JPS59232997A - Method and device for producing single crystal - Google Patents

Abstract

PURPOSE:To produce stably a single crystal having high quality by closing hermetrically the space in which the melt in a crucible is pulled up with a quartz tube and pulling up the single crystal. CONSTITUTION:A quartz tube 13 is attached to a pull-up furnace chamber 11. A crucible 2 is made into a double construction. A raw material melt GAm is put into the inside crucible 2'. A crucible having a larger upper part is used for the outside crucible 2''. A sealant B2O3 melt Bm is put between both inside and outside crucible and in the upper part of the raw material melt GAm. After the B2O3 is melted, the position of the crucible is risen and a quartz tube 13 is inserted into the B2O3 melt between both inside and outside crucibles. A single crystal is thereafter grown in the same way as in the ordinary pulling up method. Since the melt in the crucible is closed hermetically by the quartz tube, the intrusion of impurities from carbon parts and chamber wall is prevented; moreover, the quartz tube has the effect of a heat insulating cylinder and since the space in the upper part of the crucible is small, thermal flow by the convectional flow of the gas is decreased and the temp. gradient of the melt and B2O3 layer in the crucible is decreased. The stable crystal is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for producing a single crystal using the Czochralski method, and an apparatus therefor.

The production of semiconductor crystals by the conventional liquid capsule Czochralski method will be explained with reference to FIG. A crucible 2 is provided in a furnace 1 on a lower shaft (crucible shaft) 5, the crucible 2 is supported around the periphery by a carbon susceptor 4, and a carbon heater 5 is further installed outside the crucible 2. In the crucible 2, a raw material melt of GaAθ (Mel)GAm is placed, and a sealing agent (B, 03Mel)'Bm is sealed above the crucible. The temperature of the crucible is completely raised to sequentially melt the B2O3 melt, GaA, and the entire melt, and the crucible is raised and the pulling shaft (seed shaft) 6 is inserted into the melt. After growing the single crystal C on the seed, the pulling is started. It is something to do. No. 7 has a peephole that allows the entire situation inside the furnace to be observed. The disadvantage of this conventional method is that the crucible containing the raw material melt is an oven inside the furnace, so the convection of pressurized gas , carbon from carbon parts inside the furnace such as heaters and susceptors, and furthermore we, cr from the chamber walls.
, Ni, etc. are mixed into the raw material. The mixed carbon is GaAs
Among them, impurities with shallow acceptor properties adversely affect the electrical properties of the grown GaAs single crystal, and also become electrically active impurities in other semiconductor materials, affecting the electrical properties.

The purpose of the present invention is to improve the drawbacks of the conventional liquid-sealed Czochralski method.A quartz tube is attached to the rotary shaft of the seed shaft in the upper part of the furnace chamber. A sealing agent BxO is placed between the crucible.
The melt in the crucible and the space from which it is drawn can be sealed by inserting the quartz tube into the sealant by moving the crucible up and down.

The method and apparatus of the present invention will be specifically explained with reference to FIG. In the figure, the same numbers as in FIG. 1 indicate the same ones as in FIG. 6′
is the o14 heater which is the seed.

The crucible 2 that stores the raw materials has a double structure as shown in the figure, and the inner crucible 2' (here, PBN (pyrO-1yt
ic boron n1trle)], use the outer crucible 2' (made of quartz here) with a larger upper diameter, and place the crucible 2' into the crucible 2'. Crucible 2', outer crucible 2', and raw material melt of inner crucible 2')
Place the sealant B2O3 (Mel) Bm on top of GAm. The crystal growth method is the same as the normal liquid capsule Czochralski method. After raising the crucible temperature and melting B2O3, the crucible position is raised and the above steps are performed. A quartz tube is inserted into the B2O3 melt placed between the outer and inner crucibles.Then, the single crystal is lengthened in the same manner as the usual pulling method.

In the present invention, melt in the crucible)? Since it can be sealed with a quartz tube, it is possible to prevent impurities from entering the carbon parts and the chamber wall.The quartz tube also has the effect of a heat-insulating cylinder, and since the space above the crucible has a small volume, there is little heat flow due to gas convection, and the melt inside the crucible is reduced. , B, O, the temperature gradient of the layers can be reduced, and stable crystals can be obtained. The device of the present invention has a simple structure, requiring only simple changes to the conventional liquid-sealed Czochralski method device, such as adding a quartz tube and tube fittings and changing the susceptor and crucible structure.

The method and apparatus of the present invention can be applied to GaAs, Gap,
It can be effectively used in the production of I-III group compound semiconductors such as P, as well as in the production of oxide crystals using a pulling method.

Example In the apparatus shown in Fig. 2, the inner crucible was made of PBN 75wφ,
A GaAs single crystal was grown by the Czochralski method using a gold crucible made of quartz with an outer diameter of 115 Wφ in the upper part of the outer crucible, and a quartz tube with a diameter of 95 mm.

Ga 250f (5,586 morphs, A3275f (670 mols) as a raw material, B on top, 0.
It was placed in a PBN crucible inside a 120f'tl''.

Also, between the outer and inner crucibles is B, 03500 f'i.
The crucible containing the raw materials was vacuum baked at 550°C for about 6 hours. After that, the pressure was increased to about 60 atm with N gas and the temperature was raised to about 450°C to melt the B2O3, and then the crucible was gradually raised and the quartz tube was placed between the outer and inner crucibles into the B2O3 melt. It was inserted to a depth of 15-20 m. By further increasing the temperature, Ga and AB f
After reacting to form GaAs polycrystals, the gas pressure was lowered to 10 atm, and the temperature was further raised to about 1250°C to form GaAs polycrystals.
s polycrystal was melted. Thereafter, as in the usual pulling method, after the seed crystal was blended with the raw material melt, pulling of the single crystal was started. Pulling speed is 9 w@/hr, seed rotation speed is 9 rp
m, and the crucible rotation speed was 10 rpm. After pulling the single crystal, the crucible was lowered again when the temperature was lowered to about 500° C., and the quartz tube t=Bgos melt was pulled out. The pulled crystal is in a diameter of 35mm and has a length of &56n.
It was a single crystal with a weight of 410f.

When the pulled crystal was subjected to mass spectrometry (55M5, spark-once mass spectrometry), the concentration of carbon (C) in the crystal was 5 x 1015 atoms/6n'', which was compared to 1 to 6 of the crystal by the conventional liquid capsule Czochralski method. X
10” atoms/6n” Noah 2 or less,! :Iu value was obtained.

When Fθ, cr, and Ni were analyzed by SIMS, 5 x 1014 atoms/
(-The following results were obtained which were almost the same as the conventional method.

Regarding crystal defects, it was found that the EiPD (etch pit density) was reduced by about 20-50% at the front and tail parts of the crystal. That is, from the conventional 5 X 10' Confucian-2
from 9 x 10' cm-” to 7 x at the tail.
0 reduced to 10' cm-2?The apparatus and method of the present invention? All of the crystals pulled using this method showed low impurity concentrations and low dislocation densities as described above, making it clear that single crystals of high quality could be obtained stably.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view schematically showing a conventional Czochralski method for producing a single crystal and an apparatus, and Fig. 2 is a schematic diagram of the main parts inside a pulling furnace showing the features of the method and apparatus of the present invention. 0 agents in the diagram 1) Akira agent Ryo Hagiwara -

Claims (2)

[Claims] (1) In a single crystal manufacturing method in which a pulling shaft is inserted into a crucible containing molten raw material and B2O5k that seals the molten raw material in a furnace to grow and pull a single crystal,
A method for producing a single crystal, which comprises pulling a single crystal by sealing a space in a crucible for pulling the melt with a quartz tube. (2) In a single-crystal manufacturing equipment that mainly consists of a furnace, a vertically movable crucible installed in the furnace, and a pulling shaft hanging above the crucible, a quartz tube is attached to the shaft of the pulling shaft, and the entire crucible is It has a double crucible structure with a difference in the outer diameter of the upper part, and B is used as a sealant between the two crucibles.
, O, a single crystal manufacturing apparatus characterized in that a quartz tube is sealed by providing a melt.