JP2991585B2 - Single crystal growing apparatus and single crystal manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for growing a single crystal, in particular, a semiconductor such as Si, Ge, etc. by the vertical Bridgman method.
III-V compound semiconductors such as GaAs and InP, GdT
e, ZnSe and other II-IV compound semiconductors, BGO, L
A single crystal growing apparatus for growing single crystals of oxides such as BO,
And a method for producing a single crystal using the apparatus.

[0002]

2. Description of the Related Art Semiconductors such as Si and Ge, GaAs, I
III-V compound semiconductors such as nP, GdTe, ZnSe
In general, oxide single crystals such as II-IV compound semiconductors such as BGO and LBO are grown by a vertical Bridgman method, a pulling method, or the like. In this vertical Bridgman method, the raw material melt is housed in a vertical container, the container is placed in a furnace with a temperature gradient, and the raw material melt is cooled and solidified from below by moving it downward, thereby obtaining a single crystal. This single crystal growing apparatus by the vertical Bridgman method is used to obtain a good quality crystal by making a desired temperature in the furnace core tube in a necessary range in the length direction of the furnace core tube. In addition, the heating device was composed of a number of heating elements along the longitudinal direction on both sides of the furnace core tube, the heating elements were divided into a plurality of independent heating sections, and each heating section was independently temperature-controlled. One has been proposed (see JP-A-2-221180).

As a factor determining the crystal growth rate in the crystal growth method according to the Bridgman method, it is known that compositional supercooling is likely to occur. It is necessary to increase the temperature gradient in the direction, but it is easy to increase the temperature gradient when the inner diameter of the furnace core tube is small. This includes, for example, 1) dividing the furnace into a plurality of heaters, A method of increasing the set temperature of the heater at a position where the temperature gradient is desired to be increased, a method of installing a heat shielding plate at a position where the temperature gradient is desired to be increased, and a method of cooling the position at which the temperature gradient is desired to be cooled with water, etc. ing. For furnaces with a relatively large furnace core tube, it was also reported that the furnace core tube, crucible base, etc., were all made of quartz and that the temperature gradient was increased by facilitating the escape of radiant heat in the furnace from below the furnace. [See J. Cryst. Growth. 94 (1989) 373-380].

[0004]

In the growth of a single crystal by the Bridgman method, all the raw materials in a vertical vessel housed in a furnace are once melted, and then a temperature gradient is gradually set across the melting point of the single crystal to be grown. Although it is performed by moving downward, industrially it is necessary to grow a large-diameter single crystal in a short time, so it is necessary to increase the temperature gradient at the position where crystal growth is progressing. Needed. Therefore,
An industrially preferred Bridgman furnace is designed to increase the temperature gradient at the inner diameter of the furnace core and at the growing position, and not to raise the temperature of the zone for melting the raw material so much from the melting point. In order to grow large-diameter crystals, it is necessary to adopt a supporting type in which the crucible is placed on a crucible base instead of a method in which the crucible is hung.

However, in this under-supported Bridgman furnace, the inner diameter of the furnace core tube is set to 140 mm so that a crystal having a crystal system of 3 inches or more can be grown.
As described in 221180, the heating device is composed of a large number of heating elements, and the heating element is divided into a plurality of independent heating zones to increase the temperature gradient at the growing position. Temperature gradient of only 8 ° C./cm, and the temperature gradient at the growth position for the furnace core tube and the crucible base made of quartz as described in the above-mentioned document also shows the growth position of the furnace. No remarkable change was seen only by moving upward, the furnace temperature could not be equalized by using quartz, and the quality of the crystal was degraded by the overheating of the raw material, and the appearance of an unfavorable phase caused by the appearance of an undesirable phase. Decreased.

As a method of increasing the temperature gradient, a method of installing a baffle or reflector that blocks radiant heat near the growing position is known.
In this method, since the reflector needs to be enlarged to a certain extent, there is a disadvantage that even if the furnace core tube is increased, the crystal that can be grown becomes small because the inner diameter of the reflector becomes small. There is a problem that large diameter single crystals cannot be produced in a furnace.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an apparatus for growing a single crystal and a method for producing a single crystal which solves such disadvantages and problems. Having heating means provided outside the furnace core tube,
In an apparatus for moving a crucible into the furnace core tube to grow a single crystal material contained in the crucible into a single crystal, a heating element used as a heating means is made of a material having a different surface temperature and a material having a lower surface temperature. The method for producing a single crystal is characterized by growing a single crystal using the single crystal growing apparatus.

That is, the present inventors have conducted various studies to develop an apparatus for easily growing various types of single crystals by the vertical Bridgman method. Means, in a vertical Bridgman furnace containing a crucible containing a single crystal material in the furnace core tube, the heating element used as the heating means was divided into a plurality of by a conventionally known method, these The different materials
If a heater consisting of a heating element capable of raising the surface temperature is installed immediately above the single crystal growing position as a combination of a material with a low surface temperature and a material with a high surface temperature, heating from the heating element The temperature distribution of the furnace becomes sharper and the temperature gradient becomes larger, which makes it easier to grow single crystals.By using such a Bridgman furnace, various single crystals can be easily and efficiently produced. After confirming that the heating element can be manufactured well, the present invention was completed by conducting research on a method of arranging the heating element used here and a method of arranging the correlation between the heating element and the heat insulator. This will be described in more detail below.

[0009]

The present invention relates to a single crystal growing apparatus and a method for producing a single crystal. The single crystal growing apparatus has a cylindrical furnace core tube and heating means provided on the outside thereof, and the crucible is connected to the furnace core. In a device for growing a single-crystal material contained in a crucible by moving it into a tube and growing the single-crystal material into a single crystal, the heating element used as a heating means is a combination of a material having a low surface temperature and a material having a high surface temperature made of different materials This single crystal manufacturing method is characterized in that a single crystal is grown using this single crystal growing apparatus. According to this, the single crystal growing apparatus is a bridge. Since the distribution of heat is optimized as a Mann furnace, there is an advantage that various single crystals can be easily and efficiently manufactured.

The single crystal growing apparatus of the present invention is, for example, as shown in FIG. FIG. 1 is a longitudinal sectional view of a single crystal growing apparatus according to the present invention, in which a heater 3 is provided outside a furnace core tube 1 and a crucible 4 and a crucible base are provided in the furnace core tube 1. 5 and a lid 6 is further provided on the furnace core tube 1. The heater 3 is divided into a plurality of parts. -2, 3-3, and 3-4 having a high surface temperature. If the heater 3-4 having a high surface temperature is disposed near the single crystal growth position, the temperature distribution in this portion becomes 3-4. When the surface temperature is low, as shown in FIG. 2, the temperature distribution, ΔT / ΔX (T is the crystal growth temperature, X is the axial position in the furnace) gradually increases. Since this temperature distribution ΔT / ΔX becomes steep, the temperature gradient becomes large, and the growth of the single crystal becomes difficult. Advantage that becomes to be performed easily is provided.

In this case, if the distance between the heating element having a high surface temperature and the center of the furnace is shorter than the distance between the heating element having a low surface temperature and the center of the furnace, the temperature gradient in the furnace is increased. Therefore, there is an advantage that the growth of the single crystal becomes more effective.

Since the furnace core tube 1 in this apparatus is preferably made of a material having good thermal conductivity, for example, high-purity alumina, silicon nitride, and high-purity alumina lined with platinum are used. The lower part is made of a furnace core tube 2 made of quartz. In addition, the crucible 4 may be generally made of a metal material such as platinum, platinum-rhodium, iridium, etc., but the crucible base 5 is made of transparent quartz because it easily releases radiant heat downward. It is good to be made from. The heater 3 has a low surface temperature as described above.
-1, 3-2, 3-3 and 3-4 having a high surface temperature are combined, and those having a low surface temperature are Kanthal A-1, AF, A manufactured by Kanthal Gadelius. , D
For those with high surface temperature, the company's Kanthal Super 1,700, 1,800, N, etc. may be used, but as the heating element with high surface temperature, a heating element made of SiC may be used. This may be such that a metallic ring is placed around the metal and the ring is induction heated at high frequency. Further, this may be a structure in which a large temperature gradient can be obtained by making the distance between the heating element having a high surface temperature and the center of the furnace shorter than the distance between the heating element having a low surface temperature and the center of the furnace.

The heating element made of the Kanthal wire or SiC and having a high surface temperature is surrounded by a heat insulating material in a direction other than the center of the furnace like other heating elements, and is incorporated in the furnace as an independent heater. When the surface temperature of the heating element is high, it is desirable that the size of the space around the heating element 7 be 3 to 5 times the diameter of the heating element 7. The material 8 is preferably configured as shown in FIG.

In this case, in order to increase the temperature gradient in the furnace, it is desirable to transfer the heat generated by the heating element to the center of the furnace as efficiently as possible. It is preferable to cover the surface of the heat insulating material 8 around it with a reflecting material 9 made of a material that reflects radiant heat, for example, platinum or platinum-rhodium. Further, in order to take a large temperature gradient, it is only necessary to suppress the heat conduction below the independent heater. Therefore, as shown in FIG. And the distance a from the end of the heat insulating material located above the heating element to the center of the furnace is compared with the distance b from the end of the heat insulating material located below the heating element to the center of the furnace. This has the advantage that the radiant heat from the heating element is mainly transferred to the upper part of the furnace, so that the temperature gradient at the crystal growth position can be increased.

In this case, as shown in FIG. 6, two or more heating elements 7 may be provided side by side. In this case, if the temperature of the heating elements is increased, interference between the heating elements occurs, and the heating elements are blown. Care must be taken since the inconvenience described above occurs.

According to the present invention, the heating element for heating the furnace in the Bridgman furnace is a combination of a material having a low surface temperature and a material having a high surface temperature made of different materials. If heating is performed in this section, the temperature gradient in this part will increase.In this case, if high-purity alumina is used as the furnace core tube, heat conduction will be good, so that excessive heating of the raw material will be prevented, and a quartz material will be arranged as a ruthe lower base. Can effectively increase the temperature gradient because the radiant heat escapes effectively.
III-V compound semiconductors such as GaAs and InP, GdT
e, ZnSe and other II-IV compound semiconductors, BGO, L
The advantage is that a single crystal of an oxide such as BO can be easily and efficiently manufactured.

[0017]

Next, examples of the present invention will be described. Example 1 A hollow cylindrical furnace core tube 1 made of high-purity alumina and having an inner diameter of 140 mm as shown in FIG. A heating element 3-1, 3-2, 3-3 using Kanthal A-1 and a heating element 3-4 using Kanthal Super 1,800 as a heating element are installed. Was placed on a transparent quartz crucible base 5 and a lid 6 was provided on the furnace tube 1.

Then, 10,000 g of polycrystal of Bi ₄ Ge ₃ O ₁₂ (hereinafter abbreviated as BGO) is inserted into the crucible, and the temperature of the furnace center is increased by heating bodies 3-1, 3-2, and 3-3. Is heated to 1,150 ° C and the temperature of the furnace center is set to 1,200 ° C
And the crucible is lowered into the furnace core tube to
When the single crystal was grown at a growth rate of up to 1.0 mm / hour, the temperature gradient near the single crystal growth point in the longitudinal direction in the furnace core tube became 23 ° C./cm. As a result, 9,000 g of a good single crystal having no crystal defects such as a product was obtained.

Embodiment 2 The structure of the heating section of the heating element 3-4 used in Embodiment 1 was modified as shown in FIG. 5, and the furnace was heated in this state.
The temperature gradient around the single crystal growth point in the longitudinal direction in the furnace core tube is 48
℃ / cm, BGO single crystal as a good single crystal without crystal defects such as cellular inclusions,
500g was obtained.

[0020]

The present invention relates to an apparatus for growing a single crystal and a method for producing a single crystal, and as described above, this apparatus for growing a single crystal has a cylindrical furnace core tube and a heating means provided on the outside thereof. In the apparatus for moving the crucible into the furnace core tube and growing the single crystal material contained in the crucible into a single crystal, the heating element used as the heating means is made of a different material.
The method for producing a single crystal is characterized in that a single crystal is grown using this apparatus. However, when using such a single crystal growing apparatus and installing a heater consisting of a heating element that raises the surface temperature near or directly above the single crystal growing position, heating from the heating element causes a steep temperature distribution in the furnace. The temperature gradient near the single crystal growth point in the longitudinal direction in the furnace core tube becomes large, and the temperature distribution of the Bridgman furnace becomes optimal, so that various single crystals can be easily and efficiently produced without crystal defects. The advantage is that it can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a single crystal growing apparatus of the present invention.

FIG. 2 is a graph showing a correlation between a crystal growth temperature (T) and a furnace axial position (x) when a heating element having a high surface temperature is used according to the present invention and when it is not used. is there.

FIG. 3 shows a structural diagram of a heating element and a heat insulating material according to the present invention.

FIG. 4 is a structural diagram of a heating element and a heat insulating material coated with a radiant heat reflecting material according to the present invention.

FIG. 5 is a diagram showing another structure of the heating element and the heat insulating material according to the present invention.

FIG. 6 is a diagram showing still another structure of the heat generating element and the heat insulating material according to the present invention.

FIG. 7 is a longitudinal sectional view of a known single crystal growing apparatus.

[Explanation of symbols]

1 ... Alumina furnace core tube, 2 ... Quartz furnace core tube, 3 ... Heater, 4 ... Crucible, 5 ... Crucible stand, 6 ...
Lid, 7: heating element, 8: heat insulating material, 9: reflective material.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshihiko Nagao 2-13-1 Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Precision Materials Research Laboratory (56) References JP-A-2-221180 ( JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C30B 1/00-35/00

Claims (4)

(57) [Claims] A single-crystal material having a cylindrical furnace core tube and heating means provided outside the furnace core tube, wherein the single-crystal material contained in the crucible is moved by moving the crucible into the furnace core tube. The heating element used as a heating means is made of different material
An apparatus for growing a single crystal, comprising a combination of a material having a low surface temperature and a material having a high surface temperature. 1
2. The single crystal growing apparatus described in 1. above. 2. The single crystal growing apparatus according to claim 1, wherein the heating element having a high surface temperature covers a part or all of the surrounding heat insulating material with a material that easily reflects radiant heat. 3. A heat insulator having a high surface temperature, wherein a distance from an end of the heat insulator located above the heat generator to a furnace center is equal to an end of the heat insulator located below the heat generator. 3. The single crystal growing apparatus according to claim 2, wherein the single crystal growing apparatus is longer than a distance from a portion to a furnace center. 4. A method for producing a single crystal, comprising growing a single crystal using the apparatus for growing a single crystal according to claim 1.