JPH1179883A - Production of single crystal and seed crystal for single crystal production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To safely and surely grow a single crystal having a large diameter by using plural seed crystals. SOLUTION: The production of a single crystal by CZ process is carried out by preparing a seed crystal having an axial part 1b to be inserted into a seed holder 2 and a seed part 1p composed of plural seed pieces 1c interposing prescribed space between the pieces, dipping the tip ends of plural seed pieces into a molten liquid, pulling up the seed pieces to independently grow seed crystals from the plural seed pieces, enlarging the diameter of the grown single crystal and forming the straight body part by integrating the individual single crystals grown to the part near the surface of the molten liquid when the tip end of the seed part reaches a prescribed height from the surface of the molten liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a semiconductor single crystal and a seed crystal for producing a single crystal, and more particularly to a method for producing a large diameter single crystal.

[0002]

2. Description of the Related Art Single crystal silicon is generally manufactured by the CZ method. In the CZ method, polycrystalline silicon is filled in a quartz crucible installed in a single crystal manufacturing apparatus, the polycrystalline silicon is heated and melted by a heater provided around the quartz crucible, and the seed crystal attached to the seed holder is melted. Soak in the liquid. Then, the seed holder is pulled up while rotating the seed holder and the quartz crucible in the same or opposite directions to grow single crystal silicon to a predetermined diameter and length.

In a seed crystal, dislocation occurs due to thermal stress when immersed in a melt. In order to prevent the dislocation from propagating to the single crystal, the dash method is widely used. In the dash method, while pulling up a seed crystal, the diameter thereof is narrowed to about 3 to 5 mm to form a neck portion, and dislocations are released to the surface of the neck portion. Then, after the dislocation-free state is confirmed, the shoulder is formed to enlarge the single crystal to a predetermined diameter, and then the process shifts to the formation of a straight body.

In recent years, as the diameter and length of a single crystal have increased, their weight has increased, and the strength of the neck has reached its limit. Therefore, in the conventional manufacturing method, there is a possibility that the neck portion is broken during the pulling of the single crystal, and it is difficult to safely grow the single crystal.

As one of the methods for producing a large single crystal, there is a crystal growing method disclosed in Japanese Patent Application Laid-Open No. 56-54297. In this method, a seed crystal with the same cutting direction is attached to a plurality of crystal pulling axes, and when the diameter of each single crystal pulled by each crystal pulling axis becomes a predetermined diameter, the rotation of each axis rotates Is stopped, and the single crystal is joined to grow as a single crystal by further increasing the crystal growth rate, and the neck part is broken to suspend the large diameter single crystal with a plurality of seed crystals. The danger is extremely low.

[0006]

However, in the crystal growth method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 56-54297, seed crystals having the same cutting direction are independently attached to a plurality of crystal pulling axes. However, since each crystal pulling axis is rotated, it is extremely difficult to accurately match the crystal orientation of each single crystal grown from these seed crystals. If the crystal orientation is shifted, a twin crystal is formed, and there is a problem that a single crystal having good crystallinity cannot be obtained. When a plurality of seed crystals are arranged on the center of the melt and on a radius separated by a predetermined distance from the center of the melt, it is impossible to control the diameter of the seed crystals due to the temperature difference of the melt.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. A single crystal having a large diameter can be grown safely and reliably using a seed crystal composed of a plurality of seed pieces. An object of the present invention is to provide a crystal production method and a seed crystal used for the method.

[0008]

In order to achieve the above object, a first method of manufacturing a single crystal according to the present invention is provided.
In the method for producing a single crystal by the CZ method, a step of preparing a seed crystal having a shaft portion to be fitted into a seed holder and a seed portion including a plurality of seed pieces provided at a predetermined interval; An immersion step of immersing the tips of the plurality of seed pieces in a melt; a split growth step of independently growing single crystals from the plurality of seed pieces by pulling up the seed crystal; Expanding the diameter of the single crystal, when the tip of the seed portion reaches a predetermined height from the melt surface, integrating each single crystal growing near the melt surface, forming a straight body portion; It is characterized by having. According to the above configuration, since an integrated seed crystal having a seed portion composed of a plurality of seed pieces (hereinafter referred to as a multi-seed) is used as the seed crystal, the integrated single crystal is supported by the plurality of neck portions. Therefore, the withstand load increases. For example, if the diameter of the neck portion is 4 mm, the conventional method has a load bearing capacity of about 150 kg,
In the single crystal manufacturing method of the present invention, when the number of necks is two, about 3
If the load is 00 kg or three pieces, the load capacity is about 450 kg. As a result, a desired large-diameter single crystal can be safely pulled without causing breakage of the neck portion.

The second aspect of the method for producing a single crystal according to the present invention is as follows.
The method of manufacturing a single crystal according to the first invention, wherein the seed crystal is an integrated seed crystal (hereinafter, multi-seed) formed by shaping a single crystal ingot. The multi-seed is more preferable because a seed portion composed of a plurality of seed pieces is formed by cutting out one single crystal ingot, and thus the crystal orientation of each seed portion necessarily matches. That is, there is no danger of twinning even if the single crystals are integrated in the step of enlarging the diameter after dipping each seed portion in the melt to eliminate dislocations.

The third method of the present invention for producing a single crystal is as follows.
The method of manufacturing a single crystal according to the first invention is characterized in that the split growth step includes a step of temporarily reducing the diameter of the single crystal grown at the tip of the seed piece and increasing the diameter again. According to the above configuration, the diameter of the single crystal grown at the tip of the seed piece is reduced once to form a plurality of necks, and then increased to grow a large-diameter single crystal that is integrated again. I have. Thereby, since the integrated single crystal is supported by the plurality of neck portions, the diameter can be sufficiently reduced to a desired diameter, the dislocation can be eliminated, and twinning can occur. Large single crystals can be grown. In addition, since the load capacity of the neck portion increases in proportion to the number thereof, that is, the number of seed pieces, a desired large-diameter single crystal can be safely pulled without causing breakage of the neck portion.

A fourth aspect of the method for producing a single crystal according to the present invention is as follows.
The split growth step includes a step of controlling a pulling speed in accordance with an interval and a diameter of each seed piece of the seed crystal so that the diameter of the single crystal grown at the tip of the seed piece is once reduced and increased again. A method for producing a single crystal according to the first invention, characterized in that: According to such a configuration, by controlling the pulling speed in accordance with the interval and the diameter of each seed piece of the seed crystal, it is possible to favorably control the time when the process is integrated from the split growth process and shifts to the straight growth process. .

The fifth aspect of the method for producing a single crystal according to the present invention is as follows.
The immersion step is a method for producing a single crystal according to the first invention, wherein the tip of each seed piece is arranged and immersed at a position where the melt temperature is substantially the same. In the method for producing a single crystal of the present invention, a seed crystal having a plurality of seed pieces must be simultaneously immersed in a melt to eliminate dislocations and subsequently enlarge the crystal diameter. On the other hand, according to such a configuration, control of the crystal diameter in these steps largely depends on the melt temperature. According to the fifth method for producing a single crystal,
Since the tip of each seed piece of the seed crystal is arranged at a position where the melt temperature is almost equal, the diameter control of various crystals can be advanced under almost the same conditions.

A sixth aspect of the method for producing a single crystal according to the present invention is as follows.
The method of manufacturing a single crystal according to the first invention, wherein the seed pieces are arranged so that the distance between the seed pieces is at least twice the diameter of each seed piece. If the spacing between the plurality of seed pieces is less than twice the diameter of each seed piece, there is a problem that the single crystals are integrated without achieving a sufficient neck portion. According to the above configuration,
Prior to the integration of the single crystal, it is possible to form the neck portion through sufficient diameter reduction and sufficient diameter expansion, so that dislocations can be reliably eliminated and sufficient load bearing capacity can be achieved. Is obtained.

A seventh aspect of the method for producing a single crystal according to the present invention is as follows.
The method of manufacturing a single crystal according to the first invention, wherein the seed crystal is composed of a plurality of seed pieces attached to the shaft portion so as to have the same crystal orientation. According to the above configuration, since the crystal orientations of the plurality of seed pieces of the seed crystal are aligned in the same direction and the seed crystal is attached to one seed holder, the crystal orientations of various crystals can be accurately aligned. In addition, it is possible to grow a single crystal having a large diameter without the possibility of twinning. In addition, since the load capacity of the neck portion increases in proportion to the number of seed pieces, a large-diameter single crystal can be safely pulled up without breaking the neck portion.

Eighth of the method for producing a single crystal according to the present invention,
The method for producing a single crystal according to the first invention, wherein the seed piece is immersed on a concentric circle centered on the axis of the crucible. Control of the crystal diameter in these steps largely depends on the melt temperature. According to the above configuration, since the seed pieces are immersed on concentric circles centered on the axis of the crucible, a plurality of seed pieces are arranged at positions where the melt temperatures are substantially equal, and the seed pieces grow from each seed piece. The control of the diameter of the single crystal can be performed under almost the same conditions.

A ninth aspect of the method for producing a single crystal according to the present invention further includes a step of applying a magnetic field to the melt.
The immersion step is a step of arranging and immersing the plurality of seed pieces so as to be symmetric with respect to the center of the crucible, in the melt in which temperature fluctuation is suppressed by the magnetic field. The method of manufacturing a single crystal according to the first invention. When a magnetic field is applied to the melt as in the method of manufacturing a single crystal by the MCZ method, convection of the melt in a direction perpendicular to the lines of magnetic force is suppressed. According to the above configuration, the plurality of seed pieces are symmetric with respect to the center of the crucible in the melt in which convection in the depth direction of the melt is suppressed by the magnetic field and temperature fluctuation is suppressed. When the seed pieces of the seed crystal are immersed in the melt, the convection in the vertical direction of the melt at each immersion site is suppressed by the magnetic field, and thus the temporal fluctuation of the melt temperature is suppressed. Therefore, diameter control at the time of forming the neck portion is facilitated, and dislocation-free operation is reliably achieved. In addition, since the variation in temperature in the radial direction is suppressed by applying a magnetic field, by disposing each seed piece at a position symmetrical with respect to the center of the crucible, it is possible to reduce the temperature difference between each seed piece. Become.

Further, in a tenth aspect of the method for producing a single crystal according to the present invention, the split growth step is a step of pulling up while rotating the crucible without rotating the seed piece. The step of forming is a step of pulling up while rotating the seed piece and the crucible, and is a method of manufacturing a single crystal according to the first invention.
According to the above configuration, in the split growth step prior to integration,
In order to avoid the formation of ripples on the growth interface due to the rotation, the rotation of the seed crystal (that is, the seed piece) is stopped. And
When the process shifts to the process of forming the straight body portion by integrating, the rotation of the seed crystal is started. This makes it possible to obtain a uniform single crystal having excellent crystallinity.

Further, an eleventh method of manufacturing a single crystal according to the present invention is the method of manufacturing a single crystal according to the FZ method, wherein a plurality of shafts inserted at a predetermined distance from a shaft portion to be fitted into the seed holder are provided. A step of preparing a seed crystal having a seed portion composed of a seed piece, and the tip of the plurality of seed pieces,
Bonding to a polycrystalline rod and forming a plurality of bonded portions, and gradually heating and melting the polycrystalline rod from the bonded portion of the seed pieces, thereby forming single crystals independently from the plurality of seed pieces. A dividing growth step of growing, expanding the diameter of the grown single crystal, and when the single crystal reaches a predetermined distance from the tip of the seed portion, integrate each growing single crystal to form a straight body. Forming step. According to the above configuration, when producing a single crystal by the FZ method, the above-described integrated multi-seed or a seed crystal composed of a plurality of seed pieces attached to a seed holder with the same crystal orientation is used to form a polycrystal. At the end of the rod, a joining portion to be joined with the plurality of seed pieces is formed, and the two are simultaneously heated and fused, and dislocation-free by seed drawing, so that the end of the polycrystalline rod is formed into a plurality of seed pieces. Will be supported. Therefore, the production of a single crystal with a large weight is safely performed.

In a twelfth aspect of the method for producing a single crystal according to the present invention, the step of forming the plurality of joints comprises independently growing a single crystal from the plurality of seed pieces, and When the diameter of the crystal is enlarged, and when the tip of the single crystal reaches a predetermined height from the junction, the tips of the plurality of seed pieces are separated from each other so that the growing single crystals are integrated. A method for producing a single crystal according to an eleventh aspect of the present invention, wherein the method is a step of joining to a tip of a polycrystalline rod having a tip divided and formed corresponding to a piece. According to such a configuration, the divided tip is provided on the polycrystalline rod corresponding to each seed piece, and the tips of the plurality of seed pieces are respectively joined to the divided tip, so that the neck part divided more reliably. Can be formed. Therefore,
Large diameter single crystals can be safely pulled.

The thirteenth method for producing a single crystal according to the present invention.
A twelfth aspect of the present invention is the method for producing a single crystal according to the twelfth aspect, wherein the split growth step includes a step of heating the joints of the seed pieces so that the joints are melted at a uniform temperature. According to the above configuration, since the respective joints of the seed pieces are heated so as to be melted at a uniform temperature, the diameter can be easily controlled at the time of forming the neck, so that dislocation-free operation can be achieved, and a sufficient load bearing capacity Property is obtained.

The fourteenth method for producing a single crystal according to the present invention.
A twelfth aspect of the present invention is the method for producing a single crystal according to the twelfth invention, wherein the seed crystal is an integrated seed crystal formed by shaping a single crystal ingot. According to the above configuration, a multi-seed (integrated seed crystal) having a seed portion composed of a plurality of seed pieces is formed by cutting out one single-crystal ingot, and thus the crystal orientation of each seed portion is inevitable. Therefore, even if each single crystal is integrated in the step of enlarging the diameter after dipping each seed portion in the melt to eliminate dislocations, there is no possibility of twinning. Therefore, a high quality single crystal can be obtained.

The fifteenth method for producing a single crystal according to the present invention.
The method of manufacturing a single crystal according to the twelfth invention, wherein the split growth step includes a step of controlling a heating rate so as to once reduce the diameter of the single crystal grown at the tip of the seed piece and increase the diameter again. It is. According to the above configuration, the diameter of the single crystal grown at the tip of the seed piece is reduced once to form a plurality of necks, and then increased to grow a large-diameter single crystal that is integrated again. I have. At this time, since the heating rate is controlled to optimize the temperature of the melt below the polycrystalline rod, the diameter of the single crystal can be easily controlled, dislocation-free formation can be achieved, and there is no possibility of twinning. Large diameter single crystals can be grown.

The sixteenth method for producing a single crystal according to the present invention
The split growth step includes a step of controlling a pulling speed according to an interval and a diameter of each seed piece of the seed crystal so that the diameter of the single crystal grown at the tip of the seed piece is once reduced and increased again. A method for producing a single crystal according to a twelfth invention, characterized in that: According to the above configuration, by controlling the pulling speed in accordance with the interval and diameter of each seed piece of the seed crystal, it is possible to favorably control the point in time when the process moves from the split growth process to the integrated body growth process. .

The seventeenth method for producing a single crystal according to the present invention.
Means that the distance between the seed pieces is 2 of the diameter of each seed piece.
A twelfth aspect of the present invention is the method for producing a single crystal, wherein the single crystal is arranged so as to be at least twice as large. If the spacing between the plurality of seed pieces is less than twice the diameter of each seed piece, there is a problem that the single crystals are integrated without achieving a sufficient neck portion. According to the above configuration, the interval between the seed pieces is arranged so as to be at least twice the diameter of each seed piece. Through the enlargement, the neck portion can be formed. As a result, dislocations can be reliably eliminated, and sufficient load resistance can be obtained.

The eighteenth method for producing a single crystal according to the present invention.
The twelfth aspect of the present invention is the unit of the twelfth aspect, wherein the seed crystal is formed of a plurality of seed pieces separated from one seed crystal and attached to the shaft portion so as to have the same crystal orientation. This is a method for producing crystals. According to the above configuration, since the crystal orientations of the plurality of seed pieces of the seed crystal are aligned in the same direction and the seed crystal is attached to one seed holder, the crystal orientations of various crystals can be accurately aligned. In addition, it is possible to grow a single crystal having a large diameter without the possibility of twinning. Also,
Since the load capacity of the neck portion increases in proportion to the number of seed pieces, a large-diameter single crystal can be safely pulled up without breaking the neck portion.

The nineteenth embodiment of the method for producing a single crystal according to the present invention.
Is a method for producing a single crystal according to a twelfth invention, wherein the seed piece is immersed on a concentric circle centered on the axis of the polycrystalline rod. Control of the crystal diameter in these steps largely depends on the melt temperature. According to the above configuration, since the seed pieces are immersed on concentric circles centered on the axis of the polycrystalline rod, a plurality of seed pieces are arranged at positions where the melt temperatures are substantially equal, and each seed piece is arranged. The control of the diameter of the single crystal grown from the substrate can be advanced under almost the same conditions.

The twentieth aspect of the method for producing a single crystal according to the present invention.
Further includes a step of applying a magnetic field to the melt, the step of forming the plurality of joints, in the melt suppressed temperature fluctuation by the magnetic field, at the center of the polycrystalline rod A method for manufacturing a single crystal according to a twelfth aspect of the invention, wherein the plurality of seed pieces are arranged so as to be symmetrical with respect to each other and bonded to a lower portion of the polycrystalline rod. When a magnetic field is applied to the melt during the production of a single crystal by the FZ method,
Melt convection in the direction perpendicular to the magnetic field lines is suppressed. According to the above configuration, in the melt in which convection in the depth direction of the melt is suppressed by the magnetic field and temperature fluctuation is suppressed, the plurality of the plurality of melts are symmetric with respect to the center of the polycrystalline rod. Since the seed pieces are arranged, when each seed piece of the seed crystal is immersed in the melt, the vertical convection of the melt at each immersion site is suppressed by the magnetic field, and thus the time variation of the melt temperature is suppressed. . Therefore, diameter control at the time of forming the neck portion is facilitated, and dislocation-free operation is reliably achieved. In addition, since the variation in temperature in the radial direction is suppressed by applying a magnetic field,
By arranging each seed piece at a position symmetrical with respect to the center of the polycrystalline rod, it is also possible to reduce the temperature difference between each seed piece.

In the method for producing a single crystal according to the thirteenth to twentieth inventions, it is the same that the integrated multi-seed is preferably formed from one single crystal ingot.

According to a twenty-first aspect of the present invention, there is provided a seed crystal used for manufacturing a single crystal by the CZ method, wherein a plurality of shafts which are inserted into a seed holder and which are provided at a predetermined interval are provided. And a seed portion comprising a seed piece of According to the above configuration, the seed crystal having the seed portion composed of a plurality of seed pieces provided at predetermined intervals is held by one seed holder, and is used as an integral seed for the production of a single crystal by the CZ method. Used as crystals, the plurality of seed pieces are simultaneously immersed in the melt. Therefore, a plurality of neck portions can be formed uniformly,
Therefore, the neck portion can obtain a load resistance enough to support the integrated large-diameter single crystal. As a result, a large-diameter single crystal can be safely pulled.

A twenty-second invention according to the present invention is characterized in that said seed crystal is an integral seed crystal formed by processing one single crystal ingot.
It is a seed crystal for manufacturing a single crystal of the present invention. According to the above configuration,
Since the seed portion composed of a plurality of seed pieces is formed from one single crystal ingot, the crystal orientation of each seed piece necessarily matches. Therefore, there is no possibility of twinning even if each single crystal is integrated in the step of enlarging the diameter after dipping each seed piece in the melt to make it dislocation-free, and high-quality large-diameter single crystals can be obtained. can get.

According to a twenty-third aspect of the present invention, there is provided a seed crystal used for manufacturing a single crystal by the FZ method, wherein a plurality of shafts which are inserted into a seed holder and which are provided at predetermined intervals are provided. And a seed portion comprising a seed piece of According to the above configuration, the seed crystal having the seed portion composed of a plurality of seed pieces provided at predetermined intervals is held by one seed holder, and is integrated with the production of a single crystal by the FZ method. Used as crystals, the plurality of seed pieces are simultaneously immersed in the melt. Therefore, a plurality of neck portions can be formed uniformly,
Therefore, the neck portion can obtain a load resistance enough to support the integrated large-diameter single crystal. As a result, a large-diameter single crystal can be safely pulled.

[0032]

Next, an embodiment of a method for producing a single crystal according to the present invention will be described with reference to the drawings. FIG.
FIG. 2A is a front view of a seed crystal used in the first embodiment of the single crystal manufacturing method according to the present invention, FIG. 2A is a plan view of the seed crystal, and FIG.
(B) is a bottom view of the seed crystal. As is apparent from these figures, the seed crystal 1 is cut out of a single crystal ingot as an integrally processed product, and a cylindrical shaft portion 1b to be mounted on the seed holder 2 is provided above the flange portion 1a.
Below the flange 1a, two parallel
Seed part 1P composed of two prismatic seed pieces 1c, 1c
Is provided. In addition, each seed piece 1c is not limited to a prismatic shape, and may be a cylindrical shape. The shaft portion 1b has a notch 1 through which a pin 3 for fixing the seed crystal 1 to the seed holder 2 is inserted.
d. The seed holder 2 is made of graphite,
The pins 3 are made of a heat-resistant metal such as molybdenum and tungsten.

FIG. 3 is a schematic vertical sectional view showing a schematic configuration of a lower portion of the single crystal manufacturing apparatus. In a crucible 5 installed inside the chamber 4, a melt 7 of polycrystalline silicon heated by a heater 6 is stored. A diameter monitoring camera 9 is attached to a viewing window 8 provided at an upper part of the chamber 4.
The camera 9 reads the diameter of the growing single crystal, converts it into an electric signal, and inputs it to a control panel (not shown). The control panel adjusts the seed crystal pulling speed so that the diameter of the single crystal becomes a predetermined value in each step of growing the single crystal. In manufacturing a single crystal, the seed crystal 1 shown in FIG. 1 is mounted on a seed holder 2 attached to a lower end of a pulling shaft or a pulling wire (hereinafter referred to as a pulling shaft) 10.
The seed portion 1P of the seed crystal 1 is immersed in the melt 7 in the crucible 5 where the temperature 0 is lowered by about 5 to 20 mm.

FIG. 4 is a graph showing an example of the transition of the number of rotations of the seed crystal axis and the crucible axis, and FIG. 5 shows the progress from the immersion of the seed crystal to the reduction of the diameter of the straight body of the single crystal. It is a schematic diagram. In the method for producing a single crystal according to the present invention, the temperature change applied to the two seed pieces immersed in the melt is minimized, the diameter of the neck part is easily controlled, and
In order to control the two necks equally, the seed pieces 1c,
It is preferable that the temperature difference and the temperature fluctuation range of the melt contact portion 1c be 5 ° C. or less. In addition, the pulling shaft 10 is not rotated, and the crucible 5 is rotated at a low speed (2 rpm or less).

In order to remove dislocations introduced into the two seed pieces 1c and 1c by thermal stress during immersion in the melt, FIG.
As shown in (a), the crystal diameter of each crystal is gradually reduced while raising the pulling shaft 10, and dislocations are released to the surfaces of the neck portions 11, 11 formed by this operation.
The diameter of the neck 11 is controlled to a predetermined value by adjusting the seed crystal pulling speed based on a command signal from the control panel.

In the experimental example, the distance between the two seed pieces 1c and 1c was made 50 mm, and the seed pieces 1c and 1c were immersed in the melt 7 and pulled up by 100 to 150 mm. To 4mm, then 4m in diameter
m and raised about 50 mm.

When the dislocation-free state of the neck portion 11 is completed, the process proceeds to the crystal diameter enlarging step. As shown in FIG. 5 (b), the two necks 11, 11 are raised while raising the lifting shaft 10.
The diameter of the single crystals 12a, 12a grown from is gradually increased. In the above description, the step from the step of immersing in the melt to the step of before the single crystal described below is integrated is referred to as a split growth step. Then, after the two single crystals are integrated into a single crystal 12 as shown in FIG. 5 (c), the process proceeds to a constant diameter process, and the diameter of the single crystal 12 is reduced as shown in FIG. 5 (d). Expand gradually until it reaches the specified size. The rotation of the seed crystal axis is started when it is detected that the two single crystals are integrated. The rotation speed of the seed crystal shaft and the rotation speed of the crucible shaft are gradually increased to predetermined values between the time when the two single crystals are integrated and the diameter becomes constant. According to the graph of FIG. 4, the seed crystal axis rotation speed increased from 0 rpm to 12 rpm, and the crucible shaft rotation speed increased from 2 rpm to 4 rpm.

It should be noted that the pulling speed is set according to the interval between the seed pieces 1c and the maximum length of each seed piece 1c in the interval direction (the length of one side in the interval direction of the seed pieces 1c in FIG. 2). By performing the control, the diameter control can be satisfactorily controlled at the time of transition from the split growth step to the straight body growth step.
By setting the interval between the seed pieces 1c to be at least twice the maximum length of the seed pieces 1c in the interval direction (when the seed piece 1c has a cylindrical shape, the diameter thereof), a sufficient neck portion can be obtained. Can be integrated after forming, and a load-resistant neck can be reliably formed.

FIG. 6 shows a second embodiment of the single crystal manufacturing method according to the present invention.
3A and 3B show a seed holder used in the embodiment, wherein FIG. 3A is a partial perspective view of the seed holder, and FIG. 3B is a bottom view of the seed holder. A shaft portion 13a connected to the lifting shaft is provided at an upper portion of the seed holder 13, and a seed holder body 13b for mounting a seed crystal is provided at a lower portion. On the bottom surface of the seed holder body 13b, there are provided grooves 13c for inserting upper portions of a plurality of seed piece seed crystals cut into a prismatic shape, and pin holes 13d for fixing the upper portions of the seed crystals at predetermined intervals on the side surfaces. Is provided.

FIG. 7 is a perspective view of a seed crystal used in the second embodiment. When, for example, two seed crystals are mounted on the seed holder 13, cutouts 14 a and 14 a are provided on the same side surface of one prismatic seed crystal 14 cut out of a single crystal, and then divided into two at a division position A. . The notch 14a is
It is provided for inserting a pin for fixing the seed crystal 14 to the seed holder 13. After such processing, the seed crystal 14 divided into two is inserted into the groove 13c of the seed holder 13, and a pin is inserted into the pin hole 13d and the notch 14a. In the method according to the second embodiment, one seed crystal 14 is divided into two parts, and is fixed at a predetermined interval with the same mounting direction.
The crystal orientations match exactly, and twinning is prevented as in the first embodiment.

In the first and second embodiments, two seed crystals are immersed in the melt and are arranged on a straight line passing through the center of the crucible and at the same distance from the center of the crucible. When three crystals are used, various crystals are placed at a pitch of 120 ° on the circumference of the same circle centered on the center of the crucible.
In the case of a book, they may be arranged at a 90 ° pitch on the same circle around the center of the crucible.

In the third embodiment of the method for producing a single crystal according to the present invention, two seed crystals are simultaneously immersed in a melt in the production of a single crystal by the MCZ method. As the seed crystal, the one-piece seed crystal described in the first embodiment may be used, or a single seed crystal described in the second embodiment may be divided into two. A transverse magnetic field is applied to the melt to suppress temperature fluctuations due to the natural convection of the melt, and two seed crystals are placed on a straight line that passes through the center of the crucible and is parallel to the line of magnetic force, and then immersed in the melt I do. In the immersion step and the dislocation removal step, as in the first embodiment, the lifting shaft is not rotated, and the crucible is rotated at a low speed (2 rpm or less).

FIG. 8 shows that the melt is 40 for the third embodiment.
FIG. 4 is a plan view showing a melt temperature measurement position when a transverse magnetic field of 00 Gauss is applied, and a magnet is installed at a position opposite to the outside of a chamber (not shown). There are five melt temperature measurement positions, on a straight line passing through the center of the crucible 5, the centers of the magnets 15, 15 and the center of the crucible 5, and on a straight line orthogonal to the straight line and the center of the crucible 5. is there. The melt temperature was measured at a position 30 mm deep from the surface of the melt 7. Table 1 shows the measurement results. When a transverse magnetic field is applied, the temperature difference in the radial direction from the center of the melt becomes larger in the perpendicular direction than in the direction parallel to the application of the magnetic field. Further, the temporal fluctuation of the melt temperature, which is a problem in controlling the diameter of the neck portion, is significantly smaller than that in the case where there is no magnetic field because the convection in the depth direction of the melt is suppressed by applying the transverse magnetic field. In order to suppress temperature fluctuation due to natural convection of the melt, a magnetic field of 500 gauss or more may be applied to the melt.

In this embodiment, the case where a horizontal magnetic field is applied has been described. However, the present invention is not limited to the horizontal magnetic field, but is also applicable to the case where a vertical magnetic field and a cusp magnetic field are applied. When a magnetic field is applied, convection of the melt in a direction orthogonal to the lines of magnetic force is suppressed. Therefore, if the seed pieces are arranged so as to be symmetric with respect to the center of the crucible in the melt in which the temperature fluctuation is suppressed by the magnetic field, when each crystal is immersed in the melt, The convection in the vertical direction of the melt at the site is suppressed, the diameter can be easily controlled at the time of forming the neck portion, and the dislocation-free state is achieved. In addition, it is also possible to suppress a variation in temperature in the radial direction by applying a magnetic field.

[0045]

[Table 1]

The fourth embodiment of the method for producing a single crystal according to the present invention uses a plurality of seed crystals in the production of a single crystal by the FZ method. FIG. 9 is a schematic diagram showing a polycrystalline rod used as a single crystal material and a seed crystal. FIG. 9 (a)
In the same manner as in the first embodiment, the seed crystal 16 is cut out from a single crystal ingot as an integrated product, and two parallel corners are provided above the flange portion 16a at a predetermined interval. A seed portion 16P composed of columnar seed pieces 16b, 16b is erected, and a shaft portion 16c is provided below the flange portion 16a. Further, a polycrystalline rod 17 is provided.

The shaft portion 16c of the seed crystal 16 is attached to the seed holder 18, and the lower portion of the polycrystalline rod 17 is heated and melted by a high frequency induction heating coil as shown in FIG.
After being fused to the seed portions 16b, 16b, the melted portion 19 moves upward while dislocation-free by seed drawing.
The induction heating coil is moved relatively upward. At this time, seed crystal 16 and polycrystalline rod 17 are not rotated.
Alternatively, both may be rotated at the same speed in the same direction. Also, applying a magnetic field of 2000 Gauss or more during seed drawing is effective in eliminating dislocations. Also in this case, the seed crystal 16 and the polycrystalline rod 17 are not rotated. After the end of dislocation-free, seed crystal 16 and polycrystalline rod 17 are rotated at a predetermined rotation speed in the same direction at a constant speed.

The fifth embodiment of the method for producing a single crystal according to the present invention uses a seed crystal in which the growth side end is divided into a plurality in the production of a single crystal by the FZ method. FIG. 10 is a schematic diagram showing a polycrystalline rod used as a single crystal material and a seed crystal. In FIG. 10A, the seed crystal 16 is cut out from a single crystal ingot as an integrally processed product similarly to the seed crystal described in the first embodiment.
A seed portion 16P comprising two parallel prism-shaped seed pieces 16b, 16b parallel to each other at a predetermined interval is provided upright, and a shaft portion 16c is provided below the flange portion 16a. Further, at the lower end of the polycrystalline rod 17, two prism-shaped joints 17a, 17a are cut out at predetermined intervals.

In FIG. 10 (c), the shaft 16c of the seed crystal 16 is attached to the seed holder 18, and the bonding portions 17a, 1a, 1
After heating and melting 7a and fusing it to the seed portion 16P composed of the seed pieces 16b, 16b, the induction heating coil is moved relatively upward while dislocation-free by seed drawing.
At this time, seed crystal 16 and polycrystalline rod 17 are not rotated. Alternatively, both may be rotated at the same speed in the same direction. Also, applying a magnetic field of 2000 Gauss or more during seed drawing is effective in eliminating dislocations. Also in this case, the seed crystal 16 and the polycrystalline rod 17 are not rotated. After the end of dislocation-free, seed crystal 16 and polycrystalline rod 17 are rotated at a predetermined rotation speed in the same direction at a constant speed.

FIG. 10 (b) is a schematic diagram showing another example of the shape of the lower end of the polycrystalline rod 17, as shown in FIG.
The polycrystalline rod 17 may be formed into a conical shape such that the lower end of the rod 7 is branched and the distance between the respective ends becomes a predetermined dimension. Further, the seed holder 18 was provided with a seed crystal holding groove similar to that of the seed holder described in the second embodiment, and one seed crystal was cut into a plurality of pieces and mounted on the seed holder with a uniform crystal orientation. It may be used as a seed crystal.

FIG. 10 (d) shows the joint 1 of the polycrystalline rod 17.
The melts 19, 19 obtained by heating and melting the lower ends of 7a, 17a,
The state where the seed portions 16b, 16b are fused is shown. The melt 19 indicates a molten region formed by heating.

In the conventional large-diameter, heavy-weight single crystal pulling by the CZ method or the FZ method, the holding device is brought into contact with the single crystal during the pulling in order to support the heavy single crystal. However, in the CZ method, when the upper side of the single crystal is gripped by the holding device, the single crystal may be grabbed diagonally or may be shifted. In this case, the contact vibration was applied to the single crystal, and the single crystal collapsed. Also, FZ
In the method, after drawing, the lower side of the single crystal is supported by the holding device in order to increase the weight, but when the single crystal is supported diagonally or eccentrically contacts the holding device, contact vibration occurs in the single crystal. In some cases, single crystal collapse occurred. However, according to the present invention, since the single crystal is supported by the seed crystal having the tip divided into a plurality of pieces, a large weight can be supported as a whole, and a special holding device is not required. As a result, there is no vibration due to contact with the holding device,
The single crystal collapse disappeared.

As described above, according to the present invention, CZ
In growing a single crystal by the FZ method or the FZ method, a single crystal is supported by a plurality of necks formed from a plurality of seed crystals each having a uniform crystal orientation, so that the neck is broken due to an increase in crystal weight. Does not occur, and a single crystal can be grown safely. Further, a special holding device for holding a single crystal having a large diameter and a large weight is not required, so that there is no contact with the holding device, and the single crystal can be prevented from being broken by contact vibration. Note that the structure and control method of the single crystal manufacturing apparatus are not complicated.

[Brief description of the drawings]

FIG. 1 is a front view of a seed crystal used in a first embodiment of a method for producing a single crystal according to the present invention.

FIG. 2 shows the seed crystal of FIG. 1, (a) is a plan view of the seed crystal,
(b) is a bottom view of the seed crystal.

FIG. 3 is a schematic longitudinal sectional view showing a schematic configuration of a lower portion of the single crystal manufacturing apparatus.

FIG. 4 is a graph showing an example of transition of a seed crystal axis rotation speed and a crucible shaft rotation speed.

FIGS. 5A and 5B are schematic diagrams showing steps from immersion of a seed crystal to sizing of a straight body of a single crystal in a stepwise manner, wherein FIG. 5A shows a state at the end of a dislocation removal step, and FIG. (C) shows a crystal integration step, and (d) shows a sizing step.

6A and 6B show a seed holder used in a single crystal manufacturing method according to a second embodiment of the present invention, wherein FIG. 6A is a partial perspective view and FIG. 6B is a bottom view.

FIG. 7 is a perspective view of a seed crystal used in a single crystal manufacturing method according to a second embodiment of the present invention.

FIG. 8 is a plan view showing a melt temperature measurement position when a transverse magnetic field is applied.

9A is a schematic view showing a part of a polycrystalline rod for FZ and a seed crystal as a fourth embodiment of the method for producing a single crystal according to the present invention, and FIG. 9B is the shape of the polycrystalline rod for FZ. FIG. 9 is a partial schematic view showing another example of the embodiment.

10A and 10B are schematic diagrams showing a part of a polycrystalline rod for FZ and a seed crystal as a fifth embodiment of the method for producing a single crystal according to the present invention, and FIG. (C) is a schematic diagram in which a part of an FZ polycrystalline rod and a seed crystal are simultaneously heated and fused, and (d) is another example of the shape of the FZ polycrystalline rod. FIG. 3 is a partial schematic view in which a polycrystalline rod and a seed crystal are simultaneously heated and fused.

[Explanation of symbols]

 1,14,16 seed crystal 1b, 13a, 16c Shaft part 1P, 16P Seed part 1c, 16b Seed piece 2,13,18 Seed holder 3 Pin 4 Chamber 5 Crucible 7,19 Melt 9 Monitoring camera 10 Pulling shaft 11 Neck Part 12, 12a Single crystal 13b Seed holder body 13c Groove 13d Pin hole 14a Notch 15 Magnet 1a, 16a Flange part 17 Polycrystalline rod 17a Joint part

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideo Kumagai 2612 Shinomiya, Hiratsuka-shi, Kanagawa Prefecture Komatsu Electronics Metals Co., Ltd.

Claims (23)

[Claims] 1. A method for producing a single crystal by a CZ method, comprising preparing a seed crystal having a shaft part to be fitted into a seed holder and a seed part comprising a plurality of seed pieces provided at predetermined intervals. And a immersion step of immersing the tips of the plurality of seed pieces in a melt; and a split growth step of independently growing single crystals from the plurality of seed pieces by pulling up the seed crystal. When the diameter of the grown single crystal is enlarged and the tip of the seed portion reaches a predetermined height from the melt surface, the single crystals growing near the melt surface are integrated to form a straight body portion. And producing a single crystal. 2. The method for producing a single crystal according to claim 1, wherein the seed crystal is an integrated seed crystal formed by shaping one single crystal ingot. 3. The method of manufacturing a single crystal according to claim 1, wherein said dividing growth step includes a step of temporarily reducing the diameter of the single crystal grown at the tip of the seed piece and increasing the diameter again. 4. The split growth step includes controlling a pulling speed according to an interval and a diameter of each seed piece of a seed crystal such that a diameter of a single crystal grown at the tip of the seed piece is once reduced and increased again. 2. The method according to claim 1, further comprising the step of:
The method for producing a single crystal according to the above. 5. The method for producing a single crystal according to claim 1, wherein the immersion step is a step of immersing the tip of each seed piece by arranging the tip at a position where the melt temperature is substantially the same. 6. The method for producing a single crystal according to claim 1, wherein the seed pieces are arranged so that an interval between them is at least twice the diameter of each seed piece. 7. The method for producing a single crystal according to claim 1, wherein the seed crystal is composed of a plurality of seed pieces attached to the shaft portion so as to have the same crystal orientation. 8. The method according to claim 1, wherein the seed piece is immersed on a concentric circle centered on the axis of the crucible. 9. A step of applying a magnetic field to the melt, wherein the immersing step is symmetrical with respect to the center of the crucible in the melt in which temperature fluctuation is suppressed by the magnetic field. 2. The method for producing a single crystal according to claim 1, further comprising a step of arranging and immersing the plurality of seed pieces. 10. The split growth step is a step of pulling up while rotating the crucible without rotating the seed piece, and the step of forming the straight body portion includes rotating the seed piece and the crucible. 2. The method for producing a single crystal according to claim 1, wherein the step of pulling is performed. 11. In the production of a single crystal by the FZ method, a seed crystal having a shaft portion to be inserted into a seed holder and a seed portion including a plurality of seed pieces provided at predetermined intervals is prepared. And a step of forming a plurality of joints by fusing the tips of the plurality of seed pieces to a melt formed by heating and melting the lower tip of a polycrystalline rod and bonding the polycrystalline rod to the polycrystalline rod. A split growth step of independently growing a single crystal from each of the plurality of seed pieces by gradually heating and melting the polycrystalline rod from the junction of the seed pieces; and increasing the diameter of the grown single crystal. Forming a straight body portion by integrating the growing single crystals when the single crystal reaches a predetermined distance from the tip of the seed portion. . 12. The step of forming a plurality of junctions includes: independently growing a single crystal from each of the plurality of seed pieces; expanding a diameter of the grown single crystal; When reaching a predetermined height from the junction, a polycrystal having tips formed by dividing the tips of the plurality of seed pieces into pieces corresponding to the seed pieces so that the growing single crystals are integrated. The method for producing a single crystal according to claim 11, wherein the method is a step of bonding to the tip of a rod. 13. The method for producing a single crystal according to claim 12, wherein the split growth step includes a step of heating each of the joints of the seed piece so as to melt at a uniform temperature. 14. The method for producing a single crystal according to claim 12, wherein the seed crystal is an integrated seed crystal formed by processing one single crystal ingot. 15. The single crystal growth method according to claim 12, wherein said division growth step includes a step of controlling a heating rate so as to temporarily reduce the diameter of the single crystal grown at the tip of the seed piece and increase the diameter again. Method for producing crystals. 16. The split growth step includes controlling a pulling speed according to an interval and a diameter of each seed piece of a seed crystal so as to once reduce and increase the diameter of a single crystal grown at the tip of the seed piece. 13. The method for producing a single crystal according to claim 12, comprising a step of performing. 17. The method for producing a single crystal according to claim 12, wherein the seed pieces are arranged so that an interval between the seed pieces is at least twice the diameter of each seed piece. 18. The seed crystal is formed of a plurality of seed pieces separated from one seed crystal and attached to the shaft so as to have the same crystal orientation. 13. The method for producing a single crystal according to item 12. 19. The method for producing a single crystal according to claim 12, wherein said seed piece is immersed on a concentric circle centered on an axis of said polycrystalline rod. 20. The method according to claim 20, further comprising the step of applying a magnetic field to the melt, wherein the step of forming the plurality of joints includes the step of forming the polycrystalline rod in the melt in which temperature fluctuation is suppressed by the magnetic field. 13. The method for producing a single crystal according to claim 12, wherein the plurality of seed pieces are arranged so as to be symmetrical with respect to a center of the polycrystalline rod and joined to a lower portion of the polycrystalline rod. 21. A seed crystal used for producing a single crystal by the CZ method, comprising: a shaft portion to be inserted into a seed holder; and a seed portion including a plurality of seed pieces provided at a predetermined interval. A seed crystal for producing a single crystal, comprising: 22. The seed crystal for producing a single crystal according to claim 21, wherein the seed crystal is an integrated seed crystal formed by shaping a single crystal ingot. 23. A seed crystal used for manufacturing a single crystal by the FZ method, comprising: a shaft portion inserted into a seed holder; and a seed portion including a plurality of seed pieces provided at predetermined intervals. A seed crystal for producing a single crystal, comprising: