JPS6016891A - Preparation of crystal by application of magnetic field and its device - Google Patents

Abstract

PURPOSE:To prepare crystal stably by a small-sized device with small power loss, by setting a conductive material plurally wound round the same axis of an airtight container, applying DC to it, carrying out crystal growth in a state where DC magnetic field is impressed on melt heated at high temperature. CONSTITUTION:The silicon melt 1 is put in the quartz crucible 2 contained in the graphite crucible 3, the silicon single crystal 5 is being pulled up, and they are put in the cylindrical airtight container 6. The magnetic field application coil 7 is plurally wound round the same axis of the periphery of the airtight container 6. The coil 7 consists of the conductive material part 8 made of a steel material, etc., the electrical insulating part 9 such as cotton tape, etc., and the cooling water part 10. DC or pulsating current close to DC is impressed on the conductive material part 8 of the coil 7, magnetic field is generated in the silicon melt 1, and crystal is grown in the state. Since sufficient ferromagnetic field can be generated only by the small-sized coil compared with a large-sized electromagnet using a well-known iron core of magnetic material, power consumption can be reduced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a method for growing crystals from a raw material melt in a container using seed crystals (C2 method) or by melting a raw material polycrystalline rod. The floating zone method (F
This relates to crystal manufacturing methods such as the Z method, in particular the crystal manufacturing technology that improves the characteristics of crystals by applying a direct current magnetic field during the growth of crystals from conductive melts of metals, semiconductors, etc. It is something.

(Prior art) The present invention was filed in a patent application by the inventors as a method for effectively suppressing thermal convection within the melt without adversely affecting the homogeneity of the crystal when producing crystals by the CZ method, FZ method, etc. Showa 56-32
The present invention relates to a crystal manufacturing method proposed in No. 451 (Japanese Unexamined Patent Publication No. 57-149894), that is, a crystal manufacturing apparatus and method in which a direct current magnetic field is applied in a substantially perpendicular direction to the growth interface of a crystal. The present invention relates to the above basic invention, and then:
The object of the present invention is to provide a magnetic field application crystal manufacturing method and crystal manufacturing apparatus that are compact, have little power loss, and stably produce a strong magnetic field, which were obtained as a result of studying various specific magnetic field generation means. .

(Structure of the Invention) In order to achieve the above object, the present invention provides a method for separating a melting body or melting zone heated to a high temperature, a heating means and a heat retaining means provided so as to surround this, and furthermore, from an external atmosphere. A crystal manufacturing apparatus comprising an airtight container for, and a plurality of turns of a conductor coaxially wound around the airtight container,
A method for producing a crystal by application of a magnetic field, characterized in that a direct current or a pulsating current close to direct current is applied to the conductor, and crystal growth is performed in a state where a direct current magnetic field is applied to a melt or melt zone heated to a high temperature. This is the gist of the invention.

Furthermore, the present invention provides a crystal manufacturing apparatus comprising a melt or melt zone heated to a high temperature, a heating means and a heat insulating means provided to surround the melt, and an airtight container for separating it from the external atmosphere. The gist of the invention is a magnetic field application crystal manufacturing apparatus characterized by comprising a plurality of turns of a conductor coaxially wound around the circumference, means for insulating between the conductors, and means for cooling the conductor. be.

Next, embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments are merely illustrative, and it goes without saying that various changes and improvements may be made without departing from the scope of the present invention.

(Example) Next, specific embodiments of the present invention will be described using the drawings.

[Example 1] FIG. 1 shows a case where the present invention is applied to CZ method silicon single crystal growth. In Figure 1, 1 is a silicon melt, 2 is a quartz crucible, 3 is a graphite crucible containing the quartz crucible, 4 is a heating element, 5 is a grown silicon single crystal, and 6 indicates these. It is a cylindrical airtight container that accommodates. 1 indicates a magnetic field applying coil according to the present invention, which is coaxially wound around the airtight container. The number of turns is 12 times per layer, and the case is shown in which two layers are wound for a total of 24 times. Furthermore, these coils 7 are connected to a conductor part 8 made of copper or other material, an insulating part 9 made of cotton tape or the like to electrically insulate these conductors, and a cooling part to prevent temperature rise due to heat generation in the conductor part 8. (see figure b). Further, 11 is a support cylinder for holding the coils.

FIG. 2 shows an electrical connection circuit diagram of the coil l shown in FIG. The first layer of the coil I in FIG. 1 corresponds to the circuit 12, and the second layer corresponds to the circuit 13. In this embodiment, the first layer and the second layer are connected in series. 3) Not shown in this example When configuring in multiple layers of ¥i or more, the power supply 1
There is no need to explain in detail that it is sufficient to appropriately combine series and parallel connections in consideration of the characteristics of No. 4.

FIG. 3 shows a cooling water connection circuit diagram of the coil I shown in FIG. 1. The first layer of the coil I in FIG. 1 corresponds to the circuit 15, and the second layer corresponds to the circuit 16, respectively, and shows a case where they are connected in parallel. It does not need to be explained in detail that the connection of the cooling water can be made by matching the characteristics (pressure, flow rate) of the cooling water supply source and combining appropriate targets and parallel circuits in the same manner as in the case of electrical connections.

In addition, the dimensions of the coil 7 in this example are an inner diameter of 350 m.
,,outer diameter 4008 m1. The height was 300 ya, and the amount of iJi was about 50.

An example in which the magnetic field application crystal manufacturing apparatus of the present invention having the configuration described above is applied to crystal growth will be described below. A direct current of approximately 150 OA was applied to the conductor portion 8 of the coil I, and a magnetic field of approximately 10,000 e was generated at the center of the coil 2. In this case, the flow rate Q of the cooling water section 10 is about 25 cm, and the pressure difference between the inlet 17 and the outlet 18 of the cooling water circuit in Fig. 3 is about 3~r.
/Cm2. Figure 4 shows a diagram (a) of the generated magnetic field in the central axis direction in the crucible 2 and an example of measurement of the in-plane strong IW distribution (
b) Show the diagram. These distribution characteristics are the magnetic field generation coil 7.
It was confirmed that the values were in good agreement with the values calculated from the geometric relationship between the measurement location and the current value applied to the coils. Therefore, it is shown that the method of the present invention is an effective means for generating a magnetic field in which the strength and distribution of the magnetic field are not influenced by the surrounding conditions. Next, the characteristics of crystals grown under the application of such a magnetic field have already been reported (, Tpn
, J. Appl phys, 21 (1982
), L545), very excellent results were obtained in terms of uniformity of dopant concentration, controllability of oxygen concentration, and controllability of shape during crystal growth.

[Example 2] FIG. 5 shows a case where the present invention is applied to GaAs single crystal growth using the LEC method. In FIG. 5, 19 is a GaAs melt, 2
0 is a crucible made of quartz or pyrolytic boron nitride (PBN), 21 is a liquid sealant B2O3, 22 is a grown GaAs single crystal, 23 is a heating element, and these are placed inside a high pressure-resistant airtight container 24. It is located. (Reference numeral 5 indicates a coil for applying a magnetic field according to the present invention. In the case of this embodiment, it has a structure embedded in a high pressure-resistant airtight container 24, and is coaxially wound in a single layer around the periphery. The coil 2-5 is The conductor part 26 is made of a material such as a highly conductive copper material, the insulating part 27 electrically insulates the mating conductor part 26, and the cooling water part 28 which prevents temperature rise due to heat generation of the conductor part 26. The configuration is exactly the same as in the first embodiment.

Note that 29I'i is a support cylinder that holds the coil 5.

Similar to the CZ method silicon single crystal of Example 1, the GaAs single crystal produced by the above-mentioned magnetic field applied LEO method high crystal production apparatus of the present invention has a lower dopant concentration as a result of the reduction of thermal convection of the melt due to the magnetic field. Uniform characteristics with little variation were obtained. Furthermore, new effects have been revealed, such as stabilizing the temperature at the growth interface during crystal growth, forming a thin and long neck due to necking, and making diameter control much easier.

[Example 3] FIG. 6 shows a case where the present invention is applied to silicon single crystal growth using the FZ method. In Fig. 6, 30 is a raw silicon rod;
31 is a lit band, 32 is a grown silicon single crystal, 33
are work coils that heat the melting zone 31, and these are housed inside the airtight container 34. In addition, the airtight container 34
An observation window 35 is provided in the molten zone 31 during crystal growth.
can now be observed. Next 36a, 36
b shows a magnetic field applying coil according to the present invention; in this embodiment, there are two coils 36 above and below across the observation window 35;
a.

36b is provided. Even in such a structure, electromagnetism teaches that by appropriately selecting the shape and relative position of the upper coil 36a and the lower coil 36b, it is possible to apply a uniform magnetic field to the melt zone 31 where crystal growth occurs. No explanation required. Further, as in the first and second embodiments, the coils 36a and 36b are composed of a conductor section 37, an insulating section 38 (see figure b), and a cooling water section 39. In addition, the electrical connection between the second coil 36a and the lower coil 36b and the connection method between the cooling water ports 40 and 41 and the outlets 42 and 43 were also exemplified in Embodiment 1.
The same thing can be done by the method (Fig. 3). In the silicon single crystal grown by the magnetic field application FZ method of this example, the microscopic local variation in dopant concentration is significantly reduced (below 115 when phosphorus (p) is used as the dopant). This was confirmed by resistance measurements. Furthermore, it was revealed that the temperature distribution in the melt zone during crystal growth can be significantly changed by the applied magnetic field. This has the effect that it becomes possible to control the shape of the solid-liquid interface during crystal growth using the FZ method, which has been difficult in the past.

In the above explanation, we have explained the case where direct current is used as the current flowing through the coil to form a direct current magnetic field.
Even if a DC magnetic field is formed using a pulsating current close to DC, the same effect can be obtained.

(Effects of the Invention) As explained above, the magnetic field application crystal manufacturing apparatus according to the present invention has different characteristics in the configuration of the coil for generating the magnetic field, and is smaller than the large electromagnet using the known magnetic core. It is possible to generate a sufficiently strong magnetic field with only one coil, and therefore the power consumption of 11L can be reduced. In addition, as mentioned in the three examples, in addition to the 0ZpJ, FZ method, and LEC method, it can be applied to various conventional crystal manufacturing methods such as the Bridgman method and the chiroporous method, increasing the degree of freedom in design. big. Furthermore, by combining appropriately separated electrical connections of coils and cooling water in series and parallel, there are many advantages such as the ability to easily generate magnetic fields with a wide range of strengths.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an apparatus showing an embodiment of the present invention, FIGS. 2 and 3 are electrical connection diagrams and cooling water connection diagrams of the same embodiment, and FIG. 4 is a magnetic field distribution characteristic diagram. Moreover, FIGS. 5 and 6 each show a sectional view of an apparatus showing another embodiment. 1...Silicon melt, 2...5 crucibles, 3...
Graphite crucible, 4... Heating element, 5... Silicon single crystal, 6... Airtight container, I... Coil, 8...
Conductor part, 9... Insulation part, 10... Cooling water part, 11.
...Support cylinder, ]2゜13...Coil symbol showing electrical circuit, 14...Symbol showing power source, 15.
16...Cooling water circuit, 17...Cooling water inlet, 18...
・Cooling water outlet, 19...GaAs melt, 20...
21--Liquid sealant, 22--GaAe single crystal, 23--Heating element, 24--Airtight container, 25--
...Coil, 26...Conductor part, 27...Extreme part, 28...Cooling water part, 29...Support cylinder, 30--
,・Arrest silicon rod 1. 31... Melting zone, 32... Silicon single crystal, 33... Work coil, 34... Airtight container, 35... Observation window, 3dan a... Upper Koino・,°
Lower coil, 37... Conductor part, 38... Insulating part,
39...Cooling water section, 40.41...Cooling water inlet, 4
2.43... Cooling water output 1 Patent applicant Figure 1 (a) Figure 2 Figure 3 Figure 4 6008001000 Konnoha513(○e) -80-4004080 1 is ψI Distance (mm) Fig. 5 (a) (b) Fig. 6 (a) (b)

Claims (2)

[Claims] (1) A crystal manufacturing apparatus comprising a melt or a melt zone heated to a high temperature, a heating means and a heat retaining means provided to surround the melt, and an airtight container for separating the melt from the external atmosphere. A multi-turn conductor coaxially wound around an airtight container was provided, and a direct current or pulsating current close to direct current was applied to the conductor, and a direct current magnetic field was applied to the melt or melt zone heated to a high temperature. 1. A method for producing crystals by applying a magnetic field, characterized by causing crystal growth in a state in which crystals are grown. (2) In a crystal manufacturing apparatus comprising a melt or melt zone heated to a high temperature, a heating means and a heat insulating means provided to surround the melt, and an airtight container for separation from the external atmosphere, the area around the airtight container is 1. An apparatus for producing a crystal by applying a magnetic field, comprising: a plurality of turns of a conductor coaxially wound around the conductor; means for insulating the conductors; and means for cooling the conductor.