JPH07291778A - Solution crystal growing method and device therefor - Google Patents

Abstract

PURPOSE:To provide a soln. crystal growing technique in which the surface of a seed crystal is subjected to meltback by a specified amt. to obtain a grown crystal of high quality can be obtd. while abnormal growth and defects of the crystal is prevented. CONSTITUTION:This soln. crystal growing method is performed by forming temp. difference between the upper and lower part in the soln., disposing a source crystal in the high temp. part of the soln., and disposing a seed crystal in the low temp. part of the soln. to grow a crystal. This method includes a process to heat the seed crystal to specified first temp. while the seed crystal is not in contact with the soln., and to heat the soln. to a specified second temp. lower than the first temp. by specified temp, a process to bring the seed crystal into contact with the soln., and a process to produce specified temp. difference between the upper and lower part of the soln. to grow a crystal on the seed crystal.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to crystal growth, and more particularly to solution crystal growth. Solution crystal growth, which can lower the growth temperature, is expected as a bulk crystal growth technique for compound semiconductors with high vapor pressure, particularly II-VI group compound semiconductors.

[0002]

2. Description of the Related Art An example of conventional solution crystal growth is shown in FIG.
Will be described with reference to. Note that FIG. 1C is also used in the description of the embodiment of the present invention.

A quartz tube 1 having a small diameter as shown in FIG.
A quartz ampoule 1 in which a and a large diameter quartz tube 1b are connected by a horn type quartz tube 1c having a tapered inner surface is prepared. At the beginning, the upper end of the quartz ampoule 1 is left open.
A heat sink 5 is housed in the small-diameter portion 1 a of the quartz ampoule 1.

A seed crystal 4 having the same diameter as that of the heat sink is placed on the upper surface of the heat sink 5 of the quartz ampoule thus prepared. Quartz ampoule 1 beside the seed crystal 4
Seed crystal 4 by heating the sides and making it inward
To fix.

Next, after the source crystal 2 and the solvent mass 3a are charged, the inside of the quartz ampoule 1 is evacuated and the open end of the upper end is sealed. The source crystal 2 is held at a predetermined position by a protrusion or the like provided on the inner surface of the quartz ampoule 1.

The solvent block 3 is prepared by dissolving an appropriate amount of crystal component in a solvent in advance and then solidifying the crystal component. By dissolving the crystal component in the solvent mass 3a in advance, the meltback of the seed crystal can be suppressed to a small amount. The concentration of the crystal component is adjusted so as to be a saturated concentration at the temperature (growth temperature) of the seed crystal during crystal growth.

Next, the quartz ampoule prepared as shown in FIG. 1C is turned upside down or tilted and heated to melt the solvent mass 3a. Then, as shown in FIG. 2B, the seed crystal 4 is brought upright and brought into contact with the solvent 3. The temperature of the source crystal portion is set higher than that of the seed crystal, and the crystal is grown on the seed crystal 4.

[0008]

The temperature of the solvent in which the quartz ampoule 1 has been inverted and melted is not uniform because of partial variations. Therefore, when the solvent lump 3a is melted to a predetermined temperature and returned to the upright state, the temperature of the solution contacting the seed crystal 4 may be higher or lower than the predetermined temperature.

When the high temperature portion of the solvent comes into contact with the seed crystal 4, the solvent is rapidly cooled and the degree of supersaturation locally increases. When the degree of supersaturation increases, abnormal nuclei are generated, and good crystal growth cannot be performed.

Further, when it is desired to melt back the surface of the seed crystal by a predetermined amount, it becomes difficult to perform melt back with high reproducibility. Further, the surface of the seed crystal after the melt-back is not flat, and crystals are abnormally grown from the protrusions, and crystal defects are introduced, which causes deterioration of crystallinity. Further, the shape of the seed crystal surface also changes from lot to lot, and it becomes impossible to stably obtain good grown crystals.

An object of the present invention is to provide a solution crystal growth technique capable of obtaining a good quality grown crystal by melting back the seed crystal surface by a predetermined amount and preventing abnormal crystal growth and crystal defect introduction. Is.

[0012]

According to the solution crystal growth method of the present invention, a temperature difference is formed above and below the solution, a source crystal is arranged in a high temperature part of the solution, and a seed crystal is arranged in a low temperature part of the solution. In a solution crystal growth method for performing crystal growth, the seed crystal is brought to a predetermined first temperature and the solution is kept to a predetermined temperature lower than the first temperature in a state where the seed crystal and the solution are not in contact with each other. A heating step of heating to a second temperature, and a step of bringing the seed crystal into contact with the solution,
A crystal growth step of forming a predetermined temperature difference above and below the solution and growing a crystal on the seed crystal.

[0013]

If the temperature of the solvent when the solvent in which the crystal component is dissolved is brought into contact with the seed crystal is set lower than the temperature of the seed crystal, the solvent is warmed when the solvent comes into contact with the seed crystal. Therefore, the saturated solubility of the solvent is increased, and it is possible to prevent the local precipitation of the crystal component on the seed crystal surface. Further, since the seed crystal surface is melted back, a flat and clean surface can be exposed.

[0014]

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.

As shown in FIG. 1 (A), the solvent constituent substance 1
Se and Te as 0 and 11 respectively, and ZnSe as the crystal component raw material 12 are charged into the quartz ampoule 13 and vacuum sealed. The quartz ampoule 13 prepared in this way is heat-treated in a temperature environment equal to or higher than the melting points of the solvent constituents 10 and 11 to completely and completely dissolve the crystal component raw material 12 in the solvent.

As shown in FIG. 1B, a quartz ampoule 1
The inside of 3 is returned to room temperature to form a solvent mass 3a in which a predetermined amount of crystal component is dissolved. As shown in FIG. 1 (C), a quartz ampoule 1 in which a small diameter quartz tube 1a and a large diameter quartz tube 1b are connected by a horn type quartz tube 1c having a tapered inner surface is prepared. At the beginning, the upper end of the quartz ampoule 1 is open.

The quartz ampoule 1 is etched with hydrofluoric acid to clean the surface. Quartz ampoule with clean surface 1
A cylindrical heat sink 5 having a diameter substantially the same as the inner diameter of the small diameter portion 1a is housed in the lower part of the, and vacuum baked. The heat sink 5 is made of a material having a high thermal conductivity such as carbon.

A seed crystal 4 having a diameter substantially the same as the diameter of the small diameter portion 1a is placed on the upper surface of the heat sink 5. Then Zn
The source crystal 2 made of a polycrystal of Se and the solvent mass 3a formed in the step of FIG. 1 (B) are put into a quartz ampoule 1. At this time, the source crystal 2 is held at a predetermined distance from the seed crystal 4 by a projection (not shown) provided on the inner surface of the quartz ampoule 1 or the like.

The crystal growth apparatus in which the source crystal 2, the solvent mass 3a, and the seed crystal 4 are arranged in this way is connected to a vacuum exhaust apparatus, the inside of which is vacuum exhausted to 2 × 10 ⁻⁶ Torr or less, and the open end is sealed. Stop. The seed crystal 4 and the source crystal 2 are fixed by heating and denting the seed crystal 4 and the source crystal 2 portions on the side surface of the quartz ampoule 1.

As shown in FIG. 2A, the quartz ampoule 1
Is placed in a cylindrical electric furnace 7 whose inside is a heating space, and is tilted so that it is turned upside down. The solvent lump 3 a is held at the upper end of the quartz ampoule 1. At this time, the seed crystal 4 and the source crystal 2 are tilted so that the seed crystal 4 and the source crystal 2 do not come into contact with the solvent when the solvent mass 3a is completely melted. An auxiliary heater 6 is arranged so as to surround the outer periphery of the upper part of the quartz ampoule 1, that is, the part where the solvent mass 3a is held. The electric furnace 7 heats the seed crystal 4 and the source crystal 2 to a predetermined temperature, and the auxiliary heater 6 heats the solvent mass 3 a. The solvent block 3 a melts to become the solvent 3.

In this state, the temperature of the seed crystal 4 is T ₁ ,
The solvent 3 is heated until the temperature becomes T ₂ . At this time, the auxiliary heater 6 heats the entire solvent 3 to a uniform temperature. The temperature T _{2 of the} solvent 3 is preferably lower than the temperature T ₁ of the seed crystal 4 as described later.

As shown in FIG. 2B, the auxiliary heater 6 is removed and the quartz ampoule 1 and the electric furnace 7 are returned to the upright state.
The solvent 3 contacts the seed crystal 4 and the source crystal 2. The temperature of the seed crystal 4 is the temperature T heated in the step of FIG.
₂ , and a temperature gradient is provided in the electric furnace 7 so that the temperature of the source crystal 2 becomes higher than that.

The source crystal 2 in the high temperature portion is dissolved in the solvent 3 up to the saturated solubility in the high temperature portion. The source crystal component dissolved in the solvent 3 moves to the low temperature part by diffusion and makes the solvent in the low temperature part into a supersaturated state. By contacting the seed crystal 4 with the supersaturated solution, a crystal grows on the seed crystal 4.

When the quartz ampoule 1 is returned from the upside down state to the upright state, the solvent 3 comes into contact with a higher temperature seed crystal and the temperature rises, so that the saturated solubility increases. Therefore, the seed crystal 4 is melted back until the solvent near the seed crystal 4 is saturated.

Below, the temperature T ₁ of the seed crystal 4 is set to 950.
C. and the amount of irregularities on the surface of the seed crystal 4 after meltback when the temperature T _{2 of the} solvent 3 is changed will be described.
When the temperature T _{2 of the} solvent 3 was 910, 920 and 930 ° C., the unevenness amount on the surface of the seed crystal 4 was 5 μm or less.
When the temperature T _{2 of the} solvent 3 was 940 ° C. and 950 ° C., the irregularities were 20 μm and 50 μm, respectively.

Next, the expansion of the grain size in the grown crystal when a ZnSe polycrystal is used as the seed crystal 4 will be described. FIG. 3 shows the maximum grain size in the grown crystal when the temperature T ₂ of the solvent 3 at the time when the seed crystal 4 and the solvent 3 are brought into contact with each other is changed. The temperature T ₁ of the seed crystal 4 is 950 ° C. The horizontal axis represents the temperature T ₂ of the solvent 3 in the unit of ° C, and the vertical axis represents the maximum particle size on an arbitrary scale. From FIG. 3, it is understood that a large maximum particle size is obtained when the temperature T ₂ of the solvent is set to about 910 to 930 ° C., and the maximum particle size is maximized when the temperature T ₂ is set to 920 ° C. That is, the temperature T ₂ of the solvent is preferably lower than the temperature T _{1 of the} seed crystal by about 20 to 40 ° C.

From the flatness of the seed crystal surface after the melt back and the maximum grain size of the grown crystal, when the temperature T ₁ of the seed crystal 4 is 950 ° C., the temperature T ₂ of the solvent is 920 ° C.
It turns out that it is good to set it as a degree. Thus, by lowering the temperature of the solvent at the time of contact between the seed crystal and the solvent by a predetermined temperature below the temperature of the seed crystal, it is possible to grow a good quality crystal.

The quartz ampoule 1 and the electric furnace 7 may be held upright until they are heated to a predetermined temperature gradient after being upright. By holding the seed crystal 4 for an appropriate time, the seed crystal 4 is sufficiently melted back, and a more stable and smooth crystal surface can be obtained. As a result, it is possible to further suppress the deterioration of crystallinity due to abnormal crystal growth or defect introduction.

In the above embodiment, the case where the auxiliary heater is used to make the temperature of the solvent uniform has been described.
The solvent temperature may be made uniform by using other methods. FIG. 4 shows an example in which the upper periphery of the quartz ampoule 1 is covered with a heat insulating material 8 to make the temperature of the solvent uniform. FIG. 2 of the above embodiment
In the step of melting the solvent lump shown in (A), instead of disposing the auxiliary heater 6 around the upper part of the quartz ampoule 1, the upper part is covered with a heat insulating material 8. The heat insulating material 8 serves to reduce the flow of heat from the solvent 3 to the outside and to make the inside of the solvent 3 isothermal. Others are the same as those in FIG. In this way, the temperature of the solvent 3 can be made uniform by covering the area where the solvent 3 is accumulated with the heat insulating material 8. As the heat insulating material 8, for example, quartz glass wool or the like can be used.

In the above embodiments, the case where ZnSe is solution crystal-grown using the Se-Te solvent is explained, but it is also applicable to the case where another II-VI group compound semiconductor or another compound semiconductor is solution crystal-grown. Applicable.

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.

[0032]

As described above, according to the present invention,
It is possible to grow high quality crystals with few abnormal growths and crystal defects.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a solvent ampoule producing quartz ampoule and a crystal growth quartz ampoule for explaining a solvent lump producing step and a crystal growing step according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a crystal growth quartz ampoule for explaining a crystal growth process according to an example of the present invention.

FIG. 3 is a graph showing changes in the maximum grain size of grown crystals when the temperature of the solvent is changed.

FIG. 4 is a cross-sectional view of a crystal growth quartz ampoule for explaining a crystal growth process according to another embodiment of the present invention.

[Explanation of symbols]

 1 Quartz Ampoule 2 Source Crystal 3 Solvent 3a Solvent Mass 4 Seed Crystal 5 Heat Sink 6 Auxiliary Heater 7 Electric Furnace 8 Heat Insulation Material 10, 11 Solvent Constituent Material 12 Crystal Component Raw Material 13 Quartz Ampoule

Front page continuation (72) Inventor Yutaka Saito 239-1, Shimokagemori, Chichibu-shi, Saitama Prefecture (72) Toru Ikeushi 1157 Shimokagemori, Chichibu-shi, Saitama Prefecture Kirinoki Sha 307

Claims (7)

[Claims] 1. A solution crystal growth method in which a temperature difference is formed above and below a solution, a source crystal is arranged at a high temperature part of the solution, and a seed crystal is arranged at a low temperature part of the solution to perform crystal growth. A step of heating the seed crystal to a predetermined first temperature and the solution to a predetermined second temperature lower by a predetermined temperature than the first temperature in a state where the seed crystal and the solution do not come into contact with each other; And a solution, and a crystal growth step of forming a predetermined temperature difference above and below the solution to grow a crystal on the seed crystal. 2. The method for growing a solution crystal according to claim 1, wherein in the heating step, the component of the seed crystal is dissolved in the solution to a saturation solubility at the second temperature. 3. In the heating step, the seed crystal is heated by at least a heating means for heating the seed crystal, and the solution is heated by another heating means arranged only in the vicinity of the solution. Item 3. The solution crystal growth method according to Item 1 or 2. 4. The solution crystal growth method according to claim 1, wherein in the heating step, the periphery of the solution is covered with a heat insulating material and heated. 5. The second temperature is 2 more than the first temperature.
The solution crystal growth method according to any one of claims 1 to 4, which is lower by 0 to 40 ° C. 6. A solution crystal growth apparatus for forming a temperature difference above and below a solution, arranging a source crystal in a high temperature part of the solution and arranging a seed crystal in a low temperature part of the solution to perform crystal growth in an internal space. A space for accommodating a solution in which a seed crystal and a source crystal are arranged so that the seed crystal and the source crystal are in contact with each other in the first attitude, and the seed crystal and the source crystal are in contact with each other in the second attitude. A growth container that defines another space for containing the solution, a heating means for forming a predetermined temperature gradient in at least the space, and another for heating only the other space. A solution crystal growth apparatus including a heating means. 7. A solution crystal growth apparatus for forming a temperature difference above and below a solution, arranging a source crystal in a high temperature part of the solution and arranging a seed crystal in a low temperature part of the solution for crystal growth, A space for accommodating a solution in which a seed crystal and a source crystal are arranged so that the seed crystal and the source crystal are in contact with each other in the first attitude, and the seed crystal and the source crystal are in contact with each other in the second attitude. A growth container that defines another space for containing a solution, a heating means for forming a predetermined temperature gradient in the space and the other space, and only around the other space A solution crystal growth apparatus including a removable heat insulating material arranged.