TWI467632B - Method of slicing ingot using fret bar for slicing ingot - Google Patents

Description

Ingot block cutting method using ingot for ingot slicing

The present invention relates to a sliver for ingot slicing, an ingot to which the stud is attached, and an ingot using the stud, which are used to cut a cast piece into a wafer shape by a multi-wire saw. method.

In recent years, solar cells that can directly convert light energy into electricity have become more and more aware of environmental protection. They are used as clean and renewable energy sources, and are used in people's livelihood equipment, residential equipment, transportation equipment, and road management facilities. A wide range of areas such as communication facilities. In general, solar cells can be classified into terpenoids, compounds, organics, etc. depending on the type of materials used, and xenon solar cells are currently becoming mainstream due to their excellent power generation efficiency.

The tantalum substrate used in the tantalum type solar cell is thinly cut by a single crystal or polycrystalline tantalum ingot obtained by a crystal pulling method (Churkrasky method), a casting method (casting method), or the like. Wafers are produced by various processes. The size of the ingot for the solar cell of the samarium type is currently 156mm square, and other ingots of various sizes such as 125mm square and 104mm square are produced. Moreover, the shape of the ingot for the solar cell type of the solar cell has a wide range of effective occupied areas in the solar cell module, and the output is good when the ingot is processed into a wafer, and the formation of the corner column is the mainstream.

On the other hand, along with the rapid development of the information and communication field, the semiconductor ingots made of semiconductor materials such as germanium and quartz have occupied the mainstream market from the past 8 吋 (200 mm) to 12 吋 (300 mm). For the next generation, it will progress to 450mm. In order to reduce the manufacturing cost, the large diameter of the ingot for semiconductors has progressed further.

In the method of cutting these ingots into a thin wafer, a multi-wire saw is often used instead of the tool for the inner-circumferential cutting method used in the past. The multi-wire saw is a device in which a metal wire is wound and stretched between a plurality of guide rollers, and the wire is walked in a direction of one direction or back and forth to supply a slurry containing abrasive grains while moving the ingot. The metal wire is pressed against the wire to cut the ingot into a thickness of the metal wire spacing. Since a plurality of wafers can be cut at a time, high-efficiency cutting can be performed. Moreover, due to the small amount of cutting, the material loss during cutting is relatively small, and the utility model can easily correspond to the advantage of large diameter of the ingot.

In the multi-wire sawing system which has been improved in the production of wafers and the like, it has been reported that there is a system in which, for example, a liner plate having a hardness similar to an ingot is used (refer to Patent Document 1).

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-159642

In recent years, as the demand for solar cells has increased, the supply and demand relationship between materials and materials has been distressed. In addition, in order to further expand the utilization range of solar cells, it is necessary to reduce manufacturing costs, and more effective use of materials has become a problem. Because of this situation, people are exploring whether it is possible to minimize the amount of cut-off when cutting a wafer with a multi-wire saw to reduce the material loss at the time of cutting, or to make the thickness of the wafer as thin as possible, thereby increasing the number of times by one time. The number of wafers obtained by the slicing operation is taken to increase the utilization efficiency (yield) of the material. Incidentally, the thickness of wafers cut from ingots for solar cells has been mainstream from the past 320 μm to 180 μm, and it is predicted that the thickness will become thinner in the future.

In order to reduce the thickness of the wafer cut by the ingot, or to make the amount of the cut narrow, to increase the number of wafers obtained by the one-time slicing operation, various methods have been conceived as one of the methods. As far as possible, the diameter of the metal wire is made thinner so that the amount of cutting is narrow, and the method for increasing the material yield is widely studied.

However, in this way, the metal wire diameter of the metal wire is made thin and the wire is easily broken, and it becomes difficult to apply a cutting load required for cutting the ingot to the wire. If the cutting load to be borne by the wire is insufficient, the rigidity required for cutting the ingot cannot be obtained, so that the time required for the slicing process increases, and the work efficiency is lowered. Therefore, there is actually a limit to thinning the wire diameter.

In particular, when the angular column ingot is cut, if the wire diameter is thinned, it is necessary to reduce the cutting load that the wire is burdened. Moreover, it takes time to cause the deflection state of the metal wire required for cutting the ingot, so that work efficiency is also unsatisfactory. Moreover, the positional accuracy of the contact between the metal wire and the ingot is lowered, and the interval between the cut faces is not uniform.

In view of the above problems, an object of the present invention is to provide a novel technology capable of suppressing thickness unevenness between wafers obtained by cutting a cast block with a multi-wire saw, reducing material loss at the time of cutting, and improving the material. Use efficiency and shorten the time required for slicing to improve work efficiency.

In order to solve the above problems, the inventors of the present invention systematically examined the shape of the ingot and the cutting operation of the metal wire, and found that when the multi-wire saw cuts the ingot, most of the metal wires contact the wide surface of the ingot surface at the start of cutting. The lateral sloshing is caused, so that the amount of removal becomes large, resulting in an increase in material loss, and the thickness unevenness between the obtained wafers becomes large, and the state of the metal wire required to cut the ingot is caused by lateral sway, that is, scratching The curved state takes time, which leads to an increase in the slicing operation time. Moreover, such a phenomenon occurs remarkably particularly on the cylindrical ingot having a large contact area with the metal wire.

Here, the inventors of the present invention have continually discussed a method for effectively preventing lateral sway of the metal wire at the start of cutting, and as a result, it has been found that the metal wire can be reduced by minimizing the contact area between the metal wire and the ingot at the start of cutting. The degree of lateral sway, if the corner is started from the corner of the corner ingot, the contact area becomes smaller at the beginning of the cutting, but the cutting distance to the diagonal portion becomes too large, and the time is too long. In view of the discussion, it is considered that the mounting appendage is on the ingot, and it is effective to form a groove on the cutting start, and according to the related idea, a new technology is developed.

That is, the present invention is:

A column for ingot slicing, which is a columnar body attached to a part of the surface of the ingot along the longitudinal direction of the ingot when the ingot is cut by a multi-wire saw;

An ingot which is attached to a part of the surface of the ingot along the length of the ingot; and

A method for cutting an ingot by attaching the column to a part of the surface of the ingot along the length of the ingot and starting the cutting of the column first.

According to the present invention, when the cutting of the multi-wire saw is started, the metal wire and the column for ingot slicing according to the present invention are in contact on a narrow area to form a groove in the column, so that the lateral sway of the metal wire is reduced. As a result, the amount of removal is reduced, and the utilization efficiency of the material is improved. Moreover, since the lateral sway is prevented, the metal wire can be deflected in a shorter time, and the time required for slicing is shortened. And the resulting thickness unevenness between wafers is reduced.

Thus, the present invention reduces the material loss at the time of cutting, reduces the uneven thickness between the wafers, and improves the work efficiency, so it is very effective in achieving reduction in manufacturing cost, improvement in wafer thickness uniformity, and improvement in productivity. .

Best form for implementing the invention

Specific embodiments of the present invention will be described in detail below with reference to the drawings. Fig. 1 is a schematic front view showing an example of a state in which a column for ingot slicing of the present invention is attached to the surface on the cutting start side of the ingot, and Fig. 1 shows a 1 series ingot and a 2 column ingot for ingot casting. 4 is a schematic cross-sectional view showing an example of a state in which the column for ingot slicing of the present invention is attached to the opposite side of the ingot, and FIG. 5 is a view showing the ingot block of the present invention attached to the corner of the ingot. A schematic cross-sectional view of an example of the state of the bar, a 1 series ingot in Figs. 4 and 5, a column in the 2 series ingot block, and a 3 line metal wire.

The ingot 1 for cutting the object may be an ingot for a solar cell or an ingot for a semiconductor. Specifically, it is composed of a material such as a single crystal or a polycrystalline germanium, quartz, crystal, sapphire, GaP or InP compound semiconductor, and has a shape of a prismatic shape (a quadrangular prism, an octagonal prism, etc.), a cylindrical shape, or the like. Piece. However, as described above, in view of the gist of the present invention, the effect of the column for ingot slicing is to make the contact area with the metal wire narrow at the start of cutting, which is not suitable for the contact area with the metal wire at the start of cutting. That is, a small cylindrical ingot is suitable for an ingot having a large angular contact shape with a metal wire. Therefore, it is usually used in an ingot for a solar cell having a prismatic shape. The viewpoint of the effect of the invention is appropriate.

When the inner peripheral cutting method is used for slicing, the blade thickness needs to be increased as the diameter of the ingot is increased, and once the blade thickness becomes larger, the amount of cutting is inevitably increased, resulting in a large material loss. Therefore, it has been difficult to apply the inner peripheral cutting method to a cylindrical ingot having a diameter of 300 mm or more, but the present invention can also be effectively applied to a cylindrical ingot having a diameter of 300 mm or more which is difficult to cut by the inner peripheral cutting method.

The column 2 for ingot slicing according to the present invention is a columnar body for contacting a metal wire at the beginning of cutting to form a slit when the ingot is cut by a multi-wire saw, thereby preventing the metal wire from being cut. Lateral swaying causes the metal lines to be uniform along the uniform spacing and rapidly causes the state of the metal wire required to cut the ingot, that is, the state in which the metal wire is deflected.

The shape of the column 2 for ingot slicing needs to be attached to the shape of the surface of the ingot. For example, at least a part of the outer circumference of the section when cut perpendicularly to the length of the column for the ingot slicing is a straight line. The shape or shape of the arc is concave. Specifically, although a triangular column shape or a quadrangular column shape has been exemplified, the smaller the contact area between the point and the metal wire at the start of cutting, the smaller the lateral sway of the metal wire, and the fact that the groove is preferably formed quickly, and the triangular column shape is good. When it is a square column shape, as shown in FIG. 1, on the surface of the ingot which is one side of the cutting of the multi-wire saw, if the column for ingot slicing is attached, it is cut perpendicular to the ingot. When the direction of the length of the column is cut, the profile is preferably high (h in Fig. 1) 3 to 20 mm, 3 to 10 mm is better, and width (w in Fig. 1) is 3 to 20 mm, and 5 to 10 mm is better. Rectangular. If the height exceeds 20 mm, the slicing time will be extended to more than necessary, and if the width is less than 3 mm, it will be difficult in terms of formability and handling. When the thickness exceeds 20 mm, the contact area with the metal wire becomes large, and the effect of the present invention cannot be obtained. fully use. In addition, the length of the ingot for ingot slicing 2 may be appropriately determined depending on the length of the ingot to be cut.

As shown in FIG. 4, when the ingot for ingot slicing of the present invention is attached to the opposite side surface adjacent to the surface of the ingot to be cut, and the shape of the ingot for ingot slicing is a square column shape, When the cutting is perpendicular to the direction of the length of the bar for cutting the ingot, the cross section is preferably 5 to 50 mm, more preferably 10 to 40 mm, and 8 to 16 mm in width, and more preferably 5 to 10 mm.

As shown in FIG. 5, when the ingot for ingot slicing of the present invention is attached to the outer periphery of the ingot, and the shape of the ingot for ingot slicing is a quadrangular column, the column is cut perpendicular to the ingot. When the direction of the longitudinal direction is cut, the profile is preferably 5 to 50 mm high, 10 to 40 mm is more preferable, and the width is 8 to 16 mm, and 5 to 10 mm is more preferably rectangular.

Figure 2 shows various aspects of the ingot for ingot slicing. (a) is a schematic illustration of the column in the form of a triangular column, (b) is a schematic illustration of the column in the shape of a square column, and (c) is a schematic illustration of the column in a convex shape.

The ingot block sliver 2 is attached to a part of the surface of the ingot along the length direction (axial direction) of the ingot. For example, as shown in Fig. 1, the surface of the ingot block 2 in the surface of the ingot is attached to the surface of the ingot on the cutting start side. At this time, the position of the ingot block 2 for the ingot block is attached to the surface of the ingot on the cutting start side, and as shown in FIG. 1, the central portion of the ingot surface on the cutting start side or one or both edges may be used. nearby. Further, when attached to the vicinity of both edges, two ingots for slicing are used.

And the aspect of the ingot for ingot slicing is attached to the surface of the ingot on the cutting start side, and is exemplified as shown in FIG. 4, adjacent to the surface of the ingot which is one side of the cutting of the multi-wire saw. Each of the opposite sides of the surface is attached to each of the columns one by one, so as to exceed the respective corners formed by the surface of the ingot and a pair of the opposite sides; more illustratively, as shown in FIG. Separating each corner surface formed by the surface of one of the opposite sides of the ingot side adjacent to the surface of the ingot which is cut off from the side of the multi-wire saw, and each of the corners formed on the surface of the incision starting side, respectively The strips are in the form of these corners (planar or curved). When the ingot is sliced and attached to the opposite side of the surface of the ingot starting from the cutting, the ingot of the ingot is preferably attached to the ingot, and the ingot is sliced with the column. (Protruding) 0.3 to 10 mm by the surface of the ingot which is cut off and the corner formed by the opposite side of one of the surfaces of the ingot.

In order to attach the ingot and the column 2, it is sufficient to use an appropriate adhesive in consideration of such materials, costs, and the like. In addition, a satin, a concave strip, or the like is formed in advance on the ingot-attaching surface of the ingot for ingot slicing 2 to strengthen the adhesion with the adhesive, so that the adhesive remains in the casting when it is separated from the ingot 1. The motivation for reducing the possibility of the block 1 side is preferable. Further, the bar for ingot slicing illustrated in Fig. 2 does not have a curved surface, and it is understood that it is mainly used for a prismatic ingot.

Regarding the material of the column 2 for ingot slicing, it is preferable to appropriately select the adhesion of the adhesive, and it is cost-effective, and specific examples thereof include glass, carbon, synthetic resin, ceramics, and the like. It is preferred that the adhesion of the adhesive or the cost should be glass, and in particular, it should be frosted glass.

On the other hand, the bar which is cut by the thickness of the workpiece is also thinned, and when it is cut, it is broken and mixed into the cutting liquid, and then the cutting portion is further broken to cause an accident. Synthetic resin is better.

Next, a method of cutting an ingot using a column for ingot slicing according to the present invention will be specifically described with reference to FIG. Fig. 3 is an explanatory view showing a state in which a corner cylindrical ingot to which an ingot block is attached is cut and cut using a multi-wire saw.

Although a multi-wire saw is used for cutting the ingot, the multi-wire saw is conventionally known, and is not particularly limited.

The multi-wire saw illustrated in Fig. 3 is formed by winding a thin metal wire (piano wire) 3 at a pitch of a plurality of grooves provided on the three metal wire guiding rollers 4A, 4B, 4C at the ends thereof. The portion is wound on a cylinder (not shown).

In the cutting process, first, the ingot slicing is attached to a part of the surface of the ingot in the longitudinal direction of the ingot (axial direction). For example, as shown in Fig. 3, the ingot slicing column 2 is attached to a part of the ingot surface on the side of the multi-wire saw starting from the axial direction of the ingot 1 (in the vicinity of the center portion in Fig. 3).

Thereafter, as shown in FIG. 3, the ingot 1 of the liner sheet 6 adhered to the susceptor 5 by the adhesive is moved downward to be pressed against the metal wire between the horizontally disposed metal wire guiding rollers 4A, 4B. The cutting liquid (slurry) 7 in which the abrasive grains are dispersed is supplied to the contact portion of the metal wire 3 and the ingot block sliver 2 continuously and simultaneously cut. The metal wire 3 which is driven in one direction or back and forth by a driving motor (not shown) abuts against the ingot block sliver 2 attached to the ingot 1 at the start of cutting, thereby exerting a pressing force. And by the grinding action generated by the abrasive grains, the column is first cut to form a slit, and then the ingot 1 is cut. The formation of the slit in the above-described pillars at the start of the cutting is a feature of the present invention, and the thickness accuracy is improved and the material loss is reduced, and the work efficiency is improved.

In addition, as described above, each of the columns may be attached one by one to each of the opposite side surfaces adjacent to the surface of the ingot which is cut off on the side of the multi-wire saw, so that they respectively exceed the borrowing Each of the corners formed by the surface of the ingot and a pair of the opposite sides (refer to FIG. 4) may also be opposed to each other by a pair adjacent to the surface of the ingot which is cut off from the side of the multi-wire saw Each of the side surfaces is chamfered from each corner formed by the surface of the ingot on the cutting start side, and each of the studs is attached to the corner surfaces (planar or curved surface) one by one (refer to FIG. 5). Thereafter, in the same manner as described above, the bars are first cut at the same time by the wire 3 to form a slit, and then the ingot 1 is cut.

The material of the metal wire 3 is usually a piano wire containing about 0.8 to 0.9% by mass of carbon. Further, the diameter of the metal wire 3 is usually from 140 to 180 μm, but according to the present invention, the diameter thereof may be as small as 80 to 120 μm.

The laying sheet 6 is shaped to make it suitable for the surface shape of the ingot 1. When the ingot 1 has a prismatic shape, the adhesive surface of the laying plate 6 is formed into a flat surface, and if it is a cylindrical shape, it is formed into an arc-shaped concave surface. The satin, the concave strip, or the like is formed on the adhesive surface of the backing plate 6 in advance to strengthen the adhesion with the adhesive, so that the possibility of the adhesive remaining on the side of the ingot 1 when separating from the ingot 1 is reduced. In terms of motivation, it is preferred.

In the example shown in FIG. 3, although the multi-wire saw has been shown to press down the ingot 1 and abut the type of the most tight metal wire 3, it may be reversed by 180°. The type in which the ingot is pushed up and abuts against the type, and is pressed in a lateral direction by a 90° rotation.

Although the example in which the three metal wires are used to guide the rollers has been shown in FIG. 3, it may be a case where two metal wires guide the rollers or four or more.

The supply of the cutting liquid 7 may be carried out from both sides of the ingot 1, or may be supplied from the side of the metal wire 3 toward the ingot 1 (from bottom to top in Fig. 3), and is not particularly limited.

Thus, the ingot is sliced into a wafer by a multi-wire saw, and the ingot slicing column attached to the surface of the ingot is also sliced at the same time. The sliced ingot for slicing is discarded from the wafer, but it may be re-used, melted, etc., and then molded into a column for ingot slicing for reuse.

[Examples]

The present invention will be specifically described below by showing examples and comparative examples, but the present invention is not limited to the following examples.

Example 1

A polycrystalline tantalum ingot (156mm square, 200mm long) for solar cells prepared with a square column, with a cross section of the adhesive which is cut perpendicularly to the longitudinal direction thereof, is 5 mm high and 10 mm wide, and has a length of 200 mm. The ingot block for the ingot block of the rectangular columnar synthetic resin column is attached to the vicinity of the center portion of the surface of the ingot on one side of the cutting of the multi-wire saw along the longitudinal direction of the ingot (refer to FIG. 3). .

As shown in Fig. 3, the thus obtained ingot was sliced by a multi-wire saw of a piano wire. The experimental conditions at this time were an average traveling speed of the metal wire of 600 mm/min, a wire tension of 22 N, a cutting speed of 0.35 mm/min, a wire diameter of 0.12 mm, and a pitch between the wires of 0.34 mm.

As a result, the resulting wafer had a thickness of about 0.18 ± 0.010 mm, a cut-off amount of about 0.16 ± 0.010 mm, and a time required from the start to the end of the cut to about 443 minutes.

Example 2

A polycrystalline tantalum ingot (156 mm square, 200 mm long) for a solar cell for a square column is prepared, and each of the sections is cut by a length of 7 mm and a width of 3 mm in the direction perpendicular to the longitudinal direction along the longitudinal direction of the ingot. A bar of a cast piece having a rectangular shape and a length of 200 mm and a columnar synthetic resin columnar body of 200 mm in length, attached to one side of the ingot side adjacent to the surface of the ingot which is cut off from the side of the multi-wire saw. Each surface was caused to extend by 0.4 mm from each of the corners formed by the surface of the ingot and the pair of opposite sides (see Fig. 4).

The thus-obtained ingot was sliced by a multi-wire saw of a piano wire as shown in FIG. The experimental conditions at this time were an average traveling speed of the metal wire of 600 mm/min, a wire tension of 22 N, a cutting speed of 0.35 mm/min, a wire diameter of 0.12 mm, and a pitch between the wires of 0.34 mm.

As a result, the obtained wafer had a thickness of about 0.18 ± 0.010 mm, and the amount of cut was about 0.16 ± 0.010 mm, and the time required from the start to the end of the cutting was about 442 minutes.

Example 3

A polycrystalline tantalum ingot (156 mm square, 200 mm long) for a solar cell for a square column is prepared, and the cross section of each of the ingots is cut along the longitudinal direction of the ingot by a length of 7 mm and a width of 4 mm. a column for ingot block slicing having a rectangular shape and a length of 200 mm, and a columnar synthetic resin columnar body, which is attached to each of the corners of the ingot surface adjacent to one side of the multi-wire saw starting to cut. c (chamfer) surface (see Figure 5).

As shown in Fig. 5, the thus obtained ingot was sliced by a multi-wire saw of a piano wire. The experimental conditions at this time were an average traveling speed of the metal wire of 600 mm/min, a wire tension of 22 N, a cutting speed of 0.35 mm/min, a wire diameter of 0.12 mm, and a pitch between the wires of 0.34 mm.

As a result, the obtained wafer had a thickness of about 0.18 ± 0.010 mm and a cut amount of about 0.16 ± 0.010 mm, and the time required from the start to the end of the cutting was about 441 minutes. Further, although not described in the present embodiment, in the case of such an aspect, the adhesive side of the ingot slicing column is fitted to the c-curved surface and recessed to obtain a highly stable attachment.

Comparative example 1

A polycrystalline tantalum ingot (156 mm square, 200 mm long) for a solar cell of a square column was prepared, and the ingot was sliced in the same manner and in the same manner as in Example 1 except that the ingot for ingot slicing was not used.

As a result, the obtained wafer had a thickness of about 0.18 ± 0.015 mm, a cut amount of about 0.16 ± 0.015 mm, and a time required from the start to the end of the cutting to be about 445 minutes.

From the above results, it was confirmed that the amount of cut-off was small according to the present invention, the unevenness in thickness between wafers was lowered, and the time required for slicing was shortened.

1. . . Ingot

2. . . Ingot slicing

3. . . metal wires

4A, 4B, 4C. . . Metal wire guide roller

5. . . Pedestal

6. . . Lining plate

7. . . Cutting liquid (slurry)

h. . . high

w. . . width

Fig. 1 is a schematic plan view showing an example of a state in which the column for ingot slicing of the present invention is attached to the surface on the cutting start side of the ingot.

Fig. 2 is an explanatory view showing various aspects of the column for ingot slicing, (a) a schematic view of the column in the form of a triangular column, (b) a schematic view of the column in the shape of a quadrangular column, and (c) A schematic illustration of the bar with a convex profile.

Fig. 3 is an explanatory view showing a state in which a corner cylindrical ingot of a column for ingot slicing is attached and cut by a multi-wire saw.

Fig. 4 is a schematic cross-sectional view showing an example of a state in which the column for ingot slicing of the present invention is attached to the opposite side surface of the ingot.

Fig. 5 is a schematic cross-sectional view showing an example of a state in which a column for ingot slicing of the present invention is attached to a corner of an ingot.

1. . . Ingot

2. . . Ingot slicing

h. . . high

w. . . width

Claims (5)

A method for cutting an ingot, which is attached one by one to each surface of a pair of opposite sides of the ingot adjacent to the surface of the ingot which is cut off from the side of the multi-wire saw, one by one, so as to exceed By injecting the corners of the ingot surface and the pair of opposite sides, and simultaneously starting to cut the pillars, the ingot for ingot slicing is: when the square pillar ingot is cut by a multi-wire saw, A slit is formed at the beginning of the cutting, and a columnar body attached to a part of the surface of the ingot along the length of the ingot. An ingot cutting method, which is used to attach each ingot block to a corner surface adjacent to the surface of the ingot which is one side of the multi-wire saw starting to cut one by one, so that the ingot is included The plane of the surface of the ingot at the cutting start side protrudes more from the side of the wire saw, and at the same time, the cutting of the column is started. The bar for slicing the slice is: when cutting the square column ingot with a multi-wire saw, in order to cut A slit is formed at the beginning of the break, and a columnar body attached to a part of the surface of the ingot along the length of the ingot. The ingot cutting method according to claim 1 or 2, wherein the ingot for ingot slicing is a triangular column or a quadrangular column. An ingot cutting method according to claim 1 or 2, wherein the ingot for ingot slicing is made of synthetic resin. The ingot cutting method according to claim 1 or 2, wherein the ingot for ingot slicing forms a satin or a concave strip on the attachment surface to the ingot.