TWI731428B - Manuf acturing method of wafer, quality evaluation method of reuse slurry for wire saw, and quality evaluation method of used slurry for wire saw - Google Patents

Abstract

By suppressing the deterioration in processing quality that results from the quality of reuse slurry for slice processing by means of a wire saw, a wafer manufacturing method that is capable of stabilizing and improving wafer flatness is provided. An ingot is slice processed by means of the wire saw supplied by slurry including abrasive grains and coolants. Used slurry is reused, then after small particles are separated and removed, new abrasive grains and coolants shall be added and mixed to form reuse slurry. The reuse slurry is supplied to the wire saw while a new ingot is slice processed. The present invention is characterized in that small particle volume rate R_A according to the following definition of the reuse slurry is defined to be less than 5.0%. Note Small particle volume rate R_A ：While in said reuse slurry an average particle diameter in the volume particle size distribution is assumed to be R_A1 , and a small particle is defined to be a particle with the particle diameter less than the reference particle diameter R_A2 which is R_A1 /2, a volume ratio in which said small particles occupy among the particles in said reuse slurry.

Description

Wafer manufacturing method, quality evaluation method of recycled paste for wire saw, and Quality evaluation method of used slurry for wire saw

The present invention relates to a wafer manufacturing method that repeats the steps of using a wire saw that supplies slurry containing abrasive grains and a coolant to slice and process an ingot to obtain a plurality of wafers. In addition, the present invention relates to a quality evaluation method of recycled slurry for wire saws and a quality evaluation method of used slurry for wire saws.

Wafers used as substrates for semiconductor devices are manufactured by cutting ingots made of silicon or compound semiconductors. In recent years, as a cutting method of an ingot, a wire saw that supplies slurry containing abrasive grains and a coolant is used to slice and process the ingot while simultaneously obtaining free abrasive grains for multiple wafers has become the mainstream.

Here, the used slurry used in the slicing process is recovered, and after the small particles are separated and removed, new abrasive grains and coolant are added, which is regarded as reused slurry, and this is provided during the slicing process of a new ingot Reuse the slurry to the wire saw. Here, the small particles are mainly composed of silicon chips generated from the ingot during the slicing process. Others also include wire chips generated by wire cutting, and abrasive particles that are worn and reduced in diameter.

For example, Patent Document 1 describes that the effective abrasive particles are recovered from the used slurry, the worn abrasive particles are removed, and the slurry is reconstituted by adding new abrasive particles equivalent to the amount of the removed abrasive particles. The average circularity of the particles is in the range of 0.855 to 0.875, the weight ratio of the new abrasive particles is about 20%, and the average circularity of the abrasive particles contained in the reconstituted slurry is in the range of 0.870 to 0.915.

In addition, Patent Document 2 describes that an additional group of abrasive particles is prepared, the additional group of abrasive particles is added and mixed in a fixed amount in the group of abrasive particles used in the cutting process, and the mixed group of abrasive particles is subjected to classification treatment so that the size of the abrasive particles is in the first 1 Abrasive particle size or more and second abrasive particle size or less. According to this method, while reducing the amount of discarded abrasive grains, it is also possible to perform polishing treatment of the same quality as the new abrasive grain group. [Advanced Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2004-255534 [Patent Document 2] Japanese Patent Publication No. 2011-218516

The small particles contained in the slurry not only do not contribute to the cutting of the ingot, but also hinder the cutting of the medium-diameter abrasive particles, which is useful for cutting. Therefore, when the amount of small particles in the reused slurry is large, the flatness of the wafer manufactured by the slicing process using the above-mentioned reused slurry tends to deteriorate. Traditionally, in the regeneration treatment of the used slurry, the centrifugal separation method is used to separate and remove small particles from the used slurry. However, the inventors understand that depending on the amount of small particles in the recovered used slurry, etc., sometimes the small particles cannot be sufficiently removed. In that case, the amount of small particles in the reused slurry also increases. As a result, , Damage the quality of the slicing process (ie, the flatness of the wafer). Therefore, the inventors of the present invention have reached an understanding that it is necessary to appropriately evaluate and manage the amount of small particles in the used slurry and reuse the slurry.

In view of the above-mentioned problems, the present invention aims to provide a wafer manufacturing method that can stabilize and improve the flatness of wafers by suppressing the deterioration of the processing quality caused by the quality of the reused slurry provided for the slicing process of the wire saw. In addition, the present invention aims to provide a quality evaluation method that can appropriately evaluate the quality of used slurry and reused slurry.

In order to solve the above-mentioned problems, the inventors of the present invention intensively conducted research and obtained the following findings. That is, it is effective to evaluate and manage the quality of used slurry and reused slurry using a parameter called "small particle volume rate" according to the established definition. Therefore, it is understood that by making the volume ratio of small particles of the recycled slurry supplied to the wire saw surely below 5.0%, it is possible to stabilize and improve the flatness of wafers manufactured by slicing.

The gist of the present invention completed based on the above findings is constituted as follows.

(1) A method of manufacturing wafers, repeating the steps of using a wire saw supplied with slurry containing abrasive grains and coolant to slice and process ingots to obtain a plurality of wafers, including: the first step of recycling the above-mentioned slicing process and use The used slurry to the first tank; in the second step, the used slurry is supplied from the first tank to the reprocessing unit, and the reprocessing unit separates and removes small particles from the used slurry to obtain Reconstituted slurry; the third step, supply the reconstituted slurry from the reconstituted processing unit to the second tank, add and mix abrasive grains and coolant to the reconstituted slurry in the second tank, and prepare the reconstituted slurry; 4 steps, supplying the reused slurry from the second tank to the third tank; and step 5, supplying the reused slurry from the third tank to the wire saw to perform slicing of a new ingot; wherein: the wire saw supplied to the slurry recycling the small particle volume ratio R _a defined below 5.0% or less; wherein R _a small particle volume fraction: volume particle size of the above-described slurry recycling assumed distribution of the particles The average particle size in R _{A1 is} defined as R _A1 /2 with a particle size _{below the reference particle size R A2} as small particles, and the volume ratio of the small particles in the particles in the reuse slurry.

(2) The method for manufacturing a wafer as described in (1) above, wherein the used slurry supplied to the slicing process is not recovered when _{the small particle volume rate R B defined below exceeds 10.0%} The slurry goes to the first tank, and the used slurry is discarded; the volume ratio of small particles R _B : Assuming that the average particle size in the volume particle size distribution of the used slurry is R _B1 , it is defined as R _B1 Particles with a particle size below the reference particle size R _{B2 of} /2 are small particles, and the volume ratio of the small particles to the particles in the used slurry.

(3) The method for manufacturing a wafer described in (1) or (2), wherein in the third step, in order to make the specific gravity of the reused slurry a predetermined target value, the added abrasive grains and The amount of coolant.

(4) A method for producing a wafer of (3) described above, wherein the measurement acquired from the groove of the third slurry is recycled small particle volume ratio R _A, R _A measurement of 5.0% or less, from said third trench intact supplying the slurry to said recycling wire saw, slicing processing of new ingot; R _a when measured exceeds 5.0% added again in the second vessel and mixing the above-described grinding slurry recycling tablets and coolant to prepare additional recycling slurry supplied to the slurry recycling added to the third tank, whereby the above-described slurry recycling small particle volume fraction of the third tank R _a 5.0% Next, after that, the reused slurry is supplied to the wire saw to perform slicing processing of a new ingot.

(5) The method for manufacturing a wafer described in (4) above, wherein, in the second preparation, the mass ratio of abrasive grains and coolant is added to the additional reuse slurry in the second tank Respectively 35% or more and 55% or less, set the amount of abrasive grains and coolant to be added.

(6) The quality evaluation method of recycled slurry for wire saws is to separate and remove small particles from the used slurry containing abrasive grains and coolant used in the ingot slicing process of the wire saw, and then add and mix the new slurry. the abrasive grain quality estimation and reusing slurry coolant modulation, wherein: the R _a, following the evaluation of small particle volume ratio defined below the quality of recycled slurry; small particles wherein the volume ratio R _a: Assuming that the average particle size in the volume particle size distribution of the particles in the reused slurry is R _A1 , it is defined that particles with a particle size below the reference particle size R _{A2 of R A1 /2 are small particles.} The volume ratio of small particles in particles.

(7) The method for evaluating the quality of recycled slurry for wire saws described in (6) above, wherein if the small particle volume ratio R _A is 5.0% or less, it is evaluated that the above-mentioned can be reused in the slicing process of a new ingot. recycling the slurry the volume ratio R _a small particles exceeds 5.0%, the evaluation can not be reused in the above-described slurry recycling of slicing the ingot in the new.

(8) The quality evaluation method of the used slurry for the wire saw is the quality evaluation method of the used slurry containing abrasive grains and coolant used in the ingot slicing process of the wire saw. Its characteristics are as follows: Evaluate the quality of the above-mentioned used slurry according to the small particle volume rate R _{B defined below; where the small particle volume rate R B} : Assume that the average particle size in the volume particle size distribution of the particles in the above used slurry is R _B1 , Define particles with a particle size below the reference particle size R _{B2 of R B1} /2 as small particles, and the volume ratio of the above-mentioned small particles to the particles in the above-mentioned used slurry.

(9) The method for evaluating the quality of used slurry for wire saws described in (8) above, wherein if the volume ratio of small particles R _B is 10.0% or less, it is evaluated that the used slurry can be supplied for reprocessing. If the above-mentioned small particle volume ratio R _B exceeds 10.0%, it is estimated that the above-mentioned used slurry cannot be supplied for reprocessing.

According to the wafer manufacturing method of the present invention, by suppressing the deterioration of the processing quality caused by the quality of the reused slurry provided for the slicing process of the wire saw, it is possible to stabilize and improve the flatness of the wafer. In addition, according to the quality evaluation method of the reused slurry for wire saws and the quality evaluation method of the used slurry for wire saws of the present invention, the quality of the used slurry and the reused slurry can be appropriately evaluated.

(Wafer manufacturing method) Hereinafter, while referring to FIGS. 1 to 3, a wafer manufacturing method according to an embodiment of the present invention will be described. The wafer manufacturing method of the present embodiment is based on the free abrasive grain method, repeating the steps of using a wire saw that supplies slurry containing abrasive grains and coolant to cut the ingot to obtain a plurality of wafers. As the material of the ingot, silicon single crystals can be cited. Provide the silicon single crystal ingot to the silicon wafer obtained in the above slicing step, and then go through the steps of lapping, etching, double-side polishing (rough polishing), single-side polishing (mirror polishing), and cleaning in order to become Products of silicon wafers.

First, referring to Fig. 1, a general wire saw 60 that can also be used in this embodiment will be described. The wire saw 60 has a wire group 64 arranged side by side between a plurality of rollers 62A, 62B, and 62C that can be moved back and forth and stretched over, an ingot holding mechanism 66 that holds the ingot W, and a nozzle 68 that supplies slurry to the wire group 64. In the case of the free abrasive grain method, while continuously supplying the slurry 8 containing abrasive grains and coolant from the nozzle 6 to the wire group 64, the wire group 64 is moved back and forth at high speed along the extending direction Z. At the same time, the ingot holding mechanism 66 is used to move the line group 64 in the direction in which the ingot W is inserted. According to the cutting action of the abrasive grains at this time, the ingot W can be simultaneously cut out to form a plurality of wafers. In addition, in the first figure, a state where the line group 64 moves from left to right in the figure is depicted.

The slurry dispersion abrasive grains are water-soluble or oily coolants. The material of the abrasive grains can be selected from more than one type of silicon carbide, silicon nitride, boron nitride, boron carbide, aluminum oxide, diamond, etc. It is ideal to use free abrasive grains with silicon carbide as the main component. As the coolant, it is desirable to use glycol-based organic solvents such as propylene glycol and diethylene glycol as the main component. Typically, a water-soluble coolant mainly composed of propylene glycol can be used. In addition, the coolant contains about 5% by mass of water.

With reference to Fig. 2, a description will be given of the configuration of the wire saw system 100 used in this embodiment and each step of the wafer manufacturing method of this embodiment using this. The wire saw system 100 includes a wire saw device 10, a recovery tank 20 as a first tank, a remanufacturing unit 30, a mixing tank 40 as a second tank, a new coolant tank 42, a new abrasive grain tank 44, and a third tank The supply tank 50.

The wire saw system 100 usually includes about 10-20 multiple wire saw devices 10. Each wire saw device 10 includes a slurry tank 12 and a processing chamber 14. In the processing chamber 14, the wire saw 60 described in FIG. 1 is arranged. The slurry tank 12 contains slurry. There is a pipe between the slurry tank 12 and the nozzle 68 shown in FIG. 1, and the slurry is supplied from the slurry tank 12 to the nozzle 68 through the pipe. The slurry used in the slicing process is recovered and returned to the slurry tank 12. In the slicing process of an ingot, the slurry circulates between the slurry tank 12 and the processing chamber 14, instead of supplying new slurry to the wire saw device 10 Slurry tank 12.

[Step 1] In each wire saw device 10, once the slicing process of one ingot is completed, the used slurry used in the above-mentioned slicing process is recovered to the recovery tank 20 through the pipe connecting each wire saw device 10 and the recovery tank 20. The recovery tank 20 can generally contain about 1000 to 2000 L (liter) of slurry.

[Step 2] The used slurry recovered in the recovery tank 20 is supplied from the recovery tank 20 to the recycling processing unit 30. The recycling processing unit 30 separates and removes small particles from the used slurry to obtain a recycled slurry.

The reprocessing unit 30 includes at least a primary separation decanter 32, a separation tank 34, a secondary separation decanter 36, and a secondary light liquid tank 38. First, the used slurry contained in the recovery tank 20 is supplied to the primary separation decanter 32 through the pipe connecting the recovery tank 20 and the primary separation decanter 32, and is supplied to the primary separation step. The primary separation step is mainly for the purpose of recovering reusable abrasive particles. The primary separation decanter 32 is generally composed of a decanter-type centrifugal separation device. The slurry used here is given a predetermined centrifugal force to separate the primary heavy liquid and the primary light liquid. The primary heavy liquid mainly contains reusable abrasive grains (reconstituted abrasive grains), and contains a small amount of coolant. The primary light liquid mainly contains small particles that are not suitable for reuse and most of the coolant. That is, in the primary separation step, as for the particles in the used slurry, the small particles are separated to the primary light liquid side, and the rest of the reconstituted abrasive particles are separated to the primary heavy liquid side. The coolant in the used slurry, Mainly separated to the primary light liquid side. In addition, as mentioned above, the small particles are mainly composed of silicon chips generated from the ingot accompanying the slicing process, and also include abrasive particles that have been reduced in diameter due to wire chips and abrasion due to wire cutting.

The primary heavy liquid is supplied to the separation tank 34 through a pipe connecting the primary separation decanter 32 and the separation tank 34, and the separation tank 34 can contain about 500 to 2000 L of the primary heavy liquid.

The primary light liquid is supplied to the secondary separation decanter 36 via the pipe connecting the primary separation decanter 32 and the secondary separation decanter 36, and is supplied to the secondary separation step. The secondary separation step is mainly for the purpose of recovering the reusable coolant. The secondary separation decanter 36 is composed of a general decanter-type centrifugal separation device. Here, the primary light liquid is given a larger predetermined centrifugal force than in the primary separation step, and it is separated into a secondary heavy liquid and a secondary light liquid. . The secondary light liquid mainly contains reusable coolant (reconstituted coolant). The secondary heavy liquid mainly contains small particles that are not suitable for reuse and coolant that is not suitable for reuse. That is, in the secondary separation step, the coolant in the primary light liquid contains impurities such as small particles, and the refrigerant components with increased specific gravity are separated to the secondary heavy liquid side, and the rest of the reconstituted coolant is separated to the secondary light liquid. On the side, the small particles in the primary light liquid are separated to the secondary heavy liquid side.

The secondary light liquid is supplied to the secondary light liquid tank 38 via the pipe connecting the secondary separation decanter 36 and the secondary light liquid tank 38, and then via the pipe connecting the secondary light liquid tank 38 and the separation tank 34, It is supplied to the separation tank 34. The secondary light liquid tank 38 can contain about 200 to 800L of secondary light liquid. However, the secondary light liquid does not pass through the secondary light liquid tank 38 and may be directly supplied to the separation tank 34.

Since the secondary heavy liquid mainly contains small particles that are not suitable for reuse and coolant that is not suitable for reuse, it is discarded through a pipe extending from the secondary separation decanter 36. In this way, the separation tank 34 contains reconstituted slurry obtained by separating and removing small particles from the used slurry.

[Step 3] After that, the reconstituted slurry is supplied from the reconstituted processing unit 30 to the preparation tank 40. Specifically, the reconstituted slurry is supplied to the preparation tank 40 via the pipe connecting the separation tank 34 and the preparation tank 40. In the preparation tank 40, new abrasive grains and coolant are added and mixed into the reconstituted slurry to prepare a reutilized slurry. The new coolant is stored in the new coolant tank 42, and is supplied to the preparation tank 40 through the pipe connecting the new coolant tank 42 and the preparation tank 40. The new abrasive grains are stored in the new abrasive grain tank 44, and are supplied to the blending tank 40 through the piping of the new abrasive grain tank 44 and the blending tank 40. The mixing tank 40 can contain about 1,000 to 2,000 L of recycled slurry.

In this third step, in order to make the specific gravity of the prepared reused slurry a predetermined target value, it is desirable to set the amount of abrasive grains and coolant to be added. Specifically, it is desirable that the target value is in the range of 1.500 to 1.600 which is about the same as the specific gravity of the unused slurry.

In this case, the mass ratio of the new abrasive grains and the new coolant in the reuse slurry in the preparation tank 40 also fluctuates in the range of about 20-50%. The reason is that the amount of recyclable abrasive particles and coolant in the used slurry is uneven. In addition, the mass ratio of the new abrasive grains and the new coolant in the mixing tank 40 is defined as follows: the mass ratio of the new abrasive grains = the input amount of the new abrasive grains/(the input amount of the new abrasive + the abrasive grains in the reconstituted slurry the amount)

The input ratio of new coolant = the input amount of new coolant / (the input amount of new coolant + the amount of coolant in the reconstituted slurry)

[Step 4]

The reuse slurry prepared in the preparation tank 40 is supplied to the supply tank 50 via a pipe connecting the preparation tank 40 and the supply tank 50. The supply tank 50 can store about 2000 to 8000L of recycled slurry.

[Step 5]

The reused slurry contained in the supply tank 50 is supplied to each slurry tank 12 through the pipe connecting the supply tank 50 and the slurry tank 12 of each wire saw device 10, and then supplied to the wire saw 60, and then sliced in the new ingot Used in processing.

[Small particle volume rate of reused slurry]

In this embodiment, supplied to the slurry recycling wire saw according to the small particle volume ratio R _A is defined below the critical 5.0% or less; wherein R _A small particle volume fraction: volume of the assumed particle slurry recycled The average particle size in the particle size distribution is R _A1 , and particles having a particle size below the reference particle size R _{A2 of R A1} /2 are defined as small particles, and the volume ratio of the small particles in the particles in the reuse slurry.

The "small particle volume rate R _A "of the reused slurry is an index indicating the proportion of small particles in the total particles such as abrasive grains, silicon chips, and lint in the reused slurry. So far, it has not been measured as a quantitative indicator. In this embodiment, due to this small particle volume ratio R _A is 5.0% or less, can be suppressed due to the deterioration of pulp quality recycling processing quality, a result, the wafer can be stabilized and improved flatness. That is, it stabilizes and improves the flattening index such as GBIR (ideal range of the overall backside), Warp (warpage), and nanotopography (nanotopography). Further, according to the viewpoint of improving the flatness, recycling the slurry volume fraction of small particles over the smaller the R _A, but according to the suppression amount of abrasive grain, the coolant (i.e. costs) point of view, preferably at least 3.0%.

Figure 3 is a diagram showing the particle size distribution of the particles in the reused slurry used to explain the calculation method of the small particle volume ratio. First, the particle diameter (the area circle equivalent diameter) of each particle in the sample of the reused slurry is measured. The particle size distribution D calculated using the volume of particles in the reused slurry as shown in Fig. 3 is obtained. The method of measuring the particle size of each particle is not particularly limited. For example, while the slurry flows into the flow path between the small glass cells, the particles are photographed one by one with a camera. Through image processing, the particles can be measured one by one. Particle size. From the viewpoint of measurement accuracy, the amount of reused slurry provided for this measurement is preferably 2 mL (milliliter) or more.

Next, the average particle diameter R _{A1 of} the particle size distribution D is obtained, and R _A1 /2 is set as the reference particle diameter R _A2 . Small particles are defined as particles having a particle size less than _{this reference particle size R A2.} Then, based on the particle size distribution D, the volume ratio of the small particles in the particles in the reused slurry is calculated. In addition, the "average particle diameter R _A1 "is defined as the particle diameter at which the particle size distribution D lies at 50% of the cumulative.

As already mentioned, in order to make the third step of recycling the slurry prepared in specific gravity becomes a predetermined target value, the amount of abrasive grains and coolant even if the set is added, there will be a slurry of small particles reuse volume change rate R _A , More than 5.0% of cases. Specifically, when the reuse process of the used slurry is repeated more than 10 times, the used slurry recovered immediately after the slicing process will continue to accumulate small particles. As a result, the small particles in the recycled slurry after the recycling process Also become more. In such a case, reuse of the slurry of small particle volume ratio R _A is likely to exceed 5.0%. In such a case, when the reused slurry is continuously supplied to the wire saw device 10, the quality of the slicing process (that is, the flatness of the wafer) will be impaired. Therefore, as a method for ensuring that the volume ratio of small particles of the recycled slurry supplied to the wire saw is 5.0% or less, the following can be cited.

First, small particles from R _A measured volume of recycled slurry supply tank 50 is collected. Here, R _A measured at 5.0% or less, is supplied from the tank 50 is supplied unchanged to the slurry recycling wire saw apparatus 10, processing of new ingot slicing.

On the other hand, when the measured R _A than 5.0%, the preparation tank 40 again in the addition and mixing abrasive grains and new coolant recycling the slurry to prepare a slurry recycling added. Because of this additional supply of the slurry recycled to the supply tank 50, the slurry of small particles in the recycling tank 50 is supplied in a volume ratio R _A 5.0% or less, then, is supplied to the slurry recycling wire saw apparatus 10, a new Slicing processing of ingots. Further, additional supply of recycled slurry supply tank 50 to measure a small particle volume ratio R _A again to confirm 5.0% or less. According to this method, the volume ratio of small particles of the recycled slurry supplied to the wire saw can be surely below 5.0%.

At this time, in the re-preparation, in order to make the mass ratio of the new abrasive grains and the new coolant in the reused slurry added in the mixing tank 40 to 35% or more and 55% or less, set the added abrasive grains and coolant. The amount is better. In this way, the amount of abrasive particles and coolant used will not be excessive, and the volume rate of small particles of the reused slurry can be surely below 5.0%.

In the above embodiment, the case of slicing a silicon single crystal ingot is exemplified, but the present invention is not limited to this, and an ingot of any material may be used as a processing object.

[Small particle volume rate of used slurry]

Referring to Fig. 2, in this embodiment, regarding the used slurry provided for the slicing process, it is better to consider the small particle volume ratio. _{That is, when the volume ratio of small particles R B} as defined below in the used slurry provided for the slicing process exceeds 10.0%, it is better to discard the used slurry without recycling the used slurry to the recovery tank 20; wherein the volume ratio of small particles R _B : Assuming that the average particle size in the volume particle size distribution of the particles in the used slurry is R _B1 , define that the particles with the standard particle size of R _{B1 /2 and the particle size below R B2} are small particles. The above has been used The volume ratio of the above-mentioned small particles to the particles in the slurry.

The "small particle volume rate R _B "of the used slurry is an index indicating the proportion of small particles in the used slurry, such as abrasive grains, silicon chips, and thread chips. This is not a measurement as a quantitative indicator. . When the volume ratio of small particles R _{B exceeds 10.0%, it is difficult to make the volume ratio of small particles R A of the} reused slurry below 5.0% during the subsequent recycling process, or the amount of abrasive particles and coolant must be excessive. . Therefore, when the small particle volume ratio R _B exceeds 10.0%, the used slurry is not recovered to the recovery tank 20 but discarded. When the small particle volume ratio R _B is 10.0% or less, it is recovered to the recovery tank 20. In this way, the amount of abrasive particles and coolant used is not excessive, and the small particle volume rate of the reused slurry can be surely reduced to 5.0% or less. In addition, the calculation method of the "small particle volume rate R _B "is the same as the small particle volume rate R _{A of the reused slurry.}

As an embodiment of this method, it is mentioned below. First, when the slicing of one ingot in each wire saw device 10 is completed, the small particle volume rate R _{B of the} used slurry collected from the slurry tank 12 is measured, and it can be discarded or recycled based on the measured value.

In addition, the second aspect does not necessarily measure the volume rate of small particles. As mentioned earlier, in the slicing process of one ingot, the slurry circulates between the slurry tank 12 and the processing chamber 14. Therefore, the small particle volume ratio of the used slurry has a roughly positive correlation with the size (length and diameter) of the ingot provided for the slicing process. Therefore, when using a slurry with a small particle volume rate of 5.0% or less for slicing, if the ingot size and the small particle volume rate of the used slurry are obtained in advance, the size of the ingot provided for the slicing process can be Judgment for disposal or recycling.

(Quality Evaluation Method of Recycled Pulp for Wire Saw) A method for evaluating the quality of recycled slurry for wire saws according to an embodiment of the present invention will be described. In this embodiment, the used slurry containing abrasive grains and coolant used in the ingot slicing process of the wire saw is separated and removed, and then new abrasive grains and coolant are added and mixed for reuse. The quality evaluation method of slurry.

Thus, the R wherein the volume ratio of small particles in accordance with both the above-defined _A, the assessment of the quality of recycled slurry. Thereby, the quality of the reused slurry can be appropriately evaluated.

For example, if the small particle volume rate R _{A is} less than 5.0%, it is estimated that the reused slurry can be reused for slicing processing of new ingots. If the small particle volume rate R _A exceeds 5.0%, it is estimated that the reused slurry cannot be reused. Slicing of new ingots.

(Method of evaluating the quality of used slurry for wire saws) The quality evaluation method of the used slurry for wire saws of one embodiment of the present invention will be described. This embodiment is a quality evaluation method of used slurry containing abrasive grains and coolant used in the ingot slicing process of the wire saw.

Therefore, it is characterized by evaluating the quality of the used slurry based _{on the small particle volume rate R B} defined in accordance with the above-mentioned definition. In this way, the quality of the used slurry can be properly evaluated.

For example, small particle volume fraction of R _B at 10.0% or less, evaluation may be provided to the slurry recycling process has been used, small particle volume ratio R _B over 10.0%, it can not provide evaluation of the slurry used to process recycled.

Using the wire saw system shown in Fig. 2 including the wire saw shown in Fig. 1, repeat the steps of slicing and processing the silicon ingot. As abrasive grains, free abrasive grains mainly composed of #2000 silicon carbide were used. As the coolant, a water-soluble glycol-based coolant is used. The above-mentioned abrasive grains were added to the water-soluble coolant to produce a slurry with a specific gravity of 1.570, and the operation was started as an unused slurry. The used slurry used in the slicing process is recovered and reprocessed by the method described above, and used as the reused slurry in the slicing process of the new ingot. In order to set the specific gravity of the prepared reused slurry to 1.570, the amount of abrasive grains and coolant to be added was set.

The small particle volume rate R _B of the used slurry and the small particle volume rate R _{A of the} reused slurry are based on the method described above, using the particle size manufactured by Sysmex. The shape analysis device FPIA-3000 measures.

(Example 1) recycling the slurry volume fraction of small particles for use in slicing R _A is 3.73% of the cases, after the slicing comparator (As-sliced) wafer flatness 5.23% of cases. Figure 4 shows the results of determining the thickness of one wafer cut from the central part of the ingot according to the capacitance method in each level.

It is clear from Figure 4 that the _{thickness of the wafer processed with the reused slurry with a small particle volume rate of R A of} 5.23% varies locally at the center, and the flatness deteriorates. In contrast, the thickness of the wafer processed with the reused slurry with a small particle volume ratio of R _{A of} 5.23% has little local variation and good flat portions.

(Example 2) was repeated using a variety of small particle volume ratio R _A recycling slurry for slicing, wafer flatness index GBIR measured. GBIR is the overall flatness index of the backside reference, which defines the deviation between the maximum and minimum thickness of the wafer surface on the reference surface when the backside of the wafer is used as the reference surface. FIG 5, shows the relationship between the volume fraction of small particles GBIR R _A and the wafer. Further, each of the plotted points of FIG. 5 R _A display using a recycling GBIR average slurry was full of wafers from an ingot obtained.

According to FIG. 5 understand, through the use of small particle volume fraction R recycled slurry _A 5.0% or less, can be reliably controlled in GBIR 10.0μm or less.

(Example 3) When the small particle volume rate R _B of the used slurry after the slicing process has various values, the small particle volume rate R _{A of the} prepared reused slurry is measured. In addition, as mentioned earlier, when preparing the reuse slurry, the amount of abrasive grains and coolant to be added is set in order to make the specific gravity of the reuse slurry 1.570. Figure 6 shows the results.

According to Figure 6, when the volume ratio of small particles R _{B of} the used slurry is below 10.0%, the volume ratio of small particles of the reused slurry can indeed be below 5.0%. [Industrial Utilization Possibility]

According to the wafer manufacturing method of the present invention, it is possible to stabilize and improve the flatness of the wafer by suppressing the deterioration of the processing quality due to the quality of the reused slurry provided for the slicing process of the wire saw.

10: Wire saw device 12: Slurry tank 14: Processing room 20: Recovery tank (first tank) 30: Reengineering the processing unit 32: One-time separation decanter 34: Separation tank 36: Secondary separation decanter 38: Secondary light liquid tank 40: Blending slot (Second slot) 42: new coolant tank 44: New abrasive grain tank 50: Supply tank (3rd tank) 60: Wire saw 62A, 62B, 62C: Roller 64: line group 66: Ingot holding mechanism 68: Nozzle 100: Wire saw system W: Ingot

[Figure 1] is a schematic diagram showing a general wire saw 60; [Figure 2] is a schematic diagram showing the structure of a wire saw system 100 used in an embodiment of the present invention; [Figure 3] is for explaining reuse FIG small particle slurry method of calculating the volume ratio R _a; and [FIG. 4] lines showed in Example 1, the influence of the slurry FIG reuse rate R _a small particle volume distribution of the thickness of the wafer; [5 FIG. ] lines showed in Example 2, the relationship of FIG GBIR slurry recycling ratio R _a small particle volume of the wafer; and [FIG. 6] lines showed small particles in Example 3, a slurry of a volume used R _B of the diagram and reuse of the slurry volume fraction of small particles of RA.

10: Wire saw device

12: Slurry tank

14: Processing room

20: Recovery tank (first tank)

30: Reengineering the processing unit

32: One-time separation decanter

34: Separation tank

36: Secondary separation decanter

38: Secondary light liquid tank

40: Blending tank (2nd tank)

42: new coolant tank

44: New abrasive grain tank

50: Supply (circulation) tank (3rd tank)

60: Wire saw

68: Nozzle

100: Wire saw system

Claims (7)

A method for manufacturing wafers, which repeatedly uses a wire saw supplied with slurry containing abrasive grains and coolant to slice and process ingots to obtain a plurality of wafers. The method includes: the first step: recovering the previously used slicing process The used slurry is sent to the first tank; in the second step, the used slurry is supplied from the first tank to the reprocessing unit, and the reprocessing unit separates and removes small particles from the used slurry to obtain remade slurry The third step is to supply the reconstituted slurry from the reprocessing unit to the second tank, add and mix abrasive grains and coolant to the reconstituted slurry in the second tank, and prepare the reusable slurry; the fourth step , Supplying the reused slurry from the second tank to the third tank; and in the fifth step, supplying the reused slurry from the third tank to the wire saw for slicing a new ingot; characterized in: supplied to the wire saw according to the above-described slurry recycling small particle volume ratio defined below in R _a 5.0% or less; wherein R _a small particle volume fraction: assuming that the above slurry recycling particles have a volume particle size distribution The average particle size is R _A1 , and particles having a particle size less than the reference particle size R _{A2 of R A1} /2 are defined as small particles, and the volume ratio of the small particles in the particles in the reuse slurry. The method of manufacturing a wafer as described in the first item of the scope of patent application, wherein, when the volume ratio of small particles R _B defined below in the used slurry supplied to the slicing process exceeds 10.0%, the used used slurry is not recovered The slurry goes to the first tank, and the used slurry is discarded; the volume ratio of small particles R _B : Assuming that the average particle size in the volume particle size distribution of the used slurry is R _B1 , it is defined as R _B1 Particles with a particle size below the reference particle size R _{B2 of} /2 are small particles, and the volume ratio of the small particles to the particles in the used slurry. The method of manufacturing a wafer as described in claim 1 or 2, wherein, in the third step, in order to make the specific gravity of the reused slurry a predetermined target value, the added abrasive grains and coolant are set的量。 The amount. The method of manufacturing a wafer as defined in claim 3 of the scope of the item, wherein the measurement acquired from the groove of the third slurry is recycled small particle volume ratio R _A, R _A measurement of 5.0% or less, from said third trench intact supplying the slurry to said recycling wire saw, slicing processing of new ingot; R _a when measured exceeds 5.0% added again in the second vessel and mixing the above-described grinding slurry recycling tablets and coolant to prepare additional recycling slurry supplied to the slurry recycling added to the third tank, whereby the above-described slurry recycling small particle volume fraction of the third tank R _a 5.0% Next, after that, the reused slurry is supplied to the wire saw to perform slicing processing of a new ingot. The method for manufacturing a wafer as described in claim 4, wherein, in the second preparation, the mass ratio of abrasive grains and coolant is added to the additional reuse slurry in the second tank Respectively 35% or more and 55% or less, set the amount of abrasive grains and coolant to be added. A method for evaluating the quality of reused slurry for wire saws. It separates and removes small particles from the used slurry containing abrasive grains and coolant used in the ingot slicing process of the wire saw, and then adds and mixes new grinding tablets and modulation coolant recycling slurry quality estimation method, characterized in that: the volume ratio of small particles in accordance with the following definition of R _a, using the re-evaluation of the quality of the slurry, wherein the volume fraction of small particles in R _a If it is less than 5.0%, it is estimated that the reused slurry can be reused in the slicing process of the new ingot, and if the small particle volume ratio R _A exceeds 5.0%, it is estimated that the reused slurry cannot be reused in the slicing process of the new ingot. Slurry; where the volume ratio of small particles R _A : Assuming that the average particle size in the volume particle size distribution of the particles in the reused slurry is R _A1 , define particles with a particle size below the reference particle size R _{A2 of R A1 /2} Small particles, the volume ratio of the small particles in the particles in the reuse slurry. A method for evaluating the quality of used slurry for wire saws. It is a method for evaluating the quality of used slurry containing abrasive grains and coolant used in the ingot slicing process of wire saws. Its characteristics are as follows: The defined small particle volume rate R _B is used to evaluate the quality of the above-mentioned used slurry. If the above small particle volume rate R _{B is} below 10.0%, it is estimated that the above-mentioned used slurry can be supplied for reprocessing. The above-mentioned small particle volume If the ratio R _B exceeds 10.0%, it is estimated that the above-mentioned used slurry cannot be supplied for reprocessing; the volume ratio of small particles R _B : Assuming the average particle size in the volume particle size distribution of the particles in the above-mentioned used slurry is R _B1 , It is defined that _{particles having a particle size of R B1} /2 or less of the reference particle size R _B2 are small particles, and the volume ratio of the small particles in the particles in the above-mentioned used slurry.

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