Non-contact system and method for determining distance between silicon melt and reflector in crystal puller

Abstract

A measurement system includes a target object that is at least partially visible through an opening of a crystal puller. The crystal puller has: a silicon melt located in a crucible; and a reflector defining a central channel through which the crystal is pulled. A detector array captures light through the opening. The detector array is directed toward a surface of the silicon melt in the crystal puller and the target object, and a laser selectively transmits a coherent beam through the opening to the target object to produce a reflection of the target object on the surface of the silicon melt. A light modulator pulses the coherent light beam of the laser into a discrete coherent light beam having a period, and a lock-in amplifier is connected to the detector array to filter the discrete coherent light having the period from captured light.

Description

[0001] CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 357,734, filed on July 1, 2022, the entire contents of which are hereby incorporated by reference. Technical Field

[0003] The technical field generally relates to the production of silicon ingots, and more particularly, the technical field relates to non-contact methods and systems for determining the distance between a silicon melt and a reflector in a crystal puller. Background Art

[0004] Some crystal pullers include a reflector positioned above the silicon melt. During operation of the crystal puller, it may be beneficial to know the distance between the bottom of the reflector and the surface of the silicon melt (referred to as "HR"). The HR measurement accuracy is typically less than 1 mm, with an accuracy in the range of 0.1 mm to 0.2 mm being more desirable.

[0005] HR measurements are difficult to perform using known methods because measuring HR involves observing and tracking features inside an extremely hot puller under vacuum or low pressure conditions. These conditions often limit the types of sensors and materials that can be used inside the puller. Because thermal expansion will often affect components that are not actively cooled, measurements taken before the pull or run begins may not be useful or helpful after the puller is brought up to operating temperature. Additionally, the resolution and accuracy of optical sensors and detector arrays used to measure distances within the puller may be affected by the energy emissions of molten or heated materials within the puller. In particular, photoluminescence and thermoluminescence may emit incoherent light that reduces the resolution of the sensors.

[0006]

[0006] Therefore, there is a need to improve the resolution and accuracy of optical sensors and detector arrays used to measure distances within a crystal puller.

[0007] This "Background Art" section is intended to introduce the reader to various aspects of the technology that may be related to various aspects of the present disclosure that will be described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of various aspects of the present disclosure. Therefore, it should be understood that these statements should be interpreted accordingly and not as admissions of prior art. Summary of the invention

[0008] In one aspect, a crystal puller has: at least one heater; a silicon melt located in a crucible; and a measurement system for determining a distance between the silicon melt and a reflector when a crystal is pulled from the silicon melt. The system includes: a reflector defining a central passage and an opening through which the crystal is pulled; and, a measurement assembly. The measurement system further includes: a target object at least partially visible through the opening; and a detector array for capturing light passing through the opening. The detector array is directed toward a surface of the silicon melt in the crystal puller and the target object. The measurement system further includes a laser to selectively transmit a coherent beam of light through the opening to the target object to produce a reflection of the target object on the surface of the silicon melt. The measurement system further includes: an optical modulator to pulse the coherent beam of light of the laser into a discrete coherent beam of light having a period; and a controller connected to the detector array, the laser, and the optical modulator. The controller is programmed to control the laser to direct the discrete coherent light beam from the laser to the target object, control the light modulator to pulse the coherent light beam of the laser into discrete coherent light beams, and control the detector array to extract light through the opening when the discrete coherent light beam is directed at the target object. The extracted light includes at least a portion of the surface of the silicon melt on which the reflection of the target object is visible, and the controller is programmed to control the detector array to filter the discrete coherent light beam having the period from the extracted light.

[0009] In another aspect, a measurement system includes: a target object at least partially visible through an opening in a crystal puller, the crystal puller having: a silicon melt located in a crucible; and a reflector defining a central channel through which a crystal is pulled; and a detector array that captures light through the opening. The detector array is directed toward a surface of the silicon melt in the crystal puller and the target object. The measurement system further includes: a laser that selectively transmits a coherent beam of light through the opening to the target object to produce reflections of the target object on the surface of the silicon melt, and a light modulator that pulses the coherent beam of light of the laser into discrete coherent beams having a period. The measurement system further includes a lock-in amplifier connected to the detector array to filter the discrete coherent light having the period from the captured light. A controller is programmed to determine a measured distance from the surface of the silicon melt by controlling the laser to direct a coherent beam of light from the laser to a first end of the target object as the crystal is pulled from the silicon melt. The first end is visible by the laser through the opening. The controller is programmed to control the light modulator to pulse the coherent light beam of the laser, control the detector array to extract light, and control a lock-in amplifier to filter a discrete coherent light beam having the period from the extracted light. The lock-in amplifier is connected to the detector array, and the controller determines a measured distance between the surface of the silicon melt and a bottom surface of the reflector based on a position of the reflection of the target object.

[0010] In yet another aspect, a method determines a distance between a silicon melt and a reflector in a crystal puller while pulling a crystal from a silicon melt in a crucible using a measurement system. The method includes the steps of directing a coherent light beam from a laser to a target object mounted on the reflector and visible through an opening. The laser is positioned outside the crystal puller, and a light modulator is used to pulse the coherent light beam from the laser into a discrete coherent light beam having a period. The light modulator is selected from a pulse width modulator and a chopper. The pulse width modulator is connected to the laser and pulses the coherent light beam of the laser. The chopper is positioned between the laser and the target object to chopper the coherent light beam of the laser. When the discrete coherent light beam is directed toward the target object, a detector array positioned outside the crystal puller is used to capture discrete light through the opening. The captured light includes at least a portion of a surface of the silicon melt on which the reflection of the target object is visible. A controller determines the distance between the surface of the silicon melt and a bottom surface of the reflector based on the position of the reflection of the target object.

[0011] There are various improvements with respect to the features and steps set forth in the above aspects. Further features may also be incorporated into the above-mentioned aspects. These improvements and additional features may exist individually or in any combination. For example, the various features and steps discussed below with respect to each of the illustrated embodiments may be incorporated into the above-mentioned aspects individually or in any combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a cross-sectional view of an ingot puller apparatus for pulling a single crystal silicon ingot from a silicon melt.

[0013] Figure 2 is a cross-sectional view of a portion of another ingot puller apparatus for pulling a single crystal silicon ingot from a silicon melt.

[0014] Figure 3 is a cross-sectional view of another example of an ingot puller apparatus for pulling a single crystal silicon ingot from a silicon melt.

[0015] Figure 4 is a partial view of a single crystal silicon ingot grown by the Czochralski method.

[0016] Figure 5 is used for Figure 1 A simplified block diagram of a computing device in a control system of an example ingot puller apparatus.

[0017] Figure 6 yes Figure 1 A view of the geometry of the measurement assembly.

[0018] Figure 7 is used Figure 1 Flow chart of a method of measuring an assembly.

[0019] Like reference symbols in the various drawings indicate the same elements. DETAILED DESCRIPTION

[0020] Reference Figures 1 to 4 An ingot puller apparatus (or more simply, "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 at "100," for pulling a single crystal silicon ingot from a silicon melt. Figure 2 and 3 is a cross-sectional view of the ingot puller apparatus 100, and Figure 4 is a partial front view of a single crystal silicon ingot grown, for example, by the Czochralski method in the ingot puller apparatus 100 .

[0021] The ingot puller apparatus 100 includes a crystal puller housing 108 defining a growth chamber 152 for pulling a silicon ingot 113 from a melt 104 of silicon. A control system 172 (also referred to as a "controller") controls the operation of the ingot puller 100 and its components. The ingot puller apparatus 100 includes a crucible 102 disposed within the growth chamber 152 for holding a melt 104 of silicon. The crucible 102 is supported by a susceptor 106.

[0022] Crucible 102 includes a bottom plate 129 and a sidewall 131 extending upward from bottom plate 129. Sidewall 131 is generally vertical. Bottom plate 129 includes a curved portion of crucible 102 extending below sidewall 131. Within crucible 102 is a silicon melt 104 having a melt surface 111 (i.e., melt-ingot interface). Susceptor 106 is supported by shaft 105. Susceptor 106, crucible 102, shaft 105, and ingot 113 have a common longitudinal axis A or "pulling axis" A.

[0023] A pulling mechanism 114 is disposed within the ingot puller apparatus 100 for growing and pulling an ingot 113 from the melt 104. The pulling mechanism 114 includes a pulling cable 118, a seed holder or chuck 120 coupled to one end of the pulling cable 118, and a seed crystal 122 coupled to the seed holder or chuck 120 for initiating crystal growth. One end of the pulling cable 118 is connected to a pulley (not shown) or a roller (not shown), or any other suitable type of lifting mechanism (e.g., a shaft) within the pulling mechanism 114, and the other end is connected to the chuck 120 that holds the seed crystal 122. In operation, the seed crystal 122 is lowered to contact the melt 104. The pulling mechanism 114 is operated to cause the seed crystal 122 to rise. This causes the single crystal ingot 113 to be pulled from the melt 104.

[0024] During heating and crystal pulling, a crucible drive unit 107 (e.g., a motor) rotates the crucible 102 and susceptor 106. During the growth process, an elevator mechanism 112 raises and lowers the crucible 102 along the pull axis A. As the ingot grows, the silicon melt 104 is consumed and the height of the melt in the crucible 102 decreases. The crucible 102 and susceptor 106 may be raised to maintain the melt surface 111 at or near the same position relative to the ingot puller apparatus 100.

[0025] The crystal drive unit (not shown) may also rotate the pulling cable 118 and the ingot 113 in a direction opposite to the direction in which the crucible drive unit 107 rotates the crucible 102 (e.g., counter-rotation). In embodiments using co-rotation, the crystal drive unit may rotate the pulling cable 118 in the same direction in which the crucible drive unit 107 rotates the crucible 102. Additionally, during the growth process, the crystal drive unit raises and lowers the ingot 113 relative to the melt surface 111 as needed.

[0026] The ingot puller apparatus 100 may include an inert gas system to introduce and extract an inert gas, such as argon, from the growth chamber 152. The ingot puller apparatus 100 may also include a dopant feed system (not shown) for introducing dopants into the melt 104.

[0027] According to the Czochralski single crystal growth process, a certain amount of polycrystalline silicon is charged into the crucible 102 (eg, a charge of 250 kg or more). A variety of sources of polycrystalline silicon may be used including, for example, granular polycrystalline silicon produced by 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 a charge, the charge is heated to a temperature approximately above the melting temperature of silicon (e.g., approximately 1412° C.) to melt the charge. In some embodiments, the charge (i.e., the resulting melt) is heated to a temperature of at least approximately 1425° C., at least approximately 1450° C., or even at least approximately 1500° C. The ingot puller apparatus 100 includes a bottom insulator 110 and side insulators 124 to maintain heat in the ingot puller apparatus 100. In the illustrated embodiment, the ingot puller apparatus 100 includes a bottom heater 126 disposed below a crucible bottom plate 129. The crucible 102 can be moved relatively close to the bottom heater 126 to melt the polycrystalline fed into the crucible 102.

[0028] To form an ingot, a seed crystal 122 is contacted with a surface 111 of the melt 104. A pulling mechanism 114 is operated to pull the seed crystal 122 from the melt 104. The ingot 113 includes a crown 142 where the ingot transitions and gradually widens outward from the seed crystal 122 to reach a target diameter. The ingot 113 includes a constant diameter portion 145 or a cylindrical "body" of the crystal that is grown by increasing the pulling rate. The body 145 of the ingot 113 has a relatively constant diameter. The ingot 113 includes a tail or end cone (not shown) where the ingot tapers in diameter after the body 145. When the diameter becomes sufficiently small, the ingot 113 is separated from the melt 104. The ingot 113 has a central longitudinal axis A extending through the crown 142 and the terminal end of the ingot 113.

[0029] The ingot puller apparatus 100 includes side heaters 135 and a susceptor 106 surrounding the crucible 102 to maintain the temperature of the melt 104 during crystal growth. The side heaters 135 are disposed radially outward to the crucible sidewall 131 as the crucible 102 moves up and down along the pull axis A. The side heaters 135 and the bottom heater 126 can be any type of heater that allows the side heaters 135 and the bottom heater 126 to operate as described herein. In some embodiments, the heaters 135, 126 are resistive heaters. The side heaters 135 and the bottom heater 126 can be controlled by a control system 172 so that the temperature of the melt 104 is controlled throughout the pulling process.

[0030] The ingot puller apparatus 100 may also include a reflector 151 (or "heat shield") disposed within the growth chamber 152 and located above the melt 104 covering the ingot 113 during ingot growth. During crystal growth, the reflector 151 may be partially disposed within the crucible 102. The reflector 151 defines a central channel 160 for receiving the ingot 113 as the ingot is pulled by the pulling mechanism 114.

[0031] The reflector 151 may be a heat shield suitable for retaining heat beneath itself and above the melt 104. Other reflector designs and materials of construction (e.g., graphite) may be used without limitation. The reflector 151 has a bottom 138 (e.g., Figure 2 104 ) and during ingot growth, the bottom 138 of the reflector 151 is separated from the surface of the melt by a distance HR. As the ingot 113 is pulled, the distance HR increases due to consumption of the melt 104.

[0032] The terms "light", "light emission", "coherent light", "incoherent light" and "light beam" refer to photon energy emitted by sources and components of an ingot puller apparatus. The emitted light may be visible or invisible to the human eye. The light may be in a broadband spectral region (i.e., from ultraviolet to infrared). The emitted light may be "coherent" or "incoherent" light. Coherent light has a constant phase difference between the light waves from the emission source. Incoherent light has a non-constant or random phase difference between the light waves from the emission source. Coherent light may be separated out due to the enhancement of light outflow from the intensification of electromagnetic radiation. Incoherent light may be emitted due to photoluminescence and thermoluminescence of a melting or heating source. As used herein, "captured light" or "captured image" refers to light observed by a sensor or detector.

[0033] Figure 3 1 shows an example single crystal silicon ingot 113 produced by the Czochralski process. Ingot 113 includes a neck 116, a flared portion 142 (synonymous with a "crown" or "cone"), a shoulder 119, and a constant diameter body 145. Neck 116 is attached to a seed crystal 122 that is in contact with the melt and is pulled up to form ingot 113. Body 145 is suspended from neck 116. Neck 116 terminates once cone portion 142 of ingot 113 begins to form.

[0034] The constant diameter portion 145 of the ingot 113 has a circumferential edge 150, a central axis A parallel to the circumferential edge 150, and a radius R extending from the central axis A to the circumferential edge 145. The central axis A also passes through the cone 142 and the neck 116. The diameter of the main ingot 145 can vary and, in some embodiments, the diameter can be about 150 mm, about 200 mm, about 300 mm, greater than about 300 mm, about 450 mm, or even greater than about 450 mm.

[0035] The single crystal silicon ingot 113 may generally have any resistivity. The single crystal silicon ingot 113 may be doped or undoped.

[0036] Figure 5 4 is an example computing device 400 that may be used as or as part of control system 172. Computing device 400 includes processor 402, memory 404, media output component 406, input device 408, and communication interface 410. Other embodiments include different components, additional components, and / or no components. Figure 5 404. The processor 402 is configured to execute instructions. In some embodiments, executable instructions are stored in the memory 404. The processor 402 may include one or more processing units (e.g., in a multi-core configuration). The term processor (as used herein) refers to a central processing unit, a microprocessor, a microcontroller, a reduced instruction set circuit (RISC), an application-specific integrated circuit (ASIC), a programmable logic circuit (PLC), and any other circuit or processor capable of performing the functions described herein. The above are only examples, and therefore it is not intended to limit the definition and / or meaning of the term "processor" in any way. The memory 404 stores non-temporary, computer-readable instructions for executing the techniques described herein. When executed by the processor 402, such instructions cause the processor 402 to execute at least a portion of the method described herein. In some embodiments, the memory 404 stores computer-readable instructions for providing a user interface to a user via the media output component 406 and receiving and processing inputs from the 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 as being separate from processor 402, in some embodiments, memory 404 is combined with processor 402, such as in a microcontroller or microprocessor, but may still be referred to separately. The above memory types are merely examples, and therefore are not limited to the types of memory that can be used to store computer processes. Media output component 406 is configured to present information to a user (e.g., an operator of the system). Media output component 406 is any component capable of transmitting information to a user. In some embodiments, media output component 406 includes an output adapter such as a video adapter and / or an audio adapter. The output adapter is operably connected to the processor 402 and is operably connected to an output device such as a display device (e.g., a liquid crystal display (LCD), a light emitting diode (LED) display, an organic light emitting diode (OLED) display, a cathode ray tube (CRT), an "electronic ink" display, one or more light emitting diodes (LEDs)) or an audio output device (e.g., a speaker or headphones).

[0037] 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 allows the computing device 400 to receive analog and / or digital commands, instructions, or other input from a user, including visual, audio, touch, button presses, stylus taps, etc. The input device 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 touch screen), a gyroscope, an accelerometer, a position detector, an audio input device, or any combination thereof. A single component (e.g., a touch screen) may simultaneously serve as both an output device for the media output component 406 and an input device 408.

[0038] The communication interface enables the computing device 400 to communicate with remote devices and systems (e.g., remote sensors, remote databases, remote computing devices, and the like), and may include more than one communication interface for interacting with more than one remote device or system. The communication interface may be a wired or wireless communication interface that allows the computing device 400 to communicate with remote devices and systems directly or via a network. The wireless communication interface may include a radio frequency (RF) transceiver, Adapter, Wi-Fi transceiver, The wired communication interface may communicate directly using any suitable wired communication protocol, including, but not limited to, USB, RS232, I2C, SPI, analog, and proprietary I / O protocols. In some embodiments, the wired communication interface includes a wired network adapter that allows the computing device 400 to be coupled to a network (e.g., the Internet, a local area network (LAN), a wide area network (WAN), a mesh network, and / or any other network) to communicate with remote devices and systems via the network.

[0039] The computer systems discussed herein may include additional, less, or alternative functionality, including functionality discussed elsewhere herein.The computer systems discussed herein may include or be implemented via computer executable instructions stored on a non-transitory computer readable medium.

[0040] like Figures 1 to 4 As shown in FIG. 1 , the ingot puller apparatus includes a measurement assembly 170 used as part of a measurement system to determine the distance between a reflector 151 or target object 200 and a surface 111 of the melt 104. Figure 2 and 3, measurement assembly 170 can be used to determine the distance between bottom 138 of reflector 151 and the surface of the melt during ingot growth (i.e., determine HR). Measurement assembly 170, systems, and methods described herein can also be used to determine other distances from surface 111 of melt 104 within crystal puller 100. Measurement assembly 170 can be configured to measure any vertical distance (parallel to HR) using systems and methods described in further detail below. Figure 1 axis X).

[0041] The measurement assembly 170 and the controller 172 define a 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. The measurement assembly 170 includes: a target object 200, which is positioned within the growth chamber 152 of the ingot puller apparatus 100; a detection array 210, which is positioned outside the growth chamber 152 to extract light from within the growth chamber 152; a laser 208 growth chamber 152, which selectively transmits a coherent light beam to the target object 200; and a light modulator 212, which pulses the coherent light beam of the laser into a discrete coherent light beam having a period. A lock-in amplifier 214 may be connected to the detector array 210 to filter the discrete coherent light beam having a period from the extracted light. The lock-in amplifier 214 may amplify the discrete coherent light beam having a period from the incoherent light present within the growth chamber 152.

[0042] Typically, a laser 208 (e.g., a laser diode) is focused on a target object 200 that projects a laser spot on the melt surface 111. The target object 200 is translucent or opaque so that focusing the light from the laser on a first end 202 or a point of the target object 200 refracts the light to a second end 204 or a point opposite to the first end 202. The refracted light from the second end 204 or point projects the light on the melt surface 111. Figure 2 and 3 , a projection 201 is displayed on the melt surface 111. The projection 201 may have a diameter and shape substantially equal to the second end 204 of the target object 200 and emits coherent light due to refraction that can be detected by the detector array 210. The first end 202 of the target object 200 also reflects coherent light from the laser that can be detected by the detector array 210.

[0043] The laser 208 is suitably a 5 milliwatt, 520 nm wavelength, diode laser with a divergence of <0.3 and a three-beam size capable of delivering a coherent beam to the target object 200. Because the color of the melt is typically red, a green laser provides a more visible contrast between the spot and the melt than some other colors. Other embodiments may use any other suitable color laser.

[0044] The detector array 210 is positioned outside of the crystal puller housing 108 and directed to capture light emitted from at least the first end 202 of the target object 200 and the projection 210 onto the melt surface 111. The detector array 210 is positioned so that it sees the growth chamber 152 (e.g., Figure 1 During the remainder of the run, the laser spot is continuously tracked using a camera to determine the HR. The measurement system does not rely on contact with the melt to find the HR.

[0045] The detector array 210 is adapted as a photodiode or position sensor for detecting and measuring the wavelength of light along a spectrum. The detector array 210 converts the wavelength measurement into a distance measurement between the detector array 210 and the light emitting element. In some embodiments, the detector array 210 is a charge coupled device (CCD) camera or a charge injection device (CID) camera. CCD and CID cameras utilize image sensors to record visible light as electronic signals and convert the light into two-dimensional pixelated images, each image including the surface of the silicon melt in the crystal puller, the target object, and the reflection of the target object on the silicon melt.

[0046] The target object 200 may be a quartz pin made from a raw material rod. The target object 200 is optically transparent. In other embodiments, the target object 200 may be made from any high temperature refractor, such as silicon carbide (SiC), silicon nitride (SiN), tungsten carbide, tantalum carbide, quartz, sapphire, boron nitride, or any other optically transparent, heat resistant material. In general, the pin material should produce a strong, well-defined reflection at the molten surface at all interesting crystal growth stages. In one example, the raw quartz rod is a 3 mm raw material rod. Alternatively, any other diameter raw material rod may also be used. The pin may have a head made or formed from a rod, for example, when a long light traveling pin is desired. In this case, when it is desired to see the laser from the tail of the pin but the laser is displayed on the pin head, the pin is a continuous piece, rather than a pin with a sphere welded thereon, to ensure that when the laser is shining on the pin head, the light from the laser is piped to the bottom of the pin.

[0047] like Figure 2 As shown in FIG. 1 , target object 200 is positioned on the edge of bottom 138 of reflector 151. Figure 31, the target object 200 can be positioned and extended through the opening 139 in the reflector 151. The opening 139 is sized to allow the detector array 210 to see at least the first end 202 of the target object and the projection 201 displayed on the melt surface 111. The opening 139 in the reflector 151 is a compound angle to allow the target object 200 to be viewed from the lateral edge of the same port where the detector array 210 and the laser 208 are mounted. Unlike some known bar laser systems that use an "open" hot zone with a reflector that is also not insulated, the present system is used in a "closed" hot zone, where the reflector 151 fills as much of the insulating area as possible above the melt 104. The open hot zone system uses the view around the outside of the maximum crystal diameter from the port on the opposite side of the crystal as the target object 200 to observe the reflection of the bottom of one of the target objects 200 illuminated by the laser 208 in the melt. Example embodiments allow for a closed hot zone, but allow the laser spot reflection to be seen from the same port, while maintaining high resolution HR capabilities despite the steep angle of the cut. Other embodiments may use multiple ports (eg, with the camera and laser located on different ports).

[0048] Using a bright laser can provide a consistent signal across the melt. Green wavelength lasers (520nm to 532nm wavelength) that are commonly commercially available in various power ratings are generally bright enough under all conditions. This avoids the problems of some known detector arrays, optical sensors, and camera systems that rely on visual observation of features in the hot zone that can have varying light intensities due to reflection and emission of light from the silicon melt. Light intensity variations can produce shadows that can cause hot zone objects to appear to move by one or two pixels. This can produce false movement (i.e., HR variation).

[0049] The light modulator 212 is selected from a pulse width modulator or a chopper. The pulse width modulator can be connected to the laser 208 or can be integrated with the laser 208, and the coherent light beam of the laser is pulsed into a discrete coherent light beam with a period. The chopper is positioned between the laser 208 and the target object 200 to cut the coherent light beam of the laser into a discrete coherent light beam with a period. In any of the above configurations, the coherent light beam is blocked for a time period, essentially producing a brief flicker. The period can be a fraction of a second, and in some embodiments, it is invisible to the human eye. The flicker of the coherent light emitted by the laser 208 and refracted by the target object 200 is also transformed into a projection 201 displayed on the melt surface 111.

[0050] Lock-in amplifier 214 may extract periodic coherent light from the environment by synchronizing lock-in amplifier 214 with the period of optical modulator 212 , thereby improving the accuracy and sensitivity of detector array 210 by separating the periodic discrete coherent light beam from the light within growth chamber 152 .

[0051] The lock-in amplifier 214 can also filter light driven by an AC voltage having a specific frequency. Generally, electrical components operating under DC and AC voltages emit light according to the operating frequency. The heater can be operated under a DC voltage, thus emitting light without a frequency, and the laser can be operated under an AC voltage, thus emitting a coherent light beam with a frequency. The emitted coherent light beam with a frequency can be filtered from incoherent light and DC light.

[0052] Figure 6 2 is a schematic diagram of the detector array 210 and the field of view of the laser 208. The detector array 210 is positioned so that the target object 200 and the projection 201 are displayed on the melt surface 111. The detector array 210 captures light through the opening 109 in the crystal puller housing 108. The light captured by the detector array includes incoherent light from the heater 135 and the bottom heater 126, and coherent light emitted by the laser 208. The field of view of the detector array 210 includes the first end 202 of the target object 200 and the projection 201 at different distances from the second end 204 of the target object 200 (denoted as (ZD) and (ZE)). The laser 208 selectively transmits a coherent light beam 230 to the target object 200 through the opening to produce a reflection 201 of the target object on the surface 111 of the silicon melt. The light modulator 212 pulses the coherent light beam 230 of the laser 208 into a discrete coherent light beam 232 having a period. The lock-in amplifier 214 filters out the periodic coherent light beam 232 from the incoherent light.

[0053] To use the measurement system, the height (PH) of the target object 200, the diameter (PD) of the first end 202 of the target object 200, and the distance (H) that the target object 200 extends from the bottom of the reflector are known. The laser 208 and the light modulator 212 are turned on and a discrete coherent light beam with a period is irradiated on the first end 202 of the target object 200. The discrete coherent light beam is refracted by the target object 200 (to the second end 204) and a projection 201 is displayed on the melt surface 111. When the crucible lifting mechanism 112 moves the crucible 102 and the melt surface 111 relative to the bottom surface 138 of the reflector 151, the measured distance changes (as measured by Figure 6 (ZD) and (ZE) in FIG.

[0054] In some embodiments, the controller 172 locates the tangent edge, rather than finding the center directly, and the previously measured diameter (PD) of the head of the target object 200 is used to find the center of the head. The known value of the pin diameter (measured or not measured, as it is made of a stock material with a known diameter) is used to find the center of the lower edge of the pin. The measured distance to the light captured by the detector array 210 can be used to triangulate the length of the height (PH) of the target object 200 and establish a reference number, where the use ratio can be used to calculate the unknown distances (ZD) and (ZE). In the case where the detector array 210 is a camera, the resulting distance of the projection 201 can be represented using the pixel position relative to the aforementioned point.

[0055] The controller 172 is connected to the detector array 210, the laser 208, and the light modulator 212 and is programmed to perform the following functions. The controller controls the laser 208 to direct the discrete coherent light beam from the laser 208 to the target object 200, controls the light modulator 212 to pulse the coherent light beam of the laser 208 into the discrete coherent light beam, controls the detector array 210 to capture light through the opening when the discrete coherent light beam is directed to the target object 200, controls the detector array 210 to filter the discrete coherent light beam having a period from the captured light, and controls the lock-in amplifier to filter the discrete coherent light having a period from the captured light. For example, the controller calculates the measured distance between the surface of the silicon melt and the bottom surface of the reflector based on the position of the reflection 201 of the target object 200 by using the processor.

[0056] Figure 7 , an example method 500 for determining the distance between a silicon melt in a crucible and a reflector in a crystal puller when pulling a crystal from the silicon melt is shown. The method includes the steps of directing 502 a coherent light beam from a laser to a target object mounted on the reflector and visible through an opening; pulsing 504 the coherent light beam from the laser into a discrete coherent light beam having a period using an optical modulator; and capturing 506 the discrete light beam through the opening using a detector array positioned outside the crystal puller when the discrete coherent light beam is directed toward the target object. The method also includes determining 508, by a controller, 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 target object. The method may also include the step of filtering 510 the discrete coherent light beam using a lock-in amplifier connected to the detector array.

[0057] The example methods do not require a particular order or sequential sequence of steps. In addition, other steps may be included or steps may be eliminated from the described methods, and other components may be added to or removed from the described systems. It should be understood that the above embodiments, which have been described in particular detail, are merely examples or possible embodiments, and that many other combinations, additions, or alternatives exist.

[0058] Additionally, the specific naming of components, capitalization of terms, attributes, data structures, or any other programming or structural aspects are not mandatory or significant, and mechanisms implementing the disclosure or features thereof may have different names, formats, or protocols. Furthermore, the system may be implemented via a combination of hardware and software, as described, or implemented entirely in hardware components. Additionally, the specific division of functionality between the various system components described herein is merely an example and is not mandatory; functions performed by a single system component may be performed by multiple components, and functions performed by multiple components may alternatively be performed by a single component.

[0059] As used herein throughout the specification and claims, approximate language may be used to modify any quantitative representation that may permissibly vary without resulting in a change in the basic function to which it is related. Thus, a value modified by one or more terms, such as "about" and "substantially," is not limited to the precise value specified. In at least some instances, approximate language may correspond to the precision of an instrument used to measure a value. Here and throughout the specification and claims, range limitations may be combined and / or interchanged, and unless context or language indicates otherwise, such ranges are identified and include all subranges contained therein.

[0060] Those skilled in the art may consider various changes, modifications, and substitutions in the teachings of the present disclosure without departing from its intended spirit and scope. The present disclosure is intended to encompass such changes and modifications.

[0061] This written description uses examples to describe the disclosure (including specific implementations) and also to enable persons skilled in the art to practice the disclosure (including making and using any devices or systems and performing any incorporated methods). The patentable scope of the disclosure is defined by the claims, and may include other embodiments that occur to persons skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

1. A crystal puller having: at least one heater; a silicon melt located in a crucible; and a measurement system for determining a distance between the silicon melt and a reflector when a crystal is pulled from the silicon melt, the system comprising: a reflector defining a central passage and an opening through which the crystal is pulled; and The measuring assembly further comprises: a target object that is at least partially visible through the opening; a detector array for capturing light passing through the opening, the detector array being directed toward a surface of the silicon melt in the crystal puller and the target object; a laser that selectively transmits a coherent beam of light through the opening to the target object to produce a reflection of the target object on the surface of the silicon melt; an optical modulator that pulses the coherent light beam of the laser into a discrete coherent light beam having a period; and a controller connected to the detector array, the laser, and the light modulator, the controller being programmed to: controlling the laser to direct the discrete coherent light beam from the laser to the target object, Controlling the optical modulator to pulse the coherent light beam of the laser into discrete coherent light beams; controlling the detector array to extract light through the opening when the discrete coherent light beam is directed toward the target object, wherein the extracted light includes at least a portion of the surface of the silicon melt on which the reflection of the target object is visible, and The detector array is controlled to filter the discrete coherent light beams having the period from the extracted light.

2. The crystal puller of claim 1, wherein directing a discrete coherent light beam from the laser to the target object projects the reflection of the target object onto the surface of the silicon melt.

3. The crystal puller of claim 2, wherein the controller is programmed to determine a measured distance between the surface of the silicon melt and a bottom surface of the reflector based on a position of the projection of the target object in the extraction light.

4. The crystal puller of claim 1, wherein the extracted light from the detector array includes incoherent light emitted from at least the silicon melt and discrete coherent light beams from the laser and the light modulator.

5. The crystal puller of claim 4, wherein a lock-in amplifier is connected to the detector array to filter the discrete coherent light beam having the period from the extracted light.

6. The crystal puller of claim 1, wherein a lock-in amplifier is connected to the detector array to filter the discrete coherent light beam having the period from the extracted light by amplifying the discrete coherent light beam having the period.

7. The crystal puller of claim 1, wherein the target object has a first end and a second end opposite the first end, the target object being mounted to the reflector, wherein the target object refracts light between the first end and the second end.

8. The crystal puller of claim 7, wherein a projection of the target object from the second end of the target reflector produces a reflection of the target object on the surface melt.

9. The crystal puller of claim 1 , wherein the detector array is an optical sensor for converting captured light through the openings in the reflector into pixelated images, each image comprising the surface of the silicon melt in the crystal puller, the target object, and the reflection of the target object on the silicon melt.

10. The crystal puller of claim 1, wherein the light modulator is selected from a pulse width modulator or a light chopper, wherein the pulse width modulator is connected to the laser and pulses the coherent light beam of the laser, wherein the light chopper is positioned between the laser and the target object to chop off the coherent light beam of the laser.

11. A measurement system comprising: a target object at least partially visible through an opening in a crystal puller having: a silicon melt located in a crucible; and a reflector defining a central passage through which a crystal is pulled; a detector array that captures light through the opening, the detector array directed toward a surface of the silicon melt in the crystal puller and the target object; a laser that selectively transmits a coherent beam of light through the opening to the target object to produce a reflection of the target object on the surface of the silicon melt; an optical modulator for pulsing the coherent light beam of the laser into a discrete coherent light beam having a period; and a lock-in amplifier connected to the detector array to filter discrete coherent light having the period from the captured light; Wherein the controller is programmed to determine the measured distance from the surface of the silicon melt as the crystal is pulled from the silicon melt by: controlling the laser to direct a coherent light beam from the laser to a first end of the target object, the first end being visible by the laser through the opening; controlling the optical modulator to pulse the coherent light beam of the laser; controlling the detector array to capture light; controlling a lock-in amplifier to filter the discrete coherent light beam having the period from the extraction light, the lock-in amplifier being connected to the detector array; and A measured distance between the surface of the silicon melt and a bottom surface of the reflector is determined by the controller based on a position of the reflection of the target object. 12 . The measurement system of claim 11 , wherein the extracted light comprises light emitted from the silicon melt and a discrete coherent light beam having the period, wherein the lock-in amplifier filters out the light emitted from the silicon melt. 13 . The measuring system of claim 12 , wherein the second end of the target object extends a length from the bottom surface of the reflector.

14. The measurement system of claim 13, wherein the measured distance is determined at least in part on a location of the reflection at the first end of the target and a known size of the target object. 15 . The measurement system of claim 13 , wherein the measurement distance is triangulated from the first end of the target object to the reflection of the target object on the surface of the silicon melt. 16 . The measurement system of claim 11 , wherein the controller is programmed to control a crucible lifting mechanism to move the crucible to change the measurement distance between the surface of the silicon melt and the bottom surface of the reflector.

17. A method for determining the distance between a silicon melt and a reflector in a crystal puller when pulling a crystal from a silicon melt in a crucible using a measurement system: directing a coherent beam of light from a laser positioned external to the crystal puller toward a target object mounted on the reflector and visible through the opening; pulsing the coherent light beam from the laser into a discrete coherent light beam having a period using an optical modulator, wherein the optical modulator is selected from a pulse width modulator and a light chopper, wherein the pulse width modulator is connected to the laser and pulses the coherent light beam of the laser, wherein the light chopper is positioned between the laser and the target object to chopper the coherent light beam of the laser; when the discrete coherent light beam is directed toward the target object, extracting the discrete light through the opening using a detector array positioned outside the crystal puller, the extracted light including at least a portion of a surface of the silicon melt on which the reflection of the target object is visible; and A distance between the surface of the silicon melt and a bottom surface of the reflector is determined by a controller based on a position of the reflection of the target object.

18. The method of claim 17, wherein the light captured by the detector array includes the discrete coherent light beam emitted from the laser and light emitted from the silicon melt.

19. The method of claim 18, further comprising filtering the discrete coherent light beam using a lock-in amplifier connected to the detector array.

20. The method of claim 17, wherein the determining step comprises triangulating from a first end of the target object and the reflection of the target object on the surface of the silicon melt.

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