JP3697341B2 - Compound single crystal production equipment and / or heat treatment equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a compound single crystal manufacturing apparatus and / or a heat treatment apparatus, and more particularly to a single crystal manufacturing apparatus for growing (manufacturing) a compound semiconductor crystal while controlling a processing atmosphere and an apparatus for performing a heat treatment while controlling the processing atmosphere. .
[0002]
[Prior art]
The manufacturing method of III-V compound semiconductor such as GaAs and II-VI compound semiconductor single crystal such as CdTe includes horizontal Bridgman method (HB method), vertical Bridgman method (VB method), solidification with horizontal temperature gradient. A method (HGF method), a solidification method with a vertical temperature gradient (VGF method), a pulling method (CZ method), and the like are used.
Among these methods, the pulling method (CZ method) is particularly used for the production of compound semiconductors. This method is a crystal growth method that is not restricted by a crucible, but because it is a crystal growth under a large temperature gradient, there is a problem that a high-quality crystal cannot be obtained, for example, the dislocation density of the grown crystal becomes high. .
[0003]
As a method for obtaining low dislocation crystals, there is a vertical boat method in which a melt is solidified in a crucible to obtain a single crystal. The vertical boat method includes a vertical Bridgman method (VB method) and a vertical temperature gradient solidification method (VGF method). According to these methods, crystal growth can be performed under a low temperature gradient. A single crystal with good properties can be obtained.
Whether the VGF method or the VB method is used, the high dissociation pressure component is sealed in advance in an airtight container in order to prevent fluctuation of the component due to evaporation of the high dissociation pressure component from the raw material melt. It is customary that the vapor pressure is balanced with the dissociation pressure of the high dissociation pressure component of the raw material melt by heating and evaporating, and the inside of the hermetic vessel is made a high dissociation pressure component gas atmosphere in the crystal growth process. Various obstacles occur due to the pressure difference inside and outside the airtight container.
[0004]
For this reason, as disclosed in JP-A-4-77383, an airtight container (airtight chamber) is accommodated in a high-pressure container filled with an inert gas at a high pressure, so that the pressure difference between the inside and outside of the airtight container is reduced. The airtight container is provided with a pressure buffering passage (pressure equalizing passage) for pressure equalization. When using a II-VI group compound, a III-V group compound or a compound containing these as a main component as a raw material, the high dissociation pressure component gas of these compounds has a higher molecular weight than the pressurizing inert gas. As disclosed in the lower left column, line 13 to the lower right column, line 2 of the official gazette, the pressure buffer passage retains the high dissociation pressure component gas in the container and gives priority to the inert gas. In order to discharge out of the container, it is provided in the upper part of the airtight container.
[0005]
However, in the upper part of the hermetic container, the gas in the container is in a high temperature state and has high kinetic energy, so that the high dissociation pressure component gas easily escapes from the pressure buffer passage. Therefore, in order to prevent gas from flowing out, the pressure buffer passage has a complex labyrinth structure as described in the above publication, page 5, lower right column, line 18 to page 6, upper left column, line 7, and FIG. It is a meandering passage.
In addition, as described in the above publication, page 4, upper right column, lines 3-7 and lower right column, lines 13-15, the gas of high dissociation pressure component is in the process until reaching the equilibrium state. It is discharged out of the airtight container from the pressure buffer passage. Since the discharged high dissociation pressure component gas has a high temperature, it adheres to the entire surface of the low-temperature side heater element below the collective heater provided around the hermetic container and the power supply electrode. Moreover, as the production apparatus is repeatedly used, the adhesion layer of the high dissociation pressure component grows. Usually, since the high dissociation pressure component is often a conductor or a semiconductor, the power supplied to the heater fluctuates due to the adhesion of the high dissociation pressure component and the growth of the adhesion layer, and the heating temperature becomes unstable accordingly. If it is remarkable, the heater electrode is short-circuited through the adhesion layer, and the operation becomes impossible.
[0006]
Since the conventional technique disclosed in Japanese Patent Laid-Open No. 4-77383 has the problems described above, the present inventors have disclosed a heater element in a high-pressure vessel as disclosed in Japanese Patent Laid-Open No. 7-330479. A collective heater arranged in a plurality of stages in the vertical direction is provided, an airtight chamber having a pressure equalizing passage communicating with the inside and outside of the chamber is provided in the collective heater, a crucible for containing a compound raw material in the airtight chamber, and the crucible A reservoir containing the high dissociation pressure component of the raw material compound is disposed below, and an evaporation heater element for heating and evaporating the high dissociation pressure component is provided. By moving the melting point temperature range of the temperature distribution from high temperature to low temperature across the melting point relative to the crucible from below to above In the compound single crystal manufacturing apparatus for growing a cooled and solidified to single crystal from below the raw material melt in the volume, the pressure equalizing path is formed below the vaporization heater element.
[0007]
In the technique of JP-A-7-330479, as described in paragraph number 0014 of the publication,
In this apparatus, the pressure equalizing passage may be provided in a temperature range below the melting point of the high dissociation pressure component. In addition, a vapor flow suppressing means (semi-seal material) for suppressing the downward flow of the vapor of the high dissociation pressure component evaporated from the reservoir may be provided between the reservoir and the pressure equalizing passage. . Further, the high-pressure vessel has a structure including a trunk cylinder, and an upper lid and a lower lid that seal the upper and lower openings of the trunk cylinder, and the airtight chamber is attached to the lower lid, and the lower lid is the trunk It is preferable that the cylinder body is detachably mounted from above and below. The hermetic chamber is preferably constructed so as to be freely assembled and assembled. On the other hand, when used as the VB method, an elevating rod that elevates in the vertical direction is provided inside the airtight chamber, and the crucible is supported on the upper portion of the elevating rod. Note that the lowermost heater element of the collective heater can be used as an evaporation heater element.
[0008]
On the other hand, the crystal ingot is annealed in order to control the thermal history of the compound semiconductor single crystal to improve the variation between crystals and wafers related to point defects.
In particular, electronic device semi-insulating GaAs can be made uniform in electrical characteristics and optical characteristics, reduced in precipitates, and controlled in composition by annealing, so that wafer quality can be improved.
As the annealing treatment, a crystal ingot is vacuum-sealed in a quartz tube, and heat treatment is performed in a horizontal electric furnace at 750 to 1000 ° C. for 3 to 15 hours.
[0009]
[Problems to be solved by the invention]
In the technique disclosed in Japanese Patent Laid-Open No. 7-330479 described above, the vapor is kept airtight by the semi-sealing material, but the semi-sealing cannot reliably fill the air-tight chamber. In other words, as described in the publication, “almost it is possible to substantially prevent the vapor from flowing below the semi-sealing material”, but it is difficult to completely prevent it. This “semi-seal material has a sealing property that does not impair the pressure equalization”, that is, allows a certain amount of gas flow.
[0010]
With such a semi-seal structure, the yield of the high dissociation pressure component elements stored in the reservoir (ratio of the weight of the elements stored and the weight of the elements recovered after processing) is poor, and the high dissociation flowed through the semi-seal material. pressure component of the vapor is to agglomerate somewhere in the container ones unlikely that adhesion to the heater element (low point temperature), should Ru performing frequent maintenance. The object of the present invention is to provide a compound single crystal production apparatus and / or a heat treatment apparatus provided with an airtight container that isolates a crystal processing gas atmosphere and a heating apparatus atmosphere in order to solve the problems of the conventional example. It is.
[0011]
[Means for Solving the Problems]
Above compound single crystal manufacturing apparatus and / or heat treatment apparatus according to the present invention for achieving the objects of the crystal treatment gas atmosphere I covering the raw material or a compound semiconductor crystal of the compound semiconductor which is accommodated in a container having a heating element An airtight container that isolates the atmosphere from the heating device , and a gas flow into the airtight container and a container for storing the element of the high dissociation pressure component constituting the compound semiconductor in the airtight container An on-off valve is provided, and the container and the on-off valve are arranged at a lower temperature in the lower part of the hermetic container .
[0012]
In the present invention, it is desirable that an on-off valve is provided above the container for housing the element of the high dissociation pressure component constituting the compound semiconductor, and the on-off valve seal structure is a laminated graphite sheet. desirable.
Further, in the present invention, a container for housing the high dissociation pressure component elements constituting the compound semiconductor may be configured to Ru provided with opening and closing valves, also a container having a heating element, the heating element of the container It is advantageous that the airtight container provided on the inner side of the airtight container is arranged with the container axis as the vertical axis, and a valve rod for the on-off valve is inserted in the gas flow path into and out of the airtight container. It is recommended that
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, some of the embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example applied to a heat treatment of a GaAs single crystal. In FIG. 1, an upper lid 2, an outer lower lid 3, and an outer lower lid 3 are inserted into upper and lower openings of a cylindrical container 1 through a sealing material (not shown). An inner lower lid 4 is fitted and hermetically configured, and a plurality of heating elements 6 and an inverted cup for heat-treating a crystal 10 (GaAs crystal in this embodiment) as a processed product are contained in the container 1. A heat insulating layer 5 having a shape is installed to constitute a furnace.
[0014]
An airtight container 7 for covering the crystal 10 is installed inside the heating element 6, and the airtight container 7 is for isolating the crystal processing gas atmosphere from the heating apparatus atmosphere. Although it depends on the processing temperature, it is made of metal, ceramics, special carbon material (having airtightness), glass material or the like.
In the airtight container 7, a crystal 10 (GaAs crystal in this embodiment) as a processed product, a sample stage 12 for installing the crystal 10, and a reservoir that is a container for storing a high dissociation pressure component (element). 8 is installed. The reservoir 8 is also made of an airtight material (a member is selected according to operating temperature and impurities as described above) in order to isolate the atmosphere inside and outside the airtight container.
[0015]
The reservoir 8 stores a high dissociation pressure component (element) 9, which is As in this embodiment. The As storage amount stores a weight necessary for obtaining a pressure corresponding to the As dissociation pressure from the GaAs crystal at the heat treatment temperature.
An on-off valve 11 for operating a gas flow (inert gas such as argon) inside and outside the hermetic container 7 is installed above the reservoir 8. The on-off valve 11 is installed above the reservoir 8 because when the valve 11 is installed below the reservoir 8, the temperature of the valve 11 portion is lower than that of the reservoir. It is because it aggregates in 11 parts of valves. Therefore, by setting the valve 11 above the reservoir 8, the high dissociation pressure component 9 does not aggregate on the valve 11, does not cause malfunction of the valve 11, and not only ensures stable operation of the valve 11. When the high dissociation pressure component 9 is recovered after the heat treatment, the reservoir 8 is located at the lowest temperature in the hermetic container 7, so that the high dissociation pressure component 9 can be efficiently recovered in the reservoir 8. The rate is improved and the cost is effective.
[0016]
The on-off valve 11 has a valve rod 11A inserted in the gas flow path 13 and is required to open and close at the time of evacuation and gas replacement in the airtight container 7 before the start of heat treatment. Vacuuming and gas replacement in the sealed pressure vessel 1 and hermetic vessel 7 before operation is necessary not only for the lifetime of the in-furnace parts but also for the reduction of impurities. During heat treatment in which the atmosphere in the airtight container is controlled (when heat treatment is performed while controlling the As pressure), the on-off valve 11 is closed and the sealing material 14 is pressed to ensure airtightness. The on-off valve 11 is driven by connecting its valve rod 11A to a driving device 15 such as an air cylinder or an electric motor.
[0017]
Various materials are selected for the sealing material 14 depending on the operating temperature range. For use at a high temperature (500 ° C. or higher), a graphite sheet, particularly a laminated graphite sheet is most desirable.
Further, the hermetically sealed container 1 and the hermetic container 7 are arranged with the container axis as the vertical axis, thereby making it easy to maintain temperature uniformity and to ensure uniformity of processed products. . A gas inlet / outlet 12 </ b> A is formed in the sample stage 12.
The GaAs crystal annealing process will be described below using the apparatus shown in FIG.
[0018]
The inner lower lid 4 is lowered (or the pressure vessel 1, the upper lid 2, the outer lower lid 3 and the like are moved upward), and the airtight vessel 7 is removed. A φ6 inch GaAs crystal 10 was placed in a crucible (not shown) on the sample stage 12, and about 2 g of a high dissociation pressure component As was placed in the reservoir 8.
The airtight container 7 was installed, the inner lower lid 4 was inserted into the pressure container, the on-off valve 11 was set in the “open” state, a vacuum was drawn through the gas flow path 13, and gas replacement with argon gas was performed. Next, argon gas was supplied into the airtight container 7 until the pressure reached about 2 kgf / cm 2, and the on-off valve 11 was set to “closed”. At this time, the pressure inside the sealed pressure vessel 1 was also about 2 kgf / cm 2.
[0019]
Energization of the heating element 6 was started, and the temperature of the crystal 10 was controlled to be 1100 ° C. At this time, the reservoir 8 was also heated by the heating element 6 for controlling the vapor pressure so as to be controlled to a control temperature of 500 ° C.
After completing the predetermined heat treatment, the temperature was lowered to room temperature, and then the on-off valve 11 was opened to release the gas. After releasing the gas, the inner lower lid 4 was lowered and the airtight container 7 was removed. The GaAs crystal 10 was a very high quality crystal with no loss of As.
[0020]
As was recovered in the reservoir, and the weight loss was as high as about 0.1 g.
FIG. 2 shows a specific example applied to a single crystal growth (manufacturing) apparatus of the vertical Bridgman method (VB method).
The apparatus configuration shown in FIG. 2 is almost the same as that shown in FIG. 1, but the heat treatment apparatus shown in FIG. 1 has a drive device (not shown) for moving the crucible shaft for growing the crystal 10. It is a different point.
[0021]
In the example of FIG. 2, an example in which the hermetic container 7, the reservoir 8 and the like are moved downward is shown, but a method of moving only a crucible (not shown) and a crystal may be used.
The heating element 6A for controlling the vapor pressure is a heating device longer than that shown in FIG. 1. This is because the reservoir 8 also moves downward during growth, so that the temperature of the reservoir 8 is soaked even during movement. It is a long one.
In this embodiment, the vapor pressure of the high dissociation pressure component is controlled while the crystal is grown by the VB method, and the movement of the crucible is different from the configuration shown in FIG. The Note that portions common to FIG. 1 are denoted by common reference numerals.
[0022]
Referring to FIG. 3, there is shown a heat treatment apparatus in which a reservoir 8 is provided in the valve portion of the on-off valve 11, and the heater 6 </ b> A is built in the sample stage 12. 2, the vapor pressure can be controlled in more detail. In other words, in the first and second embodiments, the temperature control of the reservoir 8 is performed by the heating device 6A installed outside the hermetic container 7, so that precise control is impossible. On the other hand, since the heating device 6A for vapor pressure control is installed in the hermetic vessel 7 as in this embodiment, the vapor pressure control temperature can be more accurately controlled, and therefore, accurate vapor pressure control is possible. It is possible. Other configuration is the fact in common with configuration shown with reference to FIG. 1, the common parts are indicated by common reference numerals.
[0023]
In the configuration shown in FIG. 3, it is of course possible to use this for a crystal manufacturing apparatus.
Although not shown in the drawings, the structure of the on-off valve can be somewhat modified such as a poppet shape or the like.
[0024]
【The invention's effect】
According to the present invention, since a quartz sealed tube is not used, there is no problem of silicon impurity contamination, and there is no problem of deformation of the sealed tube. Since it is a vertical apparatus, it is easy to maintain temperature uniformity and to ensure uniformity of processed products.
In addition, the element vapor pressure of the high dissociation pressure component can be reliably sealed in the hermetic container, so that more accurate vapor pressure control is possible. The transpiration amount of the high dissociation pressure component element is small, and the yield is good and the cost can be reduced.
[0025]
Further, in the semi-sealed structure, the high dissociation pressure component evaporated from the semi-sealing material does not adhere to the heating device, but adheres somewhere in the container. In general, high dissociation pressure components of compound semiconductors are toxic and dangerous, and maintenance such as removal work is complicated and takes time, leading to an increase in cost of processed products. But it is advantageous.
[Brief description of the drawings]
1A and 1B show a first embodiment of a device of the present invention, in which FIG. 1A is a sectional view of the overall configuration, and FIG. 1B is an enlarged view of an on-off valve portion;
FIG. 2 is an overall configuration cross-sectional view showing a second embodiment of the device of the present invention.
FIG. 3 is an overall configuration cross-sectional view showing a third embodiment of the device of the present invention.
[Explanation of symbols]
1 Pressure vessel 6 Heating element 8 Reservoir (container)
9 High dissociation pressure component 10 Crystal 11 On-off valve

Claims (6)

An airtight container to isolate the heating device atmosphere crystal processing gas atmosphere I covering the raw material or a compound semiconductor crystal of the compound semiconductor which is accommodated in a container having a heating element disposed in the airtight container, constituting the compound semiconductor the opening and closing valve for performing gas flow provided to the high dissociation pressure component elements container for housing into the hermetic container, arranged in a low temperature place and said container and the opening and closing valve at the bottom of the airtight container and wherein the and the compound single crystal manufacturing apparatus and / or heat treatment apparatus. 2. The compound single crystal manufacturing apparatus and / or heat treatment apparatus according to claim 1 , wherein an opening / closing valve is provided above a container for storing an element of a high dissociation pressure component constituting the compound semiconductor. 2. The compound single crystal manufacturing apparatus and / or heat treatment apparatus according to claim 1 , wherein a container for storing an element of a high dissociation pressure component constituting the compound semiconductor is provided in the on-off valve . The compound single crystal manufacturing apparatus and / or heat treatment apparatus according to any one of claims 1 to 3, wherein a sealing structure of the on-off valve is a laminated graphite sheet .   The container having the heating element and the airtight container provided inside the heating element of the container are arranged with the container axis as the longitudinal axis, according to any one of claims 1 to 4. Compound single crystal production equipment and / or heat treatment equipment.   The compound single crystal manufacturing apparatus and / or heat treatment apparatus according to any one of claims 1 to 5, wherein a valve rod for an on-off valve is inserted in a gas flow path to the inside and outside of the hermetic container.

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