JPH07165489A - Production of compound semiconductor and production unit therefor - Google Patents

Abstract

PURPOSE:To provide a compound semiconductor designed to suppress the dissociation of volatile elements from crystal surface in order to prevent crystal surface from getting rough or prevent polycrystallization. CONSTITUTION:This production unit 10 for compound semiconductors has a crucible combination 18 made up of a crucible 14 and a susceptor 16 for holding this crucible and a heater 20 set up around the crucible combination to heat it. Besides, this production unit has a thermal shield section 30 to thermally shield the upper region in a pressure vessel 12 from the heater 20. The thermal shield section 30 extends above the heater in the transverse direction of the pressure vessel and has a thermally shielding plate 32 provided with an opening 34 with its inner diameter larger than the outer diameter of the crucible combination and a skirt-like opening sidewall 36 extending so as to downwardly enlarge the opening diameter from the opening edge of the thermally shielding plate. In pulling a single crystal, the crucible combination is pushed up into the opening of the opening sidewall of the thermal shield section, and the annular gap between the outer peripheral edge of the crucible combination and the opening sidewall of the thermal shield section is ensured to decrease as the pull length of the single crystal increases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a compound semiconductor by a pulling method and an apparatus for producing the compound semiconductor, and more specifically, to prevent surface roughness of a crystal surface and increase a single crystallization rate. The present invention also relates to a method of manufacturing a compound semiconductor by the pulling method and a manufacturing apparatus thereof.

[0002]

2. Description of the Related Art As an example of a method for producing a highly decomposable compound semiconductor crystal of GaAs, GaP, InP, etc., a liquid encapsulation method (Liquid Encapsulate) is used.
The d Czochralski method (hereinafter referred to as the LEC method) is known. Taking the production of GaAs semiconductor as an example, this L
The EC method will be described. In this method, an apparatus having a crucible and a heater arranged around the crucible in a pressure vessel is used,
Ga and As as raw materials and, for example, B ₂ O ₃ as a sealant are put into the crucible and heated by a heater to form a GaAs melt layer and a sealant melt layer, and the GaAs melt layer is sealed. It is covered with a stopper layer. On the other hand, a pressure greater than the dissociation pressure of the raw material components is applied to the GaAs melt by the inert gas such as Ar or N ₂ filled in the pressure vessel to suppress the decomposition of the raw GaAs. Then, Ga is added to the melt in the crucible.
By contacting an As seed crystal and gradually pulling this seed crystal, a GaAs single crystal is grown continuously to the seed crystal.

[0003]

By the way, the LE described above is used.
When a GaAs single crystal is manufactured by the C method, a polycrystal is generated from the middle portion in the vertical direction of the grown crystal to the tail portion, and from the outer peripheral portion to the inner side, which deteriorates the quality and yield of the GaAs single crystal. Was a problem. The following two factors can be considered as the causes of such polycrystal formation.
One is a phenomenon in which the solid-liquid interface shape between the single crystal in the crucible and the melt becomes concave toward the liquid side, thermal stress concentrates there, dislocations occur, and that portion becomes polycrystalline. The second is that when the crystal is pulled up and comes out of the sealant into an inert gas atmosphere, As on the crystal surface dissociates to cause surface roughness, and the remaining Ga propagates along the surface to form a solid-liquid interface. It is a phenomenon that it becomes a polycrystal when it flows down.

First, regarding the first cause, the operating conditions such as the pulling rate of the single crystal, the pressure in the pressure vessel, the crystal rotation speed, the rotation speed of the crucible, etc. are devised, or the position of the crucible and the constitution of the hot zone For example, the device is devised, and the heat generation amount of the heater is controlled more strictly so that the solid-liquid interface shape is not recessed toward the melt side, and thus precise control is performed. However, various proposals have been made for the second cause, As dissociation from the crystal surface,
Attempts have also been made, but the current situation is that they have not achieved satisfactory results.

In view of the above circumstances, an object of the present invention is to provide a compound semiconductor in which dissociation of volatile elements from the crystal surface is suppressed in order to prevent crystal surface roughness or polycrystallization. A manufacturing method and a manufacturing apparatus are provided.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have investigated the dissociation phenomenon of As in search of a means for suppressing the dissociation phenomenon of As from a volatile element such as a GaAs crystal from the crystal surface. By the way, the heat conduction model in the vicinity of the solid-liquid interface is expressed by the one-dimensional continuous equation of heat as shown in the following equation.
As shown in 1. KmGm + Lvd = KsGs where Km: thermal conductivity of melt Ks: thermal conductivity of crystal Gm: temperature gradient of melt Gs: temperature gradient of crystal L: latent heat of crystallization of melt v: growth rate of crystal d: Melt density

A thermal analysis near the solid-liquid interface was carried out based on the above equation. Assuming that the temperature of the pulled crystal does not decrease, the length of the pulled crystal becomes longer and the temperature gradient in the crystal increases. It was found that Gs gradually decreased. The smaller temperature gradient Gs in the crystal means that the surface temperature T _i of the sealant layer (see FIG. 11) rises and approaches the interface temperature T _m between the melt layer and the sealant layer. Means that. When the length of the pulled-up crystal becomes longer and the surface temperature T _i of the encapsulant layer rises, the surface temperature of the crystal at the place of leaving the encapsulant layer also rises, and As is dissociated from the crystal surface. , The crystal surface causes surface roughness,
Polycrystal. Therefore, in order to prevent the dissociation phenomenon of the volatile element, it is important to suppress an increase in the surface temperature of the pulled crystal, and thus an increase in the surface temperature of the encapsulant layer.

However, in the conventional manufacturing apparatus, since there is a gap between the heater and the crucible combination, the high temperature inert gas in the heater heating region passes between the crucible and the heater due to the convection phenomenon, and the pressure vessel is heated. Flows into the upper region (crystal growth region). Therefore, it has been found that the surface temperature of the sealant layer is significantly affected by the high temperature inert gas, and the temperature rise cannot be suppressed. Therefore, a means for suppressing the convection of the inert gas according to the pulling of the crystal is provided,
By reducing the flow rate of the convective inert gas, the surface temperature of the encapsulant layer, and thus the rise of the surface temperature of the crystal is suppressed,
I focused on lowering it.

In order to achieve the above-mentioned object, the method of manufacturing a compound semiconductor according to the present invention is based on the above findings.
Using a device provided with a crucible combination consisting of a crucible and a crucible susceptor for holding the crucible, and a heater arranged around the crucible combination in a pressure vessel, the pressure vessel filled with pressure In an active gas, in a method for producing a compound semiconductor in which a single crystal grown from a melt of a compound semiconductor in a crucible is pulled up continuously to a seed crystal, a crucible combination according to an increase in the pulling length of the crystal By reducing the size of the gap between the heater and the heater, the flow rate of the inert gas that passes through the gap between the crucible combination and the heater and rises to the upper region in the pressure vessel is reduced according to the pulling length of the crystal. The feature is that it is made to.

In the compound semiconductor manufacturing apparatus according to the present invention, a crucible assembly comprising a crucible for containing a compound semiconductor melt and a crucible susceptor for holding the crucible in a pressure vessel, and a crucible assembly. Is equipped with a heater for heating the melt in the crucible, and is arranged to pull up the single crystal grown from the melt continuously to the seed crystal under the pressurized inert gas filled in the pressure vessel. In the manufacturing apparatus of the compound semiconductor described above, in order to thermally shield the upper region in the pressure vessel from the heater, it extends above the heater in the transverse direction of the pressure vessel,
And a heat shield having a heat shield plate having an opening whose diameter is slightly larger than the outer diameter of the crucible assembly, and an opening side wall extending downward from the opening edge of the heat shield plate so that the opening diameter expands downward. The opening side wall of the crucible combination is arranged substantially concentric with the crucible combination, and when pulling the single crystal, the crucible combination is pushed up into the opening of the side wall of the opening of the heat shield part so that It is characterized in that the size of the annular gap between the outer peripheral edge of the crucible assembly and the side wall of the opening of the heat shield is reduced in accordance with the increase in the pulling length.

Further, another semiconductor device manufacturing apparatus according to the present invention is a crucible combination comprising a crucible for containing a melt of a compound semiconductor and a crucible susceptor for holding the crucible in a pressure vessel, and the crucible. Equipped with a heater for heating the melt in the crucible, which is arranged around the combination, and pulls the single crystal grown from the melt continuously to the seed crystal under the pressurized inert gas filled in the pressure vessel. In the compound semiconductor manufacturing apparatus as described above, in order to thermally shield the upper region in the pressure vessel from the heater, the diameter extends above the heater in the transverse direction of the pressure vessel and is slightly larger than the outer diameter of the crucible assembly. A heat shield having an opening and a side wall of an opening extending downward from the opening edge of the heat shield so that the opening diameter increases, and the heat shield is further freely lowered. The side wall of the opening is a crucible assembly The pulling length of the crystal is set to be almost concentric with the body, and when pulling the single crystal, the heat shield is lowered and the crucible combination is put into the opening of the side wall of the opening of the heat shield. As the size increases,
It is characterized in that the size of the annular gap between the outer peripheral edge of the crucible assembly and the side wall of the opening of the heat shield is made small.

The present invention can be suitably applied to a compound semiconductor manufacturing apparatus and manufacturing method by the pulling method, and particularly to a compound semiconductor manufacturing apparatus and manufacturing method by the LEC method. The type of compound semiconductor to which the present invention can be applied is not particularly limited, and Group III-V such as GaAs, GaP and InP can be used.
Group compound semiconductors and CdS, CdSe, CdT
It can be applied to the production of compound semiconductors of group II-VI elements such as e. The heat shield used in the present invention is formed of a metal plate such as a stainless steel plate or a carbon member plate. The opening diameter of the upper end of the side wall of the opening is set to be slightly larger than the outer diameter of the crucible assembly so as not to hinder the up-and-down movement of the crucible assembly in the opening. For example, diameter 10
For a crucible combination having an outer diameter of 230 mm adapted to pull up an 8 mm single crystal, the opening diameter is made 2 mm larger than the outer diameter of the crucible combination. Also, the opening diameter at the lower end of the opening side wall is
The height of the side wall should be 250 mm and the height of the side wall should be 60 mm.

The size of the annular gap between the outer peripheral edge of the crucible assembly and the side wall of the opening of the heat shield is reduced in accordance with the increase in the crystal pulling length over the entire length of the crystal pulling length. It is not necessary, and the size of the annular gap may be reduced within a specific pull-up length range. For example, when pulling a single crystal having a length of 300 mm, the pulling length of the crystal is from 0 mm, or an extremely short length, for example, a few
Make the size of the annular gap smaller depending on the pulling length from mm to 10 cm to 20 cm, and make the size of the annular gap constant for longer pulling lengths. . Further, there is no particular limitation on the ratio of the size of the annular gap to the increase of the pulling length, and for example, the width of the annular gap may be linearly reduced to the increase of the pulling length. It may be good, or it may be made non-linearly small.

[0014]

According to the invention of claim 1, a heat shield having a skirt-shaped opening side wall whose opening diameter expands downward is provided, and the crucible assembly is raised in accordance with an increase in the pulling length of the crystal, When preventing the liquid level of the melt from decreasing due to the decrease in the amount of melt in the crucible, by pushing up the crucible combination into the opening of the opening side wall, the outer peripheral upper edge of the crucible combination and the opening side wall are The size of the gap is gradually reduced as the pulling length of the crystal increases. As a result, the flow rate of the ascending flow of high-temperature inert gas from the heater heating region to the crystal growth region is gradually reduced, and the surface temperature of the encapsulant layer and the crystal surface temperature are suppressed from increasing and decrease.

According to the second aspect of the present invention, a heat shield portion having a skirt-shaped opening side wall whose opening diameter expands downward and freely descending is provided, and when pulling a single crystal, By lowering the heat shield part and inserting the crucible combination into the opening of the opening side wall, between the outer peripheral edge part of the crucible combination and the opening side wall of the heat shield part according to the increase of the pulling length of the crystal. The size of the annular gap is reduced. As a result, the flow rate of the ascending flow of high-temperature inert gas from the heater heating region to the crystal growth region is gradually reduced, and the surface temperature of the encapsulant layer and the crystal surface temperature are suppressed from increasing and decrease.

According to the third aspect of the present invention, the size of the gap between the crucible combination and the heater is reduced with respect to the increase in the pulling length of the crystal, so that the pressure is passed through the gap between the crucible combination and the heater. The flow rate of the inert gas rising to the upper region in the container is decreased according to the pulling length of the crystal. Since the flow rate of the high temperature inert gas ascending flow from the heater heating region to the crystal growth region decreases in accordance with the increase in the crystal pulling length, the increase in the sealant surface temperature and the crystal surface temperature is suppressed. ,descend.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in more detail based on embodiments with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of an embodiment of a manufacturing apparatus for a compound semiconductor according to the present invention, and FIG. 2A is an enlarged cross-sectional side view of a main part of the manufacturing apparatus shown in FIG. 1, and FIG. FIG. 3 is a sectional view taken along the line I-I ′ of FIG. As shown in FIG. 1, a compound semiconductor manufacturing apparatus (hereinafter abbreviated as a manufacturing apparatus) 10 of the present embodiment includes a pressure container 12 for pressurizing and filling an inert gas, and a vertical container for containing a raw material of a compound semiconductor. By combining the mold crucible 14 and the crucible susceptor 16 that holds the crucible 14 at its bottom and outer periphery,
The pressure vessel 12 is provided with a crucible combination body 18 and a cylindrical heater 20 arranged around the crucible combination body 18 to heat the raw material in the crucible 14.

Further, the manufacturing apparatus 10 is provided with a drive mechanism for rotating the crucible assembly 18 and moving it up and down. The drive mechanism has an upper end fixed to the bottom of the crucible assembly 18 and a lower shaft 22 extending through the bottom of the pressure vessel 12,
It is composed of a drive device (not shown) that rotates the lower shaft 22 and moves it up and down. A high-pressure seal 24 is provided at the bottom shaft penetrating portion of the bottom of the pressure container 12 to slidably seal the lower shaft 22 with respect to the pressure container 12.

Further, the manufacturing apparatus 10 is provided with a crystal pulling mechanism for pulling a crystal above the crucible 14. The crystal pulling mechanism has a lower end located above the crucible 14 and an upper shaft shaft 26 extending upward from there through the top plate of the pressure vessel 12 and the upper shaft shaft 26 for rotating, elevating, and rotating. And a drive device (not shown) for moving up and down. A high-pressure seal 28 is provided in the upper shaft shaft penetrating portion of the top plate of the pressure container 12 to slidably seal the upper shaft shaft 26 with respect to the pressure container 12.

On the upper part of the heater 20, 000 is provided in order to thermally shield the crystal growth region in the pressure vessel 12 from the heater 20.
A heat shield 30 made of metal is provided. The heat shield 30 is shown in FIG.
As shown in (a) and (b), a heat shield plate 32 and a skirt-shaped opening side wall 36 extending downward from an opening 34 provided at the center of the heat shield plate 32 are provided. . The heat shield plate 32 is an annular plate member that extends inward from the cylindrical wall of the pressure vessel 12 and covers the upper portion of the cylindrical heater 20, and the opening 34 provided in the center thereof is the crucible assembly 1
8 is slightly larger than the outer diameter of the crucible assembly 18
A gap S is formed with respect to the outer peripheral upper edge 52 of. The skirt-shaped opening side wall 36 extends in a skirt shape so that the opening diameter is concentrically expanded while forming an opening in the center downward from the peripheral edge of the opening 34 of the heat shield plate 32, The axis is arranged so as to be concentric with the axis of the crucible combination body 18.

In FIG. 1, reference numeral 38 is a supporting portion for supporting the heater 20, 40 is a heat insulating cylinder provided so as to surround the heater 20, and 42 is a heat insulating plate provided on the bottoms of the crucible assembly 18 and the heater 20. Is. Support part 38 of heater 20
Are pierced through the heat insulating plate 42 and supported by the bottom portion of the pressure vessel 12.

A gas supply pipe 44 and a gas discharge pipe 46 are connected to the pressure vessel 12 for introducing and discharging an inert gas, and respectively connect the bottom of the pressure vessel 12 and the heat insulating plate 42. It communicates with the space between. Also, pressure gauge 4
8 is provided in the pressure vessel 12, measures the pressure of the upper region in the pressure vessel 12, and the thermocouple 50 provided in the crucible combination 18 measures the temperature of the crucible bottom. In another embodiment, instead of pushing up the crucible assembly 18, the heat shield 30 is lowered. In FIG. 1, reference numeral 52 is an elevating shaft for moving the heat shield 30 up and down, which is used in this other embodiment.

Next, a method of manufacturing a compound semiconductor using the above-described manufacturing apparatus 10 will be described with reference to FIG. Crucible 14 filled with raw materials of a target compound semiconductor crystal, for example, Ga and As, and a sealant, for example, B ₂ O _3.
Are placed in the pressure vessel 12. Then, an inert gas such as Ar gas or N ₂ gas is introduced into the pressure vessel 12, the inside of the pressure vessel 12 is replaced with the inert gas, and the pressure is further increased. The heater 20 heats the crucible combination 18 to melt the raw material and the sealant. When each melts, the raw material melt layer A and the sealant layer B are formed thereon, and the raw material melt layer A becomes the sealant layer B.
Covered with. The seed crystal C is attached to the lower end of the upper shaft 26, and then the upper shaft 26 is lowered to cause the seed crystal C to penetrate the sealant layer B and contact the surface of the raw material melt layer A. Then, the upper shaft 26 is pulled while rotating to grow the single crystal D continuously with the seed crystal C. On the other hand, in accordance with the growth of the single crystal D, the raw material melt layer A
In order to maintain the height of the liquid surface at a predetermined position, the crucible assembly 18 is rotated through the lower shaft 22 and pushed up into the opening 34 of the opening side wall 36 of the heat shield 30.

When pushing up the crucible combination 18, the distance S (see FIG. 2) between the outer peripheral upper edge 52 of the crucible combination 18 and the side wall 36 of the opening of the heat shield 30 is equal to the pulling length of the single crystal D. It decreases as it increases. To explain further, FIG.
(A), (b) and (c) respectively show the heat shield 30 and the crucible combination 18 when the pulling length of the single crystal is 0, or extremely short, slightly long, and further long.
Shows the relationship with. S ₂ shown in FIG. 3B is the same as that shown in FIG.
₃ is smaller than the space S ₁ shown in FIG. 3C, and S ₃ shown in FIG. 3C is smaller than the space S ₂ shown in FIG. By reducing the size of the interval S in accordance with the increase in the pulling length of the single crystal D, the flow of the high temperature inert gas passing through the interval S and rising to the upper region of the pressure vessel 12 by convection is suppressed. Therefore, the thermal influence of the high temperature inert gas on the sealant layer B and the single crystal D is reduced. Therefore, the surface temperature of the sealant layer B, that is, the surface temperature of the single crystal D is lowered, so that the surface roughness of the single crystal D is suppressed and the single crystallization rate is improved.

A GaAs single crystal was manufactured by the above-described method using the manufacturing apparatus 10 having the above-described structure, and the quality of the obtained single crystal was evaluated. Test Example 1 In the manufacturing apparatus 10 described above, the horizontal interval S ₁ (see FIG. 3A) between the outer peripheral upper edge 52 of the crucible assembly 18 and the lower end of the opening side wall 36 of the heat shield 30 was 10 mm, and the crucible was The outer peripheral upper edge 52 of the combined body 18 and the opening side wall 36 of the heat shield 30.
The shape of the opening side wall 36 was set so that the horizontal spacing S ₃ (see FIG. 3C) from the upper end of the opening was 1 mm. The outer peripheral upper edge 52 of the crucible assembly 18 had a diameter of 230 mm. 1500 g of B as a sealant is placed in the crucible 14.
₂ O ₃ and Ga and As as compound semiconductor raw materials
However, a total of 15 kg was charged so that the composition would be a little excessive. Inert gas (Ar or nitrogen, etc.) in the pressure vessel 12
Was sealed, heated with a heater 20 while maintaining a pressure of 70 atm, and GaAs was synthesized and melted to form a GaAs melt layer A. At this time, the surface of the GaAs melt layer A was covered with the sealant layer B. Then, the pressure in the pressure vessel 12 is increased to 2
After the pressure is reduced to 0 atm, the seed crystal C is lowered and brought into contact with the GaAs melt layer A, and then the crucible assembly 18 is attached to the heat shield portion 30.
While pushing up into the opening 34 of the side wall 36 of the opening, the seed crystal C was pulled up to grow the single crystal D, and finally a single crystal having a diameter of 108 mm and a length of 300 mm was obtained as a test example product 1.

When the crucible assembly 18 is raised, the outer peripheral upper edge 52 of the crucible assembly 18 and the side wall 3 of the opening of the heat shield 30.
The distance S from 6 is maintained to maintain the relationship shown in FIG. 4 with respect to the crystal length L. That is, the interval S is such that the crystal length L is 0.
It is 10 mm between mm and 10 mm, and the crystal length L is 10 mm.
To 20 cm, as the crystal length L of the single crystal D increases, it decreases linearly, and the crystal length L is 20 cm.
Above is 1 mm. If the crystal length L is between 0 and 10 mm,
The interval S is constant because the crucible assembly 18 is not pushed up at the same time as the pulling of the single crystal.
The same applies to the following test examples. Thereby, the heat shield 3
The flow rate of the inert gas flowing through the annular gap between the opening side wall 36 of 0 and the crucible combination 18 to the upper region in the pressure vessel 12 decreases in accordance with the increase of the pulling length of the crystal, and as a result, , The thermal effect of the inert gas is reduced. This is clear from FIG. 5 which shows the relationship between the space S and the surface temperature T of the sealant layer, and the surface temperature T of the sealant decreases as the space S becomes smaller. Therefore, the surface temperature of the encapsulant layer decreases as the crystal grows, and the crystal surface temperature decreases. The surface of the single crystal of the obtained test example product 1 was observed and the single crystallization rate was measured. As a result, as shown in Table 1, no polycrystallization due to As dissociation, that is, surface roughness was observed, and the single crystallization rate was 1.
It was 00%.

[Table 1]

Test Example 2 When raising the crucible combination 18, the space S between the outer peripheral upper edge 52 of the crucible combination 18 and the opening side wall 36 of the heat shield 30.
However, except that the relationship shown in FIG. 6 is maintained with respect to the crystal length L, that is, the interval S is 10 mm when the crystal length L is between 0 mm and 10 mm, and the crystal length L is 10 mm. From 10 cm to 10 cm, the linear length of the single crystal D becomes smaller as the crystal length L becomes longer, and when the crystal length L is 10 cm or more, it becomes 1 mm, except that the crucible assembly 18 is raised. A single crystal having a diameter of 108 mm and a length of 300 mm was obtained as Test Example Product 2 in the same manner as in Test Example 1. The relationship between the space S and the temperature of the sealant layer B was as shown in FIG. 5, as in Test Example 1. The surface of the single crystal of the obtained test example product 2 was observed and the single crystallization rate was measured. As a result, as shown in Table 1, no polycrystallization due to As dissociation, that is, surface roughness was observed, and the single crystallization rate was 100%.

Test Example 3 In the manufacturing apparatus 10 described above, the horizontal distance S ₁ (see FIG. 3A) between the upper peripheral edge 52 of the crucible assembly 18 and the lower end of the side wall 36 of the opening of the heat shield 30 is 5 mm. And crucible union 1
The shape of the opening side wall 36 was set so that the horizontal interval S ₃ (see FIG. 3C) between the outer peripheral upper edge 52 of 8 and the upper end of the opening side wall 36 of the heat shield 30 was 1 mm.

When the crucible assembly 18 is raised, the upper peripheral edge 52 of the crucible assembly 18 and the side wall 3 of the opening of the heat shield 30.
6, except that the distance S between the crystal length L and the crystal length L maintains the relationship shown in FIG. 7, that is, the distance S is 5 mm when the crystal length L is between 0 mm and 10 mm. Raise the crucible assembly 18 so that the crystal length L of the single crystal D decreases linearly as the crystal length L increases in the range of the length L from 10 mm to 20 cm, and becomes 1 mm when the crystal length L is 20 cm or more. A diameter of 10 was obtained in the same manner as in Test Example 1 except that
A single crystal having a length of 8 mm and a length of 300 mm was obtained as a test example product 3.
The relationship between the space S and the temperature of the sealant layer B was as shown in FIG. 5, as in Test Example 1. The surface of the single crystal of the obtained test example product 3 was observed and the single crystallization rate was measured. The result is
As shown in Table 1, no polycrystallization due to As dissociation, that is, surface roughness was observed, and the single crystallization rate was 100%.

Test Example 4 In the manufacturing apparatus 10 described above, the horizontal interval S ₁ (see FIG. 3 (a)) between the outer peripheral upper edge 52 of the crucible assembly 18 and the lower end of the opening side wall 36 of the heat shield 30 is 5 0.5 mm, the outer peripheral upper edge 52 of the crucible assembly 18 and the opening side wall 3 of the heat shield 30.
The shape of the opening side wall 36 was set so that the horizontal distance S ₃ (see FIG. 3C) from the upper end of 6 was 1 mm.

When the crucible assembly 18 is raised, the outer peripheral upper edge 52 of the crucible assembly 18 and the opening side wall 3 of the heat shield portion 30.
8 except that the distance S with respect to the crystal length L maintains the relationship shown in FIG. 8 with respect to the crystal length L, that is, the distance S is 5.5 mm when the crystal length L is 0 cm. The crucible assembly 18 was raised so that the crystal length L of the single crystal D became linearly smaller in the range of L from 0 cm to 20 cm and became 1 mm when the crystal length L was 20 cm or more. A single crystal having a diameter of 108 mm and a length of 300 mm was obtained as Test Example product 4 in the same manner as in Test Example 1 except for. The relationship between the space S and the temperature of the sealant layer B was as shown in FIG. 5, as in Test Example 1. The surface of the single crystal of the obtained test example product 4 was observed and the single crystallization rate was measured. As a result, as shown in Table 1, no polycrystallization due to As dissociation, that is, surface roughness was observed, and the single crystallization rate was 100%.

Comparative Example 1 As shown in FIG. 9, the above-mentioned skirt-shaped opening side wall 3 is formed.
The heat shield 30 without 6 was provided in the pressure vessel so that the gap S between the edge of the opening 32 of the heat shield 30 and the crucible assembly 18 was 10 mm. Then, the distance S between the outer peripheral upper edge 52 of the crucible assembly 18 and the opening edge of the heat shield 30 was maintained at 10 mm regardless of the crystal length L, that is, FIG.
0 in the same manner as in Test Example 1 except that the crucible assembly 18 was raised in the relationship shown in FIG.
Was obtained as Test Example Product 4. The surface of the obtained single crystal of Comparative Example product 1 was observed and the single crystallization rate was measured. As a result, as shown in Table 1, polycrystallization due to As dissociation, that is, surface roughness was observed, and the single crystallization rate was 40%.

Table 1 compares the presence or absence of surface roughness due to As dissociation and the single crystallization rate of the GaAs crystals obtained in Test Examples 1, 2, 3 and 4 and Comparative Example 1. From this table, it can be seen that according to the present invention, the surface roughness was prevented and the single crystallization rate was improved.

Although the method of the present invention is applied to the LEC method as an example, the present invention is also applicable to a pulling method which does not use a sealant. Further, as compound semiconductors to be manufactured, group III-V other than GaAs, Cd
It may be a group II-group IV compound semiconductor such as S, CdSe, or CdTe. In addition, in the above-described embodiment, the heat shield portion 30.
Although the annular gap between the heat shield 30 and the crucible combination 18 is reduced by fixing the above and pushing up the crucible combination 18, the lowering device (not shown) for lowering the heat shield 30 is provided. When the single crystal is pulled up, the heat shield 30 is lowered to put the crucible combination 18 into the opening 34 of the opening side wall 36 of the heat shield, and the outer peripheral upper edge 52 of the crucible combination 18 and the heat shield. The annular gap between the opening side wall 18 of 30 may decrease with an increase in the pulling length of the single crystal D.

[0035]

According to the invention described in claims 1 and 2,
By making the size of the annular gap between the heat shield and the crucible combination smaller according to the crystal pulling length, the crystal pulling length increases and the crystal growth from the heater heating region. To realize a compound semiconductor manufacturing device with a simple and economical structure that can gradually reduce the flow rate of the high temperature inert gas upflow to the region and lower the encapsulant surface temperature, and thus the crystal surface temperature. ing. By using this manufacturing apparatus, the surface temperature of the crystal during pulling is effectively lowered, so that polycrystallization due to dissociation of volatile components from the surface of the crystal can be prevented and the single crystallization rate can be reduced. Can be greatly improved.

According to the third aspect of the present invention, the flow rate of the high temperature inert gas passing through the gap between the crucible assembly and the heater and rising to the upper region in the pressure vessel depends on the pulling length of the crystal. The method for producing a compound semiconductor is capable of lowering the surface temperature of the encapsulant, and thus the surface temperature of the crystal, by realizing a simple and economical means. By using the method of the present invention, the surface temperature of the crystal during pulling is effectively lowered, so that polycrystallization due to dissociation of volatile components from the surface of the crystal can be prevented and the single crystallization rate can be reduced. Can be greatly improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional side view of a compound semiconductor manufacturing apparatus.

2 (a) is a schematic enlarged sectional side view of a main part of the compound semiconductor manufacturing apparatus of FIG. 1, and FIG. 2 (b) is FIG. 2 (a).
FIG. 11 is a sectional view taken along line I-I ′ of FIG.

3 (a), (b) and (c) show the position of the crucible combination and the distance S between the side wall of the opening of the heat shield and the outer peripheral upper edge of the crucible combination in the present invention. It is a graph which shows the relationship of.

FIG. 4 is a graph showing a relationship between a crystal pulling length L and a distance S between an opening side wall of the heat shield and an outer peripheral upper edge of the crucible combination in Test Example 1.

FIG. 5 is a graph showing the relationship between the temperature of the surface of the sealant layer and the distance S between the side wall of the opening of the heat shield and the outer peripheral upper edge of the crucible combination.

FIG. 6 is a graph showing the relationship between the crystal pulling length L and the distance S between the side wall of the opening of the heat shield and the outer peripheral upper edge of the crucible combination in Test Example 2.

FIG. 7 is a graph showing a relationship between a crystal pulling length L and a space S between an opening side wall of the heat shield and an outer peripheral upper edge of the crucible combination in Test Example 3.

FIG. 8 is a graph showing a relationship between a crystal pulling length L and a space S between an opening side wall of the heat shield and an outer peripheral upper edge of the crucible combination in Test Example 4.

FIG. 9 is a schematic diagram showing a positional relationship between a heat shield and a crucible combination in Comparative Example 1.

FIG. 10 is a crystal pulling length L in Comparative Example 1, a space S between the side wall of the opening of the heat shield and the outer peripheral upper edge of the crucible combination.
It is a graph which shows the relationship with.

FIG. 11 is a model showing a temperature distribution at a solid-liquid interface in a crucible.

[Explanation of symbols]

 10 Example of Compound Semiconductor Manufacturing Apparatus According to the Present Invention 12 Pressure Vessel 14 Crucible 16 Crucible Susceptor 18 Crucible Combination 20 Heater 22 Lower Shaft 24 High Pressure Seal 26 Upper Shaft 28 High Pressure Seal 30 Heat Shield 32 Open 34 Heat Shield Plate 36 Opening Side Wall 38 Heater Support 40 Heat Insulation Cylinder 42 Heat Insulation Plate 44 Gas Supply Pipe 46 Gas Discharge Pipe 48 Pressure Gauge 50 Thermocouple 52 Heat Shield Lifting Axis

Claims (3)

[Claims] 1. A pressure vessel (12), a crucible assembly (18) comprising a crucible (14) and a crucible susceptor (16) for holding the crucible, and a heater arranged around the crucible assembly. A single crystal grown from the melt of the compound semiconductor in the crucible is pulled up continuously from the seed crystal under the pressurized inert gas filled in the pressure vessel by using the apparatus including (20). In the method for producing a compound semiconductor, by reducing the size of the gap between the crucible combination and the heater in accordance with the increase in the pulling length of the crystal, the gap between the crucible combination and the heater is passed and A method for producing a compound semiconductor, wherein the flow rate of an inert gas rising to the upper region is decreased according to the pulling length of the crystal. 2. A crucible assembly (18) comprising a crucible (14) and a crucible susceptor (16) for holding the crucible in a pressure vessel (12), and a heater arranged around the crucible assembly. (20), and a compound semiconductor manufacturing apparatus for pulling a single crystal grown from a compound semiconductor melt in a crucible in succession to a seed crystal under a pressurized inert gas filled in a pressure vessel In order to shield the upper area of the pressure vessel from the heater,
A heat shield plate (32) extending above the heater in the transverse direction of the pressure vessel and having an opening (34) having a diameter slightly larger than the outer diameter of the crucible assembly, and a heat shield plate (32) facing downward from the opening edge of the heat shield plate. Side wall (3) that extends so that the opening diameter increases.
6) is provided with a heat shield part (30) having an opening side wall substantially concentric with the crucible combination, and when pulling the single crystal, the heat shield part (30) is placed inside the opening of the heat shield part side wall. By pushing up the crucible combination, the size of the annular gap between the outer peripheral edge of the crucible combination and the side wall of the opening of the heat shield is reduced in accordance with the increase in the pulling length of the crystal. Characteristic compound semiconductor manufacturing equipment. 3. A crucible assembly (18) comprising a crucible (14) and a crucible susceptor (16) for holding the crucible in a pressure vessel (12), and a heater arranged around the crucible assembly. (20), and a compound semiconductor manufacturing apparatus for pulling a single crystal grown from a compound semiconductor melt in a crucible in succession to a seed crystal under a pressurized inert gas filled in a pressure vessel In order to shield the upper area of the pressure vessel from the heater,
A heat shield plate (32) extending above the heater in the transverse direction of the pressure vessel and having an opening (34) having a diameter slightly larger than the outer diameter of the crucible assembly, and a heat shield plate (32) facing downward from the opening edge of the heat shield plate. Side wall (3) that extends so that the opening diameter increases.
6) and a heat shield part (30) which is further freely lowered so that its opening side wall is arranged substantially concentrically with respect to the crucible combination, and when the single crystal is pulled up, By lowering the heat shield part and inserting the crucible combination into the opening of the side wall of the opening of the heat shield part, the outer peripheral edge part of the crucible combination part and the opening of the heat shield part are increased according to the increase in the pulling length of the crystal. An apparatus for manufacturing a compound semiconductor, characterized in that the size of an annular gap between the side wall and the side wall is reduced.