JPS62197397A - Production of single crystal - Google Patents

Abstract

PURPOSE:To easily produce the title high-grade single crystal in a short time by charging the raw material of a group III-V or group II-VI single crystal and a sealant into a crucible provided with a partition wall, then heating the material in one step, and covering only one surface of the melt with the liq. sealant. CONSTITUTION:A communicating tube 26 is arranged in an outer crucible 25 as an inner crucible, a group III or group II element 27 such as Ga and In is charged at the bottom of the outer crucible 25, a III-V or II-VI compd. material 38 is charged thereon, and the lower part of the communicating tube 26 is embedded in the materials. The sealant 29 is charged into only one (e.g., the inside of the communicating tube 26) between the inner and outer crucibles which are separated by the peripheral wall of the communicating tube 26. Only the inside of the communicating tube 26 is covered with the liq. sealant 20 by heating and melting the crucible charged with the raw material and the sealant in one step. The crystallinity is enhanced due to the impurity capturing action of the liq. sealant, the stoichiometry is secured due to the control of the vapor pressure, and further the operation process in the production of a single crystal can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing single crystals of III-V or II-VI compounds by the Czochralski method. More specifically, the present invention relates to a method for introducing a single crystal raw material of a group IV or group II-VI compound.

Conventional technology Although Si semiconductors still play a leading role in the modern semiconductor industry, the use of optical fibers has recently rapidly progressed in the communications sector, and with this, the generation and detection of optical signals has become necessary. It's coming. Regarding the generation of optical signals, Si semiconductors are currently powerless, and compound semiconductors, especially In-■ group compound semiconductors and II-V
Group I compound semiconductors are attracting attention.

On the other hand, in the compound semiconductor manufacturing process, it is essential to first form a high-quality single crystal, and since the properties of the semiconductor are sensitive to the crystal structure, there is interest in the composition of the material and the integrity of the crystal. Various single crystal growth methods have been proposed. Among them, the Czochralski method (CZ method, pulling method)
This method is often used because of its advantages such as easy single crystal growth and less waste when obtaining circular wafers.

By the way, a problem when producing single crystals of Group III-V and Group II-VI compounds is that the dissociation equilibrium vapor pressure of Group (I) and Group (II) elements is high, and therefore it is difficult to produce stoichiometric crystals. It's difficult. For this reason, various improvements have been made to the above-mentioned Czochralski method. For example, a method (hereinafter referred to as , vapor pressure control method) has been developed.

The vapor pressure control described above will be explained in more detail based on the attached FIG. 5.

That is, FIG. 5 is a schematic cross-sectional view of an apparatus for performing crystal growth using the vapor pressure control method. It has an upper shaft 2 that passes through the shaft in an airtight manner so as to be vertically movable and rotatable, and a lower shaft 3 that penetrates through the shaft from the lower part in an airtight manner so as to be vertically movable and rotatable.

A seed crystal 4 can be attached to the lower end of the upper shaft 2, and a crucible 5 is supported at the upper end of the lower shaft 3.

Also, the outside of the container 1a is divided into vertically divided heaters 6 to 6.
9 is provided. The airtightness between the upper shaft 2 and lower shaft 3 and the container 1a is ensured by sealing the penetration parts 11 and 12 of both shafts with liquid sealant 1.
3.14 ensured by covering.

When growing a single crystal using this single crystal manufacturing apparatus, first, the seed crystal 4 is attached to the lower end of the lower shaft 3, and the n-vi
Alternatively, the II-VI group compound semiconductor raw material is charged into the crucible 5 and the volatile component element 16, that is, the group V or group II element is charged into the bottom of the container 1a, and then appropriate conditions for single crystal growth are set. . This condition setting is for heater 6
This is mainly carried out by heating the container 1a by heating the container 1a by the heater 6.9, for example, by heating the penetrating portion 11.9 of the shaft 2.3.
The sealing agent provided in the crucible 5 is melted to cover the penetration part 11.12 to ensure airtightness inside, and the raw material in the crucible 5 is melted as a raw material melt 15 by heating with the heater 7.8. A temperature gradient is created in the vertical direction inside the container 1a by the heater 6.7.8.9, and a volatile single-crystal component element 16, such as a group Ⅰ or a
Heat group elements and control vapor pressure. Under such conditions,
The seed crystal 4 is immersed in the melt 15 and the upper shaft 2 is gradually pulled up relative to the lower shaft 3 to grow a single crystal 17 from the seed crystal 4.

The vapor pressure control method described above is less affected by thermal stress, compositional deviation, etc., has poor crystal stoichiometry, and produces a single crystal with a low dislocation density. However, on the other hand, there was a problem in obtaining highly pure crystals.

In addition, as a method of suppressing the evaporation of the above-mentioned group V and group
There is a method (C method), and this method uses, for example, an apparatus as shown in the attached FIG.

In this apparatus, when growing a single crystal, first a seed crystal 4 is attached to the upper shaft 2 and a raw material and a sealant are introduced into a crucible 5 on the lower shaft 3. Thereafter, a temperature gradient is created in the vertical direction by heating with the heater 7, and the raw material and the sealant are melted, so that the raw material melt 15 is covered with the liquid sealant 20. At this time, the valves 21.22 are further adjusted to introduce and discharge inert gas from the pipe means 23.24 to maintain the interior of the container lb at a predetermined high pressure, thereby preventing the evaporation of high dissociation pressure components from the melt 15. To prevent.

At this time, a heat insulating plate 25 is provided outside the heater 7 so as to maintain a temperature gradient suitable for pulling the single crystal 17. Under such conditions, the seed crystal 4 is immersed in the melt 15 and 1.
The upper shaft 2 is gradually pulled up with respect to the lower shaft 3, and a single crystal 17 is generated following the seed crystal 4.

In the above liquid sealing method, when B2O3 is used as a sealant, B20. captures impurity elements, resulting in higher purity of the grown crystal.Also, since the raw material melt is covered with a liquid sealant, the temperature stability of the raw material melt surface improves, and the crystal becomes a single crystal. It has the advantage of improving efficiency. However, there was a problem in that it was not possible to completely prevent the evaporation of high dissociation pressure elements such as group (1) or group (2), and the stoichiometry of the melt could not be maintained completely.

Under these circumstances, the present inventors developed a method for pulling single crystals (Japanese Patent Application Laid-Open No. 1769-1989) that combines the advantages of the above two methods.
No. 95) has already been developed.

That is, this invention provides a partition wall in the crucible, doubles the surface of the molten liquid of the group ■-■ group or group II-VT compound semiconductor in the crucible, covers one of the surfaces with a liquid sealant, and covers the other surface with a liquid sealant. This method is characterized by growing a compound semiconductor single crystal using the Czochralski method in which a seed crystal is immersed in the melt and pulled up while controlling the vapor pressure by bringing the seed crystal into contact with an atmospheric gas. In this case, the location where the single crystal is pulled is not particularly limited, and may be either a portion covered with a sealant or a free surface.

By employing this method, it is possible to obtain a highly pure single crystal due to the impurity trapping action of the liquid sealant in the portion of the melt surface covered with the liquid sealant. Also,
Pulling a single crystal from a surface covered with a sealant has the advantage of good temperature stability. Furthermore, vapor pressure can be controlled by the part of the melt surface that is in contact with the volatile atmospheric gas of the high dissociation pressure component element, so the resulting single crystal has high purity and stoichiometry.
This results in good properties and fewer lattice defects.

Problems to be Solved by the Invention As stated above, the inventors' patent application
According to the invention in Publication No. 5, a method that combines the advantages of the vapor pressure control method and the liquid sealing method has been developed.
It became possible to obtain a high purity single crystal with excellent J- and low dislocation density. However, this invention had the following problems.

That is, in the conventional method described above, in order to cover only one of the melt surfaces doubled by the partition wall with a liquid sealant, only the compound semiconductor is placed in a crucible provided with a partition wall having a communication portion at the bottom, and After heating with a heater and melting at least a portion of the raw material to cover the communicating part at the bottom of the partition wall with the melt, a liquid sealant was introduced, or the communicating part was closed with the raw material that had been cooled and solidified. After that, a method was adopted in which a sealant was added and heated again.

However, the above-mentioned method, i.e., charging the raw material into the crucible, heating, and charging the liquid sealant into the crucible; In order to cover only one side of the partition wall with a liquid sealant through the steps of charging and reheating, many operations are required. Furthermore, if the above heating is performed inside the container, the first step involves opening the heated container and pouring the liquid sealant into the internal crucible, which requires special equipment that can be used inside the high-temperature container. must be used. Also,
When complex and numerous processes are required as described above,
The probability of contamination with impurities during this process increases.

Solving these problems is extremely important in simplifying the single crystal manufacturing process, shortening the time required for manufacturing, and improving the quality of the product single crystal. That is also the purpose of.

Means for Solving the Problems The inventors of the present invention have conducted various studies and researches to solve the problems of the above-mentioned conventional technology.
The present invention has been developed which realizes the state of the invention disclosed in No. 995 and can achieve the above-mentioned objects of the present invention.

That is, in the method of the present invention, a partition wall is provided in a crucible, the surface of the III-V group or II-VI group compound semiconductor raw material melt in the crucible is doubled, and one of the surfaces is covered with a liquid sealant. When growing a compound semiconductor single crystal using the Czochralski method, in which a seed crystal is immersed in the melt and pulled up while controlling the vapor pressure by bringing the other side into contact with atmospheric gas, The method is characterized in that after the group or II-VI group raw material compound semiconductor and the sealant are added, the temperature is increased in one step, and only one of the surfaces is covered with the liquid sealant.

■-V group compound semiconductors that can be grown by the method of the present invention include, for example, GaAs, GaP, I
CdTeX using nP etc. as a II-VI group compound semiconductor
Zn5e etc. can be mentioned.

As a specific method for realizing the above state by heating once, for example, the above-mentioned group ■-V or I
[-Putting a group VI compound semiconductor raw material and a group III or group II element to fill the lower part of the partition wall, and then adding a sealing agent only to one side doubled by the partition wall and heating and raising the temperature in one step. By doing so, the above component elements (group III or I
A method may be proposed in which at least a portion of Group I) is first melted and the bottom of the partition wall is covered with the cough melt to prevent the sealant from melting and flowing out through the communicating portion. By filling the group (2) element, the stoichiometries (IJ-) of the obtained melt will shift, but this shift can be recovered by vapor pressure control. Also, II
There is no particular restriction on the order in which the group IV or group II-VI compound raw materials and the group III or group II elements are introduced.

As another method, at least one of the partition walls doubled is filled with the group ■-■ group or II-VI compound semiconductor raw material powder, filling the lower part of the partition wall to form a plug, and furthermore, the partition wall is An example of this method is to inject a sealant into only one of the two halves and heat and raise the temperature in one step. According to this method, by densely packing raw material powder,
Even if the sealant melts before the raw material, it will not flow out through the communication portion.

Further, the powder material may be molded so as to tightly fit into at least one of the double partition walls and cover the lower part of the partition wall.

A preferable example of the crucible structure applicable to the double crucible is a double crucible structure. Further, the shape of the inner crucible may be one in which the surface of the raw material melt is doubled by its peripheral wall and has a communicating part at the lower part, and is a cylindrical container with an open upper part, and the lower part, That is, the shape may have a communication port in at least one of the bottom wall or the lower part of the peripheral wall, or it may be a communication pipe.

Here, an example of a preferable raw material and sealant filling method of the present invention will be explained based on the attached FIG. 1 and the attached FIG. 2. That is, FIG. 1 is a schematic cross-sectional view showing a filling state of raw materials and a sealant when a continuous tubular inner crucible is used. Ga, ln are placed at the bottom of the outer crucible 25.
etc., and then add the ■-■ group or I[-VI group compound raw material 28 on top of it, so that the lower part of the communication pipe 26 is filled with these raw materials, After that, the sealing agent 29 is poured into only one of the inner portions of the outer crucible doubled by the peripheral wall of the communicating tube 26 (here, the inside of the communicating tube 26). The M-group or II-group element 27 introduced at this time must be in an amount sufficient to cover the lower part of the communicating tube 26 when melted and to obtain a double melt surface by its peripheral wall.

By heating and melting the crucible filled with raw materials and sealant in one step, as shown in FIG.
The surface of the melt 15 in the outer crucible 25 is doubled by the peripheral wall of the communicating tube 26, and only the inside of the communicating tube 26 is covered with the liquid sealant 20.
It is possible to cover it with

In the above method, the shape of the inner crucible and the portion covered by the liquid sealant are not particularly limited. For example, as shown in the attached FIG. It is also possible to use the provided inner crucible 30 to double the melt 15 in the outer crucible 25 with its peripheral wall, and cover the surface of the melt 15 inside the inner crucible 30 with the liquid sealant 20. Alternatively, as shown in the attached FIG. 4, a communicating tube with a small inner diameter may be used as the inner crucible 30, and the surface of the melt 15 outside the inner crucible 30 may be covered with the liquid sealant 20.

In addition, preferable examples of the material for the inner crucible include quartz, PBN, and SiN.

In order to solve the problems of the above-mentioned conventional technology and simplify the single crystal manufacturing process, it is possible to heat and raise the temperature in one step after putting the raw materials and sealant into the crucible as in the above method. It is preferable that the surface of the melt is doubled by a partition wall provided in the crucible, and only one of the surfaces is covered with the liquid sealant.

The first method, which has already been described as a preferred embodiment thereof, was obtained from the following findings. That is, B2O3 used as a liquid sealant has a melting point of about 577°C, and the melting point of the m-v group compound, excluding 1nsb, is 712°C to 16°C.
00℃ and melting point of II-VI group compound 1240℃~1
Very low compared to 850°C. Therefore, when the -V group compound or the If-VI group compound and the sealant are put into a crucible at one place and heated, the sealant melts first, and the communicating part at the bottom of the partition wall that doubles inside the crucible melts. It is not possible to cover only one side with sealant.

However, the m-group elements Ga and In have melting points of 29.8°C and 156.4°C, respectively, and the group-I elements 2n and Cd have melting points of 419°C and 320°C, respectively.
．． It is 9℃. Therefore, by charging the compound raw material and a sufficient amount of Group M or Group II elements into the crucible to fill the lower part of the partition wall, and placing the sealant only on one side of the partition wall and heating it, The m-group or II-group element having a low melting point melts, and it becomes possible to cover the communicating portion at the lower part of the partition wall.

Furthermore, in the second method, the lower part of the partition wall in the crucible is covered and plugged by densely filling the raw material powder in advance or by fitting the raw material powder molded body, so that the sealant melted earlier is connected to the lower part of the partition wall. This prevents the liquid from flowing out from the inside.

EXAMPLES The present invention will be explained in more detail based on Examples below, but these Examples do not limit the scope of the present invention.

The present invention was applied to the growth of a single crystal of Ga 8 using an apparatus as shown in the attached FIG. As an inner crucible, the inner diameter is 80
A quartz circular tube 26 with a diameter of mmφ (3n+n+thickness) was used, and a PBN crucible with a diameter of 4 inches was used as the outer crucible 25. Polycrystals were added to 1500 g of Ga8 produced in an HB (horizontal Bridgman) furnace as compound raw material 28, and M group element 2
Using 100 g of Ga as 7, remove these from 2
5, and then 100 g of B2O3 as a liquid sealant 20 was charged into the inner crucible. As a result, after complete melting, the state will be as shown in Figure 2, and the raw material melt 15
The excessive amount of Ga inside the container 1 could be corrected to a stoichiometric state by adjusting the pressure of the As gas inside the container 1.

As gas pressure is 1.2 atm, pulling speed is 5 mm 7
At that time, the upper/lower shaft rotation speed was 5/25 rpm.

When pulling was carried out under these conditions, it was found that the single crystallization rate of the crystal was improved, and the composition ratio of Ga and 8S in the crystal was also stoichiometric.

Effects of the Invention Thus, the method of the present invention makes it possible to double the surfaces of the crucible and cover only one side with a sealant in one heating step, which has the advantages of both the liquid sealing method and the vapor pressure control method. ,
Simplify the work process of the single crystal manufacturing method, which combines high purity of the single crystal by the impurity capture effect of the liquid sealant, high crystallization rate by the temperature stabilization effect, and securing of stoichiometry (IJ-) by controlling the vapor pressure. I was able to turn it into

[Brief explanation of drawings]

Attached FIG. 1 is a schematic cross-sectional view showing the state in which raw materials and sealant are charged into a crucible according to the method of the present invention, and attached FIG. 2 shows the crucible in the state shown in FIG. It is a schematic cross-sectional view showing the state of the raw material melt and the liquid sealant when heated, and the attached FIGS. 3 and 4 show the preferred inner crucible shape, raw material melt, and liquid sealant in the method of the present invention. 5 is a schematic cross-sectional view showing the state of the agent, attached FIG. 5 is a schematic cross-sectional view showing a device used in a conventional vapor pressure control method, and attached FIG. 6 is a schematic cross-sectional view showing a conventional liquid sealing method. FIG. (Main reference numbers) 1a... Volatile component death certificate enclosing container, 4... Seed crystal, 5... Crucible, 6-9... Heater, 15... Raw material melt, 16...・Volatile single crystal component element, 17... Single crystal, 20... Liquid sealant, 25...
- Outer crucible, 26... Communication tube, 27... Group ■ or Group ■ element, 28... Compound raw material, 29... Sealing agent, 30...
inner crucible

Claims (7)

[Claims] (1) A partition wall is provided in the crucible, and III-V in the crucible is
Divide the surface of the group or II-VI group compound semiconductor raw material melt into two parts,
One side of the surface is covered with a liquid encapsulant and the other side is brought into contact with atmospheric gas to control the vapor pressure while a compound semiconductor single crystal is immersed in the melt and pulled up using the Czochralski method. When growing, the III-V group or II-VI group single crystal raw materials and sealant are put into the crucible, and then the temperature is raised in one step, and only one of the surfaces is covered with the liquid sealant. The method for producing the compound semiconductor single crystal described above, which comprises covering the compound semiconductor single crystal. (2) The III-V group or II-VI group compound semiconductor raw material and the group III or group II element are charged into the bottom of the crucible to fill the lower part of the partition wall, and further, only one of the two parts divided by the partition wall is sealed. A patent claim characterized in that a sealing agent is introduced and the temperature is raised in one step to melt at least a portion of the group III or group II element before the sealant, and the lower part of the partition wall is covered with the melt. A method for producing a compound semiconductor single crystal according to item 1. (3) At least one of the two parts divided by the partition wall has the above
In one step, a raw material powder containing a group III-V or group II-VI compound semiconductor is densely packed, the lower part of the partition wall is filled to form a plug, and a sealant is added only to one side filled with the powder. 3. The method for producing a compound semiconductor single crystal according to claim 1 or 2, wherein the temperature is increased by heating. (4) The method for producing a compound semiconductor single crystal according to claim 3, wherein the powder raw material is shaped so as to fit tightly into at least one of the two halves divided by the partition wall. (5) The compound semiconductor monomer according to any one of claims 1 to 4, wherein the crucible has a double crucible structure, and the peripheral wall of the inner crucible is the partition wall. Method of manufacturing crystals. (6) The method for manufacturing a compound semiconductor single crystal according to claim 5, wherein the inner crucible is a cylindrical container with an open top and has a communicating hole in the bottom. (7) The method for producing a compound semiconductor single crystal according to claim 5, wherein the inner crucible is a communicating tube.