JP2006273685A - Single crystal producing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single crystal producing apparatus capable of growing a highly pure and large single crystal. <P>SOLUTION: In the single crystal producing apparatus 1, a raw material contained in a crucible 14 is heated and melted to form a melt 13, and a single crystal is grown by bringing a seed crystal 18 into contact with the surface of the melt 13 and pulling it while rotating it. The apparatus comprises a impurity-removing member 15 for removing impurities floating on the surface of the melt 13, a wire 16 for moving the impurity-removing member 15 up and down, and a pivot shaft 17 for guiding the wire 16 and retracting the impurity-removing member 15. The impurity-removing member 15 is brought into contact with the surface of the melt to allow impurities to adhere to the lower surface of the impurity-removing member 15. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a single crystal manufacturing apparatus that grows a single crystal by pulling a seed crystal in contact with a liquid surface of a raw material melt, and particularly relates to a single crystal manufacturing apparatus that can grow a large single crystal with high purity. .

  As one method for producing a single crystal, a crucible containing a raw material is heated with a coil, and the seed crystal is brought into contact with and rotated by a melt obtained by melting the raw material in the crucible with the heat. There is a Czochralski method (CZ method) in which a single crystal is grown on a seed crystal by pulling up.

  However, in the Czochralski method described above, the raw material melt is heated to cause convection in the crucible, and the impurities contained in the raw material and the crucible, or the elements constituting the crucible, dissolve into the raw material melt and float on the surface. However, a phenomenon of floating as an impurity near the center occurs. If this impurity is left unattended, it will intervene at the growth interface, which will hinder the growth of a single crystal, and a large single crystal with high purity cannot be obtained. There is a need to.

  As a method for preventing impurities on the melt surface from interposing on the growth interface, for example, there is a purge tube method, and a method is known in which a gas or the like is blown off and blown away (see, for example, Non-Patent Document 1).

T. Hikawa, Advanced Electronics Series, “Bulk Crystal Growth Technology”, Baifukan, May 20, 1994, p. 11

  However, according to the conventional single crystal manufacturing method, even if it blows off from the growth interface by the purge tube method, it cannot be removed out of the crucible, so it may appear again at the growth interface due to convection. Don't be.

  Accordingly, an object of the present invention is to provide a single crystal production apparatus capable of growing a large single crystal with high purity.

  In order to achieve the above object, the present invention provides a single crystal production apparatus for growing a single crystal by pulling a seed crystal in contact with a liquid surface of a melt melted by heating a raw material stored in a crucible. Provided is a single crystal manufacturing apparatus provided with an impurity removing means for removing impurities floating on the surface of a liquid.

  According to this configuration, in order to remove impurities floating on the surface of the melt, the seed crystal comes into contact with the melt with less impurities. Therefore, a high-purity single crystal can be grown.

  The impurity removing unit preferably includes an impurity removing member that attaches the impurity to the surface, and a driving unit that contacts and retracts the impurity removing member with respect to the melt surface.

  The impurity removing member preferably has an impurity removing portion that scoops up the impurities.

  The impurity removing member is preferably concentric with the seed crystal and has a substantially cylindrical shape whose lower end is in contact with the melt surface.

  The impurity removing member is preferably made of the same material as the raw material or a material having a melting point higher than the melting point of the raw material.

  The impurity removing means is arranged concentrically with the seed crystal, and has a cylindrical impurity removing member whose lower end is in contact with the melt surface, and the melt surface in response to a drop in the melt surface. It is preferable to include a driving unit that lowers the impurity removing member while maintaining contact.

  According to the single crystal manufacturing apparatus according to the present invention, a large single crystal with high purity can be grown.

[First Embodiment]
(Single crystal manufacturing equipment)
FIG. 1 shows a single crystal manufacturing apparatus according to a first embodiment of the present invention. This single crystal manufacturing apparatus 1 includes a chamber 10 having a viewing window 10a on its side surface and filled with an inert gas such as Ar from a gas supply port 10b formed on the upper side, and the inside of the chamber 10 having an Ar atmosphere. And a crucible 14 having a recess filled with a raw material, for example, a melt 13 of β-Ga ₂ O ₃ , a heat insulating part 11 made of ceramic or the like, a high-frequency coil 12 arranged coaxially with the heat insulating part 11, and the like. An impurity removing member 15 that is removably disposed on the crucible 14 and made of the same material as the raw material, a wire 16 that suspends the impurity removing member 15, and a wire 16 that is pulled out of the chamber 10. Is disposed above the crucible 14 and a pivot shaft 17 that is inserted into the ceiling portion 10b of the chamber 10 and is pivotally attached to the ceiling portion 10b of the chamber 10. a seed crystal 18 made of β-Ga ₂ O ₃ single crystal, a seed crystal rod 19 for holding a seed crystal 18, the weight of the high-frequency power source 20 for driving the high-frequency coil 12, mounted on the seed crystal rod 19 monocrystal And a control unit 22 for controlling the high-frequency power source 20 based on the output of the load cell 21. The rotating shaft 17 is formed with a bent portion 17a having a predetermined curvature. Impurity removing means is formed by the impurity removing member 15, the wire 16, and the rotating shaft 17.

  As for the heat insulation part 11, the recessed part 11a is formed in the upper part, and the crucible 14 is mounted in the recessed part 11a. The crucible 14 may be made of Ir, graphite, molybdenum or the like. The crucible 14 is preferably Ir in consideration of heat resistance and acid resistance.

When the raw material is, for example, β-Ga ₂ O ₃ , the impurity removing member 15 is formed by compressing and sintering the raw material powder of β-Ga ₂ O ₃ . Further, a material having higher melting point than _β-Ga 2 _{O 3,} for example, may be formed by sapphire.

(Removal of impurities)
FIG. 2 shows the arrangement of the rotating shaft 17, and FIG. 3 shows the state of generation of impurities. FIG. 4 shows an impurity removal process by the impurity removal member. In FIG. 3, the high-frequency coil 12 is not shown in order to simplify the drawing. The impurity removal operation will be described with reference to FIGS.

  In FIG. 1, the operator puts a predetermined raw material in the crucible 14, turns on the power of the single crystal manufacturing apparatus 1, supplies high-frequency power from the high-frequency power supply 20 to the high-frequency coil 12, and passes through the side wall of the crucible 14. The raw material is heated and melted to produce the melt 13. The operator observes the state of generation of impurities from the viewing window 10a when a predetermined time has elapsed.

  Here, the principle of impurity generation will be described with reference to FIG. As shown in FIGS. 3A and 3B, in the crucible 14, convection is generated in the melt 13 from the outside toward the center as indicated by an arrow A due to the heating of the high-frequency coil 12. Due to this convection, the impurity 23 stays in the center of the surface of the melt 13 while floating.

  When the impurity 23 is floating as shown in FIG. 3, the operator rotates the rotating shaft 17 by means not shown to position the impurity removing member 15 on the center portion of the crucible 14. Next, the impurity removing member 15 is lowered, and the lower surface of the impurity removing member 15 is brought into contact with the impurity 23 as shown in FIG. The operator operates the wire 16 to sink the impurities 23 or attach them to the lower surface of the impurity removing member 15 to raise the melt 13 and the impurities 23 together with the impurity removing member 15 to solidify the melt 13. The impurities 23 are adhered to the impurity removing member 15 or both are performed to remove the impurities 23 floating on the melt surface. After the removal, the pivot shaft 17 is pivoted toward the inner wall of the chamber 10 and retracted to a position where it does not contact the seed crystal 18. Next, the seed crystal 18 is lowered while being rotated, the lower surface is brought into contact with the melt 13, and then a single crystal is grown.

  The single crystal is pulled up at a constant speed and grown in a conical shape, and then the pulling speed is changed to grow a large-diameter single crystal. While this growth is being performed, a weight signal is output from the load cell 21, and based on this weight signal, the control unit 22 performs feedback control so that the single crystal has a desired diameter.

(Effects of the first embodiment)
According to the first embodiment, the following effects are obtained.
(A) Since the impurities 23 can be removed out of the crucible 14 by the impurity removing member 15, a large single crystal with high purity can be grown.
(B) Since only the impurity removing member 15, the wire 16, and the rotating shaft 17 need be added to the conventional single crystal manufacturing apparatus, the configuration can be simplified and the cost of the single crystal manufacturing apparatus can be prevented from increasing. can do.
(C) Since the raw material and the impurity removing member 15 are formed of the same material, the impurities do not increase even if the impurity removing member 15 is melted.
(D) When the impurity removing member 15 is formed of a material having a melting point higher than that of the raw material, the impurity removing member 15 is not melted by the melt 13 and therefore does not dissolve out as impurities in the raw material melt.
(E) Since the rotating shaft 17 is provided with the bent portion 17a having a predetermined curvature, the wire is not caught by the bent portion 17, so that the operation of the impurity removing member 15 is facilitated.

  In the first embodiment, the removal method of attaching the impurity 23 to the lower surface of the impurity removal member 15 has been described. However, as another method, the impurity removal member 15 is lowered to attach the impurity 23 together with the melt 13. Then, after the impurities 23 are solidified on the surface of the impurity removing member 15 by crystallization based on the temperature drop of the melt 13, the impurities 23 are removed from the melt 13 by raising the impurity removing member 15. good.

[Second Embodiment]
FIG. 5 shows an impurity removing member of a single crystal manufacturing apparatus according to the second embodiment of the present invention. The impurity removing member 15 has a circular impurity removing portion 15 a made of one wire having a melting point equal to or higher than that of the raw material, and a straight portion 15 b extending perpendicularly to the wire and having an upper end coupled to the wire 16. The other configuration of the single crystal manufacturing apparatus 1 is the same as that of the first embodiment.

  Similar to the first embodiment, when it becomes necessary to remove the impurities 23, the wire 16 is operated while observing the melt surface through the viewing window 10a to lower the impurity removing member 15 and scoop up the impurities 23. By moving the impurity removing member 15 as described above, the impurity 23 is attached so as to cover the impurity removing portion 15 a by the surface tension of the melt 13 attached to the impurity 23. The operation of the impurity removing member 15 after the impurities 23 are attached is the same as in the first embodiment.

(Effect of the second embodiment)
According to the second embodiment, since the impurity removing member 15 is provided, the impurities are removed before the single crystal is grown. Therefore, the single crystal having a high purity and a large diameter can be grown, and the impurity removing member. Since 15 can be configured very easily, the cost can be further reduced as compared with the single crystal manufacturing apparatus 1 of the first embodiment.

[Third Embodiment]
FIG. 6 shows an impurity removing member of a single crystal manufacturing apparatus according to the third embodiment of the present invention. In the second embodiment, the impurity removing member 15 has a metal net portion 15c having a melting point equal to or higher than that of the raw material, and the net portion 15c and the straight portion 15b. The structure having the connected circular support portions 15d is characterized, and the other structure is the same as that of the second embodiment. Instead of the net portion 15c, a member having a configuration in which a plurality of holes are provided in a disk processed into a concave surface may be used.

(Effect of the third embodiment)
According to the third embodiment, since the mesh portion 15c is provided as compared with the second embodiment, the effect of removing impurities can be enhanced. Since the impurity removing member 15 does not melt at the temperature of the melt 13, it does not become an impurity itself. Further, since the impurities are removed by the impurity removing member 15 before the single crystal is grown, a single crystal having a high purity and a large diameter can be grown.

[Fourth Embodiment]
FIG. 7 shows a main part of a single crystal manufacturing apparatus according to the fourth embodiment of the present invention. 8 shows a state where the seed crystal is lowered in FIG. 7, and FIG. 9 shows a step of pulling up the impurity removing member.

  In the present embodiment, instead of the impurity removing member 15 in the first embodiment, a cylindrical impurity removing portion 24 arranged concentrically with respect to the seed crystal 18 is provided. The configuration is the same as in the first embodiment. The impurity removing member 24 is formed of a material equivalent to the raw material or having a higher melting point than the raw material.

  According to the fourth embodiment, when the melt 13 is formed, the impurity removing member 24 is lowered onto the liquid surface of the melt 13. In the melt 13, the convection indicated by the arrow A is generated by heating by the high-frequency coil 12, and the impurity 23 flowing from the outside to the inside along with the convection adheres to the lower end of the outer peripheral surface of the impurity removing member 24. Therefore, the impurity 23 does not enter the growth interface. In this state, the seed crystal rod 19 is lowered and brought into contact with the liquid surface of the melt 13 as shown in FIG. When the single crystal grows, the impurity removing member 24 is pulled up from the liquid surface of the melt 13 as shown in FIG. Thereby, even if the diameter of the single crystal 25 becomes large, the impurity removing member 24 does not get in the way.

(Effect of the fourth embodiment)
According to the fourth embodiment, the effect of removing impurities can be enhanced as compared with the above embodiments. In addition, since the impurity removing member 24 is provided, a single crystal having a high purity and a large diameter can be grown.

[Fifth Embodiment]
FIG. 10 shows a main part of a single crystal manufacturing apparatus according to the fifth embodiment of the present invention. In this embodiment, an impurity removing member 26 having a star-shaped cross section is used in place of the impurity removing member 24 in the fourth embodiment, and other configurations are the same as those in the fourth embodiment. It is the same. The impurity removing member 26 removes impurities by attaching impurities to the outer peripheral portion thereof.

(Effect of 5th Embodiment)
According to the fifth embodiment, as compared with the fourth embodiment, the outer peripheral surface is in contact with the inner peripheral surface of the crucible 14 and restricts the movement of the impurity removing member 26 in the inner diameter direction. The single crystal 25 can be grown without contacting the member 26.

[Sixth Embodiment]
FIG. 11 shows a single crystal manufacturing apparatus according to the sixth embodiment of the present invention. In FIG. 11, only the main part is shown. In the fourth embodiment, the impurity removing member 24 is lowered in synchronization with the decrease in the liquid level of the melt 13 in the fourth embodiment, and other configurations are the fourth embodiment. It is the same.

  The impurity removing member 24 is attached to a driving mechanism (not shown) whose upper end moves up and down, and this driving mechanism is controlled by the control unit 22. Based on the weight signal output from the load cell 21, the control unit 22 calculates the degree of decrease in the liquid level of the melt 13, operates the drive mechanism in accordance with the calculated amount, and lowers the impurity removal member 24 by following it. Execute control. The impurity removing member 24 and the driving mechanism form impurity removing means.

  When the seed crystal 18 comes into contact with the liquid surface of the melt 13, the melt is sufficiently filled as shown in FIG. However, as the growth of the single crystal 25 proceeds, the liquid level of the melt 13 decreases by h from the height of FIG. 11A as shown in FIG. In this process, the control unit 22 operates the drive mechanism based on the weight signal from the load cell 21 and lowers the impurity removing member 24 as shown in FIG.

(Effect of 6th Embodiment)
According to the sixth embodiment, since the impurity removing member 24 can be lowered following the change in the liquid level of the melt 13, the impurities can be removed even when the liquid level is lowered. Therefore, the amount of impurities removed can be increased as compared with the fourth embodiment.

[Other embodiments]
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, a plurality of arms extending to the inner peripheral surface of the crucible 14 may be provided on the outer periphery of a cylindrical impurity removing member as shown in FIG. Thereby, the movement of the crucible 14 in the inner diameter direction can be restricted.

  Moreover, since the impurity removal member 15 does not melt in a short time contact with the melt if the difference in melting point is within 100 ° C., the impurity removal member 15 may have a melting point lower than that of the raw material.

It is a longitudinal section showing a single crystal manufacturing device concerning a 1st embodiment of the present invention. It is a top view which shows arrangement | positioning of the rotating shaft of the single crystal manufacturing apparatus of FIG. The generation of impurities in the crucible is shown, (a) is a longitudinal sectional view of the crucible, and (b) is a plan view of the crucible. It is a longitudinal cross-sectional view which shows the removal process of the impurity by an impurity removal member. It is a perspective view which shows the impurity removal member of the single-crystal manufacturing apparatus which concerns on the 2nd Embodiment of this invention. It is a perspective view which shows the impurity removal member of the single crystal manufacturing apparatus which concerns on the 3rd Embodiment of this invention. It is front sectional drawing which shows the principal part of the single-crystal manufacturing apparatus which concerns on the 4th Embodiment of this invention. It is a longitudinal cross-sectional view of the single-crystal manufacturing apparatus which shows the state which lowered | hung the seed crystal in FIG. It is a longitudinal cross-sectional view of the single crystal manufacturing apparatus which shows the raising process of an impurity removal member. It is a top view which shows the principal part of the single-crystal manufacturing apparatus which concerns on the 5th Embodiment of this invention. The main part of the single-crystal manufacturing apparatus which concerns on the 6th Embodiment of this invention is shown, (a) is a longitudinal cross-sectional view which shows the initial state which the seed crystal contacted the liquid level, (b) is a single crystal growing It is the longitudinal cross-sectional view after having performed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Single crystal manufacturing apparatus, 10 ... Chamber, 10a ... Viewing window, 10b ... Gas supply port, 11 ... Heat insulation part, 11a ... Recessed part, 12 ... High frequency coil, 13 ... Melt, 14 ... Crucible, 15 ... Impurity removal member 15a ... impurity removing portion, 15b ... straight portion, 15c ... net portion, 15d ... support portion, 16 ... wire, 17 ... rotating shaft, 18 ... seed crystal, 19 ... seed crystal rod, 20 ... high frequency power source, 21 ... Load cell, 22 ... control unit, 23 ... impurity, 24 ... impurity removing member, 25 ... single crystal, 26 ... impurity removing member

Claims (6)

In a single crystal manufacturing apparatus that grows a single crystal by pulling the seed crystal in contact with the melt surface melted by heating the raw material stored in the crucible,
An apparatus for producing a single crystal, comprising an impurity removing means for removing impurities floating on the surface of the melt. The impurity removing means includes an impurity removing member that adheres the impurities to the surface;
The single crystal manufacturing apparatus according to claim 1, further comprising driving means for bringing the impurity removing member into contact with and withdrawing from the melt surface.   The single crystal manufacturing apparatus according to claim 2, wherein the impurity removing member includes an impurity removing unit that scoops up the impurities.   The single crystal manufacturing apparatus according to claim 2, wherein the impurity removing member is concentrically arranged on the seed crystal and has a substantially cylindrical shape whose lower end is in contact with the melt surface.   The single crystal manufacturing apparatus according to claim 2, wherein the impurity removing member is made of the same material as the raw material or a material having a melting point higher than the melting point of the raw material. The impurity removing means is arranged concentrically with the seed crystal, and a cylindrical impurity removing member whose lower end is in contact with the melt surface;
2. The single crystal manufacturing apparatus according to claim 1, further comprising: a driving unit that lowers the impurity removing member while maintaining contact with the melt surface as the melt surface descends. 3.