JPH11130579A - Production of compound semiconductor single crystal and apparatus for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably seed a raw material melt by forming the solid-liquid interface of a seeding part into an upwardly convex surface in order to suppress the growth of a polycrystal from the seeding part when producing a compound semiconductor single crystal by a vertical gradient freezing(VGF) method. SOLUTION: A seed crystal 1 of the same shape as that of a diameter increasing part is arranged in the diameter increasing part increasing the diameter in the vertical directions and formed in the lower part of a growth vessel 4 and a seeding part thereof is defined in a region where a low-heat conductivity member 6 arranged on the periphery of the diameter increasing part is present. Thereby, the outflow of the latent heat generated when growing a single crystal from the seeding part to the outside of the radial direction is suppressed by the low-heat conductivity member 6 and a vessel support 7 which is a high-heat conductivity member is installed in the lower part of the growth vessel 4 to efficiently release the latent heat generated in the growth part from the lower part of the seed crystal 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to GaAs, Ga
The present invention relates to a method for manufacturing a single crystal of a III-V compound semiconductor such as P or InP or a II-VI compound semiconductor such as CdTe by a VB method, a VGF method or an LEC method, and an apparatus therefor.

[0002]

2. Description of the Related Art As a technique for producing a compound semiconductor single crystal represented by the group III-V, a pulling method or the like is known. In the production of a compound semiconductor single crystal by this pulling method, a melt is used. Due to problems such as decomposition, a liquid sealant such as boron oxide is generally used (L
EC method: Liquid Encapsulated C
zochralski method).

In recent years, the diameter of a conductive substrate for a semiconductor laser or a light emitting diode has been increased and the dislocation thereof has been reduced. As a method of growing a single crystal of a compound semiconductor represented by the group III-V, a conventional horizontal boat method has been used. (HB method, GF method)
The vertical Bridgman (VB) method and the vertical gradient freeze (VGF) method have attracted attention.

In the VB method and the VGF method, a vertical crystal in which a seed crystal is placed at a lower portion of a growth vessel (crucible) made of PBN, a compound semiconductor material is placed thereon, and a temperature distribution having a high upper portion and a lower portion is provided. In the electric furnace, the crystal is solidified from the lower part on the seed crystal side to the upper part.

[0005] When a group III-V compound semiconductor single crystal is grown by the VB method or the VGF method, a seed crystal is placed in a crystal accommodating portion at the bottom of a growth vessel, a polycrystalline material synthesized in advance is charged, and a dissociation vapor pressure is set. Or a liquid sealant (B
_The polycrystalline raw material is melted by covering the upper part with ₂ O ₃ ) to fill an inert gas in the furnace, and the upper part of the seed crystal is melted for seeding, and crystal growth is performed.

The shape of a growth vessel 4 used in a single crystal manufacturing apparatus of the VB method or the VGF method usually has a seed crystal accommodating portion a, a diameter increasing portion b, and a straight body portion c as shown in FIG. It comprises a crucible 34. That is, a straight body portion c having a vertically long cylindrical shape with a constant diameter, a diameter increasing portion b formed in a substantially conical shape below the straight body portion c, and a conical shape of the diameter increasing portion b. A seed crystal accommodating portion a comprising a seed holding thin tube portion projecting at the lowermost end to accommodate the seed crystal. The whole crucible 34
The crucible 34 is supported by a container support 17 made of graphite or quartz of a corresponding shape and moved from a high temperature part to a low temperature part in the hot zone of the electric furnace in this state.
Melting the compound semiconductor material therein to form a material melt 2;
Further, the upper part of the seed crystal 1 at the bottom is melted and seeded,
It solidifies in one direction from above to below. In FIG. 6, 9 is a solid-liquid interface, 10 is seeding (seeding).
Indicates a part.

Conventionally, it is difficult to single crystallize a compound semiconductor by the VB method and the VGF method, and it has been considered that this method is not suitable for industrial mass production. However, it has the advantage of being able to grow crystals under a low temperature gradient (several degrees Celsius / cm), and is being reviewed as a high-quality single crystal growth method with few crystal defects, and has been improved by various means. I have. As a single crystal production method improved from the VB method,
For example, Japanese Patent Publication No. 58-50757 and Japanese Patent Application Laid-Open No.
No. 2693 has been proposed.

[0008]

SUMMARY OF THE INVENTION However, VB
In the method and the VGF method, it is difficult to control the solid-liquid interface during growth, and it is difficult to perform single crystallization. In other words, for single crystal growth, it is preferable that the solid-liquid interface has a slightly convex shape toward the melt, which is preferably maintained throughout the growth. In the crystal manufacturing apparatus, even if the temperature gradient is steep, it tends to grow slightly more concavely than the seeding part 10, and the solid-liquid interface 9 of the crucible wall at the seeding part 10 tends to be concave upward. .

As shown in FIGS. 5 (a) and 5 (b), when the temperature in the radial direction of the seed crystal 1 in the seed crystal accommodating portion a is compared, the temperature of the crystal crucible wall B on the outer side of the crystal becomes: This is because the temperature becomes lower than the temperature of the crystal center portion A.
The temperature of the heater section C is also shown in FIG. 5B for reference.

When the solid-liquid interface 9 is concave upward,
Because the crystal grows from the crucible wall outside the crystal,
Material melt 2 around foreign matter and seed crystal attached to crucible wall
, The seed crystal 1 is susceptible to the influence of the surface roughness due to the inflow, and polycrystallized.

Therefore, as shown in FIG. 5 (a), by configuring the periphery of the seed crystal 1 to be covered with the liquid sealant 3 made of boron oxide (B ₂ O ₃ ), A method of stabilizing the meniscus in the above-described method and facilitating seeding has also been proposed (Japanese Patent Laid-Open No. 1-278490). However, even if such measures are taken, the surface roughness of the seed crystal and
The seeding could not be stabilized due to the thermal symmetry deviation in the circumferential direction due to the uneven thickness of the seed crystal part of the crucible.

Therefore, the present invention solves the above-mentioned problems, and
In producing a compound semiconductor single crystal by the B method or the VGF method, in order to suppress the polycrystalline growth from the seeding part as described above, the solid-liquid interface of the seeding part is convex upward, and stable seeding is possible. Accordingly, it is an object of the present invention to provide a method and an apparatus for producing a compound semiconductor single crystal, which can produce a high-quality, large-diameter compound semiconductor single crystal with high yield.

[0013]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and have found that the VB method or the VGF
In producing a compound semiconductor single crystal by the method, it has been found that the reason why the solid-liquid interface of the seeding portion is concave is that effective heat release from the central portion of the seed crystal is not performed. That is, as shown in FIG.
In the case of a structure in which the entire crucible 34 in which is filled is supported by a container support 17 made of graphite or quartz, an arrow 1 in FIG.
As shown in FIG. 1, heat flows toward the outside of the crucible 34. The solid-liquid interface 9 tends to form perpendicular to the heat flow, and as a result, the solid-liquid interface 9 has a concave shape toward the melt 2. Once it is concave, it is difficult to turn into a convex and consequently polycrystal is easily formed.

In the present invention, the seeding is performed at the enlarged diameter portion of the growth vessel.

That is, according to the method for producing a single crystal of the present invention, a seed crystal is disposed at a lower portion in a growth vessel, and a raw material melt of a compound semiconductor single crystal is disposed at an upper portion thereof, and the crystal is grown upward from the seed crystal. In the method for producing a compound semiconductor single crystal to be formed, a seed crystal having the same shape as the diameter-increased portion is arranged in an diameter-increased portion formed upward in the lower portion of the growth vessel, and A low thermal conductivity member is provided around the low thermal conductivity member, and a high thermal conductivity member is provided at the lower portion of the growth vessel so as to surround a growth vessel portion below the low thermal conductivity member, and the seeding of the low thermal conductivity member is performed. This is performed in the area of the diameter increasing portion (claim 1).

According to the present invention, since the position of the seeding portion is set in the region where the low thermal conductivity member such as a heat insulating material installed around the diameter-increasing portion is present, when the seeding portion grows from the seeding portion. The flow of the latent heat generated to the outside in the radial direction is suppressed. In addition, since a member with high thermal conductivity is installed at the center of the seed crystal bottom, the latent heat generated in the growth part can be efficiently released from the lower part of the seed crystal, and the heat flow during seeding is reduced. It is controlled to flow downward from the center. For this reason, the solid-liquid interface becomes a convex surface in the upward direction, so that seeding can be stably performed. For example, a relatively large compound semiconductor single crystal having a diameter of 75 mm or more can be manufactured in a high quality state with few defects and high yield. Will be able to In addition, since the seed crystal center is cooled, not only the seeding portion but also the straight body can be grown on a convex surface, so that a high yield of single crystal can be obtained.

According to the present invention, there is provided a growth vessel having a lower structure which does not have a normal seed crystal accommodating portion and has a diameter reduced in a downward direction as a growth vessel used for producing a compound semiconductor single crystal by the VB method or the VGF method. Not only the form using a container, but also a form using a normal growth container having a diameter increasing portion that increases in the upward direction between the seed crystal accommodating portion and the crystal growth straight body portion (Claim 2) is included. It is. In any of these types of growth vessels, a seed crystal having the same shape as the bottom of the growth vessel is arranged at the lower portion of the growth vessel. By installing a low heat conductivity member, that is, a member having a large heat capacity, and installing a high heat conductivity member, that is, a member having a small heat capacity, below the seed crystal in the growth vessel, the solid-liquid interface of the seeding portion is made convex upward, Stable seeding with suppressed polycrystalline growth can be performed. In addition, stable seeding can be achieved by using seed crystals that have been processed relatively easily, and high quality,
A large-diameter compound semiconductor single crystal can be manufactured with high yield.

Another manufacturing method of the present invention (Claim 3)
Is a method of manufacturing a compound semiconductor single crystal grown by using a pulling method, wherein a seed crystal having a tapered portion whose diameter is reduced upward is used as a seed crystal to be used, and seeding is performed at the tapered portion of the seed crystal. Is what you do. The seed crystal can be a seed crystal produced by the method of claim 1 or 2, and is melted, for example, about several mm from the point of contact with the melt to form a tapered portion of the seed crystal. Can be used for seeding.

Further, in the apparatus for producing a compound semiconductor single crystal according to the present invention, a seed crystal is disposed at a lower portion in a growth vessel, and a raw material melt of the compound semiconductor single crystal is disposed at an upper portion thereof, and upward from the seed crystal. In the form of an apparatus for manufacturing a compound semiconductor single crystal for growing a crystal (Claim 4), or a growth vessel having a diameter increasing portion which increases in diameter upward between a seed crystal accommodating portion and a crystal growth straight body portion. In the form of an apparatus for producing a compound semiconductor single crystal in which a seed crystal is disposed at a lower part of the above and a raw material melt of the compound semiconductor single crystal is disposed at an upper part thereof and the crystal is grown upward from the seed crystal, A low thermal conductivity member is installed around the enlarged diameter portion of the growth vessel, and a high thermal conductivity member is installed at the lower portion of the growth vessel so as to surround the growth vessel portion below the low thermal conductivity member, and the seeding position is set. Said low It is obtained by setting in the region of increased diameter in the presence of conductivity member.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment.

FIG. 1 shows an embodiment of a method of manufacturing a compound semiconductor single crystal according to the present invention, and FIG. 2 shows details of a manufacturing apparatus used in this embodiment.

In FIG. 2, the growth vessel 4 formed by the VB method or the VGF method has a lower portion formed in a conical shape whose diameter is reduced downward, and a diameter-increasing portion b whose diameter increases upward from the conical tip, that is, the lower end. , Followed by an upper crystal growth straight body c. That is, the growth vessel 4 here does not have the seed crystal accommodating portion a (see FIG. 6) composed of a normal seed holding capillary portion.
A crucible 14 having a lower structure whose diameter is reduced downward is used.

A seed crystal 1 having the same shape (here, a conical shape) as the bottom of the crucible 14 is arranged at a lower portion, that is, a bottom of the crucible 14. The seed crystal 1 is processed and arranged so that the upper end thereof reaches a low thermal conductivity member 6 made of a heat insulating material provided around the diameter-increased portion b of the crucible 14, that is, a member having a large heat capacity.

As a support for supporting the crucible 14, a low thermal conductivity member 6 made of the above-mentioned heat insulating material is installed on the upper part around the diameter-increasing portion b, and a growth container below the low thermal conductivity member 6 is added. A vessel support 7 made of a high thermal conductivity member having a high thermal conductivity is provided at the lower part of the growth vessel so as to surround the diameter b, that is, the periphery of the seed crystal 1.

In the present manufacturing apparatus, the seed crystal 1 is disposed in a portion having a steep temperature gradient in a growth furnace provided with the heater 5. The temperature increase is performed while monitoring the detection output of the thermocouple 8 provided in the diameter increasing portion b near the seeding portion 10, and when the heat of fusion generated when the seed crystal 1 is melted is detected,
Stop heating and start seeding.

This state is maintained for 10 hours or more.
4 is lowered at a rate of -3.0 mm / hr to start growth. Figure 1 shows the temperature distribution in the radial direction of the seed crystal 1 during growth.
(B). Curve A is the crystal center A shown in FIG.
The curve B shows the temperature of the crystal crucible wall B shown in FIG. 1A, and the curve C shows the temperature change of the heater C shown in FIG. 1A.

As can be seen from the comparison between the curves A and B in FIG. 1B, the temperature in the radial direction of the seed crystal 1 in the region where the low thermal conductivity member 6 exists is the crystal crucible outside the crystal. The temperature of the wall portion B is higher than the temperature of the crystal center portion A. This is due to the effect of installing the low thermal conductivity member 6 on the upper portion around the diameter-increased portion b and installing the container support 7 as a high thermal conductivity member around the seed crystal 1.

Therefore, the position of the seeding portion 10 is changed to the diameter increasing portion b.
Is set in a region where the low thermal conductivity member 6 made of a heat insulating material is installed around the device. Thereby, the latent heat generated when growing from the seeding portion 10 is suppressed from flowing outward in the radial direction. Further, since the container support 7 of a high thermal conductivity member having a high thermal conductivity is provided below the seed crystal 1, the latent heat generated in the growth portion can be efficiently released from the lower portion of the seed crystal 1. it can.

By the above-described effects, the heat flow in the seed crystal 1 is directed downward from the center of the seed crystal 1 as shown by an arrow 11 in FIG. It becomes a convex surface, and seeding can be performed stably. In addition, since the central part of the seed crystal 1 is cooled, not only the seeding part but also the straight body part can be grown on a convex surface, so that a high yield of single crystal can be obtained.

The above operation and effect can be obtained by using the growth container shown in FIG.
It can also be obtained by using a normal growth container (normal crucible) 34 as shown in FIG. As the seed crystal 1 to be used, a diameter-increased portion is cut out as an integral body from a single crystal seed crystal usually grown in a crucible, and seeding is performed in a region where the heat insulating material 6 provided around the diameter-increased portion b is present. The same effect as described above can be obtained. Further, it is not necessary to process a new seed crystal for seeding, and a single crystal having a high yield at a low cost can be obtained.

[0031]

【Example】

(Example 1) An example of growing a GaAs single crystal will be described with reference to FIG.

In a crucible 14 made of pyrolytic boron nitride (PBN) having no ordinary seed crystal accommodating portion, 3000 g of the seed crystal 1 and the GaAs raw material having the same shape as the crucible bottom were put and set in a VGF furnace. Thereafter, vacuuming and gas replacement are performed, and the heater is heated. The temperature is raised while monitoring the temperature of the thermocouple 8 installed in the seeding unit 10. When the melting heat reaction is detected in one part of the seed crystal, the temperature of the heater 5 is stopped, and the seeding is performed for 10 hours or more.

After holding for 10 hours or more, the temperature gradient near the solid-liquid interface 9 at the seeding portion is adjusted to about 7 ° C./cm.

Thereafter, the crystal is solidified by lowering the crucible 14 at a speed of 3 mm / hr while rotating the crucible 14 at 5 rpm.
After solidifying the whole, it is cooled to room temperature at about 50 ° C./hr,
Remove from furnace.

By this method, a GaAs single crystal having a diameter of about φ80 mm and a straight body length of about 100 mm was obtained at a high yield. When the characteristics of the obtained crystal were evaluated, 90% of the cut wafers had a dislocation density of 600 / cm ² or less as an in-plane average value, were extremely low in crystal defects, and had uniformity in the ingot. It was of high quality.

(Example 2) P having no ordinary seed crystal accommodating portion
As a substitute for the BN crucible 14, a normal PBN crucible 34 equipped with a seed crystal accommodating portion c as shown in FIG. 3 is used, and from a single crystal seed crystal grown with a crucible of the same shape to a diameter-increased portion. Cut out as one piece. This crystal block was etched with dilute aqua regia and used as a seed crystal 1. Seeding was performed at the diameter-increased portion b in the same procedure as in Example 1, and then crystal growth was performed.

Also in this case, high yield and high quality crystals could be obtained without polycrystallization from the seeding portion.

In the first and second embodiments, G
Although a single crystal growth of aAs has been described, the present invention can be applied to single crystal growth of, for example, InP, GaP, etc., in addition to GaAs. Further, the growth method may be the VB method instead of the VGF method.

(Embodiment 3) FIG.
This will be described with reference to FIG.

Raw material and liquid sealant (B_TwoO_Three)
Container support 2 with PBN crucible container 24 with lower shaft 26
7 and set in a furnace to raise the temperature. Raw material and B
_TwoO _ThreeIs melted, and the raw material melt 22 is covered with a liquid sealant 23.
After covering, the tapered seed crystal 21 set on the upper shaft 25
Lower while rotating. Seed crystal 21 becomes melt 22
Seeding is performed by melting several millimeters from the point of contact.
After seeding, lower the temperature of the heater at -0.1deg / hr,
Do the long. After the initial growth, rotate the upper shaft 25 at 2.0 rpm.
While growing, increase at a rate of 5.0 / hr to grow.
U. By using the seed crystal 21 described above,
It is possible to perform seeding and reseed
The extension of the seeding time by
The carbon generated from the fight member does not increase,
A single crystal with good characteristics was obtained.

[0041]

As described above, according to the present invention, the following excellent effects can be obtained.

(1) According to the first, second, fourth, and fifth aspects of the present invention, the seeding portion is located in the area where the low thermal conductivity member is provided around the lower diameter increasing portion of the growth vessel. , The latent heat generated when growing from the seeding portion is suppressed from flowing outward in the radial direction. Further, since the high thermal conductivity member is provided at the center of the seed crystal bottom, the latent heat generated in the growth part can be efficiently released from the lower part of the seed crystal. Because of this, the heat flow during seeding
The liquid-solid interface is controlled so as to flow downward from the center of the seed crystal, and the solid-liquid interface becomes a convex surface upward, so that the seeding can be stably performed. In addition, since the seed crystal center is cooled, not only the seeding portion but also the straight body can be grown on a convex surface, so that a high yield of single crystal can be obtained.

(2) According to the third aspect of the present invention, in the pulling method, a seed crystal having a tapered portion whose diameter is reduced in an upward direction is used, and the seed crystal is attached at the tapered portion of the seed crystal. Therefore, seeding can be performed with high probability. For this reason, the seeding time is not prolonged due to the reseeding, and the carbon generated from the graphite member in the pulling furnace does not increase, so that a single crystal with good electrical characteristics can be obtained.

[Brief description of the drawings]

FIGS. 1A and 1B are views for explaining the heat flow of a seeding unit in an embodiment of the manufacturing method of the present invention, wherein FIG. 1A is a VGF furnace part, FIG. 1B is a crystal center part in the furnace, and a crystal crucible. It is the figure which showed the temperature distribution of a wall part and a heater part.

FIG. 2 is a diagram showing a configuration of an apparatus for performing a manufacturing method in the embodiment of FIG. 1 of the present invention.

3A and 3B are diagrams for explaining the heat flow of a seeding unit in another embodiment of the manufacturing method of the present invention. FIG. 3A shows a VGF furnace part, FIG. 3B shows a crystal center part in the furnace, and FIG. It is the figure which showed the temperature distribution of a crucible wall part and a heater part.

FIG. 4 is a principle view showing a case where the present invention is suitable for a pulling method.

5A and 5B are diagrams for explaining the heat flow of a seeding part in a conventional manufacturing method by the VGF method, wherein FIG. 5A is a VGF furnace part, FIG. 5B is a crystal center part in the furnace, and a crystal crucible wall part. FIG. 4 is a diagram showing a temperature distribution of a heater unit.

FIG. 6 is a schematic view showing a conventional VGF manufacturing apparatus.

[Explanation of symbols]

 Reference Signs List 1 seed crystal 2 raw material melt 3 liquid sealant 4 growth container (crucible) 5 heater 6 low thermal conductivity member 7 container support (high thermal conductivity member) 8 thermocouple 9 solid-liquid interface 10 seeding portion 11 arrow (heat) Flow) 14 Crucible 17 Container support 21 Seed crystal 22 Raw material melt 23 Liquid sealant 24 Crucible container 25 Upper shaft 26 Lower shaft 27 Container support 34 Crucible a Seed crystal accommodating part (seed holding thin tube part) b Large diameter part c Straight body part A Crystal center part B Crystal crucible wall part C Heater part

Claims (5)

[Claims] 1. A method for producing a compound semiconductor single crystal, comprising: disposing a seed crystal at a lower portion in a growth vessel and a raw material melt of the compound semiconductor single crystal at an upper portion thereof, and growing the crystal upward from the seed crystal. A seed crystal having the same shape as the diameter-increased portion is arranged in the diameter-increased portion formed upward in the lower portion of the growth vessel, and a low thermal conductivity member is provided around the diameter-increased portion of the growth vessel. At the same time, a high thermal conductivity member is provided at a lower portion of the growth vessel so as to surround a growth vessel portion below the low thermal conductivity member, and seeding is performed in an area of a diameter increasing portion where the low thermal conductivity member exists. A method for producing a compound semiconductor single crystal, comprising: 2. A seed vessel in a lower portion of a growth vessel having a diameter-increasing section which increases in diameter between a seed crystal accommodating section and a crystal growth straight body portion, and a material melt of a compound semiconductor single crystal in an upper portion thereof. In the method for producing a compound semiconductor single crystal in which a liquid is arranged and a crystal is grown upward from the seed crystal, the liquid is placed in a volume part from the seed crystal accommodating part formed in the lower part of the growth vessel to the inside of the diameter increasing part. A seed crystal having the same shape as the above is arranged, and a low thermal conductivity member is installed around the diameter-increased portion of the growth vessel, and a lower portion of the growth vessel is surrounded by the growth vessel portion below the low thermal conductivity member. A method for producing a compound semiconductor single crystal, wherein a high thermal conductivity member is provided, and seeding is performed in a region of an increased diameter portion where the low thermal conductivity member exists. 3. A method of manufacturing a compound semiconductor single crystal grown by a pulling method, wherein a seed crystal having a tapered portion whose diameter is reduced in an upward direction is used as a seed crystal to be used. A method for producing a compound semiconductor single crystal, comprising performing seeding. 4. A compound semiconductor single crystal manufacturing apparatus in which a seed crystal is disposed at a lower part in a growth vessel and a raw material melt of a compound semiconductor single crystal is disposed at an upper part thereof, and the crystal is grown upward from the seed crystal. Placing a low thermal conductivity member around the diameter-increased portion of the growth vessel, and installing a high thermal conductivity member at a lower portion of the growth vessel so as to surround a growth vessel portion below the low thermal conductivity member; An apparatus for manufacturing a compound semiconductor single crystal, wherein a position is set in a region of an increased diameter portion where the low thermal conductivity member exists. 5. A seed vessel in a lower portion of a growth vessel having a diameter-increasing section which increases in diameter between a seed crystal accommodating section and a straight body portion for growing a crystal, and a material melt of a compound semiconductor single crystal in an upper portion thereof. In a compound semiconductor single crystal manufacturing apparatus for disposing a liquid and growing a crystal upward from the seed crystal, a low thermal conductivity member is provided around a diameter-increasing portion of the growth vessel, and the low thermal conductivity member is provided. A compound characterized in that a high thermal conductivity member is provided at a lower portion of a growth vessel so as to surround a lower growth vessel portion, and a seeding position is set in a region of a diameter increasing portion where the low thermal conductivity member exists. Semiconductor single crystal manufacturing equipment.