JP7029733B2 - A magnetic material used to raise the magnetic field application of a single crystal, and a method of raising the magnetic field application of a single crystal. - Google Patents

Description

The present disclosure relates to the technical field of semiconductors, for example, a magnetic material used for pulling up a magnetic field applied to a single crystal, and a method for pulling up a magnetic field applied to a single crystal.

Single crystal silicon is an important element in crystalline materials, a raw material for manufacturing semiconductor silicon devices, and is widely applied in the technical field of semiconductors such as large-scale integrated circuits, rectifiers, power transistors, diodes, and solar cell panels. ing.

Methods for producing single crystal silicon include a CZ method and an FZ method. Currently, single crystal silicon is usually produced using the CZ method, which uses a single crystal furnace to grow rod-shaped single crystal silicon from the melt. As a basic feature of the CZ method, the technology has matured, the crystal outer shape and electrical parameters are easy to control, and it is applied to the growth of large-diameter single crystal silicon. In recent years, with the development of very large scale integration circuits, higher demands have been placed on the dimensions and quality of single crystal silicon. However, as the crystal size increases and the thermal convection of the melt is strengthened, temperature fluctuations in the melt and local melting of the crystal occur, and the distribution of impurities such as carbon and oxygen in the crystal becomes uneven. Further, the quality of the single crystal silicon is deteriorated.

In order to solve the above problems, a technique for raising the magnetic field application of a single crystal is being developed. Based on the CZ method, a strong magnetic field is applied to the outside of the single crystal furnace, and the strong magnetic field has the ability to suppress the thermal convection of the melt. By applying a magnetic field with constant strength and uniformity to the growth system that pulls up single crystal silicon, heat convection in the silicon melt is effectively suppressed and the transport of impurities in the molten silicon is suppressed. be able to. An appropriately distributed magnetic field can reduce impurities such as oxygen, boron and aluminum from entering the melt from the quartz crucible and improve the quality of single crystal silicon.

The conventional MCZ (Magnetic field applied CZ) method magnetic field generator generally uses a permanent magnetic material and a normal electromagnet, and the MCZ method is limited to the saturation magnetization of the permanent magnetic material and the power of the normal electromagnet. Therefore, the generated magnetic field strength is often not high, and the effect of suppressing the thermal convection of the melt is general. With the development of superconducting magnetic material technology, more and more superconducting magnetic materials can replace ordinary electromagnets, and superconducting magnetic materials can generate a stronger magnetic field, and the effect of suppressing the thermal convection of the melt is more remarkable. Yes, it is possible to produce larger size or higher quality single crystal silicon for the corresponding crystal pulling process.

The magnetic field generated by the superconducting magnetic field in the MCZ method includes a cusp magnetic field, a transverse magnetic field, and a longitudinal magnetic field. Here, the longitudinal magnetic field was replaced with a cusp magnetic field and a transverse magnetic field because the inhibitory effect on the thermal convection of the melt was not remarkable.

Since the magnetic material is located outside the single crystal furnace, it is necessary to consider the problem of electromagnetic compatibility with the single crystal furnace, and the leakage magnetic field generated by the simple coil is generally large, and it is a general electronic device or It is not possible to meet the power supply usage requirements and human safety requirements. Therefore, the superconducting magnetic material reduces the leakage magnetic field by a passive shielding method that adds a yoke to the outside of the magnetic material, which causes the weight of the magnetic material to increase sharply, and in general, the weight of the yoke is the entire magnetic material. It reaches 50% or more of the above, and the manufacturing cost increases.

The present invention discloses a magnetic material used for increasing the magnetic field application of a single crystal, which can effectively reduce the leakage magnetic field and avoid an increase in the weight of the magnetic material, and a method for increasing the magnetic field application of the single crystal.

The present invention comprises a plurality of coils, the plurality of coils are connected in series and arranged so as to surround the outer periphery of the monocrystal furnace, and two of the plurality of coils are arranged facing each other. The coils are arranged symmetrically about the central axis of the single crystal furnace, and the central axis of each of the coils passes through the central point of the single crystal furnace, and each of the coils is a primary coil arranged coaxially. The secondary coil is arranged so as to be separated from the single crystal furnace with respect to the primary coil, and when the coil is energized, the current direction in the primary coil and the secondary coil are included. Provided is a magnetic material used for pulling up a magnetic field application of a single crystal opposite to the current direction in the coil.

Preferably, a predetermined distance is provided between the primary coil and the secondary coil.

Preferably, the central axis of each of the coils is orthogonal to the central axis of the single crystal furnace.

Preferably, the central axis of each of the coils forms a first angle with the central axis of the single crystal furnace.

Preferably, of the plurality of coils, the angle between the central axes of each of the two adjacent coils is the same.

Preferably, among the plurality of coils, an angle is formed between the central axes of each of the two adjacent coils, the adjacent angles are different, and the opposing angles are the same.

Preferably, the number of the plurality of coils is four, two of the four coils are arranged on the first side of the single crystal furnace, and the other two coils of the four coils are located. Is arranged to face the second side of the single crystal furnace.

Preferably, the angle between the central axes of two adjacent coils on the first side of the single crystal furnace of the four coils and the second side of the single crystal furnace of the four coils. The angle between the central axes of two adjacent coils is a predetermined angle.

Preferably, the predetermined angle range is 50 ° to 70 °.

Preferably, the plurality of coils are superconducting coils.

Preferably, the magnetic material further comprises a cryogenic vessel disposed around the single crystal furnace.

Preferably, the cryogenic container is filled with the cryogenic liquid, and the plurality of coils are placed in the cryogenic liquid.

Preferably, the plurality of coils are connected in series in order, of which the primary coils of the plurality of coils are connected in series in order, and the secondary coils of the plurality of coils are connected in series in order and connected in series. The primary coil and the secondary coil are connected in series to form two ports, a positive electrode and a negative electrode.

Preferably, the plurality of coils are connected in series in order, and among the plurality of coils, the adjacent primary coil and secondary coil are connected in series, and then connected in series as a whole, and the positive electrode is used. And two ports of the negative electrode are formed.

Preferably, the cryogenic vessel is provided with a pair of binary current leads, a first current lead and a second current lead, respectively.

The room temperature end of the first current lead is connected to the positive electrode of the power supply, and the superconducting end of the first current lead is connected to the positive electrode port to which the plurality of coils are connected in series.

The room temperature end of the second current lead is connected to the negative electrode of the power supply, and the superconducting end of the second current lead is connected to the negative electrode port to which the plurality of coils are connected in series.

Preferably, the superconducting end of the first current lead is connected to a positive electrode port in which the plurality of coils are connected in series.
The first current lead includes a first copper wire end and a first superconducting end connected to the first copper wire end, the first superconducting end extending into the cold liquid and the plurality of coils. Includes being connected to a positive electrode port connected in series.

Preferably, the superconducting end of the second current lead is connected to a negative electrode port in which the plurality of coils are connected in series.
The second current lead includes a second copper wire end and a second superconducting end connected to the second copper wire end, the second superconducting end extending into the cold liquid and the plurality of coils. Includes being connected to a negative electrode port connected in series.

Preferably, the refrigerator is arranged in the low temperature container, and the refrigerator is provided with one stage of cold heads and two stages of cold heads sequentially arranged from top to bottom.
The cold head one stage is configured to cool the first current lead and the second current lead, and the cold head two stages are configured to condense the cold liquid in the cold container.

The present invention
By arranging the magnetic material outside the single crystal furnace and energizing the magnetic material,
In the single crystal furnace, a heater for heating the crucible on which the ingot is placed is placed, and
Acquiring single crystal silicon by the CZ method, including
Further provided is a method for raising the magnetic field application of a single crystal.

In the present invention, the coil is divided into a primary coil and a secondary coil, and the magnetic field generated by the secondary coil is generated outside the primary coil by passing currents in opposite directions to the primary coil and the secondary coil, respectively. The magnetic field can be effectively canceled, and the leakage magnetic field of the magnetic material is reduced by the spontaneous shielding method. Moreover, the weight of the magnetic material is reduced, and the manufacturing cost of the magnetic material is saved.

It is a structural schematic diagram of the distribution of the magnetic material and the single crystal furnace which concerns on embodiment of this invention. It is sectional drawing of the magnetic material and the single crystal furnace which concerns on embodiment of this invention. It is a structural schematic diagram of the outside of the magnetic material and the single crystal furnace which concerns on embodiment of this invention. It is a comparison diagram of the electric field strength generated by the magnetic material which concerns on embodiment of this invention, and the electric field strength generated by another form.

10 Single crystal furnace 20 Heater 30 Rutsubo 1 Coil 11 Primary coil 12 Secondary coil 2 Low temperature container 21 1st current lead 22 2nd current lead 23 Relief valve 25 Signal line interface 26 Vacuum valve 24 Refrigerator 241 Cold head 1 stage 242 Cold head 2 steps

The present embodiment provides a magnetic material used for raising the magnetic field application of a single crystal, and as shown in FIGS. 1 and 2, the magnetic material used for raising the magnetic field application of the single crystal includes a plurality of coils 1. The plurality of coils 1 are connected in series in order and arranged so as to surround the outer periphery of the single crystal furnace 10, and among the plurality of coils 1, the two coils 1 arranged opposite to each other are single crystals. The primary coils 11 and 2 are arranged symmetrically about the central axis of the furnace 10 and the central axis of each coil 1 passes through the central point of the single crystal furnace 10, and the coils 1 are coaxially arranged. The secondary coil 12 includes the secondary coil 12, and the secondary coil 12 is arranged so as to be separated from the single crystal furnace 10 with respect to the primary coil 11, and when the coil 1 is energized, the current direction in the primary coil 11 is set. The direction of the current in the secondary coil 12 is opposite to that of the current direction.

In this embodiment, the magnetic field generated by the secondary coil 12 by dividing the coil 1 into the primary coil 11 and the secondary coil 12 and passing a current in the opposite direction through the primary coil 11 and the secondary coil 12 is 1. The next coil 11 can effectively cancel the magnetic field generated outside, and the spontaneous shielding method reduces the leakage magnetic field of the magnetic material, reduces the weight of the magnetic material, saves the manufacturing cost of the magnetic material, and the coil. When a passive shielding method in which a ferromagnetic material is added to the outside of the magnetic material is used, the leakage magnetic field is reduced and the weight of the magnetic material is prevented from increasing.

In one embodiment, a predetermined distance is provided between the primary coil 11 and the secondary coil 12. In this embodiment, by arranging the secondary coil 12 outside the primary coil 11, the effect of the primary coil 11 of the secondary coil 12 canceling the leakage magnetic field generated outside can be improved. Further, in this embodiment, the predetermined distance is not limited, and in the actual production process, the secondary coil 12 can cancel the external magnetic field generated from the primary coil 11, and the leakage magnetic field of the magnetic material is reduced. May be manufactured as needed to ensure that.

In one embodiment, the central axis of each coil 1 is orthogonal to the central axis of the single crystal furnace 10. In one embodiment, the central axis of each coil 1 forms a first angle with the central axis of the single crystal furnace 10. Of the plurality of coils 1, the two coils arranged to face each other are arranged symmetrically with respect to the central axis of the single crystal furnace 10, and an angle is provided between the central axes of the adjacent coils 1. Therefore, each coil 1 forms a transverse magnetic field in the single crystal furnace 10 to ensure that high quality crystals can be produced by the single crystal furnace 10. In one embodiment, the primary coil 11 provides the main magnetic field required for the CZ crystal, and the secondary coil 12 is a spontaneous shielding coil that carries a current in the opposite direction to the primary coil 11 to reduce the leakage magnetic field. The magnetic field generated with the primary coil 11 supplies a transverse magnetic field for pulling up the single crystal.

In one embodiment, the number of coils 1 is four, of which the four coils 1 include two pairs of correspondingly arranged coils 1 and two of the four coils 1 are , The other two coils 1 of the four coils 1 are arranged on the first side of the single crystal furnace 10 and face the second side of the single crystal furnace 10. The angle between the central axes of two adjacent coils 1 on the first side of the single crystal furnace 10 of the four coils 1 and the second side of the single crystal furnace 10 of the four coils 1. The angle between the central axes of the two adjacent coils 1 in the above is a predetermined angle, and in one embodiment, the range of the predetermined angle is 50 ° to 70 °.

In this embodiment, the transverse magnetic field generated by both the primary coil 11 and the secondary coil 12 has a constant strength and uniformity without limiting the predetermined angle, and the production of crystals in the single crystal furnace 10 is performed. It may be adjusted as needed to ensure that the quality is improved.

As shown in FIGS. 2 and 3, the magnetic material according to the present embodiment further includes a low temperature container 2 arranged around the single crystal furnace 10, and the coil 1 is arranged in the low temperature container 2. Here, the low-temperature liquid is filled in the low-temperature container 2, and the coil 1 is placed in the low-temperature liquid. In one embodiment, a vacuum intermediate layer is arranged in the low temperature container 2, a vacuum valve 26 is further arranged in the low temperature container 2, and the vacuum valve 26 can secure an external vacuum environment for the low temperature liquid and provide a heat insulating effect. As expected, the low temperature liquid is in a zero consumption state. In one embodiment, the cold liquid is liquid helium and the vacuum layer is liquid helium duel. In one embodiment, the coil may be cooled by a low temperature liquid and directly cooled by a refrigerator, or the cold liquid and the vacuum intermediate layer may be of other types. Not limited.

The low temperature container 2 is provided with a first current lead 21 and a second current lead 22 connected to a power source. Here, the first current lead 21 and the second current lead 22 are both binary current leads, and the first pull current lead 21 and the second current lead 22 are both a copper wire end and a copper wire. Including a superconducting end connected to the end, the superconducting end extends into the cold liquid and is connected to the coil 1. The first current lead 21 and the second current lead 22 are connected to the coil 1 and the power supply, respectively, to form a closed loop, and supply a magnetic field current from the power supply to the coil 1.

Further, since the relief valve 23 is further arranged in the low temperature container 2 and the storage capacity of the coil 1 is large, when the coil 1 unintentionally loses superconductivity, a large amount of heat is released and a large amount of liquid helium is evaporated. A large atmospheric pressure is generated, and in the worst case, the magnetic material may be damaged and damage to a person. At this time, in order to ensure the safety of the magnetic material, the pressure is released by the relief valve 23.

In this embodiment, by using each of the primary coil 11 and the secondary coil 12 as a superconducting coil, a superconducting state is obtained at an ultra-low temperature environment temperature, a higher current can be loaded than a normal coil, and a higher magnetic field is generated. , Ensuring the quality of single crystal silicon during manufacturing.

The refrigerator 24 is further arranged in the low temperature container 2, and the refrigerator 24 is provided with a cold head 1-stage 241 and a cold head 2-stage 242 sequentially arranged from top to bottom, where the cold head 1-stage 241 is provided. , The first current lead 21, the second current lead 22, and the radiation prevention panel (not shown) are arranged to cool, and the cold head two-stage 242 is arranged to condense the low temperature liquid in the low temperature container 2. Will be done.

A signal line interface 25 is further arranged in the low temperature container 2, and the signal line is used to access the inside of the low temperature container 2 via the signal line interface 25 and detect signals such as the temperature and voltage drop of the coil 1. To.

As shown in FIG. 4, a comparison diagram of the leakage magnetic field in the three cases of unshielded, ferromagnetic material shield, and spontaneous shielding is shown. Here, the horizontal axis represents the distance from the test point to the central magnetic field. Generally, when located at 1.6 to 1.8 meters, the strength of the magnetic field is required to be less than 500 gauss (GS). The requirement for human safety is that the magnetic field strength within 3 meters in the radial direction is less than 60 gauss (GS). As shown in FIG. 4, by using the spontaneous shielding method of this embodiment, the leakage magnetic field can be effectively reduced and the requirements for human safety can be satisfied.

The present embodiment further provides a method for raising the magnetic field application of a single crystal including the following steps.

In step 1, the magnetic material is arranged outside the single crystal furnace 10 and the magnetic material is energized.

Here, energizing the magnetic material includes energizing the coil 1, the refrigerator 24, and the like. When the coil 1 in the magnetic body is energized, a current flows in the reverse direction in the primary coil 11 and the secondary coil 12, and the magnetic field generated by the secondary coil 12 is effective due to the magnetic field generated externally by the primary coil 11. It can be canceled out and the leakage magnetic field of the magnetic material becomes small. Further, by using a passive shielding method in which a ferromagnetic material is added to the outside of the coil 1, the leakage magnetic field is reduced, the weight of the magnetic material is prevented from increasing, and the manufacturing cost of the magnetic material is saved.

In step 2, a heater 20 for heating the crucible 30 on which the ingot is placed is arranged in the single crystal furnace 10. The ingot is heated to bring it into a molten state, and the transverse magnetic field generated by the coil 1 acts on the molten material. Due to the action of the magnetic field, the conductive molten body generates an eddy current when flowing and receives Lorentz force. .. The action of Lorentz force suppresses thermal convection of the melt and suppresses oxygen, point defects, and other impurities on the liquid surface of the melt.

In step 3, single crystal silicon is obtained by the CZ method. Here, since the transverse magnetic field generated by the coil 1 has high magnetic field uniformity (about 3 ‰ to 1%) in the region from the liquid surface of the melt to about 50 mm (mm) below the liquid level, the melt. The single crystal silicon produced has high purity, the distribution of trace impurities becomes more uniform, and the quality of the single crystal silicon is improved.

Here, in the CZ method, after the melt is heated to a molten state, one seed crystal etched by a chemical method is dropped and brought into contact with the melt, and the single crystal furnace 10 is rotated to keep the melt constant. It is to continue to crystallize with a seed crystal and grow until it becomes a crystal with the diameter of.

Claims (4)

A plurality of coils (1) are provided, and the plurality of coils (1) are connected in series and arranged so as to surround the outer periphery of the single crystal furnace (10). Two coils (1) arranged to face each other are arranged symmetrically about the central axis of the single crystal furnace (10), and the central axis of each coil (1) is the single crystal furnace (10). Each said coil (1) includes a primary coil (11) and a secondary coil (12) arranged coaxially, and the secondary coil (12) is said to be the primary coil (12). 11) with respect to the single crystal furnace (10)
Arranged away from
When the coil (1) is energized, the current direction in the primary coil (11) and the current direction in the secondary coil (12) are opposite to each other.
A cryogenic vessel (2) arranged around the single crystal furnace (10) is further provided.
The room temperature end of the first current lead (21) is connected to the positive electrode of the power supply, and the first current lead (21) is connected to the positive electrode of the power supply.
) Is connected to the positive electrode port of the coil.
The room temperature end of the second current lead (22) is connected to the negative electrode of the power supply, and the second current lead (22)
22) further comprises connecting the superconducting end of the coil to the negative electrode port of the coil.
Two refrigerators (24) facing each other are arranged in the low temperature container (2), and each refrigerator (2) is arranged.
In 4), one cold head stage (241) and two cold head stages (242) arranged sequentially from top to bottom are provided, respectively.
The cold head one stage (241) is configured to cool the first current lead (21) and the second current lead (22).
The cold head two-stage (242) is configured to condense the low-temperature liquid in the low-temperature container (2).
The secondary coil (12) is arranged outside the primary coil (11).
A predetermined distance is provided between the primary coil (11) and the secondary coil (12).
The central axis of each coil (1) forms a first angle with the central axis of the single crystal furnace (10).
Of the plurality of coils (1), between the central axes of two adjacent coils (1), respectively.
The angles are formed and the adjacent angles are different, and the opposing angles are the same.
The number of the plurality of coils (1) is four, and two of the four coils (1) are used.
Il (1) is arranged on the first side of the single crystal furnace (10), and of the four coils (1).
The other two coils (1) are arranged to face the second side of the single crystal furnace (10).
Two adjacent coils on the first side of the single crystal furnace (10) out of the four coils (1).
The angle between the central axes of the coil (1) and the single crystal furnace (of the four coils (1)).
The angle between the central axes of two adjacent coils (1) on the second side of 10) is predetermined.
Is an angle
The range of the predetermined angle is 50 ° to 70 °.
The plurality of coils (1) are superconducting coils.
The low-temperature liquid is filled in the low-temperature container (2), and the plurality of coils (1) form the low-temperature liquid.
Placed inside
The superconducting end of the first current lead (21) may be connected to the positive electrode port of the coil.
,
The first current lead (21) has a first copper wire end and a first superconductivity connected to the first copper wire end.
The first superconducting end extends into the cold liquid and contacts the positive electrode port of the coil, including the end.
Including being continued
The superconducting end of the second current lead (22) may be connected to the negative electrode port of the coil.
,
The second current lead (22) has a second copper wire end and a second superconductivity connected to the second copper wire end.
The second superconducting end extends into the cold liquid and contacts the negative electrode port of the coil, including the end.
Including being continued,
A magnetic material used to raise the magnetic field application of a single crystal. The central axis of each coil (1) is orthogonal to the central axis of the single crystal furnace (10).
The magnetic material according to claim 1 . Of the plurality of coils (1), the angle between the central axes of each of the two adjacent coils (1) is the same.
The magnetic material according to any one of claims 1 and 2 . The magnetic material according to any one of claims 1 to 3 is arranged outside the single crystal furnace (10).
Energizing the magnetic material and
In the single crystal furnace (10), a heater (20) for heating the crucible (30) on which the ingot is placed is arranged.
Acquiring single crystal silicon by the CZ method, including
A method of pulling up a single crystal by applying a magnetic field.

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