JP2818271B2 - Magnetic field application lifting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention has a plurality of units arranged side by side, each of which has a crucible rotation speed, a crystal pulling speed and a rotation speed according to a pulling control set value. And an electromagnet that applies a magnetic field for suppressing convection to the melt in the crucible, controls the current of the electromagnet according to the magnetic flux density set value, and operates the electromagnet according to the moving speed set value. The present invention relates to a magnetic field application pulling device that moves between operation preparation positions.

(Prior art) Conventionally, the pull-up method (Czochralski
method) has been widely adopted.

In this method, thermal convection of the single crystal silicon melt in the crucible occurs, and at this time a large amount of oxygen melts out of the quartz crucible and mixes into the single crystal, so that it is difficult to control the oxygen concentration, and the oxygen concentration becomes uneven. It was easy to become.

In addition, dislocations, stacking faults, deposition of impurities, and the like occur in portions where the oxygen concentration is locally increased due to thermal convection of the single crystal silicon melt, which deteriorates electrical characteristics and causes product defects. I was

Furthermore, the temperature in the silicon melt greatly fluctuates due to the thermal convection of the single crystal silicon melt, making it difficult to pull up the crystal stably.

For this reason, a magnetic field application pull-up method (Magnetic Field Czochralski method) that prevents convection of the silicon melt has recently been developed.

This method pulls a single crystal while applying a strong static magnetic field from the side of the quartz crucible. According to this method, the convection of the silicon melt in the crucible is suppressed by magnetic force, so that the oxygen concentration is uniform. A crystal with few defects can be obtained, and transient fluctuation of the silicon melt can be suppressed to be small.

Generally, in the production of a silicon single crystal using such a magnetic field application pulling apparatus, many pulling apparatuses are often arranged side by side from the viewpoint of productivity, space, mass production effect, and the like. It is affected by the leakage flux of the electromagnet of the lifting device.

In this case, if the density of the leakage magnetic flux is large, the ITV for diameter detection for automatic diameter control is affected by the leakage magnetic flux, and further, other control devices are similarly affected by the leakage magnetic flux. Automatic pull-up control cannot be performed normally.

For this reason, the dimensions between the magnetic field application pulling devices were sufficiently ensured and the magnetic field shielding plate was provided between the crystal pulling devices so as not to be affected by the leakage magnetic flux. Was difficult in practice.

Therefore, in general, dimensions and intervals are provided or a shielding plate is provided so that operation can be performed without any problem even when the minimum magnetic flux density in operation and the leakage magnetic flux density from the other party is maximized. This was used as a guideline when installing a large number of magnetic field application pulling devices.

However, even if the installation interval or the specifications of the shielding plate are determined based on these guidelines, the production of a single crystal is a series of cyclic operations of loading, melting, and pulling the material into the crucible. It is necessary to move the electromagnet at the time of replacement or loading of the material, and thus it is necessary to consider the fluctuation of the magnetic field.

FIG. 3 is a schematic configuration diagram of a conventional magnetic field application pulling apparatus of this kind. In the figure, of the two magnetic field application pulling devices arranged in parallel, the A side is in the process of pulling a single crystal, and a quartz crucible is used.
The silicon melt 2A in 1A is gradually pulled up while being heated by the heater 3A to produce a silicon single crystal 4A.

For the silicon melt 2A in the quartz crucible 1A,
A magnetic field is applied from outside the heater 3A by the electromagnet 5A.

In the magnetic field application pulling device on the B side, the electromagnet 5B is lowered for replacement of the quartz crucible 1B or for loading of the silicon material. The silicon single crystal 4B is manufactured by moving it up to the position by the driving device 6B in the same state as the magnetic field application pulling device on the A side.

These driving devices 6A, 6B are attached to the electromagnets 5A, 5B, respectively, and the operator presses the up push buttons 7A, 7B or the down push buttons 8A, 8B according to the respective operating conditions.
, The drive devices 6A and 6B are controlled via the drive power supply devices 9A and 9B, and the magnetic field applying electromagnets 5A and 5B are raised and lowered.

Here, when the B side raises the electromagnet 5B while the A side is in the process of applying the magnetic field, when the B side raises the electromagnet 5B, the change of the magnetic flux density in the A side quartz crucible 1A due to the leakage magnetic flux of the electromagnet 5B and the state of the pulling control are described. It is shown in FIG.

That is, the magnetic flux density in the quartz crucible 1A on the A side
constant magnetic flux density only by approximately the A-side electromagnet 5A to t ₁ G ₁
Is held. In this state, on the A side, both the pulling speed control and the diameter control are performed normally, and the single crystal is also pulled up normally.

However, increasing the electromagnet 5B of a B-side operation preliminary position at time t _1, the influence of the leakage flux G _2,
The magnetic flux density in the quartz crucible 1A of the A-side is rapidly increased from G _1, the magnetic flux density at time t ₂ when the B-side of the electromagnet 5B reaches the operating position is G ₁ + G _2.

As described above, while the magnetic flux density in the quartz crucible 1A on the A side is changed by the movement of the electromagnet 5B on the B side, the pull-up control and the diameter control on the A side are performed as shown by curves a and b in FIG. In addition, a large hunting becomes impossible and a normal pulling up is impossible.
This is probably because the flow characteristics of the melt change due to the change in the magnetic flux density in the quartz crucible.

Even if pulling is possible, the transition is likely to occur due to the partial accumulation of impurities and the increase in oxygen concentration due to the change in the flow characteristics of the melt, which lowers the product value by deteriorating the electrical characteristics. .

In order to prevent this, conventionally, the spacing between the crystal pulling devices has been sufficiently widened, and a rigid shielding plate for reducing the leakage magnetic flux has been provided.

(Problems to be Solved by the Invention) If only a few magnetic field application pulling devices are installed, the method of increasing the mutual interval or installing a solid shielding plate as described above is certainly. It is valid. However, when a large number of pulling devices are juxtaposed in order to increase productivity, there is a problem that these methods cannot be adopted and high-quality single crystals cannot be produced.

The present invention has been made in order to solve the above-described problems.
It is an object of the present invention to obtain a magnetic field application pulling apparatus capable of producing a high quality single crystal.

[Configuration of the invention]

(Means for Solving the Problems) The present invention relates to a position storage means for storing a position where an electromagnet of a latest lifting device moves in a magnetic field in its own crucible and storing the position, and the latest lifting device. Leakage magnetic flux density calculating means for calculating the leakage magnetic flux density penetrating into its own crucible based on the magnetic flux density set value of the position storage means and the data stored in the position storage means, and the calculated leakage magnetic flux density and the nearest lifting device A magnetic flux density change rate calculating means for calculating the change rate of the magnetic flux density of the own crucible based on the moving speed set value of the crucible; and a magnetic flux density change rate calculated based on the calculated magnetic flux density change rate. And a pull-up control correction value calculating means for correcting its own pull-up control set value so as to suppress a change in the crystal pull-up state.

(Operation) In the present invention, the change of the magnetic field in its own crucible due to the movement of the electromagnet of the other pulling device closest to the storage device is stored, and the stored data and the magnetic flux density set value of the other crystal pulling device are stored. Calculate the leakage magnetic flux density that penetrates into the own crucible, and further calculates the rate of change of the magnetic flux density of the own crucible based on the leakage magnetic flux density and the moving speed set value of another crystal pulling apparatus. Calculate, and based on this magnetic flux density change rate, correct its own pulling control set value so as to suppress the change in the crystal pulling state caused by the change in leakage magnetic flux density. It is less susceptible to magnetic flux, which allows high quality single crystals to be produced.

(Embodiment) FIG. 1 is a schematic configuration diagram of an embodiment of the present invention. Here, for the sake of simplicity, two magnetic field applying and pulling-up devices which are closest and mutually affected will be exemplified.

In the figure, two magnetic field applying and pulling devices on the A side and the B side respectively include silicon melts 2A and 2A in quartz crucibles 1A and 1B, respectively.
While heating 2B with heaters 3A and 3B, silicon single crystals 4A and 4B are manufactured. The electromagnets 5A and 5B apply a static magnetic field to the silicon melts 2A and 2B in the quartz crucibles 1A and 1B from outside the heaters 3A and 3B, and pull up the silicon single crystals 4A and 4B in that state. Electromagnet 5A,
5B is a driving device 6A, 6B connected to a driving power supply device 9A, 9B accompanying the up push button 7A, 7B and the down push button 8A, 8B.
The ascending and descending are controlled. In addition, electromagnets 5A, 5B
The drive current is controlled by the drive power supply devices 9A and 9B, and a magnetic field having a magnetic flux density proportional to the current is applied to the silicon melts 2A and 2B in the quartz crucibles 1A and 1B.

In this case, both the A-side and B-side magnetic field application pulling devices have the minimum operational magnetic flux density, and can operate even when the leakage magnetic flux density from the other party is the maximum.
Check if the installation interval is left or if a shielding plate is installed.

On the other hand, the two magnetic field application pulling devices on the A side and the B side are:
The magnetic flux density setting units 13A and 13B that set the operation magnetic flux density and give the drive power supply devices 9A and 9B, and the position where the other electromagnets 5A and 5B move between the operation preparation position and the operation position are set to their own quartz crucibles. 1A, a position state storage unit 14A, 14B which is stored by converting into a leakage magnetic flux density in 1B, and further, the set values of the other magnetic flux density setters 13B, 13A, the position state storage unit
Based on the stored data of 14A and 14B, own quartz crucible 1A,
Leakage magnetic flux density calculator 15A, which calculates the magnetic flux density in 1B,
15B.

The two magnetic field application pulling devices on the A side and the B side are:
A moving speed setting device 16 for setting the set values of its own magnetic flux density setting devices 13A and 13B and the moving speed of the other electromagnets 5B and 5A.
Magnetic flux density change rate calculators 17A and 17B that calculate the magnetic flux density change rates in their own quartz crucibles 1A and 1B based on the set values of B and 16A.
It has.

Furthermore, the two magnetic field applying and pulling devices on the A side and the B side are based on the outputs of the magnetic flux density change rate calculating units 17A and 18B.
Includes pull-up control correction value calculation units 18A and 18B for calculating correction values of pull-up control set values such as the crucible rotation speed, crystal pull-up speed, and rotation speed, and outputs the correction values to pull-up control units 20A and 20B. In addition to The lifting control units 20A and 20B are based on the set values of the lifting control setting units 19A and 19B, respectively.
The single crystal rotating devices 11A and 11B and the crucible rotating devices 12A and 12B are controlled, and the pull-up control correction value calculation units 18A and 18B correct the set values.

The operation of the present embodiment configured as described above will be described below.

The magnetic field applying and pulling device on the A side raises the electromagnet 5A to the operating position and is applying the magnetic field, and the magnetic field applying and pulling device on the B side lowers the electromagnet 5B to the position shown by the solid line, that is, the operation preparation position. Let's say you were ready for operation.

Here, when the filling of the quartz crucible 1B and the silicon melt 2B of the magnetic field application pulling apparatus on the B side is completed and the actual operation starts,
The electromagnet 5B is raised to the position indicated by the broken line by the operation of the raising push button 7B by the operator.

On the other hand, the silicon single crystal 4A on the A side in the operating state is pulled up at a low speed while being rotated by the pulling and lowering device 10A and the single crystal rotating device 11A. At this time, the crucible rotating device 12
By A, the quartz crucible 1A is rotated at a low speed in the opposite direction to the silicon single crystal 4A.

Then, when the electromagnets 5A and 5B on the B side are raised to the positions indicated by the broken lines, the leakage magnetic flux density calculator 15A inputs the magnetic flux density set value of the magnetic flux density setter 13B and the storage data of the position state storage unit 14A, The leakage magnetic flux density of the quartz crucible 1A by the electromagnet 5B of the magnetic field applying and pulling apparatus on the B side is calculated. At this time, the moving speed of the electromagnet 5B on the B side is set by the moving speed setting unit 16B, and the magnetic flux density change rate calculation unit 17A calculates the moving speed set value, the set value of the magnetic flux density set unit 13A, and the leakage magnetic flux. The change rate of the magnetic flux density of the A-side quartz crucible 1A is calculated based on the output of the density calculator 15A. Lift control correction value calculator 18
A is a single crystal pulling speed, a single crystal rotation speed, which is set in advance by the pulling control setting unit 19A in accordance with the rate of change of the magnetic flux density.
A so-called correction value of a pull-up control set value such as a rotation speed of the quartz crucible 1A is calculated. The pull-up control unit 20A adds the set value of the pull-up control setting unit 19A and the correction value of the pull-up control correction value calculation unit 18A, and according to the result, raises and lowers the device 10A, the single crystal rotating device 11A, and the crucible. The rotation device 12A is controlled.

 FIG. 2 is an explanatory diagram showing these relationships.

That is, when the electromagnet 5B is raised from the operation preparation position to the operation position to enter the operation operation, the current flowing through the electromagnet 5B is constant, and thus the magnetic flux generated by the electromagnet 5B is always constant.

Now, at time t ₁ the operator pressed the rise pushbutton 7B, the electromagnet 5B increases according to the set value of the moving speed setter 16B, and reaches the operating position at time t _2. At this time,
The magnetic flux density of the quartz crucible 1A unit is held in G ₁ to time t _1,
Is held in the rapidly increased time t ₂ after the time _{t 1 (G 1 + G 2} ).

Thus, between times t ₁ ~t ₂ where the magnetic flux density of the quartz crucible 1A is changed from G ₁ to (G ₁ + G _2), pulling the control correction value calculation unit 18A is single crystal pulling speed, single crystal Since the rotation speed and the crucible rotation speed correction values are calculated and added to the pull-up controller 20A, the pull-up speed of the single crystal is changed from N ₁ to N ₁ ′ [cm / h].
Single crystal rotational speed of the N ₂ [rpm] from N _2, the crucible rotation speed is reduced respectively from N ₃ to N ₃ [rpm], suppress the flow changes in the melt in the crucible due to the increase in A-side side flux density Is performed.

Although the time t ₂ after the magnetic flux density in the quartz crucible 1A is constant, pulling rate of the single crystal, the rotational speed of the rotational speed and the crucible of the single crystal is restored almost to the original by Ke wrote the same time state I'm sullen.

Thus, according to this embodiment, when the generated magnetic flux density and the moving speed of the electromagnet are set, the pull-up control set value is corrected so as to suppress the change in the flow of the melt in the crucible.
It is possible to produce a silicon single crystal having a high space factor, excellent versatility, and good quality of products.

In the above embodiment, two magnetic field applying and pulling devices are exemplified. However, the present invention is not limited to this, and three or more magnetic field applying and pulling devices can be applied to the magnetic field applying and pulling device. Needless to say.

In the above embodiment, the description has been given of the pulling of a silicon single crystal. However, the present invention can be applied to pulling of a single crystal of another metal.

Further, in the above embodiment, the configuration in which the electromagnet is retracted below the operating position has been described, but it is apparent that the present invention can be applied to a configuration in which the electromagnet is moved in the horizontal direction.

〔The invention's effect〕

As apparent from the above description, according to the present invention,
In accordance with the change in the magnetic field in its own crucible due to the movement of the electromagnet of the other pulling device closest to it, its own pulling control set value is corrected so as to suppress the change in the crystal pulling state,
Even if a large number of units are juxtaposed, they are hardly affected by the leakage magnetic flux, so that a high-quality single crystal can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of one embodiment of the present invention, FIG. 2 is a time chart for explaining the operation of the embodiment, and FIGS. 3 (a) and (b) are conventional magnetic fields arranged side by side. FIG. 4 is a schematic configuration diagram of an application pulling-up device, and FIG. 4 is a time chart for explaining the operation of the device. 1A, 1B ... quartz crucible, 2A, 2B ... silicon melt, 3A, 3B
... heater, 4A, 4B ... silicon single crystal, 5A, 5B ... electromagnet, 6A, 6B ... drive device, 9A, 9B ... drive power supply device, 10A,
10B …… Elevator, 11A, 11B …… Single crystal rotating device, 12
A, 12B ... crucible rotating device, 13A, 13B ... magnetic flux density setting unit, 14A, 14B ... position state storage unit, 15A, 15B ... leakage magnetic flux density calculating unit, 16A, 16B ... moving speed setting unit, 17A, 17B ……
Magnetic flux density change rate calculation unit, 18A, 18B ... pull-up control correction value calculation unit, 19A, 19B ... pull-up control setting unit, 20A, 20B ... pull-up control unit.

Claims (1)

(57) [Claims] 1. A crucible according to claim 1, wherein a plurality of crucibles are arranged in parallel, each controlling a crucible rotation speed, a crystal pulling speed and a rotation speed according to a pulling control set value, and applying a convection suppressing magnetic field to the melt in the crucible. In a magnetic field application pulling apparatus that has an electromagnet to be applied, controls the current of the electromagnet in accordance with a set value of magnetic flux density, and moves the electromagnet between an operation position and an operation preparation position according to a moving speed set value, The position of the electromagnet of the upper device to which the electromagnet moves is converted into a magnetic field in its own crucible and stored, and the magnetic flux density set value of the nearest lifting device and the storage data of the position storage device are used. A leakage magnetic flux density calculating means for calculating a leakage magnetic flux density penetrating into the own crucible; and a magnetic flux of the own crucible based on the calculated leakage magnetic flux density and a moving speed set value of the nearest lifting device. Magnetic flux density change rate calculating means for calculating the change rate of the degree, and based on the calculated magnetic flux density change rate, the self-control means for suppressing the change of the crystal pulling state caused by the leakage magnetic flux penetrating into the own crucible. A magnetic field applying and raising apparatus, comprising: a lifting control correction value calculating means for correcting a pulling control set value.