JP2006073768A - Processing method of silicon wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon wafer processing method which is capable of cutting out silicon blocks or silicon stacks in vertical and horizontal directions efficiently without leaving a residual stress, chippings or the like on the surfaces of the silicon blocks or the silicon stacks. <P>SOLUTION: The silicon wafer processing method is characterized by processes of pasting a grid-like cutting guide which can be attracted by a magnet on the one side of a silicon ingot which is used for manufacturing silicon wafers, mounting and setting the side of the silicon ingot on which the cutting guide is attached on a table equipped with a built-in magnet, cutting out the silicon blocks from the silicon ingot along the cutting guide with a dicing saw in the shape of a grid of prescribed size, subjecting the end faces of the silicon blocks cut out from the silicon ingot to an etching treatment, and then slicing the silicon block subjected to etching into the silicon wafers. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for processing a silicon wafer, and more particularly to a polishing technique for flattening minute irregularities present on a side surface of a silicon block.

The demand for silicon wafers is increasing year by year with the spread of solar cells and the like. In particular, in the case of a solar cell, a single solar cell module is manufactured using about 54 rectangular silicon wafers having a side of 5 inches, so that the amount used is larger than the amount of silicon wafers such as IC and LSI. It is enormous.

Such a silicon wafer includes a polycrystal and a single crystal, and is manufactured by the following method. For the polycrystalline silicon wafer, a rectangular polycrystalline silicon ingot 101 is manufactured, and a large number of rectangular polycrystalline silicon blocks 105 are cut out from the polycrystalline silicon ingot 101 using a band saw 103 or the like (see FIG. 10). The polycrystalline silicon block 105 is manufactured by slicing (see FIG. 11). 10 and 11, reference numeral 107 denotes a side surface of the silicon block, and 111 denotes a silicon wafer.

A single crystal silicon wafer is a cylindrical single crystal silicon block having an appropriate size (usually 40 to 50 cm) from a cylindrical silicon ingot (usually 1 m or more in length) obtained by a pulling method. Then, a flat portion called orientation flat is ground, and this single crystal silicon block is further sliced.

When processing either a polycrystalline silicon block or a single crystal silicon block, grinding is performed when high dimensional accuracy of the silicon wafer is required. Specifically, grinding is performed by rotating a circular grindstone including abrasive grains or a diamond wheel (polishing wheel) at high speed, pressing a silicon block against the wheel, and moving the silicon block relative thereto.

In conventional silicon wafer manufacturing processes, processing has been carried out to increase the dimensional accuracy of silicon blocks or silicon stacks, or to eliminate surface undulations. The flattening process was not performed. Therefore, the side surface (also referred to as an end surface or an outer peripheral surface) is further processed on the silicon wafer thus obtained. The end surface treatment is performed by grinding the end surfaces of the silicon wafers one by one into a predetermined shape as in the glass substrate processing described in JP-A-10-154321 (see Patent Document 1) or by chemical polishing (etching). Etc.

In the case of silicon wafers for solar cells, the amount of silicon wafers is enormous compared to the amount of silicon wafers used in ICs and LSIs. It is expected that labor will be spent and the supply will not be able to keep up with demand industrially. In addition, the etching process requires a waste liquid treatment facility with a high treatment capacity, and this also causes a problem of facility costs.
On the other hand, if the silicon wafer end face treatment is not performed, in the case of a silicon wafer used for a solar cell, there is a problem that cracks occur in the subsequent processes, and the yield of the product is lowered, and an efficient end face Development of a processing method has been desired.

Therefore, in Japanese Patent Application Laid-Open No. 2004-6997 (see Patent Document 2), the surface roughness Ry is 8 μm or less (preferably 6 μm or less), more specifically, to improve the dimensional accuracy or eliminate the surface waviness. In addition, it has been proposed to planarize the side surface of a silicon block or silicon stack by polishing.
JP-A-10-154321 Japanese Patent Laid-Open No. 2004-6997

However, when the side surface of the silicon block or silicon stack is flattened by polishing, there is a problem that residual stress or chipping due to polishing remains on the surface of the silicon block or silicon stack.
Further, in the silicon wafer manufacturing process, it is necessary to increase the dimensional accuracy when the silicon block or the silicon stack is cut to a predetermined size. However, the conventional cutting process has a problem that it is difficult to sufficiently increase the size system, and the silicon block or the silicon stack cannot be efficiently cut vertically and horizontally.
Accordingly, the present invention provides a method for processing a silicon wafer in which residual stress, chipping or the like does not remain on the surface of the silicon block or silicon stack, and the silicon block or silicon stack can be efficiently cut vertically and horizontally. It is what.

That is, according to the silicon wafer processing method of the present invention, a cutting guide that can be attracted to a magnet is pasted on one side of a silicon ingot for manufacturing a silicon wafer in a grid shape, and the cutting guide mounting surface of the silicon ingot is a table having a magnet built therein. Mounted on and attached, and after cutting the silicon block into a predetermined size with a dicing saw along the above cutting guide, the end surface of the cut silicon block is etched, and then sliced to obtain a silicon wafer It is characterized by that.

According to the silicon wafer processing method of the present invention, the cutting guide that can be attracted to the magnet is stored in a grid-like manner in advance in an alignment jig having a storage portion that can store the cutting guide at a predetermined position. It is also characterized in that the cutting guide and the silicon ingot stored in the alignment jig are brought into contact with each other and adhered using an adhesive.

According to the silicon wafer processing method of the present invention, the table is rotatable at an angle of at least 90 degrees, a silicon ingot mounted and mounted on the table is cut in a predetermined direction, and then the table is rotated by 90 degrees. It is also characterized in that it can be cut in a direction perpendicular to the previous cutting direction.

The method for processing a silicon wafer according to the present invention is characterized in that the etching treatment is etching with an acid.

Since the present invention is configured as described above, there is no residual stress or chipping remaining on the surface of the silicon block or silicon stack, and the silicon wafer processing method can efficiently cut the silicon block or silicon stack vertically and horizontally. It became possible to provide.

Embodiments of a method for processing a silicon wafer according to the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a schematic perspective view of a silicon wafer cutting method according to the present invention, FIG. 2 is an exploded perspective view showing a state in which a cutting guide is stored in an alignment jig, and FIG. 4 is a schematic cross-sectional view thereof, FIG. 5 is a schematic perspective view of the cutting guide set on a silicon block, FIG. 6 is a schematic cross-sectional view thereof, and FIG. FIG. 8 is a schematic sectional view showing a state in which the block is cut, FIG. 8 is a schematic view showing a method for slicing a silicon wafer from a silicon block, and FIG. 9 is a block diagram showing a method for processing a silicon wafer according to the present invention.

In FIG. 1, a cutting guide 3 that can be attracted to a magnet is pasted on the bottom surface of a silicon ingot 1 for manufacturing a silicon wafer in a grid shape, and the mounting surface of the cutting guide 3 of the silicon ingot 1 is placed on a table 5 containing a magnet. It is mounted and attached. Then, the silicon ingot 1 is cut into a predetermined size in a grid shape, preferably with a disc-shaped dicing saw 7 along the cutting guide 3.

As the cutting guide 3 that can be attracted to the magnet, a material made of a ferromagnetic material such as iron (Fe), cobalt (Co), nickel (Ni) or an alloy containing them as a main component is used. Preferably used.
Further, as the table 5 incorporating magnets, magnets can be arranged on the entire surface of the table 5 or magnets can be arranged at predetermined intervals corresponding to the respective cutting guides 3. In this manner, the cutting guide 3 that can be attracted to the magnet can be attracted to the upper surface of the table 5 with a predetermined gap maintained.

As shown in FIG. 7, when the silicon ingot 1 is cut into a grid shape with the disc-shaped dicing saw 7 along the cutting guide 3, the tip of the disc-shaped dicing saw 7 enters between the left and right cutting guides 3. There is no possibility that the disc-shaped dicing saw 7 may damage the upper surface of the table 5 or the blade of the disc-shaped dicing saw 7 may be damaged.

2 to 6 show a procedure for attaching the cutting guide 3 that can be attracted to the magnet to the silicon ingot 1. The alignment jig 11 shown in FIGS. 2 to 5 includes a jig body 13 including a storage portion 15 that can store the cutting guide 3 in a predetermined position in advance, and a lid body 17.
2 and 3, the cutting guides 3 that can be attracted to the magnet are respectively stored in the storage portions 15 between the partitions 19 formed in a grid shape of the jig main body 13, and the lid body 17 is put on the lid. A small screw 25 is screwed into a screw hole 23 provided in the cutting guide 3 from a screw hole 21 provided in the body 17 to integrate them.
The lid body 17 is provided with screw holes 21 in four directions, but the cutting guide 3 is formed with a pair of screw holes 23 only on one diagonal line. In this way, when the size of the silicon block to be obtained is different, the screw guide on the one diagonal line and the screw hole on the other diagonal line are appropriately selected and the cutting guide 3 is attached. It is possible to quickly cope with changes in the system. Naturally, in that case, the interval between the cutting guides 3 is narrowed or widened.

Then, when the lid body 17 is lifted, the cutting guide 3 is extracted from the jig body 13 together with the lid body 17 as shown in FIG. If the lid 17 is mounted on the silicon ingot 1 in this state and the silicon ingot 1 and the cutting guide 3 are fixed with an adhesive, the silicon ingot 1 and the cutting guide 3 are firmly fixed as shown in FIG. Is done. What kind of adhesive is used may be appropriately selected from various adhesives in consideration of the familiarity between the material of the cutting guide 3 and the silicon ingot 1.

When the lid 17 is mounted on the silicon ingot 1, an attachment jig 27 as shown in FIG. 6 is used. The mounting jig 27 includes a holding guide 29 for holding the silicon ingot 1 around the upper surface, and a pair of mounting guides 31 are mounted on a diagonal line. On the other hand, since the guide groove 33 (see FIG. 3) is also provided in the lid 17 at a position corresponding to the attachment guide 31, the guide groove 33 of the lid 17 to which the cutting guide 3 is attached extends along the attachment guide 31. By fitting, it can be very easily mounted on the silicon ingot 1 on the mounting jig 27.

Next, the silicon ingot 1 to which the cutting guide 3 (for example, an iron plate) is fixed is reversed and mounted on the table 5. The table 5 shown in FIG. 7 is rotatable at an angle of at least 90 degrees. That is, the cutting guide 3 that can be attracted to the magnet is mounted on a table 5 in which a magnet or the like is built, and the silicon ingot 1 attached via the cutting guide 3 can be rotated along with the rotation of the table 5. ing.
Then, after the silicon ingot 1 mounted on the table 5 and attached via the cutting guide 3 is cut in a fixed direction with the blade of the disc-shaped dicing saw 7, the table 5 is rotated 90 degrees to obtain the previous cutting direction. Can be cut at right angles.
In the figure, 41 is a positioning guide arranged on the side periphery of the silicon ingot 1, 43 is an anti-falling material made of glass, for example, mounted on the positioning guide, and when the periphery of the silicon ingot 1 is cut, It is for preventing.

The silicon block 51 cut out as described above is subjected to an etching process on the end surface on the side periphery. As an etching agent used for etching, hydrofluoric acid, nitric acid, hydrochloric acid, or the like is appropriately mixed and used. What kind of acid is combined, or its blending ratio and additives can be appropriately determined in consideration of the material constituting the silicon ingot, the surface condition to be obtained, and other conditions.

The surface roughness after etching the minute irregularities present on the side surface of the silicon block by the above method is preferably 8 μm or less, more preferably 6 μm or less. If the surface roughness is 8 · m or less, when the obtained silicon block is sliced to produce a silicon wafer and a solar cell panel is produced using this, the silicon wafer is less damaged, and the solar cell Since the yield of a panel improves more, it is preferable.

As shown in FIG. 8, the etched silicon block 51 is sliced by using a predetermined slicer or the like, so that both ends are cut off and a silicon wafer 53 having a predetermined thickness can be obtained.
The obtained silicon wafer 53 had already been subjected to an etching process on its end surface, and almost no polishing process was required on its end surface.

FIG. 9 shows a silicon wafer processing method according to the present invention. A predetermined number of cutting guides prepared in advance are set on an alignment jig. An alignment jig in which the cutting guide is set is fitted on a silicon ingot manufactured separately, and the cut cutting guide and the silicon ingot are fixed with an adhesive or the like.
Next, the silicon ingot with the cutting guide attached to the bottom surface is mounted on the table so that the cutting guide side comes to the surface of the table. At that time, the table attracts a cutting guide that can be attracted magnetically by a built-in magnet, and the silicon ingot is securely held on the table.

After that, if the silicon block is cut into a grid shape with the disc-shaped dicing saw along the cutting guide, the tip of the disc-shaped dicing saw enters between the left and right cutting guides, so the disc-shaped dicing saw may damage the upper surface of the table. The silicon block can be quickly cut out from the silicon ingot without damaging the blade of the disc-shaped dicing saw.

The silicon block cut out as described above is subjected to an etching process on the end surface on the side periphery. The surface roughness after etching the minute irregularities present on the side surfaces of the silicon block is preferably 8 μm or less, more preferably 6 μm or less. Then, a silicon wafer is manufactured by slicing the obtained silicon block, and a solar cell panel or the like is manufactured using this.
The silicon wafer obtained by such a process is preferable because damage to the end face and the like is reduced and the yield of the solar cell panel is further improved.

According to the present invention, it can be applied not only to processing a rectangular silicon wafer having a side of 5 inches for manufacturing a solar cell module but also to a silicon wafer of 5 inches or more such as an IC or LSI.

It is a schematic perspective view at the time of a silicon block cutting | disconnection which shows the processing method of the silicon wafer of this invention. It is a disassembled perspective view which shows the state which accommodates a cutting guide in an alignment jig. It is a schematic perspective view which shows the state which accommodated the cutting guide in the alignment jig | tool. It is the schematic sectional drawing. It is a schematic perspective view which shows the state which set the cutting guide on the silicon block. It is the schematic sectional drawing. It is a schematic sectional drawing which shows the state which cut | disconnects a silicon block. It is the schematic which shows the slice processing method of the silicon wafer from a silicon block. It is a block diagram which shows the processing method of the silicon wafer of this invention. It is the schematic which shows the cutting-out method of the silicon block from the conventional silicon ingot. It is the schematic which shows the slice processing method of the silicon wafer from the conventional silicon block.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon ingot 3 Cutting guide 5 Table 7 Disc-shaped dicing saw 11 Alignment jig 13 Jig body 15 Storage part 17 Cover body 19 Partition 21 and 23 Screw hole 25 Small screw 27 Mounting jig 29 Holding guide 31 Installation guide 33 Guide groove 41 Positioning Guide 43 Lodging Prevention Material 51 Silicon Block 53 Silicon Wafer

Claims (4)

A cutting guide that can be attracted to a magnet is affixed to one side of a silicon ingot for manufacturing a silicon wafer, and the cutting guide mounting surface of the silicon ingot is mounted on a table with a built-in magnet and attached to the cutting guide. Next, the silicon block is cut into a predetermined size with a dicing saw along a dicing saw, and then the end surface of the cut silicon block is etched and then sliced to obtain a silicon wafer. Method. A cutting guide that can be attracted to the magnet is stored in a grid-like arrangement in advance in an alignment jig provided with a storage section that can store the cutting guide in a predetermined position, and the cutting guide and silicon ingot stored in the alignment jig in that state. The method for processing a silicon wafer according to claim 1, wherein: The table can be rotated at an angle of at least 90 degrees, and after the silicon ingot mounted and mounted on the table is cut in a certain direction, the table is rotated by 90 degrees and cut in a direction perpendicular to the previous cutting direction. The method for processing a silicon wafer according to claim 1, which is made possible. The method for processing a silicon wafer according to claim 1, wherein the etching treatment is etching with an acid.

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