JP2943430B2 - Method and apparatus for producing single crystal - Google Patents

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 producing a single crystal by the Czochralski method, and more particularly to a method for producing a single crystal.
III-V compound semiconductors such as aAs and InP, CdT
The present invention relates to a method and an apparatus for producing a single crystal such as a II-VI compound semiconductor such as e, a semiconductor such as Si and Ge, and an oxide such as LiNbO ₃ , TiO ₂ and BSO according to the Czochralski method.

[0002]

2. Description of the Related Art In the production of a single crystal by the Czochralski method, in order to suppress the occurrence of crystal defects such as polycrystallization, bicrystallization and dislocation and to form a single crystal stably, the diameter of the formed single crystal and A technique for controlling the shape of the solid-liquid interface is extremely important. Therefore, in the Czochralski method, a method and apparatus for providing a member for controlling the above in a crucible containing a raw material melt and pulling a single crystal through the member have been studied.

For example, JP-A-57-7897 and JP-A-61-63596 disclose an apparatus in which a molded body having an opening in the center is provided on a raw material melt. In these apparatuses, the shape of the crystal to be pulled is controlled by pulling the single crystal through the opening of the compact. JP-A-62-28193 discloses a method in which an inverted conical shaped body is immersed in a raw material melt contained in a crucible and a single crystal is pulled from the raw material melt flowing into the formed body. In this method, the sectional area of the supercooled melt formed in the molded body is changed by moving the molded body relative to the crucible. By adjusting the cross-sectional area in each of the steps of seeding, forming the shoulder, forming the straight body, and forming the tail, rapid growth of the crystal is suppressed. In addition, the present inventors have studied a method and an apparatus for floating a collacle having a communication hole formed at the bottom in a raw material melt and pulling a single crystal from the raw material melt flowing into the collacle through the communication hole. Have been. In order to control the shape and diameter of a single crystal to be grown, for example, it is used as described below. Referring to FIG. 20 (a), crucible 43 contains raw material melt 45 and liquid sealant 47, and immersed therein is oracle 46. Since the collacle 46 is adjusted to an appropriate specific gravity, it floats on the raw material melt. The raw material melt flows into the floating collages 46 through the communication holes 46a. The surface of the raw material melt in the oracle has an appropriate diameter. Next, as shown in FIG. 20B, the upper shaft 48 is lowered, and the seed crystal 42 provided at the lower end thereof is immersed in the raw material melt in the oracle 46. At this time, the temperature of the raw material melt is adjusted by a heater 44 provided around the crucible 43. Next, as shown in FIG. 20C, the upper shaft 48 is slowly raised, and the single crystal 10 is pulled up.

The above-described methods and apparatuses have been proposed for stably growing single crystals. However, when pulling a crystal by reducing the temperature gradient in the pulling direction, or pulling a crystal having a relatively low thermal conductivity, it is often difficult to produce a crystal having a low dislocation density by the above method and apparatus. Met.

When the above method or apparatus is used, heat release from the raw material melt is one of the important causes for increasing the dislocation density.
Was thought to be one. To suppress this heat release,
Various methods or means have been proposed. For example, Japanese Utility Model Application Laid-open No. Sho 60-172772 discloses a crystal pulling apparatus in which at least one heat shield plate is provided in a longitudinal direction of a crystal pulling axis in order to suppress heat convection from a raw material melt. Japanese Patent Application Laid-Open No. 60-81089 discloses that a long crucible is used to pull up a crystal while covering a raw material melt with a reflector provided on a crystal pulling shaft for reflecting a heat ray and a side wall of the crucible. A method is disclosed. Further, Japanese Patent Application Laid-Open No. 60-118699 discloses an apparatus in which a member for suppressing heat radiation and heat convection from a raw material melt while passing through a crystal pulling shaft is provided above a crucible.

[0006]

A conventional apparatus or method provided with a member for suppressing radiation or convection enables production of a crystal having a low dislocation density. However, when pulling the crystal by reducing the temperature gradient in the pulling direction,
Or when pulling a crystal with relatively low thermal conductivity,
With these methods or devices, it has often been difficult to suppress the rapid growth of crystals, especially at the start of pulling. Due to the rapid growth of crystals, twins and polycrystals are formed,
It has become difficult to produce single crystals with good reproducibility. In addition, when pulling a crystal of a material having a low thermal conductivity, such as CdTe, it is difficult to pull a single crystal with good reproducibility due to rapid growth at the start of pulling.

[0007] When pulling a crystal such as GaAs or CdTe, as described above, rapid growth of the crystal during pulling is an important cause due to the release of heat from the raw material melt. Conventional devices or methods were considered insufficient to effectively suppress this heat release during crystal pulling. Most of this heat release was thought to be due to radiation, so it was necessary to effectively block the radiation to effectively suppress heat release. The more this radiation is blocked at a location closer to the raw material melt, the more effectively heat release is suppressed. The mechanism for blocking radiation above the crucible as in the conventional apparatus is insufficient, and it has been necessary to block radiation from a place closer to the raw material melt. Further, even with a method or apparatus in which the effect of suppressing heat release is improved for the first time by lowering the crystal pulling shaft and bringing the radiation blocking member closer to the raw material as described above, it was considered that the blocking of radiation was insufficient.

An object of the present invention is to sufficiently suppress rapid growth of a crystal to be pulled by effectively blocking radiation from a raw material melt when a temperature gradient in a pulling direction is small, particularly at the start of pulling. It is an object of the present invention to provide a method and an apparatus capable of growing a crystal having a low dislocation density.

Another object of the present invention is to reduce the rapid growth of crystals by effectively blocking radiation when pulling a single crystal of a material having a low thermal conductivity (eg, CdTe), especially at the start of pulling. It is an object of the present invention to provide a method and an apparatus capable of sufficiently suppressing the growth of a crystal having a low dislocation density.

Another object of the present invention is to provide a method and an apparatus capable of producing a single crystal at a high yield by effectively suppressing the rapid growth of the crystal.

[0011]

According to a method for producing a single crystal according to the present invention, a seed crystal attached to the lower end of a crystal pulling shaft is brought into contact with a raw material melt, and the seed crystal is pulled up by the crystal pulling shaft. In the method of growing, a communication hole for inflow of the raw material melt is provided at the bottom part, a step of providing a collacle having an opening at the top in the raw material melt, and passing a seed crystal at the center on the collacle. The first member having an opening is placed thereon to cover the surface of the raw material melt in the oracle, thereby blocking radiation from the raw material melt to the upper part of the oracle.
When the seed crystal is brought into contact with the raw material melt,
A second radiation blocking step of blocking radiation through the opening by covering the opening with a second member supported by the crystal pulling shaft; and forming a crystal while blocking radiation by the first member and the second member. A seeding step of lowering the pulling axis to bring the seed crystal into contact with the raw material melt; and, after the seeding step, raising the crystal pulling axis while blocking the radiation by the first member and the second member, thereby forming a single crystal. A shoulder growing step for growing a shoulder, and after the shoulder growing step, a straight body growing a single crystal straight body from the raw material melt in the coll while pulling up the first member together with the crystal pulling shaft. And a process.

According to the present invention, a third member provided above the first member and having an opening for passing the second member is used during the period from the first radiation blocking step to the shoulder growing step. By covering the first member with the above, radiation can be further blocked.

It is desirable that the first member covers the raw material melt as close to the surface of the raw material melt as possible. For example, if the first member covers the surface of the raw material melt within 50 mm above the surface of the raw material melt, radiation can be effectively blocked.

According to the present invention, the radiation may be blocked by a single member in which the first member and the second member are integrated.

Further, during the period from the first radiation blocking step to the shoulder growing step, radiation from the heat source may be performed on the surface and above the raw material melt.

The method according to the invention, which has been shown above,
A liquid sealing pulling method in which a single crystal is pulled by providing a liquid sealing agent on the raw material melt can be used. Further, the method according to the present invention can be carried out under a pressurized atmosphere containing raw material components.

Further, the method according to the present invention is particularly useful for growing crystals having low thermal conductivity. For example, the method of the present invention can be applied to a CdTe crystal or Zn, S
A method for growing a CdTe crystal containing e, Mn, In, Ga, Cl, or the like as an impurity can be used.

An apparatus for producing a single crystal according to the present invention includes a crucible for accommodating a raw material melt, a lower shaft for supporting the crucible, a heater disposed around the crucible, and an opening at the top provided in the crucible. Having a communication hole at the bottom for allowing the raw material melt to flow, an upper shaft capable of rotating and elevating a seed crystal at the lower end for pulling a single crystal from the raw material melt, and a seed at the center. It has an opening for passing the crystal,
And, in order to block upward radiation from the raw material melt in the collacle, a first radiation blocking member movably mounted on the collacle and covering the surface of the raw material melt, and an opening of the first radiation blocking member. And a second radiation blocking member supported by the upper shaft and covering the opening.

The crush according to the present invention refers to a molded body provided in a crucible and containing a raw material melt in order to control the shape and diameter of a single crystal to be grown. The collacle is desirably formed of a material that is stable at a high temperature, does not react with the raw material melt, and does not contaminate the growing single crystal. Examples of the material forming the collages include carbon, quartz, BN, PBN, AlN, PBN-coated carbon, GC-coated carbon, and PG-coated carbon. In the apparatus according to the present invention, the collages may be floated on the raw material melt in the crucible, or may be fixed in another member and provided in the crucible.

Further, the device according to the present invention has an opening for passing the second radiation blocking member, and covers the first radiation blocking member to further block radiation above the first radiation blocking member. 3 radiation blocking members can be provided. It is desirable that the first radiation blocking member covers the raw material melt as close to the raw material melt surface as possible in order to improve the radiation blocking effect. For example, if the first radiation blocking member covers the surface of the raw material melt within 50 mm above the surface of the raw material melt, radiation can be more effectively blocked.

Further, in the device according to the present invention, the first radiation blocking member and the second radiation blocking member may be integrated.

Further, the first radiation blocking member can be formed by stacking a plurality of disk-shaped members having different opening diameters.

The radiation blocking member described above can block heat radiation from the raw material melt, and is made of a material that is stable at high temperatures and does not contaminate the grown single crystal. Is desirable. As a material for forming this member, for example, carbon, PG, BN, PB
N, alumina, zirconia, quartz (opaque), A
Examples include 1N, SiN, beryllia, Mo, W, Ta, and composite materials thereof.

Still further, the apparatus according to the present invention can further include a means for causing radiation from the heater to reach the surface of the raw material melt and upward. This means may be, for example, a window formed on the upper part of the crucible so that the radiation from the heater reaches the surface of the raw material melt and upward through the crucible. The window can be a hollow with nothing fitted, or it can be fitted with a suitable material that is permeable to heat rays such as quartz or PBN and does not contaminate the raw material melt. Further, as another means, by using a translucent ceramic such as quartz or PBN at least in the upper part of the crucible, heat rays from the heater can be radiated to the surface and the upper part of the raw material melt through the upper part of the crucible. Can be mentioned.

In the apparatus according to the present invention described above, a liquid sealant may be provided on the raw material melt. Further, the apparatus according to the present invention may further include a closed vessel for pulling the single crystal under the atmosphere of the volatile raw material component.

[0026]

In the method or the apparatus according to the present invention, by covering the surface of the raw material melt in the coll with the first member mounted on the coll, radiation from the raw material melt causes the opening of the first member to pass through. It will be shut off except for those that can communicate. In this way, a considerable amount of radiation is blocked before seeding. next,
When the seed crystal is brought into contact with the raw material melt, radiation through the opening of the first member is blocked by the second member supported by the crystal pulling shaft. Thereby, the entire radiation from the surface of the raw material melt is substantially blocked. Further, in the seeding step in which the seed pulling shaft is lowered to bring the seed crystal into contact with the melt, the radiation is still blocked because the second member covers the opening of the first member. After the seeding, the entire radiation is substantially blocked by the first and second members even at the stage of growing the shoulder of the crystal. If the pulling is started while blocking the radiation in this way, rapid growth of the crystal is prevented with good reproducibility. As a result, generation of a bicrystal or a polycrystal during growth of the crystal shoulder can be suppressed. After shoulder growth, the first member is pulled with the crystal pulling axis. Since the first member is placed on the collage as described above, radiation can be blocked at a location very close to the surface of the raw material melt. And the first
Since the member can be pulled up with the pulling axis as the crystal is pulled up, the opening does not need to pass through the crystal to be pulled up, and it is sufficient that the opening is large enough to pass the seed crystal. For this reason, the amount of radiation through the first member opening is hardly minimized.

In addition, when the third member is used, the heat rays escaping through the first member can be blocked by the third member. If the second member is moved below the third member together with the pulling shaft through the opening of the third member, the second member is covered by the third member. At this time, the heat rays escaping through the second member can be blocked by the third member. Interception of radiation by these three members, in particular,
It is effective when the temperature above these members is low.

Further, during the period from the first radiation blocking step to the growth of the shoulder portion of the crystal, the cooling of the raw material melt can be further suppressed by radiating the heat rays to the surface and upward of the raw material melt. Due to the radiation of the heat rays, the rapid growth of the crystal in growing the shoulder is hardly stopped.

By suppressing the release of heat from the raw material melt as described above, in the growth of crystals having a small thermal conductivity and the growth of crystals having a reduced temperature gradient in the pulling direction, rapid growth during the growth of the shoulder portion is achieved. , The generation of polycrystals and bicrystals can be significantly suppressed.

Further, according to the present invention, the collage immersed in the raw material melt keeps the diameter of the surface of the raw material melt from which crystals are pulled constant. This is because the supply amount of the raw material melt required for pulling can be appropriately controlled by introducing the raw material melt into the collage. By providing the collages in this way, it is possible to control the diameter of the straight body of the crystal to be pulled after the crystal shoulder having a gentle shape is surely grown.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the present invention will be described below. FIG. 1 schematically shows an apparatus for manufacturing a single crystal used in the first embodiment. FIG. 2 shows how a single crystal is formed using the apparatus shown in FIG. Referring to FIG. 1, in this apparatus, a crucible 3 containing a raw material melt 5 is provided in a chamber 12 while being supported by a rotatable lower shaft 11. A heater 4 is provided around the crucible 3. In the crucible 3, a collacle 6 is provided so as to float on the raw material melt 5. A communication hole 6a is formed in the bottom of the collacle 6 so that the raw material melt 5 is introduced therein. Also, on the oracle 6
Annular first radiation blocking member (hereinafter abbreviated as first member)
1 is placed, and the raw material melt in the collacle 6 is kept warm. The oracle 6 and the first member 1 are shown in FIGS. 3 and 4, respectively. The collacle 6 has a communication hole 6 at the bottom.
It is an inverted conical shaped body having a. The first member is a disk-shaped molded body having an opening 1a at the center. The surface of the raw material melt 5 is covered with a liquid sealant 7. Crucible 3
An upper shaft 8 is provided above a central portion of the crystal, which is rotatable up and down for pulling a crystal. In the apparatus configured as described above, a second radiation blocking member (hereinafter abbreviated as a second member) 9 is attached to the lower end of the upper shaft 8 together with the seed crystal 2. As shown in FIGS. 1 and 5, the second member 9 has a structure in which a circular radiation blocking plate 9b is provided on a cylindrical radiation blocking cylinder 9a so as to be movable like a piston. The lower end of the upper shaft 8 and the seed crystal 2 are attached to the center of the radiation blocking plate 9b.

The procedure for growing a single crystal using such an apparatus will be described below. The raw material melt 5 and the liquid sealant 7 are accommodated in the crucible 3, and the temperature of the raw material melt is controlled by the heater 4. The first member 1 is placed on the collacle 6 with the collacle 6 immersed in the raw material melt 5. At this time, since the oracle 6 is adjusted to an appropriate buoyancy, the first
Floats on the raw material melt 5 together with the member 1. In the floating state, the material melt is filled in the collacle 6, and the surface of the melt has an appropriate diameter. In this state, when the upper shaft 8 is lowered to lower the seed crystal 2 and the second member 9, first, FIG.
As shown in (a), the radiation blocking cylinder 9a of the second member 9 rides on the first member 1. In this state, the opening 1a of the first member is covered by the second member 9. In this manner, radiation from the raw material melt in the collacle 6 through the opening 1a is blocked. When the upper shaft is further lowered in a state where the radiation is blocked, the radiation blocking plate 9b in the second member 9 slides down in the radiation blocking cylinder 9a and descends as shown in FIG. Crystal 2 is immersed in raw material melt 5. After seeding, when the upper shaft 8 is pulled up while rotating, a shoulder portion 10a of a single crystal is formed as shown in FIG. 2 (c). The second member 9 remains on the first member 1 from seeding to shoulder formation. Moreover, since the radiation blocking plate 9b slides inside the radiation blocking cylinder 9a, the first
The opening 1 a of the member 1 is still covered with the second member 9. Therefore, seeding is performed in a state where heat radiation from the opening of the collage is sufficiently suppressed, and then the single crystal is pulled up. Further, when the upper shaft 8 is pulled up, FIG.
As shown in (d), the first member 1 rides on the shoulder portion 10a of the formed single crystal, and the straight body portion 10b of the single crystal is formed with the second member 9 riding thereon. To go. In this manner, seeding and shoulder formation are performed by covering the entire surface of the raw material melt with the first and second members, so that the crystal after seeding does not rapidly grow and polycrystals, bicrystals, etc. Can be prevented and a single crystal can be grown with good reproducibility.

Using the apparatus shown in FIG. 1, GaAs was used under the condition that the temperature gradient in the pulling direction was as small as 5 to 10 ° C./cm.
An s single crystal was grown. In the apparatus, the crucible 3 is made of PBN having a diameter of 4 inches, and the collacle 6 is made of B having a thickness of 10 mm.
It is made of N and is designed so that the diameter of the raw material melt accommodated therein is 55 mm. The first member 1 includes a collacle 6
Is a hollow disk shape having an inner diameter slightly larger than the opening diameter of 5 mm, and is made of carbon having a thickness of 5 mm. The diameter of the opening of the first member 1 was 10 mm. The second member 9 was made of carbon having a thickness of 5 mm, the diameter of the radiation blocking plate 9b was 20 mm, the upper opening diameter of the radiation blocking cylinder 9a was 15 mm, and the length was 40 mm. In the crucible 3, GaAs
Polycrystalline 1.5kg and liquid encapsulant (B ₂ O ₃₎ 200g was charged. 10 kg of Ar gas in chamber 12
/ Cm ² . 4 mm square, 30 mm long GaAs
The s <100> seed crystal 2 is placed on the upper shaft 8 via the radiation blocking plate 9b.
Attached to the lower end of the The raw material polycrystal was heated and melted by the heater 4. After descending the upper shaft 8 and immersing the seed crystal 2 in the raw material melt,
The raw material melt was adjusted to the crystal growth temperature, the pulling speed of the upper shaft 8 was 5 mm / h, the rotation speed of the upper shaft 8 was 5 rpm, and the lower shaft 11 was rotated.
At a rotation speed of 10 rpm to grow a single crystal. As a result, a GaAs single crystal with a cone angle of 90 ° at the shoulder, a diameter of the straight body of 55 mm, and a length of 100 mm could be grown. The dislocation density of the obtained single crystal, 1000cm ^{- 2} ~1500cm ^{- 2} as low as it was confirmed crystal defects are almost not seen good crystals. The single crystallinity of the pulled crystal was 90%.

On the other hand, only the first member 1 was used to keep the temperature of the outer peripheral portion of the raw material melt, and the other conditions were the same as described above to grow crystals. As a result, the crystal was likely to grow rapidly immediately after the seeding until the diameter became 10 mm, and a bicrystal was easily generated immediately below the seed crystal. The single crystallinity of the pulled crystal was reduced to 50%. From the above results, it has been clarified that the method and apparatus for producing a single crystal according to the present invention significantly improve the production yield of a single crystal as compared with the conventional method.

The second member shown in the above embodiment may be any member which covers the opening of the first member and sufficiently suppresses heat radiation. If only the plate has a sufficiently large diameter, it can be used as the second member. FIG. 6 shows an example using only this radiation blocking plate as a second embodiment. As shown in the figure, the disk-shaped radiation blocking plate 29 has a sufficient diameter to block radiation (indicated by an arrow) through the opening of the first radiation blocking member. Note that, in this apparatus, portions other than the radiation blocking plate 29 are the same as in the first embodiment.

The radiation blocking member according to the present invention includes:
Various structures can be employed in addition to the above-described embodiment. For example, FIG. 7 shows a modification of the first radiation blocking member as a third embodiment. In this device, the first radiation blocking member 71 is composed of two disk-shaped members 71a and 71b having different diameters of the openings. FIG. 8 is a perspective view of these members. In this apparatus, a disk-shaped member 71a having a large opening diameter is placed on a oracle, and a disk-shaped member 71b having a small opening diameter is mounted thereon. In the member having such a structure, as shown in FIG. 9, the disc-shaped member 71b is first pulled up when the shoulder portion of the crystal is formed. At this time, the lower disk-shaped member 71a stays on the collacle 6 and blocks radiation from the raw material melt to some extent. For this reason, the heat retention effect at the time of shoulder growth is improved.
In the above embodiment, two disc-shaped members are used, but three or more disc-shaped members may be used to constitute the first radiation blocking member.

Further, a radiation blocking member having a structure in which the first radiation blocking member and the second radiation blocking member shown in the first embodiment are integrated is shown in FIG. 10 as a fourth embodiment.
The radiation blocking member 50 of this device is mounted on the collacle 6 by lowering the upper shaft 8. Next, when the upper shaft 8 is lowered, the radiation blocking plate 59b slides in the radiation blocking cylinder 59a as in the first embodiment. After seeding in the same manner as in the first embodiment, the crystal shoulder is pulled up. The radiation blocking member 50 is pulled up together with the crystal to be grown.

In the above embodiment, the collacle is not fixed in the crucible but floats on the raw material melt. However, the collacle may be fixed to another member. FIG. 11 shows an apparatus in which a oracle is fixed as a fifth embodiment. In this device,
The oracle 6 is fixed to an insulating material 77 provided around the crucible by an oracle support 76. In this apparatus, parts other than a mechanism for fixing the collacle are the same as those in the first embodiment. In this device, the lower shaft 11 can be rotated up and down. The surface diameter of the raw material melt flowing into the collacle 6 is adjusted by moving the lower axis up and down.
Although the oracle is fixed to the heat insulating material in this apparatus, it may be fixed to another member or to another vertically movable means.

In the above-described embodiment, the surface of the raw material melt is covered with the liquid sealant. However, the liquid sealant may not be used depending on the crystal material or the growth method.

Hereinafter, a sixth embodiment according to the present invention will be described. FIG. 12 schematically shows a single crystal manufacturing apparatus used in the sixth embodiment. In this apparatus, a crucible 14 supported by a rotatable lower shaft 11 is provided in a chamber 12. A quartz crucible 13 for containing the raw material melt 5 is provided inside the crucible 14. In the quartz crucible 13, a collacle 6 is provided so as to float on the raw material melt 5. A communication hole 6a is formed in the bottom of the collacle 6 so that the raw material melt 5 is introduced therein. The portion of the crucible 14 above the surface of the raw material melt 5 is hollowed out to form a pair of windows 14a and 14b, from which the quartz crucible 13 is viewed. An annular first radiation blocking member (hereinafter, abbreviated as a first member) 1 is placed on the collacle 6, and
The raw material melt inside is kept warm. The shapes of the oracle and the first member 1 are as shown in FIGS. On the other hand, above the center of the crucible 13 is provided an upper shaft 8 which can be rotated up and down. Also, the raw material melt 5
Is covered with a liquid sealant 7. Furthermore, upper shaft 8
A second radiation blocking member (hereinafter abbreviated as a second member) 9 is attached to the lower end of the first member together with the seed crystal 2. As shown in the first embodiment, the second member 9 has a structure in which a disk-shaped radiation blocking plate 9b is provided movably like a piston on a cylindrical radiation blocking cylinder 9a. And the radiation blocking plate 9b
The upper shaft 8 and the seed crystal 2 are attached to the center of the.

The procedure for growing a single crystal using such an apparatus will be described below. Raw material melt 5 in crucible 13
And the liquid sealant 7, and the temperature is controlled by the heater 4. The first member 1 is placed on the collacle 6 with the collacle 6 immersed in the raw material melt 5. At this time, the oracle 6 is adjusted to an appropriate buoyancy and floats on the raw material melt 5 together with the first member 1. In the floating state, the material melt is filled in the collacle 6, and the surface of the melt has an appropriate diameter.
Radiation from the heater passes through the quartz crucible 13 through the windows 14a and 14b formed in the crucible 14. Therefore, the surface of the raw material melt 5 and its upper part are heated by the radiant light. When the seed crystal 2 and the second member 9 are lowered by lowering the upper shaft 8 in this state, first, as shown in FIG. Nine radiation blocking cylinders 9a are mounted on the first member 1. In this state, the opening 1a of the first member is covered by the second member 9. Since the opening is thus covered and the radiation from the heater reaches above the surface of the raw material melt, the opening 1
The heat radiation through a is suppressed. When the upper shaft 8 is further lowered in a state where the heat radiation is suppressed, the radiation blocking plate 9b of the second member 9 slides down in the radiation blocking cylinder 9a and descends. Then, as shown in FIG.
Is immersed in the raw material melt 5. After the seeding, when the upper shaft is pulled up while rotating, a shoulder portion 10a of a single crystal is formed as shown in FIG. 2 (c). The second member 9 remains on the first member 1 from seeding to shoulder formation. Moreover, since the radiation blocking plate 9b slides inside the radiation blocking cylinder 9a, the opening 1a of the first member 1 is still covered by the second member 9. Therefore, seeding is performed in a state where heat radiation from opening 1a is suppressed, and the single crystal is pulled up. When the upper shaft 8 is further pulled up, FIG.
As shown in (d), a shoulder 10 of the formed single crystal is formed.
The second member 9 rides on a, and the single-crystal straight body portion 10b is formed with the second member 9 riding thereon.

Using the apparatus shown in FIG. 12, a GaAs single crystal was grown under the condition that the temperature gradient in the pulling direction near the melt was as small as 5 to 10 ° C./cm. The temperature of the upper surface 12a of the chamber 12 was as low as about 200 ° C. In the apparatus, the crucible 13 is made of 4 inch diameter quartz,
The outer crucible 14 was made of carbon. In the crucible 14, eight circular windows having a diameter of 30 mm were formed above the melt. The collacle 6 is a 10 mm thick BN
And was designed such that the surface of the raw material melt accommodated therein was 55 mm. The first member 1 has a hollow disk shape having a diameter slightly larger than the diameter of the opening of the oracle 6, and has a thickness of 5 mm.
mm of carbon. The hollow diameter was 10 mm. The second member 9 was made of carbon having a thickness of 5 mm, the diameter of the heat retaining plate 9 b was 20 mm, the upper opening diameter of the heat retaining plate 9 a was 15 mm, and its length was 40 mm. In crucible 3, 1.5 kg of GaAs polycrystal and liquid sealant (B
₂ O ₃ ) 200 g was charged, and the inside of the chamber 12 was Ar
The pressure was increased to 10 kg / cm ² with gas. 4mm square, 40m
The m-length GaAs <100> seed crystal 2 was attached to the lower end of the upper shaft 8 via the radiation blocking plate 9b. The raw material polycrystal was heated and melted by the heater 4. After lowering the upper shaft 8 and immersing the seed crystal in the raw material melt, the raw material melt was adjusted to a crystal growth temperature. Upper shaft 8
Pulling speed of 5 mm / hr, rotation speed of upper shaft 8 at 5 r
pm, and the rotation speed of the lower shaft 11 was set to 10 rpm to grow a single crystal. As a result, the shoulder cone angle was 100
°, Ga with a straight body diameter of 55 mm and a length of 120 mm
As single crystals could be grown. The dislocation density of the obtained single crystal, 1000cm ^{- 2} ~1500cm ^{- 2} as low as it was confirmed crystal defects are almost not seen good crystals. The single crystallinity of the pulled crystal is 8
5%.

On the other hand, an experiment of crystal growth was performed using an apparatus in which the crucible was made of carbon opaque to radiation from the heater. Since the temperature of the upper surface of the chamber 12 was as low as about 200 ° C., the amount of heat that escaped upward from the raw material melt by radiation increased. As a result, the diameter was 10 immediately after seeding.
mm, rapid growth of the crystal was likely to occur, and a bicrystal was easily generated immediately below the seed crystal. The single crystallinity of the pulled crystal was reduced to 60%.

The means for causing the radiation from the heater to reach the surface and above the raw material melt can have various structures. Hereinafter, a modification of this means will be described as a seventh embodiment. Referring to FIG. 13, in this apparatus, a portion of crucible 3 above raw material melt 5 and liquid sealant 7 is cut out at an appropriate size at several places to form window 15. Other configurations are the same as those of the device shown in FIG. In this apparatus, the heat rays from the heater 4 are directly radiated to the surface of the raw material melt and the radiation blocking member through the window 15.

The first and second radiation blocking members shown in the sixth and seventh embodiments can be modified as shown in the second, third and fourth embodiments. Further, the collacle can have a fixed structure as shown in the fifth embodiment. In the above embodiment, the surface of the raw material melt is covered with the liquid sealant. However, the liquid sealant may not be used depending on the crystal material or the growth method.

An eighth embodiment according to the present invention will be described below. FIG. 14 shows an outline of the single crystal manufacturing apparatus used in the eighth embodiment. In this apparatus, a crucible 3 for accommodating a raw material melt is provided on a rotatable lower shaft in a chamber 12, and a heater 4 is provided around the crucible 3. In the crucible 3, a collacle 6 is provided so as to float on the raw material melt 5. A communication hole 6a is formed in the bottom of the collacle 6 so that the raw material melt 5 is introduced therein. Also, Oracle 6
An annular first radiation blocking member (hereinafter, abbreviated as a first member) 1 is placed on the upper side, and keeps the temperature of the raw material melt in the collacle 6. The shapes of the oracle and the first member are as shown in FIGS. The surface of the raw material melt 5 is covered with a liquid sealant 7. On the other hand, above the center of the crucible 3 is provided an upper shaft 8 which can be rotated and moved up and down. In the apparatus configured as described above, a second radiation blocking member (hereinafter abbreviated as a second member) 9 is attached to the lower end of the upper shaft 8 together with the seed crystal 2. The second member 9 is, as described above, a cylindrical radiation blocking cylinder 9a.
And a disk-shaped radiation blocking plate 9b is provided movably like a piston. The lower end of the upper shaft 8 and the seed crystal 2 are attached to the center of the radiation blocking plate 9b. Further, a third radiation blocking member (hereinafter, abbreviated as a third member) 2 in the shape of a hollow disk is interposed via a support 14 placed on the upper end of the crucible 3.
3 is provided above the first member 1. FIG. 15 shows the shape of the third member. The third member 23 has a circular hole 23a through which the upper shaft 8 and the second member 9 pass. The third member 23 covers the upper part of the oracle 6 as shown in the figure. The procedure for growing a single crystal using such an apparatus will be described below. The raw material melt 5 and the liquid sealant 7 are accommodated in the crucible 3, and the temperature is controlled by the heater 4. In a state where the collacle 6 is immersed in the raw material melt 5,
The first member 1 is placed on the oracle 6. At this time, the collage 6 is adjusted to an appropriate buoyancy, so the first member 1
Together with the raw material melt 5. In the floating state, the material melt is filled in the collacle 6, and the surface of the melt has an appropriate diameter. In this state, the first member 1 and the third member 23 block a considerable amount of radiation from the raw material melt. Next, when the upper shaft 8 is lowered and the seed crystal 2 and the second member 9 are lowered, first, as shown in FIG.
The radiation blocking cylinder 9a of the second member 9 rides on the first member 1. In this state, the opening 1a of the first member is covered by the second member 9. Since the opening is covered in this manner, radiation from the raw material melt in the collacle 6 through the opening 1a is blocked. Thus, the surface of the raw material melt is
The entirety is covered by the first and second members, and further covered by a third member above the first member. Dissipation of heat from the surface of the raw material melt is suppressed by the first and second members. Further, the first member is covered by the third member, and the second member can be moved below the third member through the opening 23a. As a result, heat dissipation from the first and second members is suppressed by the third member. When the upper shaft 8 is further lowered in a state where the heat radiation is suppressed, the radiation blocking plate 9b in the second member 9 slides down in the radiation blocking cylinder 9a and descends. Then, the seed crystal 2 is immersed in the raw material melt 5 as shown in FIG. After the seeding, when the upper shaft 8 is pulled up while rotating, the shoulder 10a is formed as shown in FIG. 16 (c). During the period from seeding to shoulder formation, the second member 9
Remain on the first member 1. Moreover, since the radiation blocking plate 9b slides inside the radiation blocking cylinder 9a, the opening 1a of the first member 1 is still covered by the second member 9. Therefore, after seeding is performed in a state where heat radiation from opening 1a is suppressed, the single crystal is pulled up. When the upper shaft 8 is further pulled up, as shown in FIG. 16D, the first member 1 rides on the shoulder portion 10a of the formed single crystal, and the second member 9 further rides on the shoulder portion 10a. In this state, a single-crystal straight body portion 10b is formed. When the upper shaft 8 is further pulled up, as shown in FIG. 16E, the third member 23 rides on the first member 1 and is pulled up together with the single crystal. As described above, the second member suppresses heat radiation from the opening 1a of the first member, and the first and third doubly provided members keep the raw material melt in a single crystal state. Since the pulling is performed, the generation of polycrystals and bicrystals is prevented without causing rapid growth of crystals at the start of pulling. Therefore, a single crystal can be grown with good reproducibility.

Next, a ninth embodiment according to the present invention will be described. In the ninth embodiment, the apparatus shown in FIG. 17 was used. This device is different from the device shown in the eighth embodiment in that
The structure of the crucible 3 is different. Crucible 3 with this device
, A window 15 is formed in a portion above the liquid surface of the liquid sealant 7. As described above, the window 15 may be left as it is without being fitted, or may be fitted with an appropriate material that easily transmits radiant heat. In this apparatus, parts other than the crucible have the same structure as the apparatus shown in FIG. In this device, heat rays from the heater 4 are radiated into the crucible through the window 15. The heat rays are radiated to the surface of the raw material melt and the space between the raw material melt and the third member. The heat retention effect of the first, second, and third members is further improved by the radiant heat. The procedure for growing a single crystal in this apparatus is the same as that in the eighth embodiment.

CdTe crystals were grown using the apparatus shown in FIG. In the apparatus, the crucible 3 was made of carbon having a diameter of 4 inches, and the window 15 was fitted with quartz. The collacle 6 was made of carbon having a thickness of 10 mm, and was provided such that the diameter of the raw material melt accommodated therein was 55 mm. The first member 1 was made of carbon having a hollow disk shape having a diameter slightly larger than the opening diameter of the collacle 6 and a thickness of 5 mm. The hollow diameter was 10 mm. The second member 9 is made of carbon having a thickness of 5 mm.
The diameter of b is 15 mm, and the opening diameter of the radiation blocking cylinder 9a is 20 m
m and its length was 40 mm. The third member 23 is
It is made of carbon with a thickness of 5 mm and the diameter of the opening is about 30 m
m. In a crucible 3, CdTe polycrystal 1.
5 kg and 200 g of liquid sealant (B ₂ O ₃ ) were charged. The inside of the chamber 12 was pressurized to 20 kg / cm ² with Ar gas. 4 mm square, 30 mm long CdTe (10
0) The seed crystal 2 was attached to the lower end of the upper shaft 8 via the radiation blocking plate 9b. The raw material polycrystal was heated and melted by the heater 4. After lowering the upper shaft 8 and immersing the seed crystal 2 in the raw material melt, the raw material melt was adjusted to a crystal growth temperature. Pulling speed of upper shaft 8 is 2m
A single crystal was grown at m / hr, a rotation speed of the upper shaft 8 of 5 rpm, and a rotation speed of the lower shaft 11 of 5 rpm. As a result, a CdTe single crystal having a shoulder cone angle of 150 °, a straight body portion diameter of 55 mm, and a length of 80 mm could be grown. The dislocation density of the obtained single crystal was 5000
cm ^{- 2} ~50000cm ^{- 2} as low as it was confirmed that the good crystals. The single crystallinity of the pulled crystal was 75%.

On the other hand, the raw material melt was kept warm using only the first member 1, and the crystal was grown in the other conditions as in the above. As a result, the diameter was 20 mm immediately after seeding.
By the time, the crystal rapidly grows easily, and twins are easily generated immediately below the seed crystal. Also,
The single crystallinity of the pulled crystal was reduced to 5%.

The first and second radiation blocking members shown in the eighth and ninth embodiments are the second, third and fourth radiation blocking members.
It can be modified as shown in the embodiment. In addition, the oracle can have a fixed structure as shown in the fifth embodiment. In the above embodiment, the surface of the raw material melt is covered with the liquid sealant, but the liquid sealant may not be used depending on the growth material or the growth method.

Hereinafter, a tenth embodiment according to the present invention will be described. FIG. 18 is a schematic diagram showing an outline of the device used in the tenth embodiment. This apparatus is obtained by adding an apparatus for obtaining an X-ray transmission image to the apparatus of the first embodiment shown in FIG. That is, outside the chamber 12, X
An X-ray tube 17 for generating X-rays and an X-ray image device 16 for detecting X-rays and forming an image are provided. In the X-ray tube 17, the X-ray emission port is
It is aimed at crucible 3 in 2. The X-ray detector (not shown) of the X-ray imaging device 16 is provided so as to face the X-ray emission port with the crucible 3 interposed therebetween. X-rays emitted from the X-ray tube 17 enter the chamber 12 and
The X-ray image device 16 can be reached through the crucible 3. By providing such a device, an X-ray transmission image in the crucible 3 can be obtained. In this apparatus, parts other than the X-ray tube 17 and the X-ray image apparatus 16 are substantially the same as those of the apparatus of the first embodiment.

A CdTe single crystal was grown using the apparatus shown in FIG. The crucible 3 is made of quartz coated with carbon and has a diameter of 4 inches. The collacle 6 is made of carbon having a thickness of 10 mm, and is designed such that the diameter of the raw material melt accommodated therein is 52 mm. The collacle 6 has an appropriate specific gravity so as to float on the raw material melt 5. The first member 1 has a hollow disk shape having a diameter slightly larger than the opening diameter of the collacle 6, is formed of carbon, has a thickness of 5 mm, and has an opening diameter of 2 mm.
0 mm. The second member 9 including the radiation blocking cylinder 9a and the radiation blocking plate 9b is made of carbon. The thickness of the radiation blocking cylinder 9a is 5 mm, the diameter is 30 mm,
The length is 50 mm. On the other hand, the thickness of the radiation blocking plate 9b is 5 mm. As the seed crystal 2, a CdTe single crystal having a size of 4 mm square and a length of 30 mm cut out in the (111) direction was used. CdTe polycrystal 1.0 k in crucible 3
g and liquid encapsulant (B ₂ O ₃₎ was charged with 100 g. Ar in the chamber 12 until the pressure becomes 15 kg / cm ^2.
The gas was replaced. After heating and melting the material polycrystal by the heater 4, the upper shaft 8 was lowered to bring the seed crystal into contact with the material melt. After bringing the seed crystal into contact with the raw material melt, the raw material melt was adjusted to the crystal growth temperature. Next, a single crystal was grown by setting the pulling speed of the upper shaft 8 to 3 mm / hr, the rotation speed of the upper shaft 8 to 5 rpm, and the rotation speed of the lower shaft 11 to 10 rpm. The state from the seeding to the lifting was monitored by an X-ray imaging apparatus. At this time, the voltage of the X-ray tube was 150 kV, and the current was 5 mA. The target for emitting X-rays was Mo. As a result of the operation described above, the diameter of the straight body is 52 mm, and the length is 100 m.
Thus, m CdTe single crystals were obtained. The single crystallization ratio of the pulled crystal was 60%.

On the other hand, the crystals were pulled up under the same conditions as above except that the first and second members were not used. However, CdTe single crystals could not be grown.

An eleventh embodiment according to the present invention will be described below. FIG. 19 is a schematic diagram showing an outline of the device used in the eleventh embodiment. Referring to FIG. 19, this device differs from the device of the tenth embodiment shown in FIG. 18 in that a crucible and a space for pulling a crystal above the crucible are surrounded by an airtight container 30. The airtight container 30 passes through the upper shaft 8 and the lower shaft 11 while maintaining a sealed state. Above the airtight container 30, a volatile component reservoir 31 is formed. A heater 32 is provided around the volatile component reservoir 31. Although a portion through which the upper shaft and the lower shaft pass is omitted in this drawing, a general structure using a liquid sealant is employed.

Using the device shown in FIG. 19, CdTe
A single crystal was grown. The airtight container 30 was formed of carbon coated with PBN. Seed crystal
The same one as in the example was used. Each part of this device is designed in the same way as the device shown in the tenth embodiment except for the airtight container. CdTe polycrystal 1.0 is placed in crucible 3.
kg was charged, and the volatile component reservoir 31 contained Cd. The temperature of the heater 32 was increased to 900 ° C., and the airtight container 30 was filled with Cd at a pressure of about 3 atm. Further, the inside of the chamber 12 was pressurized with Ar gas in accordance with the Cd pressure in the airtight container 30. Hereinafter, a single crystal was pulled under the same conditions as in the tenth embodiment. As a result, a CdTe single crystal could be grown at a single crystallization ratio of 65%.

The apparatus for obtaining the X-ray transmission images shown in the tenth and eleventh embodiments can also be provided in the apparatuses shown in the second to ninth embodiments. By providing this apparatus, it is possible to monitor the progress of growing a single crystal from seeding in the second to ninth embodiments. Further, the airtight container shown in the eleventh embodiment can be similarly provided in the devices of the second to ninth embodiments. If an airtight container is used in the second to ninth embodiments, a single crystal can be grown according to the Czochralski method of controlling the vapor pressure.

[0057]

As described above, according to the present invention, the radiation upward from the surface of the raw material melt is substantially blocked during the Czochralski process from seeding to formation of the crystal shoulder. Therefore, in the method or apparatus according to the present invention, when the temperature gradient in the pulling direction is small, rapid growth of the crystal at the start of pulling can be sufficiently suppressed. Further, a material having a low thermal conductivity (for example, Cd
Also in the case of pulling the crystal of Te), it is possible to sufficiently suppress the rapid growth of the crystal particularly when pulling the crystal. As a result, generation of polycrystal and bicrystal can be sufficiently suppressed. Therefore, a crystal having a low dislocation density can be pulled by the method or the apparatus of the present invention.
Further, by controlling the diameter of the crystal to be grown by the collacle, a single crystal having a gentle shoulder can be grown. Further, by irradiating the crucible with X-rays to obtain an X-ray transmission image in the crucible and observing the pulling state of the single crystal, the shape of the single crystal being pulled can be effectively controlled. The present invention provides a method and an apparatus capable of producing a single crystal at a high yield when the temperature gradient in the pulling direction is small or when the thermal conductivity of the crystal to be grown is low.

[Brief description of the drawings]

FIG. 1 is a schematic view of a single crystal manufacturing apparatus used in a first embodiment according to the present invention.

FIG. 2 is a schematic diagram showing a state in which a single crystal is pulled from seeding in the apparatus shown in FIG.

FIG. 3 is a perspective view showing a shape of a oracle in the apparatus shown in FIG. 1;

FIG. 4 is a perspective view showing a first radiation blocking member in the device shown in FIG. 1;

FIG. 5 is a perspective view showing a second radiation blocking member in the device shown in FIG. 1;

FIG. 6 is a schematic view showing a single crystal manufacturing apparatus according to a second embodiment of the present invention.

FIG. 7 is a schematic diagram showing a single crystal manufacturing apparatus according to a third embodiment according to the present invention.

FIG. 8 is a perspective view showing a first radiation blocking member in the device shown in FIG. 7;

FIG. 9 is a schematic view showing a state where a shoulder of a crystal is formed in the apparatus shown in FIG. 7;

FIG. 10 is a schematic diagram of a single crystal manufacturing apparatus used in a fourth embodiment according to the present invention.

FIG. 11 is a schematic diagram of a single crystal manufacturing apparatus used in a fifth embodiment according to the present invention.

FIG. 12 is a schematic diagram of a single crystal manufacturing apparatus used in a sixth embodiment according to the present invention.

FIG. 13 is a schematic diagram of a single crystal manufacturing apparatus used in a seventh embodiment according to the present invention.

FIG. 14 is a schematic view of a single crystal manufacturing apparatus used in an eighth embodiment according to the present invention.

FIG. 15 is a perspective view showing a shape of a third radiation blocking member in the device shown in FIG. 14;

FIG. 16 is a schematic diagram showing a state in which a single crystal is pulled from seeding in the apparatus shown in FIG. 14;

FIG. 17 is a schematic diagram of a single crystal manufacturing apparatus used in a ninth embodiment according to the present invention.

FIG. 18 is a schematic diagram of a single crystal manufacturing apparatus used in a tenth embodiment according to the present invention.

FIG. 19 is a schematic view of a single crystal manufacturing apparatus used in an eleventh embodiment according to the present invention.

FIG. 20 is a schematic view showing a specific example of a conventional single crystal manufacturing apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 First radiation blocking member 2 seed crystal 3 Crucible 4 Heater 5 Raw material melt 6 Collac 7 Liquid sealant 8 Upper shaft 9 Second radiation blocking member 23 Third radiation blocking member

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-271186 (JP, A) JP-A-1-301580 (JP, A) JP-A-4-37686 (JP, A) JP-A-60-1985 81089 (JP, A) JP-A-3-164494 (JP, A) JP-A-59-116194 (JP, A) JP-A-60-172772 (JP, U) JP-A-63-39181 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) C30B 1/00-35/00

Claims (17)

(57) [Claims] 1. A method for producing a single crystal, comprising bringing a seed crystal attached to a lower end of a crystal pulling shaft into contact with a raw material melt, and then pulling the seed crystal by the crystal pulling shaft to grow a single crystal. A step of providing a communication hole at the bottom for allowing the raw material melt to flow therethrough, and providing a collacle having an opening at the top in the raw material melt; and a first having an opening for passing a seed crystal at the center of the crush. A first radiation blocking step of blocking the radiation from the raw material melt to the upper part of the collage by covering the surface of the raw material melt in the collage, and placing the seed crystal in the raw material melt. A second radiation blocking step of blocking the radiation through the opening by covering the opening with a second member supported by the crystal pulling shaft when contacting the first member and the second member; Depending on the member A seeding step of lowering the crystal pulling axis while contacting the seed crystal with the raw material melt while blocking the radiation; and blocking the radiation by the first member and the second member after the seeding step. And raising the crystal pulling axis to grow a shoulder portion of the single crystal; and, after the shoulder growing step, pulling up the first member together with the crystal pulling axis, and A straight body growing step of growing a single body straight body from the raw material melt. 2. A third member provided above the first member and having an opening through which the second member passes, during a period from the first radiation blocking step to the shoulder growing step. The method for producing a single crystal according to claim 1, wherein the radiation is further cut off by covering the first member with a member. 3. The method for producing a single crystal according to claim 1, wherein said first member covers said raw material melt within 50 mm above said raw material melt. 4. The method for producing a single crystal according to claim 1, wherein said first member and said second member are integrated. 5. The method for producing a single crystal according to claim 1, wherein a liquid sealant is provided on the raw material melt. 6. The method of manufacturing a single crystal according to claim 1, wherein radiation from a heat source is performed on and above the raw material melt during the period from the first radiation blocking step to the shoulder growing step. 7. The method for producing a single crystal according to claim 1, wherein the pulling of the single crystal is performed in an atmosphere containing a volatile raw material component. 8. The method for producing a single crystal according to claim 1, wherein the raw material melt is for forming a CdTe crystal. 9. A crucible for accommodating a raw material melt, a lower shaft for supporting the crucible, a heater disposed around the crucible, an opening at the top provided in the crucible, and a bottom portion A crusher having a communication hole for allowing the raw material melt to flow therethrough, a rotatable vertical shaft on which a seed crystal is attached at a lower end for pulling a single crystal from the raw material melt, and passing the seed crystal through a central portion. A first radiation blocking member movably mounted on the collage and covering the surface of the raw material melt to block upward radiation from the raw material melt in the collage; And a second radiation blocking member supported by the upper shaft and covering the opening to block the radiation through the opening of the first radiation blocking member. 10. An opening for passing the second radiation blocking member, and above the first radiation blocking member,
The single crystal manufacturing apparatus according to claim 9, further comprising a third radiation blocking member that covers the first radiation blocking member to further block the radiation. 11. The apparatus for producing a single crystal according to claim 9, wherein said first radiation blocking member and said second radiation blocking member are integrated. 12. The apparatus for producing a single crystal according to claim 9, wherein said first radiation blocking member is configured by stacking a plurality of disc-shaped members having different opening diameters. 13. The single crystal manufacturing apparatus according to claim 9, wherein said first radiation blocking member covers said raw material melt within 50 mm above said raw material melt. 14. The apparatus for producing a single crystal according to claim 9, wherein a liquid sealant is further provided on the raw material melt. 15. The apparatus for producing a single crystal according to claim 9, further comprising a closed container for pulling the single crystal under an atmosphere of a volatile raw material component. 16. The apparatus for producing a single crystal according to claim 9, further comprising means for causing radiation from said heater to reach the surface and above the raw material melt. 17. The apparatus for producing a single crystal according to claim 16, wherein said means is a window formed on an upper portion of said crucible to receive radiation from said heater.