JP2021103753A - Manufacturing method and manufacturing apparatus of slurry for metal film - Google Patents

Abstract

To provide a manufacturing method and a manufacturing apparatus of slurry for a metal film having stable quality at low cost.SOLUTION: A manufacturing method of slurry for a metal film is a method for manufacturing acid metal film slurry 10 including abrasive grains by using alkaline slurry 1 as a starting material and includes a dilution step 2 for diluting the alkaline slurry 1 by pure water, a cation removal step for removing cations from diluted slurry after the dilution step 2 and an adjustment step 5 for adding various additives to the slurry obtained in the cation removal step. The cation removal step includes a dilution/concentration step 3 for repeating a step A for concentrating the slurry by allowing the slurry pass through an ultrafilter and a step B for diluting the concentrated slurry by adding pure water to the concentrated slurry and an ion exchange step 4 for reducing the concentration of cations.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method and an apparatus for manufacturing a slurry for a metal film used for manufacturing a semiconductor integrated circuit including a CMP process.

In the manufacture of semiconductor integrated circuits, in addition to the flattening of the wafer substrate surface, in recent years the flattening of the conductor metal embedded in the substrate by the damascene method and the flattening of the insulating material having a lower relative permittivity than _{SiO 2.} , Methods such as the production of high-density cells and the production of finer patterns of 100 nm or less, such as flattening of via holes for increasing the number of stacked cells, have become important. The chemical mechanical polishing method (hereinafter referred to as CMP process) is widely adopted for flattening the wafer and the members formed on the substrate, and it is becoming more important in the semiconductor manufacturing process. As the flattening of semiconductor materials becomes more important, the amount of CMP slurry used in the CMP process is increasing, and the proportion of the manufacturing cost of semiconductor integrated circuits is also increasing. Therefore, it is required to reduce the price while maintaining the quality of the CMP slurry.

As one method for reducing the price of CMP slurry, a method of regenerating used CMP slurry is known. Examples of the method for regenerating the CMP slurry include a concentration step of removing a part of the dispersion medium from the used CMP slurry containing abrasive grains, a dispersion medium and impurities, and a pH adjustment step of adjusting the pH of the concentrated slurry. A CMP slurry regeneration method including a recovery step of recovering abrasive grains having a predetermined particle size or less and a dispersion medium from a slurry whose pH has been adjusted is known (Patent Document 1). The purpose of Patent Document 1 is to efficiently recover abrasive grains (abrasives) by solid-liquid separation.

Further, as a CMP slurry regeneration method, a method is also known in which the used CMP slurry collected in the tank is circulated and concentrated while removing water through an ultrafiltration unit, and the pH of the concentrate is adjusted to regenerate the CMP slurry. (Patent Document 2). As the ultrafiltration unit, a membrane filter such as a ceramic filter is used.

JP-A-2002-331456 Special Table 2013-535848

Although the above-mentioned CMP slurry regeneration method is known, it is not easy to construct a CMP slurry regeneration system in a facility where the CMP process is actually performed, and there is a concern that the system may become large or complicated. In addition, personnel for operating the CMP slurry regeneration system, chemical injection, consumables replacement work, and the like are required, which may increase human labor in the CMP process facility.

Further, the slurry for a metal film is generally acidic, and it is difficult to ensure good dispersibility of the abrasive grains. In the CMP slurry regeneration method as described above, the quality of the CMP slurry after regeneration varies. There is a risk that it will end up.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method and an apparatus for producing a slurry for a metal film at a low price and with stable quality.

The method for producing a metal film slurry of the present invention is a method for producing a metal film slurry used in a CMP process, and the method uses an alkaline slurry having good dispersibility of abrasive grains as a starting material and an acidic metal. A method for producing a film slurry, wherein the alkaline slurry is diluted with pure water to further improve dispersibility, and the diluted slurry after the dilution step is a counter ion of hydroxide ions. A cation removing step of removing cations and an adjusting step of adding an oxidizing agent, an additive, and a pH adjusting agent to the slurry obtained in the cation removing step are provided in the cation removing step. (1) A step of passing a slurry through an ultrafiltration device having a permeable film that is impermeable to abrasive grains, and discharging and concentrating a permeate in which water-soluble ion components and chemical substances are dissolved. A and step B of adding pure water to the concentrated slurry obtained in step A to dilute it are repeated until the pH reaches a predetermined value, and (2) the slurry is passed through a cation exchange resin. It is characterized by including an ion exchange step of lowering the concentration of cations and setting the pH to a predetermined value by making the liquid liquid.

In the dilution / concentration step, the dilution / concentration step repeats the steps A and B until the pH value after the step B becomes 1 to 3 smaller than the pH value of the slurry before the dilution / concentration step. It is characterized by being.

In the dilution and concentration step, the dilution rate of the step B is 1.5 to 3.0 times. Here, the dilution ratio means a value obtained by dividing the volume of the slurry after dilution by the volume of the slurry before dilution, and the same applies hereinafter.

The concentration of cations in the slurry obtained after the ion exchange step is 10 ppm or less.

The starting material is an alkaline slurry containing alkali metal ions or ammonium ions.

The metal film to be polished using the metal film slurry is a metal film selected from Cu, W, Ta, and Al.

The abrasive grains are at least one of silica particles, ceria particles, and alumina particles.

The apparatus for producing a slurry for a metal film of the present invention is an apparatus for producing a slurry for a metal film used in the CMP process, and the apparatus uses an alkaline slurry having good dispersibility of abrasive grains as a starting material and an acidic metal. A device for producing a film slurry, which is a diluting means for diluting the alkaline slurry with pure water to further improve dispersibility, and a counter ion of hydroxide ions from the slurry diluted by the diluting means. A cation removing means for removing the cations of the above, and an adjusting means for adding an oxidizing agent, an additive, and a pH adjusting agent to the slurry from which the cations have been removed by the cation removing means are provided. The removing means is as follows: (1) A slurry is passed through an ultrafiltration device having a permeable film that is impermeable to abrasive grains, and a permeate in which water-soluble ion components and chemical substances are dissolved is discharged and concentrated. Means A and means B for diluting the concentrated slurry obtained by means A by adding pure water to a predetermined value are repeated until the pH of the slurry reaches a predetermined value, and (2) cation exchange of the slurry. It is characterized by having an ion exchange means for lowering the concentration of cations and setting the pH to a predetermined value by passing a liquid through a resin.

The method for producing a slurry for a metal film of the present invention is a method for producing an acidic metal film slurry containing abrasive grains used in a CMP process using an alkaline slurry having good abrasive grain dispersibility as a starting material, and is alkaline. In a diluting step of diluting the slurry to further improve dispersibility, a cation removing step of removing cations that are counter ions of hydroxide ions from the diluted slurry after the diluting step, and a cation removing step. The obtained slurry is provided with an adjusting step of adding an oxidizing agent or the like, and in the above-mentioned cation removing step, (1) the slurry is passed through a predetermined ultrafiltration device to make it water-soluble. A diluting and concentrating step of repeating the step A of discharging the permeate in which the components and the like are dissolved and concentrating, and the step B of diluting the concentrated slurry obtained in step A until the pH reaches a predetermined value, and (2). ) By passing the slurry through a cation exchange resin, an ion exchange step of reducing the concentration of cations and setting the pH to a predetermined value is included, so that the processing can be performed in a short time, so that the abrasive grains are dispersed. A metal film slurry can be produced by using an alkaline slurry having a good property and a constant composition as a raw material. As a result, it is possible to produce a slurry for a metal film of stable quality at a low price.

Since the dilution / concentration step is a dilution / concentration step in which steps A and B are repeated until the pH value after step B becomes 1 to 3 smaller than the pH value of the slurry before the dilution / concentration step, the alkaline slurry is used. It does not take an excessive amount of time to remove the ionic components and chemical substances inside, and the process load can be reduced. As a result, the time required for the entire production can be shortened, so that the production cost of the metal film slurry can be further reduced. Moreover, since the ion component can be efficiently reduced, the burden of ion exchange processing is also reduced.

In the dilution and concentration step, the dilution rate of step B can be set arbitrarily, but as a result of examining the relationship between the removal effect of the object to be removed and the amount of water added at the time of dilution, 1.5 to 3.0 times is appropriate. Met. With this dilution ratio, the amount of the permeated liquid discharged when the step A is carried out again can be reduced, and the burden of wastewater treatment of the permeated liquid is also reduced.

Since the concentration of cations in the slurry obtained after the ion exchange step is 10 ppm or less, there is no adverse effect during the subsequent pH adjustment.

Since the starting material is an alkaline slurry containing alkali metal ions or ammonium ions, ion exchange with the cation exchange resin proceeds rapidly, and the time required for production can be shortened.

Since the metal film to be polished using the metal film slurry is a metal film selected from Cu, W, Ta, or Al, it can be used with a general CMP slurry for polishing these metal films. It is possible to provide a low-cost metal film slurry having the same polishing rate.

Since the abrasive grains are at least one of silica particles, ceria particles, and alumina particles, it is possible to achieve both the price of the metal film slurry and the polishing performance by selecting the abrasive grains suitable for the metal film. it can.

The metal film slurry manufacturing apparatus of the present invention is an apparatus for producing an acidic metal film slurry containing abrasive grains used in the CMP process, using an alkaline slurry having good abrasive grain dispersibility as a starting material, and is alkaline. A diluting means for diluting the slurry to further improve dispersibility, a cation removing means for removing cations which are counter ions of hydroxide ions from the slurry diluted by the diluting means, and a cation removing means. The slurry is provided with an adjusting means for adding an oxidizing agent or the like to the slurry from which the cations have been removed in the above-mentioned cation removing means. Means A for discharging and concentrating a permeate in which a sexual ionic component or the like dissolves and means B for diluting the concentrated slurry obtained by means A by adding pure water until the pH of the slurry reaches a predetermined value. The price is low because it has a repeating diluting and concentrating means and (2) an ion exchange means for reducing the concentration of cations by passing the slurry through a cation exchange resin and setting the pH to a predetermined value. An alkaline slurry having a constant composition with good dispersibility of abrasive grains can be used as a raw material to produce a slurry for a metal film. As a result, it is possible to produce a slurry for a metal film of stable quality at a low price.
For good dispersibility of abrasive grains, it is effective to increase the absolute value of the zeta potential, and the zeta potential can be increased by setting the pH of the slurry to 10 to 12. The process of the present invention goes through a neutral slurry having a pH of less than 10, but the slurry obtained in the process of the present invention retains the same good abrasive grain dispersibility as the alkaline slurry which is the starting material. It has been confirmed that there is.

It is a process drawing which shows the manufacturing method of the slurry for a metal film of this invention. It is a figure which shows the outline of a manufacturing apparatus and a piping system.

The CMP slurry used in the CMP process is polished by silica fine particles (humped silica, colloidal silica, etc.) with good dispersibility and uniform particle size, ceria fine particles with high polishing speed, and stable alumina fine particles with high hardness. It is used as an agent. These CMP slurries are provided by a CMP slurry maker in which fine particles having a predetermined particle size and concentration are dispersed in water, diluted to a concentration suitable for each site (customer factory facility), and supplied to a CMP process machine. In addition to the abrasive, the CMP slurry contains pH adjusters such as potassium hydroxide, ammonia, organic acids, inorganic acids and amines, dispersants such as surfactants, hydrogen peroxide and potassium iodate. An oxidizing agent such as iron (III) nitrate is added in advance, or is added separately at the time of polishing.

An outline of one embodiment of the method for producing a slurry for a metal film of the present invention will be described with reference to FIG. As shown in FIG. 1, the method for producing a slurry for a metal film of the present invention reduces the ionic component of a commercially available alkaline slurry 1 to the extent that it can be used as a slurry for a metal film, and changes the liquid property from alkaline. It is a technology to make it acidic. Specifically, the method for producing the metal film slurry 10 of FIG. 1 includes a dilution step 2 in which the alkaline slurry 1 is diluted with pure water, and a dilution concentration step 3 in which the dilution slurry obtained in the dilution step 2 is diluted and concentrated. , An ion exchange step 4 in which the slurry obtained in the dilution concentration step 3 is passed through a cation exchange resin, and a preparation step 5 in which various additives are added to the slurry in which the concentration of the contained ion component is reduced by the ion exchange step 4. The slurry is provided with a filtration step 6 for removing foreign substances such as excessive agglomerates by filtration from the slurry obtained in the preparation step 5.

Here, since cations are removed in the two steps of the dilution concentration step 3 and the ion exchange step 4, these two steps are collectively referred to as a cation removal step. In the cation removal step, the order in which the dilution / concentration step and the ion exchange step are performed, and the number of each step are not limited to the above, and can be freely set.

The dilution step 2 is a step for efficiently removing cations in the next step of removing cations. If an attempt is made to concentrate the alkaline slurry without diluting it, the membrane filter used in step A in the dilution concentration step 3 is likely to be clogged, and it becomes difficult to remove ionic components and small molecules.

The dilution and concentration step 3 is a step A (hereinafter, also referred to as ultrafiltration) in which the diluted slurry obtained in the dilution step 2 is concentrated by a cross-flow filtration method using a membrane filter, and a slurry concentrated in the step A. It includes step B of adding pure water and diluting. After the dilution in step B, pH measurement 7 of the slurry is performed. If the pH value has not decreased to a predetermined value, step A, step B, and pH measurement 7 are repeated again. When the predetermined pH value is reached, the process proceeds to the ion exchange step 4. After the ion exchange step 4, the concentration of each ion component in the slurry is confirmed by performing ion chromatography measurement 8 in the ion-exchanged slurry. After confirming that the ion concentration is equal to or less than a predetermined value, the process proceeds to the adjustment step 5. In the adjusting step 5, an oxidizing agent, an additive, and a pH adjusting agent are added. The slurry obtained in the adjusting step 5 is subjected to pH measurement 9, and after it is confirmed that the slurry has a predetermined pH value, the slurry proceeds to the filtration step 6. In the filtration step 6, foreign substances such as excessive agglomerates are removed from the slurry, and the slurry is filled into a clean container without ion elution. By going through the above steps, the ionic component is significantly reduced as compared with the initial alkaline slurry 1, and the slurry 10 for a metal film having an acidic liquid property can be obtained.

The alkaline slurry 1 which is a raw material of the metal film slurry 10 can contain hydroxides such as alkali metals and alkaline earth metals and organic bases such as ammonia, amines and ammonium hydroxides as alkaline components. As a result of the alkaline component being dissolved in the slurry, the ions contained in the alkaline slurry 1 are preferably alkali metal ions or ammonium ions. In these cases, the removal of cations in the cation removal step proceeds rapidly.

As the alkaline component, for example, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide and the like are preferably used, and they are dissociated into sodium ion, potassium ion, tetramethylammonium ion and hydroxide ion in water. To do.

As the alkaline slurry, an alkaline slurry containing silica, metal oxide fine particles such as alumina and ceria can be used, or a CMP slurry for an insulating film containing not only particles but also various additives is used. May be good. Since some of these have cations exceeding 1000 ppm in the slurry, it is necessary to significantly reduce the ion concentration in order to use them as a raw material for the slurry for a metal film in CMP.

The ultrafiltration used in the dilution and concentration step of the present invention can generally remove an ionic component from a large amount of slurry, but the ionic component can be removed to a level that can be used as a slurry for a metal membrane. When trying to reduce it, a large amount of wastewater is generated and it takes a long time to remove the ionic component.
On the other hand, in the ion exchange step, the ion component can be removed in a short time by using a certain amount of the cation exchange resin, but since the cation exchange resin is expensive, the cost required for this process increases. I will end up.

Therefore, by using the dilution concentration step and the ion exchange step together, the concentration of the ionic component can be lowered to a level that can be used as a slurry for a metal film even if an alkaline slurry containing 1000 ppm or more of cations is used as a raw material. Can be done. Further, as compared with the case where the slurry for the metal film is produced only by the dilution and concentration step, the time required for reducing the ionic component is shortened, and the time required for the entire manufacturing process is shortened. Furthermore, since the number of dilution and concentration steps can be reduced, the amount of wastewater generated can also be reduced. In the ion exchange step, since it is not necessary to exchange the entire amount of the ion components, the amount of the required cation exchange resin can be reduced, and the influence on the cost can be suppressed. As a result, it is possible to produce a slurry for a metal film of stable quality at a low price.

As described above, either of the dilution and concentration steps and the ion exchange steps in the cation removal step may be performed first or alternately. For example, the ion exchange step may be performed after the dilution / concentration step, or conversely, the dilution / concentration step may be performed after the ion exchange step. Alternatively, the ion exchange step may be performed after the dilution / concentration step, and then the dilution / concentration step may be performed again. The order of each step in the cation removing step is as follows: the type of filter used in the diluting and concentrating step, the size of the ultrafiltration device, the type and amount of ion exchange resin used in the ion exchange step, and the ion exchange resin. Optimal conditions that can achieve both quality and process load can be set according to conditions such as the size of the ion exchange column filled with.

In particular, from the viewpoint of reducing the price required for the slurry for CMP, it is possible to reduce the amount of the ion exchange resin used and reduce the cost required for the manufacturing process by performing the ion exchange step after performing the dilution concentration step. Therefore, it is preferable.
For example, when an alkaline slurry having a potassium ion concentration of 4000 ppm is used as a starting material, the cation concentration in the slurry in the metal film slurry manufacturing process becomes 1000 ppm by being diluted 4-fold in the dilution step, and the dilution concentration step. Later, it becomes about 100 ppm, and after the ion exchange step, it can be reduced to 10 ppm or less.

In order to produce an acidic metal film slurry from an alkaline slurry having an initial cation concentration of several thousand ppm, it is necessary to finally reduce the cation concentration to several ppm level. However, if an attempt is made to reduce the cation concentration to about 1/1000 of the initial concentration only by the dilution and concentration step, the treatment takes a long time as described above, so that the productivity is low and the reduction to several ppm level is possible. It is practically difficult. The above-mentioned method for regenerating a slurry waste liquid (Patent Document 2), which describes a method for removing ions from a slurry, assumes removal of an ion component derived from a metal film generated by polishing, and has a large amount of cation concentration. No method has been disclosed for reducing the amount to a few ppm level. Therefore, in the known method, it takes a long time because the dilution and concentration step must be repeated many times, or even if it is repeated many times, there is a limit in sufficiently reducing the concentration of the ionic component.
In the present invention, the above-mentioned problems can be solved by treating the alkaline slurry in a predetermined process by using the dilution concentration step and the ion exchange step in combination.

Again, with reference to FIG. 1, in the dilution concentration step 3, the step A of concentration by a cross-flow filtration method using a membrane filter will be described. The filter used in the step A can be freely selected as long as it does not transmit abrasive grains but transmits an ionic component or a low molecular weight component. Since the particle size of the abrasive grains in the slurry is several tens of nm to several hundreds of nm, the pore size of the filter is preferably 10 nm to 100 nm. As a filter having a pore size of this degree, a so-called filter for ultrafiltration can be used. From the viewpoint of durability, it is preferable to use a ceramic filter.

In the dilution / concentration step 3, a step B of adding pure water to the slurry concentrated in the step A to dilute it will be described. The dilution ratio in this step is preferably in the range of 1.1 to 5.0 times. A dilution ratio of 1.5 to 3.0 times is more preferable, and a dilution ratio of 1.8 to 2.2 times is more preferable. If the dilution rate is small, the amount of processing per process can be small, but the effect of reducing the concentration of ionic components per process (performing steps A and B once) is low, so setup is performed according to the number of times. The number of man-hours increases, and the time required for the next process increases. Further, when the dilution ratio is large, the amount of processing is large, so that it is necessary to make the apparatus of the next step larger. When the dilution ratio is 1.5 to 3.0 times, the size of the device can be reduced and the cost required for the process can be suppressed. When each dilution is performed at the above dilution rate, the amount of pure water used for dilution does not become excessive, and in the next ion exchange step, a small amount of ion exchange resin is used, which is desired. It can be reduced to the ion concentration.

The slurry after dilution in step B is subjected to pH measurement 7, and it is confirmed whether or not it has reached a predetermined pH value. The predetermined pH value is preferably in the range of 1 to 3 smaller than the pH value of the slurry diluted in the above-mentioned step B with respect to the slurry before being concentrated in the step A. By lowering the pH of the slurry to this range by the dilution and concentration step, the time required for this step is not lengthened, and the cations can be removed with a small amount of ion exchange resin in the ion exchange step. ..

When the pH value obtained in the pH measurement 7 is within a predetermined range, the slurry that has undergone the dilution and concentration step 3 is transferred to the next ion exchange step 4, and an ion exchange treatment with a cation exchange resin is performed.
On the other hand, when the pH value obtained in the pH measurement 7 does not reach the predetermined range, the dilution concentration step 3 is repeated again in the order of step A, step B, and pH measurement 7 until the predetermined pH value is reached. .. In this case, the predetermined pH value is in the range of 1 to 3 smaller than the pH value of the slurry diluted in the above-mentioned step B with respect to the slurry before the first step A is performed in the dilution concentration step 3. It is preferably inside.
Moreover, not only pH measurement but also conductivity measurement and density measurement may be performed at the same time. This makes it possible to monitor the status of the slurry more accurately.

In the ion exchange step 4, the slurry obtained in the dilution and concentration step 3 is brought into contact with the cation exchange resin to reduce the concentration of cations in the slurry to several ppm level. Specifically, by passing the slurry through an ion exchange column filled with a cation exchange resin at a predetermined flow rate, for example, cations such as potassium ions and ammonium ions can be transferred into the cation exchange resin. By replacing with hydrogen ions, ionic components (here, other than hydrogen ions) are removed. The flow rate of the slurry at the time of passing the liquid is preferably in the range of SV2 to 15, and more preferably about SV5 to 10.

As the ion exchange column used in the ion exchange step 4, an ion exchange column filled with a mixture of an anion exchange resin and a cation exchange resin may be used. Since not only cations but also anions may be contained as an ion component in the slurry, it is preferable to use a cation exchange resin and an anion exchange resin in combination in order to remove both ion components.

The concentration of cations in the slurry obtained after the ion exchange step 4 is preferably less than 10 ppm, more preferably 3 ppm or less. Since the slurry for a metal film contains an oxidizing agent, it is generally used in an acidic state, but if the concentration of cations that serve as counter ions of hydroxide ions is 3 ppm or less, it will have an adverse effect when adjusting the pH later. It has no effect.

In the slurry that has undergone the ion exchange step 4, the concentration of each ion component is measured by ion chromatography measurement 8. As a result, the slurry confirmed to be below the predetermined ion concentration proceeds to the adjusting step 5. Chemicals such as an oxidizing agent, an additive, and a pH adjuster are added to the slurry and stirred to prepare a slurry for a metal film.

In the adjusting step 5, a pre-prepared oxidizing agent, an additive, and pure water are added to the slurry in the liquid storage tank, and then a pH adjusting agent is added and stirred to obtain a uniform slurry solution. To do. The adjustment procedure is not limited to this, and the oxidizing agent, the additive, and the pH adjusting agent may be collectively added to the slurry in the liquid storage tank for adjustment. Rather than directly adding all the chemicals to the slurry at once, it is preferable to add a premixed chemical other than the pH adjuster to the slurry and finally add the pH adjuster to adjust the pH. The batch injection of chemicals is to avoid the risk of having to dispose of the entire slurry in the event of a mistake in work such as a weighing error.

As the pH adjuster, a wide range of organic acids, inorganic acids, organic bases, inorganic bases and the like can be selected and used. As the acidic pH adjuster, an inorganic acid such as nitric acid or sulfuric acid is preferable because the pH can be adjusted even with a small amount of addition. As the alkaline pH adjuster, an organic base that does not generate metal ions is preferable. The oxidizing agent can be selected from, for example, iron (III) nitrate, potassium iodate, hydrogen peroxide, and the like. As the additive, a surfactant, an organic acid, a preservative and the like can be selected according to the purpose. The organic acid can be selected from, for example, malonic acid, malic acid, citric acid, maleic acid, oxalic acid, fumaric acid, phthalic acid, lactic acid, tartaric acid and the like. From the viewpoint of promoting polishing and detergency by coordinating to the surface of the metal film or the metal ions ionized from the metal film, malonic acid, which is a low molecular weight and polyvalent organic acid, is preferable.

The slurry prepared in the adjusting step 5 is subjected to pH measurement 9 to confirm that it is within a predetermined range. At this time, not only pH measurement but also conductivity measurement and density measurement may be performed at the same time. As a result, the state of the prepared slurry can be grasped more accurately. When the pH value of the slurry is within a predetermined range, the slurry shifts to the filtration step 6. If the value is not within the predetermined range, a pH adjuster is added to adjust the pH so that the value is within the predetermined range.

The prepared slurry is filtered by passing it through a filtration filter and filled in a container as a metal film slurry 10. As the filtration filter, select a filter having an appropriate pore size, structure, and material so as to capture only coarse agglomerated particles and foreign substances without capturing abrasive particles. As a type of filter, a depth filter made of polypropylene non-woven fabric is preferably used. Further, when the amount of filtration is large, the filters may be provided in multiple stages so that the filtration is not clogged or the filtration rate is lowered.

The metal film to be polished using the metal film slurry 10 can be widely selected as long as it is a metal film that can be used as metal wiring. From the viewpoint of electrical resistance, price, processability, etc., a metal film selected from Cu, W, Ta, or Al is preferable.

Various particles can be selected as the abrasive grains contained in the slurry for a metal film in the present invention. As the type of abrasive grains, inorganic particles are preferable, and metal oxide fine particles are particularly preferable, from the viewpoint of polishing speed. Specific examples of the metal oxide fine particles include silica (for example, colloidal silica and fumed silica), alumina, ceria, titania, zirconia, tin oxide and the like. The particle size is preferably 1 μm or less, and more preferably 100 nm or less.

When fumed silica is selected as the abrasive grains, the presence state of the fumed silica particles in the slurry is greatly affected by the liquid properties of the slurry, the ion concentration, and the like.
According to the DLVO theory (Deljaguin-Landau-Verway-Overbek theory), which is a theory related to the interaction between particles in a liquid, when the silica particle concentration is high, the electric double layer becomes thin and the charges on the particle surface repel each other. Since the particles approach each other without receiving a force, the contribution of the attractive force between the particles due to the van der Waals force becomes large, and particle agglomeration is likely to occur. Further, it is considered that even when the pH in the liquid is low (when it is acidic), the electric double layer on the surface of the silica particles becomes thin, the repulsive force between the charges on the particle surface decreases, and it becomes easy to aggregate.
Therefore, it is necessary to check the ion concentration and pH value in the slurry in a timely manner and control the process so that particle aggregation does not occur during the manufacturing process of the metal film slurry.

Next, an embodiment of a method for producing a slurry for a metal film and an embodiment of a production apparatus of the present invention will be described with reference to FIG. In FIG. 2, P01 to P03 are pumps, and V01 to V07 are valves for adjusting the flow direction and flow rate of the liquid.

The metal film slurry manufacturing apparatus 11 has a liquid storage tank 12 for storing liquid. Two or more liquid storage tanks 12 may be provided depending on the amount and type of slurry to be processed. The alkaline slurry 13 as a starting material is stored in the liquid storage tank 12 by closing all the valves V01 to V07 and operating the pump P01. After that, by opening only the valve V04, pure water is supplied from the pure water line to the liquid storage tank 12, and the slurry is diluted. The diluted slurry passes through the ultrafiltration device 14 (cross-flow filtration device using a membrane filter) by opening the valves V02 and V07 and operating the pump P02, circulates in the pipe, and stores the liquid. Return to tank 12 (step A). Water containing an ionic component is discharged from the ultrafiltration device 14 as permeated water through V07. The slurry returned to the liquid storage tank 12 is concentrated by discharging water containing an ionic component by the ultrafiltration device 14, and the amount of the ionic component is also reduced. Next, by opening only the valve V04 again, pure water is supplied from the pure water line to the liquid storage tank 12, and the concentrated slurry is diluted (step B).

For the slurry after performing the steps A and B, only the valve V02 is opened and the pump P02 is operated, so that the pH value after dilution is measured by the pH meter 15. At this time, the density can be measured by the density meter 16 and the conductivity can be measured by the conductivity meter 17. If the measured pH value is within the predetermined range, only the valve V01 is opened and the pump P02 is operated, so that the slurry is passed through the ion exchange column 18 filled with the cation exchange resin to exchange ions. Will be done. The ion exchange column 18 is composed of one or more ion exchange columns. The concentration of the ionic component in the slurry that has passed through the ion exchange column 18 and returned to the liquid storage tank 12 is measured by using ion chromatography. After confirming that the ion concentration is equal to or lower than the predetermined ion concentration, the process proceeds to the preparation of the metal film slurry.

An oxidizing agent, an additive, and a pH adjuster are added to the slurry to prepare a slurry for a metal film. Specifically, iron (III) nitrate as an oxidizing agent and malonic acid as an additive are charged into the compounding tank 19, and pure water is supplied to the compounding tank 19 by opening only the valve V06. In the compounding tank 19, a uniform solution containing iron (III) nitrate and malonic acid is compounded by stirring with a stirring blade. The prepared solution is transferred to the liquid storage tank 12 by opening only the valve V05 and operating the pump P03. In the liquid storage tank 12, the slurry from which the ionic component has been removed and the above-mentioned solution are stirred by the stirring blades. After that, nitric acid is added as a pH adjuster, and the entire liquid in the liquid storage tank is agitated to adjust the composition of the metal film slurry.

The pH value of the adjusted metal film slurry is measured by the pH meter 15 by opening only the valve V02 and operating the pump P02. At this time, the density can be measured by the density meter 16, and the conductivity can also be measured by the conductivity meter 17. After confirming that the pH value of the adjusted slurry was within a predetermined range, only the valve V03 was opened and the pump P02 was operated to allow the filtration filter 20 to pass through to obtain the metal film slurry 21.

In the metal film slurry manufacturing apparatus 11, the chemical and / or physical properties of the slurry that circulates between the liquid storage tank 12 and each facility through a pipe are always or timely while the apparatus is in operation. , Can be monitored. The properties to be monitored include, for example, not only pH, density, and conductivity, but also the concentration, refractive index, turbidity, particle concentration, viscosity, and particle size of abrasive grains of one or more selected ions. Can be monitored.
The operation of the device may be performed by the worker by operating the pump, valve, and each device on-site or remotely, or fully automated by a program based on the information obtained from various measuring devices installed in the device. It may be done by the machine.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to such examples.

[Example 1]
200 L (containing about 1000 ppm of potassium ions) of a diluted slurry liquid having a concentration of 5.3% by mass obtained by diluting an alkaline raw material slurry having a concentration of 22.5% by mass (hereinafter referred to as a raw material slurry) with pure water is diluted and concentrated, and then converted into an ion exchange resin. The liquid was passed through, and malonic acid, iron nitrate (III) and a pH adjuster were added to obtain a metal film slurry (hereinafter referred to as a polishing slurry) of Example 1.
Dilution and concentration were carried out under the conditions of 200 L at the time of concentration and 400 L at the time of dilution, and the operation was repeated 10 times until the total amount of pure water added for dilution became 10 times the amount of the diluted slurry. As the ion exchange resin, 0.6 L of a 1: 2 mixture of Mitsubishi Chemical's strong acid cation exchange resin SK110 and strong basic anion exchange resin SA10A was used to prepare a diluted slurry solution at SV10, that is, a flow rate of 6 L / hour. The liquid was passed. At this stage, potassium ions (K ⁺ ) and chloride ions (Cl ⁻ ) in the diluted slurry were measured using ion chromatography manufactured by Thermo Fisher Scientific Co., Ltd. Malonic acid and iron nitrate nineahydrate were added to the obtained diluted slurry liquid so as to be 600 ppm and iron content equivalent to 45 ppm, respectively. After filtering, the LPC (number of coarse particles) of the obtained polishing slurry was measured using an accelerator manufactured by Entegris Japan Ltd.

[Example 2]
200 L of a diluted slurry liquid (containing about 1000 ppm of potassium ions) having a concentration of 5.3% by mass obtained by diluting a raw material slurry having a concentration of 22.5% by mass with pure water is diluted and concentrated (diluted and concentrated 1), and then passed through an ion exchange resin. Further, dilution and concentration (dilution and concentration 2) were carried out, and malonic acid, iron nitrate (III) and a pH adjuster were added to obtain a polishing slurry of Example 2.
Dilution concentration 1 was carried out under the conditions of 200 L at the time of concentration and 400 L at the time of dilution, and the operation was repeated 8 times until the total amount of pure water added for dilution became 8 times the amount of the diluted slurry. As the ion exchange resin, 0.8 L of a mixture of Mitsubishi Chemical's strong acid cation exchange resin SK110 and strong basic anion exchange resin SA10A at a ratio of 1: 2 was used to prepare a diluted slurry solution at SV10, that is, a flow rate of 8 L / hour. The liquid was passed. Dilution concentration 2 was carried out under the conditions of 200 L at the time of concentration and 400 L at the time of dilution, and the operation was repeated twice until the total amount of pure water added for dilution was twice the amount of the diluted slurry. At this stage, potassium ions and chloride ions of the diluted slurry liquid were measured using ion chromatography manufactured by Thermo Fisher Scientific Co., Ltd. Malonic acid and iron nitrate nineahydrate were added to the obtained diluted slurry liquid so as to be 600 ppm and iron content equivalent to 45 ppm, respectively. After filtering, the LPC (number of coarse particles) of the obtained polishing slurry was measured using an accelerator manufactured by Entegris Japan Ltd.

[Comparative Example 1]
200 L (containing about 1000 ppm of potassium ions) of a diluted slurry solution having a concentration of 5.3% by mass obtained by diluting a raw material slurry having a concentration of 22.5% by mass with pure water is diluted and concentrated, and malonic acid, iron nitrate (III) and a pH adjuster. Was added to obtain the polishing slurry of Comparative Example 1.
Dilution and concentration were carried out under the conditions of 200 L at the time of concentration and 400 L at the time of dilution, and the operation was repeated 30 times until the total amount of pure water added for dilution became 30 times the amount of the diluted slurry. At this stage, potassium ions and chloride ions of the diluted slurry liquid were measured using ion chromatography manufactured by Thermo Fisher Scientific Co., Ltd. Malonic acid and iron nitrate nineahydrate were added to the obtained diluted slurry liquid so as to be 600 ppm and iron content equivalent to 45 ppm, respectively. After filtering, the LPC (number of coarse particles) of the obtained polishing slurry was measured using an accelerator manufactured by Entegris Japan Ltd.

[Comparative Example 2]
200 L of a diluted slurry solution having a concentration of 5.3% by mass (containing about 1000 ppm of potassium ions) obtained by diluting a raw material slurry having a concentration of 22.5% by mass with pure water is passed through an ion exchange resin, and malonic acid and iron nitrate (III) are passed. And a pH adjuster was added to obtain a polishing slurry of Comparative Example 2.
As the ion exchange resin, 8 L of a 1: 2 mixture of Mitsubishi Chemical's strong acid cation exchange resin SK110 and strong basic anion exchange resin SA10A was used, and a diluted slurry solution was passed through at an SV20, that is, a flow rate of 160 L / hour. did. At this stage, potassium ions and chloride ions of the diluted slurry liquid were measured using ion chromatography manufactured by Thermo Fisher Scientific Co., Ltd. Malonic acid and iron nitrate nineahydrate were added to the obtained diluted slurry liquid so as to be 600 ppm and iron content equivalent to 45 ppm, respectively. After filtering, the LPC (number of coarse particles) of the obtained polishing slurry was measured using an accelerator manufactured by Entegris Japan Ltd.

[Comparative Example 3]
200 L of a diluted slurry solution having a concentration of 5.3% by mass (containing about 1000 ppm of potassium ions) obtained by diluting a raw material slurry having a concentration of 22.5% by mass with pure water is passed through an ion exchange resin, and malonic acid and iron nitrate (III) are passed. And a pH adjuster was added to obtain a polishing slurry of Comparative Example 3.
As the ion exchange resin, 8 L of a mixture of Mitsubishi Chemical's strong acid cation exchange resin SK110 and strong basic anion exchange resin SA10A at a ratio of 1: 2 was used, and a diluted slurry solution was passed through at an SV5, that is, a flow rate of 40 L / hour. did. At this stage, potassium ions and chloride ions of the diluted slurry liquid were measured using ion chromatography manufactured by Thermo Fisher Scientific Co., Ltd. Malonic acid and iron nitrate nineahydrate were added to the obtained diluted slurry liquid so as to be 600 ppm and iron content equivalent to 45 ppm, respectively. After filtering, the LPC (number of coarse particles) of the obtained polishing slurry was measured using an accelerator manufactured by Entegris Japan Ltd.

Table 1 shows the ion concentration (concentration of potassium ion and chloride ion), LPC, the amount of pure water used for removing cations, and the amount of ion exchange resin of the polishing slurry obtained in the above Examples and Comparative Examples. Is shown. In addition, the quality of each slurry, the cost required for production, and the time, and the comprehensive evaluation result thereof are shown.

Quality was evaluated by inspection results of impurities (K ⁺ , Cl ^{−) and LPC.}
The quality evaluation results were evaluated according to the following criteria.
◎: Satisfied with the standard 〇: Satisfied with the standard △: Satisfied with the standard barely ×: Not satisfied with the standard

The cost was evaluated based on the amount of pure water used and the amount of ion exchange resin used.
The cost evaluation results were evaluated according to the following criteria.
〇: Satisfied with the assumption △: Satisfied with the assumption ×: Not satisfied with the assumption

The time was evaluated based on the estimated time required for the process of removing impurity ions.
The time evaluation results were evaluated according to the following criteria.
◎: Satisfied with the assumption 〇: Satisfied with the assumption △: Satisfied with the assumption ×: Not satisfied with the assumption

The overall evaluation was based on a comprehensive judgment of quality, cost, and time.
The results of the comprehensive evaluation were evaluated according to the following criteria.
〇: Satisfied as a mass production method △: Satisfied as a mass production method ×: Not satisfied as a mass production method

Example 1 is superior in time and cost to Comparative Example 1, and the effect of using the ion exchange step in combination can be confirmed as compared with the case of only the dilution and concentration step. Further, Example 1 shows that the cost is superior to those of Comparative Examples 2 and 3 and the quality is equal to or higher than that of Comparative Examples 2 and 3, and the problem of cost increase in the case of cation exchange using only the ion exchange resin can be solved. There is. Further, in Example 2, although the time is slightly inferior to that in Example 1, the quality is more excellent. Therefore, the amount of the ion exchange resin is increased by a small amount, and the dilution concentration step and the ion exchange step are repeated. It was confirmed that the quality was improved while suppressing the cost increase.

The method and apparatus for producing a metal film slurry of the present invention can produce a metal film slurry of stable quality at a low price, and thus can be used for manufacturing semiconductor integrated circuits such as high-density cells in recent years. ..

1 Alkaline slurry 2 Diluting process 3 Diluting and concentrating process 4 Ion exchange process 5 Adjustment process 6 Filtration process 7 pH measurement 8 Ion chromatography measurement 9 pH measurement 10 Metal film slurry 11 Metal film slurry manufacturing equipment 12 Liquid storage tank 13 Alkaline Slurry 14 Extrafiltration device 15 pH meter 16 Densitometer 17 Conductivity meter 18 Ion exchange column 19 Formulation tank 20 Filtration filter 21 Slurry for metal film

Claims (8)

A method for producing a slurry for a metal film used in a CMP process.
The method is a method for producing an acidic metal film slurry containing abrasive grains using an alkaline slurry as a starting material.
A dilution step of diluting the alkaline slurry with pure water, and
A cation removal step of removing cations from the diluted slurry after the dilution step, and
The slurry is provided with an adjusting step of adding an oxidizing agent, an additive, and a pH adjusting agent to the slurry obtained in the cation removing step.
In the cation removal step, (1) a permeate liquid in which water-soluble ion components and chemical substances are dissolved is passed through an ultrafiltration device having a permeable film that is impermeable to abrasive grains. The step A of discharging and concentrating, the step B of adding pure water to the concentrated slurry obtained in step A to dilute, and the diluting and concentrating step of repeating the steps until the pH reaches a predetermined value, and (2) the slurry. A method for producing a slurry for a metal film, which comprises an ion exchange step of reducing the concentration of cations and setting the pH to a predetermined value by passing a liquid through a cation exchange resin. In the dilution / concentration step, the dilution / concentration step repeats the steps A and B until the pH value after the step B becomes 1 to 3 smaller than the pH value of the slurry before the dilution / concentration step. The method for producing a slurry for a metal film according to claim 1, wherein the slurry is produced. In the dilution concentration step
The method for producing a slurry for a metal film according to claim 1 or 2, wherein the dilution ratio in the step B is 1.5 to 3.0 times. The method for producing a slurry for a metal film according to any one of claims 1 to 3, wherein the concentration of cations in the slurry obtained after the ion exchange step is 10 ppm or less. The production method according to any one of claims 1 to 4, wherein the starting material is an alkaline slurry containing an alkali metal ion or an ammonium ion. Any of claims 1 to 5, wherein the metal film polished using the metal film slurry is a metal film selected from Cu, W, Ta, and Al. The method for producing a metal film slurry according to item 1. The method for producing a slurry for a metal film according to any one of claims 1 to 6, wherein the abrasive grains are at least one of silica particles, ceria particles, and alumina particles. .. A device for producing slurry for metal membranes used in the CMP process.
The apparatus is an apparatus for producing an acidic metal film slurry containing abrasive grains using an alkaline slurry as a starting material.
A diluting means for diluting the alkaline slurry with pure water,
A cation removing means for removing cations from the slurry diluted by the diluting means,
An adjusting means for adding an oxidizing agent, an additive, and a pH adjusting agent to the slurry from which the cations have been removed by the cation removing means is provided.
The cation removing means (1) passes a slurry through an ultrafiltration device having a permeable film that is impermeable to abrasive grains, and discharges a permeate in which water-soluble ion components and chemical substances are dissolved. The means A for concentrating and the means B for adding pure water to the concentrated slurry obtained by the means A to dilute the mixture, and the diluting and concentrating means for repeating the process until the pH of the slurry reaches a predetermined value, and (2) the slurry. An apparatus for producing a slurry for a metal film, which comprises an ion exchange means for reducing the concentration of cations by passing a liquid through a cation exchange resin and setting the pH to a predetermined value.

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