JPH0692783A - Apparatus for production of semiconductor single crystal and producing method therefor - Google Patents

Abstract

PURPOSE:To detect the conversion of a single crystal in the single crystal having dislocations in an early period by automatically and surely discriminating the presence or absence of the ridge line appearing on the outer periphery of the single crystal, in pulling up of the single crystal by a CZ method. CONSTITUTION:A television camera which observes the solid-liquid boundary is provided and the peak exceeding the threshold level is detected by a circuit 1 from the video signal of a horizontal scanning line crossing the meniscus ring generated on the solid-liquid boundary at the time of growing the single crystal. The clock pulses thereof are counted by a counter 3. The pulses corresponding to the width, i.e., ridge line, of the meniscus ring fluctuating at a specific period in proportion to the rotating speed of the single crystal are stored in a latching circuit 6 in synchronization with a vertical synchronizing pulse. These pulses are converted by a D/A converter 7 to an analog voltage, which is inputted to a voltage discriminating circuit 9. The ridge line disappears and judgment is made that the single crystal changes to the one having the dislocations when the voltage falls to the value smaller than the reference voltage for discrimination. An alarm device is then triggered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor single crystal manufacturing apparatus and manufacturing method by the Czochralski method, and more particularly to a single crystal manufacturing apparatus equipped with means for automatically detecting dislocation formation in a pulled single crystal. It relates to a manufacturing method.

[0002]

2. Description of the Related Art The Czochralski method (hereinafter referred to as the CZ method) for pulling a cylindrical single crystal from a raw material melt in a crucible is used as one of methods for producing a silicon single crystal which is a basic material of a semiconductor integrated circuit. Has been. In the CZ method, a crucible installed in the main chamber of a single crystal manufacturing apparatus is filled with high-purity polycrystalline silicon, the polycrystalline silicon is heated and melted by a heater provided on the outer circumference of the crucible, and then attached to a seed chuck. The seed crystal is dipped in the melt, and the seed chuck is pulled up while rotating the seed chuck and the crucible in the same direction or opposite directions to grow a silicon single crystal. FIG. 6 shows a schematic configuration of a conventional general silicon single crystal manufacturing apparatus by the CZ method, in which 31 is a wire winding motor and 32 is a wire winding drum. Reference numeral 33 is a motor for imparting rotational movement to the vacuum container in which the wire winding motor 31 and the wire winding drum 32 are installed, and finally imparts rotational movement to the single crystal grown from the seed crystal through the rotation of the wire cable 34. Reference numeral 35 is a television camera, 36 is a transparent quartz glass window, and 37 is a seed chuck for holding a seed crystal.
Further, 38 is a melt surface, 39 is a graphite heater that heats and melts the polycrystalline silicon material in the crucible, 40 is a graphite heat insulating material, 41 is a motor that gives rotational motion to the crucible via a crucible pedestal, 42 It is a crucible shaft lifting device. When pulling a silicon single crystal, the melt surface 3
8 and the meniscus ring generated at the boundary between the silicon single crystal are photographed by the TV camera 35, and the obtained video signal is input to the width measurement unit 44 via the camera control unit 43, and the diameter of the single crystal that crosses the meniscus ring. Is calculated. Then, the diameter control device 45 controls the pulling rate of the seed crystal and the melt temperature to bring the diameter of the pulled single crystal close to the set value. In addition,
46 is a monitor television.

In the above-described single crystal manufacturing apparatus, it has been conventionally discriminated whether the growing single crystal is dislocation-free or dislocation-free.
It was performed based on the visual observation of the operator. As the method, the presence or absence of a ridge line appearing on the outer periphery of the growing single crystal was visually confirmed through a peephole provided in the chamber, and it was judged that dislocation was generated when the ridge line disappeared. When dislocation occurs, the single crystal is separated from the melt to interrupt the growth, and the single crystal with dislocation dissolves again. However, such a visual discrimination method is a major obstacle in automating the single crystal manufacturing process. If the visual discrimination work can be automated with high accuracy, it is possible to automate all of the interruption of single crystal growth, remelting, and resumption of single crystal growth.

As a solution to such a problem, for example, a method for producing a silicon single crystal has been proposed by Japanese Patent Laid-Open No. 58-194797. This method confirms that the weak AC component appearing in the output of the photodetector for detecting the diameter deviation provided for controlling the diameter of the single crystal corresponds to the ridge line appearing on the outer periphery of the growing single crystal. It was used. That is, a peculiar number of ridge lines are generated on the outer periphery of the single crystal in parallel with the growth direction depending on the growth direction of the single crystal, but since these ridge lines are slightly slightly convex from the outer peripheral surface of the single crystal, The output of the photodetector increases only slightly when the ridgeline enters the light-receiving range of the detector. When a single crystal is grown in the general <100> axis direction, four ridge lines are generated at equal intervals on the outer circumference of the single crystal. For this reason, a weak AC component is generated at a period of 1/4 of the rotation period of the single crystal. This alternating current component is detected to determine whether the single crystal is dislocation free or dislocation free, depending on the magnitude of the amplitude.

[0005]

The fluctuation of the diameter of the single crystal due to the ridge line appearing on the outer periphery of the single crystal is very small.
Therefore, the determination method according to the above-mentioned Japanese Patent Laid-Open No. 58-194797 becomes possible only by using a photodetector with an extremely narrow field of view of 1 to 2 mm in diameter for measuring only the diameter deviation. However, recently, there are many examples of using a one-dimensional linear image sensor or a television camera to detect the diameter of a single crystal, and measuring the diameter itself instead of the diameter deviation. Moreover, a large single crystal having a diameter of 150 to 200 mm is generally used. However, the magnitude of the diameter variation due to the ridge is almost constant regardless of the size of the diameter. Therefore, the AC component output due to the ridgeline becomes extremely small as compared with the diameter measurement output, and cannot be detected. The present invention has been made by paying attention to the above-mentioned conventional problems, and by improving the single crystal diameter measuring device using a one-dimensional linear image sensor or a television camera, it corresponds to the ridgeline along with the diameter output of the single crystal. It is an object of the present invention to provide a semiconductor single crystal manufacturing apparatus and a manufacturing method capable of surely detecting the output of an alternating current component and rapidly discriminating the occurrence of dislocations in the single crystal.

[0006]

In order to achieve the above object, a semiconductor single crystal manufacturing apparatus according to the present invention is a semiconductor single crystal manufacturing apparatus by the CZ method, and a television camera for observing a solid-liquid interface in a crucible, Means for taking out a video signal of a horizontal scanning line which crosses a meniscus ring generated at the solid-liquid interface, and measuring respective pulse widths corresponding to two peaks formed in the video signal corresponding to the meniscus ring, A means for detecting that the pulse width fluctuates in a specific cycle proportional to the number of rotations of the pulled single crystal, a means for comparing the fluctuation width with a preset value, and the fluctuation width is smaller than a set value. When a semiconductor single crystal manufacturing apparatus such as the above is provided with a means for issuing an alarm when it becomes The video signal of the horizontal scan line that crosses the horizontal axis is extracted, the clock pulses corresponding to the widths of the two peaks that exceed the preset threshold level are counted, and the specific period is proportional to the rotation speed of the pulled single crystal. The fluctuation of the pulse width that fluctuates in step S1 is taken out as a voltage, and when this voltage becomes smaller than the discrimination reference voltage, it is determined that the single crystal has dislocations and an alarm is issued.

[0007]

According to the above construction, the video signal of the horizontal scanning line which crosses the meniscus ring generated at the solid-liquid interface is extracted by using the television camera for observing the solid-liquid interface, and the two peaks due to the meniscus ring are dealt with. Each pulse width is measured, and the fluctuation of the pulse width that fluctuates in a specific cycle proportional to the rotation speed of the pulled single crystal is taken out as a voltage, and when this voltage becomes smaller than the discrimination reference voltage, the single crystal has dislocations. Since it is determined that the single crystal has a dislocation, it is possible to reliably and easily detect the dislocation of the single crystal due to the variation in the meniscus width. Further, since the present invention is a method of determining the presence or absence of a ridge line by detecting the fluctuation itself of the meniscus width itself, it can be sufficiently used even when growing a single crystal having a large diameter.

FIG. 3 is a monitor screen of a television camera for measuring a diameter when pulling a single crystal, where 11 is a single crystal, 12 is a line indicating a diameter measuring position, and 13 is a ridge. In this figure, one of the ridge lines is on the front and two are on the measurement line 12
Above, the remaining one is on the backside of the single crystal. Further, FIG. 4 is an enlarged view of a P portion of FIG. The present invention, as shown in FIG.
It was made by discovering that the meniscus width W1 at the ridge portion is at least 1.5 times or more than the meniscus width W2 other than the ridge portion. That is, the diameter of the single crystal 11 is measured on the measurement line 12, and the meniscus width is also measured. The fluctuation of the meniscus width due to the rotation of the single crystal is significantly larger than the fluctuation of the diameter output and can be sufficiently detected, and the dislocation of the single crystal can be detected by the magnitude of the fluctuation of the meniscus width.

FIG. 5 schematically shows a video signal waveform for scanning the measurement line 12 shown in FIG. 3, where 21 is a threshold level, 22 is a video signal waveform at the solid-liquid interface, and 23 is horizontal. It is a sync pulse. When measuring the diameter of the pulled single crystal, the outside of each of the two peaks of the video signal waveform 22 is the threshold level 2
The width Wd of the pulse 24 whose waveform is shaped at the intersection with 1 is obtained. Regarding the meniscus width, the above-mentioned video signal waveform 2
The width of each of the two peaks of 2 becomes a threshold level of 21 or more, that is, (a of pulse 25).
+ B) is measured. Since the size of (a + b) differs by 1.5 times or more between the ridge and the other part, the fluctuation of the meniscus width due to the rotation of the single crystal is sufficiently large, and the fluctuation of the meniscus width is 1/4 of the single crystal rotation cycle. By passing it through a circuit for selectively amplifying the generated pulse and converting it into a DC voltage, it is possible to correspond to the convex level of the ridge. This makes it possible to sufficiently clearly determine whether the single crystal being pulled is in a dislocation-free state.

[0010]

Embodiments of the semiconductor single crystal manufacturing apparatus according to the present invention will be described below with reference to the drawings. The present invention is
An attempt is made to measure the variation of the meniscus width associated with the rotation of a single crystal based on the output signal of a television camera provided in an ordinary semiconductor single crystal manufacturing apparatus for measuring the diameter of the single crystal. That is, the camera control unit 4 of the conventional semiconductor single crystal manufacturing apparatus shown in FIG.
After 3, the signal processing circuit shown in FIG. 1 is mounted. The television camera 35 has, for example, a CCD solid-state image pickup device equipped with a lens having a focal length of 55 mm, and the visual field on the melt surface of the television camera 35 is approximately 200 mm in the horizontal direction.
That is, the melt surface is viewed at an angle of 25 ° with respect to the vertical line. The video signal of the image by the television camera 35 on the measurement line is as shown in FIG. 5, and the processing method of this video signal will be described with reference to FIG.

In FIG. 1, reference numeral 1 denotes a circuit for binarizing a video signal according to a threshold level. This part is also used in a conventional diameter measuring circuit, so that it can be used. . The output of the circuit 1 is shaped into the pulse 25 of FIG. 5 and applied to the gate circuit 2. The gate circuit 2 passes a number of clock pulses which is proportional to the pulse width of the pulses 25 a and b. This is counted by the counter 3. The counter 3 counts all the scanning lines and resets after each scanning, but only when the scanning lines corresponding to the measurement lines are counted, the gate circuit 4 synchronizes with the horizontal synchronizing pulse and the latch circuit 5 The count value is stored in. The data stored in the latch circuit 5 is stored in the next latch circuit 6 in synchronization with the vertical synchronizing pulse when the scanning of one screen is completed. The data stored in the latch circuit 6 is output as an analog voltage by the D / A converter 7.

The width of the meniscus is measured every 1/60 seconds in synchronization with the vertical synchronizing pulse of the video signal and output as an analog voltage. This output is input to the filter 8 to reduce instantaneous noise and abrupt changes in voltage when updating the output. Thereafter, the output is the voltage discrimination circuit 9
And the peak voltage level is measured. Then, when this voltage becomes lower than a determination reference voltage set in advance for determining whether or not dislocation has occurred, an alarm is issued via the alarm command circuit 10. The output signal of the alarm command circuit 10 may also be input to the diameter control device 45 of FIG. 6 to increase the rotation speed of the wire winding motor 31 to separate the single crystal from the melt.

Since the number of pixels in the horizontal direction of the CCD camera used in this embodiment is 768, assuming that one clock pulse corresponds to one pixel, the meniscus portion does not exceed 10% of the horizontal field of view. 3 is less than 7 bits is sufficient. Although the 8-bit counter and the latch circuit are used in the present embodiment, the lower 6 bits are input to the upper 6 bits of the 8-bit D / A converter so that the horizontal field of view of 8.3% is D / A. It can be measured as the full scale of the A converter. In this case, the output resolution of the D / A converter is 1/64, but it is measured at 60 times / second, which is much faster than the fluctuation speed of the meniscus width, in synchronization with the vertical synchronizing signal of the television screen. In addition, since the brightness of the measurement unit constantly and randomly fluctuates due to the rotation of the single crystal and the fluctuation of the melt surface, by providing the filter 8 after the output of the D / A converter and smoothing it, a step-like step due to the output resolution can be achieved. A waveform with no significant fluctuation can be obtained.

FIG. 2 is a diagram schematically showing the above waveform. In the present embodiment, the diameter 1 that grows in the <100> axis direction is 1
The measurement was performed during the growth of a 30 mm silicon single crystal. At this time, as shown in FIG. 3, the measurement line was set at a position crossing the point where the rotation axis of the single crystal intersects with the melt surface. Therefore, the peak interval time t _i on the waveform of FIG. 2 is ¼ of the single crystal rotation period. In this embodiment, the rotation speed of the single crystal is 2
So was 0rpm, t _i became 0.75 seconds. The D / A converter used has a full-scale voltage of 10 V, but in this embodiment, the peak voltage due to the growth edge peculiar to the single crystal is about 5 V, and the base voltage is 2 to 3 V.
Met. When the single crystal has dislocations, the growth edge disappears and the voltage peak also disappears, and a substantially stable output of 2 to 2.5 V was generated. Since the method according to the present invention has high sensitivity, it is not necessary to use a synchronous detector or the like which continuously changes the passing frequency in proportion to the number of rotations of the single crystal, and the voltage discriminating circuit 9 alone is used to dislocation of the single crystal. Can be detected.

Single crystal growth was carried out 100 times using the single crystal manufacturing apparatus incorporating the signal processing circuit shown in FIG. 1, and 9 times of this growth resulted in dislocation. At this time, the signal processing circuit issued an alarm immediately after the dislocation occurred nine times, and the operator confirmed that the dislocation occurred and stopped the growth. 1 like this
Since dislocation generation of a single crystal can be detected with a probability of 00%, growth abortion and automation including re-dissolution and re-growth of a single crystal having dislocations can be easily performed with high reliability. be able to.

In the present embodiment, the meniscus width measurement line is commonly set on the diameter measurement line of the single crystal. However, the present invention is not limited to this, and the meniscus width measurement line may be arranged in front of the diameter measurement line (below the measurement line 12 in FIG. 3). It is also possible to set. In that case, the fluctuation width of the meniscus width is slightly smaller than that of the present embodiment, but by setting the meniscus width measurement line at an appropriate position, the fluctuation frequency can be set to 8 times the single crystal rotation speed, Since the fluctuating waveform also approaches a sine wave, it is not difficult to determine whether or not there is a dislocation-free state.

[0017]

As described above, according to the present invention, the video signal of the horizontal scanning line which crosses the meniscus ring generated at the solid-liquid interface is extracted by using the television camera for observing the solid-liquid interface, and the meniscus is obtained. Each pulse width corresponding to the two peaks due to the ring was measured, and it was determined that the single crystal had dislocations when the amount of pulse width fluctuation in a specific period proportional to the number of revolutions of the pulled single crystal became smaller than the set value. Since the determination system is configured, it is possible to reliably and easily detect dislocations in the single crystal. This device can be easily attached to a single crystal manufacturing device in which the diameter of the single crystal is automatically controlled by a diameter measuring device using a television camera, and the existence of the single crystal, which was conventionally judged based on the operator's visual observation, was confirmed. Since it becomes possible to automatically detect the dislocation, the observation work of the operator, which was necessary for discovering the dislocation, becomes unnecessary, and
It is possible to automate everything from single crystal growth interruption and remelting to single crystal growth restart. Further, since the present invention is a method of determining the presence or absence of a ridge line by detecting the fluctuation itself of the meniscus width itself, it can be sufficiently used even when growing a single crystal having a large diameter.

[Brief description of drawings]

FIG. 1 is a block diagram of a signal processing circuit for measuring a meniscus width.

FIG. 2 is a diagram schematically showing a monitor output waveform in FIG.

FIG. 3 is a schematic diagram of an image taken by a television camera for measuring the diameter of a single crystal.

FIG. 4 is an enlarged view of part P of FIG.

FIG. 5 is an explanatory diagram of a video signal waveform forming a scanning line on a diameter measurement line.

FIG. 6 is a diagram showing a schematic configuration of a conventional single crystal manufacturing apparatus provided with a single crystal diameter detecting means by a television camera.

[Explanation of symbols]

 1 Binarization circuit 2, 4 Gate circuit 3 Counter 5, 6 Latch circuit 7 D / A converter 9 Voltage discrimination circuit 10 Alarm command circuit 13 Ridge line 21 Threshold level 22 Video signal waveform 24, 25 pulse 35 Television camera

Claims (2)

[Claims] 1. In a semiconductor single crystal manufacturing apparatus by the Czochralski method, a television camera for observing a solid-liquid interface in a crucible and a video signal of a horizontal scanning line which crosses a meniscus ring generated at the solid-liquid interface are taken out. , Means for measuring respective pulse widths corresponding to two peaks formed in the video signal corresponding to the meniscus ring, and the pulse width varying at a specific period proportional to the number of rotations of the pulling single crystal. A semiconductor single crystal comprising means for detecting that the fluctuation range is compared with a preset value, and means for issuing an alarm when the fluctuation range becomes smaller than a set value. Manufacturing equipment. 2. A video signal of a horizontal scanning line which crosses a meniscus ring generated at a solid-liquid interface is taken out, and clock pulses corresponding to the widths of two peaks exceeding a preset threshold level are counted and then pulled up. The fluctuation of the pulse width that fluctuates in a specific cycle in proportion to the rotation speed of the single crystal is taken out as a voltage, and when this voltage becomes smaller than the judgment reference voltage, it is judged that the single crystal has dislocations and an alarm is issued. A semiconductor single crystal manufacturing method, characterized in that