A method of manufacturing an ingot using a puller apparatus having a heat shield disposed beneath a side heater

Abstract

A puller apparatus having a heat shield disposed beneath side heaters and a method for making ingots in such a puller apparatus are disclosed. In some embodiments, the side heaters are relatively short. The side heaters can be entirely above the floor of the crucible when the crucible is at its lowest position in the puller.

Description

Technical Field

[0001] This disclosure relates to spindle pulling equipment, and more specifically, to spindle pulling equipment in which a heat shield is placed below a side heater. Background Technology

[0002] Some conventional puller equipment includes relatively long side heaters in the puller's hot zone. To achieve the desired temperature profile in the melt, insulating material is removed from the bottom of the hot zone. This removal of insulation increases the energy input to the side heaters, thus reducing thermal efficiency. Furthermore, the relatively long heaters heat the bottom of the crucible and the shafts used to elevate the crucible during crystal growth, further reducing the process's energy efficiency.

[0003] There is a need for a puller device that has a hot zone that allows the desired temperature profile to be achieved while improving the efficiency of the hot zone and the heating system.

[0004] This section aims to introduce the reader to various technical aspects that may relate to the various aspects of this disclosure described and / or claimed below. This discussion is intended to help provide the reader with background information to facilitate a better understanding of the various aspects of this disclosure. Therefore, it should be understood that these descriptions should be interpreted in light of this and not be considered as prior art. Summary of the Invention

[0005] One aspect of this disclosure relates to a silicon ingot puller apparatus. The puller apparatus includes a crucible for holding molten silicon. The crucible has a bottom surface and sidewalls extending from the bottom surface. The puller apparatus includes a growth chamber for pulling the silicon ingot from the melt along a pull axis. The puller apparatus includes a lifting mechanism for raising and lowering the crucible relative to the pull axis during crystal growth. The crucible moves axially between a lowest position where a feed of melted silicon is deposited to produce the molten silicon, a seeding position where a seed crystal initially contacts the melt to pull the silicon ingot from the melt, and a terminal position where the crucible has exhausted the melt. As the crucible travels from the lowest position to the terminal position, side heaters are radially disposed outside the sidewalls of the crucible. A bottom heater is disposed below the bottom surface of the crucible. A heat shield is disposed directly below the side heaters.

[0006] Another aspect of this disclosure relates to a method for preparing an ingot in an ingot pulling apparatus, the ingot pulling apparatus comprising: a crucible having a bottom surface and sidewalls extending from the bottom surface; a side heater radially disposed outside the sidewalls of the crucible; and a heat shield disposed directly below the side heaters. When the crucible is in its lowest position, a silicon melt is formed in the crucible, and when the crucible is in the lowest position, the side heaters are completely above the bottom surface of the crucible. The melt contacts a seed crystal. The ingot is extracted from the silicon melt. The crucible rises as the ingot is extracted from the silicon melt, and when the ingot separates from the melt, the crucible is in its final position.

[0007] Various improvements exist relative to the features mentioned in the foregoing aspects of this disclosure. Additional features may also be incorporated into the foregoing aspects of this disclosure. These improvements and additional features may exist individually or in any combination. For example, various features discussed below with respect to any of the illustrated embodiments of this disclosure may be incorporated individually or in any combination into any of the foregoing aspects of this disclosure. Attached Figure Description

[0008] Figure 1 This is a cross-sectional view of a drawing device with the heat shield placed below the side heater, where the crucible is located at the lowest position;

[0009] Figure 2 This is a cross-sectional view of the ingot pulling equipment during ingot growth;

[0010] Figure 3 This is a cross-sectional view of the ingot puller, in which the crucible is located at the end position where the melt is exhausted;

[0011] Figure 4 This is a cross-sectional view of another puller device with a relatively long side heater and no heat shield installed below the side heater;

[0012] Figure 5 yes Figure 4 A schematic diagram of the temperature profiles of the melt and side heaters in the ingot pulling equipment; and

[0013] Figure 6 yes Figures 1 to 3 A schematic diagram of the temperature profile of the melt and side heater of the ingot pulling equipment.

[0014] The corresponding reference symbol indicates the corresponding part in all diagrams. Detailed Implementation

[0015] The spinning wheel equipment (or more simply called a "spinning wheel") in Figure 1The general designation is "100". The ingot pulling apparatus 100 includes a crucible 102 for holding a melt 104 of a semiconductor or solar-grade material (e.g., silicon), supported by a base 106. The ingot pulling apparatus 100 includes a section defining a section for pulling a silicon ingot 113 from the melt 104 along a pull axis A. Figure 2 The crystal puller housing 108 of the growth chamber 152.

[0016] The crucible 102 includes a bottom surface 129 and a sidewall 131 extending upward from the bottom surface 129. The sidewall 131 is generally vertical. The bottom surface 129 includes a curved portion of the crucible 102 extending below the sidewall 131. The crucible 102 includes a bottom 116, which is the lowest point of the crucible 102 relative to the pull shaft A. A silicon melt 104 having a melt surface 111 (i.e., the melt-ingot interface) is located within the crucible 102.

[0017] The base 106 is supported by the shaft 105. The base 106, crucible 102, shaft 105, and ingot 113 ( Figure 2 They have a common vertical axis A or "pull axis" A.

[0018] A pulling mechanism 114 is disposed within the ingot pulling device 100 for growing and pulling ingot 113 from melt 104. The pulling mechanism 114 includes a pulling cable 118, a seed holder or chuck 120 coupled to one end of the pulling cable 118, and a seed 122 coupled to the seed holder or chuck 120 for initiating crystal growth. One end of the pulling cable 118 is connected to a pulley (not shown) or drum (not shown) or any other suitable type of lifting mechanism (e.g., a shaft), and the other end is connected to the chuck 120 holding the seed 122. In operation, the seed 122 is lowered to contact melt 104. The pulling mechanism 114 is operated to raise the seed 122. This causes the single crystal ingot 113 (… Figure 2 ) Pulled from melt 104.

[0019] During heating and crystal pulling, the crucible drive unit 107 (e.g., an electric motor) rotates the crucible 102 and the base 106. During the growth process, the lifting mechanism 112 raises and lowers the crucible 102 along the pulling axis A. For example, as Figure 1 As shown, the crucible can be positioned at its lowest point (near the bottom heater 126) where the feed of solid polycrystalline silicon previously added to the crucible 102 is melted. Crystal growth is initiated by bringing the melt 104 into contact with the seed crystal 122 and pulling the seed crystal 122 up by the lifting mechanism 114. The crucible 102 can be raised a certain distance from its lowest point (i.e., raised to the "seed position") before the melt 104 contacts the seed crystal 122.

[0020] As the ingot grows, the silicon melt 104 is consumed and the height of the melt in the crucible 102 decreases. The crucible 102 and base 106 can be raised to maintain the melt surface 111 in or near the same position relative to the ingot pulling device 100. The crucible 102 can be... Figure 1 The diagram shows its lowest position (e.g., during melting) to the immersion position where the seed crystal initially contacts the melt to pull the silicon ingot from the melt, and the terminal position where the crucible has exhausted the melt. Figure 3 The crucible 102 moves axially between the two. The end position of the crucible 102 is higher than the soaking position (and lowest position) of the crucible 102.

[0021] The crystal driving unit (not shown) can also enable the lifting cable 118 and the ingot 113 ( Figure 2 The crystal driving unit rotates in the opposite direction to the direction in which the crucible 102 is rotated by the crucible driving unit 107 (e.g., in the opposite direction). In embodiments using co-directional rotation, the crystal driving unit can rotate the lifting cable 118 in the same direction as the crucible driving unit 107 rotates the crucible 102. Additionally, the crystal driving unit raises and lowers the ingot 113 relative to the melt surface 111 as needed during the growth process.

[0022] The puller apparatus 100 may include an inert gas system for introducing and extracting an inert gas, such as argon, from the growth chamber 152. The puller apparatus 100 may also include a dopant feeding system (not shown) for introducing dopant into the melt 104.

[0023] According to the Czochralski single-crystal growth process, a certain amount of polycrystalline silicon or polymeric silicon is loaded into crucible 102. The semiconductor or solar-grade material introduced into the crucible is melted by heat supplied from one or more heating elements. The puller apparatus 100 includes a bottom insulating material 110 and side insulating materials 124 to retain heat within the puller apparatus. In the illustrated embodiment, the puller apparatus 100 includes a bottom heater 126 disposed below the bottom surface 129 of the crucible. The crucible 102 can be moved to relatively close proximity to the bottom heater 126 to melt the polycrystalline material loaded into the crucible 102.

[0024] To form an ingot, seed crystal 122 contacts the surface 111 of melt 104. The pulling mechanism 114 is operated to pull seed crystal 122 from melt 104. (See now for reference...) Figure 2 Ingot 113 includes a crown-shaped portion 142 in which the ingot transitions and tapers outward from the seed crystal 122 to reach a target diameter. Ingot 113 includes a constant-diameter portion 145 or cylindrical "body" of the crystal grown by increasing the pulling rate. The body 145 of ingot 113 has a relatively constant diameter. Ingot 113 includes a tail or end-taper 149 in which the diameter tapers after the body 145. Figure 3When the diameter becomes sufficiently small, the ingot 113 then separates from the melt 104. The ingot 113 has a central longitudinal axis A extending through the crown portion 142 and the terminal portion 150 of the ingot 113.

[0025] The puller apparatus 100 includes a side heater 135 and a base 106 surrounding a crucible 102 to maintain the temperature of the melt 104 during crystal growth. As the crucible 102 moves up and down along the pull axis A (e.g., from a lowest position to a final position), the side heater 135 is radially positioned outside the crucible sidewall 131. The side heater 135 and the bottom heater 126 can be any type of heater that allows the side heater 135 and the bottom heater 126 to operate as described herein. In some embodiments, heaters 135, 126 are resistance heaters. The side heater 135 and the bottom heater 126 can be controlled by a control system (not shown) to control the temperature of the melt 104 throughout the pulling process.

[0026] According to embodiments of this disclosure, the side heater 135 may have a relatively short length L relative to a conventional crystal puller. 135 (i.e., height), which can reduce the amount of oxygen drawn out of ingot 113. In some embodiments, the side heater 135 may have a length L of 500 mm or less, 450 mm or less, 400 mm or less, or 350 mm or less. 135 As the crucible 102 moves between the lowest position, the soaking position, and the terminal position, at least a portion of the side heater 135 is laterally aligned with the side wall 131 of the crucible 102 (e.g., the radius extending orthogonally outward from the pull shaft A can intersect the side wall 131 and the crucible 102).

[0027] The puller apparatus 100 also includes a heat shield 140 surrounding the crucible 102 and the base 106 to maintain the temperature of the melt 104 during crystal growth. The heat shield 140 is positioned below the side heater 135 and can be separated from the side heater 135 by a gap 155. In some embodiments, the heat shield 140 is separated from the side heater 135 by no more than about 50 mm or no more than 40 mm (e.g., from 30 mm to about 50 mm). In other embodiments, the heat shield 140 is not separated from the side heater 135 (i.e., the heat shield 140 and the side heater 135 are continuous).

[0028] In the illustrated embodiment, the heat shield 140 is positioned directly below the side heater 135 (i.e., the side heater 135 and the heat shield 140 are aligned (when viewed from below) or "vertically aligned"). In some embodiments, the heat shield 140 has a thickness T greater than the heat shield 140. 140 Length L 140 ( Figure 2 The heat shield 140 may have a thickness T. 140Its thickness T is at least the thickness of the side heater 135. 135 Furthermore, in other embodiments, the thickness T of the side heater 135 is... 135 At least 1.1 times the thickness T of the side heater 135 135 At least 1.25 times the thickness of the side heater 135 T 135 At least 1.5 times (e.g., the thickness T from the side heater 135) 135 (1.0 to 2.0 times). The heat shield 140 may be radially positioned relative to the side heater 135 such that a portion of the heat shield 140 overlaps with each side of the side heater 135 (i.e., when viewed from above, a first portion of the heat shield 140 is radially inward of the side heater 135 and a second portion of the heat shield 140 is radially outward of the side heater 135).

[0029] The heat shield 140 can generally be made of any material that reduces cooling of the bottom portion of the side heater 135. The heat shield may comprise an insulating or reflective material. The heat shield may be layered. In embodiments where the heat shield is made of an insulating material, the insulating material may be covered with graphite to reduce the risk of zero misalignment of the ingot. In some embodiments, the heat shield may comprise a graphite shell in which a molybdenum sheet is disposed to block radiation.

[0030] The ingot pulling apparatus 100 may include a second heat shield 151 (e.g., where the first heat shield 140 is a "lower" heat shield and the second heat shield 151 is an "upper" heat shield). The second heat shield 151 may laterally surround the ingot 113 such that the ingot passes through the opening 160 formed by the heat shield 151. The heat shield 151 may be positioned within the crucible 102 during crystal growth (e.g., as shown in the end position of the crucible 102, such as...). Figure 3 (As shown in the image).

[0031] Crucible 102 in Figure 1 The crucible 102 is shown in its lowest position. In the illustrated embodiment, when the crucible 102 is in its lowest position, the side heater 135 is completely positioned on the bottom surface 129 of the crucible 102. For example, the distance between the bottom 116 of the crucible 102 and the side heater 135 (i.e., the distance to the bottom of the side heater 135) may be at least about 25 mm or at least about 50 mm. The distance between the bottom 116 of the crucible 102 and the top of the side heater 135 may be at least about 75 mm or at least about 100 mm. At least a portion of the heat shield 140 is above the bottom 116 of the crucible 102. At least a portion of the heat shield 140 is also below at least a portion of the bottom surface 129 of the crucible 102.

[0032] Crucible 102 in Figure 3The crucible 102 is shown in its terminal position. In the illustrated embodiment, when the crucible 102 is in the terminal position, the heat shield 140 is completely below the bottom surface 129 of the crucible 102. When the crucible 102 is in the terminal position, the heat shield 140 is also completely below the base 106.

[0033] The ingot pulling apparatus disclosed herein has several advantages over conventional ingot pulling apparatus. In embodiments in which the ingot pulling apparatus includes relatively short side heaters (e.g., when the side heaters have a length of 500 mm or less, 450 mm or less, 400 mm or less, or 350 mm or less and / or the side heaters are completely above the bottom surface of the crucible (where the crucible is at its lowest position)), as the crucible gradually rises during ingot growth, heat from the side heaters is directly conducted to the crucible and base without diverting some energy to the shaft and bottom insulation. This results in more efficient energy use and allows the melt hotspots to move upward from the melt-crucible interface. This allows for the addition of more insulation to move the hotspots downward and maintain the same temperature profile toward the bottom of the hot zone with less energy and less leakage, thereby improving efficiency. During the growth of the ingot's rear body (i.e., the portion of the constant diameter near the end cone grown when the crucible is relatively high in the pulling apparatus), the temperature range of the crucible wall can be relatively wide to allow the use of longer heaters, which allows for reduced interstitial oxygen in the rear body.

[0034] In embodiments where a heat shield is positioned below the side heater, the heat shield reduces cooling of the lower portion of the side heater because it reduces the exposure of relatively cold components near the bottom of the hot zone. This reduces the energy required for the heater to achieve its desired temperature and improves the energy efficiency of the hot zone.

[0035] Example

[0036] The process disclosed herein is further illustrated by the following examples. These examples should not be considered as intended to be limiting.

[0037] Example 1: Using a hot zone with a 525mm heater to a 325mm heat shield with a heat shield installed below the heater. mm The hot zone of the heater

[0038] Figure 5 exhibit Figure 4 The temperature profile of the hot zone configuration of the ingot pulling equipment (the cooler part of the melt and heater in) Figure 5 and 6 (The image is shown using darker dots). Figure 4 The hot zone includes a side heater 135 with a length of 525 mm and does not include a thermal shield below the side heater. The hot zone also includes a portion of insulating material that is removed towards the bottom of the hot zone to achieve the desired temperature profile. Figure 4The side heater operates at 103 kW and the bottom heater operates at 5 kW (total heat input 108 kW). When the melt hotspot is located at the melt-crucible interface... Figure 5 The temperature profile is desirable. For example... Figure 5 As shown in the temperature profile of the right-hand side heater, the lower part of the side heater is relatively cool due to the reduction in insulation material.

[0039] Figure 6 The demonstration shows the use of a relatively short side heater 135 with a length of 325mm (i.e., longer than). Figure 4 The side heater is smaller than 200mm. Figures 1 to 3 The temperature profile of the hot zone configuration of the ingot pulling equipment. The hot zone includes a heat shield 140 disposed below the side heater 135. The hot zone includes a temperature profile relative to... Figure 4 A certain amount of insulation material (approximately 1 inch) is removed from the hot zone towards the bottom of the puller equipment. The side heater 135 operates at 59 kW and the bottom heater operates at 5 kW (64 kW total heat input).

[0040] like Figure 6 As shown in the figure, the melt has roughly the same properties as... Figure 4 Hot zone (in) Figure 5 The same desired temperature profile is shown in the figure, but the puller equipment operates with a smaller 44kW power input (i.e., 41% less).

[0041] As used herein, the terms “about,” “generally,” “substantially,” and “approximately” when used in conjunction with a range of size, concentration, temperature, or other physical or chemical properties or characteristics mean to cover variations that may exist in the upper and / or lower limits of the range of properties or characteristics, including, for example, variations arising from rounding, measurement methods, or other statistical variations.

[0042] When elements of this disclosure or embodiments thereof are introduced, the articles “a / an” and “the / said” are intended to mean that one or more of the stated elements are present. The terms “comprising,” “including,” “containing,” and “having” are intended to be inclusive and mean that additional elements may be present in addition to the listed elements. Terms indicating a particular orientation (e.g., “top,” “bottom,” “side,” etc.) are used for convenience of description and do not require any particular orientation of the described items.

[0043] Since various changes can be made to the above-described construction and methods without departing from the scope of this disclosure, all substances contained in the above description and shown in the accompanying drawings are intended to be illustrative rather than limiting.

Claims

1. A silicon ingot puller apparatus for producing silicon ingots, comprising: A crucible for holding a molten silicon, the crucible having a bottom surface and sidewalls extending from the bottom surface; A growth chamber for pulling silicon ingots from the melt along a pull shaft; A lifting mechanism is used to raise and lower the crucible relative to the pull shaft during crystal growth, the crucible moving axially between the lowest position where the feed of melting silicon is produced to create the silicon melt, the immersion position where the seed crystal initially contacts the melt to pull the silicon ingot from the melt, and the terminal position where the crucible has exhausted the melt. A side heater, which is positioned radially outside the sidewall of the crucible as the crucible travels from the lowest position to the final position, the side heater having a length of 500 mm or less, and when the crucible is in the lowest position, the side heater is completely above the bottom surface of the crucible; A bottom heater is disposed below the bottom surface of the crucible; and A heat shield is disposed directly below the side heater, wherein a first portion of the heat shield is radially inside the side heater and a second portion of the heat shield is radially outside the side heater.

2. The spindle pulling device according to claim 1, wherein when the crucible is in the lowest position, at least a portion of the heat shield is above the bottom of the crucible.

3. The spindle pulling device according to claim 1, wherein when the crucible is in the lowest position, at least a portion of the heat shield is lower than at least a portion of the bottom surface of the crucible.

4. The spindle pulling device according to claim 1, wherein when the crucible is located at the terminal position, the heat shield is completely below the bottom surface of the crucible.

5. The spindle pulling device according to claim 1, wherein the side heater has a length of 350 mm or less.

6. The drawing device according to claim 1, wherein the heat shield has a length relative to the drawing shaft that is greater than the thickness of the heat shield.

7. The drawing device of claim 1, wherein as the crucible travels between the lowest position and the end position, at least a portion of the side heater is laterally aligned with the side wall of the crucible.

8. The spindle pulling device according to claim 1, wherein the side heater and the heat shield are separated by a gap.

9. The spindle pulling device according to claim 1, wherein the side heater is separated from the heat shield by no more than 40 mm.

10. The spindle pulling device according to claim 1, further comprising a base supporting the crucible, wherein the heat shield is completely below the base when the crucible is in the terminal position.

11. The spindle pulling device according to claim 1, wherein when the crucible is in the lowest position, the distance between the bottom of the crucible and the bottom of the side heater is at least 25 mm.

12. The drawing device of claim 1, wherein the side heater has a thickness and the heat shield has a thickness, the thickness of the heat shield being at least the thickness of the side heater.

13. The drawing device of claim 1, wherein the side heater has a thickness and the heat shield has a thickness, the thickness of the heat shield being at least 1.5 times the thickness of the side heater.

14. The spindle pulling device according to claim 1, comprising a bottom insulating material disposed below the heat shield, the bottom insulating material and the heat shield being separated by a gap.

15. A method for preparing an ingot in a pulling apparatus, the pulling apparatus comprising a crucible having a bottom surface and sidewalls extending from the bottom surface, a lifting mechanism for raising and lowering the crucible relative to a pulling axis during crystal growth, a side heater disposed radially outside the sidewalls of the crucible, and a heat shield disposed directly below the side heater, a first portion of the heat shield being radially inside the side heater and a second portion of the heat shield being radially outside the side heater, the method comprising: When the crucible is in its lowest position, a silicon melt is formed in the crucible, and when the crucible is in its lowest position, the side heater is completely above the bottom surface of the crucible; The melt is brought into contact with the seed crystal; Extracting an ingot from the silicon melt; and As the ingot is drawn from the silicon melt, the crucible is gradually raised, and when the ingot separates from the melt, the crucible is at the end position.

16. The method of claim 15, wherein when the crucible is in the lowest position, at least a portion of the heat shield is above the bottom of the crucible.

17. The method of claim 15, wherein when the crucible is in the lowest position, at least a portion of the heat shield is below at least a portion of the bottom surface of the crucible.

18. The method of claim 15, wherein when the crucible is raised to the terminal position, the heat shield is completely below the bottom surface of the crucible.

19. The method of claim 15, wherein the side heater has a length of 350 mm or less.

20. The method of claim 15, wherein the spindle device includes a bottom insulating material disposed below the heat shield, the bottom insulating material and the heat shield being separated by a gap.

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