Axial positioning of magnetic poles during silicon ingot manufacturing

Abstract

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

Description

[Technical Field]

[0001] This application claims priority to U.S. Non-Provisional Patent Application No. 17 / 897682, filed August 29, 2022, and U.S. Non-Provisional Patent Application No. 17 / 897685, filed August 29, 2022. Both applications are incorporated herein by reference in their entireties.

[0002] The field of the disclosure relates to methods for producing single crystal silicon ingots in a horizontal field Czochralski process and related ingot pulling apparatus for producing single crystal silicon ingots. [Background technology]

[0003] Single-crystal silicon is the starting material in many processes for manufacturing semiconductor electronic components and solar cell materials. For example, semiconductor wafers produced from silicon ingots are commonly used to manufacture integrated circuit chips with printed circuitry. In the solar cell industry, single-crystal silicon is sometimes used instead of polycrystalline silicon because it is free of grain boundaries and dislocations.

[0004] To produce semiconductor or solar wafers, monocrystalline silicon ingots may be produced using the Czochralski process by immersing a seed crystal in molten silicon held in a crucible. The seed crystal is withdrawn sufficiently to obtain the desired diameter for the ingot. After ingot formation, the silicon ingot may be machined into the desired shape from which semiconductor or solar wafers are produced.

[0005] Polished silicon wafers that meet manufacturers' requirements for the absence of agglomerated point defects, such as crystal-origin pits (COPs), are sometimes referred to as "neutral silicon" or "perfect silicon." Perfect silicon wafers are suitable for many semiconductor applications, for example, as a low-cost polished alternative to epitaxially grown wafers. During the growth of perfect silicon ingots using the horizontal-field Czochralski process, the crystal-melt interface generally has a concave shape. To produce perfect silicon, the pull rate is adjusted while controlling the thermal state of the ingot or the shape of the crystal-melt interface. To control the shape of the crystal-melt interface, the pull rate and thermal conditions (e.g., adjusting the gap between the melt surface and the reflector, controlling the bottom heater, etc.) may be continuously adjusted. Because the thermal conditions change during ingot growth, controlling the crystal-melt interface becomes complicated, and perfect silicon can only be produced within the axial window of ingot growth.

[0006] A need exists for a method of controlling a horizontal magnetic field to maintain a relatively constant crystal-melt interface, and an ingot pulling apparatus capable of implementing such a method to produce single crystal silicon ingots (e.g., perfect silicon).

[0007] 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. Summary of the Invention

[0008] One aspect of the present disclosure is directed to a method for manufacturing a silicon ingot. Polycrystalline silicon is melted in a crucible surrounded by 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 withdrawn from the melt to form a silicon ingot. The position of the maximum Gaussian plane during formation of a 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 formation of the silicon ingot from the start of formation of the constant diameter portion of the silicon ingot to an intermediate ingot length. The second stage corresponds to formation of the silicon ingot from at least the intermediate ingot length to the entire 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 lower position than the position of the maximum Gaussian plane during the first stage.

[0009] Another aspect of the present disclosure is directed to an ingot pulling apparatus for producing single crystal silicon ingots. The ingot pulling apparatus includes a crucible for holding a silicon melt. An ingot pulling 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 movement device for axially moving the magnetic poles relative to the crucible.

[0010] Various refinements exist to the features described in connection with the above-described aspects of the present disclosure. Additional features may be incorporated into the above-described aspects of the present disclosure. These refinements and additional features may exist individually or in any combination. For example, the various features described below in connection with any of the illustrated embodiments of the present disclosure may be incorporated, alone or in any combination, into any of the above-described aspects of the present disclosure. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 is a cross-sectional view of an HMCZ ingot pulling apparatus prior to silicon ingot growth. [Figure 2] FIG. 2 is a cross-sectional view of the HMCZ ingot puller of FIG. 1 during silicon ingot growth. [Figure 3] FIG. 3 is a schematic diagram showing a magnetic field applied to a crucible containing a melt in a crystal growth apparatus. [Figure 4] FIG. 4 is one embodiment of an MGP position profile during HMCZ ingot growth. [Figure 5] FIG. 5 is a block diagram of an exemplary controller for use with the ingot pulling apparatus shown in FIG. [Figure 6] Figure 6 shows a schematic diagram of the magnet and silicon melt at two different crystal lengths and magnet positions. [Figure 7] FIG. 7 is a graph showing normalized interface height as a function of ingot solidification fraction. [Figure 8] Figure 8 shows the lifetime contour map of the vertical slab and the measured crystal-melt interface. [Figure 9] Figure 9 shows the normalized height of the crystal-melt interface at different crystal positions as a function of MGP. [Figure 10] Figure 10 shows the axial Oi profiles at two different MGP positions (normalized Oi = [Oi / minimum Oi]). [Figure 11] Figure 11 shows box plots of normalized Oi at three different normalized MGP values. [Figure 12] Figure 12 shows an example of the crystal defect patterns at three different magnet positions.

[0012] Corresponding reference characters indicate corresponding parts throughout the drawings. DETAILED DESCRIPTION OF THE INVENTION

[0013] Provisions of the present disclosure relate to methods for manipulating the ingot-melt interface shape (i.e., changing the shape of the solidification front) during ingot growth. The methods and apparatus of the present disclosure may include changing the position of the maximum Gaussian plane during ingot growth to change the shape of the ingot-melt interface as the ingot grows.

[0014] The methods of the present disclosure may be generally carried out in any ingot puller configured to pull a single crystal silicon ingot and in which a horizontal magnetic field is applied to a melt. An example of an ingot puller (or more simply, an "ingot puller") is generally designated "100" in FIG. 1. The ingot puller 100 includes a crucible 102 supported on a susceptor 106 for holding a melt 104 of semiconductor or solar-grade material, such as silicon. The ingot puller 100 includes a crystal pulling housing 109 defining a growth chamber 152 for pulling a silicon ingot 113 (FIG. 2) from the melt 104 along a pulling axis A.

[0015] Crucible 102 includes a floor 128 and a sidewall 131 extending upward from floor 128. Sidewall 131 is generally vertical. Floor 128 includes a curved portion of crucible 102 that extends below sidewall 131. Within crucible 102 is silicon melt 104 having a melt surface 111.

[0016] In some embodiments, the crucible 102 is layered. For example, the crucible 102 may be made from a quartz base layer and a synthetic quartz liner disposed on the quartz base layer.

[0017] The susceptor 106 is supported by a shaft 105. The susceptor 106, crucible 102, shaft 105, and ingot 113 (FIG. 2) have a common longitudinal axis A or "pull axis" A.

[0018] The ingot pulling apparatus 100 includes a pulling mechanism 114 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 crystal 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, such as a shaft, and the other end is connected to the chuck 120, which holds the seed crystal 122. During operation, the seed crystal 122 is lowered into contact with the melt 104. The pulling mechanism 114 operates to raise the seed crystal 122, thereby pulling the single crystal ingot 113 ( FIG. 2 ) from the melt 104.

[0019] During heating and crystal pulling, a crucible drive 107 (e.g., a motor) rotates the crucible 102 and susceptor 106. An elevator mechanism 112 raises and lowers the crucible 102 along the pull axis A during the growth process. For example, the crucible 102 may be at its lowest position (near the bottom heater 126) where an initial charge of solid-phase polycrystalline silicon previously added to the crucible 102 is melted. Crystal growth begins by contacting the melt 104 with the seed crystal 122 and raising the seed crystal 122 with the pulling mechanism 114. As the ingot grows, the silicon melt 104 is consumed and the melt height within the crucible 102 decreases. The crucible 102 and susceptor 106 may be elevated to maintain the melt surface 111 at or near the same position relative to the ingot puller 100 (FIG. 2).

[0020] A crystal drive unit (not shown) may rotate the pulling cable 118 and ingot 113 (FIG. 2) in a direction opposite (e.g., counter-rotation) from the direction in which the crucible drive unit 107 rotates the crucible 102. In embodiments using unidirectional rotation, the crystal drive unit may rotate the pulling cable 118 in the same direction as the crucible drive unit 107 rotates the crucible 102. The crystal drive unit also raises or lowers the ingot 113 relative to the melt surface 111 as desired during the growth process.

[0021] The ingot puller 100 may include an inert gas system for introducing or withdrawing an inert gas, such as argon, into or from the growth chamber 152 . Ingot pulling apparatus 100 may include a dopant delivery system (not shown) for introducing dopants into melt 104 .

[0022] According to the Czochralski single crystal growth process, a quantity of polycrystalline silicon, or polysilicon, is loaded into a crucible 102. The initial semiconductor- or solar-grade material introduced into the crucible is melted by heat provided by one or more heating elements to form a silicon melt within the crucible. The ingot puller 100 includes bottom insulation 110 and side insulation 124 to maintain heat within the puller. In the illustrated embodiment, the ingot puller 100 includes a bottom heater 126 positioned below the crucible floor 128. The crucible 102 may be moved relatively close to the bottom heater 126 to melt the polycrystalline material loaded into the crucible 102.

[0023] To form an ingot, a seed crystal 122 is brought into contact with the surface 111 of the melt 104. A pulling mechanism 114 is operated to pull the seed crystal 122 from the melt 104. Referring to FIG. 2 , the ingot 113 includes a crown portion 142 where the ingot tapers as it transitions outward from the seed crystal 122 until it 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 tapers radially after the body 145. When the diameter is sufficiently small, the ingot 113 is separated from the melt 104.

[0024] The ingot puller 100 is configured to produce cylindrical semiconductor ingots having an ingot diameter of 150 mm, greater than 150 mm, more specifically in the range of about 150 mm to about 450 mm, and even more specifically about 300 mm. In other embodiments, the ingot puller 100 is configured to produce semiconductor ingots having an ingot diameter of 200 mm or an ingot diameter of 450 mm. Furthermore, in one embodiment, the system 100 is configured to produce semiconductor ingots having a total ingot length of at least 900 mm. In some embodiments, the system is configured to produce semiconductor ingots having lengths of 1950 mm, 2250 mm, 2350 mm, or greater than 2350 mm. In other embodiments, the ingot puller 100 is configured to produce semiconductor ingots having total ingot lengths ranging from about 900 mm to about 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 an overall ingot length of greater than 2000 mm.

[0025] The ingot pulling apparatus 100 includes a side heater 135 and a susceptor 106 that surrounds the crucible 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 102 moves up and down the pulling axis A. The side heater 135 and the bottom heater 126 may 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 and 126 are resistive heaters. The side heater 135 and the bottom heater 126 may be controlled by a control system (not shown) so that the temperature of the melt 104 is controlled throughout the pulling process.

[0026] The ingot pulling 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 (FIG. 2). The ingot pulling apparatus 100 may be cooled, such as 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.

[0027] 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, and no additional solid silicon is added to the crucible 102 during crystal growth.

[0028] The ingot pulling apparatus 100 of the present disclosure includes a pair of magnetic poles 129, 130 (FIG. 1) that generate a horizontal magnetic field during ingot growth. The magnetic poles 129, 130 are positioned radially outward from the crucible 102.

[0029] FIG. 3 illustrates 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 commonly referred to as the crystal-melt interface 125 (or "ingot-melt" or "solid-melt" interface), which is typically nonlinear, e.g., concave, convex, or gull-wing shaped relative to the melt surface 111. Two magnetic poles 129, 130 are arranged opposite each other to generate a magnetic field generally perpendicular to the ingot growth direction and generally parallel to the melt surface 111. The magnetic poles 129, 130 may be conventional electromagnets, superconducting electromagnets, or any other suitable magnets for generating a horizontal magnetic field of the desired strength. Application of the horizontal magnetic field generates a Lorentz force along the axial direction, opposite the fluid motion, counteracting the force driving melt convection. Therefore, melt convection is suppressed, and the axial temperature gradient within the ingot near the interface increases. The melt-ingot interface then moves upward toward the ingot to accommodate the increased axial temperature gradient in the ingot near the interface, reducing the contribution of melt convection within the crucible. The horizontal configuration has the advantage of being highly efficient at damping convection at the melt surface 111.

[0030] The poles 129, 130 may be cooled by circulating a cooling fluid through the poles 129, 130. An iron shield 155 (FIG. 1) may surround the poles 129, 130 to reduce stray magnetic fields and increase the strength of the generated magnetic field.

[0031] 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 at at least two stages of ingot growth. The MGP is characterized by a maximum magnitude of the horizontal component of the magnetic field and zero vertical component along the MGP. By moving the magnetic poles 129, 130, 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.

[0032] Referring now to FIG. 4 , which illustrates an exemplary profile of the position of the MGP during ingot growth, the position of the MGP is adjusted in a first stage S1, which corresponds to the formation of the silicon ingot from the start of the formation of the constant diameter portion of the silicon ingot to an intermediate ingot length, and a second stage S2, which corresponds to the formation of the silicon ingot from at least the intermediate ingot length to the entire length of the constant diameter portion. As shown in FIG. 4 , 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.

[0033] 4, the MGP profile includes an intermediate stage S3 corresponding to the formation of a silicon ingot 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 its position in the first stage S1 to its position in the second stage S2 during the intermediate stage S3.

[0034] In some embodiments, the position of the maximum Gaussian plane (corresponding to normalized position "1" in FIG. 4) is maintained at a position at least 20 mm above the melt free surface during the first stage, or, similar to 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.

[0035] Alternatively or additionally, the position of the maximum Gaussian plane may be maintained below the melt free surface during the second stage, or may be maintained at a position 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 a position 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.

[0036] In some embodiments, 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), as shown in Figure 4. 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.

[0037] 4, during intermediate stage S3, the position of the maximum Gaussian plane is lowered below the melt free surface. The position of the maximum Gaussian plane may be lowered by at least 40 mm (or at least 75 mm, at least 100 mm, at least 150 mm) during intermediate stage S3 (i.e., between the end of S1 and the beginning of S2) within 60% of the constant diameter portion, or, as in other embodiments, within 50% or 40% of the constant diameter portion.

[0038] The crucible 102 may move as the melt 104 is consumed to maintain a relatively constant position of the melt interface. In some embodiments, the position of the magnetic poles 129, 130 relative to the melt free surface 111 may be adjusted by moving both the magnetic poles 129, 130 and the position of the melt free surface 111 (e.g., by consuming melt or by moving the crucible 102). In other embodiments, the position of the magnetic poles 129, 130 relative to the melt free surface 111 is adjusted only by moving the magnetic poles 129, 130 (i.e., by moving the crucible 102 as the melt 104 is consumed, the melt free surface 111 is maintained in a relatively constant position).

[0039] 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% but less than 50% of the constant diameter portion, or at least 10% but less than 40% of the constant diameter portion. The first stage S1 may begin at the start of the constant diameter portion of the ingot. The position of the maximum Gaussian plane may be maintained constant during the first stage S1 or may vary during the first stage.

[0040] 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% but less than 50% of the constant diameter portion, or at least 20% but less than 50% of the constant diameter portion. The second stage S2 may extend from the end of the first stage S1 (or the end of the intermediate stage S3 in embodiments having an intermediate stage) to the end of the constant diameter portion of the ingot. The position of the maximum Gaussian plane may be maintained constant during the second stage S2, or may vary during the second stage.

[0041] The magnetic poles 129, 130 may be operated at any power that allows ingot growth to proceed as described herein. For example, during the first, second, and intermediate stages of ingot growth, the horizontal magnetic field may be generated at a flux strength of less than 0.4 Tesla, or, as in other embodiments, 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. Generally, the magnetic field strength is at the center of the maximum Gaussian plane 52.

[0042] The crucible 102 may be rotated in a direction opposite to the direction in which the ingot 113 is rotated, and the crucible 102 is rotated at a speed ranging from 0.1 RPM to 0.5 RPM (i.e., −0.1 RPM to −0.5 RPM), or 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 is rotated in the same direction as the ingot 113 is rotated, and the crucible 102 is rotated at a speed ranging from 0.1 RPM to 5.0 RPM, 0.7 RPM to 5 RPM, or 1.2 RPM to 5.0 RPM.

[0043] The ingot pulling apparatus 100 includes a movement device 160 ( FIG. 1 ) for axially moving the magnetic poles 129, 130 relative to the crucible 102 and the melt free surface 111. Any movement device 160 for moving the magnetic poles 129, 130 that enables the ingot pulling apparatus 100 to operate as described herein may be used. For example, the movement device 160 may include a guide 163 and a mount 170 for moving each magnetic pole 129, 130 relative to the guide 163. The guide 163 may include one or more rails, with the mount 170 connecting each magnetic pole 129, 130 to the one or more rails. The ingot pulling apparatus 100 includes an actuator 175 for moving the magnetic 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 movement device 160 may include other apparatus or devices that adjust the movement of the magnetic poles 129, 130.

[0044] 5 is a block diagram of an exemplary computing device 200 that may be used as or included as part of a controller 108 that adjusts the positions of magnetic poles 129, 130. Computing device 200 includes a processor 201, 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 all of the components shown in FIG.

[0045] Processor 201 is configured to execute instructions. In some embodiments, the executable instructions are stored in memory 202. Processor 201 may include one or more processing units (e.g., a multi-core configuration). As used herein, the term processor 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 foregoing is exemplary only and is not intended to limit the definition and / or meaning of the term "processor."

[0046] Memory 202 stores non-transitory computer-readable instructions for carrying out the techniques described herein. Such instructions, when executed by processor 201, cause processor 201 to perform at least a portion of the methods described herein. That is, the instructions stored in memory 202 configure controller 108 to perform the methods described herein. In some embodiments, memory 202 stores computer-readable instructions for providing a user interface to a user via media output component 204 and receiving and processing input from input device 206. Memory 202 may include, but is not limited to, random access memory (RAM), such as 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). While illustrated as separate from processor 201, in some embodiments, memory 202 is combined with processor 201, such as in a microcontroller or microprocessor, but may still be referred to separately. The above memory types are merely examples and are not intended to limit the types of memory that may be used to store computer programs.

[0047] Media output component 204 is configured to present information to a user (e.g., an operator of the system). Media output component 204 is any component capable of conveying information to a user. In some embodiments, media output component 204 includes an output adapter, such as a video adapter and / or an audio adapter. The output adapter is operably connected to processor 201 and operably connectable 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., speakers or headphones).

[0048] 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 enables the computing device 200 to receive analog and / or digital commands, instructions, or other input from a user, including visual, audio, touch, 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 (e.g., a touchpad or touchscreen), a gyroscope, an accelerometer, a position detector, an audio input device, or any combination thereof. A single component, such as a touchscreen, may function as both an output device for the media output component 204 and as the input device 206.

[0049] The communication interface 208 allows the computing device 200 to communicate with remote devices and systems, such as the motor 178 or actuator 175, remote sensors, remote databases, and remote computing devices, 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 over a network. The wireless communication interface may include a radio frequency (RF) transceiver, a Bluetooth® adapter, a Wi-Fi transceiver, a ZigBee® transceiver, a near field communication (NFC) transceiver, an infrared (IR) transceiver, and / or any other device and communication protocol for wireless communication. (Bluetooth is a registered trademark of the Bluetooth Special Interest Group, Kirkland, Washington, and ZigBee is a registered trademark of the ZigBee Alliance, San Ramon, California.) 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 enables computing device 200 to be coupled to a network such as the Internet, a local area network (LAN), a wide area network (WAN), a mesh network, and / or any other network for communicating with remote devices and systems over the network.

[0050] The computer systems discussed herein may include additional, fewer, or alternative functionality, including those 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(s).

[0051] The non-transitory memory 202 stores instructions that are executed by the processor 201 and configure the controller 108. The controller 108 according to an embodiment of the present disclosure is configured to cause the moving device 160 to move the pair of magnetic poles 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 above-described embodiments. For example, the position of the maximum Gaussian plane may be adjusted during at least two stages of ingot growth, with the position of the maximum Gaussian plane during the second stage being lower than the position of the maximum Gaussian plane during the first stage. In the above-described embodiment, the controller 108 may be configured to maintain the position of the maximum Gaussian plane at a distance from the melt free surface during at least two stages (and optional intermediate stages). The controller 108 may be configured to maintain the position of the maximum Gaussian plane so that various lengths of the first and second stages, and magnet descent speeds during the intermediate stages, can be achieved.

[0052] The controller 108 may be triggered to change the position of the magnetic poles at various stages of ingot growth (e.g., to end the first stage and move to an intermediate stage, or to end the intermediate stage and move to a second stage) by melt weight, ingot length, or time control.

[0053] Compared to conventional methods and apparatus for producing single crystal silicon, the method and apparatus of the disclosed embodiments have several advantages. By moving the magnetic poles during HMCZ ingot growth, the shape of the crystal-melt interface can be maintained relatively constant. The magnet position may be controlled to lower the height of the crystal-melt interface, thereby reducing the axial gradient variation for v / G control during perfect silicon production and widening the window for perfect silicon. The magnet position may be controlled to reduce oxygen at the seed end. The crystal-melt interface may be maintained relatively constant regardless of the melt volume and crucible position. Using a higher MGP at the seed end allows for lower oxygen at the seed end due to less oxygen being incorporated into the body. Lowering the magnet position from the middle to the latter half of the body reduces O. i The crystal-melt interface is pushed up as well as the seed end of the crystal without affecting the critical v / G. Therefore, faster pull rates can be used to produce perfect silicon, which increases productivity as the critical v / G increases from the middle to the latter half of the body. The more constant or less the axial v / G variation, the less quality degradation there is and the higher the yield. The higher the crystal-melt interface height (i.e., the larger the recession), the faster the pull rate and the higher the productivity. Oxygen control at the seed end provides flexibility in oxygen control at the seed end (customer-selected high O i (negative MGP) or low O i (either positive MGP).

[0054] [Example] The processes of the present disclosure are further illustrated by the following examples, which should not be construed in a limiting sense.

[0055] Example 1: Effect of MGP location on interface shape and ingot growth As shown in Figure 6, when the crystal growth length is short (i.e., when the melt volume is large), the positive MGP has a greater effect on the melt flow just below the melt free surface, while the negative MGP influences the melt flow toward the bottom of the crucible. Therefore, the flow rate of the positive MGP is relatively slower than that of the negative MGP, resulting in more oxygen evaporation at the melt free surface. Since the magnetic field strength is similar at the crystal-melt interface, the crystal-melt interface will also be similar.

[0056] As the crystal length increases, the flow velocity at the free surface of the melt is similar for both MGP conditions, and therefore the dissolution and evaporation of oxygen are similar. However, the direction and field lines of the magnetic field are different in the melt below the center, which can lead to different shapes of the crystal-melt interface.

[0057] The typical height of the crystal-melt interface varies with melt depth for both positive and negative MGPs, as shown in Figure 7. In the case of a positive MGP (i.e., when the maximum Gaussian plane is located above the free melt surface), the crystal-melt interface is pushed up toward the growing crystal front as the melt depth increases, and the force pushing up the interface gradually decreases as the melt volume decreases. On the other hand, a negative MGP maintains the force pushing up the crystal-melt interface regardless of the melt volume, allowing the axial crystal-melt interface height to remain relatively constant regardless of the melt depth.

[0058] Figure 8 shows the lifetime contour map of a vertical slab and the measured crystal-melt interface. A short slab was taken at a specific crystal location and heat-treated to reveal the lines of the solidification history. The xy coordinates of the image were then generated from the lifetime contour mapping. The height of the interface was directly inferred from the difference from the center to the edge of the contour map.

[0059] The height of the crystal-melt interface as a function of MGP was plotted in Fig. 9. As shown in Fig. 9, for negative MGP, the height of the crystal-melt interface was similar at both the seed end and the opposite end, which fixed one of the parameters used for axial v / G perfect silicon control.

[0060] Figure 10 shows an example of the axial oxygen profile at different MGP positions. O between the positive and negative MGP i The difference gradually decreased as the melt volume decreased due to the magnetic field in the melt region. i was caused by the enhanced evaporation due to the magnetic field near the free melt surface. As shown in Fig. 10, increasing the area ratio between the free melt surface and the wetted surface of the crucible mitigates the effect of the MGP difference.

[0061] Figure 11 shows the normalized O for three different normalized MGP values. i Figure 11 shows the box plot of O by lowering the magnet position under three different melt volume conditions. i Group A contains less than 9% O in the solidified ingot. i Data included: Group B contains 9% to 22% O in the solidified ingot. i Data included: Group C had 22% to 33.6% O in the solidified ingots. i Contains data.

[0062] Lower O i To achieve the specifications, i Higher magnet positions may be used for both the interface height and the surface area. However, as explained above, lower magnet positions may be used for better interface control. As shown in Figure 10, the O i is not sensitive to the magnet position.

[0063] Figure 12 shows the effect of lowering the magnet position on the defect profile. The crystal defects change from vacancy-rich perfect silicon (Pv) to dislocation clusters (I defects). Furthermore, the radial defect pattern changes. The crystal center becomes vacancy-dominated at a positive MGP. By lowering the magnet position, the dominant point defect at the crystal center changes to interstitial-dominated. This transition is caused by the change in the interface at a constant temperature of the crystal surface. Since the v / G at the crystal center increases while the crystal edge maintains the same v / G as at higher MGP, the defects at the crystal center change to I defects under the same pulling rate conditions with different MGP.

[0064] As used herein, the terms "about," "substantially," "essentially," and "approximately," when used in conjunction with a range of dimensions, densities, temperatures, or other physical or chemical properties or characteristics, are meant to encompass variations that may exist at the upper and / or lower limits of the range of the property or characteristic, including variations that result, for example, from rounding, measurement methods, or other statistical variations.

[0065] When introducing elements of the present disclosure or embodiment(s) thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that additional elements may be present 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 mandate any particular orientation of the articles being described.

[0066] Because various changes may be made in the above-described structures 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 be interpreted as illustrative and not in a limiting sense.

Claims

1. A method for manufacturing silicon ingots, The aforementioned method, Polycrystalline silicon is melted in a crucible surrounded by a growth chamber of an ingot pulling device to form a molten material, and the molten material has a free surface. A horizontal magnetic field is generated within the growth chamber, The seed crystal is brought into contact with the melt, In order to form the silicon ingot, the seed crystal is extracted from the melt, The crucible is raised so that the free surface of the molten liquid is maintained in the same position relative to the ingot pulling device. Adjusting the position of the maximum Gauss plane during the formation of a constant diameter portion of the silicon ingot in at least two stages of ingot growth. This includes, The above-mentioned at least two steps are, A first stage corresponding to the formation of the silicon ingot from the start of formation of the certain diameter portion of the silicon ingot up to the intermediate ingot length, A second stage corresponding to the formation of the silicon ingot from at least the intermediate ingot length to the total length of the constant diameter portion, wherein the crucible is raised between the first and second stages of ingot growth, and Equipped with, A method for adjusting the position of the maximum Gaussian surface, comprising maintaining the position of the maximum Gaussian surface in the second step at a lower position than the position of the maximum Gaussian surface during the first step, wherein the position of the maximum Gaussian surface is maintained at a position at least 100 mm below the free surface of the melt during the second step.

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

3. The method according to claim 1, wherein the position of the maximum Gauss surface during the first step is maintained above the free surface of the melt.

4. The method according to claim 1, wherein the position of the maximum Gaussian surface is maintained at a position at least 20 mm above the free surface of the melt during the first step.

5. The method according to claim 1, wherein the at least two steps include an intermediate step corresponding to the formation of the silicon ingot between the first step and the second step, and adjusting the position of the maximum Gaussian plane includes lowering the position of the maximum Gaussian plane from the position in the first step to the position in the second step during the intermediate step, the position of the maximum Gaussian plane being lowered below the free surface of the melt during the intermediate step.

6. The constant diameter portion has a length, The method according to claim 1, wherein the at least two steps include an intermediate step corresponding to the formation of the silicon ingot between the first step and the second step, and adjusting the position of the maximum Gaussian plane includes lowering the position of the maximum Gaussian plane from the position in the first step to the position in the second step during the intermediate step, wherein the position of the maximum Gaussian plane is lowered by at least 40 mm within a range of 50% or less of the length of the constant diameter portion.

7. The constant diameter portion has a length, The method according to claim 1, wherein the at least two steps include an intermediate step corresponding to the formation of the silicon ingot between the first step and the second step, and adjusting the position of the maximum Gaussian plane includes lowering the position of the maximum Gaussian plane from the position in the first step to the position in the second step during the intermediate step, wherein the position of the maximum Gaussian plane is lowered by at least 75 mm within a range of 50% or less of the length of the constant diameter portion.

8. The constant diameter portion has a length, The method according to claim 1, wherein the at least two steps include an intermediate step corresponding to the formation of the silicon ingot between the first step and the second step, and adjusting the position of the maximum Gaussian plane includes lowering the position of the maximum Gaussian plane from the position in the first step to the position in the second step during the intermediate step, wherein the position of the maximum Gaussian plane is lowered by at least 100 mm within a range of 50% or less of the length of the constant diameter portion.

9. The constant diameter portion has a length, The method according to claim 1, wherein the at least two steps include an intermediate step corresponding to the formation of the silicon ingot between the first step and the second step, and adjusting the position of the maximum Gaussian plane includes lowering the position of the maximum Gaussian plane from the position in the first step to the position in the second step during the intermediate step, wherein the position of the maximum Gaussian plane is lowered by at least 150 mm within a range of 50% or less of the length of the constant diameter portion.

10. The constant diameter portion has a length, The method according to claim 1, wherein the length of the first stage is at least 10% and less than 40% of the length of the constant diameter portion.

11. The method according to claim 10, wherein the first step begins at the starting point of the constant diameter portion of the ingot.

12. The constant diameter portion has a length, The method according to claim 1, wherein the length of the second stage is at least 20% and less than 50% of the length of the constant diameter portion.

13. The method according to claim 12, wherein the second step extends to the total length of the portion of the ingot with a certain diameter.

14. The method according to claim 1, wherein the position of the maximum Gaussian surface is constant during the first step.

15. The method according to claim 1, wherein the position of the maximum Gaussian surface changes during the first step.

16. The method according to claim 1, wherein the position of the maximum Gaussian surface is constant during the second step.

17. The method according to claim 1, wherein the position of the maximum Gaussian surface changes during the second step.

18. An ingot pulling apparatus for manufacturing single-crystal silicon ingots, The ingot lifting device is A crucible for holding the molten silicon, An ingot pulling housing defining a growth chamber for pulling up a silicon ingot from the silicon molten liquid, wherein the crucible is located within the growth chamber, and the ingot pulling housing A pair of magnetic poles arranged radially outward from the crucible, A moving device having a guide for moving the magnetic poles axially relative to the crucible, The controller comprises a processor and a non-temporary memory, the non-temporary memory storing instructions executed by the processor to constitute the controller, and the controller is configured to move the pair of magnetic poles to the moving device to adjust the position of the maximum Gauss plane during the formation of a constant diameter portion of the silicon ingot in at least two stages of ingot growth. Equipped with, The above-mentioned at least two steps are, A first stage corresponding to the formation of the silicon ingot from the start of formation of the certain diameter portion of the silicon ingot up to the intermediate ingot length, A second step corresponding to the formation of the silicon ingot from at least the intermediate ingot length to the total ingot length, Equipped with An ingot pulling apparatus, wherein the controller is configured to maintain the position of the maximum Gauss surface in the second stage at a lower position than the position of the maximum Gauss surface during the first stage, and the position of the maximum Gauss surface is maintained at a position at least 100 mm below the free surface of the molten metal during the second stage.

19. The ingot lifting device according to claim 18, wherein the moving device comprises a mount for moving each guide relative to the guide.

20. The ingot lifting device according to claim 19, wherein the guide comprises a rail, and the mount connects each magnetic pole to the rail.

21. The ingot lifting device according to claim 19, further comprising an actuator for moving the magnetic pole relative to the guide.

22. The ingot lifting device according to claim 21, wherein the actuator comprises a pneumatic cylinder or a hydraulic cylinder, a gear train having a rack and pinion, a pulley, or a ball screw.

23. The ingot lifting device according to claim 21, further comprising a motor for powering the actuator.

24. The ingot pulling apparatus according to claim 18, wherein the controller is configured to maintain the position of the maximum Gauss surface at least 20 mm above the free surface of the molten metal during the first stage.

25. The ingot pulling apparatus according to claim 18, wherein the controller is configured to maintain the position of the maximum Gauss surface at least 40 mm above the free surface of the molten metal during the first step.

26. The ingot pulling apparatus according to claim 18, wherein the controller is configured to maintain the position of the maximum Gauss surface at least 20 mm below the free surface of the molten metal during the second stage.

27. ​​The ingot pulling apparatus according to claim 18, wherein the controller is configured to maintain the position of the maximum Gauss surface at least 40 mm below the free surface of the molten metal during the second stage.

28. The ingot pulling apparatus according to claim 18, wherein the at least two steps include an intermediate step corresponding to the formation of the silicon ingot between the first step and the second step, the controller is configured to lower the position of the maximum Gauss plane from the position in the first step to the position in the second step during the preceding intermediate step, and the controller is configured to lower the maximum Gauss plane below the free surface of the molten metal during the intermediate step.

29. The ingot pulling device according to claim 18, wherein the at least two steps include an intermediate step corresponding to the formation of the silicon ingot between the first step and the second step, the controller is configured to lower the position of the maximum Gauss plane from the position in the first step to the position in the second step during the intermediate step, and the controller is configured to lower the maximum Gauss plane by at least 40 mm within a range of 60% or less of the constant diameter portion.

30. The ingot pulling device according to claim 18, wherein the at least two steps include an intermediate step corresponding to the formation of the silicon ingot between the first step and the second step, the controller is configured to lower the position of the maximum Gauss plane from the position in the first step to the position in the second step during the intermediate step, and the controller is configured to lower the maximum Gauss plane by at least 75 mm within a range of 50% or less of the constant diameter portion.

31. The ingot pulling device according to claim 18, wherein the at least two steps include an intermediate step corresponding to the formation of the silicon ingot between the first step and the second step, the controller is configured to lower the position of the maximum Gauss plane from the position in the first step to the position in the second step during the intermediate step, and the controller is configured to lower the maximum Gauss plane by at least 100 mm within a range of 40% or less of the constant diameter portion.

32. The ingot pulling device according to claim 18, wherein the at least two steps include an intermediate step corresponding to the formation of the silicon ingot between the first step and the second step, the controller is configured to lower the position of the maximum Gauss plane from the position in the first step to the position in the second step during the intermediate step, and the controller is configured to lower the maximum Gauss plane by at least 150 mm within a range of 60% or less of the previous constant diameter portion.

33. The ingot pulling device according to claim 18, wherein the controller is configured to maintain the length of the first stage at least 10% and less than 50% of the constant diameter portion.

34. The ingot pulling device according to claim 18, wherein the controller is configured to maintain the length of the second stage at least 10% and less than 50% of the constant diameter portion.

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