JP2012178418A - Method and apparatus for collecting polishing agent - Google Patents

Abstract

An abrasive recovery device and an abrasive recovery method capable of recovering a slurry in which an abrasive is concentrated to a high concentration while suppressing an increase in pressure loss and a significant decrease in recovery due to membrane clogging. provide.
An apparatus for recovering an abrasive from a used polishing slurry used in a CMP process, wherein a hole path into which the used polishing slurry is introduced has a cylindrical shape and an effective filtration portion has a length of 0. A polishing agent recovery apparatus 1 having a separation membrane 41 of 8 m or less and concentrating the polishing agent concentration of the used polishing slurry to a concentration of 10% by mass or more.
[Selection] Figure 1

Description

  The present invention relates to an abrasive recovery method and recovery apparatus, and more particularly, to an abrasive recovery method capable of concentrating used polishing slurry to a high concentration and a recovery apparatus using the same.

  The surface of a film such as an insulating film or a metal thin film formed on a semiconductor wafer is required to be a highly flat surface. In order to meet the demand, CMP (Chemical Mechanical Polishing) is employed in which polishing is performed with a polishing slurry interposed between a polishing member such as a polishing pad and a semiconductor wafer.

  As an abrasive used in CMP, silica fine particles having good dispersibility and uniform particle diameter, ceria having a high polishing rate, alumina having high hardness and stability are used. These abrasives are provided by a manufacturer as a slurry in which particles having a predetermined particle size and concentration are dispersed in water, and are used after being diluted to a predetermined concentration when supplied to a CMP machine according to each site.

  Usually, in this slurry, in addition to abrasives, pH adjusters such as potassium hydroxide, ammonia, organic acids and amines, dispersants such as surfactants, hydrogen peroxide, potassium iodate, iron nitrate (III ) Or the like is added in advance, or is added separately during polishing.

These polishing slurries are desired to be reused from the viewpoint of a large amount of use and high cost, and from the viewpoint of reducing the amount of industrial waste.
However, polishing process wastewater is diluted with a large number of cleaning process water, etc., and the concentration of the abrasive is reduced. In addition, semiconductor wafers, coating materials, polishing pad scraps, fine particles with destroyed abrasives, and agglomeration of abrasives Solid impurities with a large particle diameter generated by the mixing are mixed. For this reason, if such waste water from the polishing process is reused without being treated as an abrasive, the polishing rate for flattening decreases due to a decrease in the concentration of the abrasive, and scratches occur on the wafer surface, resulting in a decrease in product yield. Or

  Therefore, in the reuse, it is necessary to remove impurities such as coarse solids and salts from the polishing wastewater, and further carry out a concentration treatment to readjust the polishing slurry having a predetermined composition.

Conventionally, various techniques have been developed for CMP process wastewater treatment.
For example, CMP process wastewater is passed through separation membranes such as microfiltration membranes and ultrafiltration membranes for membrane treatment, and chemicals and ultrapure water are added to adjust the concentration of abrasives and dispersants and polishing. A method of reusing as an agent slurry has been proposed.
For example, in Patent Document 1, the slurry concentration of the circulating fluid in the first membrane element is maintained at a predetermined value to perform membrane separation, a part thereof is extracted, and further membrane separation is performed with the second membrane element. A membrane treatment method for CMP waste water with an improved membrane permeation flow rate is disclosed. Further, in Patent Document 2, by removing the fine particles with the ultrafiltration membrane 1m in the first step, and removing the coarse particles causing the polishing scratches with the microfiltration membrane 2m in the second step, There is disclosed a method for separating a slurry-like polishing liquid for a semiconductor, which can remove agglomerates in which fine particles are aggregated to increase the diameter and recover abrasive particles having a desired particle diameter.
Furthermore, in Patent Document 3, the abrasive waste liquid in the CMP process is concentrated to 0.90 to 0.96 times the specific gravity of the stock solution using a concentration filter such as an ultrafiltration membrane (primary concentration process), A method is disclosed in which the concentrated solution is further concentrated to 0.99 to 1.01 times the specific gravity of the stock solution (secondary concentration step), and the abrasive is recycled.
In Patent Document 4, second membrane separation means for removing coarse solids is provided in the subsequent stage, and the concentrated liquid concentrated by the first membrane separation means in the previous stage is introduced into the second membrane separation means. Thus, there has been disclosed an abrasive recovery device that reduces the amount of water passing through the membrane separation means and the amount of dispersant in the waste water, and suppresses early clogging of the membrane.

  As the hollow fiber type separation membrane used in the above example, an ultrafiltration membrane is widely used. The hollow fiber type separation membrane is superior in cost because the number of modules to be used is reduced as the effective filtration length is longer, and those having a filtration length of about 1 m are generally used.

On the other hand, in a hollow fiber type separation membrane, as the water to be treated becomes high in concentration, solid components accumulate as cake on the inner wall, and the thickness of the cake gradually increases. For this reason, the effective inner diameter of the film is narrowed, pressure loss is increased, and the film is clogged, and the recovery rate of the abrasive may be remarkably reduced. In particular, in the case of treatment of discharged water in the CMP process, this tendency becomes significant when the abrasive concentration exceeds about several percent.
For this reason, the concentration up to several percent is practically limited. Even in the technique described in the above-mentioned patent document, when a high concentration of treated water is passed, the separation membrane is clogged. It was difficult to sufficiently suppress the accompanying reduction in the recovery rate of the abrasive particles.

JP 2001-113273 A Japanese Patent Laid-Open No. 11-28338 JP 2008-34827 A JP 2002-83789 A

  In general, when the concentration of water to be treated exceeds a predetermined value in the filtration treatment with a separation membrane, the progress rate of clogging of the membrane rapidly increases. As described above, in the case of a polishing slurry, the concentration of the abrasive is reduced. When it exceeds several percent, clogging rapidly proceeds. For this reason, in conventional techniques such as wastewater treatment, the concentration as a solid content is practically limited to several percent, and at such a concentration, it is difficult to directly reuse it as a polishing slurry in the CMP process. Met.

  Further, when a hollow fiber type separation membrane is used, when the concentration of the abrasive in the slurry exceeds about several percent, as described above, the accumulation of cake gradually proceeds inside the hollow fiber. Then, when the concentration treatment was continued further, it was found that the gelled abrasive deposited on the treated water outlet side of the hollow fiber as shown in FIG. In such a state, not only cannot concentrated water be obtained, but also the module itself cannot be used continuously. Furthermore, since the abrasive is deposited in a gel state, the recovery rate of the abrasive is drastically lowered.

  The present invention has been made to solve the above-mentioned problems, and is an abrasive capable of concentrating the abrasive at a high concentration while suppressing an increase in pressure loss and a significant decrease in the recovery rate due to clogging of the membrane. An object of the present invention is to provide a recovery device and a polishing agent recovery method.

  In order to achieve the above object, the present inventor has intensively studied, and as described above, the accumulation of cake on the filtration surface of the separation membrane and the accumulation of abrasive gel material on the treated water outlet side. The presence or absence mainly depends on the effective filtration length of the separation membrane, and the present invention has been completed.

  The abrasive recovery apparatus of the present invention is an apparatus for recovering the abrasive from the used polishing slurry used in the CMP process, wherein the hole path into which the used polishing slurry is introduced is cylindrical, and an effective filtration unit The separator has a separation membrane having a length of 0.8 m or less, and the abrasive concentration of the used polishing slurry is concentrated to a concentration of 10% by mass or more.

  The concentration of the abrasive to be introduced into the separation membrane is not particularly limited because it depends on the drainage concentration at the customer factory, but generally used slurry of 0.02 to 5% by mass is introduced. Can do. It is preferable that the used polishing slurry is passed through the hollow portion of the separation membrane by a cross flow method. The separation membrane is preferably provided in an internal pressure type membrane separation means. The separation membrane is preferably a hollow fiber membrane. The inner diameter of the separation membrane is preferably 0.1 mm or more and 0.8 mm or less. The molecular weight cutoff of the separation membrane is preferably 3,000 to 30,000. The separation membrane is preferably made of polyethylene, tetrafluoroethylene, polyvinylidene fluoride, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, or polyethersulfone.

  The abrasive recovery device has the separation membrane as a second separation membrane, and has an effective filtration length equal to or greater than that of the separation membrane in the previous stage of the second separation membrane. The first separation membrane having a shape can be provided. The length L1 of the effective filtration part of the first separation membrane is preferably 0.8 to 1.5 m, and the length L2 of the effective filtration part of the second separation membrane is 0.2 to 0.8 m or less. It is preferable.

  In the method for recovering an abrasive according to the present invention, the used polishing slurry used in the CMP step is passed through a separation membrane having a cylindrical hole passage and an effective filtration part having a length of 0.8 m or less, The abrasive concentration of the used polishing slurry is concentrated to a concentration of 10% by mass or more. The used polishing slurry is preferably passed through the hollow portion of the separation membrane by a cross flow method. The inner diameter of the separation membrane is preferably 0.1 mm or more and 0.8 mm or less. Moreover, it is preferable that the circulation flow rate of the to-be-processed water in the effective filtration part of the said separation membrane is 0.5-2 m / sec.

  The method for recovering the abrasive comprises a first filtration step of concentrating the used polishing slurry by passing the used polishing slurry used in the CMP step through a first separation membrane having a cylindrical pore path. A second filtration step of passing and concentrating the concentrated water of the first separation membrane to a second separation membrane having an effective filtration part length of 0.8 m or less, and As the first separation membrane, a separation membrane having an effective filtration length longer than that of the second separation membrane can be used. The first filtration step is not particularly limited because it depends on the abrasive concentration of customer factory waste water, but generally 0.02 to 5% by weight of the used polishing slurry is filtered to a maximum of 13% by weight, more preferably. Is concentrated to 9 to 10% by mass, and in the second filtration step, the concentrated water of 13% by mass or less obtained in the first filtration step is filtered to a maximum of 26% by mass, more preferably 20 to 25%. It is preferable to concentrate to mass%. The abrasive recovery method preferably uses the above-described abrasive recovery device of the present invention.

According to the used abrasive recovery apparatus of the present invention, the use of a separation membrane having an effective filtration portion having a length equal to or less than a predetermined value allows cake accumulation on the filtration surface and polishing on the treated water outlet side. Problems such as gel deposition of the agent are less likely to occur, and the slurry can be concentrated to an abrasive concentration of about 10% or more.
Moreover, the used polishing slurry after being used in the CMP process can be concentrated to a high concentration with lower energy than before, and the slurry in which the abrasive is concentrated to a level usable as a product is recovered. be able to. Further, even if concentration is performed in such a high concentration, an increase in pressure loss in the membrane and clogging of the separation membrane can be suppressed, and a polishing agent recovery device in which a significant decrease in recovery rate is suppressed can be obtained. .

  Further, according to the method for recovering a used polishing slurry of the present invention, it is possible to recover a slurry in which an abrasive is concentrated at a high concentration to a level usable as a product without causing a significant decrease in the recovery rate. As a result, the amount of new slurry used in the CMP process can be reduced by 60% or more.

It is a figure which shows schematic structure of the collection | recovery apparatus of the abrasive | polishing agent which concerns on one Embodiment of this invention. 2 is an enlarged view showing a cross section of one hollow fiber constituting the separation membrane 41. FIG. It is a figure which shows schematic structure of the collection | recovery apparatus of the abrasive | polishing agent which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the abrasive | polishing agent density | concentration in a processing tank, and the permeated water amount (flux) discharged | emitted from a permeated water discharge piping. 3, the relationship between the abrasive concentration in the processing tank 13 and the permeated water amount (flux) discharged from the first permeated water discharge pipe 22, and the abrasive concentration in the processing tank 17 and the second permeated water. It is a figure which shows the relationship with the permeated water amount (flux) discharged | emitted from the discharge piping 24. FIG. It is a photograph which shows the state of the membrane separation means inlet at the time of the separation membrane being blocked. It is an enlarged photograph of FIG. It is a photograph which shows the state of a membrane separation means exit at the time of a separation membrane being obstruct | occluded.

  Hereinafter, the abrasive recovery device and the abrasive recovery method of the present invention will be described in detail.

(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of an abrasive recovery device according to an embodiment of the present invention.
The abrasive recovery device 1 in this embodiment is a guard filter 2 that removes coarse particles contained in a used polishing slurry S (hereinafter referred to as a used polishing slurry S) after polishing a semiconductor by a CMP process. The membrane separation means 4 including the treatment tank 3 for containing the treated water of the guard filter 2 and the separation membrane 41 for filtering the used polishing slurry S is sequentially installed along the flow path.
The guard filter 2 captures solid impurities having a large particle diameter generated by agglomeration of abrasives and polishing pad scraps when a semiconductor wafer is polished, and has a pore size larger than the particle diameter of the abrasive particles. Any material can be used without particular limitation.
The guard filter 2 and the processing tank 3 are connected by a pipe 5, and the processing tank 3 and the first membrane separation means 4 are connected by a pipe 6 provided with a pump P1. The processing tank 3 is provided with a component concentration meter C1.

The membrane separation means 4 is provided with a permeate outlet pipe 7 and a concentrated water outlet pipe 8 provided with an on-off valve B1.
The concentrated water outlet pipe 8 is opened to the concentrated water recovery tank 9 side. Between the upstream portion of the on-off valve B1 of the concentrated water outlet pipe 8 and the processing tank 3, the on-off valve B1 is closed and the on-off valve B2 is opened. Thus, a reflux pipe 10 is provided for refluxing the concentrated water obtained by the membrane separation means 4 to the treatment tank 3.

The separation membrane 41 has a cylindrical hole passage. By passing the used polishing slurry S inside or outside the hole passage, excess water in the used polishing slurry S is removed and concentrated. It is like that.
As the first separation membrane 41 having a cylindrical hole passage, for example, a hollow fiber type, a tubular type, or a flat membrane type separation membrane can be applied.
Among these, the hollow fiber type separation membrane can be suitably used as the separation membrane 41 because a large membrane area can be obtained with a small space.

The length L of the effective filtration part of the separation membrane 41 is 0.8 m or less, preferably 0.5 m or less, more preferably 0.3 m or less, depending on the target concentration.
In general, when a high-concentration slurry is passed through a separation membrane, for example, in the case of a hollow fiber type separation membrane, solid components accumulate on the filtration surface 412 of the hollow fiber 410 in the process of passing concentrated water through the effective filtration part. Then, a cake layer is formed and its thickness increases (see FIG. 2). The cake layer on the filtration surface 412 of the separation membrane 41 is more easily formed as the effective filtration length is longer, and the formation of the cake layer narrows the effective inner diameter 410S of the hollow fiber 410, thereby increasing the pressure loss and blocking the membrane. May occur, and the recovery efficiency of the abrasive may be significantly reduced. In addition, since the cake layer and the gel deposit are formed of abrasive particles, the recovery rate of the abrasive particles is reduced with the increase of the cake layer and the generation of the gel deposit.
Furthermore, as shown in FIG. 8, the abrasive is deposited in a gel form on the treated water outlet side of the hollow fiber, making it difficult to continue the filtration treatment. Further, the amount of chemicals required for cleaning the filtration surface and the cleaning time increase, which increases the cost required for the entire abrasive recovery process.

In the abrasive recovery apparatus 1 of the present invention, as the separation membrane 41, a separation membrane having an effective filtration portion length L of 0.8 m or less, preferably 0.5 m or less, more preferably 0.3 m or less. Use. When such an effective filtration length module of a predetermined value or less is used, clogging hardly occurs even when a high-concentration used slurry is passed through, and the cake layer grows on the filtration surface 412. In addition to being suppressed, no gel-like deposition occurs.
For this reason, even if high concentration water to be treated is passed, it is possible to obtain a recovery device 1 in which an increase in pressure loss in the separation membrane 41 and a clogging of the membrane are unlikely to occur, and a significant reduction in the recovery rate is suppressed. .

  Further, as described above, when a cake layer is formed on the filtration surface 412, coarse particles in which abrasive particles are gelled may be separated from the cake layer and mixed into the water to be treated. When such coarse particles are mixed in the recovered abrasive, scratches are caused on the wafer surface when it is reused in the CMP process, thereby reducing the product yield.

  In the abrasive recovery apparatus 1 of the present invention, the separation membrane 41 uses a separation membrane having an effective filtration length L in the above range, so that a cake layer is formed inside the separation membrane, or a gel-like substance. The generation of coarse particles due to the deposition of is suppressed. For this reason, the amount of coarse particles mixed into the abrasive particles after collection is extremely reduced, and even when reused in the CMP process, the surface of the wafer is hardly scratched and the polishing can be performed with high accuracy. The agent can be recovered.

  When the length L of the effective filtration portion of the separation membrane 41 exceeds 0.8 m, the thickness of the cake layer tends to increase on the filtration surface 412 of the separation membrane 41, and the pressure loss increases due to the narrowing of the effective inner diameter. In addition, the membrane is likely to be blocked.

The length L of the effective filtration part of the separation membrane 41 is preferably within the above range and 0.2 m or more. If the length L of the effective filtration portion of the separation membrane 41 is less than 0.2 m, the number of modules of the separation membrane 41 installed in the recovery device 1 increases, and it becomes difficult to install an appropriate filtration processing device. The length L of the effective filtration part of the separation membrane 41 is preferably 0.2 to 0.3 m.

The separation membrane 41 may be an organic membrane made of an organic material or an inorganic membrane made of inorganic ceramics.
Examples of the organic film include polyethylene (PE), tetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), cellulose acetate (CA), polyacrylonitrile (PAN), polyimide (PI), polysulfone ( PS), polyethersulfone (PES), and the like can be suitably used.
As the inorganic film, a ceramic material such as aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), stainless steel (SUS), glass (SPG), or the like can be used.
Among these, as the separation membrane 41, polysulfone (PS) or polyethersulfone (PES) can be suitably used.

  The separation membrane 41 may be a microfiltration membrane or an ultrafiltration membrane as long as it has a hollow fiber shape, but the abrasive particles in the concentrated liquid after recovery are most efficient. From the viewpoint of recovering well, an ultrafiltration membrane can be suitably used.

The molecular weight cutoff of the separation membrane 41 is preferably 3,000 to 30,000.
When the molecular weight cut off of the separation membrane 41 is less than 3,000, it is necessary to increase the supply pressure to the separation membrane 41 in order to pass the water to be treated through the separation membrane 41 to obtain permeated water. The efficiency may be reduced and the separation membrane 41 may be damaged.
On the other hand, when the molecular weight cut off of the separation membrane 41 exceeds 30,000, a part of the abrasive particles may pass through the separation membrane 41 and move to the permeate side, and the abrasive particles may not be efficiently recovered. . In this case, the fine particles having substantially the same diameter as the pores of the separation membrane 41 are likely to block the pores of the separation membrane 41, which may cause clogging. The molecular weight cutoff of the separation membrane 41 is more preferably 6000 to 10,000.

  When the separation membrane 41 is a hollow fiber type separation membrane or a tubular separation membrane, the inner diameter of each hollow fiber or the like is preferably 0.1 mm or more and 0.8 mm or less. When the inner diameter of each hollow fiber or the like of the separation membrane 41 is less than 0.1 mm, the pressure loss of the water to be treated flowing through the hollow portion of the membrane increases, and it becomes difficult to obtain appropriate treatment efficiency. Further, in this case, the film surface strength is reduced, and the film may be damaged as the concentration of the water to be treated increases. On the other hand, when the inner diameter of each hollow fiber or the like of the separation membrane 41 exceeds 0.8 mm, the shear rate of the water to be treated flowing through the hollow portion of the membrane is small, and abrasives and other impurities are easily deposited on the inner wall of the hollow fiber. There is a possibility that the hollow portion is blocked or a large amount of abrasive gel is generated, and the concentration of the abrasive in the concentrated liquid is lowered. Increasing the shear rate is not preferable because the equipment is enlarged and much energy is consumed. In addition, pressure resistance against external pressure may be reduced. The inner diameter of each hollow fiber or the like of the separation membrane 41 is more preferably 0.3 mm or greater and 0.8 mm or less.

  The membrane separation means 4 may be an internal pressure type separation means for passing water to be treated into the hollow fiber 410, and an external pressure type separation for passing water to be treated to the outside of the support layer 411 of the hollow fiber 410. In the case of an internal pressure type separation means, the solid component deposited on the filtration surface 412 is peeled off by the shearing force of the water to be treated that is passed through the hollow fiber 410, and the cake is removed. This is preferable because the growth of the layer can be suppressed.

  By setting it as such a collection | recovery apparatus 1, the permeated water obtained from the permeated water exit piping 7 can be collect | recovered and reused. Specifically, it can be used as raw water or the like of an ultrapure water device, for example, untreated or after being treated according to the quality of permeated water. Further, it can be used as other utilities in the factory, for example, water for daily life, water for cooling towers, and the like.

(Second Embodiment)
FIG. 3 is a diagram showing a schematic configuration of an abrasive recovery device according to an embodiment of the present invention.
The abrasive recovery device 11 in this embodiment is a guard filter 12 that removes coarse particles contained in a used polishing slurry S (hereinafter referred to as a used polishing slurry S) after polishing a semiconductor by a CMP process. The first membrane separation means 14 including the first treatment tank 13 for containing the treated water of the guard filter 12 and the first separation membrane 141 for filtering the used polishing slurry S is sequentially provided along the flow path. is set up.
The guard filter 12 captures solid impurities having a large particle diameter generated by agglomeration of abrasives and polishing pad scraps when a semiconductor wafer is polished, and has a pore size larger than the particle diameter of the abrasive particles. Any material can be used without particular limitation.
The guard filter 12 and the pretreatment tank 13 are connected by a pipe 15, and the pretreatment tank 13 and the first membrane separation means 14 are connected by a pipe 16 having a pump P <b> 2. The pretreatment tank 13 is provided with a component concentration meter C2.

In the subsequent stage of the first membrane separation means 14, a rear-stage treatment tank 17 that stores the concentrated water separated by the first membrane separation means 14 (hereinafter sometimes referred to as the first concentrated water), and the subsequent stage The second membrane separation means 18 provided with the second separation membrane 181 for filtering the first concentrated water supplied from the processing tank 17, and the concentrated water separated by the second membrane separation means 18 (hereinafter referred to as the first concentration water). 2 and a collection tank 19 for collecting the concentrated water are sequentially installed. The rear treatment tank 17 is provided with a component concentration meter C3.
The first membrane separation means 14 and the post-treatment tank 17 are connected by a pipe 20 provided with an on-off valve B3, and the post-treatment tank 17 and the second membrane separation means 18 are provided with a pump P3. 21 is connected.

  The first membrane separation unit 14 is provided with a first permeate outlet pipe 22. Moreover, between the front | former stage of the on-off valve B3 of the piping 20, and the front | former stage processing tank 13, the 1st concentrated water obtained by the 1st membrane separation means 14 by the closing of the on-off valve B3 and the opening of the on-off valve B4, A reflux pipe 23 for refluxing the upstream processing tank 13 is provided.

The second membrane separation means 18 is provided with a second permeate outlet pipe 24 and a concentrated water outlet pipe 25 having an on-off valve B5.
The concentrated water outlet pipe 25 is opened to the recovery tank 19 side, and between the upstream part of the on-off valve B5 of the concentrated water outlet pipe 25 and the rear-stage treatment tank 17, the on-off valve B5 is closed and the on-off valve B6 is opened. A reflux pipe 26 is provided for refluxing the second concentrated water obtained by the second membrane separation means 18 to the post-treatment tank 17.

The first separation membrane 141 and the second separation membrane 181 have a cylindrical hole passage. By passing the used polishing slurry S inside or outside the hole passage, Excess water is removed and concentrated.
As the first separation membrane 141 having a cylindrical hole passage, for example, a hollow fiber type, a tubular type, or a flat membrane type separation membrane can be applied.
Among these, the hollow fiber type separation membrane can be suitably used as the first separation membrane 141 and the second separation membrane 181 because a large membrane area can be obtained with a small space.

The second separation membrane 181 filters the concentrated water of the first separation membrane 141 provided in the previous stage and further concentrates it to increase the abrasive concentration. The length L2 of the effective filtration part of the second separation membrane 181 is 0.8 m or less, preferably 0.5 m or less, more preferably 0.3 m or less.
By using the separation membrane having the above effective filtration length as the second separation membrane 181, even when a high-concentration used slurry is passed through, clogging of the membrane hardly occurs and the growth of the cake layer is suppressed. . For this reason, even if a high concentration of water to be treated is passed, the recovery apparatus 11 is less likely to cause an increase in pressure loss or membrane clogging in the second separation membrane 181 and to suppress a significant reduction in the recovery rate. be able to.

When the length L2 of the effective filtration part of the second separation membrane 181 exceeds 0.8 m, the thickness of the cake layer tends to increase on the filtration surface of the second separation membrane 181 and the effective inner diameter is narrowed. Increase in pressure loss and membrane clogging are likely to occur.
The length L2 of the effective filtration portion of the second separation membrane 181 is particularly preferably 0.2 to 0.3 m for the same reason as the separation membrane 41 in the first embodiment.

The length L2 of the effective filtration portion of the second separation membrane 181 is preferably shorter than the length L1 of the effective filtration portion of the first separation membrane 141. That is, the length L1 of the effective filtration part of the first separation membrane 141 is preferably longer than the length L2 of the effective filtration part of the second separation membrane 181.
Thereby, the first separation membrane 141 efficiently filters the low-concentration used polishing slurry S diluted with the dispersion medium, and the second separation membrane 181 obtains the first separation membrane 141 with the first separation membrane 141. By further filtering the first concentrated water thus obtained, the slurry in which the abrasive particles are concentrated at a high concentration can be recovered with low energy to a level that can be reused as a product.

In recent years, the used slurry discharged in the CMP process sometimes has a daily discharge amount exceeding 1000 m ³ , and the water contained in the slurry is removed and recovered by more efficient treatment. There is a need for technology to recover the waste.
In the present embodiment, the two-stage configuration as described above allows the volume of water to be treated to be significantly reduced by the first separation membrane 141 having a large membrane area provided in the previous stage and provided in the subsequent stage. The second separation membrane 181 can concentrate the water to be treated to a higher concentration without causing clogging. For this reason, the number of modules to be used can be reduced as compared with the first embodiment.

  When the length L2 of the effective filtration portion of the second separation membrane 181 is equal to or exceeds the length L1 of the first separation membrane 141, the cake layer is formed inside the second separation membrane 181. The thickness is likely to increase, and the increase in pressure loss and membrane clogging are likely to occur due to the narrowing of the effective inner diameter.

The length L1 of the effective filtration portion of the first separation membrane 141 is not particularly limited, but is preferably 0.8 to 1.5 m in consideration of the membrane area and the like.
When the length L1 of the effective filtration part of the first separation membrane 141 is less than 0.8 m, the number of modules of the separation membrane 141 installed in the collection device 11 increases or the installation area increases, and the collection is performed. There is a possibility that a sufficient effect cannot be obtained as a device.
On the other hand, when the length L1 of the effective filtration part of the first separation membrane 141 exceeds 1.5 m, there is a possibility that the installation height of the first separation membrane 141 may be limited or the separation membrane 141 may be difficult to handle. There is. The length L1 of the effective filtration part of the first separation membrane 141 is more preferably 0.8 to 1.5 m.

  The first separation membrane 141 may be a microfiltration membrane or an ultrafiltration membrane as long as it has a cylindrical hole passage, but efficiently recovers abrasive particles (abrasive grains). In addition, an ultrafiltration membrane that keeps the particle size of the abrasive particles in the concentrated liquid after collection constant, has a small pore size, and is excellent in energy efficiency can be suitably used.

  The second separation membrane 181 may also be a microfiltration membrane or an ultrafiltration membrane as long as it has a hollow fiber shape, but polishing in the concentrated liquid after collection is also possible. From the viewpoint of keeping the recovery rate of the agent particles high, an ultrafiltration membrane can be suitably used.

The molecular weight cutoff of the first separation membrane 141 and the second separation membrane 181 is preferably 3,000 to 30,000. When the molecular weights of the first separation membrane 141 and the second separation membrane 181 are less than 3,000, the water to be treated is passed through the separation membrane to obtain permeated water. , And the energy efficiency is lowered, and the separation membrane may be damaged.
On the other hand, when the molecular weight cut-off of the first separation membrane 141 and the second separation membrane 181 exceeds 30,000, some of the abrasive particles pass through the first separation membrane 141 and move to the permeate side. The recovery efficiency of abrasive particles may be reduced. In this case, the fine particles having substantially the same diameter as the pores of the separation membrane 141 are liable to block the pores of the separation membrane 141 and the second separation membrane 181, which may cause clogging.

  In the case where the first separation membrane 141 and the second separation membrane 181 are hollow fiber type separation membranes or tubular type separation membranes, the inner diameter is preferably 0.1 mm or more and 0.8 mm or less. When the inner diameter of each hollow fiber or the like of the first separation membrane 141 is less than 0.1 mm, the pressure loss of water to be treated flowing through the hollow portion of the membrane increases, and it becomes difficult to obtain appropriate treatment efficiency. The membrane surface strength of the separation membrane 141 decreases, and the membrane may be damaged as the concentration of water to be treated increases. On the other hand, when the inner diameter of each hollow fiber or the like of the first separation membrane 141 is 0.8 mm or more, the shear rate of the water to be treated flowing through the hollow portion of the membrane is small, and abrasives and other impurities are present on the inner wall of the hollow portion. In this case, the hollow portion may be clogged, or a large amount of gel in which abrasive particles are aggregated may be generated, resulting in a decrease in the concentration of the abrasive in the concentrated liquid after collection. The inner diameters of the hollow fibers and the like of the first separation membrane 141 and the second separation membrane 181 are more preferably 0.3 mm or more and 0.8 mm or less.

The first separation membrane 141 and the second separation membrane 181 may be organic membranes made of organic materials or inorganic membranes made of inorganic ceramics.
Examples of the organic film include polyethylene (PE), tetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), cellulose acetate (CA), polyacrylonitrile (PAN), polyimide (PI), polysulfone ( PS), polyethersulfone (PES), and the like can be suitably used.
As the inorganic film, a ceramic material such as aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), stainless steel (SUS), glass (SPG), or the like can be used.
Among these, as the first separation membrane 141 and the second separation membrane 181, polysulfone (PS) and polyethersulfone (PES) can be suitably used.

  When the first separation membrane 141 and the second separation membrane 181 are hollow fiber type separation membranes, they may be internal pressure type separation means for passing water to be treated into the hollow fiber, and the hollow fiber It may be an external pressure type separation means for passing the water to be treated to the outside of the support layer, but in the case of the internal pressure type separation means, the solid component deposited on the filtration surface is contained in the hollow fiber. It is preferable because it is peeled off by the shearing force of the water to be treated and the growth of the cake layer can be suppressed.

  In such a recovery apparatus 11, the first separation membrane 141 can concentrate the diluted slurry solution to a certain extent, so that a large amount of CMP waste water can be efficiently concentrated. Particularly in a semiconductor factory with a large production scale, the amount of wastewater per day may be 1000 tons or more, but by providing the first separation membrane 141, such a large amount of wastewater is about 1/10 to 1 / The amount can be reduced to 500. Therefore, as compared with the first embodiment in which the first separation membrane 141 is not installed, the number of modules installed as a whole can be reduced.

  As described above, the abrasive recovery device 11 of the present invention has been described with reference to an example thereof, but the configuration thereof can be appropriately changed within the limits not departing from the gist of the present invention.

Next, based on FIG. 3, the abrasive | polishing agent recovery method using the abrasive | polishing agent recovery apparatus 11 of this invention is demonstrated.
In this embodiment, as the first separation membrane 141 and the second separation membrane 181, a case where the abrasive recovery device 11 including a hollow fiber type ultrafiltration membrane is used will be described. The first separation 141 may not necessarily be a hollow fiber type separation membrane as long as it has a cylindrical hole, and may be a tubular type or a flat membrane type.

The used polishing slurry S to be treated is not particularly limited as long as it contains an abrasive after being used in the CMP process (chemical mechanical polishing process). Examples of such abrasive particles include silicon particles and cerium particles.
As the abrasive particles, those having an average particle diameter of 0.01 to 1 μm are usually preferably used. Although the average particle diameter of an abrasive | polishing agent is suitably selected by CMP process, it is 0.04-0.4 micrometer, for example.

First, the used polishing slurry S used in the CMP process is supplied to the guard filter 12 via the pipe 15. The used polishing slurry S is stored in the pretreatment tank 13 after coarse particles having a particle size of several tens of μm or more are removed in the process of passing through the guard filter 12.
The concentration of the abrasive particles in the untreated stage of the used polishing slurry S is not particularly limited because it depends on the customer factory, but the concentration of the abrasive in the used polishing slurry S in the CMP process is usually 0.00. It is 02-5 mass%.

The used polishing slurry S stored in the pretreatment tank 13 includes a first separation membrane 141 via a pipe 16 by a pump P2 with the on-off valve B3 closed and the on-off valve B4 opened. The first membrane separation means 14 is pressurized and supplied.
The used polishing slurry S is passed through the guard filter 12, coarse particles having a particle size of several tens of μm or more are removed, and then water is passed through each hollow fiber of the first separation membrane 141 by a cross flow method. Excess water is permeated and concentrated in the process of passing through the effective filtration part (first filtration step). At this time, the dispersion medium of the used polishing slurry S flows out to the permeate outlet pipe 22 through the separation membrane 141, and the abrasive particles in the used polishing slurry S are concentrated water of the first separation membrane 141. It remains on the first concentrated water side.

  The first concentrated water is returned to the pretreatment tank 13 through the reflux pipe 23. After continuing this process for a predetermined time, at the stage where the concentration of the abrasive of the stored water in the pretreatment tank 13 measured by the component concentration meter C2 is 13% by mass at maximum, more preferably 9 to 10% by mass, The on-off valve B3 is opened and the on-off valve B4 is closed, and a part of the on-off valve B3 is supplied to the post-processing tank 17 via the pipe 20.

The flow rate of the water to be treated (the used polishing slurry S and the first concentrated water) passing through the effective filtration part of the first separation membrane 141 is preferably 0.5 to 2 m / sec.
When the flow rate of the water to be treated (the used polishing slurry S and the first concentrated water) in the effective filtration portion of the first separation membrane 141 is less than 0.5 m / sec, an abrasive is applied to the filtration surface of the separation membrane 141. Particles are likely to adhere, and the amount of permeated water may decrease. In this case, it is necessary to increase the number of separation membranes 141 installed, and the manufacturing cost of the recovery device 11 increases. On the other hand, when the flow rate of the water to be treated in the effective filtration part of the first separation membrane 141 exceeds 2.0 m / sec, the amount of liquid contacting the membrane surface becomes excessive, and heat may be generated. In this case, both the separation membrane 141 and the concentrated liquid may be damaged by heat and deteriorate. Further, in order to improve the flow rate of the water to be treated in the separation membrane 141, it is necessary to increase the size of each pipe, valve, etc., and the manufacturing cost of the recovery device 11 increases.
The flow rate of the water to be treated that passes through the effective filtration part of the first separation membrane 141 is more preferably 0.55 to 1.5 m / sec.

The first concentrated water stored in the post-treatment tank 17 is supplied to the second separation membrane 181 via the pipe 21 by the pump P3 with the on-off valve B5 closed and the on-off valve B6 opened. Pressure is supplied to the second membrane separation means 18 provided.
The second separation membrane 181 is shorter than the effective filtration length L1 of the first separation membrane 141 and has an effective filtration length L2 of 0.8 m or less, preferably 0.5 m or less, more preferably 0.3 m or less. The first concentrated water is passed through the hollow portion of each hollow fiber by the cross flow method. In the process of passing through the effective filtration part of the hollow fiber, the first concentrated water is permeated with excess water and concentrated (second filtration process). At this time, the dispersion medium or the like of the first concentrated water flows out to the permeate outlet pipe 24 through the separation membrane 181, and the abrasive particles contained in the first concentrated water are concentrated in the second separation membrane 181. It remains on the second concentrated water side, which is water.

The flow rate of the water to be treated (first concentrated water) passing through the effective filtration part of the second separation membrane 181 is preferably 0.5 to 2 m / sec.
When the flow rate of the water to be treated in the effective filtration portion of the second separation membrane 181 is less than 0.5 m / sec, the abrasive particles easily adhere to the filtration surface of the separation membrane 181 and the membrane is likely to be blocked. . On the other hand, when the flow rate of the water to be treated in the effective filtration part of the second separation membrane 181 exceeds 2 m / sec, an excessive amount of energy is added to the abrasive particles, and the particles may aggregate to form coarse particles. is there. When coarse particles are mixed in the recovered abrasive, scratches may be generated on the surface of the wafer or the like when recycled in the CMP process, thereby reducing the product yield. In addition, when such coarse particles are generated, a cake layer is formed on the filtration surface of the separation membrane, which may increase the cleaning time and the amount of chemicals used.
The flow rate of the water to be treated that passes through the effective filtration part of the second separation membrane 181 is more preferably 0.6 to 1 m / sec.

After the above treatment process is continued for a predetermined time, the on-off valve B5 is opened and the on-off valve B6 is opened at the stage where the concentration of the abrasive of the stored water in the post-treatment tank 17 measured by the component concentration meter C3 reaches the target concentration. Is closed, and a part thereof is supplied to the recovery tank 19 via the pipe 25.
The concentration of the stored water in the post-stage treatment tank 17 when being supplied to the recovery tank 19 via the pipe 25 is preferably 10% by mass or more and a maximum of 26% by mass, and more preferably 20 to 25% by mass. is there.

  The pressure loss of the water to be treated on the filtration surface of the second separation membrane 181 is preferably 0.1 MPa or less, and more preferably 0.08 MPa or less.

  In the abrasive recovery method of the present invention, since the second separation membrane 181 having an effective filtration length shorter than the first effective filtration length is used, the pressure loss on the filtration surface of the second separation membrane is increased. In addition, it is possible to efficiently recover the used polishing slurry S in which the abrasive particles are concentrated at a high concentration to a level that can be used as a product while suppressing clogging of the film.

  In the present embodiment, the first filtration step and the second filtration step both show a method of filtration treatment using an internal pressure type method in which water to be treated is passed through the hollow portion of the hollow fiber. Is not necessarily limited to such a form, and for example, it may be filtered by an external pressure type system in which water to be treated is passed outside the hollow fiber.

The permeate obtained from the first permeate outlet pipe 22 and the second permeate outlet pipe 24 can be recovered and reused.
For example, it can be used as raw water of an ultrapure water device or the like without being treated or after being treated according to the quality of the permeated water. It can also be used as other utilities in the factory, for example, water for daily life, water for cooling towers, and the like.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1
The used slurry was filtered in the CMP process using the abrasive recovery apparatus 1 shown in FIG.

The pump P1 in FIG. 1 is a Levitro pump “LEV300” (trade name, manufactured by Iwaki Co., Ltd.), and the membrane separation means 4 is a hollow fiber type UF membrane module “FB02-VC-FUST653” (Daisen Membrane Systems). Concentration tank (product made from PVC) was used as the processing tank 3 and the concentrated water recovery tank 9.
The hollow fiber type UF membrane module “FB02-VC-FUST653” had a molecular weight cut-off: 6000, hollow fiber inner diameter: 0.5 mm, membrane area: 0.5 m ² , effective filtration length: 0.26 m.

First, a used polishing slurry solution having an abrasive concentration of about 1% by mass (pH: 9.8) was supplied from the pipe 5 to the processing tank 3 via the guard filter 2. Next, the on-off valve B1 was closed, the on-off valve B2 was opened, and the used polishing slurry in the processing tank 3 was passed through the membrane separation means 4.
The circulation flow rate in each pipe of the used slurry was 8.1 L / min, and the linear velocity in the hollow fiber membrane 41 was 0.55 m / sec. Further, the impeller rotational speed of the pump P1 (levitro pump) and the degree of opening / closing of the on-off valve B2 downstream of the membrane separation means 4 are set so that the pressure in the vicinity of the used polishing slurry inlet in the hollow fiber membrane 41 becomes 0.2 MPa. Prepared.
The water flow treatment was performed in this state, and the abrasive concentration in the treatment tank 3 measured by the component concentration meter C1 and the permeated water amount (flux) discharged from the permeate outlet pipe were measured.

(Example 2)
Except that a hollow fiber type UF membrane module “M81S60001N” (trade name, manufactured by SPECTRUM) was used as the membrane separator 4, the used polishing slurry was passed through in the same manner as in Example 1. In the same manner as in Example 1, the abrasive concentration in the processing tank 3 was measured.
The hollow fiber UF membrane module “M81S60001N” had a hollow fiber inner diameter of 0.5 mm and an effective filtration length of 0.46 m.

(Example 3)
Except that a hollow fiber type UF membrane module “KM1S60001N” (trade name, manufactured by SPECTRUM) was used as the membrane separator 4, the used polishing slurry was treated with water in the same manner as in Example 1. In the same manner as in Example 1, the abrasive concentration in the processing tank 3 was measured.
The hollow fiber type UF membrane module “KM1S60001N” had a hollow fiber inner diameter of 0.5 mm and an effective filtration length of 0.63 m.

(Comparative Example 1)
Except that a hollow fiber type UF membrane module “KM1S30001N” (trade name, manufactured by SPECTRUM) was used as the membrane separator 4, the used polishing slurry was passed through in the same manner as in Example 1. In the same manner as in Example 1, the abrasive concentration in the processing tank 3 was measured.
The hollow fiber type UF membrane module “KM1S30001N” had a hollow fiber inner diameter of 0.5 mm and an effective filtration length of 0.81 m.

(Comparative Example 2)
Used polishing in the same manner as in Example 1 except that a hollow fiber type UF membrane module “AMK-VC-FUST653” (trade name, manufactured by Daisen Membrane Systems Co., Ltd.) was used as the membrane separator 4. The slurry was passed through, and the abrasive concentration in the treatment tank 3 was measured in the same manner as in Example 1.
The hollow fiber UF membrane module “AMK-VC-FUST653” had a hollow fiber inner diameter of 0.5 mm, an effective filtration length of 1.0 m, and a membrane area of 1.5 m ² .

In Example 1 and Comparative Example 2, FIG. 4 shows the relationship between the abrasive concentration in the processing tank 3 measured by the component concentration meter C1 and the permeated water amount (flux) discharged from the permeated water discharge pipe 7.
In FIG. 4, the broken line indicates the amount of permeated water from the permeate outlet pipe 7 in Example 1, and the solid line indicates the amount of permeated water from the permeate outlet pipe 7 in Comparative Example 2.
Moreover, in Table 1, the to-be-treated water abrasive | polishing agent at the time of a water flow start with the hollow fiber internal diameter, membrane area, effective filtration length, and material of each hollow fiber separation membrane 41 of Examples 1-3 and Comparative Examples 1-2. The concentration of the abrasive to be treated and the concentration of the water to be treated (the maximum concentration that can be concentrated) when the concentration treatment becomes impossible are shown.

As is clear from Table 1, in the recovery devices of Examples 1 to 3 in which the effective filtration length of the separation membrane 41 is 0.8 m or less, a high abrasive concentration of 20% by mass or more is obtained at the end of the filtration process. It was recognized that the maximum concentration that can be concentrated increases as the effective filtration length decreases. On the other hand, in the recovery device of Comparative Example 1 having an effective filtration length exceeding 0.8 m, the maximum concentration that can be concentrated is less than 20% by mass, and it was recognized that clogging is likely to occur in a high concentration region.
Moreover, as shown in FIG. 4, in the collection | recovery apparatus of the comparative example 2 using the separation membrane 41 which has an effective filtration length exceeding 0.8 m as the membrane separation means 4, Si concentration of to-be-processed water is 13 mass%. When it exceeded, the permeated water amount (flux) decreased rapidly, and it was difficult to perform further filtration treatment. On the other hand, in the recovery apparatus of Example 1 using the separation membrane 41 having an effective filtration length of 0.8 m or less as the membrane separation means 4, even if the concentration of water to be treated exceeds 20% by mass, the amount of permeated water is rapidly increased. No significant reduction occurred, and the filtration process could be performed stably even when the water to be treated had a high concentration.
From the above results, when the separation membrane 41 having an effective filtration length of 0.8 m or less is used as the membrane separation means 4, the low-concentration used slurry discharged from the CMP process can be stably stabilized up to the high-concentration region. It was found that it could be concentrated.

Waste liquid containing abrasive particles such as silica particles has been conventionally separated into solid and liquid because of the need to comply with wastewater standards, but even if an ultrafiltration membrane is used for solid-liquid separation, Concentration as a minute was limited to about several percent. When the concentration of the abrasive component is about several percent, it is difficult to reuse the polishing slurry as a polishing slurry in the CMP process. Therefore, the solid content is generally discarded as industrial waste.
In the present invention, as shown in Examples 1 to 3, since the concentration of the abrasive in the waste water from the CMP process can be concentrated to a concentration of about 25% that can be used as a product, the recovered concentrated solution is again subjected to CMP. It can be used in the process, and high recycling efficiency can be obtained.

  Next, the abrasive recovery apparatus 1 used in Example 1 was used, the pressure at the treated water inlet of the membrane separation means 4 was the same as in Example 1, and the pressure loss of the separation membrane was changed to 4-5 and Comparative Examples 3-6 were performed.

Example 4
The linear velocity in the hollow fiber membrane 41 was 0.6 m / sec, and the other conditions were the same as in Example 1, and the used polishing slurry was passed through the recovery device 1 and subjected to filtration. After performing this process for 80 minutes, the on-off valve B1 was opened, the on-off valve B2 was closed, and the concentrated water of the membrane separation means 4 was recovered from the concentrated water outlet pipe 8 to the concentrated water recovery tank 9.

(Example 5)
As membrane separation means 4, instead of hollow fiber type UF membrane module “FB02-VC-FUST653”, hollow fiber type UF membrane module “SLP-1053” (trade name, manufactured by Asahi Kasei Chemicals Co., Ltd., hollow fiber inner diameter 1.4 mm) Molecular weight: 10000 Membrane area: 0.12 m ² Effective filtration length 0.20 m Membrane material: Polysulfone), the used polishing slurry supplied to the processing tank 3 was subjected to an abrasive concentration of about 0.8% by mass (pH 10.5), the circulation flow rate of the used slurry in each pipe is 9.0 L / min, the pressure in the hollow fiber membrane 41 near the used polishing slurry inlet is 0.2 MPa, Except that the linear velocity was 0.69 m / sec, filtration was performed in the same manner as in Example 2, and the concentrated water of the membrane separation means 4 was recovered.

(Comparative Example 3)
As membrane separation means 4, instead of hollow fiber type UF membrane module “FB02-VC-FUST653”, hollow fiber type UF membrane module “AMK-VC-FUS0181” (trade name, manufactured by Daisen Membrane Systems Co., Ltd., hollow. Thread inner diameter 0.8 mm, molecular weight cut off: 10000 membrane area: 0.5 m ² effective filtration length 1 m membrane material: PES), and the linear velocity in the hollow fiber membrane 41 was 0.55 m / sec, Filtration was performed in the same manner as in Example 2, and the concentrated water of the membrane separation means 4 was recovered.

(Comparative Example 4)
As membrane separation means 4, instead of hollow fiber type UF membrane module “FB02-VC-FUST653”, hollow fiber type UF membrane module “AMK-VC-FUS03C1” (trade name, manufactured by Daisen Membrane Systems Co., Ltd., hollow. Thread inner diameter 1.2 mm, molecular weight cut off: 30000 membrane area: 0.3 m ² effective filtration length 1 m membrane material: PES), and the linear velocity in the hollow fiber membrane 41 was 0.85 m / sec, Filtration was performed in the same manner as in Example 2, and the concentrated water of the membrane separation means 4 was recovered.

(Comparative Example 5)
As membrane separation means 4, instead of hollow fiber type UF membrane module “FB02-VC-FUST653”, “AMK-VC-FUS03C1” (trade name, manufactured by Daisen Membrane Systems Co., Ltd., hollow fiber inner diameter 1.2 mm, Molecular weight cut off: 30000 Membrane area: 0.3 m ² Effective filtration length: 1 m Membrane material: PES), and the linear velocity in the hollow fiber membrane 41 was 1.8 m / sec. Filtration was performed, and the concentrated water of the membrane separation means 4 was recovered.

(Comparative Example 6)
As the membrane separation means 4, instead of the hollow fiber type UF membrane module “FB02-VC-FUST653”, “AMK-VC-FUST653” (trade name, manufactured by Daisen Membrane Systems Co., Ltd., hollow fiber inner diameter 0.5 mm, Fractionation molecular weight: 6000 Membrane area: 1.5 m ² Effective filtration length 1 m Membrane material: PES), the linear velocity in the hollow fiber membrane 41 is the same as in Example 2, and other conditions are the same as in Example 2. Filtration was performed, and the concentrated water of the membrane separation means 4 was recovered.

  Table 2 shows the abrasive concentration of the concentrated water recovered in the concentrated water recovery tank 9 and the recovery rate of the abrasive for Examples 4 to 5 and Comparative Examples 3 to 6. Table 2 also shows the abrasive concentration values in the concentrated liquid calculated from the linear velocity in the hollow fiber membrane 41 of Examples 4 to 5 and Comparative Examples 3 to 6, the inner diameter of the hollow fiber, and the amount of permeated water discharged. Shown in

As is clear from Table 2, in Example 4 using a separation membrane having an effective filtration length of 0.8 m or less and an inner diameter of the separation membrane of 0.1 mm or more and 0.8 mm or less, It was confirmed that the abrasive concentration exceeded 25% by mass, and a higher recovery rate could be obtained.
Further, in Example 5 in which the effective filtration length was shortened and the pressure loss was reduced by increasing the hollow fiber inner diameter as compared with Example 4, permeated water of a predetermined amount or more was supplied to a relatively high concentration region. Although obtained, it cannot be concentrated to 25% by mass or more, and the concentration of the abrasive contained in the recovered concentrated liquid is lower than the abrasive concentration (calculated value) calculated from the amount of permeated water. It was confirmed that the recovery rate of the abrasive was slightly reduced as the yarn inner diameter (fiber diameter) increased. This is probably because the abrasive component (abrasive particles) adhered to the inside of the hollow fiber to form a cake layer, and the effective inner diameter was narrowed.

  On the other hand, in Comparative Examples 3 and 6 having an effective filtration length greater than 0.8 m and a hollow fiber inner diameter in the range of 0.1 to 0.8 mm, the abrasive recovery rate is around 76%. The concentration of the abrasive contained in the concentrated liquid after the recovery was lower than the abrasive concentration (theoretical value) calculated from the amount of permeated water. Further, in Comparative Examples 4 and 5 in which the inner diameter of the hollow fiber was increased to 1.2 mm, the recovery rate of the abrasive was further lowered, and the abrasive component (polishing agent particles) adhered to the cake inside the hollow fiber. It is thought that the layer was formed and the effective inner diameter was narrowed.

(Comparative Example 7)
The ultrafiltration membrane “MLE-7101H” (manufactured by Kuraray Co., Ltd., product name. Effective filtration length: 1 m, hollow fiber inner diameter; 1.2 mm, fractional molecular weight; 13000, membrane material; polysulfone) was installed, and filtration treatment was performed. The filtration process was performed by an internal pressure type cross flow method.
The separation membrane was gradually clogged from the stage when the concentration of the abrasive contained in the concentrated solution reached 14% by mass, and then the filtration was continued by increasing the pressure of the water to be treated by increasing the output of the pump. Concentration treatment became impossible when the Si concentration of water reached 19% by mass.
FIG. 6 shows the state of the inlet of the membrane separation means 4 at the time when the filtration treatment becomes impossible, FIG. 7 shows an enlarged part of FIG. 6, and FIG. 8 shows membrane separation at the same point. The state of the means 4 outlet is shown.

  As shown in FIG. 8, the membrane separation means at the time when the concentration treatment becomes difficult is a gel-like state in which the abrasive is aggregated at the subsequent stage of the water to be treated (the outlet of the membrane separation means 4). Coarse particles are formed in one area, and the hollow portion of the separation membrane 41 is thereby blocked, making it difficult to continue the concentration process.

(Example 6)
The used slurry was filtered in the CMP process using the abrasive recovery device 11 shown in FIG.

As the pumps P2 and P3 in FIG. 3, a Levitro pump “LEV300” (trade name, manufactured by Iwaki Co., Ltd.) is used, and as the membrane separation means 14, a hollow fiber UF membrane module “AMK-VC-FUST653” (Daisen Membrane) is used.・ As a second concentration means 18, a hollow fiber type UF intermembrane module “FB02-VC-FUST653” (manufactured by Daisen Membrane Systems Co., Ltd., product name) is used. Using.
Further, as the processing tank 13 and the subsequent processing tank 17, a processing tank (manufactured by PE) was used, and as the concentrated water recovery tank 19, a concentrating tank (manufactured by PVC) was used.
The hollow fiber type UF membrane module “AMK-VC-FUST653” as the first membrane separation means 14 has a molecular weight cut-off: 6000, hollow fiber inner diameter: 0.5 mm, membrane area: 1.5 m ² , effective filtration length; The hollow fiber type UF membrane module “FB02-VC-FUST653” that is 1 m and the second membrane separation means 18 has a molecular weight cut-off: 6000, hollow fiber inner diameter: 0.5 mm, membrane area: 0.5 m ² , Effective filtration length; 0.26 m.

First, 200 L of a used polishing slurry solution having an abrasive concentration of about 1 mass% (pH: 9.8) was supplied from the pipe 15 to the processing tank 13 via the guard filter 12. Next, the on-off valve B3 was closed, the on-off valve B4 was opened, and the used polishing slurry in the processing tank 13 was passed through the first membrane separation means 14.
The circulation flow rate in each pipe of the used slurry was 8.0 L / min, and the linear velocity in the hollow fiber membrane 141 was 0.7 m / sec. In addition, the impeller rotational speed of the pump P2 (Levitro pump) and the degree of opening / closing of the on-off valve B4 downstream of the membrane separating means 14 are adjusted so that the pressure in the vicinity of the used polishing slurry inlet in the hollow fiber membrane 141 becomes 0.2 MPa. Prepared.
The water flow treatment was performed in this state, and the amount of permeate (flux) discharged from the permeate outlet pipe 22 was measured until the abrasive concentration in the treatment tank 3 measured by the component concentration meter C2 reached 9% by mass. At this time, the used polishing slurry in the processing tank 13 was about 22 L.

Next, the on-off valve B4 was closed, the on-off valve B3 was opened, and the entire amount of used polishing slurry in the processing tank 13 was supplied to the post-stage processing tank 17. Next, the on-off valve B5 was closed, the on-off valve B6 was opened, and the used polishing slurry in the post-treatment tank 17 was passed through the second membrane separation means 18. The circulation flow rate in each pipe of the used slurry was 8.0 L / min, and the linear velocity in the hollow fiber membrane 181 was 0.7 m / sec. Further, the impeller rotational speed of the pump P3 (Levitro pump) and the degree of opening / closing of the on-off valve B6 downstream of the membrane separation means 18 are adjusted so that the pressure in the vicinity of the used polishing slurry inlet in the hollow fiber membrane 181 becomes 0.2 MPa. Prepared.
The water flow treatment was performed in this state, and the amount of permeated water (flux) discharged from the permeate outlet pipe was measured until the abrasive concentration in the treatment tank 3 measured by the component concentration meter C3 reached 25% by mass.

In Example 6, the relationship between the abrasive concentration in the processing tank 13 measured by the component concentration meter C2 and the permeated water amount (flux) discharged from the first permeate discharge pipe 22, and the component concentration meter C3 are measured. FIG. 5 shows the relationship between the abrasive concentration in the processing tank 17 and the amount of permeated water (flux) discharged from the second permeated water discharge pipe 24.
In FIG. 5, the solid line indicates the permeate of the first membrane separation means 14 discharged from the first permeate discharge pipe 22, and the broken line indicates the second membrane separation discharged from the second permeate discharge pipe 24. The permeate of means 18 is shown.

Based on the measurement data of Example 1 (FIG. 4) and the measurement data of Example 6 (FIG. 5), the abrasive recovery device 1 of Example 1 (first embodiment) and the abrasive of Example 6 were used. The recovery device 11 (second embodiment) was designed and manufactured.
In the abrasive recovery device 11 of the second embodiment, the number of hollow fiber UF membrane modules used could be reduced by 87% compared to the abrasive recovery device 1 of the first embodiment. . As a result, it was possible to obtain the effects of simplification of the piping configuration as a whole recovery device, reduction in installation area, and cost reduction.

  DESCRIPTION OF SYMBOLS 1,11 ... Abrasive collection | recovery apparatus, 2,12 ... Guard filter, 3 ... Processing tank, 4 ... Membrane separation means, 41 ... Separation membrane, 410 ... Hollow fiber, 410S ... Effective internal diameter, 411 ... Support layer, 412 ... Filtration surface, 5-6 ... piping, 7 ... permeate outlet piping, 8 ... concentrated water outlet piping, 9 ... concentrated water recovery tank, 10 ... reflux piping, 13 ... pretreatment tank, 14 ... first membrane separation means, 141 ... first separation membrane, 15-16, 20-21 ... piping, 17 ... post-treatment tank, 18 ... second membrane separation means, 181 ... second separation membrane, 19 ... recovery tank, 22 ... first Permeated water outlet pipe, 23 ... reflux pipe, 24 ... second permeated water outlet pipe, 25 ... concentrated water outlet pipe, 26 ... reflux pipe, P1 to P3 ... pump, C1 to C3 ... component concentration meter, B1 to B6 ... opening and closing valve

Claims (16)

An apparatus for recovering an abrasive from a used polishing slurry used in a CMP process, wherein the hole path into which the used polishing slurry is introduced is cylindrical, and the length of an effective filtration portion is 0.8 m or less. Has a separation membrane,
A polishing agent recovery apparatus, wherein the polishing agent concentration of the used polishing slurry is concentrated to a concentration of 10% by mass or more.   The abrasive | polishing agent collection | recovery apparatus of Claim 1 with which the said used polishing slurry is water-flowed by the crossflow system in the hollow part of the said separation membrane.   The abrasive recovery device according to claim 1 or 2, wherein the separation membrane is provided in an internal pressure type membrane separation means.   The abrasive recovery device according to any one of claims 1 to 3, wherein the separation membrane is a hollow fiber membrane.   The abrasive recovery device according to any one of claims 1 to 4, wherein an inner diameter of the separation membrane is 0.1 mm or more and 0.8 mm or less.   The apparatus for recovering an abrasive according to any one of claims 1 to 5, wherein the separation membrane has a molecular weight cut-off of 3,000 to 30,000.   7. The separation membrane according to claim 1, wherein the separation membrane is made of any one of polyethylene, tetrafluoroethylene, polyvinylidene fluoride, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, and polyethersulfone. The polishing agent recovery apparatus according to claim 1.   In addition to having the separation membrane as a second separation membrane, the first separation membrane having an effective filtration length longer than the separation membrane and having a cylindrical hole path is provided in front of the second separation membrane. The abrasive | polishing agent collection | recovery apparatus of any one of Claims 1 thru | or 7.   The length L1 of the effective filtration part of the first separation membrane is 0.8 to 1.5 m, and the length L2 of the effective filtration part of the second separation membrane is 0.2 to 0.8 m or less. The abrasive | polishing agent collection | recovery apparatus of Claim 8.   The used polishing slurry used in the CMP step is passed through a separation membrane having a cylindrical hole passage and an effective filtration part having a length of 0.8 m or less, and the abrasive concentration of the used polishing slurry is A method for recovering an abrasive comprising concentrating to a concentration of 10% by mass or more.   The method for recovering an abrasive according to claim 10, wherein the used polishing slurry is passed through the hollow portion of the separation membrane by a cross flow method.   The method for recovering an abrasive according to claim 10 or 11, wherein an inner diameter of the separation membrane is 0.1 mm or more and 0.8 mm or less.   The recovery method of the abrasive | polishing agent of any one of Claims 10 thru | or 12 whose circulating flow rate of the to-be-processed water in the effective filtration part of the said separation membrane is 0.5-2 m / sec. A first filtration step of concentrating the used polishing slurry by passing the used polishing slurry used in the CMP step through the first separation membrane having a cylindrical pore path, and the length of the effective filtration portion A second filtration step of concentrating by passing the concentrated water of the first separation membrane through the second separation membrane of 0.8 m or less, and
The method for recovering an abrasive according to any one of claims 10 to 13, wherein a separation membrane having an effective filtration length longer than that of the second separation membrane is used as the first separation membrane.   In the first filtration step, the used polishing slurry is filtered and concentrated to a maximum of 13% by mass. In the second filtration step, the concentrated water obtained in the first filtration step is filtered to a maximum of 26% by mass. The method for recovering an abrasive according to any one of claims 10 to 14, wherein the abrasive is concentrated to mass%.   The abrasive recovery method according to any one of claims 10 to 15, wherein the abrasive recovery device according to any one of claims 1 to 9 is used.

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