JP2000016893A - Method and apparatus for pulling single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a volume expansion accompanied with solidification to be allowed to escape into the upper free surface of a remaining molten liquid and further enable an integrated type carbon crucible to be used without breakage by solidifying the remaining molten liquid after pulling a single crystal from the molten liquid in the crucible by using a Czochralski method, from the lower part to the upper part. SOLUTION: One method for carrying out a solidifying step of a remaining molten liquid after pulling a single crystal so that the remaining molten liquid in a crucible may be solidified from the lower part to the upper part comprises moving the remaining liquid 2 in the crucible 1 heated by a heater 3 downward so that the bottom part of the crucible 1 may be positioned at the part lower than the lower limit position 3a of the heater 3, and allowing the molten liquid to stand cool naturally. Another method comprises separating the heater for heating the crucible to upper and lower sides so as to be separately controlled, and controlling the heater so that the thermal dose by the lower side heater may be lower than that of the upper side heater to solidify the remaining molten liquid from the lower part to the upper part. The third method comprises arranging a water-cooling pipe under the crucible to cool the bottom part aggressively, to solidify the remaining molten liquid from the lower part to the upper part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for pulling a single crystal from a melt contained in a crucible using the Czochralski method.

[0002]

2. Description of the Related Art The Czochralski method is known as one of the methods for growing a single crystal such as silicon or gallium arsenide. In the Czochralski method, a heater is arranged around a crucible, and the raw material in the crucible is melted by the heater to obtain a raw material melt. Then, while keeping the temperature of the melt at a temperature suitable for pulling up by the heater, the seed crystal is immersed in the melt, and the seed crystal is slowly pulled up while rotating to grow a single crystal.

Normally, the single crystal pulling step as described above is completed with the residual melt remaining in the crucible, and the power supply to the heater is stopped upon completion.

[0004]

Considering the temperature distribution of the residual melt at the end of this process, it can be seen that even if the heating by the heater is stopped, the residual heat of the crucible may be lost due to the heat retention effect of the crucible. The interior is not cooled rapidly.
On the other hand, if the heating by the heater is stopped, the surface exposed portion of the residual melt is rapidly cooled by the atmospheric gas. Therefore, the residual melt in the crucible starts to be cooled from the surface.

Therefore, according to the above-described conventional single crystal pulling method, when the residual melt is solidified in the crucible, the residual melt is cooled from the surface and starts to solidify from the surface. Here, when the crucible is an integral crucible such as an integral carbon crucible, if a solidified portion is first formed on the surface of the residual molten liquid, the integral crucible is increased due to volume expansion accompanying subsequent solidification. May be crushed.

[0006] For this reason, it has been proposed to use a carbon crucible formed in a divided manner. In this case, silicon monoxide (SiO) gas present in the furnace reduces the thickness of the carbon crucible divided surface. There is a problem that occurs. Due to this thinning, the number of times the carbon crucible is used is limited.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a single crystal pulling method and a single crystal pulling apparatus capable of using an integrated carbon crucible.

[0008]

According to a first aspect of the present invention, there is provided a method for pulling a single crystal from a melt contained in a crucible using a Czochralski method, comprising the steps of: A crystal pulling step and a step of solidifying the residual melt are provided. In the solidifying step, the residual melt in the crucible is solidified from a lower portion to an upper portion. In the single crystal pulling method according to claim 2, in the single crystal pulling method according to claim 1, a heater is previously arranged around the crucible, and in the solidification step, the bottom of the crucible is The crucible is moved downward so as to be located below a lower limit position of the heater. According to a third aspect of the present invention, in the single crystal pulling method according to the first aspect, the crucible is provided with an upper heater and a lower heater which can be individually controlled in advance. And in the solidification step, the upper and lower heaters are controlled such that the amount of heating by the upper heater is greater than the amount of heating by the lower heater. According to a fourth aspect of the present invention, in the single crystal pulling method according to the first aspect, in the solidifying step, a bottom portion of the crucible is cooled. In the method for pulling a single crystal according to claim 5, in the method for pulling a single crystal according to claim 1, a heater is previously disposed above the crucible, and the heater is operated in the solidification step. And heating the surface of the residual melt. The apparatus for pulling a single crystal according to claim 6, wherein the single crystal is pulled from a melt contained in the crucible using the Czochralski method, wherein a heater is arranged around the crucible, The heater is characterized by having an upper heater and a lower heater that can be individually controlled. In the single crystal pulling apparatus according to claim 7,
An apparatus for pulling a single crystal from a melt contained in a crucible using the Czochralski method, wherein a cooling mechanism is provided below the crucible. 9. The apparatus for pulling a single crystal according to claim 8, wherein the single crystal is pulled from the melt contained in the crucible using the Czochralski method, wherein the single crystal is disposed above the crucible and is pulled upward. A flow pipe is provided for guiding the ambient gas supplied from the side onto the liquid surface of the melt, and a heater is arranged below the flow pipe.

According to the first aspect of the present invention, in the step of solidifying the residual melt, the residual melt in the crucible is solidified from a lower portion to an upper portion. For this reason, volume expansion during solidification can be released to the upper free surface of the residual melt, and the use of the integral carbon crucible can be performed. According to the second aspect of the present invention, in the solidifying step, the crucible is moved downward such that the bottom of the crucible is located below the lower limit position of the heater. Therefore, the upper portion of the residual melt is heated by receiving the heat from the heater, and the lower portion of the residual melt is cooled without receiving the heat of the heater. Therefore, the temperature of the residual melt becomes lower toward the lower part, and solidification from the lower part to the upper part is brought about. According to the third aspect of the invention, in the solidifying step, the upper and lower heaters are controlled such that the amount of heating by the upper heater is greater than the amount of heating by the lower heater. Therefore, the amount of heat input to the upper portion of the residual melt exceeds the amount of heat input to the lower portion of the residual melt, and the lower the temperature of the residual melt, the lower the temperature. Therefore, solidification from the lower part to the upper part is brought about. According to the fourth aspect of the invention, in the solidification step, the bottom of the crucible is cooled. Therefore, the lower part of the residual melt is rapidly cooled, and solidification from the lower part to the upper part is brought about. According to the fifth aspect of the present invention, in the solidifying step, the heater above the crucible is operated. For this reason,
The upper portion of the retentate is heated to prevent solidification of the surface, thus causing solidification from the lower portion to the upper portion. According to the invention described in claim 6, in the solidification step, the upper and lower heaters are controlled such that the amount of heating by the upper heater is greater than the amount of heating by the lower heater. Therefore, the amount of heat input to the upper portion of the residual melt exceeds the amount of heat input to the lower portion of the residual melt, and the lower the temperature of the residual melt, the lower the temperature. Therefore, solidification from the lower part to the upper part is brought about. According to the invention described in claim 7, in the solidification step,
The cooling mechanism provided below the crucible is operated. Therefore, the lower part of the residual melt is rapidly cooled, and solidification from the lower part to the upper part is brought about. According to the invention described in claim 8,
In the solidification step, the heater below the flow tube is operated. For this reason, the upper portion of the residual melt is heated to prevent solidification of the surface, and thus solidification is caused from the lower portion to the upper portion.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

The method according to the present invention is a method for pulling a single crystal from a melt contained in a crucible using the Czochralski method, comprising a single crystal pulling step and a solidifying step of a residual melt. , And ancillary steps associated therewith. The present invention has a unique feature in the solidification step of the residual melt, and the single crystal pulling step is the same as the conventional one, so that the description thereof is omitted.

The most characteristic feature of the solidifying step of the present invention is that the residual melt in the crucible is solidified from the lower part to the upper part. In the present invention, since the residual melt in the crucible is solidified from the lower part to the upper part, the volume expansion during the solidification can be released to the upper free surface of the residual melt, and the use of the integrated carbon crucible is enabled. can do. There are several embodiments for implementing this method, which will be described below in order.

[First Embodiment] FIG. 1 is a diagram showing a first embodiment of a single crystal pulling method according to the present invention. In the figure,
Reference numeral 1 denotes a crucible, 2 denotes a residual melt left in the crucible 1 after completion of the single crystal pulling step, and 3 denotes a heater arranged around the crucible 1.

In the present embodiment, the crucible 1 is moved downward so that the bottom of the crucible 1 is located below the lower end 3 a of the heater 3 in the solidification step of the residual melt after the completion of the single crystal pulling step. (FIG. 1B).

In this case, the upper part of the residual melt 2 can be heat from the heater 3 (heat generated by operating the heater 3, or the residual heat generated when the heater 3 is stopped). Solidification is prevented. In this case, a heater 3
Is located below the lower end 3a of the
It is allowed to cool naturally without receiving heat. Therefore, the temperature of the residual melt becomes lower toward the lower part, and solidification from the lower part to the upper part is realized.

[Second Embodiment] FIG. 2 is a view showing a second embodiment of the single crystal pulling method according to the present invention. In the figure,
Reference numeral 4 denotes a heater arranged around the crucible 1.

Here, the heater 4 is composed of an upper heater 4a and a lower heater 4b which can be individually controlled.

In the present embodiment, in the solidification step, the upper and lower heaters 4a and 4b are heated so that the amount of heating by the upper heater 4a is greater than the amount of heating by the lower heater 4b.
a, 4b are controlled. In the present embodiment, it is not necessary to move the crucible 1 downward. Although it is not limited, it is practical to operate the upper heater 4a with low power and stop the lower heater 4b.

Therefore, the amount of heat input to the upper portion of the residual melt 2 exceeds the amount of heat input to the lower portion of the residual melt 2, and
The lower the temperature, the lower the temperature. Therefore, solidification from the lower part to the upper part is realized.

[Modification of the Second Embodiment] FIG. 3 is a diagram showing a modification of the second embodiment. In the figure, reference numeral 5 denotes a heater arranged around the crucible 1.

Here, the heater 5 comprises an upper heater 5a, a middle heater 5b, and a lower heater 5c which can be individually controlled.

In the present embodiment, in the solidification step, the heaters 5 are set so that the amount of heating by the upper heater 5a and the middle heater 5b is greater than the amount of heating by the lower heater 5c.
Is controlled. That is, the upper heater 5a and the middle heater 5b function as an upper heater, and the lower heater 5c functions as a lower heater. The operation and effect in this case are the same as those of the second embodiment.

It is obvious that, other than this modified example, the heater may have a four-stage configuration or more.

[Third Embodiment] FIG. 4 shows a third embodiment of the single crystal pulling method according to the present invention. In the figure,
Reference numeral 6 denotes a water cooling pipe (cooling mechanism) arranged below the crucible 1.

In the present embodiment, the bottom of the crucible 1 is cooled by the water cooling pipe 6 in the solidification step. In this case, the heater 3 may or may not be operated. In cooling, it is effective to make the distance between the crucible 1 and the water-cooled pipe 6 shorter by lowering the crucible 1 or by raising the water-cooled pipe 6. Cooling water is constantly circulated through the cooling pipe 6 to protect the pipe, but it is effective to increase the amount of circulating water during cooling.

As a result, the lower portion of the residual melt 2 is rapidly cooled, and solidification from the lower portion to the upper portion is realized.

Further, as a cooling mechanism other than the water cooling pipe 6, a cooling plate 6a as shown in FIG. 4C can be used. The cooling plate 6a has a hollow structure and a structure having a partition plate 6b therein.
The cooling water can circulate through the hollow interior. Note that any other cooling mechanism other than the water cooling pipe 6 and the cooling plate 6a may be employed.

[Fourth Embodiment] FIG. 5 is a view showing a fourth embodiment of the single crystal pulling method according to the present invention. In the figure,
Reference numeral 7 denotes a flow tube disposed above the crucible 1 and for guiding an atmospheric gas supplied from above to the surface of the melt, and reference numeral 8 denotes a heater disposed below the flow tube 7. ing. The flow tube 7 has a function of guiding the rapid exhaust of silicon monoxide by the flow of the atmospheric gas even if silicon monoxide is generated in the single crystal pulling step;
And a function of blocking radiant heat from the heater 3 toward the growing single crystal.

In the present embodiment, the heater 8 below the flow tube 7 is operated in the solidification step.

As a result, the upper portion of the residual melt 2 is heated and solidification of the surface is prevented, so that solidification from the lower portion to the upper portion is realized.

[0031]

According to the single crystal pulling method and the single crystal pulling apparatus of the present invention, the following effects can be obtained. According to the method for pulling a single crystal according to claim 1, in the step of solidifying the residual melt,
Since the residual melt in the crucible is solidified from the lower part to the upper part, the volume expansion during the solidification can be released to the upper free surface of the residual melt, and the use of the integral carbon crucible can be made possible. As described above, the use of the integral type carbon crucible can avoid the problem of wall thinning which occurs in the case of the split type carbon crucible, and can increase the number of times the carbon crucible is used. According to the method for pulling a single crystal according to claim 2, in the solidification step,
Since the crucible is moved downward, solidification of the upper portion of the residual melt can be prevented by the heat from the heater, and the lower portion of the residual melt can be cooled without receiving the heat from the heater. Therefore, the temperature of the residual melt becomes lower at the lower portion, solidification from the lower portion to the upper portion is realized, and the use of the integrated carbon crucible can be made possible. According to the single crystal pulling method of claim 3, in the solidification step,
Since the upper and lower heaters are controlled so that the amount of heating by the upper heater is greater than the amount of heating by the lower heater, the amount of heat input to the upper portion of the residual melt is increased, and the lower the temperature of the residual melt, the lower the temperature. The solidification from the lower part to the upper part can be realized, thereby enabling the use of the integral carbon crucible. According to the single crystal pulling method of the fourth aspect, in the solidification step, by cooling the bottom of the crucible, the lower portion of the residual melt can be rapidly cooled, and solidification from the lower portion to the upper portion is realized. Thus, it is possible to use an integrated carbon crucible. According to the method for pulling a single crystal according to claim 5, in the solidification step,
Since the heater above the crucible is operated, the upper part of the residual melt can be heated to prevent solidification of the surface, so that solidification from the lower part to the upper part can be realized, and the use of the integrated carbon crucible can be achieved. Can be possible. According to the single crystal pulling apparatus of the sixth aspect, in the solidification step, the upper and lower heaters are controlled such that the amount of heating by the upper heater is larger than the amount of heating by the lower heater. By increasing the heat input to the upper part, the temperature of the lower part of the residual melt can be lowered, so that solidification from the lower part to the upper part can be realized and the use of an integrated carbon crucible can be achieved. Can be. According to the single crystal pulling apparatus according to the seventh aspect, in the solidification step, the cooling mechanism provided below the crucible can be operated to rapidly cool the lower part of the residual melt, and from the lower part to the upper part. And the use of an integrated carbon crucible can be realized. According to the single crystal pulling apparatus of the eighth aspect, in the solidification step, the heater at the lower part of the flow tube is operated, so that the upper part of the residual melt can be heated to prevent solidification of the surface. Thus, solidification from the top to the top can be realized, and the use of the integral carbon crucible can be made possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of a single crystal pulling method of the present invention.

FIG. 2 is a view showing a second embodiment of the single crystal pulling method of the present invention.

FIG. 3 is a diagram showing a modification of the second embodiment.

4A is a view showing a third embodiment of the single crystal pulling method of the present invention, FIG. 4B is a plan view showing a cooling mechanism in FIG. 4A, and FIG. 4C is a cooling mechanism. It is a plane sectional view showing other examples of.

FIG. 5 is a view showing a fourth embodiment of the single crystal pulling method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crucible 2 Residual melt 3 Heater 3a Lower limit position 4 Heater 4a Upper heater 4b Lower heater 5 Heater 5a Upper heater (upper heater) 5b Medium heater (upper heater) 5c Lower heater (lower heater) 6 Water cooling pipe (cooling mechanism) 6a Water cooling plate (cooling mechanism) 7 Flow tube 8 Heater

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironari Abe 1-5-1, Otemachi, Chiyoda-ku, Tokyo Within Mitsui Materials Silicon Co., Ltd. (72) Inventor Takashi Atami 1-5-1, Otemachi, Chiyoda-ku, Tokyo No. 1 Mitsubishi Material Silicon Co., Ltd. F-term (reference) 4G050 FA16 FE12 FF51 FF55 4G077 AA02 BA04 CF00 EG18 EH07

Claims (8)

[Claims] 1. A method for pulling a single crystal from a melt contained in a crucible using a Czochralski method, comprising a single crystal pulling step and a step of solidifying a residual melt. In the solidification step, the residual crystal in the crucible is solidified from a lower part to an upper part, and a single crystal pulling method is provided. 2. The method for pulling a single crystal according to claim 1, wherein a heater is previously arranged around the crucible, and in the solidification step, a bottom of the crucible is lower than a lower limit position of the heater. A single crystal pulling method, wherein the crucible is moved downward so that the single crystal is located at 3. The method for pulling a single crystal according to claim 1, wherein a heater having an upper heater and a lower heater that can be individually controlled is arranged around the crucible in advance. In the solidifying step, the upper and lower heaters are controlled such that the amount of heating by the upper heater is greater than the amount of heating by the lower heater. 4. The single crystal pulling method according to claim 1, wherein in the solidifying step, a bottom portion of the crucible is cooled. 5. The single crystal pulling method according to claim 1, wherein a heater is previously disposed above the crucible, and in the solidification step, the heater is operated to cause the surface of the residual molten liquid to move. Heating a single crystal. 6. An apparatus for pulling a single crystal from a melt accommodated in a crucible using a Czochralski method, wherein a heater is arranged around the crucible, and the heaters are individually separated from each other. A single crystal pulling apparatus comprising a controllable upper heater and a lower heater. 7. An apparatus for pulling a single crystal from a melt contained in a crucible using the Czochralski method, wherein a cooling mechanism is provided below the crucible. Single crystal pulling device. 8. An apparatus for pulling a single crystal from a melt accommodated in a crucible using a Czochralski method, comprising: an atmosphere gas disposed above the crucible and supplied from above. A single crystal pulling apparatus, comprising: a flow pipe for guiding the melt onto a liquid surface; and a heater disposed below the flow pipe.