JPH08208365A - Device and method for solution growth of crystal - Google Patents

Abstract

PURPOSE: To make it possible to produce a bulky single crystal of a desired diameter from a small seed crystal by combining a vessel for growth, a heat sink, a seed retaining member and a source crystal fixing jig in such a manner that these members make special effects. CONSTITUTION: The seed crystal 2 formed by subjecting the seed crystal 2 to mirror surface polishing, then to washing and to mirror surface etching is placed in the central part atop the heat sink. The vessel 1 for crystal growth is arranged in an electric furnace formed with a prescribed temp. distribution. The source crystal 4 in a high-temp. section is dissolved in a solvent 6 down to the saturation solubility in the high-temp. part. The source crystal component dissolved in the solvent 6 is moved by diffusion to the low-temp. part as well, by which the soln. in the low-temp. part is put into a supersatd. state. The bulky single crystal grows on the seed crystal 2. At this time, the crystal grows along the tapered surface of the seed crystal retainer 3 and the inside surface of the vessel 1 for crystal growth and, therefore, the diameter of the grown crystal increases gradually and the grown crystal of the diameter larger than the diameter of the seed crystal 2 is obtd.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to liquid crystal growth.
In particular, it relates to solution growth. Solution crystal growth capable of lowering the growth temperature is expected as a bulk crystal growth technique for compound semiconductors having a high vapor pressure, particularly II-VI group compound semiconductors.

[0002]

2. Description of the Related Art Large diameter bulk Si single crystals and III-
LEC as a method for producing a group V compound semiconductor single crystal
The method, horizontal Bridgman method, etc. are known.

FIG. 2 (A) shows a crystal growth apparatus by the LEC method. The crystal growth apparatus comprises a container 9 for containing the melt 8, a seed crystal 2a, and a crystal pulling apparatus 10.
It is configured to include.

After immersing the small-diameter seed crystal 2a in the melt 8, the seed crystal 2a is gradually pulled up while rotating. By pulling up, the temperature of the seed crystal portion becomes equal to or lower than the melting point, and a single crystal grows so as to be continuous with the seed crystal.

The growth rate can be controlled by the pulling rate,
When pulled slowly, the diameter of the grown crystal gradually increases. After reaching the desired diameter, the pulling speed is set so as to maintain the diameter.

FIG. 2 (B) shows a crystal growth apparatus and a temperature gradient by the three-temperature horizontal Bridgman method. The crystal growth apparatus includes a quartz container 11 vacuum-sealed,
Consists of a container 9 for containing the melt 8 arranged in a quartz container, a seed crystal 2b arranged in contact with the melt 8, and a compound semiconductor constituent element 10 for controlling the vapor pressure of the compound semiconductor constituent element Has been done. Seed crystal 2b
After immersing in the melt 8, move the heater to the left side of the figure,
By lowering the temperature of the seed crystal portion below the melting point, a single crystal continuously grows on the seed crystal 2b.

The above method is not suitable for easily growing a compound semiconductor crystal having a high vapor pressure of constituent elements. Robustness that can withstand dissociation of high vapor pressure component elements,
This is because a device having airtightness that can withstand the application of an inert gas is required, and the device itself and operating costs are high. Solution crystal growth, which allows crystal growth at a low temperature, is suitable for easily producing a compound semiconductor crystal having a high vapor pressure.

FIG. 3 shows an example of a solution crystal growth apparatus. A cross section of the crystal growth apparatus is shown on the left side of the figure, and a temperature distribution set in the crystal growth apparatus is shown on the right side in a graph. The crystal growth apparatus comprises a vacuum-grown crystal growth container 1b, a heat sink 7 disposed therein, a seed crystal 2 fixed on the upper surface thereof, a seed crystal retainer 3b, a source crystal 4 and a solvent 6. ing. This crystal growth container is arranged in the temperature distribution shown in the graph on the right side of the figure.

The source crystal 4 in the high temperature portion is dissolved in the solvent 6 up to the saturation solubility in the high temperature portion. The source crystal component dissolved in the solvent 6 also moves to the low temperature part by diffusion, so that the solution in the low temperature part is supersaturated. By contacting the seed crystal 2 with the supersaturated solution, a bulk single crystal grows on the seed crystal 2.

In principle, the growth temperature can be freely selected as long as it is a temperature at which the source crystal is dissolved in the solvent. By lowering the growth temperature, the vapor pressure is lowered, and the requirement for pressure resistance of the growth container is relaxed.

By lowering the growth temperature, the density of crystal defects generated at the growth temperature can be reduced.
Further, the thermal stress generated when the growth temperature is lowered to room temperature is also reduced.

[0012]

In the production of a bulk single crystal obtained by the crystal growth apparatus shown in FIG. 3, the diameter of the cross section of the columnar grown crystal is smaller than the diameter of the seed crystal 2, and the grown crystal When seed crystals are cut out from and the growth is repeated, the size gradually becomes smaller. Further, it is difficult to obtain a single crystal having a size sufficient to cut out a wafer having a desired diameter by using a small seed crystal.

An object of the present invention is to provide a crystal growth apparatus capable of producing a bulk single crystal having a desired diameter from a small seed crystal in solution crystal growth capable of crystal growth at a relatively low temperature. .

[0014]

A crystal growth apparatus of the present invention comprises a growth container that defines an airtight space, a heat sink fixed to the bottom of the growth container, a heat sink arranged on the heat sink, and a seed on the bottom surface. A seed suppressing member that can fix a crystal and defines a tapered surface whose inner surface is small on the heat sink side and has a large inner diameter on the opposite side, and a source crystal fixing jig that is formed at a predetermined distance on the heat sink and can hold the source crystal. With tools.

[0015]

Since the crystal growth is started on the small diameter side where the seed is suppressed, a small seed crystal can be used. Since the diameter of the grown crystal increases along the tapered surface that suppresses the seed,
Large-diameter grown crystals can be obtained from small-diameter seed crystals.

As described above, by solution crystal growth, it is possible to produce a large diameter bulk single crystal from a small diameter seed crystal.

[0017]

EXAMPLES Hereinafter, ZnSe of II-VI group compound semiconductors will be described.
Will be described by taking as an example the case of growing with a Se-Te solvent. ZnSe is a material expected as a blue light emitting semiconductor element.

FIG. 1A shows a crystal growth apparatus according to an embodiment of the present invention. A cross-sectional view of the crystal growth apparatus is shown on the right side of the figure, and a temperature distribution set in the furnace is shown on the left side. A crystal growth container 1 made of a quartz tube having an appropriate diameter is prepared.
The crystal growth container 1 is etched with hydrofluoric acid to clean the surface. A heat sink 7 made of a material having a high thermal conductivity such as carbon at the bottom of the crystal growth container 1 whose surface is cleaned.
And then vacuum-baked, and then a crystal growth container 1
The heat sink 7 is fixed by, for example, reducing the inner diameter of the heat sink 7.

As the seed crystal 2, a ZnSe single crystal having a plane orientation (111) plane is prepared. Note that (111)
It is also possible to use a ZnSe single crystal other than the plane. After the seed crystal 2 is mirror-polished, it is washed and mirror-etched. The seed crystal 2 thus prepared is placed on the center of the upper surface of the heat sink 7.

A recess for receiving the seed crystal 2 is preferably formed on the upper surface of the heat sink 7. In this case, it is preferable that the upper surface of the seed crystal is located above the upper surface of the heat sink.

In order to fix the seed crystal 2, a ring-shaped seed crystal retainer 3 made of quartz is placed on the seed crystal 2.
Partly adheres to the crystal growth container 1. The ring-shaped seed crystal retainer 3 has a tapered inner surface, the inner diameter of the small diameter end thereof is smaller than the diameter of the seed crystal 2, and the inner diameter of the large diameter end thereof is substantially equal to the inner diameter of the crystal growth container 1.

When the seed crystal suppressor 3 is formed by a ring-shaped member having a flat bottom surface and a mortar-like tapered surface as shown in the drawing, the central portion is thin and the peripheral portion is thick. The angle between the bottom surface and the tapered surface is 60 ° or more and less than 90 °, and
It is preferable to set the angle to not less than 80 ° and less than 80 °.

Further, the lower surface of the seed crystal side is substantially flat, and a circular step is provided in the central portion in order to secure the fixation of the seed crystal 2. This diameter is approximately equal to the diameter of the seed crystal 2 and the height is lower than the thickness of the seed crystal 2 on the heat sink.

A protrusion 5 for preventing the source crystal 4 from falling is provided at an appropriate position from the upper surface of the heat sink 7 on the inner surface of the crystal growth container 1. After that, as the solvent 6, Se- having a predetermined composition is used.
A Te mixture and a polycrystal of ZnSe as the source crystal 4 are put into the crystal growth container 1. The amount of the solvent 6 is such that the seed crystal 2 and the source crystal 4 are completely covered.

The source crystal 4 is held by the source crystal fixing jig 5. The distance between the seed crystal 2 and the source crystal 4 is preferably 20 to 80 mm, and optimally 40 to 60 mm. The source crystal 4 is preferably arranged in a position facing the seed crystal, and has a disk shape for easy holding.

In FIG. 1 (A), the case where the protrusion for preventing the source crystal from falling is provided, but the falling can be prevented by other methods. For example, if a quartz tube having a diameter larger than the diameter of the portion in which the solvent is stored is connected and a disk-shaped source crystal having a diameter similar to this quartz tube is arranged, the difference in level of the quartz tube causes It is possible to prevent the source crystal from falling.

As described above, the crystal growth container 1 in which the source crystal 4, the solvent 6, and the seed crystal 2 are arranged is connected to a vacuum exhaust device, and the inside thereof is exhausted to a vacuum degree higher than 2 × 10 ⁻⁶ Torr. , Seal the open end.

The crystal growth container is turned over or inverted to dissolve the solvent. Here, the seed crystal does not come into contact with the solvent, and only the source crystal comes into contact with the solvent to saturate the solvent with the solute. A saturated solution at that temperature is prepared by keeping the solvent near the subsequent growth temperature. Then, the crystal growth container is returned to the upright state. Since the solvent is a saturated solution, the dissolution of seed crystals is suppressed to an extremely low level.

The crystal growth vessel 1 thus prepared is placed in an electric furnace having a predetermined temperature distribution as shown on the left side of FIG. The source crystal 4 in the high temperature portion dissolves in the solvent 6 up to the saturation solubility in the high temperature portion. The source crystal component dissolved in the solvent 6 moves to a low temperature part by diffusion,
Bring the cold solution to supersaturation.

By contacting the seed crystal 2 with the supersaturated solution, a bulk single crystal grows on the seed crystal 2. At this time, since the crystal grows along the tapered surface of the seed crystal suppressor 3 and the inner surface of the crystal growth container 1, the diameter of the grown crystal gradually increases and a grown crystal having a larger diameter than that of the seed crystal 2 is obtained. be able to.

Next, the second embodiment will be described. FIG. 1B shows a crystal growth container 1a used in the second embodiment.
FIG. Quartz tube 1c with small diameter and proper diameter
And the large-diameter quartz tube 1e are connected by a horn type quartz tube portion 1d in which the diameter of one cut end is equal to the diameter of the quartz pipe 1c and the other cut end is equal to the diameter of the quartz pipe 1e. The angle α formed by the plane perpendicular to the central axis of the horn-type quartz tube portion 1d and the inclined surface is preferably in the range of 60 ° or more and less than 90 °, and most preferably 70 ° or more and less than 80 °.

The quartz tube 1c and the quartz tube portion 1d are smoothly connected to each other on the small diameter side, and the quartz tube portion 1d and the quartz tube 1e are smoothly connected to each other to produce the crystal growth container 1a. On the inner surface of the quartz tube 1e, a projection 5 for preventing source crystal drop is provided at an appropriate position.

The heat sink 7 is housed in the small diameter portion of the crystal growth container 1a, and the seed crystal 2 is placed on the upper surface of the heat sink 7.
Is placed. The seed crystal 2 is the same ZnSe single crystal as that used in the above-mentioned embodiment, and its diameter is almost equal to the inner diameter of the quartz tube 1c.

Next, a horn-type seed crystal retainer 3a having an outer surface that follows the inner surface of the quartz tube 1d is inserted along the quartz tube 1d and fixed to the quartz tube 1d to fix the seed crystal 2. . Like the inner surface of the quartz tube portion 1d, the inner surface of the seed crystal restrainer 3a has an inclination of 60 to 90 °, preferably 70 to 80 ° with respect to the surface perpendicular to the axis.

After that, as in the above-mentioned embodiment, the solvent 6 and the source crystal 4 are charged and vacuum-sealed to perform crystal growth.
At this time, since the crystal grows along the inner surfaces of the seed crystal suppressor 3a, the quartz tube portion 1d and the quartz tube 1e, it is possible to obtain a grown crystal having a diameter larger than that of the seed crystal 2.

In the first and second embodiments, ZnS
Although the example of e has been described, the present invention is not limited to ZnSe and can be applied to the growth of a bulk single crystal of a II-VI group compound semiconductor having a larger diameter than the seed crystal.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example,
It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0038]

As described above, according to the present invention,
In solution crystal growth, a bulk single crystal having a larger diameter than that of a seed crystal can be grown, and a large diameter wafer can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a crystal growth apparatus used in an example of the present invention and a graph showing a temperature distribution.

FIG. 2 is a graph showing a cross-sectional view and a temperature distribution of a conventional crystal growth apparatus.

FIG. 3 is a cross-sectional view and a graph showing a temperature distribution of a crystal growth apparatus used in a conventional solution crystal growth method.

[Explanation of symbols]

 1, 1a, 1b Crystal growth vessel 1c, 1d, 1e Quartz tube 2, 2a, 2b Seed crystal 3, 3a, 3b Seed crystal suppressor 4 Source crystal 5 Source crystal fixing jig 6 Solvent 7 Heat sink 8 Melt 9 Melt reservoir 10 Semiconductor Constituent Elements 11 Quartz Container

Claims (4)

[Claims] 1. A growth vessel (1) defining an airtight space.
And a heat sink (7) fixed to the bottom of the growth container
A seed suppression member (3) disposed on the heat sink (7), capable of fixing a seed crystal on the bottom surface thereof, and defining a tapered surface having an inner surface that is small on the heat sink side and has a large inner diameter on the opposite side; A solution crystal growth apparatus having a source crystal fixing jig (5) formed at a predetermined distance above and capable of holding a source crystal. 2. The solution crystal growth apparatus according to claim 1, wherein the seed suppressing member has a cylindrical outer peripheral surface and a tapered inner peripheral surface. 3. The solution crystal growth apparatus according to claim 1, wherein the seed suppressing member has an inner peripheral surface that defines a tapered surface whose diameter gradually increases and an outer peripheral surface that is substantially parallel to the inner peripheral surface. 4. A step of placing a seed crystal on a heat sink, a step of fixing the seed crystal by a small diameter end of a seed retainer whose inner peripheral surface is a tapered surface, and a crystal material to be grown on the seed crystal. And a step of causing solution crystal growth to occur on the seed crystal and along the inner circumferential surface of the seed presser.