JP2009212496A - Aqueous dispersion for chemical mechanical polishing and its manufacturing method, and chemical mechanical polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous dispersion for chemical mechanical polishing and a chemical mechanical polishing method using it, which cause less metallic contamination of a wafer by realizing both high polishing speed and high planarization characteristics without causing defects in a metal film and an insulating film. <P>SOLUTION: The aqueous dispersion for chemical mechanical polishing contains silica particles (A) and an organic acid (B). The silica particles (A) have such chemical properties that the sodium, potassium and ammonium ion contents determined by the elemental analysis by ICP emission spectrometry or ICP mass spectrometry and the quantitative analysis of ammonium ions by ion chromatography are as follows: the sodium content is within the range of 5-500 ppm; and the content of at least one kind selected from potassium and ammonium ions is within the range of 100-20,000 ppm. <P>COPYRIGHT: (C)2009,JPO&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 the manufacturing process of a semiconductor device, a multilayer laminated structure in which layers such as insulating films and metal films are generally laminated on a substrate is formed. In multi-layer stacking, generally, after depositing an interlayer insulating film or metal film on a substrate, the resulting irregularities are flattened by CMP, and new wiring is stacked on the flattened surface. The process to go is essential.

  In aqueous dispersions used for chemical mechanical polishing, silica particles are used as abrasive grains. As a raw material for producing such silica particles, an aqueous alkali silicate solution or an organic alkoxide solution is used. In the case of using an organic alkoxide solution, silica particles having a low impurity content can be produced by hydrolyzing an organic alkoxide solution such as ethyl silicate or methyl silicate, but this is economically expensive and undesirable.

  On the other hand, as described in Patent Document 1, when an alkali silicate aqueous solution (water glass) is used, usually, sodium is removed from the sodium silicate aqueous solution with an ion exchange resin or the like to produce and grow silica particles. To manufacture. However, there is a problem that alkaline earth metals such as sodium remain in the silica particles as impurities, and studies have been made to remove this and use it for CMP polishing, but it is still a practical technique. Absent.

JP 2003-197573 A

  An object of the present invention is to provide an aqueous dispersion for chemical mechanical polishing that achieves both high polishing rate and high planarization characteristics without causing defects in the metal film or insulating film, and has low metal contamination of the wafer, and chemicals using the same. It is to provide a mechanical polishing method.

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

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

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

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

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

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

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

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

  According to the chemical mechanical polishing aqueous dispersion, it is possible not only to cause defects in the metal film and the insulating film, but also to achieve both a high polishing rate and high planarization characteristics, and to reduce metal contamination of the wafer. Further, a method capable of performing chemical mechanical polishing without causing defects in the metal film or the insulating film is provided. Furthermore, a method for manufacturing a semiconductor device having damascene wiring and having high reliability is provided.

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

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

1. Chemical mechanical polishing aqueous dispersion The chemical mechanical polishing aqueous dispersion according to this embodiment is a chemical mechanical polishing aqueous dispersion containing (A) silica particles and (B) an organic acid, (A) Silica particles have the following chemical properties. The chemical property is “the content of sodium, potassium and ammonium ions measured from elemental analysis by ICP emission spectrometry or ICP mass spectrometry and quantitative analysis of ammonium ions by ion chromatography, but the content of sodium: The content of at least one selected from 5 to 500 ppm, potassium and ammonium ions: 100 to 20000 ppm is satisfied.

  Moreover, the pH of the chemical mechanical polishing aqueous dispersion according to the present embodiment is preferably 6 to 12, more preferably 7 to 11.5, and still more preferably 8 to 11. As a method for adjusting the pH, for example, it may be adjusted to be alkaline by adding a pH adjuster represented by basic salts such as potassium hydroxide, ammonia, ethylenediamine, and TMAH (tetramethylammonium hydroxide). it can.

  Hereinafter, each component will be described in detail.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

1.2 (B) Organic Acid The chemical mechanical polishing aqueous dispersion according to this embodiment contains (B) an organic acid. (B) By adding an organic acid, not only can the polishing rate for copper films be increased, but also the polishing rate for barrier metal films such as tantalum can be increased, and surface defects such as scratches on the copper film can be reduced. can do.

  Examples of the organic acid (B) include amino acids such as glycine, alanine, phenylalanine, histidine, cysteine, methionine, glutamic acid, aspartic acid, and tryptophan.

  (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. Alkenyl succinic acid, glutaric acid and the like.

  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, indolecarboxylic acid, xanthurenic acid, quinurenic acid, benzotriazole, benzimidazole, Examples include 7-hydroxy-5-methyl-1,3,4-triazaindolizine, allopurinol, hypoxanthine, nicotinic acid, picolinic acid, methyl picolinate, and picolinic acid.

  The content of the (B) organic acid is preferably 0.001% by mass or more and 3.0% by mass or less, more preferably 0.001% by mass or less, with respect to the total mass of the chemical mechanical polishing aqueous dispersion in use. It is 01 mass% or more and 2.0 mass% or less. When the content of the (B) 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, if the content of the organic acid (B) exceeds the above range, the chemical mechanical polishing aqueous dispersion may aggregate.

1.3 Other Additives 1.3.1 Oxidizing Agent The chemical mechanical polishing aqueous dispersion according to this embodiment may contain an oxidizing agent as necessary. Examples of the oxidizing agent include ammonium persulfate, potassium persulfate, hydrogen peroxide, ferric nitrate, diammonium cerium nitrate, iron sulfate, ozone, hypochlorous acid and its salts, potassium periodate, and peracetic acid. Etc. 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% by mass or more and 5% by mass or less, more preferably 0.08% by mass or more and 3% by mass or less, with respect to the total mass of the chemical mechanical polishing aqueous dispersion. It is. When the content of the oxidizing agent is less than the above range, a sufficient polishing rate may not be ensured. On the other hand, when the content exceeds the above range, corrosion or dishing of a metal film such as a copper film may increase.

1.3.2 Water-soluble polymer The chemical mechanical polishing aqueous dispersion according to this embodiment may contain a water-soluble polymer, if necessary. Examples of water-soluble polymers that can be used in combination with the present embodiment include polyacrylic acid and salts thereof, polymethacrylic acid and salts thereof, polyvinyl alcohol, polyvinyl pyrrolidone, and polyacrylamide. These water-soluble polymers have a polyethylene glycol equivalent weight average molecular weight (Mw) measured by GPC (gel permeation chromatography) of more than 50,000, preferably more than 200,000 and less than 5 million, more preferably Is between 500,000 and 2.5 million. When the weight average molecular weight is in the above range, polishing friction can be reduced, and metal film dishing and metal film corrosion can be suppressed. In addition, the metal film can be polished stably. When the weight average molecular weight is smaller than the lower limit, the polishing friction is reduced and the effect of suppressing metal film dishing or metal film corrosion is poor. In addition, if the weight average molecular weight is too large, the stability of the chemical mechanical polishing aqueous dispersion is deteriorated, or the viscosity of the chemical mechanical polishing aqueous dispersion is excessively increased, which places a load on the polishing liquid supply device. Problems may occur.

  The content of the water-soluble polymer is preferably 0.001% by mass or more and 1.0% by mass or less, more preferably 0.01% by mass or more, based on the total mass of the chemical mechanical polishing aqueous dispersion. 0.5% by mass or less. 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.

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

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

  Examples of the anionic surfactant include carboxylate, sulfonate, sulfate ester salt, phosphate ester salt and the like. Examples of the carboxylate include fatty acid soap, alkyl ether carboxylate, and alkenyl succinate. 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 singly or in combination of two or more.

  The content of the surfactant is preferably 0.001% by mass or more and 1.0% by mass or less, more preferably 0.005% by mass or more and 0% by mass with respect to the total mass of the chemical mechanical polishing aqueous dispersion. .5% by mass or less. 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.

2. Method for Producing Chemical Mechanical Polishing Aqueous Dispersion In the present invention, the above (A) silica particles and (B) organic acid are added to water to produce a chemical mechanical polishing aqueous dispersion, and this is used as it is. Although it may be used for mechanical polishing, an aqueous dispersion for chemical mechanical polishing containing a high concentration of each component, that is, a concentrated aqueous dispersion is produced and diluted to a desired concentration at the time of use. It may be used for polishing.

  In addition, as shown in the chemical mechanical polishing aqueous dispersion preparation kit shown below, a plurality of liquids containing any of the above components (for example, two or three liquids) are prepared and mixed at the time of use. It can also be used. 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.

2.1 Chemical Mechanical Polishing Aqueous Dispersion Preparation Kit The chemical mechanical polishing aqueous dispersion preparation kit used in the present invention (hereinafter, also simply referred to as “kit”) includes water and (A) silica particles. The kit comprises a liquid (I) that is an aqueous dispersion, and a liquid (II) containing water and (B) an organic acid, and the liquid dispersion for chemical mechanical polishing is prepared by mixing these liquids. .

  The concentration of each component in the liquids (I) and (II) should be within the range where the concentration of each component in the chemical mechanical polishing aqueous dispersion finally prepared by mixing these liquids is within the above range. If it does not specifically limit. 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.

  Thus, the storage stability of the chemical mechanical polishing aqueous dispersion can be improved by preparing the liquid (I) and the liquid (II) independently.

  When the kit is used, the mixing method and timing of 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 the 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.

3. 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.

3.1 Object to be processed FIG. 4 shows an object to be processed 100 used in the chemical mechanical polishing method according to the present 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 the low dielectric constant insulating film 20 and the insulating film 30 so as to 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, but is not limited to this and may be Ti, TiN, Co, Mn, Ru, or the like. .

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

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

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

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

Preferred polishing conditions should be appropriately set 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 can be used.
-Surface plate rotation speed: preferably 30-120 rpm, more preferably 40-100 rpm
Head rotation speed: preferably 30 to 120 rpm, more preferably 40 to 100 rpm
-Platen rotation speed / head rotation speed ratio; preferably 0.5-2, more preferably 0.7-1.5
Polishing pressure; preferably 60 to 200 gf / cm ² , more preferably 100 to 150 gf / cm ²
-Chemical mechanical polishing aqueous dispersion supply rate; preferably 50 to 300 mL / min, more preferably 100 to 200 mL / min. Examples Hereinafter, the present invention will be described by way of examples. However, the present invention is not limited to these examples.

4.1 Production of Silica Particle Dispersions A to J 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. The 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. Immediately after that, a 10% by mass aqueous potassium hydroxide solution was 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 previously adjusted to pH 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 was concentrated under reduced pressure at a boiling point of 78 ° C. to obtain a silica particle dispersion having a silica concentration of 32.0% by mass, an average particle diameter of silica: 26 nm, and pH: 9.8. Obtained. This silica particle dispersion was again passed through the hydrogen-type cation exchange resin layer to remove most of the sodium, and then added with a 10% by mass potassium hydroxide aqueous solution to obtain a silica particle concentration of 28.0% by mass, A silica particle dispersion A having a pH of 10.0 was obtained.

  Silica particles were recovered from the silica particle dispersion A by centrifugation, dissolved in dilute hydrofluoric acid, and sodium and potassium were measured by ICP-MS (manufactured by Perkin Elmer, model number “ELAN DRC PLUS”). . 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, dropped 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 destroy the particle shape on the Cu grit, using a transmission electron microscope (manufactured by Hitachi High-Technologies Corporation, “H-7650”) An image was taken, 50 colloidal silica particles were measured, the average value of the major axis and the average value of the minor axis were calculated, and the ratio of the major axis to the minor axis was calculated. As a result, Rmax / Rmin was 1.1. . Furthermore, the average particle diameter 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 component collect | recovered by concentrating and drying the silica particle dispersion A was used.

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

  The silica particle dispersion J is prepared 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 J produced.

4.2 Synthesis of water-soluble polymer 4.2.1 Preparation of aqueous solution of polyvinylpyrrolidone (K-30) 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 Polyvinylpyrrolidone (K30) was produced by adding 0.3 g of a 10% by mass aqueous t-butyl hydroperoxide 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.

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

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

4.3 Preparation of Chemical Mechanical Polishing Aqueous Dispersion Silica Particle Dispersion A containing 50 parts by mass of ion-exchanged water and 5 parts by mass in terms of silica is placed in a polyethylene bottle, and malonic acid is added to this. Part by mass, 0.2 part by mass of quinaldic acid, 0.1 part by mass of an acetylenic diol type nonionic surfactant (trade name “Surfinol 485”, manufactured by Air Products), and an aqueous polyacrylic acid solution (weight average molecular weight 20) Is added in an amount corresponding to 0.05 parts by mass in terms of polymer amount, and further 10% by mass of potassium hydroxide aqueous solution is added to adjust the pH of the chemical mechanical polishing aqueous dispersion to 10.0. . Next, 30% by mass of hydrogen peroxide solution was added in an amount corresponding to 0.2 parts by mass in terms of hydrogen peroxide, and stirred for 15 minutes. Finally, ion-exchanged water was added so that the total amount of all components was 100 parts by mass, and then filtered through a filter having a pore diameter of 5 μm, thereby obtaining a polishing aqueous dispersion S1 having a pH of 10.0.

  Silica particle components are recovered from the chemical mechanical polishing aqueous dispersion S1 by centrifugation, the silica particles are dissolved with dilute hydrofluoric acid, and sodium and potassium are added by ICP-MS (manufactured by PerkinElmer, model number “ELAN DRC PLUS”). As a result of measuring and further measuring ammonium ion by ion chromatography (manufactured by DIONEX, model number “ICS-1000”), the sodium content was 88 ppm, the potassium content was 5500 ppm, and the ammonium ion content was 5 ppm. From this result, it was possible to quantify the sodium, potassium and ammonium ions contained in the silica particles also by recovering from the chemical mechanical polishing aqueous dispersion.

  Chemical mechanical polishing aqueous dispersions S2 to S11 are the same as those described above except that the types and contents of silica particle dispersion, organic acid, and other additives are changed as shown in Tables 2 to 3. It was produced in the same manner as the 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).

4.4 Stability Test of Chemical Mechanical Polishing Aqueous Dispersion The obtained chemical mechanical polishing aqueous dispersions S1 to S11 are placed in a 100 cc glass tube, stored at 25 ° C. for 6 months, and visually checked for sedimentation. Confirmed by 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”.

4.5 Chemical Mechanical Polishing Test 4.5.1 Polishing Evaluation of Unpatterned Substrate Chemical Mechanical Polishing Equipment (Ebara Seisakusho, Model “EPO112”) and Porous Polyurethane Polishing Pad (Nitta Haas, Part Number “IC1000”) )) And supplying any one of chemical mechanical polishing aqueous dispersions S1 to S11, the following various polishing rate measurement substrates are subjected to chemical mechanical polishing treatment for 1 minute under the following polishing conditions. The polishing rate and wafer contamination were evaluated by the following methods. The results are also shown in Tables 2 to 3.

4.5.1a Polishing Rate Measurement (i) Polishing Rate Measurement Substrate. A silicon substrate with an 8-inch thermal oxide film on which a copper film having a thickness of 15,000 angstroms is laminated.
A silicon substrate with an 8-inch thermal oxide film on which a tantalum film having a thickness of 2,000 angstroms is laminated.
An 8-inch silicon substrate on which a low dielectric constant insulating film (made by Applied Materials, trade name “Black Diamond”) having a thickness of 10,000 Å is laminated.
An 8-inch silicon substrate on which a 10,000 Å thick PETEOS film is laminated.

(Ii) Polishing conditions and head rotation speed: 70 rpm
Head load: 200 gf / cm ²
・ Table rotation speed: 70rpm
-Supply rate of chemical mechanical polishing aqueous dispersion: 200 mL / min (iii) Calculation method of polishing rate For copper film and tantalum film, electric conductivity type film thickness measuring instrument (model "Omnimap RS75" manufactured by KLA Tencor) ) Was used to measure the film thickness after polishing, and the polishing rate was calculated from the film thickness decreased by chemical mechanical polishing and the polishing time. The polishing rate of the copper film is preferably 200 angstrom / min or more, more preferably 400 angstrom / min or more.

  For the PETEOS film and the low dielectric constant insulating layer, the film thickness after the polishing treatment is measured using an optical interference type film thickness measuring instrument (manufactured by Nanometrics Japan, model “Nano Spec 6100”). The polishing rate was calculated from the reduced film thickness and polishing time.

4.5.1b Wafer Contamination The PETEOS film and the BD film were polished in the same manner as in “4.5.1a Measurement of polishing rate”. For the PETEOS film, the substrate was subjected to vapor phase decomposition treatment, diluted hydrofluoric acid was dropped on the surface to dissolve the surface oxide film, and the dissolved liquid was then added to ICP-MS (manufactured by PerkinElmer, model number “ELAN DRC PLUS”). )). For the BD film, ultrapure water was dropped on the surface of the substrate to extract the residual metal on the surface of the BD film, and then the extract was quantified by ICP-MS (manufactured by Yokogawa Analytical Systems, model number “Agilent 7500s”). Wafer contamination, is preferably 3.0atom / cm ² or less, and more preferably 2.5atom / cm ² or less.

4.5.2 Polishing Evaluation of Patterned Wafers A chemical polishing machine (Ebara Corporation, 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 S11, the following patterned wafer was polished under the following polishing conditions, and the flatness and the presence or absence of defects were evaluated by the following methods. . The results are also shown in 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.

(2) Polishing conditions for the first polishing treatment step / Chemical mechanical polishing aqueous dispersion for the first polishing treatment step includes “CMS7401”, “CMS7452” (both manufactured by JSR Corporation), ion exchange A mixture of water and a 4% by mass aqueous ammonium persulfate solution at a mass ratio of 1: 1: 2: 4 was used.
-Head rotation speed: 70 rpm
Head load: 200 gf / cm ²
・ Table rotation speed: 70rpm
-Supply speed of chemical mechanical polishing aqueous dispersion: 200 mL / min In this case, the supply speed of the chemical mechanical polishing aqueous dispersion refers to a value obtained by assigning the total supply amount of all supply liquids per unit time.
Polishing time: 2.75 minutes (3) Polishing conditions of the second polishing treatment step As the aqueous dispersion for the second polishing treatment step, chemical mechanical polishing aqueous dispersions S1 to S11 were used.
-Head rotation speed: 70 rpm
Head load: 200 gf / cm ²
・ Table rotation speed: 70rpm
-Supply speed of chemical mechanical polishing aqueous dispersion: 200 mL / min In this case, the supply speed of the chemical mechanical polishing aqueous dispersion refers to a value obtained by assigning the total supply amount of all supply liquids per unit time.
Polishing time: The time at which polishing was further performed for 30 seconds from the time when the PETEOS film was removed from the surface to be polished was defined as a polishing end point, and Table 2 to Table 3 described as “patterned wafer polishing time”.

4.5.2a Flatness Evaluation For the surface to be polished of the patterned wafer after the second polishing process step, a copper wiring width (line, L) is used by using a high-resolution profiler (model “HRP240ETCH” manufactured by KLA Tencor). ) / Insulating film width (space, S) was measured for dishing amount (nm) in copper wiring portions of 100 μm / 100 μm, respectively. The results are also shown in 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 portion where the fine wiring length in the pattern in which the copper wiring width (line, L) / insulating film width (space, S) is 9 μm / 1 μm, respectively, is 1000 μm on the surface to be polished of the patterned wafer after the second polishing process. The amount of erosion (nm) was measured. The results are also shown in Tables 2 to 3. Note that the erosion amount is indicated by a minus value when the upper surface of the copper wiring is convex above the reference surface (upper surface of the insulating film). The amount of erosion is preferably −5 to 30 nm, and more preferably −2 to 20 nm.

4.5.2b Defect Evaluation Measure the number of polishing scratches (scratches) on the polished surface of the patterned wafer after the second polishing process using a defect inspection device (model “2351” manufactured by KLA Tencor). did. The results are also shown in Tables 2 to 3. In Tables 2 to 3, the number of scratches per wafer is described with the unit “piece / wafer”. The number of scratches is preferably less than 100 / wafer.

4.5.3 Evaluation Results According to Tables 2 to 3, by using the chemical mechanical polishing aqueous dispersions of Examples 1 to 5, in the polishing test for the polishing rate measuring substrate, without causing wafer contamination. A high polishing rate was obtained for the Cu film, Ta film and TEOS film. In the polishing test of the patterned wafer, it was found that generation of scratches on the surface to be polished can be suppressed, and a surface to be polished having a high level of flatness can be obtained efficiently.

  On the other hand, since S6 used in Comparative Example 1 uses the silica particle dispersion F having a high sodium content of 11250 ppm, wafer contamination occurs in the polishing test of the polishing rate measuring substrate, which is preferable. It was clear that there was no.

  Since S7 used in Comparative Example 2 uses the silica particle dispersion G having a low potassium or ammonium ion content, the storage stability of the silica particles was poor. As a result, in the polishing test of the patterned wafer, many scratches were generated, and a good polished surface could not be obtained.

  S8 used in Comparative Example 3 was not preferable because it used a silica particle dispersion H having a high sodium concentration of 700 ppm, which caused wafer contamination in the polishing test for the polishing rate measuring substrate. In the polishing test of the patterned wafer, it was found that since the average particle diameter of the silica particles was as small as 5 nm, the polishing rate for the Cu film was particularly low, and it took a long time to polish the patterned wafer and was not efficient. In addition, many scratches were generated, and a good polished surface could not be obtained.

  S9 used in Comparative Example 4 uses silica particle dispersion I with a small content of potassium or ammonium ions and a large average particle size of silica particles of 110 nm, so that the storage stability of the silica particles is high. It was bad. As a result, in the polishing test of the patterned wafer, flatness was impaired, many scratches were generated, and a good polished surface could not be obtained.

  S10 used in Comparative Example 5 uses a silica particle dispersion J obtained by a sol-gel method using tetraethoxysilane as a raw material. The silica particle dispersion J not only has a cost problem, but also has a small content of sodium, potassium or ammonium ions, and Rmax / Rmin exceeds 1.5. Then, it turned out that it is inferior to the grinding | polishing speed | rate with respect to Cu film | membrane or a TEOS film | membrane. On the other hand, in the polishing test of the patterned wafer, many scratches were generated and a good polished surface could not be obtained.

  S11 used in Comparative Example 6 corresponds to a composition obtained by removing the component corresponding to the organic acid from Example 4. In the polishing test of the substrate for polishing rate measurement, the polishing rate for the Cu film and the Ta film was remarkably reduced as compared with Example 4 because it did not contain an organic acid. Accordingly, it has been found that the polishing test of the patterned wafer requires a long time for polishing the patterned wafer and is not efficient. In addition, many scratches were generated, and a good polished surface could not be obtained. From the above results, the advantageous effect of containing an organic acid was shown.

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

Claims (6)

(A) silica particles;
(B) an organic acid;
An aqueous dispersion for chemical mechanical polishing containing
The (A) silica particle is a chemical mechanical polishing aqueous dispersion having the following chemical properties.
Sodium, potassium and ammonium ion content measured from elemental analysis by ICP emission spectrometry or ICP mass spectrometry and quantitative analysis of ammonium ion by ion chromatography, sodium content: 5 to 500 ppm, potassium and ammonium ion The content of at least one selected from: satisfies the relationship of 100 to 20000 ppm. In claim 1,
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 claim 1 or claim 2,
(A) The aqueous dispersion for chemical mechanical polishing whose average particle diameter computed from the specific surface area measured using the BET method of the said silica particle is 10-100 nm. In any one of Claims 1 thru | or 3,
An aqueous dispersion for chemical mechanical polishing having a pH of 6-12.   5. A polished surface of a semiconductor device having at least one selected from a metal film, a barrier metal film, and an insulating film is polished using the chemical mechanical polishing aqueous dispersion according to claim 1. A chemical mechanical polishing method. A method of producing an aqueous dispersion for chemical mechanical polishing by mixing at least (A) silica particles and (B) an organic acid,
Said (A) silica particle is a manufacturing method of the aqueous dispersion for chemical mechanical polishing which has the following chemical property.
Sodium, potassium and ammonium ion content measured from elemental analysis by ICP emission spectrometry or ICP mass spectrometry and quantitative analysis of ammonium ion by ion chromatography, sodium content: 5 to 500 ppm, potassium and ammonium ion The content of at least one selected from: satisfies the relationship of 100 to 20000 ppm.

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