JPH0311240Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an apparatus for producing single crystals of - group compound semiconductors and the like by a pulling method.

[Prior Art] In the production of semiconductor single crystals by the pulling method, it is very important to detect and control the shape of the single crystal during pulling in order to obtain high-quality, high-yield single crystals.

For Si (group elements), the shape of the crystal being pulled is optically observed through a viewing window installed diagonally above the pulling container, and this is fed back to the pulling speed, heater temperature, etc. to control the crystal shape and eliminate dislocations. Obtaining crystals.

On the other hand, in - group compound semiconductors, the vapor pressure of the group is very high (for example, in GaAs, the As pressure during synthesis is approximately 20 atm, and the As pressure at the melting point in the GaAs state is
1atm) Group elements volatilize during crystal pulling and growth, resulting in low-quality GaAs lacking As. To prevent this, the crystal is pulled and grown in a high-pressure container filled with high-pressure inert gas (Ar, N, etc.), and
Seal the melt in the crucible with a transparent melt of B ₂ O ₃
The LEC method is generally used as a pulling growth method for − group compound semiconductors.

However, even with this method, group elements gradually react with B ₂ O ₃ or volatilize through B ₂ O ₃ during crystal pulling, which causes turbidity of B ₂ O ₃ and clouding of the lens surface of the viewing window. Therefore, it is difficult to observe and control the bond shape using optical methods.

Therefore, in the method for pulling - group crystals, a load cell is installed on the top of the crystal pulling rod to measure the weight of the grown crystal, and the outer diameter of the crystal is calculated from this and the measured value of the pulling length. Shape control is performed based on.

[Problems to be solved by the invention] However, in order to measure the weight of a growing crystal using a pulling rod, the pulling rod must be suspended by a load cell. Since functions such as rotational movement and pressure sealing are required, the structure is complicated, and shaft wobbling occurs when the pulling shaft is rotated, making it difficult to obtain high-quality single crystals.

In addition, since the crystal growth interface is not necessarily flat and may be concave or convex, the gravimetric method, which calculates the outer diameter assuming a flat crystal growth surface, may result in a large error in the measured outer diameter value. There is a problem.

There is an outer diameter control method using X-rays that overcomes the drawbacks of the conventional outer diameter control method described above, and was previously published in Japanese Patent Publication No. 46-21804, Japanese Patent Publication No. 58-34440, and Japanese Patent Application Laid-Open No. 49-75467. No. etc. have been proposed.

In Japanese Patent Publication No. 46-21804, a single crystal is pulled and grown in a sealed quartz tube, and an X-ray outer diameter detection device is installed, which consists of an X-ray source outside the quartz tube and an X-ray screen installed on the opposite side. discloses detecting and controlling the outer diameter of a single crystal from an image projected on an X-ray screen.

Also, Japanese Patent Publication No. 58-34440 and Japanese Patent Application Publication No. 49-1989
Although it is not clear in Publication No. 75467 whether the X-ray outer diameter detection device is placed outside or inside the high-pressure container,
By irradiating a growing single crystal with X-rays and measuring the intensity of the diffracted X-rays from the single crystal, or the intensity of the X-rays that have been blocked by the single crystal and have gone straight without being absorbed (absorbed). Controlling the outer diameter is disclosed.

However, since the quartz tube used in Japanese Patent Publication No. 46-21804 is easily transparent to X-rays, the outer diameter of the single crystal can be easily controlled using X-rays, but the atmospheric pressure is high. In the high-pressure lifting method, quartz tubes cannot be used (quartz tubes can only withstand pressures at room temperature), and high-pressure vessels made of stainless steel are used.

However, due to its nature, stainless steel hardly transmits X-rays, and even if a large X-ray device is installed outside a conventional stainless steel high-pressure container, it is extremely difficult to detect the outer diameter of a single crystal. be. Therefore, it has been considered to use a material for the high-pressure container that allows X-rays to easily pass through, but this poses a problem in that the outer wall of the high-pressure container would be thick and large, or it would be quite expensive.

[Purpose of the invention] In view of the problems of the prior art described above, the purpose of the invention is to develop a small-sized single crystal outer diameter control using An object of the present invention is to provide a single crystal pulling apparatus which can be realized by using an X-ray apparatus and a high-pressure container which is almost the same in size and cost as a conventional stainless steel high-pressure container.

[Means for Solving the Problems] The gist of the present invention is that a convex X-ray transparent window having openings at two locations is provided on the side wall of a stainless steel high-pressure container through which X-rays can pass. is provided with an aluminum plate that closes the opening of the X-ray transparent window,
A corrosion protection layer is provided to chemically protect the surface of the aluminum plate exposed to the furnace atmosphere gas.

[Example] Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view showing a GaAs direct synthesis single crystal pulling apparatus equipped with a device for controlling the outer diameter of a single crystal using X-rays. In Figure a and Figure b, 1 is
GaAs grown single crystal, 2 seals GaAs melt 2
B ₂ O ₃ melt, 4 is the inner crucible, 5 is the outer crucible,
6 is a heating heater, 12 is a crucible support, 14
is the pulling axis. The X-ray outer diameter detection device includes an X-ray generation device 7, an X-ray detection device 8, an X-ray fluoroscopy device 9,
It is configured with a TV monitor 10 if necessary. However, it is not limited to these.

The X-ray transmitting window 50a on the X-ray generating device 7 side and the X-ray transmitting window 50b on the X-ray detecting device 8 side are located near the height of the single crystal growth interface, and as shown in FIG. Stainless steel high pressure vessel 1 on a straight line passing through
Both X-ray transmission windows 50a and 50b have the same structure and are convex on the outside of the stainless steel high-pressure vessel 11. In addition, X
The reason why the radiation transmitting windows 50a and 50b are made convex is to facilitate the attachment and detachment of the window portion 20.

As the window portion 20 that closes the openings of the X-ray transmitting windows 50a and 50b, one must be selected that has good X-ray transmittance and strong mechanical strength.As a result of repeated studies, the present inventors We have found that aluminum is optimal.

However, since aluminum is easily corroded by, for example, As vapor, it is necessary to provide an anti-corrosion layer 70 inside the aluminum window portion 20 to chemically protect it from As vapor. The anti-corrosion layer 70 may be made of an inorganic oxide such as Al ₂ O ₃ or SiO ₂ , an inorganic nitride such as Si ₃ N ₄ , or an organic polymer such as polytetrafluoroethylene.

Note that the window portion 20 is fixed with bolts 13 and hermetically sealed.

The present inventors used an aluminum plate with a thickness of 39 mm for the window portion 20 and Al ₂ O ₃ for the anticorrosive layer 70, and performed pulling at a pressure of 30 atm during GaAs crystal growth. The state near the crystal growth interface during growth can be observed using the X-ray transmission device 7.
X-rays are irradiated through the X-ray transmitting windows 50a and 50b.
Then, the X-rays transmitted through the chamber are detected by the X-ray detection device 8. At the same time, the condition of the internal GaAs grown crystal was observed using the X-ray fluoroscopy device 9, and the
The outer diameter of the GaAs grown crystal 1 is determined by manual measurement by visualizing it on the monitor 10 or by automatic measurement using image processing, and this is determined by the pulling device control unit (not shown).
The growth conditions (pulling speed,
A GaAs single crystal with a desired shape was obtained by controlling the heater temperature, pulling rotation speed, etc. Of the growth conditions controlled, the pulling rate was most effective.

The X-ray tube voltage required for fluoroscopy of two 39 mm thick aluminum plates was 100 to 120 Kv. Furthermore, since the crystal growth interface lowers from the X-ray viewing area as the crystal grows, the crucible support 12 and the pulling shaft 14 are raised equally, so that the height of the single crystal growth interface is always constant.

When we measured the outer diameter of the GaAs single crystal after pulling it, we obtained the results shown in Figure 2. Here, the method for calculating the measured outer diameter error x is as follows.

x = (R/R'-1) x 100 (%) R: Measured outer diameter value R': True outer diameter value In this way, the stainless steel high pressure vessel 11 is provided with X-ray transmission windows 50a and 50b made of aluminum plates.
By using X-rays to control the outer diameter of the GaAs grown crystal 1, we achieved very good results in which the outer diameter error of the pulled GaAs single crystal was within ±0.1% at all measurement points.

Furthermore, since the anti-corrosion layer 70 chemically protected the aluminum plate of the window portion 20 from As vapor, the aluminum plate did not corrode.

FIG. 3 shows a sectional view of another embodiment of the present invention.
However, the configuration other than the X-ray transmission window is the same as that in FIG. 1, so the explanation will be omitted.

A dish-shaped anti-corrosion layer 70 is attached to the inner wall of the high-pressure vessel 11, and several small holes 80 are provided in areas through which X-rays do not pass. This small hole 80
This is to prevent the anti-corrosion layer 70 from being destroyed by high pressure, and since the void 90 is filled with inert gas in advance even during single crystal growth, almost no As vapor etc. will diffuse into the window. 20 can be protected. 15 is packing for airtight sealing.

[Effects of the invention] As described above in detail, the present invention is an X-ray outer diameter detection device that detects the outer diameter of a single crystal using X-rays at a height near the single crystal growth interface outside a stainless steel high-pressure container. In a single crystal pulling apparatus equipped with By providing an aluminum plate that closes the window opening and providing an anticorrosion layer that chemically protects the surface of the aluminum plate that is exposed to the furnace atmosphere gas, the following remarkable effects are achieved.

(1) By installing an X-ray transparent window with an aluminum plate attached to the X-ray transparent part of the stainless steel high pressure vessel, and chemically protecting the aluminum plate with an anti-corrosion layer, the lifting equipment that previously used a stainless steel high pressure vessel has been improved. It is now possible to easily control the outer diameter of a single crystal using X-rays, which was difficult to achieve in the conventional method.

(2) There is no need to use ultra-large and expensive X-ray detection equipment or high-pressure containers, and it is possible to use containers that are approximately the same size and price as conventional stainless steel high-pressure containers.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing a GaAs single crystal pulling device for direct synthesis, which is an embodiment of the present invention, and Figure 2 shows a single crystal obtained using the X-ray outer diameter control method and a conventional gravimetrically controlled outer diameter control method. FIG. 3 is a cross-sectional view showing another embodiment of the present invention. 1: GaAs grown single crystal, 2: GaAs melt, 3:
B ₂ O ₃ melt, 4: inner crucible, 5: outer crucible,
6: Heating heater, 7: X-ray generator, 8: X
ray detection device, 9: X-ray fluoroscope, 10: TV monitor, 11: high pressure container, 12: crucible support, 1
3: bolt, 14: pulling shaft, 15: packing, 20: window (aluminum plate), 50: X-ray transparent window, 70: anti-corrosion layer, 80: small hole, 90: void.

Claims (1)

[Scope of utility model registration request] A stainless steel high-pressure container capable of withstanding atmospheric pressure during the synthesis reaction of the elements constituting the crystal and single crystal production during single crystal growth; 2 of the side wall of the stainless steel high pressure vessel through which the X-rays are transmitted.
A convex X-ray transmitting window having openings at certain locations is provided, an aluminum plate is provided on the X-ray transmitting window to close the openings of the X-ray transmitting window, and the aluminum plate is exposed to the furnace atmosphere gas. A single crystal pulling device characterized by being provided with an anti-corrosion layer that chemically protects the surface.