JP5358266B2 - Method for recovering useful solid components in waste slurry - Google Patents

Description

  The present invention provides a useful solid component in a waste slurry that removes the unnecessary foreign matter and metal ion component from the waste slurry containing unnecessary foreign matter and metal ion component that are discharged when a predetermined treatment is performed using the slurry. It is related with the collection method.

  In recent years, in manufacturing processes of semiconductors and various substrates, polishing of wiring metal of each layer formed on the surface of the semiconductors and various substrates is performed using a polishing slurry containing various chemicals.

  The slurry used for polishing these wiring metals is stored in a collection tank together with a used cleaning liquid (ultra pure water) after the treatment process is completed, and then discarded.

  However, since these polishing slurries are usually expensive, it is environmentally costly to recycle (recycle) useful solid components such as abrasives in the used waste slurry. Also desirable. For this reason, when abrasives are recyclable, the waste slurry is subjected to recycling treatment such as filtration and concentration, washing, etc., and it is considered to adjust the components such as solids and additive chemicals for reuse. ing.

  By the way, in these waste slurries, metal ions cause a chemical reaction while being stored in the tank to generate insoluble substances such as hydroxides, or water-soluble organic substances are oxidized to form gel-like substances. Even if diluted with a large amount of water, there is a possibility that an abrasive or the like to which a chemical is locally attached at a high concentration is reused.

  Further, there is a possibility that fine fragments of a metal layer formed on the surface of a semiconductor or the like are mixed in the collected abrasive.

  In addition, the waste slurry containing such unnecessary foreign matter causes clogging of the filter even when it is regenerated, or these foreign matters are mixed in the regenerated slurry, thereby reducing the quality of the regenerated slurry. There was a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for recovering useful solid components in waste slurry without the above-mentioned problems.

  One form of the method for recovering useful solid components in the waste slurry of the present invention includes unnecessary foreign matter that is used and discharged in a predetermined treatment step, and removes the unnecessary foreign matter from the waste slurry diluted with washing water. Then, in the method of recovering useful solid components in the waste slurry, a concentration step for concentrating the waste slurry, and a chemical solution for dissolving the foreign matter is added to the concentrated waste slurry to dissolve and dissolve the foreign matter. An operation of repeatedly filtering the foreign substance component and a part of the chemical solution and discharging it out of the system is repeated, and the step of removing the foreign substance, and the waste slurry from which the foreign substance has been removed in the concentration process, are converted into an ion exchange device and / or And an ionic component removal step of removing an ionic component in the waste slurry by passing the solution through a chelating device.

  In another embodiment of the method for recovering useful solid components in the waste slurry of the present invention, the unnecessary solid component is contained in the waste slurry that is used in a predetermined treatment step and is discharged and diluted with washing water. In the method of removing foreign matter and recovering useful solid components in the waste slurry, a concentration step for concentrating the waste slurry, and a chemical solution for dissolving the foreign matter in the waste slurry concentrated in the concentration step are continuously added. The foreign matter removing step for removing the foreign matter by continuously performing an operation of filtering and discharging a part of the dissolved foreign matter component and the chemical solution out of the system while dissolving the foreign matter, and the foreign matter removing step And an ionic component removal step of removing the ionic component in the waste slurry by passing the waste slurry from which foreign matter has been removed through an ion exchange device and / or a chelating device.

  In general, waste slurry collected through a predetermined treatment process is collected in the same tank together with a large amount of cleaning liquid (ultra pure water), so it is intended to be collected about 100 to 500 times the original slurry. If it is, it is diluted about 5 to 50 times.

  Therefore, in the concentration step of the present invention, the waste slurry is concentrated to around the specific gravity value (1.03) of the original slurry by a ceramic filter or the like.

  The waste slurry contains useful solid components.

  At this time, the discharged permeated water is reused as washing water or the like by appropriately removing dissolved components (for example, decomposition treatment of hydrogen peroxide by ultraviolet irradiation).

  In the foreign matter removing step in the present invention, unnecessary foreign matter is dissolved by one or more chemical solutions selected from acids, alkalis, oxidizing agents, reducing agents, solvents and surfactants (including ionization, the same applies hereinafter). Is done.

  All of these chemical solutions do not dissolve useful solid components (for example, inorganic particles such as abrasives) for recovery purposes in the slurry, but take into consideration chemicals and concentrations that selectively dissolve unwanted foreign substances. Select used. A chemical that reacts with the solid component to be collected or produces a reaction product insoluble with the foreign matter to be removed is not preferred. As long as these chemicals do not react with each other, a plurality of types may be used at the same time, and even chemicals that react with each other can be used with a cleaning process using ultrapure water.

  Among the chemicals used in the foreign matter removing step of the present invention, the acid includes inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as acetic acid, and the alkali includes inorganic alkalis such as caustic soda and caustic potash, An organic alkali such as tetramethylammonium hydroxide (TMAH) can be used.

  Moreover, hydrogen peroxide or ozone water can be used as the oxidizing agent, and hydrogen water can be used as the reducing agent, for example.

  As the solvent, a water-soluble organic solvent such as methanol, ethanol, and acetone can be used, and as the surfactant, for example, sodium dodecylbenzenesulfonate (DBS) is suitable. Anionic, cationic and nonionic surfactants can be used.

  The chemical solution used in the foreign matter removing step of the present invention is obtained by dissolving an acid, an alkali, an oxidizing agent, a reducing agent, a solvent and a surfactant in ultrapure water or high purity water equivalent to ultrapure water. A liquid organic solvent or the like can be used as it is without dissolving in high-purity water.

  The “chemical solutions” effective for dissolving various foreign substances are as follows.

Tungsten: Hydrochloric acid ... The amount that makes the system almost pH 2 and hydrogen peroxide ... 500ppm
Combination (or hydrogen peroxide only 500-1000ppm)
Titanium: Hydrochloric acid ... with an amount to make the system less than pH 2
Hydrogen peroxide ... 2% combination (or hydrogen peroxide only 2-3%)
Copper: Hydrochloric acid or sulfuric acid: Amount to make the system less than pH 3 Urethane: Concentrated nitric acid or concentrated sulfuric acid
Particulate DBS
These chemical solutions are used at a normal temperature or heated to a temperature of 90 ° C. or lower and a boiling point or lower in the foreign substance removing step.

  Thereafter, the chemical solution in which unnecessary foreign matters are dissolved is filtered by membrane filtration and discharged out of the system. The permeated water discharged out of the system is reused as washing water or the like by appropriately removing dissolved components by an ion exchange device or the like.

  The operation of adding a chemical solution and the operation of membrane filtration are repeated a plurality of times, preferably 5 times or more, with a sufficient time for dissolving unnecessary foreign substances therebetween.

  In this case, you may make it change the kind of chemical | medical solution for every membrane filtration.

  In addition, while adding the chemical solution continuously and injecting the chemical solution from the upper part of the processing container containing the waste slurry, the extraneous foreign matter is precipitated toward the bottom of the chemical solution in the operation of membrane filtration. It is also possible to take a method of extracting a chemical solution in which foreign matters are continuously dissolved from the bottom through a filtration membrane.

  As a membrane used for membrane filtration, a filtration membrane such as a reverse osmosis membrane, a hollow fiber type, or a ceramic membrane can be used.

  In the foreign matter removing step, the chemical solution (amount containing diluted ultrapure water, etc.) is added in an amount of about 2 to 7 times the amount of the waste slurry concentrated in the concentration step, and about 0.7 to 1.0 times. The membrane is filtered so that the volume of This chemical addition and membrane filtration are performed a plurality of times, usually 5 times or more.

  The waste slurry after the foreign substance removal step is added again with chemicals or rinsed with ultra-pure water as necessary, and passed through an ion exchange device or a chelating device to leave remaining metal ions or other ions. Ingredients are removed.

  The ion exchange apparatus used in the present invention can be used without particular limitation as long as it has been conventionally used in the production of pure water or ultrapure water, for example, a strong acid cation exchange resin, a weak acid It is possible to use a cation exchange resin, a strong base anion exchange resin, a weak base anion exchange resin, or a combination thereof.

  Examples of chelating agents used in the chelating apparatus include masking agents such as ethylenediaminetetraacetic acid (EDTA), diethylenetriamine (DTPA), glucamine, and disodium dibenzene-1,3benzenedisulfonate-hydrate (Tyrone). is there.

  The ion component is also removed in the concentration step and the foreign matter removal step, but in order to reliably remove metal ions such as K, Fe, W, and Ti to less than 1 ppm, go to the ion exchange device and / or chelation device. Is necessary.

  Useful solid components recovered in this way, such as silica, alumina, zirconia, ceria and other abrasive grains, are added with a particle size or component, for example, a substance that improves polishing performance such as ferric nitrate or hydrogen peroxide. Then, the pH can be adjusted and supplied again to the CMP (Chemical Mechanical Polishing) apparatus.

  According to the present invention, the concentrated waste slurry is added with a chemical solution that dissolves foreign matter to dissolve the foreign matter, and a part of the chemical solution is subjected to membrane filtration repeatedly, or the foreign matter is dissolved in the concentrated waste slurry. By continuously adding the chemical solution to be dissolved and dissolving the foreign matter, continuously filtering the dissolved foreign matter component and a part of the chemical solution, and further passing through the ion exchange device and / or chelation device The metal ions contained in the waste slurry can be reduced to less than 1 ppm, and solid foreign matters can be dissolved and removed.

  In particular, in the present invention, since a concentration step for discharging a large amount of liquid components such as washing water is provided before the foreign matter removal step, a considerable part of the foreign matter attached to the useful solid components at this stage is outside the system. Further, since the volume of the waste slurry to be treated is reduced, there is an advantage that the amount of the chemical solution added in the concentration step can be reduced.

  Furthermore, in the invention of claim 1, by repeatedly adding a new chemical solution while discharging a part of the added chemical solution out of the system, the surface of the foreign matter is repeatedly brought into contact with the new chemical solution and easily dissolved, Also in the invention of claim 2, since a new chemical solution is continuously added while part of the added chemical solution is continuously discharged out of the system, the surface of the foreign matter is always in contact with the new chemical solution. There is an advantage that dissolution can be performed quickly.

  Therefore, the recovered useful solid component can be effectively used as a component of a new slurry.

It is a flowchart which shows one Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a flowchart showing an embodiment of the present invention. In particular, the present embodiment is used to remove unnecessary foreign matters in waste slurry generated in a CMP (chemical mechanical polishing) process of a semiconductor manufacturing process. This shows a case where the present invention is applied to an apparatus for regenerating (recycling) waste slurry by dissolving and removing the metal ion component.

  As shown in FIG. 1, in the method for recovering useful solid components in the waste slurry of the present invention, the waste slurry diluted about 100 to 200 times with washing water or the like is passed through a ceramic filter or the like. It is concentrated to a specific gravity of about 1.03 (S1). In this example, the abrasive particle components (for example, silica, alumina, zirconia, ceria, etc.) in the waste slurry are collected on the concentration side, the permeate is discharged out of the system, the contained chemical components are removed, and washing water, etc. As reused.

  At this time, the amount of metal impurities contained in the exhaust slurry on the concentration side is about K: 20 ppm, Fe: 30 ppm, W: 10 ppm, and Ti: 20 ppm.

  Thereafter, a chemical solution that dissolves unnecessary solid foreign matters, for example, ultrapure water, 30% hydrochloric acid, and hydrogen peroxide is added to the concentrated waste slurry (S2).

  In this state, using a ceramic filter, it concentrates until it becomes about 1.03 specific gravity (S3). The permeated water generated here is also discharged out of the system, the chemical components contained are removed, and reused as washing water or the like.

  The process of adding and concentrating the chemical to the waste slurry is repeated at least 5 times (S4).

  By this step, the amount of metal impurities contained in the concentrated-side waste slurry becomes about K: 5 ppm, Fe: 3 ppm, W: 1 ppm, and Ti 5 ppm.

  After the final concentration step, the same amount of the same chemical solution is added (S5) and passed through an ion exchange resin (cation exchange resin and anion exchange resin) apparatus (S6).

  As a result, the amount of metal impurities is less than 1 ppm for all of K, Fe, W, and Ti.

  When it is confirmed that the metal ion concentration is below the specified value, the slurry on the concentration side is subjected to particle size adjustment, pH adjustment, and component adjustment and reused as a slurry (S7).

  In addition, an ion exchange resin apparatus can be used in two stages with a chelating apparatus, or can be replaced with a chelating apparatus.

  Next, examples (experimental examples) of the present invention will be described.

  As the used waste slurry, a mixed waste slurry of an acidic slurry (tungsten polishing slurry) and an alkaline slurry (oxide film polishing slurry) was used.

This waste slurry is diluted 100 to 200 times the original slurry with a cleaning liquid (ultra pure water), has a pH of about 8, a specific gravity of 1.000 to 1.001, and the components are K, Fe, W, It contains Ti, Ca, Na, HNO ₃ , silica, and organic acid, and also contains aggregated nodules that are considered to be metal hydroxides and fine particles that are considered to be metal oxides.

  The waste slurry concentrator used in this example is composed of a prefilter, a concentration tank, a pump, and a ceramic filter.

  First, 10,000 L of this waste slurry was received in a concentration tank and concentrated by a ceramic filter to make the specific gravity around 1.03 (the specific gravity of the new slurry was 1.03) (concentration about 100 times).

  Next, ultrapure water, hydrochloric acid, and an aqueous solution of hydrogen peroxide as chemicals are added to the concentrated waste slurry (ultrapure water is the amount that the waste slurry is diluted about 2 to 3 times, hydrochloric acid has a pH of An amount in the range of 1.8 to 2.0 and an amount of hydrogen peroxide in the range of 500 ppm to 1000 ppm) were added.

  In this state, using a ceramic filter, it was concentrated to the original volume, that is, the specific gravity of 1.03.

  This chemical addition and concentration operation was repeated five times.

  Thereafter, an ultraviolet irradiation device (an apparatus having a mercury lamp and a reaction tank capable of irradiating ultraviolet rays of 185 nm and 254 nm) for the purpose of sterilization, decomposition of organic impurities and decomposition of hydrogen peroxide on the concentrated slurry. In order to remove chlorine ions, the solution was passed through an anion exchange resin apparatus.

  Thereafter, the agglomerated slurry was dispersed, and KOH was added to the slurry to adjust the pH to 11 in order to remove metal impurities present on the abrasive grain surface or near the abrasive grain surface.

  Next, in order to remove the ionic silica together with the dissolved metal impurities, this slurry was passed through the anion exchange resin apparatus at SV2 to 6 / h. Thereafter, HCl is added in an amount such that the pH after treatment of the cation exchange resin in the subsequent step becomes 1.8 to 2.0, and K is removed by passing the solution through the cation exchange resin at SV2 to 6 / h. did.

  Further, hydrogen peroxide was added to the slurry so as to be 500 to 1000 ppm, and the remaining metal impurities were dissolved and ionized, and passed through the cation exchange resin at SV 2 to 6 / h.

Thereafter, UV irradiation is performed by the above-described ultraviolet irradiation apparatus until H ₂ O ₂ is decomposed, and sterilization, decomposition of organic impurities and decomposition of hydrogen peroxide are performed, and in order to further remove chlorine ions, SV2-6 / The solution was passed through the anion exchange resin with h.

  Ferric nitrate, organic acid, and nitric acid were added to the treated slurry to adjust the pH to 2.0 to 2.3. Thereafter, the particle size was adjusted with a filter capable of removing foreign matters of 0.5 μm or more.

  Polishing properties of the recycled slurry were examined from the removal rate of tungsten, in-plane uniformity, and the number of micro scratches with a CMP apparatus using an 8-inch wafer on which tungsten was deposited. The tungsten removal rate was 300 nm / min, uniform. The microscratch of the same level as that of the new solution was obtained with the same level of characteristics as 7%.

Claims (8)

In a method for recovering useful solid components in the waste slurry by removing the unnecessary foreign matter from waste slurry diluted with washing water, including unnecessary foreign matter used and discharged in a predetermined treatment step,
A concentration step of concentrating the waste slurry;
Adding a chemical solution that dissolves the foreign matter to the concentrated waste slurry to dissolve the foreign matter, filtering the dissolved foreign matter component and a part of the chemical solution, and discharging it out of the system are repeated to remove the foreign matter. A foreign matter removing step to be removed;
An ionic component removal step of removing the ionic component in the waste slurry by passing the waste slurry from which the foreign matter has been removed in the foreign matter removal step through an ion exchange device and / or a chelating device. A method for recovering useful solid components in waste slurry. In a method for recovering useful solid components in the waste slurry by removing the unnecessary foreign matter from waste slurry diluted with washing water, including unnecessary foreign matter used and discharged in a predetermined treatment step,
A concentration step of concentrating the waste slurry;
An operation of continuously adding a chemical solution that dissolves the foreign matter to the waste slurry concentrated in the concentration step to dissolve the foreign matter, and filtering and discharging a part of the dissolved foreign matter component and the chemical solution to the outside of the system Continuously removing the foreign matter, and removing the foreign matter,
An ionic component removal step of removing the ionic component in the waste slurry by passing the waste slurry from which the foreign matter has been removed in the foreign matter removal step through an ion exchange device and / or a chelating device. A method for recovering useful solid components in waste slurry. In the foreign matter removing step, the filtration is membrane filtration, and the amount of the chemical solution added to the concentrated waste slurry is 2 to 7 times the amount of the waste slurry concentrated in the concentration step. The method for recovering useful solid components in the waste slurry according to claim 1 or 2.   The dissolution of the foreign matter is performed using one or more chemical solutions selected from acids, alkalis, oxidizing agents, reducing agents, solvents and surfactants. A method for recovering useful solid components in the waste slurry according to claim 1.   The said chemical | medical solution is what dissolved the active ingredient of each chemical | medical solution in the water which melt | dissolved oxidizing or reducing gas, The usefulness in the waste slurry of any one of Claim 1 thru | or 4 characterized by the above-mentioned. A method for recovering solid components.   The method for recovering useful solid components in waste slurry according to any one of claims 1 to 5, wherein the waste slurry is heated. The method for recovering useful solid components in waste slurry according to any one of claims 1 to 6, wherein the foreign substances are dissolved by adding different chemical solutions for each chemical addition operation including a filtration operation.   The method for recovering useful solid components in waste slurry according to any one of claims 1 to 7, wherein the chemical solution or ultrapure water is added to the waste slurry before the ion component removing step. .

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