WO2012114395A1

WO2012114395A1 - Abrasive recovery method and abrasive recovery device

Info

Publication number: WO2012114395A1
Application number: PCT/JP2011/004593
Authority: WO
Inventors: 慶一郎石井; 正司日沖
Original assignee: 野村マイクロ・サイエンス株式会社
Priority date: 2011-02-25
Filing date: 2011-08-16
Publication date: 2012-08-30
Also published as: US20130333299A1; CN103347656A; KR20140001954A; JP2012178418A; TW201235090A

Abstract

Provided are an abrasive recovery method and abrasive recovery device capable of recovering a slurry comprising a highly-concentrated abrasive while avoiding increases in pressure loss and large decreases in the recovery rate due to membrane blocking. A device (1) for recovering an abrasive from a used polishing slurry which has been used in a CMP process has a separation membrane (41) with a cylindrical hole passage into which the used polishing slurry is introduced. The hole passage of the separation membrane (41) is no more than 0.8m in length in an effective filtration unit. The abrasive recovery device (1) concentrates the abrasive of the used polishing slurry to a concentration of 10 mass% or greater.

Description

Abrasive recovery method and polishing agent recovery apparatus

The present invention relates to a method and apparatus for recovering abrasives, and more particularly, to a method of recovering abrasives 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 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 a polishing agent used in CMP, silica fine particles having good dispersibility and uniform particle diameter, ceria having a high polishing rate, and alumina having high hardness and stability are used. These abrasives are provided by the manufacturer as a slurry in which particles of predetermined particle size and concentration are dispersed in water. The slurry is used after being diluted to a predetermined concentration when supplied to a CMP machine, depending on each site.

Generally, in this slurry, in addition to the polishing agent, pH adjusters such as potassium hydroxide, ammonia, organic acids and amines, dispersants such as surfactants, hydrogen peroxide, potassium iodate, iron nitrate (III And the like are added in advance. Alternatively, these components are separately added to the slurry at the time of polishing.

It is desirable that these polishing slurries be reused from the viewpoint of reducing the amount of industrial waste, as they are used in large amounts and are expensive. However, the polishing process waste water is diluted by a large number of cleaning process water and the like, and the concentration of the polishing agent is lowered. In addition, semiconductor wafers, coating materials, polishing pad scraps, fine particles in which the polishing agent is broken, and solid impurities having a large particle diameter caused by aggregation of the polishing agent are mixed in the drainage of the polishing process. . For this reason, if such polishing process waste water is recycled without treatment and as an abrasive, the polishing rate to be planarized is reduced due to the decrease in the concentration of the abrasive, and the wafer surface is scratched to reduce the product yield. Do.

Therefore, in reutilization, it is necessary to remove impurities such as coarse solids and salts from the polishing waste water, and further to perform concentration processing to readjust the polishing slurry of a predetermined composition.

Conventionally, development of various techniques has been attempted for CMP process wastewater treatment.
For example, the wastewater from the CMP process is passed through a separation membrane such as a microfiltration membrane or an ultrafiltration membrane and subjected to membrane treatment, and a drug or ultrapure water is further added to adjust the concentration of the polishing agent or the dispersing agent Methods have been proposed for reuse as abrasive slurries.

For example, in Patent Document 1, for the purpose of improving the membrane permeation flow rate, the first membrane element is subjected to membrane separation while maintaining the slurry concentration of the circulating liquid at a predetermined value, and then a portion thereof is extracted. A membrane treatment method of CMP drainage is further disclosed in which membrane separation is further performed by two membrane elements.

Further, Patent Document 2 discloses a method of separating a slurry-like polishing slurry for a semiconductor, which is capable of removing agglomerates having a large diameter by aggregating fine particles and recovering abrasive particles having a desired particle diameter. In Patent Document 2, fine particles are removed by the ultrafiltration membrane 1m in the first step, and coarse particles causing polishing scratches are removed by the microfiltration membrane 2m in the second step.

Furthermore, according to Patent Document 3, the abrasive waste liquid in the CMP step is concentrated to 0.90 times to 0.96 times the specific gravity of the stock solution using a concentration filter such as an ultrafiltration membrane (primary concentration step), A method is disclosed in which the concentrate is further concentrated to 0.99 times to 1.01 times the specific gravity of the stock solution (secondary concentration step) to recycle the abrasive.

Patent Document 4 discloses a polishing agent recovery device in which the amount of water passing through the membrane separation means and the amount of dispersant in the drainage are reduced, and early clogging of the membrane is suppressed. In Patent Document 4, the concentrated solution concentrated by the first membrane separation means at the front stage is introduced into the second membrane separation means at the rear stage, and coarse solids are removed by the second membrane separation means.

Ultrafiltration membranes are widely used as the hollow fiber type separation membranes used in the above examples. The hollow fiber type separation membrane is superior in cost because the longer the effective filtration length, the smaller the number of modules to be used, so that a filtration length of about 1 m is generally used.

On the other hand, in the hollow fiber type separation membrane, as the water to be treated has a high concentration, solid components are deposited as a 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, and an increase in pressure loss and a film clogging may occur, so that the recovery rate of the polishing agent may be significantly reduced. In particular, in the case of the treatment of the discharged water in the CMP process, this tendency becomes remarkable when the concentration of the polishing agent exceeds about several percent. For this reason, the concentration to a few percent is practically limited. Even with the technology described in the above patent documents, it is difficult to sufficiently suppress the clogging of the separation membrane and the decrease in the recovery rate of the abrasive particles accompanying this when passing high-concentration treated water. there were.

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

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

Furthermore, in the case of using a hollow fiber type separation membrane, when the abrasive concentration in the slurry is concentrated to a few percent or more, as described above, cake deposition gradually progresses inside the hollow fiber. After that, when concentration processing was further continued, as shown in FIG. 8, it was found that the gelled abrasive was deposited on the outlet side of the hollow fiber on the side of the water to be treated. In such a state, the concentrated water can not be obtained, and the module itself can not be used continuously. Furthermore, since the abrasive deposits in a gel form, the recovery rate of the abrasive drops sharply.

The present invention has been made to solve the above-mentioned problems, and suppresses the increase in pressure loss and the drastic decrease in recovery rate due to clogging of the membrane, and an abrasive that can concentrate the abrasive to a high concentration. It is an object of the present invention to provide a recovery device and a method for recovering an abrasive.

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

The apparatus for recovering an abrasive according to the present invention is an apparatus for recovering the abrasive from the used abrasive slurry used in the CMP process, and the apparatus for recovering the abrasive has a passage through which the used abrasive slurry is introduced. The separation membrane has a cylindrical shape, and the passage of the separation membrane has an effective filtration portion having a length of 0.8 m or less, and the recovery device for the polishing agent comprises the polishing agent concentration of the used polishing slurry Is concentrated to a concentration of 10% by mass or more.

The concentration of the abrasive introduced into the separation membrane is not particularly limited because it depends on the concentration of liquid discharged from the customer's factory, but in general, a used slurry having 0.02 to 5% by mass should be introduced. Can. Preferably, the used polishing slurry is passed through the hollow portion of the separation membrane in a cross flow manner. The separation membrane is preferably provided in an internal pressure membrane separation unit. 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 cut off 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 may have an upstream separation membrane having an effective filtration length longer than that of the separation membrane and a cylindrical passage in the front stage of the separation membrane. The length L1 of the effective filtration part of the pre-stage separation membrane is 0.8 to 1.5 m, and the length L2 of the effective filtration part of the post-stage separation membrane provided in the latter stage of the pre-stage separation membrane is 0.2 to 0 It is preferable that it is .8 m or less.

In the method of recovering an abrasive according to the present invention, the used abrasive slurry used in the CMP step is passed through a separation membrane having a cylindrical passage and an effective filtration portion having a length of 0.8 m or less, It is characterized in that the abrasive concentration of the used abrasive slurry is concentrated to a concentration of 10% by mass or more. Preferably, the used polishing slurry is 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. Further, the circulation flow rate of the water to be treated in the effective filtration part of the separation membrane is preferably 0.5 to 2 m / sec.

A first filtration step of passing water through the used polishing slurry used in the CMP step to concentrate the used polishing slurry in a pre-stage separation membrane having a cylindrical passage, and a length of an effective filtration portion of 0. And a second filtration step in which concentrated water of the first separation membrane is passed through and concentrated in a second-stage separation membrane having a length of 8 m or less, and the first-stage separation membrane is more than the second-stage separation membrane. A separation membrane with a long effective filtration length can be used. The first filtration step is not particularly limited because it depends on the concentration of the polishing agent in the customer factory waste water, but in general, it is preferable to filter the used polishing slurry of 0.02 to 5% by mass at maximum 13% by mass, 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%. Moreover, it is preferable to use the collection | recovery apparatus of the polishing agent of this invention mentioned above for the collection | recovery method of the said polishing agent.

According to the used abrasive recovery apparatus of the present invention, cake deposition on the filtration surface and polishing on the outlet side of the treated water can be achieved by using a separation membrane having a length of the effective filtration section equal to or less than a predetermined value. Problems such as gel-like deposition of the agent are less likely to occur. For this reason, the slurry can be concentrated to an abrasive concentration of about several tens of percent or more. In addition, the used polishing slurry after being used in the CMP process can be concentrated to a high concentration with lower energy than before, and a slurry having a high concentration of the polishing agent is recovered to a level that can be used as a product. be able to. In addition, even if concentration is performed at such a high concentration, increase in pressure loss in the membrane and blocking 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. .

In addition, according to the method of recovering a used polishing slurry of the present invention, a slurry in which the polishing agent is concentrated to a high concentration can be recovered to a level that can be used as a product without causing a significant decrease in 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 abrasives based on one Embodiment of this invention. It is a figure which expands and shows the cross section of one hollow fiber which comprises the separation membrane 41. As shown in FIG. It is a figure which shows schematic structure of the collection | recovery apparatus of the abrasives based on one Embodiment of this invention. It is a figure which shows the relationship between the abrasive | polishing agent density | concentration in a process tank, and the amount of permeated water (flux) discharged | emitted from permeated water discharge piping. The relationship between the abrasive concentration in the treatment tank 13 and the amount of permeated water (flux) discharged from the first permeated water discharge pipe 22 in the recovery apparatus of FIG. 3 and the abrasive concentration in the treatment tank 17 and the second permeated water It is a figure which shows the relationship with the amount of permeated water (flux) discharged | emitted from the discharge piping 24. As shown in FIG. It is a photograph which shows the state of the membrane separation part inlet when the separation membrane obstruct | occluded. It is an enlarged photograph of FIG. It is a photograph which shows the state of the membrane separation part exit when the separation membrane obstruct | occluded.

Hereinafter, the polishing agent recovery apparatus and the polishing agent recovery method of the present invention will be described in detail.

First Embodiment
FIG. 1 is a view showing a schematic configuration of a polishing agent recovery apparatus according to an embodiment of the present invention. The polishing agent recovery apparatus 1 according to this embodiment is a guard filter 2 for removing coarse particles contained in a used polishing slurry S (hereinafter referred to as a used polishing slurry S) after the semiconductor is polished by a CMP process. A treatment tank 3 for containing the treated water of the guard filter 2 and a membrane separation unit 4 provided with a separation membrane 41 for filtering the used polishing slurry S are sequentially installed along the flow path.

The guard filter 2 is for capturing a solid impurity having a large particle size, which is generated by aggregation of abrasives, polishing pad scraps and the like when polishing a semiconductor wafer. The guard filter 2 can be used without particular limitation as long as it has a pore diameter larger than the particle diameter of the abrasive particles.

The guard filter 2 and the processing tank 3 are connected by a pipe 5. The processing tank 3 and the membrane separation unit 4 are connected by a pipe 6 provided with a pump P1. The processing tank 3 is provided with a component densitometer C1.

A permeated water outlet pipe 7 and a concentrated water outlet pipe 8 having an on-off valve B1 are connected to the membrane separation unit 4. The concentrated water outlet pipe 8 is opened to supply the concentrated water obtained by the membrane separation unit 4 to the concentrated water recovery tank 9.

Between the processing tank 3 and the upstream portion of the on-off valve B1 of the concentrated water outlet pipe 8, the concentrated water obtained in the membrane separation unit 4 is returned to the processing tank 3 by closing the on-off valve B1 and opening the on-off valve B2. A reflux line 10 is provided.

The separation membrane 41 has a cylindrical passage. By passing the used polishing slurry S inside or outside the passage, excess water in the used polishing slurry S is removed and concentrated.

For example, a hollow fiber type, a tubular type, or a flat membrane type separation membrane can be applied as the first separation membrane 41 having a cylindrical passage. Among these, a 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 according to the target concentration concentration. In general, for example, in the case of a hollow fiber type separation membrane, when a high concentration slurry is passed through the separation membrane, solid components are deposited on the filtration surface 412 of the hollow fiber 410 while concentrated water passes through the effective filtration portion. Do. When water flow is further continued, a cake layer is formed by the solid components deposited on the filtering surface 412 and the thickness thereof 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. The formation of the cake layer narrows the effective inner diameter 410S of the hollow fiber 410, causing an increase in pressure loss and clogging of the membrane, which may significantly reduce the recovery efficiency of the polishing agent. In addition, since the cake layer and the gel-like deposit are formed of the abrasive particles, the recovery rate of the abrasive particle decreases with the increase of the cake layer and the occurrence of the gel deposit.

Furthermore, as shown in FIG. 8, the abrasive is deposited in the form of gel on the outlet side of the hollow fiber on the treated water side, making it difficult to continue the filtration process. In addition, the amount of chemicals required for cleaning the filter surface and the cleaning time increase, which causes an increase in the cost required for the entire polishing agent recovery process.

In the polishing agent recovery apparatus 1 of the present invention, as the separation membrane 41, a separation membrane having a length L of the effective filtration portion of 0.8 m or less, preferably 0.5 m or less, more preferably 0.3 m or less is used. Use. When an effective filtration length module having such a predetermined value or less is used, clogging does not easily occur even when passing through a high concentration of used slurry. Therefore, the growth of the cake layer on the filter surface 412 is suppressed, and no gel-like deposition occurs.

Therefore, even if water to be treated with high concentration passes, increase in pressure loss in the separation membrane 41 and blockage of the membrane hardly occur, and the recovery device 1 in which a significant decrease in recovery rate is suppressed can be obtained.

In addition, as described above, when the cake layer is formed on the filter surface 412, coarse particles obtained by gelation of the abrasive particles may be separated from the cake layer and mixed in the water to be treated. If such coarse particles are mixed in the recovered abrasive, they will cause scratching on the wafer surface when reused in the CMP step, leading to a reduction in the product yield.

In the polishing agent recovery apparatus 1 of the present invention, as the separation membrane 41, a separation membrane having a length L of the effective filtration portion in the above range is used. Therefore, the formation of a cake layer inside the separation membrane and the formation of coarse particles due to the deposition of the gel-like substance are suppressed, and the amount of coarse particles mixed in the abrasive particles after recovery is extremely reduced. Therefore, it is possible to recover the polishing agent which can be polished with high accuracy, without causing scratches or the like on the surface of the wafer even if it is reused in the CMP process.

If 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. And blockage of the membrane is likely to occur.

The length L of the effective filtration portion 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 part 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 treatment device. The length L of the effective filtration part of the separation membrane 41 is preferably 0.2 to 0.3 m.

The separation film 41 may be an organic film made of an organic material or an inorganic film made of an inorganic ceramic.

Examples of the organic film include polyethylene (PE), tetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), cellulose acetate (CA), polyacrylonitrile (PAN), polyimide (PI), polysulfone PS), and polyether sulfone (PES) can be suitably used.

Further, as the inorganic film, a ceramic material of 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, polysulfone (PS) and polyethersulfone (PES) can be suitably used as the separation membrane 41.

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

The molecular weight cut-off of the separation membrane 41 is preferably 3,000 to 30,000. If the molecular weight cut-off of the separation membrane 41 is less than 3,000, it is necessary to increase the pressure supplied to the separation membrane 41 in order to pass the water to be treated through the separation membrane 41 to obtain permeated water. Therefore, the energy efficiency is lowered 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 permeated water side, and the abrasive particles may not be efficiently recovered. . Further, in this case, the fine particles having substantially the same diameter as the pore diameter of the separation membrane 41 may easily block the pores of the separation membrane 41, which may cause clogging. The molecular weight cut-off of the separation membrane 41 is more preferably 6000 to 10000.

When the separation membrane 41 is a hollow fiber 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. If 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 an appropriate treatment efficiency. Also, in this case, the surface strength of the film may be reduced, and the film may be damaged as the concentration of the water to be treated is increased. On the other hand, if 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, so that the abrasive and other impurities are easily deposited on the inner wall of the hollow fiber. , There is a risk of closing the hollow portion. In addition, a large amount of abrasive gel may be generated, which may reduce the concentration of the abrasive in the concentrate. In order to increase the shear rate, it is necessary to enlarge the equipment, and it is not preferable because it consumes a large amount of energy. Furthermore, there is a possibility that the pressure resistance to 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 more and 0.8 mm or less.

The membrane separation unit 4 may be an internal pressure type separation unit for passing treated water into the hollow fiber 410, and an external pressure type separation for passing treated water outside the support layer 411 of the hollow fiber 410. It may be a part. When the membrane separation unit 4 is an internal pressure type separation unit, the solid components deposited on the filter surface 412 are peeled off by the shear force of the water to be treated passed through the hollow fiber 410, and the cake layer It is preferable because growth can be suppressed.

By setting it as such a recovery device 1, the permeated water obtained from the permeated water outlet pipe 7 can be recovered and reused. Specifically, for example, it is possible to use it as raw water or the like of the ultrapure water apparatus after processing untreated or in accordance with the quality of the permeate water. Moreover, it is also possible to use as another utility in a factory, such as domestic water, cooling tower water, etc.

Second Embodiment
FIG. 3 is a view showing a schematic configuration of a polishing agent recovery apparatus according to an embodiment of the present invention. The polishing agent recovery apparatus 11 according to this embodiment is a guard filter 12 for removing coarse particles contained in a used polishing slurry S (hereinafter referred to as a used polishing slurry S) after the semiconductor is polished by a CMP process. The front stage membrane separation unit (hereinafter referred to as “first stage separation membrane” 141 including a front stage treatment tank 13 for storing treated water of the guard filter 12 and a front stage separation membrane (hereinafter referred to as a first separation membrane) 141 , And a first membrane separation unit) 14 are sequentially installed along the flow path.

The guard filter 12 is for trapping solid impurities having a large particle size, which are generated by aggregation of abrasives, polishing pad scraps and the like when the semiconductor wafer is polished. The guard filter 12 can be used without particular limitation as long as it has a pore diameter larger than the particle diameter of the abrasive particles. The guard filter 12 and the pre-treatment tank 13 are connected by a pipe 15. The pre-treatment tank 13 and the first membrane separation unit 14 are connected by a pipe 16 provided with a pump P2. The pre-processing tank 13 is provided with a component concentration meter C2.

A post-stage processing tank 17 for storing the concentrated water separated by the first membrane separation unit 14 (hereinafter sometimes referred to as a first concentrated water) in the rear stage of the first membrane separation unit 14, and a rear stage Post-stage membrane separation unit (hereinafter, referred to as second membrane separation unit) including the post-stage separation membrane (hereinafter, referred to as second separation membrane) 181 for filtering the first concentrated water supplied from the treatment tank 17 A recovery tank 19 for recovering concentrated water separated by the second membrane separation unit 18 (hereinafter sometimes referred to as second concentrated water) is sequentially installed. The post-stage processing tank 17 is provided with a component densitometer C3.

The first membrane separation unit 14 and the post-stage processing tank 17 are connected by a pipe 20 provided with an on-off valve B3. The post-treatment tank 17 and the second membrane separation unit 18 are connected by a pipe 21 provided with a pump P3.

A first permeated water outlet pipe 22 is connected to the first membrane separation unit 14. Further, between the front stage of the on-off valve B3 of the pipe 20 and the pre-treatment tank 13, the first concentrated water obtained in the first membrane separation unit 14 is obtained by closing the on-off valve B3 and opening the on-off valve B4. A reflux piping 23 for refluxing to the pre-treatment tank 13 is provided.

The second membrane separation unit 18 is connected to a concentrated water outlet pipe 25 provided with a second permeated water outlet pipe 24 and an on-off valve B5. The concentrated water outlet pipe 25 is opened to supply the concentrated water obtained in the second membrane separation unit 18 to the recovery tank 19. The second concentrated water obtained in the second membrane separation unit 18 between the upstream portion of the on-off valve B5 of the concentrated water outlet pipe 25 and the rear processing tank 17 by closing the on-off valve B5 and opening the on-off valve B6. Is connected to the post-stage processing tank 17.

The first separation membrane 141 and the second separation membrane 181 have a cylindrical passage. By passing the used polishing slurry S inside or outside the passage, excess water in the used polishing slurry S is removed and concentrated. For example, a hollow fiber type, a tubular type, or a flat membrane type separation membrane can be applied as the first separation membrane 141 having a cylindrical passage. Among these, a 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 is to filter and further concentrate the concentrated water of the first separation membrane 141 provided in the previous stage, and to increase the concentration of the polishing agent. 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, clogging of the membrane is less likely to occur even when water is used through high concentration spent slurry, and the growth of the cake layer is suppressed. . For this reason, even if water to be treated with high concentration passes, increase in pressure loss in the second separation membrane 181 and blockage of the membrane hardly occur, and the recovery device 11 is suppressed with a remarkable drop in recovery rate. be able to.

If the length L2 of the effective filtration portion 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 internal diameter is narrowed. It is likely that the pressure loss increases and the membrane is clogged. The length L2 of the effective filtration part 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, it is preferable that the length L1 of the effective filtration part of the first separation membrane 141 be longer than the length L2 of the effective filtration part of the second separation membrane 181.

As a result, the first separation membrane 141 efficiently filters the used polishing slurry S of low concentration diluted with the dispersion medium, and the second separation membrane 181 obtains the first separation membrane 141. The first concentrated water thus obtained is further filtered. Thereby, the slurry in which the abrasive particles are concentrated to a high concentration can be recovered with low energy to a level that can be reused as a product.

In recent years, the amount of used slurry discharged in the CMP process may exceed 1000 m ³ per day. Therefore, there is a need for a technique for removing and recovering water contained in the slurry and for recovering the polishing agent component by more efficient processing.

In the present embodiment, the two-stage configuration as described above enables the volume of the water to be treated to be significantly reduced by the first separation membrane 141 having a large membrane area provided in the former stage, and is provided in the latter stage. The second separation membrane 181 can concentrate the water to be treated to a higher concentration without causing clogging. For this reason, it is possible to reduce the number of modules to be used compared to 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 of the second separation membrane 181 is formed. The thickness tends to increase, and the narrowing of the effective inner diameter tends to cause an increase in pressure loss and a blockage of the membrane.

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. If 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 recovery apparatus 11 increases or the installation area becomes large, As an apparatus, there is a possibility that a sufficient effect can not be obtained.

On the other hand, if the length L1 of the effective filtration part of the first separation membrane 141 exceeds 1.5 m, the installation height of the first separation membrane 141 is limited, or the handling of the separation membrane 141 becomes difficult There is a risk of 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 passage. Efficiently recover abrasive particles (abrasive particles), keep the particle size of the abrasive particles in the concentrated solution after recovery constant, and use an ultrafiltration membrane with a small pore diameter and excellent energy efficiency. Can.

The second separation membrane 181 may also be a microfiltration membrane or an ultrafiltration membrane as long as it has a hollow fiber type shape. An ultrafiltration membrane can be suitably used from the viewpoint of maintaining a high recovery rate of the abrasive particles in the concentrated solution after recovery.

The molecular weight cut off of the first separation membrane 141 and the second separation membrane 181 is preferably 3,000 to 30,000. If the molecular weight cut-off of the first separation membrane 141 and the second separation membrane 181 is less than 3,000, the pressure supplied to the separation membrane is sufficient for passing water to be treated through the separation membrane to obtain permeated water. Need to rise. As a result, the energy efficiency is lowered and the separation membrane may be damaged.

On the other hand, when the fractional molecular weight of the first separation membrane 141 and the second separation membrane 181 exceeds 30,000, a part of the abrasive particles passes through the first separation membrane 141 and moves to the permeated water side. The recovery efficiency of the abrasive particles may be reduced. Further, in this case, the fine particles having substantially the same diameter as the pore diameter of the separation membrane 141 may easily block the holes of the separation membrane 141 and the second separation membrane 181, which may cause clogging.

When the first separation membrane 141 and the second separation membrane 181 are hollow fiber separation membranes or tubular separation membranes, the inner diameter thereof 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 the 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 is lowered, and the membrane may be damaged as the concentration of the water to be treated is increased. On the other hand, if 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 the abrasive and other impurities are the inner wall of the hollow portion. The hollow portion may be clogged, the hollow portion may be clogged, a large amount of gel in which abrasive particles are aggregated may be generated, and the concentration of the abrasive in the concentrated solution after recovery may be reduced. The inner diameters of 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 film 141 and the second separation film 181 may be an organic film made of an organic material, or may be an inorganic film made of an inorganic ceramic. Examples of the organic film include polyethylene (PE), tetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), cellulose acetate (CA), polyacrylonitrile (PAN), polyimide (PI), polysulfone PS), and polyether sulfone (PES) can be suitably used.

Further, as the inorganic film, a ceramic material of 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, polysulfone (PS) and polyethersulfone (PES) can be suitably used as the first separation membrane 141 and the second separation membrane 181.

In the case where the first separation membrane 141 and the second separation membrane 181 are hollow fiber type separation membranes, they may be internal pressure type separation parts that allow water to be treated to flow through the hollow fiber, It may be an external pressure type separation part in which the water to be treated flows through the outside of the support layer. When it is set as an internal pressure type separation part, it is preferable because the solid component deposited on the filtration surface can be peeled off by the shear force of the water to be treated passed through the hollow fiber and the growth of the cake layer can be suppressed.

In such a recovery apparatus 11, the dilute solution of the slurry can be concentrated to a certain extent by the first separation membrane 141, so that a large amount of CMP drainage can be efficiently concentrated. In particular, in a large-scale semiconductor factory, the amount of drainage may exceed 1,000 tons per day, but by providing the first separation film 141, such a large amount of drainage can be about 1/10 to 1/500. Can be reduced to Therefore, compared with the first embodiment in which the first separation film 141 is not installed, the number of modules installed as a whole can be reduced.

As mentioned above, although the collection | recovery apparatus 11 of the abrasive | polishing agent of this invention was mentioned as the example, it can change the structure suitably in the limit which is not contrary to the meaning of this invention.

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

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 step (chemical mechanical polishing step). 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 suitably used. The average particle size of the polishing agent is appropriately selected according to the CMP process, and is, for example, 0.04 to 0.4 μm.

First, the used polishing slurry S used in the CMP step is supplied to the guard filter 12 via the pipe 15. The used polishing slurry S is stored in the pre-treatment tank 13 after coarse particles having a particle diameter 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 abrasive slurry S is not particularly limited because it depends on the customer factory. The abrasive concentration of the used polishing slurry S in the CMP step is usually 0.02 to 5% by mass.

The used polishing slurry S stored in the pre-treatment tank 13 is provided with the first separation membrane 141 via the pipe 16 by the pump P2 in a state where the on-off valve B3 is closed and the on-off valve B4 is opened. The pressure is supplied to the first membrane separation unit 14. After the coarse particles having a particle diameter of several tens of μm or more are removed in the process of passing through the guard filter 12, the used polishing slurry S is passed through the hollow fibers of the first separation membrane 141 by the cross flow method. In the process of passing through the effective filtration part, excess water is permeated and concentrated (first filtration step). At this time, the dispersion medium or the like 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. Remain on the first concentrated water side.

The first concentrated water is returned to the pre-treatment tank 13 through the reflux pipe 23. After continuing this process for a predetermined time, when the concentration of the polishing agent in the stored water in the pre-treatment tank 13 measured by the component densitometer C2 reaches a maximum of 13 mass%, more preferably 9 to 10 mass%, The on-off valve B3 is opened, the on-off valve B4 is closed, and a part of the on-off valve B4 is supplied to the post-stage 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 portion of the first separation membrane 141 is preferably 0.5 to 2 m / sec. An abrasive is applied to the filtration surface of the separation membrane 141 if the flow rate of the water to be treated (the used polishing slurry S and the first concentrated water) in the effective filtration section of the first separation membrane 141 is less than 0.5 m / sec. The particles tend to adhere and the amount of permeated water may decrease. In this case, the number of separation membranes 141 installed needs to be increased, and the manufacturing cost of the recovery apparatus 11 is increased. On the other hand, when the flow velocity of the water to be treated in the effective filtration section of the first separation membrane 141 exceeds 2.0 m / sec, the amount of liquid contacting the membrane surface becomes excessive, which may generate heat. In this case, both the separation membrane 141 and the concentrate may be damaged by heat and may be deteriorated. Moreover, in order to improve the flow velocity of the water to be treated of 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 becomes high. The flow velocity of the treated water passing through the effective filtration portion of the first separation membrane 141 is more preferably 0.55 to 1.5 m / sec.

The first concentrated water stored in the second-stage processing tank 17 is closed with the on-off valve B5 and the on-off valve B6, and the pump P3 passes the second separation membrane 181 via the pipe 21. The pressure is supplied to the provided second membrane separation unit 18. The second separation membrane 181 has an effective filtration length L2 shorter than the effective filtration length L1 of the first separation membrane 141 and 0.8 m or less, preferably 0.5 m or less, more preferably 0.3 m or less. ing. In the second separation membrane 181, the first concentrated water is passed through the hollow portion of each hollow fiber in a crossflow flow manner. In the process of passing through the effective filtration portion of the hollow fiber, the first concentrated water is permeated with excess water and concentrated (second filtration step). 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 velocity of the water to be treated (first concentrated water) passing through the effective filtration portion of the second separation membrane 181 is preferably 0.5 to 2 m / sec. When the flow velocity of the water to be treated in the effective filtration part of the second separation membrane 181 is less than 0.5 m / sec, abrasive particles are likely to adhere to the filtration surface of the separation membrane 181, and blockage of the membrane is likely to occur. . On the other hand, when the flow velocity of the treated water 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 are aggregated to form coarse particles. is there. If coarse particles are mixed in the recovered abrasive, it may cause scratches on the surface of a wafer or the like when it is recycled for use in the CMP step, which may lower the yield of the product. In addition, when such coarse particles are generated, a cake layer may be formed on the filtration surface of the separation membrane, which may increase the washing time and the amount of chemicals used. The flow velocity of the treated water passing through the effective filtration portion of the second separation membrane 181 is more preferably 0.6 to 1 m / sec.

After continuing the above-mentioned treatment process for a predetermined time, the open / close valve B5 is opened when the concentration of the polishing agent in the stored water in the post-stage treatment tank 17 measured by the component densitometer C3 becomes the target concentration. Is closed, and a portion thereof is supplied to the recovery tank 19 via the pipe 25. The concentration of stored water in the post-treatment tank 17 when supplied to the recovery tank 19 via the pipe 25 is preferably 10% by mass or more and at most 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, more preferably 0.08 MPa or less.

Since the second separation membrane 181 having an effective filtration length shorter than the first effective filtration length is used in the abrasive recovery method of the present invention, the pressure loss at 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 to a high concentration to a level that can be used as a product while suppressing the blocking of the film.

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

The permeated water obtained from the first permeated water outlet pipe 22 and the second permeated water outlet pipe 24 can be recovered and reused. For example, it is possible to use it as raw water of an ultrapure water device or the like without treatment or after treatment according to the quality of the permeate water. Moreover, it is also possible to use as another utility in a factory, for example, domestic water, cooling tower water, etc.

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples.

Example 1
Using the polishing agent recovery apparatus 1 shown in FIG. 1, the used slurry was filtered in the CMP process.

As the pump P1 in FIG. 1, a Levitro pump “LEV300” (manufactured by Iwaki Co., Ltd., trade name) is used, and as the membrane separation unit 4, a hollow fiber type UF membrane module “FB02-VC-FUST653” (Daisen Membrane Systems) Made in Japan, product name) was used. A concentration tank (made of PVC) was used as the treatment 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 of 6000, a hollow fiber inner diameter of 0.5 mm, a membrane area of 0.5 m ² and an effective filtration length of 0.26 m.

First, a used polishing slurry solution having a polishing agent concentration of about 1 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, and the on-off valve B2 was opened, and the used polishing slurry in the processing tank 3 was passed through the membrane separation unit 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. In addition, the impeller rotational speed of the pump P1 (Levitro pump) and the opening / closing degree of the on-off valve B2 in the latter stage of the membrane separation unit 4 are set so that the pressure in the hollow fiber membrane 41 near the used polishing slurry Prepared. Water treatment was performed in this state, and the abrasive concentration in the treatment tank 3 measured by the component densitometer C1 and the amount of permeated water (flux) discharged from the permeate outlet pipe were measured.

(Example 2)
A passing-through treatment of the used polishing slurry is carried out in the same manner as in Example 1 except that a hollow fiber type UF membrane module "M81S60001N" (trade name of SPECTRUM) is used as the membrane separation part 4, The abrasive concentration in the treatment tank 3 was measured in the same manner as in 1.
The hollow fiber type 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)
The used abrasive slurry is treated with water in the same manner as in Example 1 except that a hollow fiber type UF membrane module "KM1S60001N" (trade name of SPECTRUM) is used as the membrane separation unit 4, The abrasive concentration in the treatment tank 3 was measured in the same manner as in 1.
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)
A passing-through treatment of the used polishing slurry is carried out in the same manner as in Example 1 except that a hollow fiber type UF membrane module "KM1S30001N" (trade name of SPECTRUM) is used as the membrane separation unit 4, The abrasive concentration in the treatment tank 3 was measured in the same manner as in 1. 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-FUST 653” (trade name of Daisen Membrane Systems Co., Ltd.) is used as the membrane separation unit 4 The slurry was subjected to water flow treatment, and in the same manner as in Example 1, the abrasive concentration in the treatment tank 3 was measured. The hollow fiber type 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, the relationship between the abrasive concentration in the processing tank 3 measured by the component densitometer C1 and the amount of permeated water (flux) discharged from the permeated water discharge pipe 7 is shown in FIG.
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. In addition, in Table 1, the hollow fiber inner diameter, the membrane area, the effective filtration length, and the material of each of the hollow fiber separation membranes 41 of Examples 1 to 3 and Comparative Examples 1 to 2 are treated water abrasives at the water passing start time. It shows the concentration, and the concentration of the treated water abrasive (concentable maximum concentration) when concentration processing becomes impossible.

As is apparent from Table 1, in the recovery apparatus of Examples 1 to 3 in which the effective filtration length of the separation membrane 41 is 0.8 m or less, the abrasive concentration of 20 mass% or more at a high concentration is It was found that the treated water was obtained, and that the maximum concentration that can be concentrated increased as the effective filtration length became shorter. 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 easily occurs in the high concentration region.

Further, as shown in FIG. 4, in the recovery apparatus of Comparative Example 2 using the separation membrane 41 having an effective filtration length exceeding 0.8 m as the membrane separation unit 4, the Si concentration of the water to be treated is 13 mass%. When it exceeded, the amount of permeated water (flux) decreased rapidly, and it was difficult to carry out further filtration processing. 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 part 4, even if the concentration of the water to be treated exceeds 20% by mass, No reduction occurred, and the filtration process could be stably performed even if the concentration of the treated water was high.

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 unit 4, the low-concentration spent slurry discharged from the CMP step is stabilized to the high concentration region. It was found that it could be concentrated.

In the prior art, it has been practiced to separate solid solution from waste fluid containing abrasive particles such as silica particles, in order to comply with waste water standards. However, even if an ultrafiltration membrane is used for solid-liquid separation, concentration as a solid content is limited to about several percent. The solid content is generally disposed of as industrial waste because it is difficult to reuse it as a polishing slurry in a CMP process if the concentration of the abrasive grain component is about several percent.

In the present invention, as shown in Examples 1 to 3, since the polishing agent concentration of the waste water from the CMP step 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, using the polishing agent recovery apparatus 1 used in Example 1, the pressure at the treated water inlet of the membrane separation unit 4 is made the same as in Example 1, and the pressure loss of the separation membrane is changed. 4 to 5 and comparative examples 3 to 6 were performed.

(Example 4)
With the linear velocity in the hollow fiber membrane 41 set to 0.6 m / sec and the other conditions being the same as in Example 1, the used polishing slurry was passed through the recovery device 1 and filtration processing was performed. After this process was performed for 80 minutes, the on-off valve B1 was opened, the on-off valve B2 was closed, and the concentrated water in the membrane separation unit 4 was recovered from the concentrated water outlet pipe 8 into the concentrated water recovery tank 9.

(Example 5)
The filtration process was performed in the same manner as in Example 2 except that the following points were changed, and the concentrated water in the membrane separation unit 4 was recovered. A hollow fiber type UF membrane module "SLP-1053" (trade name, manufactured by Asahi Kasei Chemicals Corp .; trade name: hollow fiber inner diameter 1.4 mm, instead of the hollow fiber type UF membrane module "FB02-VC-FUST653" as the membrane separation unit 4 , Fractional molecular weight: 10000 Membrane area: 0.12 m ² Effective filtration length 0.20 m Membrane material: polysulfone) was used.

The used abrasive slurry supplied to the processing tank 3 has an abrasive concentration of about 0.8% by mass (pH: 10.5), and the circulating flow rate of the used slurry in each pipe is 9.0 L / min. The pressure in the vicinity of the used polishing slurry inlet was 41 MPa, and the linear velocity in the hollow fiber membrane 41 was 0.69 m / sec.

(Comparative example 3)
The filtration process was performed in the same manner as in Example 2 except that the following points were changed, and the concentrated water in the membrane separation unit 4 was recovered. A hollow fiber type UF membrane module "AMK-VC-FUS0181" (trade name: manufactured by Daisen Membrane Systems Co., Ltd., hollow) in place of the hollow fiber type UF membrane module "FB02-VC-FUST 653" as the membrane separation unit 4. The inner diameter of yarn: 0.8 mm, molecular weight cut off: 10,000, 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.

(Comparative example 4)
The filtration process was performed in the same manner as in Example 2 except that the following points were changed, and the concentrated water in the membrane separation unit 4 was recovered. A hollow fiber type UF membrane module “AMK-VC-FUS03C1” (trade name: manufactured by Daisen Membrane Systems Co., Ltd., hollow, instead of the hollow fiber type UF membrane module “FB02-VC-FUST 653” as the membrane separation unit 4. Yarn inner diameter: 1.2 mm, molecular weight cut off: 30,000 Membrane area: 0.3 m ² Effective filtration length: 1 m Membrane material: PES) The linear velocity in the hollow fiber membrane 41 was 0.85 m / sec.

(Comparative example 5)
The filtration process was performed in the same manner as in Example 2 except that the following points were changed, and the concentrated water in the membrane separation unit 4 was recovered. Instead of the hollow fiber type UF membrane module “FB02-VC-FUST653” as the membrane separation unit 4, “AMK-VC-FUS03C1” (trade name: manufactured by Daisen Membrane Systems Co., Ltd .; hollow fiber inner diameter: 1.2 mm, Fractional molecular weight: 30,000 Membrane area: 0.3 m ² Effective filtration length 1 m Membrane material: PES) The linear velocity in the hollow fiber membrane 41 was 1.8 m / sec.

(Comparative example 6)
The filtration process was performed under the same conditions as in Example 2 except that the following points were changed, and the concentrated water of the membrane separation unit 4 was recovered. Instead of the hollow fiber type UF membrane module “FB02-VC-FUST653” as the membrane separation unit 4, “AMK-VC-FUST653” (trade name: manufactured by Daisen Membrane Systems Co., Ltd. hollow fiber inner diameter 0.5 mm, Fractional molecular weight: 6000 Membrane area: 1.5 m ² Effective filtration length 1 m Membrane material: PES) was used. The linear velocity in the hollow fiber membrane 41 was the same as in Example 2.

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 are shown in Table 2. In addition, the linear velocity in the hollow fiber membranes 41 of Examples 4 to 5 and Comparative Examples 3 to 6, the inner diameter of the hollow fiber, and the abrasive concentration value in the concentrate calculated from the amount of permeated water are shown in Table 2 together. Shown in.

As is apparent 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, the recovered concentrated liquid It was found that the polishing agent concentration exceeded 25% by mass, and a higher recovery rate could be obtained. In addition, in Example 5 in which the effective filtration length is shortened and the inner diameter of the hollow fiber is increased to reduce the pressure loss as compared with Example 4, the permeated water having a predetermined amount or more is increased to a relatively high concentration region. Although obtained, it could not be concentrated to 25% by mass or more. Further, the concentration of the abrasive contained in the concentrated solution after recovery is lower than the abrasive concentration (calculated value) calculated from the amount of permeated water, and the abrasive is recovered with the increase of the hollow fiber inner diameter (fiber diameter). It was observed that the rate slightly decreased. It is considered that this is because the abrasive particle component (abrasive particles) adheres to the inside of the hollow fiber to form a cake layer, and the effective inner diameter is narrowed.

On the other hand, in Comparative Examples 3 and 6 in which the effective filtration length is longer than 0.8 m and the inner diameter of the hollow fiber is in the range of 0.1 to 0.8 mm, the recovery rate of the abrasive is around 76%. The concentration of the abrasive contained in the concentrated solution after recovery was lower than the concentration (theoretical value) of the abrasive calculated from the amount of permeated water. Moreover, 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 polishing agent was further lowered. It is considered that the abrasive particle component (abrasive particles) adheres inside the hollow fiber to form a cake layer, and the effective inner diameter is narrowed.

(Comparative example 7)
Ultrafiltration membrane "MLE-7101H" (made by Kuraray Co., Ltd., trade name. Effective filtration length: 1 m, hollow fiber inner diameter: 1.2 mm, fractionated molecular weight; 13000, membrane material: polysulfone) was placed, and filtration processing was performed. The filtration process was performed by an internal pressure type cross flow method. The separation membrane was gradually blocked from the stage when the concentration of the abrasive contained in the concentrate became 14% by mass. Thereafter, the output of the pump was increased to increase the pressure against the water to be treated, and the filtration process was continued. However, the concentration process became impossible when the Si concentration of the water to be treated became 19% by mass. 6 shows the inlet of the membrane separation unit 4 at the time when the filtration process becomes impossible, and FIG. 7 shows a part of FIG. 6 in an enlarged scale, and FIG. 8 shows the membrane separation at the same time. The state of the part 4 exit is shown.

As shown in FIG. 8, in the membrane separation part at the time when concentration processing becomes difficult, a gel-like material in which an abrasive is aggregated at the latter stage (outlet of the membrane separation part 4) of the water flow direction Coarse particles were formed in one area. As a result, the hollow portion of the separation membrane 41 is blocked, making it difficult to continue the concentration process.

(Example 6)
The used slurry was filtered in the CMP process using the polishing agent recovery apparatus 11 shown in FIG.

As the pumps P2 and P3 in FIG. 3, a Levitro pump "LEV300" (manufactured by Iwaki Co., Ltd., trade name) is used. As the membrane separation unit 14, a hollow fiber type UF membrane module "AMK-VC-FUST 653" · A system made by Systems Inc., a trade name, and a second membrane separation unit 18 is a hollow fiber type UF inter-membrane joule "FB02-VC-FUST 653" (a trade name made by Daisen Membrane Systems, Inc.) Was used. Further, treatment tanks (made of PE) were used as the treatment tank 13 and the post-stage treatment tank 17, and concentration tanks (made of PVC) were used as the concentrated water recovery tank 19.

The hollow fiber type UF membrane module “AMK-VC-FUST 653” which is the first membrane separation unit 14 has a molecular weight cut-off of 6000, an inner diameter of the hollow fiber of 0.5 mm, a membrane area of 1.5 m ² , an effective filtration length; The hollow fiber type UF membrane module “FB02-VC-FUST 653” which is 1 m and is the second membrane separation unit 18 has a molecular weight cut-off of 6000, a hollow fiber inner diameter of 0.5 mm, a membrane area of 0.5 m ² , The effective filtration length was 0.26 m.

First, 200 L of a used polishing slurry solution having a polishing agent concentration of about 1 mass% (pH: 9.8) was supplied from the piping 15 to the processing tank 13 via the guard filter 12. Next, the on-off valve B3 was closed, and the on-off valve B4 was opened, so that the used polishing slurry in the processing tank 13 was passed through the first membrane separation unit 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 open / close valve B4 at the rear stage of the membrane separation unit 14 are adjusted so that the pressure in the vicinity of the used polishing slurry inlet in the hollow fiber membrane 141 Prepared.

Water treatment was performed in this state, and the amount of permeated water (flux) discharged from the permeated water outlet pipe 22 was measured until the abrasive concentration in the processing tank 3 measured by the component densitometer C2 became 9 mass%. The used polishing slurry in the processing tank 13 at this time was about 22 liters.

Next, the on-off valve B4 was closed, and the on-off valve B3 was opened to supply the used polishing slurry in the processing tank 13 to the post-stage processing tank 17 as a whole. Next, the on-off valve B5 was closed, and the on-off valve B6 was opened, and the used polishing slurry in the post-stage treatment tank 17 was passed through the second membrane separation unit 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. In addition, the impeller rotational speed of the pump P3 (Levitro pump) and the open / close valve B6 at the rear stage of the membrane separation unit 18 are adjusted so that the pressure in the vicinity of the used polishing slurry inlet in the hollow fiber membrane 181 is 0.2 MPa. Prepared.
Water treatment was carried out in this state, and the amount of permeated water (flux) discharged from the permeated water outlet pipe was measured until the abrasive concentration in the processing tank 3 measured by the component densitometer C3 became 25 mass%.

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

On the basis of 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 The recovery device 11 (second embodiment) was designed and manufactured. In the polishing agent recovery apparatus 11 of the second embodiment, the number of hollow fiber UF membrane modules used can be reduced by 87% as compared with the polishing agent recovery apparatus 1 of the first embodiment. . As a result, the effects of simplification of the piping configuration as the whole recovery apparatus, reduction of the installation area and cost reduction were obtained.

DESCRIPTION OF SYMBOLS 1, 11 ... collection | recovery apparatus of abrasives, 2, 12 ... guard filter, 3 ... treatment tank, 4 ... membrane separation part, 41 ... separation membrane, 410 ... hollow fiber, 410S ... effective inside diameter, 411 ... support layer, 412 ... Filtration surface, 5-6: piping, 7: permeated water outlet piping, 8: concentrated water outlet piping, 9: concentrated water recovery tank, 10: reflux piping, 13: pre-treatment tank, 14: first membrane separation unit, 141: first separation membrane, 15 to 16, 20 to 21: piping, 17: post treatment tank, 18: second membrane separation unit, 181: second separation membrane, 19: recovery tank, 22: first Permeate water outlet piping, 23: Reflux piping, 24: Second permeation water outlet piping, 25: Concentrated water outlet piping, 26: Reflux piping, P1 to P3: Pump, C1 to C3: Component concentration meter, B1 to B6: opening and closing valve

Claims

An apparatus for recovering an abrasive from a used polishing slurry used in a CMP process, comprising:
The polishing agent recovery apparatus has a separation membrane whose passage through which the used polishing slurry is introduced is cylindrical.
In the pores of the separation membrane, the length of the effective filtration section is 0.8 m or less,
The polishing agent recovery device is characterized in that the polishing agent concentration of the used polishing slurry is concentrated to a concentration of 10% by mass or more.
The apparatus for recovering an abrasive according to claim 1, wherein the used polishing slurry is passed through the hollow portion of the separation membrane in a cross flow manner.
The abrasive recovery apparatus according to claim 1, wherein the separation membrane is provided in an internal pressure membrane separation unit.
The abrasive recovery device according to claim 1, wherein the separation membrane is a hollow fiber membrane.
The abrasive recovery apparatus according to claim 1, wherein the inner diameter of the separation membrane is 0.1 mm or more and 0.8 mm or less.
The polishing agent recovery apparatus according to claim 1, wherein a molecular weight cut off of the separation membrane is 3,000 to 30,000.
The abrasive according to claim 1, wherein the separation membrane is made of any of polyethylene, tetrafluoroethylene, polyvinylidene fluoride, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone or polyethersulfone. Recovery device.
The abrasive recovery apparatus according to claim 1 or 4, further comprising an upstream separation membrane having an effective filtration length longer than the separation membrane and having a cylindrical passage at a front stage of the separation membrane.
The length L1 of the effective filtration part of the pre-stage separation membrane is 0.8 to 1.5 m, and the length L2 of the effective filtration part of the post-stage separation membrane provided in the latter stage of the pre-stage separation membrane is 0.2 to 0 The abrasive recovery device according to claim 8, which is .8 m.
The used polishing slurry used in the CMP step is passed through a separation membrane having a cylindrical passage and having a length of effective filter of 0.8 m or less, and the concentration of the polishing slurry of the used polishing slurry is 1. A method of recovering an abrasive, comprising concentration to a concentration of 10% by mass or more.
11. The method of 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 according to claim 10, wherein the inner diameter of the separation membrane is 0.1 mm or more and 0.8 mm or less.
The method for collecting an abrasive according to claim 10, wherein a circulating flow rate of the water to be treated in an effective filtration part of the separation membrane is 0.5 to 2 m / sec.
The method for recovering an abrasive according to claim 10, wherein the abrasive concentration of the used abrasive slurry introduced into the separation film is 0.02 to 5% by mass.
A first filtration step of passing water through the used polishing slurry used in the CMP step to concentrate the used polishing slurry in a pre-stage separation membrane having a cylindrical passage, and a length of an effective filtration portion of 0. And a second filtration step in which concentrated water from the first separation membrane is passed through a second stage separation membrane having a length of 8 m or less.
The method according to claim 10, wherein a separation membrane having an effective filtration length longer than the rear separation membrane is used as the front separation membrane.
In the first filtration step, the used polishing slurry is filtered to concentrate up to 13% by mass, and in the second filtration step, the concentrated water obtained in the first filtration step is filtered to a maximum of 26%. The method for recovering an abrasive according to claim 15, wherein the concentration is concentrated to mass%.
The method for collecting an abrasive according to claim 15, wherein the concentration of the abrasive in the used abrasive slurry introduced into the pre-stage separation film is 0.02 to 5% by mass.
The method for recovering an abrasive according to claim 10, wherein the average particle diameter of the abrasive particles contained in the used abrasive slurry is 0.01 to 1 μm.