JP5333740B2 - Chemical mechanical polishing aqueous dispersion, method for producing the same, and chemical mechanical polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous dispersion for chemo-mechanical polishing having high polishing speed and high polishing selectivity to a copper film, and a small amount of metal contamination of a wafer without causing any defects in the copper film and a low dielectric-constant insulation film even under normal pressure conditions, and to provide a chemo-mechanical polishing method using the aqueous dispersion for chemo-mechanical polishing. <P>SOLUTION: The aqueous dispersion for chemical mechanical polishing is used for polishing the copper film containing a silica particle (A), an organic acid (B), and an anionic surfactant (C). The silica particle (A) should have the following chemical properties. The number of silanol groups calculated from the signal area of a<SP>29</SP>Si-NMR spectrum is 2.0-3.0&times;10<SP>21</SP>/g. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

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, high electrical conductivity is required for the wiring material, and thus copper or copper alloy is generally used. When manufacturing such a semiconductor device by the damascene method, the wiring material on the barrier metal film is usually removed by chemical mechanical polishing (first polishing process), and then the barrier metal film is removed by polishing, as necessary. Therefore, it is necessary to perform a step (second polishing step) of further polishing and planarizing the wiring material and the interlayer insulating film.

  In the first polishing step, it is required to selectively polish only the wiring material at a high speed. However, at the end of the first polishing process (when another material film such as a barrier metal film is exposed), it is very difficult to suppress dishing and erosion of the wiring portion while maintaining a high polishing rate for the wiring material. It is difficult to. For example, if only the polishing rate is increased, it may be achieved by increasing the applied pressure during polishing and increasing the frictional force applied to the wafer, but dishing and erosion of the wiring part is also accompanied by an increase in the polishing rate. The approach from the polishing method was limited because it deteriorated. Furthermore, in order to obtain a good polished surface in the second polishing step, it is necessary to suppress the copper residue (copper residue) on the fine wiring pattern at the end of the first polishing step.

  As described above, in addition to high-speed polishing performance and high planarization characteristics, removing the copper residue as it is at the end of the first polishing step or through a simple cleaning step can be achieved with the present polishing method. In order to compensate for this, it is required to develop a new aqueous dispersion for chemical mechanical polishing that can satisfy the above-mentioned characteristics.

  By the way, in general, the composition of the chemical mechanical polishing aqueous dispersion is composed of abrasive grains and additive components. In recent years, the development of aqueous dispersions for chemical mechanical polishing has centered on studies focusing on the combination of additive components, but on the other hand, studies have been made to improve polishing characteristics by controlling the properties of abrasive grains. (For example, see Patent Document 3).

  However, for example, when the abrasive grains described in Patent Document 3 are used, it is difficult to suppress dishing, erosion, and copper residue on the fine wiring pattern, and further, the stability of the particle dispersion is lacking. There was a problem of being bad.

JP 2001-308089 A JP 2001-298023 A JP 2006-26885 A

  Chemical mechanical polishing water system with high polishing rate and high polishing selectivity for copper films and low wafer metal contamination under normal pressure conditions without causing defects in copper films and low dielectric constant insulating films Dispersion and chemical mechanical polishing method using the same are provided.

  The chemical mechanical polishing aqueous dispersion according to the present invention is a chemical mechanical polishing for polishing a copper film containing (A) silica particles, (B) an organic acid, and (C) an anionic surfactant. An aqueous dispersion, wherein the silica particles (A) have the following chemical properties.

^The number of silanol groups calculated from the signal area of the ²⁹ Si-NMR spectrum is 2.0 to 3.0 × 10 ²¹ / g.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the (C) anionic surfactant is selected from a carboxyl group, a sulfonic acid group, a phosphoric acid group, and an ammonium salt and a metal salt of these functional groups. It can have at least one functional group.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the (C) anionic surfactant is an alkyl sulfate, an alkyl ether sulfate, an alkyl ether carboxylate, an alkylbenzene sulfonate, an alpha sulfo fatty acid ester salt. , Alkyl polyoxyethylene sulfate, alkyl phosphate, monoalkyl phosphate ester salt, naphthalene sulfonate, alpha olefin sulfonate, alkane sulfonate, and alkenyl succinate Can do.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the (C) anionic surfactant may be a compound represented by the following general formula (1).

(In the general formula (1), R ¹ and R ² each independently represents a hydrogen atom, a metal atom, or a substituted or unsubstituted alkyl group, and R ³ represents a substituted or unsubstituted alkenyl group or sulfonic acid group. represents a _(-SO 3 X). However, X represents a hydrogen ion, an ammonium ion or a metal ion.)
In the chemical mechanical polishing aqueous dispersion according to the invention, the organic acid (B) may be an amino acid.

  In the chemical mechanical polishing aqueous dispersion according to the present invention, the amino acid may be at least one selected from glycine, alanine, phenylalanine, tryptophan, and histidine.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the silica particles (A) may 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, 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.

  The chemical mechanical polishing method according to the present invention is a method for chemically mechanically polishing an object having a copper film formed on a barrier metal film, wherein the copper film is formed using the chemical mechanical polishing aqueous dispersion. Then, the chemical mechanical polishing is self-stopped when the barrier metal film is exposed.

  The method for producing an aqueous dispersion for chemical mechanical polishing according to the present invention comprises mixing at least (A) silica particles, (B) an organic acid, and (C) an anionic surfactant, A method for producing a system dispersion, wherein the (A) silica particles have the following chemical properties.

^The number of silanol groups calculated from the signal area of the ²⁹ Si-NMR spectrum is 2.0 to 3.0 × 10 ²¹ / g.

  According to the chemical mechanical polishing aqueous dispersion, the copper film can be selectively polished at high speed. In addition, the chemical mechanical polishing aqueous dispersion does not cause defects in the copper film and the low dielectric constant insulating film even under normal pressure conditions, and reduces metal contamination of the wafer. Can do.

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.

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

1. Chemical Mechanical Polishing Aqueous Dispersion A chemical mechanical polishing aqueous dispersion according to this embodiment includes a copper film containing (A) silica particles, (B) an organic acid, and (C) an anionic surfactant. The (A) silica particles have a silanol group number calculated from the signal area of the ²⁹ Si-NMR spectrum of 2.0 to 3.0 × 10. ²¹ / g. ”. First, each component constituting the chemical mechanical polishing aqueous dispersion according to this embodiment will be described.

1.1 (A) Silica Particle The “silanol group” of the silica particle in the present embodiment refers to a hydroxyl group directly bonded to the silicon atom of the silica particle, and the configuration or configuration is not particularly limited. Moreover, the production | generation conditions of a silanol group etc. are not ask | required.

The “number of silanol groups” in the present embodiment is the number of silanol groups per unit mass in the entire silica particles, and is an index representing the degree of condensation of the silica particles. Since the condensation degree of the silica particles is closely related to the hardness of the silica particles, the hardness of the silica particles can be estimated from the number of silanol groups. The number of silanol groups can be calculated from the signal area of the ²⁹ Si-NMR spectrum.

^{29 The} number of silanol groups calculated from the signal area of the Si-NMR spectrum is in contact with the various additives contained in the chemical mechanical polishing aqueous dispersion and the number of silanol groups present on the surface of the silica particles that can come into contact with water. It is an index that can comprehensively represent the number of silanol groups present inside silica particles that cannot be treated.

In the chemical mechanical polishing aqueous dispersion, the silanol group is normally negatively charged because H ⁺ of SiOH is dissociated and stably present in the SiO ⁻ state. Thereby, the electrical characteristics or chemical characteristics of the silica particles are developed. Additive components such as organic acids and water-soluble polymers in the vicinity of the surface of the silica particles are attracted to or rejected by the silica particles due to this electrical property or chemical property. As a result, the additive component in the chemical mechanical polishing aqueous dispersion produces a minute concentration gradient around the silica particles, forming an optimal chemical mechanical polishing aqueous dispersion to achieve good polishing characteristics. It is considered possible.

The number of silanol groups calculated from the signal area of the ²⁹ Si-NMR spectrum of (A) silica particles used in the present embodiment is 2.0 to 3.0 × 10 ²¹ / g, preferably 2.1 to 2 9 × 10 ²¹ pieces / g.

  When the number of silanol groups is within the above range, since the silanol groups of the entire silica particles are dense, the mechanical strength of the silica particles is improved and a sufficient polishing rate is obtained. Furthermore, the electrical characteristics or chemical characteristics expressed by the silanol groups present on the surface of the silica particles attract or eliminate organic acids and water-soluble polymers present in the vicinity of the silica particle surface. As a result, the additive component in the chemical mechanical polishing aqueous dispersion produces a minute concentration gradient around the silica particles, forming an optimal chemical mechanical polishing aqueous dispersion to achieve good polishing characteristics. Can be considered. Furthermore, when the number of silanol groups is within the above range, it is moderately stabilized by the interaction between the silica particles and other additives in the chemical mechanical polishing aqueous dispersion, and the dispersion stability of the silica particles can be ensured. In this case, no agglomeration causing defects occurs.

If the number of silanol groups exceeds 3.0 × 10 ²¹ / g, it is not preferable because a balanced dispersion state as described above cannot be obtained, resulting in an insufficient polishing rate ratio and planarization characteristics. In addition, the polishing rate for the barrier metal film tends to increase, which is not preferable because erosion is promoted. On the other hand, when the number of silanol groups is less than 2.0 × 10 ²¹ / g, the dispersion stability of the silica particles is inferior, and the silica particles are aggregated to deteriorate the storage stability. Further, since the mechanical strength is too high, dishing may be promoted, and polishing defects such as scratches may be caused.

(A) The ²⁹ Si-NMR spectrum of the silica particles is obtained by a known method such as centrifugation or ultrafiltration from the chemical mechanical polishing aqueous dispersion containing (A) silica particles, or from the chemical mechanical polishing aqueous dispersion. It can be obtained by measuring the recovered (A) silica particle component, (A) a dispersion of silica particles, and (A) silica particles by a known method. The number of silanol groups can be calculated by the following formula (2) from the signal area derived from ²⁹ Si in the ²⁹ Si-NMR spectrum obtained as described above.

(A) The ²⁹ Si-NMR spectrum of the silica particles is peak-separated by peak separation treatment, and the peak with a chemical shift of about −84 ppm when the silicon atom of tetramethylsilane is 0 ppm is determined as Q1, and the signal area is a ₁ , a peak at about −92 ppm is judged as Q2, a signal area is judged as a ₂ , a peak at about −101 ppm is judged as Q3, a signal area is judged as a ₃ , and a peak at about −111 ppm is judged as Q4, a signal area and _{a 4.}

In general, Q1 is considered to be derived from a silicon atom having a coordination number of silicon atoms adjacent to an oxygen atom of 1, and can be expressed as a composition formula SiO _1/2 (OH) _3. .11 g / mol. Q2 is considered to be derived from a silicon atom having a coordination number of silicon atoms adjacent to oxygen atoms of _2, and can be expressed as SiO (OH) ₂ as a composition formula, and its formula weight is 78.10 g / mol. Q3 is considered to be derived from a silicon atom whose coordination number of silicon atoms adjacent to the oxygen atom is 3, and can be expressed as a composition formula SiO _3/2 (OH), and its formula weight is 69.09 g / mol. is there. Q4 is considered to be derived from a silicon atom having a coordination number of silicon atoms adjacent to oxygen atoms of 4, and can be expressed as SiO ₂ as a composition formula, and its formula weight is 60.08 g / mol.

The number of silanol groups contained in the silica particles is determined by the following formula (2) from the coordination number of silicon atoms, the formula amounts of the signal areas a ₁ , a ₂ , a ₃ , a ₄ and Q 1, Q 2, Q 3, Q 4 components. Can be calculated.

Here, _{N A} is Avogadro's number: representing a 6.022 × ^{10 23.}

  The silica particles (A) used in the present embodiment can preferably contain sodium in an amount of 5 to 500 ppm, more preferably 10 to 400 ppm, and particularly preferably 15 to 300 ppm. Furthermore, 100-20000 ppm can be contained 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 It may be in the range of 10,000 ppm.

  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 the content of potassium contained in the silica particles described above are values determined using ICP emission spectrometry (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 diameter calculated from the specific surface area measured using the BET method of silica particles is preferably 10 to 100 nm, more preferably 10 to 90 nm, and particularly preferably 10 to 80 nm. When the average particle diameter of the silica particles is within the above range, it is excellent in storage stability as a chemical mechanical polishing aqueous dispersion, and a smooth polished surface free from defects can be obtained. If the average particle size of the silica particles is less than the above range, the polishing rate for the copper film becomes too small, which is not practical. On the other hand, when the average particle diameter of the silica particles exceeds the above range, the storage stability of the silica particles is inferior, which is not preferable.

  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 (3) can be derived.

Average particle diameter (nm) = 2727 / S (m ² / g) (3)
In addition, all the average particle diameters of the silica particles in this specification are calculated based on the formula (3).

  The ratio Rmax / Rmin of the major axis (Rmax) and minor axis (Rmin) of the silica particles is 1.0 to 1.5, preferably 1.0 to 1.4, more preferably 1.0 to 1.3. When Rmax / Rmin is within the above range, a high polishing rate and high planarization characteristics 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%. (A) When the content of the 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 (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.

  Further, as a conventionally known method, there is a method of producing silica particles by removing alkali from an alkali silicate aqueous solution. 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 The chemical mechanical polishing aqueous dispersion according to this embodiment contains (B) an organic acid. The content of the organic acid (B) is preferably 0.001 to 3.0% by mass, more preferably 0.01 to 2.0% by mass with respect to the total mass of the chemical mechanical polishing aqueous dispersion. is there. (B) If the content of the organic acid is less than the above range, dishing of the copper film may not be suppressed to 30 nm or less. On the other hand, when the content of (B) the organic acid exceeds the above range, the silica particles may aggregate.

  As said (B) organic acid, an amino acid is preferable. Amino acids tend to form coordination bonds with copper ions and have chelate coordination ability with respect to the surface of the copper film. Thereby, it is possible to increase the affinity with copper and copper ions and accelerate the polishing rate while adsorbing to the surface of the copper film to suppress surface roughness and maintain high flatness. Particularly preferred amino acids include glycine, alanine, phenylalanine, histidine, cysteine, methionine, glutamic acid, aspartic acid, glycylglycine and tryptophan. The amino acids exemplified above can be easily coordinated to copper ions eluted to the chemical mechanical polishing aqueous dispersion by polishing the copper film, and can prevent the precipitation of copper. As a result, polishing defects such as scratches can be suppressed. In addition, by containing the amino acids exemplified above, sodium ions that are crushed during polishing and eluted from the silica particles, potassium ions can inhibit the adsorption to the copper film surface and promote the release into the solution, As a result, it can be effectively removed from the surface of the object to be polished.

  (B) Organic acids other than amino acids include amidosulfuric acid, formic acid, lactic acid, acetic acid, tartaric acid, fumaric acid, glycolic acid, phthalic acid, maleic acid, oxalic acid, citric acid, malic acid, anthranilic acid, malonic acid. And glutaric acid.

  Examples of the organic acid (B) other than the organic acids exemplified above include organic acids containing a heterocyclic 6-membered ring containing at least one N atom, organic acids containing a heterocyclic compound consisting of a heterocyclic 5-membered ring, and the like. More specifically, quinaldic acid, quinolinic acid, 8-quinolinol, 8-aminoquinoline, quinoline-8-carboxylic acid, 2-pyridinecarboxylic acid, xanthurenic acid, quinurenic acid, benzotriazole, benzimidazole, 7-hydroxy- Examples include 5-methyl-1,3,4-triazaindolizine, allopurinol, hypoxanthine, nicotinic acid, picolinic acid, methyl picolinate and picolinic acid.

  Since the silanol group (A) of the silica particles and the organic acid (B) can interact appropriately, the dispersion stability of the silica particles in the polishing composition can be improved.

1.3 (C) Anionic surfactant The chemical mechanical polishing aqueous dispersion according to this embodiment contains (C) an anionic surfactant. In general, when abrasive grains containing a large amount of sodium or potassium are used in the chemical mechanical polishing aqueous dispersion, sodium or potassium derived from the abrasive grains remains on the surface of the workpiece even after the cleaning operation after polishing. It has been considered that it causes deterioration of the electrical characteristics of the product, and its use has been avoided. However, the (C) anionic surfactant has a high affinity with copper and copper ions, and is thought to selectively adsorb to copper rather than cations such as sodium ions and potassium ions to protect the surface. Therefore, it becomes possible to effectively suppress the adsorption of sodium ions, potassium ions and the like that are crushed during polishing and eluted from the silica particles to the surface of the object to be polished. For this reason, even if it is an aqueous dispersion for chemical mechanical polishing using an alkali silicate aqueous solution (water glass) in which alkali metal such as sodium remains in silica particles as impurities, a simple cleaning operation can be performed after polishing. Sodium and potassium can be removed from the surface to be polished, and chemical mechanical polishing can be performed without excessive contamination of the copper wiring.

  The (C) anionic surfactant is considered to be able to enhance the dispersion stability of the particles by adsorbing to the surface of the silica particles. As a result, the storage stability of the particles and the number of scratches estimated to be caused by the aggregated particles can be greatly suppressed.

Silanol groups present on the surface of the silica particles are stably present in the state of SiO ^{− due} to dissociation of H ⁺ , so that the silica particles are excessively adsorbed on the surface of the copper film and deteriorate flatness There is. However, the anionic surfactant (C) interacts with the silanol groups present on the surface of the silica particles to increase the dispersion stability of the silica particles during the polishing process, thereby causing such local aggregation of silica particles. Is suppressed, erosion and scratches are suppressed, and flatness is improved. Furthermore, the (C) anionic surfactant can be efficiently coordinated to the surface of the copper film as the surface to be polished. As a result, the surface of the copper film is effectively protected, and excessive adsorption of silica particles to the surface of the copper film can be suppressed, erosion and scratches are suppressed to improve flatness, and cleaning is facilitated. Silica particles can be removed from the surface of the copper film. Furthermore, since the (C) anionic surfactant can be easily removed by a cleaning operation, it does not remain on the surface of the copper film and deteriorate the electrical characteristics of the device.

  The content of the (C) anionic surfactant is preferably 0.0001 to 2.0% by mass, more preferably 0.0005 to 1.0%, based on the total mass of the chemical mechanical polishing aqueous dispersion. % By mass. (C) When the content of the anionic surfactant is less than the above range, the protective action of the copper film surface is weakened, and as a result of corrosion and excessive etching, dishing and erosion may not be suppressed to 30 nm or less. . On the other hand, if the content of the (C) anionic surfactant exceeds the above range, the protective effect on the surface of the copper film becomes too strong, so that a sufficient polishing rate cannot be obtained and copper residue (copper residue) may be generated. is there. Moreover, there is a possibility that the silica particles are aggregated, which causes practical problems such as intense foaming.

  The (C) anionic surfactant used in this embodiment has a carboxyl group, a sulfonic acid group, a phosphoric acid group, and at least one functional group selected from ammonium salts and metal salts of these functional groups. It is preferable.

  Such (C) anionic surfactants include fatty acid salts, alkyl sulfates, alkyl ether sulfate esters, alkyl ester carboxylates, alkyl benzene sulfonates, linear alkyl benzene sulfonates, alpha sulfo fatty acid ester salts, Alkyl polyoxyethylene sulfate, alkyl phosphate, monoalkyl phosphate ester salt, naphthalene sulfonate, alpha olefin sulfonate, alkane sulfonate, alkenyl succinate and the like can be mentioned. Of these, alkylbenzene sulfonate, linear alkylbenzene sulfonate, naphthalene sulfonate, and alkenyl succinate are more preferable. These anionic surfactants can be used singly or in combination of two or more.

  The alkenyl succinate is particularly preferably a compound represented by the following general formula (1).

In the general formula (1), R ¹ and R ² are each independently a hydrogen atom, a metal atom, or a substituted or unsubstituted alkyl group. When R ¹ and R ² are alkyl groups, it is preferably a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms. Moreover, when R < ¹ >, R < ² > is a metal atom, it is preferable that it is an alkali metal atom, and it is more preferable that it is sodium or potassium. R ³ represents a substituted or unsubstituted alkenyl group or a sulfonic acid group (—SO ₃ X). When R ³ is an alkenyl group, it is preferably a substituted or unsubstituted alkenyl group having 2 to 8 carbon atoms. When R ³ is a sulfonic acid group (—SO ₃ X), X is a hydrogen ion, an ammonium ion, or a metal ion. When X is a metal ion, X is preferably a sodium ion or a potassium ion.

As a specific trade name of the compound represented by the general formula (1), a trade name “New Coal 291-M” (available from Nippon Emulsifier Co., Ltd.) having a sulfonic acid group (—SO ₃ X) in R ³ ), Trade name “New Coal 292-PG” (available from Nippon Emulsifier Co., Ltd.), trade name “Perex TA” (available from Kao Corporation), and trade name “Latemul ASK” which is dipotassium alkenyl succinate. (Available from Kao Corporation).

  The compound represented by the general formula (1) has a particularly high effect of adsorbing on the surface of the copper film and protecting it from excessive etching and corrosion. Thereby, a smooth to-be-polished surface can be obtained.

  The present invention is that the most effective combination of the (C) anionic surfactant is a combination of ammonium dodecylbenzenesulfonate, which is an alkylbenzene sulfonate, and dipotassium alkenyl succinate, which is an alkenyl succinate. It has been clarified by studies by the authors.

1.4 Other Additives 1.4.1 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. Of these oxidizing agents, ammonium persulfate, potassium persulfate, and hydrogen peroxide are particularly preferable in view of oxidizing power, compatibility with a protective film, ease of handling, and the like. These oxidizing agents can be used alone or in combination of two or more. 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 the above range, a sufficient polishing rate for the copper film may not be obtained. On the other hand, when the content exceeds the above range, dishing or corrosion of the copper film may be caused.

1.4.2 Water-soluble polymer The chemical mechanical polishing aqueous dispersion according to this embodiment may contain a water-soluble polymer, if necessary. By adding a water-soluble polymer, dishing and corrosion of the copper film can be effectively suppressed.

  Examples of the water-soluble polymer include polyacrylic acid and salts thereof, polymethacrylic acid and salts thereof, polyvinyl alcohol, polyvinyl pyrrolidone, and polyacrylamide. These water-soluble polymers can be used singly or in combination of two or more.

  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 has a weight average molecular weight (Mw) of preferably 10,000 to 1,500,000, more preferably 40,000 to 1,200,000. When the weight average molecular weight is within the above range, polishing friction can be reduced, and dishing and erosion of the copper film can be suppressed. In addition, the copper film can be polished stably. If the weight average molecular weight is less than 10,000, the effect of reducing polishing friction is small, so that dishing and erosion of the copper film may not be suppressed. On the other hand, when the weight average molecular weight exceeds 1,500,000, the dispersion stability of the silica particles is impaired, and the aggregated silica particles may increase the scratches on the copper film. In addition, the viscosity of the chemical mechanical polishing aqueous dispersion may increase excessively, causing a problem such as a load on the slurry supply apparatus.

  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. It is. If the content of the water-soluble polymer is less than the above range, dishing of the copper film cannot be effectively suppressed. On the other hand, when the content of the water-soluble polymer exceeds the above range, the silica particles may be aggregated or the polishing rate may be reduced.

  In general, when abrasive grains containing a large amount of sodium or potassium are used in the chemical mechanical polishing aqueous dispersion, sodium or potassium derived from the abrasive grains remains on the surface of the object to be polished even by a cleaning operation after polishing. It is thought to cause deterioration of the electrical characteristics of the device, and its use has been avoided. However, by adding the water-soluble polymer, the surface of the copper film is effectively protected, and adsorption of sodium and potassium to the surface of the copper film can be suppressed. It becomes possible to remove sodium and potassium. Furthermore, since the water-soluble polymer can be easily removed by a cleaning operation, it does not remain on the surface of the copper film and deteriorate the electrical characteristics of the device.

1.5 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, hydrogen bonds between silanol groups present on the surface of the silica particles cannot be broken, and the silica particles may be aggregated. 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.

1.6 Method for Producing Chemical Mechanical Polishing Aqueous Dispersion The chemical mechanical polishing aqueous dispersion according to this embodiment comprises (A) silica particles, (B) an organic acid, and (C) an anionic surfactant in pure water. It can be prepared by adding an agent and other additives and 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.

  As a specific example, liquid (I) which is an aqueous dispersion containing water and (A) silica particles, water, (B) a liquid (II) containing an organic acid and (C) an anionic surfactant, A kit for mixing the liquid to prepare the chemical mechanical polishing aqueous dispersion may be mentioned.

  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 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.

1.7 Applications The chemical mechanical polishing aqueous dispersion according to this embodiment can be suitably used for chemical mechanical polishing of an object to be processed (for example, a semiconductor device) having a copper film on its surface. That is, according to the chemical mechanical polishing aqueous dispersion according to this embodiment, (B) the polishing rate for the copper film is accelerated by the action of the organic acid, and (C) the surface of the copper film is made by the action of the anionic surfactant. Since it can be appropriately protected, the surface of the copper film can be selectively polished at high speed without causing defects in the copper film and the low dielectric constant insulating film even under normal polishing pressure conditions. Moreover, according to the chemical mechanical polishing aqueous dispersion according to this embodiment, metal contamination of the wafer can be reduced.

  More specifically, the chemical mechanical polishing aqueous dispersion according to the present embodiment uses, for example, a damascene method in which a semiconductor device using a low dielectric constant insulating film as an insulating film and copper or a copper alloy as a wiring material is used. In the manufacturing process, the present invention can be applied to a process (first polishing process) in which the copper film on the barrier metal film is removed by chemical mechanical polishing.

  In the present specification, the “copper film” refers to a film formed from copper or a copper alloy, and the copper content in the copper alloy is preferably 95% by mass or more.

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 In order to remove the copper film 60 deposited on the barrier metal film 50 of the object 100, chemical mechanical polishing is performed using the chemical mechanical polishing aqueous dispersion according to the present invention. First, the copper film 60 is continuously polished by chemical mechanical polishing until the barrier metal film 50 is exposed. Usually, it is necessary to stop the polishing after confirming that the barrier metal film 50 is exposed. However, the chemical mechanical polishing aqueous dispersion according to the present invention has a very high polishing rate for the copper film, but hardly polishes the barrier metal film. For this reason, as shown in FIG. 5, since the chemical mechanical polishing cannot proceed when the barrier metal film 50 is exposed, the chemical mechanical polishing can be self-stopped.

  Moreover, since the chemical mechanical polishing aqueous dispersion according to the present invention contains (C) an anionic surfactant, polishing friction can be greatly reduced. Thereby, even if chemical mechanical polishing is continued after the barrier metal film 50 is exposed, dishing of the copper film as shown in FIG. 6 does not occur.

  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 400 mL / min, more preferably 100 to 300 mL / min As described above, in this example, a semiconductor device having excellent flatness of the surface to be polished is obtained. In addition, chemical mechanical polishing can be self-stopped without excessive polishing of the copper film. Further, even if polishing is performed with a normal polishing pressure, the polishing friction can be significantly reduced, so that the load on the lower insulating film 30 and the low dielectric constant insulating film 20 can be reduced.

3. 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.

The obtained silica particle dispersion A was subjected to ²⁹ Si-NMR spectrum measurement by DD-MAS method using “Nuclear Magnetic Resonance Spectrometer AVANCE300 for solid measurement” manufactured by Bruker, and peak separation was performed using peak separation software WinFit. Then, the signal area ratio of the silicon in the Q1, Q2, Q3, and Q4 states was determined, and the number of silanol groups was calculated according to the above formula (2). As a result, it was 2.3 × 10 ²¹ / g.

  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.

  The silica particle dispersions B to E and G to I were obtained by the same method as described above while controlling the heat aging time, the type of basic compound and the amount added.

The silica particle dispersion F was produced as follows. First, 35 kg of high-purity colloidal silica (product number: PL-2; solid content concentration 20 mass%, pH 7.4, average secondary particle size 66 nm) manufactured by Fuso Chemical Industry Co., Ltd. and 140 kg of ion-exchanged water were charged into a 40 L autoclave. Hydrothermal treatment was performed at 160 ° C. for 3 hours under a pressure of 0.5 MPa. Next, the dispersion aqueous solution containing the silica particles was concentrated under reduced pressure at a boiling point of 78 ° C. to obtain a silica particle dispersion F having a silica concentration of 20% by mass, an average secondary particle size of 62 nm, and a pH of 7.5. . The obtained silica particle dispersion A was subjected to ²⁹ Si-NMR spectrum measurement by DD-MAS method using “Nuclear Magnetic Resonance Spectrometer AVANCE300 for solid measurement” manufactured by Bruker, and peak separation was performed using peak separation software WinFit. Then, the signal area ratio of silicon in the Q1, Q2, Q3, and Q4 states was obtained, and the number of silanol groups was calculated according to the above formula (2), and was 2.9 × 10 ²¹ / g.

  The silica particle dispersion J is produced by a known method using a sol-gel method using tetraethoxysilane as a raw material.

  The silica particle dispersion K was obtained by obtaining a dispersion by the same method as the method for preparing the silica particle dispersion A, followed by further hydrothermal treatment (in the preparation of the silica particle dispersion A, the autoclave treatment was performed for a longer time. And silanol condensation was carried out).

The silica particle dispersion L was produced as follows. First, 35 kg of high-purity colloidal silica (product number: PL-2; solid content concentration 20 mass%, pH 7.4, average secondary particle size 66 nm) manufactured by Fuso Chemical Industry Co., Ltd. was dispersed in 140 kg of ion-exchanged water to obtain a silica concentration. Obtained a silica particle dispersion K having a solid content concentration of 20% by mass, an average secondary particle diameter of 62 nm, and a pH of 7.5. The silica particle dispersion K thus obtained was subjected to ²⁹ Si-NMR spectrum measurement by DD-MAS method using “Nuclear Magnetic Resonance Spectrometer AVANCE300 for solid measurement” manufactured by Bruker, and peak separation was performed using peak separation software WinFit. Then, the signal area ratio of silicon in the Q1, Q2, Q3, and Q4 states was obtained, and the number of silanol groups was calculated according to the above formula (2), and was 2.9 × 10 ²¹ / g.

  Table 1 summarizes the physical property values of the silica particle dispersions A to L produced.

3.2 Additives 3.2.1 Preparation of aqueous solution of polyvinylpyrrolidone 60 g of N-vinyl-2-pyrrolidone, 240 g of water, 0.3 g of 10% by weight aqueous sodium sulfite solution and 10% by weight of t-butyl hydroper Polyvinylpyrrolidone (K30) was produced by adding 0.3 g of an aqueous oxide solution and stirring for 5 hours under a nitrogen atmosphere at 60 ° C. The obtained polyvinylpyrrolidone (K30) was measured 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). As a result, the weight average molecular weight (Mw) in terms of polyethylene glycol was 40,000. Further, the amount of amino group calculated from the charged amount of monomer was 0 mol / g, and the amount of cationic functional group was 0 mol / g.

  Moreover, polyvinylpyrrolidone (K60) was produced | generated by adjusting the addition amount of the said component, reaction temperature, and reaction time suitably. In addition, as a result of measuring the weight average molecular weight (Mw) of the obtained polyvinyl pyrrolidone (K60) by the method similar to the above, it was 700,000. The amount of amino group calculated from the charged amount of monomer was 0 mol / g, and the amount of cationic functional group was 0 mol / g.

3.2.2 Other Additives In Table 3, the vinyl pyrrolidone / vinyl acetate copolymer is trade name “PVP / VA copolymer S-630” (manufactured by ISP Japan, molecular weight 45,000, vinyl pyrrolidone: vinyl acetate. = 60: 40) was used.

  In Table 2, the trade name “PVA205” (manufactured by Kuraray Co., Ltd., polymerization degree 500, molecular weight 2200) was used as the polyvinyl alcohol.

  In Table 3, the trade name “Daicel HEC SP900” (manufactured by Daicel Chemical Industries, Ltd., molecular weight of 1.4 million) was used as hydroxyethyl cellulose.

  In Table 3, the trade name “PEG-1500” (manufactured by Sanyo Chemical Co., Ltd., number average molecular weight 550) was used as the polyethylene glycol.

  In Tables 2 to 3, the acetylenic diol type nonionic surfactant is trade name “Surfinol 485” (manufactured by Air Products, 2,4,7,9-tetramethyl-5-decyne-4,7-diol. -Dipolyoxyethylene ether).

  In Table 3, the trade name “Emulgen 104P” (manufactured by Kao Corporation, polyoxyethylene lauryl ether) was used as the alkyl ether type nonionic surfactant.

3.3 Preparation of Chemical Mechanical Polishing Aqueous Dispersion 50 parts by mass of ion-exchanged water and silica particle dispersion A containing 0.5 parts by mass in terms of silica are placed in a polyethylene bottle, and 1 is added to alanine. 0.2 parts by mass, 0.03 parts by mass of dipotassium alkenyl succinate (trade name “Latemul ASK”, manufactured by Kao Corporation), and 0.02 parts by mass of polyvinylpyrrolidone (K30) aqueous solution (weight average molecular weight 40,000) in terms of polymer amount An amount corresponding to 05 parts by mass was added, and further a 10% by mass aqueous potassium hydroxide solution was added to adjust the pH of the chemical mechanical polishing aqueous dispersion to 9.3. Next, 1.5 parts by mass of ammonium persulfate was added and stirred for 15 minutes. Finally, ion-exchanged water is added so that the total amount of all the components becomes 100 parts by mass, and then filtered through a filter having a pore size of 5 μm to obtain a chemical mechanical polishing aqueous dispersion S1 having a pH of 9.3. It was.

Silica particles are recovered from the chemical mechanical polishing aqueous dispersion S1 by centrifugation, and ²⁹ Si-NMR spectrum measurement is performed by DD-MAS method using a Bruker's “Nuclear Magnetic Resonance Spectrometer AVANCE300 for solid measurement”. Peak separation was performed using separation software WinFit, the signal area ratio of silicon in the Q1, Q2, Q3, and Q4 states was calculated, and the number of silanol groups was calculated according to the above formula (2). 2.3 × 10 ²¹ / g. From this result, it was found that even when silica particles were recovered from the chemical mechanical polishing aqueous dispersion, the number of silanol groups in the silica particles could be quantified, and the same result as the silica particle dispersion was obtained.

  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 S16 are the same except that the types and contents of the silica particle dispersion, organic acid, surfactant, and other additives are changed as shown in Tables 2 to 3. It was produced in the same manner as the chemical mechanical polishing aqueous dispersion S1.

  The obtained chemical mechanical polishing aqueous dispersions S1 to S16 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 Tables 2 to 3. In Tables 2 to 3, when the particle sedimentation and the difference in density are not recognized, “◯”, when only the density difference is recognized as “Δ”, when both the particle sedimentation and the density difference are recognized. Evaluated as “x”.

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 while supplying any one of the chemical mechanical polishing aqueous dispersions S1 to S16, the following various polishing rate measurement substrates were 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 Tables 2 to 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.

(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 was measured using an electroconductive film thickness measuring instrument (model “Omnimap RS75”, manufactured by KLA Tencor). The polishing rate was calculated from the film thickness decreased by mechanical polishing and the polishing time.

3.4.1b Wafer contamination The copper film was polished in the same manner as in “3.4.1a Measurement of polishing rate”. Subsequently, ultrapure water was dropped on the surface of the sample to extract the residual metal on the surface of the copper film, and the extract was quantified by ICP-MS (manufactured by Yokogawa Analytical Systems, model number “Agilent 7500s”). The results are shown in Tables 2 to 3. 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 S16, with respect to the following patterned wafer, the point at which the tantalum film was detected on the surface to be polished was determined as the polishing end point. The polishing treatment was performed in the same manner as the polishing conditions in “4.1a Measurement of polishing rate”, and the flatness and the presence or absence of defects were evaluated by the following methods. The results are also shown in Tables 2 to 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.

3.4.2a Evaluation of flatness Copper wiring width (line, L) / insulation per surface to be polished of the patterned wafer after the polishing process using a high resolution profiler (model “HRP240ETCH” manufactured by KLA Tencor) The dishing amount (nm) in the copper wiring portion having a film width (space, S) of 100 μm / 100 μm was measured. The results are also shown in Tables 2 to 3. Note that the dishing 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 layer). The dishing amount is preferably -5 to 30 nm, more preferably -2 to 20 nm.

  The amount of erosion in the portion where the fine wiring length in the pattern of 9 μm / 1 μm in the copper wiring width (line, L) / insulating film width (space, S) is continuously 1000 μm per polished surface of the patterned wafer after the polishing process (Nm) was measured. The results are also shown in Tables 2 to 3. Note that the erosion amount is negative when the upper surface of the insulating layer of the fine wiring portion is above the field surface (the upper surface of the wide insulating layer that is not the wiring portion). The erosion amount is preferably -5 to 30 nm, more preferably -2 to 20 nm.

3.4.2b Corrosion Evaluation 10 nm ² using a defect inspection apparatus (manufactured by KLA Tencor, model “2351”) for a copper area of 1 cm × 1 cm per surface to be polished of the patterned wafer after the polishing process. The number of defects having a size of ˜100 nm ² was evaluated. In Tables 2 to 3, ◯ is the most preferable state with 0 to 10 corrosions. Δ is 11 to 100, which is a preferable condition. X is a state where 101 or more corrosions exist, and it is determined that the polishing performance is poor.

3.4.2c Evaluation of copper residue on fine wiring pattern For the surface to be polished of the patterned wafer after the polishing process, a wiring portion having a width of 0.18 μm and an insulating portion having a width of 0.18 μm (both are 1.6 mm in length). For a portion where 1.25 mm of a pattern in which alternating patterns are continuously arranged in a direction perpendicular to the length direction is used, an ultrahigh resolution field emission scanning electron microscope “S-4800” (manufactured by Hitachi High-Technology Corporation) is used. The presence or absence of copper residue (copper residue) in the isolated wiring portion having a width of 0.18 μm was evaluated. Tables 2 to 3 show the evaluation results of the remaining copper. The evaluation item “copper residue” in the table represents a copper residue on the pattern, and “◯” represents that the copper residue is completely eliminated and is the most preferable state. “Δ” represents a slightly preferable state in which copper residues are present in some patterns. “X” indicates that copper residue is generated in all patterns and the polishing performance is poor.

3.4.3 Evaluation Results In Examples 1 to 8, the polishing rate for the copper film is sufficiently high as 8,000 angstrom / min or more, and the polishing rate for the barrier metal film is sufficiently low as 1 to 3 angstrom / min. Therefore, it was found that the polishing selectivity for the copper film was excellent. In any of the examples, there was almost no wafer contamination, no defects were observed, and the storage stability of the chemical mechanical polishing aqueous dispersion was good.

  On the other hand, since S9 used in Comparative Example 1 does not contain (C) an anionic surfactant, it suppresses the occurrence of copper film dishing and insulating film erosion in the polishing test of the patterned wafer. I could not. Further, in the polishing test of the polishing rate measuring substrate, the polishing rate for the tantalum film was 20 angstroms / minute, and it could not be said that the polishing selectivity for the copper film was excellent. Furthermore, although S9 uses the silica particle dispersion G containing 11250 ppm of sodium, since it does not contain (C) an anionic surfactant, the occurrence of wafer contamination could not be suppressed.

S10 used in Comparative Example 2 uses a silica particle dispersion H having a silanol group number of 2.5 × 10 ²¹ / g, but (C) an alkyl ether type nonion instead of an anionic surfactant. Since a surfactant was used, the storage stability was not good. Moreover, in the polishing test of the patterned wafer, the effect of suppressing copper film dishing and insulating film erosion was poor, and a good polished surface could not be obtained. On the other hand, in the polishing test of the substrate for polishing rate measurement, the polishing rate for the tantalum film was 12 Å / min, and it could not be said that the polishing selectivity for the copper film was excellent.

S11 used in Comparative Example 3 uses a silica particle dispersion I having a silanol group number of 2.9 × 10 ²¹ / g, but (C) an alkyl ether type nonion instead of an anionic surfactant. Since a surfactant was used, the storage stability was not good. Further, in the polishing test for the polishing rate measuring substrate, a decrease in the polishing rate with respect to the copper film was observed. On the other hand, in the polishing test of the patterned wafer, a copper residue was generated and a good polished surface could not be obtained.

S12 used in Comparative Example 4 uses a silica particle dispersion J having a silanol group number exceeding 3.0 × 10 ²¹ / g and further does not contain (C) an anionic surfactant. Therefore, in the polishing test of the substrate for measuring the polishing rate, a decrease in the polishing rate with respect to the copper film was recognized as compared with Example 5 in which other components and the content thereof were the same. On the other hand, in the polishing test of the patterned wafer, a copper residue was generated and a good polished surface could not be obtained.

  S13 used in Comparative Example 5 does not contain (B) an organic acid. Therefore, in the polishing test of the substrate for polishing rate measurement, a significant decrease in the polishing rate with respect to the copper film was recognized as compared with Example 1 in which other components and the contents thereof were the same. On the other hand, in the polishing test of the patterned wafer, a copper residue was generated and a good polished surface could not be obtained.

  S14 used in Comparative Example 6 does not contain (A) silica particles. Therefore, in the polishing test of the polishing rate measuring substrate, the polishing rate for the copper film was remarkably reduced, and it could not be said to be a practical slurry.

S15 used in Comparative Example 7 uses a silica particle dispersion K having a silanol group number of less than 2.0 × 10 ²¹ / g. Therefore, in the polishing test of the patterned wafer, since the mechanical strength of the silica particle dispersion K is too high, the occurrence of copper film dishing is recognized, and the occurrence of corrosion and copper residue is also recognized, and a good polished surface is obtained. I couldn't.

S16 used in Comparative Example 8 uses a silica particle dispersion L having a silanol group number exceeding 3.0 × 10 ²¹ / g, and (C) an acetylenic diol type nonion instead of an anionic surfactant. A surfactant is used. Therefore, in the polishing test of the polishing rate measuring substrate, the polishing rate for the tantalum film was remarkably increased, and the high polishing selectivity for the copper film was lost.

  From the above results, it was found that the chemical mechanical polishing aqueous dispersions of Examples 1 to 8 have a high polishing rate and high polishing selectivity with respect to the copper film, and can reduce metal contamination and polishing defects of the wafer.

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, 100 ... Object to be processed

Claims (12)

(A) silica particles;
(B) an organic acid;
(C) an anionic surfactant;
An aqueous dispersion for chemical mechanical polishing for polishing a copper film containing
The (A) silica particle is a chemical mechanical polishing aqueous dispersion having the following chemical properties.
^The number of silanol groups calculated from the signal area of the ²⁹ Si-NMR spectrum is 2.0 to 3.0 × 10 ²¹ / g. In claim 1,
The (C) anionic surfactant is a chemical mechanical polishing water having a carboxyl group, a sulfonic acid group, a phosphoric acid group, and at least one functional group selected from ammonium salts and metal salts of these functional groups. System dispersion. In claim 2,
The (C) anionic surfactant is an alkyl sulfate, an alkyl ether sulfate, an alkyl ether carboxylate, an alkyl benzene sulfonate, an alpha sulfo fatty acid ester, an alkyl polyoxyethylene sulfate, an alkyl phosphate, An aqueous dispersion for chemical mechanical polishing, which is one selected from monoalkyl phosphate salts, naphthalene sulfonates, alpha olefin sulfonates, alkane sulfonates, and alkenyl succinates. In any one of Claims 1 thru | or 3,
The (C) anionic surfactant is a chemical mechanical polishing aqueous dispersion, which is a compound represented by the following general formula (1).

(In the general formula (1), R ¹ and R ² each independently represents a hydrogen atom, a metal atom, or a substituted or unsubstituted alkyl group, and R ³ represents a substituted or unsubstituted alkenyl group or sulfonic acid group. represents a _(-SO 3 X). However, X represents a hydrogen ion, an ammonium ion or a metal ion.) In any one of Claims 1 thru | or 4,
The (B) organic acid is an aqueous dispersion for chemical mechanical polishing, which is an amino acid. In claim 5,
The chemical mechanical polishing aqueous dispersion, wherein the amino acid is at least one selected from glycine, alanine, phenylalanine, tryptophan, and histidine. In any one of Claims 1 thru | or 6,
Further, the (A) silica particles are chemical mechanical polishing aqueous dispersions 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 any one of Claims 1 thru | or 7,
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 to 8,
(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 to 9,
An aqueous dispersion for chemical mechanical polishing having a pH of 6-12. A method for chemically mechanically polishing an object having a copper film formed on a barrier metal film,
The chemical mechanical polishing is carried out using the chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 10, and the chemical mechanical polishing is self-stopped when the barrier metal film is exposed. , Chemical mechanical polishing method. A method of producing a chemical mechanical polishing aqueous dispersion by mixing at least (A) silica particles, (B) an organic acid, and (C) an anionic surfactant,
Said (A) silica particle is a manufacturing method of the aqueous dispersion for chemical mechanical polishing which has the following chemical property.
^The number of silanol groups calculated from the signal area of the ²⁹ Si-NMR spectrum is 2.0 to 3.0 × 10 ²¹ / g.

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