JP6090154B2 - Slicing method - Google Patents

Description

  The present invention relates to a slicing method for cutting a silicon ingot into a wafer using a wire saw.

In a general silicon wafer manufacturing method, a grown silicon single crystal ingot is first cut into blocks of a certain resistivity range after first inspecting resistivity and crystallinity. The grown ingot is not completely cylindrical and the diameter is not uniform. Therefore, each block body is subjected to outer peripheral grinding so that the diameter is uniform. Next, in order to show a specific crystal orientation, an orientation flat and a notch are given to the block body which carried out the outer periphery grinding.
Subsequently, each block body is cut into a number of wafers, and each wafer is chamfered, mechanically ground (lapping), etched, gettering treatment, oxygen donor erasing heat treatment, mirror polishing (polishing) and cleaning steps, etc. Constructed and produced as a wafer with high precision flatness.

  Slicing from each block body has been mainly performed with an inner peripheral blade when a wafer having a diameter of 200 mm or less is made. In the slice with the inner peripheral blade, a blade having an outer diameter 4 to 5 times the diameter of the block body is required, so that it is difficult to cope with a slice of a large diameter block having a diameter of 300 mm or more. For this reason, instead of the conventional slicing by the inner peripheral blade, the slicing by a wire saw has come to be frequently used.

In slicing with a wire saw, the wire extending from the wire supply reel is spirally wound around the two or more wire guides so as to have a predetermined tension, and then extended toward the wire take-up reel. This is performed by a wire saw having a different configuration.
In such a wire saw, for example, in the case of the loose abrasive type, the wire is run from the wire supply reel to the wire take-up reel through the wire guide while supplying the coolant containing the abrasive grains to the wire, and the ingot The block body of the ingot is cut by bringing the block body into contact with the wire stretched between the wire guides.
In the fixed abrasive type, a wire to which abrasive grains are fixed is used, and the block body of the ingot is cut while supplying a coolant containing no abrasive grains to the wire.
In the wire saw having such a configuration, since the wire is spirally wound around the wire guide, the wire is arranged in parallel at a predetermined interval at a position in contact with the block body. A plurality of wafers can be obtained by cutting the block body.

  A wire used for a wire saw is generally made of a wire such as a steel wire, and a copper alloy plating layer such as a copper plating layer or a brass plating is formed on the surface of the wire. . The reason for applying a copper plating layer or a copper alloy plating layer on the surface of the wire is to give a wire to a die having a predetermined hole diameter in order to give a rust prevention effect and in a wire drawing process in which the wire is drawn stepwise. This is in order to obtain a lubrication effect when passing through. However, when a wire having copper plating on the surface is used, there is a problem that the sliced wafer is contaminated by high-concentration copper.

As a measure to solve the copper contamination caused by the wire for such a wire saw, a copper or copper alloy plating layer is formed on the surface of a wire made of iron or an iron alloy, and the final finish is drawn. Or the manufacturing method of the wire for wire saws which peels a copper alloy plating layer is disclosed (for example, refer patent document 1).
In the method of Patent Document 1, lubrication is smoothly performed at the time of wire drawing, the surface is hardly damaged, and quality characteristics as a wire saw wire are not impaired. Then, since the copper or copper alloy plating layer on the surface is peeled off and used as a wire saw wire, it is described that the cut wafer or the like is not contaminated with metal impurities.

  Moreover, the process of slicing a semiconductor ingot into a large number of semiconductor wafers using a wire saw wire with a zinc wire or nickel plating on the surface of the steel wire, and both sides of the obtained semiconductor wafer are 20 μm or less on one side A semiconductor wafer manufacturing method including a lapping step of lapping with a lapping amount of 2 is disclosed (for example, see Patent Document 2). In the manufacturing method of patent document 2, it is described that the copper contamination of the semiconductor wafer sliced using the wire saw can be reduced by using the wire for wire saws with which zinc plating or nickel plating was performed.

JP 9-254145 A JP 2005-57054 A

However, even when the wire saw wires shown in Patent Document 1 and Patent Document 2 described above are used, a plurality of single crystal silicon blocks are sliced using a plurality of wire saws, and wafers obtained from the respective silicon blocks When investigating the internal copper contamination concentration, the copper contamination concentration varies greatly from wafer to wafer, and some copper contamination exceeds 1 × 10 ¹² atoms / cm ³ , and the conventional method has the effect of reducing copper contamination. There wasn't always enough. Since copper contamination greatly affects the characteristics of semiconductors, a method for reliably reducing copper contamination of single crystal silicon due to wire saw slices has been demanded.

  An object of the present invention is to provide a slicing method capable of stably obtaining a silicon wafer with high cleanliness with reduced copper contamination using a wire saw.

  In order to achieve the above object, the present invention uses a wire saw and presses a silicon ingot against a wire while running the wire while supplying coolant to the wire wound around a plurality of wire guides. A slicing method for obtaining a plurality of sliced wafers, wherein a copper concentration in a coolant supplied to the wire is 80 ppm or less.

  In this way, copper contamination in a silicon wafer manufactured by slicing can be sufficiently reduced, and a silicon wafer with high cleanliness can be stably manufactured. In the conventional method, the copper contamination concentration varies from slice wafer to slice wafer. However, in the present invention, the copper contamination concentration is kept low and constant, and the variation can be extremely suppressed.

  At this time, before supplying the coolant to the wire, the copper concentration in the coolant is measured in advance, and a coolant of 80 ppm or less can be used.

  In this way, the copper concentration can be supplied to the wire using the coolant suppressed to a low concentration of 80 ppm or less, and a highly clean silicon wafer can be manufactured more stably. it can.

  In addition, the coolant after being supplied to the wire is collected in the tank, and when the coolant contained in the tank is supplied to the wire and circulated, the copper concentration of the coolant in the tank is controlled to 80 ppm or less. can do.

  If it does in this way, the coolant after using at the time of a cutting | disconnection can be reused, and while being able to reduce cost, the coolant by which copper concentration was restrained low more reliably can be supplied to a wire.

  Moreover, the dopant added in order to adjust the specific resistance of the silicon ingot to be cut can be boron.

  Boron interacts with copper to promote the penetration of copper into silicon, and copper contamination is likely to occur. As described above, since the present invention can reduce copper contamination, it is particularly effective when boron, which easily causes copper contamination, is used as a dopant.

  The specific resistance of the silicon ingot to be cut can be set to 0.03 Ω · cm or less.

  When the specific resistance is 0.03 Ω · cm or less, since a large amount of dopant is contained, more copper easily enters. Therefore, when the contamination reaches the saturation level, the copper contamination concentration in the slice wafer becomes a relatively high value, and the present invention that can reduce the copper contamination is particularly effective.

  In addition, the pH of the coolant supplied to the wire can be in the range of 5-7.

  By controlling the pH within such a range, generation and promotion of copper contamination on the slice wafer can be further suppressed.

  The diameter of the silicon ingot can be 450 mm or more.

  The temperature of the silicon ingot when slicing with a wire saw increases as the diameter of the ingot increases, and the diffusion of copper into silicon becomes easier as the temperature increases. The present invention that can reduce copper contamination is particularly effective when the diameter of the silicon ingot to be cut is large, such as when the diameter is 450 mm or more.

  Further, the coolant may include abrasive grains.

  Thus, the present invention can also be used in, for example, a loose abrasive wire saw slice in which coolant containing abrasive grains is supplied to a wire.

  As described above, according to the slicing method of the present invention, it is possible to reduce copper contamination on a sliced wafer obtained by cutting using a wire saw, and to provide a silicon wafer with high cleanliness stably. it can.

It is a graph which shows the relationship between the copper concentration in a coolant in case a specific resistance is 0.03 ohm * cm, and the copper contamination density | concentration detected from the wafer. It is a graph which shows the relationship between the copper concentration in a coolant in case a specific resistance is 0.02 ohm * cm, and the copper contamination density | concentration detected from the wafer. It is a graph which shows the relationship between the copper concentration in a coolant in case a specific resistance is 0.01 ohm * cm, and the copper contamination density | concentration detected from the wafer. It is the schematic which shows an example of the wire saw which can be used with the slicing method of this invention.

Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.
As a result of intensive studies on the slicing method using the wire saw by the present inventors, it has been found that the copper concentration in the coolant is greatly related to the copper contamination generated in the slice wafer. Furthermore, it has been found that when the copper concentration in the coolant exceeds 80 ppm, the copper contamination concentration of the slice wafer increases and reaches a saturated state. On the other hand, if it is 80 ppm or less, it has been found that the copper contamination concentration of the slice wafer can be kept low, and thereby the variation of the copper contamination concentration for each slice wafer can be suppressed, and the present invention has been completed.

  FIG. 4 is a schematic view showing an example of a wire saw that can be used in the slicing method of the present invention. As shown in FIG. 4, the wire saw 1 mainly includes a wire 2 for cutting a silicon ingot (hereinafter simply referred to as a work W), a plurality of wire guides 3 around which the wire 2 is wound, and tension on the wire 2. It comprises a wire tension applying mechanism 4, 4 ′ for applying, a work feeding mechanism 5 for holding and cutting the work W to be cut, a coolant supply mechanism 6, and the like.

  The workpiece W is bonded to the workpiece plate via a joining member, and the workpiece plate is held by the workpiece holding portion of the workpiece feeding mechanism 5. The workpiece W held by the workpiece holding portion in this way can be sent out to the wire 2 disposed below using the LM guide of the workpiece feeding mechanism 5.

The wire 2 is fed out from one wire reel 7 and enters the wire guide 3 via the wire tension applying mechanism 4. The wire 2 is formed by winding the wire 2 around the wire guide 3 about 300 to 400 times. Then, the wire 2 is wound around the wire reel 7 'through the other wire tension applying mechanism 4'.
Tension is applied to the wire 2 wound in this manner, and the drive motor 10 can reciprocate at a reversal cycle time and travel speed set in the axial direction in advance.

  Here, in the fixed abrasive method, the abrasive particles are fixed to the surface of the wire 2 such as a steel wire. For example, an electrodeposited diamond wire in which diamond abrasive grains are fixed to the wire element by Ni bonding can be used. In this electrodeposited diamond wire, diamond abrasive grains are firmly fixed to the wire element by nickel electrodeposition. Therefore, there is an advantage that the wire life is long. The fixing method is not particularly limited as long as the abrasive grains can be fixed to the wire.

  Further, a nozzle 8 is disposed above the wire 2 so that the coolant 9 can be supplied to the wire 2. The number of nozzles 8 and the like are not particularly limited and can be determined as appropriate. As the coolant 9, for example, a propylene glycol (PG) mixed solution can be used.

  On the other hand, the abrasive grains are not fixed to the wire 2 in the loose abrasive system. Instead, a coolant 9 ′ containing abrasive grains is prepared and can be supplied from the nozzle 8. As an abrasive grain in this coolant, what consists of SiC, for example can be used.

  Further, the coolant supply mechanism 6 is provided with a tank 11 for collecting the used coolant 9 (or coolant 9 ') supplied to the wire 2 at the time of cutting. The coolant 9 whose temperature is adjusted from the tank 11 via the temperature adjusting mechanism 12 can be circulated and supplied from the nozzle 8.

  The coolant supply mechanism 6 is not limited to the tank 11 and the temperature adjustment mechanism 12. For example, a centrifuge can be further provided to remove or collect chips, abrasive grains, and other impurities in the used coolant. And the coolant 9 which performed those necessary treatments is stored in the tank 11. In addition, a part of the coolant can be collected or removed from the tank 11, and on the contrary, new clean coolant and abrasive grains can be additionally added to the tank 11.

Next, the slicing method of the present invention using the wire saw of FIG. 4 will be described.
First, a silicon ingot is prepared. The silicon ingot prepared here is not particularly limited, and for example, a silicon single crystal rod grown by a CZ (Czochralski) method or an FZ (Floating Zone) method can be used.

Moreover, it does not limit about various conditions, such as the diameter, the dopant added, and a specific resistance, It can determine suitably. In particular, when the conditions are such that copper contamination is likely to occur, the effectiveness of the present invention that copper contamination can be reduced can be more effectively exhibited.
For example, the diameter can be a relatively large one of 450 mm or more. This is because the larger the diameter of the silicon ingot, the higher the temperature when cutting with a wire saw, and the more easily copper diffuses into the silicon.
The dopant can be boron. This is because boron interacts with copper and promotes the penetration of copper into silicon, and copper contamination is likely to occur. Further, the specific resistance can be 0.03 Ω · cm or less. This is because, in such a low resistivity slice wafer, copper is more likely to penetrate, and when the copper contamination reaches, for example, a saturation level, the concentration value at that time is relatively high and adversely affects the semiconductor characteristics. .

Next, the silicon ingot is cut into a wafer using the wire saw 1.
First, the prepared silicon ingot is processed into an appropriate shape by cutting it into blocks (work W), the work W is held by the work holding portion of the work feed mechanism 5, and sent downward.
Then, the coolant 9 (or coolant 9 ′) stored in the tank 11 is supplied from the nozzle 8 to the wire 2.
Further, the wire 2 is fed out from the wire reel 7 and wound around the wire reel 7 ′ through the wire tension applying mechanisms 4, 4 ′, thereby causing the wire 2 to travel.
In this way, while supplying the coolant 9 to the wire 2, the workpiece W is pressed against the reciprocating wire 2 to cut it into a wafer shape to obtain a slice wafer.
Then, the used coolant 9 is collected into the tank 11 after appropriately performing necessary processing (centrifugation or the like) and supplied to the wire 2 again. Thus, cost can be reduced by reusing and supplying the coolant 9 after use.

In addition, the coolant supplied to the wire 2 is not particularly limited except the copper concentration as described later. The pH is not limited, but can be in the range of 5 to 7, for example. For example, Japanese Patent Laid-Open No. Sho 63-272460 describes that copper contamination is caused by processing silicon with a processing liquid (alkali solution) containing copper, but by adjusting the pH to 7 or less, This phenomenon can be prevented more effectively. At this time, an organic acid typified by citric acid can be added to the coolant to ensure that the pH is 7 or less. In addition, by setting the pH of the coolant to 5 or more, promotion of copper ionization in the coolant can be suppressed, and copper contamination of the silicon wafer can be further reduced.
Moreover, when an abrasive grain is included, the abrasive grain is not particularly limited, and may be made of SiC, for example, as conventionally used.

Here, the copper concentration in the coolant will be described in detail. The copper concentration in the coolant is 80 ppm or less. More preferably, it is 40 ppm or less. In order to avoid copper contamination on the slice wafer, naturally, the lower the better.
When a coolant containing abrasive grains is used as in the free abrasive grain method (that is, when the coolant is composed of abrasive grains and a dispersion medium), the value of 80 ppm or less is calculated from the weight of the dispersion medium in the coolant. Value.
On the other hand, when using a coolant that does not contain abrasive grains as in the fixed abrasive system, the value is calculated from the weight of the coolant itself.

In order to supply the coolant in which the copper concentration is more reliably suppressed to 80 ppm or less to the wire 2, for example, the copper concentration in the coolant is actually measured in advance before supply and confirmed to be 80 ppm or less. However, the coolant is preferably supplied to the wire.
More specifically, the copper concentration of the coolant stored in the tank 11 connected to the nozzle 8 serving as the supply means is controlled to 80 ppm or less. The management method is not particularly limited, and can be appropriately determined according to the cost and the target copper concentration. For example, the coolant in the tank 11 is periodically collected and its copper concentration is measured. If the measured value is high and is likely to exceed 80 ppm, a new coolant is added to the tank 11 to dilute it and the copper concentration is reduced. Can be lowered. Alternatively, a part of the coolant in the tank 11 can be replaced with a new coolant, thereby reducing the copper concentration.

In addition, the measuring method of the copper concentration in a coolant is not specifically limited. It can be measured using an atomic absorption method or the like.
As an example, a measurement method using a coolant 9 ′ containing SiC abrasive grains is shown below. First, an appropriate amount is weighed from the coolant collected from the tank 11 to prepare a sample, mixed with a mixed acid of nitric acid and hydrofluoric acid, decomposed with microwaves, and diluted with a nitric acid solution to prepare a test solution. This test solution is diluted appropriately, and the amount of copper contained is determined by atomic absorption spectrometry. In the measurement pretreatment, since the SiC abrasive grains contained in the coolant are not decomposed, the copper concentration in the coolant is the SiC concentration in the coolant that has been measured in advance (weigh an appropriate amount from the slurry as a sample, This can be measured by weighing the residue obtained by evaporation to dryness), and the weight of the dispersion medium in the coolant is determined and calculated as the concentration relative to the weight of the dispersion medium.
When the coolant does not include abrasive grains (coolant 9), the copper concentration can be similarly calculated using the atomic absorption method. In this case, it is calculated from the weight of the entire coolant.

  By keeping the copper concentration in the coolant supplied to the wire saw wire low as described above, for example, even if a slice wafer is manufactured using a plurality of wire saws, the copper contamination concentration in the slice wafer can be reduced, and The copper contamination concentration can be made more uniform than before. Therefore, it is possible to stably manufacture a slice wafer having a high cleanliness with respect to copper which is an impurity as compared with the conventional case.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Examples 1-9, Comparative Examples 1-6)
Using the wire saw of FIG. 4, the wire is reciprocated while supplying coolant to the wire, and the silicon single crystal ingot is sliced into a wafer. At this time, in Examples 1-9, the coolant which adjusted the copper concentration to 80 ppm or less like this invention is supplied to a wire. On the other hand, in Comparative Examples 1 to 6, unlike the present invention, a coolant whose copper concentration is adjusted to be higher than 80 ppm is supplied to the wire.

Preparation of the coolant from which the copper concentration in Examples 1-9 and Comparative Examples 1-6 differs is explained in full detail.
First, SiC abrasive grains were dispersed in a glycol-based dispersion medium. The copper concentration of the coolant thus prepared was 5 ppm. Therefore, the manufactured coolant is filled in a wire saw similar to that shown in FIG. 4, and a silicon block is sliced by using a wire having brass plating on the surface, and copper is mixed into the coolant by wearing the plated portion of the wire surface. The copper concentration in the coolant was adjusted. Since the amount of brass plating on the surface of the wire and the composition of the plating are known, the copper concentration in the coolant was adjusted to the target concentration by adjusting the distance of the wire to be worn.

Then, using the coolants having different copper concentrations for Examples 1 to 9 and Comparative Examples 1 to 6 produced in this manner, a single crystal silicon block having a diameter of 300 mm was sliced as a main test.
The block to be sliced was added with boron as a dopant and pulled up by the MCZ method. Three types of blocks having different specific resistances such as 0.03 Ω · cm, 0.02 Ω · cm, and 0.01 Ω · cm were prepared. And about each, the copper contamination density | concentration of the slice wafer was computed for every used coolant, and the density | concentration was compared.
In this test, a wire having no surface plating was used as the wire to prevent copper from being mixed into the coolant from the wire during slicing.

The copper concentration in the coolant was analyzed by the following method.
250 mg is weighed from the coolant sampled from the wire saw, used as a sample, mixed with a mixed acid of nitric acid and hydrofluoric acid, decomposed with microwaves, and diluted with a nitric acid solution to prepare a test solution. This test solution was diluted appropriately and the amount of copper contained was quantified by atomic absorption spectrometry. In the measurement pretreatment, since the SiC abrasive grains contained in the coolant are not decomposed, the copper concentration in the coolant is obtained from the SiC concentration in the coolant measured in advance, and the weight of the dispersion medium in the coolant is obtained. The concentration was calculated as the concentration relative to the weight of the dispersion medium.

Moreover, the measurement of the copper contamination density | concentration of a slice wafer was performed with the following method.
It is known that a wafer sliced with a wire saw has a crack layer and a strained layer on the surface, and this portion contains copper and other metals in a high concentration. For this reason, in order to measure the density | concentration of the copper diffused inside the wafer, this part must be removed. Therefore, the 50-micron surface portion (100 microns on both sides) of the slice wafer was removed by etching with a mixture of hydrofluoric acid and nitric acid, and the remaining portion was used as a sample for analysis.
Further, the sample for analysis was washed with a washing solution in which hydrofluoric acid, hydrochloric acid, hydrogen peroxide solution and pure water were mixed, and dissolved in the whole amount by the method disclosed in JP-A-2002-368052 to obtain a sample solution.

That is, by placing the sample for analysis and the mixed acid solution of hydrofluoric acid and nitric acid in the same sealed container and heating, the vapor containing hydrofluoric acid and nitric acid is exposed to the sample to decompose the entire amount of the sample. By heating at 100 to 150 ° C. for 2 to 24 hours, the decomposition product was subjected to silicon removal treatment, and then the residue obtained by evaporation to dryness was dissolved in dilute hydrofluoric acid to prepare a sample solution.
The obtained sample solution was appropriately diluted with a nitric acid solution and analyzed by ICP-MS. These operations were performed using an analysis chip obtained by cleaving the slice wafer.

  The results of experiments conducted in this way are summarized in Tables 1 to 3 and FIGS. The results of the specific resistance of the block of 0.03 Ω · cm are shown in Table 1 and FIG. 1, the results of 0.02 Ω · cm are shown in Table 2 and FIG. 2, and the results of 0.01 Ω · cm are shown in Table 3 and FIG. Show.

  As is clear from Tables 1 to 3 and FIGS. 1 to 3, the copper concentration in the coolant is set to 80 ppm or less (Examples 1 to 9), and when it is higher than 80 ppm (Comparative Examples 1 to 6). In comparison, the copper contamination concentration contained in the sliced wafer can be reduced to about 1/5 or less. In addition, when the specific resistance in the ingot is the same, the copper contamination concentration can be made uniform at the low value, as can be seen by comparing each of Examples 1 to 3. As can be seen by comparing each of Examples 4 to 6 and Examples 7 to 9, similarly, a slice wafer having a low copper contamination concentration can be stably obtained.

  In addition, when the specific resistance is higher than 0.03 Ω · cm (specifically 0.04 Ω · cm), a slice wafer was produced in the same manner as in the above examples and comparative examples. Regarding the relationship of the copper contamination concentration of the slice wafer, the same tendency as in FIGS. 1 to 3 and Tables 1 to 3 was observed. That is, when the copper concentration in the coolant was 80 ppm or less, the copper contamination concentration of the wafer was kept low, and at a copper concentration higher than that, the copper contamination concentration was high.

  The amount of copper diffusing into single crystal silicon increases as the concentration of boron contained in silicon increases. As described above, copper is easily diffused into silicon by forming a bond with boron. Therefore, when cutting a silicon single crystal having a relatively high boron concentration and a low specific resistance (0.03 Ω · cm or less) as in Examples 1 to 9, the boron concentration is lower than that and the specific resistance is high. Depending on the copper concentration in the coolant, the copper contamination concentration of the slice wafer tends to be higher than (for example, 0.04 Ω · cm or more). Therefore, the present invention that suppresses the copper concentration in the coolant to 80 ppm or less is particularly effective when the specific resistance is 0.03 Ω · cm or less.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  For example, in the embodiment, the slicing method of the present invention using the loose abrasive type wire saw has been shown. However, as described above, the present invention can naturally be applied to the slicing method using the fixed abrasive type wire saw. It is.

1 ... Wire saw, 2 ... Wire, 3 ... Wire guide,
4, 4 '... wire tension applying mechanism, 5 ... work feeding mechanism,
6 ... Coolant supply mechanism 7, 7 '... Wire reel, 8 ... Nozzle,
9, 9 '... coolant, 10 ... drive motor, 11 ... tank,
12 ... Temperature adjustment mechanism.

Claims (7)

Using a wire saw, while supplying coolant to the wires wound around a plurality of wire guides, while running the wires, the silicon ingot is pressed against the wires and cut to obtain a plurality of slice wafers A method,
Before supplying the coolant to the wire, the copper concentration in the coolant is measured in advance, and the copper concentration in the coolant supplied to the wire is set to 80 ppm or less by using a coolant of 80 ppm or less. Slicing method. When the coolant after being supplied to the wire is collected in a tank, and the coolant contained in the tank is supplied to the wire for circulation use,
The slicing method according to claim 1 , wherein the copper concentration of the coolant in the tank is controlled to 80 ppm or less. 3. The slicing method according to claim 1, wherein the dopant added to adjust the specific resistance of the silicon ingot to be cut is boron. The slicing method according to any one of claims 1 to 3 , wherein a specific resistance of the silicon ingot to be cut is 0.03 Ω · cm or less. The slicing method according to any one of claims 1 to 4 , wherein a pH of the coolant supplied to the wire is set within a range of 5 to 7. The slicing method according to any one of claims 1 to 5 , wherein a diameter of the silicon ingot is 450 mm or more. The slicing method according to any one of claims 1 to 6 , wherein the coolant includes abrasive grains.

Images