JP3719198B2 - Single crystal bend growth detection method, single crystal bend growth detection apparatus, and single crystal manufacturing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single crystal bend growth detection method, a single crystal bend growth detection apparatus, and a single crystal manufacturing apparatus that solve the problem of bend growth that occurs when a silicon single crystal is pulled.
[0002]
[Prior art]
There are various methods for producing a silicon single crystal used for a semiconductor substrate. One of them is the Czochralski method (hereinafter referred to as CZ method), which is a rotary pulling method, and is widely used. FIG. 2 is a schematic view showing an apparatus for producing a single crystal by the CZ method. In the figure, reference numeral 1 denotes a crucible disposed in the chamber. The crucible 1 is composed of a quartz inner layer holding container 1a having a bottomed cylindrical shape and a similarly bottomed cylindrical graphite outer layer holding container 1b adapted to hold the outside of the inner layer holding container 1a. Has been. The crucible 1 is fixed to the upper end of a support shaft 6 that can be rotated and lifted. A resistance heating type heater 2 is concentrically arranged outside the crucible 1, and the crucible 1 is filled with a melt 13 obtained by melting a raw material of a predetermined weight by the heater 2. On the central axis of the crucible 1, a pulling shaft (or a wire, hereinafter referred to as “pulling shaft”) 5 that rotates at a predetermined speed in the opposite direction or in the same direction as the support shaft 6. The seed crystal 15 is suspended from the pulling shaft 5.
[0003]
In such a single crystal manufacturing apparatus, the raw material for crystal is put into the crucible 1 and melted in the heater 2 disposed around the crucible 1 in an inert gas atmosphere under reduced pressure. Thereafter, the seed crystal 15 suspended from the pulling shaft 5 is immersed in the melt 13, and the pulling shaft 5 is pulled upward while rotating the crucible 1 and the pulling shaft 5, and the single crystal 12 is formed at the lower end of the seed crystal 15. Grow. In the CZ method, first, the seed crystal is narrowed down to about 3 mm in diameter in order to remove the dislocations originally contained in the seed crystal and the dislocations introduced by the heat shock at the time of landing (this is called a neck process). Thereafter, the diameter is gradually increased to a predetermined diameter and the constant diameter portion is pulled up.
[0004]
[Problems to be solved by the invention]
However, in the conventional single crystal manufacturing apparatus, there is a phenomenon that when the pulling speed is excessively high or when the pulling shaft 5 is shaken, the crystal is twisted and grown. This wavy growth is a growth state in which the growth interface appears to be twisted when rotated because the growth interface is pulled up to one side as shown in FIG.
[0005]
In single crystal production, a diameter measuring means is provided to monitor the growth state of the single crystal. As this diameter measuring means, for example, an optical one-dimensional line sensor as shown in Japanese Patent Publication No. 53-42476 is generally used. The growth state is monitored by measuring the diameter of the single crystal with this one-dimensional line sensor.
[0006]
However, when the bend growth occurs as described above, the fusion ring 18 fluctuates as shown in FIG. 4, so that the diameter is measured as if fluctuated greatly as shown in FIG. As a result, the pulling speed and the heater temperature control intervened by the control device also fluctuate, so that stable pulling cannot be performed, and there is a case where the product does not deviate from the set pulling diameter.
[0007]
In addition, dislocation is likely to occur, and in some cases, the pulling itself may be impossible. And this waviness growth becomes more prominent with a large-diameter crystal having a diameter of 300 mm.
[0008]
The present invention has been made in view of such circumstances, and the object of the present invention is to reliably detect and suppress a single-crystal pulling when wavily growing is detected and suppressed. It is an object of the present invention to provide a single crystal bend growth detection method, a single crystal bend growth detection apparatus, and a single crystal production apparatus.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a single crystal bend growth detection method according to a first aspect of the present invention is a method in which a raw material is filled in a crucible and melted, and a seed crystal is immersed in the melt and pulled up while being rotated, and single crystal In a single crystal bend growth detection method for detecting crystal bend growth that occurs when a crystal is grown, a fusion ring on the crystal growth surface is formed. diameter Compare the fluctuation period and the crystal rotation period, The diameter fluctuation period is half of the crystal rotation period. It is characterized in that it is determined that the single crystal bends.
[0010]
In the above configuration, in the state where the wavy growth occurs, the center of the crystal growth interface is shifted from the vertical center of the pulling axis. Diameter variation Period is crystal rotation Half the cycle It matches. For this reason, the fusion ring on the crystal growth surface diameter Of fluctuation period and crystal rotation period Half Can be judged as single crystal bend growth.
[0011]
The single crystal bend growth detection apparatus according to the second invention is a crystal bend produced when a crucible is filled with a raw material and melted, and a seed crystal is immersed in the melt and pulled up while rotating to grow a single crystal. In a single-crystal bend growth detector for detecting growth, a fusion ring of the crystal growth surface diameter Detected by a fluctuation period detecting means for detecting a fluctuation period, a crystal rotation period detecting means for detecting a crystal rotation period, and the fluctuation period detecting means. diameter Comparing the fluctuation period and the crystal rotation period detected by the crystal rotation period detection means The diameter fluctuation period is half of the crystal rotation period. It is characterized in that it is provided with a comparing means for judging that it is sometimes a single crystal bend growth.
[0012]
With the above configuration, the fluctuation ring detecting means can be used for the fusion ring of the crystal growth surface. diameter Detect the fluctuation period. The crystal rotation period is detected by the crystal rotation period detection means. Then, the comparison means detects the fluctuation period detection means. diameter The fluctuation period is compared with the crystal rotation period detected by the crystal rotation period detection means. By this comparison, the fusion ring of the crystal growth surface diameter Fluctuation period and crystal rotation period Half of Is determined to be a single crystal bend growth for the above-mentioned reason.
[0013]
The fluctuation period detection means includes a light intensity detection unit that detects a light intensity on the detection region by scanning a growth interface on the melt where the crystal is pulled up as a detection region, and a detection value at the light intensity detection unit. A diameter measuring unit that detects the position of the fusion ring from the fusion ring and measures the diameter of the crystal at the melt surface from the fusion ring, and analyzes the change in the measured value at the diameter measuring unit to analyze the crystal at the melt surface. It is desirable to comprise the analysis part which detects the fluctuation period of the diameter of this.
[0014]
With the above configuration, the position of the fusion ring is detected from the difference in light intensity in the region detected by the light intensity detection unit, and the diameter of the crystal on the melt surface is measured from the fusion ring by the diameter measurement unit. And the change of the measured value in a diameter measurement part is analyzed in an analysis part, and the fluctuation period of the diameter of the crystal | crystallization in the said melt surface is detected.
[0015]
It is desirable that the light intensity detection part of the fluctuation period detection means is constituted by a two-dimensional camera.
[0016]
With the above-described configuration, even when the fluctuation amount of the fusion ring increases, the two-dimensional camera can be used to reliably follow and bend detection can be reliably detected.
[0017]
A single crystal production apparatus according to a third aspect of the present invention is the single crystal production apparatus in which a raw material is filled in a crucible and melted, and a seed crystal is immersed in the melt and pulled up while rotating to grow a single crystal. One of the single crystal bend growth detection devices and a control unit that changes an operation parameter when single crystal bend growth detection is detected by the single crystal bend growth detection device.
[0018]
With the above configuration, the single crystal bend growth detector reliably detects single crystal bend growth, and the control unit changes the operation parameter. Thereby, the bend growth of the single crystal can be reliably suppressed.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a single crystal bend growth detection method, a single crystal bend growth detection apparatus, and a single crystal production apparatus according to embodiments of the present invention will be described with reference to the drawings.
[0020]
[Single crystal bend growth detection method]
The single crystal bend growth detection method of this embodiment is a method of detecting crystal bend growth that occurs when a crucible is filled with a raw material and melted, and a seed crystal is immersed in the melt and pulled up while rotating to grow a single crystal. It is a method for detecting. In this single crystal bend growth detection method, the fluctuation cycle of the fusion ring on the crystal growth surface is compared with the crystal rotation cycle, and when these coincide, it is determined that the single crystal bend growth has occurred.
[0021]
Crystal bend growth occurs when the center of rotation of the growth interface deviates from the vertical axis due to deflection of the pulling axis, resulting in eccentric rotational movement, and the period coincides with the crystal rotation period. As the pulling speed increases, the bias increases and the waviness growth increases.
[0022]
The reason for this will be described with reference to FIG. When the center of the growth interface deviates from the vertical axis C and performs an eccentric rotational motion, the single crystal 12 revolves while rotating. In FIG. 6A and FIG. 6B, the presence of the four single crystals 12 indicates that the single crystals 12 are revolving. When the eccentric rotation period that is the revolution period and the crystal rotation period that is the rotation period coincide with each other, the growth interface of the single crystal 12 always faces the same temperature distribution as shown in FIG. That is, the point A of the growth interface of the single crystal 12 is always located outside the revolution locus, and the point B is always located inside the revolution locus. At this time, if there is a slight difference in temperature distribution between the center position of revolution (vertical axis C) and the peripheral position, the difference in temperature distribution is similarly generated at points A and B of the single crystal 12. That is, a slight temperature difference occurs between the points A and B. As a result, a difference occurs in the growth amount per unit time at the points A and B of the growth interface, and the difference is gradually accumulated. As a result, as shown in FIG. 7A, there is a large difference in the growth amount between point A and point B, resulting in overall uneven growth. In fact, if you grow to some extent, the change in the center of gravity accompanies, so you end up growing like a spiral. However, when the temperature difference is large, the growth may be greatly biased in one direction within a relatively short time, and thus the pulling itself may be impossible.
[0023]
On the other hand, when the eccentric rotation period is deviated from the crystal rotation period, even if the eccentric rotational movement occurs, the points A and B move on the inner and outer sides of the revolution locus as shown in FIG. Thus, the point A and the point B move on different temperature distributions periodically. As a result, even if there is a difference in the growth amount due to the difference in temperature distribution, as shown in FIG. 7B, the growth amount changes alternately at the points A and B, and the same growth amount in the long term. It becomes. This suppresses the bend growth.
[0024]
In the present invention, as described above, attention is paid to the fact that the eccentric rotation period and the crystal rotation period of the growth interface of the single crystal 12 coincide with each other when the bend growth occurs. That is, the coincidence between the eccentric rotation period and the crystal rotation period can be regarded as a condition for occurrence of waviness growth.
[0025]
As shown in FIG. 4 and FIG. 5, when the bend growth has occurred, the diameter measurement value detected by the camera is periodically twice during one rotation of the crystal ((a) and ( c) twice). Therefore, if the fluctuation cycle of the diameter is examined and it coincides with the crystal rotation half cycle, it can be determined that the eccentric rotation cycle and the crystal rotation cycle coincide with each other, and that bend growth occurs. That is, it is possible to detect waviness growth.
[0026]
By the way, there are the following means for detecting a variation in diameter measurement.
[0027]
Japanese Patent No. 3099724 (Comparative Example 1) describes means for detecting torsional vibration during pulling. However, torsional vibration occurs in the shaft, that is, in the neck due to the difference in moment of inertia, with a narrow neck and large diameter crystal straight body in a relationship like a thin and long shaft and a large cylinder attached to the tip. This is a vibration phenomenon and is completely different from the bend growth that is the subject of the present invention. Furthermore, this publication is characterized by detecting fluctuations in the time interval in which the crystal habit line part passes through the line sensor part, which is a phenomenon peculiar to single crystal growth, as a means for detecting diameter fluctuations. Since vibration is at a high frequency relative to the period of waviness growth, on average, there is no significant difference from the value obtained by dividing the number of crystal rotations by the number of crystal habit lines. Since it disappears, it can no longer be detected. Therefore, this method cannot detect waviness growth.
[0028]
“Bend growth” should also be called “spiral growth” in which the body grows just like a twist. FIG. 8 shows a crystal in which waviness growth occurs. If this twisting growth occurs during crystal growth, it is recognized that a diameter variation has occurred in the measurement, so that the control becomes unstable, and if further progressed, it is distorted at all and falls into a state where it cannot be pulled up.
[0029]
The “seam portion” in Comparative Example 1 is a “crystal habit line” peculiar to single crystal growth. This part is in a state of protruding about 1-2 mm outside compared to the other parts. Therefore, when each seam portion passes through the line sensor by rotation, it is detected that the diameter has temporarily increased. This period is the “seam part detection period”, and the period is “crystal rotation period / number of crystal habit lines”. For example, if the (100) orientation is pulled up, there are four crystal habit lines, which is a quarter of the crystal rotation period. Accompanying the generation of torsional vibrations, crystal vibrations and liquid surface fluctuations occur, and the interval through which each crystal habit line passes is disturbed, making it possible to detect torsional vibrations. However, when dislocation is generated, the seam disappears, so that it is impossible to detect torsional vibration.
[0030]
On the other hand, in the bend growth, the semi-elliptical fusion ring observed by the eccentric rotational motion moves up and down like a seesaw. For this reason, the measured value of the diameter fluctuates in accordance with the half cycle of crystal rotation. Since no seam is required, measurement is possible even after dislocation.
[0031]
Japanese Patent Publication No. 7-091149 (Comparative Example 2) describes a method of detecting a crystal shake, but the crystal shake is a simple pendulum system, and the wobbling growth is an eccentric rotational motion. It is a completely different phenomenon. Even if crystal wobbling occurs, bend growth does not occur unless the above-described conditions are satisfied. Therefore, this method cannot distinguish between bend growth and wobbling.
[0032]
That is, in waviness growth, it is certain that the wobbling is one of the causes, but the wobbling does not necessarily occur after the waviness growth occurs. Also, waviness growth occurs in a shaft furnace with very small runout. Therefore, the eccentric rotational motion of the growth interface is completely different from the vibration of the single pendulum system.
[0033]
Thus, bend growth is a completely different phenomenon from torsional vibration and crystal vibration. In Comparative Examples 1 and 2, it is difficult to detect the bend growth. On the other hand, when the fluctuation cycle of the fusion ring is measured as in the single crystal bend growth detection method of the present embodiment, it can be reliably detected regardless of the state of the crystal, and by comparison with the crystal rotation cycle. Thus, it is possible to reliably detect the bend growth of a single crystal.
[0034]
[Single crystal bend growth detector]
Next, means for realizing the above-described single crystal bend growth detection method will be described below.
[0035]
Single crystal bend growth detector is a device for detecting crystal bend growth that occurs when a crucible is filled with a raw material and melted, and a seed crystal is immersed in the melt and rotated while being pulled to grow a single crystal. Device. Specifically, it is configured to include a fluctuation period detection means, a crystal rotation period detection means, and a comparison means.
[0036]
The fluctuation period detecting means is means for detecting the fluctuation period of the fusion ring on the growth surface of the single crystal 12. The fluctuation period detection means includes a light intensity detection unit that detects a light intensity on the detection region by scanning a growth interface on the melt from which the single crystal 12 is pulled up, and a light intensity detection unit. A diameter measuring unit that detects the position of the fusion ring from the detected value and measures the diameter of the crystal at the melt surface from the fusion ring, and analyzes the change in the measured value at the diameter measuring unit to And an analysis unit for detecting a fluctuation cycle of the diameter of the single crystal 12. The light intensity detection unit was constituted by a two-dimensional camera.
[0037]
Thereby, the position of the fusion ring can be detected from the difference in light intensity in the region detected by the light intensity detector. From this fusion ring, the diameter of the single crystal 12 on the melt surface is measured by a diameter measuring unit. And the change of the measured value of the diameter of the single crystal 12 measured by the diameter measuring unit is analyzed by the analyzing unit, and the fluctuation period of the crystal diameter on the melt surface is detected. At this time, by using a two-dimensional camera as the light intensity detection unit, even if the fluctuation amount of the fusion ring increases, it is possible to reliably follow.
[0038]
As a conventional diameter measuring apparatus, an optical one-dimensional line sensor is generally used as disclosed in, for example, Japanese Patent Publication No. 53-42476. The diameter measurement value from the sensor is passed through, for example, a Fourier transformer to check the period. However, in the case of a one-dimensional camera, since the scanning line position is generally fixed, if the bend growth is large, the fluctuation amount of the fusion ring may be large and deviate from the scanning line position. On the other hand, by using a two-dimensional camera in which the scanning line position can move following the fusion ring, it is possible to detect the bend growth more stably.
[0039]
The crystal rotation period detecting means is means for detecting the crystal rotation period. In particular, The crystal rotation period detecting means calculates the crystal rotation period from the crystal rotation number at that time which is a kind of operating condition, or Image of two-dimensional CCD camera 20 Analyzing Thus, the crystal rotation period is detected.
[0040]
The comparison means is means for comparing the fluctuation period detected by the fluctuation period detection means with the crystal rotation period detected by the crystal rotation period detection means.
[0041]
Then, the fluctuating period detecting means is used to detect the fusion ring of the crystal growth surface. diameter The fluctuation period is detected, the crystal rotation period is detected by the crystal rotation period detection means, and the fluctuation period is detected by the comparison means. diameter Compare the fluctuation period and the crystal rotation period detected by the crystal rotation period detection means, diameter Fluctuation period and crystal rotation period Half of Is determined to be a single crystal bend growth for the above-mentioned reason.
[0042]
When the single crystal bend growth detector detects bend growth, the bend growth can be suppressed by changing the crystal rotation period or the like. That is, after detecting the bend growth by the above-mentioned means, by having a mechanism for changing the operation parameters such as the crystal rotation speed and the pulling speed, the bend growth can be suppressed and stable crystal pulling operation becomes possible. .
[0043]
[Single crystal manufacturing equipment]
Hereinafter, the single crystal manufacturing apparatus of this embodiment will be described.
[0044]
FIG. 1 is a schematic cross-sectional view of a single crystal manufacturing apparatus according to this embodiment. Parts corresponding to those of the conventional single crystal manufacturing apparatus shown in FIG.
[0045]
In the figure, reference numeral 7 denotes a hollow cylindrical chamber. The chamber 7 includes a cylindrical main chamber 7a and a small-diameter cylindrical pull chamber 7b connected and fixed to the main chamber 7a.
[0046]
The crucible 1 includes an inner layer holding container 1a and an outer layer holding container 1b. A side heater 2 a is disposed outside the crucible 1, and a bottom heater 2 b is disposed below the crucible 1. A heat insulation cylinder 8a is concentrically arranged outside the side heater 2a, and a heat insulation plate 8b is arranged at the bottom.
[0047]
The crucible 1 is filled with 200 kg of a crystal raw material and melted by the heater 2. On the central axis of the crucible 1, a pulling shaft 5 (wire) that is rotatable about the same axis as the support shaft 6 and can be lifted and lowered is suspended through a pull chamber 7 b, and a seed crystal 15 is suspended at the lower end of the pulling shaft 5. It is installed. The pulling shaft 5 is attached to a pulling shaft winding mechanism 9. The pulling shaft winding mechanism 9 is attached to the pulling shaft rotating mechanism 10. As a result, the pulling shaft 5 is wound up by a set amount by the pulling shaft winding mechanism 9 and rotated by the set amount by the pulling shaft rotating mechanism 10.
[0048]
At a position outside the chamber 7 and facing the growth interface in the crucible 1, a two-dimensional CCD camera 20 is installed to take an image of the growth interface. An image analyzer 21 is connected to the two-dimensional CCD camera 20, and the diameter is output via the image analyzer 21. The image analyzer 21 binarizes and processes the image from the CCD camera, counts the number of pixels from end to end of the high-intensity fusion ring, and multiplies it by a preset constant to convert it into a diameter. The diameter of the single crystal output from the image analyzer 21 is input to a control PLC (Programmable Logic Controller) 30 and also input to a Fourier transform logic 22. The Fourier transform logic 22 has a function of FFT (Fast Fourier Transform) analysis and is input Diameter Detect frequency components from time series data Output diameter fluctuation cycle To do. The crystal rotation period is calculated from the crystal rotation number. Alternatively, the image analyzer 21 detects the crystal rotation period by analyzing the image from the two-dimensional CCD camera 20. A period comparison logic 23 is connected to the Fourier transform logic 22.
[0049]
The Fourier transform logic 22 and the period comparison logic 23 are as follows.
[0050]
The Fourier analysis in the Fourier transform logic 22 is generally known, and details thereof are omitted here. Generally, a commercially available FFT (Fast Fourier Transform) analyzer is passed through or has the same function. The period comparison logic 23 compares the frequency output with the actual crystal rotation period. The crystal rotation period may be calculated directly from the crystal rotation speed. The image analyzer 21 analyzes and obtains the image from the two-dimensional CCD camera 20. May be.
[0051]
The diameter fluctuation period output from the Fourier transform logic 22 is compared with the crystal rotation period by the period comparison logic 23. In the period comparison logic 23, the crystal rotation period from the PLC 30 and the diameter fluctuation period from the Fourier transform logic 22 are stored and compared at any time. Then, when the diameter variation period shows 90% coincidence with the half period of the crystal rotation in the set time interval, it is detected that the bend growth has occurred, and a flag is transmitted to the control PLC 30. In the control PLC 30 that has received the flag, a command is issued to change operation parameters such as the crystal rotation speed, pulling speed, and heater temperature. In general, the heater temperature is instructed to increase so that the crystal rotation speed and pulling speed decrease. The specific amount depends on the pulling conditions, but the crystal rotation speed is preferably 1-2 rpm, the pulling speed is 0.01-0.2 mm / min, and the heater temperature is preferably 1-5 ° C.
[0052]
Next, a method for growing a silicon single crystal having a product diameter of 300 mm using the crystal growth apparatus as described above will be described.
[0053]
The inside of the chamber 7 was decompressed to 25 Torr, and 100 L / min Ar was introduced as an inert gas. Then, silicon as a crystal silicon material and boron as an impurity were put into the crucible 1, and both were completely melted by the heater 2.
[0054]
Then, after immersing the seed crystal in the melt and adjusting the melt temperature, the single crystal was pulled in the order of the neck 12a, the increased diameter portion 12b, and the constant diameter portion 12c.
[0055]
In the constant diameter portion 12c, the pulling speed was 0.8 mm / min, and the rotation speed of the crucible 1 was 5 rpm. The rotational speed of the pulling shaft 5 was 12 rpm close to the resonance point. At this rotational speed, the pulling shaft is shaken because it is close to the resonance point, and bend growth tends to occur.
[0056]
First, single crystal pulling was performed in a conventional apparatus in which the present invention was not installed. In this case, wavy growth occurred when the crystal length exceeded 300 mm, but the conventional apparatus cannot detect it, so the pulling speed fluctuates with fluctuations in the measured diameter, as shown in FIG. Bending growth became intense and the crystals were greatly deformed. As a result, a part smaller than the product diameter was generated in part, resulting in a decrease in yield.
[0057]
Next, the case where a single crystal is pulled in the pulling apparatus in which the present invention is installed will be described in detail. The data collection cycle of Fourier transform was 1 sec, and the collection time required for determination was set to 20 min. Since the coincidence of the diameter fluctuation period and the crystal rotation half-cycle was detected from the position of 300 mm after starting the pulling of the constant diameter portion, the crystal rotation speed was changed to 10 rpm and the pulling speed was changed to 0.75 mm / min. The temperature was set to increase 2 ° C. from that point. As a result, as shown in FIG. 9, no bend growth occurred, and the film could be pulled up stably.
[0058]
Further, in a crystal pulled by a conventional crystal pulling apparatus, an oxygen concentration in-plane distribution defined by [(maximum value−minimum value) ÷ minimum value] has a crystal pulled by the present invention as shown in FIG. It was found that the deterioration was significant. There is no difference between them up to about 200 mm, but after that, the crystals pulled by the conventional crystal pulling apparatus have deteriorated significantly. This is due to the following reason. When grinding the outer periphery of a single crystal, it is ground into a cylindrical shape, so that when it enters the crystal side of the bend growth part, the outer periphery that would otherwise be ground remains, and this part has oxygen concentration. This is a cause of deterioration of the in-plane distribution due to the large drop of the surface.
[0059]
Further, the same pulling was performed by 5 Bt at a time with the conventional pulling apparatus and the pulling apparatus according to the present invention. As a result, as shown in FIG. 11, all the conventional devices caused tortuous growth, and dislocations occurred at an early time of 4 Bt. However, all the pulling apparatuses according to the present invention can detect and cope with bend growth in advance, have only 2 Bt dislocations, and have a long dislocation length.
[0060]
【The invention's effect】
(1) In the single crystal bend growth detection method, the fusion ring on the crystal growth surface diameter Compare the fluctuation period and the crystal rotation period, The diameter fluctuation period is half of the crystal rotation period. In some cases, it is determined that the single crystal bends, so that the single crystal bend can be reliably detected.
[0061]
(2) In the single crystal bend growth detector, the fusion ring on the crystal growth surface diameter Detected by a fluctuation period detecting means for detecting a fluctuation period, a crystal rotation period detecting means for detecting a crystal rotation period, and the fluctuation period detecting means. diameter Comparing the fluctuation period and the crystal rotation period detected by the crystal rotation period detection means The diameter fluctuation period is half of the crystal rotation period. And a comparison means for determining that the single crystal bends and grows. diameter The fluctuation period is detected by the crystal rotation period means, respectively, and the comparison means is used. diameter By comparing the fluctuation period and the crystal rotation period, the single crystal bend growth can be reliably detected. That is, by the above comparison, Diameter fluctuation period is half of the crystal rotation period If they match, it is determined that the single crystal bends.
[0062]
(3) A light intensity detection unit that detects the light intensity on the detection region by scanning the growth interface on the melt from which the crystal is pulled up as a detection region, and the light intensity detection unit. A diameter measuring unit that detects the position of the fusion ring from the detected value of the fusion ring and measures the diameter of the crystal at the melt surface from the fusion ring, and analyzes the change in the measured value at the diameter measuring unit to analyze the melt surface. And an analysis unit that detects the fluctuation cycle of the crystal diameter at the liquid crystal, so that the position of the fusion ring is detected to measure the crystal diameter, the change in the measured value is analyzed, and the melt surface level is analyzed. The fluctuation period of the diameter of the crystal can be detected.
[0063]
(4) Since the light intensity detection part of the fluctuation period detecting means is constituted by a two-dimensional camera, even if the fluctuation amount of the fusion ring increases, the two-dimensional camera can be used to reliably follow and stabilize. It is possible to detect twisting growth.
[0064]
(5) Since the single crystal manufacturing apparatus includes any one of the above-described single crystal bend growth detectors and a control unit that changes an operation parameter when the single crystal bend growth detector detects the single crystal bend growth. The single crystal bend growth detection device can reliably detect single crystal bend growth, and the control parameter can be changed by the control unit to reliably suppress single crystal bend growth.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a single crystal manufacturing apparatus according to the present invention.
FIG. 2 is a schematic diagram showing an embodiment of a conventional CZ method.
FIG. 3 is a schematic diagram showing a mode of bend growth.
FIG. 4 is a schematic diagram showing the behavior of the fusion ring at the growth interface during bend growth.
FIG. 5 is a graph showing a state of a diameter variation during bend growth.
FIG. 6 is a model diagram of eccentric rotational motion for explaining the principle of bend growth.
FIG. 7 is a graph for explaining the influence of the relationship between the eccentric rotation period and the crystal rotation period on the difference in growth amount at two points on the growth interface of the single crystal.
FIG. 8 is an external view of a crystal that has been bent and pulled by a conventional apparatus.
FIG. 9 is an external view of a crystal pulled in a pulling apparatus according to the present invention under conditions that cause bend growth.
FIG. 10 is a graph comparing oxygen concentration in-plane distributions of a crystal pulled by a conventional apparatus and the present invention.
FIG. 11 is a graph comparing dislocation-free pulling lengths when the conventional apparatus and the apparatus of the present invention are pulled up by 5 Bt.
[Explanation of symbols]
1: crucible, 2: heater, 5: pulling shaft, 6: crucible support shaft, 7: chamber, 8: heat retaining cylinder, 9: pulling shaft winding mechanism, 10: pulling shaft rotating mechanism, 12a: crystal neck portion, 12b: Crystal enlarged portion, 13: melt, 15: seed crystal, 18: fusion ring, 20: two-dimensional CCD camera, 21: image analyzer, 22: Fourier transform logic, 23: period comparison logic.

Claims (5)

In a single crystal bend growth detection method for detecting crystal bend growth that occurs when a raw material is filled in a crucible and dissolved, and a seed crystal is immersed in the melt and rotated while being pulled to grow a single crystal.
Comparing the diameter fluctuation period of the fusion ring on the crystal growth surface with the crystal rotation period, and determining that the single crystal bend growth is when the diameter fluctuation period is half of the crystal rotation period. Growth detection method. In a single crystal bend growth detector for detecting crystal bend growth that occurs when a raw material is filled in a crucible and dissolved, and a seed crystal is immersed in the melt and rotated while being pulled to grow a single crystal,
A fluctuation period detecting means for detecting a diameter fluctuation period of the fusion ring on the growth surface of the crystal;
A crystal rotation period detecting means for detecting a crystal rotation period;
Comparison diameter fluctuation period by comparing the a crystal rotation period detecting determines that the single crystal Bend growth at half the crystal rotation period is detected diameter fluctuation cycle and the crystal rotation period detecting means by the fluctuation cycle detecting means And a single-crystal bend growth detecting device. In the single-crystal bend growth detector according to claim 2,
The fluctuation period detecting means is
A light intensity detector that scans the growth interface on the melt from which the crystal is pulled as a detection region and detects the light intensity on the detection region;
A diameter measurement unit that detects the position of the fusion ring from the detection value in the light intensity detection unit and measures the diameter of the crystal on the melt surface from the fusion ring;
A single-crystal bend growth detection apparatus comprising: an analysis unit that analyzes a change in a measurement value in the diameter measurement unit and detects a fluctuation period of the diameter of the crystal on the melt surface. In the single-crystal bend growth detector according to claim 3,
A single crystal bend growth detection apparatus, wherein the light intensity detection unit is constituted by a two-dimensional camera. In a single crystal manufacturing apparatus for filling a raw material in a crucible and dissolving it, immersing a seed crystal in the melt and rotating it while pulling it up to grow a single crystal,
A single-crystal bend growth detector according to any one of claims 2 to 4,
A single crystal manufacturing apparatus, comprising: a control unit that changes an operation parameter when single crystal bend growth is detected by the single crystal bend growth detection apparatus.

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