JP2008188683A - Silicon ingot cutting method and cutting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase service life of slurry by separating cutting chips of the silicon ingot from the slurry even during cutting of the silicon ingot, and improving stability of the slurry during cutting. <P>SOLUTION: In the silicon ingot cutting method, the slurry containing a polar solvent used in cutting the silicon ingot is recovered and reused. By adding a solvent with low polarity causing phase separation with the slurry containing the polar solvent to the slurry containing the polar solvent, it is separated into a slurry phase containing the polar solvent and a solvent layer with low polarity. The silicon ingot cutting method is characterized in that at least one part of the slurry phase containing the polar solvent is used in cutting of the silicon ingot. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for cutting a monocrystalline, polycrystalline or amorphous silicon ingot to produce semiconductor and solar cell wafers.

Conventionally, for cutting a silicon ingot, a wire saw capable of cutting a large number of wafers at a time has been used. Cutting a silicon ingot using this wire saw is performed by supplying a cutting slurry containing abrasive grains to a traveling wire and pressing the wire against the silicon ingot. In cutting a silicon ingot, silicon particles generated as chips (hereinafter referred to as silicon ingot cutting scraps) are mixed into the slurry. When the amount of silicon ingot cutting scraps mixed increases as cutting progresses, the slurry viscosity changes and cutting efficiency decreases. As a result, the cutting state changes and the surface state of the resulting wafer also changes, which is not preferable. Finally, the slurry cannot be used. In order to obtain a large number of silicon ingots at low cost, it is necessary to separate the silicon ingot cutting waste from the slurry and regenerate the slurry.
Therefore, as a countermeasure to such a problem, after heating the used slurry containing the abrasive component and the lubricating liquid component to reduce the viscosity, the solid portion is separated into the liquid portion, and water is poured into the solid portion. A method of adding a suspension and separating the suspension into a suspension containing reusable abrasive grains and a suspension containing silicon ingot cutting waste or the like has been proposed (for example, see Patent Document 1). ).
Further, the used slurry is separated into a dispersion mainly containing abrasive grains and a dispersion mainly containing silicon ingot cutting waste by a method such as sedimentation separation, and then mainly containing silicon ingot cutting waste by a method such as centrifugation. A method for recovering the dispersion medium from the dispersion has been proposed (see, for example, Patent Document 2).

Special Table 2002-519209 JP 2003-340719 A

However, in the conventional method described above, it is possible to regenerate the used slurry, but it is not possible to remove silicon ingot cutting scraps during cutting, and it is impossible to suppress changes in slurry characteristics during cutting. There is.
Therefore, the present invention has been made in view of the above circumstances, and even during cutting of a silicon ingot, the silicon ingot cutting waste is separated from the slurry to improve the stability of the slurry during cutting, and the slurry can be made longer. The purpose is to extend the service life.

Thus, as a result of intensive research and development to solve the above-described conventional problems, the present inventors have solved polarities that cause phase separation with the polar solvent-containing slurry. It is effective to use a polar solvent-containing slurry phase from which silicon ingot swarf has been removed for silicon ingot cutting by adding a low solvent to a polar solvent-containing slurry to move the silicon ingot swarf to a less polar solvent phase. As a result, the present invention has been completed.
That is, the present invention is a silicon ingot cutting method for recovering and reusing a polar solvent-containing slurry used to cut a silicon ingot, and a low-polarity solvent that causes phase separation from the polar solvent-containing slurry. A silicon characterized in that it is separated into two phases of a polar solvent-containing slurry phase and a low-polarity solvent phase by adding to the polar solvent-containing slurry, and at least a part of the polar solvent-containing slurry phase is used for cutting a silicon ingot This is an ingot cutting method.
In addition, the present invention supplies polar solvent-containing slurry from a slurry tank to a running wire, and presses the wire against the silicon ingot to cut the silicon ingot while collecting the polar solvent-containing slurry supplied to the wire in the slurry tank. A silicon ingot cutting device to be reused, wherein at least a part of the polar solvent-containing slurry phase is separated from the slurry tank out of the polar solvent-containing slurry phase and the low-polarity solvent phase separated into two phases in the slurry tank. A silicon ingot cutting device comprising a mechanism for taking out and a mechanism for supplying the taken-out polar solvent-containing slurry to a wire.

  According to the present invention, even during the cutting of a silicon ingot, the silicon ingot cutting waste can be separated from the slurry to improve the stability of the slurry during cutting, and the life of the slurry can be extended.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a silicon ingot cutting device 1 used in the silicon ingot cutting method according to Embodiment 1 of the present invention. FIG. 2 is a diagram illustrating a silicon ingot cutting process by the silicon ingot cutting device 1. It is a figure for doing.
1 and 2, the silicon ingot cutting device 1 includes a silicon ingot feeding mechanism 2 and a wire feeding mechanism 3. The silicon ingot feeding mechanism 2 includes a fixing mechanism that fixes the silicon ingot 4 and an ingot moving mechanism that pushes down or pulls the fixed silicon ingot 4 toward the wire 5. The wire feeding mechanism 3 includes a wire feeding mechanism 6 for feeding the wire 5, a wire winding mechanism 7 for winding the wire 5, and a tension control roller 8 for keeping the tension of the wire 5 constant. ing.

  In the silicon ingot cutting device 1, two rotating rollers 9 a and 9 b that rotate synchronously are disposed at positions below the silicon ingot feeding mechanism 2. A groove for guiding the wire 5 is formed in a spiral shape on the outer peripheral wall surfaces of the rotating rollers 9a and 9b. In the wire feed mechanism 3, the wire 5 is pulled out from the wire feed mechanism 6 and guided around the grooves of the rotary rollers 9 a and 9 b, so that the wire 5 spirals between the rotary rollers 9 a and 9 b and the wire feed mechanism 6. And a wire take-up mechanism 7 so as to be able to run while maintaining a constant tension. Examples of the wire 5 used here include a metal one and a resin one, and a metal one is preferable from the viewpoint of cutting efficiency.

  Moreover, the silicon ingot cutting device 1 collects the slurry for collecting the polar solvent-containing slurry 10 used for cutting the silicon ingot 4 or the polar solvent-containing slurry 10 that has fallen off the wire 5 without being used for cutting. A part 11, a slurry supply mechanism 12 for supplying the polar solvent-containing slurry 10 to the wire 5, and a slurry tank 13 for temporarily storing the polar solvent-containing slurry 10 are provided. The slurry recovery unit 11 is disposed below the rotary rollers 9 a and 9 b and is connected to the slurry tank 13 via the slurry recovery pipe 14. The polar solvent-containing slurry 10 recovered by the slurry recovery unit 11 is configured to return to the slurry tank 13 through the slurry recovery pipe 14. The slurry supply mechanism 12 is disposed above the rotating roller 9a disposed on the upstream side of the portion for cutting the silicon ingot 4 and the portion for cutting the silicon ingot 4. Further, the slurry tank 13 includes a mechanism, for example, a pump, for taking out the polar solvent-containing slurry phase from the polar solvent-containing slurry phase separated into two phases in the slurry tank 13 and the low-polarity solvent phase. This polar solvent-containing slurry phase extraction mechanism is connected to the slurry supply mechanism 12 via the slurry supply pipe 15. In this way, at least a part of the polar solvent-containing slurry phase separated in the slurry tank 13 is taken out from the slurry tank 13 by the polar solvent-containing slurry phase take-out mechanism, and passes through the slurry supply pipe 15 and the slurry supply mechanism 12. It is configured to be supplied to the wire 5.

  In such a silicon ingot cutting device 1, when the wire feeding mechanism 6 and the wire winding mechanism 7 are driven, the wire 5 travels at a predetermined speed in a certain direction while the tension is maintained constant by the tension control roller 8. To do. Since the wires 5 are guided along the grooves of the rotating rollers 9a and 9b, the rows of the wires 5 are arranged with a constant tension under the silicon ingot feeding mechanism 2 while running in parallel. At this time, the rotation rollers 9 a and 9 b rotate synchronously at a rotation speed corresponding to the traveling speed of the wire 5.

  In order to cut the silicon ingot 4 by the silicon ingot cutting device 1 configured as described above, the silicon ingot feeding mechanism 2 pushes the silicon ingot 4 toward the wire 5 as shown in FIGS. 1 and 2. Thus, the silicon ingot 4 comes into contact with the traveling wire 5 and is pressed. At this time, when the polar solvent-containing slurry 10 is supplied from the slurry supply mechanism 12 and supplied to the traveling wire 5, the slurry 10 is carried to the cutting portion of the silicon ingot 4 by the traveling wire 5. The silicon ingot 4 is cut and cut by the lapping action or chemical action of the polar solvent-containing slurry 10. The polar solvent-containing slurry 10 used for cutting the silicon ingot 4 and the polar solvent-containing slurry 10 dropped from the wire 5 without being used for cutting are collected in the slurry tank 13. In FIG. 2, the silicon ingot feeding mechanism 2 is omitted.

  The polar solvent-containing slurry 10 used in the present embodiment contains at least abrasive grains and a polar solvent. As the abrasive, it is preferable to use highly hydrophilic particles that are familiar to polar solvents. When a low-polarity solvent having a low-polarity part in the whole molecule or a part of the molecule is added to the polar-solvent-containing slurry 10 in the slurry tank 13, the low-polarity solvent causes phase separation with the polar solvent-containing slurry 10, A polar solvent-containing slurry phase and a less polar solvent phase are formed. Silicon ingot cutting waste generated by cutting is less hydrophilic than the abrasive grains. For this reason, the solvent having a low polarity is more familiar to the solvent than the polar solvent. When the polar solvent-containing slurry phase and the low-polarity solvent phase are mixed, the silicon ingot cutting waste mixed in the polar solvent-containing slurry 10 is moved to the low-polarity solvent phase. Naturally, at this time, since the abrasive grains remain in the polar solvent-containing slurry phase, only the silicon ingot cutting waste moves from the polar solvent-containing slurry phase to the solvent phase having a low polarity. By removing at least a part of the polar solvent-containing slurry phase from which silicon ingot cutting waste has been selectively removed from the slurry tank 13 and reusing it for cutting the silicon ingot 4, the change in the slurry characteristics accompanying the cutting of the silicon ingot 4 And the life of the slurry can be extended.

Here, a mixing method of the polar solvent-containing slurry 10 and the low polarity solvent in the present embodiment will be described. A solvent having a low polarity tends to float on the surface of the slurry because the specific gravity is smaller than that of the polar solvent-containing slurry 10. In this state, since the contact area between the polar solvent-containing slurry 10 and the low-polarity liquid is small and the movement efficiency of the silicon ingot cutting waste may be low, stirring is preferable.
Usually, the slurry tank 13 is provided with a stirring mechanism for causing the whole slurry to flow, so if the entire polar solvent-containing slurry 10 to which a low polarity solvent is added is sufficiently stirred by this stirring mechanism, The removal effect of silicon ingot cutting waste can be obtained. However, this stirring mechanism alone does not sufficiently mix the polar solvent-containing slurry phase separated into two phases and the low-polarity solvent phase, and the silicon ingot cutting waste may not be efficiently transferred to the low-polarity solvent phase. is there. In order to sufficiently mix the polar solvent-containing slurry phase and the low-polarity solvent phase, a method in which the slurry stored in the slurry tank 13 is vigorously stirred by the stirring mechanism can be considered. In this method, a low-polarity solvent is used. Disperses throughout the slurry. When the low-polarity solvent is dispersed throughout the slurry, a large amount of low-polarity solvent is introduced into the cutting portion of the silicon ingot 4 to reduce cutting efficiency or remove silicon ingot cutting waste that has moved to the low-polarity solvent phase. This is not realistic because it can be difficult. Therefore, as a method for efficiently transferring silicon ingot cutting scraps to a low-polarity solvent phase, the slurry tank 13 is provided with a mechanism for partially stirring and mixing the polar solvent-containing slurry phase and the low-polarity solvent phase. It is valid.

  FIG. 3 shows an example of a mechanism for partially stirring and mixing the polar solvent-containing slurry phase 16 and the low-polarity solvent phase 17. In the mechanism shown in FIG. 3, a stirrer 18 equipped with stirring blades is installed in the vicinity of the slurry liquid level in the slurry tank 13, and a discharge port and a pump are provided in the vicinity of the bottom of the slurry tank 13. A polar solvent-containing slurry phase extraction mechanism 19 is provided. When the stirrer 18 is actuated, the stirring blades rotate to generate a vortex flow, a liquid having a low polarity on the slurry liquid surface is entrained in the vortex flow, and the polar solvent-containing slurry phase 16 and the low polarity solvent phase 17 partially Are mixed with stirring. Due to this vortex flow, a part of the low-polarity liquid is dispersed in the polar solvent-containing slurry phase 16 but re-floats at a portion where the flow of the slurry is not intense, and the low-polarity liquid collects on the slurry liquid surface. In this way, by providing a mechanism for partially stirring and mixing the polar solvent-containing slurry phase 16 and the low-polarity solvent phase 17 in the slurry tank 13, the contact area between the polar solvent-containing slurry and the low-polarity solvent is expanded. The moving efficiency of silicon ingot cutting waste can be greatly improved.

  In addition, as the silicon ingot 4 is continuously cut, silicon ingot cutting scraps are gradually accumulated in the solvent phase having low polarity, and the fluidity of the solvent phase having low polarity is lowered, and the movement efficiency of the silicon ingot cutting scraps is lowered. Or may adversely affect the cutting portion of the silicon ingot 4. Therefore, if the silicon ingot cutting waste can be separated (removed) from the solvent phase having a low polarity, the effect of suppressing the change in slurry characteristics and the effect of extending the life of the slurry are increased. Therefore, it is effective to provide the silicon ingot cutting apparatus 1 with a mechanism for separating silicon ingot cutting waste from a low-polarity solvent phase.

FIG. 4 shows an example of a mechanism for separating silicon ingot cutting waste from a solvent phase with low polarity. The mechanism shown in FIG. 4 includes a low-polarity solvent phase suction mechanism 20 (for example, a pump) for sucking up a part of a low-polarity solvent phase containing silicon ingot cutting scraps in the vicinity of the slurry liquid level in the slurry tank 13. ), And a solid-liquid separator 21 for separating the low polarity solvent including the silicon ingot cutting waste sucked by the low polarity solvent phase suction mechanism 20 into the silicon ingot cutting waste and the low polarity solvent, A low-polarity solvent return pipe 22 for returning the low-polarity solvent from which the silicon ingot cutting waste has been removed by the liquid separator 21 to the slurry tank 13 is provided. In the mechanism thus configured, a part of the low polarity solvent phase gathered near the slurry liquid surface is sucked up by the low polarity solvent phase suction mechanism 20, and then introduced into the solid-liquid separator 21, It is separated into silicon ingot cutting waste and a less polar solvent. The low polarity solvent from which the silicon ingot cutting waste has been removed is returned to the slurry tank 13 through the low polarity solvent return pipe 22 (re-added to the polar solvent-containing slurry 10).
Moreover, since the polar solvent-containing slurry 10 may be mixed into the sucked-down low-polarity solvent, the mechanism 23 for separating the low-polarity solvent and the polar solvent-containing slurry 10 as shown in FIG. May be installed between the low solvent phase suction mechanism 20 and the solid-liquid separator 21. In the mechanism 23 shown in FIG. 5, the polar solvent-containing slurry 10 having a low viscosity and a large specific gravity is allowed to flow through the separation filter 24 by flowing the sucked low-polarity solvent over the separation filter 24 installed at an inclination. While falling through, the low polarity solvent flows on the separation filter 24 and is introduced into the solid-liquid separator 21. The polar solvent-containing slurry 10 that has dropped through the separation filter 24 is returned to the slurry tank 13 via the solvent return pipe 22 having a low polarity. The opening of the separation filter 24 is not particularly limited, and may be appropriately determined in consideration of the viscosity of the polar solvent-containing slurry 10. By providing such a mechanism 23 in the silicon ingot cutting device 1, the effect of suppressing the change in slurry characteristics and the effect of extending the slurry life can be further enhanced.

  In FIG. 4, a low-polarity solvent containing silicon ingot cutting waste is poured into a rotatable cylindrical filter, and the sucked low-polarity solvent is continuously used using a solid-liquid separator that is filtered by centrifugal force. However, it is not necessary to carry out the treatment continuously, and the operation of batch-treating the sucked-down low-polarity solvent back may be repeated. FIG. 4 shows a method of sucking up a part of the solvent phase having a low polarity by the solvent phase suction mechanism 20 having a low polarity. However, the method is not particularly limited to this method, A portion of the lower solvent phase may be skimmed off.

  Examples of the polar solvent constituting the polar solvent-containing slurry 10 in the present embodiment include water, alcohols, polyhydric alcohols such as glycerin and ethylene glycol, polar organic solvents such as ethanolamines, DMF, DMA, and NMP. These can be used alone or as a mixture of two or more.

  As the abrasive grains in the present embodiment, any particles that are generally used as an abrasive and are highly hydrophilic particles that are familiar with the above polar solvent may be used. For example, silicon carbide, cerium oxide, boron nitride, aluminum oxide Zirconium oxide and silicon dioxide can be mentioned, and these can be used alone or in combination of two or more. Such abrasive grains are commercially available. Specifically, as silicon carbide, trade names GC (Green Silicon Carbide) and C (Black Silicon Carbide) (manufactured by Fujimi Incorporated), and as aluminum oxide, products Names include FO (Fujimi Optical Emery), A (Regular Fused Aluminum), WA (White Fused Aluminum), and PWA (Platelet Calcined Alumina) (manufactured by Fujimi Incorporated). Although the average particle diameter of an abrasive grain is not specifically limited, Preferably it is 1 micrometer-60 micrometers, More preferably, it is 5 micrometers-20 micrometers. When the average particle diameter of the abrasive grains is less than 1 μm, the cutting speed is remarkably slow, which is not practical. When the average particle diameter of the abrasive grains exceeds 60 μm, the surface roughness of the silicon wafer surface after cutting is large. This is not preferable because the wafer quality may deteriorate. Although content of an abrasive grain is not specifically limited, Preferably it is 30 mass%-70 mass% with respect to the mass of the whole polar solvent containing slurry. When the content of the abrasive grains is less than 30% by mass, the cutting speed becomes slow and the practicality may become poor. When the content of the abrasive grains exceeds 70% by mass, the viscosity of the polar solvent-containing slurry 10 is low. It may become excessive and it will become difficult to introduce the polar solvent containing slurry 10 into the cutting part of the silicon ingot 4.

  Moreover, alkaline metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide, and alkaline earth hydroxides such as magnesium hydroxide, calcium hydroxide and barium hydroxide with respect to the polar solvent-containing slurry 10 Basic substances such as these may be added. In this case, there is an effect of reducing the resistance between the wire 5 and the silicon ingot 4. Various anionic, cationic and nonionic surfactants may be added. In this case, there is an effect of improving the stability of the viscosity of the polar solvent-containing slurry 10 and improving the familiarity between the polar solvent-containing slurry 10 and the wire 5 or the silicon ingot 4. High molecular or low molecular thickeners may be mixed. In this case, there is an effect that the polar solvent-containing slurry is efficiently introduced into the cutting portion of the silicon ingot 4 or the settling of abrasive grains in the polar solvent-containing slurry 10 is suppressed.

  The polar solvent-containing slurry 10 in the present embodiment can be prepared by mixing the above components at a desired ratio. The method of mixing each component is arbitrary, for example, it can carry out by stirring with a wing-type stirrer. The order of mixing the components is also arbitrary. Further, for the purpose of purification or the like, the prepared polar solvent-containing slurry 10 may be further processed, for example, filtration treatment, ion exchange treatment, and the like.

The low-polarity solvent in the present embodiment does not have to be completely insoluble in the polar solvent-containing slurry 10, has a lower specific gravity than the polar solvent, and is completely dissolved in the polar solvent-containing slurry 10 when added. Any material that forms a separate liquid phase with the polar solvent-containing slurry 10 without causing (phase separation) may be used. Such a solvent can be a compound having a structure with low polarity in the whole molecule or a part thereof. Examples of the compound having a low polarity structure include aliphatic and aromatic hydrocarbons, polysiloxanes, polyoxyalkylenes, polyoxyethylene / polyoxypropylene block copolymers, and organic substances containing fluorine and chlorine. As long as it causes phase separation with the polar solvent-containing slurry 10, it may have a hydrophilic group in the molecule. A low polarity solvent having a suitable hydrophilic group, for example, a functional group containing nitrogen, sulfur, oxygen, etc., has a highly polar portion locally formed in the molecule. It functions like a chemical agent, and the silicon ingot cutting waste can be easily transferred to a solvent having a low polarity. In addition, among the above-mentioned low-polarity solvents, by using those having a functional group that specifically adsorbs on the silicon surface, the movement of silicon ingot cutting waste from the polar solvent-containing slurry phase to the low-polarity solvent phase can be further improved. Can be easily woken up. In addition, silicon ingot cutting waste is easily oxidized, and oxidation is particularly remarkable when the polar solvent-containing slurry 10 is alkaline. In such a case, there is a possibility that the characteristics of the polar solvent-containing slurry 10 may change due to oxidation of the silicon ingot cutting waste, but by using a solvent having a functional group that specifically adsorbs to the silicon surface, Oxidation can be suppressed (anticorrosion). Examples of such adsorptive functional groups include amino groups, alkylamino groups, hydroxyamino groups, imino groups, cyano groups, nitro groups, nitroso groups and other nitrogen atoms (N), mercapto groups, sulfinyl, sulfonyl groups, and the like. Examples include various substituents having a sulfur atom (S), an oxygen atom (O) such as a carbonyl group or an ether group. Among the solvents with low polarity described above, from the viewpoint of low vapor pressure and high work safety, the molecular weight of polydimethylsiloxane, polyoxyethylene / polyoxypropylene block copolymer, polyoxyethylene alkylamine ether, etc. It is preferable to use a large liquid.
The addition amount of the low polarity solvent is preferably set to an amount that does not adversely affect the cutting of the silicon ingot 4. Specifically, it is preferable to add a low polarity solvent to the polar solvent-containing slurry 10 at 0.1% by mass or more and less than 20% by mass, and 0.15% by mass or more and less than 10% by mass. More preferably. If the addition amount of the low polarity solvent is less than 0.1% by mass, the addition effect of the low polarity solvent may not be sufficiently obtained, and if it is 20% by mass or more, the low polarity solvent There is a possibility that the cutting part of the silicon ingot 4 may enter and have an adverse effect. In other words, by setting the range as described above, a low-polarity solvent exists in a small amount in the polar solvent-containing slurry phase in the form of droplets or attached to silicon ingot cutting scraps or abrasive grains. Since most of them collect on the slurry liquid surface, the influence on the cutting of the silicon ingot 4 can be remarkably reduced.
The low-polarity solvent may be added in advance to the polar solvent-containing slurry 10 in the slurry tank 13 before or at the start of cutting of the silicon ingot 4, or after the start of cutting of the silicon ingot 4, the silicon ingot 4. You may add from the place which does not have a bad influence on cutting of this, for example, the slurry collection | recovery part 11, the slurry collection | recovery piping 14, the slurry tank 13, etc.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to these.

[Examples 1 to 3 and Comparative Example 1]
40 kg of water, 20 kg of glycerin, and 50 kg of SiC abrasive grains (manufactured by Fujimi Incorporated, GC # 1200) were mixed to obtain a polar solvent-containing slurry. Using this polar solvent-containing slurry and a silicon ingot cutting device (multi-wire saw) having the same configuration as that shown in FIGS. 1 and 2, a polycrystalline silicon ingot (150 mm square, 25 mm length) under the cutting conditions shown below. ) Was cut until it was cut.

<Cutting conditions>
Wire diameter: 100 μm
Cutting allowance: 0.13mm
Cutting pitch: 0.39 mm
Cutting speed: 0.35 mm / min Wire traveling speed: 600 m / min

  In Examples 1 to 3, the low polarity solvent shown in Table 1 was added to the slurry tank at the start of cutting. In Comparative Example 1, no low polarity solvent was added. Changes in the viscosity of the polar solvent-containing slurry before and after cutting are shown in Table 1.

表１中、＊１は、信越シリコーン製、商品名ＫＦ−９６−２００ｃｓであり、＊２は、アデカ製、商品名Ｌ−３１である。

In Table 1, * 1 is a product name KF-96-200cs made by Shin-Etsu Silicone, and * 2 is a product name L-31 made by ADEKA.

  As can be seen from Table 1, in Comparative Example 1, the viscosity of the polar solvent-containing slurry was increased by cutting the silicon ingot. In contrast, in Examples 1 to 3, the change in the viscosity of the polar solvent-containing slurry before and after cutting was extremely small, and the increase in viscosity could be significantly suppressed by the addition of a low polarity solvent. This is because the silicon ingot cutting waste mixed in the polar solvent-containing slurry can be moved to the solvent phase having a low polarity.

[Examples 4 to 6 and Comparative Example 2]
40 kg of water, 20 kg of glycerin, 50 kg of SiC abrasive grains (manufactured by Fujimi Incorporated, GC # 1200) and 500 g of sodium hydroxide were mixed to obtain a polar solvent-containing slurry. The silicon ingot was cut in the same manner as in Examples 1 to 3 using this polar solvent-containing slurry.

表２中、＊１は、信越シリコーン製、商品名ＫＦ−９６−２００ｃｓであり、＊２は、アデカ製、商品名Ｌ−３１であり、＊３は、アデカ製、商品名ＴＲ７０１である。

In Table 2, * 1 is a product name KF-96-200cs made by Shin-Etsu Silicone, * 2 is an ADEKA product name L-31, and * 3 is an ADEKA product name TR701.

  As can be seen from Table 2, in Comparative Example 2, the viscosity of the polar solvent-containing slurry was greatly increased by cutting the silicon ingot. This is influenced by the oxidation of silicon ingot cutting scraps by alkali in addition to the mixing of silicon ingot cutting scraps. In contrast, in Examples 4 to 5, the change in viscosity of the polar solvent-containing slurry before and after cutting was extremely small, and the increase in viscosity could be significantly suppressed by the addition of a low polarity solvent. This is because the silicon ingot cutting waste mixed in the polar solvent-containing slurry can be moved to a solvent phase having a low polarity and the oxidation of the silicon ingot cutting waste can be suppressed. Moreover, in Example 6, since the polyoxyethylene alkylamine ether added as a low-polarity solvent is easy to adsorb | suck to the silicon ingot cutting waste, the nitrogen atom in a molecule | numerator, and since the anticorrosion action with respect to a silicon ingot cutting waste is strong, a polar solvent The viscosity change of the containing slurry could be further suppressed.

It is the schematic of the silicon ingot cutting device used for the silicon ingot cutting method which concerns on Embodiment 1 of this invention. FIG. 3 is an enlarged view of a cutting part of the silicon ingot in the first embodiment. It is the schematic of the mechanism in which the polar solvent containing slurry phase and low polarity solvent phase in Embodiment 1 are partially stirred and mixed. It is the schematic of the mechanism which isolate | separates a silicon ingot cutting waste from the low polarity solvent phase in Embodiment 1. FIG. FIG. 2 is a schematic diagram of a mechanism for separating a low polarity solvent and a polar solvent-containing slurry in the first embodiment.

Explanation of symbols

  1 Silicon Ingot Cutting Device, 2 Silicon Ingot Feeding Mechanism, 3 Wire Feeding Mechanism, 4 Silicon Ingot, 5 Wire, 6 Wire Feeding Mechanism, 7 Wire Winding Mechanism, 8 Tension Control Roller, 9a, 9b Rotating Roller, 10 Contains Polar Solvent Slurry, 11 Slurry recovery unit, 12 Slurry supply mechanism, 13 Slurry tank, 14 Slurry recovery piping, 15 Slurry supply piping, 16 Polar solvent-containing slurry phase, 17 Low polarity solvent phase, 18 Stirrer, 19 Polar solvent-containing slurry phase extraction Mechanism, 20 Low-polarity solvent phase suction mechanism, 21 Solid-liquid separator, 22 Low-polarity solvent return piping, 23 Mechanism that separates low-polarity solvent and polar solvent-containing slurry, 24 Separation filter.

Claims (6)

A method for cutting a silicon ingot that recovers and reuses a slurry containing a polar solvent used to cut a silicon ingot,
A low-polarity solvent that causes phase separation with the polar solvent-containing slurry is added to the polar solvent-containing slurry to separate the polar solvent-containing slurry phase and the low-polarity solvent phase into at least one of the polar solvent-containing slurry phases. A silicon ingot cutting method, wherein the portion is used for cutting a silicon ingot.   2. The silicon according to claim 1, wherein at least a part of the low-polarity solvent phase is taken out and subjected to solid-liquid separation, and then the low-polarity solvent as a liquid component is added again to the polar solvent-containing slurry. Ingot cutting method.   The silicon ingot cutting method according to claim 1 or 2, wherein a solvent having a functional group adsorbing to silicon is used as the low-polarity solvent. Supplying the polar solvent-containing slurry from the slurry tank to the running wire, pressing the wire against the silicon ingot to cut the silicon ingot, and collecting the polar solvent-containing slurry supplied to the wire into the slurry tank for reuse An ingot cutting device,
Among the polar solvent-containing slurry phase and the low-polarity solvent phase separated into two phases in the slurry tank, a mechanism for taking out at least a part of the polar solvent-containing slurry phase from the slurry tank;
A silicon ingot cutting device comprising: a mechanism for supplying the extracted polar solvent-containing slurry to a wire.   The silicon ingot cutting device according to claim 4, further comprising a mechanism for partially mixing the polar solvent-containing slurry phase separated into two phases in the slurry tank and the low-polarity solvent phase. A mechanism for removing from the slurry tank at least a part of the low-polarity solvent phase separated in the slurry tank;
A mechanism for solid-liquid separation of the extracted low polarity solvent;
6. The silicon ingot cutting device according to claim 4, further comprising a mechanism for returning a low-polarity solvent as a liquid component subjected to solid-liquid separation to the slurry tank.

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