JP4908299B2 - Superconducting magnet device - Google Patents

Description

  The present invention relates to a superconducting magnet device that provides a uniform magnetic field in a relatively large space. In particular, the present invention relates to a superconducting magnet device applied to a single crystal pulling apparatus for manufacturing a semiconductor wafer used for a memory of a computer or the like.

  Semiconductors such as silicon and gallium arsenide are used for memory of computers from small to large, and there is a demand for large capacity, low cost, and high quality storage devices.

  As a single crystal pulling method, a Czochralski (CZ) method for pulling a single crystal from a molten semiconductor material in a crucible is widely known. In recent years, the CZ method has been developed, and a magnetic field is applied to a melted semiconductor material to suppress convection of the semiconductor material, and a large-diameter and high-quality semiconductor wafer is manufactured.

  The application of a magnetic field to a semiconductor material is generally roughly divided into two types depending on the type of magnetic field distribution. One is a Helmholtz type that applies a magnetic field transverse to the pulling direction of the single crystal, and the other is a cusp type that applies a reverse magnetic field so as to cancel each other above and below the single crystal pulling position. In general, a superconducting magnet device is often applied to a Helmholtz type that requires a large magnetomotive force.

In the Helmholtz type superconducting magnet device, as described in Patent Document 1, superconducting coils are arranged to face each other so as to sandwich a crucible. The simplest configuration is a configuration in which two circular solenoid coils are arranged opposite to each other, and the superconducting coil can be easily manufactured and assembled. On the other hand, a configuration in which saddle-shaped coils are arranged to face each other is also known.
JP 2004-51475 A

  However, in the above-described superconducting magnet device, in order to apply a Helmholtz-type magnetic field, when a circular solenoid coil is disposed opposite to the superconducting coil, the superconducting coil moves away from the center of the crucible when the single crystal to be pulled up becomes large. Thus, in order to secure a necessary magnetic field at the center of the crucible, there has been a problem that the magnetomotive force and empirical magnetic field of the superconducting coil must be significantly increased.

  In addition, when the shape of the superconducting coil is devised to be a saddle type, the external dimensions of the device can be reduced compared to a circular solenoid coil of the same condition, and at the same time, the magnetomotive force and empirical magnetic field of the saddle type superconducting coil itself can be reduced. Although there is an advantage that it does not become as large as a circular solenoid coil, a saddle-type superconducting coil is manufactured by winding a conductive wire around a three-dimensional curved surface, so that there is a problem that the manufacturing is complicated and troublesome.

  An object of the present invention is to provide a superconducting magnet device that can suppress the empirical magnetic field and magnetomotive force of a superconducting coil and has good manufacturability.

The present invention relates to a superconducting magnet device composed of a plurality of superconducting coils, wherein at least two superconducting coils form a pair, and the superconducting coils that form the pair are inserted inside one of the other, Rutotomoni equatorial plane is constructed are inclined arranged to intercept, respectively constructive mutually magnetic field is a horizontal direction generated, is configured to weaken each other in the vertical direction, the superconducting coil pairs are Each of the superconducting coils that are formed in different areas, each having a different magnetomotive force so that the strength of the generated magnetic field is substantially the same, and the pair of superconducting coils set at a right angle In addition, a room temperature bore is provided in a space surrounded by these superconducting coils, and each of the superconducting coils forming a pair is adjacent to or separated from the same axis. Is characterized in that it has been configured differently by a plurality of superconducting coils of location has been diameters.

  According to the present invention, the superconducting coils forming a pair are arranged so as to be inclined so that the other penetrates inside one and the equator planes intersect each other. Therefore, the superconducting coils are surrounded by the pair of superconducting coils. It is possible to mutually intensify the components of the magnetic field generated by each superconducting coil within the defined space. Accordingly, it is not necessary to increase the magnetic field generated in each superconducting coil in order to obtain the required magnetic field strength in this space. As a result, the magnetomotive force and empirical magnetic field of each superconducting coil can be suppressed.

  In addition, each of the superconducting coils forming a pair is not a special coil such as a saddle-shaped coil formed by winding a conducting wire around a three-dimensional curved surface, but a normal coil is sufficient. The manufacturability of the apparatus can be improved.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[A] First embodiment (FIGS. 1 to 9)
FIG. 1 is a perspective view showing a first embodiment of a superconducting magnet apparatus according to the present invention. 2 is a cross-sectional view taken along line II-II in FIG. 3 is a cross-sectional view taken along line III-III in FIG.

  A superconducting magnet apparatus 10 shown in FIGS. 1 to 3 is a Helmholtz type superconducting magnet apparatus that applies a horizontal magnetic field (transverse magnetic field) to a single crystal pulling apparatus 11 for manufacturing a semiconductor wafer. The generation of convection in the molten semiconductor material in the crucible of the single crystal pulling apparatus 11 is suppressed, and a large-diameter and high-quality semiconductor wafer can be manufactured.

  In this superconducting magnet device 10, a ring-shaped vacuum container 12 houses a refrigerant container 13 having the same shape, and at least two, for example, two superconducting coils 14A and 14B form a pair in the refrigerant container 13. Arranged. These superconducting coils 14A and 14B are both circular, and for example, the superconducting coil 14B penetrates into the inside of the superconducting coil 14A and is inclined so that the respective equatorial planes 15 (FIG. 4) intersect. Here, the coil center plane that bisects each of the superconducting coils 14A and 14B in the coil axis direction is defined as the equator plane 15.

  The refrigerant container 13 is filled with a refrigerant R such as liquid helium or liquid nitrogen, and the superconducting coils 14A and 14B are immersed in these refrigerants and cooled. By securing such a cooling structure for the superconducting coils 14A and 14B, the bore 16 formed through the vertical direction as the inner space of the vacuum vessel 12 is maintained at room temperature and functions as a room temperature bore. The above-described single crystal pulling apparatus 11 is disposed in the bore 16.

  Although not shown, the vacuum vessel 12 has a current lead for introducing current into each of the superconducting coils 14A and 14B, a port having an inlet for injecting refrigerant into the refrigerant vessel 13 and an outlet for discharging the refrigerant. And are installed. A ring-shaped radiation shield (not shown) similar to the vacuum container 12 and the refrigerant container 13 is disposed between the vacuum container 12 and the refrigerant container 13.

  Currents in the directions of arrows α and β are supplied to the superconducting coils 14A and 14B through the current leads (see FIGS. 1 and 4), whereby the magnetic field B1 is applied to the superconducting coil 14A and the magnetic field B2 is applied to the superconducting coil 14B. Each occurs. These magnetic fields B1 and B2 are provided so as to strengthen the horizontal components B1x and B2x and weaken the vertical components B1z and B2z, and the horizontal components B1x and B2x are added together to generate a horizontal magnetic field. B is generated.

  The horizontal magnetic field B is generated in a vertical space 17 surrounded by a pair of intersecting superconducting coils 14A and 14B, and the bore 16 of the vacuum vessel 12 is provided in the space 17. Therefore, the horizontal magnetic field B described above is applied to the single crystal pulling apparatus 11 disposed in the bore 16 in the horizontal direction (lateral direction) orthogonal to the single crystal pulling direction.

Since the superconducting coil 14B penetrating inside the superconducting coil 14A is formed to have a smaller diameter than the superconducting coil 14A, the area surrounded by the superconducting coil 14B is provided smaller than the area surrounding the superconducting coil 14A. Here, the strength H of the magnetic fields B1 and B2 generated by the superconducting coils 14A and 14B is defined as Φ as the magnetomotive force of the superconducting coils 14A and 14B, and S as the area surrounded by the superconducting coils 14A and 14B.
[Equation 1]
H = Φ / S
It becomes. Therefore, by setting the magnetomotive force of the small-diameter superconducting coil 14B to be smaller than the magnetomotive force of the large-diameter superconducting coil 14A, the strengths H of the magnetic fields B1 and B2 generated by the superconducting coils 14A and 14B are set substantially the same. It becomes possible to do. For example, the magnetomotive force of the large-diameter superconducting coil 14A is set to 1 MA, and the magnetomotive force of the small-diameter 14B is set to 0.95 MA.

When the number of windings of the superconducting coils 14A and 14B is N and the current flowing through the superconducting coils 14A and 14B is I, the magnetomotive force Φ of the superconducting coils 14A and 14B is
[Equation 2]
Φ = I × N
Therefore, as a method of making the magnetomotive force Φ different between the superconducting coils 14A and 14B, for example, the number of windings N and the coil shape of the conducting wires of the superconducting coils 14A and 14B are made different and introduced into these superconducting coils 14A and 14B. A method of making the values of the current I to be the same is preferable.

  As described above, since the strengths of the magnetic fields B1 and B2 generated in the superconducting coils 14A and 14B are substantially the same, the vertical component B1z of the magnetic field B1 generated by the superconducting coil 14A and the superconducting coil The vertical component B2z of the magnetic field B2 generated by 14B is canceled out, and the magnetic field (hereinafter referred to as empirical magnetic field) to which each of the superconducting coils 14A and 14B is exposed is suppressed.

  Further, since the strengths of the magnetic fields B1 and B2 generated in the superconducting coils 14A and 14B are substantially the same, the horizontal component B1x of the magnetic field B1 generated by the superconducting coil 14A and the superconducting coil 14B generate. The horizontal magnetic field B, which is the sum of the horizontal components B2x of the magnetic field B2, is a highly uniform and symmetric magnetic field distribution. FIG. 5 shows an example of the magnetic field distribution in the horizontal plane 18 (FIG. 4) at the point where the superconducting coils 14A and 14B intersect. In FIG. 5, it can be seen that a concentric uniform magnetic field is formed around the central axis O in the space 17 surrounded by the pair of intersecting superconducting coils 14A and 14B. Note that the x-axis and y-axis in FIG. 5 indicate two axes orthogonal to each other in the horizontal plane 18.

  The crossing angle θ (FIG. 4) between the pair of superconducting coils 14A and 14B intersecting with each other may be any angle, but these superconducting coils 14A and 14B are approximately 45 degrees with respect to the horizontal plane 18, respectively. It is preferable that the angle of inclination is set to be a right angle. As shown in FIG. 6, the horizontal magnetic field B generated by the superconducting coils 14A and 14B and the space 17 surrounded by the superconducting coils 14A and 14B each have a trigonometric function dependency on the crossing angle θ. When one is larger, the other is smaller. As shown in FIG. 6, in order to set both the horizontal magnetic field B and the space 17 large, it is most appropriate that the crossing angle θ is a right angle (90 degrees). Thereby, the horizontal magnetic field B can be efficiently generated in the space 17 having a sufficient space.

  Therefore, according to the present embodiment, the following effects (1) to (7) are obtained.

  (1) The superconducting coils 14A and 14B forming a pair are configured such that the small-diameter superconducting coil 14B penetrates inside the large-diameter superconducting coil 14A and the equator planes 15 intersect with each other. In a space 17 surrounded by the pair of superconducting coils 14A and 14B, the horizontal components B1x and B2x of the magnetic fields B1 and B2 generated by the superconducting coils 14A and 14B are strengthened to generate a horizontal magnetic field B. It becomes possible to do. Therefore, it is not necessary to increase the magnetic fields B1 and B2 generated in the superconducting coils 14A and 14B in order to obtain the required magnetic field strength in the space 17. As a result, the empirical magnetic field and magnetomotive force of each superconducting coil 14A, 14B can be suppressed.

  Thus, since the empirical magnetic field of the superconducting coils 14A and 14B can be suppressed, the electromagnetic stress when a current flows through these superconducting coils 14A and 14B can be reduced. As a result, since it is not necessary to manufacture the superconducting coils 14A and 14B using a highly rigid conductive wire, a highly flexible coil design can be realized.

  Furthermore, since the empirical magnetic field of the superconducting coils 14A and 14B is suppressed, the upper limit temperature of the superconducting coils 14A and 14B, which is a function of the empirical magnetic field, can be set high. As a result, the temperature margin that is the difference between the temperature during operation of the superconducting coils 14A and 14B and the upper limit temperature can be expanded.

  Further, since the magnetomotive force of the superconducting coils 14A and 14B can be suppressed, the number of windings of the conducting wires in these superconducting coils 14A and 14B can be reduced, and the coil structure can be simplified.

  (2) Each of the superconducting coils 14A and 14B forming a pair is not a special coil such as a saddle coil formed by winding a conductive wire around a three-dimensional curved surface, but a normal coil is sufficient. 14B can be easily manufactured, and the superconducting magnet device 10 can be manufactured with good quality.

  (3) Since the superconducting coil 14B penetrating inside the superconducting coil 14A has a smaller diameter than the superconducting coil 14A, the magnetomotive force of the superconducting coil 14B is made smaller than that of the large-diameter superconducting coil 14A. The strengths of the magnetic fields B1 and B2 generated by the superconducting coils 14A and 14B are substantially the same. Therefore, the vertical components B1z and B2z of the magnetic fields B1 and B2 cancel each other, and the empirical magnetic field of the superconducting coils 14A and 14B can be suppressed satisfactorily. At the same time, it is possible to improve the uniformity and symmetry of the horizontal magnetic field B obtained by adding the horizontal components B1x and B2x of the magnetic fields B1 and B2.

  (4) Since the crossing angle θ between the superconducting coils 14A and 14B is set at a right angle, the horizontal magnetic field B can be efficiently generated in the space 17 surrounded by the superconducting coils 14A and 14B. A sufficient space of 17 can be secured.

  (5) Since the superconducting coils 14A and 14B are immersed and cooled in the refrigerant filled in the refrigerant container 13, the cooling structure can be simplified because it is not a special cooling structure but a simple cooling structure. .

  (6) Since the superconducting coils 14A and 14B are immersed in the coolant and cooled well, it is not necessary to set the bore 16 of the vacuum vessel 12 in a low temperature space, and the superconducting coils 14A and 14B can be held in a room temperature space. For this reason, there is no restriction | limiting in the utilization of the bore 16 used as the magnetic field space in which the horizontal magnetic field B exists, and free utilization of the bore 16 is realizable.

  (7) The single crystal pulling device 11 is disposed in the bore 16 of the vacuum vessel 12 where the horizontal magnetic field B is generated, and a magnetic field can be applied to the molten semiconductor material in the crucible of the single crystal pulling device 11. Therefore, even when the single crystal pulling diameter by the single crystal pulling apparatus 11 is increased, the empirical magnetic field and magnetomotive force of the superconducting coils 14A and 14B are not excessively increased, and the superconducting coils 14A and 14B can be manufactured. It is possible to manufacture a high-quality semiconductor wafer while avoiding the complication of.

  In the present embodiment, as shown in FIG. 7, the superconducting coil 14A is arranged such that a plurality of (for example, two) superconducting coils 19 and 20 arranged on the same axis are adjacent to or separated from each other. May be configured. Similarly, the superconducting coil 14B may be configured by arranging a plurality of (for example, two) superconducting coils 21 and 22 arranged on the same axis. In the superconducting coils 14A and 14B, since the empirical magnetic field becomes stronger toward the inner side, the outer superconducting coils 20 and 22 can be configured with lower-rigidity conducting wires, and the cost can be reduced.

  In the present embodiment, superconducting coils 14A and 14B may be formed in an elliptical shape shown in FIG. 8, a race track shape shown in FIG. 9, or a rectangular shape. Superconducting coils 14A and 14B having such a shape are also easier to manufacture than a saddle coil manufactured by winding a conducting wire around a three-dimensional curved surface, and an assembly operation for crossing superconducting coils 14A and 14B is also easy. Therefore, a superconducting magnet device with good manufacturability can be realized.

[B] Second embodiment (FIG. 10)
FIG. 10 is a longitudinal sectional view showing a second embodiment of the superconducting magnet apparatus according to the present invention. In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description will be simplified or omitted.

  The superconducting magnet device 25 of the present embodiment is different from the superconducting magnet device 10 of the first embodiment in that the refrigerant container 13 and the refrigerant R of the superconducting magnet device 10 are omitted, and the superconducting coils 14A and 14B are vacuumed. In the vacuum atmosphere in the container 12, the refrigerant is indirectly cooled by the refrigerator 26 via the heat transfer member 27. One or more refrigerators 26 are installed in the vacuum vessel 12.

  The superconducting magnet device 25 according to the present embodiment also has the following effects (8) in addition to the same effects as the effects (1) to (7) of the first embodiment.

  (8) Since the superconducting coils 14A and 14B are cooled by the refrigerator 26, and the refrigerant container 13 and the refrigerant R are no longer required in the vacuum container 12, the space for the refrigerant container 13 is reduced, and the superconducting magnet device 25 It is possible to realize a reduction in size and to realize a weight reduction of the superconducting magnet device 25 by omitting the refrigerant container 13 and the refrigerant R.

[C] Third embodiment (FIGS. 11 and 12)
FIG. 11 is a longitudinal sectional view showing a third embodiment of the superconducting magnet apparatus according to the present invention. In the third embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description will be simplified or omitted.

  The superconducting magnet device 30 of the present embodiment is different from the superconducting magnet device 10 of the first embodiment in that it is outside the vacuum vessel 12 outside the superconducting coils 14A and 14B. This is the point where an iron yoke 31 as a magnetic body for capturing the leaking magnetic field 32 is installed. The iron yoke 31 is formed in a cylindrical shape and is disposed outside the vacuum vessel 12. In addition to the iron yoke 31 made of iron, the magnetic body may be a cylindrical yoke made of cobalt or nickel.

  Therefore, according to this embodiment, in addition to the same effects (1) to (7) as in the first embodiment, the following effect (9) is achieved.

  (9) Since the iron yoke 31 is installed outside the vacuum vessel 12 outside the superconducting coils 14A and 14B and the leakage magnetic field 32 leaking outside the vacuum vessel 12 is captured, the outside of the superconducting magnet device 30 The leakage magnetic field 32 can be reduced.

  Instead of installing the iron yoke 31 outside the vacuum vessel 12, a part of the vacuum vessel 12 may be made of a magnetic material.

[D] Fourth embodiment (FIGS. 13 and 14)
FIG. 13 is a longitudinal sectional view showing a fourth embodiment of the superconducting magnet apparatus according to the present invention. In the third embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description will be simplified or omitted.

  The superconducting magnet device 40 of the present embodiment differs from the superconducting magnet device 10 of the first embodiment in that a cancel coil 41 is disposed outside the superconducting coils 14A and 14B in the refrigerant container 13. . The cancel coil 41 generates a magnetic field 42 that cancels out the leakage magnetic field 43 that leaks to the outside of the vacuum vessel 12 that is outside the superconducting coils 14A and 14B, and reduces the leakage magnetic field 43.

  Therefore, according to the present embodiment, in addition to the same effects (1) to (7) as in the first embodiment, the following effect (10) is achieved.

  (10) The cancel coil 41 is disposed outside the vacuum vessel 12 that is outside the superconducting coils 14A and 14B. The magnetic field 42 generated by the cancel coil 41 cancels out the leakage magnetic field 43 that leaks outside the vacuum vessel 12. Therefore, the leakage magnetic field 43 to the outside of the superconducting magnet device 40 can be reduced. In particular, the weight of the superconducting magnet device 40 can be reduced as compared with the case of the superconducting magnet device 30 including the iron yoke 31.

  As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to this.

  For example, also in the second to fourth embodiments, as in the first embodiment, each of the superconducting coils 14A and 14B includes a plurality of superconducting coils 19 arranged on the same axis and having different diameters. 20 or the like, and may be constituted by superconducting coils 21 and 22 or the like. Furthermore, the superconducting coils 14A and 14B are not limited to a circular shape, and may be formed in an elliptical shape, a race track shape, or a rectangular shape.

The perspective view which shows 1st Embodiment of the superconducting magnet apparatus which concerns on this invention. Sectional drawing which follows the II-II line | wire of FIG. Sectional drawing which follows the III-III line of FIG. (A) is IV arrow sectional drawing of the superconducting coil which makes the pair in FIG. 1, (B) is explanatory drawing explaining the direction of the magnetic field which the coil produces | generates. The magnetic field distribution figure which shows distribution of the magnetic field in the horizontal surface in the position where the superconducting coil which makes the pair of FIGS. The graph which shows the relationship between the crossing angle of the superconducting coil which makes a pair in FIGS. 1-4, the space surrounded by these superconducting coils, and the horizontal magnetic field generated by a superconducting coil. It is another 1st aspect of the superconducting coil which comprises the pair of FIGS. 1-4, (A) is a perspective view, (B) is VII arrow sectional drawing of FIG. 7 (A). The perspective view which shows the other 2nd aspect of the superconducting coil which makes the pair of FIGS. 1-4. The perspective view which shows the other 3rd aspect of the superconducting coil which makes the pair of FIGS. 1-4. The longitudinal cross-sectional view which shows 2nd Embodiment of the superconducting magnet apparatus which concerns on this invention. The longitudinal cross-sectional view which shows 3rd Embodiment of the superconducting magnet apparatus which concerns on this invention. Sectional drawing which follows the XII-XII line | wire of FIG. The longitudinal cross-sectional view which shows 4th Embodiment of the superconducting magnet apparatus which concerns on this invention. Sectional drawing which follows the XIV-XIV line | wire of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Superconducting magnet apparatus 11 Single crystal pulling apparatus 14A, 14B Superconducting coil 15 Equatorial plane 16 Bore 17 Spaces 19, 20, 21, 22 Superconducting coil 25 Superconducting magnet apparatus 26 Refrigerator 30 Superconducting magnet apparatus 31 Iron yoke (magnetic material)
32 Leakage magnetic field 40 Superconducting magnet device 41 Cancel coil 42 Magnetic field 43 Leakage magnetic field B Horizontal magnetic field B1, B2 Magnetic field R Refrigerant θ Crossing angle

Claims (2)

In a superconducting magnet device composed of a plurality of superconducting coils,
Form at least two superconducting coils pair, superconducting coils constituting the pair, either to one of the other penetration inside, is configured by inclined arranged so that each of the equatorial plane intersecting Rutotomoni, respectively The generated magnetic fields are configured to strengthen each other in the horizontal direction and to weaken each other in the vertical direction .
Further, the superconducting coils forming a pair are formed with different areas surrounding each other, and each magnetomotive force is configured to be substantially the same as the strength of the magnetic field generated by each,
Furthermore, the superconducting coils that form a pair have a crossing angle set at a right angle, and a room temperature bore is provided in a space surrounded by these superconducting coils.
Further, each of the superconducting coils forming a pair is composed of a plurality of superconducting coils having different diameters arranged adjacent to or spaced apart from each other on the same axis . 2. The superconducting magnet device according to claim 1, wherein each of the superconducting coils forming a pair is formed in a circular shape, an elliptical shape, a rectangular shape, or a racetrack shape.

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