JP2001181085A - Method for growing compound semiconductor crystal and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for growing a compound semiconductor crystal, enabling single crystal growth and crystal growth of low dislocation density by controlling the temperature of a growing vessel in the circumferential direction to eliminate unevenness of the temperature, and provide an apparatus therefor. SOLUTION: This method for growing a compound semiconductor crystal comprises vertically installing a cylindrical growing vessel 7 having bottom in which a seed crystal 5 and a raw material 1 are put and heating the above raw material 7 in a prescribed temperature distribution by a heating element 9a of an electric oven provided so as to enclose the growing vessel 1 to melt the above raw material 7. In the crystal growing method, a cylindrical resistor 3 vertically cut into at least three portions in vertical direction is installed between the above growing vessel and the above heating element 9a of the electric oven so as to enclose the above growing vessel 1 and the current is applied to the resistor 3 to generate heat in the resistor 3 and the temperature is independently controlled. Thereby, temperature distribution of the above growing vessel 1 in the circumferential direction is made uniform to grow the crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for growing a compound semiconductor crystal by the vertical Bridgman method, and more particularly to a method for measuring a circumferential temperature distribution of a quartz glass growth vessel or a pyrolytic boron nitride (PBN) growth vessel. TECHNICAL FIELD The present invention relates to a compound semiconductor crystal growth method for controlling and growing a compound semiconductor crystal and an apparatus therefor.

[0002]

2. Description of the Related Art In recent years, φ3 ″ (diameter 3 inches: 7.62)
cm), a method for obtaining a GaAs crystal having a large dislocation density and a low dislocation density is a liquid sealing pulling method (LEC method).
Instead, the vertical Bridgman method has attracted attention.

[0003] In this method, a seed crystal is placed at a lower portion of a growth vessel, a GaAs material is placed thereon, and a lower portion on a seed crystal side is placed in a vertical electric furnace having a high upper portion and a lower portion having a low temperature distribution. This is a method of solidifying crystals from the top toward the top.

[0004] In general, a growth container (crucible) made of pyrolytic boron nitride (PBN) is used, and a structure in which the container is held by a quartz glass container is used. Alternatively, the quartz glass container itself may be used as a crucible.

[0005]

However, in the conventional vertical Bridgman growth apparatus, the electric furnace heating element (heater) around the growth vessel is composed of several zones in the growth axis direction (vertical direction), Although a (vertical) temperature gradient can be formed, it is difficult to make the temperature in the circumferential direction of the growth vessel uniform in the manufacture of the heater, and the mounting axis between the heater center and the growth vessel is displaced, and the growth vessel circle is formed. There was also variation in heat conduction in the circumferential direction, and temperature unevenness in the circumferential direction was likely to occur.

Further, when the growth vessel has uneven temperature, there is no function of adjusting the temperature, and therefore, single crystal growth is difficult and the dislocation density is partially increased.

Therefore, an object of the present invention is to control the temperature in the circumferential direction of the growth vessel, which is a problem of the above-described prior art, to eliminate temperature unevenness, thereby achieving single crystal growth and crystal growth with a low dislocation density. It is an object of the present invention to provide a compound semiconductor crystal growth method and an apparatus thereof which enable the method.

[0008]

According to a first aspect of the present invention, a bottomed cylindrical growth vessel containing a seed crystal and a raw material is installed vertically so as to surround the growth vessel. In the compound semiconductor crystal growth method of heating and melting the above-mentioned raw materials at a predetermined temperature distribution by an electric furnace heating element provided in the compound semiconductor crystal to grow a compound semiconductor crystal in a vertical direction,
A cylindrical resistor vertically cut into at least three in the vertical direction is disposed between the growth vessel and the electric furnace heating element so as to surround the growth vessel, and a current flows through the resistors to generate heat. In addition, the temperature is independently controlled to grow the crystal with a uniform temperature distribution in the circumferential direction of the growth vessel.

According to a second aspect of the present invention, there is provided a bottomed cylindrical growth vessel in which a seed crystal and a raw material are placed and which is provided so as to surround the growth vessel, and the raw material is heated at a predetermined temperature distribution. An electric furnace heating element for growing the compound semiconductor crystal in the vertical direction by dissolving and growing the compound semiconductor crystal in the vertical direction. A cylindrical resistor that is installed between an electric furnace heating element and generates heat by passing an electric current, a presser support that supports the resistor around the growth vessel, and an electric current that flows through the resistor. In order to make the temperature distribution in the circumferential direction of the growth vessel uniform, temperature control means for independently controlling the temperature of each resistor is provided.

According to a third aspect of the present invention, the growth vessel is made of quartz glass.

According to a fourth aspect of the present invention, the growth container is a PBN.
It is formed by.

According to a fifth aspect of the present invention, the resistor and the holding member are formed of ceramics.

According to a sixth aspect of the present invention, the resistor and the holding support are formed of silicon carbide.

According to a seventh aspect of the present invention, the resistor and the holding support are made of graphite.

That is, the gist of the present invention is to provide a method and an apparatus for growing a single crystal by the vertical Bridgman method, wherein a temperature gradient in a growth axis direction (vertical direction) is generated by an electric furnace heating element (heater) around a growth vessel. When forming
A tubular resistor that is longitudinally cut into at least three in the axial direction (vertical direction) is prepared, and the divided tubular resistor is connected to an electric furnace heating element so as to surround the tubular quartz glass growth vessel. And the temperature distribution in the circumferential direction can be controlled by applying a current to each cylindrical resistor to generate heat.

Here, the vertical Bridgman method includes a vertical gradient freezing method (VGF method) in which the growth is performed only by the temperature gradient, a vertical bridgeman method (VB method) in which the growth vessel is relatively lowered, and further, As. Any of a method of controlling the pressure and a method of covering the melt surface with B ₂ O ₃ to prevent As from volatilizing are included.

According to the above configuration, the temperature distribution in the circumferential direction of the growth vessel is controlled by the resistor, and the crystal grows in a uniform state. As a result, a compound semiconductor crystal having a low dislocation density grows.

[0018]

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

FIG. 1 is a schematic sectional view of a compound semiconductor crystal growth apparatus according to the present invention.

As shown in FIG. 1, a compound semiconductor crystal growth apparatus according to the present invention comprises a cylindrical quartz glass growth vessel 1 containing a seed crystal 5 and raw materials,
And a vertical electric furnace 9 for growing the single crystal 6 by heating and melting the raw material therein at a predetermined temperature gradient.

The vertical electric furnace 9 includes a quartz glass growth vessel 1.
An electric furnace heating element 9 a for heating the raw material via the inside is provided outside the growth vessel 1 so as to surround the growth vessel 1.

When a current is applied between the quartz glass growth vessel 1 and the electric furnace heating element 9a, the temperature variation in the circumferential direction of the quartz glass growth vessel 1 is reduced, and when the current is not applied, In addition, a cylindrical resistor 3 for equalizing heat so that heat from the electric furnace heating element 9a is evenly transmitted to the raw material, and for keeping the quartz glass growth vessel 1 warm during crystal solidification, is formed from above and below. Are provided in the vicinity of the quartz glass growth vessel 1 by an upper holding support 2a and a lower holding support 2b which support and fix around the quartz glass growth vessel 1.

In the lower part of the quartz glass growth vessel 1,
A drive base 10 for rotatably supporting the quartz glass growth vessel 1 and lowering it in accordance with crystal growth is provided.

More specifically, the quartz glass growth vessel 1
Is a small-diameter neck in which the seed crystal 5 is installed, a large-diameter trunk in which the raw material is accommodated and the grown crystal is accommodated, and the neck is gradually expanded from the neck to the trunk to connect the neck and the trunk. A quartz glass cap 4 for sealing the inside of the quartz glass growth vessel 1 in a vacuum is welded and supported by a shoulder susceptor 8 with its neck downward so that the seed crystal 5 is arranged on the lower side. It is arranged vertically (vertically).

The electric furnace heating element 9a is formed by stacking an upper heater, an intermediate heater, and a lower heater in three stages vertically along a growth axis so that a desired temperature gradient can be formed as a whole. Specifically, the temperature is controlled so as to be low at the lower part, solidified at a single crystal in the intermediate part, and high at the upper part to hold the material melt.

FIG. 2 is a perspective view of a cylindrical resistor.

As shown in FIG. 2, this cylindrical resistor 3 is
It has three segments 3a, 3a, 3a formed by dividing a ceramic material or the like into three in the vertical direction (vertical direction), and a current flows through each of the segments 3a, 3a, 3a. Terminals 11 are provided.

The cylindrical resistor 3 is formed to have an inner diameter slightly larger than the outer diameter of the quartz glass growth vessel 1 so that it is close to the quartz glass growth vessel 1 when fixed by the holding supports 2a and 2b as described above. Is formed.

Further, inside each of the segments 3a, 3a, 3a, a thermocouple 12 as a temperature control means for measuring the temperature of the segment 3a and controlling the temperature is provided.

In FIG. 2, the segment 3 in the foreground is shown.
a, the terminal 11 and the thermocouple 12 are shown in FIG.
The three segments 3a, 3a are omitted because they have the same configuration.

Next, a compound semiconductor crystal growing method using this apparatus will be described together with its operation.

First, after the seed crystal 5 and the raw material are put into the quartz glass growth vessel 1, the quartz glass growth vessel 1 is sealed in a vacuum. The quartz glass growth container 1 is surrounded by the cylindrical resistor 3 together with the shoulder susceptor 8, and the cylindrical resistor 3 and the quartz glass growth container 1 are further pressed from the upper and lower ends by the holding supports 2 a and 2 b, and the driving frame is 10 and the vertical electric furnace 9 is heated in the atmosphere.

Then, the temperature setting of the heating element 9a in each zone of the vertical electric furnace 9 is changed so that the lower part where the seed crystal 5 is located is, for example, about 1235 ° C.
After adjusting the temperature to 5 ° C. and dissolving the raw materials to form a melt, seeding is performed.

Thereafter, the temperature gradient at the solid-liquid interface is set to about 4 ° C./c.
The quartz glass growth vessel 1 is rotated with or without rotation while adjusting to m, and the quartz glass growth vessel 1 is lowered at a speed of 3 mm / hr as indicated by an arrow to solidify the crystal.

At this time, based on the temperature of each thermocouple 12 in the cylindrical resistor 3 divided into three, each segment 3a
Is controlled so that the temperatures at three locations become uniform.

In this temperature control, if there is temperature unevenness in the circumferential direction of the quartz glass growth vessel 1, a current is applied to the segment 3a corresponding to a low temperature portion, and heating is performed until the temperature unevenness portion disappears. Further, when the temperature unevenness is eliminated, or when there is no temperature unevenness in the circumferential direction of the quartz glass growth vessel 1,
The cylindrical resistor 3 acts as a heat equalizing tube for uniformly transmitting heat from the heating element 9a to the quartz glass growth vessel 1, and acts as a heat retaining tube during solidification of the crystal, and the temperature distribution in the radial direction and the growth axis direction is moderate. become.

As a result, the crystal grows in a state where the temperature distribution is uniform (no temperature unevenness) in the circumferential direction of the growth axis of the quartz glass growth vessel 1.

Then, after solidifying the whole, about 100 ° C. /
After cooling to room temperature at hr, the quartz glass growth vessel 1 is taken out of the vertical electric furnace 9 together with the tubular resistor 3.

As described above, by growing the crystal in a state where the temperature in the circumferential direction of the quartz glass growth vessel 1 is uniform, a compound semiconductor crystal having a low dislocation density can be grown.

[0040]

Next, a more specific embodiment will be described.

(Example 1) An example of GaAs single crystal growth will be described with reference to FIGS.

As shown in FIG. 1, when growing a GaAs single crystal, a seed crystal 5 is placed in a quartz glass growth vessel 1.
And 6000 g of GaAs material, and then the quartz glass growth vessel 1 is sealed in a vacuum. A cylindrical ceramic resistor 3 divided into three parts in the vertical (vertical) direction surrounds the quartz glass growth vessel 1 together with the shoulder susceptor 8, and is formed of ceramic ceramic holding members 2a and 2b from upper and lower ends. The resistor 3 and the quartz glass growth vessel 1 are held down, placed on the drive stand 10, and the temperature of the vertical electric furnace 9 is raised in the atmosphere.

The temperature of each zone of the electric furnace 9 was changed, and the lower part where the seed crystal 5 was located was adjusted to about 1235 ° C. and the upper part where the raw material was located was adjusted to about 1245 ° C. , Seeding. Thereafter, while adjusting the temperature gradient at the solid-liquid interface to about 4 ° C./cm, the quartz glass growth vessel 1 is rotated or lowered without rotating, and the quartz glass growth vessel 1 is lowered at a speed of 3 mm / hr as indicated by an arrow. Then, crystal solidification is performed.

At this time, as shown in FIG. 2, the segment 3 of each ceramic resistor 3 is determined based on the temperature of each thermocouple 12 in the ceramic resistor 3 divided into three.
The power amount of a is controlled so that the temperatures at three locations become uniform.

After solidifying the whole, about 100 ° C. /
After cooling to room temperature for hr, the quartz glass growth vessel 1 is taken out of the vertical electric furnace 9 together with the cylindrical ceramic resistor 3.

According to this method, before the ceramic resistor 3 is mounted on the conductive substrate, the temperature difference in the circumferential direction is 2 ° C., and the dislocation density at the location where the temperature difference is about 20 ° C.
00 months / cm ² it was was, but after mounting a ceramic resistor 3, the temperature difference in the circumferential direction becomes 0.5 ℃ less, dislocation density can be reduced to about 200 months / cm ² .

Embodiment 2 As Embodiment 2, when a GaAs single crystal is grown in the same manner as in Embodiment 1, a graphite resistor and a ceramic holding member 2a, 2b are used instead of the ceramic resistor 3 and the ceramic holding supports 2a, 2b. A holding support was used.

Then, the same raw materials as in Example 1 were used in the same amounts,
Crystal growth was performed under the same conditions and procedure.

Also in this case, the temperature difference in the circumferential direction shown in Example 1 is 0.5 ° C. or less, and the dislocation density is about 200 / c.
A result almost equal to the result of m ² was obtained.

Embodiment 3 As Embodiment 3, when a GaAs single crystal is grown in the same manner as in Embodiment 1, silicon carbide (SiC) is used instead of the ceramic resistor 3 and the ceramic holding supports 2a, 2b. A resistor and a holding support were used.

Then, the same raw materials as in Example 1 were used in the same amounts,
Crystal growth was performed under the same conditions and procedure.

Also in this case, the temperature difference in the circumferential direction is 0.5 ° C. or less and the dislocation density is about 200
A result almost equal to the result of m ² was obtained.

Further, as another example, in this embodiment, the case where the growth is performed using the quartz glass growth vessel 1 itself as a growth crucible has been described.
Even when the growth is performed in a crucible and the whole crucible is covered with a quartz ampule, the quartz ampule is supported around by the divided resistor 3 described in the present embodiment, so that the temperature in the circumferential direction can be improved. The distribution can be made uniform and a low dislocation single crystal can be obtained.

Further, in the present embodiment, the cylindrical resistor 3 is divided into three parts, but it is needless to say that finer temperature control can be performed by dividing the resistance into four or more.

In this embodiment, the single crystal growth of GaAs has been described.
It is also possible to apply to the growth of single crystals such as P and GaP.

[0056]

In summary, according to the present invention, a single crystal is grown in a quartz glass growth vessel by the vertical Bridgman method, and the quartz glass growth vessel is covered with a cylindrical resistor.
Resistor 3 which is fixed from the lower part by a holding support and divided into three parts
The current is passed through each of them to generate heat,
The uneven temperature of the quartz glass growth vessel 1 due to the electric furnace heating element 9a can be corrected by controlling the electric power of the three-divided resistor, so that the circumferential temperature distribution of the quartz glass growth vessel 1 can be made uniform.

As a result, the compound semiconductor crystal grows in a state in which the temperature distribution in the circumferential direction is uniform, so that a low dislocation single crystal can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a compound semiconductor crystal growth apparatus according to the present invention.

FIG. 2 is a perspective view of a cylindrical resistor used in the compound semiconductor crystal growth apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz glass growth container 3 Cylindrical resistor 5 Seed crystal 7 Raw material melt (raw material) 9a Electric furnace heating element

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenya Iya 5-1-1, Hidaka-cho, Hitachi-shi, Ibaraki F-term in the Hidaka Factory of Hitachi Cable, Ltd. (Reference) 4G077 AA02 BE46 CD02 EG02 EG20 EH07 5F053 AA09 AA11 AA22 BB06 BB08 BB13 DD03 DD07 DD11 DD20 FF04 GG01 HH04 RR03

Claims (7)

[Claims] A bottomed cylindrical growth vessel containing a seed crystal and a raw material is installed vertically, and the raw material is heated at a predetermined temperature distribution by an electric furnace heating element provided to surround the growth vessel. In the compound semiconductor crystal growth method of growing a compound semiconductor crystal in the vertical direction, the growth container is vertically cut into at least three in the vertical direction, and the growth container is surrounded by the growth container so as to surround the growth container. It is installed between the heating element and the electric furnace, and heat is generated by applying a current to those resistors, and the temperature is controlled independently to grow the crystal with a uniform temperature distribution in the circumferential direction of the growth vessel. A method for growing a compound semiconductor crystal, comprising: 2. A growth vessel having a bottomed cylindrical shape, which is provided with a seed crystal and a raw material, and is vertically disposed. The raw material is provided to surround the growth vessel, and the raw material is heated and melted at a predetermined temperature distribution. An electric furnace heating element for growing a compound semiconductor crystal in a vertical direction.
A tubular resistor that is vertically cut into at least three sections and is disposed between the growth vessel and the electric furnace heating element so as to surround the growth vessel and that generates heat by passing an electric current; And a temperature controller for independently controlling the temperature of each resistor so that current flows through the resistor and the temperature distribution in the circumferential direction of the growth container becomes uniform. And a means for growing a compound semiconductor crystal. 3. The compound semiconductor crystal growth apparatus according to claim 2, wherein said growth vessel is formed of quartz glass. 4. The compound semiconductor crystal growth apparatus according to claim 2, wherein said growth vessel is made of PBN. 5. The compound semiconductor crystal growth apparatus according to claim 2, wherein said resistor and said holding member are formed of ceramics. 6. The compound semiconductor crystal growth apparatus according to claim 2, wherein said resistor and said holding support are formed of silicon carbide. 7. The compound semiconductor crystal growth apparatus according to claim 2, wherein said resistor and said holding support are made of graphite.