Manufacturing method of silicon ingot by horizontal magnetic field Czochralski method

Abstract

A method for producing a silicon ingot is disclosed in which a horizontal magnetic field is generated. A number of process parameters are adjusted during ingot growth, including crucible wall temperature, silicon monoxide (SiO) transport from the crucible to the single crystal, and the evaporation rate of SiO from the melt. Controlling the number of process parameters can include controlling the position of the maximum Gaussian plane of the horizontal magnetic field, controlling the strength of the horizontal magnetic field, and controlling the rotation speed of the crucible.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 180,993, filed April 28, 2021, which is incorporated by reference herein in its entirety. [Technical field]

[0002] The field of the disclosure relates to methods for producing single crystal silicon ingots by horizontal field Czochralski technique, and in particular, to methods for producing single crystal silicon ingots with reduced oxygen content. [Background technology]

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

[0004] To produce semiconductor or solar wafers, single crystal silicon ingots can be produced by the Czochralski process by immersing a seed crystal in molten silicon held in a crucible. The seed crystal is withdrawn in a sufficient manner to achieve the diameter desired for the ingot, and the ingot is grown at that diameter. In a continuous process for single crystal silicon, the process is similar to the batch process, except that polysilicon is fed and melted simultaneously with the crystal growth. The silicon ingot is then machined into the desired shape to produce the semiconductor or solar wafer.

[0005] During the process, oxygen (Oi) is introduced into the silicon crystal ingot through the melt-crystal interface. Oxygen can cause various defects in the wafers produced from the ingot and reduce the yield of the semiconductor devices manufactured using the ingot. For example, insulated gate bipolar transistor (IGBT), high quality radio frequency (RF), high resistivity silicon-on-insulator (HR-SOI), and charge trapping layer SOI (CTL-SOI) applications typically require relatively low oxygen concentrations to achieve high resistivity and avoid the formation of PN junctions.

[0006] At least some known methods use float zone materials to achieve low oxygen concentration and high resistivity. However, the float zone materials are relatively expensive and are limited in use to the production of ingots less than about 200 mm in diameter. Thus, these known methods are unable to produce larger diameter silicon crystal ingots with relatively low oxygen concentrations.

[0007] A need exists for a method for producing single crystal silicon ingots with relatively low oxygen concentrations.

[0008] 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

[0009] One aspect of the present disclosure relates to a method for producing a silicon ingot. The method includes melting polycrystalline silicon in a crucible sealed in a vacuum chamber to form a melt. The melt has a melt-free surface. A horizontal magnetic field is generated in the vacuum chamber. A seed crystal is immersed in the melt. The seed crystal is removed from the melt to form a silicon ingot. Multiple process parameters are simultaneously controlled to reduce oxygen concentration in the silicon ingot. The multiple process parameters include a wall temperature of the crucible, transport of silicon monoxide (SiO) from the crucible to the silicon ingot, and evaporation rate of SiO from the melt.

[0010] Various refinements exist in the features noted in relation to the above aspects of the disclosure. Further features may also be incorporated into the above aspects of the disclosure. These refinements and additional features may exist individually or in any combination. For example, the various features described below in relation to any of the illustrated embodiments of the disclosure may be incorporated alone or in any combination into any of the above aspects of the disclosure. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a top view of one embodiment of a crucible and a cylindrical coordinate system. [Diagram 2] FIG. 2 is a side view of the crucible and a cylindrical coordinate system. [Diagram 3] FIG. 3 is a schematic diagram showing a cusp magnetic field applied to a crucible containing a melt in a crystal growing apparatus. [Figure 4] FIG. 4 is a block diagram of one embodiment of a crystal growing apparatus. [Diagram 5] FIG. 5 is a diagram of the magnitude of the horizontal and vertical components of the horizontal magnetic field in the molten and crystalline regions showing the maximum Gaussian plane (MGP). [Figure 6]Figure 6 is a flow field diagram showing the in-plane flow trajectories along the plane perpendicular to the horizontal magnetic field (X = 0 (central plane), X = -32 m, X = +32 m) when the MGP is 80 mm above the melt-free surface (+80 mm) and when the MGP is 80 mm below the melt-free surface (-80 mm). [Figure 7] Figure 7 is a graph comparing the radial velocity along the melt-free surface at the parallel center plane when the MGP is 80 mm above the melt-free surface (+80 mm) and when the MGP is 80 mm below the melt-free surface (-80 mm). [Figure 8] Figure 8 is a flow field diagram showing the in-plane flow trajectories along a plane parallel to the horizontal magnetic field (Y = 0 (central plane), Y = -32 m, Y = +32 m) when the MGP is 80 mm above the melt-free surface (+80 mm) and when the MGP is 80 mm below the melt-free surface (-80 mm). [Figure 9] Figure 9 is a graph comparing the radial velocity at the vertical center plane along the melt-free surface when the MGP is 80 mm above the melt-free surface (+80 mm) and when the MGP is 80 mm below the melt-free surface (-80 mm). [Figure 10] FIG. 10 is a graph showing the evaporation rate of SiO gas from the melt-free surface when the MGP is 80 mm below the melt-free surface (upper row) and when the MGP is 80 mm above the melt-free surface (lower row). [Figure 11] FIG. 11 shows the radial profiles of Oi in a single crystal silicon ingot when the MGP is 80 mm below the melt-free surface (−80 mm) and when the MGP is 80 mm above the melt-free surface (+80 mm). [Figure 12] FIG. 12 is a graph comparing Oi with experimental data versus MGP position in the HMCZ process. [Figure 13]Figure 13 is a flow field diagram showing the in-plane flow trajectories along the plane perpendicular to the horizontal magnetic field at X = 0 (center plane), X = -32 m, and X = +32 m for the cases of crucible reverse rotation at -0.6 RPM and MGP position 80 mm below the melt-free surface (left panel) and crucible reverse rotation at -1.6 RPM and MGP position 80 mm above the melt-free surface (right panel). [Figure 14] FIG. 14 is a graph of the radial profile of Oi within a single crystal silicon ingot for crucible counter rotations of −0.6 RPM and −1.6 RPM. [Figure 15] FIG. 15 is a graph of the radial profile of Oi within a single crystal silicon ingot for magnetic field strengths of 0.22T and 0.44T.

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

[0013] The provisions of the present disclosure relate to a method for producing relatively low-oxygen monocrystalline silicon ingots by the Horizontal Magnetic Czochralski (HMCZ) method. Referring initially to Figures 1 and 2, an example crucible for use in the method of the present disclosure is generally indicated at 10. The cylindrical coordinate system of the crucible 10 includes a radial direction R12, an angular direction θ14, and an axial direction Z16. The crucible 10 contains a melt 25 having a melt surface 36. A crystal 27 grows from the melt 25. The melt 25 may include one or more convection cells 17, 18 induced by heating the crucible 10 and rotation of the crucible 10 and / or the crystal 27 in the angular direction θ14. The structure and interaction of these one or more convection cells 17, 18 are regulated via control of one or more process parameters and / or application of a magnetic field, as described in more detail below.

[0014] FIG. 3 illustrates the application of a horizontal magnetic field to a crucible 10 containing a melt 25 in a crystal growing apparatus. As shown, the crucible 10 contains a silicon melt 25 from which a crystal 27 is grown. The transition between the melt and the crystal is commonly referred to as the crystal-melt interface (or melt-crystal, solid-melt, or melt-solid interface) and is typically nonlinear, e.g., concave, convex, or gull-wing shaped with respect to the surface of the melt. Two magnetic poles 29 are arranged opposite each other to generate a magnetic field that is approximately perpendicular to the crystal growth direction and approximately parallel to the surface 36 of the melt. The magnetic poles 29 may be conventional electromagnets, superconducting electromagnets, or other suitable magnets for generating a horizontal magnetic field of desired strength. The application of the horizontal magnetic field creates a Lorentz force along the axial direction, in a direction opposite to the fluid motion, which opposes the forces promoting melt convection. This suppresses convection in the melt and increases the axial temperature gradient in the crystal near the interface. The melt-crystal interface then moves upwards towards the crystal to accommodate the increasing axial temperature gradient in the crystal near the interface, and the contribution of melt convection in the crucible decreases. The horizontal arrangement has the advantage of being more efficient at damping convection at the melt surface 36.

[0015] FIG. 4 is a block diagram of a crystal growth apparatus 100. The apparatus 100 employs the Czochralski crystal growth method to produce semiconductor ingots. In this embodiment, the apparatus 100 is configured to produce cylindrical semiconductor ingots having an ingot diameter of 150 mm, 150 mm or more, more specifically in the range of about 150 mm to 460 mm, and even more specifically about 300 mm. In other embodiments, the apparatus 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 apparatus 100 is configured to produce semiconductor ingots having a total ingot length of at least 900 mm. In some embodiments, the apparatus is configured to produce semiconductor ingots having a length of 1950 mm, 2250 mm, 2350 mm, or greater than 2350 mm. In other embodiments, the apparatus 100 is configured to produce semiconductor ingots having a total ingot length ranging from about 900 mm to about 1200 mm, from about 900 mm to about 2000 mm, or from about 900 mm to about 2500 mm. In some embodiments, the apparatus is configured to produce semiconductor ingots having a total ingot length of greater than 2000 mm.

[0016] The crystal growing apparatus 100 includes a vacuum chamber 101 that surrounds the crucible 10. A side heater 105, e.g., a resistive heater, surrounds the crucible 10. A bottom heater 106, e.g., a resistive heater, is disposed below the crucible 10. During heating and crystal pulling, a crucible drive unit 107 (e.g., a motor) rotates the crucible 10, e.g., in a clockwise direction as indicated by arrow 108. The crucible drive unit 107 can also raise and / or lower the crucible 10 as needed during the growth process. Within the crucible 10 is a silicon melt 25 having a melt level or melt surface 36. In operation, the apparatus 100 pulls a single crystal 27 from the melt 25 starting from a seed crystal 115 attached to a pulling shaft or cable 117. One end of a lifting shaft or cable 117 is connected via a pulley (not shown) to a drum (not shown), or any other suitable type of lifting mechanism, e.g., a shaft, and the other end is connected to a chuck (not shown) that holds the seed crystal 115 and the crystal 27 grown from the seed crystal 115.

[0017] The crucible 10 and the single crystal 27 have a common axis of symmetry 38. The crucible drive unit 107 can raise the crucible 10 along the axis 38 as the melt 25 decreases to maintain the melt surface 36 at a desired height. The crystal drive unit 121 similarly rotates the pulling shaft or cable 117 in a direction 110 opposite to the direction in which the crucible drive unit 107 rotates the crucible 10 (e.g., counter-rotation). In embodiments using equal rotation, the crystal drive unit 121 can rotate the pulling shaft or cable 117 in the same direction that the crucible drive unit 107 rotates the crucible 10 (e.g., in a clockwise direction). Equal rotation is also referred to as co-rotation. Additionally, the crystal drive unit 121 can raise or lower the crystal 27 relative to the melt surface 36 as desired during the growth process.

[0018] According to the Czochralski single crystal growth process, a quantity of polycrystalline silicon, or polysilicon, is loaded into crucible 10. A heater power supply 123 energizes resistive heaters 105 and 106, and insulation 125 lines the interior walls of vacuum chamber 101. A gas supply 127 supplies an inert gas, such as argon, to vacuum chamber 101 via gas flow controller 129 as a vacuum pump 131 removes gas from vacuum chamber 101. An outer chamber 133, which is supplied with cooling water from reservoir 135, surrounds vacuum chamber 101.

[0019] The cooling water is then discharged to a cooling water return manifold 137. Typically, a temperature sensor such as a photocell 139 (or pyrometer) measures the temperature of the melt 25 at its surface, and a diameter transducer 141 measures the diameter of the silicon ingot 27. In this embodiment, the apparatus 100 does not include a top heater. The presence or absence of a top heater changes the cooling characteristics of the crystal 27.

[0020] Magnetic pole 29 is located outside of vacuum chamber 101 and generates a horizontal magnetic field. Although shown approximately centered on melt surface 36, the position of magnetic pole 29 relative to melt surface 36 can be varied to adjust the location of the maximum Gaussian plane (MGP) relative to melt surface 36. A reservoir 153 (FIG. 4) supplies cooling water to magnetic pole 29 before it is discharged via cooling water return manifold 137. An iron shield 155 surrounds magnetic pole 29 to reduce stray magnetic fields and increase the strength of the electric field generated.

[0021] The control unit 143 is used to control a number of process parameters, including but not limited to at least one of the following: crystal rotation speed, crucible rotation speed, and magnetic field strength. In various embodiments, the control unit 143 may include a memory 173 and a processor 144 to process signals received from various sensors of the apparatus 100, including but not limited to the photocell 139 and the diameter transducer 141, and to control one or more devices of the apparatus 100, including but not limited to the crucible drive unit 107, the crystal drive unit 121, the heater power supply 123, the vacuum pump 131, the gas flow controller 129 (e.g., an argon flow controller), the pole power supply 149, and any combination thereof. The memory 173 may store instructions that, when executed by the processor 144, cause the processor to perform one or more of the methods described herein. That is, the instructions configure the control unit 143 to perform one or more of the methods, processes, procedures, etc. described herein.

[0022] The control unit 143 may be a computer system. A computer system as described herein refers to any known computing device and computer system. As described herein, all such computer systems include a processor and a memory. However, a processor in a computer system as referred to herein may refer to one or more processors, and the processor may be in one computing device or in multiple computing devices operating in parallel. Furthermore, any memory in a computer system as referred to herein may refer to one or more memories, and the memory may be in one computing device or in multiple computing devices operating in parallel. Furthermore, the computer system may be located near the apparatus 100 (e.g., in the same room or in an adjacent room) or may be located remotely and connected to the rest of the system via a network such as Ethernet, the Internet, etc.

[0023] The term processor as used herein refers to a central processing unit, microprocessor, microcontroller, reduced instruction set circuit (RISC), application specific integrated circuit (ASIC), logic circuit, and other circuit or processor capable of performing the functions described herein. The above are merely examples and are not intended to limit in any way the definition and / or meaning of the term "processor". Memory includes, but is not limited to, random access memory (RAM), such as dynamic RAM (DRAM) and static RAM (SRAM), read only memory (ROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), non-volatile RAM (NVRAM), and the like.

[0024] In one embodiment, a computer program enabling the control unit 143 is provided, the program being embodied in a computer readable medium. The computer readable medium may include the memory 173 of the control unit 143. In an exemplary embodiment, the computer system is implemented in a single computer system. Alternatively, the computer system may have multiple computer systems, connections to server computers, cloud computing environments, etc. In some embodiments, the computer system includes multiple components distributed across multiple computing devices. One or more of the components may be in the form of computer executable instructions embodied in a computer readable medium.

[0025] The computer systems and processes are not limited to the specific embodiments described herein. Furthermore, each computer system component and each process can be implemented independently and separately from other components and processes described herein. Each component and process can also be used in combination with other assembly packages and processes.

[0026] In one embodiment, the computer system may be configured to receive measurements from one or more sensors, including but not limited to temperature sensor 139, diameter transducer 141, and any combination thereof, and may be configured to control one or more devices of apparatus 100, including but not limited to crucible drive unit 107, crystal drive unit 121, heater power supply 123, vacuum pump 131, gas flow controller 129 (e.g., argon flow controller), pole power supply 149, and any combination thereof, as described herein and shown in one embodiment in Figure 4. The computer system performs all steps used to control one or more devices of apparatus 100 as described herein.

[0027] According to an embodiment of the present disclosure, a horizontal magnetic field is generated in the vacuum chamber 101 while simultaneously controlling multiple process parameters to reduce the oxygen concentration in the silicon ingot 27. The multiple process parameters include the crucible wall temperature, the transport of silicon monoxide (SiO) from the crucible to the single crystal, and the evaporation rate of SiO from the melt.

[0028] In this embodiment, three process parameters are controlled simultaneously to facilitate the production of silicon crystal ingots with low oxygen concentration. Specifically, the wall temperature of the crucible 10, the flow (i.e., transport) of silicon monoxide (SiO) from the crucible 10 to the single crystal 27, and the evaporation of SiO from the melt 25 are controlled. The wall temperature of the crucible 10 corresponds to the melting rate of the crucible 10. Specifically, the higher the wall temperature of the crucible 10, the more a portion of the crucible 10 reacts with and dissolves in the melt 25, producing SiO, and the higher the oxygen concentration of the crystal 27. Thus, as used herein, decreasing the wall temperature of the crucible 10 is equivalent to decreasing the melting rate of the crucible 10.

[0029] The oxygen concentration of the ingot 27 can be reduced by decreasing the wall temperature of the crucible 10 (i.e., decreasing the melting rate of the crucible 10), decreasing the flow (i.e., transport) of SiO from the crucible 10 to the single crystal 27, and increasing the evaporation of SiO from the melt 25. To control the three process parameters, several conditions are controlled. Each condition affects at least one of the three process parameters. In some embodiments, the controlled conditions are the position of the maximum Gaussian plane, the strength of the magnetic field, and the rotation speed of the crucible. Each condition is described in detail herein.

[0030] In some embodiments, controlling the multiple process parameters includes maintaining a position of a maximum Gaussian plane ("MGP") of the horizontal magnetic field above the melt-free surface 36. The MGP is characterized by a maximum horizontal component of the magnetic field and zero vertical component along the MGP. The position of the magnetic pole 29 relative to the melt-free surface 36 can be varied to adjust the position of the maximum Gaussian plane (MGP) relative to the surface 36 of the melt. In some embodiments, the maximum Gaussian plane is maintained at a position at least 20 mm above the melt-free surface 36, or at least 40 mm above the melt-free surface 36, at least 60 mm above the melt-free surface 36, 150 mm above the melt-free surface from the melt-free surface 36, or 100 mm above the melt-free surface from the melt-free surface 36. In some embodiments, the maximum Gaussian plane is maintained at this position (i.e., the same position) during the growth of the entire ingot body (i.e., the constant diameter portion of the ingot).

[0031] In some embodiments, simultaneously controlling multiple process parameters includes generating a horizontal magnetic field with 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 0.15 Tesla to about 0.4 Tesla. Generally, the strength of the magnetic field is its magnitude at the center of the maximum Gaussian plane 52 (FIG. 5).

[0032] In some embodiments (e.g., when Oi concentration is low), controlling multiple process parameters simultaneously includes rotating the crucible in a direction opposite to the direction in which the ingot is rotated and rotating the crucible at a speed ranging from 0.1 RPM to 5.0 RPM (i.e., -0.1 RPM to -5.0 RPM), or even 0.1 RPM to 1.6 RPM (i.e., -0.1 RPM to -1.6 RPM), or 0.1 RPM to 1.2 RPM (i.e., -0.1 RPM to -1.2 RPM). In other embodiments, controlling multiple process parameters simultaneously includes rotating the crucible in the same direction in which the ingot is rotated and rotating the crucible 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.

[0033] In accordance with embodiments of the present disclosure, one or more methods for simultaneously controlling multiple process parameters described above may result in a silicon ingot having a relatively low concentration of oxygen incorporated therein. For example, the resulting silicon ingot may have an oxygen concentration of less than about 15 ppma, less than about 8 ppma, or even less than about 5 ppma. EXAMPLES

[0034] The processes of the present disclosure are further illustrated by the following examples, which should not be construed in a limiting sense.

[0035] Example 1: Effect of MGP location on Oi concentration Figure 6 compares the flow fields along a plane perpendicular to the applied horizontal magnetic field when the maximum Gaussian plane is 80 mm below the surface of the melt (hereafter referred to as "MGP-80mm") and when the maximum Gaussian plane is 80 mm above the surface of the melt (hereafter referred to as "MGP-80mm"). Figure 8 compares the flow fields along a plane parallel to the magnetic field.

[0036] The flow characteristics of the two locations have some commonality: the recirculation flow cells are only in the vertical plane, not in the parallel plane, and in both MGP locations, buoyancy cells occur in the bulk of the melt and Taylor-Proud-Mann cells occur below the rotating crystal.

[0037] Figures 7 and 9 compare the radial velocities along the melt surface for the two cases in the parallel and perpendicular central planes (Fig. 7 perpendicular to the applied horizontal magnetic field, and Fig. 9 parallel to the applied horizontal magnetic field). The superficial melt velocity was found to be generally higher in both planes when the MGP was located above the melt surface compared to when the MGP was located below the melt surface. A higher superficial melt velocity enhances the evaporation rate of SiO gas and reduces the oxygen concentration in the melt for a comparable crucible melting rate.

[0038] Figure 10 shows that the net SiO gas evaporation rate from the melt surface is higher when the MGP is 80 mm above the melt-free surface (lower graph) than when the MGP is 80 mm below the melt-free surface (upper graph), and the higher flow velocity at the melt surface enhances the evaporation rate, which is consistent with the flow field. This leads to lower oxygen levels in the melt and more Oi entrapment in the crystal for comparable crucible melting rates, as shown in Figure 11, which compares the Oi radial profiles in the crystal for the two cases.

[0039] To clarify the relationship between Oi and the MGP position, the model calculations were repeated for various other MGP positions. As shown in Figure 12, the relationship was found to be non-monotonic, with the smallest Oi values ​​occurring around the MGP position of 80 mm above the melt-free surface. Furthermore, the model results were compared with experimental measurements of Oi obtained from ingots grown under conditions where the MGP was 80 mm below and 80 mm above the melt-free surface (other process conditions were kept the same in the model and experiment). Although the absolute values ​​of Oi differ, the model follows the directionality of Oi with respect to the MGP position observed experimentally.

[0040] Example 2: Effect of the crucible counter-rotation speed on Oi concentration The reverse rotation speed of the crucible was increased from 0.6 RPM to 1.6 RPM. The model predicted that the flow structure in the vertical center plane changed obviously. In the latter case, the buoyancy cells were squeezed and the Taylor-Proud-Mann cell driven by the crystal rotation occupied most of the melt, as shown in Figure 13. The flow was mainly upward in the center, which promoted the transport of oxygen from the bottom of the crucible to the ingot. In addition, the buoyancy cells were not exposed to the surface of the melt, which caused a decrease in the SiO evaporation rate. These effects led to a higher oxygen concentration in the latter case, as shown in Figure 14, which is consistent with the experimental results shown below. TIFF2024515991000002.tif37161Table 1: Comparison of model and experimental values

[0041] Example 3: Effect of magnetic field strength on Oi concentration Referring now to Figure 15, the model predicts that Oi becomes non-monotonic as the magnetic field strength increases. Increasing the magnetic field suppresses melt convection and turbulence, which affect the boundary layer thickness at the crucible / melt interface (reducing the melting rate) and the melt / gas interface (reducing the evaporation rate). At the optimal magnetic field strength, the resulting melt flow slows the melting rate of the crucible, resulting in a low Oi, with relatively little effect on the evaporation rate. As shown in Figure 15, reducing the magnetic field strength to 0.22 T reduced the oxygen concentration in the ingot.

[0042] Example 4: Effect of MGP position and crucible rotation speed on Oi concentration Two 300mm ingots were grown with a constant magnetic field strength of approximately 3000 Gauss. The crucible rotation speed was kept constant at -2 RPM (i.e., counter-rotation) for both ingots. "Ingot 1" was grown with the MGP 130mm below the melt-free plane (-130mm MGP) and "Ingot 2" was grown 80mm above the melt-free plane (+80mm MGP). Lower oxygen was achieved with the higher MGP of +80mm, as shown in Table 2 below.

[0043] "Ingot 3" was a 300mm ingot similarly grown at a constant magnetic field strength of approximately 3000 Gauss. Ingot 3 was grown with MGP at +80mm and the crucible rotation speed was reduced to -0.1RPM. Lowering the crucible rotation speed to -0.1RPM resulted in lower oxygen as can be seen by comparing Ingot 2 and Ingot 3. TIFF2024515991000003.tif50170Table 2: Comparison of Oi with different MGP and crucible rotation

[0044] As used herein, the terms "about," "substantially," "essentially," and "approximately," when used in conjunction with a range of dimensions, concentrations, 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, for example, variations due to rounding, measurement method, or other statistical variations.

[0045] When introducing elements of this disclosure or embodiments thereof, the articles "a," "an," "the," and "said" mean that there is one or more of the element. The terms "comprising," "including," "containing," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. Use of specific orientation terms (e.g., "top," "bottom," "side," etc.) is for convenience of description and does not require a particular orientation of the items being described.

[0046] Because various changes may be made in the above structures and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

Claims

1. A method for producing a silicon ingot, comprising: melting polycrystalline silicon in a crucible surrounded by a vacuum chamber to form a melt having a melt-free surface; generating a horizontal magnetic field within the vacuum chamber; Immersing a seed crystal into the melt; Pulling the seed crystal from the melt to form the silicon ingot; and simultaneously controlling a plurality of process parameters to reduce an oxygen concentration in the silicon ingot; the plurality of process parameters include a wall temperature of the crucible, a transport of silicon monoxide (SiO) from the crucible to the silicon ingot, and an evaporation rate of SiO from the melt; Simultaneously controlling a plurality of process parameters includes maintaining a position of a maximum Gaussian plane of the horizontal magnetic field above the melt-free surface. method.

2. The maximum Gaussian plane is maintained at a position at least 20 mm above the melt-free surface, or at least 40 mm above the melt-free surface, at least 60 mm above the melt-free surface, or at least 150 mm above the melt-free surface; The method of claim 1.

3. Simultaneously controlling a plurality of process parameters includes generating the horizontal magnetic field at a magnetic flux density of less than 0.4 Tesla, or less than 0.35 Tesla, or less than 0.3 Tesla, or less than 0.25 Tesla, or from 0.15 Tesla to about 0.4 Tesla. The method of claim 1.

4. and simultaneously controlling a plurality of process parameters includes rotating the crucible in a direction opposite to the direction in which the ingot is rotated, the crucible being rotated at a speed ranging from 0.1 RPM to 5.0 RPM. The method of claim 1.

5. and simultaneously controlling multiple process parameters includes rotating the crucible in a direction opposite to the direction in which the ingot is rotated, the crucible being rotated at a speed ranging from 0.1 RPM to 1.6 RPM. The method of claim 1.

6. adjusting multiple process parameters simultaneously includes rotating the crucible in a direction opposite to the direction in which the ingot is rotated, the crucible being rotated at a speed ranging from 0.1 RPM to 1.2 RPM; The method of claim 1.

7. and simultaneously controlling a plurality of process parameters includes rotating the crucible in the same direction as the ingot is rotated, the crucible being rotated at a speed ranging from 0.1 RPM to 5.0 RPM. The method of claim 1.

8. and simultaneously controlling a plurality of process parameters includes rotating the crucible in the same direction as the ingot is rotated, the crucible being rotated at a speed ranging from 0.7 RPM to 5.0 RPM. The method of claim 1.

9. and simultaneously controlling a plurality of process parameters includes rotating the crucible in the same direction as the ingot is rotated, the crucible being rotated at a speed ranging from 1.2 RPM to 5.0 RPM. The method of claim 1.

10. The silicon ingot has a diameter of 300 mm or more. The method of claim 1.

11. The silicon ingot has a diameter of 300 mm. The method of claim 1.

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