JP2001163695A - Heater for growing single crystal and device for producing compound semiconductor single crystal using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater for growing a single crystal, with which the temperature difference in the circumferential direction at the abutting part of a high-temperature furnace and a low-temperature furnace is made small and a crystal almost free from dislocations over whole crystal can be obtained, and to provide a device for producing a compound semiconductor single crystal using the heater. SOLUTION: In a vertical type heater for growing a single crystal, which is obtained by spirally forming a heater wire 13 and used in a vertical Bridgeman method and a device for producing a compound semiconductor single crystal using the heater, the heater wire 13 is horizontally arranged in each turn and the connecting part between adjacent turn parts is formed in the inclined form or the right-angled form and further the length of the connecting part is set to be <=1/10 of the length of one turn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal growth heater used in a vertical Bridgman method for growing a low dislocation compound semiconductor single crystal such as GaAs and an apparatus for manufacturing a compound semiconductor single crystal using the same. It is.

[0002]

2. Description of the Related Art As a method for growing a compound semiconductor crystal, a growth method called a vertical bridgeman (VB) method is known.

FIG. 4 is a sectional view of a vertical Bridgman (VB) device used in the VB method.

As shown in FIG. 4, a VB device is provided vertically upright and has a compound semiconductor material disposed therein.
Quartz ampoule 4 containing BN crucible 5 and its PBN
A heater 11 having a spiral heating wire (heater wire) 1 provided to surround a quartz ampoule 4 to heat a compound semiconductor material disposed in a crucible 5, and to surround the heater 11. And an electric furnace 10 composed of a tubular heat insulating material 3 provided in the upper and lower parts and stacked in two upper and lower stages.

The electric furnace 10 includes an upper high-temperature furnace 10A and a lower low-temperature furnace 10B. In the electric furnace 10, a lower shaft 12 for supporting the quartz ampule 4 from below is provided. Have been.

Also, the PBN housed in the quartz ampoule 4
In the crucible 5, a compound semiconductor material such as a seed crystal (seed) 6, a crystal 7, a raw material melt 8, and B ₂ O ₃ 9 are arranged in this order from the lower side.

When a single crystal of a compound semiconductor is grown by the VB apparatus, the raw material is melted and seeded in a high-temperature furnace 10A, and the lower shaft 12 is lowered to lower the low-temperature furnace 1A.
The single crystal is grown by lowering the quartz ampoule 4 to the 0B side.

[0008]

The VB method is known as a method that can easily obtain crystals with low dislocation.

However, the conventional VB apparatus has a configuration in which the high-temperature furnace 10A and the low-temperature furnace 10B are vertically stacked.
An abutting portion 10t is formed between them, and the temperature distribution becomes non-uniform at the abutting portion 10t, causing dislocation in the crystal.

The abutting portion 10t is necessary to take out the heater terminal 2 from the heater wire 1 and to support the heater 11 itself, and to take a vertical temperature gradient, that is, a solid-liquid during crystal growth. Since the interface is generally located at or slightly above the abutting portion 10t, dislocations occurring at this portion were unavoidable in this configuration.

For this reason, conventionally, the heater wire 1 cannot be wound up to the very end of the electric furnace 10, and at least about 20 mm on one side, the lower part of the high-temperature furnace 10A and the low-temperature furnace 10
When the upper part of B is combined, a portion without the heater wire 1 is generated for about 40 mm, and this portion is usually buried with a heat insulating material to prevent heat from escaping outward. Even if the heat release from the portion without the heater wire 1 was prevented, the dislocation generated at the butted portion 10t could not be prevented.

Therefore, as a result of studying the cause, it is not actually the butted portion 10t having the heater wire 1 itself that affects the crystal defect, but the portion without the heater wire 1 depends on the location (in the circumferential direction). It turned out that changing was a problem.

More specifically, since the conventional heater wire 1 is formed in a spiral shape, a difference of one pitch between the near side and the far side of the heater wire 1 occurs. , Due to the difference in the vertical position of the heater wire 1,
During the cooling process of the crystal after solidification, partial non-uniform temperature distribution occurs, and dislocations occur in the crystal.

FIGS. 5 and 6 are perspective views of a general heater.

As shown in FIG. 5, this heater has both ends 21t of the heater wire 21 arranged at the same position in the upper and lower portions and has the same total number of windings. It is not possible to eliminate the difference in the vertical position between the heater wire 21 and the heater wire 21 on the back side.

As shown in FIG. 4, this heater not only has a vertical position difference between the front heater wire 31 and the rear heater wire 31, but also has both ends of the heater wire 31. There is a difference of one pitch in the number of turns between the portion sandwiched by 31t and the other portion.

As a measure for improving the difference between the upper and lower positions of the heater wire 1, the area around the quartz ampoule 4 was covered with a soaking tube made of SiC or the like. It turned out not to be.

Specifically, φ3 ″ (3 inches in diameter: 7.
62 cm) In the case of Si-doped crystals, the dislocation density level is mostly at the level of 100 co / cm ^{2 for the} most part, whereas it is 1,000 to 2,000 co / cm ² for the part.
It is.

Accordingly, an object of the present invention is to provide a heater for growing a single crystal for reducing a circumferential temperature difference in a butt portion between a high-temperature furnace and a low-temperature furnace to obtain a low dislocation crystal in the whole crystal, and to use the heater. An object of the present invention is to provide an apparatus for manufacturing a compound semiconductor single crystal.

[0020]

To solve the above-mentioned problems, the invention of claim 1 is used in a vertical Bridgman method,
In the vertical type single crystal growth heater in which the heater wire is formed in a substantially spiral shape, the heater wire of each turn is horizontally arranged, and the connection between the turns is formed obliquely or at a right angle, and , The length of the connection is one turn long
/ 10 or less.

According to a second aspect of the present invention, the material of the heater wire is made of metal, carbon, or ceramics.

According to a third aspect of the present invention, there is provided an apparatus for manufacturing a compound semiconductor single crystal using a vertical single crystal growth heater which is used in a vertical Bridgman method and in which a heater wire is formed in a substantially spiral shape. Are arranged horizontally, the connection between the turns is formed obliquely or at a right angle, and the length of the connection is 1/1 of the length of one turn.
It is 10 or less.

That is, the gist of the present invention is that one of the heater wires
In order to eliminate the temperature difference corresponding to the pitch, the heater wire for each turn is completely horizontal, and the connection with the heater wire adjacent above and below (the connection portion) is at least 1/10 or less of the heater circumference. At a point where they are connected obliquely or at right angles. This connection portion may be bent, welded, or formed in accordance with the material of the heater wire.

According to the above configuration, 9/1 of the entire heater wire is provided.
In portions other than the connection portion occupying 0 or more, since the heater wires are arranged horizontally, there is no temperature difference in the circumferential direction, and no dislocation occurs.

[0025]

Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a schematic diagram of a VB apparatus according to the present invention.

As shown in FIG. 2, a PBN crucible 5 is provided standing upright and has a compound semiconductor material disposed therein.
And a heater 15 having a spiral heating wire (heater wire) 13 provided so as to surround the quartz ampoule 4 to heat the compound semiconductor material disposed in the PBN crucible 5. And an electric furnace 20 composed of a cylindrical heat insulating material 3 provided so as to surround the heater 15.

FIG. 1 is a perspective view of the heater 15.

As shown in FIG. 1, the heater 15 according to the present invention is formed of a circular APM wire having a diameter of 8 mm (diameter: 8 mm), and is formed in an annular shape having a length w of 1/10 or less of the circumference. One end of the annular heater wire 13c and the heaters adjacent to the upper and lower heaters are arranged so that the heaters 13c are vertically arranged with a large number of heater wires 13c at predetermined intervals, and the entire heating portion is connected almost spirally. It is composed of a connecting portion 13s for connecting the other end of the wire 13c obliquely or at a right angle, and a heater lead wire 2 for connecting the heater wire 13c to an external power supply.

The heater wire 13c has a connection portion 13s having a length w of 1/10 or less of the heater circumference. However, if the connection is made obliquely longer than that, the circumferential uniformity cannot be said to be good. This is because the crystal is unlikely to grow to low dislocations.

Further, the electric furnace 20 is an upper high-temperature furnace 2.
The electric furnace 20 includes a lower shaft 12 for supporting the quartz ampule 4 from below.

The PBN housed in the quartz ampoule 4
In the crucible 5, a seed crystal (seed) 6, a raw material melt 8, and a compound semiconductor material of B ₂ O ₃ 9 are arranged in this order from the lower side.

Next, the operation will be described.

When a single crystal of a compound semiconductor is grown by the VB apparatus, the seed crystal 6 is placed on the lower end of the PBN crucible 5.
Is placed, and the raw material melt 8 and B ₂ O ₃ 9 are put thereon, and sealed in a quartz ampule 4 under vacuum. Then, after placing this quartz ampule 4 on the lower shaft 12,
A and placed in the low-temperature furnace 20B. Then, the high temperature furnace 20
A and the low temperature furnace 20B are heated to generate a temperature gradient between these furnaces.

At the time of this heating, the butt 2 of the electric furnace 20
At 0t, no temperature difference occurs in the circumferential direction because the heater wires 13 of the heater 15 are arranged horizontally.

Further, by gradually lowering the lower shaft 12 in this state, the crystal 7 grows between the seed crystal 6 and the raw material melt 8.

Then, the entire grown crystal is transferred to the low-temperature furnace 20B.
, The lower shaft 12 stops descending, and is gradually cooled to room temperature, whereby a single crystal having a desired size is manufactured.

Since the single crystal thus produced has grown without any temperature difference in the circumferential direction during the crystal growth, when cut into wafers, the in-plane variation of dislocations is small.

As described above, according to the present invention, since a low dislocation crystal wafer can be manufactured, a wafer for a semiconductor laser requiring a low dislocation wafer can be provided, and the yield can be improved. Mass productivity is improved.

Next, a modified example of this embodiment will be described.

FIG. 3 shows a heater in which the connecting portions of the respective stages are connected vertically.

As shown in FIG. 3, the heater 17 has a large number of annular heater wires 17c, each of which has a length of not more than 1/10 of the entire circumference thereof, cut out at predetermined intervals. A heating portion, and a connecting portion 17 for vertically connecting one end and the other end of each of the annular heater wires 17c.
h, and a heater lead wire 2 for connecting the heater wire 17c to an external power supply.

In this case, a material having a low resistance value such as copper is used as the material of the connection portion 17h so that a large difference does not occur between the resistance values of the uppermost heater wire 17c and the lowermost heater wire 17c. Is preferred.

With this configuration, as in this embodiment, there is no difference in temperature in the circumferential direction, the occurrence of dislocations can be reduced, and the heater can be easily manufactured.

In this embodiment, the heater wire 13c is formed by winding a single thick wire, but a thin wire wound in a coil shape is formed into a shape as shown in FIG. Further, as the material of the heater wire 13c, metal, carbon, ceramics or the like is used.

Although only the vertical heater is described in the present embodiment, it is considered that the same effect can be obtained with the horizontal heater.

Next, the dislocation densities of the present invention and the prior art will be compared.

First, in this comparative experiment, as an example, GaAs was used under the conditions described later using the apparatus shown in FIG.
A single crystal was produced, and as a comparative example, a GaAs single crystal was produced using the apparatus shown in FIG. 4 under the same conditions as in the example.

(Example) 3000 g of GaAs as a raw material
s was used to grow a Si-doped single crystal.

A seed crystal is placed at the lower end of the PBN crucible, and 3000 g of GaAs poly raw material and dopant Si
And 1.5g, put B ₂ O ₃ 50g, was vacuum sealed in a quartz ampoule. After placing this quartz ampule on the lower shaft, it was placed in a high-temperature furnace and a low-temperature furnace. Then, GaAs
Is melted by heating and seeding is performed.
It was lowered at a speed of mm / hr. Then, the crystal was lowered by 200 mm, and the entire crystal was moved into a low-temperature furnace (about 1180 ° C.). Then, the movement was stopped and the crystal was gradually cooled to room temperature. The maximum temperature gradient between the furnaces was about 5.0 deg / cm.

After completion of the crystal growth, the quartz ampule is opened,
φ3 ”(diameter 3 inches: 7.62 cm), length 100 m
The crystals of m were taken out.

The GaAs of these examples and the comparative example
The wafer was cut out from the seed side and the tail side of the single crystal, and the characteristics were measured.

As a result, the dislocation densities of the examples were all over the entire surface, and the average dislocation density (EPD) was 100
cm ² , maximum dislocation density (EPD) 500 / c
m ² or more. No in-plane variation of dislocation was observed. The carrier concentration is 1.0 × 10 ¹⁸ c on the seed side.
m ^-3 .

On the other hand, the dislocation density of the comparative example is such that only a part of the seed-side wafer has a dislocation density (EPD) of about 200.
It was 0 cells / cm ² . The dislocation density (EP
D) was less than 100 pieces / cm ² . On the tail side, the entire surface had a dislocation density (EPD) of less than 100 cores / cm ² . Then, as a result of investigating a portion having many dislocations, a portion where a step is generated in a portion where the high temperature furnace and the low temperature furnace have no heater and where there is no heater coincides with a portion having many dislocations. I understood that. This is considered to have occurred in a portion that was cooled unevenly after solidification of the crystal.

As described above, although the average dislocation density is not significantly changed between the example and the comparative example, in the portion where the dislocation density is maximum, the example has a low dislocation of 1/4 or less of the comparative example. You can see that.

[0056]

In summary, according to the present invention, low dislocation crystals can be obtained relatively easily by the BV method. This improves the mass productivity of semiconductor laser wafers that require low-order crystal wafers.

[Brief description of the drawings]

FIG. 1 is a perspective view of a heater for growing a single crystal according to the present invention.

2 is a cross-sectional view of an apparatus for manufacturing a compound semiconductor single crystal using the single crystal growth heater of FIG.

FIG. 3 is a perspective view of a modification of the single crystal growth heater of FIG. 2;

FIG. 4 is a sectional view of an apparatus for manufacturing a compound semiconductor single crystal according to a conventional invention.

FIG. 5 is a perspective view of a conventional single crystal growth heater.

FIG. 6 is a perspective view of a conventional single crystal growth heater.

[Explanation of symbols]

 13 Heater wire 13s Connection

Continued on the front page (72) Inventor Kenya Iya 5-1-1, Hidaka-cho, Hitachi-shi, Ibaraki F-term in the Hidaka Plant of Hitachi Cable, Ltd. (Reference) 4G077 AA02 BE46 CD02 EG18 MB04 MB22 5F053 AA11 BB06 BB13 BB60 DD03 FF04 GG01 HH04 LL03 RR03

Claims (3)

[Claims] In a vertical single crystal growth heater used in a vertical Bridgman method and having a heater wire formed in a substantially spiral shape, a heater wire of each turn is horizontally arranged and a turn of each turn is provided. The connecting portion is formed obliquely or at a right angle, and the length of the connecting portion is 1/10 of the length of one turn.
A single crystal growth heater characterized by the following. 2. The heater for growing a single crystal according to claim 1, wherein the material of the heater wire is made of metal, carbon, or ceramics. 3. In a compound semiconductor single crystal manufacturing apparatus using a vertical single crystal growth heater in which a heater wire is formed in a substantially spiral shape used in a vertical Bridgman method, a heater wire of each turn is horizontal. And a connecting portion between the turns is formed obliquely or at a right angle, and the length of the connecting portion is 1/10 or less of one turn length. An apparatus for manufacturing a compound semiconductor single crystal using a heater.