JPS6011298A - Method and device for producing compound single crystal with high dissociation pressure - Google Patents

Abstract

PURPOSE:To suppress thermal decomposition on the surface of a III-V group compd. single crystal and to prevent generation of a defect in production of 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 16 provided with a sealing tray 14d via a tubular part 15 at the top is fitted to the crucible 3 in a pressure vessel 1 and the inside of the vessel 1 is held at 2-60atm by an inert gas. The crucible 3 is heated by a heater 4 to melt the material charged preliminarily therein to form a gallium arsenide melt 9 and a liquid sealing bath 10 consisting of boron oxide. On the other hand, the upper part of the cover 16 and the tray 14 are heated to 400- 700 deg.C by auxiliary heaters 4a, 4b to form a liquid sealing bath 20 and at the same time the arsenic vapor atmosphere of 7Torr-4atm partial pressure is maintained in the sealing space in the cover 16. 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 6 (a symbol 8 is a seed crystal) of a pulling up shaft 5 according to the conventional method.

Description

Detailed Description of the Invention The present invention provides a method and apparatus for producing a single crystal of a high dissociation pressure compound (hereinafter abbreviated as compound) for semiconductors containing volatile components such as gallium arsenide, indium arsenide, gallium phosphide, and indium phosphide. In particular, it prevents the thermal decomposition of seed single crystals and compound single crystals during 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, a 5iOz or BN crucible (3) is installed, and a heater (4) is installed outside of it.
), and a pulling shaft (5) that rotates freely up and down from the upper wall of the pressure vessel (1) toward the inside of the crucible (3).
It is manufactured in the following manner using a device equipped with a force bar (6) passing through the center of the seed single crystal (6) and a support (7) for attaching the seed single crystal (8) to the lower end of the force bar (6). . That is, the seed single crystal (8) is attached to the support (7), the compound raw material and boron oxide for liquid sealing bath are charged into the crucible (2), and the inside of the pressure vessel (1) is filled with an inert gas such as NZ, A, etc.
The tank is filled with 3 to 60 atmospheres of pressure using He, etc., and the compound raw material and boron oxide are heated and melted using a heater (4), and the compound melt (9) is poured into a liquid sealing bath (10) made of boron oxide.
Seed single crystal (
8) is brought into contact with the compound melt (9) and pulled up while rotating to produce a compound single crystal (11).

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

It is known that defects (dislocations) in the 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 in the pulling process. For example, by setting the temperature gradient in the liquid sealing bath to 100°C/cm or less, a compound single crystal with low defects can be obtained. However, by improving the temperature environment, the temperature gradient in the liquid sealing bath can be reduced by 100%.
℃/cm or less, the surface temperature of the liquid sealing bath after 20 seconds of thickness will be 1100℃ or more, and the vFA element will evaporate and dissipate from the surface of the seed single crystal and compound single crystal directly above the liquid sealing bath due to thermal decomposition. The drawback is that the seed single crystal gradually becomes thinner and cannot withstand the weight of the compound single crystal during or after pulling and breaks, making pulling not only impossible but also causing an accident of the pulled single crystal falling. , and inside the pulled single crystal there is ■
This has the disadvantage that group elements remain, causing defects such as twins.

In view of this, as a result of various studies, the present invention has been developed by providing a sealed space above the liquid sealing bath of the crucible and creating a vapor atmosphere of Group Ⅰ elements, which are volatile elements, in the space to prevent thermal decomposition of the single crystal surface. As a result of further investigation, we developed a method and apparatus for producing compound single crystals that can pull low-defect single crystals using a low temperature gradient.

In the production method of the present invention, a compound melt is held in a crucible as a liquid seal with a boron oxide melt in a pressure vessel with an inert gas pressure of 2 to 60 atmospheres, and a seed single crystal is attached to the lower end of a force bar of a rotating shaft. In the production of compound single crystals that are pulled up from the surface of the compound melt, a quartz lid is attached to the crucible, its lower end is held in the liquid sealing bath inside the crucible, and a seal 1 is inserted through the force bar through the top of the lid. Form a tubular part at the upper end, charge the boron oxide melt into the seal (2) and seal it, heat the upper part of the lid and the sealing plate to a temperature of 400 to 700°C, and create a partial pressure inside the lid of 7 Torr to 4 atm. The method is characterized in that the compound single crystal is pulled in a volatile element vapor atmosphere with a temperature gradient of 100° C./cm or less in the liquid sealing bath.

In addition, the device of the present invention holds a compound melt in a crucible in a pressure vessel maintained at 2 to 60 atmospheres with an inert gas, and a seed single crystal attached to the lower end of a force bar of a rotating shaft. Compound melting point In a compound single crystal production device that is pulled from the liquid level, a quartz lid is attached to the crucible, its lower end is held in a liquid sealing bath inside the crucible, and a sealing plate is placed at the upper end, through which a force bar is passed through the top of the lid. forming a tubular part with a auxiliary heater on the top of the lid and outside of the sealing plate;
It is characterized in that boron oxide is melted and sealed in the sealing dish, and the inside of the lid is made into a volatile element vapor atmosphere with a partial pressure of 7 Torr to 4 atmospheres.

That is, as shown in FIG. 2, the present invention provides a graphite crucible holder (2) in a pressure vessel (1), attaches a crucible (3), and arranges a heater (4) outside of the crucible (3). A compound raw material and a liquid sealing bath (1) to form a compound melt (9) in
Charge boron oxide to form 0). Pressure vessel (1)
A pulling shaft (5) that rotates freely up and down toward the inside of the crucible (3) from the earthen wall, and a force bar (6) passing through the center of the shaft (5) are provided, and a force bar (6) is installed on the crucible (3). A tubular part (1) having a seal book (14) at one end through which a force bar (6) is passed.
5) Attach the quartz ￥ A lid <16) and
), install a support (7) at the lower end of the force bar (6), attach the seed single crystal (8), insert 1 to 100 g of volatile element into the lid (16), and! (16) Place the lower end in the crucible (3)
It is kept in a liquid sealing bath (10) inside.

j shown in this diagram: depth of sea urchin compound melt (9) [m
and 1(16), the lower end height tp is in the relationship tρ>tm, and as shown in FIG. 3, the depth b of the liquid sealing bath (10) at the end of pulling the compound single crystal (11)! (16) The amount of boron oxide and the height of the lower end of the lid (16) are determined so that the height 1p of the lower end satisfies the relationship tb>tp, and the lower end of M (16) is brought into contact with the compound melt (9). In addition to preventing s1 contamination, leakage of volatile element vapor from the lower end of 'ri (1G) is also prevented.

! To hold (16), as shown in the figure, a high-purity BN cylinder (17) whose upper end protrudes into the liquid sealing bath (10) from the surface of the compound melting point liquid (9) is installed in the crucible (3). Hold the lower end of the lid (16) or attach the arm (
18) to fix R1 (16). ! (16) and outside the sealing pan (14) are auxiliary heaters (4).
A), (4h) is placed, and a sea IIL, III (14) Inside Nicir bath (20> ヲ -shaped K "Jul Q9

After reducing the pressure inside the pressure vessel (1) through the trachea (23) in this way, inert gas is introduced through the gas introduction pipe (22) to bring the inside of the vessel (1) to 2 to 60 atmospheres, and the lid is closed. (16
) and the sealing plate (14) with the auxiliary heater (4a), (
4b)1. myosu 400~700℃ near J [I iQ
j. Melt the boron oxide in the seal book (14) to form a seal bath (20), and re-evaporate the volatile element (21) condensed on the upper part of ta (1G). Next, the crucible (3) is heated by the heater (4) to melt the compound raw material and boron oxide, and the compound melt'a (9) is heated in the liquid sealing bath (10).
) to liquid seal. At this time! The volatile element inserted in (16) evaporates, and! (16) Seal inside +111 (14)
2 to 6 introduced before the sealing bath (20) in
A volatile element vapor atmosphere with an inert gas of 0 atm and a partial pressure of 7 Torr to 4 atm is created, which prevents the evaporation of volatile elements from the compound melting point liquid (9), and also prevents the seed single crystal and the pulled compound single crystal ( 11), the temperature environment of the heater (4) is adjusted to control the humidity gradient in the liquid sealing bath (10) to 100°C/cm or less, and the seed unit at the lower end of the force bar (6) is A compound single crystal is produced by bringing the crystal (8) into contact with the surface of the compound melting point liquid (9) and pulling it up while rotating.

The sealing bath (20) in the sealing dish (14) is connected to the tubular part (15).
) and the force bar (6) by gravity, but in reality, the seal bath (20) made of boron oxide has a high viscosity, and the force bar (6) is
Since it is pulled at a speed of hr, it hardly flows down and a perfect sealing effect is obtained during pulling of the compound single crystal.

In the top view, (13) indicates a rotating shaft provided on the crucible holding table (2), which is used to rotate the crucible (3) as necessary. Further, (19) shows a weight sensor that detects the weight of crystals in the pulled compound.

The present invention will be explained below with reference to examples.

Using the apparatus shown in Figure 2, pyrolysis B with a diameter of 100 mm was used.
Using an N crucible, 1.000 (
] and 200g of boron oxide for liquid sealing, 500g of boron oxide for sealing bath in a seal book, a seed single crystal attached to the lower end of the force bar, and 5g of arsenic in the lid.
The lower end of the lid was inserted into the crucible, and the crucible was held in a liquid-sealed bath at a height of 2 mm higher than the level of the compound melt.

After reducing the pressure inside the pressure vessel in this way, argon gas was introduced to bring the pressure to 3 atmospheres, and the upper part of the lid and seal book were heated to 580°C using an auxiliary heater to melt the boron oxide in the seal pan and create a seal bath. Formed.

Next, the crucible was heated with a heater to melt the compound polycrystal and boron oxide, and the compound melt was liquid-sealed. At this time, all of the arsenic put into the lid evaporates and condenses on the upper part of the inner wall of the lid, where the partial pressure of arsenic vapor is 0.0, which corresponds to the temperature of the low temperature part of 580°C.
A pressure of 52 atmospheres was created.

Next, the seed single crystal was brought into contact with the surface of the gallium arsenide melt and pulled up. The melting point of gallium arsenide is 1238°C, and if the temperature gradient in the liquid sealing bath is 50°C/cm, the thickness of the liquid sealing bath is about 16# and its surface temperature is 1158°C. When a gallium arsenide single crystal was produced under these conditions, thermal decomposition of the seed single crystal and gallium arsenide single crystal was completely prevented, and a single crystal with metallic luster was obtained. Similarly, a gallium arsenide single crystal was produced with a temperature gradient of 30° C./mm in the liquid sealing bath.

In this case as well, thermal decomposition of the seed single crystal and gallium arsenide single crystal could be completely prevented.

For comparison, a gallium arsenide single crystal was produced using the conventional apparatus shown in FIG. 1 under similar conditions. As a result, arsenic evaporates from the surface of the seed single crystal due to thermal decomposition, causing the seed single crystal to break, or arsenic evaporates from the surface of the resulting single crystal, and the remaining gallium enters the interior, causing twin crystals and the like. defects occur,
High quality single crystals could not be obtained.

Note that the dislocation density of a gallium arsenide single crystal with a diameter of 40 mm shows a W-shaped distribution in the conventional method, whereas in the method of the present invention, no W-shaped distribution is observed at all, the dislocation density is less than 5000 pieces/cM, and the diameter is 55 mm. 10,000 single crystals of reward/
It was less than tri. Also, the silicon concentration in the single crystal is 0
．． It was confirmed that the O concentration was 1 ppm or less, and there was no problem of silicon contamination from the quartz lid. Furthermore, in the method of the present invention, the crystal diameter can be controlled while measuring the weight of the single crystal, similar to the conventional method.

Although we have explained the production of gallium arsenide single crystals above, the production is not limited to this, but includes indium arsenide, gallium phosphide,
It can also be applied to the production of single crystals of high dissociation pressure compounds such as indium phosphide.

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 the compound single crystal in the single crystal pulling process, and to reduce the breakage of the seed single crystal and the dislocation density of the compound single crystal. This has a significant industrial effect.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of a conventional compound single crystal production method, Fig. 2 is an explanatory diagram showing an example of the compound single crystal production method of the present invention, and Fig. 3 is a compound single crystal production method in the same production method. It is an explanatory view showing the end of pulling. 1, Pressure vessel 2, Crucible holder 3, Crucible 4, Heaters 4a, 4b, Auxiliary heater 5, Pull shaft 6, Force bar 7, Support 8, Seed single crystal 9, Compound melt 10, W system 11, Compound single crystal 14, Seal 15, Tubular part 16, Quartz lid 17, BN [Cylinder 20, Seal bath

Claims (2)

[Claims] (1) In a pressure vessel maintained at 2 to 60 atmospheres with an inert gas, the high dissociation pressure compound melt is held in a crucible by the boron oxide melt, and the seeds are attached to the lower end of the force bar of the rotating pulling shaft. In the production of compound single crystals in which the single crystal is pulled up from the surface of the compound melt, a quartz lid is attached to the crucible, its lower end is held in the liquid sealing bath inside the crucible, and a seal book is used to pass a force bar through the top of the lid. Form a tubular part having a molten boron oxide at the ten ends, charge the seal booklet with boron oxide melt, seal it, heat the upper part of the lid and the seal book to a temperature of 400 to 700°C, and heat the inside of the lid to a pressure of 7 Torr to 4 atm. A high-fi method characterized by pulling a compound single crystal in a volatile element vapor atmosphere with a partial pressure and with a temperature gradient of 100°C/cm or less in a liquid sealing bath.
! Method for producing decompression compound single crystals. (2) In a pressure vessel heated to 2 to 60 atmospheres with inert gas, the melt of the high dissociation pressure compound is held in a crucible by the boron oxide melt, and the seed unit is attached to the lower end of the force bar of the rotating pulling shaft. Is quartz placed on the crucible in the production of compound single crystals in which the crystal is pulled from the surface of the compound melt? jm is attached, its lower end is held in a liquid sealing bath in the crucible, a tubular part is formed at the upper end with a sealing plate through which a force bar is passed through the upper part of the lid, and an auxiliary seater is attached to the upper part of the lid and outside of the seal book. established,
An apparatus for producing a single crystal of a high dissociation pressure compound "A", which is characterized by melting and sealing boron oxide in a sealing dish and creating a volatile element vapor atmosphere with a partial pressure of 7 Torr to 4 atm inside the lid. ) A high dissociation pressure compound single crystal manufacturing apparatus according to claim 2, wherein a high purity BN cylinder protruding from the surface of the compound melt is provided in the crucible and the lower end of the lid is supported in the liquid 11 bath.