Non-contact system and method for determining the distance between the silicon melt and the reflector of a crystal pulling apparatus.

Abstract

This invention provides a non-contact method and system for determining the distance between a silicon melt and a reflector in a crystal pulling apparatus. [Solution] The measurement system comprises a reflector 151 defining a central passage and an aperture, a measurement assembly 170, and a controller 172. The measurement assembly comprises a lampin having a head visible through the aperture, a camera that takes an image through the aperture of the reflector, and a laser that sends coherent light through the aperture to the head of the lampin, causing a reflection of the lampin on the surface of the silicon melt 104. The controller is programmed to control the laser to direct the coherent light from the laser to the lampin, to control the camera to take an image through the aperture of the reflector while the coherent light is directed to the lampin, and to determine the distance between the surface of the silicon melt and the bottom surface of the reflector based on the position of the lampin's reflection in the captured image.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims priority based on U.S. Provisional Patent Application No. 63 / 198870, filed on November 19, 2020. All disclosures of the application on which the priority is based are hereby incorporated by reference in their entirety into this application.

[0002] This disclosure generally relates to the production of silicon ingots, and more particularly to non - contact methods and systems for determining the distance between a silicon melt and a reflector in a crystal pulling apparatus.

Background Art

[0003] Some crystal pulling apparatuses have a reflector installed above the silicon melt. During the operation of the crystal pulling apparatus, it is beneficial to know the distance between the bottom surface of the reflector and the surface of the silicon melt (referred to as "HR").

[0004] The requirements for HR measurement are less than 1 mm, and an accuracy range of 0.1 - 0.2 mm is desirable. Measuring HR involves observing and tracking features within a very high - temperature pulling apparatus under vacuum or low - pressure conditions, so it is difficult to measure by known methods. Under such conditions, generally, sensors and materials available for measurement inside the pulling apparatus are limited. Thermal expansion generally moves components that are not actively cooled, so measurements taken before pulling or start - up of operation may not be usable or may not be useful after the pulling apparatus is heated to its operating temperature. Therefore, errors occur in known methods (such as camera images) that rely on measured or known cold distances.

[0005] Known methods include using a camera to determine the HR (Hypertorch Level). Such methods typically rely on input values ​​from theoretical geometry. Errors can arise due to differences between the actual geometry and the theoretical geometry. These methods may involve calibrating the camera on a separate fixture made to match the theoretical distance and angle that the lifting device should have. In this case, further errors can arise due to differences between the actual geometry and the theoretical geometry of the calibration fixture itself. Furthermore, such methods often rely on the geometric features of the graphite component in the reflection of the molten material in the camera image to determine the HR. Since the brightness intensity of these images can change significantly during operation, it is difficult to obtain a consistent signal, and HR variability can occur during operation.

[0006] Known methods can also have software-related problems. For example, HR measurements can be partially based on variations in crystal diameter, resulting in HR variations of as much as 0.5 mm. This variation in the measured HR is due to how the crystal center is determined and its relationship to the center of the reflector used to determine the reflector's position. Furthermore, changes in the radial position of the reflector can be converted into vertical changes, which directly affect the HR. Camera measurements also typically rely on detecting the leading edge of the hot crucible wall reflected by a convex lens. The position of this edge is used to measure the melt height to determine the height. Thus, the height depends on both the shape of the convex lens, which changes as a function of the crystal growth pulling rate, and the surface curvature of the melt surface, which is a function of the crucible rotation. Calculating variations due to the leading edge is difficult. Variations in melt curvature are easily calculated and can vary by as much as 7 mm in total height.

[0007] Another method used to determine the HR is the dipstick method. In this method, a quartz pin extending a known distance from the bottom of the reflector is immersed in the molten metal. The distance between the bottom of the pin and the bottom of the reflector is measured before the reflector is attached to the lifting device, so the HR at the moment the pin contacts the molten metal is determined. This only provides an initial measurement, and other methods (such as camera tracking) are needed to determine the HR at different molten metal altitudes. In practice, this method is difficult to implement because when a quartz pin is brought into contact with the molten metal, the surface tension of the molten silicon can cause silicon wicking along the outside of the pin. This makes it difficult to determine exactly when the pin has contacted the molten metal surface (rather, the silicon is close enough to the molten metal surface to contact the pin). Also, because the pin is in direct contact with the molten metal, there are problems in maintaining the length of the pin during operation. This is problematic when recalibration is desired during operation, as the distance between the bottom of the pin and the bottom of the reflector becomes unknown.

[0008] This background information section is intended to introduce readers to various aspects of the technology that may be relevant to the various aspects of the disclosure described and / or claimed below. This discussion is intended to be useful in providing readers with background information to better understand the various aspects of the disclosure. Therefore, these statements should be read in this context and should not be understood as an admission of prior art. [Overview of the Initiative]

[0009] One aspect of the present disclosure is a real-time measurement system in a crystal pulling apparatus for determining the distance between a silicon melt in a crucible and a reflector while a crystal is being pulled from the silicon melt. The measurement system comprises a central passage through which the crystal is pulled, a reflector defining an aperture, a measurement assembly, and a controller. The measurement assembly comprises a lampin having a head visible through the aperture, a camera for taking images through the aperture of the reflector, and a laser for selectively directing coherent light through the aperture to the head of the lampin, causing a reflection of the lampin on the surface of the silicon melt. Each image taken by the camera includes the surface of the silicon melt in the crystal pulling apparatus. The controller is connected to the camera and the laser. The controller controls the laser to direct the coherent light from the laser to the lampin, and controls the camera to take images through the aperture of the reflector while the coherent light is directed to the lampin, and is programmed to determine the distance between the surface of the silicon melt and the bottom of the reflector based on the position of the lampin's reflection in the captured image, which includes at least a portion of the surface of the silicon melt where the reflection of the lampin is visible.

[0010] Another aspect of the present disclosure is a method for determining the distance between a silicon melt in a crucible and a reflector of a crystal pulling apparatus while a crystal is being pulled from the silicon melt, using a measurement system comprising a camera, a laser, a lampin, and a controller. The method comprises directing coherent light from a laser onto a lampin mounted on the reflector and visible through the aperture of the reflector, taking an image through the aperture of the reflector using a camera while the coherent light is directed onto the lampin, the captured image including at least a portion of the surface of the silicon melt where the reflection of the lampin is observed, and determining the distance between the surface of the silicon melt and the bottom of the reflector using a controller based on the position of the reflection of the lampin in the captured image.

[0011] Various improvements exist to the features described in relation to the embodiments described above. Similarly, further features may be incorporated into the embodiments described above. These improvements and additional features may exist individually or in any combination. For example, various features described below in relation to any of the illustrated embodiments may be incorporated into the embodiments described above, individually or in any combination. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a cross-sectional view of an ingot pulling device used to pull single-crystal silicon ingots from a silicon melt. [Figure 2] Figure 2 is a cross-sectional view of the ingot lifting device. [Figure 3] Figure 3 is a partial front view of a single-crystal silicon ingot grown by the Czochralski method. [Figure 4] Figure 4 is a block diagram of the computing devices used in the control system of the ingot lifting machine shown in Figure 1. [Figure 5] Figure 5 shows the measurement assembly used in the ingot lifting device shown in Figure 1. [Figure 6] Figure 6 is a diagram of the camera assembly of the measurement assembly shown in Figure 5. [Figure 7] Figure 7 is a diagram of the laser assembly of the measurement assembly shown in Figure 5. [Figure 8] Figure 8 is a cross-sectional view of the laser assembly along line AA in Figure 7. [Figure 9] Figure 9 shows the measurement system and the reflector used in Figure 5. [Figure 10] Figure 10 is a view of the reflector assembly directly below the cutout in Figure 9. [Figure 11] Figure 11 is a magnified view of the ramp pins and anchor pins of the measurement system attached to the reflector in Figure 9. [Figure 12] Figure 12 shows the anchor pin from Figure 11 extending beyond the bottom of the reflector. [Figure 13] Figure 13 is a side view of the anchor pin of Figure 11. [Figure 14] Figure 14 is an example of the field of view of the camera of Figure 6 during anchoring. [Figure 15] Figure 15 is an example of the field of view of the camera of Figure 6 during anchoring after the melt has dropped from the field of view of Figure 14. [Figure 16] It is a diagram of the geometry and values used for the determination of the HR value using the measurement system of Figure 5. [Figure 17] Figure 17 is an example of the field of view of the camera of Figure 6 when calibrating the camera after anchoring. [Figure 18] Figure 18 is an example of the field of view of the camera when calibrating after the melt has dropped from the field of view of Figure 17. [Figure 19] Figure 19 is an example of the field of view of the camera when calibrating after the melt has dropped from the field of view of Figure 18. [Figure 20] Figure 20 is a diagram of pins of other examples used as anchor pins or ramp pins of the measurement system. [Figure 21] Figure 21 is a diagram of pins of other examples used as anchor pins or ramp pins of the measurement system. [Figure 22] Figure 22 is a diagram of a pin from within the aperture of the reflector in an embodiment using a single pin with a single spherical head. [Figure 23] Figure 23 is a diagram of the pin of Figure 22 as seen from below the aperture of the reflector. [Figure 24] Figure 24 is a diagram of a pin from within the aperture of the reflector in an embodiment where a single pin with a single spherical head extending from the wall of the reflector aperture is dressed. [Figure 25] Figure 25 is a diagram of the pin of Figure 22 as seen from below the aperture of the reflector. [Figure 26] Figure 26 is an example of an image of an illuminated pin and the reflection of the pin taken by the camera at the start of operation. [Figure 27]Figure 27 shows an example of an image of an illuminated pin and its reflection captured by a camera during operation.

[0013] Similar reference numerals in various drawings indicate similar elements. [Modes for carrying out the invention]

[0014] Referring to Figures 1-3, an ingot puller apparatus (or more simply, an "ingot puller" or "crystal puller") for growing single-crystal silicon ingots is described. Figure 1 is a cross-sectional view of an ingot puller apparatus, generally indicated as "100," used to pull single-crystal silicon ingots from a silicon melt. Figure 2 is a cross-sectional view of ingot puller apparatus 100, and Figure 3 is a partial front view of a single-crystal silicon ingot grown by the Czochralski method in, for example, ingot puller apparatus 100.

[0015] The ingot pulling device 100 includes a crystal pulling housing 108 that defines a growth chamber 152 for pulling a silicon ingot 113 from a silicon molten 104. A control system 172 (also referred to as the “controller”) controls the operation of the ingot pulling device 100 and its components. The ingot pulling device 100 is located within the growth chamber 152 and includes a crucible 102 for holding the silicon molten 104. The crucible 102 is supported by a susceptor 106.

[0016] The crucible 102 includes a floor 129 and a side wall 131 extending upward from the floor 129. The side wall 131 is generally vertical. The floor 129 includes a curved portion of the crucible 102 that extends below the side wall 131. A silicon melt 104 having a melt surface 111 (i.e., a melt-ingot interface) is contained within the crucible 106. The susceptor 106 is supported by a shaft 105. The susceptor 106, crucible 102, shaft 105, and ingot 113 share a common longitudinal axis A or “pulling axis” A.

[0017] A lifting mechanism 114 for growing the ingot 113 and lifting it from the melt 104 is located within the ingot lifting device 100. The lifting mechanism 114 includes a lifting cable 118, a seed holder or chuck 120 connected to one end of the lifting cable 118, and a seed crystal 122 connected to the seed holder or chuck 120 for initiating crystal growth. One end of the lifting cable 118 is connected to a pulley (not shown) or drum (not shown), or any other suitable type of lifting mechanism (e.g., a shaft), and the other end is connected to the chuck 120 that holds the seed crystal 122. During operation, the seed crystal 122 descends to come into contact with the melt 104. The lifting mechanism 114 operates to raise the seed crystal 122. This lifts the single-crystal ingot 113 from the melt 104.

[0018] During heating and crystal pulling, the crucible drive unit 107 (e.g., a motor) rotates the crucible 102 and susceptor 106. The lifting mechanism 112 raises and lowers the crucible 102 along the pulling axis A during the growth process. As the ingot grows, the silicon molten 104 is consumed, and the height of the molten material in the crucible 102 decreases. The crucible 102 and susceptor 106 may be raised to maintain the molten surface 111 in the same position or near the ingot pulling device 100.

[0019] A crystal drive unit (not shown) may rotate the pull-up cable 118 and the ingot 113 in the opposite direction to the direction in which the crucible drive unit 107 rotates the crucible 102 (e.g., reverse rotation). In embodiments using unidirectional rotation, the crystal drive unit may rotate the pull-up cable 118 in the same direction as the direction in which the crucible drive unit 107 rotates the crucible 102. The crystal drive unit may also raise or lower the ingot 113 relative to the molten surface 111 as desired during the growth process.

[0020] The ingot lifting apparatus 100 may include an inert gas system for introducing an inert gas, such as argon, into or out of the growth chamber 152. The ingot lifting apparatus 100 may also include a dopant supply system (not shown) for introducing a dopant into the molten liquid 104.

[0021] According to the Czochralski single crystal growth process, a large amount of polycrystalline silicon, i.e., polysilicon, is charged into the crucible 102 (e.g., 250 kg or more of charge). Various sources of polycrystalline silicon can be used, including, for example, granular polycrystalline silicon produced by the thermal decomposition of silane or halosilane in a fluidized bed reactor, or polycrystalline silicon produced in a Siemens reactor. Once the polycrystalline silicon is added to the crucible to form the charge, the charge is heated to a temperature above the melting point of silicon (e.g., 1412°C) and melted. In some embodiments, the charge (i.e., the resulting melt) is heated to a temperature of at least about 1425°C, at least about 1450°C, or at least about 1500°C. The ingot lifting apparatus 100 includes bottom insulation 110 and side insulation 124 for retaining heat within the ingot lifting apparatus 100. In the embodiments described, the ingot lifting device 100 includes a bottom heater 126 located below the floor 129 of the crucible. The crucible 102 may be moved to a position relatively close to the bottom heater 126 in order to melt the polycrystalline material charged into the crucible 102.

[0022] To form an ingot, a seed crystal 122 is brought into contact with the surface 111 of the molten metal 104. A pulling mechanism 114 is operated to pull the seed crystal 122 from the molten metal 104. The ingot 113 includes a crown portion 142, in which the ingot tapers as it moves outward from the seed crystal 122 until it reaches a target diameter. The ingot 113 includes a portion 145 or cylindrical “body” of the crystal that grows by increasing the pulling speed. The body 145 of the ingot 113 has a relatively constant diameter. The ingot 113 includes a tail cone or end cone (not shown) after the body 145, in which the ingot tapers radially. When the diameter is small enough, the ingot 113 is separated from the molten metal 104. The ingot 113 has a central longitudinal axis A that extends through the crown portion 142 and the end of the ingot 113.

[0023] The ingot pulling apparatus 100 comprises a side heater 135 and a susceptor 106 surrounding the crucible 102 to maintain the temperature of the molten metal 104 during crystal growth. The side heater 135 is positioned radially outward of the side wall 131 of the crucible as the crucible 102 moves up and down on the pulling axis A. The side heater 135 and bottom heater 126 may be any type of heater capable of operating as described herein. In some embodiments, the heaters 135,126 are resistance heaters. The side heater 135 and bottom heater 126 may be controlled by a control system 172 so that the temperature of the molten metal 104 is controlled throughout the pulling process.

[0024] The ingot lifting device 100 includes a reflector 151 (or "heat shield") positioned within the growth chamber 152 and above the molten liquid 104 surrounding the ingot 113 during ingot growth. The reflector 151 may be partially positioned within the crucible 102 during crystal growth. The heat shield 151 defines a central passage 160 that receives the ingot 113 when it is lifted by the lifting mechanism 114.

[0025] The reflector 151 is generally a heat shield adapted to retain heat below the heat shield itself and above the molten 104. In this regard, any reflector design and material known in the art may be used without limitation. The reflector 151 has a bottom 138 (shown in Figure 2), the bottom 138 of the reflector 151 is at a distance HR from the surface of the molten during ingot growth.

[0026] The ingot pulling device includes a measuring assembly 170 used as part of a measuring system to determine the distance between the bottom 138 of the reflector 151 and the surface of the molten metal during ingot growth (i.e., to determine the HR).

[0027] Figure 3 shows a single-crystal silicon ingot 113 manufactured according to an embodiment of the present disclosure, generally by the Czochralski process. The ingot 113 includes a neck 116, an outwardly flared portion 142 (synonymous with "crown" or "cone"), a shoulder 119, and a body 145 of a constant diameter. The neck 116 is in contact with the molten metal and attached to a seed crystal 122 that has been drawn to form the ingot 113. The body 145 is suspended from the neck 116. The neck 116 terminates when the cone portion 142 of the ingot 113 begins to form.

[0028] A portion 145 of the ingot 113 of a certain diameter has a periphery 150, a central axis A parallel to the periphery 150, and a radius R extending from the central axis to the periphery 145. The central axis A passes through the cone portion 142 and the neck 116. The diameter of the body 145 of the ingot may vary, and in some embodiments, the diameter may be about 150 mm, about 200 mm, about 300 mm, greater than about 300 mm, about 450 mm, or greater than about 450 mm.

[0029] The single-crystal silicon ingot 113 may generally have any resistivity. The single-crystal silicon ingot 113 may be doped or undoped.

[0030] Figure 4 shows an example of a computing device 400 that may be used as part of a control system 172. The computing device 400 includes a processor 402, memory 404, a media output component 406, an input device 408, and a communication interface 410. Other embodiments include different components, additional components, and / or do not include all the components shown in Figure 4.

[0031] The processor 402 is configured to execute instructions. In some embodiments, the executable instructions are stored in memory 404. The processor 402 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 illustrative and is not intended to limit the definition and / or meaning of the term “processor”.

[0032] Memory 404 stores non-temporary computer-readable instructions for performing the techniques described herein. When such instructions are executed by the processor 402, they cause the processor 402 to perform at least a portion of the methods described herein. In some embodiments, memory 404 stores computer-readable instructions for providing a user interface to the user via a media output component and for receiving and processing input from an input device 408. Memory 404 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). Although illustrated separately from the processor 402, in some embodiments, memory 404 is combined with the processor 402 in a microcontroller or microprocessor, etc., and may be referred to separately. The types of memory described above are illustrative and therefore not limiting the types of memory that can be used to store computer programs.

[0033] The media output component 406 is configured to display information to a user (e.g., a system operator). The media output component 406 is any component capable of conveying information to a user. In some embodiments, the media output component 406 includes output adapters such as a video adapter and / or an audio adapter. The output adapter is operably connected to the processor 402 and operably connectable to output devices such as a display device (e.g., a liquid crystal display (LCD), a light-emitting diode (LED) display, an organic light-emitting diode (OLED) display, a cathode ray tube (CRT), an "electronic ink" display, one or more light-emitting diodes (LEDs)) or an audio output device (e.g., a speaker or headphones).

[0034] The computing device 400 includes, or is connected to, an input device 408 for receiving input from a user. The input device 408 is any device that enables the computing device 400 to receive analog and / or digital commands, instructions, or other inputs from a user, including visual, auditory, touch, button press, stylus tap, etc. The input device 408 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 406 and an input device 408.

[0035] The communication interface may enable the computing device 400 to communicate with remote devices or systems such as 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 communication interface or a wireless communication interface that enables the computing device 400 to communicate with remote devices and systems directly or via a network. The wireless communication interface may include radio frequency (RF) transceivers, Bluetooth® adapters, Wi-Fi transceivers, Zigbee® transceivers, near-field communication (NFC) transceivers, infrared (IR) transceivers, and / or any other devices and communication protocols for wireless communication (Bluetooth® is a registered trademark of the Bluetooth Special Interest Group in Kirkland, Washington, and Zigbee® is a registered trademark of the ZigBee Alliance in San Ramon, California). The wired communication interface may use any suitable wired communication protocol for direct communication, including but not limited to USB, RS232, SPI, analog, and proprietary I / O protocols. In some embodiments, the wired communication interface includes a wired network adapter that enables the computing device 400 to connect 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.

[0036] The computer systems discussed herein may include additional, fewer, or alternative functions, including those discussed elsewhere in this specification. The computer systems discussed herein may include, and may be executed through, computer-executable instructions stored on non-temporary computer-readable media or other media.

[0037] The measurement assembly 170 and controller 172 constitute the measurement system. The measurement assembly 170 is used by the controller 172 to determine the distance between the bottom 138 of the reflector 151 and the surface 111 of the silicon melt 104. Typically, the laser is focused onto a quartz pin, and the HR anchor value is determined using a camera that views the laser dot reflected on the melt surface 111, along with a curve fitting algorithm. The laser is then moved to different quartz pins, and initial calibration is performed to establish a relationship between the pixel position at the center of the reflected laser dot image in the melt and the HR. For the remainder of the operation, the laser dot is constantly tracked by the camera to determine the HR.

[0038] The measurement system uses a camera, a laser, and one or two pins and does not rely on contact with the melt to measure HR. Both the camera and the laser operate in a single notch provided in a reflector covered by a window. In exemplary embodiments, the pins are quartz pins produced from rods. In other embodiments, the pins may be made from any high-temperature refractory such as silicon carbide (SiC), silicon nitride (SiN), tungsten carbide, tantalum carbide, or boron nitride. Generally, any material selected for the pins must produce a strong and clear reflection on the melt surface at all crystal growth stages of interest. In exemplary embodiments, the quartz rods are 3 mm rods. Alternatively, rods of any other diameter may be used. When a pin with a long light travel distance is required, the pin has a head formed from the rod. In this case, the laser beam needs to be seen from the tail of the pin, but to ensure that the light from the laser reaches the bottom of the pin when the laser beam is directed at the head of the pin, it is a continuous pin rather than a pin with a sphere welded to it. In embodiments using a single spherical pin, the sphere may be a separate part welded to the part that is attached to the reflector to prevent excess light from leaking out of the sphere. In other embodiments of a single spherical pin, the sphere may be formed from the same material as the rest of the pin to facilitate manufacturing. The notch provided in the reflector is a composite angle so that the quartz pin can be seen from the side edge of the same port to which the camera and laser are mounted. Unlike some known oil gauge laser systems that use an "open" hot zone with a reflector that is not adequately insulated, this system is used in a "closed" hot zone where the reflector 151 covers as large an area as possible above the molten 104 with insulation. The open hot zone system views the outside of the crystal's maximum diameter through a port located on the opposite side of the crystal, which is a quartz pin, in order to observe the reflection from the bottom of one of the pins irradiated by a laser in the molten state.In an exemplary embodiment, a closed hot zone is enabled that maintains high HR resolution despite a steep notch angle, while allowing the reflection of the laser dot to be viewed from the same port from which the laser is irradiated. In other embodiments, multiple ports may be used (for example, the camera and laser are located in different ports).

[0039] In an exemplary embodiment, a laser is shone onto the head of a quartz focusing pin. First, the laser is shone onto the longer "anchor" pin. The observed height of the pin and the reflection position of the laser dot on the molten metal are obtained from the camera image. This is used to obtain the current HR value. This generates the anchor value. Note that for this method to work, the quartz pin is not immersed in the molten metal. Next, the laser is shone onto the shorter quartz "ramp" pin. Calibration of the ramp pin and anchor pin is performed by moving through various HR values ​​using the reflection image of the laser dot. The ramp pin is then used during operations including reloading, and no recalibration is required unless the temperature of the lifting device changes substantially (e.g., if it is reheated after returning to room temperature).

[0040] Using a bright laser provides a consistent signal on the melt during both calibration and operation. Various commercially available green wavelength lasers with different power ratings (wavelengths from 520nm to 532nm) are typically bright enough under all conditions. This avoids problems with some known camera systems that rely on visually observing features in the hot zone, where light intensity can vary due to reflection and emission from the silicon melt. These variations in light intensity can create shadows, causing objects in the hot zone to appear to move one or two pixels. This can lead to false movement (i.e., changes in HR). A consistent laser intensity provides a stable HR value, which is desirable because HR is used directly as input for controlling crystal growth.

[0041] Figure 5 shows a portion of the measurement assembly 170, which is located outside the crystal pulling housing 108. The measurement assembly 170 includes a camera assembly 500, a laser assembly 502, and ramp pins and anchor pins (not shown in Figure 5). The ramp pins and anchor pins are mounted inside the crystal pulling housing 108, such as on a reflector 151. The measurement system includes the measurement assembly 170 and a controller 172 (not shown in Figure 5). The camera assembly and laser assembly are positioned over an opening 504 (sometimes referred to as a “port”) that penetrates the crystal pulling housing 108, allowing the camera assembly 500 and laser assembly 502 to view the molten metal 104. The opening 504 is covered by a window 506.

[0042] The camera assembly 500 is shown separately in Figure 6. A long focal length lens 600 is used with a high-resolution (large pixel count) camera 602 to provide high resolution of HR with respect to the motion of the reflection of the laser dot in the camera image. In one example embodiment, the focal length of lens 600 is 100 mm, and the resolution of camera 602 is 2560 × 1920 pixels. The focal length is determined by the desired range of HR to be measured. If the HR range is very wide, a short focal length is required so that the reflection of the laser in the melt is always contained in the camera image. If HR measurement in a narrow range is desired, using a short focal length results in a higher resolution of mm / pixels and thus higher accuracy. The design of the crystal pulling apparatus is such that the precise positioning of the ports is not always inexpensive and simple, so the position of the port to which camera 602 is mounted is generally not known precisely while designing these new parts. Thus, these unknowns combined with the apex focal length lens 600 result in a camera field of view that is usually unpredictable and not repeatable from machine to machine. Therefore, camera 602 is mounted on a geared tripod head 604 to allow for precise movement of the camera image in order to encompass the head of the laser pin and the full range of HR movement of the reflection of the laser dot. The geared tripod head 604 is mounted on a two-axis moving table 606 to allow for further fine-tuning of the center position of the angular rotation (pan, tilt, pitch) provided by the geared head. A cylinder 608 of a thinly rolled metal sheet is attached to the end of the camera lens 600 and loosely interacts with another cylinder (not attached to anything) that rests on the window 506 (Figure 5). These two rolled sheets provide cover for the window 506 and prevent shadows from affecting the camera image. Normally, such cover is not necessary as camera 602 is close enough to the window, but because camera 602 is on the tripod mount 604, camera 602 needs to be far enough away from the window so that camera 602 can be adjusted sufficiently without colliding with the window 506.

[0043] Figure 7 shows a diagram of the separated laser assembly 502. The laser 700 is mounted on a two-axis moving table 702 so that the laser can be moved precisely. The laser itself is mounted on a two-axis gimbal 704 with a micrometer adjustment device so that the laser 700 can be precisely adjusted so that the beam strikes the head of the pin. Since the dot has no orientation in the roll (tilt) direction, only pitch and pan (yaw) are required for the angular motion of the laser. In one example embodiment, the laser 700 is a diode laser with 5 milliwatts, a wavelength of 520 nm, a divergence angle of less than 0.3, and a beam diameter of 3 mm. Since the melt is generally reddish in color, a green laser makes the contrast between the dot and the melt more visible than other colors. In other embodiments, any other suitable color laser may be used.

[0044] The window 506 (shown in Figure 5) covering the aperture 904 is a coated window designed to protect the components outside the window by reflecting some of the heat from the molten material back to the pull-up device. The coating is a multi-atom-layer thickness coating designed to reflect as much infrared energy as possible and most visible light. The coating may be, for example, a gold dielectric, chromium oxide, or any other suitable coating. If the laser 700 must be irradiated through the coating, it may not be able to produce a bright signal on the quartz pin. Therefore, the coating is removed in the area near where the laser strikes window 904. However, removing the coating releases a large amount of heat from window 904, so the laser 700 needs to be protected by a thermal shield.

[0045] Figure 8 is a cross-sectional view along line AA in Figure 7, showing the thermal protection of the laser 700. A ceramic shield 702, having a small hole 704 through which the laser passes, directly surrounds the laser. A plastic body 706 is wrapped around the ceramic shield 702, holding it away from the metal surface 708 below and forming a low-friction bearing surface for the laser 700 to gimbal. A thin plate 710 beneath the laser 700 is a radiation shield to prevent the metal body 708 from becoming hot enough to damage the components it is mounted on.

[0046] Figure 9 shows a reflector 151. An opening 904 (sometimes referred to as a “notch” or “cutout”) extends through the reflector 151, allowing a camera assembly 500 and a laser assembly 502 (not shown in Figure 9) to view the molten 104 through the reflector 151. In other embodiments, the opening 904 does not intersect the central passage 160. In the exemplary embodiment, the opening 904 is angled away from the central passage 160 as the opening 904 extends away from the bottom surface 138.

[0047] Pin 900 is barely visible near the center of the image within the notch 904. Figure 10 is a view directly below the notch 904, showing pin 900 more clearly. Pin 900 is mounted to a separate component 1000 (also referred to as a “mount,” “holder,” “shelf,” or “bracket”) extending from the reflector 151 to prevent stress, as holes or protrusions on the edge of the reflector 151 would create stress concentration points and potentially cause cracks during operation. In other embodiments, pin 900 rests directly on a hole provided in the reflector 151, rather than on a separate component 1000. Figure 11 is a magnified view of pin 900. Pin 900 includes an anchor pin 1100 and a ramp pin 1102.

[0048] In the exemplary embodiment, the anchor pin 1100 and ramp pin 1102 are attached to the reflector 151 (via part 1000). In other embodiments, the ramp pin 1102 is attached to any other surface on which the head of the ramp pin is illuminated by a laser, so that the reflection of the laser in the melt is visible over the entire desired HR range. In this case, it is desirable to use an actively cooled surface so that the ramp pin 1102 does not move in position during the thermal expansion of the rest of the hot zone or from turn to turn. An example of such a surface is a cooling jacket (water jacket). However, it should be noted that this only determines the absolute height of the melt, not the HR. The absolute height of the reflector still has to be determined by other means, and the HR can be calculated from the difference between the two heights. The absolute height of the reflector is determined by finding the HR using the anchor method described above and combining the result with the absolute height of the melt. The absolute height of the reflector is the difference between the HR and the absolute height of the melt.

[0049] To use the measurement system, an anchoring step is performed using anchor pin 1100 to calibrate the system. After the anchoring step is performed, ramp pin 1102 is used to determine the HR during crystal pulling.

[0050] The anchoring step only needs to be performed once at the start of operation. The first step is performed before attaching the reflector 151 to the lifting device 100. As shown in Figures 12 and 13, three items are measured: the height of the anchor pin (PH), the diameter of the anchor pin head (PD), and the distance (H) from which the anchor pin protrudes from the bottom of the reflector.

[0051] After the reflector 151 (including the reflector assembly 900) is attached to the lifting device 100, the laser 700 is turned on to illuminate the head of the anchor pin 1100, and the camera 602 captures an image. Figure 14 is an example of the field of view that the camera 602 can see. Because the laser is shining on the anchor pin 1100, the reflection 1400 from the bottom of the pin appears on the molten metal 104 as a circle having the color of the laser light from the laser 700. The controller 172 determines the number of pixels along distances marked as A and B. A is the number of pixels from the center of the head of the anchor pin 1100 to the bottom of the pin (the bottom is the center of the ellipse created by perspective). In some embodiments, the controller 172 does not directly determine the center, but rather determines the center of the head by locating the position of the tangent end and using the previously measured diameter (PD) of the pin head. The center of the bottom end of the pin is determined using a known value of the pin's diameter (which is either measured or unmeasured, as it is made from a rod-shaped material with a known diameter). B is the number of pixels from the center of the anchor pin 1100 head to the center of the reflection 1400 on the melt.

[0052] Next, the height of the melt 104 is lowered using the crucible lift 112 by a known recorded distance (known from feedback from the crucible lift), while ensuring that the reflected dot 1400 does not move out of the field of view of the camera 602. The distance the melt is lowered is denoted as ZE. This movement moves the laser dot reflector 1400 downward, as shown in Figure 15. Distance C is the number of pixels from the center of the anchor pin 1100 to the center of the position of the dot 1400.

[0053] Figure 16 shows the shape and values ​​described above, which are used to determine the HR value. The following formula is used in conjunction with Figure 16 to calculate the HR: D=BA (1) E=CB (2) Ratio A=RA=A / PH (3) Ratio E = RE = E / ZE (4) The value of X represents the distance along the X-axis in Figure 16. Each X is the midpoint of the subscripted line segment: XA = A / 2 (5) XD = A + D / 2 (6) XE = B + E / 2 (7) The curve fit of the ratio to the pixel distance is calculated as follows: Slope = m = (RE - RA) / (XE - XA) (8) Intercept = k = RA - m * XA (9) RD is solved using linear fitting: RD = m * XD + k (10) ZD can be calculated using the following formula: ZD = D / RD (11) Finally, HR can be calculated using the following formula. HR = H + ZE + ZD (12)

[0054] In some embodiments, a higher-order curve fit is used instead of a linear fit using equations (8) and (9) by adding more elevation changes and recording pixel movement. A new change in vertical distance (Z value) and a new ratio calculated similarly to the ratios already shown are added to the points used for the curve fit.

[0055] In some other embodiments, the reduction in the altitude of the melt by a known recorded distance, denoted as ZE, is omitted. In such embodiments, a simple ratio between A, PH, B, and PH+ZD is used to determine ZD (thus the melt is at altitude ZD, and HR can be determined as HR=[PH+ZD]-PH+H). However, this simple ratio ignores the camera's perspective, which can result in errors of more than 1 millimeter depending on the angle of the camera's central field axis relative to the pin's principal axis, with smaller angle values ​​resulting in larger errors. The complete anchoring described above (i.e., including ZE) allows for interpolation that takes the camera's perspective into account.

[0056] Since the HR has been determined, camera 602 may be calibrated to determine the HR during operation. First, the laser is shone on the head of rampin 1102 without moving the crucible lift away from the end of the HR anchor. The resulting position of the reflected dot 1400 represents a pixel position correlated with the previously determined HR anchor value. Figure 17 is an example of a camera image from this step. Next, the height of the melt 104 is lowered by a known recorded distance via the crucible lift 112. The pixel position of the reflect 1400 changes and is recorded, as shown in the example camera image in Figure 18. The position of the reflect 1400 changes and is recorded as shown in the exemplary camera image in Figure 18. Using the recorded pixel position and the known change in HR (from the recorded change in the height of the melt 104), a curve fit of HR as a function of pixel position is created. The relationship between HR and pixel position includes a sine term. Therefore, a minimum quadratic curve fit is used to avoid an error of the 1 millimeter range that would result from a linear fit.

[0057] After performing the steps above, the center of the laser dot reflection 1400 on the camera image is determined, and the HR can be determined at any time during operation by using the relationship generated above to find the HR.

[0058] In some other embodiments, instead of performing hot calibration, the laser reflection 1400 can be observed using the first surface mirror of the cold lifting device 100. This allows the corresponding HR value to be determined prior to operation. However, calculations must be performed to estimate the thermal expansion of the reflector 151 in order to adjust for the offset of the pixel position of the laser dot 1400 on the camera image. This cold calibration method may introduce unnecessary errors because the exact temperature and material properties may not be precisely known.

[0059] In some embodiments, a reflector 151 that moves during operation is included. As a result, a moving component of the laser dot is added to the camera image, and additional points that require calibration are added.

[0060] In the exemplary embodiment, separate pins are used for the ramp pin 1102 and the anchor pin 1100 because the entire height of the anchor pin 1100 needs to be visible during anchoring in order to determine the HR without immersing the anchor pin 1100 in the melt 104. However, it is undesirable to see the entire height of the pins during operation. By using separate pins, the camera can more easily determine the center of the laser dot reflection in the melt during operation, if the laser dot reflection is nearly circular. For this reason, the ramp pin 1102 is significantly shorter than the anchor pin 1100 and is substantially coplanar so that the reflection 1400 at the bottom of the ramp pin 1102 is mainly visible in the melt 1104. Longer pins are more prone to breakage, and shortening the pins provides protection against loss of measurement capability in the event of pin breakage. Even if the anchor pin 1100 breaks after calibration, the ability to determine the HR is not affected because the ramp pin 1102 is used to determine the HR. Other embodiments include a single pin used as both the anchor pin and the ramp pin.

[0061] The lifespan of commonly available lasers varies from a few months to just over a year when operated at a 100% duty cycle (constant illumination). Since HR does not need to be known more than once every few seconds, the measurement system can extend the lifespan of laser 700 by simply turning it on as needed every few seconds. With a 1-second on time and a 9-second off time, a laser operating at a 100% duty cycle for one year can be made to last for 10 years. Laser 700 may also be turned off when the lifting device 100 is not hot, which further extends its lifespan. In a different embodiment, the laser may be left on continuously, in which case the replacement frequency simply increases.

[0062] Figures 20 and 21 are side views of two alternative pins 2000, 2100 that can be used as a ramp pin 1102, an anchor pin 1100, or a combination of ramp / anchor pins in a single-pin setup. Pin 2000 has a spherical head 2002 with a flat top 2004. In exemplary embodiments, the head 2002 has a diameter of approximately 4.5 mm. The body portion 2006 of pin 2000 is generally cylindrical. Around height 2008, where pin 2000 begins to extend beyond the bottom of reflector 151 during installation, pin 2000 tapers toward a smaller spherical end 2010. In exemplary embodiments, the spherical end 2010 has a diameter of approximately 3.0 mm. In some embodiments, the tapered portion of pin 2000, the top of the spherical end 2010, and the bottom of the body portion 2006 are transparent, while the rest of pin 2000 is opaque. The pin 2100 in Figure 21 is substantially the same as the pin 200, but has a spherical head 2102. In exemplary embodiments, the head 2102 has a diameter of approximately 4.5 mm. The body portion 2106 of the pin 2100 is generally cylindrical. Around height 2108, where the pin 2100 begins to extend beyond the bottom of the reflector 151 during installation, the pin 2100 tapers toward a smaller spherical end 2110. In exemplary embodiments, the spherical end 2110 has a diameter of approximately 3.0 mm. In some embodiments, the tapered portion of the pin 2100, the upper part of the spherical end 2110, and the lower part of the body portion 2106 are transparent, while the rest of the pin 2100 is opaque.

[0063] In another embodiment, a single pin consisting of only one sphere (head) is used. The single-sphere pin is used with the laser illuminating the sphere. The top of the sphere is visible to the laser and the camera, and the reflection from the molten base of the sphere is visible to the camera. The single sphere may be at the end of a long pin used to support the pin, or it may be a small sphere with minimal other components. The laser illuminates the top surface of the pin. The reflection from the molten base, as described in other embodiments for calibration and HR determination, is the reflection from the base of the sphere. There is no substantial change to the method described in other embodiments for calibrating or determining the HR. The last four figures show an example of a single-sphere pin.

[0064] Figures 22 and 23 illustrate the single-pin embodiment described above, in which the pin 2200 includes a spherical head 2202. The remaining portion 2204 of the pin 2200 is for attaching the pin 2200 to the reflector 151 and is not used to direct the laser beam. Figure 22 is a view of the pin 2200 from inside the aperture 904 of the reflector 151, roughly horizontal, with portion 2204 of the pin 2200 attached to the wall of the reflector 151 within the aperture 904. Figure 23 is a view of the pin 2200 below the aperture 904 (e.g., as seen by camera 602), with the laser beam shining on the top (e.g., the portion visible in Figure 23).

[0065] Figures 24 and 25 illustrate another embodiment of the single pin described above, in which the useful portion of the pin 2400 is only the spherical head 2402. Figure 24 is a view from within the aperture 904 of the reflector 151, with the pin 2400 extending from the wall of the reflector 151 within the aperture 904 and viewed roughly horizontally. Figure 25 is a view of the pin 2400 below the aperture 904 (e.g., as seen by camera 602). In this embodiment, the upper part of the spherical head 2402 (e.g., the portion shown in Figure 25) receives strong green monochromatic light from the laser, as described in other embodiments, and the lower part of the quartz sphere (e.g., the portion opposite to the portion shown in Figure 25) is matte or translucent to scatter light to produce a distinct spherical reflection on the molten surface (not shown in Figure 25). The translucent portion is made using a surface coating or etching of the surface of the pin. Any suitable coating or other method may be used to manufacture the translucent, light-scattering portion of the pin. In other embodiments, different or additional portions of the pin may also be semi-transparent and light-scattering.

[0066] In the embodiments shown in Figures 22-25, the calibration process is similar to that of the other embodiments described above, but uses only a single spherical head and a single reflection. As the melt position changes, three separate image positions ("high," "medium," and "low" positions) of the centroid of the spherical reflection are captured. The X and Y image pixel coordinates are captured and stored at each position. The position of the crucible lift system that moves the melt up and down is also captured and stored. Furthermore, the position of the sphere is captured, and similarly, the X and Y coordinates of the sphere's center are captured and stored for each position.

[0067] Using the coordinates and crucible position saved in the first step, quadratic fit parameters are calculated to generate the crucible position given the centroid coordinates of the spherical reflection. Using these parameters along with the image coordinates, the crucible position can be calculated within the entire range of motion.

[0068] Next, the coordinates of the center of gravity of the spherical head captured in step 2, along with the measurement from the center of the spherical head to the bottom of the reflector, are added to correct the calibration so that the distance between the top of the molten material and the bottom of the reflector can be calculated using the fitting parameters.

[0069] As shown in Figures 17-19, when the camera 602 is in a fixed position, the reflector 1400 should move linearly as the melt height changes, and the ramp pin 1102 (or a combination of ramp pin and anchor pin) should remain in the same position in each image captured by the camera. If the ramp pin 1102 moves in the image plane or tilts relative to the camera 602 during operation, the reflector 1400 may not move in the expected linear direction, and adjustments to the calculations described above may be necessary. Such movement may be caused, for example, by vibrations experienced by the ingot lifting device 100, or by expansion or contraction of the material of the pins, mounts 1000, or other components in the growth chamber 152 due to thermal conditions in the growth chamber.

[0070] Figures 26 and 27 are examples of images taken by the camera during operation (after the system has been calibrated as described above). In Figure 26, the illuminated pin 2602 is aligned to the center of the first target 2604. Reflector 1400 is aligned to the center of the second target 2606 (visible in Figure 27). Line 2608 is the tracking line that reflector 1400 is expected to move as the melt height changes during operation. Additional target 2610 is an additional registration point defined during calibration.

[0071] Figure 27 shows the illuminated pin 2602 and reflection 1400 at a later time than that shown in Figure 26. That is, the ingot lifting device 100 has been operating for some time after the image in Figure 26 was taken. As can be seen, pin 2602 has shifted from its original position. Reflection 1400 has also shifted from the tracking line 2608.

[0072] To at least partially correct the misalignment, an offset vector is determined from the center of the first target 2604 to the center of the illuminated pin (shown in Figure 27), and the same offset vector is applied to the reflection 1400. In some embodiments, the offset vector is determined by determining the distance of pixels in the X and Y directions of the image from the center of the first target 2604 to the center of the pin 2602. This correction aligns the reflection of the pinhead to the position of the pinhead by adding the same offset to the reflection.

[0073] The logical flow depicted in the diagram does not require a specific order or sequence shown to obtain the desired result. Furthermore, other steps may be added to the described flow, steps may be removed from the described flow, other components may be added to the described system, or components may be removed from the described system. Accordingly, other embodiments are included in the following claims.

[0074] The embodiments described in particular in detail above are merely illustrative or possible embodiments, and it should be understood that many other combinations, additions, or substitutions are possible.

[0075] Furthermore, specific names, capitalization of terms, attributes, data structures, or other programming or structural aspects of components are not required or important, and mechanisms implementing this disclosure or its features may have different names, formats, or protocols. Moreover, the system may be implemented via a combination of hardware and software as described, or it may be implemented entirely with hardware elements. Also, specific divisions of functionality between the various system components described herein are merely examples and not required. Functions performed by a single system component may instead be performed by multiple components, and functions performed by multiple components may instead be performed by a single component.

[0076] The approximate expressions used throughout this specification and the claims may be applied to modify any quantitative expression that may change acceptablely without altering the fundamental function to which it pertains. Thus, values ​​modified by terms such as “about” or “substantially” are not limited to the exact values ​​specified. In at least some instances, approximate expressions may correspond to the precision of the instrument used to measure the values. Throughout this specification and the claims, scope limitations may be combined and / or replaced, and such scopes include all sub-scopes specified and contained therein, unless the context or wording indicates otherwise.

[0077] Various changes, modifications, and alterations to the teachings in this disclosure can be attempted by those skilled in the art without departing from the spirit and scope of their intent. This disclosure is intended to include such changes and alterations.

[0078] This specification uses examples to illustrate the best mode of the disclosure and to enable a person skilled in the art to carry out the disclosure, including the manufacture and use of any device or system, and the execution of any method incorporating it. The patentable scope of the disclosure is defined by the claims and may include other examples that a person skilled in the art can conceive. Such other examples are intended to be included in the claims if they have structural elements that are not different from the language of the claims, or if they include equivalent structural elements that are substantially different from the language of the claims.

Claims

1. A real-time measurement system in a crystal pulling apparatus for determining the distance between the silicon melt in the crucible and a reflector while the crystal is being pulled from the silicon melt, The aforementioned measurement system is A reflector that defines the central passage through which the crystal is pulled up and the opening, Measurement assembly and Equipped with, The aforementioned measurement assembly is A lamppin having a head visible through the aforementioned opening, A camera that captures images through the aperture of the reflector, and each captured image includes the surface of the silicon melt in the crystal pulling apparatus. A laser that selectively sends coherent light to the head of the lampin through the aperture, causing reflection of the lampin onto the surface of the silicon melt, A controller connected to the camera and the laser. Equipped with, The aforementioned controller, The laser is controlled so that coherent light is directed from the laser to the lampin. While the coherent light is directed towards the lampin, the camera is controlled to capture an image through the aperture of the reflector, and the captured image includes at least a portion of the surface of the silicon melt in which the reflection of the lampin is visible. Based on the position of the reflection of the lamppin in the captured image, the distance between the surface of the silicon melt and the bottom surface of the reflector is determined. A measurement system programmed to do so.

2. The measuring system according to claim 1, wherein the lamp pin is attached to the reflector.

3. The measuring system according to claim 1 or 2, wherein the lamppin includes the end of the lamppin opposite to the head, the reflection of the lamppin is the reflection of the end of the lamppin, and the end of the lamppin is not visible to the camera through the opening.

4. The measurement system according to any one of claims 1 to 3, wherein the lampin comprises a quartz lampin.

5. The measuring system according to any one of claims 1 to 4, wherein the ends of the rampin are sized and positioned such that the rampin does not touch the surface of the silicon melt when the crystal is being pulled up from the silicon melt.

6. The reflector further comprises an anchor pin attached to it, The anchor pin includes a head and an end opposite to the head, The measurement system according to any one of claims 1 to 5, wherein the anchor pin is sized to extend through the bottom surface of the reflector.

7. The controller is programmed to calibrate the measurement system using the anchor pin without the anchor pin touching the silicon melt. The measurement system according to claim 6, wherein the calibration is performed while the crystal is being pulled out of the silicon melt, before determining the distance between the surface of the silicon melt and the bottom surface of the reflector.

8. The aforementioned controller, The laser is controlled so that coherent light is directed from the laser to the head of the anchor pin. While the coherent light is directed toward the anchor pin, the camera is controlled to capture an image through the aperture of the reflector assembly, the captured image including at least a portion of the anchor pin and at least a portion of the surface of the silicon melt showing the reflection of the end of the anchor pin. The distance between the surface of the silicon melt and the bottom surface of the reflector is determined, at least partially based on the position of the reflection at the end of the anchor pin in the captured image, the known dimensions of the anchor pin, and the amount by which the anchor pin extends beyond the bottom surface of the reflector. The measurement system according to claim 7, which is programmed to calibrate the measurement system by doing so.

9. The aforementioned controller, The camera is controlled to capture images during the calibration of the system by controlling the camera to capture images through the aperture of the reflector assembly while the surface of the silicon melt is at a first distance from the bottom surface of the reflector and the coherent light is directed towards the head of the anchor pin, and controlling the camera to capture a second image through the aperture of the reflector assembly while the surface of the silicon melt is at a second distance from the bottom surface of the reflector and the coherent light is directed towards the head of the anchor pin, Based at least partially on the first and second images, the distance between the surface of the silicon melt and the bottom surface of the reflector is determined during the calibration of the system. The measurement system according to claim 8, which is programmed to do so.

10. The measurement system according to claim 9, wherein the controller is programmed to move the crucible and control the crucible lift such that the distance between the surface of the silicon melt and the bottom surface of the reflector changes by a known amount.

11. The aforementioned controller, When the surface of the silicon melt is at the second distance from the bottom surface of the reflector, the laser is controlled to direct the coherent light from the laser to the lampin. While the coherent light is directed towards the lamppin, the camera is controlled to capture a ran calibration image through the aperture of the reflector assembly, the ran calibration image including at least a portion of the surface of the silicon melt showing the reflection of the end of the lamppin. The position of the reflection at the end of the ramp pin in the ramp calibration image is corrected to the position of the reflection at the end of the anchor pin in the second image. The measurement system according to claim 9 or 10, which is programmed to calibrate the measurement system by doing so.

12. A crucible for holding the molten silicon, The measurement system according to any one of claims 1 to 11 and A system for manufacturing silicon ingots, including [the specified component].

13. A wafer produced from a silicon ingot manufactured using the system described in claim 12.

14. A method for determining the distance between the silicon melt in a crucible and the reflector of a crystal pulling apparatus while a crystal is being pulled from the silicon melt, using a measurement system including a camera, laser, lampin, and controller, The aforementioned method, From the laser, coherent light is directed towards the lampin, which is attached to the reflector and visible through the aperture of the reflector. While the coherent light is directed at the lampin, the camera is used to capture an image through the aperture of the reflector, the captured image including at least a portion of the surface of the silicon melt where the reflection of the lampin is observed. The controller determines the distance between the surface of the silicon melt and the bottom surface of the reflector based on the position of the reflection of the lampin in the captured image. A method that includes doing so.

15. The measuring system includes an anchor pin attached to the reflector, having a head and an end opposite to the head. The anchor pin is sized to extend beyond the bottom surface of the reflector. The method according to claim 14, further comprising calibrating the measuring system using the anchor pin without the anchor pin touching the silicon melt, before determining the distance between the surface of the silicon melt and the bottom surface of the reflector while the crystal is being pulled out of the silicon melt.

16. Calibrating the aforementioned measurement system is Direct coherent light from the laser towards the head of the anchor pin, While the coherent light is directed toward the anchor pin, the camera is used to capture an image through the aperture of the reflector assembly, the captured image including at least a portion of the anchor pin and at least a portion of the surface of the silicon melt in which the reflection of the end of the anchor pin is observed. The distance between the surface of the silicon melt and the bottom surface of the reflector is determined, at least partially based on the position of the reflection at the end of the anchor pin in the captured image, the known dimensions of the anchor pin, and the amount by which the anchor pin extends beyond the bottom surface of the reflector. The method according to claim 15, further comprising the following:

17. While the coherent light is directed towards the anchor pin, taking an image through the aperture of the reflector assembly using the camera is: A first image is taken through the aperture of the reflector assembly while the surface of the silicon melt is at a first distance from the bottom surface of the reflector and the coherent light is directed toward the head of the anchor pin. A second image is taken through the aperture of the reflector assembly while the surface of the silicon melt is at a second distance from the bottom surface of the reflector and the coherent light is directed towards the head of the anchor pin. This includes, The method according to claim 16, wherein during the calibration of the measurement system, the distance between the surface of the silicon melt and the bottom surface of the reflector is determined at least in part based on the first image and the second image.

18. The method according to claim 17, further comprising moving the crucible to control the crucible lift such that the distance between the surface of the molten silicon and the bottom surface of the reflector changes by a known amount.

19. A crucible for holding the molten silicon, The measuring system configured to perform the method described in any one of claims 14 to 18 A system for manufacturing silicon ingots, including [the specified component].

20. A wafer produced from a silicon ingot manufactured using the system described in claim 19.

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