JPS6348837B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an apparatus for growing an arsenic compound single crystal useful as a substrate for a laser or an IC.

Conventional technology GaAs single crystal, which is a conventional arsenic compound semiconductor,
It is manufactured using either the HB method or the LEC method, but each method has its own drawbacks and is not satisfactory.

In other words, substrates for lasers or ICs are required to have a (100) circular shape and no defects, but in the HB method, an ingot with a <111> orientation is grown on a boat, so the (100) To obtain a circular wafer, the direction of crystal growth must be
After cutting at an angle of 54.7°, it must be punched out into a circular shape.

Furthermore, although the LEC method allows growth in the <100> orientation, it is difficult to stably produce ingots with few defects.

As a way to solve these problems,
No. 55-80796 proposes a method for growing a high dissociation pressure compound semiconductor single crystal for semiconductors by a double melt seal pulling method and an apparatus therefor. This method can obtain circular wafers with (100) planes, and
Although it is advantageous because it yields wafers with a crystal defect density comparable to or lower than the HB method, it uses quartz as a container to maintain the arsenic atmosphere, so when it is maintained at 1240°C, which is the melting point of gallium arsenide. The problem is that the quartz container deforms when pressure fluctuations occur, and in order to grow large crystals of 40φ or more, it was necessary to develop an arsenic-sealed container.

To explain this specifically using drawings, the first
The figure shows a conventional pulling device using an arsenic sealed container made of quartz. 1 in the figure is a metal container,
2 is a rotating crucible made of quartz, 3 and 23 are after heaters, 4 is an upper fitting lid, 5 and 22 are boron oxide for sealing, 6 is a rotating pulling shaft, 7 is a main heater, 8 is a high dissociation pressure compound, and 9 is a Rotating axis, 1
0 is a graphite susceptor, 11 is a chuck, 12 is a seed crystal, 13 is an inert gas introduction system, 14 is an exhaust system, 1
5 is single crystal, 16 is boron oxide for coating, 17,2
4 is a saucer, 18 is a support stand, 19 is a drive stand, 20
is the furnace core tube, and 21 is the lower fitting lid. As a result of detailed temperature measurements in such a device, the internal observation area of the arsenic sealed container is limited to 1050-1150℃, and if there is no coating boron oxide on the melt, the observation area is limited to 1080-1150℃. I will pray. 950~1080
In the °C range, the inside of the quartz arsenic sealed container was coated with arsenic gallium, making it unsuitable for internal observation. Furthermore, since the inside of the after-heater 3 is hidden, it was considered to be an inappropriate part for observation and was ignored. However, according to the detailed observation results of the present inventors, the inside of the quartz arsenic sealed container is transparent during the pulling operation in the temperature range of 610 to 950°C.
I came to believe that by changing the observation angle, it would be useful as an internal observation section.

On the other hand, if a pressure difference occurs between the inside and outside of the quartz furnace core tube 20, especially when the pressure on the outside becomes high, the furnace core tube 20 will collapse and the graphite susceptor 10 will collapse.
rotation becomes impossible. In order to obtain large crystals, a large core tube is inevitably required, and the larger the core tube, the smaller the resistance to deformation, so it is necessary to reduce the pressure difference between the inside and outside of the core tube. Become. Naturally, in order to effectively seal arsenic within the quartz core tube 20, it is required to maintain a higher pressure on the outside of the core tube than on the inside; It was necessary to select a material that has higher temperature strength than quartz, can withstand arsenic gas, and can be sealed against arsenic gas.

Purpose In view of the above points, the present invention is capable of withstanding high temperatures of 1240°C or higher, which is the melting point of gallium arsenide, and is capable of sealing arsenic gas while withstanding arsenic gas. This provides a container that can

Structure The present invention provides an apparatus for pulling an arsenic compound single crystal while controlling the pressure of arsenic gas sealed in a container, in which the container is equipped with at least one type of quartz window for internal observation, a quartz rod penetrating the container, or a fiber scope. and is composed of one or more of molybdenum or molybdenum alloy, gas-impermeable carbon, silicon nitride, alumina-based oxide, and zirconia, and further,
An apparatus characterized in that the container can be divided into upper and lower halves, a boron oxide holding part is provided in the halves of the container, and arsenic gas is sealed by immersing the lower end of the upper container in the boron oxide. It is.

As mentioned above, in order to effectively seal arsenic inside the reactor core tube, it must not change even when it comes into contact with arsenic gas at 1250℃, and it must not deform even if there is a pressure difference between the inside and outside of the arsenic sealed container at 1250℃. and that the B ₂ O ₃ sealant will not be damaged when it solidifies.
It is necessary to select a material that satisfies requirements such as being able to be processed into a structure to seal in arsenic gas and not allowing arsenic gas to pass through.
We have found that molybdenum or molybdenum alloys, gas-impermeable carbon, silicon nitride, alumina-based oxides, and zirconia are suitable materials for such purposes, and that even when these materials come into contact with boron oxide used as a sealant, Because it has unbreakable characteristics, it can be used repeatedly. The container is divided into two parts and sealed with boron oxide, so
It is advantageous for charging raw materials and taking out crucibles and crystals. For large containers in which large crystals are to be made, it is not possible to satisfy both sealing and removal using the conventional sliding method, so in the present invention, a sealing method using boron oxide is adopted.

It was also found that by using a quartz rod or fiberscope for internal observation and setting the temperature of the tip to 610 to 950°C, it was possible to observe clear images without adhering to arsenic or gallium arsenide. .

The embodiment will be explained below based on FIG. 2. In the figure, 25 is an electric furnace for controlling arsenic pressure, 26 and 26' are arsenic gas sealed containers, 27 is boron oxide for shaft sealing, and 28 is a quartz rod for internal observation. quartz fiber, 29 is a pulling shaft, 30 is boron oxide for arsenic gas sealing, 31 is a heater, 32 is a crucible, 33 is an arsenic compound melt, 34 is an arsenic compound single crystal, 35 is a pedestal, 36 is an inert gas introduction system ,3
7 is a vacuum evacuation system, and 38 is a crucible rotation shaft.

Example 1 Special gas-impermeable carbon was used as the arsenic gas sealed containers 26, 26', and the lifting shaft 2
9. For the shaft seal of the crucible rotating shaft 38, boron oxide 27 for shaft sealing was used.

Boron oxide 30 for sealing arsenic gas is used to seal an opening larger than the crucible that is required to take out the crucible 32.

In this sealing means, by raising and lowering the arsenic gas sealed container 26' (lower chamber),
Sealing can be done freely. In addition, arsenic gas sealed container 2
The structure is such that the crucible 32 can be moved up and down independently of the crucibles 6 and 26'.

In the crucible 32 of such a device, GaAs2Kg,
The arsenic compound single crystal 34 was pulled up by charging 15 g of As and 0.6 g of Si, and the EPD and carrier concentration of the wafer were measured. For EPD center part 40φ
EPD2000/cm ² or less, outside 2000~10000/
It was about ^cm2 . On the other hand, the carrier concentration is 1×10 ¹⁸ /
cm ² or more, and an ingot that can be used satisfactorily as a substrate for semiconductor lasers was grown.

In this case, no deformation was observed in the special carbon of the arsenic gas sealed container, and it could be used repeatedly. Furthermore, the inside of the container could be clearly observed using the quartz rod 28 for internal observation.

Example 2 The material of the arsenic gas sealed containers 26, 26' is as follows:
The structure was the same as in Example 1 except that a gas-impermeable alumina-based oxide was used.

Further, PBN was used as the crucible 32 for holding the arsenic compound melt 33, and 1 kg of Ga+As was charged and synthesized directly in an arsenic gas-tight container, and then a GaAs single crystal was pulled. The EPD of the front part of this crystal is approximately 3000/ ^cm2 , and the EPD of the back part is approximately
A semi-insulating crystal of 7000/cm ² was obtained.

Effects The present invention is as described above, and it becomes possible to obtain a large-diameter arsenic compound using a large-diameter container, and it is possible to easily produce materials useful as substrates for lasers or ICs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an example of a conventional single crystal growth apparatus, and FIG. 2 is a sectional view of an embodiment of the present invention. 1... Metal container, 2... Quartz rotary crucible, 3 and 23... After heater, 4... Upper fitting lid, 5, 22... Boron oxide for sealing, 6... Rotating pulling shaft, 7... Main heater, 8... High Dissociation pressure compound, 9...Rotating shaft, 10...Graphite susceptor, 11...Chuck, 12...Seed crystal, 13...Inert gas introduction system, 14...Exhaust system, 15...Single crystal, 16...Boron oxide for coating, 17 , 24... saucer, 18... support stand, 19... drive stand, 20... furnace core tube, 21... lower fitting lid, 25... electric furnace for arsenic pressure control, 26,2
6'... Arsenic gas sealed container, 27... Boron oxide for shaft seal, 28... Quartz rod or quartz fiber for internal observation, 29... Pulling shaft, 30...
Boron oxide for arsenic gas sealing, 31...Heater, 3
2... Crucible, 33... Arsenic compound melt, 34... Arsenic compound single crystal, 35... Pedestal, 36... Inert gas introduction system, 37... Vacuum exhaust system, 38... Crucible rotation shaft.

Claims (1)

[Claims] 1. In an apparatus for pulling an arsenic compound single crystal while controlling the pressure of arsenic gas sealed in a container,
The container is equipped with a quartz window for internal observation or at least one of quartz rods or fiberscopes penetrating the container, and is made of molybdenum or a molybdenum alloy, gas-impermeable carbon, silicon nitride, alumina-based oxide, or zirconia. The container is made up of one or more of the above, and can be further divided into upper and lower parts, and the divided container is provided with a boron oxide holding part, and the lower end of the upper container is immersed in the boron oxide. An apparatus for growing an arsenic compound single crystal, characterized in that it is made by sealing arsenic gas.