JP5333739B2 - 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 dispersing element for chemical mechanical polishing having high polishing speed and high polishing selectivity to a copper film without causing any defects to the copper film and a low-dielectric-constant insulation film even under normal pressure conditions, and having a small amount of metal contamination in a wafer, and to provide a chemical mechanical polishing method using the aqueous dispersing element for chemical mechanical polishing. <P>SOLUTION: The aqueous dispersing element for chemical mechanical polishing polishes the copper film. The copper film contains: a silica particle A; an organic acid B; and a water-soluble polymer C having properties as a Lewis base of which weight-average molecular weight is not less than ten thousand and not more than a million and a half. The silica particle A has the following chemical properties of a silanol group calculated from signal area of a<SP>29</SP>Si-NMR spectrum being 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 step (when another type of material film such as a barrier metal film is exposed), it is extremely 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 comprises:
(A) silica particles;
(B) an organic acid;
(C) a water-soluble polymer having properties as a Lewis base having a weight average molecular weight of 10,000 to 1,500,000,
An aqueous dispersion for chemical mechanical polishing for polishing a copper film containing silane, 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.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the (C) water-soluble polymer may have at least one molecular structure selected from a nitrogen-containing heterocyclic ring and a cationic functional group.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the water-soluble polymer (C) is a homopolymer having a nitrogen-containing monomer as a repeating unit or a copolymer having a nitrogen-containing monomer as a repeating unit. be able to.

  In the chemical mechanical polishing aqueous dispersion according to the present invention, the nitrogen-containing monomer is N-vinylpyrrolidone, (meth) acrylamide, N-methylolacrylamide, N-2-hydroxyethylacrylamide, acryloylmorpholine, N, N-. Selected from dimethylaminopropylacrylamide and its diethyl sulfate, N, N-dimethylacrylamide, N-isopropylacrylamide, N-vinylacetamide, N, N-dimethylaminoethyl methacrylic acid and its diethyl sulfate, and N-vinylformamide Can be at least one.

  In the chemical mechanical polishing aqueous dispersion according to the present invention, the nitrogen-containing monomer may be N-vinylpyrrolidone.

  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 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 at least (A) silica particles, (B) an organic acid, and (C) a Lewis base property having a weight average molecular weight of 10,000 to 1,500,000. And (A) the silica particles have the following chemical properties: a method for producing a chemical mechanical polishing aqueous dispersion.

^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 The chemical mechanical polishing aqueous dispersion according to this embodiment comprises (A) silica particles, (B) an organic acid, and (C) a Lewis having a weight average molecular weight of 10,000 to 1,500,000. An aqueous dispersion for chemical mechanical polishing for polishing a copper film containing a water-soluble polymer having a property as a base, wherein the (A) silica particle has a signal area of ²⁹ Si-NMR spectrum. The number of silanol groups calculated from is 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 (1) 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 (1) 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 equation and converting the unit, the following equation (2) can be derived.

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

  In addition, all the average particle diameters of the silica particle in this specification are calculated based on (2) Formula.

  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. Since the exemplified amino acids can be easily coordinated to copper ions eluted into the chemical mechanical polishing aqueous dispersion by polishing the copper film, precipitation of copper can be prevented. As a result, polishing defects such as scratches can be suppressed. Furthermore, the water-soluble polymer (C) to be described later may be adsorbed on the surface of the copper film depending on the type and amount of addition, which may hinder the polishing and reduce the polishing rate. Thus, (C) there is an effect of increasing the polishing rate of the copper film despite the addition of the water-soluble polymer. In addition, by containing the exemplified amino acids, sodium ions and potassium ions that are crushed during polishing and eluted from the silica particles are inhibited from being adsorbed on the surface of the copper film, thereby promoting release into the solution. As a result, it can be effectively removed from the surface of the workpiece.

  (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.

1.3 (C) Water-soluble polymer The chemical mechanical polishing aqueous dispersion according to this embodiment comprises (C) a water-soluble polymer having a property as a Lewis base having a weight average molecular weight of 10,000 to 1.5 million ( Hereinafter, it is also simply referred to as “water-soluble polymer”). The (C) water-soluble polymer has properties as a Lewis base, so that it is easily adsorbed (coordinated bond) on the surface of the copper film, and has an effect of suppressing the occurrence of dishing and corrosion of the copper film.

  The (C) water-soluble polymer preferably has at least one molecular structure selected from a nitrogen-containing heterocyclic ring and a cationic functional group. The cationic functional group is more preferably an amino group. The nitrogen-containing heterocyclic ring and the cationic functional group have properties as a Lewis base, and are effective in adsorbing (coordinating bonds) on the surface of the copper film and suppressing the occurrence of dishing and corrosion of the copper film. Moreover, since it can be easily removed in the cleaning step, it is preferable that the object to be polished is not contaminated.

  The (C) water-soluble polymer is more preferably a homopolymer having a nitrogen-containing monomer as a repeating unit or a copolymer containing a nitrogen-containing monomer as a repeating unit. Examples of the nitrogen-containing monomer include N-vinylpyrrolidone, (meth) acrylamide, N-methylolacrylamide, N-2-hydroxyethylacrylamide, acryloylmorpholine, N, N-dimethylaminopropylacrylamide and its diethyl sulfate, N , N-dimethylacrylamide, N-isopropylacrylamide, N-vinylacetamide, N, N-dimethylaminoethylmethacrylic acid and its diethyl sulfate, and N-vinylformamide. Among these monomers, N-vinylpyrrolidone having a nitrogen-containing hetero five-membered ring in the molecular structure is particularly preferable. N-Vinylpyrrolidone is easy to form a coordination bond with a copper ion via a nitrogen atom on the ring, increases the affinity with copper and the copper ion, and can be adsorbed on the surface of the copper film to be appropriately protected. it can.

  When the (C) water-soluble polymer is a copolymer containing a nitrogen-containing monomer as a repeating unit, not all the monomers need to be nitrogen-containing monomers, and at least one of the nitrogen-containing monomers described above As long as it is included. Examples of the monomer that can be copolymerized with the nitrogen-containing monomer include acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, vinyl ethyl ether, divinylbenzene, vinyl acetate, and styrene.

  The (C) water-soluble polymer is preferably a homopolymer or copolymer having a cationic functional group. For example, at least one of the repeating units represented by the following general formula (3) or (4) It may be a homopolymer or copolymer (hereinafter also referred to as “specific polymer”).

(In the above general formulas (3) and (4), R ¹ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and R ² represents a substituted or unsubstituted methylene group or 2 carbon atoms. Represents a substituted or unsubstituted alkylene group having 8 to 8, R ³ , R ⁴ and R ⁵ each independently represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and A represents a single bond or — .M representing O- or a -NH- ^- represents an anion).

  A in the repeating unit represented by the general formulas (3) and (4) represents —O— or —NH—, and —O— is more preferable. When A is —NH—, the stability of the silica particles is lowered in relation to the content of the specific polymer or other components, and the abrasive grains may settle when stored for a long time. In such a case, redispersion processing such as ultrasonic dispersion is required before use, which increases the work burden.

The counter anion (M ⁻ ) is preferably a halide ion, an organic anion, or an inorganic anion. More preferred are hydroxide ion, chloride ion, bromide ion, NH ₃ -conjugated base NH _2- , alkyl sulfate ion, perchlorate ion, hydrogen sulfate ion, acetate ion and alkylbenzene sulfonate ion. Particularly preferred are chloride ion, alkyl sulfate ion, hydrogen sulfate ion, acetate ion and alkylbenzene sulfonate ion. By using an organic anion, metal contamination of the object to be polished can be avoided, and alkyl sulfate ions are particularly preferable from the viewpoint that they can be easily removed after completion of polishing.

  Furthermore, the specific polymer is more preferably a copolymer containing a repeating unit represented by the following general formula (5). The copolymer containing the repeating unit represented by the following general formula (5) is represented by the repeating unit represented by the general formula (3) and the general formula (4) and the following general formula (5). The polymer may be a polymer in which the repeating units are randomly bonded, and the repeating unit represented by the general formula (3) and the general formula (4) and the repeating unit represented by the following general formula (5). It may be a block copolymer.

(In the general formula (5), R ⁶ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.)

  When the specific polymer is a copolymer including the repeating unit represented by the general formula (3) and the repeating unit represented by the general formula (4), the repeating represented by the general formula (3) is used. When the number of moles of the unit is n and the number of moles of the repeating unit represented by the general formula (4) is m, sufficient performance can be obtained even when the molar ratio n / m is a ratio of 10/0 to 0/10. Although it can be obtained, good results can be obtained when the ratio is preferably 10/0 to 1/9, more preferably 10/0 to 2/8, particularly preferably 9/1 to 3/7. it can.

  In addition, content of the repeating unit represented by the said General formula (3) and the repeating unit represented by the said General formula (4) is computed from the preparation amount of the monomer containing an amino group, and subsequent neutralization amount. It can also be measured by titrating a specific polymer with an acid or a base.

  When the specific polymer is a copolymer containing the repeating unit represented by the general formula (3) or (4) and the repeating unit represented by the general formula (4), When the number of moles of the repeating unit represented is q and the number of moles of the repeating unit represented by the general formula (3) or (4) is p, the molar ratio q / p is 9/1 to 1/9. Particularly good results can be obtained when it is within the range.

  The amino group content of the specific polymer can be from 0 to 0.100 mol / g, preferably from 0.0005 to 0.010 mol / g, more preferably when calculated from the monomer charge. Is 0.002 to 0.006 mol / g.

  The cationic functional group content of the specific polymer can be 0 to 0.100 mol / g, preferably 0.0005 to 0.010 mol / g, when calculated from the monomer charge. More preferably, it is 0.002-0.006 mol / g.

  As the weight average molecular weight of the (C) 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 (C) water-soluble polymer has a weight average molecular weight (Mw) of 10,000 to 1,500,000, 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. Furthermore, when a fine wiring pattern is polished, the occurrence of copper residue on the pattern becomes remarkable, which is not practical.

  The content of the water-soluble polymer (C) is preferably 0.001 to 1.0% by mass, more preferably 0.01 to 0.00%, based on the total mass of the chemical mechanical polishing aqueous dispersion. 5% by mass. 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 dispersion, sodium or potassium derived from the abrasive grains remains on the surface of the workpiece even after a 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, since the (C) water-soluble polymer has properties as a Lewis base, it 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 adsorption of sodium and potassium to the surface of the copper film can be suppressed, and the sodium and potassium can be easily removed from the surface of the copper film by washing. It becomes. Further, since the water-soluble polymer (C) 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.

1.4 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. 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 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 Surfactant The chemical mechanical polishing aqueous dispersion according to this embodiment may contain a surfactant as necessary. Examples of the surfactant include nonionic surfactants, anionic surfactants, and 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. Moreover, silicone type surfactant, polyvinyl alcohol, cyclodextrin, polyvinyl methyl ether, hydroxyethyl cellulose and the like are also included.

  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.

1.5 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 Manufacturing Method of Chemical Mechanical Polishing Aqueous Dispersion The chemical mechanical polishing aqueous dispersion according to this embodiment has (A) silica particles, (B) organic acid, and (C) weight average molecular weight directly in pure water. It can be prepared by adding a water-soluble polymer having properties as a Lewis base of 10,000 to 1,500,000 and less, 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 specific examples, liquid (I) which is an aqueous dispersion containing water and (A) silica particles, water, (B) an organic acid, and (C) a property as a Lewis base having a weight average molecular weight of 10,000 to 1,500,000. And a kit for preparing the aqueous dispersion for chemical mechanical polishing by mixing these liquids.

  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 are used. 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 to obtain a more uniform 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 the present embodiment, by containing a water-soluble polymer having specific physical properties, polishing friction with the surface to be polished can be reduced. Even under pressure conditions, the copper film on the surface can be selectively polished at high speed without causing defects in the copper film and the low dielectric constant insulating film. 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.

  Further, the chemical mechanical polishing aqueous dispersion according to the present invention contains (C) a water-soluble polymer having a property as a Lewis base having a weight average molecular weight of 10,000 to 1,500,000. It 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 chemical polishing aqueous dispersion supply rate; preferably 50 to 400 mL / min, more preferably 100 to 300 mL / min

  As described above, in this specific example, a semiconductor device having excellent flatness of a surface to be polished can be obtained, and chemical mechanical polishing can be self-stopped without excessively polishing 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. The obtained spectrum was subjected to peak separation using peak separation software WinFit, and the signal area ratio of Q1, Q2, Q3, and Q4 was calculated, and the number of silanol groups was calculated by the above formula (1). 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 F was subjected to ²⁹ Si-NMR spectrum measurement by DD-MAS method using “Nuclear Magnetic Resonance Spectrometer AVANCE300 for solid measurement” manufactured by Bruker. The obtained spectrum was subjected to peak separation using the peak separation software WinFit, the signal area ratio of Q1, Q2, Q3, and Q4 was determined, and the number of silanol groups was calculated according to the above formula (1) to find 2.9 × 10 ^21. Pieces / g.

  The silica particle dispersion J 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 K was prepared by a known method by a sol-gel method using tetraethoxysilane as a raw material. Table 1 summarizes the physical property values of the silica particle dispersions A to K produced.

3.2 Synthesis of water-soluble polymer 3.2.1 Preparation of aqueous polyvinylpyrrolidone solution In a flask, 60 g of N-vinyl-2-pyrrolidone, 240 g of water, 0.3 g of a 10% by mass sodium sulfite aqueous solution and 10% by mass of t -Polyvinylpyrrolidone (K30) was produced | generated by adding 0.3 g of butyl hydroperoxide aqueous solution, and stirring for 5 hours under 60 degreeC nitrogen atmosphere. 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, polyvinyl pyrrolidone (K60) and polyvinyl pyrrolidone (K90) were produced by appropriately adjusting the addition amount of the above components, reaction temperature, and reaction time. In addition, as a result of measuring the weight average molecular weight (Mw) of the obtained polyvinyl pyrrolidone (K60) and polyvinyl pyrrolidone (K90) by the method similar to the above, they were 700,000 and 1.2 million, respectively. 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 Vinylpyrrolidone / diethylaminomethyl methacrylate copolymer A flask equipped with a reflux condenser, a dropping funnel, a thermometer, a glass tube for nitrogen substitution, and a stirrer was equipped with 70 parts by mass of diethylaminomethyl methacrylate and cetyl acrylate 5 Part by weight, 10 parts by weight of stearyl methacrylate, 10 parts by weight of N-vinylpyrrolidone, 5 parts by weight of butyl methacrylate, and 100 parts by weight of isopropyl alcohol, 0.3 parts by weight of azobisisobutyronitrile (AIBN) are added, The polymerization reaction was carried out at 60 ° C. for 15 hours under a nitrogen stream. Next, diethyl sulfate having a molar number of 0.35 times that of 1 mol of diethylaminoethyl methacrylate was added and heated under reflux at 50 ° C. for 10 hours under a nitrogen stream to synthesize a vinylpyrrolidone / diethylaminomethyl methacrylate copolymer. .

  As a result of measuring the obtained copolymer 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 100,000. Further, the amount of amino group calculated from the charged amount of monomer was 0.001 mol / g, and the amount of cationic functional group was 0.0006 mol / g.

  In addition, vinylpyrrolidone / diethylaminomethyl methacrylate copolymers having a weight average molecular weight of 400,000 and 1.8 million were synthesized by appropriately adjusting the addition amount of the above components, reaction temperature, and reaction time.

3.2.3 Vinylpyrrolidone / vinyl acetate copolymer “PVP / VA copolymer W-735 (molecular weight 32,000, vinylpyrrolidone: vinyl acetate = 70: 30)” (manufactured by ISP Japan) was used.

3.2.4 Vinylpyrrolidone / dimethylaminopropylacrylamide copolymer A flask equipped with a reflux condenser, a dropping funnel, a thermometer, a glass tube for nitrogen substitution, and a stirrer was mixed with water, 2,2′-azobis (2 -Methylpropionamidine) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., trade name “V-50”) was added in an amount of 0.6 parts by mass, and the temperature was raised to 70 ° C. Next, 70 parts by mass of N-vinylpyrrolidone and 30 parts by mass of DMAPAA (N, N-dimethylaminopropylacrylamide) were added, and a polymerization reaction was performed at 75 ° C. for 5 hours in a nitrogen stream. Subsequently, 0.2 part by mass of 2,2′-azobis (2-methylpropionamidine) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., trade name “V-50”) was added, and the mixture was 6 at 70 ° C. under a nitrogen stream. The mixture was heated under reflux for an hour to obtain an aqueous dispersion containing 11% by mass of vinylpyrrolidone / dimethylaminopropylacrylamide copolymer. The polymerization yield was 99%.

  Next, 0.32 times as many moles of diethyl sulfate as 1 mole of 2,2′-azobis (2-methylpropionamidine) dihydrochloride (trade name “V-50” manufactured by Wako Pure Chemical Industries, Ltd.) Then, the amino group was partially cationized by heating at 50 ° C. for 10 hours under a nitrogen stream.

  As a result of measuring the obtained copolymer 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 600,000. The amount of amino group calculated from the charged amount of monomer is 0.0010 mol / g, and the amount of cationic functional group is 0.0006 mol / g.

3.2.5 Polyacrylic acid 500 g of a 20% by mass aqueous acrylic acid solution was stirred at 70 ° C. under reflux in a 2 liter container charged with 1000 g of ion-exchanged water and 1 g of 5% by mass ammonium persulfate aqueous solution. It was dripped evenly over time. 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.

3.2.6 Polyethylene glycol The polyethylene glycol used was a trade name “PEG-1500” (molecular weight 550) manufactured by Sanyo Chemical Industries.

3.2.7 Hydroxyethyl cellulose The product name “Daicel HEC SP900” (molecular weight 1.4 million) manufactured by Daicel Chemical Industries, Ltd. was used.

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. .2 parts by mass, 0.03 parts by mass of an acetylenic diol type nonionic surfactant (trade name “Surfinol 485”, manufactured by Air Products), and an aqueous polyvinylpyrrolidone (K30) solution (weight average molecular weight 40,000) An amount corresponding to 0.05 parts by mass was added, and a 10% by mass aqueous potassium hydroxide solution was further 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 particle components were recovered from the chemical mechanical polishing aqueous dispersion S1 by centrifugation, and ²⁹ Si-NMR spectrum measurement was performed by the DD-MAS method using a Bruker's “Nuclear Magnetic Resonance Spectrometer AVANCE300 for solid measurement”. . The obtained spectrum was subjected to peak separation using peak separation software WinFit, the signal area ratio of Q1, Q2, Q3, and Q4 was determined, and the number of silanol groups was calculated according to the above formula (1). 2.3 × 10 ²¹ Pieces / 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 contained in the silica particles can be quantified, and the same result as the silica particle dispersion can be obtained. I understood.

  Chemical mechanical polishing aqueous dispersions S2 to S20 are the same except that the types and contents of silica particle dispersion, organic acid, water-soluble polymer, and other additives are changed as shown in Tables 2 to 3. This was prepared in the same manner as the chemical mechanical polishing aqueous dispersion S1. In Tables 2 to 3, the trade name “Emulgen 104P” (manufactured by Kao Corporation, polyoxyethylene lauryl ether) was used as the “alkyl ether type nonionic surfactant”. 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).

  The obtained chemical mechanical polishing aqueous dispersions S1 to S20 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 S20, the following various polishing rate measurement substrates were subjected to 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 also 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 S20, with respect to the wafer with the following pattern, 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. 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 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. The amount of erosion was expressed as minus when the upper surface of the insulating layer of the fine wiring portion was above the field surface (the upper surface of the wide insulating layer that was 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 each of Examples 1 to 11, the polishing rate for the copper film was sufficiently high as 8,000 angstrom / min or more, and the polishing rate for the barrier metal film was sufficiently low as 1 to 2 angstrom / min. It was. 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 S12 used in Comparative Example 1 uses a water-soluble polymer having a weight average molecular weight of 1.8 million, the polishing rate for the copper film is 4,000 in the polishing test of the polishing rate measuring substrate. It was reduced to angstrom / min. Further, in the polishing test of the patterned wafer, copper residue was generated and a good polished surface could not be obtained.

  S13 used in Comparative Example 2 does not contain (C) a water-soluble polymer. For this reason, in the polishing test of the patterned wafer, the occurrence of copper film dishing and insulating film erosion could not be suppressed, and a good polished surface could not be obtained.

  Since S14 used in Comparative Example 3 uses polyethylene glycol having a weight average molecular weight of 550, the storage stability is slightly poor. Further, in the polishing test of the patterned wafer, the occurrence of copper film dishing and insulation film erosion could not be suppressed, and a good polished surface could not be obtained.

  S15 used in Comparative Example 4 does not contain (C) a water-soluble polymer. Therefore, in the polishing test of the patterned wafer, the occurrence of copper film dishing and insulating film erosion could not be suppressed, and the occurrence of corrosion was recognized, and a good polished surface could not be obtained.

Since S16 used in Comparative Example 5 uses the silica particle dispersion J having a silanol group number of less than 2.0 × 10 ²¹ / g, the silica particles aggregate and storage stability is poor.

  S17 used in Comparative Example 6 does not contain (B) an organic acid. Therefore, in the polishing test of the polishing rate measuring substrate, the polishing rate for the copper film was remarkably reduced. Further, in the polishing test of the patterned wafer, the copper film dishing could not be suppressed. Furthermore, the copper wiring was easily corroded only by protection with the water-soluble polymer, and corrosion occurred.

  S18 used in Comparative Example 7 does not contain (A) silica particles. Therefore, the polishing rate for the copper film is remarkably reduced, and it cannot be said to be a practical slurry.

S19 used in Comparative Example 8 uses a silica particle dispersion J having a silanol group number of less than 2.0 × 10 ²¹ / g, but unlike Comparative Example 5, storage stability is achieved by balancing the composition. The property was good. However, in the polishing test of the polishing rate measuring substrate, occurrence of wafer contamination was observed. Moreover, in the polishing test of the patterned wafer, the generation of copper film dishing, corrosion, and copper residue could not be suppressed, and a good polished surface could not be obtained.

S20 used in Comparative Example 9 uses a silica particle dispersion L in which the number of silanol groups exceeds 3.0 × 10 ²¹ / g. Therefore, in the polishing test for the polishing rate measuring substrate, the polishing rate for the copper film decreased, while the polishing rate for the barrier metal film increased to 30 angstroms / minute. Further, in the polishing test of the patterned wafer, the occurrence of copper film dishing, insulating film erosion, corrosion, and copper residue was observed, and a good polished surface could not be obtained.

  From the above results, it was found that the chemical mechanical polishing aqueous dispersions of Examples 1 to 11 have a high polishing rate and a high polishing selectivity for 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) a water-soluble polymer having properties as a Lewis base having a weight average molecular weight of 10,000 to 1,500,000,
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) water-soluble polymer is an aqueous dispersion for chemical mechanical polishing having at least one molecular structure selected from a nitrogen-containing heterocyclic ring and a cationic functional group. In claim 1,
The water-soluble polymer (C) is an aqueous dispersion for chemical mechanical polishing, which is a homopolymer having a nitrogen-containing monomer as a repeating unit or a copolymer having a nitrogen-containing monomer as a repeating unit. In claim 3,
The nitrogen-containing monomer includes N-vinylpyrrolidone, (meth) acrylamide, N-methylolacrylamide, N-2-hydroxyethylacrylamide, acryloylmorpholine, N, N-dimethylaminopropylacrylamide and its diethyl sulfate, N, N An aqueous dispersion for chemical mechanical polishing, which is at least one selected from dimethylacrylamide, N-isopropylacrylamide, N-vinylacetamide, N, N-dimethylaminoethylmethacrylic acid and its diethyl sulfate, and N-vinylformamide body. In claim 3,
The aqueous dispersion for chemical mechanical polishing, wherein the nitrogen-containing monomer is N-vinylpyrrolidone. In any one of Claims 1 thru | or 5,
The (B) organic acid is an aqueous dispersion for chemical mechanical polishing, which is an amino acid. 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. Chemical mechanical polishing by mixing at least (A) silica particles, (B) organic acid, and (C) a water-soluble polymer having a property as a Lewis base having a weight average molecular weight of 10,000 to 1,500,000. A method for producing an aqueous dispersion comprising:
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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