Ingot lifting device with silicon supply tube equipped with kick plate

Abstract

An ingot pulling apparatus is disclosed that includes a silicon supply tube for adding solid silicon to a crucible assembly, the silicon supply tube including a conduit portion having an inner diameter and a kick plate disposed below the conduit portion, the kick plate extending across at least 60% of the inner diameter of the conduit portion.

Description

Cross-reference of related applications

[0001] This application claims the interests of U.S. Provisional Patent Application No. 63 / 313,988, filed on 25 February 2022, which is incorporated herein by reference in its entirety. [Technical Field]

[0002] The field of this disclosure relates to silicon supply tubes for adding solid silicon to crucible assemblies, and more particularly to ingot pulling apparatus having silicon supply tubes having a kick plate at the outlet of the silicon supply tube. [Background technology]

[0003] Single-crystal silicon ingots can be grown by the so-called Czochralski process, in which a silicon seed crystal is brought into contact with a silicon melt. The silicon seed crystal is drawn out of the melt, forming a silicon single-crystal ingot suspended from the seed crystal. In the batch Czochralski process, an initial charge of solid silicon is added to a crucible assembly, and the melt is formed by melting the charge. Further solid silicon can be added to this initial melt to form floating clusters or "islands" of solid silicon on top of the silicon melt. The portion of the island in contact with the melt liquefies, thereby increasing the size of the melt. The size of the island increases if the rate of solid silicon added to the crucible assembly is greater than the melting rate. As the island grows, it can become unbalanced and tilt or flip over into the melt. In such cases, the supply of solid silicon is stopped, and heater power is controlled to prevent the tilted or flipped island from colliding with the hot zone. There is a need for ingot pulling equipment that can produce more stable solid silicon islands and / or reduce melting time and / or heater power. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] This section is intended to introduce to the reader various aspects of the technology that may be relevant to various aspects of this disclosure, which are described and / or claimed below. We believe this discussion is useful in providing the reader with background information to facilitate a better understanding of the various aspects of this disclosure. Therefore, these descriptions should be understood to be read in this context and not as prior art acknowledgments. [Means for solving the problem]

[0005] One aspect of the present disclosure is directed to an ingot pulling apparatus for manufacturing single-crystal silicon ingots. The ingot pulling apparatus includes a crucible assembly for holding a silicon melt. A crystal pulling housing defines a growth chamber for pulling a silicon ingot from the silicon melt. The crucible assembly is located inside the growth chamber. The apparatus includes a silicon supply tube for adding solid silicon to the crucible assembly. The silicon supply tube includes a conduit portion having an inner diameter and a kick plate located below the conduit portion. The kick plate extends over at least 60% of the inner diameter of the conduit portion.

[0006] Another aspect of the present disclosure is directed to an ingot pulling apparatus for manufacturing single-crystal silicon ingots. The ingot pulling apparatus includes a crucible assembly for holding a silicon melt. A crystal pulling housing defines a growth chamber for pulling a silicon ingot from the silicon melt. The crucible assembly is located inside the growth chamber. The apparatus includes a silicon supply tube for adding solid silicon to the crucible assembly. The silicon supply tube includes a conduit portion and a kick plate partially located below the conduit portion. The kick plate has height. The conduit portion overlaps the kick plate by less than 70% of its height.

[0007] Various improvements exist to the features pointed out in relation to the aforementioned embodiments of this disclosure. Further features can also be incorporated into the aforementioned embodiments of this disclosure. These improvements and additional features may exist individually or in any combination. For example, the various features described below in relation to any illustrated embodiment of this disclosure may be incorporated individually or in any combination into any of the aforementioned embodiments of this disclosure. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of an example of an ingot lifting device in which silicon charges are placed inside a crucible assembly. [Figure 2] This is a cross-sectional view of an ingot pulling device where the initial melt is formed from a silicon charge. [Figure 3] This is a cross-sectional view of an ingot lifting device in which a silicon supply pipe is positioned above the initial melt. [Figure 4] This is a cross-sectional view of an ingot pulling device in which islands of solid silicon are placed on a silicon melt. [Figure 5] This is a cross-sectional view of an ingot pulling device in which a silicon seed crystal has been lowered to come into contact with the molten metal in order to initiate ingot growth. [Figure 6] This is a cross-sectional view of an ingot pulling machine during ingot growth. [Figure 7] This is a cross-sectional view of a silicon supply tube. [Figure 8] This is a perspective view of the guide portion of the silicone supply tube. [Figure 9] This is a cross-sectional view of the guide portion of the silicone supply tube. [Figure 10] This is a schematic diagram of solid silicon islands with a pyramidal shape and solid silicon islands with a volcanic shape. [Figure 11] This is a schematic diagram illustrating the various stages of island formation and growth in molten silicon. [Figure 12] This includes box plots of heater power and melting time for a conventional silicon supply tube and the silicon supply tube shown in Figure 7.

[0009] Corresponding reference letters indicate the corresponding parts throughout the drawing. [Modes for carrying out the invention]

[0010] An exemplary ingot puller (or more simply, an "ingot puller") is schematically shown as "100" in Figure 1. The ingot puller 100 includes a crucible assembly 102 for holding a molten silicon (Figure 5) of semiconductor or solar cell grade raw material. The crucible assembly 102 is supported by a susceptor 106. The ingot puller 100 includes a crystal pull housing 108 that defines a growth chamber 152 for pulling a silicon ingot 113 (Figure 6) from the molten silicon 104 along a pull axis A.

[0011] The crucible assembly 102 has side walls 131 (Figure 1) and a floor 129 and rests on a susceptor 106. The susceptor 106 is supported by a shaft 105. The susceptor 106, crucible assembly 102, shaft 105, and ingot 113 (Figure 6) have a common longitudinal axis or “lifting axis” A.

[0012] A lifting mechanism 114 (Figure 5) is provided inside the ingot lifting device 100 to grow and lift an ingot 113 (Figure 6) from the molten metal 104. The lifting mechanism 114 includes a lifting cable 118, a seed holder or chuck 120 connected to one end of the lifting cable 118, and a seed crystal 122 connected to the seed holder or chuck 120 to initiate crystal growth. One end of the lifting cable 118 is connected to a pulley (not shown) or drum (not shown) or other suitable type, such as a shaft, of the lifting mechanism 114, and the other end is connected to a chuck 120 that holds the seed crystal 122. During operation, the seed crystal 122 is lowered to contact the surface 111 (Figure 5) of the molten metal 104. The lifting mechanism 114 is operated to raise the seed crystal 122. This causes the single-crystal ingot 113 (Figure 6) to be lifted from the molten metal 104.

[0013] During heating and crystal pulling, the crucible drive unit 107 (e.g., a motor) rotates the crucible assembly 102 and the susceptor 106. The lift mechanism 112 raises and lowers the crucible assembly 102 along the pulling axis A during the growth process. For example, the crucible assembly 102 may be at the lowest position (near the bottom heater 126) where the charge of solid polycrystalline silicon 133 previously added to the crucible assembly 102 is melted. Crystal growth is initiated by bringing the melt 104 (Figure 5) into contact with the seed crystal 122 and lifting the seed crystal 122 by the pulling mechanism 114.

[0014] A crystal drive unit (not shown) can also rotate the pulling cable 118 and the ingot 113 (Figure 6) in a direction opposite to the direction in which the crucible drive unit 107 rotates the crucible assembly 102 (e.g., counter-rotation). In embodiments using the same rotation, the crystal drive unit can rotate the pulling cable 118 in the same direction as the crucible drive unit 107 rotates the crucible assembly 102.

[0015] The ingot pulling apparatus 100 includes a bottom heat insulator 110 and a side heat insulator 124 to retain heat within the pulling apparatus 100. In the illustrated embodiment, the ingot pulling apparatus 100 includes a bottom heater 126 disposed below the crucible floor 129. The crucible assembly 102 can be moved into relatively close proximity to the bottom heater 126 to melt the solid silicon charged into the crucible assembly 102, as further described below.

[0016] According to the Czochralski single-crystal growth process, a certain amount of solid silicon 133 (Figure 1), such as polycrystalline silicon, or "polysilicon," is initially charged into a crucible assembly 102. The semiconductor or solar cell grade solid silicon introduced into the crucible assembly 102 is melted by heat supplied from one or more heating elements. The size of the solid silicon charge 133 may correspond to a desired size of melt when ingot growth begins, or, as in embodiments of the present disclosure, a smaller charge may be used and further silicon may be added by a silicon supply system 200 (Figure 3) to form the initial volume of melt present at the start of ingot growth.

[0017] Once the initial charge of solid silicon 133 is added to the crucible assembly 102, the bottom heater 126 and side heaters 135 may be powered to melt the charge 133 and form the initial melt of silicon 115 (Figure 2). To form the remainder of the melt, solid silicon is added to the melt 115 by the silicon supply system 200 (Figure 3) through the supply tube 190 (Figure 3). The solid silicon supplied to the crucible assembly 102 by the silicon supply system 200 may be, for example, granular, lumpy, chipped, or a combination thereof. The silicon supply system 200 may include components suitable for adding solid silicon to the crucible assembly and may include a container and / or supply tray for holding the solid silicon. A vibrating motor may be powered to vibrate the supply tray to move the solid silicon from the container to the supply tube 190. The outlet of the supply tray may be connected to the supply tube 190. A valve mechanism can be used to seal the supply pipe 190 during periods when silicon is not being supplied to the supply pipe 190 (for example, the valve mechanism may be removably engaged with the outlet of the tray). Examples of components of the silicon supply system 200 are shown and described in U.S. Patent No. 10,577,717, which is incorporated herein by reference for all relevant and consistent purposes.

[0018] Before adding solid silicon to the initial melt 115, the silicon supply system 200 is docked (e.g., via an isolation valve) to the ingot lifting device 100, and the supply pipe 190 is lowered (e.g., using a motor-driven gear system) into the growth chamber 152. The silicon is introduced into the silicon supply pipe 190 by the silicon supply system 200. The solid silicon passes through the pipe 190 and is discharged through the outlet 132 (Figure 3) of the supply pipe 190. The discharged solid silicon accumulates on the surface of the initial melt 115. The silicon forms islands of solid silicon 139 (Figure 4) floating on the melt 115. The solid silicon within the islands melts, thereby increasing the size of the melt. If the rate of addition of solid silicon exceeds the melting rate, the islands increase in size as shown in Figure 11.

[0019] Once the melt is fully formed, the silicon supply tube 190 is removed from the growth chamber 152. The seed crystal 122 (Figure 5) is lowered and brought into contact with the surface 111 of the melt 104. The pull-up mechanism 114 is activated to pull the seed crystal 122 from the melt 104. Referring here to Figure 6, the ingot 113 includes a crown portion 142 that tapers outward from the seed crystal 122 to reach the target diameter. The ingot 113 includes a constant diameter portion 145 or cylindrical "body" of the crystal that is grown by increasing the pull-up rate. The body 145 of the ingot 113 has a relatively constant diameter. The ingot 113 includes a tail or end cone (not shown) where the ingot becomes thinner in diameter after the body 145. When the diameter is sufficiently small, the ingot 113 is then separated from the melt 104. Generally, the crystal growth process involves first forming a silicon melt in the crucible assembly without any further solid silicon being added to the crucible assembly 102 during crystal growth. to This is a batch process (in contrast to the continuous Czochralski process, where a certain amount of silicon is added to the crucible assembly during ingot growth).

[0020] The ingot pulling device 100 includes side heaters 135 and a susceptor 106 surrounding the crucible assembly 102 to maintain the temperature of the molten metal 104 during crystal growth. The side heaters 135 are positioned radially outward relative to the crucible sidewalls 131 as the crucible assembly 102 moves up and down along the pulling axis A. The side heaters 135 and bottom heater 126 may be any type of heater that enables the side heaters 135 and bottom heater 126 to operate as described herein. In some embodiments, the heaters 135,126 are resistance heaters. The side heaters 135 and bottom heater 126 may be controlled by a control system (not shown) so that the temperature of the molten metal 104 is controlled throughout the pulling process.

[0021] The ingot pulling device 100 may include a heat shield 151. The heat shield 151 can enclose the ingot 113 and may be placed inside the crucible assembly 102 during crystal growth (Figure 6). The ingot pulling device 100 may include an inert gas system for introducing and withdrawing an inert gas, such as argon, from the growth chamber 152.

[0022] Referring here to Figure 7, the silicon supply tube 190 includes an inlet 128 (which may engage with a supply tray located above the tube 190) and an outlet 132. The silicon supply tube 190 includes a conduit portion 150 through which solid silicon passes. A kick plate 153 located below the conduit portion 150 directs the solid silicon into the crucible assembly 102 (for example, away from the center of the crucible assembly, as shown in Figure 11). The conduit portion 150 of the silicon supply tube 190 includes a baffle (not shown) that controls the velocity of the solid silicon passing through the tube 190. In the illustrated embodiment, the silicon supply tube 190 includes a guide portion 166 (Figure 8) and a tube portion 168 (Figure 7) located above the guide portion 166. The guide portion 166 and the tube portion 168 may be connected by any suitable method such as friction fitting, threads, adhesive, or fasteners (e.g., grooves and pins, flanges, or couplings). Although the guide portion 166 and the tube portion 168 of the silicon supply tube 190 are shown and described herein as separate components that are connected, in other embodiments the guide portion 166 and the tube portion 168 are formed from a single piece (i.e., are integral). The tube portion 168 may also include various interconnected parts.

[0023] In the illustrated embodiment, the kick plate 153 is part of the guide portion 166. As shown in Figure 8, the guide portion 166 also includes at least a portion of the conduit portion 150 of the pipe 190. The remainder of the conduit portion 150 is part of the pipe portion 168 (Figure 7). In other embodiments, the pipe portion 168 may include the entire conduit portion 150 of the pipe 190.

[0024] The illustrated silicon supply tube 190 is an example, and the silicon supply tube can be modified without departing from the scope of the present disclosure (for example, by including additional or fewer parts, or by including various bends).

[0025] In some embodiments of the present disclosure, the silicone supply tube 190 or any portion thereof (e.g., kick plate 153, conduit portion 150, guide portion 166, and / or tube portion 178) is made of silicone.

[0026] Referring now to Figure 9, the kick plate 153 forms an angle λ with the longitudinal axis A of the supply pipe 190 190 . The angle λ may range from 20° to 60°.

[0027] The conduit portion 150 of the silicon supply pipe 190 has an inner diameter D 150 (i.e., the inner diameter at which the conduit portion 150 contacts the kick plate 153, such as when the diameter of the conduit portion 150 varies). The kick plate 153 extends over at least a portion of the inner diameter as indicated by L 153 . In some embodiments, the kick plate 153 extends over at least 60% of the inner diameter D 150 (i.e., the ratio L 153 / D 150 is at least 0.6). In other embodiments, the kick plate extends over at least 70% of the inner diameter D of the conduit portion 150 150 , or over at least 75%, at least 80%, 60% to 100%, 70% to 100%, 80% to 100%, 60% to 90%, or 70% to about 90% of the inner diameter D of the conduit portion 150 150 .

[0028] The kick plate 153 and the conduit portion 150 of the silicon supply pipe 190 form an inner corner 179 and an outer corner 180. The kick plate 153 has an upper end 185 aligned with the inner corner 179, and has a lower end 182. The kick plate 153 has a height H extending from the upper end 185 to the lower end 182 153 .

[0029] The conduit portion 150 has a lower end 175. In the illustrated embodiment, the conduit portion 150 (e.g., the portion opposite the kick plate 153 as in the illustrated embodiment) includes a portion that vertically overlaps with the kick plate 153 . The length of this portion overlapping the kick plate 153 is denoted as H in Figure 9150 As shown by [translate]. In some embodiments, the conduit portion 150 is at the height H of the kick plate. 153 Overlapping by less than 70% (i.e., percentage H) 150 / H 153 (This is less than 0.7). In some embodiments, the conduit portion 150 overlaps the kick plate 153 by less than 60% of its height, or by less than 50%, less than 40%, 20% to 70%, or 20% to 60% of its height.

[0030] Compared to conventional silicon supply tubes, the silicon supply tube of this disclosure offers several advantages. By using a kick plate that extends to at least 60% of the inner diameter of the conduit section, the solid silicon exits the silicon supply tube away from the center of the crucible assembly, creating islands of solid silicon floating in the molten material that have a “volcano” shape rather than a pyramidal shape (Figure 10). The volcano-shaped islands are more stable on the molten material, less likely to tilt or tip over, and allow melting to proceed with less manual control. The volcano-shaped islands also reduce melting time and the amount of heater power required to melt the solid silicon. By using a conduit section that overlaps the kick plate height by less than 70% (e.g., 20% to 70%), the radial distance from which the solid silicon is discharged from the tube can be improved and more precisely controlled.

[0031] Examples The processes described herein are further illustrated by the following embodiments, which should not be considered limiting.

[0032] Example 1: Reduction of supply time and heater power To add solid silicon to the initial silicon melt, a silicon supply tube having a guide section as shown in Figure 9 was used. Conventional silicon supply tubes were also used to add solid silicon to the initial silicon melt, which had a guide tube with a kick plate extending over less than 60% of the inner diameter of the conduit section, and a conduit section that overlapped by more than 70% of the height of the kick plate.

[0033] As shown in Figure 12, using the supply pipe with the guide portion shown in Figure 9 ("New") reduced the total melting time by approximately 2 hours and the heater power consumption during melting by 10 kW compared to the conventional silicon supply pipe ("POR").

[0034] As used herein, when used in conjunction with ranges of dimensions, concentrations, temperatures, or other physical or chemical properties or characteristics, the terms “about,” “substantially,” “essentially,” and “approximately” mean to cover the variations that may exist in the upper and / or lower limits of the range of properties or characteristics, including, for example, variations resulting from rounding, measurement methodologies, or other statistical variations.

[0035] When describing elements or embodiments of the present disclosure, the articles “a,” “an,” “the,” and “said” are intended to indicate that there is one or more elements. The terms “comprising,” “including,” “containing,” and “having” are intended to indicate comprehensiveness and mean that there may be additional elements other than those listed. The use of terms indicating a particular orientation (e.g., “top,” “bottom,” “side”) is for explanatory convenience and does not require a specific orientation of the item being described.

[0036] Various modifications can be made to the above structure and method without departing from the scope of this disclosure, so all matters included in the above description and shown in the accompanying drawings are intended to be illustrative and not restrictive.

Claims

1. A method for manufacturing single-crystal silicon ingots, The solid-phase silicon is added to a crucible placed inside the growth chamber, The initial melt is a material containing solid silicon which melts in order to form an initial melt having a surface, The method involves lowering the silicon supply tube into the growth chamber, The aforementioned silicon supply pipe, A conduit portion having an inner diameter, and A kick plate extending from the conduit portion and positioned below the conduit portion, having a kick plate that extends over 60% to 90% of the length of the inner diameter of the conduit portion, for lowering a silicone supply pipe, The method involves adding further solid-state silicon to the initial melt through the silicon supply pipe, wherein the further solid-state silicon is in the form of lumpy solid-state silicon, and the further solid-state silicon accumulates on the surface of the initial melt, forming an island having a volcanic shape with a central recess and a surrounding raised portion. Removing the aforementioned silicon supply tube from the growth chamber, The further solid-phase silicon islands are melted to increase the size of the melted area, Lowering the seed crystal and bringing it into contact with the molten surface, The process involves pulling up the aforementioned seed crystal to form a single-crystal silicon ingot, A method of having.

2. The kick plate extends over 70% to 90% of the length of the inner diameter of the conduit portion. The method according to claim 1.

3. The silicone supply tube has a longitudinal axis, and the kick plate and the longitudinal axis intersect to form an angle between 20° and 60°. The method according to claim 1.

4. The kick plate has height, the conduit portion overlaps a portion of the kick plate along its height, and the length of the portion of the kick plate overlapped by the conduit portion is less than 70% of the height of the kick plate. The method according to claim 1.

5. The single-crystal silicon ingot is formed without any further solid-phase silicon being added to the crucible during the growth of the single-crystal silicon ingot. The method according to claim 1.

6. A method for manufacturing single-crystal silicon ingots, The solid-phase silicon is added to a crucible placed inside the growth chamber, The initial melt is a material containing solid silicon which melts in order to form an initial melt having a surface, The method involves lowering the silicon supply tube into the growth chamber, The aforementioned silicon supply pipe, A conduit portion having an inner diameter, and A kick plate extending from the conduit portion and positioned below the conduit portion, having a kick plate that extends over 60% to 90% of the length of the inner diameter of the conduit portion, for lowering a silicone supply pipe, The process involves adding further solid-state silicon to the initial melt through the silicon supply pipe, wherein the further solid-state silicon is in the form of lumpy solid-state silicon, and the further solid-state silicon accumulates on the surface of the initial melt. Removing the aforementioned silicon supply tube from the growth chamber, The further solid-phase silicon is melted to increase the size of the melt, Lowering the seed crystal and bringing it into contact with the molten surface, The seed crystal is pulled up to form a single-crystal silicon ingot without any further solid-phase silicon being added to the crucible during the growth of the single-crystal silicon ingot, A method of having.

7. The kick plate extends over 70% to 90% of the length of the inner diameter of the conduit portion. The method according to claim 6.

8. The silicone supply tube has a longitudinal axis, and the kick plate and the longitudinal axis intersect to form an angle between 20° and 60°. The method according to claim 6.

9. The kick plate has height, the conduit portion overlaps a portion of the kick plate along its height, and the length of the portion of the kick plate overlapped by the conduit portion is less than 70% of the height of the kick plate. The method according to claim 6.

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