JPS6011299A - Method and device for producing compound single crystal with high dissociation pressure - Google Patents

Abstract

PURPOSE:To suppress thermal decomposition on the surface of III-V group compd. single crystal and to prevent generation of a defect in a process for producing said single crystal by a melt-pulling up method by maintaining the vapor atmosphere of a volatile element (V group element) in the sealing space above the liquid sealing bath of a crucible. CONSTITUTION:A quartz cover 14 provided with a tubular opening 15 at the top is fitted to the crucible 3 in a pressure vessel 1 and the inside of the vessel 1 is maintained under 3-60atm, by an inert gas. The upper part of the cover 14 is heated to 400-700 deg.C by auxiliary heaters 4a, 4b and the crucible 3 is heated by the heater 4 to melt the raw material charged preliminarily therein and to form a gallium aresenide melt 9 and a liquid sealing bath 10 consisting of boron oxide. The sealing space in the cover 14 is maintained in the arsenic vapor atmosphere under 7Torr-4atm. partial pressure. While the temp. gradient in the bath 10 is kept at <=100 deg.C/cm, a gallium arsenide single crystal is pulled up with the force bar (a symbol 6 is a seed crystal) of a pulling up shaft 5 according to the conventional method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for producing single crystals of high dissociation pressure compounds for semiconductors (hereinafter simply referred to as compounds) such as gallium arsenide, indium arsenide, gallium phosphide, and indium phosphide. In particular, it prevents thermal decomposition of seed single crystals and compound single crystals in the single crystal pulling process, making it possible to produce single crystals with fewer defects (dislocations).

Generally, a compound single crystal is stored in a pressure vessel (1
A graphite crucible holder (2) is installed inside the pressure vessel (1), a 5iOz or BN crucible (3) is attached, and a graphite heater (4) is placed outside of the crucible (2).
3) A pulling shaft (5) that rotates inward and can freely move up and down, and a force bar (6) that passes through the center of the shaft (5) are provided,
It is manufactured in the following manner using an apparatus provided with a support (7) for attaching the seed single crystal (8) to the lower end of the force bar (6). That is, a seed single crystal (8) is attached to a support (7), and a compound raw material is placed in a crucible (3), which is melted by heating and floats on top of the compound melt (9). A substance that prevents the evaporation of group V elements, such as boron oxide, is charged. Next, the inside of the pressure vessel (1) is filled with an inert gas at a pressure higher than the decomposition pressure at the melting point of the compound, such as N2, Δr.
, He, etc. to a pressure of 3 to 60 atmospheres, heat the compound with a heater (4), melt it, and place it on the compound melt (9) for liquid sealing (1).
After forming 0), the seed single crystal (8) is brought into contact with the compound melt in the same manner as in the usual pulling method, and pulled while being rotated to produce a pulled compound single crystal (11).

In the plan view, (12) indicates a heat insulating material, and (13) indicates a rotation shaft of a crucible holding table (2), and the rotation shaft (13) is used to rotate the crucible (3) as required.

It is known that defects (dislocations) in a single crystal obtained by such a compound single crystal production method depend on the temperature gradient at the solid-liquid interface of the single crystal during the pulling process. For example, it is known that when the temperature gradient in a liquid sealing bath is 100°C/cm or more, the dislocation density becomes tens of thousands/cm or more, and by setting the temperature gradient to 100°C/cm or less, defects can be reduced. can be expected. However, if you improve the temperature environment and reduce the temperature gradient in the liquid sealing bath to 100℃/cm or less, the thickness will decrease to 2.
The surface temperature for liquid sealing around 0 mm reaches 1100℃ or higher, and group V elements evaporate and dissipate from the surface of the seed single crystal and compound single crystal directly above liquid sealing due to thermal decomposition, and the seed single crystal gradually becomes thinner. During or after pulling, the compound single crystal cannot withstand the weight of the single crystal and breaks, making it impossible to pull it up.There is also the drawback that the pulled single crystal may fall. There was a drawback that group (Ⅰ) elements remained, causing defects such as twins.

In view of this, as a result of various studies, the present invention has found that thermal decomposition of the single crystal surface can be suppressed by providing a semi-closed space above the liquid sealing bath and creating a vapor atmosphere of group V elements, which are volatile elements. As a result of this knowledge and further investigation, we have developed a method and apparatus for producing compound single crystals that can be pulled into low-defect single crystals at low temperature gradients.

In the production method of the present invention, a compound melt is kept in a liquid seal in a crucible in a pressure vessel maintained at 3 to 60 atmospheres with an inert gas, and a seed single crystal attached to the lower end of a force bar of a rotating pulling shaft is placed in a pressure vessel with an inert gas pressure of 3 to 60 atmospheres. In the manufacturing method of single crystals, which are pulled from a surface while being rotated, a quartz lid with a tubular opening at the top through which a force bar is passed is attached to the crucible, the lower end of which is held in a liquid sealing bath, and the upper part of the lid is In addition to heating to a temperature of ~700°C, a saucer is provided in the lid to hold and evaporate volatile elements, creating a volatile element vapor atmosphere with a partial pressure of 7 Torr ~ 4 atm inside the lid, and reducing the temperature in the liquid sealed bath. gradient to 100℃
This method is characterized by pulling a single crystal with a thickness of less than / cm.

In addition, the device of the present invention holds the compound melt in a liquid seal in a crucible in a pressure vessel with an inert gas pressure of 3 to 60 atmospheres,
A quartz lid with a tubular opening at the top for passing the force bar over the crucible is used in single crystal production equipment in which a seed single crystal attached to the lower end of a force bar on a rotating pulling shaft is pulled from the compound melt surface while rotating. Attach the cap and hold its lower end in a liquid bath, install an auxiliary heater on the outside of the top of the lid, install a tray for volatile elements at the bottom of the force bar inside the lid to evaporate the volatile elements, and heat the inside of the lid to 7 Torr. It is characterized by a volatile element vapor atmosphere of ~4 atm.

That is, in the present invention, as shown in FIG.
A crucible holding stand (2) is placed in a pressure vessel (1) with a pressure of 60 atmospheres.
A crucible (3) is attached to the crucible, and a heater (
4), place the crucible (3) from the upper wall of the pressure vessel (1).
A pull-up @ (5) that rotates vertically inward and the shaft (5)
) with a force bar (6) passing through the center of the crucible (3) and a tubular opening (15) through which the force bar (6) passes.
) with 6 pieces Wlfi on the top? (14) and its lower end for sealing the compound melt (9) in the crucible (3) (
10) Hold inside. Made of quartz! The force bar inside (14) (6) has a support (7) for the seed single crystal (8) at the lower end!
A volatile element receptacle (16) is provided inside (14), and W(
14) Using a device equipped with an auxiliary heater on the outside of the upper part,
A compound single crystal is produced in the following manner.

In the plan view, (12) is the heat insulating material, (13) is the crucible (3
) to move up and down and rotate as necessary,
(18) is the arm that fixes the lid (14) to the insulation material (12), and (19) is! (14) Volatile elements condensed in (
20) is the Ji-emitting element held in the receiving booklet (16), (
21) Ha! (14) Thermal lightning pair that detects the temperature of the upper part, (2
2) is the observation window, <23) is the inert gas inlet, and (2) is the inert gas inlet.
4) indicates the inert gas outlet.

First, in the same manner as before, a seed single crystal is attached to the support at the lower end of the force bar, and the compound raw material is placed in the crucible 1-J1.The seed single crystal is melted by heating and floats on the compound melt, and V in the compound melt.
b' is charged with a substance that prevents the evaporation of elements, such as boron liquefied. Next, the inside of the pressure vessel is heated with inert gas for 3 to 6 hours.
The pressure was filled to 0 atm, and the temperature at the top of the lid was measured with a thermal lightning pair, and the crucible was heated to 400 to 700°C with an auxiliary heater, and the crucible was heated and melted with a heater to seal the compound, and the inside of the lid was heated to 7 T orr to 4 A volatile element vapor atmosphere with a partial pressure of atmospheric pressure is created, and if necessary, a volatile element is placed in advance in a volatile element receiver. In addition, the bottom end of the lid is always in the liquid sealing bath and does not touch the compound melt, so the thickness for the liquid sealing is made sufficiently thick, and if necessary, the rotating shaft of the crucible holder can be moved up and down or rotated. to prevent the bottom edge of the lid from coming into contact with the compound melt.

In this way, the temperature environment of the heater is adjusted, the temperature gradient in the liquid seal bath is controlled to 100°C or less, the single crystal at the lower end of the force bar is brought into contact with the compound melt, and the single crystal is pulled while rotating.
A single crystal of a compound is produced by this method.

According to the present invention, the upper part of the lid is heated to 400 to 700°C.
By heating to a temperature of This effectively suppresses thermal decomposition of seed single crystals and compound single crystals.

In addition, in the present invention, the pressure inside the lid is the partial pressure of volatile elements,
Consisting of an inert gas pressure, the escape of volatile elements occurs by diffusion through the tubular opening. In order to effectively prevent this, a fibrous barrier material (25) is interposed within the tubular opening (15) as shown in FIG. 17b
) To thirst K mu regular use? , 'Fl vs. (21a
), (21'b), and (21c) are provided, the outlet side of the tubular opening (15) is heated to a sufficiently high temperature to prevent volatile elements from condensing, and the lid side is heated with a heater (17) to generate steam. It is preferable to use it as an evaporation source to form an atmosphere so that it does not interfere with the operation of the force bar (6) and the measurement of crystal weight.

The present invention will now be described with reference to embodiments.

Using the apparatus shown in Figure 2, a pyrolytic BN crucible with a diameter of 100 mm was charged with 1.0009 g of gallium arsenide polycrystal and 2009 g of boron oxide for a liquid sealing bath, and when heated and melted, the lower end of the lid was on the surface of the liquid moon bath. Uke placed 59 ounces of arsenic in the dish so that it was 2 mm from the center. In this way, a seed single crystal is attached to the lower end of the force bar, argon gas is injected into the pressure vessel at 3 atm, and gallium arsenide and boron oxide are melted by heating with a heater. It was sealed with liquid. During this process, all the arsenic in the saucer was evaporated, and solid arsenic was evaporated into the low-temperature part below 620° C. in the upper part of the lid.

Next, while heating the upper part of the lid to 580'C with an auxiliary heater, the seed single crystal is rotated in the direction of the arrow and lowered into contact with the gallium arsenide melt. Now, we pulled a gallium arsenide single crystal. During this process, the arsenic adhering to the upper part of the lid started to evaporate, forming an atmosphere with an arsenic vapor partial pressure of 0.52 atm inside the lid. Assuming that the melting point of gallium arsenide is 1238°C, the temperature gradient in the boron oxide melt is 50°C/cm2, and the thickness of the boron oxide melt is approximately 16 mm, so the surface temperature is approximately 11 cm2.
It becomes 60℃. When a gallium arsenide single crystal was pulled under these conditions, thermal decomposition of the single crystal was completely suppressed.
Crystals with good metallic luster were obtained. In the same manner, a gallium arsenide single crystal was pulled up with a temperature gradient of 30° C./cm in the boron oxide solution. In this case as well, thermal decomposition of the single crystal surface exposed to high temperatures could be completely suppressed. Note that the crucible (9) was rotated in the direction of the arrow by the rotating shaft (13).

For comparison, a conventional device shown in Figure 1 was used to pull-F a gallium arsenide single crystal under similar conditions, but arsenic evaporated from the surface of the seed single crystal due to thermal decomposition and the seed single crystal broke. Arsenic evaporates from the surface of the single crystal obtained,
The remaining gallium invaded the interior, causing defects such as twins, making it impossible to obtain a high-quality single crystal.

Regarding the dislocation density of a gallium arsenide single crystal with a diameter of 40 #, a W-shaped valve cloth is observed in the conventional method, whereas no W-shaped valve cloth is observed in the method of the present invention, and the dislocation density distribution is 5000 pieces/dislocation density.
Less than ci, even a single crystal with a diameter of 55 mm can produce io, ooo pieces/
It was less than ci. Also, the concentration of silicone in the single crystal is 0.
．． It was confirmed that at 0.01 ppm or less, there was no problem of silicon contamination from the quartz lid. Furthermore, in the method of the present invention as well as in the conventional method, it was possible to control the crystal diameter while measuring the weight of the single crystal.

The above explanation is about the production of gallium arsenide single crystals, but it is not limited to this, and it is of course applicable to the production of single crystals of high dissociation pressure compounds such as indium arsenide, gallium phosphide, and indium phosphide. This method can also be applied to the case where a single crystal is synthesized from gallium and arsenic and then a single crystal is pulled.

As described above, according to the present invention, it is possible to prevent the evaporation of volatile elements due to thermal decomposition of the seed single crystal and compound single crystal in the single crystal pulling process, thereby reducing the breakage of the seed single crystal and the dislocation density of the compound single crystal. This has a remarkable industrial effect.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a conventional method for producing a single crystal of a compound, FIG. 2 is an explanatory diagram showing an example of a method for producing a single crystal of a compound of the present invention, and FIG. 3 is an explanatory diagram showing an example of a method for producing a single crystal of a compound of the present invention. It is an explanatory view showing the principal part in an example of the square. 1. Pressure vessel 2, crucible holding table 3, crucible 4, heater 5, pulling shaft 6, force bar 7, fixture 8, seed single crystal 9, compound melt 10, liquid sealing bath 11, compound mono Crystal 14, quartz lid 15, tubular opening 16, saucer 17, auxiliary heater 21, power coupler

Claims (2)

[Claims] (1) A high dissociation pressure compound melt is held in a liquid seal in a crucible in a pressure vessel with an inert gas atmosphere of 3 to 60 atmospheres,
In a single crystal production method in which a seed single crystal attached to the lower end of a force bar on a rotating pulling shaft is pulled from the compound melt surface while rotating, a quartz lid with a tubular opening at the top for passing a force bar over the crucible is used. Attach the lid and hold its lower end in a liquid bath, heat the upper part of the lid to a temperature of 400 to 700 degrees Celsius, and install a receiving curve inside the lid to retain and evaporate volatile elements. A volatile element vapor atmosphere with a partial pressure of 7 Torr to 4 atm, and a temperature gradient of 100°C in the liquid sealing bath.
1. A method for producing a single crystal of a high dissociation pressure compound, characterized by pulling the single crystal under a pressure of 1/cm I. (2) In a pressure vessel maintained at 3 to 60 atmospheres with inert gas, a crucible holds the high dissociation pressure compound melt in a liquid seal, and the seed single crystal attached to the lower end of the force bar of the rotating pull-up shaft is placed in the compound melt. In an apparatus for producing single crystals that is pulled while rotating on plane J, a quartz lid with a tubular opening at the top is attached to the crucible through which a force bar is passed, and the lower end of the lid is held in a liquid sealing bath. An auxiliary heater is installed on the outside of the lid.
A high dissociation pressure compound monomer, characterized in that a volatile element receiving tray is provided at the lower part of the force bar inside the lid to evaporate the volatile element, and the inside of the lid is made into a volatile element vapor atmosphere with a partial pressure of 7 TOrr to 4 atm. Crystal manufacturing and electrical manufacturing.