Ingot pulling apparatus having silicon supply tube 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 TO RELATED APPLICATIONS

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

[0002] The field of the disclosure relates to an ingot puller apparatus having a silicon feed tube for adding solid silicon to a crucible assembly, and in particular a silicon feed tube having a kick plate at the outlet of the silicon feed tube. [Background technology]

[0003] Single crystal silicon ingots can be grown by the so-called Czochralski process, in which a silicon seed crystal is contacted with a melt of silicon. The silicon seed crystal is withdrawn from the melt to form a silicon single crystal ingot suspended on the seed crystal. In the batch Czochralski process, a melt is formed by adding an initial charge of solid silicon to a crucible assembly and melting the charge. Additional solid silicon can be added to this initial melt to form floating clusters or "islands" of solid silicon on top of the silicon melt. Portions of the islands that contact the melt liquefy, thereby increasing the size of the melt. If the rate of solid silicon added to the crucible assembly is greater than the melting rate, the size of the islands increases. As the islands grow, they may become unbalanced and tilt or tip over into the melt. In such a case, the supply of solid silicon is stopped and the heater power is controlled to prevent the tilted or tip over islands from impinging on the hot zone. A need exists for an ingot pulling apparatus that produces more stable islands of solid silicon and / or reduces melting times and / or heater power. Summary of the Invention [Problem to be solved by the invention]

[0004] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. As such, it should be understood that these statements are to be read in this light, and not as admissions of prior art. [Means for solving the problem]

[0005] One aspect of the disclosure is directed to an ingot pulling apparatus for producing a single crystal silicon ingot. 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 disposed within 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 includes a kick plate disposed below the conduit portion. The kick plate extends across at least 60% of the inner diameter of the conduit portion.

[0006] Another aspect of the disclosure is directed to an ingot pulling apparatus for producing a single crystal silicon ingot. 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 disposed within 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 disposed partially below the conduit portion. The kick plate has a height. The conduit portion overlaps less than 70% of the height of the kick plate.

[0007] Various refinements exist in the features noted in relation to the above-mentioned aspects of the disclosure. Additional features may be incorporated into the above-mentioned aspects of the disclosure as well. These refinements and additional features may exist individually or in any combination. For example, various features described below in relation to any of the illustrated embodiments of the disclosure may be incorporated alone or in any combination into any of the above-mentioned aspects of the disclosure. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of an example of an ingot pulling apparatus with a silicon charge disposed within a crucible assembly. [Diagram 2] FIG. 2 is a cross-sectional view of an ingot pulling apparatus in which an initial melt is formed from a silicon charge. [Diagram 3] FIG. 2 is a cross-sectional view of an ingot pulling apparatus in which a silicon supply pipe is disposed above the initial melt. [Figure 4] FIG. 1 is a cross-sectional view of an ingot puller in which an island of solid silicon is disposed above a silicon melt. [Diagram 5] FIG. 2 is a cross-sectional view of an ingot puller with a silicon seed crystal lowered into contact with the melt to initiate ingot growth. [Figure 6] FIG. 2 is a cross-sectional view of an ingot pulling apparatus during ingot growth. [Figure 7] FIG. 2 is a cross-sectional view of a silicon supply pipe. [Figure 8] FIG. 13 is a perspective view of a guide portion of a silicon supply tube. [Figure 9] FIG. 4 is a cross-sectional view of a guide portion of a silicon supply pipe. [Figure 10] 1A-1C are schematic diagrams of solid silicon islands having pyramid and volcano shapes; [Figure 11] 1A-1D are schematic diagrams of various stages of silicon melt island formation and growth. [Figure 12] 8 includes box plots of heater power and melt time for a conventional silicon supply tube and the silicon supply tube shown in FIG.

[0009] Corresponding reference characters indicate corresponding parts throughout the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An exemplary ingot pulling apparatus (or more simply "ingot puller") is shown generally as "100" in FIG. 1. The ingot pulling apparatus 100 includes a crucible assembly 102 for holding a melt 104 (FIG. 5) of semiconductor or solar grade source silicon. The crucible assembly 102 is supported by a susceptor 106. The ingot pulling apparatus 100 includes a crystal pulling housing 108 that defines a growth chamber 152 for pulling a silicon ingot 113 (FIG. 6) from the melt 104 along a pulling axis A.

[0011] The crucible assembly 102 has sidewalls 131 (FIG. 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 (FIG. 6) have a common longitudinal axis or "pull axis" A.

[0012] A pulling mechanism 114 (FIG. 5) is provided within the ingot pulling apparatus 100 to grow and pull an ingot 113 (FIG. 6) from the melt 104. The pulling mechanism 114 includes a pulling cable 118, a seed holder or chuck 120 connected to one end of the pulling cable 118, and a seed crystal 122 connected to the seed holder or chuck 120 to initiate crystal growth. One end of the pulling cable 118 is connected to a pulley (not shown) or drum (not shown) of the pulling mechanism 114, or other suitable type, e.g., shaft, and the other end is connected to the chuck 120, which holds the seed crystal 122. In operation, the seed crystal 122 is lowered to contact the surface 111 (FIG. 5) of the melt 104. The pulling mechanism 114 is actuated to raise the seed crystal 122. This causes a single crystal ingot 113 (FIG. 6) to be pulled from the melt 104.

[0013] During heating and crystal pulling, a crucible drive unit 107 (e.g., a motor) rotates the crucible assembly 102 and the susceptor 106. A 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 a lowest position (near the bottom heater 126) where a charge of solid phase polycrystalline silicon 133 previously added to the crucible assembly 102 is melted. Crystal growth begins by contacting the melt 104 (FIG. 5) with the seed crystal 122 and lifting the seed crystal 122 by the pulling mechanism 114.

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

[0015] The ingot pulling apparatus 100 includes bottom insulation 110 and side insulation 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 a crucible floor 129. The crucible assembly 102 can be moved into relatively closer proximity to the bottom heater 126 to melt solid silicon charged into the crucible assembly 102, as described further below.

[0016] According to the Czochralski single crystal growth process, a quantity of solid phase silicon 133 (FIG. 1), such as polycrystalline silicon or "polysilicon," is initially charged to the crucible assembly 102. The semiconductor or solar grade solid silicon introduced into the crucible assembly 102 is melted by heat provided from one or more heating elements. The size of the solid phase silicon charge 133 may correspond to the desired size of the melt when ingot growth begins, or, as in an embodiment of the present disclosure, a smaller charge is used and additional silicon is added by the silicon supply system 200 (FIG. 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 the side heater 135 may be powered to melt the charge 133 and form the initial melt of silicon 115 (FIG. 2). To form the remainder of the melt, solid silicon is added to the melt 115 by the silicon supply system 200 (FIG. 3) through a supply tube 190 (FIG. 3). The solid silicon supplied to the crucible assembly 102 by the silicon supply system 200 may be, for example, in granular, chunk, chip, or combinations thereof. The silicon supply system 200 may include components suitable for adding the solid silicon to the crucible assembly and may include a container and / or a supply tray for holding the solid silicon. A vibration motor may be powered to vibrate the supply tray to move the solid silicon from the container to the supply tube 190. An outlet of the supply tray may be connected to the supply tube 190. A valve mechanism can be used to seal the tube 190 during periods when silicon is not being added to the supply tube 190 (e.g., the valve mechanism removably engages an outlet of a tray). Examples of components of a 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 consistent purposes.

[0018] Prior to adding solid silicon to the initial melt 115, the silicon supply system 200 is docked to the ingot puller 100 (e.g., via an isolation valve) and the supply tube 190 is lowered (e.g., using a motor-driven gear system) into the growth chamber 152. Silicon is introduced into the silicon supply tube 190 by the silicon supply system 200. The solid silicon passes through the tube 190 and is discharged through the outlet 132 (FIG. 3) of the supply tube 190. The discharged solid silicon collects on the surface of the initial melt 115. The silicon forms islands 139 (FIG. 4) of solid silicon that float 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 FIG. 11.

[0019] Once the melt is fully formed, the silicon supply tube 190 is removed from the growth chamber 152. The seed crystal 122 (FIG. 5) is lowered and contacted with the surface 111 of the melt 104. The pulling mechanism 114 is actuated to pull the seed crystal 122 from the melt 104. Now referring to FIG. 6, the ingot 113 includes a crown portion 142 that transitions outwardly from the seed crystal 122 and tapers as the ingot reaches a target diameter. The ingot 113 includes a constant diameter portion 145 or cylindrical "body" of the crystal that is grown by increasing the pulling 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 narrows in diameter after the body 145. When the diameter becomes small enough, the ingot 113 is then separated from the melt 104. Generally, the crystal growth process is a batch process in which solid silicon is initially added to the crucible assembly 102 to form a silicon melt without additional solid silicon being added to the crucible assembly 102 during crystal growth (as opposed to a continuous Czochralski process in which a quantity of silicon is added to the crucible assembly during ingot growth).

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

[0021] The ingot pulling apparatus 100 may include a heat shield 151. The heat shield 151 may encase the ingot 113 and may be positioned within the crucible assembly 102 during crystal growth (FIG. 6). The ingot pulling apparatus 100 may include an inert gas system for introducing and withdrawing an inert gas, such as argon, from the growth chamber 152.

[0022] 7, silicon supply tube 190 includes inlet 128 (which may be engaged with a feed tray disposed above tube 190) and outlet 132. Silicon supply tube 190 includes a conduit section 150 through which solid silicon passes. A kick plate 153 disposed below conduit section 150 directs the solid silicon into crucible assembly 102 (e.g., away from the center of the crucible assembly, as shown in FIG. 11). Conduit section 150 of silicon supply tube 190 includes a baffle (not shown) that controls the velocity of solid silicon through tube 190. In the illustrated embodiment, silicon supply tube 190 includes a guide section 166 (FIG. 8) and a tube section 168 (FIG. 7) disposed above guide section 166. Guide section 166 and tube section 168 may be connected by any suitable method, such as a friction fit, threads, adhesive, or fasteners (e.g., groove and pin, flange, or coupling). Although the guide portion 166 and the tube portion 168 of the silicone 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 portions.

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

[0024] The illustrated silicone supply tube 190 is an example, and the silicone supply tube may be modified (e.g., by including additional or fewer sections, or by including various bends) without departing from the scope of the present disclosure.

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

[0026] 9, the kick plate 153 is aligned with the longitudinal axis A of the supply tube 190. 190 and form an angle λ, which may range from 20° to 60°.

[0027] The conduit portion 150 of the silicon supply tube 190 has an inner diameter D 150 (i.e., the inner diameter where the conduit section 150 meets the kick plate 153, such as when the diameter of the conduit section 150 changes). 153 In some embodiments, the kick plate 153 extends across at least a portion of the inner diameter D 150 (i.e., the ratio L 153 / D 150 In another embodiment, the kick plate is axially spaced apart from the inner diameter D of the conduit section 150. 150 or the inner diameter D of the conduit portion 150. 150 of the stencil.

[0028] Kick plate 153 and conduit portion 150 of silicone supply tube 190 form an inner corner 179 and an outer corner 180. Kick plate 153 has an upper end 185 aligned with inner corner 179 and has a lower end 182. Kick plate 190 has a height H extending from upper end 179 to lower end 182. 153 has.

[0029] The conduit portion 150 has a lower end 175. In the illustrated embodiment, the conduit portion 150 (e.g., the portion facing the kick plate 153 as in the illustrated embodiment) includes a portion that vertically overlaps the kick plate 150. The length of this portion that overlaps the kick plate 153 is indicated by H in FIG. 150In some embodiments, the conduit portion 150 has a kick plate height H 153 overlap by less than 70% (i.e., the ratio H 150 / H 153 is less than 0.7). In some embodiments, the conduit portion 150 overlaps less than 60% of the height of the kick plate 153, or less than 50%, less than 40%, 20% to 70%, or 20% to 60% of the height of the kick plate 153.

[0030] Compared to conventional silicon feed tubes, the silicon feed tube of the present disclosure has several advantages. By using a kick plate that extends to at least 60% of the inner diameter of the conduit section, solid silicon exits the silicon feed tube away from the center of the crucible assembly, causing islands of solid silicon floating in the melt that have a "volcano" shape (FIG. 10) rather than a pyramidal shape. The volcano-shaped islands are more stable on the melt and less prone to tipping or tipping, allowing 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 conduit sections that overlap less than 70% (e.g., 20% to 70%) of the height of the kick plate, the radial distance that the solid silicon exits the tube can be improved and more precisely controlled.

[0031] Working Example The processes of the present disclosure are further illustrated by the following examples, which should not be construed in a limiting sense.

[0032] Example 1: Reduction of supply time and heater power To add solid silicon to the initial silicon melt, a silicon feed tube having a guide portion as shown in Figure 9 was used. A conventional silicon feed tube having a guide tube with a kick plate extending across less than 60% of the inside diameter of the conduit portion and having a conduit portion overlapping more than 70% of the height of the kick plate was also used to add solid silicon to the initial silicon melt.

[0033] As shown in FIG. 12, the use of a supply tube having the guide portion shown in FIG. 9 ("New") reduced the total melting time by approximately 2 hours and reduced the heater power during melting by 10 kW compared to the conventional silicon supply tube ("POR").

[0034] As used herein, when used in conjunction with a range of dimensions, concentrations, temperatures, or other physical or chemical properties or characteristics, the terms "about," "substantially," "essentially," and "approximately" are meant to cover the variation that may exist at the upper and / or lower limits of the range of the property or characteristic, including, for example, the variation that results from rounding, measurement methodology, or other statistical variations.

[0035] When introducing an element of the disclosure or embodiment(s) thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the element. The terms "comprising," "including," "containing," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of specific orientation terms (e.g., "top," "bottom," "side," etc.) is for convenience of description and does not require a particular orientation of the items being described.

[0036] Because various changes may be made in the structures and methods described above without departing from the scope of the present disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

Claims

1. A method for producing a single crystal silicon ingot, comprising: adding a solid phase silicon charge to a crucible disposed within a growth chamber; melting the solid phase silicon charge to form an initial melt having a surface; lowering a silicon supply line into the growth chamber; The silicon supply pipe a conduit section having an inner diameter; and lowering a silicon supply tube extending from the conduit section and having a kick plate positioned below the conduit section, the kick plate extending 60% to 90% of an inner diameter of the conduit section; adding additional solid silicon to the initial melt through the silicon supply tube, the additional solid silicon being chunky solid silicon, the additional solid silicon collecting on a surface of the initial melt and forming islands having a volcano shape; removing the silicon supply tube from the growth chamber; melting the additional islands of solid silicon to increase the size of the melt; lowering a seed crystal into contact with the surface of the melt; Pulling the seed crystal to form a single crystal silicon ingot; A method having the following.

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

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

4. The kick plate has a height, and the conduit portion overlaps less than 70% of the height of the kick plate. The method of claim 1.

5. The silicon supply pipe and the single crystal silicon ingot move along a common axis. The method of claim 1.

6. A method for producing a single crystal silicon ingot, comprising: adding a solid phase silicon charge to a crucible disposed within a growth chamber; melting the solid phase silicon charge to form an initial melt having a surface; lowering a silicon supply line into the growth chamber; The silicon supply pipe a conduit section having an inner diameter; and lowering a silicon supply tube extending from the conduit section and having a kick plate positioned below the conduit section, the kick plate extending 60% to 90% of an inner diameter of the conduit section; adding additional solid silicon to the initial melt through the silicon supply tube, the additional solid silicon being chunky solid silicon, the additional solid silicon collecting at a surface of the initial melt; removing the silicon supply tube from the growth chamber; melting the additional islands of solid silicon to increase the size of the melt; lowering a seed crystal into contact with the surface of the melt; Pulling the seed crystal to form a single crystal silicon ingot, wherein the silicon supply pipe and the single crystal silicon ingot move along a common axis; A method having the following.

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

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

9. The kick plate has a height, and the conduit portion overlaps less than 70% of the height of the kick plate. The method of claim 6.

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