JP6665798B2 - Single crystal manufacturing method and single crystal manufacturing apparatus - Google Patents

Description

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

  Most silicon single crystals are manufactured by pulling by the Czochralski method (CZ method). FIG. 6 shows an example of an apparatus used for producing a silicon single crystal by such a CZ method. 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 provided coaxially with the crucible holding shaft 105, and a wire 108 for pulling up the seed chuck 107. You. The crucible holding shaft 105 has a mechanism for rotating and raising and lowering the crucible 102, and the wire 108 has a mechanism for raising, lowering and rotating the seed chuck 107. The operation of each mechanism unit is such that preset control setting data is sent from the external system to the diameter control unit 110, and the diameter control unit 110 sends the control setting data to each of the crucible holding shaft 105 and the wire 108 based on the control setting data. The driving 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 a crucible 102, which is heated by a heater 103 to about 1420 ° C., which is the melting point of silicon, to be melted to obtain a silicon melt 106. Next, the wire 108 is unwound to bring the tip of the seed crystal 111 held by the seed chuck 107 into contact with the liquid surface of the silicon melt 106. Thereafter, the wire 108 is wound up at a predetermined speed while rotating the crucible holding shaft 105 and the wire 108 in a predetermined rotation direction and a predetermined rotation speed, and the seed crystal 111 is pulled up. Is formed. At the time of growing the silicon single crystal 112, after forming a narrowed portion for dislocating the crystal by making the diameter of the silicon single crystal 112 smaller and pulling it up, the diameter of the silicon single crystal 112 is gradually enlarged (diameter expansion). ) To form a cone portion, expand to a desired diameter, and then pull up while maintaining that diameter to form a straight body portion.

  In the above-mentioned single crystal manufacturing method, it is important to stably manufacture a silicon single crystal having a desired diameter in order to prevent a production loss and increase a product yield. Therefore, during the pulling of the single crystal, 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 as shown in FIG. By changing the winding speed of the wire 108, the rising speed of the crucible 102, and the heating temperature of the heater 103 in accordance with the value, control for obtaining a desired crystal diameter (hereinafter, diameter control) is performed.

  A method of measuring the diameter of a single crystal using a CCD camera, which is performed in diameter control, will be described. The CCD camera photographs a high-luminance annular portion (hereinafter, meniscus ring) observed 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 by 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 camera field of view is adjusted so that the distance from the center of the silicon single crystal to the meniscus ring, that is, the radius length, can be measured, and the obtained radius length is adjusted. By doubling the diameter, the diameter value can be measured.

  In order to perform the diameter control with high accuracy, it is necessary that the diameter data obtained by the diameter measurement using a camera has high accuracy.

  With the recent increase in crystal diameter, the range of view required for a camera that images silicon single crystals must be widened in accordance with the crystal diameter. Since it becomes difficult to read the change in the crystal diameter from the photographed image, the accuracy of the crystal diameter data is reduced as a result, and high-precision diameter control cannot be performed.

  On the other hand, Patent Literature 1 discloses a method of installing a camera for measuring the diameter of a straight body and a camera for measuring the diameter of a cone, and an imaging range for detecting the diameter of the cone. Is disclosed in which two cameras are installed by dividing the camera into two, and the cameras are switched and used during the formation of the cone portion. It is stated that the diameter measurement can be performed with high accuracy by using two cameras having a narrow field of view for measuring the diameter of a silicon single crystal having a large diameter.

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

JP 2010-100452 A

  However, in the diameter measurement method using a camera, 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 at a predetermined position. Therefore, different measurement results are shown 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 a predetermined position.

  Therefore, in particular, in the method of measuring the diameter of the cone portion using two cameras, the difference between the measurement 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 the switching. Ideally, there is no measurement deviation between the cameras A and B at the time of the switching process. However, since this measurement method is performed after the cameras are installed at different positions and angles, each camera view is different. 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 its generation is difficult to predict.

  Therefore, in the conventional method of measuring the diameter of the cone portion 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 eliminate. There is a problem that when this data is applied to diameter control, unintended diameter control processing is performed and pulling failures such as dislocation of the single crystal 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 when a camera is switched, thereby preventing unintended execution of a diameter control process and causing a pulling failure. It is an object of the present invention to provide a single crystal manufacturing method and a single crystal manufacturing apparatus that can prevent the occurrence of the single crystal.

  In order to achieve the above object, the present invention provides a method for producing a single crystal by the Czochralski method of pulling a single crystal from a silicon melt contained in a crucible, while pulling a seed crystal that has been brought into contact with the silicon melt. In the cone part forming step of expanding the single crystal to form a cone part, while measuring the diameter value of the cone part during diameter expansion with a camera, the cone part based on the measured value of the diameter value A method for producing a single crystal in which a diameter is controlled and grown, wherein a first camera capable of measuring a 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 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, and a part of the visual field range on the silicon melt surface overlaps with each other. So that In the cone portion forming step, the measured value of the diameter of the cone portion obtained from the first camera while the outer peripheral end of the cone portion during diameter expansion is located in the overlapping visual field range, By performing a switching process to converge to the measured value of the diameter of the cone portion obtained from the second camera, the measured value used to control the diameter of the cone portion, from the measured value obtained from the first camera And switching to the measurement value obtained from the second camera.

  According to the method for producing a single crystal of the present invention, the diameter value of a single crystal can be measured by a camera by performing the above-described switching processing when switching between cameras while performing high-precision measurement of the diameter value with two cameras. Since the value does not fluctuate abruptly, it is possible to prevent the diameter control process from being performed unintentionally and prevent the occurrence of 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 from the start of the diameter expansion. Controlling the diameter of the cone portion as the diameter value of the cone portion until reaching, after the outer peripheral edge of the cone portion reaches the predetermined position, by the switching process, the measurement obtained from the first camera The value during switching, which is sequentially calculated so that the value gradually approaches the measurement value obtained from the second camera, controls the diameter of the cone portion as the diameter value of the cone portion, and performs the measurement during switching. After the value becomes equal to the measured value obtained from the second camera, the diameter of the cone portion is controlled by using the measured value obtained from the second camera as the diameter value of the cone portion. Door is preferable.

  As described above, the camera switching process used for the diameter control uses the above-described switching intermediate value, so that the fluctuation of the measured value of the diameter used for the control can be gently reduced. Implementation can be prevented, and occurrence of pulling failure can be reliably prevented.

Also, at this time, the switching measurement value is the switching measurement value d _m , the measurement value obtained from the first camera is d _t1 , the measurement value obtained from the second camera is 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 the time when the outer peripheral end of the cone portion reaches the predetermined position. the time until the the measured value and the same value can be sequentially calculated by the following equation 1 when the t _{c.
d m = d t1 + {(} d t2 -d t1) × (t / t c)} ··· Equation 1
(Where, t satisfies 0 ≦ _t ≦ t _c.)

  By sequentially calculating the measured value during switching so as to satisfy the above equation 1, and using the measured value as the measured value for diameter control during camera switching, it is possible to make the fluctuation of the measured value of the diameter used for control gentler. it can.

  In addition, it is preferable that the diameter of the cone part is enlarged so that the maximum diameter becomes 200 mm or more.

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

  Further, in order to achieve the above object, the present invention provides a crucible for accommodating a silicon melt and a diameter value of a cone portion of a single crystal which is expanded while pulling up a seed crystal which has been brought into contact with the silicon melt. A single crystal production by a Czochralski method having a camera for measuring and having a function of controlling the diameter of the cone portion based on the measured value of the diameter value while measuring the diameter value of the cone portion with the camera. An apparatus, a first camera capable of measuring the diameter 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 is the predetermined value. A second camera capable of measuring the diameter value of the cone portion after reaching the value is installed so that a part of the visual field range on the silicon melt surface overlaps with each other, and the cone portion during diameter expansion is installed. 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 switching processing function switches a measurement value used for controlling the diameter of the cone portion from the measurement value obtained from the first camera to the measurement value obtained from the second camera. The present invention provides a single crystal manufacturing apparatus characterized by the following.

  The single crystal manufacturing apparatus of the present invention can measure the diameter value with high accuracy by using two cameras, and by performing the above-described switching processing when switching between cameras, the measured value of the diameter of the single crystal by the camera can be reduced. Since it does not fluctuate rapidly, it is possible to prevent the unintended execution of the diameter control process 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 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 or From both, comprising a diameter control unit for controlling the diameter of the cone, the diameter control unit has the switching processing function, the measured value of the diameter of the cone obtained from the first camera, From the start of diameter expansion, the diameter of the cone portion is controlled as a diameter value of the cone portion until the outer peripheral end of the cone portion during diameter expansion reaches a predetermined position in the overlapped visual field range, and the diameter of the cone portion is adjusted to the predetermined position. After the outer peripheral end of the cone portion reaches, by the switching processing function, the measured value obtained from the first camera is gradually reduced to the measured value of the diameter of the cone portion obtained from the second camera. To get closer The sequentially measured value during switching, the diameter of the cone portion is controlled as the diameter value of the cone portion, and after the measured value during switching becomes the same value as the measured value obtained from the second camera, Preferably, the measurement value obtained from the second camera is used as a diameter value of the cone portion to control the diameter 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-described switching intermediate value, so that the fluctuation of the measured value of the diameter used for control is gently reduced. Therefore, unintended execution of the diameter control process can be prevented, and the occurrence of pulling failure can be reliably prevented.

Also, the diameter control unit may be configured to perform the switching measurement, the switching measurement d _m , the measurement obtained from the first camera d _t1 , and the measurement obtained from the second camera. the d _t2, the elapsed time from when the outer peripheral edge of the cone portion has reached a predetermined position t, the said switching of values measured from when the outer peripheral edge of the cone portion has reached the predetermined position the second it is preferred the time until the measured value and equivalence obtained from the camera is to successively calculated by the following equation 1 when the t _{c.
d m = d t1 + {(} d t2 -d t1) × (t / t c)} ··· Equation 1
(Where, t satisfies 0 ≦ _t ≦ t _c.)

  The diameter control unit sequentially calculates the measured value during switching so as to satisfy the above equation 1, and uses the measured value as the measured value for diameter control during switching of the camera, so that the single crystal manufacturing apparatus of the present invention can control the diameter used for control. The fluctuation of the measured value can be made gentler, and the occurrence of the pulling failure can be prevented.

  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 a rapid change in the diameter measurement data generated when the camera is switched. By doing so, it is possible to prevent unintended execution of the diameter control process and prevent occurrence of a 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 measurement 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 processing in the present invention. (A) In 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 Example, it is a graph which shows the measured value used for the 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 the 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 measurement method of the cone part by two cameras in the conventional single crystal manufacturing apparatus.

  Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

  As described above, in the conventional measurement of the diameter of the cone portion while expanding the diameter using two cameras, the measured value fluctuates abruptly when the camera is switched. However, there is a problem in that pulling failure of the single crystal such as the formation of a crystal is caused.

  Therefore, the present inventors have intensively studied to solve such a problem. As a result, the two cameras were installed so that the fields of view overlapped, and the measured value of the diameter of the cone obtained from the first camera while the outer peripheral edge of the cone was positioned within the overlapping field of view. By performing a switching process for converging to a measured value of the diameter of the cone obtained from the second camera, it is possible to prevent a sudden change in the measured value, and thus completed the present invention.

  As shown in FIG. 1, a single crystal manufacturing apparatus 20 of the present invention is an apparatus for pulling a silicon single crystal by the Czochralski method, and includes at least a chamber 1 containing a crucible 2 containing a silicon melt 6 and a crucible. A crucible holding shaft 5 for holding the crucible 2, a heater 3 provided on the outer periphery of the crucible 2, a heater insulating material 4 provided on the outer periphery of the heater 3, and the like may be provided. Further, 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, which are 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 includes 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 immersed in the silicon melt 6. And a second camera 9b. Note that 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 the time when the first camera 9a starts expanding the diameter until the diameter value of the cone portion 13 reaches a predetermined value. Can measure the diameter value of the latter half of the cone portion 13 after the diameter value of the cone portion 13 reaches a predetermined value. That is, it is installed so that the first camera 9a can mainly measure the diameter of the cone portion 13 when the diameter is small, and the second camera 9b can mainly measure the diameter of the cone portion 13 when the diameter is large. This makes it possible to measure the diameter of a large-diameter 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 9a and the second camera 9b It is installed to overlap. Within this overlapping field of view, both the first camera 9a and the second camera 9b provide measurements of the diameter of the cone.

  The single crystal manufacturing apparatus 20 of the present invention measures the diameter of the single crystal cone portion 13 (top side) while using the first camera 9a and the second camera 9b as cameras. It has a function of controlling the diameter of the cone portion 13 based on the value. The diameter control can be performed by the diameter control unit 10 that controls the diameter of the cone unit 13 based on the measurement value obtained by one or both of the first camera 9a and the second camera 9b. More specifically, a drive command signal is output from the diameter control unit 10 to each mechanism of the crucible holding shaft 5 and the wire 8, and a heating command signal is output to the heater 3 to raise the crucible holding shaft 5 and the wire 8. By appropriately controlling the speed and the heating temperature of the heater 3, the diameter of the cone portion 13 can be controlled. Control setting data set in advance is input to the diameter control unit 10 from an external system. Based on the input control setting data, measurement obtained by the first camera 9a or the second camera 9b is performed. The rising speed of the crucible holding shaft 5, the winding speed of the wire 8, and the heating temperature may be adjusted according to the values.

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

  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 9 a and the second camera 9 b are installed, the first camera 9 a uses the visual field range (X to X ′ in FIG. 2) in which imaging and measurement can be performed in the first half of the cone portion formation. '), The second camera 9b has a visual field 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 visual field range is the same as that of the other camera. It is installed so as to overlap a part of the field of view. In the overlapping camera field of view (X ′ to X ″ in FIG. 2), the diameter measurement values of both the first camera 9 a and the second camera 9 b are obtained at the same time.

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

  In the step of forming the cone portion, first, the measured value obtained from the first camera 9a is measured within the visual field range in which the outer peripheral end of the cone portion during the diameter expansion is overlapped (X ′ in FIG. 2) from the start of the diameter expansion. ~ X ''), the diameter of which is controlled by the diameter control unit 10 as the diameter value of the cone until reaching the predetermined position.

  Next, while both the first camera 9a and the second camera 9b are detecting the diameter of the cone portion 13 within the overlapping camera field of view (X ′ to X ″ in FIG. 2), Is performed. That is, the camera switching process is performed while the outer peripheral end of the cone section 13 during the diameter expansion is located within the overlapping visual field range. The switching process uses the measured value of the diameter of the cone portion obtained from the first camera 9a while the outer peripheral end of the cone portion 13 during the diameter expansion is within the overlapping visual field range, and 9b, the measured value of the diameter of the cone portion 13 is converged to the measured value of the diameter of the cone portion 13. By performing the switching process, the measured value used for controlling the diameter of the cone portion 13 is converted to the measured value obtained from the first camera 9a. Is switched to the measurement value obtained from the second camera 9b. More specifically, for example, the measurement value during switching, which is sequentially calculated so that the measurement value obtained from the first camera 9a gradually approaches the measurement value obtained from the second camera 9b, is referred to as the diameter of the cone portion. The diameter of the cone 13 is controlled by the diameter controller 10 as a value.

Such a switching process will be described with reference to FIG. FIG. 3 shows an example of a flowchart of the switching process. In performing the switching process, in advance, the time t _c required from the start of the switching process to the completion of the switching process, that is, from the time when the outer peripheral edge of the cone portion reaches a predetermined position in the overlapping visual field range, the measured value during switching. The elapsed time t _c (hereinafter, also referred to as a switching set time t _c ) until is obtained is the same as the measurement 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 It is desirable to set the time to about 30 to 60 minutes. Then, 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), starts the switching process. After calculating the division result (hereinafter also referred to as the switching ratio) of the elapsed time t (hereinafter also referred to as the switching elapsed time t) from the switching setting time, the calculated difference is multiplied by the switching ratio (hereinafter, referred to as the switching ratio). This multiplication result is also referred to as a switching intermediate value). Next, the result of addition 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 _m is a diameter value used for diameter control.
_{d m = d t1 + {(} d t2 -d t1) × (t / t c)} ··· Equation 1
(Where, 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 This is the same value as the measured value _{dt2 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 processing can be performed by the diameter control unit 10 having a switching processing function of performing the calculation of the above equation 1.

Moreover, after the measured value d _m in changeover it 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 a diameter value of the cone portion.

  With the single crystal manufacturing apparatus 20 of the present invention as described above, highly accurate diameter control can be performed by measuring a highly accurate diameter value using two cameras, and the camera can be obtained from the first camera 9a at the time of camera switching. By performing a switching process for converging the measured value obtained from the second camera 9b to the measured value obtained from the second camera 9b, the measured value of the diameter of the single crystal due to the switching of the camera does not fluctuate sharply. It is possible to prevent the processing from being performed and prevent the occurrence of pulling failure.

  Next, a single crystal manufacturing method of the present invention using the single crystal manufacturing apparatus 20 will be described.

  The method for producing a single crystal according to the present invention is based on the Czochralski method of pulling a single crystal from the silicon melt 6 contained in the crucible 2. A raw material melting step of melting into a silicon melt 6, a cone part forming step of forming a cone part 13 by expanding the diameter of a single crystal while pulling up the seed crystal 11 immersed in the silicon melt 6, and a cone part formation Thereafter, a single body is formed by pulling up the single crystal while maintaining the diameter to form a straight body. After forming the straight body, the single crystal is reduced in diameter and then cut off from the silicon melt 6 to form a tail. And a tail forming step. These are performed in the usual Czochralski method.

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

  In the cone part forming step, 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, by performing a switching process of 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, the overlapping visual field is obtained. The camera is switched within the range. Also, for the switching process, the measured value during switching, which is sequentially calculated using Equation 1, may be used.

  With such a single crystal manufacturing method of the present invention, high-precision diameter control can be performed by measuring a high-precision diameter value using two cameras, and the above-described switching processing is performed when the cameras are switched. In addition, since the measured value of the diameter of the single crystal does not fluctuate abruptly due to the switching of the camera, it is possible to prevent an unintended diameter control process and prevent a pulling failure.

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

  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)
According to the single crystal manufacturing apparatus of the present invention as shown in FIG. 1, a silicon single crystal having a cone portion with a maximum diameter of 200 mm was pulled up 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 the raw material was melted was within a range of 150 mm from the crystal center, and the visual field range of the second camera was 200 mm from the position of 100 mm from the center of the diameter. The range up to the position was adjusted so that imaging and diameter measurement could be performed, and the visual field ranges of the two cameras were adjusted so as to partially overlap. In addition, a measurement error of about -5 mm in crystal diameter is generated with respect to the second camera, that is, a measurement deviation of about 5 mm is generated between measurement values of the first camera and the second camera. Made some adjustments. In this state, during the formation of the cone portion, a switching process was applied in a flow as shown in FIG. 3, and the transition of the measured value of the diameter of the cone portion at that time was observed.

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

  As a result, even if a measurement deviation as shown in FIG. 4A occurs between the two cameras, as shown in FIG. 4B, an abrupt change in the cone diameter measurement value used for the diameter control occurs. There was no change and the camera was switched smoothly. Further, in the cone portion of the silicon single crystal manufactured in the example, no pulling failure such as dislocation of the single crystal caused by the camera switching occurred.

(Comparative example)
A silicon single crystal was pulled 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 related 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 center of the diameter to 200 mm from the center of the diameter. It was adjusted so that the field of view of the two cameras did not overlap. In addition, a measurement error of about -5 mm in crystal diameter is generated with respect to the second camera, that is, a measurement deviation of about 5 mm is generated between measurement values of the first camera and the second camera. Made some adjustments. 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 values of the diameter of the cone obtained from the first camera and the measured values of the diameter of the cone obtained from the second camera are shown in FIG. Are shown in FIG. 5 (b). As shown in FIG. 5B, when the camera was switched (190 minutes), a large local variation occurred in the cone diameter measurement value. At this time, unintended heating control was performed in the diameter control process due to local fluctuation, and as a result, dislocations occurred in the silicon single crystal during the formation of the cone portion.

  Note that the present invention is not limited to the above embodiment. The above embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and has the same effect. Within the technical scope of

1 ... chamber, 2 ... crucible, 3 ... heater, 4 ... heater insulation,
5: crucible holding shaft, 6: silicon melt, 7: seed chuck, 8: wire,
9a: first camera, 9b: second camera, 10: diameter controller, 11: seed crystal,
13: cone part, 20: single crystal production equipment.

Claims (7)

In the method for manufacturing a single crystal by the Czochralski method of pulling a single crystal from a silicon melt accommodated in a crucible, the diameter of the single crystal is increased while the seed crystal immersed in the silicon melt is pulled up to form a cone portion. In the cone portion forming step of forming, while measuring the diameter value of the cone portion during diameter expansion with a camera, a single crystal manufacturing method of growing by controlling the diameter of the cone portion based on the measured value of the diameter value. So,
In advance, 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 the diameter value of the cone portion reaches the predetermined value. And the second camera capable of measuring the diameter value of the cone after the, is installed so that a part 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 expanding cone is located within the overlapping field of view, a measurement of the diameter of the cone obtained from the first camera is obtained from the second camera. By performing a switching process to converge to the measured value of the diameter of the cone portion, the measured value used to control the diameter of the cone portion, from the measured value obtained from the first camera, the second camera A method for producing a single crystal, characterized by switching to the measured value obtained from the above. In the cone part forming step,
The measured value obtained from the first camera, from the start of diameter expansion, as the diameter value of the cone portion until the outer peripheral end of the cone portion during diameter expansion reaches a predetermined position in the overlapping visual field range Controlling the diameter of the cone,
After the outer peripheral end of the cone portion reaches the predetermined position, the switching process allows the measured value obtained from the first camera to gradually approach the measured value obtained from the second camera. The switching measurement value sequentially calculated in the control of the diameter of the cone portion as a diameter value of the cone portion,
After the measurement value during the switching becomes the same value as the measurement value obtained from the second camera, the measurement value obtained from the second camera is used as the diameter value of the cone portion, and the diameter of the cone portion is used. The method for producing a single crystal according to claim 1, wherein the method is controlled. The measured value during switching is d _m , the measured value obtained from the first camera is d _t1 , the measured value obtained from the second camera is d _t2 , and the measured value obtained from the second camera is d _t2 , at the predetermined position. The elapsed time from when the outer peripheral edge of the cone portion has reached t, the measurement value during the switching from the time when the outer peripheral edge of the cone portion has reached the predetermined position and the measured value obtained from the second camera and The single crystal manufacturing method according to claim 2, wherein the calculation is performed sequentially according to the following equation 1 when the time until the value becomes the same is t _c .
_{d m = d t1 + {(} d t2 -d t1) × (t / t c)} ··· Equation 1
(Where, 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 the maximum diameter becomes 200 mm or more. A crucible containing a silicon melt, and a camera for measuring a diameter value of a cone portion of a single crystal whose diameter is expanded while pulling up a seed crystal immersed in the silicon melt, and using the camera to measure a diameter value of the cone portion. While measuring the diameter value, a single crystal manufacturing 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 A second camera capable of measuring the diameter value of the cone portion is installed such that a part of a visual field range on the silicon melt surface overlaps with each other,
While the outer peripheral end of the expanding cone is located within the overlapping field of view, a measurement of the diameter of the cone obtained from the first camera is obtained from the second camera. Has a switching processing function to converge to the measured value of the diameter of the cone portion, the measurement value used for controlling the diameter of the cone portion by the switching processing function, from the measured value obtained from the first camera A single crystal manufacturing apparatus characterized by switching to the measured value obtained from the second camera. 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, the diameter controlling the diameter of the cone portion Equipped with a control unit,
The diameter control unit has the switching processing function,
The measured value of the diameter of the cone portion obtained from the first camera, from the start of diameter expansion, the cone until the outer peripheral end of the cone portion during diameter expansion reaches a predetermined position in the overlapping visual field range Controlling the diameter of the cone portion as the diameter value of the portion,
After the outer peripheral edge of the cone reaches the predetermined position, the switching processing function is used to measure the measurement value obtained from the first camera and measure the diameter of the cone obtained from the second camera. The switching measurement value sequentially calculated to gradually approach the value, controlling the diameter of the cone portion as the diameter value of the cone portion,
After the measurement value during the switching becomes the same value as the measurement value obtained from the second camera, the measurement value obtained from the second camera is used as the diameter value of the cone portion, and the diameter of the cone portion is used. The single crystal manufacturing apparatus according to claim 5, wherein the apparatus is controlled. The diameter control unit calculates the switching measurement value, the switching measurement value d _m , the measurement value obtained from the first camera d _t1 , and the measurement value obtained from the second camera d d _t2 , the elapsed time from the time when the outer peripheral edge of the cone portion reaches the predetermined position is t, and the measured value during the switching from the time when the outer peripheral edge of the cone portion reaches the predetermined position is obtained from the second camera. The single crystal manufacturing apparatus according to claim 6, wherein the calculation is performed sequentially according to the following equation 1 when a time until the obtained measured value becomes the same value is t _c .
_{d m = d t1 + {(} d t2 -d t1) × (t / t c)} ··· Equation 1
(Where, t satisfies 0 ≦ _t ≦ t _c.)

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