JP2002029881A - Method for manufacturing compound semiconductor single crystal - Google Patents

Abstract

[PROBLEMS] To provide a method for producing a compound semiconductor single crystal which is excellent in mass productivity and can obtain a homogeneous single crystal with a small number of dislocations in the crystal at low cost. In a state where a liquid sealant (2) is interposed between a surface of a compound semiconductor raw material (6) charged into a crystal growth container (1) and an inner surface of the crystal growth container (1), the compound semiconductor raw material (1) is removed. 6 is gradually moved in the heating furnace 7 provided with a temperature gradient within a range including the melting point of 6, and the compound semiconductor raw material 6 is melted in the heating furnace 7 at a temperature portion equal to or higher than the melting point of the compound semiconductor raw material 6, and then melted below the melting point. The compound semiconductor single crystal 5 is grown at the temperature portion of and after the completion of the growth of the compound semiconductor single crystal 5,
The liquid sealant 2 and the compound semiconductor single crystal 5 are heated at a temperature from 200 ° C. to the melting point of the compound semiconductor single crystal 5.

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 single crystal, and more particularly to a method for producing a compound semiconductor single crystal which is excellent in mass productivity and which can obtain a homogeneous single crystal with few dislocations in the crystal at low cost. It relates to a manufacturing method.

[0002]

2. Description of the Related Art In recent years, large-diameter G
As a method for producing a single crystal of a compound semiconductor such as aAs or InP, a vertical Bridgman method (Vertical B
Ridgman Method) is used.

In this vertical Bridgman method, a crystal growth vessel into which a compound semiconductor raw material is charged is gradually moved in a heating furnace provided with a temperature gradient within a range including a melting point of the compound semiconductor raw material, and the compound growth in the heating furnace is performed. After melting the compound semiconductor raw material at a temperature portion higher than the melting point of the semiconductor raw material, a compound semiconductor single crystal is grown at a temperature portion lower than the melting point.

On the other hand, in this method of manufacturing a compound semiconductor single crystal, a crucible made of boron nitride or quartz glass is used as a crystal growth vessel. Since these crystal growth vessels have fine irregularities on the inner surface, when the raw material melt and the inner surface of the crucible come into contact with each other when growing a compound semiconductor single crystal, the compound semiconductor crystal obtained by generating crystal nuclei is formed. There has been a problem that polycrystallization occurs. For this reason, a manufacturing method for growing a compound semiconductor single crystal in a state where boron oxide (B ₂ O ₃ ) is interposed between the surface of the compound semiconductor raw material and the inner surface of the crystal growth container as a liquid sealing agent is disclosed. (JP-A-1-278490, JP-A-2-188485, etc.).

However, in this manufacturing method, when the crystal growth container is cooled to room temperature after the completion of the growth of the compound semiconductor single crystal, the liquid encapsulant solidifies, so that the compound semiconductor single crystal formed via the liquid encapsulant is formed. Adhered to the crystal growth vessel, and its removal was very difficult. For this reason, as shown in FIG. 8, conventionally, a crystal growth container 21 containing a compound semiconductor single crystal 25 is immersed in an organic solvent 17 such as methanol, and boron oxide (B ₂ O) as a liquid sealing agent 222 is formed. ₃ ) was dissolved and the compound semiconductor single crystal 25 was taken out.

However, since the dissolution time of boron oxide (B ₂ O ₃ ) as the liquid sealing agent 22 is extremely long as 1 to 20 days, it takes a long time to take out the compound semiconductor 25 in the conventional manufacturing method. In short, mass production was not always sufficient. In addition, boron oxide (B
If the dissolution of ₂ O ₃ ) is insufficient, the compound semiconductor single bond 2
When the crystal growth container 21 is taken out, the inner wall of the crystal growth container 21 may be peeled off, so that the life of the crystal growth container 21 is shortened and the cost of the compound semiconductor single crystal 25 is increased. Was.

On the other hand, a method has been proposed in which, after the growth of the compound semiconductor single crystal, the liquid sealant is heated and softened at a temperature equal to or higher than the softening point to dissociate the compound semiconductor single crystal from the crystal growth vessel. (JP-A-5-70288).

According to this manufacturing method, the compound semiconductor single crystal can be quickly taken out of the crystal growth container, so that mass productivity can be improved and the inner wall of the crystal growth container is peeled off when the compound semiconductor single crystal is taken out. Therefore, the life of the crystal growth container can be extended, and the cost of the compound semiconductor single crystal can be reduced.

[0009]

However, in this manufacturing method, since the quality of the compound semiconductor single crystal is not particularly taken into consideration, the dislocation density of the crystal is increased, and the electric characteristics may vary. . Accordingly, it is an object of the present invention to provide a method for producing a compound semiconductor single crystal which is excellent in mass productivity and can obtain a homogeneous single crystal with few dislocations in the crystal at low cost.

[0010]

The present invention provides the following method for producing a compound semiconductor single crystal in order to achieve the above object.

[1] In a state where a liquid sealing agent is interposed between the surface of the compound semiconductor raw material charged into the crystal growth container and the inner surface of the crystal growth container, the crystal growth container is mixed with the compound semiconductor raw material. Is gradually moved in a heating furnace provided with a temperature gradient within a range including the melting point of the compound semiconductor raw material in the heating furnace at a temperature higher than the melting point of the compound semiconductor raw material. Growing a compound semiconductor single crystal in a portion, and after the growth of the compound semiconductor single crystal, heat-treating the liquid sealant and the compound semiconductor single crystal at a temperature from 200 ° C. to the melting point of the compound semiconductor single crystal. A method for producing a compound semiconductor single crystal, comprising:

[2] The production of the compound semiconductor single crystal according to [1], wherein the heat treatment of the liquid sealant and the compound semiconductor single crystal is performed at a temperature from 500 ° C. to the melting point of the compound semiconductor single crystal. Method.

[3] The liquid sealant and the compound semiconductor single crystal are heated at a temperature from 1100 ° C. to the melting point of the compound semiconductor single crystal for 1 hour or more.
Cooling to 500 ° C at a cooling rate of 120 ° C / hour, 50
Heat at 0 to 600 ° C for 3 hours or more, and heat to 800 ° C at a heating rate of 40 to 60 ° C / hour, and 800 to 950 ° C.
The method for producing a compound semiconductor single crystal according to the above [1] or [2], wherein the method is performed by heating at a cooling rate of 90 to 110 ° C./hour to room temperature for 3 hours or more.

[4] The heat treatment of the liquid sealant and the compound semiconductor single crystal is performed by setting the crystal growth container so that an opening thereof is directed sideways or downward. The method for producing a compound semiconductor single crystal according to any one of the above.

[0015]

Embodiments of the present invention will be specifically described below with reference to the drawings. As shown in FIG. 1A, in the method for producing a compound semiconductor single crystal of the present invention, first, a liquid is placed between the surface of the compound semiconductor raw material 6 charged into the crystal growth container 1 and the inner surface of the crystal growth container 1. With the sealing agent 2 interposed, the crystal growth vessel 1 is gradually moved in a heating furnace 7 provided with a temperature gradient within a range including the melting point of the compound semiconductor raw material 6 so that the compound semiconductor raw material in the heating furnace 7 6
After the compound semiconductor raw material 6 is melted at a temperature portion equal to or higher than the melting point, the compound semiconductor single crystal 5 is grown at a temperature portion equal to or lower than the melting point.

The crystal growth vessel 1 used in the present invention may be, for example, one made of boron nitride or quartz glass.

Examples of the compound semiconductor raw material 6 used in the present invention include GaAs, InP, GaP and the like. Further, in the present invention, it is preferable that the seed crystal 6a is charged together with the compound semiconductor raw material 6 in advance.

Examples of the liquid sealant 2 used in the present invention include boron oxide (B ₂ O ₃ ). The liquid sealant 2 may be any material as long as it is interposed between the surface of the molten compound semiconductor raw material 6 and the inner surface of the crystal growth container 1.
And may be applied to the inner surface of the crystal growth vessel 1 in advance.

The heating furnace 7 used in the present invention is provided with a temperature gradient within a range including the melting point of the compound semiconductor raw material 6, and this temperature gradient is used to suppress an increase in the dislocation density of the crystal due to thermal strain. 1 to 10 ° C / cm is preferred. The moving speed of the crystal growth vessel 1 in the heating furnace 7 is preferably 4 mm / hour or less in order to form a large-diameter crystal.

In the method for producing a compound semiconductor single crystal according to the present invention, after the compound semiconductor single crystal is grown, the liquid sealing agent and the compound semiconductor single crystal are heated at a temperature from 200 ° C. to the melting point of the compound semiconductor single crystal for at least one hour. Heat treatment. 200 ° C
If it is less than 1, it becomes difficult to take out the compound semiconductor single crystal. On the other hand, if it exceeds the melting point temperature, it will not be possible to take it out as crystals.

It is preferable that the heat treatment is performed while controlling the temperature distribution of the crystal growth vessel 1 within ± 20 ° C. After the heat treatment, it is preferable to slowly cool to room temperature at a cooling rate of −50 ° C./cm or less.

As shown in FIG. 2, in the method for producing a compound semiconductor single crystal of the present invention, the liquid sealant and the single crystal are subjected to a heat treatment in the following steps, so that the electric characteristics are uniform. An insulating compound semiconductor single crystal can also be obtained.

In this heat treatment step, first, a compound semiconductor single crystal component such as As is uniformly dissolved in a solid solution.
Heating is performed for 1 hour or more at a temperature from ℃ to the melting point of the compound semiconductor single crystal. Next, in order to prevent the precipitation of a compound semiconductor single crystal component such as As, the cooling is performed at a cooling rate of -100 ° C / hour or more to 500 ° C to 600 ° C. Next, in order to uniformly disperse a compound semiconductor single crystal component such as As in a supersaturated state, the mixture is heated at 500 ° C. to 600 ° C. for 3 hours or more.
Next, in order to form EL2 without inhibiting uniform dispersion of a compound semiconductor single crystal component such as As, the substrate is heated from 500 ° C. to 600 ° C. at a heating rate of 50 ° C./hour or more. Finally, in order to form EL2 to obtain a semi-insulating compound semiconductor single crystal, heating is performed at 900 ° C. to 950 ° C. for 3 hours or more.
Cool to room temperature at a cooling rate of 90-110 ° C / hour.
It is preferable that the heat treatment is performed while controlling the temperature distribution of the crystal growth vessel 1 within ± 20 ° C.

As shown in FIGS. 1 (b) and 1 (c), the heat treatment of the liquid encapsulant and the single crystal in the present invention is performed by using a crystal growth vessel 1 containing a compound semiconductor single crystal 5, for example, a quartz ampoule. It is preferable that the opening 1a is placed in the heating furnace 7 so that the opening 1a faces sideways or downward.

When the liquid semiconductor (B ₂ O ₃ ) is heated above the softening point and the compound semiconductor single crystal 5 is dissociated from the inner wall of the crystal growth vessel 1, the compound semiconductor single crystal 5 is moved by gravity to the crystal growth vessel. To fall naturally into the opening 1a
The compound semiconductor single crystal 5 can be easily taken out. When the liquid sealant (B ₂ O ₃ ) is dissolved by heating, the liquid sealant (B ₂ O ₃ ) naturally flows out of the opening 1 a of the crystal growth container 1.

Note that the heat treatment is preferably performed in an inert gas atmosphere or the like by introducing an inert gas or the like from the gas introduction unit 11 in order to prevent impurities from being mixed into the crystal. Further, a buffer 4 made of, for example, glass fiber or the like may be provided below the opening 1a of the crystal growth container 1 in order to prevent damage when the crystal is dropped.

[0027]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

Example 1 First, a GaAs seed crystal, 6,500 g of GaAs, and 2.0 g of Si (dopant) were sequentially charged into a crystal growth vessel made of quartz glass, and then the inside of the crystal growth vessel was evacuated. Next, the crystal growth vessel made of quartz glass was placed in a heating furnace, and then the heating furnace was heated. The temperature of the heating furnace was about 1200 ° C. in the lower part with the seed crystal, and about 1245 ° C. in the upper part with GaAs and Si. The temperature gradient at the solid-liquid interface was adjusted to about 10 ° C./cm. The quartz glass crystal growth vessel was lowered from the upper part at a rate of 3 mm / hour, and GaAs and Si melted at the upper part were grown sequentially. Ga
After the melts of As and Si were all solidified and crystal growth was completed, the quartz glass crystal growth vessel 1 was cooled to room temperature at a rate of about -30 ° C / hour.

Next, the quartz glass crystal growth vessel containing the crystal is taken out of the heating furnace and inserted into a quartz ampoule.
This quartz ampule was placed in a heating furnace such that the opening of the crystal growth vessel was downward, and nitrogen gas was supplied at a rate of 1 liter /
The heat treatment was performed at a flow rate of 1 minute. The heat treatment is performed while controlling the temperature of the entire furnace to be within ± 5 ° C.
The crystal growth vessel was heated at a heating rate of 0 ° C./hour until the temperature reached 600 ° C., heated at 600 ° C. for 2 hours, and then cooled to room temperature at a cooling rate of −50 ° C./hour. After the heat treatment, the crystal was removed from the opening of the crystal growth vessel to obtain a cylindrical GaAs single crystal having a diameter of about 80 mm and a length of about 200 mm. When the dislocation density of the obtained GaAs single crystal was measured with a transmission electron microscope, the dislocation density was extremely low.

Example 2 First, after a GaAs seed crystal, 6500 g of GaAs, and 2.0 g of Si (dopant) were sequentially charged into a crystal growth vessel made of boron nitride, Ar gas was introduced into the crystal growth vessel.
The inside of the crystal growth vessel was set to an inert gas atmosphere.

Next, after setting the crystal growth vessel made of boron nitride in the heating furnace, the heating furnace was heated. The temperature of the heating furnace was set to about 1200 ° C. in the lower part having the seed crystal, and GaAs and Si were used.
The temperature at the top of the sample was about 1245 ° C. The temperature gradient at the solid-liquid interface was adjusted to about 10 ° C./cm. The quartz glass crystal growth vessel was lowered from the upper part at a speed of 3 mm / hour, and GaAs and Si melted at the upper part were grown sequentially. After all the melts of GaAs and Si are solidified and crystal growth is completed, the quartz glass crystal growth vessel is heated to about -30 ° C.
/ Hr at room temperature.

Next, the crystal growth vessel made of boron nitride containing the GaAs crystal is taken out of the heating furnace, and set again in the heating furnace so that the opening of the crystal growth vessel is directed downward, and argon (Ar) is added. Was introduced into a heating furnace, and heat treatment was performed in an inert gas atmosphere.

The heat treatment is performed at a heating rate of 90 ° C./hour for 1 hour.
Heat to 100 ° C, heat at 1100 ° C for 6 hours, -3
Cool to 500 ° C at a cooling rate of 00 ° C / hour,
4 hours at 950 ° C. at a heating rate of 110 ° C./hour.
To 950 ° C for 6 hours, -110 ° C /
The cooling was performed at room temperature at a cooling rate of time. At this time, the temperature of the entire crystal was controlled so as to have a temperature distribution within ± 5 ° C.

After the heat treatment, the GaAs crystal is removed from the opening of the crystal growth vessel, and has a diameter of about 100 mm and a length of about 1 mm.
A 50 mm cylindrical GaAs single crystal was obtained. G obtained
When the dislocation density of the aAs single crystal was measured with a transmission electron microscope, the density was extremely low. In addition, the obtained Ga
The As single crystal was cut into a wafer and the PL intensity distribution in the wafer plane was measured with a photometer. As shown in FIG. 3 (b), the variation was extremely small at 5% or less. Further, when the specific resistance was measured, it was a semi-insulating property of 1E7 Ω · cm or more.

Comparative Example 1 GaAs was produced in the same manner as in Example 2 except that the heat treatment was not performed after the completion of the GaAs crystal growth.
Was produced.

When the GaAs crystal was cut into a wafer and the specific resistance was measured, it was semi-insulating at 1E7 Ω · cm or more. When the PL intensity distribution was measured with a photometer,
As shown in (a), a large variation in PL intensity was observed at about 20%. Further, the dislocation density was measured by a transmission electron microscope, and was found to be high.

[0037]

As described above, according to the method for producing a compound semiconductor single crystal of the present invention, a compound semiconductor single crystal which is excellent in mass productivity and can obtain a homogeneous single crystal with few dislocations in the crystal at low cost. Can be provided.

[0038]

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing an example of an apparatus for carrying out a method for producing a compound semiconductor single crystal of the present invention;
(A) is sectional drawing which shows the state at the time of a crystal growth,
(B) is a cross-sectional view showing a state during a heat treatment after completion of the crystal growth, and (c) is a cross-sectional view showing a state where the crystal is dissociated from the inner wall of the crystal growth vessel.

FIG. 2 is an explanatory diagram showing an example of heat treatment conditions after completion of single crystal growth in one embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a PL intensity distribution of a compound semiconductor single crystal obtained according to an example of the present invention.

FIG. 4 is a cross-sectional view schematically showing a step of dissociating a compound semiconductor single crystal from an inner wall of a crystal growth vessel after completion of single crystal growth in an example of a conventional method for manufacturing a compound semiconductor single crystal.

[Explanation of symbols]

1: crystal-growth vessel 1a: opening 2: liquid sealant (B ₂ 0 ₃₎ 4: buffer 5: a compound semiconductor single crystal 6: a compound semiconductor material 7: oven 8: Liquid sealant receiving 9: crystalline Cradle 11: Gas introduction unit 12: Chamber 17: Organic solvent (methanol) 18: Organic solvent container 21: Crystal growth container 22: Liquid sealant (B ₂ O ₃ ) 25: Compound semiconductor single crystal

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroshi Sasabe 880 Sunazawa-cho, Hitachi City, Ibaraki Prefecture Inside the Takasago Plant of Hitachi Cable Co., Ltd. F-term (reference) 4G077 AA02 BE46 CD02 FE12 FE13 FE18 FE18

Claims (4)

[Claims] 1. A method according to claim 1, wherein a liquid sealing agent is interposed between a surface of the compound semiconductor raw material charged into the crystal growth container and an inner surface of the crystal growth container. After gradually moving in a heating furnace provided with a temperature gradient within a range including the melting point and melting the compound semiconductor material at a temperature portion equal to or higher than the melting point of the compound semiconductor material in the heating furnace, a temperature portion equal to or lower than the melting point After growing the compound semiconductor single crystal, heating the liquid sealant and the compound semiconductor single crystal at a temperature from 200 ° C. to the melting point of the compound semiconductor single crystal after the completion of the growth of the compound semiconductor single crystal. A method for producing a compound semiconductor single crystal, which is characterized in that: 2. The method for producing a compound semiconductor single crystal according to claim 1, wherein the heat treatment of the liquid sealant and the compound semiconductor single crystal is performed at a temperature from 500 ° C. to a melting point of the compound semiconductor single crystal. 3. The heat treatment of the liquid sealant and the compound semiconductor single crystal is performed by heating at a temperature from 1100 ° C. to the melting point of the compound semiconductor single crystal for 1 hour or more.
Cooling to 500 ° C at a cooling rate of 500 ° C / hour,
Heat at 00 ° C for 3 hours or more, heat to 800 ° C at a heating rate of 40 to 60 ° C / hour, heat at 800 ° C to 950 ° C for 3 hours or more, and cool to room temperature at a cooling rate of 90 to 110 ° C / hour. The method for producing a compound semiconductor single crystal according to claim 1, wherein the method is performed. 4. The method according to claim 1, wherein the heat treatment of the liquid sealant and the compound semiconductor single crystal is performed by setting the crystal growth container so that an opening thereof is directed sideways or downward. The production method of the compound semiconductor single crystal according to the above.