JP2004238225A - Semiconductor crystal manufacturing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor crystal manufacturing apparatus in which the dissipation of heat from a member for fixing a seed crystal is performed efficiently even in the initial stage of crystal growth and thereby the conversion of a single crystal into polycrystal can be inhibited. <P>SOLUTION: The semiconductor crystal manufacturing apparatus 13 has a seed crystal 36 for growing the semiconductor crystal 33, a seed crystal fixing adapter 37 for fixing the seed crystal 36, and a pulling shaft 35 for pulling the seed crystal 36, which is connected to the seed crystal fixing adapter 37, and is characterized in that a tool 38 for heat exchange is attached to the seed crystal fixing adapter 37. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor crystal manufacturing apparatus, and more particularly to an apparatus for growing a semiconductor crystal by a liquid-sealed Czochralski method.
[0002]
[Prior art]
2. Description of the Related Art A conventional semiconductor crystal manufacturing apparatus using a liquid-encapsulated Czochralski process (hereinafter, referred to as an LEC method) is known (for example, see Patent Document 1). The LEC method means that a container made of pyrolytic boron nitride (PBN) containing a polycrystalline raw material and a sealant such as B ₂ O ₃ is placed in a pressure-resistant container filled with an inert gas. Then, the PBN container is heated to turn the polycrystalline raw material into the raw material melt, and the seed crystal is brought into contact with the raw material melt, and the seed crystal and the PBN container are relatively moved to grow a single crystal. .
[0003]
FIG. 5 schematically shows an interface state and a heat flow state at the time of pulling a single crystal. As shown in FIG. 5, a seed crystal fixing adapter 3 is attached to the pulling shaft 1, and a seed crystal 5 is attached to the seed crystal fixing adapter 3. The pulling shaft 1 and the seed crystal fixing adapter 3 are placed in an inert gas. The seed crystal 5 pulls up the raw material melt 7, and a layer of the B ₂ O ₃ melt 8 in which the sealing agent is melted is formed on the upper layer of the raw material melt 7.
[0004]
[Patent Document 1]
JP-A-7-2594 (page 2, FIG. 6)
[0005]
[Problems to be solved by the invention]
However, in the conventional semiconductor crystal manufacturing apparatus, in the process of growing the single crystal 11, the crystal lattice is shifted due to thermal strain, and dislocation has occurred. When dislocations accumulate, polycrystallization occurs, and a high-quality single crystal cannot be obtained. Since the dislocation propagates perpendicularly to the solid-liquid interface 9, even if the dislocation occurs at a plurality of locations on the solid-liquid interface 9, the solid-liquid does not accumulate at the center of the single crystal 11 and goes out of the crystal. It is necessary to make the shape of the interface 9, that is, a large convex to the raw material melt 7 side.
[0006]
Therefore, it is necessary to efficiently transfer the heat in the single crystal 11 to the seed crystal fixing adapter 3 in order to greatly raise the solid-liquid interface 9. However, in the initial stage of the crystal growth, since the tip side of the single crystal 11 is not exposed from the B ₂ O ₃ melt 8, compared with the case where the tip side of the single crystal 11 is covered with the inert gas, There is a problem that heat conduction from 7 to the tip side of single crystal 11 is not promoted, and heat radiation from the crystal head is not sufficiently performed. As a result, the solid-liquid interface 9 may be partially concave, and the single crystal 11 may be polycrystallized.
[0007]
In view of the above circumstances, the present invention provides a semiconductor crystal manufacturing apparatus capable of efficiently dissipating heat from a seed crystal fixing member even in the initial stage of crystal growth and suppressing polycrystallization of a single crystal. The purpose is to:
[0008]
[Means for Solving the Problems]
A semiconductor crystal manufacturing apparatus according to claim 1, wherein a seed crystal for growing the semiconductor crystal, a seed crystal fixing member for fixing the seed crystal, and a seed crystal fixed to the seed crystal fixing member for pulling up the seed crystal. A semiconductor crystal manufacturing apparatus having a pulling shaft, wherein a heat radiating member is attached to the seed crystal fixing member.
[0009]
According to the first aspect of the present invention, since the heat radiating member is attached to the seed crystal fixing member, the temperature gradient in the seed crystal becomes large, and heat from the semiconductor crystal during pulling is efficiently transmitted to the seed crystal fixing member. The transferred heat is radiated into the atmosphere from the heat radiating member in contact with the seed crystal fixing member. Therefore, the solid-liquid interface between the semiconductor crystal and the raw material melt can be greatly raised toward the raw material melt, and polycrystallization of the semiconductor crystal, which tends to occur in the initial stage of crystal growth, can be suppressed. it can.
[0010]
A semiconductor crystal manufacturing apparatus according to claim 2, wherein a seed crystal for growing the semiconductor crystal, a seed crystal fixing member for fixing the seed crystal, and a seed crystal connected to the seed crystal fixing member for pulling up the seed crystal. A semiconductor crystal manufacturing apparatus having a pulling shaft, wherein a heat radiating portion is formed on the seed crystal fixing member.
[0011]
According to the second aspect of the present invention, since the heat radiating portion is formed on the seed crystal fixing member, heat from the semiconductor crystal being pulled is efficiently transmitted to the seed crystal fixing member, and the transmitted heat is transmitted to the seed crystal fixing member. The heat is radiated into the atmosphere from the heat radiating portion formed on the fixing member. Therefore, the solid-liquid interface between the semiconductor crystal and the raw material melt can be greatly raised toward the raw material melt, and polycrystallization of the semiconductor crystal, which tends to occur in the initial stage of crystal growth, can be suppressed. it can.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is an explanatory view showing one embodiment of a semiconductor crystal manufacturing apparatus of the present invention. The semiconductor crystal manufacturing apparatus 13 of this embodiment has a cylindrical chamber 15. A cup-shaped PBN container 17 is provided in the chamber 15, and the PBN container 17 contains a polycrystalline raw material and a sealant. Here, about 7 kg of GaAs is loaded as a polycrystalline raw material, and about 300 mg of B ₂ O ₃ is loaded as a liquid sealant. GaAs tends to have higher thermal conductivity than other semiconductor materials. For example, at room temperature, it exhibits a thermal conductivity of 54 W / (m · K). This is about the same value as carbon steel. On the other hand, for example, at room temperature, ZnSe is 19 W / (m · K), ZnTe is 18 W / (m · K), CdTe is 20 W / (m · K), InSb is 17 W / (m · K), and CdTe. Indicates a thermal conductivity of 7.5 W / (m · K).
[0014]
At the open end of the PBN container 17, a support member 21 made of molybdenum steel, which is a material having high heat resistance, is provided. A heat shield plate 23 made of graphite is provided on the distal end side of the support member 21, and a cylindrical heat reflection plate 25 made of molybdenum is provided on the heat shield plate 23.
[0015]
Further, in the chamber 15, a coil portion 27 for electromagnetically heating the PBN container 17 and a protection member 29 arranged to cover the coil portion 27 and protect the coil portion 27 are provided.
[0016]
A rotation shaft 31 is connected to the center of the bottom of the PBN container 17 for rotating the PBN container 17 to make the state of the polycrystalline raw material and the sealant in the PBN container 17 uniform in the circumferential direction. A pulling shaft 35 for pulling up the semiconductor crystal 33 is inserted from above the chamber 15, and a seed crystal fixing adapter 37 to which a seed crystal 36 is attached is provided at the tip of the pulling shaft 35. ing. Seed crystal 36 has a (100) plane orientation in the vertical direction in order to start growing semiconductor crystal 33. A heat exchange jig 38 as a heat radiating member is provided around the seed crystal fixing adapter 37.
[0017]
Next, the heat exchange jig 38 will be described in detail with reference to FIG. The heat exchange jig 38 includes a half-divided divided portion 40A and a divided portion 40B, and four hexagon bolts 42 and four nuts 44 for fastening the divided portion 40A and the divided portion 40B. Have.
[0018]
The divided portion 40A is formed with a cylindrical main body 40a, a pair of annular heat radiation fins 40b provided on the outer periphery of the main body 40a, and a through hole 40c through which the hexagon bolt 42 is inserted. And four fastening plate portions 40d. The fastening plate portion 40d is located substantially at the opening end of the divided portion 40A. Also, on the inner wall 40e of the main body 40a, ridges 40f are formed at three places. The inner peripheral surface 40g of the ridge portion 40f presses the outer peripheral surface of the seed crystal fixing adapter 37 and plays a role of holding the seed crystal fixing adapter 37.
[0019]
Further, the dividing portion 40B is also formed in the same shape as the dividing portion 40A. Note that molybdenum steel having excellent heat resistance and corrosion resistance is used as a material of the divided portions 40A and 40B. The thermal conductivity of molybdenum steel is 138 W / (m · K) at 300 K and 126 W / (m · K) at 600 K. That is, the thermal conductivity is higher than that of GaAs, which is the material of the semiconductor crystal 33, and the heat radiation from the heat radiation fins 40b can be effectively performed. Conversely, if a material having a low thermal conductivity is used for the divided portions 40A and 40B, for example, heat from the semiconductor crystal 33 cannot be sufficiently dissipated in the initial stage of crystal growth, and the solid-liquid interface 49 (see FIG. 4) ) Cannot be made convex.
[0020]
Next, a method of attaching the heat exchange jig 38 to the seed crystal fixing adapter 37 will be described. In attaching the heat exchange jig 38 to the seed crystal fixing adapter 37, first, the division part 40A is grasped with one hand, the division part 40B is grasped with the other hand, and the respective fastening plate parts 40d face each other. , So that the seed crystal fixing adapter 37 is located inside. Next, the divided portion 40A and the divided portion 40B are brought into contact with each other, and the ridge portion 40f is brought into contact with the seed crystal fixing adapter 37.
[0021]
Next, this state is maintained while holding the divisions 40A and 40B with one hand, and the hexagon bolt 42 is inserted into each of the four through holes 40c. Then, since the divided portion 40A and the divided portion 40B are temporarily fixed, the hand is released from the divided portions 40A and 40B, and the hexagonal bolt 42 and the nut 44 are fastened while using both hands. Finally, it is confirmed that the four hexagonal bolts 42 and the nuts 44 are securely fastened, and the attachment of the heat exchange jig 38 is completed.
[0022]
Further, a heat exchange jig 38A as shown in FIG. 3 is also conceivable. In the heat exchange jig 38A, instead of being attached to the seed crystal fixing adapter 37 with hexagon bolts and nuts as in the heat exchange jig 38 shown in FIG. Attach it to the fixed adapter 37. When fixing with a hexagonal bolt and nut, the threaded portion may be crushed due to heat or adhesion of scattered matter in the chamber, but such inconvenience can be solved by fixing with a tungsten wire. .
[0023]
Next, a method of using the semiconductor crystal manufacturing apparatus 13 will be described. In using the semiconductor crystal manufacturing apparatus 13, first, GaAs and B ₂ O ₃ are stored as polycrystalline materials in a PBN container 17, and residual gas in the chamber 15 is sucked by a pump (not shown). Is evacuated. Next, an inert gas such as an Ar gas is introduced into the chamber 15 and pressurized to about 6 kg / cm ² . Next, a high-frequency current having a frequency of 5 kHz is applied to the coil portion 27, and a carbon ring (not shown) provided in the chamber 15 is heated by electromagnetic induction in order to increase the melting speed of GaAs. Then, the solid GaAs and B ₂ O ₃ contained in the PBN container 17 begin to melt, and the molten GaAs itself has sufficient electric conductivity for high-frequency induction. Directly heated by electromagnetic induction. GaAs and B ₂ O ₃ are high melting point materials, and the melting point of GaAs is about 1500K.
[0024]
Next, after the GaAs and B ₂ O ₃ polycrystalline raw materials are all melted, the rotation shaft 31 is rotated by operating a rotation control device (not shown). Thereby, the state of the melt in the PBN container 17 is made uniform in the circumferential direction, and a good semiconductor crystal 33 is obtained. Next, the power of the electromagnetic induction heating using the coil unit 27 is reduced to a power suitable for manufacturing the semiconductor crystal 33.
[0025]
Next, the seed crystal fixing adapter 37 is lowered by lowering the pulling shaft 35, and the seed crystal 36 is brought into contact with the GaAs melt 39. Finally, the pulling shaft 35 is pulled up at a predetermined speed to form the semiconductor crystal 33. The lifting speed of the pulling shaft 35 is, for example, about 20 mm / hr. The formula for calculating the lifting speed is shown below.
[0026]
V = (1 / ρH) × (KS × (dTS / dZ) −KL × (dTL / dZ))
V: pulling speed ρ: density of single crystal H: latent heat of solidification KS: thermal conductivity of single crystal KL: thermal conductivity of melt TS: temperature of single crystal TL: temperature of melt Z: temperature of pulling axis FIG. 4 shows an interface state and a heat flow state at the time of pulling a GaAs single crystal. As shown in the figure, a seed crystal fixing adapter 37 is attached to the pulling shaft 35, and a seed crystal 36 is attached to the seed crystal fixing adapter 37. A heat exchange jig 38 is provided on the outer periphery of the seed crystal fixing adapter 37. The periphery of the pulling shaft 35 is covered with an inert gas space 47. The seed crystal 36 pulls up the raw material melt 43, and a layer of a B ₂ O ₃ melt 45 in which a sealant is melted is formed on the upper layer of the raw material melt 43.
[0027]
Further, the raw material melt 43 during the pulling of the single crystal 33 is insulated by the B ₂ O ₃ melt 45, and the temperature difference with the inert gas space 47 reaches several hundred K. Further, the B ₂ O ₃ melt 45 suppresses the volatilization of As in the highly volatile raw material melt 43.
[0028]
Next, the operation in the semiconductor crystal 33 due to the provision of the heat exchange jig 38 will be described. In this embodiment, since the heat exchange jig 38 is provided on the seed crystal fixing adapter 37, the amount of heat radiated from the semiconductor crystal 33 to the inert gas space 47 via the seed crystal fixing adapter 37 increases. Therefore, the heat flow from the crystal bottom 33a to the crystal head 33b becomes stronger, and the solid-liquid interface 49 is formed perpendicular to the direction of the heat flow, so that the crystal bottom 33a becomes more prominent. Since the dislocations generated by the thermal strain propagate perpendicular to the interface shape, the concentration of the dislocations is reduced when the convexity of the crystal bottom 33a becomes remarkable. Therefore, stress concentration and increase in dislocation density at the solid-liquid interface 49, which occur when the crystal bottom 33a is depressed, are suppressed.
[0029]
As described above, according to one embodiment of the present invention, since the heat exchange jig 38 is attached to the seed crystal fixing adapter 37, heat from the semiconductor crystal 33 during pulling is efficiently transferred to the seed crystal fixing adapter 37. The heat is transmitted to the heat exchange jig 38, and is mainly radiated to the atmosphere from the radiation fins 40b of the heat exchange jig 38. Therefore, the solid-liquid interface 49 between the semiconductor crystal 33 and the raw material melt 43 can be largely convex toward the raw material melt 43 side, and the polycrystal of the semiconductor crystal 33 which is likely to be generated in the initial stage of crystal growth. Can be suppressed.
[0030]
Further, according to the embodiment of the present invention, since GaAs having a relatively high thermal conductivity is used as the semiconductor for the material of the semiconductor crystal 33, heat radiation from the heat radiation fins 40b is also promoted, and the solid-liquid interface 49 is enlarged. Can be convex.
[0031]
In the above-described embodiment, an example is described in which the heat exchange jig 38 having the radiating fins 40b is attached to the seed crystal fixing adapter 37, but the heat radiating portion is formed directly on the seed crystal fixing adapter 37. You may do it.
[0032]
Further, in the above-described embodiment, an example has been described in which GaAs is melted using the principle of electromagnetic induction heating, but heating may be performed by radiant heat from a heater.
[0033]
Furthermore, in the above-described embodiment, an example in which the GaAs semiconductor crystal 33 is manufactured has been described, but the present invention is not limited to this. However, the higher the thermal conductivity of the material when it becomes a semiconductor crystal, the more the convexity can be promoted.
[0034]
【The invention's effect】
As described above, according to the present invention, since the heat radiating member is attached to the seed crystal fixing member, heat from the semiconductor crystal during pulling is efficiently transmitted to the seed crystal fixing member, and the semiconductor crystal and the raw material melt Can be greatly convex toward the raw material melt side, and polycrystallization of a semiconductor crystal, which tends to occur in an initial stage of crystal growth, can be suppressed.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing one embodiment of a semiconductor crystal manufacturing apparatus of the present invention.
FIG. 2 is an explanatory diagram showing details of the heat exchange jig of FIG. 1;
FIG. 3 is another explanatory view showing details of the heat exchange jig of FIG. 1;
FIG. 4 is an explanatory diagram showing an interface shape and a heat flow state when pulling a semiconductor crystal by the semiconductor crystal manufacturing apparatus of FIG. 1;
FIG. 5 is an explanatory diagram showing an interface shape and a heat flow state when a semiconductor crystal is pulled by a conventional semiconductor crystal manufacturing apparatus.
[Explanation of symbols]
13 Semiconductor crystal manufacturing apparatus 33 Semiconductor crystal 36 Seed crystal 37 Seed crystal fixing adapter 35 Pull-up shaft 38 Heat exchange jig 38A Heat exchange jig 40b Radiation fin 40h Recess

Claims (2)

A seed crystal for growing a semiconductor crystal;
A seed crystal fixing member for fixing the seed crystal,
A pulling shaft connected to the seed crystal fixing member for pulling the seed crystal,
A semiconductor crystal manufacturing apparatus having
A semiconductor crystal manufacturing apparatus, wherein a heat radiation member is attached to the seed crystal fixing member. A seed crystal for growing a semiconductor crystal;
A seed crystal fixing member for fixing the seed crystal,
A pulling shaft connected to the seed crystal fixing member for pulling the seed crystal,
A semiconductor crystal manufacturing apparatus having
A semiconductor crystal manufacturing apparatus, wherein a heat radiating portion is formed on the seed crystal fixing member.

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