Apparatus for manufacturing single-crystal silicon ingots and method for manufacturing single-crystal silicon ingots

Abstract

The present invention provides a single-crystal silicon ingot manufacturing apparatus and manufacturing method that can improve the crystal quality of single-crystal silicon ingots. [Solution] The single-crystal silicon ingot manufacturing apparatus 1 comprises a quartz crucible 8, a heat shield 13 provided above the quartz crucible 8 and having a cylindrical shield body 13A and an inner flange portion 13B that protrudes inward from the lower end of the shield body 13A and defines an opening for the passage of the single-crystal silicon ingot, a camera 15 that photographs the inner flange portion 13B, and a control unit 20 that adjusts control factors for growing the single-crystal silicon ingot. The inner flange portion 13B has notches 131 provided at one or more locations on the end portion 13D that defines the opening. The control unit 20 calculates the circumferential position of the notches 131 as seen in the image captured by the camera 15 and adjusts the control factors based on the circumferential position of the notches 131.

Description

Technical Field

[0001] The present disclosure relates to an apparatus for manufacturing a single crystal silicon ingot and a method for manufacturing a single crystal silicon ingot.

Background Art

[0002] Conventionally, in an apparatus for manufacturing a single crystal silicon ingot, a method of observing a melt surface through a slot provided as a notch in a cover that covers the upper part of a crucible (or is installed above the crucible) is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It has been newly found that a notch provided in a heat shield corresponding to a cover that covers the upper part of a crucible (or is installed above the crucible) affects the crystal quality of a single crystal silicon ingot pulled up from the melt surface. There is a need to improve the crystal quality of a single crystal silicon ingot in an apparatus for manufacturing a single crystal silicon ingot in which a notch is provided in the heat shield.

[0005] Therefore, an object of the present disclosure is to provide an apparatus for manufacturing a single crystal silicon ingot and a method for manufacturing a single crystal silicon ingot that can improve the crystal quality of a single crystal silicon ingot even when a notch is provided in the heat shield.

Means for Solving the Problems

[0006] One embodiment of the present disclosure for solving the above problems is as follows. [1] A quartz crucible for containing a silicon melt, A chamber for housing the quartz crucible, A heat shield is provided above the quartz crucible, surrounding the single-crystal silicon ingot to be pulled up from the silicon molten liquid, and having a cylindrical shield body and an inner flange portion that protrudes inward from the lower end of the shield body and defines an opening for the passage of the single-crystal silicon ingot. A camera that photographs the surface of the silicon molten liquid and the inner flange portion of the heat shield through the space between the shield body and the single-crystal silicon ingot, A control unit for adjusting the control factors for growing the single-crystal silicon ingot, Equipped with, The inner flange portion has notches provided at one or more locations on the end portion that defines the opening, The control unit, The circumferential position of the notch as seen in the image captured by the camera is calculated. The control factor is adjusted based on the circumferential position of the notch. A manufacturing device for single-crystal silicon ingots. [2] The single-crystal silicon ingot manufacturing apparatus according to [1] above, wherein the control unit calculates the magnitude of the circumferential positional displacement of the notch when the heat shield is installed at a predetermined position in the chamber, with respect to the circumferential position of the notch when the heat shield is installed above the quartz crucible, and adjusts the control factor based on the magnitude of the circumferential positional displacement of the notch. [3] The apparatus for manufacturing a single crystal silicon ingot according to [1] or [2] above, wherein the control factor includes the flow rate of inert gas supplied into the chamber, the pressure inside the chamber, or the rotation speed of the quartz crucible. [4] A method for manufacturing single-crystal silicon ingots by the Czochralski method, The control factors for growing the single-crystal silicon ingot are adjusted based on the circumferential position of notches provided at one or more locations on the end of the inner flange portion of a heat shield provided above the quartz crucible in the chamber, which defines an opening for the passage of the single-crystal silicon ingot being pulled up from the silicon molten liquid in the quartz crucible. Growing the aforementioned single-crystal silicon ingot and A method for manufacturing single-crystal silicon ingots, including [the specified component]. [5] A method for manufacturing a single crystal silicon ingot according to [4], comprising calculating the magnitude of the circumferential positional displacement of the notch when the heat shield is installed at a predetermined position in the chamber, with respect to the circumferential position of the notch when the heat shield is installed above the quartz crucible, and adjusting the control factor based on the magnitude of the circumferential positional displacement of the notch. [6] The method for manufacturing a single crystal silicon ingot according to [5] above, wherein, based on the magnitude of the displacement of the circumferential position of the notch, a factor related to adjusting the oxygen concentration of the single crystal silicon ingot is adjusted as the control factor. [7] A method for manufacturing a single crystal silicon ingot according to any one of [4] to [6] above, wherein the control factor includes the flow rate of inert gas supplied into the chamber, the pressure inside the chamber, or the rotation speed of the quartz crucible. [8] A method for manufacturing a single-crystal silicon ingot according to any one of [4] to [7] above, comprising: dissolving the silicon raw material in the quartz crucible to obtain the silicon melt, and before starting the growth of the single-crystal silicon ingot, calculating the circumferential position of the notch from a photograph of the end of the inner flange portion of the heat shield. [Effects of the Invention]

[0007] According to the single-crystal silicon ingot manufacturing apparatus and single-crystal silicon ingot manufacturing method described herein, the crystal quality of the single-crystal silicon ingot can be improved even when a notch is provided in the heat shield. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing an example of the configuration when a seed crystal is brought into contact with a silicon melt in the manufacturing apparatus for single-crystal silicon ingots according to this disclosure. [Figure 2] This is a schematic diagram showing an example of the configuration when a seed crystal is pulled from the silicon melt to form a straight cylinder in the single-crystal silicon ingot manufacturing apparatus according to this disclosure. [Figure 3] This is a perspective view showing an example of a heat shield configuration. [Figure 4A] This is a plan view showing the case where the circumferential displacement of the heat shield is zero. [Figure 4B] This is a plan view showing the case where the circumferential displacement of the heat shield is 3 degrees. [Figure 5] This graph shows examples of oxygen concentrations in single-crystal silicon ingots pulled from a heat shield, both with and without circumferential displacement. [Figure 6] This is a schematic diagram illustrating the method for calculating the position of notches in a heat shield. [Figure 7] This graph shows an example of the oxygen concentration in single-crystal silicon ingots after adjusting the control factors. [Figure 8] This flowchart shows an example of the procedure for the control method related to this disclosure. [Modes for carrying out the invention]

[0009] (Example configuration of single-crystal silicon ingot manufacturing apparatus 1) Hereinafter, a configuration example of a manufacturing apparatus 1 for a single crystal silicon ingot according to an embodiment of the present disclosure will be described with reference to the drawings. The manufacturing apparatus 1 is used to execute a method for manufacturing a single crystal silicon ingot by the Czochralski method. As shown in FIGS. 1 and 2, the manufacturing apparatus 1 for a single crystal silicon ingot includes a chamber 2, a control unit 20, and an image processing unit 30. The pulling state of the single crystal silicon ingot is different between the configuration example of FIG. 1 and the configuration example of FIG. 2. The configuration example of FIG. 1 represents a state before a seed crystal described later contacts the liquid surface of the silicon melt MD and the pulling of the single crystal silicon ingot is started. The configuration example of FIG. 2 represents a state where the pulling of the single crystal silicon ingot is started and the straight body portion SM appears above the liquid surface of the silicon melt MD.

[0010] The chamber 2 includes a main chamber 2a and a pull chamber 2b. The main chamber 2a is a bottomed cylindrical chamber that houses a crucible having a double structure of a quartz crucible 8 and a carbon crucible 9 inside. The pull chamber 2b is a cylindrical chamber having the same central axis as the main chamber 2a and provided above the main chamber 2a, with a smaller diameter than the main chamber 2a. A gate valve may be provided between the main chamber 2a and the pull chamber 2b. The opening and closing of the gate valve causes the space in the main chamber 2a and the space in the pull chamber 2b to communicate with or be blocked from each other. The pull chamber 2b includes a gas inlet at the upper part, to which a gas supply source 5 and a mass flow controller 4 for introducing an inert gas such as Ar gas into the main chamber 2a are connected. The main chamber 2a includes a gas outlet at the bottom, to which a vacuum pump 18 and a valve 17 for sucking and discharging the gas in the main chamber 2a are connected.

[0011] The quartz crucible 8 and the carbon crucible 9 are arranged at the center of the main chamber 2a and house the silicon melt MD. The quartz crucible 8 directly supports the silicon melt MD on its inner surface. The carbon crucible 9 supports the quartz crucible 8 outside the quartz crucible 8. The quartz crucible 8 and the carbon crucible 9 are hereinafter also simply referred to as crucibles.

[0012] The manufacturing apparatus 1 further includes a heat shield 13, a support member 12, a cylindrical heater 11, and a cylindrical heat insulating cylinder 10 inside the main chamber 2a.

[0013] The heat shield 13 is provided above the crucible so as to surround the straight body portion SM (see FIG. 2) of the single crystal silicon ingot pulled up from the silicon melt MD. The heat shield 13 has a function of adjusting the amount of incident high-temperature radiant heat from the silicon melt MD, the heater 11, and the side wall of the crucible to the single crystal silicon ingot being grown, and adjusting the amount of heat diffusion near the crystal growth interface. Further, the heat shield 13 has a function of controlling the temperature gradient in the pulling direction at the central portion and the outer peripheral portion of the single crystal silicon ingot. In addition, since the heat shield 13 also has a function of guiding Ar gas toward the silicon melt MD in the quartz crucible 8, it may be referred to as a flow straightening cylinder.

[0014] As shown in Figures 1, 2, and 3, the heat shield 13 includes a cylindrical shield body 13A having an inner wall surface, an inner flange portion 13B extending inward from the lower end of the shield body 13A and defining an opening inside the shield body 13A, and an outer flange portion 13C extending horizontally outward from the upper end of the shield body 13A. The shape of the shield body 13A may be a shape along the side surface of a cylinder, i.e., a cylindrical shape, or a shape along the side surface of a frustocone whose diameter decreases downward. The opening defined by the inner flange portion 13B is provided to allow the single crystal silicon ingot being grown to pass through, and is circular when viewed toward the central axis of the cylindrical shield body 13A. In other words, the inner flange portion 13B defines a circular opening inside the shield body 13A. The portion of the inner flange portion 13B that defines a circular opening inside the shield body 13A is also called the end portion 13D. The shape of the end portion 13D is such that the inner flange portion 13B extends horizontally from the portion connected to the shield body 13A to the end portion 13D. In other words, in the direction along the central axis of the shield body 13A, the end portion 13D may be at the same height as the portion where the inner flange portion 13B connects to the shield body 13A. The inner flange portion 13B may extend downward from the shield body 13A to the end portion 13D. In other words, in the direction along the central axis of the shield body 13A, the end portion 13D may be positioned lower than the portion where the inner flange portion 13B connects to the shield body 13A. The heat shield 13 is installed in the open main chamber 2a by engaging the outer flange portion 13C onto the support member 12. In the heat shield 13, a notch 131 is provided in the inner end portion 13D of the inner flange portion 13B. The notch 131 is recessed outwards, in the direction from the end 13D toward the part where the inner flange portion 13B is connected to the shield body 13A. The notch 131 is provided at one or more locations on the end 13D of the inner flange portion 13B. The notch 131 is provided so that the liquid surface of the silicon molten MD can be photographed through the notch 131 by the camera 15, which will be described later, when the straight body portion SM of the single crystal silicon ingot is above the liquid surface of the silicon molten MD.

[0015] The cylindrical heater 11 is positioned within the main chamber 2a so as to surround the crucible. The heater 11 is a resistance heating heater made of carbon, which melts the silicon raw material placed in the crucible to form a silicon melt MD, and heats the crucible to maintain the formed silicon melt MD.

[0016] The cylindrical heat-insulating tube 10 is positioned below the upper end of the heat shield 13, spaced apart from the outer surface of the heater 11, and along the inner surface of the main chamber 2a. The heat-insulating tube 10 provides a heat-retaining effect to the chamber 2, particularly to the area below the heat shield 13, and has the function of making it easier to maintain the silicon molten MD in the crucible.

[0017] The manufacturing apparatus 1 includes a crucible lifting mechanism 7 for raising and lowering the crucible. The crucible lifting mechanism 7 rotates and raises the crucible via a shaft that passes vertically through the bottom of the main chamber 2a and supports the crucible from below.

[0018] The manufacturing apparatus 1 comprises a wire 6 passing through a pull chamber 2b and a seed chuck SC attached to the lower end of the wire 6. The seed chuck SC holds a seed crystal that is brought into contact with the surface of the silicon molten liquid MD in order to pull up a single-crystal silicon ingot from the silicon molten liquid MD contained in a crucible. The manufacturing apparatus 1 is equipped with a lifting drive unit 3 above the pull chamber 2b that drives the seed chuck SC vertically via the wire 6 to pull up the single-crystal silicon ingot. The lifting drive unit 3 raises and lowers the wire 6 while rotating it at a predetermined speed.

[0019] The manufacturing apparatus 1 further includes a magnetic field generator 16 that generates a magnetic field to be applied inside the main chamber 2a. The magnetic field generator 16 is located outside the main chamber 2a, within a height range that includes the crucible. The magnetic field generator 16 may have a coil such as a superconducting coil. The magnetic field generator 16 generates a horizontal magnetic field that forms a horizontal magnetic field distribution with respect to the silicon molten MD by passing an electric current through the coil. The magnitude of the magnetic flux density applied to the silicon molten MD is controlled by the magnitude of the electric current flowing through the coil.

[0020] The manufacturing apparatus 1 further comprises a lifting drive unit 3, a mass flow controller 4 and a gas supply source 5, a magnetic field generator 16, a valve 17 and a vacuum pump 18, and a control unit 20 that controls the crucible lifting mechanism 7.

[0021] The control unit 20 may include one or more processors. The processors can execute programs that implement various functions of the control unit 20. The processors may be implemented as a single integrated circuit. Integrated circuits are also called ICs (Integrated Circuits). The processors may be implemented as multiple communicably connected integrated circuits and discrete circuits. The processors may be implemented based on various other known technologies. The control unit 20 may include dedicated circuits.

[0022] The control unit 20 may further include a storage unit. The storage unit stores various information or data used by the control unit 20, or programs executed by the control unit 20. The storage unit may include an electromagnetic storage medium such as a magnetic disk, or a memory such as a semiconductor memory or magnetic memory. The storage unit may include a non-temporary computer-readable medium. The storage unit may function as the work memory of the control unit 20. At least a part of the storage unit may be configured separately from the control unit 20.

[0023] The control unit 20 may include a communication device for sending and receiving information or data to and from each component of the manufacturing apparatus 1. The communication device may be connected to each component via wired or wireless communication. The communication device may include a communication interface configured to enable communication based on a communication standard such as a LAN (Local Area Network). The communication interface is not limited to the example described above and may be configured to enable communication based on various other communication standards.

[0024] The manufacturing apparatus 1 further includes a camera 15 and an image processing unit 30 for observing the inside of the main chamber 2a. The camera 15 photographs the inside of the main chamber 2a through an observation window 14 provided in the main chamber 2a. The camera 15 may include a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor, etc. The image processing unit 30 processes the image captured by the camera 15 and outputs the processing result to the control unit 20. The image processing unit 30 may include a processor or a dedicated circuit. The image processing unit 30 may include a storage unit or a communication device. The processor, storage unit or communication device of the image processing unit 30 may be configured in the same way as the processor, storage unit or communication device of the control unit 20. The image processing unit 30 may be configured as part of the control unit 20.

[0025] Camera 15 is positioned to photograph the surface of the silicon molten MD through the space between the shield body 13A of the heat shield 13 and the single-crystal silicon ingot being grown. As shown in Figure 2, when the straight section SM of the single-crystal silicon ingot is above the surface of the silicon molten MD, the surface of the silicon molten MD is almost completely shielded from the camera 15 by the single-crystal silicon ingot and the inner flange portion 13B of the heat shield 13. In other words, camera 15 is positioned to photograph the surface of the silicon molten MD and the inner flange portion 13B through the space between the shield body 13A of the heat shield 13 and the single-crystal silicon ingot being grown. The notch 131 provided in the inner flange portion 13B of the heat shield 13 is provided to allow camera 15 to photograph the surface of the silicon molten MD even in this state.

[0026] (Example of operation of single-crystal silicon ingot manufacturing apparatus 1) The single-crystal silicon ingot manufacturing apparatus 1 produces a single-crystal silicon ingot by heating and melting silicon material in a crucible to obtain a silicon melt MD, and then bringing a seed crystal attached to a seed chuck SC into contact with the silicon melt MD and pulling it up. When manufacturing a single-crystal silicon ingot, the conditions of each control factor are set so that the oxygen concentration in the ingot to be grown reaches a desired oxygen concentration before the growth of the single-crystal silicon ingot begins. The values ​​set as conditions for each control factor are also called set values. Examples of control factors for controlling the oxygen concentration include the flow rate of an inert gas such as Ar gas supplied into the chamber 2, the pressure inside the chamber 2, i.e., the furnace pressure inside the chamber 2, or the rotation speed of the crucible. The control factors may include any of the flow rate of the inert gas supplied into the chamber 2, the pressure inside the chamber 2, or the rotation speed of the quartz crucible 8.

[0027] In the manufacturing apparatus 1 according to this disclosure, a notch 131 is provided in the inner flange portion 13B of a heat shield 13 that is arranged to surround a single crystal silicon ingot in the main chamber 2a. The installation of the heat shield 13 is performed manually. Therefore, depending on the operator, the position of the notch 131 may cause the heat shield 13 to be placed at a position that is shifted from the predetermined position where the heat shield 13 should be installed in the main chamber 2a. The displacement of the position of the heat shield 13 from the predetermined position includes a translational displacement included in the horizontal plane perpendicular to the central axis of the shield body 13A of the heat shield 13, or a rotational displacement within the horizontal plane. The rotational direction corresponds to the circumferential direction of the heat shield 13 when the cylindrical heat shield 13 is viewed along the central axis. The inventors have discovered that even if the circumferential displacement of the notch 131 is very small, if the position of the notch 131 is shifted circumferentially from a predetermined position, this circumferential displacement of the notch 131 will affect the oxygen concentration distribution in the longitudinal direction of the single-crystal silicon ingot that is subsequently grown.

[0028] Here, the circumferential displacement of the notch 131 will be explained with reference to the plan views of the heat shield 13 shown in Figures 4A and 4B. In Figures 4A and 4B, the dashed-dotted line extending vertically is used as the reference line. The notch 131 of the heat shield 13 shown in Figure 4A is located on the reference line. The reference line is a line that represents the circumferential position of the notch 131 when the heat shield 13 is installed in a predetermined position. The fact that the notch 131 is located on the reference line indicates that the position of the heat shield 13 is not shifted circumferentially from its predetermined position. In other words, there is no circumferential displacement of the position of the heat shield 13 in Figure 4A. On the other hand, the notch 131 of the heat shield 13 shown in Figure 4B is located on a dashed-dotted line that is tilted 3 degrees clockwise from the reference line. In other words, there is a circumferential displacement of the position of the heat shield 13 in Figure 4B. The magnitude of the circumferential displacement of the heat shield 13 from the reference position may be expressed as an angle. The magnitude of the circumferential displacement of the heat shield 13 from the reference position may also be expressed as the distance the notch 131 is shifted from the reference position in the direction along the end 13D of the inner flange portion 13B. The circumferential displacement of the heat shield 13 from the reference position is also referred to as the circumferential positional displacement of the heat shield 13. The magnitude of the circumferential displacement of the heat shield 13 from the reference position is also referred to as the amount of circumferential positional displacement of the heat shield 13.

[0029] Figure 5 shows an example of data comparing the oxygen concentration of a single-crystal silicon ingot pulled up with circumferential displacement of the heat shield 13 and the oxygen concentration of a single-crystal silicon ingot pulled up without circumferential displacement of the heat shield 13. The horizontal axis of the graph in Figure 5 represents the solidification rate. The solidification rate is an index corresponding to the position of the single-crystal silicon ingot in the pulling direction. The vertical axis represents the oxygen concentration. The oxygen concentration of a single-crystal silicon ingot pulled up without circumferential displacement of the heat shield 13 is represented by a triangle (△) plot. The oxygen concentration of a single-crystal silicon ingot pulled up with circumferential displacement of the heat shield 13 is represented by a circle (○) plot. When there is no circumferential displacement of the heat shield 13, although there is variation in the oxygen concentration at each position, the plots at all positions fall between the upper and lower limits of the oxygen concentration standard. On the other hand, when there is a circumferential misalignment of the heat shield 13, some plots show oxygen concentrations below the lower limit of the standard.

[0030] The circumferential displacement of the heat shield 13 can be reduced by checking it when the heat shield 13 is placed inside the main chamber 2a. However, for some reason, the melting of the silicon raw material in the crucible may start while the circumferential displacement of the heat shield 13 remains. For example, although the camera 15 is positioned to photograph the inside of the main chamber 2a, there is no light source inside the main chamber 2a, so it is not possible to photograph the inside of the main chamber 2a, i.e., the heat shield 13, when the main chamber 2a is closed, and the heat shield 13 can only be photographed after heating of the crucible has started. However, even if circumferential displacement of the heat shield 13 is detected from the image taken of the heat shield 13 after heating of the crucible has started, the circumferential position of the heat shield 13 cannot be adjusted by opening the chamber 2a to the atmosphere because high-temperature molten silicon MD is present in the main chamber 2a.

[0031] Therefore, the inventors of this disclosure considered setting control factors to prevent a decrease in the crystal quality of the single-crystal silicon ingot when pulling up the single-crystal silicon ingot while the circumferential displacement of the heat shield 13 occurs. Specifically, they conceived of experimentally determining a correlation table in advance between the amount of circumferential displacement of the heat shield 13 and the change in oxygen concentration in the single-crystal silicon ingot being grown due to the circumferential displacement of the heat shield 13. After melting the silicon raw material to obtain a silicon melt MD, and before starting the growth of the single-crystal silicon ingot, detecting the amount of displacement of the notch 131 using an optical detection means, and adjusting the control factors for growing the single-crystal silicon ingot in the manufacturing apparatus 1 based on the detected amount of displacement and the aforementioned correlation table, so that a single-crystal silicon ingot with a desired oxygen concentration can be obtained.

[0032] The camera 15 of the manufacturing apparatus 1 photographs the inside of the main chamber 2a and generates an image of the inner flange portion 13B of the heat shield 13, i.e., a captured image, as illustrated in Figure 6. The timing at which the camera 15 generates the captured image must be a process in which the position of the crucible remains constant during the series of operations for pulling up the single crystal silicon ingot, and may be unified at a specific timing. This specific timing may be, for example, when the silicon material is melted, when the seed crystal is brought into contact with the surface of the silicon molten liquid MD, or when the pulling up process begins. By unifying the timing at which the camera 15 generates the captured image, changes in the brightness of the captured image caused by changes in the brightness inside the main chamber 2a due to changes in the position of the crucible are reduced. By reducing changes in the brightness of the captured image, the accuracy of the detection process for circumferential displacement of the heat shield 13, which will be described later, is improved.

[0033] The image processing unit 30 acquires the captured image from the camera 15 and performs image processing using an image processing library such as OpenCV. The image processing unit 30 may also perform filtering on the captured image.

[0034] The image processing unit 30 detects the coordinates of the notch 131 in the heat shield 13 that is visible in the captured image. The image processing unit 30 may use a Harris corner detector to detect the coordinates of the notch 131.

[0035] The image processing unit 30 detects four locations on the end 13D of the inner flange portion 13B of the heat shield 13 as detection points 133. The image processing unit 30 may detect the detection points 133 from the end 13D of the inner flange portion 13B by binarizing the captured image and performing line tracing.

[0036] The shape of the end portion 13D of the inner flange portion 13B is circular when viewed along the central axis of the shield body 13A, i.e., in a plan view, while it is approximated as an ellipse in the image captured obliquely from the camera 15. The image processing unit 30 applies the coordinates of the four detection points 133 to the ellipse equation to calculate the coordinates of the center point 132 of the ellipse. The center point 132 is a point on the central axis of the heat shield 13.

[0037] The image processing unit 30 calculates the circumferential angle θ of the position of the notch 131 of the heat shield 13 with respect to the position of the intersection point between the end portion 13D and the reference line, based on the coordinates of the center point 132 and the coordinates of the notch 131. The reference line is assumed to be a dashed line extending horizontally through the center point 132 in the captured image. In the captured image of Figure 6, the horizontal direction coincides with the major axis of the ellipse approximating the end portion 13D. The reference line is not limited to the example described above and may be a line extending in any direction through the center point 132.

[0038] The image processing unit 30 approximates the shape of the end portion 13D of the inner flange portion 13B of the heat shield 13 with an ellipse and calculates the coordinates of its center point 132. This allows the image processing unit 30 to calculate the circumferential angle θ of the position of the notch 131 of the heat shield 13 with respect to the position of the intersection point between the end portion 13D and the reference line, regardless of the horizontal position of the heat shield 13.

[0039] The control unit 20 obtains the circumferential angle θ of the notch 131 of the heat shield 13 from the image processing unit 30. On the other hand, it is assumed that the circumferential angle of the notch 131 is known when the heat shield 13 is installed so as not to shift circumferentially relative to a predetermined position. The control unit 20 calculates the difference between the circumferential angle θ of the notch 131 of the heat shield 13 and the circumferential angle of the notch 131 when the heat shield 13 is installed so as not to shift circumferentially relative to a predetermined position as the amount of circumferential displacement of the heat shield 13.

[0040] The control unit 20 may adjust the control factor based on the relationship between the amount of circumferential displacement of the heat shield 13 and the crystal quality of the single-crystal silicon ingot. As described above, the amount of circumferential displacement of the heat shield 13 is calculated as the difference between the circumferential angle θ of the notch 131 of the heat shield 13 and the circumferential angle of the notch 131 when the heat shield 13 is installed so as not to shift circumferentially relative to a predetermined position. The difference between the circumferential angle θ of the notch 131 of the heat shield 13 and the circumferential angle of the notch 131 when the heat shield 13 is installed so as not to shift circumferentially relative to a predetermined position is also called the amount of circumferential displacement of the notch 131. The control unit 20 may adjust the control factor based on the relationship between the amount of circumferential displacement of the notch 131 and the crystal quality of the single-crystal silicon ingot.

[0041] The control unit 20 adjusts the control factors to increase the oxygen concentration if the oxygen concentration tends to decrease due to circumferential displacement of the heat shield 13. For example, if reducing the Ar flow rate increases the oxygen concentration, the control unit 20 adjusts the control factors to reduce the Ar flow rate and increase the oxygen concentration. For example, if increasing the furnace pressure in chamber 2 increases the oxygen concentration, the control unit 20 adjusts the control factors to increase the furnace pressure in chamber 2 and increase the oxygen concentration. In other words, the control unit 20 may adjust factors related to adjusting the oxygen concentration of the single-crystal silicon ingot as control factors.

[0042] The control unit 20 may adjust control factors not limited to oxygen concentration as a measure of crystal quality, but also focusing on other indicators such as BMD density. The control unit 20 may also adjust other factors not limited to Ar flow rate or furnace pressure in chamber 2, such as crucible rotation speed, as control factors.

[0043] The control unit 20 may adjust the control factor based on a table or formula representing the relationship between the circumferential displacement of the heat shield 13 or the circumferential displacement of the notch 131 and the crystal quality of the single-crystal silicon ingot. The control unit 20 may adjust the control factor using a model that outputs a target value for adjusting the control factor when the circumferential displacement of the heat shield 13 or the circumferential displacement of the notch 131 is input. The model may be a trained model generated by performing training using training data that associates the circumferential displacement of the heat shield 13 or the circumferential displacement of the notch 131 with the control factor and the crystal quality of the single-crystal silicon ingot.

[0044] Figure 7 shows an example of oxygen concentration data for single-crystal silicon ingots grown by adjusting the control factor according to the circumferential displacement of the heat shield 13. The horizontal axis of the graph in Figure 7 represents the solidification rate, and the vertical axis represents the oxygen concentration. The oxygen concentration of single-crystal silicon ingots grown with the control factor adjusted despite the circumferential displacement of the heat shield 13 is represented by an X-shaped (×) plot. The oxygen concentration of single-crystal silicon ingots grown with the circumferential displacement of the heat shield 13 and without adjusting the control factor is represented by a circular (○) plot, similar to Figure 5. Furthermore, the oxygen concentration of single-crystal silicon ingots grown without the circumferential displacement of the heat shield 13 is represented by a triangular (△) plot, similar to Figure 5.

[0045] The graph in Figure 7 shows that even with circumferential displacement of the heat shield 13, adjusting the control factor allows the oxygen concentration to be brought within specifications where it would otherwise be outside specifications. In other words, by adjusting the control factor according to the circumferential displacement of the heat shield 13 and growing a single-crystal silicon ingot, the influence of the circumferential displacement of the heat shield 13 on crystal quality can be reduced. As a result, crystal quality can be improved.

[0046] If the circumferential displacement of the heat shield 13 is too large, the correlation between the circumferential displacement of the heat shield 13 and the crystal quality of the single-crystal silicon ingot may become unclear. If the correlation between the circumferential displacement of the heat shield 13 and the crystal quality of the single-crystal silicon ingot is unclear, the control unit 20 does not need to adjust the control factor according to the circumferential displacement of the heat shield 13. The control unit 20 may output an alert indicating that the circumferential displacement of the heat shield 13 is large.

[0047] The control unit 20 may adjust the control factor based on the circumferential position of the notch 131 in the inner flange portion 13B of the heat shield 13. For example, the control unit 20 can adjust the control factor without calculating the amount of circumferential displacement of the notch 131 by knowing in advance the relationship between the circumferential position of the notch 131 and the control factor. The relationship between the circumferential position of the notch 131 and the control factor can be uniquely determined by using the circumferential position of the notch 131 as the reference position when the heat shield 13 is installed so as not to shift circumferentially relative to a predetermined position.

[0048] <Example of a procedure for manufacturing single-crystal silicon ingots> The single-crystal silicon ingot manufacturing apparatus 1 may perform a single-crystal silicon ingot manufacturing method that includes the steps of the flowchart illustrated in Figure 8. The single-crystal silicon ingot manufacturing method may be implemented as a single-crystal silicon ingot manufacturing program to be executed by a processor constituting the control unit 20 or the image processing unit 30. The single-crystal silicon ingot manufacturing program may be stored on a non-temporary computer-readable medium.

[0049] The image processing unit 30 acquires an image of the heat shield 13 from the camera 15 (step S1). The image processing unit 30 performs a filter (step S2).

[0050] The control unit 20 calculates the amount of circumferential displacement of the notch 131 of the heat shield 13 (step S3). Specifically, the image processing unit 30 calculates the coordinates of the notch 131 and the coordinates of the center point 132 of an ellipse that approximates the end 13D of the inner flange portion 13B of the heat shield 13 by analyzing the captured image, and calculates the circumferential angle of the notch 131 with respect to the intersection point of the reference line and the ellipse in the captured image. The control unit 20 calculates the amount of circumferential displacement of the notch 131, which is the difference between the circumferential angle of the notch 131 calculated by the image processing unit 30 and the circumferential angle of the notch 131 when the heat shield 13 is installed so that it does not shift circumferentially relative to a predetermined position. The control unit 20 may consider the amount of circumferential displacement of the notch 131 as the amount of circumferential displacement of the heat shield 13.

[0051] The control unit 20 adjusts the control factor based on the amount of circumferential displacement of the notch 131 (step S4). Specifically, the control unit 20 adjusts the control factor based on the relationship between the amount of circumferential displacement of the notch 131 and the crystal quality of the single-crystal silicon ingot. After executing the procedure in step S4, the control unit 20 finishes executing the flowchart in Figure 8. After executing the flowchart in Figure 8, the control unit 20 controls each component of the manufacturing apparatus 1 to pull up the single-crystal silicon ingot. The control unit 20 may calculate the amount of circumferential displacement of the notch 131 as the amount of circumferential displacement of the heat shield 13 in the procedure in step S3, and adjust the control factor based on the amount of circumferential displacement of the heat shield 13 in the procedure in step S4. The control unit 20 may adjust the control factor based on the circumferential position of the notch 131 without calculating the amount of circumferential displacement of the notch 131.

[0052] The control factor adjustment procedure described above may be performed after melting the silicon raw material in the quartz crucible 8 to obtain molten silicon MD, and before starting the growth of the single-crystal silicon ingot. If a circumferential misalignment of the heat shield 13 is discovered after obtaining the molten silicon MD, it is difficult to rearrange the heat shield 13. By adjusting the control factors after obtaining the molten silicon MD, even if a circumferential misalignment of the heat shield 13 is discovered after obtaining the molten silicon MD, the crystal quality of the single-crystal silicon ingot grown with the circumferential misalignment of the heat shield 13 can be maintained or improved.

[0053] (summary) As described above, the single-crystal silicon ingot manufacturing apparatus 1 according to this disclosure can adjust the control factor when pulling up the single-crystal silicon ingot according to the circumferential displacement of the heat shield 13. In this way, even if the pulling up of the single-crystal silicon ingot is started while the circumferential displacement of the heat shield 13 is still present, it becomes possible to adjust the crystal quality of the single-crystal silicon ingot. As a result, the crystal quality is improved.

[0054] While embodiments relating to this disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art can make various modifications or alterations based on this disclosure. Therefore, it should be noted that these modifications or alterations are included within the scope of this disclosure. For example, the functions included in each component or step can be rearranged in a logically consistent manner, and multiple components or steps can be combined into one or divided. While embodiments relating to this disclosure have been described primarily in terms of apparatus, embodiments relating to this disclosure can also be realized as methods including steps performed by each component of the apparatus. Embodiments relating to this disclosure can also be realized as methods, programs, or storage media recording programs executed by a processor in the apparatus. These should also be understood to be included within the scope of this disclosure.

[0055] The graphs included in this disclosure are schematic. Scales and other elements may not necessarily correspond to reality. [Industrial applicability]

[0056] According to the embodiments of this disclosure, the crystal quality of the single-crystal silicon ingot can be improved even when a notch is provided in the heat shield. [Explanation of Symbols]

[0057] 1 Manufacturing equipment 2 chambers (2a: main chamber, 2b: pull chamber) 3. Lifting drive unit 4 Mass Flow Controller 5. Gas supply sources 6 wires 7. Crucible Lifting Mechanism 8 Quartz Crucible 9 Carbon fiber crucibles 10 Heat insulation cylinder 11 Heater 12 Support members 13. Heat shield (13A: Shield body, 13B: Inner flange, 13C: Outer flange, 13D: End, 131: Notch, 132: Center point, 133: Detection point) 14 Observation window 15 Cameras 16 Magnetic field generator 17 valves 18 Vacuum pump 20 Control Unit 30 Image Processing Unit SC Seed Chuck SM single crystal silicon ingot straight section MD Silicon Melt

Claims

1. A quartz crucible for containing the silicon melt, A chamber for housing the quartz crucible, A heat shield is provided above the quartz crucible, surrounding the single-crystal silicon ingot to be pulled up from the silicon molten liquid, and having a cylindrical shield body and an inner flange portion that protrudes inward from the lower end of the shield body and defines an opening for the passage of the single-crystal silicon ingot. A camera that photographs the surface of the silicon molten liquid and the inner flange portion of the heat shield through the space between the shield body and the single-crystal silicon ingot, A control unit for adjusting the control factors for growing the single-crystal silicon ingot, Equipped with, The inner flange portion has notches provided at one or more locations on the end portion that defines the opening, The control unit, The circumferential position of the notch as seen in the image captured by the camera is calculated. The control factor is adjusted based on the circumferential position of the notch. A manufacturing device for single-crystal silicon ingots.

2. The apparatus for manufacturing a single crystal silicon ingot according to claim 1, wherein the control unit calculates the magnitude of the circumferential positional displacement of the notch when the heat shield is installed at a predetermined position in the chamber, with respect to the circumferential position of the notch when the heat shield is installed above the quartz crucible, and adjusts the control factor based on the magnitude of the circumferential positional displacement of the notch.

3. The apparatus for manufacturing a single crystal silicon ingot according to claim 1 or 2, wherein the control factor includes any of the flow rate of inert gas supplied into the chamber, the pressure inside the chamber, or the rotation speed of the quartz crucible.

4. A method for manufacturing single-crystal silicon ingots using the Czochralski method, The control factors for growing the single-crystal silicon ingot are adjusted based on the circumferential position of notches provided at one or more locations on the end of the inner flange portion of a heat shield provided above the quartz crucible in the chamber, which defines an opening for the passage of the single-crystal silicon ingot being pulled up from the silicon molten liquid in the quartz crucible. Growing the aforementioned single-crystal silicon ingot and A method for manufacturing single-crystal silicon ingots, including [the specified component].

5. A method for manufacturing a single crystal silicon ingot according to claim 4, comprising calculating the magnitude of the circumferential positional displacement of the notch when the heat shield is installed at a predetermined position in the chamber, with respect to the circumferential position of the notch when the heat shield is installed above the quartz crucible, and adjusting the control factor based on the magnitude of the circumferential positional displacement of the notch.

6. A method for manufacturing a single-crystal silicon ingot according to claim 5, wherein, based on the magnitude of the displacement of the circumferential position of the notch, a factor related to adjusting the oxygen concentration of the single-crystal silicon ingot is adjusted as the control factor.

7. The method for manufacturing a single crystal silicon ingot according to any one of claims 4 to 6, wherein the control factor includes the flow rate of inert gas supplied into the chamber, the pressure inside the chamber, or the rotation speed of the quartz crucible.

8. A method for manufacturing a single-crystal silicon ingot according to any one of claims 4 to 6, comprising: dissolving the silicon raw material in the quartz crucible to obtain the silicon melt, and before starting the growth of the single-crystal silicon ingot, calculating the circumferential position of the notch from an image of the end of the inner flange portion of the heat shield.

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