JPH11157994A - Production of silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the production of silicon single crystal that can produce single silicon crystal of good quality with no dislocation by surely preventing the thin neck of the silicon rod from being broken, when the silicon single crystal of a large diameter and a large weight is pulled up. SOLUTION: In the production of silicon single crystal by the Czochralski process, the neck part (2) between the seed crystal (1) and the silicon single crystal (3) is heated in the temperature range from 550 deg.C to the 800 deg.C with the heater (17), when the silicon single crystal is pulled up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a silicon single crystal by the Czochralski method. More specifically, it is possible to improve the strength of a neck portion interposed between a seed crystal and a silicon single crystal in order to remove dislocations, stably pull up a large-diameter and heavy silicon single crystal, and manufacture the silicon single crystal. The present invention relates to a method for manufacturing a silicon single crystal.

[0002]

2. Description of the Related Art In a method of manufacturing a silicon single crystal by the Czochralski method, a seed crystal is brought into contact with a silicon melt and gradually pulled up at a predetermined pulling speed while rotating. Is grown to a silicon single crystal having a diameter of in this way,
When the seed crystal is brought into contact with the molten silicon, dislocation occurs in the crystal due to the thermal shock, and the dislocation multiplies throughout the growing crystal, so that a neck portion is formed between the seed crystal and the single crystal ingot, Dislocations must be completely removed in the region of the neck.

[0003] As a means for removing the dislocation, the most widely known dash neck method is a method of removing a diameter of about 2 to 4 mm.
Is grown at a high crystal pulling rate of about 6 mm / min to completely remove dislocations before growing a silicon single crystal ingot.
When dislocations are removed by forming the neck portion with a small diameter in this way, it is undeniable that the strength of the neck portion is reduced. The neck portion, which is the most vulnerable portion, is easily broken during the growth and pulling of the crystal, and the crystal ingot may fall into the crucible by breaking. The drop of the crystal ingot destroys the crucible, regenerator, heater, etc. due to the impact of the ingot itself and the molten silicon that has jumped up, and the recovery of the molten silicon becomes impossible, resulting in enormous damage. . Furthermore, the scattered molten silicon must be cleaned and removed, and in order to restore cleanliness, a long time must be spent for restoration, and the work is dangerous. There is concern about secondary damage to workers, and there is also a problem with safety.

For this reason, at present, in order to reduce the weight of the single crystal ingot to such a level that the above-mentioned small diameter neck portion does not break, for example, the ingot is 300 mm (1 mm in diameter).
In the case of 2 inches), the growth is limited to about 75 cm in length, and the above-described drop of the silicon single crystal is prevented. However, in recent years, there has been a strong demand for a silicon single crystal having a large diameter from the viewpoint of manufacturing efficiency and the like, and earnest research has been progressing toward realization thereof. In addition to the weight, the crystal growth also takes a long time, so that a tensile stress due to the heavy silicon single crystal acts on the neck portion for a long time.

[0005] In order to produce such a large-diameter and large-weight silicon single crystal, there have been proposed many means for preventing breakage of the neck portion. For example, in JP-A-9-2898,
Attempts have been made to form dislocation-free, large-diameter necks so that larger-diameter, dislocation-free single crystals can be produced. According to the publication, when pulling a crystal at a speed of less than about 4.0 mm / min, 10
It is stated that dislocations can be removed at the neck of a crystal having a diameter exceeding mm. If the diameter of the neck portion is 10 mm or more, it can be predicted that it will be possible to pull up a large-diameter and heavy silicon single crystal without breaking the neck portion. However, generally in the art, diameters of one
Considering that it is impossible to consistently remove dislocations from a large-diameter neck portion exceeding 0 mm,
There is no guarantee that a dislocation-free silicon single crystal can be manufactured by the method described in the publication.

Japanese Patent Application Laid-Open No. Hei 9-183694 discloses a holding device in which an engaging step is formed between a neck portion and a silicon single crystal ingot, and the step is nipped by a hanging jig and pulled up. Have been. However, when using such a holding device, since the neck portion having a small diameter is fragile as described above, the step portion must be securely clamped without giving an impact to the neck portion by the hanging jig. In addition, extremely high-precision control of the positioning and the clamping force is required for the clamping. In addition, during the holding, the ingot is pulled up at a predetermined speed and the ingot is rotated as described above, so that the holding device pulls up in synchronization with the pulling speed and the rotation speed. And rotation, and the control becomes more complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. In order to produce a large-diameter and heavy-weight silicon single crystal, a small-diameter and fragile neck portion employs a special holding device. It is an object of the present invention to provide a method of manufacturing a silicon single crystal that can increase strength without causing breakage at the neck portion and can efficiently manufacture a high-quality silicon single crystal without dislocation.

[0008]

Here, according to the report of Equality ("Mechanical Strength of Neck of CZ-Si Single Crystal" on page 382 of the 58th Annual Meeting of the Japan Society of Applied Physics), The axial orientation is <100> and its diameter is 2-5mm
The neck portion formed by the Czochralski method, which fluctuates irregularly within the range of, was used as a test piece as it was, and the fracture strength was measured by a tensile test at room temperature, 600 ° C, and 900 ° C. Despite the large variation, there are many data of 400MPa or more, exceeding the average value of the breaking strength of this type of conventional test piece. From this data, there is no problem in supporting a crystal with a heavy weight of 320Kg at a 4mm diameter neck. It has been reported. However,
From the graph attached to this report, there are certainly samples with a breaking strength of 400 MPa or more,
Values below MPa have also been measured. From this data,
It is questionable to assert that it is feasible to immediately produce a heavy (320 Kg) single crystal by the Czochralski method with a neck of 4 mm diameter.

Therefore, the present inventors have further studied by focusing on the correlation between the mechanical strength of the crystal and the temperature, which has been not paid much attention in the past, although this is the only report mentioned above. A silicon single crystal was cut into a test piece having an axial orientation of <100>, and a bending strength test as a criterion for determining tensile strength was performed on the test piece. Since the neck portion at the time of pulling up the silicon single crystal is provided for removing dislocations as described above, the neck portion is a fragile portion where dislocations are also observed at the upper part. In order to ensure that sufficient strength can be obtained even in such a fragile part, a polishing treatment is performed to reduce the concentration of stress on the surface of the crystal growth surface in order to bring the test piece closer to the state of the neck part. The test piece was used as it was in the cut form without any particular operation.

With respect to this test piece, the measurement temperature was set to room temperature, 2
00 ° C, 400 ° C, 500 ° C, 600 ° C, 650 ° C, 7
The measurement was performed at nine points of 00 ° C, 800 ° C, and 900 ° C. FIG. 8 shows the result. It can be seen from the figure that the breaking stress significantly increases when the temperature is in the range of about 550 ° C. to 800 ° C. It was also confirmed that the test piece of silicon single crystal started plastic deformation when the temperature exceeded 800 ° C.

From the above considerations, the present invention provides a method for manufacturing a silicon single crystal by the Czochralski method, in which a neck formed between a seed crystal and a silicon single crystal at least at the time of pulling up the silicon single crystal has a temperature of 550 ° C. or more and 800 ° C.
The main configuration is a method for producing a silicon single crystal characterized by heating and holding in the following temperature range.

By heating and maintaining the neck portion in the temperature range, the required strength of the neck portion is secured, and the silicon single crystal has a large diameter even if the neck portion has a small diameter of about 4 mm. A heavy silicon single crystal can be reliably supported, and the neck portion does not break during pulling and the silicon single crystal does not fall.

In FIG. 8, it should be noted that the breaking stress of the silicon single crystal has a peak value when the temperature range is 620 ° C. or more and 750 ° C. or less. It can be confirmed that an extremely large value is obtained. It was also found that in this temperature range, a breaking stress of 20 kg / mm ² was ensured even if there were some scratches on the neck.

In order to prevent breakage and accidents due to the drop of the silicon single crystal even after completion of the pulling, the silicon single crystal must be cooled or transported to a storage unit until the silicon single crystal is separated from the neck. In addition, it is preferable that the neck is heated in the temperature range.

An infrared heater, a coil heater, or the like can be used for the heating and holding, and a reflection mirror can be used in combination with these heaters. In that case, the heat of the heater can be applied to the neck without escaping, and radiant heat from the silicon single crystal below the neck can also be applied to the neck, so that the neck can be efficiently formed. Can be heated and held. In addition to the heater, laser light or hot air may be used.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG.
1 is a schematic diagram of a silicon single crystal manufacturing apparatus used in the manufacturing method of the present invention.

The manufacturing apparatus 10 includes a closed vessel 11 having a large-diameter chamber 11a and a small-diameter chamber 11b formed above the large-diameter chamber 11a. Gas is filled. The large-diameter chamber 11
a, a quartz crucible 12 having a bowl shape or a bottomed cylindrical shape with an open upper side is provided.
Is filled with molten silicon. The quartz crucible 1
2 is a graphite support 1 having a rotation axis 13a at the bottom center.
3 is detachably fitted to and held by the graphite support 1
At the same time as the rotation of 3, the quartz crucible 12 also rotates. Further, the graphite support 13 is provided inside the large-diameter chamber 11a.
The heater 14 is installed annularly so as to surround the periphery of the
The molten silicon in the quartz crucible 12 is heated.
A heating cylinder 15 is further provided around the heater 14.

The small diameter chamber 11b is provided with cooling means such as water cooling or air cooling. Further, a single crystal pulling mechanism 16 is disposed above the small diameter chamber 11b, and the single crystal pulling wire 16a of the pulling mechanism 16 is driven up and down while rotating in a direction opposite to the rotation direction of the quartz crucible 12. Is done. At the tip of the wire 16a, a silicon single crystal seed crystal 1 is attached via a seed chuck. The single crystal pulling mechanism 16 further includes a heater pulling wire 16b, and a coil heater 17 is attached to the tip of the wire 16b, and is driven up and down in synchronization with the pulling of the single crystal.

In order to manufacture a silicon single crystal by the above-described manufacturing apparatus 10, first, the single crystal pulling wire 16
The seed crystal 1 at the tip of a is immersed in molten silicon. Thereafter, the wire 16a is wound up while rotating in a direction opposite to the rotation direction of the quartz crucible 13,
The seed crystal 1 is pulled at a predetermined pulling speed while rotating. At this time, the diameter of the seed crystal 1 was 4 mm below the seed crystal 1.
Is formed, and dislocations are completely removed before growing the silicon single crystal ingot 3.

Thereafter, the heater 17 is connected to the neck 2.
While heating the neck portion 2 while facing it, the pulling speed is further appropriately changed, and the silicon ingot 3 of silicon single crystal is grown to a predetermined diameter and pulled up while rotating. At this time, the heater pulling wire 16b is wound in synchronization with the single crystal pulling wire 16a, and the neck portion 2 is always heated even during pulling of the ingot. In addition,
The temperature of the heater 17 is 550.degree.
° C or lower, preferably 620 ° C or higher and 750 ° C or lower.

Further, the ingot 3 is moved to the small-diameter chamber 1 above.
1b, and the ingot 3 is moved to the small-diameter chamber 11.
b. After that, the ingot 3 is connected to the wire 1
6a is transported to the storage unit in a state of being suspended. Even when the ingot 3 is pulled up and cooled, the neck portion 2 of the ingot 3 is always heated by the heater 17 and its strength is significantly increased. For example, the neck portion 2 has a diameter of 4 mm and a small diameter. In addition, even when a large-diameter and heavy-weight ingot 3 is manufactured, the ingot 3 is not broken at the neck portion 2 and the accident or damage due to the drop of the ingot 3 can be prevented.

When the ingot 3 is transported together with the single crystal pulling mechanism 16 while being suspended from the single crystal pulling mechanism 16, the neck 2 is heated by the heater 17. It can be transported in a state where it is done. Alternatively, even in the case of transporting by detaching from the pulling mechanism 16, it is possible to transport the neck portion 2 in a heated state by arranging a separate heater along the transport route.

An infrared heater can be used instead of the coil heater 17, or the first heater shown in FIG.
As in the modification, a plurality of hot air introduction holes 11c are formed at the upper end of the small diameter chamber 11b, and a plurality of hot air discharge holes 11d are formed at the lower end of the small diameter chamber 11b. Hot air is supplied through the hot air introduction hole 11c, and is exhausted to the outside of the room from the hot air discharge hole 11d by an intake source (not shown). The temperature of the neck portion 2 is kept constant by controlling the amount of air supply and exhaust. The inner peripheral surface of the heater 17 may be mirror-finished. In this case, the heat reflected by the mirror surface can be used in addition to the direct heating by the heater, and the neck portion 2 can be efficiently used with small energy. Can be well heated and maintained.

FIG. 3 is a schematic view showing a manufacturing apparatus 20 which is a second modification of the above-described manufacturing apparatus 10. As shown in FIG. According to this modification, the same configuration as that of the above-described manufacturing apparatus 10 is provided except that the heating unit of the neck portion 2 in the above-described manufacturing apparatus 10 is different. The manufacturing apparatus 20 is provided with a reflection mirror 21 in an umbrella shape with respect to the neck portion 2 instead of the heater 17,
A heater 22 is provided at a predetermined gap on the inner surface of the mirror 21. The neck portion 2 is heated by the heater 22 and is reflected by the reflection mirror 21 without escaping the amount of heat of the heater 22, and further reflects heat from the lower ingot 3, thereby forming the neck portion 2.
Is more efficiently heated.

FIG. 4 is a schematic view showing a manufacturing apparatus 30 which is a third modification of the above-described manufacturing apparatus 10, and further shows another means for heating the neck portion 2. As shown in FIG. The manufacturing apparatus 30 has a heater 31 on the inner wall surface of the small diameter chamber 11b of the closed vessel 11,
The small-diameter chamber 11b is arranged in multiple stages in the length direction (vertical direction). Therefore, it is possible to continuously heat only the neck portion 2 by sequentially turning on and off the switches following the upward pulling of the neck portion 2. Furthermore, by pulling up the single crystal, cooling it, and then transporting it to the storage unit, by arranging heaters in multiple stages at a portion facing the neck portion 2 along the transport route,
The neck portion 2 can be continuously heated even during transportation.

FIG. 5 is a schematic view showing a manufacturing apparatus 40 which is a fourth modification of the above-described manufacturing apparatus 10. As shown in FIG. Manufacturing equipment 4
Reference numeral 0 denotes a laser beam from a laser light source attached to the upper end portion of the small-diameter chamber 11b by installing one or more reflecting mirrors 41 whose angle can be changed on the inner wall surface of the small-diameter chamber 11b of the closed vessel 11. Is irradiated on the neck portion 2 to heat the neck portion 2. By controlling the angle of the reflection mirror 41, the neck portion 2 can be easily heated following the upward movement of the neck portion 2. In addition, when transporting the cooled ingot 3 to the storage unit, the laser light source is rotated, and the neck portion 2 is continuously irradiated with laser light, so that the neck portion 2 can be heated and held during transportation. .

FIG. 6 is a schematic diagram showing a manufacturing apparatus 50 which is a fifth modification of the above-described manufacturing apparatus 10. As shown in FIG. Manufacturing equipment 5
The number 0 is determined by using a plurality of monitoring windows 11e made of a synthetic quartz sealing plate normally provided in the large-diameter chamber 11a of the closed vessel 11 and using the plurality of monitoring windows 11e. A laser beam is emitted from the monitoring window 11e. In one of the monitoring windows 11e, a surface thermometer 51 capable of measuring a surface temperature from a remote distance is installed. In the manufacturing apparatus 50,
The comparison circuit 56 sets the temperature (Tf) set by the command unit 52.
° C) and the actually measured temperature (T
c ° C.), and the comparison result (ΔT) is transmitted to the laser light generator 54 via the power amplifier 53,
In the device 54, the irradiation amount of the laser beam is controlled. The laser light from the laser light generator 54 is reflected at a predetermined angle using a first movable mirror 55a that scans in the X-axis direction, and then is scanned in the Y-axis direction. The angle is changed by using 55b, and the light is reflected to irradiate the neck portion 2.

When the ingot 3 is pulled, the seed chuck 4 is attached to the tip of the single crystal pulling wire 16a.
, The seed crystal 1 is eccentrically fixed and the neck portion 2 is eccentrically rotated. The first movable mirror 55a
By simultaneously controlling and scanning the second movable mirror 55b, the irradiation of the laser beam can be made to follow the eccentric rotation of the neck portion 2 with high accuracy.

The neck portion 2 can be heated by using the reflecting mirror 41 according to the above-described fourth modified example when the neck portion 2 is pulled up to the small diameter chamber 11b, or the wall surface of the small diameter chamber 11b can be heated. It is also possible to form a window made of a synthetic quartz sealing plate and irradiate the laser beam from the window in the same manner.

FIG. 7 is a schematic view of a manufacturing apparatus 60 according to a sixth modification in which the neck portion 2 is heated by using a laser beam similarly to the fifth modification. The manufacturing apparatus 60 also irradiates a laser beam to the neck portion 2 of the ingot 3 in the large-diameter chamber 11a by using a monitoring window 11e formed of a synthetic quartz sealing plate provided in the large-diameter chamber 11a. At the same time, the surface temperature of the neck portion 2 is measured by the surface thermometer 51. In the manufacturing apparatus 60, the laser light from the laser light generator 54 is transmitted to the monitoring window 11 e by the optical fiber 61. Since the laser light is transmitted using the flexible optical fiber 61, in order to irradiate the laser light to the neck 2, the emission port at the tip of the fiber 61 faces the neck 2. Just move it. That is, a slide member 62a having the tip of the optical fiber 61 fixed downward is attached to the screw rod 62c, and the rod 62c is rotated by the servo motor 62b, so that the slide member 62a is parallel to the monitoring window 11e. The laser beam can be applied to the neck portion 2 and the driving thereof is easy.

Further, since the light is transmitted by the optical fiber 61, the light is not diffused, the light can always be irradiated with a constant energy regardless of the irradiation angle, the temperature can be easily controlled, and the loss of light energy is small. Furthermore, laser light can be irradiated at many points over the vertical dimension of the neck part 2 by the large number of optical fibers 61,
It is possible to heat the entire length of the neck portion 2 uniformly.

[0032]

As described above, it has been found that there is a temperature region where the strength of silicon single crystal is remarkably improved, and the temperature region is determined. By heating the neck portion in the above temperature range, the strength of the neck portion is significantly increased,
Even when a large-diameter and heavy silicon single crystal is pulled, the silicon single crystal is not broken by the neck portion, and the silicon single crystal can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a silicon single crystal manufacturing apparatus used in the manufacturing method of the present invention.

FIG. 2 is a schematic view showing a manufacturing apparatus which is a first modified example of the manufacturing apparatus.

FIG. 3 is a schematic view showing a manufacturing apparatus which is a second modified example of the manufacturing apparatus.

FIG. 4 is a schematic view showing a manufacturing apparatus which is a third modified example of the manufacturing apparatus.

FIG. 5 is a schematic view showing a manufacturing apparatus which is a fourth modified example of the manufacturing apparatus.

FIG. 6 is a schematic view showing a manufacturing apparatus which is a fifth modification of the above-mentioned manufacturing apparatus.

FIG. 7 is a schematic view showing a manufacturing apparatus which is a sixth modification of the manufacturing apparatus.

FIG. 8 is a graph showing a correlation between mechanical strength of silicon single crystal and temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 seed crystal 2 neck part 3 ingot 4 seed chuck 10 silicon single crystal manufacturing device 11 closed vessel 11a large diameter chamber 11b small diameter chamber 11c hot air introduction hole 11d hot air discharge hole 11e monitoring window 12 quartz crucible 13 graphite support 13a rotation axis 14 heater 15 Heat retaining cylinder 16 Single crystal pulling mechanism 16a Single crystal pulling wire 16b Heater pulling wire 17 Heater 20 Silicon single crystal manufacturing device 21 Reflection mirror 22 Heater 30 Silicon single crystal manufacturing device 31 Heater 40 Silicon single crystal manufacturing device 41 Reflection mirror 50 Silicon single crystal Manufacturing apparatus 51 Surface thermometer 52 Command section 53 Power amplifier 54 Laser light generator 55a First movable mirror 55b Second movable mirror 56 Comparison circuit 60 Silicon single crystal manufacturing apparatus 61 Optical fiber 62a Slide member 62b servo motor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Inagaki 3679-1 Okazaki, Hiratsuka-shi, Kanagawa Prefecture (72) Inventor Shoei Kurosaka 358-1 Maki, Hiratsuka-shi, Kanagawa Prefecture

Claims (8)

[Claims] In a method of manufacturing a silicon single crystal by the Czochralski method, at least at the time of pulling up a silicon single crystal, a neck formed between a seed crystal and the silicon single crystal is heated in a temperature range of 550 ° C. or more and 800 ° C. or less. A method for producing a silicon single crystal, comprising: holding a silicon single crystal. 2. The method according to claim 1, wherein said temperature range is 620 ° C. or more and 750 ° C. or less. 3. The method according to claim 1, further comprising heating the neck portion in the temperature range until the silicon single crystal is cut off. 4. The method according to claim 1, wherein the heating and holding are performed by an infrared heater. 5. The method according to claim 1, wherein the heating and holding are performed by a coil heater. 6. The manufacturing method according to claim 4, wherein reflection heating is further performed by a reflection mirror in addition to the heating and holding. 7. The method according to claim 1, wherein the heating and holding are performed by a laser beam. 8. The method according to claim 1, wherein the heating and holding are performed by hot air.
4. The production method according to any one of claims 1 to 3.