JPH02180790A - Method and device for measuring vibration of molten metal surface - Google Patents

Abstract

PURPOSE:To precisely grasp the vibrating state of the molten metal surface to eliminate the cause of the vibration and to obtain a high quality silicon single crystal by the Czochralski method by setting a CCD camera and measuring the change of luminance at the same position of the molten metal surface with the lapse of time. CONSTITUTION:A CCD camera 6 sending video signals a and trigger signals b is set and the change of luminance at the same position of the molten metal surface 9 in a crucible 1 in a Czochralski furnace 5 with the lapse of time is measured with the camera 6. The vibrating state of the surface 9 is precisely grasped, the cause of the vibration is eliminated and a high quality silicon single crystal is obtd.

Description

[Detailed Description of the Invention] L! The present invention relates to a method and apparatus for measuring the vibration of a hot water surface during the manufacturing process of single crystal silicon using the Czochralski method.

In the Czochralski method, raw materials are melted in a resistance heating furnace or high-frequency furnace, and small pieces of single crystal held in a chuck (hereinafter referred to as "seeds") are dipped into the melt from above and rotated. It is a method of growing a single crystal by gradually pulling it up, and it is excellent in mass production as it can obtain a single crystal with a large diameter.

In the Czochralski method, when the raw material is placed in a resistance heating furnace or the like and melted, the surface of the melt vibrates due to the influence of heat, a so-called molten surface vibration phenomenon.

Due to this surface vibration phenomenon, the melt surface, especially the solid-liquid interface in the crystal growth area, becomes thermally or physically unstable, making it difficult to pull single crystal silicon from a resistance heating furnace, etc. in good condition. Not only is this difficult, but it also has the disadvantage of inhibiting dislocation-free single crystallization of silicon crystal.

Therefore, in order to produce high-quality single crystal silicon using the Czochralski method, it is first necessary to accurately understand the conditions under which the molten metal surface vibration occurs.

However, in the past, the state of vibration of the hot water surface was only observed visually, and the state of vibration of the hot water surface was not measured or recorded. For this reason, it has been difficult to accurately understand and analyze the molten metal surface vibration phenomenon.

The present invention was devised in view of these problems, and an object of the present invention is to provide a method and apparatus for measuring hot water surface vibration, which can measure scene vibrations in a simple manner.

・In order to achieve the above object, the method for measuring hot water surface vibration according to the present invention uses a CCD camera that emits a video signal and a trigger signal to measure changes in brightness over time at the same location on the hot water surface. It is characterized by measurement.

Further, the hot water level vibration measuring device according to the present invention includes a CCD camera for measuring a diameter of a single crystal that emits a video signal and a trigger signal, a delay pulse circuit that emits a delay pulse signal in response to the trigger signal, and a delay pulse circuit that emits a delay pulse signal in response to the trigger signal. The present invention is characterized in that it includes a sample and hold circuit that applies a sample and hold to the video signal when the video signal is generated, and is configured to be connectable to a recording means that records the video signal that has been subjected to the sample and hold.

■ The vibration of the hot water surface is thought to have a correlation with the brightness change on the hot water surface. It is generally known that, especially in relatively short time intervals, changes in the brightness of the hot water surface are mainly controlled by the vibrations of the hot water surface.

Therefore, the CCD that emits the video signal and the trigger signal
By using a (charge-coupled device) camera to measure changes in brightness over time at the same location on the hot water surface, it is possible to accurately understand the vibration status of the hot water surface.

Further, according to the above-mentioned hot water level vibration measuring device, a video signal and a trigger signal are emitted from the CCD camera, and a delay pulse signal in response to the trigger signal is further emitted by the delay pulse circuit. In this case, when the delay pulse signal is emitted at a position corresponding to a measurement point on the hot water surface, a sample hold is applied to the video signal at this point by a sample hold circuit, and the video signal maintains the content at the measurement point. The sample and hold circuit outputs the luminance as it is.

Furthermore, this measuring device is configured to be connectable to a recording means for recording the video signal.

The brightness emitted from the video signal, that is, the vibration situation can be displayed and recorded on the recording means.

! Give it to me EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of the present invention will be explained in detail based on the drawings.

FIG. 2 is a structural diagram schematically showing the outline of a resistance-heated Czochralski type to which the method for measuring liquid surface vibration according to the present invention is applied, and the Czochralski type is injected with polycrystalline silicon or a dopant. A quartz crucible 1, a carbon heater 2 that heats the crucible 1, a chuck 4 that holds the seeds 3, and a heating furnace body 5 that houses the crucible 1, the carbon heater 2, etc. C as an observing sensor
It is constructed with a CD camera 6 as its main part.

The CCD camera 6 receives a video signal a for observing the growth state of the single crystal and measuring the diameter of the single crystal, and a trigger signal for giving a predetermined "trigger" to the water level vibration measuring device described later. It is configured so that the following is emitted.

In the Czochralski family, single crystal silicon is produced as follows.

First, the pressure inside the heating furnace body 5 is reduced to a predetermined pressure, and an inert gas such as argon is introduced into the heating furnace body 5.
Next, polycrystalline silicon and a dopant (hereinafter simply referred to as "raw materials") are injected into the crucible I. Here, the doping agent is used so that the single crystal silicon to be manufactured has a predetermined resistivity (Ω・
Cm).

Next, a voltage is applied to the pair of left and right electrodes 8a and 8b, and the carbon heater 2 is energized to heat the crucible 1 to a predetermined temperature, thereby melting the raw material in the crucible 1 and producing a melt 7. After that, the seeds 3 held by the chuck 4 are lowered from above to the bottom (arrow E in the figure), and the tips of the seeds 3 are moved to the melt 7.
Soak in At this time, the chuck 4 and the crucible 1 are rotated in the direction of the arrow F and the direction of the arrow G, respectively, in order to stir the melt 7 and equalize the temperature. After this, the growth state of the crystal is observed by the CCD camera 6 which is emitting the video signal a, and after confirming that the crystal grown in the liquid phase has a predetermined diameter by the CCD camera 6, the chuck is 4 upward while rotating in the direction of arrow F (arrow H in the figure)
to complete the production of single crystal silicon. The diameter of single crystal silicon is measured by aiming the CCD camera 6 at the crystal growth interface and reading the contrast between the optical axis and the surroundings that appear around the crystal growth interface.

By the way, in the above-described manufacturing process of single-crystal silicon, after the raw material is melted in the crucible 1, a phenomenon generally occurs in which the surface of the melt 7, that is, the molten metal surface 9, vibrates due to the influence of heat or the like.

Therefore, in the Czochralski method for producing single crystal silicon, the single crystal silicon becomes thermally and physically unstable due to the vibration phenomenon of the hot water surface 9, and high quality single crystal silicon is obtained. The disadvantage is that it is difficult to

In order to eliminate this drawback and obtain high-quality single crystal silicon, it is first necessary to accurately understand the vibration situation of the hot water surface 9.

The present invention uses a CCD camera 6 for measuring the diameter of single-crystal silicon to measure changes in brightness that are correlated with the vibrations of the hot water surface 9, and to accurately grasp the vibration status of the hot water surface 9. .

The method for measuring the vibration of the molten metal surface will be explained in detail below.

FIG. 1 is a block diagram showing an example of a measuring device used in the method for measuring hot water surface vibration according to the present invention, in which 11 is a sample hold circuit, 12 is a delay pulse circuit, and 13
is a recording means for recording changes in brightness.

This measuring device operates as follows.

First, a video signal a and a trigger signal are emitted from the CCD camera 6, and the video signal a is sent to the sample hold circuit 1.
1, and the trigger signal S is input to the delay pulse circuit 12.The delay pulse circuit 12, which has received the trigger signal S, generates a delay signal having a constant time delay Δt with respect to the trigger signal S. A pulse is generated and the delayed pulse signal C is transmitted to the sample and hold circuit 11. The sample and hold circuit 11 that has received this delayed pulse signal C applies a sample hold to the video signal a from the CCD camera 6 at this point, and stores the video while maintaining the content of the video signal a at the time when the delayed pulse signal C was transmitted. The signal a is outputted from the sample and hold circuit ll, and is sent as the luminance d to a recording means 13 such as a recorder or display device.
Display and record.

FIG. 3 shows the correlation between the vibration state of the hot water surface and the video signal a, trigger signal S, etc.

In the figure, point X is the measurement point for measuring the vibration situation, and lO is the aforementioned optical axis. In addition, (A) is a waveform diagram of the video signal a for the hot water level 9, (B) is the generation timing of the trigger signal S,
(C) is the generation timing of the delay pulse signal C, (D
) respectively indicate the brightness d at the measurement point X obtained by the video signal a, the vertical axis represents voltage (V), and the horizontal axis represents time (t).

The CCD camera 6 is aimed at the crystal growth interface and along the approximate center of the hot water surface 9 so as to cross the crystal (indicated by Y in the figure).The video signal a from the CCD camera 6 is Emitted from a point Z in contact with the inner wall 1a of the crucible 1 along the Y direction so as to capture the state of the molten metal surface 9 over time,
The waveform shown in (A) is drawn. Here, point P,
Point Q corresponds to optical axis lO, and by measuring the distance between PQ, the diameter of single crystal silicon is measured.

Further, the trigger signal S is emitted at the point Z where the transmission of the video signal a starts, as shown in (B).

The delay pulse circuit 12 that has received the trigger signal A performs the following steps so as to correspond to the measurement point X through which the video signal a passes.
A delay pulse signal C having a time delay Δt as shown in (C) is generated. Conversely, the measurement point X will be determined by the set time of the time delay Δt.

Next, this delayed pulse signal C is transmitted to the sample and hold circuit 11. The video signal a input from the CCD camera 6 to the sample and hold circuit 11 is subjected to sample and hold when this delayed pulse signal C is generated, and as shown in (D), the luminance d corresponding to the measurement point X, that is, the vibration The situation is displayed and recorded on the recording means 13.

In this figure, the waveform of the video signal a changes every cycle T as shown in (A), and when the hot water surface 9 vibrates, the brightness d also changes (D). It can be seen that there is a fluctuation as shown in the figure. Moreover, such a measurement process is performed instantaneously with time T as one cycle, and the hot water level 9
The brightness d at the measurement point X is continuously obtained as a change over time, and the vibration state of the hot water surface 9 can be accurately grasped.

Figures 4 and 5 are waveform diagrams of brightness d when the temporal change in the vibration of the hot water surface is recorded using the measurement method according to the present invention, and Figure 3 (D) corresponds to the compressed one. do.

FIG. 4 shows a case where the condition of the hot water surface vibration is relatively moderate, and FIG. 5 shows a case where the condition of the hot water surface vibration is relatively gentle. The vertical axis is voltage (V), and the horizontal axis is time (minutes).The measurement was started immediately after all the raw materials were melted in the crucible 1.

Table 1 shows the experimental conditions.

It can be seen that by capturing the vibration state as a change in brightness d in this manner, the vibration state of the hot water surface 9 can be accurately grasped. Therefore, by analyzing this data as basic data, it is possible to manufacture single crystal silicon under favorable conditions, and it is expected that high quality single crystal silicon can be obtained.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that changes can be made without departing from the scope of the invention. Needless to say, the present invention is not limited to this, and can also be applied to high-frequency Czochralski types.

As described in detail above, the method for measuring the vibration of the hot water surface according to the present invention uses a COD camera that emits a video signal and a trigger signal to measure the vibration of the hot water surface during the manufacturing process of single crystal silicon using the Czochralski method. Since we decided to measure the change in brightness over time at the same location on the surface, it is possible to accurately grasp the state of the hot water surface vibration, which has a good correlation with brightness.

Therefore, even in the Czochralski method, which is excellent in mass production, by analyzing these data, it is possible to always obtain high quality single crystal silicon.

Further, as described above, the hot water surface vibration measuring device according to the present invention includes a single crystal diameter measuring CCD camera that emits a video signal and a trigger signal, and a delay pulse circuit that generates a delay pulse signal in response to the trigger signal. Since the main part consists of a sample and hold circuit that samples and holds the video signal when the delay pulse signal is generated, it is possible to measure the vibration of the hot water surface by simply adding a control circuit. There is no need to introduce special measuring equipment.

Therefore, the measuring device can be implemented without requiring significant improvements to the conventional Czochralski furnace and without causing a significant increase in cost.

In addition, since a recording means for recording the video signal can be connected to the measuring device, it is possible to immediately grasp the vibration situation, and by analyzing the measured and saved data, high-quality single crystals can be produced. It becomes possible to use it for manufacturing silicon.

[Brief explanation of the drawing]

Fig. 1 is a block diagram schematically showing a hot water level vibration measuring device according to the present invention, Fig. 2 is a structural diagram schematically showing an outline of a manufacturing device for single crystal silicon using the Czochralski method, and Fig. 3 is a hot water level vibration measuring device. FIG. 4 is a waveform diagram showing an example of scene vibration measured by the method for measuring vibration on a hot water surface according to the present invention. FIG. 5 is a diagram for explaining a method for measuring vibration on a hot water surface according to the present invention. FIG. 3 is a waveform diagram showing another example of the vibration of the hot water surface measured by the method. 6... CCD camera, 9... Hot water surface, 11... Sample hold circuit, 12... Delay pulse circuit, 1
3...Recording means, a...Video signal, b...-Trigger signal, C...Delay pulse signal, d...Brightness. Patent applicant: Sumitomo Metal Industries, Ltd. Agent:
Patent Attorney Ryuji Bennai Figure 1 Figure 2 ○

Claims (2)

[Claims] (1) A method for measuring the vibration of the hot water surface during the manufacturing process of single crystal silicon using the Czochralski method, which measures the change in brightness over time at the same location on the hot water surface using a CCD camera that emits a video signal and a trigger signal. A method of measuring hot water surface vibration characterized by the following. (2) A CCD camera for measuring the diameter of a single crystal that emits a video signal and a trigger signal, a delay pulse circuit that emits a delay pulse signal in response to the trigger signal, and a sample hold on the video signal when the delay pulse signal is generated. What is claimed is: 1. A hot water surface vibration measuring device, comprising: a sample hold circuit, wherein the sample hold circuit is configured to be connectable to a recording means for recording the video signal subjected to the sample hold.