JP4614583B2 - Crystal growth furnace and crystal growth method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a crystal growth furnace and a crystal growth method for growing a crystal by solidifying while pulling up a melt.
[0002]
[Prior art]
In the crystal growth furnace of the Czochralski method, where a seed crystal is immersed in a melt of a material placed in a crucible, and the melt that comes along the seed crystal is solidified while being slowly pulled up, the crystal grows. In order to prevent adverse radiant heat, a radiant heat shield is placed above the crucible in the furnace vessel. Regarding such a radiant heat shield, a shield mounting jig of Japanese Patent Laid-Open No. 2000-86381 and a single crystal pulling apparatus of Japanese Patent Laid-Open No. 1-160891 are known. In each of the crystal growth furnaces disclosed in Japanese Patent Application Laid-Open Nos. 2000-86381 and 1-160891, an appropriate shaft is passed through the ceiling surface of the furnace vessel, and a radiant heat shield is suspended from the lower end of the shaft. Therefore, the radiant heat shield is fixed at an appropriate height.
[0003]
[Problems to be solved by the invention]
However, since the upper part in the furnace vessel becomes high temperature, there is a concern that if the seal portion that penetrates the shaft is on the ceiling surface of the furnace vessel, the seal portion may be damaged by heat. In order to protect from this damage, it is necessary to cool the seal portion. However, if it is cooled, the material volatilized from the crucible tends to adhere to the seal portion and the cooled shaft. If the material adheres to the seal part or the shaft in this way, the gas tightness may be lowered and gas leakage may occur from the inside of the furnace vessel.
[0004]
For this reason, conventionally, it was necessary to open the furnace vessel every time the crystal growth operation was completed, clean the seal part and shaft, and replace parts. Conventionally, the shaft penetrating the ceiling of the furnace vessel is moved up and down by a drive mechanism located at the top of the furnace vessel, and it is difficult to visually check the origin position of the radiant heat shield with the furnace vessel opened. It was.
[0005]
On the other hand, in the case of crystal growth by the Czochralski method, in order to suppress the occurrence of crystal defects at the crystal growth interface and the side surface of the growth crystal, the heating amount of the material contained in the crucible (heat flow rate toward the bottom of the crucible) is set. Control is important, and it is also important to control the amount of radiant heat from the heater and melt surface. According to the knowledge of the present inventors, when controlling the amount of radiant heat, the distance between the surface of the sealing material filled on the melt surface and the lower end of the radiant heat shield is one of the important factors. I understood that.
[0006]
Here, in the conventional crystal growth furnace, since the height of the radiant heat shield is fixed, for example, by raising the crucible as the crystal is pulled up, the liquid level in the crucible and the lower end of the radiant heat shield are reduced. If the distance is kept constant, the positional relationship between the crucible and the heater will change. As a result, the amount of heating with respect to the melt changes, and there is a concern that the generation of crystal defects at the crystal growth interface and the crystal growth side cannot be effectively suppressed. Further, the crystal growth proceeds, and the distance is changed in accordance with the size of the grown ingot in order to prevent a temperature drop of the ingot.
[0007]
In addition, when trying to raise and lower the radiant heat shield in a conventional crystal growth furnace, the seal portion that penetrates the shaft supporting the radiant heat shield is located on the ceiling surface of the furnace vessel, so the shaft is raised and lowered during crystal growth. In addition, there is a concern that the sealing performance of the sealed part may be impaired by heat. In addition, it is considerably difficult to control the raising and lowering of the radiant heat shield with high accuracy in a state where the seal portion is heated.
[0008]
The object of the present invention is to provide a crystal growth furnace that does not adversely affect the seal portion thermally, has excellent airtightness and is easy to maintain, and is capable of generating crystal defects at the crystal growth interface and the crystal growth side. An object is to provide a crystal growth method that can be suppressed.
[0009]
[Means for solving the problems]
In order to achieve this object, the present invention is a crystal growth furnace for growing a crystal by pulling up the molten liquid in the crucible and is disposed above the molten liquid placed in the crucible. the radiant heat shield is supported by a lift member that, said lifting member to penetrate into the furnace vessel bottom, connected to a lifting mechanism that is disposed outside the furnace vessel, a heat insulating material is disposed so as to surround the peripheral sides and bottom of the crucible A crystal growth furnace is provided. On the bottom surface of the furnace vessel, a seal bearing may be provided at a location through which the elevating member penetrates.
[0010]
Further, in the present invention, a crystal growth method for growing a crystal by solidifying while pulling up a melt in a crucible,
In the crystal growth furnace, there is provided a crystal growth method characterized by raising and lowering a radiant heat shield disposed above a melt placed in a crucible as the crystal is pulled up. In this case, it is preferable to control the raising and lowering of the radiant heat shield so that the distance between the surface of the sealing material filled on the melt surface and the lower end of the radiant heat shield is kept constant.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view schematically showing the internal structure of a crystal growth furnace 1 according to an embodiment of the present invention.
[0012]
The top surface of the cylindrical furnace vessel 10 whose bottom surface is closed and whose top surface is open is closed by a lid 11 so as to be freely opened and closed. A cylindrical crucible 12 having a closed bottom surface and an open top surface is accommodated at substantially the center inside the furnace vessel 10. The crucible 12 is supported on the upper end of a support column 13 provided vertically through the center of the bottom surface of the furnace vessel 10.
[0013]
A heater 15 is disposed so as to surround the entire peripheral side surface of the crucible 12. The heater 15 has a cylindrical shape with a size that can accommodate the crucible 12 therein, and the heater 15 is open at the top and bottom.
[0014]
A heat insulating material 16 is disposed so as to surround the entire peripheral side surface of the heater 15 and the bottom surface of the crucible 12. The heat insulating material 16 has a cylindrical shape having a size capable of accommodating the crucible 12 and the heater 15 therein, and the bottom surface of the heat insulating material 16 is closed and the upper surface is opened. However, in the center of the bottom surface of the heat insulating material 16, a hole 17 is formed for passing the support column 13 supporting the crucible 12.
[0015]
In the crucible 12, a raw material a for growing a single crystal is placed. The raw material a is, for example, GaAs, InP or the like. Thus, the upper part of the raw material a put in the crucible 12 is filled with the sealing material b. For example, B ₂ O ₃ is used for the sealing material b.
[0016]
A cylindrical radiant heat shield 20 having a size capable of entering the crucible 12 is disposed above the raw material a and the sealing material b placed in the crucible 12 as described above. As shown in FIGS. 1 and 2, the radiant heat shield 20 is formed by inserting an inner cylinder 21 having a cylindrical shape with upper and lower openings into an outer cylinder 22 having a cylindrical shape with upper and lower openings. The inner cylinder 21 is protruded from the inside.
[0017]
A hook part bent inward is formed at the lower end of the outer cylinder 22, and a hook part bent outward is formed at the upper end of the inner cylinder 21. Further, by engaging the hook portion at the lower end of the outer cylinder 22 and the hook portion at the upper end of the inner cylinder 21, the inner cylinder 21 is prevented from falling off from the lower end of the outer cylinder 22. In the illustrated example, the length of the inner cylinder 21 protruding from the lower side of the outer cylinder 22 is adjusted by sandwiching a ring-shaped spacer (not shown) having an appropriate height between these hook portions. The overall length (height) of the radiant heat shield 20 is set as desired. Note that the spacer may be omitted and the hook portions may be brought into direct contact with each other.
[0018]
A donut-shaped support plate 30 having an open center is attached to the upper end of the radiant heat shield 20 (the upper end of the outer cylinder 22). The lower surface of the support plate 30 is supported by the upper ends of the pair of left and right lifting members 31 so that the radiant heat shield 20 is disposed at a predetermined height inside the furnace vessel 10.
[0019]
These elevating members 31 are preferably made of a material such as molybdenum having high fire resistance. The elevating member 31 is provided so as to penetrate the heat insulating material 16 and the bottom surface of the furnace vessel 10, and the lower end of the elevating member 31 protrudes downward from the bottom surface of the furnace vessel 10. Thus, the elevating mechanism 32 is connected to the lower end of the elevating member 31 protruding downward from the bottom surface of the furnace vessel 10, and by operating these elevating mechanisms 32, the left and right elevating members 31 are integrally raised and lowered, The radiant heat shield 20 is configured to move up and down. The elevating mechanism 32 is a gear mechanism composed of, for example, a worm and a worm wheel, and can move the radiant heat shield 20 up and down to an arbitrary height through the left and right elevating members 31.
[0020]
Further, seal bearings 33 are provided at locations where the elevating member 31 is penetrated on the bottom surface of the furnace vessel 10. Thereby, even if the raising / lowering member 31 moves up and down, the airtightness in the location where the raising / lowering member 31 of the bottom face of the furnace vessel 10 penetrates is maintained.
[0021]
In the center of the lid 11 covering the upper surface of the furnace vessel 10, an upper rod 35 that can be moved up and down is vertically penetrated. A seed crystal (not shown) of the raw material a placed in the crucible 12 is attached to the lower end of the upper rod 35.
[0022]
And this upper rod 35 and the above-mentioned support | pillar 13 are arrange | positioned in the same straight line form. The crucible 12, the heater 15, the heat insulating material 16, and the furnace vessel 10 are all arranged concentrically with the upper rod 35 and the support column 13 as the central axes.
[0023]
In the crystal growth furnace 1 according to the embodiment of the present invention configured as described above, when pulling up the single crystal of the raw material a, first, the inside of the furnace vessel 10 closed by the lid 11 is argon gas. The raw material a previously put in the crucible 12 is melted by heating with the heater 15. Then, the raw material a (melt) in the crucible 12 is maintained at a temperature suitable for pulling the single crystal.
[0024]
Next, the upper rod 35 is lowered, and the seed crystal attached to the lower end of the upper rod 35 is immersed in the raw material a in the crucible 12. Then, by pulling up the upper rod 35, the raw material a (melt) in the crucible 12 is attached to the seed crystal, cooled while being pulled, and solidified to grow the crystal.
[0025]
Further, when the raw material a is pulled up in this way, the radiant heat shield 20 supported by the elevating member 31 is placed in the crucible 12 and disposed above the raw material a and the sealing material b. Then, the crystal grown by being attached to the seed crystal is pulled up while passing through the radiant heat shield 20 by the rising of the upper rod 35.
[0026]
Thus, by pulling up the grown crystal within the radiant heat shield 20, it is possible to produce a single crystal in a preferable state without being affected by the radiation of heat rays.
[0027]
As the crystal grows, the raw material a (melt) in the crucible 12 gradually decreases, and the surface of the sealing material b filled in the upper part of the raw material a gradually falls. Thus, as the surface of the sealing material b is lowered, the lifting member 31 is moved up and down at a lifting speed of, for example, a maximum speed of 10 mm / hr (controlled in units of 1 mm / hr) by operating the lifting mechanism 32. The distance between the surface and the lower end of the radiant heat shield 20 (the lower end of the inner cylinder 21) may be kept at an optimum size (for example, a constant distance). The optimum value of the distance between the surface of the sealing material b and the lower end of the radiant heat shield 20 can be obtained by calculation based on the position where the surface of the sealing material b descends, for example. By doing so, it is possible to control the amount of radiant heat from the heater 15 to the raw material a in the crucible 12 and the amount of radiant heat to be emitted from the raw material a in the crucible 12 to the outside. Further, since the height of the crucible 12 is constant, the positional relationship between the crucible 12 and the heater 15 does not change, and the heating amount of the raw material a in the crucible 12 (heat flow rate toward the bottom of the crucible 12) can be controlled to be constant. It becomes like this. For this reason, generation | occurrence | production of the crystal defect in a crystal growth interface and the growth crystal side surface can be suppressed.
[0028]
When the crystal is grown in this manner, in the crystal growth furnace 1 according to the embodiment of the present invention, the heat insulating material 16 is disposed so as to surround the entire peripheral side surface of the heater 15 and the bottom surface of the crucible 12. The furnace atmosphere near the bottom surface of the container 10 is thermally cut off from the heater 15 and the crucible 12. For this reason, the seal bearing 33 that penetrates the elevating member 31 does not become high temperature, and there is almost no fear that the seal bearing 33 is damaged by heat. Even if the raw material a evaporates from the crucible 12, the volatilized component is solidified at a low temperature before reaching the vicinity of the seal bearing 33. Few. As a result, foreign matter is less likely to enter the seal bearing 33 and airtightness is less likely to deteriorate.
[0029]
Further, in the crystal growth furnace 1 according to the embodiment of the present invention, since the deterioration of the seal bearing 33 is small, the replacement of the seal bearing 33 is small, and the work such as cleaning of the lifting member 31 and the seal bearing 33 is reduced. it can. Furthermore, even when the raw material a is put into the crucible 12, the work can be performed with the radiant heat shield 20 attached to the furnace vessel 10, so that the raw material can be charged easily. Further, the raw material a in the crucible 12 and the radiant heat shield 20 can be easily seen from above, and an installation error can be prevented.
[0030]
As mentioned above, although an example of preferable embodiment of this invention was shown, this invention is not limited to the form demonstrated here. For example, in FIG. 1, the crucible 12 is described based on the LEC method (liquid sealing Czochralski method) in which the sealing material b is filled in the upper part of the raw material a. The present invention may be applied to the Larsky method. Moreover, although the example which provided the raising / lowering mechanism 32 in each of the two right and left raising / lowering members 31 was shown, you may move the two raising / lowering members 31 right and left by the common raising / lowering mechanism 32 up and down. The radiant heat shield 20 is not limited to two, but may be one or three or more. Moreover, although the example which has penetrated the heat insulating material 16 and arrange | positioned the raising / lowering member 31 was shown, you may arrange | position the raising / lowering member 31 in the outer side of the heat insulating material 16 in the furnace vessel 10. FIG.
[0031]
【Example】
Crystal growth was performed by using GaAs as a raw material in the crucible using the crystal growth furnace described in FIG. Before and after crystal growth, the elevating member penetrating through the seal bearing at the bottom of the crystal growth furnace is moved up and down, and the distance between the sealant liquid surface and the lower end of the radiant heat shield is in the range of 1 to 60 mm depending on the solidification rate. Was raised and lowered. In addition, the whole raising / lowering distance is 100 mm or more. This operation was performed for each crystal growth to grow 10 crystals. As a result, the leak in the seal bearing was within the allowable range.
[0032]
【The invention's effect】
According to the present invention, the bottom surface of the furnace vessel does not become high temperature, and there is almost no fear that the seal bearing is damaged by heat. In the vicinity of the seal bearing, there is little adhesion of the raw material to the elevating member, and the hermeticity is hardly deteriorated. For this reason, the number of times of replacement of the seal bearing can be reduced, and the lifting member and the seal bearing can be easily cleaned. In addition, even when the furnace vessel is opened with the lid removed, the material can be charged easily because the operation can be performed with the radiant heat shield attached to the furnace vessel. In addition, the raw material in the crucible and the radiant heat shield can be easily seen from above, preventing installation errors.
[0033]
In addition, according to the present invention, it is possible to control the amount of heat of the material contained in the crucible and the amount of radiant heat from the heater and the surface of the melt, thereby preventing the generation of crystal defects at the crystal growth interface and the crystal growth side. It becomes possible to suppress.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view schematically showing an internal structure of a crystal growth furnace according to an embodiment of the present invention.
FIG. 2 is a perspective view of a radiant heat shield as viewed obliquely from below.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crystal growth furnace a Raw material b Sealing material 10 Furnace container 11 Cover 12 Crucible 15 Heater 16 Heat insulating material 20 Radiation heat shield 21 Inner cylinder 22 Outer cylinder 30 Support plate 31 Elevating member 32 Elevating mechanism 35 Upper rod

Claims (4)

A crystal growth furnace for growing a crystal by pulling up the melt in the crucible
A radiant heat shield placed above the melt placed in the crucible is supported by the elevating member,
The elevating member is passed through the bottom of the furnace vessel and connected to an elevating mechanism arranged outside the furnace vessel ,
A crystal growth furnace in which a heat insulating material is arranged so as to surround a peripheral side surface and a bottom surface of the crucible . The crystal growth furnace according to claim 1, wherein a seal bearing is provided at a location through which the elevating member penetrates on the bottom surface of the furnace vessel. A crystal growth method for growing a crystal by pulling up the melt in the crucible and radiating heat disposed above the melt put in the crucible in the crystal growth furnace according to claim 1 or 2. A crystal growth method, wherein the shield is moved up and down as the crystal is pulled up. A crystal growth method for growing a crystal by solidifying while pulling up a melt in a crucible, wherein in the crystal growth furnace according to claim 1, a surface of a sealing material filled on a liquid surface of the melt A crystal growth method characterized by maintaining a constant distance from a lower end of a radiant heat shield disposed above a melt placed in a crucible.

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