Axial positioning of magnetic poles in production of silicon ingots

Abstract

A method for producing a silicon ingot is disclosed in which a horizontal magnetic field is generated. The magnet position is controlled in at least two stages of ingot growth. The pole may be in a first position during a second stage of ingot growth and lowered to a second position during the second stage of ingot growth. The crystal-melt interface shape may be relatively constant by controlling the magnet position.

Description

[0001] CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Non-Provisional Patent Application No. 17 / 897,682 filed on August 29, 2022 and U.S. Non-Provisional Patent Application No. 17 / 897,685 filed on August 29, 2022. The entire contents of both applications are incorporated herein by reference. Technical Field

[0003] The field of the present disclosure relates to methods for producing single crystal silicon ingots in a horizontal magnetic field Czochralski process and related ingot puller apparatus for producing single crystal silicon ingots. Background Art

[0004] Single crystal silicon is the starting material in many processes used to manufacture semiconductor electronic components and solar materials. For example, semiconductor wafers produced from silicon ingots are often used to produce integrated circuit chips on which circuit systems are printed. In the solar industry, single crystal silicon can be used instead of polycrystalline silicon due to the absence of grain boundaries and dislocations.

[0005] For the production of semiconductor or solar wafers, a single crystal silicon ingot can be produced in a Czochralski process by dipping a seed crystal into molten silicon held in a crucible. The seed crystal is withdrawn in a manner sufficient to achieve the desired diameter of the ingot. After the ingot is formed, the silicon ingot is processed into the desired shape from which semiconductor or solar wafers can be produced.

[0006] Polished silicon wafers that meet manufacturer requirements for the absence of coagulation point defects, such as crystal-induced micropits (COPs), may be referred to as "neutral silicon" or "perfect silicon". Perfect silicon wafers are preferred for many semiconductor applications as lower cost polished wafers in place of, for example, epitaxially deposited wafers. During the growth of a perfect silicon ingot in a horizontal magnetic field Czochralski process, the crystal-melt interface shape is typically concave. To produce perfect silicon, the thermal conditions of the ingot or crystal-melt interface shape are controlled while adjusting the pull rate. The pull rate and thermal conditions (e.g., by adjusting the gap between the melt surface and the reflector and controlling the bottom heater) may be continuously adjusted to control the shape of the crystal-melt interface. The thermal conditions change during the growth of the ingot to complicate the control of the crystal-melt interface, so that perfect silicon is produced only in the axial window of ingot growth.

[0007] What is needed are methods for controlling a horizontal magnetic field to maintain a relatively constant crystal-melt interface and ingot puller apparatus in which such methods may be implemented to produce single crystal silicon ingots (eg, perfect silicon).

[0008] This section hopes to introduce the reader to various aspects of the technology that may be related to the various aspects of the present disclosure that will be described and / or claimed below. We believe that this discussion is helpful in providing the reader with background information to facilitate a preferred understanding of the various aspects of the present disclosure. Therefore, it should be understood that these descriptions should be interpreted in light of this and should not be interpreted as an admission of the prior art. Summary of the invention

[0009] One aspect of the present disclosure relates to a method for producing a silicon ingot. Polycrystalline silicon is melted in a crucible enclosed in a growth chamber to form a melt. The melt has a melt free surface. A horizontal magnetic field is generated in the growth chamber. A seed crystal is brought into contact with the melt. The seed crystal is extracted from the melt to form the silicon ingot. The position of the maximum Gaussian plane during the formation of the constant diameter portion of the silicon ingot is adjusted in at least two stages of ingot growth. The at least two stages include a first stage and a second stage. The first stage corresponds to the formation of the silicon ingot from the formation of the constant diameter portion of the silicon ingot until an intermediate ingot length. The second stage corresponds to the formation of the silicon ingot from at least the intermediate ingot length to the total length of the constant diameter portion. Adjusting the position of the maximum Gaussian plane includes maintaining the position of the maximum Gaussian plane in the second stage at a position lower than the position of the maximum Gaussian plane during the first stage.

[0010] Another aspect of the present disclosure relates to an ingot puller apparatus for manufacturing a single crystal silicon ingot. The ingot puller apparatus includes a crucible for holding a silicon melt. An ingot puller housing defines a growth chamber for pulling a silicon ingot from the silicon melt. The crucible is disposed within the growth chamber. A pair of magnetic poles are disposed radially outward from the crucible. The apparatus includes a translation device for axially moving the magnetic poles relative to the crucible.

[0011] There are various improvements with respect to the features mentioned in the above aspects of the present disclosure. Further features may also be incorporated into the above aspects of the present disclosure. These improvements and additional features may exist independently or in any combination. For example, various features discussed below with respect to any illustrative embodiment of the present disclosure may be incorporated into any of the above aspects of the present disclosure alone or in any combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a cross section of the HMCZ ingot puller equipment before silicon ingot growth;

[0013] Figure 2 During the growth of silicon ingots Figure 1 Cross section of the HMCZ ingot puller equipment;

[0014] Figure 3 is a schematic diagram illustrating a magnetic field applied to a crucible containing a melt in a crystal growing apparatus;

[0015] Figure 4 is an example of the MGP position distribution during HMCZ ingot growth;

[0016] Figure 5 is used for Figure 1 A block diagram of an example controller in the ingot puller apparatus shown in FIG.

[0017] Figure 6 is a schematic diagram of the magnet and silicon melt at two different crystal lengths and magnet positions;

[0018] Figure 7 is a graph showing normalized interface height as a function of percent solidification of an ingot;

[0019] Figure 8 Displays lifetime contour plots of vertical lamellae and measured crystal-melt interfaces;

[0020] Fig. 9 Shows the normalized height of the crystal-melt interface as a function of the MGP at different crystal positions;

[0021] Fig.10 Demonstration of axial O with two different MGP positions i Distribution (normalized Oi = [Oi / minimum Oi]);

[0022] Fig.11 is a box plot of normalized Oi at three different normalized MGP values; and

[0023] Fig.12 are examples of crystal defect patterns at three different magnet positions.

[0024] Corresponding reference characters indicate corresponding parts throughout the drawings. DETAILED DESCRIPTION

[0025] The present disclosure provides methods for manipulating the shape of the ingot-melt interface during ingot growth (i.e., changing the shape of the solidification front). The methods and apparatus of the present disclosure may involve changing the position of the maximum Gaussian plane during ingot growth to change the shape of the ingot-melt interface as the ingot grows.

[0026] The methods of the present disclosure may generally be implemented in any ingot puller apparatus configured to pull a single crystal silicon ingot and in which a horizontal magnetic field is applied to the melt. Figure 1The ingot puller apparatus 100 includes a crucible 102 for holding a melt 104 of a semiconductor or solar grade material, such as silicon, which is supported by a susceptor 106. The ingot puller apparatus 100 includes a crystal puller housing 109 that defines a silicon ingot 113 ( Figure 2 )'s growth chamber 152.

[0027] The crucible 102 includes a bottom surface 128 and a sidewall 131 extending upward from the bottom surface 128. The sidewall 131 is substantially vertical. The bottom surface 128 includes a curved portion of the crucible 102 extending below the sidewall 131. A silicon melt 104 having a melt surface 111 is within the crucible 102.

[0028] In some embodiments, the crucible 102 is layered. For example, the crucible 102 can be made of a quartz base layer and a synthetic quartz liner disposed on the quartz base layer.

[0029] The support 106 is supported by the shaft 105. The support 106, the crucible 102, the shaft 105 and the ingot 113 ( Figure 2 ) have a common longitudinal axis A or "pulling axis" A.

[0030] A pulling mechanism 114 is provided within the ingot puller apparatus 100 for growing and pulling an ingot 113 from the 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 silicon 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 a roller (not shown) or any other suitable type of lifting mechanism (e.g., a shaft) and the other end is connected to the chuck 120 that holds the seed 122. In operation, the seed 122 is lowered to contact the melt 104. The pulling mechanism 114 is operated to cause the seed 122 to rise. This causes the single crystal ingot 113 ( Figure 2 ).

[0031] During heating and crystal pulling, the crucible 102 and susceptor 106 are rotated by a crucible drive unit 107 (e.g., a motor). The lifting mechanism 112 raises and lowers the crucible 102 along the pulling axis A during the growth process. For example, the crucible 102 may be in a lowest position (close to the bottom heater 126) where an initial charge of solid polycrystalline silicon previously added to the crucible 102 is melted. Crystal growth is initiated by contacting the melt 104 with the seed crystal 122 and lifting the seed crystal 122 by the pulling mechanism 114. 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 susceptor 106 may be raised to maintain the melt surface 111 at or near the same position relative to the ingot puller apparatus 100 ( Figure 2 ).

[0032] The crystal drive unit (not shown) can also rotate the pulling cable 118 and the ingot 113 ( Figure 2 ) rotation (e.g., counter-rotation). In embodiments using co-rotation, the crystal drive unit can rotate the pull cable 118 in the same direction that the crucible drive unit 107 rotates the crucible 102. In addition, the crystal drive unit raises and lowers the ingot 113 relative to the melt surface 111 as needed during the growth process.

[0033] The ingot puller apparatus 100 may include an inert gas system to introduce and remove an inert gas, such as argon, from the growth chamber 152. The ingot puller apparatus 100 may also include a dopant feed system (not shown) for introducing dopants into the melt 104.

[0034] According to the Czochralski single crystal growth process, a certain amount of polycrystalline silicon or multicrystalline silicon is fed into the crucible 102. The initial semiconductor or solar grade material introduced into the crucible is melted by heat provided from one or more heating elements to form a silicon melt in the crucible. The ingot puller apparatus 100 includes a bottom insulation 110 and a side insulation 124 to keep the heat in the puller apparatus. In the illustrated embodiment, the ingot puller apparatus 100 includes a bottom heater 126 disposed below the crucible bottom surface 128. The crucible 102 can be moved into relatively close proximity to the bottom heater 126 to melt the polycrystalline silicon fed into the crucible 102.

[0035] To form an ingot, the seed crystal 122 is brought into contact with the surface 111 of the melt 104. The pulling mechanism 114 is operated to pull the seed crystal 122 from the melt 104. Figure 2 , ingot 113 includes a crown portion 142 where the ingot transitions outward from seed crystal 122 and tapers to reach a target diameter. Ingot 113 includes a constant diameter portion 145 or cylindrical "body" of the crystal that grows by increasing the pull rate. The body 145 of ingot 113 has a relatively constant diameter. Ingot 113 includes a tail or end cone (not shown) where the diameter of the ingot tapers after body 145. When the diameter becomes sufficiently small, ingot 113 is then separated from melt 104.

[0036] The ingot puller apparatus 100 is configured to produce a cylindrical semiconductor ingot having an ingot diameter of 150 mm, greater than 150 mm, more specifically in a range from about 150 mm to about 450 mm, and more specifically, a diameter of about 300 mm. In other embodiments, the ingot puller apparatus 100 is configured to produce a semiconductor ingot having an ingot diameter of 200 mm or an ingot diameter of 450 mm. Additionally, in one embodiment, the apparatus 100 is configured to produce a semiconductor ingot having a total ingot length of at least 900 mm. In some embodiments, the system is configured to produce a semiconductor ingot having a length of 1950 mm, 2250 mm, 2350 mm, or longer than 2350 mm. In other embodiments, the ingot puller apparatus 100 is configured to produce a semiconductor ingot having a total ingot length in a range of about 900 mm to 1200 mm, between about 900 mm and about 2000 mm, or between about 900 mm and about 2500 mm. In some embodiments, the system is configured to produce semiconductor ingots having a total ingot length greater than 2000 mm.

[0037] The ingot puller apparatus 100 includes side heaters 135 and a susceptor 106 surrounding the crucible 102 to maintain the temperature of the melt 104 during crystal growth. The side heaters 135 are disposed radially outward to the crucible sidewall 131 as the crucible 102 travels upward and downward along the pulling axis A. The side heaters 135 and the bottom heater 126 can be any type of heater that allows the side heaters 135 and the bottom heater 126 to operate as described herein. In some embodiments, the heaters 135, 126 are resistive heaters. The side heaters 135 and the bottom heater 126 can be controlled by a control system (not shown) so that the temperature of the melt 104 is controlled during the entire pulling process.

[0038] The ingot puller apparatus 100 may include a heat shield 151. The heat shield 151 may cover the ingot 113 and may be disposed within the crucible 102 during crystal growth ( Figure 2 ). The ingot puller apparatus 100 may be cooled, for example, by circulating a cooling fluid through an outer chamber of the apparatus. A cooling jacket 154 is disposed within the growth chamber 152 for cooling the ingot 113.

[0039] The crystal growth process of the present disclosure may be a batch process in which solid silicon is initially added to the crucible 102 to form a silicon melt without additional solid silicon being added to the crucible 102 during crystal growth.

[0040] The ingot puller apparatus 100 of the present disclosure includes a pair of magnetic poles 129, 130 ( Figure 1 ). The magnetic poles 129 , 130 are disposed radially outward from the crucible 102 .

[0041] Figure 31 is a diagram illustrating a horizontal magnetic field applied to a crucible 102 containing a melt 104 from which an ingot 113 is grown. The transition between the melt and the ingot is generally referred to as the crystal-melt interface 125 (alternatively, the "ingot-melt" or "solid-melt" interface) and is typically non-linear, for example, concave, convex, or gull-wing relative to the melt surface 111. Two magnetic poles 129, 130 are opposedly positioned to generate a magnetic field that is generally perpendicular to the ingot growth direction and generally parallel to the melt surface 111. The magnetic poles 129, 130 may be conventional electromagnets, superconductor electromagnets, or any other suitable magnets for generating a horizontal magnetic field of the desired strength. The application of the horizontal magnetic field results in a Lorantz force in the axial direction, in the opposite direction to the fluid motion, opposing the force driving the melt convection. Convection in the melt is thus suppressed and the axial temperature gradient in the ingot near the interface increases. The melt-ingot interface then moves up to the ingot side to accommodate the increased axial temperature gradient in the ingot near the interface and the contribution from melt convection in the crucible decreases.The horizontal configuration has the efficiency advantage of attenuating convective flows at the melt surface 111.

[0042] The poles 129, 130 may be cooled by circulating a cooling fluid through the poles 12. Iron shield 155 ( Figure 1 ) may surround the magnetic poles 129, 130 to reduce stray magnetic fields and enhance the strength of the generated magnetic field.

[0043] According to an embodiment of the present disclosure, the position of the Maximum Gaussian Plane ("MGP") during the formation of the constant diameter portion of the silicon ingot is adjusted in at least two stages of ingot growth. The MGP is characterized by a maximum magnitude of the horizontal component of the magnetic field and a zero vertical component along the MGP. The position of the magnetic poles 129, 130 relative to the melt free surface 111 (or more simply, the "melt surface") is changed during ingot growth by moving the magnetic poles 129, 130.

[0044] Reference Figure 4 , wherein an example distribution of the position of the MGP during ingot growth is shown, the position of the MGP being adjusted in a first stage S1 corresponding to silicon ingot formation starting from formation of a constant diameter portion of the silicon ingot up to an intermediate ingot length, and a second stage S2 corresponding to silicon ingot formation from at least the intermediate ingot length to the total length of the constant diameter portion. Figure 4 As shown in , adjusting the position of the maximum Gaussian plane includes maintaining the position of the maximum Gaussian plane in the second stage S2 at a position lower than the position of the maximum Gaussian plane during the first stage S1. For example, the position of the maximum Gaussian plane during the first stage S1 is maintained above the melt free surface. The position of the maximum Gaussian plane during the second stage S2 is maintained below the melt free surface.

[0045] exist Figure 4In an embodiment, the MGP distribution includes an intermediate stage S3 corresponding to the silicon ingot formation between the first stage S1 and the second stage S2. Adjusting the position of the maximum Gaussian plane may include lowering the position of the maximum Gaussian plane from the position in the first stage S1 to the position in the second stage S2 during the intermediate stage S3.

[0046] In some embodiments, during the first phase, the position of the maximum Gaussian plane (corresponding to Figure 4 The normalized position "1" in the figure) is maintained at a position of at least 20 mm above the melt free surface, or as in other embodiments, at least 40 mm above the melt free surface, at least 60 mm above the melt free surface, from the melt free surface to 150 mm above the melt free surface, from 20 mm above the melt free surface to 150 mm above the melt free surface, or from 40 mm above the melt free surface to 150 mm above the melt free surface during the first stage.

[0047] Alternatively or in addition, the position of the maximum Gaussian plane may be maintained below the melt free surface during the second stage or at least 20 mm below the melt free surface during the second stage. In some embodiments, the position of the maximum Gaussian plane is maintained at least 40 mm below the melt free surface, at least 60 mm below the melt free surface, at least 80 mm below the melt free surface, at least 100 mm below the melt free surface, from the melt free surface to 200 mm below the melt free surface, from 20 mm below the melt free surface to 200 mm below the melt free surface, or from 20 mm below the melt free surface to 150 mm below the melt free surface during the second stage.

[0048] In some embodiments and Figure 4 As shown in FIG. 5 , the MGP may be farther from the melt free surface in the second stage S2 than in the first stage S1 (i.e., the absolute distance is greater in the second stage). The ratio of (1) the distance from the MGP to the melt free surface in the second stage S2 to (2) the distance from the MGP to the melt free surface in the first stage S1 may be at least 1.0, at least 1.25, at least 1.4, or at least 1.5.

[0049] exist Figure 4 In an embodiment of the invention, the position of the maximum Gaussian plane is lowered below the free surface of the melt during the intermediate stage S3. The position of the maximum Gaussian plane may be lowered by at least 40 mm (or by at least 75 mm, at least 100 mm, or at least 150 mm) in the intermediate stage S3 (i.e., between the end of S1 and the beginning of S2) over no more than 60% of the constant diameter portion, or as in other embodiments no more than 50% or no more than 40% of the constant diameter portion.

[0050] The crucible 102 may be moved as the melt 104 is consumed to maintain a relatively constant position of the melt interface. In some embodiments, the position of the poles 129, 130 relative to the melt free surface 111 may be adjusted by moving both the poles 129, 130 and the position of the melt free surface 111 (e.g., allowing the melt to be consumed or by moving the crucible 102). In other embodiments, the position of the poles 129, 130 relative to the melt free surface 111 is adjusted only by moving the poles 129, 130 (i.e., the melt free surface 111 is maintained at a relatively constant position by moving the crucible 102 as the melt 104 is consumed).

[0051] The length of the first stage S1 may be at least 10% of the constant diameter portion, or as in other embodiments, at least 20% of the constant diameter portion, at least 10% and less than 50% of the constant diameter portion, or at least 10% and less than 40% of the constant diameter portion. The first stage S1 may start at the beginning of the constant diameter portion of the ingot. The position of the maximum Gaussian plane may remain constant during the first stage S1 or may vary during the first stage.

[0052] The length of the second stage S2 may be at least 10% of the length of the constant diameter portion, or as in other embodiments, at least 20% of the constant diameter portion, at least 30% of the constant diameter portion, at least 10% and less than 50% of the constant diameter portion, or at least 20% and less than 50% of the constant diameter portion. The second stage S2 may extend from the end of the first stage S1 (or in embodiments with intermediate stages, the end of the intermediate stage S3) to the end of the constant diameter portion of the ingot. The position of the maximum Gaussian plane may remain constant during the second stage S2 or may vary during the second stage.

[0053] The magnetic poles 129, 130 may be operated at any power capable of consistent ingot growth as described herein. For example, during the first, second, and intermediate stages of ingot growth, the horizontal magnetic field may be generated at a magnetic flux density of less than 0.4 Tesla, or less than 0.35 Tesla, less than 0.3 Tesla, less than 0.25 Tesla, or from about 0.2 Tesla to about 0.4 Tesla, as in other embodiments. In general, the strength of the magnetic field is its magnitude at the center of the maximum Gaussian plane 52.

[0054] The crucible 102 may rotate in a direction opposite to the direction in which the ingot 113 rotates, wherein the crucible 102 rotates at a rate in a range of 0.1 RPM to 5.0 RPM (i.e., -0.1 RPM to -5.0 RPM), or even from 0.1 RPM to 1.6 RPM (i.e., -0.1 RPM to -1.6 RPM), or from 0.1 RPM to 1.2 RPM (i.e., -0.1 RPM to -1.2 RPM). In other embodiments, the crucible 102 rotates in the same direction in which the ingot 113 rotates, wherein the crucible 102 rotates at a rate in a range of 0.1 RPM to 5.0 RPM, from 0.7 RPM to 5 RPM, or from 1.2 RPM to 5.0 RPM.

[0055] The ingot puller apparatus 100 includes a translation device 160 ( Figure 1 ). Any translation device 160 for moving the poles 129, 130 that allows the ingot puller apparatus 100 to operate as described herein may be used. For example, the translation device 160 may include a guide 163 and a mount 170 that moves each pole 129, 130 relative to the guide 163. The guide 163 may include one or more rails, wherein the mount 170 connects each pole 129, 130 to the one or more rails. The ingot puller apparatus 100 includes an actuator 175 that moves the poles 129, 130 relative to the guide 163. For example, the actuator 175 may be a pneumatic or hydraulic cylinder, a rack and pinion, a pulley, or a gear train with a ball screw. A motor 178 may power the actuator 175. The motor 178 may be controlled by the controller 108. Alternatively, the translation device 160 may include other devices or means to adjust the movement of the poles 129, 130.

[0056] Figure 5 2 is a block diagram of an example computing device 200 that may be used as or included as part of the controller 108 for adjusting the position of the magnetic poles 129, 130. The computing device 200 includes a processor 201, a memory 202, a media output component 204, an input device 206, and a communication interface 208. Other embodiments include different components, additional components, and / or do not include Figure 5 All components shown in .

[0057] The processor 201 is configured to execute instructions. In some embodiments, executable instructions are stored in the memory 202. The processor 201 may include one or more processing units (e.g., in a multi-core configuration). The term "processor" as used herein refers to a central processing unit, a microprocessor, a microcontroller, a reduced instruction set circuit (RISC), an application specific integrated circuit (ASIC), a programmable logic circuit (PLC), and any other circuit or processor capable of performing the functions described herein. The above are only examples and therefore do not intend to limit the definition and / or meaning of the term "processor".

[0058] The memory 202 stores non-temporary computer-readable instructions for executing the techniques described herein. Such instructions, when executed by the processor 201, cause the processor 201 to execute at least a portion of the methods described herein. That is, the instructions stored in the memory 202 configure the controller 108 to execute the methods described herein. In some embodiments, the memory 202 stores computer-readable instructions for providing a user interface to a user via the media output component 204 and receiving and processing input from the input device 206. The memory 202 may include, but is not limited to, random access memory (RAM) (e.g., dynamic RAM (DRAM) or static RAM (SRAM)), read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and non-volatile RAM (NVRAM). Although described as being separated from the processor 201, in some embodiments, the memory 202 is combined with the processor 201, such as in a microcontroller or microprocessor, but can still be mentioned separately. The above memory types are only examples and are therefore not limited to memory types that can be used to store computer processes.

[0059] The media output component 204 is configured to present information to a user (e.g., an operator of the system). The media output component 204 is any component capable of conveying information to a user. In some embodiments, the media output component 204 includes an output adapter, such as a video adapter and / or an audio adapter. The output adapter is operatively connected to the processor 201 and operatively connected to an output device, such as a display device (e.g., a liquid crystal display (LCD), a light emitting diode (LED) display, an organic light emitting diode (OLED) display, a cathode ray tube (CRT), an "electronic ink" display, one or more light emitting diodes (LEDs)) or an audio output device (e.g., a speaker or a headset).

[0060] The computing device 200 includes or is connected to an input device 206 for receiving input from a user. The input device 206 is any device that allows the computing device 200 to receive analog and / or digital commands, instructions, or other input from a user, including visual, auditory, tactile, button presses, stylus taps, etc. The input device 206 may include, for example, a variable resistor, an input dial, a keyboard / keypad, a pointing device, a mouse, a stylus, a touch-sensitive panel (such as a touchpad or touch screen), a gyroscope, an accelerometer, a position detector, an audio input device, or any combination thereof. A single component, such as a touch screen, may serve as both an output device of the media output component 204 and an input device 206.

[0061] The communication interface 208 enables the computing device 200 to communicate with remote devices and systems (e.g., motor 178 or actuator 175, remote sensors, remote databases, remote computing devices, and the like) and may include one or more communication interfaces for interacting with one or more remote devices or systems. The communication interface may be a wired or wireless communication interface that allows the computing device 200 to communicate with remote devices and systems directly or via a network. The wireless communication interface may include a radio frequency (RF) transceiver, Adapter, Wi-Fi transceiver, The wired communication interface may use any suitable wired communication protocol for direct communication, including, but not limited to, USB, RS232, I2C, SPI, analog, and proprietary I / O protocols. In some embodiments, the wired communication interface includes a wired network adapter that allows the computing device 200 to couple to a network (e.g., the Internet, a local area network (LAN), a wide area network (WAN), a mesh network, and / or any other network) to communicate with remote devices and systems via the network.

[0062] The computer systems discussed herein may include additional, fewer, or alternative functionality, including functionality discussed elsewhere herein.The computer systems discussed herein may include or be implemented via computer-executable instructions stored on a non-transitory computer-readable medium.

[0063] The non-transitory memory 202 stores instructions executed by the processor 201 to configure the controller 108. According to an embodiment of the present disclosure, the controller 08 is configured to cause the translation device 160 to move the magnetic pole pairs 129, 130 to adjust the position of the maximum Gaussian plane during the formation of the constant diameter portion of the silicon ingot according to the embodiments described above. For example, the position of the maximum Gaussian plane can be adjusted in at least two stages of ingot growth, wherein the position of the maximum Gaussian plane in the second stage is a position lower than the position of the maximum Gaussian plane during the first stage. The controller 108 can be configured to maintain the position of the maximum Gaussian plane at the distance from the free surface of the melt in the embodiments described above in at least two stages (and also including the optional intermediate stage). The controller 108 can be configured to maintain the position of the maximum Gaussian plane so that various lengths of the first and second stages described above and the rate of reducing the magnet in the intermediate stage can be achieved.

[0064] The controller 108 may be triggered to change the position of the magnetic poles in various stages of ingot growth (eg, terminate the first stage and move to an intermediate stage or terminate the intermediate stage and move to a second stage) by the weight of the melt, the length of the ingot, or by timing control.

[0065] Compared with conventional methods and apparatus for producing single crystal silicon, the methods and apparatus of the embodiments of the present disclosure have several advantages. The shape of the crystal-melt interface can be maintained relatively constant by moving the magnetic poles during the growth of the HMCZ ingot. The magnet position can be controlled to reduce the crystal-melt interface height, which reduces the variation of the axial gradient of v / G control during the production of perfect silicon, thereby increasing the perfect silicon window. The magnet position can be controlled to reduce the seed end oxygen. The crystal-melt interface can be maintained relatively constant, regardless of the melt volume and the position of the crucible. Using a higher MGP at the seed end can reduce the seed end oxygen due to less oxygen incorporation into the body. The ramping down of the magnet position in the middle to late body pushes the crystal-melt interface to be similar to the seed end portion of the crystal without affecting Oi. Therefore, the critical v / G is increased at the middle to late body and a higher pull rate is used to produce perfect silicon, which improves productivity. Constant or less variation of axial v / G leads to less quality loss and increased yield. Increasing the crystal-melt interface height (i.e., more concave) results in increased pull speed and improved productivity. Oxygen control at the seed end results in flexible oxygen control at the seed end (higher O selected by the customer) i (negative MGP) or lower O i (Positive MGP)).

[0066] Examples

[0067] The process of the present disclosure is further illustrated by the following examples. These examples should not be considered as limiting.

[0068] Example 1: Effect of MGP position on interface shape and ingot growth

[0069] like Figure 6 As shown in , in the case of short crystal growth length (i.e., larger melt volume), the positive MGP has a greater effect on the melt flow just below the melt free surface, while in the case of negative MGP, the effect on the melt flow is towards the bottom of the crucible. This causes the flow velocity of the positive MGP to be relatively slower than that of the negative MGP, which means higher oxygen evaporation at the melt free surface. Since the strength of the magnetic field is similar at the crystal-melt interface, the crystal-melt interface will be similar.

[0070] With increasing crystal length, the flow velocity at the free surface of the melt is similar for both MGP conditions, so the dissolution and evaporation of oxygen are similar. However, the crystal-melt interface shape may be different due to different magnetic field directions and lines in the melt below the center.

[0071] The typical height of the crystal-melt interface varies with the melt depth for both positive and negative MGPs, as Figure 7 . In the case of positive MGP (i.e., the maximum Gaussian plane is positioned above the melt free surface), the crystal-melt interface is pushed into the growing crystal front at larger melt depths and the force used to push the interface gradually decreases as the melt volume decreases. Meanwhile, negative MGP maintains the force used to push the crystal-melt interface regardless of the melt volume, which achieves a relatively constant axial crystal-melt interface height regardless of the melt depth.

[0072] Figure 8 Displays the life contour map of the vertical lamellae and the measured crystal-melt interface. A short lamellae is used at a specific crystal location and heat treated to define the stripes of its solidification history. Next, the xy coordinates of the image from the life contour map are generated. The height of the interface is directly inferred by the difference from the center to the edge of the contour map.

[0073] exist Fig. 9 The height of the crystal-melt interface is plotted as a function of the MGP. Fig. 9 As shown in , in the case of negative MGP, the height of the crystal-melt interface is similar at both the seed end and the opposite end, thereby fixing one parameter for axial v / G perfect silicon control.

[0074] Fig.10 Examples showing the axial oxygen distribution at different MGP positions. i The difference gradually decreases with the decrease of melt volume due to the magnetic field in the melt region. i Caused by the proximity of the magnetic field to the free surface of the melt, thereby enhancing evaporation. Fig.10As shown in , increasing the area ratio between the free melt surface and the wetted surface of the crucible alleviates the effect of poor MGP.

[0075] Fig.11 is the normalized O at three different normalized MGP values i Box plot of . Fig.11 It is shown that Oi is increased by lowering the magnet position at three different conditions of melt volume. Group A contains less than 9% O from the solidified ingot. i Data, Group B contains 9% to 22% Oi data from the solidified ingot, and Group C contains 22% to 33.6% Oi data from the solidified ingot.

[0076] To achieve a lower Oi specification, i and interface height using a higher magnet position. However, as explained above, a lower magnet position can be used for optimal interface control. Fig.10 As shown in the figure, O i Insensitive to magnet position.

[0077] Fig.12 The effect of lowering the magnet position on the defect distribution is demonstrated. Crystal defects change from vacancy-rich perfect silicon (Pv) to dislocation clusters (I defects). In addition, the radial defect pattern changes. The crystal center becomes vacancy-dominated at the positive MGP. By lowering the magnet position, the dominant point defects at the crystal center change to interstitial-dominated. This transition is caused by interface changes under constant temperature conditions at the crystal surface. The v / G at the crystal center increases and the crystal edge maintains the v / G the same as at the high MGP, so the defects in the crystal center transform to I defects under the same pull rate conditions under different MGP conditions.

[0078] As used herein, the terms "about," "substantially," "substantially," and "approximately" when used in conjunction with ranges of size, concentration, temperature, or other physical or chemical properties or characteristics are meant to encompass variations that may exist in the upper and / or lower limits of the range of the property or characteristic, including variations resulting, for example, from rounding, measurement method, or other statistical variations.

[0079] When introducing elements of the present disclosure or embodiments thereof, the articles "a," "an," and "the" are intended to mean that there are one or more of the elements. 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 terms indicating a particular orientation (e.g., "top," "bottom," "side," etc.) is for convenience of description and does not require any particular orientation of the items being described.

[0080] As various changes could be made in the above constructions and methods 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 shall be interpreted as illustrative rather than limiting.

Claims

1. A method for producing a silicon ingot, the method comprising: melting polycrystalline silicon in a crucible enclosed in a growth chamber to form a melt having a melt free surface; generating a horizontal magnetic field within the growth chamber; contacting a seed crystal with the melt; extracting the seed crystal from the melt to form the silicon ingot; and adjusting the position of the maximum Gaussian plane during formation of the constant diameter portion of the silicon ingot in at least two stages of ingot growth, the at least two stages comprising: a first phase corresponding to the formation of the silicon ingot starting from the formation of the constant diameter portion of the silicon ingot up to an intermediate ingot length; and a second phase corresponding to the formation of the silicon ingot from at least the intermediate ingot length to the total length of the constant diameter portion; and Wherein adjusting the position of the maximum Gaussian plane includes maintaining the position of the maximum Gaussian plane in the second stage at a position lower than the position of the maximum Gaussian plane during the first stage.

2. The method of claim 1 , wherein the at least two stages include an intermediate stage corresponding to the formation of the silicon ingot between the first stage and the second stage, wherein adjusting the position of the maximum Gaussian plane includes lowering the position of the maximum Gaussian plane from the position in the first stage to the position in the second stage during the intermediate stage.

3. A method according to claim 1 or claim 2, wherein the position of the maximum Gaussian plane during the first stage is maintained above the melt free surface.

4. The method of claim 3, wherein the position of the maximum Gaussian plane during the second stage is maintained below the melt free surface.

5. The method of any one of claims 1 to 4, wherein the position of the maximum Gaussian plane is maintained at a position of at least 20 mm above the melt free surface during the first stage, or at least 40 mm above the melt free surface during the first stage, at least 60 mm above the melt free surface, from the melt free surface to 150 mm above the melt free surface, from 20 mm above the melt free surface to 150 mm above the melt free surface, or from 40 mm above the melt free surface to 150 mm above the melt free surface.

6. The method of any one of claims 1 to 5, wherein the position of the maximum Gaussian plane is maintained at a position of at least 20 mm below the melt free surface during the second stage, or at least 40 mm below the melt free surface, at least 60 mm below the melt free surface, at least 80 mm below the melt free surface, at least 100 mm below the melt free surface, from the melt free surface to 200 mm below the melt free surface, from 20 mm below the melt free surface to 200 mm below the melt free surface, or from 20 mm below the melt free surface to 150 mm below the melt free surface during the second stage.

7. The method of any one of claims 1 to 6, wherein the at least two stages include an intermediate stage corresponding to the formation of the silicon ingot between the first stage and the second stage, wherein adjusting the position of the maximum Gaussian plane includes lowering the position of the maximum Gaussian plane from the position in the first stage to the position in the second stage during the intermediate stage, wherein the position of the maximum Gaussian plane is lowered below the melt free surface during the intermediate stage.

8. The method of any one of claims 1 to 7, wherein the at least two stages include an intermediate stage corresponding to the formation of the silicon ingot between the first stage and the second stage, wherein adjusting the position of the maximum Gaussian plane includes lowering the position of the maximum Gaussian plane from the position in the first stage to the position in the second stage during the intermediate stage, wherein the position of the maximum Gaussian plane is lowered by at least 40 mm over no more than 60% of the constant diameter portion, over no more than 50% or over no more than 40% of the constant diameter portion.

9. The method of any one of claims 1 to 7, wherein the at least two stages include an intermediate stage corresponding to the formation of the silicon ingot between the first stage and the second stage, wherein adjusting the position of the maximum Gaussian plane includes lowering the position of the maximum Gaussian plane from the position in the first stage to the position in the second stage during the intermediate stage, wherein the position of the maximum Gaussian plane is lowered by at least 75 mm over no more than 60% of the constant diameter portion, no more than 50% or no more than 40% of the constant diameter portion.

10. The method of any one of claims 1 to 7, wherein the at least two stages include an intermediate stage corresponding to the formation of the silicon ingot between the first stage and the second stage, wherein adjusting the position of the maximum Gaussian plane includes lowering the position of the maximum Gaussian plane from the position in the first stage to the position in the second stage during the intermediate stage, wherein the position of the maximum Gaussian plane is lowered by at least 100 mm over no more than 60% of the constant diameter portion, no more than 50% of the constant diameter portion, or no more than 40% of the constant diameter portion.

11. The method of any one of claims 1 to 7, wherein the at least two stages include an intermediate stage corresponding to the formation of the silicon ingot between the first stage and the second stage, wherein adjusting the position of the maximum Gaussian plane includes lowering the position of the maximum Gaussian plane from the position in the first stage to the position in the second stage during the intermediate stage, wherein the position of the maximum Gaussian plane is lowered by at least 150 mm over no more than 60% of the constant diameter portion, no more than 50% or no more than 40% of the constant diameter portion.

12. The method of any one of claims 1 to 11, wherein the length of the first stage is at least 10% of the constant diameter portion, at least 20% of the constant diameter portion, at least 10% and less than 50% of the constant diameter portion, or at least 10% and less than 40% of the constant diameter portion.

13. The method of claim 12, wherein the first stage begins at the beginning of the constant diameter portion of the ingot.

14. The method of any one of claims 1 to 13, wherein the length of the second stage is at least 10% of the constant diameter portion, at least 20% of the constant diameter portion, at least 30% of the constant diameter portion, at least 10% and less than 50% of the constant diameter portion, or at least 20% and less than 50% of the constant diameter portion.

15. The method of claim 14, wherein the second stage extends to the entire length of the constant diameter portion of the ingot.

16. The method of any one of claims 1 to 15, wherein the position of the maximum Gaussian plane is constant during the first phase.

17. The method of any one of claims 1 to 15, wherein the position of the maximum Gaussian plane changes during the first stage.

18. The method of any one of claims 1 to 17, wherein the position of the maximum Gaussian plane is constant during the second phase.

19. The method of any one of claims 1 to 18, wherein the position of the maximum Gaussian plane changes during the second stage.

20. An ingot puller device for manufacturing a single crystal silicon ingot, the ingot puller device comprising: a crucible for holding a silicon melt; an ingot puller housing defining a growth chamber for pulling a silicon ingot from the silicon melt, the crucible being disposed within the growth chamber; a pair of magnetic poles disposed radially outward from the crucible; and A translation device is provided to axially move the magnetic pole relative to the crucible.

21. The ingot puller apparatus according to claim 20, wherein the translation device comprises: Guides; and A mount is provided to move each pole relative to the guide.

22. The ingot puller apparatus of claim 21, wherein the guide comprises a rail and the mount connects each pole to the rail.

23. An ingot puller apparatus as claimed in claim 21 or claim 22, comprising an actuator to move the pole relative to the guide.

24. Ingot puller apparatus according to claim 23, wherein the actuator comprises a pneumatic or hydraulic cylinder, a rack and pinion, a pulley or a gear train with a ball screw.

25. Ingot puller apparatus according to claim 23 or claim 24, comprising a motor to power the actuator.

26. The ingot puller apparatus of any one of claims 20 to 25, comprising a controller including a processor and a non-transitory memory storing instructions, the instructions being executed by the processor to configure the controller, the controller being configured to cause the translation device to move the pair of magnetic poles to adjust the position of the maximum Gaussian plane during formation of the constant diameter portion of the silicon ingot in at least two stages of ingot growth, the at least two stages comprising: a first phase corresponding to the formation of the silicon ingot starting from the formation of the constant diameter portion of the silicon ingot up to an intermediate ingot length; and The second phase corresponds to the formation of the silicon ingot from at least the intermediate ingot length to the total ingot length.

27. The ingot puller apparatus of claim 26, wherein the controller is configured to maintain the position of the maximum Gaussian plane in the second stage at a position lower than the position of the maximum Gaussian plane during the first stage.

28. The ingot puller apparatus of claim 27, wherein the controller is configured to maintain the position of the maximum Gaussian plane at least 20 mm above the melt free surface during the first stage, or at least 40 mm above the melt free surface during the first stage, at least 60 mm above the melt free surface, from the melt free surface to 150 mm above the melt free surface, from 20 mm above the melt free surface to 150 mm above the melt free surface, or from 40 mm above the melt free surface to 150 mm above the melt free surface.

29. The ingot puller apparatus of claim 27 or claim 28, wherein the controller is configured to maintain the position of the maximum Gaussian plane at least 20 mm below the melt free surface during the second stage or at least 40 mm below the melt free surface, at least 60 mm below the melt free surface, at least 80 mm below the melt free surface, at least 100 mm below the melt free surface, from the melt free surface to 200 mm below the melt free surface, from 20 mm below the melt free surface to 200 mm below the melt free surface, or from 20 mm below the melt free surface to 150 mm below the melt free surface during the second stage.

30. The ingot puller apparatus of any one of claims 26 to 29, wherein the at least two stages include an intermediate stage corresponding to formation of the silicon ingot between the first stage and the second stage, wherein the controller is configured to lower the position of the maximum Gaussian plane from the position in the first stage to the position in the second stage during the intermediate stage, and wherein the controller is configured to lower the maximum Gaussian plane below the melt free surface during the intermediate stage.

31. The ingot puller apparatus of any one of claims 26 to 30, wherein the at least two stages include an intermediate stage corresponding to the formation of the silicon ingot between the first stage and the second stage, wherein the controller is configured to lower the position of the maximum Gaussian plane from the position in the first stage to the position in the second stage during the intermediate stage, and wherein the controller is configured to lower the maximum Gaussian plane by at least 40 mm over no more than 60% of the constant diameter portion, no more than 50% of the constant diameter portion, or no more than 40% of the constant diameter portion.

32. The ingot puller apparatus of any one of claims 26 to 30, wherein the at least two stages include an intermediate stage corresponding to the formation of the silicon ingot between the first stage and the second stage, wherein the controller is configured to lower the position of the maximum Gaussian plane from the position in the first stage to the position in the second stage during the intermediate stage, and wherein the controller is configured to lower the maximum Gaussian plane by at least 75 mm over no more than 60% of the constant diameter portion, no more than 50% of the constant diameter portion, or no more than 40% of the constant diameter portion.

33. The ingot puller apparatus of any one of claims 26 to 30, wherein the at least two stages include an intermediate stage corresponding to the formation of the silicon ingot between the first stage and the second stage, wherein the controller is configured to lower the position of the maximum Gaussian plane from the position in the first stage to the position in the second stage during the intermediate stage, and wherein the controller is configured to lower the maximum Gaussian plane by at least at least 100 mm over no more than 60% of the constant diameter portion, no more than 50% of the constant diameter portion, or no more than 40% of the constant diameter portion.

34. The ingot puller apparatus of any one of claims 26 to 30, wherein the at least two stages include an intermediate stage corresponding to the formation of the silicon ingot between the first stage and the second stage, wherein the controller is configured to lower the position of the maximum Gaussian plane from the position in the first stage to the position in the second stage during the intermediate stage, and wherein the controller is configured to lower the maximum Gaussian plane by at least at least 150 mm over no more than 60% of the constant diameter portion, no more than 50% of the constant diameter portion, or no more than 40% of the constant diameter portion.

35. A billet puller apparatus according to any one of claims 26 to 34, wherein the controller is configured to maintain the length of the first stage to at least 10% of the constant diameter portion, at least 20% of the constant diameter portion, at least 10% and less than 50% of the constant diameter portion, or to at least 10% and less than 40% of the constant diameter portion.

36. A billet puller apparatus according to any one of claims 26 to 35, wherein the controller is configured to maintain the length of the second stage to at least 10% of the constant diameter portion, at least 20% of the constant diameter portion, at least 30% of the constant diameter portion, at least 10% and less than 50% of the constant diameter portion, or to at least 20% and less than 50% of the constant diameter portion.

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