JP2018012821A - Grinding liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding liquid having relatively high recovery efficiency by centrifugal separation while suppressing reduction of dispersibility when abrasive grain is contained.SOLUTION: The grinding liquid has total content of an alcoholic solvent and an ether solvent in whole solvent of the grinding liquid of 95 mass% to 100 mass%, and a ratio of mass of the ether solvent to the alcoholic solvent of 1 time to 5 times. Viscosity of the ether solvent at 25°C is lower than viscosity of the alcoholic solvent and viscosity difference of the ether solvent and the alcoholic solvent is preferably 15 mPa s to 20 mPa s.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a grinding fluid.

  In recent years, demand for difficult-to-process substrates such as glass, sapphire, and silicon carbide is increasing as substrates for precision electronic devices such as hard disks, LEDs, and power devices.

  For polishing such difficult-to-process substrates, a fixed abrasive pad is generally used. The processing using the fixed abrasive polishing pad can be performed using, for example, a commercially available double-side polishing machine. Specifically, the substrate held by the carrier is sandwiched between the upper and lower surface plates to which the polishing pad is fixed, and the substrate and the upper and lower surface plates are relatively moved to simultaneously grind both surfaces of the substrate. At this time, the grinding liquid is supplied to both surfaces of the substrate in order to cool the processed surface of the substrate or to accelerate the processing.

  As the above-mentioned grinding fluid, for example, a slurry-like grinding fluid containing abrasive grains such as alumina particles and silica particles is known. In order for the abrasive grains to effectively contribute to polishing during grinding, the abrasive grains must be in a dispersed state in the grinding liquid. For this reason, from the viewpoint of the dispersibility of the abrasive grains, alcohol solvents such as ethylene glycol are generally used as the solvent for the grinding fluid.

  The grinding fluid is reused to reduce manufacturing costs and environmental burdens. In the above-described polishing, grinding waste is generated from the substrate and mixed into the grinding fluid. Therefore, when the grinding fluid is reused, the amount of grinding waste contained in the grinding fluid increases. When the amount of grinding waste contained in the grinding liquid increases in this way, the substrate grinding efficiency decreases and the substrate is easily damaged. Therefore, in order to reuse the grinding fluid, it is necessary to separate and collect grinding scraps from the used grinding fluid. Examples of the separation / recovery method include centrifugation, separation with a filter, and washing / separation with a strong acid or strong alkali. Among these, separation by a filter requires a high-performance filter, so the cost of the filter is high. In addition, in the washing and separation using strong acid or strong alkali, the waste liquid treatment cost and environmental load are large. For this reason, centrifugal separation is generally used for separating the grinding waste.

  When the alcohol-based solvent grinding fluid is centrifuged, it is particularly difficult to collect small grinding scraps having a particle size of 100 nm or less, and the grinding fluid recovery efficiency tends to be reduced. As a method for increasing the recovery efficiency, for example, there is a method of recovering grinding scraps having a smaller particle diameter by membrane separation after centrifugation (see JP 2010-221337 A). However, if a separation step other than centrifugation is added to increase the recovery efficiency in this way, the manufacturing equipment cost increases and the number of steps for reusing the grinding fluid increases. For this reason, it is required to increase the recovery efficiency of the grinding fluid by centrifugation.

JP 2010-221337 A

  The present invention has been made in view of these disadvantages, and an object of the present invention is to provide a grinding liquid that has a relatively high recovery efficiency by centrifugation while suppressing a decrease in dispersibility in the case of containing abrasive grains. It is to be.

  As a result of intensive studies on the recovery efficiency of the grinding fluid by centrifugation, the present inventors have added a predetermined amount of an ether solvent to the alcohol solvent as a solvent for the grinding fluid. The present inventors have found that the following small grinding scraps can also be collected and completed the present invention.

  That is, the invention made to solve the above problems is a grinding liquid used for grinding a substrate material, which contains an alcohol solvent and an ether solvent, and the alcohol solvent and ether in the whole solvent of the grinding liquid. The total content of the system solvent is 95% by mass or more and 100% by mass or less, and the mass ratio of the ether solvent to the alcohol solvent is 1 to 5 times.

  The grinding fluid contains an alcohol solvent and an ether solvent, the total content of the alcohol solvent and the ether solvent in the entire solvent of the grinding fluid is within the above range, and the alcohol solvent of the ether solvent. The ratio of the mass to is within the above range. Thus, by using a solvent obtained by adding a predetermined amount of an ether solvent to an alcohol solvent, the grinding liquid can reduce the density of the solvent while suppressing a decrease in the viscosity of the entire solvent. By suppressing the decrease in the viscosity of the solvent, the grinding fluid can ensure the dispersibility of the abrasive grains even when the abrasive grains are contained. Further, since the density of the grinding scrap is generally larger than the density of the solvent, the grinding liquid can increase the density difference between the solvent and the grinding scrap by reducing the density of the solvent as described above. By increasing the density difference between the solvent and the grinding waste in this way, the grinding fluid can be easily separated by centrifugation even if it is a relatively light substance, that is, grinding waste having a relatively small particle size. Therefore, the recovery efficiency by centrifugation can be made relatively high while suppressing a decrease in dispersibility when the abrasive is contained by the grinding liquid.

  The viscosity of the ether solvent at 25 ° C. is lower than the viscosity of the alcohol solvent, and the viscosity difference between the ether solvent and the alcohol solvent is preferably 15 mPa · s or more and 20 mPa · s or less. The ease of centrifugation is improved when the viscosity of the solvent is lowered, but when the viscosity of the solvent is lowered, it is difficult to ensure the dispersibility of the abrasive grains when the abrasive liquid contains the abrasive grains. Dispersion of abrasive grains by mixing an ether solvent having a relatively high abrasive dispersibility with an ether solvent having a lower viscosity than this, and setting the difference in viscosity between the ether solvent and the alcohol solvent within the above range. In addition, it is possible to further accelerate the recovery of the grinding scraps by centrifugal separation while ensuring the performance, and to improve the recovery efficiency of the grinding fluid.

  Here, “ether” refers to an organic compound having a structure (—O—) in which two organic groups are connected by an oxygen atom. “Alcohol” refers to a compound in which a hydrogen atom of an aliphatic hydrocarbon is substituted with a hydroxyl group (—OH), excluding a compound belonging to ether.

  As described above, the grinding fluid of the present invention has a relatively high recovery efficiency by centrifugal separation while suppressing a decrease in dispersibility when containing abrasive grains.

It is a flowchart which shows the grinding method of the board | substrate material which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of a well-known grinding apparatus. It is a photograph which shows the state of the grinding fluid before and behind centrifugation in an Example.

  Hereinafter, embodiments of the present invention will be described in detail.

<Grinding fluid>
The grinding liquid according to one embodiment of the present invention is used for grinding a substrate material, for example, a surface grinding process of a fixed abrasive system. The grinding fluid contains an alcohol solvent and an ether solvent. Moreover, the said grinding liquid has an abrasive grain disperse | distributed to the said solvent.

(solvent)
Although it does not specifically limit as said alcohol solvent, For example, ethylene glycol, propylene glycol, butylene glycol, oleyl alcohol etc. can be mentioned. Among these, ethylene glycol is preferable because it has a relatively low viscosity and easily ensures dispersibility of the abrasive grains. Although the said alcohol solvent may be used independently, you may mix and use 2 or more types.

  The ether solvent is not particularly limited, but methyl glycol, methyl diglycol, methyl triglycol, isopropyl glycol, isopropyl diglycol, butyl glycol, butyl diglycol, butyl triglycol, isobutyl glycol, isobutyl diglycol, hexyl Glycol, hexyl diglycol, 2-ethylhexyl glycol, 2-ethylhexyl diglycol, allyl glycol, phenyl glycol, phenyl diglycol, benzyl glycol, methylpropylene glycol, methylpropylene diglycol, methylpropylene triglycol, propylpropylene glycol, propylpropylene Diglycol, butyl propylene glycol, butyl propylene diglycol, phenyl B propylene glycol and the like. Of these, isobutyl diglycol that facilitates enhancing the recovery efficiency of the grinding fluid is preferred. The ether solvents may be used alone or in combination of two or more.

  The lower limit of the total content of the alcohol solvent and ether solvent in the entire solvent of the grinding fluid is 95% by mass, and more preferably 97% by mass. If the total content is less than the lower limit, it may be difficult to centrifuge grinding scraps having a small particle size. On the other hand, the upper limit of the total content is 100% by mass.

  The lower limit of the mass ratio of the ether solvent to the alcohol solvent is 1 and more preferably 2 times. On the other hand, the upper limit of the mass ratio is 5 times, more preferably 4 times. If the mass ratio is less than the lower limit, it may be difficult to collect grinding scraps having a small particle diameter by centrifugation. Conversely, if the mass ratio exceeds the upper limit, the dispersibility of the abrasive grains may be insufficient.

Here, the reason why it is possible to collect grinding scraps having a small particle diameter by centrifugal separation while ensuring the dispersibility of the abrasive grains by containing an alcohol solvent and an ether solvent in the grinding liquid. The ease of centrifugation can be expressed by the sedimentation coefficient s [s] shown in the following formula (1).
In the above formula (1), d [cm] is the diameter of the particle to be separated, σ [g / cm ³ ] is the particle density, ρ [g / cm ³ ] is the solvent density, and η [g / cm · s. ] Represents the viscosity of the solvent.

  Since the density σ of the grinding scrap is considered to be substantially constant regardless of the particle diameter, for example, when using a grinding fluid using EG as a solvent, it is difficult to collect grinding scrap having a small particle diameter using this formula (1). ) Shows that d is small. In addition, the sedimentation coefficient s can be increased by increasing the density of the solvent. The sedimentation coefficient s can also be increased by reducing the viscosity of the solvent. Thus, it turns out that it becomes easy to collect | recover grinding scraps with a small particle size by adjusting the density or viscosity of a solvent from said Formula (1). However, when the viscosity of the solvent is lowered, the dispersibility of the abrasive grains is lowered, so that the processing acceleration of the grinding fluid is lowered. Thus, as a result of intensive studies to achieve both grinding scrap recovery and grinding fluid processing acceleration, the present inventors have found that a predetermined amount of an ether solvent may be added to an alcohol solvent as a solvent for the grinding fluid. Got. That is, as shown in Table 1, since the alcohol solvent and the ether solvent have a relatively high viscosity compared to the density (the viscosity / density value is relatively large), the total content of the alcohol solvent and the ether solvent is determined as follows. The present inventors have found that by setting the amount to 50% by mass or more of the whole solvent, the sedimentation coefficient s can be increased while suppressing a decrease in the viscosity of the solvent.

  Furthermore, when the present inventors considered the ratio of the mass of the ether solvent to the alcohol solvent, when the mass ratio is less than 1, it is difficult to collect grinding waste having a small particle diameter by centrifugation, and the mass described above. It has been found that when the ratio exceeds 5 times, it is difficult to disperse the abrasive grains in the solvent. From the above results, the present inventors can achieve both grinding scrap recovery and grinding fluid processing acceleration by setting the mass ratio of the ether solvent to the alcohol solvent to be 1 to 5 times. I knew.

  The lower limit of the viscosity of the alcohol solvent at 25 ° C. is preferably 15 mPa · s, and more preferably 20 mPa · s. On the other hand, the upper limit of the viscosity of the alcohol solvent is preferably 30 mPa · s, more preferably 25 mPas. If the viscosity of the alcohol solvent is less than the lower limit, the dispersibility of the abrasive grains may be insufficient. On the contrary, when the viscosity of the alcohol solvent exceeds the upper limit, the sedimentation coefficient s is not sufficiently increased, and it may be difficult to collect grinding scraps having a small particle diameter.

  The lower limit of the viscosity of the ether solvent at 25 ° C. is preferably 3 mPa · s, and more preferably 4 mPa · s. On the other hand, the upper limit of the viscosity of the ether solvent is preferably 10 mPa · s, more preferably 7 mPa · s. If the viscosity of the ether solvent is less than the above lower limit, the ether solvent tends to lower the viscosity of the entire solvent, which may make it difficult to ensure the dispersibility of the abrasive grains. On the other hand, when the viscosity of the ether solvent exceeds the upper limit, the sedimentation coefficient s is not sufficiently increased by the ether solvent, and it may be difficult to collect grinding scraps having a small particle diameter.

  As a minimum of the viscosity of the whole solvent in 25 degreeC, 7 mPa * s is preferable and 8 mPa * s is more preferable. On the other hand, the upper limit of the viscosity of the whole solvent is preferably 15 mPa · s, and more preferably 12 mPa · s. There exists a possibility that the dispersibility of an abrasive grain may become inadequate that the viscosity of the said whole solvent is less than the said minimum. On the other hand, if the viscosity of the entire solvent exceeds the upper limit, the sedimentation coefficient s cannot be sufficiently increased, and it may be difficult to collect grinding scraps having a small particle size.

  The viscosity of the ether solvent at 25 ° C. is lower than the viscosity of the alcohol solvent. Thus, by adding an ether solvent having a viscosity lower than that of an alcohol solvent to an alcohol solvent having a relatively high abrasive dispersibility, the abrasive particles are recovered by centrifugation while ensuring the dispersibility of the abrasive grains. And the recovery efficiency of the grinding fluid can be increased.

  The lower limit of the difference in viscosity between the ether solvent and the alcohol solvent at 25 ° C. is preferably 15 mPa · s, and more preferably 17 mPa · s. On the other hand, the upper limit of the viscosity difference is preferably 20 mPa · s, and more preferably 19 mPa · s. If the viscosity difference is less than the lower limit, the settling coefficient s cannot be sufficiently increased by the ether solvent, and it may be difficult to collect grinding scraps having a small particle size. On the contrary, if the viscosity difference exceeds the upper limit, the viscosity of the whole solvent is likely to be lowered by the ether solvent, so that it is difficult to increase the sedimentation coefficient s while ensuring the dispersibility of the abrasive grains. . When using a mixture of a plurality of solvents as the ether solvent or alcohol solvent, the “viscosity difference between the ether solvent and the alcohol solvent” is an ether averaged according to the mass ratio, respectively. It means the difference between the viscosity of the system solvent and the viscosity of the alcohol solvent.

The upper limit of the density of the alcohol-based solvent in 20 ° C., preferably from ^{1.3g / cm 3, 1.2g / cm} 3 is more preferable. When the density of the alcohol solvent exceeds the upper limit, the sedimentation coefficient s is not sufficiently increased even if an ether solvent is added, and it may be difficult to collect grinding scraps having a small particle diameter. On the other hand, the lower limit of the density of the alcohol solvent is not particularly limited, but is usually about 0.7 g / cm ³ .

The upper limit of the density of the ether solvent at 20 ° C., preferably from 1.1 g / cm ^3, more preferably 1 g / cm ^3, more preferably 0.95 g / cm ^3. If the density of the ether solvent exceeds the upper limit, the sedimentation coefficient s is not sufficiently increased by the ether solvent, and it may be difficult to collect grinding scraps having a small particle size. On the other hand, the lower limit of the density of the ether solvent is not particularly limited, but is usually about 0.7 g / cm ³ .

As an upper limit of the density of the whole solvent at 20 ° C., 1.2 g / cm ³ is preferable, and 1.1 g / cm ³ is more preferable. When the density of the whole solvent exceeds the upper limit, the sedimentation coefficient s is not sufficiently increased, and it may be difficult to collect grinding scraps having a small particle size. On the other hand, the lower limit of the density of the whole solvent is not particularly limited, but is usually about 0.7 g / cm ³ .

  As a minimum of the boiling point of the said alcohol solvent, 150 degreeC is preferable and 180 degreeC is more preferable. On the other hand, the upper limit of the boiling point of the alcohol solvent is preferably 300 ° C, more preferably 250 ° C. When the boiling point of the alcohol solvent is less than the lower limit, the solvent evaporates due to frictional heat generated by polishing, and the composition of the grinding fluid may change. Conversely, if the boiling point of the alcohol solvent exceeds the upper limit, the viscosity of the solvent becomes too high, and it may be difficult to collect grinding scraps having a small particle size.

  As a minimum of the boiling point of the said ether solvent, 150 degreeC is preferable and 180 degreeC is more preferable. On the other hand, the upper limit of the boiling point of the ether solvent is preferably 300 ° C, more preferably 250 ° C. When the boiling point of the ether solvent is less than the lower limit, the solvent evaporates due to frictional heat generated by polishing, and the composition of the grinding fluid may change. On the other hand, when the boiling point of the ether solvent exceeds the upper limit, the viscosity of the solvent becomes too high, and it may be difficult to collect grinding scraps having a small particle size.

  The upper limit of the absolute value of the difference between the boiling point of the alcohol solvent and the boiling point of the ether solvent is preferably 60 ° C, more preferably 30 ° C. When the absolute value of the difference between the boiling points exceeds the upper limit, the amount of the solvent evaporated by the frictional heat generated by polishing differs between the alcohol solvent and the ether solvent. For this reason, the ratio of the mass of the ether solvent to the alcohol solvent changes during polishing, which may reduce the dispersibility of the abrasive grains and the recovery efficiency of the grinding fluid. On the other hand, the lower limit of the absolute value of the difference between the boiling points is not particularly limited, and may be 0 ° C.

(Abrasive grains)
The abrasive grains contained in the grinding fluid are not particularly limited, and examples thereof include various abrasive grains such as alumina abrasive grains, silica abrasive grains, ceria abrasive grains, and silicon carbide abrasive grains.

  The lower limit of the average particle diameter of the abrasive grains is preferably 1 μm and more preferably 3 μm. On the other hand, the upper limit of the average particle diameter is preferably 20 μm, and more preferably 15 μm. If the average particle diameter of the abrasive grains is less than the lower limit, the processing promoting effect by the abrasive grains may not be sufficiently obtained. Conversely, if the average particle diameter of the abrasive grains exceeds the upper limit, the substrate material may be damaged during processing. The “average particle size” means a 50% value (50% particle size, D50) of a volume-based cumulative particle size distribution curve measured by a laser diffraction method or the like.

  As a minimum of content of the above-mentioned abrasive grain in the grinding fluid, 2.5 mass% is preferred and 5 mass% is more preferred. On the other hand, the upper limit of the content of the abrasive is preferably 50% by mass, and more preferably 30% by mass. If the content of the abrasive grains is less than the lower limit, the processing acceleration effect by the abrasive grains may not be sufficiently obtained. Conversely, if the content of the abrasive grains exceeds the upper limit, the life of the polishing pad may be reduced, the substrate material may be damaged during processing, and the abrasive grains may be difficult to disperse.

(Other ingredients)
The grinding fluid may contain various additives as necessary. Examples of the additive include a dispersant that increases the dispersibility of abrasive grains, a polishing rate improver that improves the polishing rate, a leveling agent that reduces unevenness on the surface to be polished, a pH adjuster that adjusts pH to a desired value, pH PH buffering agent etc. which suppress change of the above can be mentioned. These may be used alone or in combination of two or more additives. Further, the content of the additive in the grinding fluid is not particularly limited, but can be, for example, 0.0001 mass% or more and 5 mass% or less.

  Further, the grinding fluid may contain other solvent such as water as necessary, but the total content of the alcohol solvent and ether solvent in the whole solvent is 100% by mass, that is, other solvent is added. It is preferable to use a grinding fluid that does not contain. When the grinding fluid contains another solvent, the polishing performance may be lowered due to the decrease in the dispersibility of the slurry abrasive grains, and the recovery efficiency of the grinding fluid by centrifugation may be lowered.

<Grinding method of substrate material>
As shown in FIG. 1, the grinding method mainly includes a substrate material placement step S1, a substrate material grinding step S2, a grinding fluid storage step S3, a grinding dust removal step S4, and a grinding fluid resupply step S5. . In the grinding method, the above-described grinding liquid is used as the grinding liquid.

(Grinding device)
The grinding method can be performed by a known grinding apparatus, for example, a grinding apparatus mainly including a storage tank 1, a polishing machine 2, a recovery tank 3, and a centrifuge 4 as shown in FIG. The storage tank 1 is configured to store the grinding liquid and supply the grinding liquid to the substrate material disposed in the polishing machine 2. The polishing machine 2 is a polishing machine for polishing a substrate material, and a known polishing machine such as a single-side polishing machine or a double-side polishing machine can be used. The recovery tank 3 is configured to recover the grinding liquid used in polishing the substrate material of the polishing machine 2. The centrifuge 4 is configured to be able to centrifuge the grinding liquid collected in the collection tank 3. The centrifuge 4 is also configured to be able to send the grinding fluid after centrifugation to the storage tank 1.

(Substrate material placement process)
In the substrate material arranging step S1, the substrate material to be polished is arranged in the polishing machine 2. For example, in the case of a double-side polishing machine, a polishing pad is fixed to the upper and lower surface plates of the polishing machine 2, and the substrate material held by the carrier is sandwiched between the upper and lower surface plates.

  Although it does not specifically limit as said board | substrate material, Compound semiconductors, such as glass, sapphire, GaN, SiC, etc. can be mentioned. The shape of the substrate material is not particularly limited as long as it can be fixed to the polishing machine 2, but may be, for example, a plate shape.

(Substrate material grinding process)
In the substrate material grinding step S2, the substrate material is ground by rotation of the polishing pad while supplying a grinding liquid. Specifically, while the grinding liquid stored in the storage tank 1 is supplied to the substrate material to be polished by the polishing machine 2, the surface plate on which the polishing pad is fixed is rotated so that the substrate material and the polishing pad are relatively The substrate material is ground by moving to.

  The grinding liquid enters between the polishing pad and the substrate material, cools the processed surface of the substrate material, and accelerates the processing by the contained abrasive grains. The amount of the grinding fluid supplied is appropriately determined depending on the type and size of the substrate material, and can be, for example, 10 ml / min or more and 50 ml / min or less.

(Grinding fluid storage process)
In the grinding fluid storage step S3, the grinding fluid used in the substrate material grinding step S2 is stored in the collection tank 3. This grinding liquid contains grinding scraps by grinding the substrate material. Further, the grinding fluid stored in the recovery tank 3 is normally stirred so that the abrasive grains contained in the grinding fluid do not precipitate or aggregate.

(Grinding waste removal process)
In the grinding waste removal step S4, the grinding waste is removed from the stored grinding liquid by centrifugation. Specifically, the grinding fluid stored in the recovery tank 3 is periodically or continuously sent to the centrifuge 4 to collect and remove grinding debris from the grinding fluid.

  The centrifuge 4 is not particularly limited, but is selected depending on the amount of grinding fluid to be processed. Among these, a decanter type centrifuge capable of performing a separation process stably for a long time is preferable.

  As a lower limit of the centrifugal force of the centrifugal separation in the grinding dust removing step S4, 1500G is preferable, and 2000G is more preferable. If the centrifugal force is less than the lower limit, grinding scraps having a particularly small particle size may not be sufficiently separated. On the other hand, the upper limit of the centrifugal force is not particularly limited, but can be, for example, 5000G. When the centrifugal force exceeds the above upper limit, the centrifuge 4 becomes expensive and the production equipment cost may increase.

  The centrifugation time in the grinding dust removal step S4 depends on the capacity and throughput of the centrifuge 4, but the lower limit of the centrifugation time is preferably 3 minutes and more preferably 5 minutes. On the other hand, the upper limit of the centrifugation time is preferably 30 minutes, and more preferably 20 minutes. If the centrifugation time is less than the lower limit, grinding scraps having a particularly small particle size may not be sufficiently separated. On the contrary, when the time of the centrifugation exceeds the upper limit, the processing efficiency for reusing the grinding fluid may be reduced.

  In the grinding method, since the above-described grinding liquid is used as the grinding liquid, grinding scraps having a small particle diameter can be recovered by centrifugation. For this reason, in this grinding method, it is not necessary to collect grinding scraps having a small particle diameter by a method other than centrifugal separation such as membrane separation. Therefore, in the grinding method, the grinding liquid from which the grinding dust is removed by centrifugation can be reused as it is.

  Since the abrasive grains are removed together with the grinding scraps in the grinding scrap removing step S4, the abrasive grains may be added to the grinding liquid as necessary. New abrasive grains may be used, but the abrasive grains and grinding scraps collected in the grinding scrap removal step S4 may be further centrifuged to collect abrasive grains and reuse them.

(Grinding fluid resupply process)
In the grinding fluid resupply step S5, the grinding fluid after the grinding dust removal step S4 is resupplied to the substrate material. Specifically, the grinding liquid after the grinding scrap removing step S4 is supplied to the storage tank 1. The grinding liquid supplied to the storage tank 1 is mixed with the grinding liquid stored in the storage tank 1 to adjust the abrasive grain content and the like, and then supplied again to the substrate material in the substrate material grinding step S2.

<Substrate manufacturing method>
The substrate manufacturing method is a method of manufacturing a substrate by grinding a substrate material, and uses the grinding method. Specifically, by the grinding method, a substrate can be manufactured from a substrate material by surface grinding using a fixed abrasive method using a polishing pad and a grinding liquid. Although it does not specifically limit as a board | substrate manufactured by the manufacturing method of the said board | substrate, Compound semiconductor substrates, such as a glass substrate, a sapphire substrate, GaN, SiC, etc. can be mentioned.

<Advantages>
The grinding fluid contains an alcohol solvent and an ether solvent, and the total content of the alcohol solvent and the ether solvent in the entire solvent of the grinding fluid is 95% by mass to 100% by mass, and the ether solvent. The mass ratio with respect to the alcohol solvent is 1 to 5 times. Thus, by using a solvent obtained by adding a predetermined amount of an ether solvent to an alcohol solvent, the grinding liquid can reduce the density of the solvent while suppressing a decrease in the viscosity of the entire solvent. By suppressing the decrease in the viscosity of the solvent, the grinding fluid can ensure the dispersibility of the abrasive grains even when the abrasive grains are contained. Further, since the density of the grinding scrap is generally larger than the density of the solvent, the grinding liquid can increase the density difference between the solvent and the grinding scrap by reducing the density of the solvent as described above. By increasing the density difference between the solvent and the grinding waste in this way, the grinding fluid can be easily separated by centrifugation even if it is a relatively light substance, that is, grinding waste having a relatively small particle size. Therefore, the recovery efficiency by centrifugation can be made relatively high while suppressing a decrease in dispersibility when the abrasive is contained by the grinding liquid.

  Moreover, in the said grinding method, even if it is a grinding dust with a small particle size, it can isolate | separate by centrifugation by using the said grinding fluid. For this reason, by using the grinding method, the recovery efficiency of the grinding fluid can be made relatively high while suppressing an increase in manufacturing equipment costs and man-hours for reusing the solvent. Therefore, the substrate manufacturing method using the grinding method has a relatively low substrate manufacturing cost.

[Other Embodiments]
The present invention is not limited to the above-described embodiment, and can be implemented in a mode in which various changes and improvements are made in addition to the above-described mode.

  Although the case of the grinding fluid containing abrasive grains has been described in the above embodiment, the present invention includes a grinding fluid that does not contain abrasive grains. Even in a grinding liquid that does not contain abrasive grains, grinding scraps having a small particle diameter can be recovered by centrifugation, so that the grinding liquid has a relatively high recovery efficiency.

  In the above-described embodiment, the method of re-feeding the grinding liquid to the substrate material via the storage tank has been described as the grinding method. However, it is not essential to pass through the storage tank. For example, the grinding liquid is directly re-supplied to the substrate material. May be.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, the said invention is not limited to a following example.

[Example 1]
Ethylene glycol (EG) as an alcohol solvent and isobutyl diglycol (isoBDG) as an ether solvent are prepared, so that the total content of the solvent is 50% by mass, that is, an alcohol solvent of an ether solvent. The mixture was mixed so that the mass ratio to the solvent was 1. To this mixed solvent, alumina abrasive grains (white alumina WA # 1000, average particle size 12 μm) were mixed so that the content in the grinding fluid was 5 mass%, and the grinding fluid of Example 1 was obtained.

[Examples 2 to 4, Comparative Examples 1 to 4]
In the same manner as in Example 1, except that the content ratio of EG and isoBDG was changed and the mass ratio of the ether solvent to the alcohol solvent was a value shown in Table 2, Examples 2 to 4 and The grinding fluids of Comparative Examples 1 to 4 were obtained.

[Examples 5 to 7]
Implemented except that the ether solvents were butyl diglycol (BDG), isopropyl diglycol (isoPDG), and methyl triglycol (MTG), respectively, and mixed so that the mass ratio of the ether solvent to the alcohol solvent was 3. In the same manner as in Example 1, the grinding fluids of Examples 5 to 7 were obtained.

[Grinding conditions]
The sapphire substrate was polished using the grinding fluids of Examples 1 to 7 and Comparative Examples 1 to 4. As the sapphire substrate, three sapphire substrates having a diameter of 2 inches, a specific gravity of 3.97, and a c-plane were used.

A known double-side polishing machine was used for the polishing. The carrier of the double-side polishing machine was a glass epoxy plate, and the average thickness was 0.4 mm. Polishing was performed for 10 minutes under the conditions of an upper surface plate rotation speed of 25 rpm, a lower surface plate rotation speed of 50 rpm, and a SUN gear rotation speed of 8 rpm. The polishing pressure was 200 g / cm ² . At that time, the grinding fluids of Examples 1 to 7 and Comparative Examples 1 to 4 were supplied at 30 ml / min.

[Evaluation method]
About some or all of the grinding fluids of Examples 1 to 7 and Comparative Examples 1 to 4, the viscosity of the grinding fluid is measured, the dispersibility is evaluated when the sapphire substrate is polished, and the grinding fluid is recovered after the polishing. Sexuality was evaluated. The results are shown in Table 2.

<Viscosity measurement>
About the said Examples 1-7 and Comparative Examples 1-4, the viscosity in 25 degreeC of each grinding fluid before use was measured. The viscosity was measured with respect to the solvent before mixing the abrasive grains. For the measurement, a vibration viscometer (“VISCOMATE VM-100A” manufactured by Yamaichi Electronics Co., Ltd.) was used.

<Dispersion evaluation of grinding fluid>
The evaluation of the dispersibility of the grinding liquid was performed by visually checking the state in the piping tube that supplies the grinding liquid during the polishing, and evaluated based on the following criteria.
(Judgment criteria for dispersibility evaluation)
A: Abrasive grain accumulation is not recognized in the tube, and the dispersibility of the abrasive grains is excellent.
B: A slight accumulation of abrasive grains is observed in the tube, but the dispersibility of the abrasive grains is good.
C: Abrasive grain accumulation is recognized in the tube, and the dispersibility of the abrasive grains is poor.

<Evaluation of grinding fluid recovery>
Grinding waste was separated and collected from each grinding fluid used for polishing by centrifugation to obtain a grinding fluid from which grinding waste was removed. The centrifugal separation was performed using a table top multi-centrifuge (“8420” manufactured by Kubota Corporation).

  FIG. 3 shows photographs of the grinding fluid before and after centrifugation of the grinding fluid of Comparative Example 1. In FIG. 3, (1) is the grinding fluid before centrifugation, (2) is 10 minutes with a centrifugal force of 210 G, (3) is 10 minutes with a centrifugal force of 2280 G, and (4) is a centrifugal force of 2280 G. The grinding fluid after centrifugation for 20 minutes. As described above, the recovery efficiency by centrifugation tends to improve as the centrifugal force increases and the time for centrifugation increases. However, the evaluation of grinding liquid recovery takes into account the performance and processing efficiency of the centrifuge. Then, centrifugation was performed at a centrifugal force of 1500 G for 10 minutes, 20 minutes, and 50 minutes for evaluation.

The recoverability of the grinding fluid was evaluated based on the following judgment criteria by visually confirming the transparency of the grinding fluid after removing grinding debris. In addition, the case where there was transparency of 10 cm or more was judged to be high in transparency. For example, in FIG. 3, in the cases (3) and (4), it is determined that the transparency is high.
(Judgment criteria for recoverability evaluation)
A: A highly transparent grinding fluid is obtained by centrifugation for 10 minutes or less, and the recoverability is excellent.
B: A highly transparent grinding fluid is obtained by centrifugation for more than 10 minutes and not more than 30 minutes, and the recoverability is good.
C: A highly transparent grinding liquid cannot be obtained even after centrifugation for more than 30 minutes, and the recoverability is poor.

  In Table 2, “−” in the mass ratio in the “alcohol / ether” column means that either one of the alcohol solvent and the ether solvent is 0, and thus is not defined.

  From Table 2, the grinding fluids of Examples 1 to 7 have the same dispersibility and excellent recoverability as compared with the grinding fluids of Comparative Examples 1 and 2. Further, the grinding fluids of Examples 1 to 7 have the same recoverability and excellent dispersibility as compared with the grinding fluids of Comparative Examples 3 and 4. On the other hand, the grinding fluids of Comparative Examples 1 and 2 are considered to have a high viscosity of the whole solvent and poor recoverability because the mass ratio of the alcohol solvent alone or the ether solvent to the alcohol solvent is less than 1. It is done. Moreover, since the mass ratio of the grinding fluids of Comparative Examples 3 and 4 is an ether solvent alone or an ether solvent to an alcohol solvent is more than 5, the viscosity of the whole solvent is low and the dispersibility is considered to be poor.

  From this, the grinding fluid has a recovery ratio by centrifugation while suppressing a decrease in the dispersibility of the abrasive grains by setting the mass ratio of the ether solvent to the alcohol solvent to be 1 to 5 times. It can be seen that

  In more detail, from the comparison of Examples 1 to 4 in which the ether solvent is isoBDG, the grinding fluids of Examples 2 and 3 have the same dispersibility as the grinding fluid of Example 1, and the recoverability is high. Excellent. Further, the grinding fluids of Examples 2 and 3 have the same recoverability and excellent dispersibility as compared with the grinding fluid of Example 4. From this, it can be understood that the dispersibility and the recoverability of the grinding fluid are further improved by setting the mass ratio of the ether solvent to the alcohol solvent to be 2 times or more and 4 times or less.

<Evaluation of average particle size dependency and content dependency of abrasive grains>
[Example 8]
In order to evaluate the influence of the average particle diameter of the abrasive grains on the dispersibility and recoverability, the alumina abrasive grains added to the mixed solvent were alumina abrasive grains having an average particle diameter of 7 μm (white alumina WA # 2000). In the same manner as in Example 2, a grinding liquid of Example 8 was obtained.

[Examples 9 to 11]
In order to evaluate the influence of the content of the abrasive grains on the dispersibility and recoverability, the content of the alumina abrasive grains added to the mixed solvent was changed to the content shown in Table 3, and the same examples as in Example 2 9 to 11 grinding fluids were obtained.

[Evaluation]
About Examples 8-11, the dispersibility and recoverability of the grinding fluid were evaluated. The results are shown in Table 3.

  From the results of Table 3, even if the average particle size and content of the abrasive grains are changed, the influence on the dispersibility and recoverability is small, and the dispersibility and recoverability of Examples 8 to 11 are equivalent to those of Example 2. is there. From this, regardless of the average particle diameter and content of the abrasive grains, the grinding fluid has an abrasive solvent dispersibility of 1 to 5 times the mass ratio of the ether solvent to the alcohol solvent. It can be seen that the recovery efficiency by centrifugation can be increased while suppressing the decrease in the pressure.

  As described above, the recovery efficiency by centrifugation is relatively high while suppressing a decrease in dispersibility when the abrasive grains of the present invention are contained.

DESCRIPTION OF SYMBOLS 1 Storage tank 2 Polishing machine 3 Collection tank 4 Centrifuge

Claims (2)

A grinding fluid used for grinding a substrate material,
Containing an alcohol solvent and an ether solvent,
The total content of the alcohol solvent and ether solvent in the whole solvent of the grinding fluid is 95% by mass or more and 100% by mass or less,
A grinding fluid having a mass ratio of the ether solvent to the alcohol solvent of 1 to 5 times. The viscosity of the ether solvent at 25 ° C. is lower than the viscosity of the alcohol solvent;
2. The grinding fluid according to claim 1, wherein a difference in viscosity at 25 ° C. between the ether solvent and the alcohol solvent is 15 mPa · s or more and 20 mPa · s or less.