JP5413571B2 - Chemical mechanical polishing aqueous dispersion, method for producing the same, and chemical mechanical polishing method - Google Patents

Description

  The present invention relates to an aqueous dispersion for chemical mechanical polishing, a method for producing the same, and a chemical mechanical polishing method.

  In recent years, the use of a low dielectric constant interlayer insulating film (hereinafter also referred to as “low dielectric constant insulating film”) has been studied in order to prevent an increase in signal delay due to the multilayer wiring of a semiconductor device. As such a low dielectric constant insulating film, for example, materials described in Patent Document 1 and Patent Document 2 have been studied. When the low dielectric constant insulating film as described above is used as the interlayer insulating film, copper or copper alloy is usually used because the wiring material is required to have high conductivity. When manufacturing such a semiconductor device by the damascene method, it is usually necessary to remove the wiring material on the barrier metal film by chemical mechanical polishing (first polishing process), and then remove the barrier metal film by polishing. Accordingly, it is necessary to perform a step of further polishing and planarizing the wiring material and the interlayer insulating film (second polishing step).

  In the first polishing process, a characteristic for polishing the wiring material at a high speed is required, but in the second polishing process, a characteristic for polishing the surface to be polished smoothly is particularly required. In order to further improve the flatness of the surface to be polished in the second polishing step, a change in the design of the semiconductor device structure has been studied. Specifically, when using a low dielectric constant insulating film having low mechanical strength, (1) surface defects called peeling or scratches are generated on the surface to be polished by chemical mechanical polishing, and (2) fine When polishing a wafer having a wiring structure, the polishing rate of the low dielectric constant insulating film is remarkably increased, so that it is impossible to obtain a flat and highly accurate finished surface. (3) Barrier metal film and low dielectric constant For example, a structure in which a coating film called a cap layer made of silicon dioxide or the like is formed as an upper layer of a low dielectric constant insulating film has been studied for reasons such as poor adhesion to the dielectric insulating film.

  In the second polishing step in such a structure, it is necessary to quickly polish and remove the upper cap layer to suppress the polishing rate of the lower low dielectric constant insulating film as much as possible. That is, the relationship between the cap layer polishing rate (RR1) and the low dielectric constant insulating film polishing rate (RR2) is required to satisfy RR1> RR2.

  On the other hand, in order to prevent breakdown of the low dielectric constant insulating film and interfacial delamination with other laminated materials, there is a method of reducing the frictional force applied to the wafer by reducing the applied pressure during polishing. However, in this method, since the polishing speed is lowered by reducing the applied pressure during polishing, the production efficiency of the semiconductor device is significantly reduced. In order to solve this problem, Patent Document 3 describes a technique that can improve the polishing rate by including a water-soluble polymer in the chemical mechanical polishing aqueous dispersion. It could not be said that the polishing rate in the second polishing step was sufficient. As described above, there has been a demand for the development of a new aqueous dispersion for chemical mechanical polishing that has a high polishing rate and high planarization characteristics for the barrier metal film and the cap layer while preventing damage to the low dielectric constant insulating film. .

JP 2001-308089 A JP 2001-298023 A International Publication No. 2007/116770 Pamphlet

  An object of the present invention is a chemical mechanical polishing aqueous system that has high storage stability of silica particles, realizes a high polishing rate for a barrier metal film without causing defects in a metal film or an insulating film, and has less metal contamination of a wafer Dispersion and chemical mechanical polishing method using the same are provided.

The chemical mechanical polishing aqueous dispersion according to the present invention comprises:
(A) silica particles;
(B) an organic acid having two or more carboxyl groups;
An aqueous dispersion for chemical mechanical polishing containing the above (A) The silica particles have the following chemical properties.

  Sodium, potassium and ammonium ion content measured from elemental analysis by ICP emission spectrometry or ICP mass spectrometry and quantitative analysis of ammonium ion by ion chromatography, sodium content: 5 to 500 ppm, potassium and ammonium ion The content of at least one selected from: satisfies the relationship of 100 to 20000 ppm.

  In the chemical mechanical polishing aqueous dispersion according to the invention, (B) the acid dissociation index pKa of an organic acid having two or more carboxyl groups at 25 ° C. (however, two in the case of an organic acid having two carboxyl groups) The pKa of the third carboxyl group is taken as the index of the pKa of the third carboxyl group in an organic acid having 3 or more carboxyl groups.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the organic acid (B) having two or more carboxyl groups may be at least one selected from maleic acid, malonic acid, and citric acid.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the ratio (Rmax / Rmin) of the major axis (Rmax) to the minor axis (Rmin) of the (A) silica particles is 1.0 to 1.5. Can do.

  In the chemical mechanical polishing aqueous dispersion according to the present invention, the average particle diameter calculated from the specific surface area of the (A) silica particles measured using the BET method may be 10 nm to 100 nm.

  In the chemical mechanical polishing aqueous dispersion according to the present invention, the pH may be 6-12.

  A chemical mechanical polishing method according to the present invention polishes a surface to be polished of a semiconductor device having at least one selected from a metal film, a barrier metal film, and an insulating film, using the chemical mechanical polishing aqueous dispersion. It is characterized by that.

  The chemical mechanical polishing aqueous dispersion according to the present invention includes a chemical mechanical polishing aqueous dispersion obtained by mixing at least (A) silica particles and (B) an organic acid having two or more carboxyl groups. The (A) silica particles have the following chemical properties.

  Sodium, potassium and ammonium ion content measured from elemental analysis by ICP emission spectrometry or ICP mass spectrometry and quantitative analysis of ammonium ion by ion chromatography, sodium content: 5 to 500 ppm, potassium and ammonium ion The content of at least one selected from: satisfies the relationship of 100 to 20000 ppm.

  According to the chemical mechanical polishing aqueous dispersion, the storage stability of silica particles contained as abrasive grains can be enhanced. Moreover, according to the chemical mechanical polishing aqueous dispersion, a high polishing rate for the barrier metal film can be realized without causing defects in the metal film or the insulating film, and metal contamination of the wafer can be reduced.

It is the conceptual diagram which showed the major axis and minor axis of the silica particle typically. It is the conceptual diagram which showed the major axis and minor axis of the silica particle typically. It is the conceptual diagram which showed the major axis and minor axis of the silica particle typically. It is sectional drawing which showed the to-be-processed object used for the chemical mechanical polishing method of this invention. It is sectional drawing for demonstrating the grinding | polishing process of the chemical mechanical grinding | polishing method of this invention. It is sectional drawing for demonstrating the grinding | polishing process of the chemical mechanical grinding | polishing method of this invention. It is sectional drawing for demonstrating the grinding | polishing process of the chemical mechanical grinding | polishing method of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

1. Chemical mechanical polishing aqueous dispersion The chemical mechanical polishing aqueous dispersion according to the present embodiment includes (A) silica particles and (B) an organic acid having two or more carboxyl groups. In the system dispersion, the (A) silica particles have the following chemical properties. The chemical property is “the content of sodium, potassium and ammonium ions measured from elemental analysis by ICP emission spectrometry or ICP mass spectrometry and quantitative analysis of ammonium ions by ion chromatography, but the content of sodium: The content of at least one selected from 5 to 500 ppm, potassium and ammonium ions: 100 to 20000 ppm is satisfied. First, each component constituting the chemical mechanical polishing aqueous dispersion according to this embodiment will be described.

1.1 (A) Silica Particles The (A) silica particles used in the present embodiment contain 5 to 500 ppm, preferably 10 to 400 ppm, particularly preferably 15 to 300 ppm of sodium. Further, it contains 100 to 20000 ppm of at least one selected from potassium and ammonium ions. When said (A) silica particle contains potassium, content of potassium becomes like this. Preferably it is 100-20000 ppm, More preferably, it is 500-15000 ppm, Most preferably, it is 1000-10000 ppm. When said (A) silica particle contains ammonium ion, content of ammonium ion becomes like this. Preferably it is 100-20000 ppm, More preferably, it is 200-10000 ppm, Most preferably, it is 500-8000 ppm. Further, even when potassium or ammonium ions contained in the silica particles (A) are not within the above range, the total content of potassium and ammonium ions is 100 to 20000 ppm, preferably 500 to 15000 ppm, more preferably 1000 to If it is within the range of 10,000 ppm, the effect of the present invention can be obtained.

  If the sodium content exceeds 500 ppm, wafer contamination after polishing occurs, which is not preferable. On the other hand, in order to make sodium less than 5 ppm, it is necessary to perform the ion exchange treatment a plurality of times, which involves technical difficulties.

  If at least one selected from potassium and ammonium ions exceeds 20000 ppm, the pH of the silica particle dispersion may become too high and silica may be dissolved. On the other hand, if at least one selected from potassium and ammonium ions is less than 100 ppm, the dispersion stability of the silica particles is lowered, and the silica particles are aggregated, thereby causing defects on the wafer. .

  In addition, the content of sodium and potassium contained in the silica particles described above is a value determined using ICP emission analysis (ICP-AES) or ICP mass spectrometry (ICP-MS). As the ICP emission analyzer, for example, “ICPE-9000 (manufactured by Shimadzu Corporation)” or the like can be used. As the ICP mass spectrometer, for example, “ICPM-8500 (manufactured by Shimadzu Corporation)”, “ELAN DRC PLUS (manufactured by Perkin Elmer)”, or the like can be used. Further, the content of ammonium ions contained in the silica particles described above is a value quantified using an ion chromatography method. As the ion chromatography method, for example, a non-suppressor ion chromatograph “HIS-NS (manufactured by Shimadzu Corporation)”, “ICS-1000 (manufactured by DIONEX)”, or the like can be used. The sodium and potassium contained in the silica particles may be sodium ion and potassium ion, respectively. By measuring the content of sodium ions, potassium ions, and ammonium ions, sodium, potassium, and ammonium ions contained in the silica particles can be quantified. In addition, content of the sodium, potassium, and ammonium ion described in this specification is the weight of sodium, potassium, and ammonium ions with respect to the weight of the silica particles.

  By containing sodium and at least one selected from potassium and ammonium ions within the above range, the silica particles can be stably dispersed in the chemical mechanical polishing aqueous dispersion. Aggregation of silica particles that cause defects does not occur. Moreover, if it is in the said range, the metal contamination of the wafer after grinding | polishing can be prevented.

  The average particle size calculated from the specific surface area of the (A) silica particles measured using the BET method is preferably 10 to 100 nm, more preferably 10 to 90 nm, and particularly preferably 10 to 80 nm. . (A) When the average particle diameter of the silica particles is in the range of 10 to 100 nm, it is excellent in storage stability as an aqueous dispersion for chemical mechanical polishing, and a smooth polished surface having no defects can be obtained. (A) If the average particle diameter of the silica particles is less than 10 nm, the polishing rate for the interlayer insulating film (cap layer) such as the TEOS film becomes too small, which is not practical. On the other hand, when the average particle diameter of (A) silica particles exceeds 100 nm, it is not preferable because the storage stability of the silica particles is poor.

  (A) The average particle diameter of the silica particles is calculated from the specific surface area measured using the BET method with a flow-type specific surface area automatic measuring device “micrometrics FlowSorb II 2300 (manufactured by Shimadzu Corporation)”, for example.

  Below, the method to calculate an average particle diameter from the specific surface area of a silica particle is demonstrated.

Assuming that the shape of the silica particle is a true sphere, the particle diameter is d (nm) and the specific gravity is ρ (g / cm ³ ), the surface area A of n particles is A = nπd ² . N particles mass N becomes N = ρnπd ^3/6. The specific surface area S is represented by the surface area of all the constituent particles per unit mass of the powder. Then, the specific surface area S of n particles is S = A / N = 6 / ρd. Substituting the specific gravity ρ = 2.2 of the silica particles into this formula and converting the unit, the following formula (1) can be derived.

Average particle diameter (nm) = 2727 / S (m ² / g) (1)

  In addition, all the average particle diameters of the silica particles in this specification are calculated based on the formula (1).

  The ratio (Rmax / Rmin) of the major axis (Rmax) to the minor axis (Rmin) of the (A) silica particles is preferably 1.0 to 1.5, more preferably 1.0 to 1.4, and particularly preferably 1. 0-1.3. When Rmax / Rmin is within the above range, a high polishing rate and a high planarization characteristic can be exhibited without causing defects in the metal film or the insulating film. If Rmax / Rmin is greater than 1.5, defects after polishing occur, which is not preferable.

  Here, the major axis (Rmax) of the silica particles means the longest distance among the distances connecting the end portions of the images of one independent silica particle image taken by a transmission electron microscope. . The short diameter (Rmin) of the silica particles means the shortest distance among the distances connecting the end portions of the image of one independent silica particle image taken with a transmission electron microscope.

  For example, when the image of one independent silica particle 10a photographed by a transmission electron microscope as shown in FIG. 1 is elliptical, the major axis a of the elliptical shape is determined as the major axis (Rmax) of the silica particle, The elliptical minor axis b is determined as the minor axis (Rmin) of the silica particles. As shown in FIG. 2, when an image of one independent silica particle 10b photographed by a transmission electron microscope is an aggregate of two particles, the longest distance c connecting the end portions of the image is expressed as follows. The longest diameter (Rmax) of the silica particles is determined, and the shortest distance d connecting the end portions of the image is determined as the short diameter (Rmin) of the silica particles. As shown in FIG. 3, when the image of one independent silica particle 10c photographed by a transmission electron microscope is an aggregate of three or more particles, the longest distance e connecting the end portions of the image is shown. Is the long diameter (Rmax) of the silica particles, and the shortest distance f connecting the end portions of the image is determined to be the short diameter (Rmin) of the silica particles.

  For example, by measuring the major axis (Rmax) and minor axis (Rmin) of 50 silica particles by the above-described determination method, and calculating the average value of major axis (Rmax) and minor axis (Rmin), the major axis and The ratio to the minor axis (Rmax / Rmin) can be calculated and obtained.

  The content of the silica particles (A) is preferably 1 to 20% by mass, more preferably 1 to 15% by mass with respect to the total mass of the chemical mechanical polishing aqueous dispersion at the time of use. Preferably it is 1-10 mass%. When the content of the (A) silica particles is less than the above range, a sufficient polishing rate cannot be obtained, which is not practical. On the other hand, when the content of the (A) silica particles exceeds the above range, the cost increases and a stable chemical mechanical polishing aqueous dispersion may not be obtained.

  The method for producing (A) silica particles used in the present embodiment is not particularly limited as long as silica particles in which the content of sodium, potassium and ammonium ions is within the above range are obtained, and a conventionally known method is applied. be able to. For example, it can be produced according to the method for producing a silica particle dispersion described in JP-A No. 2003-109921 and JP-A No. 2006-80406.

  Moreover, as a conventionally well-known method, there exists a method of producing a silica particle by removing an alkali from alkali silicate aqueous solution, for example. Examples of the alkali silicate aqueous solution include a sodium silicate aqueous solution, an ammonium silicate aqueous solution, a lithium silicate aqueous solution, and a potassium silicate aqueous solution that are generally known as water glass. Examples of ammonium silicate include silicates made of ammonium hydroxide and tetramethylammonium hydroxide.

Below, one of the specific preparation methods of the (A) silica particle used for this embodiment is demonstrated. A dilute silicic acid solution containing 20 to 38% by mass of silica and diluting an aqueous sodium silicate solution having a SiO ₂ / Na ₂ O molar ratio of 2.0 to 3.8 with water to have a silica concentration of 2 to 5% by mass A sodium aqueous solution is used. Subsequently, a dilute sodium silicate aqueous solution is passed through the hydrogen-type cation exchange resin layer to generate an active silicate aqueous solution from which most of the sodium ions have been removed. The aqueous silicic acid solution is aged with heat while adjusting the pH to 7-9 with alkali, and grown to the desired particle size to produce colloidal silica particles. During this thermal aging, an active silicic acid aqueous solution and small particles of colloidal silica are added little by little to prepare silica particles having a target particle size in the range of, for example, an average particle size of 10 to 100 nm. The silica particle dispersion thus obtained is concentrated to increase the silica concentration to 20 to 30% by mass, and then passed again through the hydrogen-type cation exchange resin layer to remove most of the sodium ions and pH with an alkali. By adjusting the pH, silica particles containing 5 to 500 ppm of sodium and 100 to 20000 ppm of at least one selected from potassium and ammonium ions can be produced.

  In addition, (A) the content of sodium, potassium and ammonium ions contained in the silica particles is obtained by recovering the silica component by a known method such as centrifugation, ultrafiltration, etc., of the chemical mechanical aqueous dispersion containing the silica particles, It can be calculated by quantifying sodium, potassium and ammonium ions contained in the recovered silica component. Therefore, by analyzing the silica component recovered from the chemical mechanical polishing aqueous dispersion by the above method by a known method, it can be confirmed that the constituent requirements of the present invention are satisfied.

1.2 (B) Organic acid having two or more carboxyl groups The chemical mechanical polishing aqueous dispersion according to this embodiment contains (B) an organic acid having two or more carboxyl groups. The following points are mentioned as an effect of the organic acid having two or more carboxyl groups.

  (1) Coordination to metal ions such as copper, tantalum, and titanium eluted into the chemical mechanical polishing aqueous dispersion by polishing can prevent metal deposition. As a result, polishing defects such as scratches can be suppressed.

  (2) There is an effect of increasing the polishing rate for polishing objects such as a copper film, a barrier metal film, and a TEOS film. When a water-soluble polymer described later is added, the water-soluble polymer may cause a decrease in the polishing rate by protecting the surface to be polished. Even in such a case, the polishing rate for the polishing object can be increased by using an organic acid having two or more carboxyl groups in combination.

  (3) As described above, it has the ability to coordinate to metal ions, so it coordinates to sodium ions and potassium ions that are crushed during polishing and eluted from silica particles, and sodium ions and potassium ions are adsorbed on the surface to be polished. Can be inhibited. As a result, sodium ions and potassium ions are liberated into the solution and can be easily removed.

  (4) It is considered that the dispersion stability of the silica particles can be enhanced by adsorbing to the surface of the silica particles. As a result, the storage stability of silica particles and the number of scratches estimated to be caused by aggregated particles can be greatly suppressed.

  On the other hand, even if an organic acid having one carboxyl group, such as formic acid, acetic acid, propionic acid, is used, high coordination ability to metal ions cannot be expected, and the polishing rate for the polishing object is increased It is thought that it is not possible.

  The (B) organic acid having two or more carboxyl groups preferably has an acid dissociation index (pKa) at 25 ° C. in at least one dissociation stage of 5.0 or more. The acid dissociation index (pKa) in the present invention is based on the pKa value of the second carboxyl group for an organic acid having two carboxyl groups, and the third carboxyl for an organic acid having three or more carboxyl groups. The pKa value of the group is used as an index. When the acid dissociation index (pKa) is 5.0 or more, it has higher coordination ability to metal ions such as copper, tantalum, and titanium that are eluted into the chemical mechanical polishing aqueous dispersion by polishing. Metal precipitation can be prevented. Thereby, scratches on the surface to be polished can be prevented. Furthermore, the pH change in the polishing composition during the polishing process can be suppressed by buffering, and the (A) silica particles used in the present invention are suppressed from aggregating due to the pH change during the polishing process. can do. On the other hand, when the acid dissociation index (pKa) is less than 5.0, the above effect cannot be expected.

  The acid dissociation index (pKa) is, for example, (a) The Journal of Physical Chemistry vol. 68, number 6, page 1560 (1964), (b) a method using an automatic potentiometric titrator (COM-980Win, etc.) manufactured by Hiranuma Sangyo Co., Ltd., and (c) Chemical Society of Japan It is possible to use the acid dissociation index described in the chemical manual of the edition (revised edition 3, June 25, 1984, published by Maruzen Co., Ltd.), (d) a database such as pKaBASE manufactured by Comprugrug, etc. it can.

  Examples of organic acids having two or more carboxyl groups having an acid dissociation index (pKa) of 5.0 or more include the organic acids listed in Table 1. The pKa values shown in Table 1 represent the pKa value of the second carboxyl group in the case of an organic acid having two carboxyl groups, and the pKa value of the third carboxyl group in an organic acid having three or more carboxyl groups. Represents a value.

  Among organic acids having two or more carboxyl groups listed in Table 1, maleic acid, malonic acid, and citric acid are more preferable, and maleic acid is particularly preferable. These organic acids not only have a preferable pKa value, but also have a small steric hindrance in terms of their molecular structure. Therefore, these organic acids are used for metal ions such as copper, tantalum, and titanium that are eluted into the chemical mechanical polishing aqueous dispersion by polishing. On the other hand, it has high coordination ability and can prevent metal precipitation.

  The content of the organic acid (B) having two or more carboxyl groups is preferably 0.001 to 3.0% by mass, more preferably 0.00%, based on the total mass of the chemical mechanical polishing aqueous dispersion. 01-2.0 mass%. When the content of the organic acid (B) is less than the above range, surface defects such as a large number of scratches on the copper film may occur. On the other hand, when the content of the organic acid (B) exceeds the above range, the silica particles may be aggregated and storage stability may be impaired.

  In addition, the effect of this invention will be acquired if at least 1 sort (s) of the organic acid which has the said 2 or more carboxyl group is contained. Therefore, in this invention, you may add organic acids other than the organic acid which has a 2 or more carboxyl group for the other objective.

1.3 Other Additives 1.3.1 Oxidizing Agent The chemical mechanical polishing aqueous dispersion according to this embodiment may contain an oxidizing agent as necessary. Examples of the oxidizing agent include ammonium persulfate, potassium persulfate, hydrogen peroxide, ferric nitrate, diammonium cerium nitrate, iron sulfate, ozone, hypochlorous acid and its salts, potassium periodate, and peracetic acid. Is mentioned. These oxidizing agents can be used alone or in combination of two or more. Of these oxidizing agents, ammonium persulfate, potassium persulfate and hydrogen peroxide are particularly preferred in view of oxidizing power, compatibility with the protective film, ease of handling, and the like. The content of the oxidizing agent is preferably 0.05 to 5% by mass, more preferably 0.08 to 3% by mass, based on the total mass of the chemical mechanical polishing aqueous dispersion. When the content of the oxidizing agent is less than 0.05% by mass, a sufficient polishing rate may not be ensured. On the other hand, when the content exceeds 5% by mass, the copper film may be corroded or dished.

1.3.2 Water-soluble polymer The chemical mechanical polishing aqueous dispersion according to this embodiment may contain a water-soluble polymer, if necessary.

  Examples of the water-soluble polymer include polyacrylic acid and its salt, polymethacrylic acid and its salt, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide and the like. Among these water-soluble polymers, polymethacrylic acid having a carboxyl group in a repeating unit and a salt thereof, polyacrylic acid and a salt thereof, or a derivative thereof is preferable. Polyacrylic acid and polymethacrylic acid are more preferred because they do not affect the stability of (A) silica particles. Polyacrylic acid is particularly preferable because it can impart an appropriate viscosity to the chemical mechanical polishing aqueous dispersion according to the present embodiment.

  As the weight average molecular weight of the water-soluble polymer, for example, a weight average molecular weight (Mw) in terms of polyethylene glycol measured by GPC (gel permeation chromatography) can be applied. The water-soluble polymer may have a weight average molecular weight (Mw) of 50,000 to 5,000,000, preferably 200,000 to 5,000,000, more preferably 200,000 to 1,500,000. When the weight average molecular weight is within the above range, the polishing friction can be greatly reduced, so that the load on the low dielectric constant insulating film can be reduced. In addition, the surface to be polished can be stably polished while suppressing dishing and corrosion of the copper film. When the weight average molecular weight is smaller than the lower limit, the effect of reducing polishing friction is small, and the effect of suppressing the dishing or corrosion of the copper film is poor. On the other hand, if the weight average molecular weight is larger than the above upper limit, the storage stability of the silica particles may be impaired, and the viscosity of the chemical mechanical polishing aqueous dispersion is excessively increased, which imposes a load on the polishing liquid supply apparatus. Such problems may occur.

  Moreover, the water-soluble polymer exemplified above can be efficiently coordinated to the surface of the copper film as the surface to be polished. Thereby, the surface of the copper film is effectively protected, the excessive adsorption action by the silanol groups present on the surface of the (A) silica particles on the copper film surface can be suppressed, and the polishing rate for the copper film can be reduced. Can be suppressed. As a result, it is possible to optimally adjust the polishing rate balance of the surface to be polished composed of various materials such as copper, barrier metal, insulating film material, and to improve flatness by suppressing erosion and corrosion. it can. Moreover, since the water-soluble polymer exemplified above inhibits (A) adsorption of silica particles to the surface to be polished, (A) silica particles can be easily removed from the surface to be polished by washing after polishing is completed. . Furthermore, since the exemplified water-soluble polymer can be easily removed by a cleaning operation, it does not remain on the surface to be polished and deteriorate the electrical characteristics of the device.

  The content of the water-soluble polymer is preferably 0.001 to 1.0 mass%, more preferably 0.01 to 0.5 mass%, based on the total mass of the chemical mechanical polishing aqueous dispersion. is there. When the content of the water-soluble polymer is less than the above range, the effect of reducing polishing friction is small, and the effect of suppressing the dishing or corrosion of the copper film is inferior. On the other hand, when the content of the water-soluble polymer exceeds the above range, the silica particles may be aggregated.

1.3.3 Surfactant The chemical mechanical polishing aqueous dispersion according to this embodiment may contain a surfactant as necessary. Surfactants include nonionic surfactants, anionic surfactants or cationic surfactants.

  As said nonionic surfactant, the nonionic surfactant which has a triple bond is mentioned, for example. Specifically, acetylene glycol and its ethylene oxide adduct, acetylene alcohol, etc. are mentioned. Also included are silicone surfactants, polyvinyl alcohol, cyclodextrin, polyvinyl methyl ether, and hydroxyethyl cellulose.

  Examples of the anionic surfactant include carboxylate, sulfonate, sulfate ester salt, phosphate ester salt and the like. Examples of the carboxylate include fatty acid soap and alkyl ether carboxylate. Examples of the sulfonate include alkyl benzene sulfonate, alkyl naphthalene sulfonate, α-olefin sulfonate, and the like. Examples of sulfate salts include higher alcohol sulfate salts, alkyl ether sulfate salts, polyoxyethylene alkylphenyl ether sulfate salts, and the like. Examples of the phosphate ester salt include alkyl phosphate ester salts.

  Examples of the cationic surfactant include aliphatic amine salts and aliphatic ammonium salts. These surfactants can be used alone or in combination of two or more.

  The content of the surfactant is preferably 0.001 to 1.0% by mass, more preferably 0.005 to 0.5% by mass, based on the total mass of the chemical mechanical polishing aqueous dispersion. When the content of the surfactant is within the above range, it is possible to achieve both an appropriate polishing rate and a good surface to be polished.

1.3.4 Organic Acid Having Nitrogen-containing Heterocycle and Carboxyl Group The chemical mechanical polishing aqueous dispersion according to this embodiment may contain an organic acid having a nitrogen-containing heterocycle and a carboxyl group as optional components. . The organic acid having a nitrogen-containing heterocyclic ring and a carboxyl group has a property of easily forming a coordinate bond with a copper ion, and forms a coordinate bond on the surface of the copper film to be polished. Thus, the surface roughness of the copper film can be suppressed and high flatness can be maintained, the affinity with copper and copper ions can be increased, and the polishing rate for the copper film can be promoted. Examples of the organic acid having a nitrogen-containing heterocycle and a carboxyl group include organic acids containing a hetero 6-membered ring having at least one nitrogen atom, and organic acids containing a hetero compound consisting of a hetero 5-membered ring. More specifically, quinaldic acid, quinolinic acid, quinoline-8-carboxylic acid, picolinic acid, xanthurenic acid, quinurenic acid, nicotinic acid, indole carboxylic acid, anthranilic acid and the like can be mentioned.

  The content of the organic acid having a nitrogen-containing heterocyclic ring and a carboxyl group is preferably 0.001 to 3.0 mass%, more preferably 0.01 to the total mass of the chemical mechanical polishing aqueous dispersion. 2.0% by mass. If the content of the organic acid having a nitrogen-containing heterocyclic ring and a carboxyl group is less than the above range, dishing of the copper film may be caused. On the other hand, when the content of the organic acid having a nitrogen-containing heterocyclic ring and a carboxyl group exceeds the above range, the silica particles may aggregate.

1.4 pH
The pH of the chemical mechanical polishing aqueous dispersion according to this embodiment is preferably 6 to 12, more preferably 7 to 11.5, and particularly preferably 8 to 11. When the pH is less than 6, (A) the hydrogen bond between silanol groups present on the surface of the silica particles cannot be broken, and aggregation of the silica particles may be caused. On the other hand, if the pH is higher than 12, the basicity is too strong, which may cause wafer defects. As a means for adjusting the pH, for example, adjusting the pH by adding a pH adjuster represented by a basic salt such as potassium hydroxide, ammonia, ethylenediamine, TMAH (tetramethylammonium hydroxide), etc. Can do.

1.5 Method for Producing Chemical Mechanical Polishing Aqueous Dispersion The chemical mechanical polishing aqueous dispersion according to this embodiment comprises (A) silica particles directly in pure water, and (B) an organic acid having two or more carboxyl groups. , And other additives, and can be prepared by mixing and stirring. The chemical mechanical polishing aqueous dispersion thus obtained may be used as it is, but a chemical mechanical polishing aqueous dispersion containing each component in a high concentration (concentrated) is prepared and desired at the time of use. It may be used after diluting to a concentration of.

  It is also possible to prepare a plurality of liquids (for example, two or three liquids) containing any of the above-mentioned components and to use them by mixing them at the time of use. In this case, after preparing a chemical mechanical polishing aqueous dispersion by mixing a plurality of liquids, this may be supplied to the chemical mechanical polishing apparatus, or a plurality of liquids may be supplied individually to the chemical mechanical polishing apparatus. A chemical mechanical polishing aqueous dispersion may be formed on a surface plate.

  Specific examples include a liquid (I) which is an aqueous dispersion containing at least water and (A) silica particles, and a liquid (II) containing at least water and (B) an organic acid having two or more carboxyl groups. A kit for preparing the chemical mechanical polishing aqueous dispersion by mixing the above solution.

  The concentration of each component in the liquids (I) and (II) is particularly as long as the concentration of each component in the chemical mechanical polishing aqueous dispersion finally prepared by mixing these liquids is within the above range. It is not limited. For example, liquids (I) and (II) containing each component at a concentration higher than the concentration of the chemical mechanical polishing aqueous dispersion are prepared, and the liquids (I) and (II) are diluted as necessary at the time of use. Then, these are mixed to prepare a chemical mechanical polishing aqueous dispersion in which the concentration of each component is in the above range. Specifically, when the liquids (I) and (II) are mixed at a weight ratio of 1: 1, the liquids (I) and (I) having a concentration twice the concentration of the chemical mechanical polishing aqueous dispersion. II) may be prepared. Moreover, after preparing liquid (I) and (II) of the density | concentration of 2 times or more of the density | concentration of the chemical mechanical polishing aqueous dispersion, and mixing these by 1: 1 weight ratio, each component becomes the said range. You may dilute with water. As described above, the storage stability of the chemical mechanical polishing aqueous dispersion can be improved by separately preparing the liquid (I) and the liquid (II).

  When the kit is used, the method and timing of mixing the liquid (I) and the liquid (II) are not particularly limited as long as the chemical mechanical polishing aqueous dispersion is formed at the time of polishing. For example, after the liquid (I) and the liquid (II) are mixed to prepare the chemical mechanical polishing aqueous dispersion, this may be supplied to a chemical mechanical polishing apparatus, or the liquid (I) and the liquid ( II) may be supplied independently to a chemical mechanical polishing apparatus and mixed on a surface plate. Alternatively, the liquid (I) and the liquid (II) may be independently supplied to the chemical mechanical polishing apparatus and mixed in line in the apparatus, or a mixing tank is provided in the chemical mechanical polishing apparatus, You may mix. In line mixing, a line mixer or the like may be used in order to obtain a more uniform chemical mechanical polishing aqueous dispersion.

2. Chemical Mechanical Polishing Method A specific example of the chemical mechanical polishing method according to the present embodiment will be described in detail with reference to the drawings.

2.1 Object to be processed FIG. 4 shows an object to be processed 100 used in the chemical mechanical polishing method according to this embodiment.

(1) First, the low dielectric constant insulating film 20 is formed by a coating method or a plasma CVD method. Examples of the low dielectric constant insulating film 20 include inorganic insulating films and organic insulating films. Examples of the inorganic insulating film include a SiOF film (k = 3.5 to 3.7), a Si—H containing SiO ₂ film (k = 2.8 to 3.0), and the like. As the organic insulating film, a carbon-containing SiO ₂ film (k = 2.7 to 2.9), a methyl group-containing SiO ₂ film (k = 2.7 to 2.9), a polyimide film (k = 3.0). To 3.5), Parylene film (k = 2.7 to 3.0), Teflon (registered trademark) film (k = 2.0 to 2.4), amorphous carbon (k = <2.5) (Where k represents a dielectric constant).

  (2) An insulating film 30 is formed on the low dielectric constant insulating film 20 by using a CVD method or a thermal oxidation method. Examples of the insulating film 30 include a TEOS film.

  (3) The wiring recess 40 is formed by etching so that the low dielectric constant insulating film 20 and the insulating film 30 communicate with each other.

  (4) The barrier metal film 50 is formed using the CVD method so as to cover the surface of the insulating film 30 and the bottom and inner wall surface of the wiring recess 40. The barrier metal film 50 is preferably Ta or TaN from the viewpoint of excellent adhesion to the copper film and diffusion barrier properties with respect to the copper film. However, the barrier metal film 50 is not limited to this and is Ti, TiN, Co, Mn, Ru, or the like. May be.

  (5) By depositing copper on the barrier metal film 50 to form the copper film 60, the workpiece 100 is obtained.

2.2 Chemical Mechanical Polishing Method (1) First, in order to remove the copper film 60 deposited on the barrier metal film 50 of the object 100, the chemical mechanical polishing aqueous dispersion for the copper film is used. Perform mechanical polishing. As shown in FIG. 5, the chemical mechanical polishing is stopped when the barrier metal film 50 is exposed.

  (2) Next, using the chemical mechanical polishing aqueous dispersion according to the present embodiment, the barrier metal film 50 and the copper film 60 are simultaneously subjected to chemical mechanical polishing. As shown in FIG. 6, even after the insulating film 30 is exposed, the chemical mechanical polishing is continued to remove the insulating film 30. As shown in FIG. 7, the semiconductor device 90 is obtained by stopping the chemical mechanical polishing when the low dielectric constant insulating film 20 is exposed.

  In the chemical mechanical polishing method according to the present embodiment, a commercially available chemical mechanical polishing apparatus can be used. As a commercially available chemical mechanical polishing apparatus, for example, “EPO-112” and “EPO-222” manufactured by Ebara Manufacturing Co., Ltd .; “LGP-510” and “LGP-552” manufactured by Lapmaster SFT, Applied Materials Manufactured, model “Mirra” and the like.

Preferred polishing conditions should be set as appropriate depending on the chemical mechanical polishing apparatus to be used. For example, when “EPO-112” is used as the chemical mechanical polishing apparatus, the following conditions may be used.
-Surface plate rotation speed: preferably 30-120 rpm, more preferably 40-100 rpm
Head rotation speed: preferably 30 to 120 rpm, more preferably 40 to 100 rpm
-Platen rotation speed / head rotation speed ratio; preferably 0.5-2, more preferably 0.7-1.5
Polishing pressure; preferably 60 to 200 gf / cm ² , more preferably 100 to 150 gf / cm ²
-Chemical mechanical polishing aqueous dispersion supply rate; preferably 50 to 300 mL / min, more preferably 100 to 200 mL / min. Examples Hereinafter, the present invention will be described by way of examples. However, the present invention is not limited to these examples.

3.1 Preparation of Silica Particle Dispersion No. 3 water glass (silica concentration: 24% by mass) was diluted with water to obtain a diluted sodium silicate aqueous solution having a silica concentration of 3.0% by mass. This diluted sodium silicate aqueous solution was passed through a hydrogen-type cation exchange resin layer to obtain an active silicic acid aqueous solution of pH 3.1 from which most of the sodium ions were removed. Thereafter, 10% by weight aqueous potassium hydroxide solution was immediately added with stirring to adjust the pH to 7.2, followed by further heating and boiling for 3 hours. To the resulting aqueous solution, 10 times the amount of the active silicic acid aqueous solution whose pH was previously adjusted to 7.2 was added little by little over 6 hours to grow the average particle size of the silica particles to 26 nm.

  Next, the dispersion aqueous solution containing the silica particles is concentrated under reduced pressure (boiling point 78 ° C.), and the silica concentration is 32.0 mass%, the average particle diameter of silica is 26 nm, and the pH is 9.8. Got. This silica particle dispersion is again passed through the hydrogen-type cation exchange resin layer to remove most of sodium, and then 10% by mass of potassium hydroxide aqueous solution is added, and the silica particle concentration: 28.0% by mass, pH A silica particle dispersion A of 10.0 was obtained.

  Silica particles are recovered from the silica particle dispersion A by centrifugation, the silica particles recovered with dilute hydrofluoric acid are dissolved, and sodium is added using ICP-MS (manufactured by PerkinElmer, model number “ELAN DRC PLUS”). And potassium was measured. Furthermore, ammonium ion was measured using ion chromatography (manufactured by DIONEX, model number “ICS-1000”). As a result, the sodium content was 88 ppm, the potassium content was 5500 ppm, and the ammonium ion content was 5 ppm.

  Silica particle dispersion A was diluted to 0.01% with ion-exchanged water, placed on a collodion membrane having Cu grit having a mesh size of 150 μm, and dried at room temperature. Thus, after preparing a sample for observation so as not to break the particle shape on the Cu grit, using a transmission electron microscope (H-7650, manufactured by Hitachi High-Technologies Corporation) Images were taken, the major axis and minor axis of 50 colloidal silica particles were measured, and the average value was calculated. When the ratio (Rmax / Rmin) was calculated from the average value of the major axis (Rmax) and the average value of the minor axis (Rmin), it was 1.1.

  The average particle size calculated from the specific surface area measured using the BET method was 26 nm. In addition, in the surface area measurement of the colloidal silica particle by BET method, the value which measured the silica particle collect | recovered by concentrating and drying the silica particle dispersion A was used.

  Silica particle dispersions B to D and F were obtained by the same method as described above while controlling the heat aging time, the type and amount of the basic compound, and the like.

  Silica particle dispersion E was prepared by subjecting the silica particle dispersion A to the autoclave treatment for a longer time and proceeding with the condensation of silanol.

  Table 2 summarizes the physical property values of the silica particle dispersions A to F produced.

3.2 Synthesis of water-soluble polymer 3.2.1 Synthesis of polyacrylic acid 20% by mass of acrylic acid aqueous solution in a 2 liter container containing 1000 g of ion-exchanged water and 1 g of 5% by mass ammonium persulfate aqueous solution 500 g was added dropwise uniformly over 8 hours with stirring at 70 ° C. under reflux. After completion of the dropwise addition, the solution was further kept under reflux for 2 hours to obtain an aqueous solution containing polyacrylic acid. As a result of measuring the obtained polyacrylic acid by gel permeation chromatography (manufactured by Tosoh Corporation, apparatus model number "HLC-8120", column model number "TSK-GEL α-M", eluent is NaCl aqueous solution / acetonitrile), The weight average molecular weight (Mw) in terms of polyethylene glycol was 1,000,000.

  Moreover, the polyacrylic acid with a weight average molecular weight (Mw) of 200,000 was obtained by adjusting the addition amount of the said component, reaction temperature, and reaction time suitably.

3.3 Preparation of Chemical Mechanical Polishing Aqueous Dispersion Silica Particle Dispersion A containing 50 parts by mass of ion-exchanged water and 5 parts by mass in terms of silica is placed in a polyethylene bottle, and 1 mass of malonic acid is added thereto. Part, 0.2 part by weight of quinaldic acid, 0.1 part by weight of acetylenic diol type nonionic surfactant (trade name “Surfinol 465”, manufactured by Air Products), polyacrylic acid aqueous solution (weight average molecular weight 200,000) ) In terms of polymer amount was added in an amount corresponding to 0.05 parts by mass, and a 10% by mass aqueous potassium hydroxide solution was added to adjust the pH of the chemical mechanical polishing aqueous dispersion to 10.0. . Next, 30% by mass of hydrogen peroxide solution was added in an amount corresponding to 0.05 part by mass in terms of hydrogen peroxide, and stirred for 15 minutes. Finally, ion-exchanged water is added so that the total amount of all components is 100 parts by mass, and then filtered through a filter with a pore size of 5 μm to obtain a chemical mechanical polishing aqueous dispersion S1 having a pH of 10.0. It was.

  Silica particles are recovered from the chemical mechanical polishing aqueous dispersion S1 by centrifugation, and the silica particles recovered with dilute hydrofluoric acid are dissolved. Then, ICP-MS (manufactured by PerkinElmer, model number “ELAN DRC PLUS”) is used. Used to measure sodium and potassium. Furthermore, ammonium ion was measured using ion chromatography (manufactured by DIONEX, model number “ICS-1000”). As a result, the sodium content was 88 ppm, the potassium content was 5500 ppm, and the ammonium ion content was 5 ppm. From this result, even if silica particles are recovered from the chemical mechanical polishing aqueous dispersion, sodium, potassium, and ammonium ions contained in the silica particles can be quantified, and the same result as the silica particle dispersion can be obtained. I understood it.

  The chemical mechanical polishing aqueous dispersions S2 to S10, except that the silica particle dispersion, the organic acid, the water-soluble polymer, the surfactant, the type and content of the oxidizing agent were changed as shown in Table 3, It was produced in the same manner as the chemical mechanical polishing aqueous dispersion S1. In Table 3, the trade name “Emulgen 104P” (manufactured by Kao Corporation, polyoxyethylene lauryl ether) was used as the “alkyl ether type nonionic surfactant”. In Table 3, “acetylenediol type nonionic surfactant” is a trade name “Surfinol 465” (manufactured by Air Products, 2,4,7,9-tetramethyl-5-decyne-4,7-diol-di Polyoxyethylene ether) was used.

  The obtained chemical mechanical polishing aqueous dispersions S1 to S10 were put in a 100 cc glass tube and stored at 25 ° C. for 6 months, and the presence or absence of sedimentation was confirmed visually. The results are shown in Table 3. In Table 3, “◯” indicates that no sedimentation and density difference of the particles are observed, “Δ” indicates that only the density difference is observed, and “×” indicates that both of the sedimentation and density differences of the particles are observed. It was evaluated.

3.4 Chemical Mechanical Polishing Test 3.4.1 Polishing Evaluation of Unpatterned Substrate Chemical Mechanical Polishing Equipment (Ebara Seisakusho, Model “EPO112”) and Porous Polyurethane Polishing Pad (Nitta Haas, Part Number “IC1000”) )) And supplying any one of the chemical mechanical polishing aqueous dispersions S1 to S10, the following various polishing rate measuring substrates are subjected to a polishing treatment under the following polishing conditions for 1 minute. The polishing rate and wafer contamination were evaluated by the above method. The results are also shown in Table 3.

3.4.1a Polishing rate measurement (1) Polishing rate measuring substrate-A silicon substrate with an 8-inch thermal oxide film on which a copper film having a thickness of 15,000 angstroms is laminated.
A silicon substrate with an 8-inch thermal oxide film on which a tantalum film having a thickness of 2,000 angstroms is laminated.
An 8-inch silicon substrate on which a low dielectric constant insulating film (made by Applied Materials, trade name “Black Diamond”) having a thickness of 10,000 Å is laminated.
An 8-inch silicon substrate on which a 10,000 Å thick PETEOS film is laminated.

(2) Polishing conditions and head rotation speed: 70 rpm
Head load: 200 gf / cm ²
・ Table rotation speed: 70rpm
-Supply speed of chemical mechanical polishing aqueous dispersion: 200 mL / min In this case, the supply speed of the chemical mechanical polishing aqueous dispersion refers to a value obtained by assigning the total supply amount of all supply liquids per unit time.

(3) Polishing rate calculation method For the copper film and the tantalum film, the film thickness after the polishing treatment is measured using an electric conduction film thickness measuring instrument (manufactured by KLA Tencor, model “Omnimap RS75”), The polishing rate was calculated from the film thickness reduced by chemical mechanical polishing and the polishing time.

  For PETEOS film and low dielectric constant insulating film, the film thickness after polishing is measured using an optical interference film thickness measuring instrument (Nanometrics Japan, model “Nanospec6100”) and reduced by chemical mechanical polishing. The polishing rate was calculated from the obtained film thickness and polishing time.

3.4.1b Wafer Contamination The PETEOS film and the low dielectric constant insulating film were polished in the same manner as in “3.4.1a Measurement of polishing rate”. For the PETEOS film, the substrate was subjected to vapor phase decomposition treatment, diluted hydrofluoric acid was dropped on the surface to dissolve the surface oxide film, and the dissolved liquid was then added to ICP-MS (manufactured by Perkin Elmer, model number “ELAN DRC”). PLUS "). For the low dielectric constant insulating film, ultrapure water is dropped on the surface of the substrate to extract the residual metal on the surface of the low dielectric constant insulating film, and then the extracted solution is ICP-MS (manufactured by Yokogawa Analytical Systems, model number “Agilent 7500s”). )). Wafer contamination, is preferably 3.0atom / cm ² or less, and more preferably 2.5atom / cm ² or less.

3.4.2 Polishing Evaluation of Patterned Wafer A chemical polishing machine (Ebara Seisakusho, model “EPO112”) is equipped with a porous polyurethane polishing pad (Nitta Haas, product number “IC1000”). While supplying any one of the mechanical polishing aqueous dispersions S1 to S10, the following patterned wafer was polished under the following polishing conditions, and the flatness and the presence or absence of defects were evaluated by the following methods. . The results are also shown in Table 3.

(1) Patterned wafer A silicon nitride film having a thickness of 1,000 angstroms was deposited on a silicon substrate, and a low dielectric constant insulating film (black diamond film) was sequentially laminated on the film to 4,500 angstroms, and further a PETEOS film having a thickness of 500 angstroms. Thereafter, a “SEMATECH 854” mask pattern was processed, and a test substrate in which a 250 angstrom tantalum film, a 1,000 angstrom copper seed film and a 10,000 angstrom copper plating film were sequentially laminated thereon was used.

(2) Polishing conditions for the first polishing treatment step / Chemical mechanical polishing aqueous dispersion for the first polishing treatment step includes “CMS7401”, “CMS7452” (both manufactured by JSR Corporation), ion exchange A mixture of water and a 4% by mass aqueous ammonium persulfate solution at a mass ratio of 1: 1: 2: 4 was used.
-Head rotation speed: 70 rpm
Head load: 200 gf / cm ²
・ Table rotation speed: 70rpm
-Supply speed of chemical mechanical polishing aqueous dispersion: 200 mL / min In this case, the supply speed of the chemical mechanical polishing aqueous dispersion refers to a value obtained by assigning the total supply amount of all supply liquids per unit time.
Polishing time: 2.75 minutes (3) Polishing conditions of the second polishing treatment step As the aqueous dispersions for the second polishing treatment step, chemical mechanical polishing aqueous dispersions S1 to S10 were used.
-Head rotation speed: 70 rpm
Head load: 200 gf / cm ²
・ Table rotation speed: 70rpm
-Supply speed of chemical mechanical polishing aqueous dispersion: 200 mL / min In this case, the supply speed of the chemical mechanical polishing aqueous dispersion refers to a value obtained by assigning the total supply amount of all supply liquids per unit time.
Polishing time: The time when polishing was further performed for 30 seconds from the time when the PETEOS film was removed from the surface to be polished was defined as the polishing end point, and Table 3 shows the “patterned wafer polishing time”.

3.4.2a Evaluation of flatness For the surface to be polished of the patterned wafer after the second polishing process, a copper wiring width (line, L) is used using a high resolution profiler (KLA Tencor, model “HRP240ETCH”). ) / Insulating film width (space, S) was measured for dishing amount (nm) in copper wiring portions of 100 μm / 100 μm, respectively. The results are also shown in Table 3. It should be noted that the dishing amount is displayed as negative when the upper surface of the copper wiring is convex above the reference surface (upper surface of the insulating film). The dishing amount is preferably -5 to 30 nm, more preferably -2 to 20 nm.

  The portion where the fine wiring length in the pattern in which the copper wiring width (line, L) / insulating film width (space, S) is 9 μm / 1 μm, respectively, is 1000 μm on the surface to be polished of the patterned wafer after the second polishing process. The amount of erosion (nm) was measured. The results are also shown in Table 3. Note that the erosion amount is indicated by a minus value when the upper surface of the copper wiring is convex above the reference surface (upper surface of the insulating film). The amount of erosion is preferably −5 to 30 nm, and more preferably −2 to 20 nm.

3.4.2b Defect Evaluation Measure the number of polishing scratches (scratches) on the polished surface of the patterned wafer after the second polishing process using a defect inspection device (model “2351” manufactured by KLA Tencor). did. The results are also shown in Table 3. In Table 3, the number of scratches per wafer is described with the unit “piece / wafer”. The number of scratches is preferably less than 100 / wafer.

3.4.3 Evaluation Results In each of Examples 1 to 4, the silica particles are excellent in storage stability. Particularly, the polishing rate for the Ta film is sufficiently high at 650 Å or more, and the polishing rate for the low dielectric constant insulating film is high. It was sufficiently low, 130 angstroms or less. Moreover, in Examples 1-4, it was excellent in the flatness of the to-be-polished surface, and the number of scratches was also restrained low.

  On the other hand, S5 used in Comparative Example 1 was not excellent in storage stability because it uses the silica dispersion D having a very low content of sodium, potassium and ammonium ions. As a result, in the polishing test of the patterned wafer, 180 scratches / wafer were generated on the copper film, and the state of the polished surface was poor.

  Since S6 used in Comparative Example 2 uses the silica particle dispersion E having a very low content of potassium and ammonium ions, the storage stability was not excellent. As a result, in the polishing test of the patterned wafer, 150 scratches / wafer were generated on the copper film, and the state of the polished surface was poor. On the other hand, since the silica dispersion E contains sodium at a high concentration (11250 ppm), the contamination of the low dielectric constant insulating film and the PETEOS film was observed in the polishing test of the polishing rate measuring substrate.

  S7 used in Comparative Example 3 corresponds to a composition obtained by deleting the component corresponding to “(B) organic acid” from S3 used in Example 3. When the results of Example 3 and Comparative Example 3 were compared, the storage stability of the silica particles was good. However, in the polishing test of the substrate for polishing rate measurement, Comparative Example 3 has a clearer copper film polishing rate (600 → 400 Å / min) and Ta film polishing rate (900 → 200 Å / min) than Example 3. Decreased. Further, in the polishing test of the patterned wafer, the number of scratches on the copper film was significantly increased in Comparative Example 3 than in Example 3 (45 → 120 / wafer). From the above results, the superiority of using the organic acid (B) was shown.

  In S8 used in Comparative Example 4, components corresponding to “(B) organic acid”, “water-soluble polymer”, and “surfactant” are not added. When the results of Comparative Example 3 and Comparative Example 4 were compared, it was found that the water-soluble polymer and the surfactant contributed to the suppression of the polishing rate of the low dielectric constant insulating film and the flatness of the surface to be polished.

  S9 used in Comparative Example 5 corresponds to a composition using “acetic acid” instead of “maleic acid” of S2 used in Example 2. When the results of Example 2 and Comparative Example 5 were compared, the storage stability of the silica particles was good. However, in the polishing test of the polishing rate measuring substrate, in Comparative Example 5, the decrease in the polishing rate of the Ta film (650 → 200 Å / min) was more remarkable than in Example 2. From this result, the superiority of using “(B) an organic acid having two or more carboxyl groups” was shown.

  S10 used in Comparative Example 6 does not contain silica particles. In S10, since the polishing rate is too low for any film, it is not practical.

  From the above results, the chemical mechanical polishing aqueous dispersions of Examples 1 to 4 have high storage stability of silica particles, and the chemical mechanical polishing aqueous dispersion causes defects in the metal film and the insulating film. It has been found that a high polishing rate for the barrier metal film can be realized without any problem and a good polished surface with less metal contamination of the wafer can be obtained.

10a, 10b, 10c ... silica particles, 20 ... low dielectric constant insulating film, 30 ... insulating film (cap layer), 40 ... recess for wiring, 50 ... barrier metal film, 60 ... copper film, 90 ... semiconductor device, 100 ... Object to be processed

Claims (8)

(A) silica particles;
(B) an organic acid having two or more carboxyl groups;
An aqueous dispersion for chemical mechanical polishing containing
The (A) silica particle is a chemical mechanical polishing aqueous dispersion having the following chemical properties.
Sodium, potassium and ammonium ion content measured from elemental analysis by ICP emission spectrometry or ICP mass spectrometry and quantitative analysis of ammonium ion by ion chromatography, sodium content: 5 to 500 ppm, potassium and ammonium ion The content of at least one selected from: satisfies the relationship of 100 to 20000 ppm. In claim 1,
(B) Acid dissociation index pKa of an organic acid having 2 or more carboxyl groups at 25 ° C. (However, in the case of an organic acid having 2 carboxyl groups, the pKa of the second carboxyl group is 3 or more carboxyls) In the case of an organic acid having a group, the pKa of the third carboxyl group is used as an index.) Is an aqueous dispersion for chemical mechanical polishing of 5.0 or more. In claim 2,
(B) The chemical mechanical polishing aqueous dispersion, wherein (B) the organic acid having two or more carboxyl groups is at least one selected from maleic acid, malonic acid, and citric acid. In any one of Claims 1 thru | or 3,
The ratio (Rmax / Rmin) of the major axis (Rmax) to the minor axis (Rmin) of the (A) silica particles is 1.0 to 1.5, and is an aqueous dispersion for chemical mechanical polishing. In any one of Claims 1 thru | or 4,
(A) The aqueous dispersion for chemical mechanical polishing whose average particle diameter computed from the specific surface area measured using the BET method of the said silica particle is 10-100 nm. In any one of Claims 1 thru | or 5,
An aqueous dispersion for chemical mechanical polishing having a pH of 6-12.   A surface to be polished of a semiconductor device having at least one selected from a metal film, a barrier metal film, and an insulating film is polished using the chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 6. , Chemical mechanical polishing method. A method of producing a chemical mechanical polishing aqueous dispersion by mixing at least (A) silica particles and (B) an organic acid having two or more carboxyl groups,
Said (A) silica particle is a manufacturing method of the aqueous dispersion for chemical mechanical polishing which has the following chemical property.
Sodium, potassium and ammonium ion content measured from elemental analysis by ICP emission spectrometry or ICP mass spectrometry and quantitative analysis of ammonium ion by ion chromatography, sodium content: 5 to 500 ppm, potassium and ammonium ion The content of at least one selected from: satisfies the relationship of 100 to 20000 ppm.

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