JP2011003665A - Aqueous dispersant for chemical-mechanical polishing, and chemical-mechanical polishing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous dispersant for chemical-mechanical polishing simultaneously, having a high polishing speed and high planarization characteristics for a wiring material and a barrier metal film and an interlayer insulating film, and to provide a chemical-mechanical polishing method that uses the dispersant.SOLUTION: The aqueous dispersant for chemical mechanical polishing contains (A) abrasive grains, (B) a compound having at least two carbonyl groups, and (C) a heterocyclic compound, and is used for the method of polishing a substrate provided with a cobalt-containing film on the substrate.

Description

  The present invention relates to a chemical mechanical polishing aqueous dispersion (hereinafter referred to as “chemical mechanical polishing aqueous dispersion”, which is also abbreviated as “aqueous dispersion”) used in the manufacture of semiconductor devices.

The damascene wiring mounted on the LSI is formed using chemical mechanical polishing (hereinafter also referred to as “CMP”). In CMP for forming a damascene wiring, a first polishing process for mainly polishing a wiring metal such as copper and a second polishing process for polishing a wiring metal, a barrier metal film, and an insulating film are sequentially performed.
In such a damascene wiring, tantalum, tantalum nitride, titanium, titanium nitride or the like is generally used as a material for the barrier metal film. For this reason, in the second polishing step, an aqueous dispersion for chemical mechanical polishing in which the polishing rate ratio between the specific barrier metal film, the wiring metal and the insulating film is optimized has been studied. For example, Patent Documents 1 and 2 disclose a technique for controlling a polishing rate ratio of a barrier metal film such as tantalum or titanium, a wiring metal, and an insulating film using a triazole compound.

  In recent years, with further miniaturization of wiring, it is required to reduce the thickness of the barrier metal film. However, tantalum and titanium, which are conventional materials, are difficult to produce a dense thin film, and barrier properties that suppress diffusion of wiring metal species are deteriorated by making the film thin. For this reason, use of a film containing cobalt as a new barrier metal material has been studied. However, unlike conventional barrier metal films such as tantalum and titanium, the barrier metal film containing cobalt differs greatly in polishing characteristics, so that conventional barrier metal films such as tantalum and titanium are used. The chemical mechanical polishing aqueous dispersion for polishing cannot simply be diverted. For this reason, development of a new chemical mechanical polishing aqueous dispersion for polishing a film containing cobalt is required.

JP 2002-164310 A JP 2004-71673 A JP 2009-76615 A

  An object of the present invention is to provide an aqueous dispersion for chemical mechanical polishing simultaneously having a high polishing rate and high planarization characteristics for a wiring material, a barrier metal film containing cobalt and an interlayer insulating film, and a chemical mechanical polishing method using the same. It is to provide.

The chemical mechanical polishing aqueous dispersion according to the present invention comprises:
(A) abrasive grains;
(B) a compound having two or more carbonyl groups;
(C) a heterocyclic compound;
And an aqueous dispersion for chemical mechanical polishing used in a method for polishing a substrate having a cobalt-containing film formed on a semiconductor substrate.

  According to the chemical mechanical polishing aqueous dispersion, a wiring material (for example, a copper film), a barrier metal film such as a cobalt film, and an interlayer insulating film (for example, TEOS) can be used while preventing damage to the low dielectric constant interlayer insulating film. The polishing rate for the film) can be increased to the same extent, and a surface to be polished having excellent flatness can be obtained. Furthermore, according to the chemical mechanical polishing aqueous dispersion, polishing defects such as dishing and erosion can be reduced.

It is sectional drawing which shows the to-be-processed object used for the chemical mechanical polishing method which concerns on this embodiment. It is sectional drawing which shows typically the grinding | polishing process of the chemical mechanical grinding | polishing method which concerns on this embodiment. It is sectional drawing which shows typically the grinding | polishing process of the chemical mechanical polishing method which concerns on this embodiment. It is sectional drawing which shows typically the grinding | polishing process of the chemical mechanical polishing method which concerns on this embodiment.

  Hereinafter, preferred embodiments according to the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, Various modifications implemented in the range which does not change the summary of this invention are also included.

1. Chemical mechanical polishing aqueous dispersion The chemical mechanical polishing aqueous dispersion according to this embodiment comprises (A) abrasive grains, (B) a compound having two or more carbonyl groups, and (C) a heterocyclic compound. It is a chemical mechanical polishing aqueous dispersion used in a method for polishing a substrate containing a cobalt-containing film.

The chemical mechanical polishing aqueous dispersion according to the present embodiment is used for polishing a film containing cobalt formed on a semiconductor substrate.
Titanium-based materials and tantalum-based materials conventionally used as barrier metals, and cobalt, for example, have different mechanical characteristics and chemical characteristics as shown in Table 1. For example, cobalt has an ionization tendency equivalent to that of tantalum when judged from ionization energy, but hardness, which is a guideline for mechanical strength, is smaller than that of titanium and tantalum. (The special characteristics of cobalt are described in Japanese Patent Application Laid-Open No. 2008-121110.) For this reason, when a conventional aqueous dispersion for barrier metal polishing is used, mechanical polishing action and chemical polishing action (etching action) Etc.) and the conventional chemical mechanical polishing aqueous dispersion cannot be used.
Furthermore, although it cannot be shown as such physical and chemical characteristics, the cobalt-based material has an adhesion property with an insulating film and a wiring metal, and the titanium-based material and the tantalum-based material that are conventionally used as a barrier metal. Unlike the above materials, it is necessary to suppress the occurrence of polishing defects due to the difference in adhesion.

株式会社東京化学同人 第１版１９８９年１０月２０日発行 「化学大辞典」

Tokyo Chemical Dojin Co., Ltd. 1st edition, published on October 20, 1989

  The chemical mechanical polishing aqueous dispersion according to this embodiment has been invented in view of the particularity of the cobalt-based material as described above. First, each component contained in the chemical mechanical polishing aqueous dispersion according to this embodiment will be described in detail. Hereinafter, the components of (A) abrasive grains or (C) heterocyclic compounds may be abbreviated as (A) to (C), respectively.

1.1 (A) Abrasive Grains The chemical mechanical polishing aqueous dispersion according to this embodiment contains (A) abrasive grains.
(A) As abrasive grains, fumed silica synthesized by the fumed method in which silicon chloride and the like are reacted with oxygen and hydrogen in the gas phase, and silica synthesized by the sol-gel method synthesized by hydrolytic condensation from metal alkoxide And colloidal silica synthesized by an inorganic colloid method in which impurities are removed by purification. In particular, (A) abrasive grains are preferably colloidal silica synthesized by an inorganic colloid method or the like in which impurities are removed by purification.
(A) The shape of the abrasive grains is preferably spherical. Here, the spherical shape includes a substantially spherical shape that does not have an acute angle portion, and is not necessarily close to a true sphere. By using spherical abrasive grains, it is possible to polish at a sufficient polishing rate and to suppress the occurrence of scratches on the surface to be polished.

  (A) The average particle diameter of the abrasive grains is preferably 0.01 to 0.3 μm, more preferably 0.01 to 0.2 μm, and particularly preferably 0.015 to 0.1 μm. Abrasive grains having an average particle diameter in this range can provide a stable chemical mechanical polishing aqueous dispersion that has a sufficient polishing rate and does not cause sedimentation or separation of particles. If the average particle size is less than 0.01 μm, a chemical mechanical polishing aqueous dispersion having a sufficiently high polishing rate may not be obtained. When the average particle diameter exceeds 1 μm, it is not easy to obtain a stable aqueous dispersion due to sedimentation and separation of the abrasive grains. In addition, the average particle diameter of (A) abrasive grain can be measured by observing with a transmission electron microscope.

  (A) Content of abrasive grains is preferably 1 to 15% by mass, more preferably 2 to 12% by mass, and further preferably 3 to 9% by mass with respect to the total mass of the chemical mechanical polishing aqueous dispersion. It is. (A) When the content of the abrasive grains is less than the above range, a sufficient polishing rate may not be obtained, and it may take a long time to complete the polishing step. On the other hand, when the content of the (A) abrasive grains exceeds the above range, the cost increases, and the storage stability of the chemical mechanical polishing aqueous dispersion decreases, which is not preferable.

1.2 (B) Compound having two or more carbonyl groups The chemical mechanical polishing aqueous dispersion according to this embodiment contains (B) a compound having two or more carbonyl groups. By containing the compound having two or more carbonyl groups, the polishing rate for the barrier metal film made of cobalt and / or cobalt nitride can be increased.

  For example, (B) component includes oxalic acid, malonic acid, tartaric acid, glutaric acid, malic acid, citric acid, and maleic acid. Among them, particularly preferred compounds having two or more carbonyl groups are maleic acid and malic acid, which easily form a coordinate bond with cobalt ions via two or more carbonyl groups, and have an affinity for cobalt and cobalt ions. It is presumed that the metal complex film is formed on the polished surface by adsorbing to the surface of cobalt and / or cobalt nitride by improving the property.

  The reason for this is that maleic acid has a structure having two carboxyl groups having a π bond as shown in the following formula (1), and is a three-dimensional structure of two cis-type carbonyl groups. The structure is presumed to be easily complexed. Therefore, it is presumed that it is difficult to cause dishing or corrosion.

  Furthermore, as shown in the following formula (1), malic acid has a carboxyl group and a hydroxyl group as an anionic functional group, so that it can easily form a coordinate bond with cobalt or cobalt ion as a cation. Presumed to be. Since cobalt is in a stable state with a divalent valence, it is presumed that a complex is efficiently formed by bidentate coordination with an organic acid having two or more carbonyl groups such as malic acid. Furthermore, since the hydrophilicity is increased by having a hydroxyl group, the precipitation of the metal chelate salt dissolved in the polishing liquid is particularly easily suppressed, which can prevent scratching, dishing and corrosion on the surface to be polished. Guessed.

In addition, maleic acid and malic acid have a plurality of carboxyl groups, so they are highly soluble in water, and the generated metal chelate salt is unlikely to precipitate, which makes it difficult to scratch and dish on the surface to be polished. .

However, it is presumed that a metal having low solubility such as titanium is difficult to dissolve in maleic acid, malic acid or the like, and the metal remains as it is and causes problems such as dishing.
In addition, for metals with high mechanical strength such as tantalum, the complex after dissolving with maleic acid or malic acid becomes a complex having hardness compared to cobalt, so it is presumed that scratches, dishing and corrosion are likely to occur. The

1.3 (C) Heterocyclic Compound The chemical mechanical polishing aqueous dispersion according to this embodiment contains (C) a heterocyclic compound. By adding the heterocyclic compound, the copper ion eluted in the aqueous dispersion by the polishing of the wiring metal such as copper and the heterocyclic compound can be coordinated to prevent the precipitation of copper. Thereby, surface defects such as scratches on the wiring metal can be suppressed.
(C) As the heterocyclic compound, pyrrole, pyrroline, pyrrolidone, indole, indolenine, indoline, oxindole, dioxindole, oxylindole, isatin, indoxyl, pyrazole, 2H-1,2,3-triazole, 1 , 2,3-triazole, 4H-1,2,4-triazole, 1H-1,2,4-triazole, 1H-1,2,3,4-triazole, 2H-1,2,3,4 -Triazole, benzimidazole, 1,2-benzopyrazole, 2,1-benzopyrazole, 1-benzotriazole, 2-benzotriazole, pyridine, 2,2-bipyridinyl, quinoline, isoquinoline, pyridazine, cincinoline, phthalazine, phthalazinone, Pyrimidine, purine, pteridine, quinazoline, pic Razine, quinoxaline, triazine, tetrazine, tetrazole and one or more selected from the group consisting of derivatives in which the hydrogen atom in these compounds is substituted with an alkyl group, a hydroxyl group, an amino group, a carbonyl group or an aldehyde group.

  Further, (C) the heterocyclic compound is preferably a nitrogen-containing heterocyclic compound, more preferably a nitrogen-containing heterocyclic compound having a carboxyl group adjacent to the nitrogen atom. Examples of the nitrogen-containing heterocyclic compound having a carboxyl group adjacent to the nitrogen atom include benzotriazole such as 5-methyl-1H-benzotriazole, tolyltriazole, benzimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzothiadiazole, 2 -Mercaptobenzoxazole, 2-aminobenzothiazole, 2-mercaptobenzothiazole, 2-amino-6-methylbenzothiazole, quinolinic acid, quinaldic acid and the like. Among them, particularly preferred nitrogen-containing heterocyclic compounds are benzotriazole and 5-methyl-1H-benzotriazole or quinaldic acid, which easily forms a coordinate bond with a copper ion via a cyclic nitrogen atom. Can be adsorbed on the surface of a wiring material such as copper and appropriately protected. The nitrogen-containing heterocyclic compound having a carboxyl group adjacent to the nitrogen atom is more likely to form a coordinate bond with the copper ion, and the above effects are easily obtained.

The content of the component (C) is preferably 0.005 to 0.3% by mass, more preferably 0.01 to 0.1% by mass with respect to the total mass of the chemical mechanical polishing aqueous dispersion at the time of use. %, Particularly preferably 0.02 to 0.05% by mass. When the content of the component (C) is less than the above range, the wiring material such as copper or the corrosion of the barrier metal film may occur.
On the other hand, if the content of the component (C) exceeds the above range, a sufficient polishing rate may not be obtained for the copper film, and it may take a long time to complete the polishing step.

1.4 pH adjuster Examples of means for adjusting the pH of the chemical mechanical polishing aqueous dispersion according to this embodiment include basic substances such as potassium hydroxide, ammonia, ethylenediamine, and TMAH (tetramethylammonium hydroxide). The pH can be adjusted by adding a pH adjusting agent represented by a salt.

  The pH value is 7-9, preferably 7.5-8.5. When the pH value is less than 7, hydrogen bonds between silanol groups present on the surface of the silica particles cannot be broken, and aggregation of the silica particles may occur. In addition, the etching action on the wiring material such as copper and the barrier film becomes strong, and dishing, erosion, and the like may easily occur. On the other hand, when the pH value is larger than 9, cobalt is in a stable chemical state, so that a sufficient polishing rate cannot be obtained. In addition, when the slurry is stored for a long time, some silica particles present in the slurry may be dissolved. As a result, the polishing characteristics of the slurry change, the insulating film is excessively polished, and a good wiring pattern may not be obtained.

1.5 Other Additives The chemical mechanical polishing aqueous dispersion according to this embodiment may contain an oxidizing agent. By containing the oxidizing agent, the polishing rate is further improved. A wide range of oxidizers can be used as the oxidizer, but as a suitable oxidizer, hydrogen peroxide solution, oxidizable metal salt, oxidizable metal complex, non-metal oxidizer such as peracetic acid and periodic acid. Iron ions such as nitrate, sulfate, EDTA, citrate, potassium ferricyanide, aluminum salts, sodium salts, potassium salts, ammonium salts, quaternary ammonium salts, phosphonium salts, or other cationic salts of peroxides, chloric acid Salts, perchlorates, nitrates, permanganates, persulfates and mixtures thereof.

Among these oxidizing agents, hydrogen peroxide is particularly preferable. At least a part of hydrogen peroxide is dissociated to generate hydrogen peroxide ions. “Hydrogen peroxide” means one containing the hydrogen peroxide ions in addition to molecular hydrogen peroxide.
The content of the oxidizing agent is preferably 0.1 to 5% by mass, more preferably 0.55 to 2% by mass, and particularly preferably the total mass of the chemical mechanical polishing aqueous dispersion at the time of use. 0.8 to 1.2% by mass. If the content of the oxidizing agent is less than 0.1% by mass, a sufficient polishing rate may not be obtained for the surface to be polished, and it may take a long time to complete the polishing step. On the other hand, if the content of the oxidizing agent exceeds 5% by mass, the wiring material such as copper and the barrier metal film may be corroded.

A nonionic surfactant, an anionic surfactant or a cationic surfactant can be blended in the chemical mechanical polishing aqueous dispersion of the present invention, if 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 aliphatic soap, sulfate ester salt,
And phosphoric acid ester salts. Examples of the cationic surfactant include:
Examples thereof include aliphatic amine salts and aliphatic ammonium salts. These surfactants are
It is also possible to use 1 type individually or in combination of 2 or more types.

Among these surfactants, acetylene glycol and its ethylene oxide adduct and dodecylbenzene sulfonate are particularly preferable.
The content of the oxidizing agent is preferably 0.01 to 0.2% by mass, more preferably 0.01 to 0.15% by mass, based on the total mass of the chemical mechanical polishing aqueous dispersion at the time of use. Especially preferably, it is 0.01-0.1 mass%. When the content of the surfactant is less than 0.01% by mass, the polishing rate may not be sufficiently controlled with respect to the surface to be polished. On the other hand, when the content of the surfactant exceeds 0.2% by mass, the storage stability of the aqueous dispersion may be impaired.

1.6 Application The chemical mechanical polishing aqueous dispersion according to the present embodiment has a copper film polishing rate (R _Cu ) and cobalt when a copper film, a cobalt-containing barrier metal film, and an insulating film are polished under the same conditions. The ratio (R _Cu / R _co ) to the polishing rate (R _co ) of the contained barrier metal film is 0.1 to 1.5, and the polishing rate (R _co ) of the cobalt barrier metal film and the insulating film The ratio (R _co / R _In ) to the polishing rate (R _In ) is 0.5 to 1.8. Since the chemical mechanical polishing aqueous dispersion according to this embodiment has the above-described characteristics, it is desirable to use it in the second polishing step in the damascene wiring forming step.

The “same condition” means that a specific type of polishing apparatus is used, and the rotation speed of the platen and the head, the polishing pressure, the polishing time, the type of polishing pad, and the supply amount of the aqueous dispersion per unit time Means the same.
The “ratio” of the polishing rate can be calculated from the value of each polishing rate by separately polishing the copper film, the cobalt-containing barrier metal film, and the insulating film under the same conditions as described above. The polishing can be performed using a wafer provided with a copper film, a cobalt-containing barrier metal film, or an insulating film.

The ratio (R _Cu / R _co ) between the polishing rate of the copper film (R _Cu ) and the polishing rate (R _co ) of the cobalt-containing barrier metal film is 0.2 to 1.5, preferably 0.2 To 1, more preferably 0.5 to 0.8. When this ratio (R _Cu / R _co ) is less than 0.1, the polishing rate for the copper film is insufficient. For example, in the first polishing step in the two-step polishing method, if the removal of the copper film other than the wiring recess on the insulating film is incomplete, it takes a long time to remove the unnecessary portion of the copper film in the second polishing step. . On the other hand, when the ratio (R _Cu / R _co ) exceeds 1.5, since the copper film is excessively polished, dishing may occur, and good damascene wiring may not be formed.
Polishing rate of the cobalt-containing barrier metal film _{(R Co)} and the polishing rate of the insulating film _{(R an In)} and the ratio of _(R co _/ R _In) is 0.2 to 2, preferably 0.5 to 1 .8, more preferably 0.7 to 1.5. When this ratio (R _co / R _In ) is less than 0.5, the insulating film is excessively polished and a good damascene wiring cannot be formed. On the other hand, when the ratio (R _co / R _In ) exceeds 2, the barrier metal film is excessively polished, which causes dishing and cannot be a sufficiently flat finished surface with high accuracy.

The copper forming the copper film is not only pure, but also includes an alloy containing 95% by weight or more of copper, such as copper-silicon and copper-aluminum.
The metal forming the barrier metal film includes cobalt, tantalum, titanium, and the like, and may be nitrides or oxides thereof. Examples of the nitride include cobalt nitride, tantalum nitride, and titanium nitride. Cobalt, tantalum, and titanium are not limited to pure cobalt, pure tantalum, and pure titanium, but include alloys such as tantalum-niobium. For example, in the present embodiment, not only a single cobalt-containing barrier metal film but also a multi-layer barrier metal film can be used in consideration of adhesion to wiring. At that time, the stacking order of the barrier metal films can be appropriately handled at the time of design.

In addition to the SiO ₂ film, the insulating film includes a low dielectric constant interlayer insulating film for the purpose of improving the performance of the VLSI. As the low dielectric constant interlayer insulating film, fluorine-added SiO ₂ (dielectric constant: about 3.3 to 3.5), polyimide resin (dielectric constant: about 2.4 to 3.6; manufactured by Hitachi Chemical Co., Ltd.) Product name “PIQ”; manufactured by Allied Signal, product name “BCB”, etc., hydrogen-containing SOG (dielectric constant: about 2.5 to 3.5), and organic SOG (dielectric constant: about 2.9; Hitachi Chemical) An interlayer insulating film made of Kogyo Co., Ltd., trade name “HSGR7”, etc.).

1.8 Chemical Mechanical Polishing Aqueous Dispersion Kit The chemical mechanical polishing aqueous dispersion according to this embodiment comprises (A) abrasive grains directly in pure water, (B) a compound having two or more carbonyl groups, ( C) It can be prepared by adding a heterocyclic compound, other additives, and a pH adjuster, 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 components and to use them by mixing them at the time of use. In this case, after preparing a chemical mechanical polishing aqueous dispersion by mixing a plurality of liquids, this may be supplied to the chemical mechanical polishing apparatus, or a plurality of liquids may be supplied individually to the chemical mechanical polishing apparatus. A chemical mechanical polishing aqueous dispersion may be formed on a surface plate.

  As a specific example, when dividing into two-component kits, storage stability can be improved by separating the components at a certain ratio. In that case, at least water and (A) an aqueous dispersion containing abrasive grains, liquid (I) having a pH of 7 to 9, at least water, (B) a compound having two or more carbonyl groups, (C) A kit for preparing the above-mentioned chemical mechanical polishing aqueous dispersion may be mentioned, which comprises a liquid (II) containing a heterocyclic compound and having a pH of 5 to 7, and mixing these liquids. If the pH of the liquid (I) is previously adjusted to 8 by adding a pH adjuster, (A) the dispersion stability of the abrasive grains can be ensured.

  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 an aqueous dispersion for chemical mechanical polishing 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. So that it may be diluted with water. As described above, the storage stability of the aqueous dispersion can be improved by separately preparing the liquid (I) and the liquid (II).

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

2. Chemical mechanical polishing method A chemical mechanical polishing method according to an embodiment of the present invention will be described in detail below.
2.1 To-be-processed object FIG. 1: is sectional drawing which shows the to-be-processed object used for the chemical mechanical polishing method which concerns on this embodiment.
(1) First, the low dielectric constant insulating film 10 is formed by a coating method or a plasma CVD method. Examples of the low dielectric constant insulating film 10 include an inorganic insulating film and an organic insulating film. 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), polytetrafluoroethylene film (k = 2.0 to 2.4), amorphous carbon (k = <2.5), etc. (Where k represents a dielectric constant).
(2) The insulating film 20 is formed on the low dielectric constant insulating film 10 by using a CVD method or a thermal oxidation method. The cap layer 20 serves as a cap layer for protecting the low dielectric constant insulating film 10. Examples of the cap layer 20 include a TEOS film.
(3) The wiring recess 30 is formed by etching the low dielectric constant insulating film 10 and the cap layer 20 so as to communicate with each other.
(4) The barrier metal film 40 is formed using the CVD method so as to cover the surface of the cap layer 20 and the bottom and inner wall surface of the wiring recess 30. The barrier metal film 40 is preferably cobalt, cobalt nitride, or a cobalt alloy from the viewpoint of excellent adhesion to the copper film and diffusion barrier properties with respect to the copper film. At this time, a single layer of the cobalt-containing barrier film may be used, but a plurality of layers may be used in combination with other materials.
(5) By depositing copper on the barrier metal film 40 to form the copper film 50, the workpiece 100 is obtained.
2.2 Chemical Mechanical Polishing Method FIGS. 2 to 4 are cross-sectional views schematically showing a polishing process of the chemical mechanical polishing method according to the present embodiment. In this polishing process, a first polishing process for mainly polishing a copper film and a second polishing process for polishing unnecessary copper, a barrier metal film, and an insulating film are performed.

2.2.1 First Polishing Step First, in order to remove the copper film 50 deposited on the barrier metal film 40 of the workpiece 100, a chemical mechanical polishing chemical dispersion using a chemical mechanical polishing aqueous dispersion for the copper film is used. Polish. As shown in FIG. 2, in the first polishing step, the chemical mechanical polishing is stopped when the barrier metal film 40 is exposed. In the first polishing process, the deposited copper film 50 is polished at a high speed immediately before the barrier metal film 40 is exposed, and the barrier metal film 40 exposes the copper film 50 remaining in the bulk polishing process. It is possible to carry out by dividing it into a fine polishing step of polishing up to.

2.2.2 Second Polishing Step Next, the barrier metal film 40 and the copper film 50 are simultaneously subjected to chemical mechanical polishing using the chemical mechanical polishing aqueous dispersion according to the present invention. As shown in FIG. 3, even after the cap layer 20 is exposed, the chemical mechanical polishing is continued to remove the cap layer 20. By stopping chemical mechanical polishing when the low dielectric constant insulating film 10 is exposed, a semiconductor device 200 as shown in FIG. 4 is obtained. Since the chemical mechanical polishing aqueous dispersion according to the present invention can make polishing rates for the cap layer 20, the barrier metal film 40, and the copper film 50 substantially equal, the semiconductor device can be finished in one step.

2.2.3 Polishing Apparatus and Polishing Conditions In the chemical mechanical polishing method according to this 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 And “Mirra”, “Reflexion LK” and the like.
Preferable polishing conditions should be set as appropriate depending on the chemical mechanical polishing apparatus to be used. For example, when “Reflexion LK” 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 450 gf / cm ² , more preferably 200 to 400 gf / cm ²
Chemical chemical polishing aqueous dispersion supply rate; preferably 50 to 400 mL / min, more preferably 100 to 300 mL / min

3. Examples Hereinafter, the present invention will be described by way of examples. However, the present invention is not limited to these examples.

3.2 Preparation of aqueous dispersion for chemical mechanical polishing 3.2.1 Preparation of dispersion When the total mass of the aqueous dispersion for chemical mechanical polishing is 100% by mass, malic acid, maleic acid or glycine is 1% by mass. , Benzotriazole (BTA), 5-methylbenzotriazole or quinaldic acid 0.03 or 0 mass%, colloidal silica aqueous dispersion as solid content 5 mass%, potassium hydroxide 0.9 mass%, all components After adding ion-exchanged water to a polyethylene bottle so that the amount of water becomes 100% by mass and stirring for 1 hour, it is filtered with a filter having a pore size of 1 μm, and the pH is adjusted to an arbitrary value with potassium hydroxide. 30 mass% hydrogen peroxide water in an amount corresponding to 1 mass% in terms of hydrogen was sequentially added to obtain dispersions S1 to C8 described in Table 2 (below).
Chemical mechanical polishing aqueous dispersions S1 to C8 are the same as the chemical mechanical polishing aqueous dispersion described above except that the type or content of component (B) or (C) and the pH are changed as shown in Table 2. It was produced in the same manner as in Example 1.

3.3 Chemical mechanical polishing test Chemical mechanical polishing equipment (Applied Materials, model “Reflexion LK”) and porous polyurethane polishing pad (Fujibo, product number “H800-type1 (3-1S) 775”) And supplying the chemical mechanical polishing aqueous dispersion S1, the following various polishing rate measurement substrates were polished for 1 minute under the following polishing conditions, and the polishing rate, flatness and The presence or absence of defects was evaluated.
Further, the chemical mechanical polishing aqueous dispersions S2 to C8 were evaluated by the same operation as described above. These results are shown in Table 2.

3.3.1 Evaluation of polishing rate (1) Substrate for measuring polishing rate-A silicon substrate with a 12-inch thermal oxide film on which a copper film having a thickness of 15,000 angstroms is laminated.
A silicon substrate with a 12-inch thermal oxide film on which a 2,000 Å-thick cobalt film is laminated.
A 12-inch silicon substrate on which PETEOS with a film thickness of 20,000 angstroms is laminated.
(2) Polishing conditions and head rotation speed: 87 rpm
Head load: 350 gf / cm ²
・ Table rotation speed: 98rpm
-Supply speed of chemical mechanical polishing aqueous dispersion: 300 mL / min The supply speed of chemical mechanical polishing aqueous dispersion in this case refers to a value obtained by assigning the total supply amount of all the supply liquids per unit time.
(3) Calculation method of polishing rate For copper film and cobalt film, the film thickness after polishing treatment is measured using an electric conduction type film thickness measuring instrument (model OMNIMAP RS100, manufactured by KLA-Tencor Corporation). The polishing rate was calculated from the film thickness reduced by chemical mechanical polishing and the polishing time.
For the PETEOS film, the film thickness after polishing was measured using an optical interference film thickness measuring instrument (manufactured by KLA-Tencor Corporation, model “ASET F5X”). The polishing rate was calculated from the time. Here, the ratio (R _Cu / R _Co ) between the polishing rate (R _Cu ) for the copper film and the polishing rate (R _Co ) for the cobalt barrier metal film is preferably 0.2 to 1, more preferably 0. .5 to 0.8. The ratio of the polishing rate of the cobalt barrier metal film _{(R Co)} and the polishing rate for the PETEOS film _{(R In) (R Co /} R In) is preferably 0.5 to 1.8, more preferably 0.7-1.5. Further, the ratio (R _Co / R _Ta ) between the polishing rate (R _Co ) for the cobalt barrier metal film and the polishing rate (R _Ta ) for the tantalum film is preferably 0.4 to 1, more preferably 0.8. 5 to 0.9.

3.3.2 Evaluation of flatness By calculating the polishing rate and the ratio of the copper film, the cobalt film and the PETEOS film calculated in the evaluation of the blanket wafer, the chemical mechanical polishing aqueous dispersion according to this example can be used. Basic polishing characteristics can be confirmed. However, it is known that in a CMP of a pattern wafer on which a groove serving as a wiring pattern is formed, a portion that is excessively polished locally occurs. This is because the surface of the pattern wafer before CMP has irregularities reflecting the grooves serving as wiring patterns on the surface of the metal film, and when CMP is performed, locally high pressure is applied according to the pattern density. This is because the polishing rate is increased. Therefore, by polishing and evaluating a pattern wafer imitating a semiconductor substrate, it is possible to confirm the polishing characteristics of the chemical mechanical polishing aqueous dispersion according to this example in a state where it is actually used.

3.3.3
(1) A PETEOS film is sequentially stacked on a patterned wafer silicon substrate at 5,000 angstroms, and then a “SEMATECH 854” mask pattern is processed thereon. Then, a 125 angstrom cobalt film, a 125 angstrom tantalum film, 1,000 Using a test substrate in which an angstrom copper seed film and a 10,000 angstrom copper film were sequentially laminated,
An object to be polished was obtained.
(2) Polishing conditions and chemical mechanical polishing equipment Applied Materials, Model “Mirra”
-Head rotation speed: 67 rpm
Head load: 350 gf / cm ²
・ Table rotation speed: 73rpm
-Supply rate of chemical mechanical polishing aqueous dispersion: 200 mL / min The supply rate of chemical mechanical polishing aqueous dispersion in this case refers to a value obtained by assigning the total supply amount of all supply liquids per unit time.
The polishing time was set to 1.2 times the time from the start of polishing to the end point detected by infrared rays emitted from the table.

3.3.4 Copper Corrosion Evaluation Method A 1 cm × 1 cm copper region is used for the polished surface of the patterned wafer after the polishing process step, using a defect inspection device (model “2351” manufactured by KLA Tencor). were evaluated number of defects in the size of 10 nm ² ~ 100 nm ^2. In Table 2, “◯” represents a preferable state in which the number of corrosion is 0 to 100. X is a state where 101 or more corrosions exist, and it is determined that the polishing performance is poor.

3.3.5 Cobalt Elution Evaluation Method Chemistry in which a 1 cm x 1 cm cobalt cut wafer with a film thickness of 2,000 angstroms was added with 30 mass% hydrogen peroxide water in an amount equivalent to 1 mass% in terms of hydrogen peroxide. It was immersed in the mechanical polishing aqueous dispersions S1 to C8 for 1 minute. After 1 minute, the cut wafer was taken out, washed with distilled water and dried, and then the cut wafer surface was observed. ○ is a preferable state in which there is no abnormal oxidation or corrosion on the cobalt film surface. In x, abnormal oxidation and corrosion are observed, and the cobalt barrier film is eluted, and it is judged that the polishing performance is poor.

3.3.6 Dishing Evaluation Method Using a high-resolution profiler (type “HRP240” manufactured by KLA Tencor) for the polished surface of the patterned substrate after polishing treatment, the copper wiring width (line, L) / insulating film The dishing amount (nm) in the copper wiring portion having a width (space, S) of 100 μm / 100 μm was measured. Here, “dishing” refers to a difference in height between the upper surface of the PETEOS film sandwiching the copper wiring at the measurement position and the lowest part of the copper wiring at the measurement position on the polished surface after polishing. 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 0 to 30 nm, and more preferably 0 to 20 nm. In the evaluation column of Table 2, when the dishing amount was 0 to 30 nm, “◯” was indicated, and when it was outside the above range, “x” was indicated.

3.3.7 Evaluation Results When the chemical mechanical polishing aqueous dispersions according to Examples S1 to S8 are used, the values of R _Cu / R _Co and R _Co / R _In are within the preferable ranges. The polished surface on which the copper film, the cobalt film, and the PETEOS film (hereinafter also referred to as “three films”) are present can be polished in one step. Moreover, when a substrate with a pattern is polished using the chemical mechanical polishing aqueous dispersion according to Examples S1 to S8, surface defects such as dishing can be suppressed, and the surface to be polished has good flatness. Could be realized.

Since the chemical mechanical polishing aqueous dispersion according to Comparative Example 1 does not contain a heterocyclic compound, R _Cu / R _Co is greater than 0.8. Therefore, the copper film is excessively polished and loses balance, and it is difficult to polish the surface to be polished on which the three films exist in one step. Further, when the patterned substrate was polished, dishing occurred and a good polished surface could not be obtained.

Since the chemical mechanical polishing aqueous dispersion according to Comparative Example 2 uses glycine having a low pH and a high etching ability, the copper film is excessively polished and loses balance, and the surface to be polished on which the three films exist is formed in one step. It is difficult to polish. Further, when the patterned substrate was polished, dishing occurred and a good polished surface could not be obtained.

Since the chemical mechanical polishing aqueous dispersion according to Comparative Example 3 uses glycine having high etching ability, the copper film is excessively polished and loses balance, and the surface to be polished having three films is polished in one step. It is difficult. Further, when the patterned substrate was polished, dishing occurred and a good polished surface could not be obtained.

Since the chemical mechanical polishing aqueous dispersion according to Comparative Example 4 uses glycine having high etching ability, R _Cu / R _Co becomes larger than 1. The copper film is excessively polished and loses balance, and it is difficult to polish the surface to be polished on which the three films exist in one step. Further, when the patterned substrate was polished, dishing occurred and a good polished surface could not be obtained.

Since the chemical mechanical polishing aqueous dispersion according to Comparative Example 5 uses glycine having high etching ability, R _Cu / R _Co is larger than 1. The copper film is abnormally polished and loses balance, and it is difficult to polish the surface to be polished on which the three films exist in one step. Further, when the patterned substrate was polished, dishing occurred and a good polished surface could not be obtained.

The chemical mechanical polishing aqueous dispersion according to Comparative Example 6 uses glycine having a high etching ability, and further does not have a heterocyclic compound. Therefore, the copper film is excessively polished and loses its balance. It is difficult to polish an existing surface to be polished in one step. Further, when the patterned substrate was polished, dishing occurred and a good polished surface could not be obtained.

In the chemical mechanical polishing aqueous dispersion according to Comparative Example 7, the copper film is excessively polished and loses balance, and it is difficult to polish the surface to be polished on which the three films exist in one step. Further, when the patterned substrate was polished, dishing occurred and a good polished surface could not be obtained.

Since the chemical mechanical polishing aqueous dispersion according to Comparative Example 8 does not have a heterocyclic compound, the copper film is excessively polished and loses balance, and the surface to be polished having three films is polished in one step. It is difficult. Further, when the patterned substrate was polished, dishing occurred and a good polished surface could not be obtained.

  The chemical mechanical polishing aqueous dispersion according to the present invention can exhibit good polishing performance particularly in a damascene wiring having a cobalt-containing barrier metal film.

DESCRIPTION OF SYMBOLS 10 ... Low dielectric constant insulating film, 20 ... Insulating film, 30 ... Recess for wiring, 40 ... Barrier metal film, 50 ... Copper film, 100 ... To-be-processed object, 200 ... Semiconductor device

Claims (7)

(A) abrasive grains;
(B) a compound having two or more carbonyl groups;
(C) a heterocyclic compound;
An aqueous dispersion for chemical mechanical polishing used in a method for polishing a substrate containing a cobalt-containing film on the substrate.   2. The chemical mechanical polishing aqueous dispersion according to claim 1, wherein the component (B) is malic acid and / or maleic acid.   The chemical mechanical polishing aqueous dispersion according to claim 1, wherein the component (C) is a nitrogen-containing heterocyclic compound.   The aqueous dispersion for chemical mechanical polishing according to any one of claims 1 to 3, wherein the component (C) is a benzotriazole and / or a benzotriazole derivative. The chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 4, wherein the pH is 7 to 9.   The chemical mechanical polishing aqueous dispersion according to claim 1, wherein the component (A) is silica.   A method for polishing a substrate having a copper film, an insulating film, and a cobalt-containing film formed on a semiconductor substrate, using the chemical mechanical polishing aqueous dispersion according to claim 1.

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