided as a cylindrical drum and the direction of winding of the fibrous material of the first solid felt in the first section is in a direction close to normal to the upper portion of the outer drum.

6. A crystal puller as set forth in claim 5 wherein the lower portion of the inner barrel includes a horizontally disposed flat surface or a radially downwardly sloping surface, the direction of winding of the fibrous material of the second solid felt in the second section being along a direction which is closer to normal to the lower portion of the inner barrel.

7. A crystal puller as set forth in claim 3 wherein the direction of extension of the fibrous material of the first solid felt in the first section is in the range of 75 ° to 105 ° from normal to the side wall of the upper portion of the inner barrel.

8. A crystal puller as set forth in claim 3 wherein the direction of extension of the fibrous material of the second solid felt in the second section is at an angle in the range of 75 ° to 105 ° to normal to the lower portion of the inner barrel.

9. A crystal puller as set forth in claim 2 wherein the fiber material of the first solid felt in the first section extends in a direction parallel to a side wall of the upper portion of the inner barrel.

10. A crystal puller as set forth in claim 2 wherein the fibrous material of the second solid felt in the second section extends in a direction parallel to the lower portion of the inner barrel.