CN110735180A - crystal pulling furnace - Google Patents
crystal pulling furnace Download PDFInfo
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- CN110735180A CN110735180A CN201810806334.6A CN201810806334A CN110735180A CN 110735180 A CN110735180 A CN 110735180A CN 201810806334 A CN201810806334 A CN 201810806334A CN 110735180 A CN110735180 A CN 110735180A
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- crystal puller
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 36
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Classifications
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
Abstract
The invention provides an crystal pulling furnace for producing defect-free silicon single crystal rods, which comprises a furnace body, a crucible, a side heater, a heat insulation layer and a bottom heater, wherein a cavity is arranged in the furnace body, the crucible is arranged in the cavity, the side heater is arranged on the outer side of the crucible, the heat insulation layer is arranged on the inner wall of the furnace body, the bottom heater is arranged between the bottom of the crucible and the heat insulation layer at the bottom of the furnace body, the bottom heater comprises a plurality of concentric annular heating parts and electrode interface parts arranged in the annular heating parts, and the concentric annular heating parts are electrically connected through the electrode interface parts.
Description
Technical Field
The invention relates to the field of crystal growth equipment, in particular to an crystal pulling furnace.
Background
The artificial crystal plays more and more important roles in the fields of scientific technology and industrial production, particularly, silicon single crystal is used as semiconductor materials and is applied to more and more in integrated circuits and other electronic components, most of the existing silicon single crystals are grown in a crystal pulling furnace by adopting the Czochralski method, the processes of melting, seeding, shouldering, isometric diameter, ending, cooling and the like are required for growing the silicon single crystal by adopting the Czochralski method, the growth of the large-size silicon single crystal becomes mainstream for reducing the production cost, and the feeding amount in the crystal growing process is increased to 400kg and the size of a crucible is increased to 32 inches and larger along with the increase of the diameter of the crystal in the process of preparing the large-size silicon single crystal and the development of the large-scale industrialization at present from 150 mm.
At the same time, the thermal field size of the growing crystal in the crystal pulling furnace is also gradually growing to a larger size, and a 32 inch large size thermal field is already in large scale use and gradually grows to 36 inches. In thermal fields of smaller dimensions, the quality requirements for semiconductor silicon wafers are not strong, but only that they are required to meet requirements, for example, for the absence of dislocations, resistivity ranges, dopant species, Oxidation Induced Stacking Faults (OISF), and since 1978 the impurity gettering capabilities of Bulk Micro Defects (BMDs) have been required, and because of the oxygen precipitation behavior during crystal pulling, wafer manufacturers have begun to make their own crystal pulling apparatuses. At the same time, the wafer manufacturer begins to control not only the Oi precipitation (i.e., oxygen precipitation) behavior, but also the point defect behavior during the crystal pull. Vacancies (vacancies) or dislocations are generated due to the accumulation of point defects during the crystal pull, which defects affect semiconductor device performance. The range of draw rates that can be selected is very narrow in order to minimize the agglomeration of vacancy atoms produced at higher draw rates and the agglomeration of additional silicon atoms produced at lower draw rates. Because each crystal puller has a different part life, accurate control over mass production is very easy.
Around 1990, wafer manufacturers have begun to reduce and minimize defects in mass production. Due to the compactness of the thermal field structure, the minimization of crystal defects is easier to achieve for a wafer with a diameter of 150mm than for a wafer with a diameter of 200 mm. The current 32-34 inch thermal field and larger thermal fields become more difficult to control to minimize intra-crystal defects for large scale production. Therefore, there is a need for more precise control of thermal field configurations.
In a small-size thermal field, the silicon material in the quartz crucible is heated mainly through the side heater, and along with the increase of the size and the feeding amount of the crucible, the bottom of the crucible is difficult to be uniformly heated only by the side heater, so that the temperature distribution in the silicon melt is uneven, the defects in the grown silicon single crystal are increased, and the quality of the silicon single crystal is influenced.
Therefore, in view of the above problems, it is necessary to propose new crystal pulling furnaces.
Disclosure of Invention
The concept of series in simplified form is introduced in the summary of the invention section, which is described in further detail in the detailed description section the 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 to identify key features or essential features of the claimed subject matter.
In view of the deficiencies of the prior art, the present invention provides an crystal pulling furnace for producing a defect-free monocrystalline silicon ingot, comprising:
a furnace body with a cavity inside;
the crucible is arranged in the cavity;
a side heater disposed outside the crucible;
the heat insulation layer is arranged on the inner wall of the furnace body;
the bottom heater is arranged between the bottom of the crucible and the heat insulation layer at the bottom of the furnace body;
the bottom heater comprises a plurality of concentric annular heating parts and an electrode interface part arranged in the annular heating parts, wherein the plurality of concentric annular heating parts are electrically connected through the electrode interface part.
Illustratively, the bottom heater comprises two electrode interface parts which are respectively positioned at two sides of the center of the bottom heater, wherein the centers of the two electrode interface parts and the center of the bottom heater are positioned on the same straight line, and the distance between the centers of the two electrode interface parts and the center of the bottom heater is equal.
Illustratively, different ones of the annular heating portions have different shapes, or at least any two of the annular heating portions have the same shape.
Illustratively, the electrode connecting port part penetrates through the upper and lower surfaces of at least annular heating parts, and/or
The peripheral side walls of the electrode interface part protrude outwards from the side wall of the annular heating part where the electrode interface part is located.
Illustratively, the peripheral side wall of the electrode interface portion is electrically connected with each annular heating portion outside the electrode interface portion.
Exemplary said crystal pulling furnace further comprises: the electrode supporting legs are arranged below the crucible, fixed at the bottom of the furnace body and upwards penetrate through the heat insulation layer, and the bottom heater is supported by the electrode supporting legs.
Exemplarily, the electrode interface part is provided with a through hole, the electrode supporting leg is provided with a screw hole, and the through hole and the screw hole are fixed through a bolt, so that the connection between the electrode interface part and the electrode supporting leg is realized.
Illustratively, a conductive gasket is respectively arranged between the electrode interface part and the screw hole.
Illustratively, the material of the bolt is graphite or a C-C composite material, and the conductive gasket is graphite paper.
Illustratively, the crystal pulling furnace further comprises:
and the crucible tray is arranged below the crucible, wherein the bottom heater is arranged between the crucible tray and the heat insulation layer at the bottom of the furnace body.
Illustratively, the crystal pulling furnace further comprises a crucible supporting shaft which is arranged below the crucible tray and connected with the crucible supporting shaft, the crucible supporting shaft is used for supporting the crucible tray and driving the crucible to lift and rotate, wherein the bottom heater is provided with a central through hole, and the supporting shaft penetrates through the central through hole.
Illustratively, the central through hole has a size larger than an outer diameter of the crucible supporting shaft.
Illustratively, each of the annular heating portions is symmetrical with respect to a straight line passing through a center of the bottom heater and a center of the electrode interface portion.
Illustratively, the annular heating portion has a shape of a circular ring, a wave shape, a polygonal ring, or a polygonal line.
Illustratively, the number of the annular heating parts is 3-8.
Illustratively, the material of the bottom heater is graphite or a C-C composite material, and is an body molding structure.
Illustratively, the radial dimensions of the different annular heating parts are respectively between 50mm and 450 mm.
Illustratively, the cross-sectional area of each annular heating part is 400mm2～3600mm2In the meantime.
Illustratively, the bottom heater is connected with an IGBT power supply through the electrode supporting legs, and the heating power of the bottom heater is controlled through a Programmable Logic Controller (PLC) so as to uniformly heat the bottom of the crucible.
Exemplarily, the heating power is between 0 and 60 KW.
The crystal pulling furnace comprises the bottom heater arranged below the crucible, the bottom heater can improve the material melting time in the process of the growth process of the silicon single crystal rod and the uniformity of temperature distribution in the crystal growth process, so that the heat of a thermal field is uniformly distributed, the temperature distribution in a melt is uniform and has small fluctuation, and the power of the bottom heater can be controlled to adjust the temperature gradient of a solid-liquid interface, thereby achieving the purpose of accurately controlling the difference between the inside and the outside of the V/G crystal rod and the oxygen precipitation degree, producing the defect-free silicon single crystal rod and improving the quality of the produced silicon single crystal.
Drawings
The following drawings of the present invention are included to provide an understanding of the invention as part of and are included to provide a further understanding of the invention.
In the drawings:
FIG. 1 shows a schematic partial cross-sectional view of an embodiment of a crystal pulling furnace of the present invention;
fig. 2 shows a top view of the bottom heater of embodiments of the present invention.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, it will be apparent to those skilled in the art that the present invention may be practiced without or more of these details.
It is to be understood that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals refer to like elements throughout.
It will be understood that when an element or layer is referred to as being "on.. another," "adjacent to.," connected to, "or" coupled to "other elements or layers, it can be directly on, adjacent to, connected to, or coupled to the other elements or layers, or intervening elements or layers may be present.
For example, if the device in the figures is turned over, then elements or features described as "below" or "beneath" would then be oriented "on" other elements or features.
As used herein, the singular forms "," "," and "the/the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, it is also to be 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 or more other features, integers, steps, operations, elements, components, and/or groups thereof.
In order to provide a thorough understanding of the present invention, a detailed structure will be set forth in the following description in order to explain the present invention. The following detailed description of the preferred embodiments of the invention, however, the invention is capable of other embodiments in addition to those detailed.
As the particle size of the substrate material is above 1/3 of the ULSI characteristic line width, the defect which is fatal to the photolithography technique becomes a critical factor which influences the GOI performance of the ultra-microelectronic element, and the device failure is caused, and the cavity type primary micro defect (COP) existing in the Czochralski silicon single crystal has a larger influence on the GOI performance of the ultra-microelectronic element, and becomes a key factor which influences the reliability and the yield of the integrated circuit.
In order to solve the above technical problems and produce a defect-free silicon single crystal rod, the present application proposes kinds of crystal pulling furnaces, mainly comprising:
a furnace body with a cavity inside;
the crucible is arranged in the cavity;
a side heater disposed outside the crucible;
the heat insulation layer is arranged on the inner wall of the furnace body;
the bottom heater is arranged between the bottom of the crucible and the heat insulation layer at the bottom of the furnace body;
the bottom heater comprises a plurality of concentric annular heating parts and an electrode interface part arranged in the annular heating parts, wherein the plurality of concentric annular heating parts are electrically connected through the electrode interface part.
The crystal pulling furnace comprises the bottom heater arranged below the crucible, the bottom heater can improve the material melting time in the process of the growth process of the silicon single crystal rod and the uniformity of temperature distribution in the crystal growth process, so that the heat in the whole radial direction is uniformly distributed, the uniform fluctuation of the temperature distribution in the solution is small, the temperature gradient of a solid-liquid interface is adjusted, and the purposes of accurately controlling the difference inside and outside the V/G crystal rod and the oxygen precipitation degree are achieved, so that the defect-free silicon single crystal rod is produced, and the quality of the produced silicon single crystal is improved.
The structure of the crystal pulling furnace of the present invention is described in detail below with reference to fig. 1 and 2, wherein fig. 1 shows a schematic partial cross-sectional view of an embodiment of the crystal pulling furnace of the present invention, and fig. 2 shows a top view of a embodiment of the bottom heater of the present invention.
Specifically, as shown in fig. 1, the crystal pulling furnace 1 comprises a furnace body 10, and a cavity 11 in the furnace body 10, wherein a crucible is arranged in the cavity 11. Illustratively, an insulating layer 18 is further disposed on the wall of the furnace body 10 for isolating heat exchange with the outside and stabilizing the thermal field in the cavity. The material of the insulating layer 18 can be any insulating material suitable for the crystal pulling furnace, the insulating material can play a role in isolation and can bear the high temperature in the crystal pulling furnace, and for example, the material of the insulating layer 18 can be carbonized or graphitized carbon fiber felt.
In examples, the crystal pulling furnace comprises a crucible for placing molten silicon material, wherein the crucible comprises a graphite crucible 13 and a quartz crucible 12 which are arranged from bottom to top in sequence, namely the quartz crucible 12 is arranged in the graphite crucible 13, and when in use, the quartz crucible 12 is filled with the molten silicon material.
, the crystal pulling furnace further comprises a crucible tray 14 and a crucible support shaft 15, wherein the crucible tray 14 is disposed below the crucible, for example, below the graphite crucible 13, and is connected to the crucible support shaft 15, wherein the crucible support shaft 15 is further disposed on the inner wall of the bottom of the furnace body through the insulating layer 18 at the bottom of the furnace body 10, and the crucible support shaft 15 is used for supporting the crucible tray 14 and driving the crucible to lift and rotate.
In examples, the crystal pulling furnace further comprises a side heater 16 disposed outside the crucible, the side heater 16 cylindrically surrounding the crucible for heating the silicon feedstock in the crucible to form a silicon melt and to form a thermal field, for example, outside the graphite crucible 13, alternatively, the side heater 16 may be any suitable side heater 16 known to those skilled in the art, such as a graphite heater, processed from graphite or carbon fiber, and having electrical conductivity, alternatively, an electrode quartz jacket (not shown) processed from quartz material may be disposed around the side heater 16 for electrical insulation.
In examples, the crystal pulling furnace further comprises an electrode supporting foot (not shown) which is arranged below the crucible, fixed at the bottom of the furnace body and penetrates through the heat insulation layer upwards, and the bottom heater is supported by the electrode supporting foot.
As the size and the amount of charge of the crucible increase, it is difficult to heat the bottom of the crucible uniformly only by the side heater 16, resulting in a larger degree of non-uniformity of the temperature distribution inside the silicon melt, leading to a larger distribution of defects in the grown silicon single crystal, and in particular, a reduction in pulling conditions without COP defects, thereby lowering the production efficiency of high quality silicon single crystals, and therefore, the bottom heater 17 is added to the crystal pulling furnace 1 of the present invention, and the bottom heater 17 and the side heater heat the silicon charge in the crucible together.
Illustratively, in order to ensure that the heat of the bottom heater 17 can be transferred to the crucible, the bottom heater 17 of the present invention is disposed between the bottom of the crucible and the insulating layer 18 of the bottom of the furnace body, for example, the bottom heater 17 is disposed between the crucible tray 14 and the insulating layer 18 of the bottom of the furnace body.
The structure of the bottom heater 17 of the present invention is described in detail below with reference to fig. 2, wherein fig. 2 shows a top view of the bottom heater 17 of embodiments of the present invention.
As an example, as shown in fig. 2, the bottom heater 17 includes a plurality of concentric annular heating portions 171 and an electrode interface portion 172 disposed in the annular heating portions 171, wherein the plurality of concentric annular heating portions 171 are electrically connected through the electrode interface portion 172, so that when a current is applied to the bottom heater through the electrode supporting legs, the bottom heater generates heat.
A plurality of concentric annular heating portions 171 are sleeved at , wherein adjacent annular heating portions 171 may have the same interval therebetween, or may have different intervals therebetween, for example, the interval between adjacent annular heating portions 171 decreases or increases from the center to the outside, and specifically, may be adjusted appropriately according to the distribution of the actual heat field.
Where, when each of the annular heating portions 171 has a certain thickness, concentrically means that the annular heating portions 171 have the same central axis, and further , each of the annular heating portions 171 is symmetrical about the center.
Preferably, in order to make the bottom of the crucible heated more uniformly, each of the annular heating portions 171 is about a straight line (shown as a dotted line in fig. 2) passing through the center of the bottom heater and the center of the electrode interface portion 172.
Further , the shape of each annular heating portion 171 may be any suitable ring shape, such as a circular ring shape, a wavy shape, a polygonal ring shape or a polygonal line shape, wherein the square ring shape may be a square ring shape, or the polygonal ring shape is preferably a square polygonal ring shape.
It is also possible to make different the annular heating portions have different shapes, or at least any two of the annular heating portions have the same shape.
The number of the heating parts included in each bottom heater can be reasonably set according to actual equipment needs, the number of the annular heating parts is 3-8, and the setting can also be set according to the in-plane size of the thermal field, for example, as shown in fig. 2, the bottom heater 17 includes 3 annular heating parts 171 in a circular ring shape, the three annular heating parts 171 in a circular ring shape are concentric, have different radiuses, and are sequentially sleeved from outside to inside at .
The bottom heater 17 may be made of any suitable conductive material, for example, the bottom heater 17 may be made of graphite or a C-C composite material and may be formed of bodies, especially the high-purity material bodies, i.e. the electrode connecting portion 172 and the plurality of annular heating portions 171 .
The size of the annular heating part 171 is appropriately designed according to the size of the crucible in the crystal pulling furnace, for example, the radial sizes of the annular heating parts 171 are respectively 50mm to 450mm, for example, the inner diameter (diameter) of the annular heating part 171 located at the innermost ring of the bottom heater is 100mm at the minimum, and the outer diameter (diameter) of the annular heating part 171 located at the outermost ring of the bottom heater is 900mm at the maximum.
, the cross-sectional area of the annular heating part 171 is important to the heat generation efficiency of the bottom heater, and can be selected reasonably according to the actual thermal field requirement, for example, the cross-sectional area of each annular heating part 171 is 400mm2～3600mm2In the meantime.
By adjusting the control of the temperature distribution of the melt portion in the production of single crystal silicon by the Czochralski method through the variation of the shape and size of the annular heating portion 171, further the convection of the melt is controlled, thereby creating growth conditions for producing perfect crystals.
In examples, as shown in fig. 2, the electrode interface 172 penetrates the upper and lower surfaces of at least annular heating portions 171, for example, the electrode interface 172 penetrates the intermediate annular heating portions 171, the number of the intermediate annular heating portions 171 may be any suitable number, the peripheral side wall of the electrode interface 172 is electrically connected to each of the annular heating portions outside the electrode interface, the inner side wall of the annular heating portion 171 located at the outermost ring is electrically connected to the outer side wall of the electrode interface 172, the outer side wall of the annular heating portion 171 located at the innermost ring is electrically connected to the outer side wall of the electrode interface 172, and thus the electrode interface 172 is electrically connected to the plurality of annular heating portions 171.
Illustratively, for electrical connection with the annular heating portions 171 of the outermost and innermost rings, the peripheral side walls of the electrode interface portion 172 protrude outward of the side walls of the annular heating portion 171 where the electrode interface portion 172 is located.
The bottom heater comprises two electrode interface parts 172 respectively located at two sides of the center of the bottom heater, wherein the centers of the two electrode interface parts 172 and the center of the bottom heater are located on the same line , and the distance between the centers of the two electrode interface parts 172 and the center of the bottom heater is equal, for example, when the annular heating part 171 is circular, the two electrode interface parts 172 are located at two ends of the diameter of the annular heating part 171 and are symmetrical with respect to the center of the circle.
Because the electrode interface part 172 is connected with the electrode supporting legs, the electrode supporting legs can support the bottom heater, so that more than two electrode interface parts can be arranged to ensure the stability and balance of the support, only two of the electrode interface parts can be connected with the anode and the cathode of the power supply to supply power to the bottom heater, the rest of the electrode interface parts can be used as auxiliary supports, and the electrode interface parts 172 can be uniformly distributed around the bottom heater.
The two electrode interface portions 172 may be substantially the same size or different sizes, and may have circular ring shapes or other suitable shapes such as square ring shapes or polygonal ring shapes.
It is worth to mention that each electrode interface 172 may correspond to electrode support legs, that is, the number of electrode support legs corresponds to the number of electrode interface 172.
In cases, each of the electrode connecting portions 172 has through holes 1721, the electrode supporting legs (not shown) have screw holes (not shown) corresponding to each of the through holes 1721, and each of the through holes and the screw holes are fixed by bolts (not shown), so that each of the electrode connecting portions 172 is connected to the electrode supporting legs to support and energize the bottom heater.
, for better contact between the bottom heater and the electrode, a conductive gasket (not shown) is disposed between each electrode interface 172 and the screw hole.
In examples, in order to achieve good contact between the bolt and the bottom heater, and further steps to ensure better contact between the bottom heater and the electrode, a conductive gasket (not shown) may also be disposed between the head (e.g., hexagonal head) of the bolt disposed in each electrode interface portion 172 and the electrode interface portion 172, respectively.
The material of the bolt and the conductive gasket can be any suitable conductive material, the conductive material can bear the high temperature in the crystal pulling furnace, preferably, the material of the bolt is graphite or C-C composite material, and the conductive gasket is graphite paper.
, the bottom heater 17 has a center through hole 173, as shown in FIGS. 1 and 2, the bottom heater 17 is located below the crucible tray 14, and the crucible supporting shaft 15 penetrates the center through hole 173. in order to allow the crucible supporting shaft 15 to penetrate the center through hole 173 without affecting the rotation and up-down movement of the crucible supporting shaft 15, the center through hole 173 has a size larger than the outer diameter of the crucible supporting shaft 15.
It is worth to mention that the structure of the bottom heater 17 shown in fig. 2 is only an example, and the technical solution of the present invention may also include modifications of the above-mentioned embodiment and other realizable embodiments without being limited to the example, such as the shape and number of the annular heating portion, etc., which are not listed in .
In cases, the bottom heater 17 is connected to an IGBT power supply (not shown) through the electrode support legs, and the heating power of the bottom heater 17 is controlled by a Programmable Logic Controller (PLC) to heat the bottom of the crucible assembly uniformly, and the temperature gradient of the solid-liquid interface can be adjusted by controlling the power of the bottom heater, so as to achieve the purpose of accurately controlling the difference between the inside and outside of the V/G crystal bar and the degree of oxygen precipitation, thereby producing defect-free silicon single crystal bars and improving the quality of the produced silicon single crystal.
Other components may be included in the completed crystal pulling furnace, such as a guide cylinder 19, the guide cylinder 19 is disposed above the crucible, the bottom end of the guide cylinder is located in the crucible, as shown in fig. 1, the bottom end of the guide cylinder is located in the quartz crucible 12, and the top end of the guide cylinder 19 is connected to the top end of the insulating layer 18, the guide cylinder is used for isolating heat generated from the heater and guiding the air flow to circulate, and further description of other possible components is omitted from .
In summary, the bottom heater is arranged below the crucible, the side heater and the bottom heater are heated by current introduced through the electrodes, silicon raw materials in the crucible are melted to form silicon solution, and then silicon crystals are pulled out from the liquid level of the silicon solution through seed crystal induction.
Since the silicon single crystal ingot is formed by solidifying the molten silicon material, the temperature gradient of the solid-liquid interface has a great effect on the quality of the formed ingot during the solidification process, for example, if the temperature gradient of the solid-liquid interface in the solid is too large, interstitial silicon atoms and even dislocation groups are easily generated in the formed ingot, and if the temperature gradient of the solid-liquid interface in the solid is too small, vacancies and even COP defects are easily formed, and the proper V/G affects the quality of the ingot, the concentration of the single crystal point defects is related to the V/G, when the V/G is equal to or more than a certain critical value of , the concentration of the interstitial atoms is reduced, when the V/G is less than a certain critical value of , the concentration of the vacancies is very small, and the two critical values are about 1.3X 10-3cm-2min-1K-1(or 2.2X 10)-5cm-2sec-1K-1) Left and right. Therefore, it is more difficult to cause a proper V/G at the temperature difference between the inside and outside of the large-diameter ingot. Therefore, the accurate control of the V/G is vital to the growth of defect-free silicon single crystal rods, and the crystal pulling furnace is additionally provided with the bottom heater, the bottom heater is connected with an IGBT power supply through the electrode supporting feet, the heating power of the bottom heater is controlled through a Programmable Logic Controller (PLC), and the heating power of the bottom heater can be adjusted according to the distribution of an actual thermal field, so that the temperature gradient of a solid-liquid interface can be adjusted, the aim of accurately controlling the V/G is fulfilled, the density of COP defects and dislocation groups during production is reduced, the defect-free silicon single crystal rods (such as COP defects and dislocation groups) are produced, and the quality and the production efficiency of the produced silicon single crystal rods are finally improved.
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 (20)
- A crystal pulling furnace of the type for producing a defect-free monocrystalline silicon rod, comprising:a furnace body with a cavity inside;the crucible is arranged in the cavity;a side heater disposed outside the crucible;the heat insulation layer is arranged on the inner wall of the furnace body;the bottom heater is arranged between the bottom of the crucible and the heat insulation layer at the bottom of the furnace body;the bottom heater comprises a plurality of concentric annular heating parts and an electrode interface part arranged in the annular heating parts, wherein the plurality of concentric annular heating parts are electrically connected through the electrode interface part.
- 2. A crystal puller as set forth in claim 1 wherein the bottom heater includes two of the electrode interface portions located on either side of a center of the bottom heater, wherein the centers of the two electrode interface portions are located on the same line as the center of the bottom heater and the distances between the centers of the two electrode interface portions and the center of the bottom heater are equal.
- 3. A crystal puller as set forth in claim 1 wherein different ones of the annular heating sections have different shapes or at least any two of the annular heating sections have the same shape.
- 4. A crystal puller as set forth in claim 1 wherein the electrode interface portions extend through upper and lower surfaces of at least of said annular heaters and/orThe peripheral side walls of the electrode interface part protrude outwards from the side wall of the annular heating part where the electrode interface part is located.
- 5. A crystal puller as set forth in claim 1 wherein the peripheral side wall of the electrode interface is electrically connected to each of the annular heaters outside the electrode interface.
- 6. A crystal puller as set forth in claim 1 wherein the crystal puller further comprises: the electrode supporting legs are arranged below the crucible, fixed at the bottom of the furnace body and upwards penetrate through the heat insulation layer, and the bottom heater is supported by the electrode supporting legs.
- 7. A crystal pulling furnace as set forth in claim 6 wherein the electrode interface portion has a through hole and the electrode support foot has a threaded hole, the through hole being bolted to the threaded hole to effect connection of the electrode interface portion to the electrode support foot.
- 8. A crystal puller as set forth in claim 7 wherein a conductive gasket is disposed between each of the electrode interface and the screw hole.
- 9. A crystal puller as set forth in claim 8 wherein the bolt material is graphite or a C-C composite and the conductive pad is graphite paper.
- 10. A crystal puller as set forth in claim 1 further comprising:and the crucible tray is arranged below the crucible, wherein the bottom heater is arranged between the crucible tray and the heat insulation layer at the bottom of the furnace body.
- 11. A crystal pulling furnace as set forth in claim 10 further comprising a crucible support shaft disposed below and connected to the crucible support shaft for supporting the crucible tray and driving the crucible up and down and to rotate, wherein the bottom heater has a central throughbore through which the support shaft extends.
- 12. A crystal puller as set forth in claim 11 wherein the central throughbore is sized larger than the outer diameter of the crucible support shaft.
- 13. A crystal puller as set forth in claim 1 wherein each of the annular heaters is symmetrical about a line passing through the center of the bottom heater and the center of the electrode interface portion.
- 14. A crystal puller as set forth in claim 1 wherein the annular heating section is in the shape of a circular ring, a wave, a polygonal ring or a dogleg.
- 15. A crystal puller as set forth in claim 1 wherein the number of the plurality of annular heaters is 3 to 8.
- 16. A crystal puller as set forth in claim 1 wherein the material of the bottom heater is graphite or a C-C composite and is an body form.
- 17. A crystal puller as set forth in claim 1 wherein the different annular heaters each have a radial dimension of between 50mm and 450 mm.
- 18. A crystal puller as set forth in claim 1 wherein each of said annular heating segments has a cross-sectional area of 400mm each2～3600mm2In the meantime.
- 19. A crystal pulling furnace as set forth in claim 6 wherein the bottom heater is connected to an IGBT power supply through the electrode support legs and the heating power of the bottom heater is controlled by a Programmable Logic Controller (PLC) to provide uniform heating of the crucible bottom.
- 20. A crystal puller as set forth in claim 19 wherein the heating power is between 0 and 60 KW.
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| CN201810806334.6A CN110735180A (en) | 2018-07-20 | 2018-07-20 | crystal pulling furnace |
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| CN201810806334.6A CN110735180A (en) | 2018-07-20 | 2018-07-20 | crystal pulling furnace |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111424315A (en) * | 2020-05-18 | 2020-07-17 | 西安奕斯伟硅片技术有限公司 | Single crystal furnace thermal field heater assembly and single crystal furnace |
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