JP2004161559A - Apparatus for manufacturing compound semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a growth vessel supporting structure with which heat flow control to make solid-liquid boundary to a shape of a convex on a liquid phase side is possible in an apparatus for manufacturing a compound semiconductor. <P>SOLUTION: The apparatus for manufacturing the compound semiconductor by a vertical type growth method grows a single crystal by supporting the crystal growth vessel having a seed crystal housing section 3a, an increased diameter section 3b and a crystal growth section 3c disposed in a vertical type inside heaters 5 and 6 with the increased diameter section of its lower part supported with a support 1 and by solidifying a semiconductor melt gradually from the lower side toward the upper side in the crystal growth vessel. The support 1 for supporting the increased diameter section 3b of the growth vessel 3 is a tubular and consists of a structure having a space 1a under the lower side of the growth vessel. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for manufacturing a compound semiconductor crystal by a vertical growth method in which a semiconductor melt is gradually solidified from below in a crystal growth vessel upward to grow a single crystal, and particularly to a support structure of the growth vessel. The present invention relates to a crystal growth apparatus for obtaining a single crystal with high reproducibility and high yield by making a solid-liquid interface convex during crystal growth.
[0002]
[Prior art]
A vertical growth method in which a semiconductor raw material melt is housed in a container (crucible) and solidified gradually above a seed crystal previously arranged at the bottom of the container to grow a single crystal, that is, a vertical Bridgman method (VB method) ) And the vertical temperature gradient solidification method (VGF method) have the advantage that a single crystal having a relatively large diameter and a low dislocation density in the crystal can be produced. It is an important technique as a method for growing a group III compound semiconductor crystal.
[0003]
In both the vertical Bridgman method (VB method) and the vertical temperature gradient solidification method (VGF method), a semiconductor raw material melt is stored in a container (crucible), and crystal growth is started from a seed crystal previously arranged at the bottom of the container. This is common in that the crystallization is advanced by gradually solidifying the material upward, and finally the entire raw material melt is crystallized. However, the vertical Bridgman method (VB method) grows by relatively lowering the growth vessel, whereas the vertical temperature gradient solidification method (VGF method) grows only by the temperature drop. . In any case, since the crystal can be grown under a small temperature gradient (a gentle temperature gradient) as compared with the liquid sealing pulling method (LEC method), a compound semiconductor single crystal having few crystal defects such as dislocations can be obtained. it can.
[0004]
In the vertical growth method such as the VB method or the VGF method, a seed crystal is placed in a lower portion of a growth vessel, and a compound semiconductor polycrystal is placed thereon, and placed in a furnace capable of providing a temperature gradient in a vertical direction, A single crystal is manufactured by growing a crystal upward from a seed crystal, and is characterized in that a crystal having a large diameter exceeding 76 mm and having few crystal defects can be easily grown.
[0005]
FIG. 3 schematically shows a conventional crystal growth apparatus. The growth apparatus includes a cylindrical growth vessel 3 containing a seed crystal 7, a GaAs raw material 8, and a liquid sealant 4, a support 1 supporting the same, and a heater (heater) capable of forming a predetermined temperature gradient. (Heating elements) 5 to 6 and a lower shaft 2 which can move vertically downward as it grows.
[0006]
As a conventional example, an example in which a single crystal of gallium arsenide (GaAs), which is a kind of III-V compound semiconductor, is grown by a vertical Bridgman method (VB method) will be described for the VB furnace shown in FIG.
[0007]
The crystal growth vessel 3 has a seed crystal accommodating portion 3a having a small cross-sectional area, a diameter-increasing portion 3b having a gradually increasing cross-sectional area, and a crystal growing portion 3c having a large cross-sectional area and a substantially constant subsequent size. It is a container made of PBN.
[0008]
First, a GaAs seed crystal 7 is inserted into a seed crystal accommodating portion 3a at the bottom of a PBN container, and GaAs polycrystalline material and boron trioxide (B ₂ O ₃ ) as a liquid sealant 4 are charged. The crystal growth vessel 3 is supported by the support 1 and the lower shaft 2 and loaded into a pressure vessel. The inside of the pressure vessel is replaced with an inert gas, pressurized, and power is supplied to the heaters 5 and 6 so that the GaAs polycrystalline raw material and B ₂ O ₃ is melted into a GaAs melt layer and a B ₂ O ₃ liquid sealant melt layer, and seeding is performed. Next, a temperature gradient of, for example, 5 ° C./cm is set near the seeding portion, and crystal growth is performed by the vertical Bridgman method in which the crystal growth vessel 3 is lowered at a speed of 5 mm / hr.
[0009]
The point of obtaining a single crystal with good reproducibility by the vertical Bridgman method is to control the shape of the interface between the melt and the crystal part (hereinafter, “solid-liquid interface”), and the solid-liquid interface is convex toward the melt. It is generally known that the point of controlling the shape of the solid-liquid interface to control the shape is the control of the heat flow during the crystal growth process. For this reason, it has been proposed to arrange a heat shield member surrounding the outer periphery of the growth vessel between the growth vessel (crucible) and the heater (for example, see Patent Document 1).
[0010]
[Patent Document 1]
JP-A-5-24964
[Problems to be solved by the invention]
However, the prior art has the following problems.
[0012]
FIG. 2B schematically shows the solid-liquid interface shape and the heat flow of the conventional crystal growth apparatus described with reference to FIG. In order to support the load of the growth vessel 3, the entire surface of the growth vessel taper portion (the diameter increasing portion 3 b) is covered with the support 1. For this reason, most of the latent heat generated by crystallization solidification escapes from the crystal side surface where heat can be easily dissipated, and the direction of the total heat flow is outward as shown by the arrow A. As a result, the solid-liquid interface has a convex shape toward the solid phase, and dislocations accumulate inside the crystal as it grows, which causes a problem of polycrystallization.
[0013]
On the other hand, the method of arranging a heat shield member surrounding the outer periphery of the growth vessel as in Patent Document 1 requires an additional member and may hinder heat transfer from the heater.
[0014]
Therefore, an object of the present invention is to solve the above problems and provide a growth container supporting structure capable of controlling a heat flow such that a solid-liquid interface is convex toward the liquid phase side in a compound semiconductor manufacturing apparatus. Therefore, dislocations are prevented from accumulating inside and polycrystallizing, and the production yield of single crystals is improved.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows.
[0016]
The compound semiconductor manufacturing apparatus according to the first aspect of the present invention has a seed crystal housing part, a diameter increasing part that has a gradually increasing cross-sectional area following the seed crystal housing part, and a crystal growth part that has a large and substantially constant cross-sectional area that follows. The crystal growth vessel is vertically arranged in the heating device with the lower diameter increasing portion supported by a support, and the semiconductor melt is gradually solidified from below to above in the crystal growth vessel to form a single crystal. In the apparatus for producing a compound semiconductor crystal by the vertical growth method, the support for supporting the increased diameter portion of the growth vessel is tubular, and has a space below the growth vessel.
[0017]
According to a second aspect of the present invention, in the compound semiconductor manufacturing apparatus according to the first aspect, the support for supporting the increased diameter portion of the growth vessel is formed of a tubular body that is opened upward, and the crystal growing section in the increased diameter portion. It is characterized by supporting near the boundary with.
[0018]
According to a third aspect of the present invention, in the compound semiconductor manufacturing apparatus according to the first or second aspect, the support for supporting the diameter-increasing portion of the growth container is a hollow member provided on a vertically movable lower shaft. It is characterized by comprising a cylindrical member.
[0019]
<The gist of the invention>
According to the present invention, in a crystal growth apparatus based on the VB method or the VGF method, the support has a tubular shape and a structure having a space below the growth vessel.
[0020]
Since only a part of the tapered portion (increased diameter portion 3b) of the growth vessel is covered by the tip of the tubular support 1, most of the latent heat generated by crystal solidification is reduced by the conventional tapered portion (increased diameter portion 3b). As in the case where the diameter portion 3b) is covered with the support, the crystal portion does not escape from the crystal side surface where heat can be easily dissipated (see the arrow A in FIG. 2B), and the direction of the total heat flow is directed straight downward. (See arrow A in FIG. 2A). As a result, the solid-liquid interface becomes convex or flat on the melt side.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on the illustrated embodiments.
[0022]
FIG. 1 schematically shows a compound semiconductor crystal growth apparatus according to an embodiment of the present invention. As with the conventional crystal growth apparatus, this growth apparatus includes a cylindrical crystal growth vessel 3 containing a seed crystal 7, a GaAs raw material 8, and a sealant 4, a support 1 supporting these, and a predetermined temperature. It is composed of heaters (heating elements) 5 to 6 as heating devices capable of forming a gradient, and a lower shaft 2 which can move vertically downward as it grows and has the support 1 attached to the upper part. The crystal growth vessel 3 is made of PBN, and has a seed crystal accommodating section 3a provided at the bottom of the vessel and having a small cross-sectional area, a diameter increasing section 3b having a gradually increasing cross-sectional area, and a subsequent cross-sectional area. And a crystal growing portion 3c having a substantially constant diameter.
[0023]
The support 1 that supports the increased diameter portion 3b of the growth vessel is formed of a tubular member that is open upward, and has a structure that supports the vicinity of the boundary between the increased diameter portion and the crystal growing portion. Therefore, due to this tubular support 1, a space 1a exists on the lower side of the growth vessel, more precisely, on the tapered portion of the diameter-increased portion 3b.
[0024]
When the support 1 is formed in a tubular shape and the space 1a is provided below the growth vessel 3 as described above, heat can be easily dissipated below the crystal, and as shown in FIG. Among them, the heat that escapes from the crystal side surface is relatively reduced. As a result, the total heat flow goes straight downward as shown by the arrow A in FIG. 2A, and the solid-liquid interface shape B becomes convex.
[0025]
In other words, the latent heat generated during the solidification of the crystal, when there is no object in contact with the lower side of the growth vessel, radiates most of the heat radiation instead of conduction. Therefore, the heat flow is directed downward, and the shape of the solid-liquid interface becomes convex.
[0026]
【Example】
Embodiments of the present invention will be described using a GaAs crystal growth apparatus as an example.
[0027]
As shown in FIG. 1, 11 kg of a seed crystal 7, 11 kg of a GaAs raw material 8 and 600 g of a sealant 4 are put in a growth vessel 3. The growth vessel 3 containing the raw material is placed on the lower shaft 2 via the support 1. The heating elements 5 to 6 formed a predetermined temperature gradient, and the growth was performed by lowering the growth vessel 3 containing the raw material and the lower shaft 2 on which the support 1 was placed at a speed of 1 to 3 mm / hour.
[0028]
When the solid-liquid interface shape of the crystal grown by the above method was confirmed, it became convex toward the contact liquid side as shown in FIG. In addition, a single crystal having a diameter of 4 inches and a length of 150 mm was obtained by this method.
[0029]
When crystal growth was performed 50 times by the same method, the production yield of single crystal growth was 70% or more. This value is significantly improved as compared with the single crystal production yield of 50% in the prior art.
[0030]
In the above-described embodiment, a GaAs single crystal manufacturing apparatus has been described. However, the present invention can be applied to all apparatus for growing compound semiconductor crystals, such as InP and GaP, which perform crystal growth by the VB method or the VGF method. The same effect of controlling the solid-liquid interface as described above can be obtained.
[0031]
In the above embodiment, the diameter of the growth vessel is supported by the top of the tubular member whose top is open. However, the present invention is not limited to this. That is, the support for supporting the diameter-increased portion of the growth vessel is formed of a tubular body that is opened upward, and has a step portion that supports the vicinity of the boundary between the diameter-increased portion and the crystal growth portion in the middle thereof ( (See FIG. 2A).
[0032]
The compound semiconductor single crystal obtained by the device according to the present invention not only has a higher single crystal production yield than the conventional device, but also tends to have fewer dislocation accumulation parts than the compound semiconductor single crystal obtained by the conventional device. Therefore, when a compound semiconductor wafer obtained by the present invention is used to form a device, it is possible to prevent a reduction in the device yield due to dislocation, and the economic effect in industrial production is great.
[0033]
【The invention's effect】
As described above, according to the present invention, in the crystal growth apparatus using the vertical growth method such as the VB method or the VGF method, the support is tubular and the space is provided below the growth vessel, so there is no space. As compared with the case, the heat flow is directed downward, whereby the solid-liquid interface shape becomes convex on the liquid side, that is, upward. As a result, dislocations are prevented from accumulating inside the crystal as the crystal grows, and the production yield is improved without polycrystallization. In addition, the solid-liquid interface during crystal growth can be made convex toward the liquid phase by a simple and local means of changing the structure of a conventional support, thereby providing good reproducibility and high yield. Thus, a single crystal can be obtained.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a configuration of a compound semiconductor manufacturing apparatus according to the present invention.
FIG. 2 shows a heat flow and a solid-liquid interface shape of a grown crystal. FIG. 2 (B) is a cross-sectional view showing a heat flow and a solid-liquid interface shape of a crystal grown by a conventional apparatus. FIG. 3 is a cross-sectional view showing a heat flow and a solid-liquid interface shape of a crystal grown by the apparatus of the present invention.
FIG. 3 is a cross-sectional view illustrating a configuration of a conventional compound semiconductor manufacturing apparatus using a vertical growth method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Support 1a Space 2 Lower axis 3 Crystal growth container 3a Seed crystal accommodating part 3b Diameter increasing part 3c Crystal growing part 4 Liquid sealant 5, 6 Heater 7 seed crystal 8 GaAs raw material

Claims (3)

Supports a crystal growth vessel that has a seed crystal housing part, a diameter increasing part that has a gradually increasing cross-sectional area following it, and a crystal growth part that has a large and substantially constant cross-sectional area following it. Production of compound semiconductor crystal by vertical growth method in which a semiconductor melt is vertically arranged in a heating device while being supported by a body, and the semiconductor melt is gradually solidified from below in a crystal growth vessel to grow a single crystal. In the device,
An apparatus for manufacturing a compound semiconductor, wherein a support for supporting a diameter-increasing portion of the growth vessel is tubular and has a space below the growth vessel. The compound semiconductor manufacturing apparatus according to claim 1,
A compound semiconductor manufacturing apparatus, wherein a support for supporting the increased diameter portion of the growth vessel comprises a tubular body opened upward, and supports a vicinity of a boundary between the increased diameter portion and a crystal growing portion. The compound semiconductor manufacturing apparatus according to claim 1 or 2,
A compound semiconductor manufacturing apparatus, wherein a support for supporting the diameter-increased portion of the growth vessel comprises a hollow cylindrical member provided on a vertically movable lower shaft.

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