JP2018115102A - Method and apparatus for manufacturing single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for manufacturing a single crystal by the Czochralski method, capable of suppressing rapid variation of diameter measurement data generated when switching cameras, preventing unintended diameter control processing from being performed and preventing defective pulling from occurring.SOLUTION: A method for manufacturing a single crystal can control the diameter of a cone part 13 on the basis of a measured value while measuring the diameter value of the cone part 13 during diameter expansion by a camera so as to grow the single crystal. A first camera 9a that can measure the diameter of the cone part 13 until the diameter value of the cone part 13 reaches a predetermined value from when the diameter starts to expand, and a second camera 9b that can measure the diameter of the cone part 13 after the diameter of the cone part 13 reaches the predetermined value are placed so that parts of visual field ranges overlap each other. In the step of forming the cone part 13, switching processing for converging a value measured by the first camera 9a on a value measured by the second camera 9b is performed while the outer peripheral end of the cone part 13 is positioned within the overlapped visual field ranges during the diameter expansion.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a single crystal manufacturing method and a single crystal manufacturing apparatus.

  Many silicon single crystals are manufactured by pulling by the Czochralski method (CZ method). An example of an apparatus used for manufacturing a silicon single crystal by the CZ method is shown in FIG. 6 includes a chamber 101, a crucible 102 having a double structure of an inner quartz crucible and an outer graphite crucible, a crucible holding shaft 105 for holding the crucible 102, and a heater provided on the outer periphery of the crucible 102. 103, a heater heat insulating material 104 provided on the outer periphery of the heater 103, a seed chuck 107 for holding the seed crystal 111 and a wire 108 for pulling up the seed chuck 107 provided on the same axis as the crucible holding shaft 105. The The crucible holding shaft 105 has a mechanism part for rotating and raising and lowering the crucible 102, and the wire 108 has a mechanism part for winding, lowering, and rotating the seed chuck 107. As for the operation of each mechanism unit, preset control setting data is sent from the external system to the diameter control unit 110, and the diameter control unit 110 applies the respective mechanism units of the crucible holding shaft 105 and the wire 108 based on the control setting data. The drive command signal is controlled by outputting a heating command signal to the heater 103.

  Next, a method for manufacturing a silicon single crystal using the silicon single crystal manufacturing apparatus 120 will be described. First, a high-purity silicon polycrystal is accommodated in the crucible 102, and this is heated and melted to about 1420 ° C., which is the melting point of silicon, with a heater 103 to obtain a silicon melt 106. Next, the wire 108 is wound down to bring the tip of the seed crystal 111 held on the seed chuck 107 into contact with the liquid surface of the silicon melt 106. Thereafter, the wire 108 is wound at a predetermined speed while the crucible holding shaft 105 and the wire 108 are rotated at a predetermined rotation direction and rotation speed, respectively, and the seed crystal 111 is pulled up, whereby the silicon single crystal 112 is placed under the seed crystal 111. Is formed. When the silicon single crystal 112 is grown, the diameter of the silicon single crystal 112 is gradually increased by expanding the diameter of the silicon single crystal 112 after forming a constricted portion for making the crystal dislocation-free by reducing the diameter of the silicon single crystal 112 and pulling it up. ), The cone portion is formed and enlarged to a desired diameter, and then the straight barrel portion is formed by pulling up while maintaining the diameter.

  In the single crystal manufacturing method described above, it is important to stably manufacture a silicon single crystal having a desired diameter in order to prevent production loss and increase product yield. Therefore, during the pulling of the single crystal, as shown in FIG. 6, the diameter of the silicon single crystal 112 being formed is usually measured by a camera 109 such as a CCD camera (Charge Coupled Device Camera) fixed to the chamber viewing window. By controlling the winding speed of the wire 108, the rising speed of the crucible 102, and the heating temperature by the heater 103 in accordance with the values, control to achieve a desired crystal diameter (hereinafter, diameter control) is performed.

  A single crystal diameter measurement method using a CCD camera, which is performed in diameter control, will be described. The CCD camera takes a picture of a high-luminance annular portion (hereinafter referred to as meniscus ring) seen at the interface between the silicon single crystal and the silicon melt in the furnace. The position of the meniscus ring is measured from the photographed image with an image processing device, and the measured value of the diameter of the silicon single crystal is calculated based on information such as the angle at which the camera is attached and the distance between the silicon single crystal and the camera. . In addition, since the silicon single crystal is formed in a cylindrical shape centered on the seed crystal, the distance from the center of the silicon single crystal to the meniscus ring, that is, the radial length can be measured, and the camera field of view is adjusted to obtain the obtained radial length. The diameter value can also be measured by doubling the thickness.

  In order to perform the diameter control with high accuracy, the diameter data obtained by the diameter measurement using the camera needs to be highly accurate.

  As the crystal diameter increases in recent years, the field of view required for a camera that images a silicon single crystal needs to be widened according to the crystal diameter. Since it becomes difficult to read the change of the crystal diameter from the photographed image, the accuracy of the crystal diameter data is lowered as a result, and the diameter control with high accuracy cannot be performed.

  On the other hand, Patent Document 1 discloses a method of installing a camera for measuring the diameter of the straight body part and a camera for measuring the diameter of the cone part, and an imaging range for detecting the diameter of the cone part. A method is disclosed in which two cameras are installed in two, and the cameras are switched during the formation of the cone portion. It is said that the diameter can be measured with high accuracy by using two cameras having a narrow field-of-view range for measuring the diameter of a large-diameter silicon single crystal.

  FIG. 7 shows details of a general cone diameter measuring method performed using two cameras. In FIG. 7, two cameras A and B are installed as cameras for crystal diameter measurement. At this time, the two camera fields of view do not overlap each other, and by combining the two camera fields of view, the entire cone radius (X to X ″ in FIG. 7) can be captured. In Fig. 7, as an example, the camera A has a field of view (X to X 'in Fig. 7) in which imaging and diameter measurement can be performed in the first half of cone formation, and the camera B is in the second half of cone formation. It was set as the visual field (X'-X "of FIG. 7) which can measure a diameter. In the first half of the cone portion formation, measurement is performed using a camera A that can image the crystal at that time. When the cone portion grows beyond the visual field range of camera A and imaging becomes possible within the visual field range of camera B, the camera used for measurement is switched from camera A to B. The diameter value (radius × 2) of the entire cone portion can be obtained by combining the measurement data of the visual field range that can be captured by each of the cameras A and B.

JP 2010-100452 A

  However, the diameter measurement method using the camera is a method in which the diameter value is calculated on the assumption that the camera is fixed at a predetermined position and angle and the melt surface position is a predetermined position. Therefore, when there is a difference in the position and angle of the camera, or when the melt surface position during crystal pulling is different from the predetermined position, different measurement results are shown.

  Therefore, in particular, in the cone diameter measuring method using two cameras, the difference between the measured values of the cameras A and B at the time of the camera switching process (X ′ in FIG. 7) (hereinafter also referred to as measurement deviation). Therefore, the diameter data has a sudden change in the measured value before and after switching. Ideally, there is no measurement deviation between the cameras A and B at the time of the switching process, but this measurement method is performed after the cameras are installed at different positions and angles. The appearance of the silicon single crystal in the range and the measurement result thereof are different, and a measurement deviation always occurs. In particular, it is difficult to cope with a measurement deviation caused by a change in the melt surface position that occurs during crystal production because it is difficult to predict the occurrence.

  Therefore, conventionally, in the cone diameter measurement method using two cameras, there is a problem that a sudden change in the diameter measurement data generated at the time of camera switching occurs due to a measurement deviation that is difficult to resolve. When this data is applied to diameter control, there is a problem that unintended diameter control processing is performed and pulling defects such as dislocation of single crystals occur.

  The present invention has been made in view of the above-described problems, and suppresses a sudden change in diameter measurement data that occurs at the time of camera switching, thereby preventing unintended diameter control processing from being performed and causing a pulling failure. An object of the present invention is to provide a single crystal manufacturing method and a single crystal manufacturing apparatus capable of preventing the above.

  In order to achieve the above object, the present invention provides a method for pulling a seed crystal that has been deposited on the silicon melt in a Czochralski method for pulling a single crystal from a silicon melt accommodated in a crucible. In the cone portion forming step of expanding the single crystal to form a cone portion, while measuring the diameter value of the cone portion during diameter expansion with a camera, the cone portion is measured based on the measured value of the diameter value. A single crystal manufacturing method for controlling and growing a diameter, wherein the first camera is capable of measuring the diameter value of the cone portion from the start of diameter expansion until the diameter value of the cone portion reaches a predetermined value in advance. And a second camera capable of measuring the diameter value of the cone portion after the diameter value of the cone portion reaches the predetermined value, a part of the visual field range on the silicon melt surface overlaps each other Install the In the step of forming the cone portion, the measured value of the diameter of the cone portion obtained from the first camera while the outer peripheral end of the cone portion being expanded is located within the overlapping visual field range, By performing a switching process for converging on the measured value of the cone part diameter obtained from the second camera, the measured value used for controlling the diameter of the cone part is obtained from the measured value obtained from the first camera. The method for producing a single crystal is characterized by switching to the measured value obtained from the second camera.

  With the single crystal manufacturing method of the present invention, it is possible to measure the diameter value with high accuracy by two cameras, and to measure the diameter of the single crystal by the camera by performing the switching process as described above when switching the cameras. Since the value does not fluctuate abruptly, it is possible to prevent unintended diameter control processing from being performed and to prevent a pulling failure.

  At this time, in the cone portion forming step, the measured value obtained from the first camera is set at a predetermined position within the visual field range where the outer peripheral end of the cone portion during the diameter expansion overlaps from the start of the diameter expansion. The diameter of the cone part is controlled as the diameter value of the cone part until it reaches, and after the outer peripheral end of the cone part reaches the predetermined position, the measurement obtained from the first camera by the switching process The diameter of the cone part is controlled as the diameter value of the cone part, and the measurement value during the switching is sequentially calculated so that the value is gradually approximated to the measurement value obtained from the second camera. After the value becomes equal to the measured value obtained from the second camera, the diameter of the cone part is controlled using the measured value obtained from the second camera as the diameter value of the cone part. Door is preferable.

  As described above, since the change process of the diameter used for the control can be surely moderated by using the switching intermediate value in the switching process of the camera used for the diameter control, the unintended diameter control process can be performed. Implementation can be prevented and occurrence of pulling defects can be reliably prevented.

At this time, the switching-in-progress value measurement, the switch in the measurement d _m, the first the measurement values obtained from the camera d _t1, the second the measurement values obtained from the camera d _t2, The elapsed time from when the outer peripheral end of the cone portion reaches the predetermined position is t, and the measured value during switching is obtained from the second camera from when the outer peripheral end of the cone portion reaches the predetermined position. It can be sequentially calculated by the following formula 1 when the time until the same value as the measured value is t _c .
d _m = d _t1 + {(d _t2 −d _t1 ) × (t / t _c )} Equation 1
(However, t satisfies 0 ≦ t ≦ t _c .)

  By sequentially calculating the measurement value during switching so as to satisfy the above-mentioned formula 1 and using it as the measurement value for diameter control during camera switching, it is possible to reliably moderate the variation in the measurement value of the diameter used for control. it can.

  Moreover, it is preferable to expand the cone portion so that the maximum diameter becomes 200 mm or more.

  The present invention can reliably prevent the occurrence of pulling failure in pulling a large-diameter single crystal that often requires two such cameras.

  In order to achieve the above object, the present invention provides a crucible for storing a silicon melt and a diameter value of a cone portion of a single crystal that is expanded while pulling up a seed crystal that has been applied to the silicon melt. A single crystal manufacturing by the Czochralski method having a function of measuring a diameter value of the cone part with the camera and having a function capable of controlling the diameter of the cone part based on the measured value of the diameter value A first camera capable of measuring a diameter value of the cone part from the start of diameter expansion until the diameter value of the cone part reaches a predetermined value; and the diameter value of the cone part is the predetermined value A second camera capable of measuring the diameter value of the cone part after reaching the value, and the cone part being expanded in diameter, installed so that part of the visual field range on the silicon melt surface overlaps each other The outer peripheral edge of the A switching processing function for converging the measured value of the diameter of the cone obtained from the first camera to the measured value of the diameter of the cone obtained from the second camera. The measurement value used for controlling the diameter of the cone portion is switched from the measurement value obtained from the first camera to the measurement value obtained from the second camera by the switching processing function. A single crystal production apparatus characterized by the above is provided.

  The single crystal manufacturing apparatus of the present invention can measure the diameter value with high accuracy by two cameras, and by performing the switching process as described above when switching the camera, the measured value of the diameter of the single crystal by the camera can be obtained. Since it does not fluctuate rapidly, it is possible to prevent unintended diameter control processing from being performed and to prevent the occurrence of pulling failure.

  At this time, the single crystal manufacturing apparatus of the present invention is either one of the measurement value of the diameter of the cone portion obtained from the first camera and the measurement value of the diameter of the cone portion obtained from the second camera, or From both, it comprises a diameter control unit for controlling the diameter of the cone part, the diameter control part has the switching processing function, the measured value of the diameter of the cone part obtained from the first camera, The diameter of the cone portion is controlled as the diameter value of the cone portion from the start of the diameter expansion until the outer peripheral end of the cone portion being expanded reaches the predetermined position within the overlapping visual field range, After the outer peripheral edge of the cone portion reaches, the measured value obtained from the first camera is gradually changed to the measured value of the diameter of the cone portion obtained from the second camera by the switching processing function. Get closer After the sequentially calculated measurement value during switching, the diameter of the cone part is controlled as the diameter value of the cone part, and after the measurement value during switching becomes the same value as the measurement value obtained from the second camera, The diameter of the cone portion is preferably controlled using the measured value obtained from the second camera as the diameter value of the cone portion.

  In the case of a single crystal manufacturing apparatus having such a diameter control unit, the switching process of the camera used for diameter control uses the above-mentioned switching intermediate value, so that the fluctuation of the measured value of the diameter used for the control is surely moderated. Therefore, it is possible to prevent unintentional diameter control processing from being performed, and to reliably prevent the occurrence of pulling failure.

Further, the diameter control unit, the switching during measurement, the switch in the measurement d _m, the measurements obtained from the first camera d _t1, the measurement values obtained from said second camera D _t2 , t is an elapsed time from when the outer peripheral end of the cone portion reaches the predetermined position, and the measured value during switching from the time when the outer peripheral end of the cone portion reaches the predetermined position is the second value. It is preferable that the time until the measurement value obtained from the camera is equal to the measured value is sequentially calculated by the following formula 1 where t _c is used.
d _m = d _t1 + {(d _t2 −d _t1 ) × (t / t _c )} Equation 1
(However, t satisfies 0 ≦ t ≦ t _c .)

  The single crystal manufacturing apparatus of the present invention uses the diameter used for control by sequentially calculating the measurement value during switching so that the diameter control unit satisfies the above-mentioned formula 1, and using it as the measurement value for diameter control during camera switching. The fluctuation of the measured value can be surely moderated to prevent the occurrence of a pulling failure.

  With the single crystal manufacturing method and single crystal manufacturing apparatus of the present invention, it is possible to measure and control the diameter value with high accuracy by using two cameras, and to suppress the rapid change in the diameter measurement data that occurs when the cameras are switched. By doing so, it is possible to prevent unintended diameter control processing from being performed and to prevent the occurrence of pulling failure.

It is the schematic which showed an example of the single crystal manufacturing apparatus of this invention. It is the schematic which shows the diameter measuring method of the cone part by two cameras in the single crystal manufacturing apparatus of this invention. It is a flowchart of an example of the switching process in this invention. (A) In an Example, it is a graph which shows the measured value of the diameter of the cone part obtained by the 1st, 2nd camera. (B) In an Example, it is a graph which shows the measured value used for diameter control of a cone part. (A) In a comparative example, it is a graph which shows the measured value of the diameter of the cone part obtained by the 1st, 2nd camera. (B) In a comparative example, it is a graph which shows the measured value used for diameter control of a cone part. It is the schematic which showed an example of the general single crystal manufacturing apparatus. It is the schematic which shows the diameter measuring method of the cone part by the two cameras in the conventional single crystal manufacturing apparatus.

  Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to this.

  As described above, when measuring the diameter of a cone part during diameter expansion using two conventional cameras, the measured value fluctuates abruptly when the camera is switched. There has been a problem that it causes a pulling failure of the single crystal such as crystallization.

  Therefore, the present inventor has intensively studied to solve such problems. As a result, two cameras are installed so that the field of view overlaps, and while the outer peripheral edge of the cone part is located within the overlapping field of view, the measured diameter of the cone part obtained from the first camera The present invention has been completed by conceiving that rapid fluctuation of the measured value can be prevented by performing a switching process for converging the measured value to the measured value of the diameter of the cone portion obtained from the second camera.

  As shown in FIG. 1, the single crystal manufacturing apparatus 20 of the present invention is an apparatus for pulling up a silicon single crystal by the Czochralski method, and includes at least a chamber 1 for storing a crucible 2 containing a silicon melt 6, and a crucible. 2, a crucible holding shaft 5, a heater 3 provided on the outer periphery of the crucible 2, a heater heat insulating material 4 provided on the outer periphery of the heater 3, and the like. The single crystal manufacturing apparatus 20 may include a seed chuck 7 for holding the seed crystal 11 and a wire 8 for pulling up the seed chuck 7 provided coaxially with the crucible holding shaft 5. . The crucible 2 may have a double structure including an inner quartz crucible and an outer graphite crucible.

  Furthermore, the single crystal manufacturing apparatus 20 of the present invention is a first camera 9a for measuring the diameter value of the cone portion 13 of the single crystal that is expanded while pulling up the seed crystal 11 that has been applied to the silicon melt 6. And a second camera 9b. A CCD camera can be used as the first camera 9a and the second camera 9b.

  These two cameras can measure the diameter value of the first half of the cone portion 13 from when the first camera 9a starts to expand the diameter until the diameter value of the cone portion 13 reaches a predetermined value. The camera 9b can measure the diameter value of the latter half of the cone part 13 after the diameter value of the cone part 13 reaches a predetermined value. That is, the first camera 9a is installed so as to mainly measure the diameter of the cone part 13 when the diameter is small, and the second camera 9b is installed so as to mainly measure the diameter of the cone part 13 when the diameter is large. This makes it possible to measure the diameter of a large single crystal with increased resolution. Furthermore, in the single crystal manufacturing apparatus 20 of the present invention, as shown in FIG. 1, the first camera 9 a and the second camera 9 b are arranged on the liquid surface of the silicon melt 6, and a part of each visual field range is mutually. It is installed so that it may overlap. Within this overlapping field of view, a measurement of the cone diameter is obtained from both the first camera 9a and the second camera 9b.

  The single crystal manufacturing apparatus 20 of the present invention measures the diameter value while measuring the diameter value of the cone portion 13 (top side) of the single crystal using the first camera 9a and the second camera 9b as cameras. It has a function capable of controlling the diameter of the cone portion 13 based on the value. The diameter control can be performed by the diameter controller 10 that controls the diameter of the cone portion 13 based on the measurement value obtained by one or both of the first camera 9a and the second camera 9b. More specifically, the diameter control unit 10 outputs a drive command signal to the respective mechanism units of the crucible holding shaft 5 and the wire 8 and outputs a heating command signal to the heater 3 to raise the crucible holding shaft 5 and the wire 8. The diameter of the cone portion 13 can be controlled by appropriately controlling the speed and the heating temperature of the heater 3. Preliminary control setting data is input to the diameter control unit 10 from an external system, and measurement obtained by the first camera 9a and the second camera 9b based on the input control setting data. What is necessary is just to adjust the raising speed of the crucible holding shaft 5, the winding speed of the wire 8, and the heating temperature according to the values.

  The single crystal manufacturing apparatus 20 of the present invention measures the diameter of the cone 13 obtained from the first camera 9a while the outer peripheral end of the cone 13 being expanded is located within the overlapping visual field range. Is switched to the measured value of the diameter of the cone portion 13 obtained from the second camera 9b, and the measured value used for the control of the diameter of the cone portion 13 is obtained by this switching processing function. The measurement value obtained from one camera 9a is switched to the measurement value obtained from the second camera 9b. That is, the single crystal manufacturing apparatus 20 completes the switching process by using the measurement value obtained from the first camera 9a before the camera switching process and the measurement value calculated by the switching process function during the camera switching process. Later, the measurement value obtained from the second camera 9b is used for controlling the diameter of the cone portion 13. For example, the diameter control unit 10 preferably includes this switching processing function.

  Here, the switching processing function will be described more specifically with reference to FIGS. First, in the example of FIG. 2, when the first camera 9a and the second camera 9b are installed, the first camera 9a can capture and measure the field of view (X to X ′ in FIG. 2) in the first half of the cone portion formation. 2) The second camera 9b has a field-of-view range (X ′ to X ″ ′ in FIG. 2) in which the cone part can be imaged and measured in the latter half of the cone part formation, and a part of each field-of-view range is that of the other camera. It is installed so as to overlap part of the field of view. In the camera visual field range (X ′ to X ″ in FIG. 2) overlapped by this camera installation method, the diameter measurement values of both the first camera 9a and the second camera 9b are obtained simultaneously.

  Here, to what extent the overlapping visual field range (X ′ to X ″ in FIG. 2) of the first camera 9a and the second camera 9b is set is a visual field that can be captured by each camera. It is judged from the diameter measurement resolution obtained by the range and the visual field range and the crystal diameter to be manufactured. As the overlapping visual field range, for example, the width in the diameter direction of the single crystal is preferably about 50 mm. However, if it is as wide as possible, diameter data with less variation can be obtained as a result of the camera switching process described later.

  In the step of forming the cone portion, first, the measurement value obtained from the first camera 9a is measured within the visual field range where the outer peripheral end of the cone portion during the diameter expansion overlaps from the start of the diameter expansion (X ′ in FIG. 2). The diameter control unit 10 controls the diameter as a diameter value of the cone part until reaching a predetermined position of ˜X ″).

  Next, while both the first camera 9a and the second camera 9b detect the diameter of the cone portion 13 within the overlapping camera visual field range (X ′ to X ″ in FIG. 2), the camera The switching process is performed. That is, the camera switching process is performed while the outer peripheral end of the cone portion 13 whose diameter is being expanded is located within the overlapping visual field range. In the switching process, the measured value of the diameter of the cone portion obtained from the first camera 9a is converted to the second camera while the outer peripheral end of the cone portion 13 whose diameter is being expanded is located within the overlapping visual field range. It is made to converge on the measured value of the diameter of the cone part 13 obtained from 9b, and the measurement value used for controlling the diameter of the cone part 13 by this switching process is obtained from the first camera 9a. To the measured value obtained from the second camera 9b. More specifically, for example, the measured value during switching, which is sequentially calculated so that the measured value obtained from the first camera 9a gradually approaches the measured value obtained from the second camera 9b, is represented by the diameter of the cone portion. The diameter control unit 10 controls the diameter of the cone part 13 as a value.

Such switching processing will be described with reference to FIG. FIG. 3 shows an example of a flowchart of the switching process. In performing the switching process, the time t _c required from the start of the switching process to the completion of the switching process, that is, the measured value during switching from when the outer peripheral end of the cone portion reaches a predetermined position within the overlapping visual field range. Is set to an elapsed time t _c (hereinafter also referred to as a switching setting time t _c ) until the value becomes equal to the measured value obtained from the second camera. For the switching setting time t _c at this viewing range overlapping of each camera, forming recipe (wire hoisting speed, the crucible lifting speed, the heater heating temperature, etc.) of the cone portion, considering cone diameter speed of at cone portion formed However, it is desirable to set it to about 30 to 60 minutes. As shown in FIG. 3, in the switching process, first, the result of subtracting the measurement value d _t1 of the first camera from the measurement value d _t2 of the second camera (hereinafter also referred to as a difference), the switching process starts. After calculating a division result (hereinafter also referred to as a switching ratio) between the elapsed time t from (hereinafter also referred to as switching elapsed time t) and the switching set time, the calculated difference is multiplied by the switching ratio (hereinafter referred to as “switching ratio”). This multiplication result is also expressed as a switching intermediate value). Next, the addition result of the measurement value of the first camera and the switching intermediate value is sequentially calculated as the switching measurement value d _m , that is, the diameter measurement result. That is, according to the following formula 1, sequentially calculates the measured value d _m in changeover, until the measured value d _m in changeover becomes equivalent and measured value d _t2 of the second camera, sequentially calculated switched during the measurement value d _{Let m be the} diameter value used for diameter control.
d _m = d _t1 + {(d _t2 −d _t1 ) × (t / t _c )} Equation 1
(However, t satisfies 0 ≦ t ≦ t _c .)

Immediately after the switching process is started, since the switching elapsed time t is 0, then the calculation result of the switching rate and switching the intermediate value is 0, the measured value of the result of switching in the measured value d _m first camera d _t1 Is equivalent to Further, at the time of switching process is completed, will switch the elapsed time t and the switching setting time t _c is the same value, the calculation result of the subsequent switching intermediate values to indicate the difference and equality, the result of switching in the measured value d _m, the second It becomes the same value as the measured value d _{t2 of the} camera. Therefore, the measured value d _m in switching with time during the switching process changes as measured d _t1 of the first camera is smoothly converged to a second camera measurements d _t2. This switching process can be performed by the diameter control unit 10 having a switching process function for performing the calculation of the above formula 1.

Moreover, after the measured value d _m in changeover was a measured value and the same value obtained from the second camera, that is, after the completion of the switching process at the diameter control unit 10 of FIG. 2, obtained from the second camera The measured value is controlled as the diameter value of the cone part.

  With the single crystal manufacturing apparatus 20 of the present invention as described above, it is possible to control the diameter with high accuracy by measuring the diameter value with high accuracy by two cameras, and obtain from the first camera 9a when switching the cameras. Since the measured value of the single crystal due to the switching of the camera does not change abruptly by performing a switching process for converging the measured value to the measured value obtained from the second camera 9b, unintended diameter control It is possible to prevent the processing from being performed and to prevent the occurrence of a pulling failure.

  Next, the single crystal manufacturing method of the present invention when the single crystal manufacturing apparatus 20 is used will be described.

  The single crystal manufacturing method of the present invention is based on the Czochralski method of pulling up a single crystal from the silicon melt 6 accommodated in the crucible 2, and after the polycrystalline silicon raw material is accommodated in the crucible 2, this is heated by the heater 3. A raw material melting step for melting into a silicon melt 6, a cone portion forming step for expanding a single crystal to form a cone portion 13 while pulling up a seed crystal 11 deposited on the silicon melt 6, forming a cone portion After that, the straight body forming step of forming the straight body by pulling up the single crystal while maintaining the diameter, after forming the straight body, the tail is formed by reducing the diameter of the single crystal and then separating it from the silicon melt 6 A tail portion forming step. These are what is done in the normal Czochralski method.

  The single crystal manufacturing method of the present invention controls the diameter of the cone portion 13 based on the measured value of the diameter value while measuring the diameter value of the cone portion 13 during diameter expansion with a camera in the cone portion forming step. Cultivate. Note that diameter control using a camera may also be performed in the straight body forming step.

  In the cone portion forming process, the diameter is controlled using the first camera 9a and the second camera 9b as shown in FIG. This diameter control method is the same as described above with reference to FIGS. That is, the overlapping field of view is obtained by performing a switching process for converging the measured value of the diameter of the cone 13 obtained from the first camera 9a to the measured value of the diameter of the cone 13 obtained from the second camera 9b. Camera switching processing is performed within the range. In addition, for the switching process, the measured value during switching that is sequentially calculated using Equation 1 may be used.

  With such a single crystal manufacturing method of the present invention, it is possible to control the diameter with high accuracy by measuring the diameter value with high accuracy by two cameras, and to perform the switching process as described above when switching the cameras. Since the measured value of the diameter of the single crystal due to the camera switching does not fluctuate abruptly, unintended diameter control processing can be prevented and the occurrence of pulling failure can be prevented.

  The method for producing a single crystal of the present invention is particularly preferably used when the diameter of the cone portion is expanded so that the maximum diameter is 200 mm or more. When pulling up a single crystal having a maximum diameter of 200 mm or more, particularly 300 mm or more, it is often necessary to measure the diameter value with two cameras with high accuracy. By using, it is possible to prevent the occurrence of pulling failure.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to the examples.

(Example)
In the single crystal manufacturing apparatus of the present invention as shown in FIG. 1, a silicon single crystal having a maximum cone diameter of 200 mm was pulled according to the single crystal manufacturing method of the present invention. At this time, the visual field range of the first camera on the silicon melt after melting the raw material is a range within 150 mm from the crystal center, and the visual field range of the second camera is 100 mm from the diameter center and 200 mm from the diameter center. The range up to the position was imaged and the diameter could be measured, and the viewing range of the two cameras was adjusted to partially overlap. In addition, a measurement error of about −5 mm in crystal diameter is generated for the second camera, that is, a measurement deviation of about 5 mm is generated between the measurement values of the first camera and the second camera. Minor adjustments were made. In this state, during the formation of the cone part, the switching process was applied according to the flow as shown in FIG. 3, and the transition of the measured value of the diameter of the cone part at that time was observed.

  The measured diameter of the cone obtained from the first camera and the measured diameter of the cone obtained from the second camera are shown in FIG. The measured values are shown in FIG. The camera switching process of the present invention is set to be performed from 190 minutes to 60 minutes of 250 minutes (switching setting time) of the cone formation elapsed time in FIGS. 4A and 4B. The execution period of acquisition of the measured value of the diameter of the cone portion of the camera and calculation of the measured value during switching using the acquired measured value was set to 1 minute.

  As a result, even if a measurement deviation as shown in FIG. 4 (a) occurs between the two cameras, the cone diameter measurement value used for diameter control is abrupt as shown in FIG. 4 (b). There was no fluctuation and the camera was switched smoothly. Further, in the cone part of the silicon single crystal manufactured in the example, no pulling failure such as dislocation of the single crystal due to camera switching occurred.

(Comparative example)
The silicon single crystal was pulled up under the same conditions as in the example except that the camera was switched without using the switching process as in the present invention as in the prior art. At this time, the field of view of the first camera is within 100 mm from the crystal center, and the field of view of the second camera is from 100 mm from the diameter center to the range from the diameter center to 200 mm. It was adjusted so that the field of view of the two cameras would not overlap. In addition, a measurement error of about −5 mm in crystal diameter is generated for the second camera, that is, a measurement deviation of about 5 mm is generated between the measurement values of the first camera and the second camera. Minor adjustments were made. In this state, when the cone portion formation elapsed time was 190 minutes, the conventional instantaneous switching from the first camera to the second camera was performed, and the transition of the measured value of the diameter of the cone portion at that time was observed.

  The measured value of the cone part diameter obtained from the first camera and the measured value of the cone part diameter obtained from the second camera are shown in FIG. The measured values are shown in FIG. As shown in FIG. 5B, a large local variation occurred in the cone diameter measurement value when the camera was switched (190 minutes). At this time, as a result of unintended heating control in the diameter control process due to local fluctuations, the silicon single crystal was dislocated during the formation of the cone portion.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

1 ... chamber, 2 ... crucible, 3 ... heater, 4 ... heater insulation,
5 ... crucible holding shaft, 6 ... silicon melt, 7 ... seed chuck, 8 ... wire,
9a ... 1st camera, 9b ... 2nd camera, 10 ... Diameter control part, 11 ... Seed crystal,
13 ... cone part, 20 ... single crystal manufacturing apparatus.

Claims (7)

In the method for producing a single crystal by the Czochralski method for pulling up the single crystal from the silicon melt contained in the crucible, the diameter of the single crystal is expanded while pulling up the seed crystal soaked in the silicon melt to form a cone portion. In the cone part forming step to form, while measuring the diameter value of the cone part during diameter expansion with a camera, the diameter of the cone part is controlled and grown based on the measured value of the diameter value. There,
A first camera that can measure the diameter value of the cone portion from the start of diameter expansion until the diameter value of the cone portion reaches a predetermined value, and the diameter value of the cone portion reaches the predetermined value in advance. And a second camera capable of measuring the diameter value of the cone portion after being set so that parts of the visual field range on the silicon melt surface overlap each other,
In the cone part forming step,
While the outer peripheral end of the cone portion during diameter expansion is located within the overlapping field of view, a measurement value of the diameter of the cone portion obtained from the first camera is obtained from the second camera. The measurement value used for controlling the diameter of the cone portion is converted from the measurement value obtained from the first camera by performing a switching process for converging to the measurement value of the cone portion diameter. A method for producing a single crystal, which is switched to the measured value obtained from In the cone part forming step,
The measured value obtained from the first camera is the diameter value of the cone part from the start of diameter expansion until the outer peripheral end of the cone part during diameter expansion reaches a predetermined position within the overlapping visual field range. Control the diameter of the cone,
After the outer peripheral end of the cone portion reaches the predetermined position, the measurement value obtained from the first camera is gradually brought closer to the measurement value obtained from the second camera by the switching process. The diameter of the cone part is controlled as the diameter value of the cone part, with the measured value during switching sequentially calculated in
After the measurement value during switching becomes the same value as the measurement value obtained from the second camera, the diameter of the cone portion is set to the measurement value obtained from the second camera as the diameter value of the cone portion. The method for producing a single crystal according to claim 1, wherein the method is controlled. The switching-in-progress value measurement, the switch in the measurement d _m, the measurements obtained from the first camera d _t1, the measurement values obtained from the second camera d _t2, the predetermined position The elapsed time from the time when the outer peripheral end of the cone portion has reached is t, and the measured value during the switching from the time when the outer peripheral end of the cone portion reaches the predetermined position is obtained from the second camera. 3. The method for producing a single crystal according to claim 2, wherein the time until the same value is obtained is calculated sequentially according to the following formula 1, where t _c is used.
d _m = d _t1 + {(d _t2 −d _t1 ) × (t / t _c )} Equation 1
(However, t satisfies 0 ≦ t ≦ t _c .)   The method for producing a single crystal according to any one of claims 1 to 3, wherein the cone portion is expanded so that a maximum diameter is 200 mm or more. A crucible for containing a silicon melt; and a camera for measuring a diameter value of a cone portion of a single crystal that is expanded while pulling up a seed crystal that has been deposited in the silicon melt. While measuring the diameter value, it is a single crystal production apparatus by the Czochralski method having a function capable of controlling the diameter of the cone portion based on the measured value of the diameter value,
A first camera capable of measuring the diameter value of the cone portion from the start of diameter expansion until the diameter value of the cone portion reaches a predetermined value; and after the diameter value of the cone portion reaches the predetermined value And a second camera capable of measuring the diameter value of the cone part, is installed so that a part of the visual field range on the silicon melt surface overlap each other,
While the outer peripheral end of the cone portion during diameter expansion is located within the overlapping field of view, a measurement value of the diameter of the cone portion obtained from the first camera is obtained from the second camera. And a switching processing function for converging to the measured value of the diameter of the cone portion, and by the switching processing function, the measured value used for controlling the diameter of the cone portion is obtained from the measured value obtained from the first camera. The single crystal manufacturing apparatus is characterized in that it switches to the measurement value obtained from the second camera. The diameter for controlling the diameter of the cone portion from one or both of the measured value of the diameter of the cone portion obtained from the first camera and the measured value of the diameter of the cone portion obtained from the second camera. A control unit,
The diameter control unit has the switching processing function,
The measured cone diameter obtained from the first camera is measured from the start of expansion until the outer peripheral end of the expanded cone reaches a predetermined position within the overlapping field of view. Control the diameter of the cone as the diameter of the part,
After the outer peripheral end of the cone portion reaches the predetermined position, the measurement value obtained from the first camera is measured by the switching processing function, and the diameter of the cone portion obtained from the second camera is measured. Controlling the diameter of the cone part as the diameter value of the cone part, the measured value during switching calculated so as to gradually approach the value,
After the measurement value during switching becomes the same value as the measurement value obtained from the second camera, the diameter of the cone portion is set to the measurement value obtained from the second camera as the diameter value of the cone portion. The single crystal manufacturing apparatus according to claim 5, wherein the single crystal manufacturing apparatus is controlled. Said diameter control unit, the switching during measurement, the switch during the measurement value d _m, the first the measurement values obtained from the camera d _t1, the measurement values obtained from the second camera d _t2 is an elapsed time from when the outer peripheral end of the cone portion reaches the predetermined position t, and the measured value during switching from the second camera when the outer peripheral end of the cone portion reaches the predetermined position. The single crystal manufacturing apparatus according to claim 6, wherein the single crystal manufacturing apparatus is sequentially calculated according to the following formula 1, where t _c is a time until the measured value is equal to the measured value.
d _m = d _t1 + {(d _t2 −d _t1 ) × (t / t _c )} Equation 1
(However, t satisfies 0 ≦ t ≦ t _c .)

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