Method and system for obtaining transient thermal response of a region of a crystal puller - Patents.com

Abstract

A system for producing silicon ingots includes a crystal puller, a pyrometer, an infrared (IR) camera, and a controller. The crystal puller includes a hot zone having one or more components therein, within which a silicon ingot can be pulled. The pyrometer is positioned to monitor a region of interest within the hot zone. The IR camera is positioned to monitor one or more additional regions of interest within the hot zone. A controller is connected to the crystal puller, the pyrometer, and the IR camera. The controller is programmed to control the crystal puller to produce the silicon ingot, to receive temperature data of the region of interest within the hot zone from the pyrometer while producing the silicon ingot, and to receive IR images of the one or more additional regions of interest from the IR camera while producing the silicon ingot.

Description

Cross-reference to application

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 200,119, filed February 16, 2021, the entire disclosure of which is incorporated herein by reference in its entirety. [Technical field]

[0002] The present disclosure relates generally to crystal pullers and the production of single crystal ingots, and more particularly to methods and systems for capturing the transient thermal response of regions within a crystal puller. [Background technology]

[0003] Single crystal ingots are produced under high temperature and vacuum conditions in a crystal puller. The temperature of the crystal, the melt that pulls the crystal, and the components within the crystal puller affect the production of silicon ingots. During the production of silicon ingots, these temperatures change in response to changing conditions and variables. Currently, there is no practical, reliable, and accurate method to measure the transient characteristics of the temperature field inside the crystal puller. In particular, there is no such method to measure the transient characteristics of the temperature field of the silicon ingot (also referred to herein as the crystal), the melt that pulls the ingot, or the surfaces within the hot zone of the crystal puller. Common contact or non-contact measurement methods have difficulty measuring the static temperature field of the crystal furnace or hot zone, much less the transient characteristics of such a temperature field.

[0004] One known method monitors the crystal surface temperature at a single selected point, for example using a pyrometer. This measurement can be used in conjunction with the crystal pulling rate to calculate the cooling and quenching rates over time. Such methods only capture the temperature at a single point and do not capture complete information about the temperature field or transient characteristics.

[0005] This background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure that are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to better understand the various aspects of the present disclosure. As such, it should be understood that these statements are to be read in this light, and not as admissions of prior art. Summary of the Invention

[0006] One aspect of the disclosure is a system for producing an ingot, the system including a crystal puller, a pyrometer, an infrared (IR) camera, and a controller. The crystal puller includes a hot zone having one or more components therein, within which a silicon ingot can be pulled. The pyrometer is positioned to monitor a region of interest within the hot zone. The IR camera is positioned to monitor one or more additional regions of interest within the hot zone. A controller is connected to the crystal puller, the pyrometer, and the IR camera. The controller is programmed to control the crystal puller to produce a silicon ingot, to receive temperature data of the region of interest within the hot zone from the pyrometer while producing the silicon ingot, and to receive IR images of the one or more additional regions of interest from the IR camera while producing the silicon ingot.

[0007] In another aspect, a system for producing silicon ingots includes a crystal puller, a pyrometer, an infrared (IR) camera, and a controller. The crystal puller includes a hot zone having a plurality of components therein, within which a silicon ingot can be pulled. The pyrometer is positioned to monitor a region of interest within the hot zone. The IR camera is positioned to monitor one or more additional regions of interest within the hot zone. The controller is coupled to the crystal puller, the pyrometer, and the IR camera. The controller is programmed to control the crystal puller to introduce a step change in a property of one or more of the plurality of components. The controller is programmed to receive one or both of temperature data of the region of interest within the hot zone from the pyrometer before, during, and after the step change to the property is introduced and / or receive IR images of the one or more additional regions of interest from the IR camera before, during, and after the step change to the property is introduced.

[0008] Another aspect of the disclosure is a method. The method includes positioning a pyrometer to monitor a region of interest within a hot zone of a crystal puller, the hot zone of the crystal puller having a first configuration including a first plurality of components therein. An infrared (IR) camera is positioned to monitor one or more additional regions of interest within the hot zone. The crystal puller is controlled to introduce a step change to a property of one or more components of the plurality of components. The method includes receiving first temperature data of the region of interest within the hot zone from the pyrometer before, during, and after the step change to the property is introduced, and / or receiving first IR images of the one or more additional regions of interest from the IR camera before, during, and after the step change to the property is introduced. At least one component within the hot zone of the crystal puller is altered to produce a second configuration of the hot zone having a second plurality of components. The crystal puller is controlled to reintroduce the step change to the property of the second configuration of the hot zone. The method includes receiving second temperature data of a region of interest within the hot zone from the pyrometer before, during, and after the incremental change to the property is reintroduced to the second configuration of the hot zone, and / or receiving second IR images of one or more additional regions of interest from the IR camera before, during, and after the incremental change to the property is reintroduced to the second configuration of the hot zone.

[0009] Various refinements exist in the features described in relation to the above aspects. Additional features may be incorporated into the above aspects as well. These refinements and additional features may exist individually or in any combination. For example, the various features described below in relation to any of the illustrated embodiments may be incorporated into the above aspects alone or in any combination. [Brief description of the drawings]

[0010] [Figure 1]FIG. 1 is a cross-sectional view of an ingot pulling apparatus that pulls a single crystal ingot from a silicon melt. [Diagram 2] FIG. 2 is a cross-sectional view of the ingot pulling apparatus. [Diagram 3] FIG. 3 is a partial front view of a single crystal silicon ingot grown by the Czochralski method. [Figure 4] FIG. 4 is a block diagram of a computing device used in the control system of the ingot pulling apparatus of FIG. [Diagram 5] FIG. 5 is an example of an image taken by the IR camera of the ingot pulling apparatus of FIG. [Figure 6] FIG. 6 is a graph of temperature profiles in the first region of the ingot pulling apparatus of FIG. 1 at three different combinations of crucible height and heater power measured with an IR camera, as well as simulated temperature profiles in the same regions and combinations. [Figure 7] FIG. 7 is a graph of the temperature profile of a second region of the ingot pulling apparatus of FIG. 1 measured using an IR camera and simulated temperature profiles for three different combinations of crucible height and heater power. [Figure 8] FIG. 8 is a graph illustrating the introduction of step changes in the power to the side and bottom heaters of an ingot puller. [Figure 9] FIG. 9 is a graph of the side heater power and the susceptor temperature as measured by the pyrometer for the step changes shown in FIG. [Figure 10] FIG. 10 is a graph of the temperature of the susceptor as measured by the pyrometer and the rate of change of the susceptor temperature during the step changes shown in FIG. [Figure 11] FIG. 11 is a graph showing a step change in the position of the susceptor (and the crucible in which it is mounted) and the temperature of the susceptor over the same time. [Figure 12] FIG. 12 is a graph of some of the data from FIG. [Figure 13]FIG. 13 is a graph of a first transient Δ1 when two different hot zones provide two different temperature settings for the ingot pulling apparatus relative to the ingot pulling apparatus of FIG. [Figure 14] FIG. 14 is a graph of the second transient Δ2 for the two different hot zones at the two different power settings used in FIG. [Figure 15] FIG. 15 is a graph of the time constant of the second transient Δ2 for the two different hot zones at the two different power settings used in FIGS.

[0011] Like reference symbols in the various drawings indicate like elements.

[0012] An ingot pulling apparatus (or more simply "ingot puller" or "crystal puller") for growing single crystal ingots is generally designated "100" in FIG. 1. The ingot pulling apparatus 100 includes a crystal puller housing 108 that defines a growth chamber 152 for pulling an ingot 113 from a melt 104 of silicon or similar semiconductor material. A control system 172 (also referred to as a "controller") controls the operation of the ingot pulling apparatus 100 and its components. The ingot pulling apparatus 100 includes a crucible 102 disposed within the growth chamber 152 for holding the silicon melt 104. The crucible 102 is supported by a susceptor 106.

[0013] The crucible 102 includes a floor 129 and a sidewall 131 extending upwardly from the floor 129. The sidewall 131 is generally vertical. The floor 129 includes a curved portion of the crucible 102 that extends below the sidewall 131. Within the crucible 102 is a silicon melt 104 having a melt surface 111 (i.e., a melt-ingot interface). A susceptor 106 is supported by a shaft 105. The susceptor 106, crucible 102, shaft 105, and ingot 113 have a common longitudinal axis A or "pull axis" A.

[0014] Disposed within the ingot pulling apparatus 100 is a pulling mechanism 114 for growing and pulling an ingot 113 from the melt 104. The pulling mechanism 114 includes a pulling cable 118, a seed holder or chuck 120 coupled to one end of the pulling cable 118, and a seed crystal 122 coupled to the seed holder or chuck 120 for initiating crystal growth. One end of the pulling cable 118 is connected to a pulley (not shown) or drum (not shown) or other suitable type of lifting mechanism, such as a shaft, and the other end is connected to the chuck 120 which holds the seed crystal 122. In operation, the seed crystal 122 is lowered into contact with the melt 104. The pulling mechanism 114 is operated to raise the seed crystal 122, thereby pulling the single crystal ingot 113 from the melt 104.

[0015] During heating and crystal pulling, a crucible drive unit 107 (e.g., a motor) rotates the crucible 102 and susceptor 106. A lift mechanism 112 raises and lowers the crucible 102 along pull axis A during the growth process. As the ingot grows, the silicon melt 104 is consumed and the melt height in the crucible 102 decreases. The crucible 102 and susceptor 106 can be raised to maintain the melt level 111 at or near the same position relative to the ingot pulling apparatus 100.

[0016] The crystal drive unit (not shown) can also rotate the pulling cable 118 and ingot 113 in a direction opposite (e.g., counter-rotation) from the direction that the crucible drive unit 107 rotates the crucible 102. In embodiments using equal rotation, the crystal drive unit can rotate the pulling cable 118 in the same direction that the crucible drive unit 107 rotates the crucible 102. Additionally, the crystal drive unit raises and lowers the ingot 113 relative to the melt level 111 as needed during the growth process.

[0017] The ingot pulling system 100 may include an inert gas system for introducing and withdrawing an inert gas, such as argon, from the growth chamber 152. The ingot pulling system 100 may also include a dopant supply system (not shown) for introducing dopants into the melt 104.

[0018] According to the Czochralski single crystal growth process, a quantity of polycrystalline silicon, or polysilicon, is loaded into a crucible 102 (e.g., a load of 250 kg or more). A variety of sources of polycrystalline silicon can be used, such as, for example, granular polycrystalline silicon produced by pyrolysis 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 generally above the melting temperature of silicon (e.g., about 1412° C.) to melt the charge. 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 puller 100 includes bottom insulation 110 and side insulation 124 to retain heat within the puller 100. In the illustrated embodiment, the ingot pulling apparatus 100 includes a bottom heater 126 disposed below the crucible floor 129. The crucible 102 may be moved relatively close to the bottom heater 126 to melt the polycrystal loaded into the crucible 102.

[0019] To form an ingot, the seed crystal 122 is contacted with the 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 portion 142 where the ingot transitions and tapers outward from the seed crystal 122 to reach a target diameter. The ingot 113 includes a constant diameter portion 145 or cylindrical "body" of the crystal that is grown by increasing the pulling rate. The body 145 of the ingot 113 has a relatively constant diameter. The ingot 113 includes a tail or end cone (not shown) where the diameter of the ingot tapers after the body 145. Once the diameter is sufficiently small, the ingot 113 is separated from the melt 104. The ingot 113 has a central longitudinal axis A that extends through the crown portion 142 and the terminal end of the ingot 113.

[0020] The ingot pulling apparatus 100 includes a side heater 135 and a susceptor 106 that surrounds the crucible 102 to maintain the temperature of the melt 104 during crystal growth. The side heater 135 is positioned radially outward relative to the crucible sidewall 131 as the crucible 102 moves up and down the pull axis A. The side heater 135 and the bottom heater 126 may be any type of heater that allows the crucible 102 to operate as described herein. In some embodiments, the heaters 135, 126 are resistive heaters. The side heater 135 and the bottom heater 126 may be controlled by a control system 172 such that the temperature of the melt 104 is controlled throughout the pulling process.

[0021] The ingot pulling apparatus 100 also includes a reflector 151 (or "heat shield") disposed within the growth chamber 152 over the melt 104 that covers the ingot 113 during ingot growth. The reflector 151 may be disposed partially within the crucible 102 during crystal growth. The heat shield 151 defines a central passage 160 for receiving the ingot 113 as it is pulled by the pulling mechanism 114.

[0022] The reflector 151 is generally a heat shield adapted to retain heat beneath it and above the melt 104. Any reflector design and material of construction known in the art (e.g., graphite or gray quartz) may be used in this regard without limitation. The reflector 151 has a bottom 138 (FIG. 2), which is spaced a distance HR from the surface of the melt during ingot growth.

[0023] The pyrometer 174 and infrared (IR) camera 176 are positioned to view selected areas of the hot zone (i.e., the lower portion of the growth chamber 152, such as the crucible 102 and susceptor 106), the crystal ingot 113, or the melt 104 during the production of the silicon crystal ingot. Collectively, the pyrometer 174 and the IR camera 176 may be referred to herein as a temperature monitoring system.

[0024] The pyrometer 174 is typically selected to have the capability to measure temperatures over the temperature range desired to be monitored by the pyrometer. As an example, the pyrometer 174 is capable of measuring temperatures from 700° C. to 3500° C. In another example, the pyrometer 174 can measure temperatures from 200° C. to 1400° C. In these examples, the pyrometer may include two different sensors, one that measures temperature and one that measures emissivity. Other embodiments may include a pyrometer camera 174 operable to measure temperatures over any other suitable temperature range, including a wider or narrower temperature range.

[0025] The IR camera 176 is also typically selected for its ability to measure temperatures within the range of temperatures monitored by the IR camera 176. As an example, the IR camera 176 may measure temperatures from 600° C. to 1600° C. In another embodiment, the IR camera 176 may measure temperatures from 800° C. to 3000° C. Other embodiments may include an IR camera 176 operable to measure temperatures over any other suitable temperature range, including a wider or narrower temperature range.

[0026] The pyrometer 174 is mounted on top of the puller 100 and aligned along the central axis A of the crystal puller 100 and ingot 113. In the illustrated embodiment, the pyrometer 174 is mounted on a portion of the pulling mechanism 114. From this position, the pyrometer 174 can monitor at least a portion of the susceptor 106, the melt level 111, the crystal ingot 113, and the reflector 151. Portions of the crystal puller 100 may obstruct the view of the pyrometer 174 during operation. Thus, the pyrometer may be aimed at the location to be monitored during the crystal pulling operation and re-aimed as needed.

[0027] The IR camera 176 is positioned to view the interior of the growth chamber 152 through a viewport 178, which may be an operator's viewport or any other portion through which IR light passes. The IR camera 176 may view the melt 104, the surface of the crystal ingot 113, and at least a portion of the reflector 151 through the viewport 178. In an exemplary embodiment, the IR camera 176 captures images in the near infrared wavelength range of about 780 nm to 1080 nm. In other embodiments, images of any other suitable infrared wavelength or infrared wavelength range may be captured by the IR camera 176. In an exemplary embodiment, the IR camera 176 is mounted on a three-axis geared camera head (not shown) such that the IR camera can be adjusted to a desired position and held in that position at all times or moved to a desired position consistently and repeatedly. In some embodiments, the IR camera 176 and the pyrometer 174 may be calibrated to align a common area monitored by both the IR camera 176 and the pyrometer 174.

[0028] A single crystal silicon ingot 113 produced according to an embodiment of the present disclosure and generally in accordance with the Czochralski process is shown in Figure 3. The ingot 113 includes a neck 116, an outwardly flaring portion 142 (synonymously "crown" or "cone"), a shoulder 119, and a body 145 of constant diameter. The neck 116 is attached to a seed crystal 122 which is contacted with the melt and pulled to form the ingot 113. The body 145 is suspended from the neck 116. The neck 116 ends when the cone portion 142 of the ingot 113 begins to form.

[0029] 3, the constant diameter portion 145 of the ingot 113 has a perimeter 150. A central axis A is parallel to the perimeter 150, and a radius R extends from the central axis A to the perimeter 145. The central axis A also passes through the cone section 142 and the neck 116. The diameter of the main ingot body 145 (i.e., twice the radius R) 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 even greater than about 450 mm.

[0030] The single crystal silicon ingot 113 can generally have any resistivity. The single crystal silicon ingot 113 can be doped or undoped.

[0031] 4 is an example of a computing device 400 that can be used as or as part of the control system 172. The computing device 400 includes a processor 402, a 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 of the components shown in FIG. 4. Furthermore, some embodiments include a computing device 400 separate from (or in addition to) the control system 172. The separate computing device 400 can be used, for example, to receive and process data (e.g., obtained using the techniques described herein), perform crystal pulling simulations, and adjust simulation parameters based on the received data.

[0032] The processor 402 is configured to execute instructions. In some embodiments, the executable instructions are stored in the 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 other circuits or processors capable of performing the functions described herein. The above are merely examples and are not intended to limit in any way the definition and / or meaning of the term "processor."

[0033] The memory 404 stores non-transitory computer-readable instructions for carrying out the techniques described herein. Such instructions, when executed by the processor 402, cause the processor 402 to carry out at least a portion of the methods 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 input from the input device 408. The 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 shown separately from the processor 402, in some embodiments the memory 404 is combined with the processor 402, such as in a microcontroller or microprocessor, but may still be referred to individually. The types of memory listed above are examples and are not intended to limit the types of memory that may be used to store computer programs.

[0034] The media output component 406 is configured to present information to a user (e.g., an operator of the system). The media output component 406 is any component capable of conveying information to a user. In some embodiments, the 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 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., speakers or headphones).

[0035] 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 input from a user, including visual, voice, touch, button presses, stylus taps, and the like. 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, such as a touch screen, may also function as an output device for both the media output component 406 and the input device 408.

[0036] The communication interface allows the computing device 400 to communicate with remote devices and systems, such as remote sensors, remote databases, remote computing devices, and may include multiple communication interfaces to communicate with multiple remote devices or systems. 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 over a network. The wireless communication interface may include a radio frequency (RF) transceiver, a Bluetooth adapter, a Wi-Fi transceiver, a ZigBee transceiver, a near field communication (NFC) transceiver, an infrared (IR) transceiver, and / or any other device and communication protocol for wireless communication. (Bluetooth is a registered trademark of Bluetooth Special Interest Group, Kirkland, Washington, and ZigBee is a registered trademark of the ZigBee Alliance, San Ramon, California). The wired communication interface may use any suitable wired communication protocol for direct communication, including, but not limited to, USB, RS232, I2C, SPI, analog, and proprietary I / O protocols. In some embodiments, the wired communication interface includes a wired network adapter that enables the computing device 400 to be coupled to a network, such as the Internet, a local area network (LAN), a wide area network (WAN), a mesh network, and / or any other network for communicating with remote devices and systems via the network.

[0037] The computer systems described herein may include additional, less, or alternative functionality, including those described elsewhere herein. The computer systems discussed herein may include or be implemented via computer-executable instructions stored on a non-transitory computer-readable medium or media.

[0038] The IR camera 176 and pyrometer 174 are used to continuously monitor the surface temperature of selected portions of the hot zone, crystal, or melt. The monitored temperatures can be used to monitor the temperature of areas of interest during the silicon ingot 113 pulling process. These monitored temperatures are compared to simulated temperatures and used to calibrate and improve the crystal pulling process simulation. Additionally, in some embodiments, a step change or a series of step changes can be introduced at selected process conditions such as heater 135 and 126 power, crucible 102 position, and reflector 151 position while capturing the temperature of selected areas using the IR camera 176 and pyrometer 174. In doing so, the transient characteristics of the temperature field caused by the step changes can be captured and compared across different hot zones and processes. This includes, but is not limited to, the surface temperature changes induced at certain predefined locations by radiative and conductive heating or cooling effects from key hot zone components. Quantifying these transient characteristics can aid in the design of efficient hot zone and crystal processes.

[0039] 5 is an example of an image 500 captured by the IR camera 176. Three regions of interest are marked in the image 500. The first region 502 is the center of the susceptor 106. The second region 504 is a part of the reflector 151, e.g., a notch in the reflector 151. The third region 506 is a linear region connecting the first region 502 and the outer edge of the susceptor 106. Temperature and gradient profiles of the regions of interest (e.g., the first region 502, the second region 504, and the third region 506) can be extracted from the image captured by the IR camera 176 (example image 500).

[0040] With reference to Figures 6 and 7, the data collected from the IR camera 176 and pyrometer 174 can be used to provide a calibration basis for the thermal simulation, improving its accuracy and reducing error from input properties such as the thermal conductivity of the hot zone material. Figure 6 is a graph of the temperature profile of a first region 502 (i.e., the center of the susceptor 106 - shown in Figure 5) measured by the IR camera 176 at three different combinations of crucible 102 height and heater 135, 126 power, as well as the simulated temperature profile for the same region and combination. Figure 7 is a graph of the temperature profile of a second region 504 (i.e., a portion of the reflector 151 - shown in Figure 5) measured by the IR camera 176 at three different combinations of crucible 102 height and heater 135, 126 power, as well as the simulated temperature profile for the same region and combination. Looking at Figures 6 and 7, it can be seen that the temperature profile measured by the IR camera 176 closely follows the trend of the simulated temperature profile, but shows certain deviations. Therefore, by using the data obtained from the IR camera 176, such biases can be eliminated or reduced by modifying the input characteristics while performing a calibration on the temperature profile measured by the IR camera 176. As a result, a more accurate simulated temperature profile can be produced as needed.

[0041] While the data described above was obtained using IR camera 176, the same techniques can be applied to data obtained using pyrometer 174. IR camera 176 and pyrometer 174 may be used to capture temperature data for the same point on the crystal puller 100, or each may capture data for different points on the crystal puller. In some embodiments, IR camera 176 is used to capture the temperature of multiple selected spots over a period of time or short periods of time, and pyrometer 174 is used to capture the temperature of one particular spot over a relatively long period of time. Additional examples are described below with reference to temperature data obtained by pyrometer 174, although similar data may be obtained using IR camera 176 (additionally or alternatively) and used for similar purposes.

[0042] The temperature monitoring system may be used to monitor temperature transients within the crystal puller 100 in response to step changes in one or more variables of the operation of the crystal puller 100. That is, one or both of the IR camera 176 and pyrometer 174 may collect temperature data of regions of interest within the crystal puller 100 while a control variable of the crystal puller 100 (such as crucible height, power to various heaters, etc.) is purposefully changed by known amounts. The techniques described below may be performed with or without silicon in the crucible and during crystal growth.

[0043] 8, 9 and 10, a step change in the power of the heaters 135, 126 is introduced while the pyrometer 174 measures the temperature of the susceptor 106. FIG. 8 is a graph showing a step change in the power of the side heater 135 and the bottom heater 126 is introduced at about 260 minutes. The side heater power is increased from 0 kW to 60 kW and the bottom heater power is increased from 0 kW to 5 kW. FIG. 9 is a graph of the side heater power and the temperature of the susceptor 106 measured by the pyrometer 174. The pyrometer 174 used in this example had a low temperature detection threshold of 700° C., so no temperature data below 700° C. is obtained. Other embodiments can include a pyrometer 174 with a temperature detection threshold lower than 700° C., allowing for the acquisition of additional temperature data. FIG. 10 is a graph of the temperature of the susceptor 106 measured by the pyrometer 174 and the rate of change of the temperature of the susceptor 106. As shown in Figure 10, in this particular crystal puller 100 (using the particular heaters 126, 135, the particular susceptor 106, and other particular components of the puller 100), the time constant of the temperature transient caused by a step change in side heater power from 0 kW to 60 kW and bottom heater power from 0 kW to 5 kW is 900 minutes or 15 hours, as shown by the decay of the temperature change rate. Thus, from the results shown in Figure 10, it can be seen that this particular change (and no other changes) will take approximately 15 hours to reach a substantially steady state. Furthermore, the particular temperature at any time within that 15 hour period can be calculated and predicted based on the decay of the temperature change rate.

[0044] Another application of the temperature monitoring system is shown in Figures 11-14. In this application, the susceptor 106 is raised in a stepwise manner at four hour intervals, closer to the reflector 151 and cooling jacket (not shown), which are the heat shield and active cooling device of the hot zone. The stepwise change in the position of the susceptor 106 (determined by the position of the crucible 102 in which the susceptor 106 is mounted) is shown in Figure 11. Figure 11 also shows the monitored temperature of the susceptor 106, monitored by the pyrometer 174, during the period including the stepwise change in the position of the susceptor 106. The area 1200 in Figure 11 is expanded in Figure 12. As shown in Figure 11, the stepwise change generates two temperature transients at each step, which are explained in detail in Figure 12. T1 and T2 in Figure 12 are the temperatures of the susceptor at the end of each transient and also at the start of the next transient. Δ1 and Δ2 are the differences in the susceptor temperature at the start and end of each transient. In each step change, the susceptor 106 approaches the cooling jacket and the reflector 151, and the temperature transient of the susceptor 151 is caused by the cooling effect from the cooling jacket and the radiation shielding effect from the reflector 151. By measuring the time constants of Δ1 and Δ2, the transient characteristics caused by moving the susceptor 106 toward these two parts can be captured.

[0045] By comparing such transient characteristics between different hot zone designs, one can determine which design can achieve the desired efficiency. For example, the above measurements were performed at two different power settings for two different hot zones, respectively. Figure 13 is a graph of Δ1 for two different hot zones (LH - long heater configuration, SH - short heater configuration) at two different temperature settings (60 kW side heater power and 5 kW bottom heater power, and 90 kW side heater power and 5 kW bottom heater power). As can be seen, the SH configuration has a larger effect at higher crucible positions, but has a smaller effect at crucible positions below 225 mm. The other temperature transients in each step change are caused by nearby hot zone components such as reflectors and side insulation. The change in temperature and position of the susceptor 106 in the first transient Δ1 causes temperature changes in the hot zone components near them through a combination of radiation and conduction. The second transient Δ2 is the result of these components reaching temperature equilibrium and again affecting the temperature of the susceptor 106. That is, Δ2 is the change in temperature when the hot zone components stabilize (e.g., reach equilibrium or steady state) after introducing a step change at a fixed position while the crucible 102 is held at a fixed position. FIG. 14 is a graph of Δ2 for two different hot zones at two different power settings. As can be seen, the SH configuration has a larger impact at all positions of the crucible and at both power settings. The second transient Δ2 is caused by the hot zone components stabilizing in temperature, so its time constant (e.g., duration of the transient) is longer, reflecting the thermal characteristics of the associated hot zone components. FIG. 15 is a graph of the time constant Δ2 for two different hot zones at two different power settings. As shown in FIG. 15, the SH configuration has a longer transient time at all positions of the crucible 102. In each configuration (SH or LH), the time constant is substantially the same at the different power settings. This indicates that the power settings of the heaters 126, 135 do not significantly affect the thermal properties of the materials that govern this transient.

[0046] While the above has been described with reference to stepwise changes in the position of the susceptor 106 (and the crucible 102 to which it is attached), the techniques described above can be applied to any operational setting that involves movements, stepwise changes, or significant changes to any component of the hot zone or that may affect the temperature field. This process can be used to compare different changes that affect the same hot zone, or to compare different hot zones. Additionally, while the above description relied on temperature measurements from a pyrometer, temperature measurements from an IR camera (e.g., measuring areas of interest not visible from a pyrometer, or measuring larger areas of interest or temperature gradients) may be used as well. Thus, these techniques are useful for evaluating the capabilities of the hot zone and the crystal growth process.

[0047] The logic flows depicted in the figures do not require any particular order or sequential order to achieve desirable results. Additionally, other steps may be added to or removed from the described flows, and other components may be added or removed from the described systems. Accordingly, other embodiments are within the scope of the following claims.

[0048] It will be understood that the above embodiments, particularly those described in detail, are merely exemplary or possible embodiments, and that many other combinations, additions, or alternatives are possible.

[0049] Also, the particular naming of components, capitalization of terms, attributes, data structures, or other programming or structural aspects are not required or important, and the mechanisms for implementing the disclosure or its functionality may have different names, formats, or different protocols. Furthermore, the system may be implemented using a combination of hardware and software as described, or may be implemented entirely with hardware elements. Also, the particular division of functionality between various system components described herein is merely exemplary 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.

[0050] Approximate language as used herein throughout the specification and claims may be applied to modify any quantitative expression that may vary acceptably without resulting in a change in the basic function to which it pertains. Thus, values ​​modified with terms such as "about" or "substantially" are not limited to the exact value specified. In at least some instances, the approximation language may correspond to the precision of an instrument for measuring the value. Throughout the specification and claims, range limitations may be combined and / or interchangeable, and such ranges are specified and include all subranges contained therein, unless the context or language indicates otherwise.

[0051] Various changes, modifications, and alterations in the teachings of the present disclosure may occur to those skilled in the art without departing from the intended spirit and scope thereof, and the present disclosure is intended to cover such changes and modifications.

[0052] This specification uses examples to explain the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems, and performing any methods incorporated therein. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those 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 that do not differ substantially from the literal language of the claims.

Claims

1. Positioning a pyrometer to monitor an area of ​​interest within a hot zone of a crystal puller; the hot zone of the crystal puller having a first configuration including a first plurality of components therein; positioning an infrared (IR) camera within the hot zone to monitor one or more additional target areas; controlling the crystal puller to introduce a gradual change in a property of one or more components of the plurality of components; One or both of the following: receiving first temperature data from the pyrometer of the area of ​​interest within the hot zone before, during and after the step change in property is introduced; and, receiving a first IR image of the one or more additional target regions from the IR camera before, during and after the gradual change in the property is introduced; To carry out modifying at least one component within the hot zone of the crystal puller to produce a second configuration of the hot zone having a second plurality of components; controlling the crystal puller to reintroduce the step change in the property of the second configuration of the hot zone; and One or both of the following: receiving second temperature data from the pyrometer of the area of ​​interest within the hot zone before, during and after the graded change in property is reintroduced to the second configuration of the hot zone; and, receiving a second IR image of the one or more additional target areas from the IR camera before, during and after the gradual change in property is reintroduced into the second configuration of the hot zone; To carry out The method includes:

2. Additionally, the computing device may be used to The first temperature data and the second temperature data; the first IR image and the second IR image; or the first temperature data, the second temperature data, the first IR image, and the second IR image; and comparing thermal characteristics of the first configuration of the hot zone to the second configuration of the hot zone. The method of claim 1.

3. selecting the first configuration of the hot zone or the second configuration of the hot zone as having preferred thermal characteristics. The method of claim 2.

4. and controlling the crystal puller to produce a silicon ingot having a selected one of the first configuration of the hot zone or the second configuration of the hot zone. The method according to claim 3.

5. the one or more components within the hot zone include a susceptor, a reflector, a crucible, a side heater, a bottom heater, and a cooling jacket; When a silicon ingot is being produced, the silicon melt in the crucible and the silicon ingot being drawn from the silicon melt are included. The method of claim 1.

6. the target area within the hot zone includes a portion of the susceptor or a portion of a surface of the silicon melt; The method according to claim 5.

7. The one or more additional target areas are selected from a portion of the reflector, a portion of the silicon ingot, and a portion of a surface of the silicon melt. The method according to claim 5.

8. The gradual change in the characteristic of the one or more components may include: A stepwise change in the position of the crucible; A stepwise change in the position of the susceptor; a step change in power output of the side heater; a step change in power output of the bottom heater; A stepwise change in the position of the reflector; A stepwise change in the position of the cooling jacket; and changing the position of the side heater or the bottom heater; The method according to claim 5.

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