JPH01215791A - Apparatus for pulling up single crystal - Google Patents

Abstract

PURPOSE:To suppress vibration of a heater and grow a high-quality single crystal, by providing a phase-shifting means, shifting a phase difference of currents supplied to the heater and an exciting coil and enabling both the currents to offset electromagnetic forces thereof. CONSTITUTION:This apparatus for pulling up a single crystal is formed of a heater 2, an exciting coil (1a), a phase-shifting means for providing a phase difference of ripples of DC current supplied to the exciting coil and heater 2 and a filter. The above-mentioned heater 2 is arranged around a vessel 5 for containing a melt (L) of a semiconductor. The afore-mentioned coil (1a) is supplied with a DC current containing ripples for generating a magnetic field across opposite magnetic poles positioned at places sandwiching the above- mentioned heater 2 and vessel 5. Furthermore, the afore-mentioned filter is capable of converting the wave form of both the above-mentioned ripples into since waves.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a single crystal pulling apparatus that is widely used to obtain a semiconductor single crystal.

[Prior art]

When a single crystal of a semiconductor is to be obtained, for example, a single crystal pulling apparatus as shown in FIG. a heater 2 to which is supplied; the heater 2 and a container 5;
A single crystal pulling apparatus is used which is equipped with an excitation coil 1a to which a direct current is supplied to generate a magnetic field between opposing magnetic poles N and S that are placed between them. Then, the tip of the single crystal seed A whose upper end side has been chucked by the pulling chuck 4 is immersed in the melt pool heated by supplying the DC current to the heater 2, and then the single crystal seed A is By pulling at a predetermined pulling speed, a semiconductor single crystal is grown.

By the way, it is known that the vibration of the liquid surface of the melt and the thermal convection in the liquid have a large effect on the quality of the single crystal grown as described above, but it is necessary to minimize this effect. As a measure to reduce the amount of melt, a magnetic field is generated between the opposing magnets iN and S by supplying the DC current to the excitation coil 1a, and the above-mentioned operation is performed in the magnetic field. efforts are being made to increase the effective viscosity of the material, thereby suppressing the vibrations and thermal convection.

[Problem that the invention seeks to solve]

Although the DC current supplied to the heater 2 and the excitation coil 1a is obtained by rectifying alternating current, the output of the rectifying circuit is not direct current and inevitably contains ripples.

Therefore, ripples in the current in the heater flowing within the magnetic field cause it to vibrate, which causes the melt in the container 5 to vibrate, and since the ripple also has an effect on the magnetic field, the vibrations caused by this are superimposed. Become.

To deal with this, a method has been proposed in which the vibrations of the heater 2 are suppressed by supplying a DC current whose content rate for the heater 2 helix is below a certain value (
Special Publication No. 58-50951).

However, the actual vibration of the heater 2 is caused by the structure 1 of the heater 2.
The strength, installation method, direction and strength of the magnetic field around the heater 2, etc. may be complexly related and become noticeable, so as long as the ripple component is included in the DC current supplied to the heater 2, the vibration of the heater 2 will be reduced. There were circumstances in which this was not sufficiently suppressed, and it sometimes became noticeable.

The present invention has been made in view of such circumstances, and its purpose is to provide a means that can more reliably solve the above-mentioned problems.

[Means for solving problems]

A single crystal pulling apparatus according to the present invention includes a heater arranged around a container containing a semiconductor melt and to which a direct current including ripple is supplied, and a heater arranged in a position sandwiching the heater and the container. In order to generate a magnetic field between opposing magnetic poles, the single crystal pulling apparatus is equipped with an excitation coil to which a DC current including a ripple component is supplied, in order to generate a magnetic field between opposing magnetic poles. The present invention is characterized by comprising a phase shift means for making a phase difference of 180° from the ripple portion of the DC current supplied to the DC current, and a filter for making the waveform of both the ripple portions into a sine wave.

[Effect]

When using such a device of the present invention, the phase difference between the two ripples can be shifted by 180° by the phase shifting means, and the waveform of the two ripples can be made into a sine wave by the filter. It becomes possible to cancel each other out the electromagnetic force due to the ripple portion of the DC current supplied to the excitation coil of the electromagnet and the electromagnetic force due to the ripple portion of the DC current supplied to the excitation coil of the electromagnet. Therefore, it is possible to cancel out the magnetic forces of both types, thereby suppressing the influence of the electric factor that causes vibrations in the heater, that is, the ripple component of the DC current, and reliably suppressing the vibrations of the heater.

〔Example〕

The present invention will be described below based on drawings showing embodiments thereof.

FIG. 2 is a schematic diagram of a single crystal pulling apparatus according to the present invention (hereinafter simply referred to as the apparatus of the present invention).

In the figure, 2 is a heater arranged around a container 5 made of a quartz crucible or the like for containing a semiconductor melt. Reference numeral 1 denotes an electromagnet having an excitation coil 1a for generating a magnetic field between opposing magnetic poles N and S placed between the heater 2 and the container 5.

That is, the electromagnet 1 has an excitation coil 1a wound around each open end of a rectangular yoke 1b with an open top, and by energizing the excitation coil la, the two ends are connected to opposing magnetic poles N and S. The heater 2 and the container 5 are arranged in the open upper part of the yoke 1b.

Then, after immersing the tip of the single crystal seed A whose upper end side has been chucked by the pulling chuck 4 in the melt pool heated by supplying a direct current to the heater 2, the single crystal seed A By pulling at a predetermined pulling speed, a semiconductor single crystal is grown. Further, by supplying a DC current to the excitation coil la, a magnetic field is generated between the opposing magnetic poles N and S, and by performing the above-mentioned operation in the magnetic field, the effective viscosity of the melt is increased. This makes it possible to suppress vibrations in the liquid surface of the melt and thermal convection within the liquid.

FIG. 1 is a circuit diagram showing a power supply section that supplies direct current to the excitation coil 1a and heater 2, respectively.

In the figure, 11.21 is a transformer installed in the circuit on the excitation coil la side and the circuit on the heater 2 side, and the primary winding thereof is a delta connection in the transformer 11, and a hexagonal connection in the transformer 21. Both pressure regulators 11 and 21 are connected to the three-phase power supply 10. In addition, the secondary winding of each transformer 11.21 is a combination of delta connection and star connection, and the secondary winding is connected to the input side of the rectifier circuit 12.22 consisting of a group of thyristors, that is, each Each is connected to the anode side of the cyrisk.

The output side of the rectifier circuit 12.22, that is, the cathode side of each sirisk, is connected together for each circuit 12.22, and is respectively connected to the input end of a filter 13.23 consisting of a reactor and a capacitor. and the filter 13.2
3 is connected to the connection terminal 15.3 of the excitation coil la of the electromagnet l via a current detector 14.24. They are connected to connection terminals 25 of the heater 2, respectively. and the current detector 1
The output of 4.24 is input to the subtracter 17 together with the output of the current setting device 16.26, a subtraction process is performed in the subtracter 17, and the output related to the difference is sent to the Cyrisk ignition circuit 18.2.
8. Cyrisk ignition circuit 18.28 has current setting device 16.26 output and current detector 1
4.24 A trigger signal is generated at the conduction phase in which the difference with the output should be zero, and this is applied to the gate of the rectifier circuit 12.22.

When using such a device of the present invention, the transformer 11.21 and the rectifier circuit 12.22 adjust the phase difference between the ripple component of the DC/current supplied to the heater and the ripple component of the DC current supplied to the excitation coil of the electromagnet. becomes 180@. That is, due to the difference in the wiring system of transformer 11 and transformer 21, the voltage vector of the secondary winding will be shifted by 15", and furthermore, the voltage vector of the secondary winding will be shifted by 15" in the rectifier circuit 12.22.
Due to the phase rectification, the phase of the output current corresponding to the ripple is shifted by 180' (π). Furthermore, the ripple component passes through the filter 13.23, so that its waveform becomes a sine wave.

Therefore, the electromagnetic force due to the ripple of the DC current supplied to the heater and the electromagnetic force due to the ripple of the DC current supplied to the excitation coil of the electromagnet can cancel each other out.

This relationship will be specifically explained using a mathematical formula.

The electromagnetic force F given to the heater by supplying the DC current can be expressed as shown below (Equation 11).

F': BI Hsin θ -K I, 'IN sin θ ・(1) However, ■,: Heater current (DC current supplied to the heater) 1.4: Excitation coil current (DC current supplied to the excitation coil of the electromagnet (Current) B: Strength of magnetic field due to excitation coil current K: Constant determined by excitation coil, electromagnet gap, etc. θ: Angle at which the magnetic field and heater intersect Taking into account the ripple current component, the following equation (2) is obtained.

FcCK(1)4 +ΔIN sin(ilt)(
IM +ΔIHsin(ωt +π))sinθ”
N141)l +l14 ΔIN 5in(ωt +
1+1. ΔIN sinω is 10Δ1. ΔIH sinωt 5in (ωt +7ri)
sinθ...(2) However, Δ1. sinωt: ripple component ΔIH of exciting coil current
sin(ω(+π); ripple component of heater current (both ripple components have a phase of 180 @(π) due to the phase shifting means)
In equation (2) above, the first term is only a direct current component, and for example, the electromagnetic force exerted on the heater due to a change in IH is only a change in ■□ and is not vibrational.

Also, the second, third, and fourth terms are the frequency “(−ω/2
The fundamental wave of π) becomes the electrical and oscillatory force, but the second term includes 5in(ω[+π) and the third term includes s
Since inωt is included, if the second term increases, the third term decreases, and conversely, if the second term decreases, the third term increases, so the excitation of the electromagnet is adjusted so that the following equation (3) holds true. If the number of turns of the coil is designed, the sum of the second and third terms in equation (2) becomes approximately constant.

1, ΔIH#INΔ■9 (3) The number of turns of the excitation coil of the electromagnet can be easily designed if the required distance between opposing magnetic poles and the magnetic flux at the center point thereof are specified. Furthermore, the fourth term in equation (2) above is sinω[and 5i
It includes the product of n(ωt+π), and the increase/decrease of Δ■i and Δ
■□ increases and decreases are reversed and offset, and Δ■9Δ■8
is essentially a minute amount, so the first term ~ in equation (2) above
It is extremely small compared to the added value of the second term and can be ignored.

Next, the angle θ at which the magnetic field and the heater intersect exists relatively continuously from O to 2π, but it is maximum at the point where sin θ = 1, that is, the point where the magnetic field and the heater are perpendicular to each other, and becomes 1 at other points. The following becomes 0 at the parallel point, but by giving the above-mentioned canceling effect to the vibration element in the electromagnetic force F applied to the heater, the vibration of the heater can be suppressed regardless of the position of the heater with respect to the magnetic field. becomes possible.

It goes without saying that the apparatus of the present invention is not limited to the above embodiments. For example, the wiring system of the transformer 11.21, the configuration of the rectifier circuit 12.22, etc. are not limited to those shown in FIG.
The method is not limited to the method shown in the figure.

〔effect〕

As described in detail above, according to the present invention, it is possible to reliably suppress vibrations caused by electrical factors of the heater in a single crystal pulling apparatus. Therefore, by using the apparatus of the present invention, it is possible to grow high quality single crystals.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a power supply section that supplies direct current to the heater and excitation coil, respectively, in the apparatus of the present invention, and FIG. 2 is a schematic configuration diagram of the single crystal pulling apparatus. la: Excitation coil 2: Heater 5: Container L: Semiconductor melt N, S: Magnetic pole patent Applicant: Agent for Osaka Titanium Manufacturing Co., Ltd.
Patent Attorney Noboru Kono 1 Illustration 2 Illustration

Claims (1)

[Claims] 1. A heater arranged around a container containing a semiconductor melt and to which a direct current including ripple is supplied, and opposing magnetic poles arranged at positions sandwiching the heater and the container. In a single crystal pulling apparatus equipped with an excitation coil to which a DC current including a ripple component is supplied in order to generate a magnetic field between the ripple component of the DC current supplied to the heater and the ripple component of the DC current supplied to the excitation coil. A single crystal pulling device comprising: a phase shifter that makes a phase difference of 180° from a ripple component of a direct current; and a filter that makes the waveform of both ripple components a sine wave.