JPH02267192A - Production of single crystal and apparatus therefor - Google Patents

Abstract

PURPOSE:To prevent a twin or polycrystal from forming in crystal growth and grow a homogeneous crystal over the whole length by providing an apparatus with an auxiliary heater divided into plural parts in the circumferential direction in the form of a concentric circle with a main heater and independently controlling the heating value of the auxiliary heater. CONSTITUTION:In a rotating pulling up apparatus for a single crystal, a circular arc auxiliary heater 12 divided into >=2 parts is provided by partially or wholly dipping the heater 12 in a melt in a crucible 3 corresponding to a main heater 5. The divided auxiliary heater 12 is independently controlled to eliminate nonuniformity of temperature distribution caused by heat generation with the main heater 5. Thereby, asymmetry of the temperature distribution can be eliminated to carry out homogeneous crystal growth.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method and apparatus for producing a single crystal that can produce a single crystal with excellent uniformity in good yield.

[Conventional technology]

Single crystals of inorganic compounds (hereinafter referred to as rm-v group compounds) consisting of elements of groups MB and VB of the periodic table, especially single crystals of gallium arsenide and gallium phosphide, are used in field effect transistors and Schottky Barrier diode, integrated circuit (
It is widely used in the manufacture of various semiconductor devices such as ICs.

Single crystals used in the manufacture of these semiconductor devices require atoms to be spatially regularly arranged in a solid state.

■-■ group compounds, especially single crystals of gallium arsenide, used for substrates such as integrated circuits, are often grown by the so-called LEC method, which uses diboron trioxide as a sealant. . This is because the LEC method has less contamination with impurities, so that highly pure crystals can be obtained.

However, the inside of the lifting device for the LEC method has a complicated structure, and the inside of the container is filled with high-pressure inert gas, so the inside of the device has an unsteady and asymmetrical temperature distribution. Therefore, during the growth of a single crystal, abnormal growth occurs when it solidifies from a liquid to a solid, and the crystallinity is disturbed, often resulting in twinning and polycrystalization. If twinning or polycrystalization occurs, that portion cannot be used as a substrate for integrated circuits or the like, so twinning or polycrystalization causes a significant decrease in product yield.

Therefore, conventionally, an annular heater is floated on the melt so that the temperature distribution on the surface of the B2O3 melt is axially symmetrical (Japanese Patent Application Laid-open No. 1983-62892), and an annular heater is immersed in the B2O3 melt. A device in which the diameter of the single crystal is controlled by controlling the temperature and
232996) and the like have been proposed.

[Problem to be solved by the invention]

However, when a resistance heating element is used to heat the melt, the resistance heating element (itself a heating element) has a heat generation distribution in which the temperature is low near the electrode part and the temperature is high in the middle part between the electrodes due to its structure. This point will be explained with reference to FIGS. 4 and 5.

FIG. 4 is a diagram showing a conventional single crystal pulling apparatus. In the figure, ■ is an airtight container, 2 is a heat insulator, 3 is a crucible, 4 is a susceptor, 5 is a heater, 6 is a pulling shaft, 7 is a crucible support shaft, 8 is a seed crystal, 9 is a crystal, 10 is a raw material melt , 11 is a sealant.

In the figure, a raw material melt 10 is sealed with a liquid sealant 11 and placed in a crucible 3 supported by a susceptor 4, an airtight container 1 is filled with inert gas to create a high pressure state, and a heater 5 is energized. The crucible 3 is rotated by heating and preventing heat dissipation by the heat insulating material 2 and rotating the support shaft 7, and the crystal is grown by pulling the crucible 3 while rotating the pulling shaft 6 with a seed crystal attached to the tip.

By the way, as shown in FIG. 5, the heater 5 has electrodes 5a and 5b for energizing, and since heat is transferred through the electrodes and dissipates, the temperature of the electrode portion decreases. Therefore, the temperature distribution in the cross section of the apparatus shown in FIG. 4 becomes as shown by the broken line in FIG. That is, the temperatures of representative isothermal curves from the center of the crucible circle to the periphery are T3, T2, and T, respectively.
3. Also, if the temperature of a typical isothermal curve of the heater portion is T4, then the relationship is T,>T3>T2>TI. That is, the heater portion has the highest temperature, and the temperature gradually decreases toward the inside, and the temperature decreases from the heater toward the outside. The area near the electrodes 5a and 5b becomes low temperature because heat is transferred through the electrodes and escapes, and the area between the electrodes becomes high temperature. Therefore, the isotherm curve is the fifth
The shape shown in the figure is asymmetrical.

In this way, in the conventional method, the temperature distribution inside the crucible becomes asymmetrical, which is difficult to eliminate, and furthermore,
The amount of heat generated by the resistance heating element is changed depending on the amount of crystal growth, but since changing the amount of heat generated also changes the distribution of heat generation, it is difficult to achieve the same temperature distribution from the beginning to the end of crystal growth. It was possible.

[Means to solve the problem]

The present inventors have conducted intensive research aimed at preventing twinning and polycrystalization that occur during crystal growth, improving yield, and obtaining uniform crystals over the entire length.
We have discovered that the above problem can be solved by installing an auxiliary heater divided into two or more in the circumferential direction concentrically with the main heater in the crucible and controlling the amount of heat generated by the auxiliary heater, and have arrived at the present invention. This is what I did.

The above-mentioned object of the present invention is to reduce the amount of heat generated by the auxiliary heater, which is arranged concentrically with the main heater and divided into positions in the circumferential direction, and which can independently control the amount of heat generated, from the temperature caused by the heat generated by the main heater. This can be achieved by controlling to eliminate non-uniformity of distribution.

FIG. 1 is a longitudinal cross-sectional view of the single crystal pulling apparatus of the present invention, and FIG.
The figure is a cross-sectional view, and the same numbers as in FIG. 4 indicate the same contents. Note that 12 is an auxiliary heater.

The present invention provides an arcuate auxiliary heater 12 divided into two parts,
It is provided at a position in the crucible corresponding to the electrodes 5a, 5b, partially or completely immersed in the melt. Since the auxiliary heater is immersed in the melt, it is desirable to coat the surface of the heater with boron nitride to prevent impurities from eluting.

As explained in FIG. 5, the temperature of the electrode portion decreases due to heat escaping through heat transfer through the electrode, but the auxiliary heater 12
By providing and heating the crucible, the temperature of this portion can be increased, and as a result, the isothermal curve inside the crucible can be made approximately symmetrical, as shown in FIG. The amount of heat generated by the auxiliary heater should be enough to compensate for the temperature drop and eliminate uneven temperature distribution.)

In the above description, the auxiliary heater is divided into two parts, but the number of divisions may be further increased.

[Effect]

In the present invention, since an auxiliary protector is provided at a position corresponding to the electrode in the crucible, it is possible to prevent temperature drop due to heat radiation from the electrode and eliminate asymmetry in temperature distribution. It becomes possible to cause crystal growth,
It is possible to prevent the occurrence of twinning and polycrystalization.

〔Example〕

The single crystal rotational pulling device uses the device shown in Figure 1.
A two-part heater as shown in FIG. 2 was used as the auxiliary heater.

The crucible was made of PBN and had an outer diameter of 15 cm and a height of 14 cm. The raw material is high-purity GaAs polycrystal 5Kg,
3600 g of B2O was used. After melting the raw material, 20 atm
75 m at a pulling speed of 6 mm/h in an argon atmosphere.
It was possible to grow crystals with a diameter of m.

Heating was performed with a power of 9KW for the main heater and 0.8KW for the auxiliary heater, and twinning occurred only 4 times in 100 crystal growths.

[Comparative example]

Crystal growth was performed without using an auxiliary heater, with other conditions being the same.

For those using an auxiliary heater, 100 times of growth will result in 2
0 twins occurred.

〔Effect of the invention〕

As described above, according to the present invention, the incidence of twins among the produced gallium crystals has been reduced to one-fifth of the conventional rate. If twins are confirmed immediately after seeding, pulling is stopped, the twins are melted again, and the seeding operation is performed again. However, the number of remelting operations is reduced by three times compared to the conventional method. It was reduced to 1.

[Brief explanation of drawings]

Figure 1 is a vertical view of the single crystal pulling device of the present invention.
FIG. 2 is a cross-sectional view, FIG. 3 is a diagram showing an isothermal curve in the present invention, and FIG. 4 is a diagram showing a conventional single crystal drawing and burning device.
FIG. 5 is a diagram showing isothermal curves in a conventional single crystal drawing device. 1... Airtight container, 2... Heat insulator, 3... Crucible, 4
・Susceptor, 5... Heater, 6... Pulling shaft,
7. Crucible support shaft, 8... Seed crystal, 9... Crystal, 1
0... Raw material melt, 11... Sealing agent, 12... Auxiliary heater. Applicant Mitsubishi Monzanto Chemicals Co., Ltd. (1 other person)

Claims (6)

[Claims] (1) In a single crystal manufacturing method in which crystal growth is performed by putting a raw material melt and a liquid sealant in a crucible and heating it with a main heater installed around the crucible and pulling up a seed crystal while rotating, the main heater Divide into at least two parts in the circumferential direction concentrically with the main heater at positions corresponding to the electrode parts of the main heater, immerse part or all of the heat generating part in the sealant, install the auxiliary heater, A method for producing a single crystal, characterized in that asymmetry in temperature distribution is improved by independently controlling the amount of heat generated by each auxiliary heater. (2) The single crystal manufacturing method according to claim 1, wherein the auxiliary heater is covered with boron nitride. (3) The method for producing a single crystal according to claim 1 or 2, wherein the single crystal is grown in an airtight container filled with an inert gas. (4) an airtight container filled with an inert gas, a crucible supported within the airtight container and containing a raw material melt and a liquid sealant;
It is equipped with an annular main heater installed around the crucible in an airtight container, and the main heater heats the inside of the crucible, and crystal growth is performed by pulling up the seed crystal while rotating a pulling shaft with a seed crystal attached to the tip. In a single-crystal manufacturing apparatus, the annular main heater is divided into at least two parts in the circumferential direction, concentrically with the main heater, at a position in the crucible corresponding to the electrode part of the annular main heater, and each part has an independent calorific value. A single crystal manufacturing device characterized by being equipped with an auxiliary heater that can control. (5) The single crystal manufacturing apparatus according to claim 4, wherein part or all of the heat generating portion of the auxiliary heater is immersed in the sealant B_2O_3 during crystal growth. (6) The single crystal manufacturing apparatus according to claim 5, wherein the auxiliary heater is covered with boron nitride.