JP2009255203A - The reclaiming method of polishing slurry - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reclaiming method of polishing slurry, performing a stable polishing, compared with an unused one in its polishing performance, when reusing used polishing slurry. <P>SOLUTION: The reclaiming method reclaims the polishing slurry by removing impurities from the used polishing slurry and adding a correction liquid, a catalyst, and organic acid, nitric acid and a disinfectant are added as the correction liquid to control zeta potential of abrasive particles in the polishing slurry. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for regenerating a polishing slurry (hereinafter abbreviated as polishing slurry) used in a polishing step, and in particular, a predetermined correction liquid is added to used polishing slurry recovered in a semiconductor manufacturing process. The present invention relates to a method for regenerating a slurry.

  The semiconductor manufacturing process includes a process for making basic materials and manufacturing apparatus members such as glass for wafers, liquid crystals and masks, and a device manufacturing process for processing these materials to form elements and patterns.

  In recent years, with the increase in the speed of computers, semiconductor integrated circuits (ICs) used in computers have been required to have a higher degree of integration. In order to adapt to such high integration of ICs, it is indispensable to adopt a multilayer laminated structure together with miniaturization of wiring patterns.

  In order to employ a multilayer stack structure, the unevenness of each layer of the wafer itself and the multilayer stack structure as a base material is made smaller than before, and the coverage (step coverage) at the step portion during film formation is deteriorated and lithography is performed. It is necessary to avoid problems such as fluctuations in the coating thickness of the photoresist in the process.

  In order to eliminate unevenness of each layer of such a multilayer laminated structure, polishing is performed on a wafer as a base material and the surface of each layer formed on the wafer using a polishing slurry.

  In addition, when forming contact holes or via holes by CVD (chemical vapor deposition) using tungsten W, or when embedding copper Cu in the damascene structure by plating, a tungsten film or copper film formed on the surface is used. The tungsten film or copper film formed on the surface leaving only the hole part and the damascene structure part is polished until it is flush with the surrounding insulating film. In this case as well, polishing using a polishing slurry is performed. .

  In general, a polishing step in a semiconductor manufacturing process is performed by bringing the surface of a wafer attached to a spindle into contact with a polishing pad on the surface of a rotary table and rotating the rotary table while supplying polishing slurry to the contact portion.

  The polishing slurry used in the polishing process in the semiconductor manufacturing process disperses abrasives such as fumed silica in ultrapure water, and depending on the purpose, components such as oxidizing agents such as hydrogen peroxide, iron salts, organic acids, etc. A special composition in which is dissolved is used.

  The wafer after the polishing process is cleaned with ultrapure water, and the used polishing slurry is stored in a recovery tank together with the cleaning liquid.

The used polishing slurry collected in the collection tank is adjusted in concentration by removing excess water with a ceramic filter, the ionic components are removed by ion exchange resin, etc., and the components lacking relative to the original composition are replenished Further, excessive particles such as removed polishing waste are removed through a particle size adjusting filter and reused as a polishing slurry (see, for example, Patent Document 1).
JP-A-11-010540

  In the conventional polishing slurry regenerating method described above, the polishing slurry after being used for polishing is recovered in a storage tank and subjected to a regeneration process, and the polishing slurry remaining on the polishing pad is washed with washing water. It is removed and stored in a waste tank and then discarded.

  However, depending on the pH condition of the polishing slurry to be regenerated, scratches such as scratches may occur on the surface of the polishing object such as a wafer when the polishing slurry is reused and the yield decreases. There was a problem to do.

  In view of the above-mentioned problems, the present invention provides polishing that can perform stable polishing without remarkably comparing the polishing performance with that of an unused one when recycling a used polishing slurry. It is an object of the present invention to provide a method for regenerating a slurry for use.

  As a result of intensive studies to eliminate such problems, the present inventors use a material containing a predetermined component when adding a correction liquid for re-preparation to a used polishing slurry. Thus, the present inventors have found that the zeta potential of the abrasive grains can be controlled, whereby the slurry can be regenerated as a polishing slurry that is excellent in polishing performance and can perform stable polishing.

  That is, the polishing slurry regeneration method of the present invention is a polishing slurry regeneration method in which impurities are removed from a used polishing slurry and regenerated by adding a correction solution. An acid, nitric acid and a bactericidal agent are added to control the zeta potential of the abrasive grains in the polishing slurry.

  In the present invention, the polishing slurry to be regenerated is, for example, as disclosed in JP-A-10-265766 and JP-A-11-116948, and specifically, 0.02 μm or more. Particle size distribution (median diameter) Volume-based fumed silica fine particles and components such as oxidizers such as hydrogen peroxide, ferric nitrate, and organic acids are dispersed or dissolved in water. .

An example of the composition of the unused polishing slurry is shown below.
Specific gravity 1.03
pH 2.0-2.3
Average particle size [μm] <0.2
Fe concentration [ppm] <75
Ti concentration [ppm] <1
B concentration [ppm] <1
Na concentration [ppm] <1
Mg concentration [ppm] <1
Al concentration [ppm] <2
K concentration [ppm] <2.5
Ca concentration [ppm] <2
Mn concentration [ppm] <1
Cr concentration [ppm] <2
Mn concentration [ppm] <1
Ni concentration [ppm] <2
Cu concentration [ppm] <1
Zn concentration [ppm] <1
Pb concentration [ppm] <1
Co concentration [ppm] <1
Zr concentration [ppm] <1
Cl concentration [ppm] <10

  The polishing slurry having the above composition contains a specific metal ion depending on the composition of the object to be polished by being used in the semiconductor polishing step. As it is, it is stored in a storage tank that receives waste liquid. When the polishing process is completed, the cleaning slurry and polishing debris remaining on the polishing pad are cleaned with a cleaning liquid made of ultrapure water by the cleaning process, which is also stored in the storage tank and sent to the regeneration process. There is also a case.

  Hereinafter, the method for regenerating the polishing slurry according to the present invention will be described. This is because the used polishing slurry stored in the storage tank and recovered as described above is filtered, chelated, reacted, etc. It is achieved by performing any one of the selected treatments or a combination thereof to remove impurities, adding a correction liquid containing a predetermined chemical solution, and adjusting the pH if necessary. Is.

  When the polishing slurry collected here is used in a polishing process for polishing a semiconductor, specific metal ions are contained depending on the composition of the object to be polished, and the ion concentration becomes high. Therefore, first, in order to remove these metal ions and to remove polishing debris, they are brought into contact with an impurity removing means such as a filtration membrane device, an ion exchange device, and a chelate formation treatment device.

  The filtration membrane device used for the regeneration of the present invention can be used without particular limitation as long as it has been conventionally used for the production of pure water or ultrapure water, and is larger than the pore size of the filtration membrane such as polishing scraps. The prefilter is used for removing particulate impurities having a predetermined particle diameter, for example, about 0.5 to 10 μm, and is first brought into contact with the recovered used polishing slurry. Examples of the filtration membrane device include a device provided with an ultrafiltration membrane or a microfiltration membrane.

  In addition, the ion exchange apparatus used for the regeneration of the present invention can be used without particular limitation as long as it has been conventionally used for the production of pure water or ultrapure water. Examples include an exchange resin, a weakly acidic cation exchange resin, a strongly basic anion exchange resin, and a weakly basic anion exchange resin. It is also possible to combine a cation exchange resin and an anion exchange resin.

  Further, the chelate forming treatment apparatus used for the regeneration of the present invention comprises a base material on which a functional group having a metal chelate forming ability is immobilized, and a chelate forming treatment using a conventionally known chelate resin or chelate fiber. An apparatus can be used.

  Examples of the functional group having the ability to form a metal chelate immobilized on a substrate in the present invention include groups containing aminocarboxylic acids (including aminopolycarboxylic acids), amines, hydroxylamines, phosphoric acids, and thio compounds. Is preferred. Here, among aminocarboxylic acids, aminomonocarboxylic acids include iminoacetic acid and aminoacetic acid, and aminopolycarboxylic acids include nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraaminehexaacetic acid, glutamic acid diacid. Examples include acetic acid, ethylenediamine disuccinic acid, and iminodiacetic acid. Examples of amines include ethylenediamine, diethylenetriamine, triethylenetetramine, polyethylene polyamine, polyethyleneimine, polyallylamine, pyrrole, polyvinylamine, and Schiff base. Examples of hydroxylamines include oxime, amidooxime, oxine (8-oxyquinoline), glucamine, dihydroxyethylamine, and hydroxamic acid. Examples of phosphoric acids include aminophosphoric acid and phosphoric acid. Examples of thio compounds include thiol, thiocarboxylic acid, dithiocarbamic acid, and thiourea.

  The type of polymer used as a base material for the ion exchange apparatus and chelate formation treatment apparatus used in the present invention is not particularly limited, and is a resin or fiber, and a functional group having an ion exchange group or metal chelate forming ability is introduced. Possible materials can be used singly or as a mixture, and examples thereof include cellulose, polyvinyl alcohol, polyethyleneimine, polyester, polyvinyl chloride, polyacrylonitrile, polyamide, and polyolefin.

  As the material used for the substrate, it is preferable to use a fiber from the viewpoint of excellent contact efficiency with the slurry, and the long fiber monofilament, multifilament, short fiber spun yarn or these are woven or knitted into a woven or knitted shape. Examples of such fabrics and non-woven fabrics are also possible, and fibers or woven / knitted fabrics in which two or more kinds of fibers are combined or blended can also be used. Considering the contact efficiency with metal ions and the capturing speed as described above, the fiber used, particularly the single fiber diameter as a long fiber is preferably 1 to 500 μm, more preferably 5 to 200 μm, and the length is 10 mm. Longer ones are suitable.

  The long fiber type material has a feature that it can be easily processed into a sheet shape or a felt shape, while the short fiber type has a feature that the contact efficiency with the polishing slurry is higher than that of the long fiber type. When these characteristics are taken into consideration, the short fiber type is preferably used for the purpose of removing ultra-low concentration metal ions in the polishing slurry as in the polishing process of wafer production. Further, in the polishing process of wafer manufacturing such as the CMP process of device manufacturing, it is not necessary to remove metal ions to a very low concentration (the metal ion concentration in the polishing slurry is generally 100 times or more). The long fiber type, which is easy to process so as to be easy to handle, is preferable for the requirement that the load of metal ions on the forming fiber is large and the exchange frequency is relatively high.

  In any case, substantially all of the ion exchange groups or chelate-forming functional groups introduced on the surface of the thin fiber molecule effectively act on the capture of metal ions, which is superior to the case of using a resin. Demonstrate the ability to capture metal ions.

  Moreover, it is also possible to use what made at least one part of an acid type functional group alkali metal salt or ammonium salt according to pH of the slurry for grinding | polishing to process.

  As described above, there are a plurality of types of impurity removal means used in the present invention, and these may be used alone or in combination. In particular, in order to enhance the effect of removing impurities, it is preferable to use a combination of a filtration membrane device that removes particulate impurities, an ion exchange device that removes ion components, and / or a chelate formation treatment device.

  As a specific form applied to the purification of the polishing slurry, there can be mentioned a module in which the above-described polishing slurry purification resin or fiber is fixedly filled in a container. In this case, the polishing slurry refining resin or fiber is formed into a sheet or felt shape, placed in the flow path of the semiconductor polishing slurry, and the polishing slurry is passed through the sheet or felt shaped material. You may make it make it.

  In addition, as another form, for example, a resin or fiber is filled so as to be flowable into a container having an inlet and an outlet of an abrasive slurry, and is prevented from flowing out of the container with a filter or a strainer. Can be mentioned.

  In either method, while removing the metal ions present in the polishing slurry to be processed, all of the processed polishing slurry is supplied to the semiconductor polishing step, or at least a part or all of the polishing slurry is originally processed. It can be re-introduced into the slurry and circulated to further increase the metal ion removal level and then supplied to the semiconductor polishing step.

  In this way, the used polishing slurry that has been subjected to concentration adjustment and removal of ionic components lacks added components due to consumption in the polishing process or removal of ionic components, so composition adjustment It is necessary to do. Although the addition of such a deficient component can be added individually, it is not preferable to arrange a large number of pipes and nozzles for replenishing additives in the regeneration process in order to make the apparatus compact.

  Therefore, after the used polishing slurry is subjected to ion exchange or chelate formation treatment, correction is performed in advance so that the used polishing slurry has the same composition as the unused polishing slurry. It is preferable to perform correction by adding a predetermined amount of liquid.

  In determining the composition of the correction liquid, it is necessary to know the composition of the used polishing slurry after the ion exchange or chelate formation treatment. This composition should be measured continuously or intermittently with a sensor or the like. You can also.

  At this time, the correction liquid contains chemical components such as a catalyst, an organic acid, and nitric acid as components having the same composition as the unused polishing slurry. In the present invention, in addition to them Further, a bactericidal agent is added to control the zeta potential of the abrasive grains in the slurry.

  Here, the catalyst makes it possible to transfer electrons from the metal that is oxidized in the polishing process to the oxidant (or similarly to transfer an electrochemical current from the oxidant to the metal). The selected catalyst or catalysts may be metal, non-metal, or a mixture thereof, which must be able to move electrons between the oxidant and the metal substrate surface efficiently and quickly. Don't be. Preferably, the catalyst is a metal having a multi-oxidation state, such as Ag, Co, Cr, Cu, Fe, Mo, Mn, Nb, Ni, Os, Pd, Ru, Sn, Ti and V (but not limited thereto). Not selected). As used herein, the term “polyoxidation state” refers to atoms and / or compounds having a valence that can be increased as a result of losing one or more negative charges in the form of electrons. The most preferred metal catalysts are Ag, Cu and Fe compounds and mixtures thereof. Particularly preferred are iron catalysts such as iron inorganic salts, iron halides, and organic iron (II or III) compounds. Examples of iron inorganic salts include iron nitrate (II or III), iron sulfate ( II or III) and the like, and examples of the iron halide include iron fluoride, chloride, bromide, iodide, perchlorate, perbromate, periodate, etc. Examples of II or III) compounds include acetates, acetylacetonates, citrates, gluconates, oxalates, phthalates, succinates, etc., and a mixture in which a plurality of these catalysts are mixed. It may be.

  The organic acid is a stabilizer that suppresses the reaction of the catalyst with an oxidizing agent added before polishing of the polishing slurry. For example, malonic acid, adipic acid, citric acid, orthophthalic acid, EDTA, etc. A preferable organic acid is malonic acid.

  Moreover, nitric acid is used to adjust the pH of the polishing slurry to be regenerated. At this time, what has been conventionally adjusted to about pH 2.0 to 2.3 is the upper limit of pH in the present invention. Therefore, it is possible to prevent the occurrence of defects on tungsten CMP polishing.

  And as a bactericidal agent that can control the zeta potential of abrasive grains in the slurry, (definition) use of isothiazone or isothiazolone that can suppress the growth of viable bacteria and has excellent bactericidal and sterilizing effects. Specifically, SE100 (manufactured by Nomura Micro Science Co., Ltd., RO, EDI scale prevention bactericide) and the like can be mentioned.

  At this time, the chemical component in the correction liquid to be added is the polishing slurry regenerated by adding the correction liquid, the iron concentration of iron nitrate is 50 to 2000 ppm, the organic acid is 300 to 1000 ppm, and the germicide is 1-1000 ppm. It is preferable to add in a concentration range. At this time, it is preferable to add nitric acid in such an amount that the pH of the regenerated slurry can be adjusted to 2.0 to 2.3.

  Then, by adding this bactericidal agent, the potential value is controlled to be positive so that the zeta potential of the abrasive grains in the slurry becomes larger than 0 mV, and the range of +0.1 mV to +1.0 mV can be set. Preferably, it is +0.1 mV to +0.5 mV.

  In this way, the reason why it is preferable to make the zeta potential of the abrasive grains in the slurry positive is because the surface potential of the wafer to be polished is positive, and if the zeta potential is negative. This is because the abrasive grains and the wafer attract each other and stay on the wafer surface, and cause a scratch due to scratches or the like on the wafer surface in the polishing process.

  On the other hand, if the zeta potential of the abrasive grains in the slurry is made positive, they can repel each other on the surface of the wafer or the like to be polished and can be stably polished, and the yield of the product is not lowered.

  In addition, it has been conventionally known that the zeta potential can be controlled by pH. However, in pH control, extremely limited conditions such as strong acidity had to be set. However, in the present invention, it has been found that the zeta potential is controlled by the addition of a bactericidal agent, so that the restriction on pH can be more relaxed, thereby stabilizing the zeta potential at a positive value even at about pH 2.3. Can be maintained.

  In addition, when the same polishing operation is continuously performed over a long period of time in the addition of the correction liquid, the composition of the polishing slurry is previously measured in detail by an analytical technique, and based on the measurement result, A necessary amount may be adjusted in advance by determining the composition of the correction liquid having the same composition as that of the unused polishing slurry.

  According to this method, the correction liquid can be added with one pipe and one valve, so that the equipment can be simplified and reduced in size, and maintenance and control are facilitated.

  The regenerated polishing slurry which has been adjusted is reused by removing coarse abrasives and shavings through a particle size adjusting filter.

  In addition, in a semiconductor manufacturing process, particularly in a process of polishing a hard metal surface, such as a polishing process of a semiconductor having a tungsten plug, an oxidizing agent such as hydrogen peroxide is dissolved in the polishing slurry to form a tungsten surface. Polishing is performed while oxidizing.

  In order to recycle the polishing slurry used in such a polishing step, contact with a functional group having an ion exchange group or a chelate-forming ability of a chelate-forming fiber, and these functional groups are oxidized to remove metal ions. May deteriorate.

  In order to prevent this, the used polishing slurry is brought into contact with an oxidant decomposition catalyst or irradiated with ultraviolet rays, and then ion exchange or chelate formation is performed, thereby having ion exchange groups and chelate formation ability. It is preferable to remove the metal ions so that the functional group is not deteriorated by the action of the oxidizing agent.

  Further, the conductivity or pH of the polishing slurry after removing impurities by performing at least one treatment selected from filtration, chelate formation reaction and ion exchange reaction and before adjusting the components by adding a correction liquid It is also possible to confirm that the impurities have been sufficiently removed.

  Then, before polishing using the regenerated polishing slurry, an oxidant is also added as necessary. As an oxidant used at this time, the catalyst is oxidized, and an inorganic or organic Examples of the peroxide include hydrogen peroxide, ozone, active oxygen, and various radicals (such as OH radical).

  According to the method for regenerating a polishing slurry of the present invention, the zeta potential of abrasive grains in the polishing slurry can be controlled when adjusting the composition of the polishing slurry recovered efficiently by adding a correction liquid, Thus, the regenerated polishing slurry has stable polishing performance, and can be reused without reducing the yield of products in the polishing step.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a regeneration system for explaining a method for regenerating a polishing slurry according to the present invention.

  In this embodiment, the polishing slurry regeneration system 1 includes a pre-filter 3, a chelate formation treatment device 4, and a composition adjustment tank 5 obtained from the regeneration polishing slurry obtained by the recovery system 2 that performs the polishing slurry recovery method. The particle size adjusting filter 6 is installed so as to sequentially flow along the flow path.

  In this embodiment, the polishing slurry for regeneration recovered by the recovery system 2 is first sent to the prefilter 3 and particulate impurities such as polishing debris are removed in the process of passing through the prefilter 3.

  Next, this polishing slurry is sent to the chelate formation processing device 4 where metal ions and organic ions are removed, and the composition adjustment tank 5 has the same composition as that of the unused polishing slurry and the zeta potential of the abrasive grains. The amount of the correction liquid is added, and finally, the particles having excessive particle size are removed by the particle size adjusting filter 6 and supplied to the polishing apparatus again as a slurry for regenerated polishing.

  At this time, the zeta potential of the abrasive grains in the polishing slurry after the correction liquid is added may be controlled based on data obtained in advance based on the pH and the addition amount of the bactericide. After adding the correction liquid, the zeta potential in the polishing slurry may be measured and controlled by a zeta potential measuring device.

  The above is an example in which the used polishing slurry is configured to remove metal ions after removing coarse particles, but the present invention is not limited to such a configuration example. For example, an ultraviolet irradiation device 7 can be provided in front of the pre-filter 3 so that hydrogen peroxide can be decomposed by ultraviolet irradiation. The recovery system 2 → the ultraviolet irradiation device 7 → the chelate formation process as follows: It can also be configured as device 4 → prefilter 3 → composition adjustment tank 5 → particle size adjustment filter 6. Further, an ion exchange device may be used instead of the chelate formation processing device 5, or a chelate formation processing device and an ion exchange device may be used in combination.

  When the ultraviolet irradiation device 7 is provided, the oxidizing agent contained in the polishing slurry being processed is decomposed and removed, and it is possible to suppress the subsequent filtration membrane and the like from being deteriorated by the oxidizing agent. Also, at this time, if a filter having a specific aperture is provided after the ultraviolet irradiation device, tungsten colloidalized by the ultraviolet irradiation and hydrogen peroxide can be removed by the filter, and the load of the chelate formation processing device and the ion exchange device is reduced. Can also be reduced.

  Next, examples and comparative examples embodying the present invention will be described.

(Example)
The polishing slurry used in the flattening process was recovered by a recovery system, and then regenerated by the regeneration system shown in FIG. 1 as follows.

  First, while supplying the polishing slurry on the rotary table at 200 mL / min, the platen and the head started to rotate after 5 seconds, and CMP polishing of the semiconductor wafer was performed until 160 seconds passed from the supply of the polishing slurry. After all these operations were stopped, ultrapure water was then supplied onto the turntable at 1 L / min for 30 seconds to wash the turntable, and dressing was performed for 20 seconds.

  Simultaneously with this semiconductor polishing, the used polishing slurry is stored in the storage tank as a waste liquid, and the conductivity of the polishing slurry stored in the slurry storage section provided in the lower part of the storage tank is determined by the conductivity meter ES-51 ( While measuring with a Horiba Seisakusho, trade name), the pipe with a diameter of 30A was passed through the pipe to the collection / disposal tank side while passing through the gravity feed.

  The air actuated valve is set so that the conductivity measured by the conductivity meter is switched at 200 mS / m. When the air actuated valve is less than 200 mS / m, the air actuated valve on the waste tank side opens, and when it is 200 mS / m or more The air actuated valve on the recovery tank side was opened, and either one of the air actuated valves was opened so that both could not be opened at the same time.

  As a result of the above operation, the used polishing slurry having a conductivity of 200 mS / m or more is efficiently recovered in the recovery tank, and the used waste having a conductivity of less than 200 mS / m is disposed on the waste tank side. A polishing slurry was accommodated.

  The polishing slurry contained in the recovery tank was first filtered through a prefilter having a pore size of 5 μm to remove particulate impurities such as polishing debris contained in the polishing slurry. The prefilter can be used in order of 10 μm, 5 μm, 3 μm, and 1 μm.

  Next, the tungsten (hereinafter referred to as W) impurity contained in the polishing slurry drainage was removed using chelate-forming fibers. Here, as a chelate-forming fiber, a product name: CG-50 manufactured by Kirest Co., Ltd. was used. The W impurity concentration of the polishing slurry drain is about 100 to 1000 ppm. 5 kg of chelate-forming fiber CG-50 was packed in a cylindrical container having a diameter of 150 mm and a length of 850 mm. This product (metrate) was passed at a flow rate of 0.3 L / min to remove W impurities to <10 ppm. In the analysis of W concentration, after removing silica abrasive grains with a UF film, the sample is sent to inductively coupled plasma to ionize and measure the spectrum of Auger electrons emitted (ICP-AES).

  Thereafter, ferric nitrate, organic acid, and bactericidal agent (trade name: SE100, manufactured by Nomura Micro Science Co., Ltd.) were added to the metrate treatment solution. Furthermore, nitric acid was added to adjust the pH to 2.3. After adding the chemical, the particle size was adjusted using a depth filter. Circulation was performed at a flow rate of 7 L / min, and processing was performed in which 100 L polishing slurry was replaced 50 times.

  After the polishing slurry is regenerated, the liquid is sampled, and the particle size distribution is measured with a dynamic light scattering particle size distribution analyzer (manufactured by Horiba, Ltd., trade name: LB-550), and Accusizer-780 (Particle Sizing System) ), And the number of particles of 0.5, 1.0 μm or more was measured.

  The metal impurity concentration was analyzed by ICP-AES for the back solution from which the silica abrasive grains were removed with the UF film. As a result, the particle size distribution was the same as that of the new polishing slurry and the amount of metal impurities was the same. When the zeta potential of the silica abrasive grains in the regenerated polishing slurry was examined, it was +0.5 mV. The zeta potential was measured by an ultrasonic colloid oscillating current (CVI) method using a zeta potentiometer (Nomura Micro Science Co., Ltd., trade name: NMS-CMP06).

Then, when this regenerated polishing slurry was reused to polish a similar semiconductor wafer, the surface could be polished with scratches and the like greatly reduced compared to the conventional case. The results are shown in FIG.
FIG. 2 also shows the change in the number of scratches caused by changing the zeta potential. However, as the zeta potential becomes positive, the number of scratches decreases. In particular, the potential exceeds about +0.2 mV. It was found that the number of scratches suddenly decreased as the value increased.

(Comparative example)
The polishing slurry was regenerated by adding and operating the same chemical solution as in the Examples except that no bactericidal agent was added. At this time, the surface was scratched by scratches. The number of scratches was about 6 times that in the case where the zeta potential was controlled to be positive as in the example. The results are shown in FIG.

(Test example)
Each of the polishing slurries was regenerated by the operations in Examples and Comparative Examples. At this time, the zeta potential of the silica abrasive grains immediately after the regeneration was both +0.2 mV. The time course of zeta potential when each polishing slurry was stored at room temperature (25 ° C.) was examined, and the results are shown in FIG.
As a result, it was found that the polishing slurry regenerated according to the present invention to which a bactericidal agent was added can stably maintain the zeta potential on the plus side and contribute to stable polishing regardless of changes over time. .

It is a figure which shows schematic structure of the reproduction | regeneration system of the slurry for grinding | polishing of this invention. It is the figure which showed the relationship between the zeta potential of an abrasive grain and the number of scratches after polishing. 3 is a graph showing the change with time of the zeta potential of abrasive grains in the regenerated polishing slurry of Example 1 and Comparative Example 1. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Polishing slurry reproduction | regeneration system, 2 ... Recovery system, 3 ... Pre filter, 4 ... Chelate formation processing apparatus, 5 ... Composition adjustment tank, 6 ... Particle size adjustment filter

Claims (4)

In the method for regenerating the polishing slurry, which is regenerated by removing impurities from the used polishing slurry and adding a correction liquid,
A catalyst, an organic acid, nitric acid and a bactericidal agent are added as the correction liquid, and the zeta potential of the abrasive grains in the polishing slurry is controlled to be a positive potential value greater than 0 mV. Slurry regeneration method.   The method for regenerating a polishing slurry according to claim 1, wherein the catalyst is iron nitrate, the organic acid is malonic acid, and the bactericide is isothiazoline or isothiazolone.   The method for regenerating a polishing slurry according to claim 2, wherein the iron nitrate is added in a concentration range of 50 to 200 ppm in iron concentration, 300 to 1000 ppm of malonic acid, and 1 to 1000 ppm of the disinfectant.   The method for regenerating a polishing slurry according to any one of claims 1 to 3, wherein the zeta potential is +0.1 to 1.0 mV.

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