JPS6090895A - Growing method of compound semiconductor single crystal having volatility - Google Patents

Abstract

PURPOSE:To grow a uniform and high-quality single crystal by covering the upper layer of the melt with a liquid capsuling material layer, and incorporating a specific melt floating layer into the lower layer in pulling up a III-V group compd. semiconductor single crystal from the melt in a crucible and drying. CONSTITUTION:The surface of a GaAs melt layer 23 in a quartz crucible 21 is covered with a liquid capsuling material layer (B2O3)22, and a melt floating material layer (Bi2O3)24 which does not react with the melt 23 and whose specific gravity and specific heat are higher than those of the melt 23 is placed under the layer 22. In addition, a film 25 of the melt floating material is formed on the inner surface of the crucible 21 contacting with the melt 24. Under said conditions, a seed crystal 29 supported by a lifting shaft 28 is passed through the liquid capsuling material layer 22, brought into contact with the melt layer 23, and lifted up while rotating to gradually grow a GaAs single crystal 30. The change of thermal conditions due to the decrease in the amt. of the melt during the growth of the single crystal is prevented by the liquid capsuling material layer 22, and the optimum conditions are maintained. The intrusion of impurities from the crucible 21 is prevented by the melt floating material layers 24 and 25, and the high-quality single crystal 30 can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for growing a volatile compound semiconductor single crystal of a group ■-V compound such as gallium arsenide (GaAS) or indium phosphide (TnP) by pulling it out of its melt. Conventionally, during the single crystal growth, the single crystal raw material melt layer in the crucible is covered with a liquid Kabhill material and a melt flotation material to improve the thermal environment and prevent contamination from the crucible. Liquid Encapsulation C
zochralski (abbreviated LEC method) uses an apparatus as shown in FIG.
Boron oxide ([3203>), which is an encapsulant, is placed on top of it, heated and melted to form a liquid encapsulant layer 3 on the melt layer 2, and isolate the melt layer 2 from the outside atmosphere.
Seed crystal 4 while preventing volatilization of elements from its surface.
The single crystal 6 is grown by being pulled up from the melt layer 2 by rotating a pulling shaft 5 marked with .

7 is a carbon susceptor, 8 is a high frequency heating coil, 9
10 is a crucible susceptor, and 10 is an internal observation window. In this high-pressure container 11, for example, when gallium arsenide is used as a single crystal raw material, an inert gas 12 such as argon is kept at about 5 atm to suppress dissociation of arsenic. It is enclosed in.

In such conventional methods, the single crystal raw material comes into direct contact with the inner wall of the quartz crucible before and after melting, and thus is always contaminated by the inner wall of the quartz crucible, thereby introducing silicon into the melt.

Furthermore, when growing a large-diameter single crystal using such a conventional method, as the growth speeds up, the amount of melt decreases, the interface between the crystal and the melt gradually lowers, and the thermal environment changes significantly. Therefore, the optimal conditions for growing high-quality, uniform-diameter crystals are significantly disrupted, and as the amount of melt decreases, the shape of the bottom of the crucible (bowl-shaped) appears to be affected, and crystal diameter calculation and control using gravimetric methods becomes difficult.

The present invention has been made in order to eliminate the drawbacks of the conventional method for growing single crystals of group ■-v compound semiconductors.
When the single crystal is pulled up from the melt and grown, the surface of the melt layer in the single crystal growth furnace 9 crucible is covered with a liquid encapsulant layer, and the layer below is made of a non-reactive material with a specific gravity of 1.
, accommodates a layer of molten flotation material with a greater specific heat,
The inner surface of the crucible in contact with the melt layer is coated with the melt flotation material, or boron nitride (PvrolytiCBoror+N1t) is coated at a predetermined interval in the crucible of the growth furnace.
An inner cylinder made of boron nitride is inserted and installed, and a melt layer and a liquid encapsulant layer are accommodated therein, and a layer of molten flotation material is placed in the lower layer so as to fill the inside and outside of the lower part of the cylinder made of boron nitride. This is a compound semiconductor single crystal growing method that improves the thermal environment of the crucible and prevents contamination from the crucible.

A layer of molten flotation material, which has a larger specific gravity and specific heat than the melt, is accommodated in the lower layer of the crucible to form a thermal edge Ili layer, and the melt layer is held in a floating state on top of this layer. By covering the upper layer with a liquid encapsulant layer, it is possible to prevent changes in the thermal environment caused by a decrease in the amount of melt during single crystal growth, and maintain optimal conditions for growth, resulting in uniform overall growth. It is possible to grow high-quality single crystals with unique properties. In addition, by coating the inner surface of the crucible that is in contact with the melt with a molten flotation material coating, or by inserting and installing a boron nitride cylinder into the crucible, contact between the melt and the inner surface of the crucible can be completely blocked. It is possible to prevent contamination of the melt due to contamination of impurities from. The present invention will be described below with reference to the drawings and an example in which a gallium arsenide single crystal is grown.

FIG. 2 shows a partial sectional view of the single crystal growth furnace.

In this furnace, each raw material is first loaded into a quartz crucible 21.
Liquid encapsulant layer inside (boron oxide (8203)) 2
2. Hold the gallium arsenide melt layer 23 and the molten buoyant material layer (bismuth oxide (Biz Og > ) 24 in a predetermined state as shown in the figure, and apply a molten buoyant material coating to the inner surface of the crucible in contact with the melt layer 23. Various methods can be considered for this purpose. An example of this is shown in FIG. After filling the capsule material 24' with a lid of the capsule material 22' formed into a plate shape, this material is loaded into the crucible 21 and heated by the carbon heater 26 while the furnace is evacuated to expel the contents. The vacuuming has the effect of removing moisture from the contents.When the temperature reaches approximately 460°C, the encapsulant 22' melts to form a liquid encapsulant layer 22, which covers the surface of the crushed gallium arsenide 23'. become.

Thereafter, the inside of the furnace is filled with an inert gas to prevent the decomposition of arsenic from the crushed gallium arsenide 23'.

At approximately 820 DEG C., the flotation material 24' begins to melt, wetting the inner surface of the crucible and forming a coating 25 thereon, forming an initial molten flotation layer 24 along the bottom of the crucible 21.

Since the molten buoyant material has a high viscosity, the molten buoyant material coating 25 formed on the inner surface of the crucible remains in that state for a long time, blocking contact between the inner wall of the crucible and the melt layer 23. Then, when the temperature reaches about 1240°C, crushed gallium arsenide 2
3' is melted to form a melt layer 23. As a result, the specific gravity of the liquid encapsulant layer (8205) 22 is 1.52 (
1000°C), and the specific gravity of the gallium arsenide melt layer 23 is s:r
l (1240°C) 1, the specific gravity of the molten flotation material layer 24 is 8.4
(1000°C), as shown in the figure, the gallium arsenide melt layer 23 is formed on the liquid encapsulant layer 1;
2 and a molten flotation material layer 24, and its sides are surrounded by a molten flotation material coating 25, so that the entire body is held in a state of being enveloped by them. Next, while looking through the observation window 27, the seed crystal 29 supported by the pulling shaft 28 is brought into contact with the melt layer 23 through the liquid H-bucel material layer 22 to blend it, and then the seed crystal 29 is brought into contact with the melt layer 23 while rotating at 3 to 20 revolutions per minute. The gallium arsenide single crystal 30 is gradually grown by pulling upward at a speed of 1 to 100 m+ per hour. 31 is a carbon susceptor, 32 is a susceptor paste, and 33 is a high pressure vessel. In this way, as the growth of the single crystal 30 progresses, the length of the melt layer 23 decreases. Constant pressure specific heat 15.0 cal
/deg mol,) and the molten flotation material layer 24 (constant pressure specific heat 27.1 cal/deg mol) Since the top and bottom are covered with garlic, there is little change in the thermal environment, and the conditions for crystal growth are not disrupted. .

In particular, the bismuth oxide of the molten flotation material layer 24, which has a large heat capacity, does not react with gallium arsenide and is itself stable.
Even at 00°C, the vapor pressure is less than several amH (l), and it serves as a buffer material to maintain the thermal environment of the melt layer 23, thereby relaxing the temperature gradient of the melt layer 23. In addition, since the inner surface of the crucible is covered with the molten flotation material coating 25 and contact with the melt layer 23 is cut off, contamination of the melt 11123 due to the mixing of silica from the crucible 21 can be prevented. In the conventional method, as the amount of melt decreases, heat escapes through heat conduction from the susceptor base 32, and the thermal environment of the melt layer changes, and the conditions for crystal growth deteriorate significantly, resulting in the bottom part of the single crystal being pulled up. However, in the present invention, as described above, since the conditions for crystal growth are not changed, a gallium arsenide single crystal 30 having high quality and uniform properties can be obtained until the melt layer 23 disappears. In the conventional method, in addition to changes in the thermal environment, changes in the shape of the crucible bottom (inverted bowl shape) due to a decrease in the amount of melt had an adverse effect on crystal shape control, but in the present invention, the melt The diameter is maintained in the same cylindrical shape by the two ends, and the diameter can be easily controlled automatically by the weight change rate of the melt or the gallium arsenide single crystal.

Next, other embodiments of the present invention will be described.

FIG. 4 shows a partial cross-sectional view of a medium-sized crystal growth furnace with the external high-pressure vessel omitted. Inside the quartz crucible 41, a boron nitride cylinder 4 is placed at a predetermined distance from the inner wall and bottom surface of the quartz crucible 41.
2 is inserted, and the cylinder 42 has carbon insulation 1
, 143 supporting 1.1. It is fixed to the bent carbon plate 44 with a stopper 45. Each raw material is loaded into this width and heated and melted to form a liquid encapsulant layer (Bz 03) 46
, gallium arsenide melt layer 47, melt flotation material layer (Biz
Og>48 is maintained in the state shown in the figure, for example, by first loading a predetermined floatation material, followed by polycrystalline gallium arsenide, and finally a capsule material formed into a disc shape, and then loading the above-mentioned example. As shown in FIG. 2, the carbon is heated and melted by the carbon heater 49 while the inside of the furnace is evacuated. Note that polycrystalline gallium arsenide can also be directly synthesized by loading gallium and arsenic. As in the previous embodiment, the contents are prepared by first melting the capsule material and forming a liquid capsule layer 4.
6 to cover the polycrystalline gallium arsenide, then the flotation material melts and fills the bottom of the crucible 41 and the lower part of the boron nitride cylinder 42 to form a molten flotation material layer 48, and finally the intermediate polycrystalline arsenide The gallium melts and forms a melt layer 47. As a result, as shown in the figure, gallium arsenide melt I47
has a liquid encapsulant layer 46 and a molten flotation material layer 48 above and below.
The side surface is held in contact with the inner surface of the boron nitride cylinder 42. Next, as in the previous embodiment, the seed crystal 51 supported by the pulling shaft 50 is passed through the liquid encapsulant layer 46 and brought into contact with the melt layer 47, and then pulled in the L direction at a predetermined speed while rotating. 16 o 53 is a carbon susceptor, 54 is a susceptor pace, and 55 is a crucible lower shaft. In this way, as the growth of the single crystal 52 progresses, the pull of the melt layer 47 decreases; Changes in the physical environment are minimized, and the conditions for crystal growth are not disrupted.

Further, since the side surface of the melt layer 47 is in contact with the inner surface of the boron nitride cylinder 42 from beginning to end and does not come into contact with the quartz crucible 41, contamination due to silica can be prevented. Furthermore, after growing the single crystal, the quartz crucible 41 is pushed down and the boron nitride cylinder 42 is separated from the contents in the crucible 41, so that the contents are solidified by cooling.
The cylinder 42 can be prevented from being damaged by H and can be used repeatedly.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a device for a conventional melt capsule crystal pulling method, Figure 2 is a partial cross-sectional view of a single crystal growth furnace used in an example of wood crystallization, and Figure 3 is a method of loading raw materials in an example. FIG. 4 is a partial sectional view of a single crystal growth furnace used in another embodiment of the present invention. 21.24 ... Quartz crucible 22.46 ... Liquid encapsulant layer 23.47 ・
... Gallium arsenide melt layer 24.48 ... Melt flotation material layer 25 ...... Melt flotation material coating 26.49
・・・ Carbon heater 27 ・・・・・・・・・
Observation window 28.50 ... Pulling shaft 29.51 ... Seed crystal 30.52 ... Gallium arsenide single crystal 31.53
・・・Carbon Susceptor 32.54 ・・・Susceptor Pace 33 ・・・・・・・・・True R”*Return 4
2 ...... Boron nitride cylinder 43 ...
・・・・・・ Carbon insulation month 44 ・・・・・・・・・
・ Carbon plate 45 ...... Stopper

Claims (7)

[Claims] (1) When growing a ■-V group compound semiconductor single crystal from its melt in a single crystal growth furnace, the surface of the melt layer in the crucible of the growth furnace is covered with a liquid encapsulant layer, and the underlying layer is contains a layer of molten flotation material that is non-reactive with the melt and has a specific gravity and specific heat return, and the inner surface of the crucible in contact with the melt layer is coated with the melt flotation material to maintain its thermal environment. A method for growing a compound semiconductor single crystal, characterized in that it improves the properties of the compound semiconductor and simultaneously prevents contamination from the crucible. (2) A predetermined amount of flotation material molded into a crucible shape.
A crushed V-group compound semiconductor single crystal raw material is filled, and a cap of capsule material molded into a plate is placed on top of the crushed material, which is placed in a crucible of a single crystal growth furnace and heated to form a wet nail. A patent claim in which the surface of the melt layer of the single-crystal raw material is covered with a liquid encapsulant layer, a melt flotation material layer is accommodated in the lower layer thereof, and the inner surface of the crucible in contact with the melt layer is coated with the melt flotation material. The method for growing compound semiconductor single crystals according to scope (1). (3) Claims in which the III-V compound semiconductor is either gallium arsenide or indium phosphide (
The compound semiconductor single crystal growth method described in item 1) or item (2). (4) The compound semiconductor single crystal according to any one of claims (1) to (3), wherein the encapsulant is boron oxide (Bz 03 ) and the buoyant material is bismuth oxide (8iz 03 ). Cultivation method. . (5) When pulling up and growing a ■-V group compound semiconductor single crystal from its melt in a single crystal growth furnace, ``a cylinder made of boron nitride is inserted at a predetermined interval into the crucible of the growth furnace; A melt layer and a liquid encapsulant layer are accommodated in the upper layer, and the lower layer is filled with a material that is non-reactive with the melt and has a higher specific gravity and specific heat. A compound semiconductor single crystal growth method characterized by accommodating a large molten floating material layer to improve its thermal environment and at the same time preventing contamination from the crucible. (6) I [Claims in which the IV group compound semiconductor is either gallium arsenide or indium phosphide (
5) Compound semiconductor single crystal growth method described in section 5). (7) The method for growing a compound semiconductor single crystal according to claim 5 or 6, wherein the encapsulant is boron oxide (BZ 03 ) and the buoyant material is bismuth oxide (BizO3').