WO2019181498A1

WO2019181498A1 - Polishing agent recycle processing system and polishing agent recovery/regeneration method

Info

Publication number: WO2019181498A1
Application number: PCT/JP2019/008807
Authority: WO
Inventors: 扶美子月形; 前澤　明弘; 崇南條
Original assignee: コニカミノルタ株式会社
Priority date: 2018-03-23
Filing date: 2019-03-06
Publication date: 2019-09-26
Also published as: CN112272600A; CN112272600B; JPWO2019181498A1; JP7192851B2

Abstract

The present invention addresses the problem of providing a polishing agent recycle processing system and a polishing agent recovery/regeneration method for efficiently recovering a polishing agent from a used polishing agent slurry and reusing the polishing agent as a regenerated polishing agent slurry. This polishing agent recycle processing system continuously performs a polishing process while controlling the concentration of the constituent components of a polishing agent in a polishing agent slurry used for polishing and the constituent components of an object being polished, and removes the constituent components of the object being polished from the used polishing agent slurry to recover/regenerate the polishing agent. The polishing agent recycle processing system is characterized by: comprising a polishing process step section and a polishing agent slurry recovery step section which has a slurry supply tank that stores the polishing agent used for polishing; and supplying the regenerated polishing agent slurry to the slurry supply tank while controlling the concentration of the constituent components of the polishing agent in the slurry supply tank to be equal to or less than the initial concentration at the time of starting the polishing process step.

Description

Abrasive recycling system and abrasive recovery / regeneration method

The present invention relates to an abrasive recycling system and an abrasive recovery / regeneration method, and more specifically, polishing for efficiently recovering an abrasive from a processed abrasive slurry and reusing it as a recycled abrasive slurry. Agent recycling system.

As abrasives (also called abrasives) for precisely polishing optical glass and quartz oscillators in the finishing process, diamond, boron nitride, silicon carbide, alumina, alumina zirconia, zirconium oxide, cerium oxide and the like have been conventionally represented. Fine particles having high hardness are used.

Generally, some of the main constituent elements of abrasives are obtained from minerals that are not produced in Japan, and some of them are resources that depend on imports and are expensive in terms of material prices.

Since these abrasives are fine particles with high hardness, they are important resources that are used in large quantities as optical abrasives related to electronic parts such as optical lenses, semiconductor silicon substrates, and glass plates for liquid crystal screens. It is one of the resources that are strongly desired to use. In addition, the polishing agent for optical polishing is mainly composed of the above-described compounds, and may contain transition metal elements such as sodium salts and chromium salts, and fine particles of rare earth elements such as yttrium and decyprosium, and is simple. Disposal is strongly prohibited by the environment. For this reason, development of a processing technique for making the waste liquid used for polishing pollution-free is strongly desired. Therefore, regarding the optical abrasive waste liquid containing the processed abrasive, it is an important problem to recycle resources or to deal with pollution-free.

Generally, wastewater containing suspended fine particles generated in various industrial fields is treated by aggregating and separating suspended fine particles using a neutralizing agent, inorganic flocculant, polymer flocculant, etc., and then the treated water is discharged. However, at present, the coagulated and separated sludge is disposed of by incineration or other means.

In addition, these abrasives are usually used in a large amount in the polishing process, and the constituents of the object to be polished, such as optical glass scraps, coexist in the waste liquid. Since it is difficult to efficiently separate the product from the waste, as described above, the abrasive waste liquid is often discarded after use, in terms of environmental burden and disposal cost. Also has a problem.

Therefore, in recent years, it has become an important issue to efficiently reuse the main constituent elements of abrasives to save resources of elements with high rare values.

Regarding the method for regenerating the constituents of the abrasive, for example, an electrolyte substance is added to the processed abrasive, the abrasive is coagulated, and the constituents derived from the polished object (the constituent to be polished) are dissolved. However, a method for solid-liquid separation is disclosed (for example, see Patent Document 1). In the method described in Patent Document 1, alkali metal hydroxide, alkali metal carbonate, alkali metal salt, and ammonium salt are used as the electrolyte substance.

In addition, a method of regenerating a fine abrasive by mixing sodium hydroxide and potassium hydroxide solution with a processed abrasive and sieving solids by solid-liquid separation is disclosed (for example, , See Patent Document 2). Further, a method is disclosed in which a rare earth and a rare metal are dissolved by adding sulfuric acid to a processed abrasive and heat-treated to separate and remove it from aggregates such as silica in the abrasive slurry (for example, , See Patent Document 3).

Further, as a method of recovering the colloidal silica-based abrasive, agglomeration treatment is performed by adding an alkali to the CMP (Chemical Mechanical Polishing) waste liquid in the presence of magnesium ions and adjusting the pH value to 10 or more. Is disclosed (for example, see Patent Document 4). Further, Non-Patent Document 1 provides a review on the above-described metal recovery technology.

Generally, “abrasive regeneration amount = abrasive use amount × recovery rate × regeneration rate”, and improvement of the recovery rate and the regeneration rate is important. However, the above-described technique mainly focuses on the improvement of the recovery rate of the recovered processed abrasive, and the study on the improvement of the recovery rate has not been sufficient in the past. If the recovery rate is not improved, the abrasive cannot be regenerated efficiently.

For example, when glass polishing is continued with an abrasive slurry containing a constant concentration of abrasive, the silicon oxide concentration of the object to be polished in the abrasive slurry increases. When the silicon oxide concentration is increased, silicon oxide is precipitated and solidified to become foreign matters in the abrasive slurry. Since this foreign matter causes defects such as scratches, the abrasive slurry cannot be used. Further, the increase in the viscosity of the abrasive slurry causes scattering, adhesion, etc. to the periphery of the polishing apparatus, resulting in a decrease in the amount of recovered abrasive components.

Japanese Patent Laid-Open No. 06-254664 JP-A-11-90825 Japanese Patent Laid-Open No. 11-50168 JP 2000-254659 A

The present invention has been made in view of the above problems and situations, and a solution to the problem is to efficiently recover the abrasive from the processed abrasive slurry and reuse it as a regenerated abrasive slurry. An abrasive recycling system and an abrasive recovery / regeneration method are provided.

In order to solve the above-mentioned problems, the present inventor performs the abrasive recycling process in the course of examining the cause of the above-mentioned problems, and the concentration of the abrasive in the abrasive slurry being processed is equal to or less than the initial concentration at the start of polishing. It has been found that by suppressing the amount to be reduced, precipitation and solidification of the object to be polished can be suppressed, and efficient recovery becomes possible.

That is, the above-mentioned problem according to the present invention is solved by the following means.

1. While continuing the polishing process while controlling the concentration of the constituents of the abrasive and the constituents of the object to be polished in the abrasive slurry used for polishing, the constituents of the object to be polished are removed from the processed abrasive slurry, An abrasive recycling system for recovering and recycling the abrasive,
A polishing process unit for polishing using a polishing machine, and an abrasive slurry recovery process unit having a slurry supply tank for storing the abrasive slurry used for polishing supplied to the polishing machine,
Polishing characterized in that the recycled abrasive slurry is supplied into the slurry supply tank while controlling the concentration of the constituents of the abrasive in the slurry supply tank to be equal to or lower than the initial concentration at the start of the polishing process. Agent recycling system.

2. The concentration of the constituents of the abrasive in the slurry supply tank is in the range of 20 to 90% at the end point concentration at the end of the polishing step relative to the concentration at the start of the polishing step, and during the polishing step The concentration of the constituent component of the abrasive is always equal to or higher than the end point concentration, and the variation range of the concentration of the constituent of the abrasive in the next processing batch relative to the previous processing batch is controlled within ± 1.0 mass%. The abrasive recycling system according to item 1, characterized in that:

3. The concentration of the constituents of the abrasive in the slurry supply tank is within the range of 30 to 80% at the end point concentration at the end of the polishing step relative to the concentration at the start of the polishing step, and during the polishing step The concentration of the constituent component of the abrasive is always equal to or higher than the end point concentration, and the variation range of the concentration of the constituent of the abrasive in the next processing batch relative to the previous processing batch is controlled within ± 1.0 mass%. The abrasive recycling system according to item 1, characterized in that:

4. Any one of the items 1 to 3, further comprising a separation / concentration process unit and a regenerated abrasive slurry preparation process unit in addition to the polishing process unit and the abrasive slurry recovery process unit The abrasive recycling system according to one item.

5). In the abrasive slurry recovery process section, the slurry supply tank that stores the abrasive slurry supplied to the polishing process section, and a recovery liquid mixture tank that stores a mixed liquid of the processed abrasive slurry and cleaning water And
The separation / concentration process section includes a separation / concentration tank that separates the mixed solution into a permeate and an abrasive concentrate,
The regenerated abrasive slurry preparation process section includes a regenerated abrasive slurry storage tank for storing a liquid containing the regenerated abrasive from which the constituents of the object to be polished have been removed, and the abrasive slurry is placed between the process sections. 5. The abrasive recycling system according to item 4, further comprising a circulation line for supplying and a control unit for adjusting the supply amount.

6. 6. The abrasive recycling system according to

item

4 or 5, further comprising an abrasive particle size adjusting step for adjusting the particle size of the abrasive obtained in the separation / concentration step.

7. Any one of Items 1 to 6, wherein the regenerated abrasive slurry contains a maleic acid-acrylic acid copolymer in a range of 0.04 to 1.5 g / L. The abrasive | polishing agent recycling processing system of clause.

8. The abrasive recycling system according to any one of claims 1 to 7, wherein the abrasive contains a metal oxide, and the object to be polished contains silicon (Si). .

9. The abrasive recycling system according to any one of items 1 to 8, wherein the abrasive contains cerium oxide.

10. The abrasive recycling system according to any one of Items 4 to 9, wherein an alkaline earth metal salt is used as an aggregating agent for the abrasive in the separation / concentration process section.

11. The abrasive recycling system according to item 10, wherein the alkaline earth metal salt is a magnesium salt.

12 While continuing the polishing process while controlling the concentration of the constituents of the abrasive and the constituents of the object to be polished in the abrasive slurry used for polishing, the constituents of the object to be polished are removed from the processed abrasive slurry, An abrasive recovery / regeneration method for recovering / regenerating the abrasive,
Control the concentration of the constituents of the abrasive in the slurry supply tank for storing the abrasive slurry used for polishing supplied to the polishing machine to be equal to or lower than the initial concentration of the constituents of the abrasive at the start of the polishing process. An abrasive recovery / regeneration method comprising: supplying a recycled abrasive slurry to the polishing process section and recovering the processed abrasive slurry.

13. The concentration of the constituents of the abrasive in the slurry supply tank is in the range of 20 to 90% at the end point concentration at the end of the polishing step relative to the concentration at the start of the polishing step, and during the polishing step The concentration of the constituent component of the abrasive is always equal to or higher than the end point concentration, and the variation range of the concentration of the constituent of the abrasive in the next processing batch relative to the previous processing batch is controlled within ± 1.0 mass%. 13. The method for recovering and regenerating an abrasive according to item 12.

14. The concentration of the constituents of the abrasive in the slurry supply tank is within the range of 30 to 80% at the end point concentration at the end of the polishing step relative to the concentration at the start of the polishing step, and during the polishing step The concentration of the constituent component of the abrasive is always equal to or higher than the end point concentration, and the variation range of the concentration of the constituent of the abrasive in the next processing batch relative to the previous processing batch is controlled within ± 1.0 mass%. 13. The method for recovering and regenerating an abrasive according to item 12.

15. Any one of Items 12 to 14, wherein the recycled abrasive slurry contains a maleic acid-acrylic acid copolymer in a range of 0.04 to 1.5 g / L. The method for recovering and recycling the abrasive according to the item.

By the above means of the present invention, an abrasive recycling system and an abrasive recovery / regeneration method for efficiently recovering an abrasive from a processed abrasive slurry and reusing it as a recycled abrasive slurry are provided. be able to.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

In the conventional abrasive recycling system, the aim was to keep the abrasive concentration in the abrasive slurry constant during the polishing process. For this reason, as the polishing progresses, the concentration of the object to be polished increases, the viscosity increases or locally becomes high temperature, and the recovery rate decreases due to the precipitation of the object to be polished, and the polishing process quality is adversely affected. By reducing the abrasive concentration in the abrasive slurry during processing, the concentration of the object to be polished also decreases, reducing the adhesion of the abrasive slurry to the polishing machine, and increasing the recovery rate of the processed abrasive slurry. It seems that it can be improved.

Conceptual diagram showing the relationship between the polishing time, the concentration of the abrasive in the abrasive slurry being processed, and the concentration of the components of the object to be polished Conceptual diagram showing the relationship between the polishing time, the concentration of the abrasive in the abrasive slurry being processed, and the concentration of the components of the object to be polished Schematic showing an example of the abrasive recycling system of the present invention SEM photo of polishing pad after polishing SEM photo of polishing pad after polishing

The abrasive recycling processing system of the present invention continues the polishing process while controlling the concentration of the constituents of the abrasive and the constituents of the object to be polished in the abrasive slurry used for polishing, from the processed abrasive slurry, A polishing agent recycling system that removes constituents of an object to be polished and collects and regenerates the polishing agent, and is used for the polishing process unit for polishing using a polishing machine and the polishing supplied to the polishing machine. An abrasive slurry recovery process unit having a slurry supply tank for storing the abrasive slurry, and the concentration of the constituents of the abrasive in the slurry supply tank is controlled to be equal to or lower than the initial concentration at the start of the polishing process. Meanwhile, the recycled abrasive slurry is supplied into the slurry supply tank. This feature is a technical feature common to or corresponding to each of the following embodiments.

The concentration of the constituents of the abrasive in the slurry supply tank is such that the end point concentration at the end of the polishing process is within the range of 20 to 90%, more preferably 30 to 80% with respect to the concentration at the start of the polishing process. Within the range, the concentration of the constituent component of the abrasive during the polishing process is always equal to or higher than the end point concentration, and the variation width of the change in the concentration of the constituent component of the abrasive in the next processing batch relative to the previous processing batch Is preferably controlled within ± 1.0% by mass.

In addition to the polishing process section and the abrasive slurry recovery process section, the separation / concentration process section and the regenerated abrasive slurry preparation process section have the effect of improving the efficiency of the abrasive recycling system. Since it is obtained, it is preferable.

Further, in the present invention, the abrasive slurry recovery process section includes a slurry supply tank for storing the regenerated abrasive slurry supplied to the polishing process section, and a mixed liquid of the processed abrasive slurry and the washing water. And the separation / concentration process unit includes a separation / concentration tank that separates the mixture into a permeate and an abrasive concentrate, and the regenerated abrasive slurry preparation step. The part includes a recycle abrasive slurry storage tank for storing a liquid containing the regenerated abrasive from which the constituents of the object to be polished are removed, and a circulation line for supplying the abrasive slurry between the process parts. It is preferable to provide a control unit for adjusting the supply amount from the viewpoint of improving the recovery / regeneration rate.

As an embodiment of the present invention, it is preferable to have an abrasive particle size adjusting step for adjusting the particle size of the abrasive obtained in the separation / concentration step from the viewpoint of manifesting the effects of the present invention.

Furthermore, it is preferable that the recycled abrasive slurry contains a maleic acid-acrylic acid copolymer in the range of 0.04 to 1.5 g / L.

In addition, it is preferable that the abrasive contains a metal oxide and the object to be polished contains silicon (Si) because the effects of the present invention can be easily obtained.

As an embodiment of the present invention, it is preferable that the abrasive contains cerium oxide from the viewpoint of polishing rate.

Further, in the separation / concentration process section, it is preferable to use an alkaline earth metal salt as the aggregating agent of the abrasive, and that the alkaline earth metal salt is a magnesium salt from the viewpoint of the efficiency of recovery and regeneration of the abrasive. preferable.

Further, in the present invention, the polishing process is continued while controlling the concentration of the constituents of the abrasive and the constituents of the object to be polished in the abrasive slurry used for polishing. The abrasive recovery / regeneration method of removing the constituents and recovering / regenerating the abrasive,
Control the concentration of the constituents of the abrasive in the slurry supply tank for storing the abrasive slurry used for polishing supplied to the polishing machine to be equal to or lower than the initial concentration of the constituents of the abrasive at the start of the polishing process. On the other hand, the present invention can be applied to an abrasive recovery / regeneration method that includes supplying an abrasive slurry to the polishing process section and recovering the processed abrasive slurry.

Further, the concentration of the constituents of the abrasive in the slurry supply tank is within the range of the end point concentration at the end of the polishing step of 20 to 90% with respect to the concentration at the start of the polishing step, more preferably 30 to 80 %, And the concentration of the constituent component of the abrasive during the polishing process is always equal to or higher than the end point concentration, and the change in the concentration of the constituent component of the abrasive in the next processing batch relative to the previous processing batch It is preferable that the fluctuation range is controlled within ± 1.0% by mass in the abrasive recovery / regeneration method.

Further, it is preferable that the recycled abrasive slurry is an abrasive recovery / regeneration method in which a maleic acid-acrylic acid copolymer is contained in the range of 0.04 to 1.5 g / L.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

Further, in the present invention, the abrasive slurry refers to a slurry that is generically expressed including the following various abrasive slurries according to the polishing process. From the viewpoint of the polishing process, the “initial abrasive slurry” refers to a processing liquid at the initial stage of polishing, which contains an abrasive component and water and does not substantially contain an object component to be polished. “Abrasive slurry that is being processed or has been processed” refers to an abrasive slurry that contains a constituent of an object to be polished or an abrasive slurry that has finished its life. The “regenerated abrasive slurry” refers to an abrasive slurry from which the constituents to be polished have been removed or an abrasive slurry that has been concentrated after the constituents to be polished have been removed.

1 << Overview of basic configuration of abrasive recycling system >>
The abrasive recycling processing system of the present invention continues the polishing process while controlling the concentration of the constituents of the abrasive and the constituents of the object to be polished in the abrasive slurry used for polishing, from the processed abrasive slurry, A polishing agent recycling system that removes constituents of an object to be polished and collects and regenerates the polishing agent, and is used for the polishing process unit for polishing using a polishing machine and the polishing supplied to the polishing machine. An abrasive slurry recovery process unit having a slurry supply tank for storing the abrasive slurry, and the concentration of the constituents of the abrasive in the slurry supply tank is controlled to be equal to or lower than the initial concentration at the start of the polishing process. Meanwhile, the recycled abrasive slurry is supplied into the slurry supply tank.

In the conventional abrasive recycling system, the aim was to keep the concentration of the abrasive in the abrasive slurry constant during polishing. For this reason, as the polishing progresses, the concentration of the object to be polished increases, the viscosity rises and the temperature locally increases, and the recovery rate decreases due to precipitation of the object to be polished.

For example, in a conventional polishing process section that polishes an object to be polished, the temperature of the abrasive slurry in the polishing process section may rise to about 40 to 60 ° C. due to the polishing process. When glass is used as an object to be polished, when the concentration of silicon oxide is increased by polishing, the viscosity of the abrasive slurry being processed increases and adheres to the processed part. Furthermore, since the temperature of the polished portion increases due to processing, precipitation of silicon oxide and solidification are accelerated. The abrasive component adhering to the polished portion by polishing is washed with washing water and recovered as a rinse slurry containing the abrasive component.

There are silicon oxide precipitated solids that are collected as a rinse slurry and those that remain in the polished portion. Residues in the polished portion are present both inside and outside the polishing pad and affect the processing quality.

Therefore, since the frequency of replacing the polishing pad increases, the number of polishing processes decreases. Moreover, what is recovered as the rinse slurry needs to remove the precipitated solid substance of silicon oxide which becomes a foreign substance in order to reuse and recycle. Incorporating a silicon oxide deposited solids removal process reduces the abrasive recovery.

In the slurry supply tank, the initial abrasive slurry prepared in advance is repeatedly circulated between the slurry supply tank and the polishing machine while being replenished with the regenerated abrasive slurry. By polishing, the silicon component of the object to be polished is in a state dissolved in the abrasive slurry. When the silicon concentration in the abrasive slurry is increased, silicon oxide is precipitated and solidified to become foreign matter in the abrasive slurry. Since the foreign matter causes a defect such as a scratch, the abrasive slurry cannot be used. In order to reuse the processed abrasive slurry, it is necessary to remove precipitated silicon oxide solids that are foreign matters. Incorporating a silicon oxide deposited solids removal process reduces the abrasive recovery.

In order to solve this problem, the present invention regenerates while controlling the concentration of the constituents of the abrasive contained in the abrasive slurry being processed to be equal to or less than the initial concentration of the abrasive at the start of the polishing process. This can be solved by supplying the abrasive slurry to the polishing machine.

FIG. 1A and FIG. 1B are conceptual diagrams showing the relationship between the polishing time, the concentration of the abrasive in the abrasive slurry being processed, and the concentration of the components of the object to be polished. FIG. 1A shows the abrasive concentration in the abrasive slurry with respect to the polishing time. In the conventional polishing process, the polishing agent concentration is kept constant as shown by the dotted line even if polishing progresses. Therefore, as shown by the relationship between the polishing time and the concentration of the constituents of the object to be polished in FIG. 1B, the concentration of the constituents of the object to be polished in the abrasive slurry increases as the polishing time increases. And when this density | concentration reached a, precipitation of the to-be-polished object occurred and the abrasive slurry could not be used.

On the other hand, in the present invention, as shown by the solid line in FIG. 1A, the abrasive concentration in the abrasive slurry is kept below the initial concentration of the polishing process as the polishing time progresses. As a result, the increase in the concentration of the constituents of the object to be polished in the abrasive slurry can be suppressed as indicated by the solid line in FIG. 1B, and the abrasive slurry life can be extended. Moreover, since the viscosity of the abrasive slurry is hardly increased, the recovery rate of the abrasive can be increased.

2 << Configuration Example of Embodiment of Abrasive Recycling System >>
The abrasive recycling system of the present invention includes at least a polishing process unit that performs polishing using a polishing machine and an abrasive slurry recovery process unit that includes a slurry supply tank that stores an abrasive slurry supplied to the polishing process unit. Have. It is preferable that the abrasive slurry recovery process unit further includes a recovery mixed liquid tank that stores a mixed liquid of the processed abrasive slurry and cleaning water.

In addition, a separation / concentration process section that separates the abrasive from the processed abrasive slurry, an abrasive particle diameter adjustment process section that adjusts the particle diameter of the recovered processed abrasive particles, and a regeneration that stores the regenerated abrasive slurry. It is preferable to have an abrasive slurry preparation step.

In addition, the abrasive recovery / regeneration method of the present invention continues the polishing process while controlling the concentrations of the constituents of the abrasive and the constituents of the object to be polished in the abrasive slurry used for polishing. An abrasive recovery / regeneration method for removing constituents of an object to be polished from a slurry and recovering / regenerating the abrasive,
Control the concentration of the constituents of the abrasive in the slurry supply tank for storing the abrasive slurry used for polishing supplied to the polishing machine to be equal to or lower than the initial concentration of the constituents of the abrasive at the start of the polishing process. On the other hand, it is characterized by having a step of supplying the abrasive slurry to the polishing step and recovering the processed abrasive slurry.

The abrasive recovery / regeneration method of the present invention includes a polishing process for polishing using a polishing machine, an abrasive slurry recovery process having a slurry supply tank for storing an abrasive slurry supplied to the polishing process section, Separation / concentration step for separating the abrasive from the finished abrasive slurry, abrasive particle size adjusting step for adjusting the particle size of the recovered processed abrasive particles, and regenerated abrasive slurry preparation step for storing the regenerated abrasive slurry It is preferable to have.

FIG. 2 is a schematic view showing an example of the abrasive recycling system of the present invention. The abrasive recycling system shown in FIG. 2 includes a polishing process section 1, an abrasive slurry collection process section 2, a separation / concentration process section 3, an abrasive particle diameter adjustment process section 4, and a recycled abrasive slurry preparation process section 5. It is shown. Hereinafter, each process part will be described in detail.

(1) Polishing process section In the polishing process section 1, the polishing machine 12 has a polishing surface plate to which a polishing cloth composed of a nonwoven fabric, a synthetic resin foam, a synthetic leather and the like is attached. The board is rotatable. During the polishing operation, the polishing surface plate is rotated while pressing an object to be polished (for example, optical glass or the like) against the polishing surface plate with a predetermined pressing force N using a holder. Further, cleaning water for cleaning the polishing machine 12 is stored in the cleaning water tank 11, and cleaning is performed by spraying the polishing unit from the cleaning water spray nozzle. The polishing process is a process performed in the polishing process unit 1.

(Abrasive)
Generally, as constituents of abrasives such as optical glass and semiconductor substrates, fine particles such as bengara (αFe ₂ O ₃ ), cerium oxide, aluminum oxide, manganese oxide, zirconium oxide, colloidal silica are dispersed in water or oil. Although a slurry is used, the polishing agent recovery / regeneration method of the present invention provides a sufficient processing speed while maintaining flatness with high accuracy in the polishing process of the surface of a semiconductor substrate and glass. Diamond, boron nitride, silicon carbide, alumina, alumina zirconia, zirconium oxide and cerium oxide, applicable to chemical mechanical polishing (CMP), polishing with both physical and chemical action to obtain It is preferable to apply to at least one kind of recovery selected from

Examples of the constituents of the abrasive according to the present invention include diamonds such as synthetic diamond (for example, manufactured by Nippon Micro Coating Co., Ltd.), natural diamonds, and boron nitrides such as cubic boron nitride BN. (For example, manufactured by Showa Denko KK). The boron nitride system has hardness next to diamond. Moreover, as a silicon carbide type | system | group, a silicon carbide, green silicon carbide, black silicon carbide (For example, the product made by Mipox etc.), etc. can be mentioned. In addition to alumina, examples of the alumina system include brown alumina, white alumina, light red alumina, pulverized alumina, and alumina zirconia (for example, manufactured by Saint-Gobain). Examples of zirconium oxide include BR series zirconium oxide for abrasives manufactured by 1st Rare Element Chemical Industry Co., Ltd., and zirconium oxide manufactured by China HZ Company.

In addition, cerium oxide (for example, manufactured by C-I Kasei Co., Ltd., manufactured by Technolize Co., Ltd., manufactured by Wako Pure Chemical Industries, Ltd.) is called bust nesite, which is called bust necite, rather than pure cerium oxide. Many pulverized products are used. Although cerium oxide is the main component, it contains rare earth elements such as lanthanum, neodymium, and praseodymium as other components, and may contain fluorides in addition to oxides.

The abrasive used in the present invention is preferable because the effect is large when the content of the constituents of the above-described abrasive is 50% by mass or more. More preferably, it is in the range of 95 to 100% by mass, and still more preferably 100% by mass.

Polishing can be performed with the polishing machine 12 of the polishing process section 1 as shown in FIG. In this invention, it is an abrasive | polishing agent recycle processing system which reproduces | regenerates an abrasive | polishing agent by using the processed abrasive | polishing agent slurry used in such a grinding | polishing process part 1 as a reproduction | regeneration abrasive | polishing slurry.

Taking the polishing of a glass substrate as an example, in the polishing process section 1, the polishing process and the cleaning of the polishing section constitute one polishing process section.

(1-1) Polishing A polishing pad (polishing cloth) and an object to be polished (for example, a glass substrate) are brought into contact with each other, and an abrasive slurry is supplied to the contact surface while the pad and the glass substrate are relatively moved under pressure. Exercise.

The polishing pad can be subjected to pad dressing or pad brushing after continuous polishing. The pad dressing is a process of keeping the pad state constant by roughening the surface while physically cutting the pad. On the other hand, pad brushing is a process performed to remove polishing debris contained in the irregularities of the pad without cutting the pad.

Also, polishing may be performed using a plurality of polishing machines in one batch of processing. In such a case, the change width of the processing time per batch of the next batch with respect to the previous batch is preferably within 10%. Within this range, it is possible to suppress variations in polishing processing time among a plurality of polishing machines. Here, one batch means a unit of polishing process, and for example, six glass substrates can be polished in one batch.

In the present invention, the concentration adjustment of the abrasive in the slurry supply tank 21 is performed for each batch from the viewpoint of reducing the concentration change of the constituents of the abrasive in the abrasive slurry of the next processing batch relative to the previous processing batch. It is preferable to carry out.

(1-2) Cleaning A large amount of abrasive is adhered to the glass substrate immediately after being polished and the polishing machine. Therefore, after polishing, water or the like is supplied from the cleaning water tank 11 instead of the abrasive slurry, and the abrasive adhered to the glass substrate and the polishing machine is cleaned.

This cleaning operation discharges a certain amount of abrasive out of the system, reducing the amount of abrasive in the system. In order to compensate for this decrease, a new recycled abrasive slurry is added to the slurry supply tank 21 from the recycled abrasive slurry storage tank 51. The addition method may be performed for each batch or may be performed for several batches, but it is desirable to supply an abrasive that is sufficiently dispersed in the solvent.

(2) Abrasive slurry recovery process part The abrasive slurry recovery process part has a slurry supply tank 21 for storing the abrasive slurry used for polishing, and the polishing machine 12 and the cleaning in the abrasive slurry recovery process part. The processed abrasive slurry discharged from the system comprising the water tank 11 is recovered.

The abrasive slurry recovery process unit 2 preferably has a recovery mixed liquid tank 22 in addition to the slurry supply tank 21. The slurry supply tank 21 uses the processed abrasive slurry discharged from the polishing machine and the regenerated abrasive slurry and water supplied from the regenerated abrasive slurry storage tank 51 to initialize the abrasive at the start of the polishing process. Controlled below concentration. Then, the abrasive slurry in the slurry supply tank 21 is supplied to the polishing machine 12 via a pump.

In the present invention, the processed abrasive slurry refers to an abrasive slurry discharged out of the system of the polishing process section 1 composed of the polishing machine 12 and the washing water tank 11.

Note that the processed abrasive slurry to be recovered includes two types of abrasive slurry 1 including the cleaning water and abrasive slurry 2 including the processed abrasive slurry. The recovered abrasive slurry generally contains an abrasive in the range of 0.1 to 40% by mass.

After each abrasive slurry is recovered, it may be transferred immediately to the separation step or stored until a certain amount is recovered. In any case, the recovered abrasive slurry is always stirred. It is preferable to prevent aggregation and sedimentation of particles and maintain a stable dispersion state.

In the present invention, the abrasive slurry 1 and the abrasive slurry 2 recovered in the abrasive slurry recovery process unit 2 are mixed and prepared as a mother liquor in the recovered mixed liquid tank 22, and then processed in the subsequent separation / concentration process unit 3. Is preferred.

In the present invention, the regenerated abrasive slurry is supplied to the slurry supply tank 21 while controlling the concentration of the constituents of the abrasive in the slurry supply tank 21 to be equal to or lower than the initial concentration at the start of the polishing process.

(Adjustment of abrasive slurry concentration)
The concentration is adjusted by controlling the flow rate of water, the regenerated abrasive slurry, and the processed abrasive slurry discharged from the polishing process through the pipe, which are put into the slurry supply tank 21. it can. Supply to the polishing machine 12 is performed from a slurry supply tank 21 by a pump (not shown) provided in the piping of the polishing machine 12. The control unit has a flow meter and a pump, and the flow rate is controlled by a circulation line for supplying abrasive slurry between the process units and piping for supplying other additives.

In the present invention, the end point concentration of the constituents of the abrasive in the slurry supply tank at the end of the polishing process is 20 to 90% of the concentration of the constituents of the abrasive in the slurry supply tank at the start of the polishing process. Within the range, more preferably within the range of 30 to 80%.

By reducing the abrasive concentration in this way, it is possible to suppress an increase in temperature and viscosity of the abrasive slurry, to prevent precipitation of silicon oxide, to prevent scratches on the object to be polished, and to improve the recovery rate. .

If the end point concentration of the constituents of the abrasive in the slurry supply tank at the end of the polishing process is 20% or more with respect to the initial concentration of the polishing process, the influence of the decrease in the polishing lubricant is small and the polishing rate is also low. There is no significant decrease. Moreover, if it is 90% or less, it is preferable at the point which can make a collection rate high.

Also, since a certain amount of abrasive is discharged out of the system by the cleaning operation, the concentration of the abrasive in the slurry supply tank 21 varies when a new regenerated abrasive slurry is added. The fluctuation range of the abrasive concentration in the abrasive supply tank 21 is controlled within ± 1.0 mass% of the fluctuation range of the concentration change of the constituents of the abrasive in the abrasive slurry of the next processing batch relative to the previous processing batch. It is preferable that the concentration of the abrasive at the start of the polishing process is not exceeded.

The abrasive concentration in the slurry supply tank 21 can be measured using, for example, a UCUF-04K small-diameter ultrasonic flowmeter detector (manufactured by Tokyo Keiki Co., Ltd.). Specifically, a calibration curve between the abrasive concentration and the flow rate is prepared, and the target abrasive concentration is measured by measuring the flow rate of the abrasive slurry in the slurry supply tank 21, and the recycled abrasive slurry storage tank. Feedback is provided to the control unit 51.

The above UCUF-04K small-diameter ultrasonic flowmeter detector (manufactured by Tokyo Keiki Co., Ltd.) should be measured under the condition that the temperature of the target abrasive slurry is 30 ° C. and the flow pressure is 0.2 MPa. Can do. The measurement of the abrasive slurry concentration in the slurry supply tank 21 may be performed online, or the abrasive slurry may be sampled and measured as appropriate.

In order to start polishing first, in the slurry supply tank 21, when preparing an abrasive solution at the start of polishing, for example, the concentration range of 1 to 40% by mass of the abrasive powder with respect to a solvent such as water The initial abrasive slurry can be prepared by adding and dispersing so that. This initial abrasive slurry is stored in the slurry supply tank shown in FIG. The fine particles used as the abrasive are preferably particles having an average particle size of several tens of nm to several μm.

It is preferable to prevent the agglomeration of the abrasive particles by adding a dispersing agent or the like and maintain the dispersed state by constantly stirring using a stirrer or the like. In general, a tank for abrasive slurry should be installed next to the polishing machine, a dispersion state should always be maintained using a stirrer, etc., and a method of circulating supply to the polishing machine using a supply pump should be adopted. Is preferred.

(3) Separation / Concentration Process Unit Next, the separation / concentration process unit 3 separates and concentrates only the abrasive with respect to the mixed slurry of processed abrasive slurry and washing water collected in the slurry collection process unit.

The separation / concentration process unit 3 in the present invention separates and concentrates the abrasive from the mother liquor. As a method for separating and concentrating, a known method may be used. In particular, an alkaline earth metal salt is added as an inorganic salt to the abrasive slurry recovered in the abrasive slurry recovery step 2, and an abrasive is added. It is preferable that the abrasive is separated from the mother liquor and concentrated in a state where only the agglomerates are aggregated and the components to be polished are not aggregated. As a result, only the abrasive component is coagulated and precipitated, and then the glass component is almost present in the supernatant to separate the agglomerate, thereby simultaneously separating the abrasive component and the glass component and concentrating the abrasive slurry. be able to.

A known method can be used as the separation and concentration method. A membrane separation method or a sedimentation method can be employed.

(3-1) Separation step For separation, an alkaline earth metal salt is added as an inorganic salt as described above, and only the abrasive is agglomerated, and the abrasive is removed from the mother liquor without aggregating the components to be polished. It is preferable to separate more.

In the solid-liquid separation operation, solid-liquid separation by natural sedimentation may be performed without applying forced separation means. In this way, the mother liquor is separated into a supernatant liquid containing an object to be polished and a concentrate containing a recovered abrasive that has settled at the bottom, and then the decantation method, for example, tilting the kettle to drain the supernatant liquid. Or the drainage hype is inserted to near the interface between the supernatant and concentrate in the separated kettle, and only the supernatant is discharged out of the kettle to recover the abrasive.

The recovered processed abrasive slurry is in a state where glass components derived from the object to be polished are mixed. In addition, the concentration decreases due to the mixing of cleaning water, and in order to use the recovered abrasive again for polishing, it is necessary to separate the glass component that is the object to be polished and concentrate the abrasive. is there.

(Alkaline earth metal salt)
In the present invention, it is a preferred embodiment that the inorganic salt used for agglomeration of the abrasive is an alkaline earth metal salt.

Examples of the alkaline earth metal salt according to the present invention include calcium salts, strontium salts, and barium salts. Furthermore, in the present invention, elements belonging to Group 2 of the periodic table are also broadly defined. , Defined as an alkaline earth metal. Therefore, beryllium salts and magnesium salts also belong to the alkaline earth metal salts referred to in the present invention.

The alkaline earth metal salt according to the present invention is preferably in the form of a halide, sulfate, carbonate, acetate or the like.

The inorganic salt according to the present invention is preferably an alkaline earth metal salt, more preferably a magnesium salt.

Further, the magnesium salt applicable to the present invention is not limited as long as it functions as an electrolyte, but from the viewpoint of high solubility in water, magnesium chloride, magnesium bromide, magnesium iodide, magnesium sulfate, Magnesium acetate and the like are preferred, and magnesium chloride and magnesium sulfate are particularly preferred from the viewpoint that the pH change of the solution is small and the settled abrasive and waste liquid can be easily treated.

(Inorganic salt addition method)
Next, a method for adding the inorganic salt to the abrasive slurry (mother liquor) according to the present invention will be described.

a) Concentration of inorganic salt The inorganic salt to be added may be directly supplied to the abrasive slurry (mother liquor) or may be dissolved in a solvent such as water and then added to the abrasive slurry (mother liquor). Although it is good, it is preferable to add in the state dissolved in the solvent so that it may become a uniform state after adding to an abrasive | polishing agent slurry.

A preferable concentration of the inorganic salt is an aqueous solution having a concentration range of 0.5 to 50% by mass. In order to suppress the pH fluctuation of the system and improve the efficiency of separation from the glass component, it is more preferable that the concentration is in the range of 10 to 40% by mass.

b) Addition temperature of inorganic salt The temperature at which the inorganic salt is added is not less than the temperature at which the recovered abrasive slurry is frozen and can be appropriately selected as long as it is in the range up to 90 ° C. From the viewpoint of efficiently performing the separation, it is preferably in the range of 10 to 40 ° C, more preferably in the range of 15 to 35 ° C.

c) Addition rate of inorganic salt The addition rate of the inorganic salt to the abrasive slurry (mother liquor) is uniform without causing a high concentration region locally as the concentration of the inorganic salt in the recovered abrasive slurry. It is preferable to add such that. The addition amount per minute is preferably 20% by mass or less of the total addition amount, and more preferably 10% by mass or less.

d) pH value during addition of inorganic salt In the abrasive recovery / regeneration method of the present invention, when adding an inorganic salt in the separation / concentration process unit 3, the pH value of the previously recovered abrasive slurry may not be adjusted. This is a preferred embodiment. Generally, the pH value of the recovered abrasive slurry is somewhat alkaline because it contains a glass component, and is in the range of less than 8 to 10, and it is not necessary to adjust the pH value of the recovered abrasive slurry in advance. Therefore, in the present invention, it is preferable to perform separation and concentration under the condition that the pH value of the mother liquor in terms of 25 ° C. is less than 10.0.

In the present invention, the pH value can be a value measured at 25 ° C. using a Lacom Tester desktop pH meter (pH 1500, manufactured by As One Co., Ltd.).

In the present invention, it is preferable to add an inorganic salt and then maintain the pH at or below the inorganic salt addition until the concentrate is separated. The pH value at the time of inorganic salt addition here means the pH value immediately after the addition of the inorganic salt is completed.

ＰＨ Maintain the pH value or less at the time of adding inorganic salt until the precipitated aggregates are separated. Preferably, less than 10 is maintained as a pH value at 25 ° C. By setting the pH value to less than 10, it is possible to prevent aggregation of glass components contained in the waste liquid, so that the purity of cerium oxide at the time of recovery can be increased, which is preferable.

The lower limit of the pH value at the time of adding the inorganic salt is preferably 6.5 or more from the viewpoint of purity reduction and operability due to the pH adjusting agent.

e) Stirring after addition of inorganic salt After adding the inorganic salt, stirring is preferably continued for at least 10 minutes, more preferably 30 minutes or more. Aggregation of the abrasive particles starts simultaneously with the addition of the inorganic salt, but maintaining the stirring state makes the aggregation state uniform throughout the system, narrowing the particle size distribution of the concentrate, and facilitating subsequent separation.

The separation / concentration process unit 3 separates the concentrate containing the glass component and the concentrate containing the recovered abrasive particles, and then recovers the concentrate.

(3-2) Concentration step In the present invention, from the viewpoint of obtaining a high-purity recycled abrasive without mixing impurities (for example, polished glass coarse particles) as much as possible into the concentrate that settles at the bottom, As the primary concentration method, it is preferable to apply natural sedimentation.

Since the recovered abrasive particles aggregate due to the addition of the inorganic salt and are separated from the supernatant in this state, the concentrate has a higher specific gravity than the recovered slurry and is concentrated. The concentrate contains the recovered abrasive at a concentration higher than the recovered slurry.

As an example of a method for separating the condensed abrasive concentrate and the supernatant liquid, after separating into a supernatant liquid containing the object to be polished and a concentrate containing the recovered abrasive precipitated in the lower part by natural sedimentation Then, it is inserted to near the interface between the supernatant and the concentrate, and only the supernatant is discharged out of the kettle using a pump, and the concentrate containing the abrasive can be recovered.

(4) Regeneration of abrasive (4-1) Abrasive particle size adjustment step The abrasive particle size adjustment step 4 redisperses the aggregated abrasive to obtain a desired particle size distribution. For example, the particle size distribution level is adjusted to a level close to that of an unused (before polishing) abrasive. In the present invention, it is preferable to perform a particle size control treatment of the abrasive particles on the concentrated and separated abrasive slurry.

In the abrasive slurry concentrated and separated by the above method, since the abrasive particles form aggregates (secondary particles) via inorganic salts, water and a dispersing agent are used to unravel the state close to independent primary particles. And is dispersed to a desired particle size using a dispersion apparatus.

As a method of redispersing the aggregated abrasive particles, for example, a) a method of adding water to reduce the concentration of inorganic ions having an aggregating action on the abrasive in the treatment liquid, and b) a dispersant (also referred to as a metal separating agent) And a method of forcibly flocculating aggregated abrasive particles using a disperser or the like.

These methods may be used singly or in combination, but a method of combining at least b) is preferable, and a method of combining a), b) and c) is more preferable. .

In the case of adding water, the amount added is appropriately selected depending on the volume of the concentrated abrasive slurry, and is generally 5 to 50% by volume, preferably 10 to 40% by volume of the concentrated slurry.

(Dispersant)
A known dispersant can be used as the dispersant. The amount added can be in the range of 0.01 to 5.0 g / L with respect to the recycled abrasive slurry.

In the present invention, a polycarboxylic acid polymer dispersant having a carboxy group is preferably exemplified, and an acrylic acid-maleic acid copolymer is particularly preferable.

When the polishing of the glass substrate is continued, the pH of the abrasive slurry being processed increases with the dissolution of the object to be polished such as polysilicic acid and shifts to the alkali side. When shifting to the alkali side, defects such as burns on the surface of the object to be polished (a phenomenon in which the appearance of the glass gradually turns white) tend to occur. If the pH is adjusted by adding an acid to prevent this defect, the dissolved polysilicic acid is likely to solidify, which may cause a reduction in the yield rate of the object to be polished.

Such a phenomenon can be reduced by using a copolymer of acrylic acid-maleic acid as a dispersant. In addition to its function as a dispersing agent, the buffering effect against pH fluctuation of the abrasive slurry during processing acts due to the equilibrium state of maleic acid hydrolysis, and the dissolved polysilicic acid is stably dissolved without solidifying. It is thought that it is because it can keep.

The maleic acid-acrylic acid copolymer has a buffering effect against pH fluctuation and is useful as an additive having a dispersing function. It is not only used as a dispersant in the abrasive particle size adjusting step 4 but also added as a dispersant. As an agent, it may be added separately to the slurry supply tank 21 or the recycled abrasive storage tank 51.

From the viewpoint of keeping the pH value in the slurry supply tank 21 stable, the regenerated abrasive slurry in the regenerated abrasive storage tank 51 in the regenerated abrasive-containing liquid preparation process unit 5 contains 0 maleic acid-acrylic acid copolymer. It is preferably contained within the range of 0.04 to 1.50 g / L.

<Acrylic acid-maleic acid copolymer>
As an additive having a dispersing function, the water solubility of a copolymer in which the molar ratio of (a) acrylic acid to (b) (anhydrous) maleic acid is (a) / (b) = 50/50 to 95/5 An acrylic acid-maleic acid copolymer consisting of a salt and having a molecular weight distribution (Mw / Mn) of 3.5 to 10 is preferred.

The molecular weight distribution (Mw / Mn) of the copolymer is preferably 3.5-7. The number average molecular weight of the copolymer is in the range of 1000 to 20000, preferably 1000 to 10,000. If necessary, other copolymerization monomers may be copolymerized.

As the polymerization initiator, a combination of a persulfate such as ammonium persulfate, potassium persulfate, or sodium persulfate and a reducing agent such as phosphorous acid, hypophosphorous acid, or a salt thereof is preferable. Particularly preferred is sodium hypophosphite. Both persulfate and reducing agent are preferably used in an amount of 1 to 6 mol% based on the monomer, and the total amount of persulfate and reducing agent is preferably less than 10 mol% based on the monomer. A specific synthesis method is described in JP-A-7-316999.

Specific examples of the acrylic acid-maleic acid copolymer include Polyty A-550 (manufactured by Lion Corporation), Mighty 21HP (manufactured by Kao Corporation), and the like. A combination of an acrylic acid-maleic acid copolymer and a known dispersant can also be used.

Also, as the disperser, an ultrasonic disperser, a medium stirring mill such as a sand mill or a bead mill can be applied, and it is particularly preferable to use an ultrasonic disperser.

As the ultrasonic disperser, various devices are commercially available from, for example, SMT Co., Ltd., Ginsen Co., Ltd., Taitec Co., Ltd., BRANSON, Kinematica Co., Ltd., Nippon Seiki Seisakusho Co., Ltd. ) SMT UDU-1, UH-600MC, Ginsen GSD600CVP, Nippon Seiki Seisakusho RUS-600TCVP, etc. can be used. The frequency of the ultrasonic wave is not particularly limited.

As a circulation system device that performs mechanical stirring and ultrasonic dispersion simultaneously, SMT Co., Ltd. UDU-1, UH-600MC, Ginseng Co., Ltd. GSD600RCVP, GSD1200RCVP, Nippon Seiki Seisakusho Co., Ltd. RUS600-TCVP, etc. However, it is not limited to these.

For example, after adding an aqueous dispersion of an abrasive having a reduced inorganic salt concentration by adding water, and then adding a dispersant (for example, a polymer dispersant) from an addition vessel while stirring with a stirrer. Then, a dispersion treatment is performed with an ultrasonic disperser 44 by a pump, and the agglomerated abrasive particles are unraveled. Subsequently, the particle size distribution of the abrasive particles after dispersion is monitored by a particle size measuring device 45 provided on the downstream side thereof, and the particle size distribution of the abrasive dispersion can be made into a desired particle size distribution profile. .

As the particle size distribution obtained in this step, it is desirable that the particle size distribution has little variation with time and the average particle size variation after one day has little.

(4-2) Recycled Abrasive Slurry Preparation Step Unit In the recycle abrasive slurry preparation step unit 5, the necessary additives are added in this way, and the regenerated abrasive slurry storage tank 51 is made to have a predetermined concentration. Store in.

In the present invention, the final regenerated abrasive slurry obtained in the regenerated abrasive slurry preparation step 5 contains a high-purity abrasive of 98% by mass or more, has a small variation with time in the particle size distribution, and is recovered. The content of the inorganic salt is preferably in the range of 0.0005 to 0.08 mass%.

As described above, a high-quality and high-purity recycled abrasive can be obtained as a recycled abrasive slurry by a simple method.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "%" is used in an Example, unless otherwise indicated, "mass%" is represented.

Example 1
<< Preparation of Recycled Abrasive >>
First, a regenerated abrasive slurry was prepared using the abrasive recycling system shown in FIG.

1) Abrasive slurry recovery process part 2
After polishing the glass substrate in the polishing process section 1 shown in FIG. 2, 210 l of the abrasive slurry 1 containing the cleaning water is collected into the recovered mixed liquid tank 22 and polished after being processed from the slurry supply tank 21. 30 liters of the abrasive slurry 2 containing the agent was recovered to 240 liters as a recovered slurry liquid. The recovered slurry liquid in the recovered mixed liquid tank 22 has a specific gravity of 1.03 and contains 8.5 kg of cerium oxide.

2) Separation / concentration process section 3
Next, the recovered slurry liquid is transferred to the separation / concentration tank 32, and the liquid temperature of the recovered slurry liquid is controlled within a range of 20 ± 1 ° C. While stirring to such an extent that cerium oxide does not settle, 10% by mass of magnesium chloride 2.5 liters of aqueous solution was added over 10 minutes. Immediately after the magnesium chloride was added, the pH value in terms of 25 ° C. was 8.60, and this condition was maintained.

After stirring for 30 minutes in the above state, the mixture was allowed to stand for 1.5 hours, and the supernatant liquid and the aggregate were settled and separated by a natural sedimentation method. After 1.5 hours, the supernatant was discharged using a drain pump, and the aggregate was separated and recovered. The collected aggregate was 60 liters.

3) Abrasive particle diameter adjustment process part 4
The separated agglomerates were transferred to the abrasive separation liquid storage tank 42 and 22.5 liters of water were added. Furthermore, 300 g of Polyty A-550 (manufactured by Lion Corporation), an additive having a dispersing function as a dispersing agent, was added, stirred for 30 minutes, filtered through a 10 micron membrane filter 43, and further ultrasonically dispersed. The machine 44 was used to disperse and loosen the agglomerates to obtain a regenerated abrasive containing an abrasive having a predetermined particle size.

4) Recycled abrasive slurry preparation process part 5
The regenerated abrasive was transferred to the regenerated abrasive slurry storage tank 51, the concentration was adjusted, and 80 liters of regenerated abrasive slurry containing regenerated cerium oxide was obtained. The cerium oxide concentration was 10% by mass, the particle size (D90 <2.0 μm), and the magnesium content was 0.01% by mass. The concentration of Polyty A-550, which is an additive having a dispersing function in the regenerated abrasive slurry, was 0.50 g / L with respect to the regenerated abrasive slurry.

[Abrasive recycling system 1]
The slurry supply tank 21 was filled with a regenerated abrasive slurry containing cerium oxide having an initial concentration of 10.0% by mass, and 200 batches of glass substrates were polished in the polishing step as follows. In the abrasive slurry collecting step 2, the abrasive slurry remaining in the polishing step is washed away with cleaning water every time the glass substrate is polished. The abrasive slurry 1 containing the washing water was recovered in the recovery liquid mixture tank 22. Further, the processed abrasive slurry was recovered from the abrasive slurry supply tank 21 to the recovery mixture tank 22 after the 200 batch processing was completed. Thereafter, in the separation / concentration process unit 3, the abrasive particle size adjustment process unit 4 and the regenerated abrasive slurry preparation process unit 5, a regenerated abrasive was prepared as a regenerated abrasive slurry in the same manner as the regenerated abrasive preparation. .

[Polishing process section]
During polishing, the concentration of the polishing agent in the slurry supply tank 21 for storing the polishing agent slurry used for polishing is controlled to be equal to or less than the initial concentration (10.0% by mass) at the start of the polishing process, and polishing is performed. One batch (one process) while controlling the concentration of cerium oxide in the slurry supply tank 21 so that the concentration in the slurry supply tank at the end of the processing step is 50% (5.0 mass%) of the initial concentration. At the end of this processing, the regenerated abrasive slurry and water as needed were supplied into the slurry supply tank.

Specifically, the slurry supply tank 21 was first supplemented with a regenerated abrasive slurry containing an initial concentration of 10.0 mass% abrasive. Next, the polishing process is performed, and the polishing slurry 2 containing the processed polishing agent is returned to the slurry supply tank 21 at the end of each batch of polishing processing, the polishing machine is washed with water, and a predetermined thickness is obtained. 200 batches of polishing were repeated.

At this time, the concentration of the abrasive (cerium oxide) in the abrasive slurry supply tank 21 is 10.0% by mass or less, and the concentration of the abrasive in the slurry supply tank 21 at the end of the polishing process is the initial concentration. In the slurry supply tank 21 so that the fluctuation range of the concentration change of the abrasive in the abrasive slurry of the next processing batch with respect to the previous processing batch is within ± 1.0% by mass so as to be 50% (5% by mass). While controlling the concentration of cerium oxide in each batch, the regenerated abrasive slurry and water as needed were supplied into the slurry supply tank every time one batch (one process) was completed.

[Abrasive slurry during and after processing]
After the glass substrate is polished, the abrasive slurry remaining in the polishing step is washed away with cleaning water. The abrasive slurry 1 containing the washing water was recovered in the recovery liquid mixture tank 22. Further, the processed abrasive slurry was recovered from the abrasive slurry supply tank 21 to the recovery mixture tank 22 after the 200 batch processing was completed.

The concentration of the abrasive in the slurry supply tank 21 supplied to the polishing machine 12 during polishing was measured using the UCUF-04K small-diameter ultrasonic flowmeter detector (manufactured by Tokyo Keiki Co., Ltd.) under the following usage conditions. It was measured.

terms of use:
Slurry temperature: 30 ° C
Slurry fluid pressure: 0.2 MPa
Detection of cerium oxide concentration: Abrasive slurry that grasps cerium oxide content and silicon oxide content was measured, and a calibration curve was created so that the cerium oxide content could be grasped.

<Evaluation>
The abrasive recycling system was evaluated based on four items: the recovery rate of the abrasive after polishing, the non-defective rate of the glass substrate, the life of the polishing pad, and the change width of the polishing time between batches. The life of the polishing pad was evaluated by continuing polishing after 200 batches of polishing were completed.

[Abrasive recovery rate]
The recovery rate was calculated by the following formula and evaluated according to the following evaluation criteria. The recovery rate should be at least 50%.

Recovery rate = (total mass of abrasive recovered from abrasive slurry contained in processing slurry and cleaning water after 200 batch polishing / mass of abrasive used for polishing) × 100 (%)
◎: Recovery rate of 90% or more ○: Recovery rate of 70% or more, less than 90% △: Recovery rate of 50% or more, less than 70% ×: Recovery rate of less than 50%
The glass substrate was visually observed, and a non-scratched product was evaluated as a non-defective product according to the following evaluation criteria. An evaluation rank Δ or higher was considered acceptable.

◎: Good product rate of 80% or more ○: Good product rate of 60% or more and less than 80% △: Good product rate of 50% or more and less than 60% ×: Good product rate of less than 50% [life of polishing pad]
The polishing pad was removed and SEM (scanning electron microscope) photograph observation was performed. When silicon oxide is deposited during polishing, silicon oxide is deposited on the foamed portion of the polishing pad and is observed white by SEM observation. For example, although no precipitation is observed in FIG. 3A, white silicon oxide is observed to fill the foamed portion of the polishing pad in FIG. 3B. The evaluation was based on the method of removing precipitates remaining on the polishing pad in 200 processing batches and the degree of recovery of the surface physical properties of the polishing pad. An evaluation rank Δ or higher was considered acceptable.

A: When the polishing pad is brushed, the physical properties of the polishing pad surface are recovered. In addition, precipitation was observed when the number of processing was 300 batches or more. (Precipitates can be removed without grinding the polishing pad.)
○ When the polishing pad is brushed, the physical properties of the polishing pad surface are restored. Precipitation was observed when the number of processing was 250 batches or more. (Precipitates can be removed without grinding the polishing pad.)
Δ: Dressing the polishing pad recovers the physical properties of the polishing pad surface, but does not recover by brushing. (The polishing pad is cut out to remove the precipitate.)
X: Even if the polishing pad is dressed, the physical properties of the polishing pad surface are not recovered. (A large amount of polishing pad is removed to remove precipitates, and the physical property change on the polishing pad surface is large.)
[Change in machining time]
The change width of the processing time per batch of the next batch with respect to the previous batch was measured, and the maximum change width of the processing time per batch of the next batch with respect to the previous batch when 200 batch polishing was performed was evaluated. An evaluation rank Δ or higher was considered acceptable.

◎: Change width of processing time per batch of the next batch relative to the previous batch is less than ± 5% ○: Change width of processing time per batch of the next batch relative to the previous batch is ± 5% or more, less than ± 10% △: Previous The change width of the processing time per batch of the next batch with respect to the batch is ± 10% or more and less than ± 15% X: The change width of the processing time per batch of the next batch with respect to the previous batch is ± 15% or more [Abrasive recycling system 2 ~ 5 and 7-13]
The abrasive cycle systems 2 to 5 and 7 to 13 are the abrasive concentration of the end point in the slurry supply tank 21 in the abrasive slurry recovery process unit 2 in the abrasive recycle system 1, the abrasive in the next processing batch relative to the previous processing batch. Polishing was carried out by changing the fluctuation range of the concentration change, the maximum concentration, the dispersant in the regenerated abrasive slurry and the amount thereof as shown in Table I. Adjustment of the dispersing agent and its amount in the regenerated abrasive slurry was performed by adjusting the dispersing agent and its amount to be added to the abrasive particle size adjusting step 4.

In the abrasive recycling system 12, after the slurry supply tank 21 is filled with the regenerated abrasive slurry containing cerium oxide having an initial concentration of 10% by mass in the abrasive recycle system 1, the regenerated abrasive slurry is filled in the slurry supply tank 21. Without supplying cerium oxide powder and water, 200 batch polishing was performed with the initial concentration of 10% by mass or less in the slurry supply tank 21 at the polishing end point.

Furthermore, the abrasive recycling system 12 did not control the fluctuation range of the change in the abrasive concentration of the next processing batch relative to the previous processing batch.

For this reason, in the abrasive recycling system 12, the maximum concentration of the abrasive in the slurry supply tank exceeded 10.0% by mass.

[Abrasive recycling system 6]
Abrasive slurry was similarly applied to the abrasive recycling system 1 except that the separation / concentration process unit 3 was changed from the sedimentation separation method to the membrane separation method. That is, it was carried out in the same manner as the abrasive recycling system 1 except that it was changed to a micro-zalab module using an MF membrane (micro-za: manufactured by Asahi Kasei Co., Ltd.) having an abrasive slurry pore size of about 0.5 μm.

≪Evaluation of abrasive recycling system 2-13≫
As with the evaluation of the abrasive recycling system 1, the evaluation of the abrasive recycling systems 2 to 13 was performed. The results are shown in Table I.

In the table, the following abbreviations were used for the seeds of the dispersant.

A: Polyty A-550 (maleic acid-acrylic acid copolymer: manufactured by Lion Corporation)
B: Mighty 21HP (maleic acid-acrylic acid copolymer: manufactured by Kao Corporation)
C: Nop Cosperth 5600 (manufactured by San Nopco)

Table I shows that the abrasive recycling system of the present invention has an excellent recovery rate, a high yield rate, and a long polishing pad life.

The abrasive recycling system of the present invention can efficiently recover an abrasive from a processed abrasive slurry and reuse it as a recycled abrasive slurry. For this reason, it can contribute to resource saving of elements with a high rare value such as cerium used as an abrasive.

DESCRIPTION OF SYMBOLS 1 Polishing process part 2 Abrasive slurry collection | recovery process part 3 Separation / concentration process part 4 Abrasive particle diameter adjustment process part 5 Recycled abrasive slurry preparation process part 11 Washing water tank 12 Polishing machine 21 Slurry supply tank 22 Recovery liquid mixture tank 31 Additive tank 32 Separation / concentration tank 41 Additive tank 42 Abrasive separation liquid storage tank 43 Membrane filter 44 Ultrasonic disperser 45 Particle size measuring device 51 Recycled abrasive slurry storage tank

Claims

While continuing the polishing process while controlling the concentration of the constituents of the abrasive and the constituents of the object to be polished in the abrasive slurry used for polishing, the constituents of the object to be polished are removed from the processed abrasive slurry, An abrasive recycling system for recovering and recycling the abrasive,
A polishing process unit for polishing using a polishing machine, and an abrasive slurry recovery process unit having a slurry supply tank for storing the abrasive slurry used for polishing supplied to the polishing machine,
Polishing characterized in that the recycled abrasive slurry is supplied into the slurry supply tank while controlling the concentration of the constituents of the abrasive in the slurry supply tank to be equal to or lower than the initial concentration at the start of the polishing process. Agent recycling system.
The concentration of the constituents of the abrasive in the slurry supply tank is in the range of 20 to 90% at the end point concentration at the end of the polishing step relative to the concentration at the start of the polishing step, and during the polishing step The concentration of the constituent component of the abrasive is always equal to or higher than the end point concentration, and the variation range of the concentration of the constituent of the abrasive in the next processing batch relative to the previous processing batch is controlled within ± 1.0 mass%. The abrasive recycling system according to claim 1.
The concentration of the constituents of the abrasive in the slurry supply tank is within the range of 30 to 80% at the end point concentration at the end of the polishing step relative to the concentration at the start of the polishing step, and during the polishing step The concentration of the constituent component of the abrasive is always equal to or higher than the end point concentration, and the variation range of the concentration of the constituent of the abrasive in the next processing batch relative to the previous processing batch is controlled within ± 1.0 mass%. The abrasive recycling system according to claim 1.
4. In addition to the said grinding | polishing process part and the said abrasive | polishing agent slurry collection | recovery process part, it has a isolation | separation and concentration process part, and a reproduction | regeneration abrasive | polishing agent slurry preparation process part, The any one of Claim 1 to 3 characterized by the above-mentioned. The abrasive recycling system according to one item.
In the abrasive slurry recovery process section, the slurry supply tank that stores the abrasive slurry supplied to the polishing process section, and a recovery liquid mixture tank that stores a mixed liquid of the processed abrasive slurry and cleaning water And
The separation / concentration process section includes a separation / concentration tank that separates the mixed solution into a permeate and an abrasive concentrate,
The regenerated abrasive slurry preparation process section includes a regenerated abrasive slurry storage tank for storing a liquid containing the regenerated abrasive from which the constituents of the object to be polished have been removed, and the abrasive slurry is placed between the process sections. The abrasive recycling system according to claim 4, further comprising a circulation line for supplying and a control unit for adjusting the supply amount.
6. The abrasive recycling system according to claim 4 or 5, further comprising an abrasive particle size adjusting step for adjusting the particle size of the abrasive obtained in the separation / concentration step.
7. The regenerated abrasive slurry contains a maleic acid-acrylic acid copolymer in a range of 0.04 to 1.5 g / L. The abrasive | polishing agent recycling processing system of clause.
The abrasive recycling system according to any one of claims 1 to 7, wherein the abrasive contains a metal oxide, and the object to be polished contains silicon (Si). .
The abrasive recycling system according to any one of claims 1 to 8, wherein the abrasive contains cerium oxide.
The abrasive recycling system according to any one of claims 4 to 9, wherein an alkaline earth metal salt is used as a flocculant of the abrasive in the separation / concentration process section.
The abrasive recycling system according to claim 10, wherein the alkaline earth metal salt is a magnesium salt.
While continuing the polishing process while controlling the concentration of the constituents of the abrasive and the constituents of the object to be polished in the abrasive slurry used for polishing, the constituents of the object to be polished are removed from the processed abrasive slurry, An abrasive recovery / regeneration method for recovering / regenerating the abrasive,
Control the concentration of the constituents of the abrasive in the slurry supply tank for storing the abrasive slurry used for polishing supplied to the polishing machine to be equal to or lower than the initial concentration of the constituents of the abrasive at the start of the polishing process. An abrasive recovery / regeneration method comprising: supplying a recycled abrasive slurry to the polishing process section and recovering the processed abrasive slurry.
The concentration of the constituents of the abrasive in the slurry supply tank is in the range of 20 to 90% at the end point concentration at the end of the polishing step relative to the concentration at the start of the polishing step, and during the polishing step The concentration of the constituent component of the abrasive is always equal to or higher than the end point concentration, and the variation range of the concentration of the constituent of the abrasive in the next processing batch relative to the previous processing batch is controlled within ± 1.0 mass%. The abrasive recovery / regeneration method according to claim 12.
The concentration of the constituents of the abrasive in the slurry supply tank is within the range of 30 to 80% at the end point concentration at the end of the polishing step relative to the concentration at the start of the polishing step, and during the polishing step The concentration of the constituent component of the abrasive is always equal to or higher than the end point concentration, and the variation range of the concentration of the constituent of the abrasive in the next processing batch relative to the previous processing batch is controlled within ± 1.0 mass%. The abrasive recovery / regeneration method according to claim 12.
The regenerated abrasive slurry contains a maleic acid-acrylic acid copolymer in a range of 0.04 to 1.5 g / L. The method for recovering and recycling the abrasive according to the item.