JP2850581B2 - Semiconductor crystal manufacturing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a semiconductor crystal for growing a crystal by gradually solidifying a semiconductor melt from below in a crucible upward.

[0002]

2. Description of the Related Art A vertical growth method for growing a single crystal by gradually solidifying a semiconductor melt from a lower portion to an upper portion in a crucible, that is, a vertical slow cooling method (VGF method) or a vertical Bridgman method (VB method) Method), etc., have a relatively large diameter,
In addition, since a single crystal having a low dislocation density in a crystal can be formed, it is attracting attention as a method for growing a semiconductor crystal, particularly, a III-V compound semiconductor crystal.

A conventional III-V compound semiconductor crystal growth by the VGF method will be described below with reference to a VGF furnace shown in FIG.

A seed crystal 9 is disposed at the lower end of a crucible 3 made of pBN, and a polycrystal of a group III-V compound is accommodated in the crucible 3. Then, the crucible 3 is set on the crucible support 4 in the growth vessel 2. Below the crucible support 4,
A group V element 10 is provided for the purpose of keeping the inside of the growth vessel 2 in a group V element atmosphere. The upper opening of the growth vessel 2 is closed with a lid 1 provided with a gap 1a so that the pressure inside the vessel becomes equal to the external pressure.
Outside the growth vessel 2, a heater 5 for heating the melt having a temperature gradient such that the lower portion is lower than the upper portion, and a heater 6 for heating the group V element for vaporizing and evaporating the group V element are provided. ing.

The crystal growth is performed by first melting the polycrystal in the crucible 3 by the heater 5 to form a melt 7 of a III-V compound, and then gradually cooling the heater 5 to form a seed crystal in the crucible 3. This is performed by solidifying and growing a single crystal 8 of a group III-V compound having the same orientation as 9 upward from below.

[0006]

When a crystal is grown by a vertical growth method such as the VGF method or the VB method, the biggest problem is that the crystal is polycrystallized during the growth. For the vertical growth method,
Since the heat diffusion from the crystal is smaller than other growth methods such as the liquid sealing pulling method (LEC method) and the horizontal boat method (HB method), the crystal must be grown by lowering the melt temperature. No. Therefore, the temperature gradient in the inner diameter direction of the melt at a position near the solid-liquid interface of the crystal has a low temperature distribution on the crucible wall as shown in FIG. This tendency is particularly severe during seeding at the beginning of growth and during shoulder formation. Since the crystal grows faster as the temperature of the melt is lower, the solid-liquid interface shape of the crystal becomes concave toward the melt in the melt having a temperature distribution as shown in FIG. That is, since the temperature of the melt drops quickly from the periphery, the flow of heat is as indicated by the arrow in FIG. Since the solid-liquid interface tends to be perpendicular to the flow of heat, the shape of the solid-liquid interface is necessarily concave. If the shape of the solid-liquid interface is concave, dislocations that propagate in the crystal as it grows are likely to accumulate at the center of the crystal, and if it is densely integrated, the crystal will be polycrystallized from that position. In order to obtain a single crystal, it is desirable that the solid-liquid interface shape be flat or slightly convex toward the melt.However, for such reasons, the conventional vertical growth method or Difficult with that device.

Further, in the vertical growth apparatus, the seed crystal may be melted by heating when melting the raw material polycrystal due to its structure, so that the growth may become impossible.

An object of the present invention is to provide a novel semiconductor crystal manufacturing method and apparatus capable of preventing a concave-convex shape of a solid-liquid interface shape in the prior art and manufacturing a high-quality crystal with good reproducibility. Is to do.

[0009]

According to the method of manufacturing a semiconductor crystal of the present invention, a seed crystal is arranged at the bottom of a crucible, and a semiconductor melt contained in the crucible is brought into contact with the seed crystal and is moved upward from below. In a method of manufacturing a semiconductor crystal in which a single crystal is manufactured by gradually solidifying, a seed crystal portion is forcibly forced so that a solid-liquid interface shape between the crystal and the semiconductor melt is flat or convex toward the melt. It is intended to be cooled.

[0010] The apparatus for manufacturing a semiconductor crystal according to the present invention comprises:
A crucible that has a seed crystal disposing part for disposing a seed crystal at the bottom and contains a semiconductor melt at the top, and a melt heating that forms a temperature gradient outside the crucible such that the lower part is lower than the upper part. Means for producing a crystal by solidifying a semiconductor melt in contact with a seed crystal upward from below, wherein a refrigerant passage is provided around the outer periphery of the seed crystal arrangement portion at the bottom of the crucible. And a cooling means for cooling the seed crystal disposing portion by flowing a liquid through the cooling device.

Further, the apparatus for manufacturing a semiconductor crystal according to the present invention has a coolant passage having radiating fins on an outer peripheral portion of the seed crystal disposing portion at the bottom of the crucible. Is provided with a cooling means for cooling the water.

As a method for producing a semiconductor crystal, in addition to the VGF method, a VB method or a furnace moving method for solidifying a crystal by lowering a crucible containing raw materials in a vertically arranged heater (Traveling Furnace). (TF) method).

As the refrigerant used for cooling the seed crystal, water is the simplest and most reliable liquid if it is a liquid, but other refrigerants such as Freon and Freon can be used. It is also possible to use a medium.

The semiconductor material applicable to the present invention is GaAs.
III-V compounds such as s, InAs, GaSb, InSb, GaP, InP, CdTe, ZnSe, ZnS, H
A group II-VI compound such as gTe, or a group IV element of Si or Ge, and a mixed crystal containing at least one of these.

[0015]

When the temperature of the melt drops rapidly from the periphery, the shape of the solid-liquid interface necessarily becomes concave. However, when the seed crystal is forcibly cooled as in the present invention, the amount of heat dissipation from the crystal is larger than that of the melt. Since the solid-liquid interface tends to be perpendicular to the flow of heat, if the amount of heat dissipation flowing from the melt side to the crystal side increases, the solid-liquid interface becomes flat or convex toward the melt. Thereby, accumulation of dislocations is less likely to occur, and a high-quality crystal can be obtained. Further, the seed crystal does not melt when the raw material polycrystal is melted.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 A GaAs single crystal was grown using a VGF apparatus having a structure for cooling a seed crystal with water as shown in FIG. This apparatus has basically the same configuration as that of FIG. 3 described in the conventional example.
The cooling water passage 11 is provided inside the crucible support 4 so as to surround the seed crystal disposing portion 3 a provided at the lower end of the crucible 3. The growth was carried out while flowing cooling water at 22 ° C. and 10 l / min through this channel. The crucible used was 55 mm in diameter and 250 mm in total length, and the charge amount of GaAs polycrystal was 1700 g. As a crystal, a complete single crystal was obtained over a total length of 155 mm from the seed crystal to the terminal end of the crystal. The crystal was cut vertically, etched, and the solid-liquid interface shape 15 was examined. As a result, it was confirmed that the crystal had a convex shape over the entire region.

Example 2 A single crystal of GaAs was grown by gas cooling the seed crystal. FIG. 2 shows a cross-sectional view of the used apparatus. This apparatus also has basically the same configuration as that of FIG. 3 described in the conventional example, except that the crucible support 4 is hollow to form a refrigerant passage 12, and the passage 12 has a gas inlet / outlet 12a for cooling a seed crystal. Is provided to allow the seed crystal 9 to be cooled by flowing gas around the seed crystal disposing portion 3a. In order to increase the cooling efficiency of the seed crystal 9, a radiating fin 13 is provided around the seed crystal arrangement portion 3 a inside the refrigerant passage 12. Use dry air as a cooling gas, and add 20 l of gas at 18 ° C during growth.
/ Min. Other growth conditions are the same as in the first embodiment. The crystal thus obtained was a complete single crystal as in Example 1. Observation of the solid-liquid interface shape
It was confirmed that the crystal was convex over the entire area of the crystal.

COMPARATIVE EXAMPLE 1 Using the conventional apparatus according to the VGF method shown in FIG.
A GaAs crystal was grown under the same conditions as described above. The grown crystal was polycrystallized during the growth. When the crystal was cut vertically and the starting point of polycrystallization was examined, 40 m from the seed crystal
At position m, polycrystallization had begun from the center of the crystal.
As a result of etching observation, it was confirmed that the shape of the solid-liquid interface was concave, and that dislocations were accumulated at a high density at the starting point of polycrystallization.

[0020] According to the present embodiment example, the solid-liquid interface shape that is Totsuka,
Dislocations propagating perpendicularly to the interface during the growth can be prevented from locally accumulating. For this reason, the uniformity in the wafer surface cut out from the grown crystal is improved. This is effective not only in the uniformity of the distribution of defects (dislocations) but also in the distribution of impurities deposited on the dislocations.

Further, since dislocations can be prevented from locally accumulating, defects (lineage) in which dislocations are formed in a continuous line can be reduced, and a large number of dislocations can be generated due to a high density of dislocations. Crystallization can be effectively prevented.

Further, since the polycrystallization of the crystal can be prevented, productivity is greatly improved, and defective crystals due to characteristic failure and polycrystallization are reduced, so that not only economic efficiency is improved, but also
Since polycrystallization during crystal growth can be prevented, a longer crystal can be manufactured. Further, when the seed polycrystal is melted, the seed crystal may be melted by heating to make growth impossible, but such an accident can be prevented by cooling the seed crystal.

As described above, according to the present invention, various effects are obtained, but the effect is particularly large when VGF which is known as a method of manufacturing a large GaAs crystal at low cost is employed. Note that the present invention can be applied to a polycrystalline synthesis apparatus.

[0024]

According to the present invention, the following effects are exhibited.

(1) According to the method of the present invention, since the concave-convex shape of the solid-liquid interface shape can be prevented, high-quality single crystals can be produced with good reproducibility by preventing polycrystallization of the crystals.

(2) According to the present apparatus, a high-quality crystal can be manufactured by making only a slight change of adding a cooling means to the conventional apparatus.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a VGF furnace equipped with a water cooling mechanism, showing one embodiment of a semiconductor crystal manufacturing apparatus according to the present invention.

FIG. 2 is a cross-sectional view of a VGF furnace provided with a gas cooling mechanism showing one embodiment of the semiconductor crystal manufacturing apparatus of the present invention.

FIG. 3 is a cross-sectional view of a conventional VGF furnace used for a group III-V compound crystal.

FIG. 4 is a characteristic diagram showing a temperature distribution in a melt inner diameter direction near a solid-liquid interface when crystal growth is performed by a VGF method.

FIG. 5 is an explanatory view schematically showing the flow of heat at a solid-liquid interface when a conventional example is implemented.

FIG. 6 is an explanatory diagram schematically showing the flow of heat at the solid-liquid interface when the present invention is implemented.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cover 2 Growth container 3 Crucible 3a Seed crystal placement part 4 Crucible support 5 Heater for melt heating 6 Heater for group V element heating 7 Melt 8 Crystal 9 seed crystal 10 V group element 11 Cooling channel 12 Refrigerant channel 12a Gas inlet / outlet 13 Heat radiation fin 15 Solid-liquid interface shape

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C30B 1/00-35/00 H01L 21/208

Claims (3)

(57) [Claims] 1. A crucible containing a semiconductor melt contained in a crucible.
A seed crystal arranged at the seed crystal arrangement part provided at the bottom of
In the contact state, the above half
A method for manufacturing semiconductor crystals that gradually solidifies a conductor melt
And forcibly place the seed crystal around the seed crystal arrangement part.
A cooling means for cooling is provided so that the semiconductor crystal and the
Flatten the solid-liquid interface between the semiconductor melt and the semiconductor
A method of manufacturing a semiconductor crystal, wherein the semiconductor crystal is controlled to be convex toward a body melt side . 2. A seed crystal disposing portion for disposing a seed crystal at a bottom portion.
A crucible for accommodating a semiconductor melt at the top and a crucible support provided below the crucible;
Provided outside the pot and a melt heating means downwardly to form a temperature <br/> degree gradient becomes cooler than the upper, the semiconductor melt
With the liquid in contact with the seed crystal,
In a semiconductor crystal manufacturing apparatus for gradually solidifying the semiconductor melt toward the direction, the inside of the crucible support is cooled.
A seed crystal cooling means including a medium passage is provided.
An apparatus for manufacturing a semiconductor crystal, wherein a liquid is flowed in a passage to forcibly cool the seed crystal . 3. A seed crystal disposing portion for disposing a seed crystal at a bottom portion.
A crucible for accommodating a semiconductor melt at the top and a crucible support provided below the crucible;
Provided outside the pot and a melt heating means downwardly to form a temperature <br/> degree gradient becomes cooler than the upper, the semiconductor melt
With the liquid in contact with the seed crystal,
In a semiconductor crystal manufacturing apparatus for gradually solidifying the semiconductor melt toward the direction, the inside of the crucible support is
Seed crystal cooling hand consisting of a refrigerant passage with radiating fins on the side
A step is provided, and a gas is caused to flow through the refrigerant passage so that the seed crystal is formed.
A semiconductor crystal manufacturing apparatus characterized in that a semiconductor crystal is forcibly cooled .