JPS62252396A - Apparatus for pulling up single crystal - Google Patents

Abstract

PURPOSE:To automatically shift a supporting point of a wire to a position able to prevent the deflection of a seed holder and the wire, by using a detecting device, a controlling device and a shifting device and combining the devices in a manner to act a specific action. CONSTITUTION:When a wire 31 of a single crystal pulling-up apparatus 2 is deflected, the extent and direction of the deflection of the wire 31 are detected by a deflection detecting device 35 and a rotary position detecting device 36. The direction and length of a supporting point 32 to be shifted to decrease the deflection of the wire 31 are calculated by a controlling device. The supporting point 32 is shifted by an XY table 29 according to the calculated data to decrease the deflection of the wire 31. Consequently, the seed holder 33 and the wire can be rotated at a speed near or above the resonance point and the quality of the single crystal can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a single crystal pulling apparatus for producing a single crystal of silicon or the like used in semiconductors, for example.

"Prior Art" Generally, a Czochralski-type pulling device is often used as a device for pulling semiconductor single crystals such as silicon. There are two types of lifting devices: rod type and wire set, but the overall height of the machine can be lowered.
In recent years, rod-type lifting has become popular due to the following reasons: magnetic fluid can be used for the seal of the drive part, it is flexible against vibrations, and wire is thinner than rods, so there is less chance of dust sticking and falling. Many devices are being avoided, and a complete wire pulling device is now being used.

Conventionally, as this type of single crystal pulling apparatus, for example, a single crystal pulling apparatus 1 as shown in FIG. 3 is known. This single crystal pulling device 1 includes a frame It, a support 12 rotatably provided at the upper end of the frame 11, a winding device 13 installed on the support 12, and one end connected to the old winding device 13. A wire 14 that is wound and suspended so as to pass through the rotational axis of the support I2, a sheet holder 15 attached to the lower end of this wire 14, and a crucible disposed below this sheet holder 15. I6, and the crucible 16 contains molten silicon 17.
is stored in the seat holder! 5 has a structure in which a seed 18 is held with its lower part immersed in molten silicon 17.

In such a single crystal pulling apparatus 1, in order to manufacture a silicon single crystal, the wire 1 is rotated while the support 12 is rotated and the winding device 13 is operated.
4 and the sheet holder 15, the seed 18 is gradually raised from the molten silicon 17 while being rotated, and a silicon single crystal is deposited on the seed 18 to produce it.

"Problems to be Solved by the Invention" By the way, in the single crystal pulling apparatus 1 described above, since the sheet holder 15 is simply suspended by the wire 14, the wire 14 and the sheet holder 15 may sway horizontally. Cheap. Therefore, there was a problem in that the seed boulder 15 and the wire 14 could not be rotated at a rotation speed near or above their resonance point, and the quality of the single crystal could not be improved.

In other words, in recent years, high-quality silicon crystals used in VLSI etc. are required to have uniform resistivity distribution and oxygen concentration distribution within the crystal, but it is difficult to manufacture such high-quality crystals. In order to do this, it is necessary to increase the rotation speed of the seat holder to two to three times the current speed. However, the resonant rotation speed of a seat holder suspended by a wire is very low, and even if an attempt is made to increase the rotation speed of the seat holder, resonance will occur at a low rotation speed, making it impossible to increase the rotation speed. This makes it extremely difficult to produce high quality crystals.

On the other hand, the following methods have been considered to prevent the wire from swinging during high-speed rotation.

First, there is a method in which the fulcrum of the wire is lowered to increase the free frequency during crystal pulling, and the fulcrum is raised upward only when the crystal is being taken out. This method uses 20 rotations/
The wire length is about 2.2m for up to 3 minutes, but
If the target is 0 revolutions per minute or more, the wire length must be 1 m or less, which is impractical.

Another method is to suspend the seat holder using two or three wires. This method has the disadvantage that the adjustment is complicated because it is necessary to strictly match the pulling amounts of two or three wires, and the driving device is complicated.

Furthermore, a strong magnetic field is applied to the lower end or middle of the wire,
There is a method in which the wire is made of ferromagnetic material.

This method requires the magnet to be installed outside the furnace body, since it is necessary to avoid the vacuum or high-temperature parts of the furnace.

As described above, various methods have been tried, but all of them have their own drawbacks and are not practical.

[Object of the Invention] An object of the present invention is to provide a single crystal pulling apparatus that can automatically move the fulcrum of the wire to a position where the deflection of the sheet holder and the wire can be prevented.

``Structure of the Invention'' This invention provides a detection device that detects the amount and direction of runout from the rotation axis of a seat holder and a wire support, and , a control device that calculates a fulcrum position of the wire that can prevent swinging of the seat holder and the wire, and a moving device that moves the fulcrum of the wire to the fulcrum position of the wire calculated by the control device. It is structured as follows.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a diagram showing a single crystal pulling apparatus 2 according to the present invention. This single crystal pulling apparatus 2 includes a cylindrical frame 21. At the bottom of this frame 21,
A crucible 22 is provided.

This crucible 22 stores molten silicon 23 that has been heated and melted by a heater (not shown).

Meanwhile, a neck portion 24 is formed at the upper portion of the frame 21 . This neck portion 24 is provided with a support body 25 . This support body 25 is connected to the neck portion 2 through a bearing 26.
4 in an airtight manner, and is rotatable about a vertical axis. This support body 25 is rotated via a belt 28 by a drive device 27 provided on the outer peripheral wall of the neck portion 24 .

On the support body 25 is an X-Y table (moving device) 2.
9 is provided. This X-Y table 29 is capable of moving an object placed thereon in any direction within a horizontal plane, and is also capable of detecting the amount of displacement thereof. A hoisting drum 30 is provided on this XY table 29. This winding drum 30 can be rotated by a drive device (not shown). This winding drum 30
One end of the wire 31 is wrapped around and suspended. This wire 31 is connected to the winding drum 3.
The fulcrum 32 suspended from the support 25
is located on the rotation axis of the

A seat holder 33 is attached to the lower end of the wire 31. A seed 34 is fixed to the sheet holder 33, and the lower end of the seed 34 is immersed in the molten silicon 23 in the crucible 22. Then, the seed 34 is raised while being rotated and stroked so as to precipitate a silicon single crystal.

On the other hand, below the neck portion 24 of the frame 21, a shake detection device (detection device) 35 is provided. This deflection detecting device 35 includes the support body 25 of the wire 31.
It is possible to detect the direction and amount of shake from the rotation axis of the machine, and a non-contact type sensor such as an image sensor is used. Further, the neck portion 24 is provided with a rotational position detection device (detection device) 36. This rotational position detection device 36 is for detecting the rotational position of the support body 25 in the circumferential direction, and uses an absolute type encoder.

Such a single crystal pulling apparatus 2 is provided with a control device (not shown). This control device is for moving the fulcrum 32 in a direction that reduces the deflection of the wire 31. This control device first detects the deflection amount and deflection direction of the wire 31 detected by the deflection detection device 35 and the rotational position of the support body 25 in the circumferential direction detected by the rotational position detection device 36. The amount and direction of shake with respect to the support body 25 are calculated. Next, from the deflection amount and deflection direction of the wire 31 with respect to the support body 25,
The direction and amount of movement of the fulcrum 32 necessary to reduce the deflection of the wire 31 are calculated. Then, by outputting the command to the XY table 29, the XY table 29 is moved.

The amount of movement of the fulcrum 32 is controlled by PID in accordance with the swing amplitude of the wire 31, and its gain is experimentally set in accordance with the wire length. In addition, regarding the direction in which the support i32 is moved, generally the support point of the vibration system is X=α
When performing a simple harmonic motion called sinωt, let the relative displacement between the vibrating body and its fulcrum be Xl, then the solution of the forced vibration of xl is as follows: 1-λ2)!+(2ζλ)ri/!ta
nδ=2ζλ/(1−λt) ζ: damping coefficient ratio, λ: forced frequency ratio.

Since the phase difference δ is determined by the forced vibration ratio (the ratio of the actual rotational speed to the free frequency) and the damping coefficient ratio, it changes depending on the conditions and is largely determined experimentally. The direction in which the fulcrum of the wire should be moved is the direction of the deflection at that time! The direction is the sum of 80°+δ. That is, in order to cancel the vibration at that time, vibration shifted by δ is applied to cause forced vibration with a phase difference of 180°.

In this way, in this single crystal pulling apparatus 2, when the wire 31 swings, the swing amount and direction of the wire 31 are detected by the swing detection device 35 and the rotational position detection device 36, and the control device controls the swing of the wire 31. The moving direction and amount of movement of the fulcrum 32 to reduce the runout are calculated, and the fulcrum 32 is moved by the XY chip pool 29 to reduce the runout of the wire 31. Therefore, deflection of the seat holder 33 and the wire 31 can be promptly prevented. Therefore, the sheet holder 33 and the wire 31 can be rotated at a rotation speed near or above their resonance point, and the quality of the single crystal can be improved. In addition, since the fulcrum 32 can be automatically moved in the direction where the deflection is the least, there is no need to align the fulcrum completely with the rotational axis of the support when assembling the device, making the assembly work easier. It can be carried out.

FIG. 2 is a diagram showing a single crystal pulling apparatus 4 which is another embodiment of the present invention. In this single crystal pulling device 4, a winding drum 30 is provided on a support body 25, and a guide piece 42 having a through hole (fulcrum) 41 penetrating in the vertical direction is provided on an XY table 29. . Further, the wire 31 is passed from the winding drum 30 through the through hole 41 of the guide piece 42.
It is suspended on 2. And the wire 31
If a deflection occurs in the wire 31, the guide piece 42 provided on the XY plate 29 is moved in the horizontal direction to prevent the wire 31 from deflecting. Of course, this single crystal pulling apparatus 4 also provides the same effects as those of the above embodiment.

In the above embodiment, the shake detection device 35 is provided near the neck portion 24 of the frame 21, but it is not limited to this, and may be provided at the lower part of the frame 21, and furthermore, the shake detection device 35 is provided near the neck portion 24 of the frame 21. Runout may also be measured.

"Effects of the Invention" As explained above, according to the present invention, there is provided a detection device that detects the amount and direction of deflection of the seat holder and the wire support from the rotation axis, and A control device that calculates a fulcrum position of the wire that can prevent the sheet holder and the wire from wobbling based on the amount of deflection and the direction of deflection; and a control device that moves the fulcrum of the wire to the fulcrum position of the wire calculated by the control device. Since the fulcrum is automatically moved, it is possible to prevent the seat holder and the wire from wobbling. It can be rotated at a rotational speed of 1000, which improves the quality of the single crystal, and eliminates the need to align the fulcrum perfectly with the rotational axis of the support when assembling the device, which reduces the assembly work. This has the effect that it can be easily performed.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, FIG. 2 is a sectional view showing another embodiment of the present invention, and FIG. 3 is a sectional view showing an example of a conventional single crystal pulling apparatus. . 2...Single crystal pulling device, 4...Single crystal pulling device, 25...Support, 29...
...XY table (moving device), 31...
Wire, 32... Fulcrum, 33... Seat holder, 35... Shake detection device (detection device), 36... Rotation position detection device (detection device) ),
41...Through hole (fulcrum).

Claims (1)

[Claims] A support body that rotates about a vertical axis, a wire suspended from a fulcrum provided on the support body, and a seat holder attached to the lower end of the wire, and the support body rotates about the axis center. In a single crystal pulling apparatus that rotates the sheet holder by rotating the sheet holder about a center and pulls up the sheet holder by pulling up the wire, the sheet holder and the wire run out from the rotation axis of the support. a detection device that detects the amount and direction of deflection; a control device that calculates a fulcrum position of the wire that can prevent deflection of the seat holder and the wire from the amount and direction of deflection detected by the detection device; A single crystal pulling device comprising: a moving device that moves the fulcrum of the wire to a fulcrum position of the wire calculated by the device.