JP4078156B2 - Single crystal pulling apparatus and single crystal pulling method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single crystal pulling apparatus and a single crystal pulling method, and in particular, controls the diameter of a single crystal using a major axis of an ellipse calculated based on a circular arc shape of a meniscus formed at a solid-liquid interface as a tail diameter. The present invention relates to a single crystal pulling apparatus and a single crystal pulling method.
[0002]
[Prior art]
In general, in order to manufacture a silicon wafer, a silicon single crystal ingot is made from polycrystalline silicon by the Czochralski method (hereinafter referred to as CZ method), and this ingot is cut into a predetermined thickness with a slicing machine. Manufacturing.
[0003]
For pulling such a silicon single crystal, a single crystal pulling apparatus as shown in FIG. 8 is used.
[0004]
In such a growth step of the conventional single crystal device 21 of single crystal using twice the narrowing step as dislocation is not generated in the single crystal Ig ₁ to be grown is performed. The first narrowing step is a neck portion growing step, and this neck portion N ₁ is formed in the silicon melt M ₁ in the quartz crucible 24 in which the seed crystal 22 is heated and melted by the heater 23 in the initial stage of crystal growth. Since dislocation occurs in the single crystal Ig ₁ due to the temperature shock caused by the contact, the neck portion N ₁ is grown at a relatively high speed to completely remove the dislocation. Second narrowing process is a tail portion growth step, the tail portion T ₁ performs a reduced diameter to crystal growth end of the straight body portion B ₁ after development of maximum diameter, disconnect the single crystal Ig ₁ from the melt M ₁ dislocations is for preventing from occurring in the single crystal Ig ₁ when.
[0005]
However, in the conventional single crystal pulling apparatus, the diameter of the meniscus formed at the solid-liquid interface is imaged by the two-dimensional camera provided on the upper part of the apparatus, and the single crystal diameter is controlled based on this. In the tail growing step for reducing the diameter of the single crystal as described above, as shown in FIG. 7, from the initial stage of the tail T growing step shown in FIG. 7 (a), the middle stage shown in FIG. 7 (b), As shown in FIG. 7C, the meniscus m gradually disappears toward the final stage, and it becomes difficult to directly capture the complete crystal diameter (crystal width). Since it is an obstacle and the diameter of the meniscus m cannot be accurately imaged, it is difficult to control the diameter of the tail portion T based on the image of the meniscus m.
[0006]
Conventionally, in the Czochralski method, various methods have been proposed in which a meniscus is imaged and the diameter of the tail portion is controlled based on this image.
[0007]
In Patent Document 1, the single crystal pulling apparatus has an image plane for creating a partial image pattern of a bright ring near the crystal using a two-dimensional camera, and this image plane depends on the position of the two-dimensional camera relative to the silicon crystal. In order to correct the distortion of the generated image pattern, it is made substantially parallel to the surface of the silicon melt, and the detection circuit for detecting the feature of the image pattern and the edge of the bright region are defined as a function of the detected feature and the bright region And a measuring circuit for defining a shape including a defined edge, wherein the measuring circuit determines a dimension of the defined shape, whereby the dimension of the silicon crystal is determined as a function of the determined dimension of the defined shape. is there. The single crystal pulling apparatus described in this publication can automatically measure the crystal diameter, but in order to obtain an image circle on the image plane, the imaging system including the two-dimensional camera becomes complicated, and the tail portion During the growing process, as described above, it is difficult to image the meniscus as a complete arc, and since the meniscus diameter cannot be accurately imaged, the meniscus is imaged and the tail portion is based on this. It is difficult to control the diameter.
[0008]
Also, in Patent Document 2, a single crystal pulling apparatus uses a plurality of two-dimensional cameras to switch a two-dimensional camera having a specific image angle for each growth process, and create a partial image pattern of a glitter ring near the crystal. The crystal diameter is obtained from an elliptical arc shape that is completely imaged. Since the single crystal pulling apparatus described in this publication uses a perfect elliptical arc shape, a plurality of two-dimensional cameras are required, so that the structure of the apparatus becomes complicated and expensive.
[0009]
[Patent Document 1]
JP-A-9-175896 (paragraph number 29 on page 6, FIG. 4)
[0010]
[Patent Document 2]
Japanese Patent Laid-Open No. 11-153418 (paragraph numbers 0049 to 0062 on page 7-8, FIG. 10)
[0011]
[Problems to be solved by the invention]
Therefore, a single crystal pulling apparatus which can easily and accurately control the diameter of the tail part easily and accurately based on the image of the meniscus using a general imaging means, and has a simple and inexpensive structure. It was requested.
[0012]
The present invention has been made in consideration of the above-mentioned circumstances, and images a meniscus using a general imaging means, and based on this, automatic control of the diameter of the tail portion can be easily and accurately performed, and An object of the present invention is to provide a single crystal pulling apparatus having a simple and inexpensive structure.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, according to one aspect of the present invention, a crucible provided in a chamber, a heater for heating and melting polysilicon loaded in the crucible, and a grown single crystal are drawn. A crystal pulling means for raising, an image pickup means for picking up an image of a meniscus formed at a solid-liquid interface, and binarizing a meniscus image signal from the image pickup means and controlling the crystal pulling means inputted through an image processing means And a tail growth process for reducing the diameter of the single crystal in a single crystal pulling apparatus that pulls the single crystal by immersing the seed crystal in a melt in which polysilicon is melted. when images the arc shape of the meniscus by the imaging means, calculates an ellipse using the average transfer method by the image processing means in the captured arc shape based on, tail the major axis of the ellipse Single crystal pulling apparatus is provided which is characterized by controlling the crystal pulling means by the control means as the diameter is performed to foster tail. This makes it possible to image a meniscus using a general imaging means, and easily and accurately control the diameter of the tail portion based on this, and the apparatus structure is simple and inexpensive. Is realized.
[0014]
In a preferred example, during the step of growing the straight body portion where the single crystal is grown with a constant diameter, the diameter of the meniscus is imaged by the imaging means, and the straight body portion is grown using this as the diameter of the straight body portion. Thereby, in the straight body part growing step, the complete meniscus is imaged and the diameter is calculated based on the crystal diameter image information, and in the tail growing process, the meniscus arc shape that can be partially imaged is used as a basis. Since the ellipse is calculated and the major axis of the ellipse is used as the tail diameter, automatic control of the crystal diameter can be performed efficiently and reliably.
[0015]
According to another aspect of the present invention, a Czochralski method for imaging a meniscus formed at a solid-liquid interface, binarizing a meniscus image signal, performing image processing, and inputting the diameter information to control a single crystal diameter In the method of pulling a single crystal using the method, during the tail growing process for reducing the diameter of the single crystal, the arc shape of the meniscus is imaged, and an ellipse is calculated using the average moving method based on the imaged arc shape, There is provided a single crystal pulling method characterized in that the tail portion is grown while controlling the crystal diameter with the major axis of the ellipse as the tail portion diameter. Thereby, automatic control of the diameter of a tail part can be performed easily and correctly.
[0016]
In a preferred example, during the step of growing the straight body for growing the single crystal with a constant diameter, the diameter of the meniscus is imaged and this is used as the diameter of the straight body to grow the straight body.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a single crystal pulling apparatus according to the present invention will be described with reference to the accompanying drawings.
[0018]
FIG. 1 is a conceptual diagram of an embodiment of a single crystal pulling apparatus according to the present invention.
[0019]
As shown in FIG. 1, a single crystal pulling apparatus 1 includes a water-cooled furnace body 2, a quartz crucible 3 that melts polysilicon, which is a raw material housed in the furnace body 2, into molten silicon M, and the quartz crucible. 3, a graphite crucible 4 that holds 3, and a heater 5 that surrounds the graphite crucible 4. This graphite crucible 4 passes through the furnace body 2, is connected to a motor 6, is rotated, and is attached to a crucible rotating shaft 8 that is lifted and lowered by a lifting device 7. Above the quartz crucible 3, a pulling wire 11 to which a seed chuck 10 for holding a seed crystal 9 for pulling a single crystal is attached is provided. This wire 11 is provided outside the furnace body 2 and is attached with a wire rotating device 12 as a crystal pulling means for winding and rotating the wire 11 while being energized by a motor Mt.
[0020]
Further, the outer wall of the shoulder 2a of the furnace body 2 is provided with a camera port 13 capable of transmitting light by closing a through hole with heat-resistant glass, and a normal 2 as an imaging means having an optical axis L penetrating the camera port 13 is provided. The dimensional camera 14 is installed with its focal point aligned with the single crystal growth region A, and images the meniscus formed in the growth region of the single crystal Ig.
[0021]
The two-dimensional camera 14 is connected to an AD conversion circuit 15 so that a crystal diameter signal from the two-dimensional camera 14 is transmitted to the AD conversion circuit 15. The crystal diameter signal is binarized by the AD conversion circuit 15 and transmitted to the image processing device 16 as image processing means. The image processing device 16 performs image processing and outputs it as crystal diameter data to be sent to the control device 17. It has become.
[0022]
As shown in FIG. 2, the image processing device 16 includes a camera information calculation processing unit 16a that processes crystal diameter data from the two-dimensional camera 14, and a memory 16b. The control device 17 is a general computer. A control unit 17a that controls each controller to be described later and a memory 17c provided with a table memory 17b are used. The table memory 17b includes crystal shape information (crystals for tail length). Optimum pulling conditions such as the diameter reduction amount), the pulling speed necessary for making the shape, the heater input, the crucible rotation speed, the crucible rising speed, etc. are preset and stored. The various data and the like of the optimum pulling conditions are composed of optimum values respectively obtained corresponding to various crystal shapes theoretically or by past experience or experiment.
[0023]
As a control system for actually controlling these, the control device 17 includes a heater controller 5c that controls the amount of power supplied to the heater 5 that controls the temperature of the silicon melt, and a motor that controls the rotational speed of the quartz crucible 3. A controller 6c, a lifting device controller 7c for controlling the height of the quartz crucible 3, a wire reel rotating device controller 12c for controlling the pulling speed and the number of rotations of the grown crystal, and the like are connected and controlled. , 6c, 7c, 12c, etc. are controlled to change the pulling conditions and control the diameter of the grown crystal.
[0024]
During the single crystal growth process, control of each of these controllers 5c, 6c, 7c and 12c and an argon supply controller controller (not shown) by the controller 17 is a control programmed in the controller 17 in advance. This is performed according to a procedure, and is performed by an input from an input means (not shown) provided in the control device 17 as necessary. In addition, the camera information calculation processing unit that processes the crystal diameter data from the two-dimensional camera may be provided in the image processing device or may be formed integrally with the control device. PID and fuzzy control are effective as a method for controlling the pulling speed.
[0025]
Next, the silicon single crystal pulling method according to the present invention will be described.
[0026]
As shown in FIG. 1, polysilicon is put in a quartz crucible 3, and the growth is automatically performed by a programmed growth process. At this time, as shown in FIG. 3A, in the neck portion growing step, the two-dimensional camera 14 focuses on the neck growth region An, for example, a position displaced 3 mm outward from the center of the quartz crucible 3. In addition, the power is turned on so that imaging can be performed from the start of growth.
[0027]
After completion of the pulling preparation, as shown in FIG. 1, for example, argon gas is allowed to flow into the furnace body 2 from above the furnace body 2, the heater 5 is energized to heat the quartz crucible 3, and the crucible rotation motor 6 is energized. The quartz crucible 3 is rotated by rotating the crucible rotating shaft 8 coupled to the lever crucible rotation motor 6.
[0028]
After a certain period of time has passed, the wire 11 is lowered and the seed 9 is brought into contact with the surface of the silicon melt M and allowed to become familiar.
[0029]
Thereafter, the growth is started, and the width (diameter) of the meniscus of the neck portion N of the neck growth region An is imaged by the two-dimensional camera 14 as shown in FIG. 3A, and as shown in FIGS. The crystal diameter image information of the two-dimensional camera 14 is transmitted to the AD conversion circuit 15 to be binarized, subjected to image processing by the image processing device 16, and the net diameter value is calculated by the camera information calculation unit 16a from the crystal diameter image data. The crystal diameter data is sent to the control device 17, the diameter is calculated by the control unit 17a, and the diameter is compared with the diameter stored in the table memory 17b. The control device 17 controls the heater controller 5c and the motor control. The device 6c, the lifting device controller 7c, and the wire winding device controller 12c are controlled, and the growth is continued until the neck N has a certain length, for example, 300 mm.
[0030]
When the neck N becomes 300 mm, the heater controller 5c, the motor controller 6c, the lift controller 7c, and the wire take-up controller 12c are connected via the controller 17 according to the process program incorporated in the memory 17c. The growth of the single crystal enters the crown C growth step shown in FIG. Subsequently, the crown growth region _AC is monitored by the two-dimensional camera 14, and the diameter is calculated based on the crystal diameter image information of the two-dimensional camera 14 and compared with the diameter stored in the table memory 17b as described above. The controller 17e controls the controllers 5c, 6c, 7c, and 12c, and the crown portion C is grown.
[0031]
Further, as shown in FIG. 3C, the straight body portion B is grown.
[0032]
In the straight body part growing process, similarly to the neck part growing process and the crown part growing process, a meniscus as shown in FIG. 4 is imaged by the two-dimensional camera 14, and the diameter is calculated based on the crystal diameter image information. Comparison with the diameter stored in the memory 17b is performed, and the controller 17c controls the controllers 5c, 6c, 7c, and 12c, and the straight body portion B is grown.
[0033]
When the growth of the straight body portion B having the maximum diameter, which is the main portion of the single crystal Ig, is completed, the tail portion T starts to be grown as shown in FIG.
[0034]
In this tail part growing process, the meniscus gradually ceases to shine from the initial stage of the tail part T shown in FIG. 7 (a) to the middle stage shown in FIG. 7 (b) and the final stage shown in FIG. 7 (c). It becomes difficult to directly image the complete crystal diameter (meniscus width).
[0035]
7A to 7C, the complete meniscus width cannot be directly imaged. Therefore, a partial arc shape of the meniscus is imaged, and the captured arc shape is used as a basis. Then, the ellipse is calculated, and the major axis of the ellipse is used as the tail diameter.
[0036]
For example, as shown in FIG. 5, by the two-dimensional camera 14 captures the partial arc shape of the meniscus, is binarized by the AD converter 15, the image processing apparatus 16, a indicates to arcs shape in FIG. 6 Based on the image of 30 points (n1, n2,..., N30) on this arc-shaped line, a measurement image is created, the major axis is measured for the measurement image, the ellipse is calculated, and the major axis of the ellipse is calculated. To do.
[0037]
Here, if the simple ellipse calculation method is used, a large calculation error may occur if the single crystal is shaken during the pulling process. In the present invention, in order to minimize such an error, the average moving method is used. To calculate. In this average moving method, for example, first, 30 images are captured (n ₁ , n ₂ ... N ₃₀ ), and the average of the diameter values calculated therefrom is used as initial data. taken up _{(n 31),} the average value of _n 2 ... _{n 31} and following data are sequentially _{n 3 ... n 32, n 4} ... how we take the average value of _{n 33.}
[0038]
The control device 17 regards the calculated major axis of the ellipse as the crystal diameter (D) and compares it with the target diameter (D _T ) that is preset and stored in the table memory 17b.
[0039]
If the crystal diameter (D) is within an allowable range with respect to the target diameter (D _T ), the growth is continued. When the crystal diameter (D) is smaller than the target diameter (D _T ) (D <D _T ), the controller 17 causes the motor controller 6c, the lift controller 7c, and the wire winding device controller 12c to be Control to reduce the pulling speed and correct the crystal diameter (D) to increase.
[0040]
When the crystal diameter (D) is larger than the target diameter (D _T ) (D> D _T ), the controller 17 corrects the crystal diameter (D) to be increased by increasing the pulling rate. .
[0041]
In this way, in the tail growing process in which the crystal diameter (width) cannot be directly measured, an ellipse is calculated based on the arc shape of the meniscus that can be partially imaged by one two-dimensional camera, and the major axis of the ellipse is calculated. By using as the tail diameter, the crystal diameter can be automatically controlled. In the straight body part growing step, a complete meniscus is imaged and the diameter is calculated based on the crystal diameter image information. In the tail growing process, an elliptical shape based on the arc shape of the meniscus that can be partially imaged is used. Since the major axis of this ellipse is used as the tail diameter, automatic control of the crystal diameter can be performed efficiently and reliably. Furthermore, since only one two-dimensional camera needs to be installed, a single crystal pulling apparatus with a simple and inexpensive structure can be realized.
[0042]
【The invention's effect】
According to the single crystal pulling apparatus according to the present invention, the meniscus is imaged using a general image pickup means, and the automatic control of the diameter of the tail portion can be easily and accurately performed based on the image. However, a simple and inexpensive single crystal pulling apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a single crystal pulling apparatus according to the present invention.
FIG. 2 is a control circuit diagram used in the single crystal pulling apparatus according to the present invention.
FIG. 3 is a process conceptual diagram of a single crystal pulling method according to the present invention.
FIG. 4 is a conceptual diagram of a crystal diameter imaging state of a straight body portion of a single crystal pulling method according to the present invention.
FIG. 5 is a crystal diameter control process diagram of a tail portion growing step of the single crystal pulling method according to the present invention.
FIG. 6 is a conceptual diagram of a crystal diameter calculation method in a tail portion growing step of a single crystal pulling method according to the present invention.
FIGS. 7A to 7C are conceptual diagrams of imaging states of a meniscus in a tail growing process of a general single crystal pulling method.
FIG. 8 is a conceptual diagram of a single crystal pulling apparatus using a conventional Czochralski method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Single crystal pulling apparatus 2 Furnace body 2a Shoulder 3 Quartz crucible 4 Graphite crucible 5 Heater 5c Heater controller 6 Motor 6c Motor controller 7 Lifting apparatus 7c Lifting apparatus controller 8 Crucible rotating shaft 9 Seed crystal 10 Seed chuck 11 Wire 12 Wire Rotating device 12c Wire reel rotating device control device 13 Camera port 14 Two-dimensional camera 15 AD conversion circuit 16 Image processing device 16a Camera information calculation processing unit 16b Memory 17 Control device 17a Control unit 17b Table memory 17c Memory

Claims (4)

Imaging a crucible provided in the chamber, a heater for heating and melting polysilicon loaded in the crucible, a crystal pulling means for pulling up the grown single crystal, and a meniscus formed at the solid-liquid interface An imaging unit; and a control unit that binarizes the meniscus image signal from the imaging unit and is input via the image processing unit to control the crystal pulling unit to control a single crystal diameter. In a single crystal pulling apparatus for pulling up a single crystal by immersing it in a melt in which silicon is melted, the arc shape of the meniscus is picked up by the image pickup means at the time of growing a tail portion for reducing the diameter of the single crystal, and this image pickup the arc shape based on calculating the ellipse using the average transfer method by the image processing means, control the crystal pulling means by said control means the major axis of the ellipse as a tail portion diameter A single crystal pulling apparatus and performing growth of the tail part was.   2. The apparatus for pulling up a single crystal according to claim 1, wherein the diameter of the meniscus is imaged by an imaging means when the straight body is grown to grow the single crystal with a constant diameter. A single crystal pulling apparatus characterized in that growth is performed. In a single crystal pulling method using the Czochralski method in which a meniscus formed at a solid-liquid interface is imaged, a meniscus image signal is binarized, image-processed and input as diameter information to control the single crystal diameter, During the tail-growing process for reducing the diameter of the crystal, the arc shape of the meniscus is imaged, an ellipse is calculated using the average moving method based on the imaged arc shape, and the major axis of the ellipse is used as the tail diameter. A method for pulling a single crystal, characterized in that a tail portion is grown while controlling a diameter.   4. The method for pulling up a single crystal according to claim 3, wherein the diameter of the meniscus is imaged and this is used as the diameter of the straight body portion when the straight body portion is grown to grow the single crystal with a constant diameter. A method for pulling a single crystal, which is performed.

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