JP7427516B2 - Method for producing seeds for polycrystalline silicon production - Google Patents

Description

The present invention relates to a method for manufacturing a seed for producing polycrystalline silicon and a cutting jig for cutting a seed serving as a silicon core rod when producing polycrystalline silicon from a silicon rod.

The Siemens method is known as a polycrystalline silicon manufacturing method. In the Siemens method, a seed (core rod) for silicon deposition is set up in a reduction reaction container, and silicon is deposited on the surface of the seed by a reduction reaction using chlorosilane gas and hydrogen gas or a thermal decomposition reaction. Seeds for silicon precipitation are formed into long shapes by manufacturing from molten silicon by a pulling method or cutting from polycrystalline or single crystal silicon rods (hereinafter simply referred to as silicon rods). is used.

When producing seeds from silicon rods, place a cylindrical silicon rod horizontally on a table, lower the rotary cutting blade from above, and cut parallel to the length of the silicon rod from one end of the rod. By cutting into a plurality of plate-shaped members, the plate-shaped members are further cut perpendicularly to the plane to obtain seeds having a rectangular cross section.

When producing such long seeds, since the silicon rod from which they are cut is a brittle material, it is necessary to prevent cracks or fractures from occurring due to vibrations during cutting.

In Patent Document 1, when supporting a silicon rod on a table, a bottom plate is provided under the silicon rod, a magnet or a backing plate is provided between the side surface of the silicon rod, and a set of comb-shaped The end members are brought into contact with both end faces of the silicon rod via the cushion member, and with these end members pressing the silicon rod in the axial direction, the plurality of plate members are guided between the comb teeth while guiding the cutting blade. It is disclosed that it will be produced. The plate member is further cut into narrow widths to produce a plurality of seeds each having a rectangular cross section.

Further, in Patent Document 2, plate-like members are sequentially cut from the silicon rod while both ends of the silicon rod are held by rod holders, and the silicon rod is cut at 90° or 180° on the axis between two successive cuts. A method is disclosed in which damage to silicon rods and thin rods is avoided in the manufacture of thin rods by rotating the rods without heat treatment.

Patent Document 3 describes an ingot support jig that is placed under the ingot (silicon rod) when it is cut into wafers, and has a concave curved surface that follows the surface shape of the silicon rod, and a plurality of ingot supports that extend along the longitudinal direction of the concave curved surface. A jig made of a hollow structure made of ceramics and having a cavity inside is disclosed.

Japanese Patent Application Publication No. 2010-83743 Japanese Patent Application Publication No. 2012-134489 Japanese Patent Application Publication No. 2007-118354

By the way, if parts of both ends of the silicon rod are simply fixed with a holder as in Patent Document 2, cutting at a portion away from the fixed axis is likely to receive vibrations during cutting. Patent Document 3 discloses a structure of a jig that suppresses distortion and cracking of the wafer due to the stress received from the cutting blade and the distortion of the cutting blade when cutting the ingot with the cutting blade, together with a supporting fixture. Although the jig has a configuration in which the radius of curvature in the radial direction is the same, when cutting a rod-shaped object in the longitudinal direction, the effect of vibration during cutting is different, so it is necessary to devise a fixing method. is necessary.

On the other hand, the cutting method of Patent Document 1 is relatively stable as a fixing method because both ends and side surfaces of the silicon rod are supported by magnets and backing plates. However, the shape may not be uniform, and the diameter of the cross section with respect to the long axis may differ partially, or there may be a slight warp with respect to the long axis, in which case the support may not be sufficient.

The present invention has been made in view of the above circumstances, and is a method for producing seeds for producing polycrystalline silicon by cutting silicon rods in the longitudinal direction. The purpose is to reduce processing defects and improve processing yield.

The method for producing seeds for producing polycrystalline silicon of the present invention includes a slicing step of slicing a silicon rod in parallel along the longitudinal direction to produce a plurality of plate-like members, and cutting the plate-like member in the length direction. A method for producing seeds for producing polycrystalline silicon, comprising: a seed forming step of producing a plurality of seeds for producing polycrystalline silicon having a rectangular cross section,
In the slicing step, the silicon rod is placed horizontally on at least two mounting tables arranged horizontally with an interval in the length direction of the silicon rod, and the silicon rod is lengthened by a cutting blade. It is cut vertically in the axial direction,
The mounting table has a mounting surface formed in a concave shape with a smaller curvature than the outer surface of the silicon rod.

According to this manufacturing method, by placing the silicon rod on a concave placement surface with a curvature smaller than the curvature of the outer surface of the silicon rod, it is possible to reduce vibration in the direction perpendicular to the long axis of the silicon rod. By providing at least two mounting tables at intervals in the length direction of the silicon rod, the silicon rod can be stably supported and a plate-like member with uniform thickness can be produced. .
Moreover, it is possible to hold the cut object when cutting the side portion of the silicon rod by the concave mounting surface, and damage caused by vibration during cutting can be prevented.

In the method for producing seeds for producing polycrystalline silicon, in the slicing step, one side of the silicon rod is cut off by the cutting blade while the silicon rod is placed on the mounting table, and then the cut surface is cut off. The silicon rod may be rotated on a mounting table so as to face upward, and then the silicon rod may be sliced by the cutting blade.

When cutting a silicone rod, cracks or small chips are likely to occur in the silicone rod at the last part where the cutting blade cuts through. Furthermore, as the cutting blade approaches the state where it can cut through, the cut object and the silicon rod become more likely to vibrate, making them more likely to be chipped or cracked. In addition, since one side of the silicon rod is cut into an arcuate surface, depending on the diameter of the silicon rod, it may be difficult to ensure sufficient thickness to form seeds over the entire width direction. Can not. For this reason, if the seed cannot be secured, that part will be removed, but by first cutting off one side and slicing the cut surface upward, there will be a small chip in the part where the cutting blade cuts through. Even if chipping occurs, the chipped portion can be cut and removed in the subsequent seed forming step, so it is possible to suppress a decrease in yield.
Moreover, even in this state of rotation by 90 degrees, the arcuate outer circumferential surface of the silicon rod can be stably supported by the concave mounting surface.

In the method for producing seeds for producing polycrystalline silicon, the curvature of the placement surface is preferably 0.985 times or more and 0.989 times or less of the curvature of the outer peripheral surface of the silicon rod.

If the curvature of the mounting surface exceeds 0.989 times the curvature of the outer peripheral surface of the silicone rod, the gap between the mounting surface and the silicone rod will become smaller, so if the silicone rod is warped, The positioning work when placing the item on the mounting table becomes difficult. If it is less than 0.985 times, the silicon rod placed on the mounting table tends to swing in the direction perpendicular to the long axis direction, which may deteriorate the fixation state during cutting.

In the method for producing seeds for producing polycrystalline silicon, the upper end surface of the mounting table is the same as or lower than the center height position of the silicon rod when the silicon rod is mounted on the mounting surface, In addition, it is preferable that the lower end position of the silicon rod is set higher than the lower end position when one side of the silicon rod is cut off.

Since the top end of the mounting table is the same as or lower than the center height of the silicon rod, the upper part of the concave mounting surface of the mounting table is open, making it difficult to place the silicon rod on the mounting table. becomes easier. Also, when the side of the silicon rod is cut, the cut object falls downward, but since the upper end of the mounting table is set higher than the lower cutting end, it is placed below the silicon rod. Since the surfaces are close to each other and the falling distance of the cut object is reduced, damage during cutting can be prevented.

In the method for producing seeds for producing polycrystalline silicon, in the slicing step, at least two positioning tables for placing the silicon rod and suppressing lateral movement are provided at intervals in the length direction of the silicon rod, It is preferable that the positioning table abuts on two circumferentially spaced locations on the outer circumferential surface of the silicon rod.
By providing a positioning table separately from the mounting table, movement in the vertical direction to the long axis of the silicon rod due to differences in the curvature of the mounting surface of the mounting table and the silicon rod can be suppressed more reliably, improving cutting dimensional accuracy. In addition, the occurrence of chipping during cutting can be further reduced.

In the method for producing seeds for producing polycrystalline silicon, the surface of the positioning table that contacts the silicon rod may be inclined at an angle of 30° or more and 40° or less with respect to the horizontal direction. If the angle of the positioning table is smaller than 30°, the silicon rod will move easily on the positioning table during cutting, and if the angle is larger than 40°, the height position of the silicon rod on the mounting table and the positioning table will be different. It may become difficult to adjust the height position of the silicon rod, and it may become difficult to adjust the stable holding state on the mounting table.
By setting the abutment surface of the positioning table at an inclination angle within this range, the silicon rod can be held more stably.

The mounting table of the present invention is a mounting table on which the silicon rod is placed when manufacturing seeds for producing polycrystalline silicon, and the surface on which the silicon rod is placed is formed into an arcuate surface.

Further, the positioning table of the present invention is a positioning table on which the silicon rod is placed to suppress lateral movement when manufacturing seeds for producing polycrystalline silicon, and the positioning table is arranged at intervals in the circumferential direction of the outer peripheral surface of the silicon rod. Contact surfaces are provided that are inclined in the direction of moving away from each other from the bottom to the top so as to come into contact with two places spaced apart from each other.

According to the present invention, in a method of manufacturing seeds for producing polycrystalline silicon by cutting a silicon rod in the longitudinal direction, processing defects such as cracks and chips are reduced during cutting, and processing yield is improved. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating an embodiment of a method for manufacturing seeds for producing polycrystalline silicon according to the present invention, in which (a) shows a silicon rod before cutting, and (b) shows a silicon rod in which cutting positions in a slicing process are shown by chain lines. , (c) are perspective views showing the plate-like member after the slicing process. FIG. 2 is a front view showing a manufacturing apparatus used in a method for manufacturing seeds for producing polycrystalline silicon. FIG. 3 is a cross-sectional view of the vicinity of the cutting blade of the manufacturing apparatus shown in FIG. 2; FIG. 1 is a perspective view showing an embodiment of a mounting table according to the present invention. FIG. 5 is a side view of the silicon rod placed on the mounting table of FIG. 4; 1 is a perspective view showing an embodiment of a positioning table according to the present invention. FIG. 7 is a side view of the silicon rod placed on the mounting table of FIG. 6; 3 is a side view of an end support used in the manufacturing apparatus of FIG. 2. FIG. It is a sectional view explaining an example of the cutting method of a silicon rod.

EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of the manufacturing method of the seed for polycrystalline silicon manufacturing based on this invention is described with reference to drawings.

The method for manufacturing seeds for producing polycrystalline silicon according to the present embodiment is as follows: A silicon rod 1 of polycrystalline silicon having a substantially cylindrical shape as shown in FIG. There is a slicing step in which a plurality of plate-like members 2 as shown in FIG. ) As shown by the chain lines in ), by further cutting parallel to the direction perpendicular to the direction of the cut surface, a plurality of seeds 3 for manufacturing polycrystalline silicon having a rectangular cross section (for example, about 10 mm square) are produced.Seed formation It has a process.
Among these, in the slicing process, a seed manufacturing apparatus 100 for manufacturing polycrystalline silicon shown in FIG. 2 is used.

This seed manufacturing device 100 has a table 11 that supports a silicon rod 1 on a base 10, and a cutting blade 12 that cuts the silicon rod 1 on the table 11. This device is installed horizontally on top of the silicon rod 1, and lowers a rotating cutting blade 12 from above to cut the silicon rod 1 from one end in parallel to its length direction (long axis direction). A table 11 is supported on the base 10 so as to be movable in the length direction, and on the table 11, a mounting table 30 on which the silicon rod 1 in a horizontal state is placed and the silicon rod 1 are positioned in the left and right direction. A positioning stand 40 and end support stands 51 and 52 for supporting both end faces of the silicon rod 1 are provided, and the cutting blade 12 and its drive mechanism are supported on the base 10.

At least two mounting tables 30 are installed on the table 11 at intervals in the length direction of the silicon rod 1. As shown in FIGS. 4 and 5, the mounting table 30 has a flat lower surface 31 and a concave mounting surface 32 on the upper surface. The mounting surface 32 is formed into a circular arc surface, and its curvature (1/R1) is smaller than the curvature (1/R0) of the outer peripheral surface 1a of the silicon rod 1 to be mounted, and is 0.985 of 1/R0. It is set to more than twice and less than 0.989 times.
Further, the upper end surface 33 of the mounting table 30 is at the same height as or lower than the height position of the center 1b of the silicon rod 1 when the silicon rod 1 is mounted on the mounting surface 32, and the upper end surface 33 is at the same level as the height position of the center 1b of the silicon rod 1. As shown in , it is set higher than the cut lower end position 1d when one side surface portion 1c of one side of both sides of the silicon rod 1 is cut off.

In other words, if the height of the mounting table 30 is H1 and the height to the lowest position of the mounting surface 32 is H2, then when the silicon rod 1 is placed horizontally on the table 11, the height of the mounting surface 32 is the lowest point. The vertical distance (H1-H2) from the lowest position to the highest position of the mounting surface 32 is set to be equal to or slightly smaller than the radial dimension R0 of the silicon rod 1. Further, it is set to be higher than the height H3 of the cut lower end position 1d of the cut surface 1e formed when one side surface portion 1c is first cut off from the substantially cylindrical silicon rod 1.
Note that this mounting table 30 is made of wood, for example.

Although the specific dimensions are not necessarily limited, depending on the diameter size of the silicon rod, for example, the curvature (1/R0) is 0.010/mm to 0.033/mm, and the length L0 is 100 cm to 250 cm. For the following silicone rod 1, the width W1 is 80 mm or more and 250 mm or less, the height H1 is 50 mm or more and 120 mm or less, the length L1 is 50 mm or more and 100 mm or less, and the lowest point from the lower surface 31 to the mounting surface (concave curved surface) 32. The height H2 to the position (lowest point) is set to 10 mm or more and 20 mm or less, and the curvature (1/R1) of the mounting surface 32 is set to 0.024/mm or more and 0.028/mm or less.

As shown in FIG. 7, the positioning table 40 has a V-shape so that the lower surface 41 is a flat surface and the upper surface abuts on two circumferentially spaced locations on the outer circumferential surface 1a of the silicon rod 1. Two inclined surfaces 42 are formed to face each other. These sloped surfaces 42 are sloped so as to be gradually spaced apart from the bottom toward the top, and the slope angle θ1 with respect to the horizontal direction is formed to be 30° or more and 40° or less. The lower ends of both inclined surfaces 42 are connected by a horizontal bottom surface 43.

Although the specific dimensions of the positioning table 40 are not necessarily limited, depending on the diameter size of the silicon rod, for example, for the silicon rod 1 having the above-mentioned dimensions, the width W2 is 80 mm or more and the height H4 is 80 mm or more and 250 mm or less. The length L2 is set to 30 mm or more and 70 mm or less, the length L2 is set to 50 mm or more and 100 mm or less, the height H5 from the lower surface 41 to the bottom surface 43 is set to 10 mm or more and 20 mm or less, and the width W3 of the bottom surface 43 is set to 15 mm or more and 30 mm or less.
Note that this positioning table 40 is made of wood, for example.

Two or more of these mounting tables 30 and positioning tables 40 are installed on the table 11 at intervals, depending on the length of the silicon rod 1, with their axial directions aligned. When installing two at a time, as shown in FIG. 2, it is preferable to arrange the positioning tables 40 at both ends and the mounting table 30 between them.

Then, the silicon rod 1 is placed horizontally on the mounting table 30 and the positioning table 40. Both inclined surfaces 42 of the positioning table 40 abut against the outer circumferential surface 1a of the silicon rod 1. Since the mounting surface 32 of the mounting table 30 is set to have a curvature (1/R1) smaller than the curvature (1/R0) of the outer circumferential surface 1a of the silicon rod 1, silicon can be placed at the lowest position of the mounting surface 32. The outer peripheral surface 1a of the rod 1 contacts in a linear manner along the axial direction. In this case, the silicon rod 1 comes into contact with both inclined surfaces 42 of the positioning table 40 in a line contact state, but in contact with the mounting table 30, it moves from the bottom of the mounting surface 32 to the top, and the outer circumferential surface 1a This is a contact that suppresses movement in the circumferential direction.

Note that two end support stands 51 and 52 are provided on the table 11 with an interval between them, and the silicon rod 1 is supported between them in a pressed state in the longitudinal direction. One of the end face support stands 51 is provided with a pressing mechanism 53, and is capable of pressing the end face of the silicon rod 1. In addition, the end support stands 51 and 52 (only the end support stand 51 is shown in FIG. 8) have grooves 55 for passing the cutting blade 12 that correspond to the thickness of the target plate member 2. A plurality of them are formed at the same pitch.
The cutting blade 12 is formed into a disk shape by, for example, a single blade of a diamond wheel, and is attached to a fixed base 13 fixed on the base 10 via a vertical sliding mechanism 14 and a horizontal sliding mechanism 15. It is supported together with the drive section 16. In this mounting position, the cutting blade 12 is arranged vertically. Note that reference numeral 17 in FIG. 3 is a cover that covers the upper part of the cutting blade 12.

Next, a method for manufacturing seeds 3 from silicon rod 1 using this seed manufacturing apparatus 100 will be described. Manufacturing this seed 3 includes a slicing step in which the silicon rod 1 is sliced to form the plate-like member 2, and a seed forming step in which the plate-like member 2 is further cut to form the seed 3. Each step will be explained below.

(slicing process)
As described above, with the mounting table 30 and the positioning table 40 lined up on the table 11, the silicon rod 1 is placed horizontally on the table 11, and both end surfaces of the silicon rod 1 are supported by the end support tables 51 and 52. Hold it in a pressed state in the long axis direction.
In this state, by moving the table 11 in the long axis direction of the silicon rod 1 while rotating the cutting blade 12, the silicon rod 1 is cut vertically in the long axis direction from one end to the other end of the silicon rod 1. After cutting, return the table 11 to its original position and slide the cutting blade 12 laterally (in the radial direction of the silicone rod 1) at a pitch corresponding to the thickness of the target plate-shaped member 2. Make the cut. This process is repeated one after another to slice the silicon rod 1 into plate shapes. The thickness of the plate member 2 formed at this time is, for example, 5 mm or more and 15 mm or less.

Also, in the first cutting, one side surface 1c of the silicon rod 1 is cut off, but the vertical distance (H1-H2) from the lowest position of the mounting surface 32 to the highest position of the mounting surface 32 is The radius dimension R0 is set to be the same as or slightly smaller than the radius dimension R0. That is, the upper end surface 33 of the mounting table 30 is set to be the same as or lower than the height position of the center 1b of the silicon rod 1 when the silicon rod 1 is placed on the mounting table 30. In addition, since the upper end surface 33 of the mounting table 30 is set to be higher than the lowermost cut position 1d of the cut surface 1e formed when the first side surface 1c of the silicon rod 1 is cut off, The cut object (one side surface portion 1c) falls onto the mounting surface 32. Furthermore, since the difference between the curvature of the mounting surface 32 and the curvature of the outer circumferential surface of the silicon rod 1 is small, the falling distance of the cut object is also small, and no breakage or the like occurs due to the cut object falling.
As a result, it can be expected that the yield (obtaining rate) of collecting seeds from a cut object by cutting one side of the seed will be improved.

The height H1 to the highest point of the mounting surface 32 (the height of the upper end surface 33) is as high as possible, which makes it easier to hold the cut object on the mounting surface 32. Considering the workability when placing the silicon rod 1, the vertical distance (H1-H2) from the lowest position of the placing surface 32 to the highest position of the placing surface 32 should be the same as the radial dimension R0 of the silicon rod 1, or Slightly smaller dimensions are preferred.
After cutting off the first side portion 1c, the silicon rod 1 is sliced while shifting the cutting blade 12 by a predetermined dimension in the diametrical direction of the silicon rod 1, thereby producing a plurality of plate-like members 2.
Note that when cutting the silicon rod 1, the cutting blade 12 may cut a part of the mounting table 30 and the positioning table 40 arranged below the silicon rod 1.

(Seed formation process)
Finally, the plate member 2 is sliced in a direction perpendicular to the surface direction to form a plurality of seeds 3. In this seed forming step, instead of using the single cutting blade 12 shown in FIG. 3, a multi-cutter with a plurality of cutting blades arranged in parallel is used to simultaneously form a plurality of seeds 3 from one plate-shaped member 2. Is possible.

(Other embodiments of slicing process)
Note that after cutting off one side surface 1c of the silicon rod 1, the silicon rod 1 may be sliced sequentially in the same position, but as shown in FIG. 9, after cutting off the first side surface 1c, the silicon rod 1 is After the cutting surface 1e is turned upward by rotating the cutting surface 1e, the cutting blade 12 may be arranged in a direction perpendicular to the cutting surface 1e to perform slicing.

When cutting the silicon rod 1, the silicon rod 1 or the cut object may have small chips ( chipping) is likely to occur. For this reason, if the cutting blade 12 is sequentially sliced while moving the cutting blade 12 in the radial direction after cutting this one side surface portion 1c, there is a risk of chipping occurring at the end of the cut surface of each plate member 2, and if that portion is removed, , the width of the obtained plate member 2 becomes smaller.

On the other hand, the one side surface 1c of the silicon rod 1 has a thickness sufficient to form the seed 3 depending on the size after cutting, since all surfaces other than the cut surface 1e of the resulting cut object are circular arc surfaces. It becomes difficult to secure the entire width in the width direction. For this reason, the number of seeds obtained from the cut object of this one side surface portion 1c also decreases. If such a cut object (a cut object whose surfaces other than the cut surface 1e are all arcuate surfaces) does not change the direction of the silicon rod 1, it will be cut on both sides as shown by 1c and 1f in Fig. 1(b). It is formed.

After first cutting off one side surface 1c, the silicon rod 1 is rotated 90 degrees and the cut surface 1e is sliced upward, so that even if a chip is generated in the part where the cutting blade 12 cuts through, the The portion is the side surface portion (1f) opposite to the first side surface portion 1c, and is the portion that is originally cut and removed, so in the subsequent seed forming process, if the chipped portion is cut and removed. good. As a result, the width of the plate-shaped member obtained by slicing the silicon rod 1 by changing its direction by 90 degrees is larger than that of the plate-shaped member 2 obtained by slicing it in the same direction without changing the direction of the silicon rod 1. It is possible to improve the yield.
In addition, even when the silicon rod 1 is rotated by 90 degrees, the arcuate outer circumferential surface of the silicon rod 1 can be stably supported by the concave mounting surface 32, which prevents chipping during cutting. It becomes difficult. Furthermore, since this reduces defects during processing, it is expected that the seed acquisition rate will also improve.
Furthermore, since the surface of the polycrystalline silicon rod is a deposit resulting from a silicon precipitation reaction, it cannot necessarily be said to be smooth depending on the reaction conditions, and the formation of irregularities on the surface is unavoidable. For this reason, chipping is likely to occur when the cutting blade comes into contact with the outer peripheral surface of the rod during cutting, so in order to reduce the chances of such a situation, when cutting one side of the silicon rod, From the viewpoint of improving seed yield, it is also desirable to perform cutting by rotating 90 degrees and changing the direction.

Next, a confirmation experiment was conducted to confirm the effects of the present invention.
(Example 1)
Assuming that seeds with a square cross section of approximately 7 mm on a side were to be cut from a silicon rod with a diameter of 76 mm and a length of approximately 2 m, the seed acquisition rate was investigated whether or not a mounting table was used. The mounting tables used were placed at positions approximately 60 to 80 cm from both ends of the silicon rod in the longitudinal direction. Also, the specifications of the mounting table are: height (H1) of the upper end surface = approximately 55 mm, length (L1) = approximately 80 mm, width (W1) = approximately 100 mm, height from the bottom surface to the mounting surface (H2) = The diameter was approximately 15 mm and wood was used. In this case, the silicon rod was sliced parallel to the longitudinal direction to form a plurality of plate-like members, and these plate-like members were further cut to produce seeds.
The mounting table used was one in which the ratio of the curvature of the mounting surface to the curvature of the outer circumferential surface of the silicon rod was as shown in Table 1 (curvature ratio). The diameter of the silicon rod is the average value of the diameter at the center in the length direction and the diameter at both ends. Sample No. No. 8 did not use a mounting table.
Check the number of seeds obtained per silicon rod with cracks and chips within the allowable level, and calculate the acquisition rate by setting the number of seeds obtained when cutting without using a mounting table as "1". The number of acquisitions when using is expressed by its index.
The results are shown in Table 1.

As can be seen from Table 1, when performing seed cutting processing from a silicon rod, it was confirmed that by using a mounting table, the seed acquisition rate was improved compared to the case where a mounting table was not used. At that time, if the ratio of the curvature of the mounting surface to the curvature of the outer peripheral surface of the silicon rod of the mounting table used is smaller than 0.985, the seed acquisition rate will improve, but there will be a tendency for the acquisition rate to decrease. Ta. This is because when the curvature ratio decreases, the fixation of the silicon rod by the mounting table becomes weaker when cutting a plate-like member, and this results in less vibration suppression during cutting, making it easier for chips and cracks to occur. Ru.
It is determined that if the percentage of cracks and chips that occur during cutting exceeds the allowable value, the processing yield will be good, and if the percentage is high, the processing yield will be poor. In relation to the above-mentioned acquisition rate, the higher the acquisition rate, the better the processing yield, and the lower the acquisition rate, the worse the processing yield.

(Example 2)
Seeds were cut in the same manner as in Example 1 for a plurality of silicon rods from different manufacturing lots in the silicon rod precipitation reaction, and the seed acquisition rate was confirmed depending on whether or not a mounting table was used. The curvature of the mounting surface of the mounting table used was 0.986 to 0.989 times the curvature of the outer peripheral surface of each silicon rod.
When cutting, one side of the silicon rod is cut off, and then the silicon rod is rotated 90 degrees and sliced with the cut surface facing directly upward to form plate-like members, and each plate-like member is further cut. Seeds were prepared.
The results are shown in Table 2. In Table 2, the acquisition rate average value is the average value of the acquisition rates determined for each lot. The rod side surface acquisition rate is the ratio of seeds acquired from the side surface of the silicon rod, with the case where the mounting table is not used being "1".

As is clear from Table 2, chips such as chipping during seed cutting can occur when using a mounting table, both for multiple lots of silicon rods and for the side parts cut from silicon rods. It was confirmed that the seed acquisition rate was improved.

(Example 3)
A silicon rod was cut in the same manner as in Example 2, using a positioning table as well as a mounting table. The positioning table has two specifications: 33° and 37° inclined surface, height (H4) = approximately 40 mm, length (L2) = approximately 80 mm, width (W2) = approximately 100 mm, bottom surface. The height (H5) from the top to the bottom was approximately 15 mm, and wood was used as the material.
Note that, with respect to the arrangement of the mounting tables in Examples 1 and 2, one positioning table was placed on both ends of the silicon rod (approximately 20 to 30 cm from both ends).
The results are shown in Table 3. The positioning table column shows the angle of the slope. Each acquisition rate is a ratio when the average value of the seed acquisition rate when the mounting table is not used in Example 2 and the average value of the seed acquisition rate from the rod side surface are set to "1".

When cutting seeds from silicon rods, it was confirmed that by using a positioning table in addition to the mounting table, the seed acquisition rate was further improved compared to when cutting seeds using only the mounting table. .

Note that the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention.
For example, although the object to be cut is a polycrystalline silicon rod, the method for producing seeds for producing polycrystalline silicon of the present invention can also be applied to cutting monocrystalline silicon rods and other silicon rods.
Further, although the positioning tables used in the present invention are arranged on both ends of the silicon rod, they may also be arranged between the mounting tables.
Further, the intervals between the mounting table and the positioning table may be set to an appropriate position where the silicon rod can be easily fixed, or an appropriate position where cutting is not hindered.
Moreover, the mounting table and the positioning table do not have to be integrated, but may be formed by assembling several parts processed into one piece.
Further, the mounting table and the positioning table may be coated (Si, SiO ₂ ) or the like on the contact portions to prevent contamination from the pedestal during cutting.
Further, in this embodiment, the mounting table is made of wood, but any material other than wood may be used as long as it absorbs vibrations during cutting, such as resin.
Further, in this embodiment, the mounting table and the positioning table are arranged on the table of the cutting device, but as a method for fixing the mounting table and the positioning table themselves on the table, for example, a fixing jig may be used. By eliminating movement of the mounting table and positioning table, more stable cutting work can be performed.

1 Silicon rod 1a Outer peripheral surface 1b Center 1c One side 1d Lowermost cutting end position 1e Cut surface 2 Plate member 3 Seed (seed for polycrystalline silicon production)
100 Seed manufacturing device 11 Table 12 Cutting blade 30 Mounting table 31 Lower surface 32 Mounting surface 33 Upper end surface 40 Positioning table 41 Lower surface 42 Inclined surface 43 Bottom surface

Claims (6)

A slicing step in which a silicon rod is sliced in parallel along the long axis direction to produce a plurality of plate-like members, and the plate-like member is cut in the length direction to produce a plurality of seeds for producing polycrystalline silicon with a rectangular cross section. A method for producing seeds for polycrystalline silicon production, comprising a seed forming step of
In the slicing step, the silicon rod is placed horizontally on at least two mounting tables arranged horizontally with an interval in the length direction of the silicon rod, and the silicon rod is lengthened by a cutting blade. It is cut vertically in the axial direction,
The method for producing a seed for producing polycrystalline silicon, wherein the mounting table has a mounting surface formed in a concave shape with a curvature smaller than the curvature of the outer surface of the silicon rod. In the slicing step, with the silicon rod placed on the mounting table, one side of the silicon rod is cut off by the cutting blade, and then the silicon rod is placed with the cut surface facing upward. 2. The method of manufacturing seeds for producing polycrystalline silicon according to claim 1, wherein the silicon rod is rotated on a table and then the silicon rod is sliced by the cutting blade. The production of seeds for producing polycrystalline silicon according to claim 1 or 2, wherein the curvature of the placing surface is 0.985 times or more and 0.989 times or less of the curvature of the outer peripheral surface of the silicon rod. Method. The upper end surface of the mounting table is the same as or lower than the center height position of the silicon rod when the silicon rod is placed on the mounting surface, and one side surface of the silicon rod is cut off. 4. The method of manufacturing a seed for producing polycrystalline silicon according to any one of claims 1 to 3, wherein the cutting position is set higher than the lower end position of the cut. In the slicing step, at least two positioning tables for placing the silicon rod and suppressing lateral movement are provided at intervals in the length direction of the silicon rod; 5. The method of manufacturing a polycrystalline silicon seed according to claim 1, wherein the seed contacts the seed at two positions spaced apart from each other in the circumferential direction. Manufacturing a seed for producing polycrystalline silicon according to claim 5, wherein the contact surface of the positioning table that contacts the silicon rod is inclined at an angle of 30° or more and 40° or less with respect to the horizontal direction. Method.

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