JP2000264780A - Melting detection method and detector for use in semiconductor single crystal pulling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting the melting of a semiconductor raw material, which enables automatic detection of the completion of melting of the semiconductor raw material and the completion of remelting of a silicon ingot, in a melting stage performed in a semiconductor pulling-up device, also reduction in operator load and further automation of the shift operation from the melting stage to a pulling stage, and also to provide a detector for the method. SOLUTION: The melting detector 2 for detecting the melting of a semiconductor raw material 108 (or silicon ingot), for use in a semiconductor pulling device 1, consists of: a two-dimensional CCD(charge coupled device) camera 201 for photographing the inside of a crucible 102; and a picture processor 202 for converting the photographed picture by the CCD camera 201 into a black- and -while binary picture, counting the number of black or white pixels inside the crucible 102 in the converted binary picture and detecting the completion of melting of the semiconductor raw material 108 in the crucible 102 from the counted number of black or white pixels.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for detecting melting in a semiconductor single crystal pulling apparatus.

[0002]

2. Description of the Related Art Semiconductor single crystal pulling apparatus, for example, CZ
In a silicon single crystal pulling apparatus using the method, rod-shaped polycrystalline silicon crushed into small pieces is put into a crucible made of quartz glass and melted (melt process), and becomes a nucleus of crystal growth on the silicon melt surface. The seed crystal (seed) is suspended and immersed in a wire, and the seed crystal is pulled up while slowly rotating (pulling step), so that single-crystal silicon is grown from the tip of the seed crystal. As described above, in order to grow single-crystal silicon from the tip of the seed crystal, it is necessary to confirm that the semiconductor material such as rod-shaped polycrystalline silicon charged into the crucible has been completely melted in the above-described melting step. is there. Conventionally, the completion of the melting of the semiconductor material in the melt process has been confirmed visually by an operator looking into the crucible from a viewing window.

[0003] When a crystal is changed from a single crystal to a polycrystal in the single crystal pulling step, the pulled ingot may be re-melted and pulled again. In this case as well, it is necessary to confirm that the ingot once pulled has completely melted, as in the case described above.
Conventionally, the completion of remelting of the ingot has been visually checked by an operator looking into the crucible from a viewing window.

[0004]

By the way, since it takes a considerable amount of time until the semiconductor raw material or the ingot is completely melted, it is necessary for an operator to repeatedly monitor at regular intervals in the case of visual confirmation. there were. For this reason, the burden on the operator is increased, and the judgment of the completion of melting by the operator varies, which makes automation difficult. Further, if the monitoring timing does not match, the worker does not notice even though the melting is completed, which causes a decrease in throughput, an increase in the amount of power, a deterioration of members, and the like.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can automatically detect the completion of melting of a semiconductor material in a melt process of a semiconductor single crystal pulling apparatus, thereby imposing a burden on an operator. It is an object of the present invention to provide a method for detecting melting in a semiconductor single crystal pulling apparatus and an apparatus thereof, which can reduce the number of steps and can automate the transition from the melt step to the pulling step. Also, the present invention
A method and apparatus for detecting the melting of a semiconductor single crystal pulling apparatus capable of automatically detecting the completion of remelting of an ingot, reducing the burden on the operator, and automating the transition to the repulling step. The purpose is to provide.

[0006]

In order to achieve the above object, a melting detection method according to the present invention takes an image of the inside of a crucible by an imaging means, converts the captured image into a black-and-white binary image, and then converts the image. The number of white or black pixels in a crucible in a binary image is counted, and the completion of melting of the semiconductor material in the crucible is detected from the counted number of white or black pixels.

With this configuration, the completion of the melting of the semiconductor raw material in the melt process of the semiconductor single crystal pulling apparatus can be automatically detected by image processing. For this reason, visual monitoring by the operator can be eliminated.

[0008] Further, the melting detection device of the present invention comprises an image pickup means for photographing the inside of the crucible, an image taken by the image pickup means being converted into a black-and-white binary image, and And an image processing device for counting the number of white pixels or black pixels and detecting the completion of melting of the semiconductor raw material in the crucible from the counted number of white pixels or black pixels.

With this configuration, the completion of the melting of the semiconductor material in the melt process of the semiconductor single crystal pulling apparatus can be automatically detected by image processing, so that the burden on the operator can be reduced and the pulling up from the melt process can be performed. It is possible to obtain a semiconductor raw material melting detector capable of automating the transition to the process.

Further, according to the melting detection method of the present invention, a monitoring area for melting detection is previously set at a predetermined position of the ingot in the crucible or at a predetermined position including both the ingot and the semiconductor melt surface near the ingot. After setting, the monitoring area is photographed by the imaging means, the photographed image of the monitoring area is converted into a black and white binary image, and the number of white pixels or black pixels in the monitoring area is calculated using the converted binary image. Is counted, and the completion of melting of the ingot is detected from a change in the counted number of white pixels or black pixels.

With this configuration, completion of remelting of the ingot can be automatically detected by image processing. For this reason, visual monitoring by the operator can be eliminated.

Further, the melting detecting apparatus of the present invention is provided for detecting a melting preset at a predetermined position of an ingot in a crucible or at a predetermined position including both an ingot and a semiconductor melt surface near the ingot. An imaging unit that captures an image of a monitoring area; and a captured image captured by the imaging unit is converted into a black-and-white binary image, and the number of white pixels or black pixels in the monitoring area in the converted binary image is counted. And an image processing device for detecting the completion of melting of the ingot from the change in the counted number of white pixels or black pixels.

With such a configuration, the completion of the remelting of the ingot can be dynamically detected by image processing, so that the burden on the operator can be reduced and the transition to the pulling process can be automated. Can be obtained.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. First, an embodiment of a melting detection device and a detection method for detecting the melting of a semiconductor raw material will be described with reference to FIGS. Here, FIG. 1 is an overall structural view of a CZ type silicon single crystal pulling apparatus provided with a semiconductor raw material melting detecting apparatus according to the present invention, and FIG.
FIG. 2 is a diagram illustrating a circuit example of the image processing apparatus in FIG. 1.

In FIG. 1, reference numeral 1 denotes a CZ type silicon single crystal pulling apparatus (hereinafter abbreviated as "single crystal pulling apparatus"), and 2 denotes a semiconductor material melting detecting apparatus (hereinafter, "melting detecting apparatus") according to the present invention. (Abbreviation) 3 is a seed crystal.

The single crystal pulling apparatus 1 includes a graphite heater 1.
The crucible 102 made of quartz glass is heated by the temperature of 01 or the like. The outer periphery of the crucible 102 is supported by a graphite crucible 120 and the rotating shaft 1
21 rotatably supported. The crucible 102 is surrounded by a vacuum vessel 103.
At the upper end of the neck of the vacuum vessel 103, a crystal rotating / elevating mechanism 104 composed of a motor, a hoisting drum and the like is installed. The seed crystal 3 serving as a nucleus for crystal growth is suspended by being held by a seed chuck or the like at the tip of a wire 105 made of stainless steel or molybdenum connected to the crystal rotating / elevating mechanism 104. The mechanism 104 is configured to be rotatable and vertically movable.

The crucible 102 is provided on a crucible rotating / elevating mechanism 106, and is configured to freely rotate / elevate the entire crucible. Vacuum vessel 103
A transparent viewing window 107 made of quartz glass is provided at the shoulder of the camera, and a two-dimensional CCD camera 201, which will be described later, is installed toward the inside of the crucible 102 in this window portion. Reference numeral 108 denotes a silicon lump as a semiconductor raw material put into the crucible 102, and reference numeral 109 denotes a melt surface of the molten silicon.

The melting detector 2 is provided with a silicon lump 108 in the crucible 102 and a silicon melt surface 109 through the viewing window 107.
Two-dimensional CCD camera (imaging means) 201 for photographing
An image processing device 202 for detecting the molten state of the silicon lump 108 by image processing, a monitor television 203,
It comprises a buzzer 204 and an indicator light 205 as a notification means.

As shown in FIG. 2, the image processing apparatus 202 includes a binary image converter 206 for converting an image captured by the two-dimensional CCD camera 201 into a black and white binary image. A black pixel counting unit 207 for counting the number of black pixels in the crucible in the binary image, and as a complete melting of the silicon block 108 when the counted number of black pixels becomes smaller than a preset comparison reference value. It comprises a melting judgment unit 208 for judging, and a signal output unit 209 for outputting a detection signal of the completion of melting in accordance with the judgment result of the melting judgment unit 208. The image processing apparatus 202 may be configured as software on a program using a personal computer or the like, or may be configured as a dedicated hardware circuit.

First, before describing the details of the melting detecting operation by the melting detecting device 2 of the present invention, the melt process of the single crystal pulling device 1 and the subsequent single crystal pulling process will be briefly described.

The rod-shaped polycrystalline silicon as a raw material is crushed into blocks, put into a crucible 102 in the form of a silicon lump 108, and melted by heating with a graphite heater 101 or the like (melt process). On the other hand, the seed crystal 3 is held at the tip of the wire 105 by a seed chuck (not shown) or the like, and is suspended above the center of the crucible 102. Then, when the silicon mass 108 is completely melted, the seed,
The process shifts to the single crystal pulling process consisting of the neck and body processes.

That is, when the processing shifts to the single crystal pulling step, the wire 1
05 is lowered downward, the tip of the seed crystal 3 suspended from the tip of the wire 105 is immersed in the silicon melt 109 in the crucible 102, and the crystal rotation / elevation mechanism 104 and the crucible rotation / elevation mechanism 106 A predetermined driving is started, and the seed crystal and the crucible 102 are slowly rotated at a predetermined speed in opposite directions to each other, and the pulling is started (seed step). Thus, the growth of the single crystal starts from the tip of the seed crystal 3.

At the point when the single crystal has grown to some extent from the tip of the seed crystal 3, the process shifts from the seed step to the neck step in order to eliminate dislocation of the single crystal, and pulls up while narrowing the diameter of the growing crystal. Go. Then, after pulling up a predetermined distance with a small diameter, shift to a body process for stably growing a large diameter single crystal as a product, and slowly pull up a large diameter single crystal ingot. Thus, a silicon single crystal is manufactured. The melting detecting device 2 constantly monitors the melting state of the silicon lump in the above-described melting step of melting the silicon lump 108, and automatically detects and informs that the silicon lump has completely melted.

Next, the operation of the melting detecting device 2 will be described with reference to FIG. Two-dimensional CCD camera 20
1 is a silicon lump 1 in the crucible 102 from the viewing window 107.
08 and the silicon melt surface 109 are photographed, and a photographed image as shown in FIG.

The binary image converter 20 of the image processing device 202
6 is a diagram of FIG. 3 sent from the two-dimensional CCD camera 201.
Is converted into a digital signal, and then converted into a black and white binary image at a predetermined threshold level (threshold). The captured image converted to a black-and-white binary image is sent to the monitor television 203 and displayed on the screen, and is also sent to the black pixel counting unit 207.

As shown in FIG. 3, when the silicon mass 108 has not yet been melted or is in the process of being melted, the temperature thereof is low, so that the silicon mass 108 appears black on the screen. On the other hand, since completely melted silicon becomes a high temperature liquid, the crucible 1
The silicon melt surface 109 in 02 is brightly whitish and bright on the screen. Therefore, if the photographed image in FIG. 3 is binarized into black and white at an appropriate threshold level (threshold), the silicon mass 108 is converted into black pixels and the silicon melt surface 109 is converted into white pixels. can do.

The black pixel counting unit 207 is used to detect the crucible 1 in the black and white binary image sent from the binary image conversion unit 206.
The number m of black pixels in 02 (corresponding to the area of the silicon block 108) is counted and sent to the melting determination unit 208. Note that, in order to avoid the influence of the reflection due to the fluctuation of the silicon melt surface 109, it is preferable to perform processing so that only the black pixels existing at the same position continuously for a certain period of time are determined to be the silicon mass 108.

The melting judging section 208 includes a black pixel counting section 207.
Is compared with a comparison reference value S set in advance. Then, when the number m of black pixels becomes smaller than the comparison reference value S, it is determined that the melting of the silicon block 108 has been completed, and the determination result is output to the signal output unit 20.
Send to 9.

That is, when the silicon mass 108 is completely melted, the inside of the crucible 102 is entirely filled with the silicon melt surface 109.
, And there is almost no black pixel except for foreign matter, and there is only a white pixel. Therefore, if the comparison reference value S is set to a predetermined value in consideration of foreign matter mixing or an error in fluctuation of the silicon melt surface 109, it is detected that the silicon mass 108 in the crucible 102 has completely melted. be able to.

The signal output unit 209 outputs a detection signal according to the determination result sent from the melting determination unit 208. For example, the buzzer 204 sounds, the indicator lamp 205 is turned on, and the silicon block 108 is completely Notify the worker that it has melted. If necessary, the detection signal is sent to a pulling control device (not shown) of the single crystal pulling apparatus 1 to control the operation of the crystal rotating / elevating mechanism 104 and the crucible rotating / elevating mechanism 106, and Automatically shifts to the lifting process.

As described above, in the case of using the melting detecting device 2 according to the above embodiment, the complete melting of the silicon lump 108 in the crucible 102 can be automatically detected.
For this reason, the visual monitoring of the worker becomes unnecessary, and the burden on the worker can be reduced. In addition, since the monitoring timing does not become inconsistent, the process can be immediately shifted to the single crystal pulling process, so that a decrease in throughput, an increase in power consumption, deterioration of members, and the like can be prevented.

When the crucible 102 is slowly rotated by the crucible rotating / elevating mechanism 106 when the silicon lump 108 is melted, as shown in FIG. Silicon lump 10
What is necessary is just to process so that it may be judged as 8.

Next, a second embodiment will be described. In the second embodiment, a description will be given of a melting detection device and a detection method for detecting re-melting of an ingot once pulled up. The melting detection device and the detection method according to the second embodiment basically have the same configuration as the first embodiment, but in the second embodiment, a predetermined position of the ingot in the crucible is set. Alternatively, a monitoring area for melting detection is set in advance at a predetermined position including both the ingot and the semiconductor melt surface in the vicinity of the ingot, and the monitoring area is photographed by the imaging means, and white pixels or black pixels in the monitoring area are set. It is characterized in that the number of pixels is counted and the completion of remelting of the ingot is detected from the counted number of white pixels or black pixels.

Next, the operation of the melting detecting device 2 will be described with reference to FIGS. FIG. 5 is an explanatory view of a monitoring area for monitoring melting of the ingot, FIG.
FIG. 3 is a diagram showing an example of a black and white binary image of an ingot and a silicon melt surface in a monitoring area.

First, a monitoring area 111 to be photographed by the two-dimensional CCD camera 201 is set.
The two-dimensional CCD camera 201 is arranged at a position where an image can be taken. Other configurations are the same as those of the melting detection device 2 in the first embodiment. Then, a predetermined range in the crucible including the monitoring area 4 for monitoring set in advance is photographed from the viewing window 107 by the two-dimensional CCD camera 201, and the photographed image is sent to the image processing device 202. In the case of this embodiment, the monitoring area 111 is set at a position where the right edge of the ingot 110 and the silicon melt surface 109 near the right edge simultaneously enter the same screen.

The binary image converter 20 of the image processing device 202
6 converts the captured image signal sent from the two-dimensional CCD camera 201 into a digital signal, and then converts it into a monochrome binary image at a predetermined threshold level (threshold). The captured image converted to the black and white binary image is sent to the monitor TV 203 and displayed on the screen,
It is sent to the black pixel counting unit 207.

The black pixel counting unit 207 counts the number m (corresponding to the area of the ingot 110) of black pixels existing in the monitoring area 4 from the transmitted black and white binary image, and determines whether or not the image is fused. To the unit 208. The melting determination unit 208
It is monitored whether or not the counted number m of pixels is smaller than a preset reference number of pixels, and when it is smaller than the comparison reference value, it is determined that the ingot 110 has melted.

That is, in the melting detecting device 2 of the present invention,
The ingot during re-melting (melt back) is converted to black and displayed.
The color changes to the same white as that of No. 9 and the entire screen becomes white. Therefore, by monitoring whether or not the black pixel count value m of the black pixel counting unit 207 has become 0, the completion of the meltback can be automatically known. Further, the meltback completion signal thus obtained is sent to the pulling control device of the single crystal pulling apparatus 1, and the re-pulling of the single crystal is automatically restarted.

In the first and second embodiments, the case where the portion of the silicon block 108 and the portion of the ingot 110 are converted to black and the portion of the silicon melt surface 109 is converted to white is taken as an example. Conversely, even if the parts of the silicon mass 108 and the ingot 110 are converted to white and the part of the silicon melt surface 109 is converted to black, only the black and white are reversed.
As described above, the silicon lump 108 and the ingot 110
Can be detected.

The viewing window 10 of the single crystal pulling apparatus 1
If the two-dimensional CCD camera 201 installed at 7 is detachable, and the entire melting detection device 2 including the monitor television 203 is mounted on a movable carriage or the like to be a portable device, the melting detection device is not attached. It can be shared with other single crystal pulling devices. Further, the melting detection device 2 of the present invention can be applied to the detection of foreign matter when foreign matter is mixed in a melted semiconductor.

[0041]

As described above, according to the melting detection method and apparatus of the present invention, the following excellent effects can be obtained. (1) The completion of the melting of the semiconductor raw material in the melt process of the semiconductor single crystal pulling apparatus and the completion of the remelting of the ingot can be constantly monitored and automatically detected, and the burden on the operator can be reduced. (2) Since visual monitoring is not required, labor saving can be achieved. (3) Since the completion of the melting of the semiconductor material and the completion of the remelting of the ingot can be immediately detected, it is possible to immediately shift from the melt process to the pulling process, thereby reducing the throughput, increasing the electric energy, and deteriorating the members. Can be prevented.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a CZ type silicon single crystal pulling apparatus provided with a semiconductor raw material melting detection apparatus according to the present invention.

FIG. 2 is a diagram illustrating a circuit example of the image processing device in FIG. 1;

FIG. 3 is a diagram illustrating an example of an image captured in a crucible by a two-dimensional CCD camera.

FIG. 4 is a diagram illustrating an example of a captured image when the crucible is rotating.

FIG. 5 is a diagram illustrating a monitoring area according to a second embodiment.

FIG. 6 is a diagram illustrating an example of a black-and-white binary image of an ingot and a silicon melt surface according to the second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 CZ type silicon single crystal pulling apparatus 2 melting detector 3 seed crystal 101 heater 102 crucible 103 vacuum vessel 104 crystal rotating / elevating mechanism 105 wire 106 crucible rotating / elevating mechanism 107 viewing window 108 silicon lump (semiconductor material) 109 silicon melt Surface 110 Ingot 111 Monitoring area 120 Graphite crucible 121 Rotating axis 201 Two-dimensional CCD camera (imaging means) 202 Image processing device 203 Monitor television 204 Buzzer 205 Indicator light 206 Binary image conversion unit 207 Black pixel counting unit 208 Melting determination unit 209 Signal output section

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuyuki Iwata No. 1 Minamifuji, Ogakie-cho, Kariya-shi, Aichi F-term in the Toshiba Ceramics Corporation Kariya Works (reference) 4G077 AA02 BA04 CF06 CF10 EH10 PE27

Claims (4)

[Claims] 1. A method for detecting melting in a semiconductor single crystal pulling apparatus, comprising: photographing an inside of a crucible by an imaging means; converting the photographed image into a black-and-white binary image; and a crucible in the converted binary image. A melting detection method in a semiconductor single crystal pulling apparatus, comprising: counting the number of white pixels or black pixels in the crucible; and detecting completion of melting of the semiconductor raw material in the crucible from the counted number of white pixels or black pixels. 2. A melting detection device in a semiconductor single crystal pulling apparatus, comprising: an image pickup means for photographing the inside of a crucible; and a photographed image photographed by the image pickup means is converted into a black and white binary image. An image processing device that counts the number of white or black pixels in the crucible in the image and detects the completion of melting of the semiconductor material in the crucible from the counted number of white or black pixels. A melting detector in a semiconductor single crystal pulling apparatus. 3. A method for detecting melting in a semiconductor single crystal pulling apparatus, comprising: detecting a melt in advance at a predetermined position of an ingot in a crucible or at a predetermined position including both the ingot and a semiconductor melt surface near the ingot. A monitoring area for the monitoring area, photographing the monitoring area by an imaging unit, converting a captured image of the monitoring area into a black-and-white binary image, and using the converted binary image, a white pixel in the monitoring area. Alternatively, a melting detection method in a semiconductor single crystal pulling apparatus, wherein the number of black pixels is counted, and completion of melting of the ingot is detected based on the counted number of white pixels or black pixels. 4. A method for detecting melting in a semiconductor single crystal pulling apparatus, comprising: setting a melting point in advance at a predetermined position of an ingot in a crucible or at a predetermined position including both the ingot and a semiconductor melt surface near the ingot. Imaging means for photographing a monitoring area for detection; converting an image photographed by the imaging means into a black and white binary image, and determining the number of white pixels or black pixels in the monitoring area in the converted binary image. An image processing device that counts and detects the completion of melting of the ingot from the counted number of white pixels or black pixels, and a melting detection device in the semiconductor single crystal pulling apparatus.