JP2004224585A - Method and apparatus for manufacturing single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for manufacturing a single crystal which realize automatic control over the whole process for manufacturing the single crystal by surely detecting the separation of the tail part of a single crystal from a molten liquid. <P>SOLUTION: In the method for manufacturing the single crystal by which the single crystal having a straight drum part is pulled from a raw material molten liquid in a crucible by the Czochralski method and the diameter of the straight drum part is gradually reduced to form a tail part which is then separated from the raw material molten liquid, the separation of the tail part from the raw material molten liquid is detected from a change in the weight of the single crystal. Preferably, voltage is applied between the single crystal and the crucible when the change in the weight of the single crystal shows zero and the separation of the tail part of the single crystal from the raw material molten liquid is detected by a fact that current is not passed between the single crystal and the crucible. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a single crystal by the Czochralski Method (Czochralski Method, also referred to as CZ method or pulling method) and an apparatus for producing the same.
[0002]
[Prior art]
A single crystal manufacturing apparatus used when manufacturing a silicon single crystal by the CZ method is generally configured as shown in FIG. The single crystal production apparatus 40 accommodates a crucible 1 for accommodating the raw material melt 6 and a main chamber 2 having a heating element (heater) 5 and a single crystal rod 3 pulled up from the raw material melt 6 and takes it out. And a pull chamber 4.
[0003]
The crucible 1 is composed of an inner quartz crucible and an outer graphite crucible. The crucible 1 is mounted on a pedestal 7 and can be moved up and down while being rotated via a rotating shaft 9 by a crucible control means 8 provided below. I can do it. A heating element 5 made of a graphite material is disposed around the crucible 1.
In addition, an optical system (CCD camera) 11 for measuring the diameter of the growing single crystal rod 3 is provided above the main chamber 2 to control and pull up the silicon single crystal to a predetermined diameter. A diameter measuring device is provided.
[0004]
The pull chamber 4 is configured to be openable so that the grown single crystal can be taken out, and a crystal pulling means 12 for pulling the single crystal 3 while rotating the single crystal 3 via a wire 13 (or a shaft) is provided above. is set up.
[0005]
In order to manufacture a silicon single crystal using such an apparatus 40, first, polycrystalline silicon as a raw material is filled in a crucible 1 and the chambers 2 and 4 are set to an argon gas atmosphere. Heat to obtain a raw material melt 6. Thereafter, the wire 13 is gently lowered from above, and a columnar or prismatic seed crystal 15 having a diameter or a side of about 10 to 20 mm suspended from the holder 14 at the lower end of the wire 13 is immersed in the melt surface 10. Let it.
[0006]
Next, the single crystal is grown while rotating the seed crystal 15, but the seed crystal 15 is gently pulled upward while rotating the seed crystal 15 in order to eliminate slip dislocations generated in the seed crystal and dislocations existing in the seed crystal due to thermal shock. Necking to gradually reduce the diameter. In this necking, squeezing is performed until the minimum diameter is about 3 to 5 mm. When the length of the neck reaches about 10 to 20 mm and slip dislocations can be completely removed, the pulling speed and melt temperature are adjusted to reduce the squeezing. The diameter of the portion is expanded, and the process shifts to growing the cone portion of the single crystal rod. After expanding the cone to a predetermined diameter, the pulling speed and the melt temperature are adjusted again, and the process proceeds to the growth of the straight body of the single crystal rod.
It should be noted that the raw material melt decreases with the growth of the single crystal, and the crucible 1 is raised in accordance with the lowering of the melt surface 10, so that the level of the melt surface 10 during the growth of the single crystal is maintained at a constant level. Is adjusted so that the single crystal rod 3 has a predetermined diameter.
[0007]
The straight body must have a constant diameter in order to increase the yield of the wafer. During growth of the single crystal, a bright ring (fusion ring) generated at the melt boundary between the single crystal and the melt is formed by an optical system. 11, the output of the heating element 5, the pulling speed of the single crystal, the rising speed of the crucible 1, etc., so that the diameter of the straight body is maintained with a substantially constant value based on the measured value. Is controlled.
[0008]
When the straight body is grown to a predetermined length, the thermal equilibrium between the melt and the single crystal present at the crystal growth interface collapses and a sudden thermal shock is applied to the crystal, resulting in quality such as slip dislocation and abnormal oxygen precipitation. In order to prevent the occurrence of abnormalities, the diameter is gradually reduced from the straight body to form a conical tail (rounded portion), and then the single crystal is separated (separated) from the silicon melt. . Thereafter, the temperature of the single crystal is lowered while gradually increasing the distance from the melt surface so that a rapid temperature change is not applied to the single crystal. The growth of the single crystal is completed.
[0009]
In recent years, in such a series of silicon single crystal growing steps, the steps from the deposition of the seed crystal 15 on the melt surface 10 to the growth of the straight body of the single crystal rod to the formation of the tail portion have been automated. Single crystal rods can be grown without the need for operator intervention.
For example, a device for accurately measuring the diameter using a CCD camera has been proposed (see Patent Document 1 and Patent Document 2), and highly accurate automatic control is possible.
[0010]
However, it has been difficult to automate the step of finally separating the single crystal from the melt surface after the formation of the tail portion. In particular, when the single crystal is separated from the melt surface, it is necessary to reduce the diameter of the tail portion sufficiently before cutting in order to reduce the effect of thermal shock applied to the single crystal rod. Furthermore, the length of the tail portion is required to be a predetermined length in order to suppress abnormal oxygen precipitation generated in the straight body portion due to the influence of heat of the heating element accompanying the formation of the tail portion. That is, from the viewpoint of crystal quality, it is necessary to separate the tail portion from the melt after controlling the tail portion to a predetermined shape.
[0011]
Therefore, in recent years, a method has been proposed for detecting the separation of the tail portion of the grown single crystal from the raw material melt from the temperature change on the melt surface (see Patent Document 3). The temperature of the silicon melt surface is detected by the temperature sensor provided in the sensor, and it is possible to detect that the tail portion of the single crystal has separated from the melt when the amount of temperature change with time increases rapidly. .
[0012]
[Patent Document 1]
JP-A-6-166590
[Patent Document 2]
Japanese Patent Publication No. 7-26817
[Patent Document 3]
JP 2000-26197 A
[0013]
[Problems to be solved by the invention]
However, the method of detecting a temperature change on the melt surface has a problem that there is a time delay between the time when the single crystal is separated from the melt surface and the time when the temperature on the melt surface rises. Further, there is a problem that the furnace internal structure blocks the surface of the melt and there is a restriction on a place where the temperature sensor is installed.
[0014]
On the other hand, as another method for detecting that the tail portion of the single crystal has separated from the melt, for example, a bright ring generated at the growth interface of the single crystal is captured by an optical device using a two-dimensional camera such as a CCD camera, and an image is captured. Can be conceived by applying image processing for binarizing a dark portion and a bright portion to automatically detect the image. However, because the shape of the tail is an inverted cone, the two-dimensional camera mounted on the upper part of the chamber captures the bright ring in the latter half of the formation of the tail, hidden behind the single crystal straight body. It is difficult to accurately capture the shape of the tail ring and the distance from the melt surface because the bright ring is irregularly distorted because it becomes impossible or the growth interface is photographed obliquely from above. . In particular, with the recent increase in the diameter of the crystal to 200 mm or more, in the formation of the tail portion, the bright ring becomes more and more hidden in the straight body, making detection extremely difficult.
[0015]
Also, at the time of growing the tail portion of the single crystal, the amount of melt in the crucible is considerably reduced, and the tail of the quartz crucible wall and the tail portion formed in an inverted cone shape are reflected on the melt surface, On the melt surface, a bright portion almost as bright as the bright ring appears on the melt surface. Due to this effect, in the method of controlling by taking in an image with a two-dimensional camera and performing binarization processing, it is not possible to distinguish the reflected image on the melt surface from the bright ring, and it is easy to fall into an uncontrollable state. is there.
[0016]
Due to these problems, during the latter half of the tail part forming process until the tail part is separated from the melt, the operator performs manual operations such as observing the inside of the chamber and confirming the separation of crystals. This has been a great hindrance to automating the silicon single crystal growing operation throughout the entire process.
[0017]
The present invention has been made in view of such a problem, and a method and apparatus for manufacturing a single crystal capable of reliably detecting the separation between the tail portion of the single crystal and the melt and enabling automatic control over the entire process. The purpose is to provide.
[0018]
[Means for Solving the Problems]
To achieve the above object, according to the present invention, a single crystal having a straight body is pulled up from a raw material melt in a crucible by the Czochralski method, and the straight body is gradually reduced in diameter to form a tail. A method for producing a single crystal, which is separated from the raw material melt after the method, wherein the method for producing a single crystal, wherein the tail portion is separated from the raw material melt is detected from the weight change amount of the single crystal. Provided (Claim 1).
[0019]
As described above, if the separation of the grown single crystal from the melt surface is detected from the amount of change in weight, there is a problem of detection delay that occurs when the conventional single crystal is detected from the change in temperature of the melt surface, and the temperature sensor The separation between the melt and the crystal can be reliably and promptly detected without any problem due to restrictions on the installation location of the crystal. Therefore, when separating the tail portion of the single crystal rod, it is not necessary for an operator to always observe the inside of the chamber and check the separation between the crystal and the melt, and the seed crystal is grown after the seed crystal is immersed in the melt. The entire process until the single crystal rod is separated from the melt can be completely automated. Further, even after the separation of the crystal, the setting of the pulling machine can be automatically transferred to the next step without manual operation, and the burden on the operator can be reduced.
[0020]
In this case, the weight of the single crystal being pulled is detected, and the weight change per unit time or per unit length is calculated and obtained. It is preferable to determine that the tail is separated from the raw material melt (claim 2).
[0021]
Since the tail portion of the single crystal rod is formed by gradually reducing the diameter from the straight body portion, the contact area between the melt and the single crystal gradually decreases as the tail portion grows, and the increase in weight also decreases. When the tail portion is formed and separated from the silicon melt, the amount of change in the crystal weight becomes zero. Therefore, by grasping the inflection point of the weight change of the crystal with respect to the time axis or the length axis of the crystal, it can be more accurately determined that the single crystal rod has separated from the melt.
[0022]
Further, when the weight change of the single crystal becomes 0, a voltage is applied between the single crystal and the crucible, or an electric current is passed, and the fact that the tail portion of the single crystal is separated from the raw material melt is described. It is preferable that the detection is performed by preventing the current from flowing between the single crystal and the crucible (claim 3).
[0023]
When manufacturing a large-diameter crystal having a diameter of 200 mm or more, particularly 300 mm, the weight of the crystal becomes as large as 200 to 300 kg, so that the sensor for detecting the weight of the crystal is designed to measure up to a high weight accordingly. There is a need. However, in the case of such a weight detection sensor, since the detection resolution is reduced, the weight change amount may be erroneously detected as 0 even when the crystal is not yet separated from the melt. Therefore, when the weight change of the single crystal becomes 0 as described above, a DC or AC voltage is applied between the single crystal and the crucible, or a DC or AC current is passed, and the current flow is interrupted. By detecting that the tail portion has separated from the melt, it can be detected more accurately and reliably.
[0024]
In addition, it can be determined that the tail portion of the single crystal has certainly separated from the raw material melt after a lapse of a predetermined time from when the weight change amount of the single crystal has become zero (claim 4).
Even if it is detected that the weight change of the single crystal has become zero, the tail part may not actually be separated from the melt in the case of a particularly heavy single crystal. If it is determined that the tail portion of the single crystal has separated from the melt after a lapse of a predetermined time, for example, several tens of minutes, the single crystal is manufactured even when a large-diameter crystal having a diameter of 300 mm or more is manufactured. It can be reliably determined that the tail of the crystal has separated from the melt.
[0025]
Further, it is preferable that an operator be notified by an alarm that the tail portion of the single crystal has separated from the raw material melt (claim 5).
For example, when the weight change per unit time or unit length of the single crystal becomes 0, or when the current stops flowing between the single crystal and the crucible, or when the weight change becomes 0 If an alarm is sounded after a lapse of a predetermined time, it is possible for the operator to know that the tail has separated from the raw material melt without constantly monitoring, and it is possible to further reduce the work load.
[0026]
Further, according to the present invention, there is provided a single crystal manufacturing apparatus used for pulling a single crystal from a raw material melt by the Czochralski method, wherein at least a crucible containing the raw material melt and a heat generating source for heating the raw material melt are used. And a crucible control means for raising and lowering the single crystal while rotating the crucible by rotating the single crystal via a wire or a shaft. A weighing scale that detects the weight of the single crystal that is detected, and calculates the weight change per unit time or unit length of the detected single crystal to detect that the tail of the single crystal has separated from the melt The apparatus for producing a single crystal is further provided with a separation detecting means for performing the separation (light 6).
[0027]
When a single crystal is manufactured using the apparatus having such a configuration, the amount of change in weight of the single crystal per unit time or per unit length is calculated, and the amount of change in the weight of the single crystal becomes zero. The separation of the rod from the melt can be reliably detected. Therefore, if a single crystal is grown using such an apparatus and the fact that the tail is separated from the melt is automatically detected based on the amount of weight change, the entire crystal growth can be performed without the intervention of an operator. It is also possible to promote automation in the process.
[0028]
A load cell can be suitably used as the weighing scale (claim 7).
By using the load cell as the weigh scale, the weight of the single crystal can be detected with high accuracy and stability, and the reliability can be further improved.
[0029]
Preferably, a voltage source or a current source is provided so that a current flows between the single crystal being pulled and the crucible through a wire or a shaft (claim 8).
Thus, if the apparatus is provided with a DC or AC voltage source or a DC or AC current source that allows a current to flow between the single crystal and the crucible, for example, a large-diameter crystal having a diameter of 200 mm or more, particularly 300 mm can be manufactured. Even in this case, the fact that the single crystal has separated from the melt can be detected more accurately because the weight change amount has become zero and the current flow has been interrupted.
[0030]
Further, it is preferable that the apparatus further includes an alarm linked to the separation detecting means (claim 9).
If such a warning device is further provided, the worker can be notified of the separation between the crystal and the melt by a warning sound or a warning lamp, so that monitoring of the worker becomes unnecessary and the single crystal Manufacturing can be further automated.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described, but the present invention is not limited thereto.
When growing a single crystal, the weight of the single crystal rod increases as the single crystal grows. When the single crystal is separated from the melt surface, the diameter of the single crystal is gradually reduced to form an inverted conical tail portion. At this time, the weight increase of the crystal rod is reduced. . Furthermore, when the tail part moves away from the melt, the weight increase of the single crystal rod becomes zero.
The present inventors paid attention to the increase in the weight of the single crystal rod in the single crystal growing process, and determined the point at which the single crystal rod suddenly changed in weight when the single crystal rod was separated from the melt surface. The present invention was completed by finding that the present invention can be utilized for the determination.
[0032]
FIG. 1 shows an example of a single crystal manufacturing apparatus according to the present invention. This single crystal manufacturing apparatus 30 includes a crucible 1 for accommodating a raw material melt 6 in a main chamber 2 and a heating element 5 for heating the raw material melt, as in the conventional apparatus, and moves up and down while rotating the crucible 1. And a crucible control means 8 for performing the operation. Above the pull chamber 4, a crystal pulling means 12 for pulling the single crystal 3 while rotating it via a wire 13 is provided, and further as a weighing scale for detecting the weight of the single crystal pulled by the crystal pulling means. , A load cell 16 are provided. Further, a control device 17 is provided outside the chambers 2 and 4, and the control device 17 calculates a weight change amount per unit time or unit length of the weight of the single crystal 3 detected by the load cell 16. There are provided separation detecting means for detecting that the tail portion of the single crystal 3 has been separated from the melt by processing, and an alarm interlocked with the separation detecting means.
[0033]
Further, in this single crystal manufacturing apparatus, a voltage source 18 is provided so that a current flows between the single crystal being pulled up through the wire 13 and the crucible, and an ammeter for detecting whether or not the current is flowing. 19 and a switch mechanism 20 for turning ON / OFF the voltage application.
Although the voltage source is used here, it is needless to say that the voltage source may be replaced with a current source, or a direct current or an alternating current may be used.
[0034]
By growing a single crystal using such a single crystal manufacturing apparatus 30, it is possible to detect from the amount of change in the weight of the single crystal that the tail portion has separated from the raw material melt.
FIGS. 2A and 2B schematically show the amount of weight change with respect to the growing time when a single crystal is manufactured. As shown in FIG. 2 (A), where the neck portion 21 is formed and then the straight body portion 23 is formed to obtain a crystal of a predetermined length, the weight of the crystal gradually increases at a constant rate over time. To increase. When the tail portion 24 is formed, the weight increase becomes gradual, and when the tail portion 24 is separated from the melt, the weight increase becomes constant. Here, the weight increase amount is zero. Therefore, when the single crystal is manufactured, if the amount of change in weight of the single crystal with respect to the growing time is always detected, it is possible to detect from the amount of change in weight of the single crystal that the tail portion 24 has separated from the raw material melt. Can be.
[0035]
FIG. 2B shows the single crystal being pulled in terms of the amount of weight change per unit time. As shown in FIG. 2B, the amount of increase increases sharply when the cone portion 22 is formed, and the amount of weight increase becomes constant during formation of the straight body portion. When the tail portion is formed, the weight is substantially saturated, and the weight increase rapidly decreases. When the tail portion of the single crystal is separated from the melt, the increase amount becomes zero.
[0036]
Therefore, when the weight W of the single crystal during the growth of the single crystal is detected and the growth time is represented by T, the weight change dW / dT with respect to the time axis is calculated and obtained, and the value of dW / dT suddenly becomes 0. It can be determined that the tail portion of the single crystal has been separated from the melt when. In addition, since the length of the crystal increases almost constantly as the growth time elapses, the amount of weight change per unit length of the crystal, that is, when the crystal length is L, the amount of weight change with respect to the length axis By calculating and calculating dW / dL, it can be similarly determined that the tail has separated from the melt.
[0037]
As described above, it is possible to detect that the tail portion is separated from the raw material melt based on the amount of change in weight of the single crystal. Therefore, the detection resolution decreases. Therefore, even if the increase is detected as 0, the tail may not actually be separated from the melt. Therefore, by using the detection based on the amount of change in weight and the detection based on the electric current together, it is possible to more accurately determine that the tail portion is separated from the raw material melt.
[0038]
FIG. 3 shows a control device connected to the load cell and a signal processing flow. The diameter of the single crystal rod is determined from image information captured by a CCD camera (optical system), and this information is fed back to a control system such as a pulling speed and a temperature, so that the diameter of the single crystal rod can be set to a predetermined value in each growing step. Value can be controlled. Then, in the formation of the tail portion (rounding step), the crystal weight is measured by the load cell, and the amount of change in crystal weight per unit time (dW / dT) is calculated. When the weight change of the single crystal becomes 0 (dW / dT = 0), a voltage of, for example, DC 12 V is applied between the single crystal and the crucible, and the current is measured. At this time, when the tail portion is not separated from the melt, current flows through the grown single crystal and the melt, but when separated, no current flows. Therefore, if it is determined that the crystal and the melt have separated from each other when the current stops flowing, and an alarm sound is issued, the operator can be reliably informed.
[0039]
It has long been practiced to apply a voltage between a single crystal and a quartz crucible to cause a current to flow, but this may have an effect on the quality of the single crystal. There is a possibility that. However, if the current is caused to flow when the weight change amount of the crystal becomes 0 as described above, even if the tail portion is not separated from the melt, the current flow is separated in a short time and the current flows. Since it is discontinued, there is almost no effect on the grown single crystal or quartz crucible.
[0040]
In addition to detecting the presence or absence of an electric current, it can also be determined that the tail portion of the single crystal has separated from the raw material melt after a lapse of a predetermined time from when the weight change amount of the single crystal becomes zero. . For example, if the tail is not actually separated from the melt even if the increase becomes zero, the time from when the increase becomes zero to the actual separation of the tail from the melt is measured in advance. It can be determined that the tail part has surely separated from the melt at least at the time when the amount of increase has become zero. According to such a method, it is not necessary to provide a device for flowing a current between the crystal and the melt, and the determination can be made easily.
[0041]
According to an experiment conducted by the present inventors, in a crystal having a diameter of 300 mm, about 20 mm in diameter may be in contact with the molten metal surface when the weight change becomes zero. Since the pulling speed is about 0.4 to 1.0 mm / min depending on the product type, after a time of at least 30 mm (30 minutes or more) in the pulling axial direction from the time when the weight change becomes 0, the single crystal is removed. What is necessary is just to determine that the tail part was separated from the melt.
[0042]
【Example】
Hereinafter, examples of the present invention will be described.
<Example 1>
This is a single crystal pulling apparatus as shown in FIG. 1, in which a crucible is filled with the raw material polycrystalline silicon, heated and melted, and then the wire is drawn using a single crystal pulling apparatus having a diameter of 6 inches (150 mm) and 50 kg or less. The seed crystal held at the lower end of the sample was immersed in the melt. After the temperature of the seed crystal becomes about the same as the melt temperature, the temperature of the melt and the pulling speed are adjusted to grow the neck, cone, and shoulder in order, and then a straight body with a constant diameter Part was formed. After the straight body reached a predetermined length, the pulling speed and the temperature of the melt were increased, and the crystal diameter was gradually reduced to form a tail.
[0043]
In the tail growing process, the weight change dW / dT value was determined one by one by a control device built in a computer connected to the load cell. Then, when dW / dT = 0 (the amount of change in weight was 0), it was determined that the gap between the tail portion of the single crystal and the melt, that is, the growth of the single crystal rod was completed.
When the control device determines the separation between the melt and the tail portion of the single crystal rod, the single crystal rod gradually increases the distance from the melt surface, lowers the temperature of the single crystal while avoiding a sudden temperature change, and reduces the temperature of the single crystal to room temperature. When lowered to the vicinity, the single crystal rod was removed from the pull chamber, and the growth of the single crystal was completed.
[0044]
In this way, unattended automatic control is possible over the entire process from the completion of the growth of the single crystal from the deposition of the seed crystal on the melt to the removal of the single crystal rod from the apparatus.
Moreover, the manufactured single crystal rod was of high quality and high wafer yield.
[0045]
<Example 2>
In a device for a large-diameter single crystal having a diameter of 12 inches (300 mm), 200 kg or more, and a long and heavy crystal, the weight of the crystal is constantly detected by a load cell and a signal is sent to a control device. Calculation of change has started.
When the change in the crystal weight has ceased (when the increase in the crystal weight per unit time or unit length has become zero, that is, when the change in the crystal weight has fallen below the detection limit), it is judged to be near the end of rounding. did. After it was determined that the rounding had been completed, a current flowing by applying an AC voltage of 12 V between the wire and the crucible was detected, and when the detected current stopped flowing, it was determined that the rounding was completed.
Thereby, it was possible to accurately detect that the tail part was separated from the melt. Also in this case, unattended automatic control became possible over the entire process from completion of the growth of the single crystal from the deposition of the seed crystal on the melt to the removal of the single crystal rod from the apparatus.
Moreover, the manufactured single crystal rod was of high quality and high wafer yield.
[0046]
Note that the present invention is not limited to the above embodiment. The above embodiment is merely an example, and any embodiment having substantially the same configuration as the technical idea described in the claims of the present invention and having the same function and effect will be described. It is included in the technical scope of the invention.
[0047]
【The invention's effect】
As described above, in the present invention, the separation of the tail portion of the single crystal from the melt is detected from the amount of change in the weight of the single crystal rod. When growing the single crystal, the tail portion was separated from the raw material melt by applying a voltage between the single crystal and the crucible when the weight change of the single crystal became 0 and the current stopped flowing. Can be instantaneously and reliably determined.
[0048]
Therefore, the separation of the single crystal from the melt, which has been considered difficult so far, can be automatically detected, and the production by the unmanned automatic control can be performed over the entire single crystal production process. This can greatly contribute to the introduction of a centralized monitoring system for pulling equipment managed in one place. In recent years, for the production of large-diameter and long crystals, the introduction of MCZ machines in which magnets are arranged around a pulling device is progressing. However, by applying the present invention, workers can be kept without being kept in a high magnetic field. Crystals can be manufactured, and the burden on the worker's body can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a single crystal manufacturing apparatus according to the present invention.
FIG. 2 is a diagram schematically illustrating a change in weight with respect to a growth time when a single crystal is manufactured according to the present invention.
(A) Crystal weight with respect to growing time
(B) Weight change per unit time with respect to growing time
FIG. 3 is a flowchart showing an example of a method for producing a single crystal according to the present invention.
FIG. 4 is a schematic view showing a conventional single crystal manufacturing apparatus.
[Explanation of symbols]
1: Crucible, 2: Main chamber, 3: Single crystal rod,
4 ... pull chamber, 5 ... heating element (heater), 6 ... raw material melt,
7: pedestal, 8: crucible rotation mechanism, 9: crucible rotation axis,
10: melt surface, 11: optical system device (CCD camera),
12: crystal pulling rotation mechanism, 13: wire, 14: holder,
15: seed crystal, 16: load cell, 17: control device, 18: voltage source,
19: ammeter, 20: switch mechanism, 21: neck, 22: cone,
23: straight body, 24: tail.

Claims (9)

Production of a single crystal having a straight body portion pulled up from the raw material melt in the crucible by the Czochralski method, gradually reducing the diameter of the straight body portion to form a tail portion, and then separating from the raw material melt. The method for producing a single crystal according to the method, wherein the fact that the tail portion is separated from the raw material melt is detected from a weight change amount of the single crystal. The weight of the single crystal during the pulling is detected, and the weight change per unit time or per unit length is calculated and obtained. When the weight change per unit time or per unit length becomes zero, the tail portion is obtained. 2. The method for producing a single crystal according to claim 1, wherein it is determined that the material is separated from the raw material melt. When the weight change amount of the single crystal becomes 0, a voltage is applied between the single crystal and the crucible, or a current is applied, and the single crystal is determined to have a tail portion separated from the raw material melt. The method for producing a single crystal according to claim 1, wherein the detection is performed when the current stops flowing between the crucible and the crucible. The method according to claim 1, wherein it is determined that the tail portion of the single crystal is surely separated from the raw material melt after a lapse of a predetermined time from the time when the weight change amount of the single crystal becomes zero. The method for producing a single crystal according to the above. The method for producing a single crystal according to any one of claims 1 to 4, wherein an operator is notified by an alarm that the tail portion of the single crystal has separated from the raw material melt. A single crystal manufacturing apparatus used when pulling a single crystal from a raw material melt by the Czochralski method, comprising at least a crucible containing the raw material melt and a heating element for heating the raw material melt A crystal pulling means for pulling up while rotating the single crystal via a wire or a shaft, and a crucible control means for raising and lowering while rotating the crucible, wherein the weight of the single crystal pulled up by the crystal pulling means is reduced. A weighing scale for detecting, and separation detecting means for calculating that the weight change per unit time or unit length of the detected single crystal weight and detecting that the tail portion of the single crystal has separated from the melt. An apparatus for producing a single crystal, further comprising: The single crystal manufacturing apparatus according to claim 6, wherein the weighing scale is a load cell. The single crystal manufacturing apparatus according to claim 6 or 7, further comprising a voltage source or a current source so that a current flows between the single crystal being pulled and the crucible through the wire or the shaft. . The apparatus for producing a single crystal according to any one of claims 6 to 8, further comprising an alarm linked to the separation detecting means.

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