JP2001302393A - Silicon single crystal pulling equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positional relationship between a surface of a raw material melt in a crucible and a Bz = 0 plane (a plane in which a vertical magnetic field component Bz of a cusp magnetic field becomes 0) and a radial magnetic field on a crucible wall surface. Provided is a silicon single crystal pulling apparatus provided with a magnetic field measuring device capable of easily measuring a Bz = 0 plane required for obtaining a value. SOLUTION: This is a silicon single crystal pulling apparatus in which a magnet for applying a cusp-type magnetic field to a raw material melt in the crucible is disposed around a chamber for accommodating the crucible, the heat insulating supporting a coil portion of the magnet. A magnetic field sensor is installed on the side of the vacuum vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon single crystal pulling apparatus, and more particularly, to a magnetic field application for applying a magnetic field to a raw material melt in a crucible in a silicon single crystal pulling apparatus to produce a single crystal of a desired quality. Type silicon single crystal pulling device (so-called MCZ silicon single crystal pulling device)
It is about.

[0002]

2. Description of the Related Art A conventional MCZ silicon single crystal pulling apparatus is disclosed in, for example, Japanese Patent Publication No. Sho 61-2826296. FIG. 8 is an explanatory view of a configuration of a subsection of this device. 8, 1 is a chamber, 2 is an upper axis, 3 is a lower axis, 4 is a crucible, 5 is a seed crystal, 7
Is a raw material melt, 8 is an electromagnet, and 9 is a magnetic field sensor.

In the above MCZ silicon single crystal pulling apparatus, a silicon raw material melt 7 is provided in a chamber 1,
The single crystal 6 is grown by pulling up the seed crystal 5 attached to the upper shaft 2 while rotating. At this time, a magnetic field is applied by the magnet 8 to control the oxygen concentration and the like in the single crystal. The conventional magnet 8 is a solenoid type magnet, and generates a substantially uniform vertical magnetic field in the crystal growth portion. Also,
Numeral 9 denotes a magnetic field sensor for detecting a magnetic field generated by the magnet, which is attached to a lower central portion of the rotating crucible.

[0004]

Since the conventional MCZ silicon single crystal pulling apparatus is constructed as described above, it is effective when the solenoid type magnet 8 generates a substantially uniform magnetic field in the vertical direction. Although it can be said that this is a magnetic field sensor, in a silicon single crystal pulling apparatus that applies a cusp magnetic field that has recently been used, the mounting position of the magnetic field sensor 9 is not appropriate. It could not be measured. Therefore, the value of the radial magnetic field on the crucible wall, which is an important control element in the silicon single crystal pulling apparatus for applying the cusp magnetic field, and the surface of the raw material melt in the crucible and the plane where the vertical magnetic field component of the cusp magnetic field is zero It was difficult to determine the positional relationship between the two. In addition,
In the following description, the crystal growth direction, that is, the vertical direction is the z direction, the crucible radial direction is the r direction, the vertical magnetic field component of the cusp magnetic field is Bz, and the vertical magnetic field component of the cusp magnetic field is 0. Is referred to as Bz = 0 surface, and the value of the magnetic field in the radial direction on the wall surface of the crucible 4 is referred to as Br, respectively.

Further, in the conventional MCZ silicon single crystal pulling apparatus, since the magnetic field sensor 9 is mounted below the rotating crucible 4, there is a problem that it is difficult to connect with an external measuring instrument. Furthermore, in a silicon single crystal pulling apparatus that applies a cusp magnetic field, an electric current is applied to upper and lower coils constituting a magnet in order to generate a cusp magnetic field, and the current value is changed to thereby obtain a liquid of the silicon raw material melt. Although it is necessary to raise and lower the cusp magnetic field in accordance with the surface change, the magnetic field sensor in the conventional silicon single crystal pulling apparatus is not a measurement position set in consideration of such a case,
As a matter of course, there is a problem that the measurement cannot be performed in accordance with a change in the vertical position of the cusp magnetic field.

The present invention has been made in view of such problems existing in the prior art, and it is an object of the present invention to provide a method in which the surface of a raw material melt in a crucible and the Bz = 0 plane (vertical surface of a cusp magnetic field) Silicon single crystal pulling equipped with a magnetic field measuring device capable of easily measuring the Bz = 0 plane required for obtaining the positional relationship with the magnetic field component Bz in the direction (the plane where the magnetic field component Bz becomes 0) and the value of the magnetic field in the radial direction on the crucible wall surface It is to provide a device.

[0007]

To achieve the above object, a silicon single crystal pulling apparatus of the present invention applies a cusp-type magnetic field to a raw material melt in a crucible around a chamber accommodating the crucible. 1. A silicon single crystal pulling apparatus provided with a magnet to be mounted, wherein a magnetic field sensor is installed on a side surface of a heat-insulating vacuum vessel supporting a coil portion of the magnet.

In this case, it is preferable that the magnetic field sensor is configured to move up and down along the side surface of the heat insulating vacuum vessel.

The magnetic field sensor may be arranged at an intermediate height between upper and lower coil parts constituting the magnet, and a plurality of elements for measuring a vertical magnetic field component may be vertically arranged. it can.

The magnetic field sensor may comprise an element for measuring a vertical magnetic field component, and the element may be rotated by 180 degrees around a vertical axis at a central portion of the element. .

[0011] The magnetic field sensor may comprise an element for measuring a vertical magnetic field component, and the element may be rotated by 180 degrees around a radial axis of the crucible.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a first embodiment in which the present invention is embodied in a silicon single crystal pulling apparatus will be described.
Will be described with reference to the drawings. Parts common to the above-described conventional devices are denoted by the same reference numerals as those of the conventional device, and description thereof will be simplified or omitted.

In FIG. 1, reference numerals 9a and 9b denote a pair of coil portions of a magnet for generating a cusp magnetic field. Then, a cusp magnetic field is applied to the raw material melt by passing currents in opposite directions through the coil portions 9a and 9b. In recent years, with the increase in the size of the single crystal, a superconducting coil has been used for the magnetic field generating coil of the magnet from the viewpoint of energy saving, and the apparatus has been downsized. This superconducting coil portion is held in a heat-insulated vacuum container 12 at room temperature via a heat-insulating support structure 11. And the insulated vacuum vessel 1
The magnetic field sensor 13 is attached to the outer wall of the second. The magnetic field sensor 13 includes a Hall element, and is configured to be able to measure the values Bz and Br of the magnetic field in two axial directions, that is, the vertical direction and the radial direction.

As described above, in the first embodiment, since the magnetic field sensor 13 is attached to the outer wall of the heat-insulating vacuum vessel 12, if the values Bz and Br of the magnetic field in the two axial directions are measured, B
The z = 0 plane can be easily measured, and the positional relationship between the Bz = 0 plane and the crucible melt surface can be easily measured. Further, the magnetic field in the crucible 4 can be measured by comparing the output of the magnetic field sensor 13 with the magnetic field distribution of the mounting position of the magnetic field sensor 13 obtained in advance by the control system. Further, in the first embodiment, since the mounting position of the magnetic field sensor 13 is the outer wall of the heat insulating vacuum vessel 12 which is a stationary body, the reliability of the magnetic field sensor 13 is improved. The mounting position of the magnetic field sensor 13 is the same
The same effect as described above can be obtained even with the inner wall portion 2. Also, if the magnetic field is measured by moving the magnetic field sensor 13 in the vertical direction along the adiabatic vacuum vessel 12, the magnetic field distribution on the crucible wall surface can be more accurately obtained by a preset measurement formula. Further, in the first embodiment, since the magnetic field sensor 13 is provided on the outer wall of the heat-insulating vacuum vessel 12, the magnetic field sensor 13 and the external device can be combined well.

Embodiment 2 Next, a second embodiment will be described with reference to FIGS. Embodiment 2 shows another example of the magnetic field sensor. Embodiment 2
2 and 3, a Hall element 14 that measures the value Bz of the magnetic field in the vertical direction, as shown in FIGS.
Are arranged in the up-down direction (z-direction), and the Hall element 14 located at the center of the magnetic field sensor 13 is arranged at a substantially intermediate position between the upper and lower coil portions 9a and 9b. The other configuration is the same as that of the first embodiment.

In the second embodiment, since the magnetic field sensor 13 is configured as described above, it is possible to directly read the Bz = 0 plane. Also, even when the Bz = 0 plane moves up and down,
By comparing with the calculation result obtained in advance, it becomes possible to detect the Bz = 0 plane with higher accuracy. The magnetic field sensor 13 may be arranged at an intermediate height between the upper and lower coil portions 9a and 9b of the magnetic field sensor 13 in place of a sensor capable of measuring in two axial directions. Also,
In this case, the mounting position of the magnetic field sensor 13 is
The position is not limited to the intermediate position between the upper and lower coil portions 9a and 9b, and may be an arbitrary position. In this case, similarly to the first embodiment, the magnetic sensor 13 Magnetic field distribution of mounting position and magnetic field sensor 13
By comparing this output with the control system, the magnetic field distribution in the crucible 4 can be obtained. In addition, the magnetic field sensor 13
Is mounted on the outer wall of the heat-insulating vacuum vessel 12, so that the magnetic field sensor 13 and the external device can be combined well as in the first embodiment.

Embodiment 3 Next, a third embodiment will be described with reference to FIGS. The third embodiment shows another example of a method of attaching the magnetic field sensor according to the first embodiment.

In the silicon single crystal pulling apparatus for applying a cusp type magnetic field, the upper and lower coil portions 9 of the superconducting magnet are used.
It is necessary to accurately determine the Bz = 0 plane, which is a magnetically symmetric plane when a and 9b have the same current value. In this case, Bz
It is conceivable to attach a Hall element for measuring the height B to a horizontal mounting table and move the Hall element up and down to search for the Bz = 0 plane. However, when the Hall element is mounted in this manner, it is difficult to mount the Hall element horizontally without error. That is, as shown in FIG. 4, a horizontal mounting table 16 for mounting the Hall element 15 is usually used.
Is inevitably inclined at a slight angle θ with respect to the horizontal plane. In FIG. 4, the angle θ is drawn with emphasis.

In this case, the output V ₁ of the Hall element 15 is as follows. V ₁ = Bzcos θ + Brsin θ (1) In this equation (1), since the mounting angle θ is extremely small, cos θ is a value close to 1, and sin θ is 0.
However, since Bz << Br at the measurement position, the two terms on the right side of the above equation (1) are almost the same size as the same term. Therefore, only the measurement of the output V ₁ was it is difficult to measure the exact Bz = 0 plane.

FIG. 5 is a diagram showing a state in which the Hall element 15 of FIG. 4 is rotated by 180 degrees about the z-direction axis (an axis parallel to the axis of the crucible 4) at the center of the Hall element 15. The output V ₂ of 15 is as follows. V ₂ = Bzcos θ−Brsin θ (2) From the above equations (1) and (2), V ₁ + V ₂ = 2Bzcos θ (3), and the term Br is canceled. Also, in this equation (3), cos θ is a value close to 1;
By measuring V ₁ + V ₂ , the Bz = 0 plane can be accurately obtained without being affected by errors in the mounting surface of the Hall element 15.

In the third embodiment, the Hall element 15 can be rotated by 180 degrees in the z-axis direction. The rotating structure of the Hall element 15 may be any suitable structure. For example, as shown in FIG. 6, a rectangular sheath 18 in the vertical direction is protruded from the outer periphery of the insulated vacuum vessel 12 to attach the Hall element 15 thereto. The legs 16 of the mounting base 16 as they are
It is conceivable to manually pull the leg 16a upward, manually rotate it 180 degrees in the horizontal direction about the vertical axis at the center of the Hall element, and then insert the leg 16a into the sheath 18 again. Although not specifically shown in FIG. 6, the mounting height position of the Hall element 15 is preferably substantially the middle position between the coil portions 9a and 9b of the superconducting magnet. Also, near this intermediate position,
Further, it is preferable to adopt a structure which can be moved up and down in accordance with the movement of the Bz = 0 plane. Further, a mechanism that can automatically perform the rotation of the Hall element 15 may be used.

Embodiment 4 Next, a fourth embodiment will be described with reference to FIG. In the third embodiment, the Hall element 15 is rotated in the horizontal direction about the vertical axis. However, there are various structures around the silicon single crystal pulling apparatus. In some cases, it is difficult to rotate in a horizontal direction. The embodiment corresponds to such a case, and as shown in FIG. 7, the Hall element 15 is rotated up and down around a horizontal axis in the normal direction of the heat insulating vacuum vessel. In this case, the output of the Hall element is also the same as that of the equation (2), and as in the third embodiment, Bz = The zero plane can be accurately obtained. Although not specifically shown in FIG. 7, the mounting height position of the Hall element 15 is preferably substantially the middle position between the coil portions 9a and 9b of the superconducting magnet. In the vicinity of the intermediate position, B
It is preferable to adopt a structure that can be moved up and down in accordance with the movement of the z = 0 plane. Further, a mechanism that can automatically perform the rotation of the Hall element 15 may be used.

In the third and fourth embodiments, the mounting base 16 is provided as an easy-to-understand structure and the Hall element 15 is mounted thereon. However, the mounting base 16 is not shown in the drawings. The mounting base 16 need not be provided, and the mounting base 16 may not be provided. In the third and fourth embodiments, the case where a single Hall element is used has been described. However, if a plurality of Hall elements are used as in the second embodiment, the Bz = 0 plane can be measured more accurately. Can be.

[0024]

Since the present invention is configured as described above, the following effects can be obtained. According to the invention according to claims 1 to 5, there is provided a silicon single crystal pulling apparatus in which a magnet for applying a cusp-type magnetic field to a raw material melt in the crucible is provided around a chamber accommodating the crucible, Since the magnetic field sensor was installed on the side of the insulated vacuum container supporting the coil portion of the magnet, Bz = 0
The surface can be easily measured, and based on the result, the control system compares the magnetic field distribution of the mounting position of the magnetic field sensor, which was obtained in advance, with the output of the magnetic field sensor.
The positional relationship between the z = 0 plane and the surface of the raw material melt in the crucible and the magnetic field in the crucible can be obtained. In addition, since the magnetic field sensor is arranged on the side surface of the heat-insulating vacuum container, the connection with the measuring device arranged outside is improved.

According to the second aspect of the present invention, since the magnetic field sensor can be moved up and down along the side surface of the heat-insulating vacuum vessel, a more accurate crucible magnetic field distribution can be obtained. You can ask.

According to the third aspect of the present invention, the magnetic field sensor includes a plurality of elements that are disposed at substantially the middle height of the upper and lower coil portions constituting the magnet and that measure a vertical magnetic field component. Since the sheets are arranged in the vertical direction, it is possible to directly read the Bz = 0 plane and measure with higher accuracy.

According to the fourth aspect of the present invention, the magnetic field sensor comprises an element for measuring a vertical magnetic field component, and can rotate by 180 degrees around a vertical axis at a central portion of the element. Bz = Bz = without being affected by errors in the mounting surface of the Hall element.
The zero plane can be measured accurately.

According to a fifth aspect of the present invention, the magnetic field sensor comprises an element for measuring a vertical magnetic field component, and is parallel to the axis of the crucible in the radial direction of the crucible and at the center of the element. Since it is configured to be able to rotate by 180 degrees around the axis, the Bz = 0 plane can be accurately measured without being affected by errors in the mounting surface of the Hall element, as in the invention according to claim 5. Can be.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a silicon single crystal pulling apparatus according to a first embodiment of the present invention, which is an explanatory view of a configuration of the entire apparatus.

FIG. 2 is a configuration explanatory view of a magnetic field sensor mounting portion of a silicon single crystal pulling apparatus according to a second embodiment of the present invention.

FIG. 3 is an enlarged view of a part III in FIG. 2;

FIG. 4 is a diagram for explaining a problem when a Hall element is attached according to the third embodiment of the present invention.

FIG. 5 is a configuration explanatory view of a Hall element mounting portion of a silicon single crystal pulling apparatus according to a third embodiment of the present invention.

FIG. 6 is a structural explanatory view of a Hall element mounting portion of a silicon single crystal pulling apparatus according to a third embodiment of the present invention.

FIG. 7 is a configuration explanatory view of a Hall element mounting portion of a silicon single crystal pulling apparatus according to a fourth embodiment of the present invention.

FIG. 8 is a longitudinal sectional view of a conventional silicon single crystal pulling apparatus, and is a configuration explanatory view of the entire apparatus.

[Explanation of symbols]

1 chamber, 2 upper axis, 3 lower axis, 4 crucibles, 5
Seed crystal, 6 single crystal, 7 raw material melt, 8 magnet,
Reference Signs List 9 magnetic field sensor, 9a, 9b coil part, 10 cusp magnetic field, 11 heat insulating support structure, 12 heat insulating vacuum vessel, 13
Magnetic field sensor, 14, 15 Hall element, 16 mounting base, 16a Mounting base leg, 18 sheath.

Claims (5)

[Claims] 1. A silicon single crystal pulling apparatus in which a magnet for applying a cusp-type magnetic field to a raw material melt in a crucible is provided around a chamber for accommodating the crucible, and supports a coil portion of the magnet. A silicon single crystal pulling apparatus characterized in that a magnetic field sensor is installed on the side of an insulated vacuum vessel. 2. The silicon single crystal pulling apparatus according to claim 1, wherein the magnetic field sensor can be moved up and down along a side surface of the heat insulating vacuum vessel. 3. The magnetic field sensor according to claim 1, wherein the magnetic field sensor is arranged at a substantially intermediate height position between upper and lower coil portions constituting the magnet, and a plurality of elements for measuring a vertical magnetic field component are vertically arranged. The silicon single crystal pulling apparatus according to claim 1 or 2, wherein: 4. The magnetic field sensor according to claim 1, wherein the magnetic field sensor comprises an element for measuring a vertical magnetic field component, and is rotatable by 180 degrees around a vertical axis at a central portion of the element. The silicon single crystal pulling apparatus according to claim 1. 5. The magnetic field sensor according to claim 1, comprising an element for measuring a vertical magnetic field component, and rotating the element by 180 degrees around a radial axis of the crucible. The silicon single crystal pulling apparatus according to claim 1.